Embankment Construction

- 1 -

TIRE SHREDS AS LIGHTWEIGHT FILL FOREMBANKMENT CONSTRUCTION OVER SOFT GROUND

Dana N. Humphrey, Ph.D., P.E.Professor of Civil Engineering

University of Maine1

Presented at:URS Greiner Woodward Clyde Seminar on

Embankment Construction Over Soft GroundSt. Louis, Missouri

June 5, 1999

ABSTRACTTire shreds are scrap tires that have been cut into 3 to 12-in. (75 to 300-mm) pieces.

They have an in-place unit weight between 45 and 58 pcf (0.72 to 0.93 Mg/m3). Whencombined with their widespread availability and relatively low cost, they are findingincreasing use as lightweight fill for embankment construction on weak, compressiblefoundation soils. Moreover, they produce low earth pressure when used as backfill behindretaining walls and bridge abutments. Tire shreds have a shear strength that is comparableto or greater than the shear strength of typical embankment soils. Procedures to calculate thein-place unit weight and immediate compression of the tire shred layer due to the weight ofoverlying soil are available. To prevent the compressibility of the tire shreds from affectingthe longevity of the overlying pavement, the tire shred layer should generally be covered byat least 39 in. (1 m) of soil and base course aggregate. Under some circumstances less soilcover is acceptable. Although three embankments experienced a self-heating reaction,guidelines are now available to limit self-heating and embankments have been successfullybuilt following the guidelines. For most circumstances, tire shreds have a negligible impacton groundwater quality.

Two case histories are described. Tire shreds were used to improve the stability of a 32-ft (9.8-m) high embankment constructed on weak marine clay. In the second project, a 14-ft(4.3-m) thick tire shred layer was used to improve the stability of a slope that supports anapproach fill for a new bridge. Use of tire shreds on these projects was substantially cheaperthan other ground improvement or lightweight fill alternatives.

1 Dept. of Civil and Environmetnal Engineering, University of Maine, 5711 Boardman Hall, Orono, Maine04469-5711. Phone: 207-581-2176; FAX: 207-581-3888; Home office phone/fax: 207-938-4252;E-mail: [email protected]

- 2 -

INTRODUCTIONTire shreds are scrap tires that have been cut into pieces with a maximum size ranging

from 2 to 12 in. (50 to 300 mm) (ASTM, 1998). This material is lightweight, free draining,and compressible. Moreover they have a thermal resistivity that is about seven times higherthan soil and they produce low earth pressure. Because of their special properties tire shredsare increasingly being used as lightweight fill for embankments constructed on weakfoundation soils (Humphrey, et al., 1998; Whetten, et al., 1997), lightweight backfill forretaining walls and bridge abutments (Tweedie, et al., 1997, 1998a,b; Humphrey, et al.,1998), compressible inclusions behind integral abutment and rigid frame bridges (Humphrey,et al., 1998; Reid and Soupier, 1998), thermal insulation to limit frost penetration beneathroads (Humphrey and Eaton, 1995; Lawrence, et al., 1998), and drainage layers for road(Lawrence, et al., 1998) and landfill applications (Jesionek, et al., 1998). In 1996, anestimated 10 million scrap tires were used for civil engineering applications (STMC, 1997).By 1998, this figure had grown to 18 million tires2. The reasons for this growth are simple –tire shreds have properties that civil engineers need and using tire shreds can significantlyreduce construction costs.

The cost of tire shreds varies from about $5/ton (approx. $3.50/c.y.) to $25/ton (approx.$18/c.y.). This is a very economical price for lightweight fill and for other applications thatcan make use of the special properties of tire shreds. The reason for this low cost is thatscrap tire processors are paid to collect scrap tires – thus, they are paid to take in the rawmaterial, a unique situation in the construction industry. In some states the scrap tireprocessors are paid by tire retail outlets, while in other states they are paid from a state-runtire fund, but the effect is the same – scrap tire processors only have to make a small portionof their income by selling their product.

Civil engineering applications of tire shreds did experience a significant setback in 1995and early 1996 when three thick tire shred fills (each greater than 26 ft (7.9 m) thick)experienced a serious self-heating reaction, however, guidelines to limit self-heating are nowavailable (Ad Hoc Civil Engineering Committee, 1997; ASTM, 1998). Future growth ofcivil engineering applications will be aided by the recently published ASTM D6270-98,Standard Practice for Use of Scrap Tires in Civil Engineering Applications (ASTM, 1998).This document will help many civil engineers undertake their first projects using tire shreds.

This paper will present the properties of tire shreds that are needed to design lightweightfill applications. This includes gradation, unit weight, compressibility, time-dependentsettlement, and shear strength. Procedures to calculate the in-place unit weight andimmediate compression of the tire shreds under the weight of overlying soil are given. Theguidelines to limit self-heating and water quality effects of tire shreds will be discussed.Two case histories using tire shreds as lightweight fill for highway embankments arepresented. From the information presented below, it will be clear that tire shreds are a viableand economical material for use as lightweight fill for highway construction and otherapplications. 2 Presentation made by John Serumgard of the Scrap Tire Management Council at Rubber Recycling’98,Toronto, Ontario, October 22, 1998.

- 3 -

ENGINEERING PROPERTIES OF TIRE SHREDS

Gradation

Large size shreds are desirable when the tire shred zone is greater than 3.3 ft (1 m) thick,because they are less susceptible to self-heating (as will be discussed in more detail below).However, when the shreds contain a significant number of pieces larger than 12 in. (300mm), they tend to be difficult to spread in a uniform lift thickness. Thus, a typicalspecification requires that a minimum of 90% (by weight) of the shreds have a maximumdimension, measured in any direction, of less than 12 in. (300 mm) and 100% of the shredshave a maximum dimension less than 18 in. (450 mm). Moreover, at least 75% (by weight)must pass an 8-in. (200-mm) sieve and at least one sidewall must be severed from the treadof each tire. To minimize the quantity of small shreds, which can be susceptible to self-heating, the specifications require that no more than 25% (by weight) pass the 1.5-in. (38-mm) sieve and no more than 1% (by weight) pass the No. 4 (4.75-mm) sieve. When takingsamples for gradation analysis, they should be taken directly from the discharge conveyor ofthe tire shredding machine. This ensures that that the minus No. 4 fraction will berepresentative, which is not the case when samples are taken by shoveling shreds from astockpile.

Tire shreds meeting the size requirements given above generally have a uniformgradation. Typical results are shown in Fig. 1. The combination of large size shreds anduniform gradation generally dictates that a geotextile be used as a separator between the tireshreds and adjacent soil to prevent fines from migrating into the shreds over time.

Compacted Unit Weight

The compacted unit weight of tire shreds has been investigated in the laboratory forshred sizes up to 3-in. (75-mm). These were generally done with 10-in. (254-mm) or 12-in.

Figure 1. Gradation of tire shreds used as lightweight fill for Portland Jetport Interchange.

GRAVEL SAND FINESBOULDERS

1e+003 100 10 1 0.1 0.01GRAIN DIAMETER (mm)

0

10

20

30

40

50

60

70

80

90

100

PER

CEN

T PA

SSIN

G

- 4 -

(305-mm) inside diameter compaction molds and impact compaction. Compacted dry unitweights ranged from 38 to 43 pcf (0.61 to 0.69 Mg/m3) (ASTM, 1998). The in-place dry unitweight of a 2-ft (0.6-m) thick tire shred layer constructed for a highway project by Nickels(1995) was 42 pcf (0.68 Mg/m3). The tire shred layer would compress slightly under its ownself weight, so it is reasonable that the field dry unit weight is near the upper bound of thelaboratory values. Thus, laboratory compaction tests give a good estimate of field unitweight of 3-in. (75-mm) maximum size shreds, however, the unit weight of tire shredsincreases they are compressed by the weight of overlying material. This will be discussedfurther in a later section.

The effect of compaction energy and compaction water content was investigated.Increasing the compaction energy from 60% of standard Proctor to 100% of modified Proctorincreased the compacted unit weight by only 1.2 pcf (0.02 Mg/m3) showing that compactionenergy has only a small effect on the resulting unit weight. Unit weights were about thesame for air dried samples and samples at saturated surface dry conditions (about 4% watercontent) indicating that water content has a negligible effect on unit weight (Manion andHumphrey, 1992; Humphrey and Manion, 1992). One significance of this finding is thatthere is no need to control moisture content of tire shreds during field placement.

Measuring the compacted unit weight of shreds with a 12-in. (300-mm) maximum sizeis impractical in the laboratory. However, results from a highway embankment constructedwith large shreds suggest that the unit weight of 12-in. (300-mm) maximum size shreds isless than for 3-in. (75-mm) maximum size shreds (Humphrey, et al., 1998). This will bediscussed further in the section on the Portland Jetport Interchange case history.

Compressibility

The compressibility of tire shreds is needed for two reasons. The first is that the unitweight of tire shreds increases as they are compressed under their own self-weight and theweight of overlying soil and pavement. Since the tire shreds are being used as lightweightfill, the final in-place unit weight is an important design parameter. The second is that thetop of the tire shred layer must be overbuilt to account for the immediate compression of thetire shreds as the overlying soil and pavement is placed.

The compressibility of shreds with a 3-in. (75-mm) maximum size has been measured inthe laboratory. An apparatus used by Nickels (1995) had a 14-in. (356-mm) inside diameterand could accommodate a sample up to 14-in. (356-mm) thick. One challenge to measuringthe compressibility of tire shreds is friction between the tire shreds and the inside wall of thetest container. The apparatus used by Nickels (1995) had load cells to measure the loadcarried by the specimen both at the top and bottom of the sample as shown in Fig. 2. Eventhough Nickels (1995) used grease to lubricate the inside of the container, up to 20% of theload applied to the top of the sample was transferred to walls of the container by friction.

Compressibility of shreds with a 3-in. (75-mm) maximum size is shown in Fig. 3. Theinitial unit weights ranged from 32.1 to 40.1 pcf (0.51 to 0.64 Mg/m3). There is a generaltrend of decreasing compressibility with increasing initial unit weight. The results for testsMD1 and MD4 are most applicable to using tire shreds as lightweight fill since they have aninitial unit weight that is typical of field conditions. Compressibility for stresses up to 70 psi

- 5 -

Figure 2. Compressibility apparatus used by Nickels (1995).

0 1 2 3 4 5 6 7 8 9

Average Vertical Stress (psi)

0

5

10

15

20

25

30

35

40

Verti

cal S

train

(%)

Legend Title

Humphrey et al. (1992)-Not Recorded

Test NY2 - 32.1 pcf

Test NY3 - 32.4 pcf

Test NY4 - 37.3 pcf

Test NY5 - 37.2 pcf

Test MD1 - 40.1 pcf

Test MD2 - 36.5 pcf

Test MD3 - 38.0 pcf

Test MD4 - 39.6 pcf

0

5

10

15

20

25

30

35

40

Figure 3. Compressibility of tire shreds with a 3-in. (75-mm) maximum size (Nickels, 1995).

- 6 -

(480 kPa) are given by Manion and Humphrey (1992) and Humphrey and Manion (1992).Laboratory data on the compressibility of shreds with a maximum size greater than 3 in. (75mm) are not available, however, field measurements indicates that shreds with a 12-in. (300-mm) maximum size are less compressible than smaller shreds. This will be discussed furtheras part of the Portland Jetport Interchange case history.

Time Dependant Settlement

Tire shreds exhibit a small amount of time dependant settlement. Time dependentsettlement of thick tire shred fills was measured by Tweedie, et al. (1997). Three types of tireshreds were tested with maximum sizes ranging from 1.5 to 3 in. (38 to 75 mm). The fill was14 ft (4.3 m) thick and was surcharged with 750 psf (36 kPa), which is equivalent to about 6ft (1.8 m) of soil. Vertical strain versus elapsed time is shown in Fig. 4. It is seen thatsignificant time dependent settlement occurred for about 2 months after the surcharge wasplaced. During the first two months about 2% vertical strain occurred which is equivalent tomore than 3 in. (75 mm) of settlement for this 14-ft (4.3-m) thick fill. When tire shreds areused as backfill behind a pile supported bridge abutment or other structure that willexperience little settlement, it is important to allow sufficient time for most of the timedependent settlement of the shreds to occur prior to final grading and paving. Timedependant settlement is of less concern when the ends of the tire shred fill can be taperedfrom the full thickness to zero over a reasonable distance.

Figure 4. Time dependent settlement of tire shreds subjected to a surcharge of 750 psf (36kPa) (Tweedie, et al, 1997).

- 7 -

Shear Strength

The shear strength of tire shreds has been determined using direct shear and triaxialshear apparatus. The large tire shreds typically used for civil engineering applicationsrequires that specimen sizes be several times greater than used for common soils. Because ofthe limited availability of large triaxial shear apparatus this method has generally been usedfor tire chips 1-in. (25-mm) in size and smaller. Moreover, the triaxial shear apparatus isgenerally not suitable for tire shreds that have steel belts protruding from the cut edges of theshreds since the wires puncture the membrane used to surround the specimen.

The shear strength of tire shreds has been measured using triaxial shear by Bressette(1984), Ahmed (1993), and Benda (1995); and using direct shear by Humphrey, et al. (1992,1993), Humphrey and Sandford (1993), Cosgrove (1995), and Gebhardt, et al. (1998).Failure envelopes determined from direct shear and triaxial tests for shreds with a maximumsize ranging from 0.37 to 35 in. (9.5 to 900 mm) are shown in Fig. 5. Although the range oftire shred sizes and applied stresses are incomplete, available data suggest that shear strengthis not affected by tire shred size. Moreover, results from triaxial and direct shear tests aresimilar. Overall, the failure envelopes appear to be concave down. Thus, best fit linear

Figure 5. Failure envelopes for tire shreds with maximum sizes ranging from 0.37 to 35 in.(9.5 to 900 mm).

0 10 20 30 40 50 60 70 80 90 100NORMAL STRESS (kPa)

0

10

20

30

40

50

SHEA

R S

TRES

S (k

Pa)

Tire Shred Supplier, Maximum Shred Size, Test MethodF&B, 38-mm max. size, direct shear (Humphrey and Sandford, 1993)Palmer, 75-mm max. size, direct shear (Humphrey and Sandford, 1993)Pine State, 75-mm max. size, direct shear (Humphrey and Sandford, 1993)Pine State, 75-mm max. size, direct shear (Humphrey and Sandford, 1993)Dodger Enterprises, 900-mm max. size, direct shear (Gebhardt, et al., 1998)Unknown, 9.5-mm max.size, triaxial shear (Benda, 1995)Unknown, 9.5-mm max. size, triaxial shear (Benda, 1995)

- 8 -

failure envelopes are applicable only over a limited range of stresses. Friction angles andcohesion intercepts for linear failure envelopes for the data shown in Fig. 5 are given inTable 1. Tire shreds require sufficient deformation to mobilize their strength (Humphrey andSandford, 1993). Thus, a conservative approach should be taken when choosing strengthparameters for tire shred embankments founded on sensitive clay foundations.

Table 1. Strength parameters for tire shreds.Supplier Maximum

shred sizeTest

methodApplicable range of

normal stressφ Cohesion

interceptin. mm psf kPa deg. psf kPa

F&B 0.5 38 D.S. 360 to 1300 17 to 62 25 180 8.6Palmer 3 75 D.S. 360 to 1300 17 to 62 19 240 11.5Pine State 3 75 D.S. 360 to 1400 17 to 68 21 160 7.7Pine State 3 75 D.S. 310 to 900 15 to 43 26 90 4.3Dodger 35 900 D.S. 120 to 580 5.6 to 28 37 0 0Unknown 0.37 9.5 Triaxial 1100 to 1700 52 to 82 24 120 6.0Unknown 0.37 9.5 Triaxial 230 to 400 11 to 19 36 50 2.4Note: D.S. = Direct Shear

DESIGN CONSIDERATIONS

Final In-place Unit Weight

The final in-place unit weight of the tire shreds must be estimated during design. Thismust consider compression of the tire shreds under their own self-weight and the weight ofoverlying soil and pavement. The calculation procedure is straight forward and is outlinedbelow:

Step 1. From laboratory compaction tests or typical values, determine the initialuncompressed, compacted dry unit weight of tire shreds (γdi) (for shreds witha 3-in. (75-mm) maximum size, use 40 pcf (0.64 Mg/m3)).

Step 2. Estimate the in-place water content of tire shreds (w) and use this todetermine the initial uncompressed, compacted total (moist) unit weight oftire shreds: γti = γdi (1+w). Unless better information is available, use w = 3or 4 %.

Step 3. Determine the vertical stress in center of tire shred layer (σv-center). To do this,make a first guess of the compressed unit weight of tire shreds (γtc) (50 pcf(0.80 Mg/m3) is suggested for the first guess).

σv-center = tsoil(γt-soil) + (tshreds/2)(γtc)where: tsoil = thickness of overlying soil layer

γt-soil = total (moist) unit weight of overlying soiltshreds = compressed thickness of tire shred layer(Note: In the equation, the thickness of the tire shred layer is dividedby 2 since we are computing the stress in the center of the layer)

- 9 -

Step 4. Determine the percent compression (εv) using σv-center and the measuredlaboratory compressibility of the tire shreds; for shreds with a 3-in. (75-mm)maximum size, use the results for test MD1 or MD4 in Fig. 3.

Step 5. Determine the compressed moist unit weight of the shreds: γtc = γti/(1-εv). Ifnecessary return to step 3 with a better estimate of the compressed moist unitweight.

This procedure was used to predict the compressed unit weight of a 14-ft (4.3-m) thick tireshred fill covered by 6 ft (1.8 m) of soil built in Topsham, Maine. Shreds with a 3-in. (75-mm) maximum size were used in the upper third of the fill while shreds with a 6-in. (150-mm) maximum size were used in the lower part of the fill. The predicted compressed moistunit weight was 57 pcf (0.91 Mg/m3). The actual in-place unit weight determined from thefinal volume of the tire shred zone and the weight of tire shreds delivered to the project wasalso 57 pcf (0.91 Mg/m3). This validates the reliability of the laboratory compressibility testsand the procedure to estimate the compressed moist unit weight for shreds with maximumsizes between 3 and 6 in. (75 and 150 mm). However, when the procedure was applied toshreds with a 12-in. (300-mm) maximum size, the predicted unit weight was greater thandetermined in the field. For a highway embankment built in Portland, Maine with shredswith a 12-in. (300-mm) maximum size, the predicted compressed moist unit weight was 58pcf (0.93 Mg/m3) compared to an actual unit weight of 49 pcf (0.79 Mg/m3). The reasons forthe difference appear to be a lower initial uncompressed unit weight and lowercompressibility for these larger shreds.

Calculation of Overbuild

The tire shred layer will be compressed by the weight of the overlying soil andpavement. It is therefore necessary to overbuild the top of the tire shred layer to compensatefor this immediate compression. The starting condition is that the tire shreds have beenplaced and are compressed under their own self-weight. Thus, it is necessary to calculate theadditional immediate compression that will occur as the overlying soil and pavement isplaced. The procedure to estimate the amount of overbuild is outlined below.

Step 1. Determine the final in-place total unit weight of tire shreds using theprocedure outlined above.

Step 2. Determine the vertical stress in the center of the tire shred layer due to justthe weight of the tire shreds with no soil cover. σv-0 = (tshreds/2) [(γti + γtc)/2]In this equation, the average is taken between the initial (uncompressed) andfinal (compressed) unit weights of the tire shreds since the unit weight of theshreds before placing the overlying soil cover is between these two values.(A more accurate calculation of the unit weight before placement of the soilcover is possible using the procedure given in the previous section, but isprobably not worth the effort).

Step 3. Determine vertical stress in center of tire shred layer after placement of thesoil cover: σv-center = tsoil(γt-soil) + (tshreds/2)(γtc)

- 10 -

Step 4. Using compressibility data for tire shreds, determine the vertical straincorresponding to σv-0, which we will call εv0, and corresponding to σv-center,which we will call εvf (for shreds with a 3-in. (75-mm) maximum size usethe data for tests MD1 or MD4 in Fig. 3).

Step 5. The overbuild (OB) required to compensate for compression of the tire shredlayer under the weight of the overlying soil cover is given by OB = tshreds(εvf - εv0)

This procedure was applied to the 14-ft (4.3-m) thick tire shred fill in Topsham, Mainedescribed in the previous section. The calculated overbuild was 18 in. (0.46 m). Themeasured compression was 20.4 in. (0.52 m). At least part of this difference was due to timedependent settlement, which would be expected to be about 3 in.(0.075 m) for this fillthickness. Time dependent settlement was not considered when calculating the overbuild.

Thickness of Overlying Soil Cover

Sufficient soil cover must be placed over the compressible tire shred layer to preservethe durability of the overlying pavement. This was investigated by Nickels (1995) andHumphrey and Nickels (1997). They showed that the tensile strain at the base of asphalticconcrete pavement with 30 in. (760 mm) of soil cover over the tire shred layer was the sameas a control section underlain by conventional aggregate and soil. However, to beconservative a minimum of 39 in. (1 m) of soil cover is recommended for most applications.For applications with low truck traffic, such as parking lots and rural roads, less soil covermay be acceptable.

Guidelines to Limit Heating

Three thick tire shred fills (greater than 26 ft (7.9 m) thick) have undergone a self-heating reaction. Two of these projects were located in Washington State and one was inColorado. These projects were constructed in 1995 and each experienced a serious self-heating reaction within 6 months after completion (Humphrey, 1996). The lessons learnedfrom these projects were condensed into design guidelines developed by the Ad Hoc CivilEngineering Committee (1997), a partnership of government and industry dealing with reuseof scrap tires for civil engineering purposes. The overall philosophy behind development ofthe guidelines was to minimize the presence of factors that could contribute to self-heating.The guidelines were subsequently published by ASTM (1998) and distributed by the FederalHighway Administration. For tire shred layers ranging in thickness from 3.3 to 10 ft (1 to 3m), the guidelines give the following recommendations:

• Tire shreds shall be free of contaminants such as oil, grease, gasoline, dieselfuel, etc., that could create a fire hazard

• In no case shall the tire shreds contain the remains of tires that have beensubjected to a fire

• Tire shreds shall have a maximum of 25% (by weight) passing 1½-in. (38-mm) sieve and a maximum of 1% (by weight) passing no. 4 (4.75-mm) sieve

- 11 -

• Tire shreds shall be free from fragments of wood, wood chips, and otherfibrous organic matter

• Tire shreds shall have less than 1% (by weight) of metal fragments that are notat least partially encased in rubber

• Metal fragments that are partially encased in rubber shall protrude no morethan 1 in. from the cut edge of the tire shred on 75% of the pieces and no morethan 2 in. on 100% of the pieces

• Infiltration of water into the tire shred fill shall be minimized• Infiltration of air into the tire shred fill shall be minimized• No direct contact between tire shreds and soil containing organic matter, such

as topsoil• Tire shreds should be separated from the surround soil with a geotextile• Use of drainage features located at the bottom of the fill that could provide

free access to air should be avoided

The guidelines further recommend that a tire shred layer be no greater than 10 ft (3 m) thick.The guidelines also give less stringent requirements for tire shred layers less than 3.3 ft (1 m)thick (Ad Hoc Civil Engineering Committee, 1997; ASTM, 1998).

Water Quality Effects

Several studies have shown that tire shreds can be used in most applications withnegligible effects on ground water quality. Humphrey, et al. (1997), studied the effect of tireshreds placed above the water table in a test project in North Yarmouth, Maine. In this study,two 10 ft x 10 ft (3 m x 3 m) geomembrane-lined collection basins are used to collect waterafter it has passed through a 2-ft (0.61-m) thick layer of tire shreds. The shreds had a 3-in.(75-mm) maximum size and a significant amount of exposed steel belts. A third basin wasoverlain only by soil and served as a control. Water samples have been taken quarterly sinceJanuary, 1994. Samples were analyzed for metals with primary and secondary drinkingwater standards3. For metals with a primary drinking water standard, the levels are about thesame for basins overlain by tire shreds compared to the control basin overlain by soil. As anexample, the results for chromium (Cr) are shown in Fig. 6. Similar results were found formetals with secondary (aesthetic) standards except for manganese (Mn) and, to a lesserextent, iron (Fe). Manganese consistently had higher levels in the basins overlain by tireshreds compared to the control basin (Fig. 7). The source of the manganese is thought to bethe exposed steel belts, which contain 2 to 3% manganese by weight. On some samplingdates, iron was higher in the basins overlain by tire sheds as shown in Fig. 8. Volatile andsemi-volatile organics were tested on two dates. On both dates all substances were below thetest method detection limits. Similar results for metals and organics were found for theWitter Farm Road test project (Humphrey, 1999a).

Tire shreds placed below the water table were the subject of another study at theUniversity of Maine (Downs, et al., 1996; Humphrey, 1999b). In this study, 1.5 tons (1.4 3 Metals with a primary standard are a known or suspected health risk. Metals with a secondary standard are ofaesthetic concern, which means that they may impart some taste, odor, and/or color to water but they do notpose a health risk.

- 12 -

Figure 6. Chromium levels for filtered samples at North Yarmouth field trial.

Figure 7. Manganese levels for filtered samples at North Yarmouth field trial.

1/1/

94

4/1/

94

7/1/

94

10/1

/94

1/1/

95

4/1/

95

7/1/

95

10/1

/95

1/1/

96

4/1/

96

7/1/

96

10/1

/96

1/1/

97

4/1/

97

7/1/

97

10/1

/97

1/1/

98

4/1/

98

7/1/

98

10/1

/98

1/1/

99

4/1/

99

DATE

0.000

0.025

0.050

0.075

0.100

0.125

0.150

0.175

CO

NC

ENTR

ATIO

N (m

g/L)

FILTERED

CONTROL

SECTION C

SECTION D

R.A.L. = 0.1 mg/L

.

1/1/

94

4/1/

94

7/1/

94

10/1

/94

1/1/

95

4/1/

95

7/1/

95

10/1

/95

1/1/

96

4/1/

96

7/1/

96

10/1

/96

1/1/

97

4/1/

97

7/1/

97

10/1

/97

1/1/

98

4/1/

98

7/1/

98

10/1

/98

1/1/

99

4/1/

99

DATE

02468

101214161820

CO

NC

ENTR

ATIO

N (m

g/L)

FILTERED

CONTROL

SECTION C

SECTION D

R.A.L. = 0.05 mg/L

.

- 13 -

Figure 8. Iron levels for filtered samples at North Yarmouth field trial.

metric tons) of tire shreds were buried below the water table in three different soil types(marine silty clay, glacial till, and peat). Samples were taken over a three year period fromthe tire shred filled trench and from wells located 10 ft (3.0 m) up-gradient (control wells), 2ft (0.6 m) down-gradient, and 10 ft (3.0 m) down-gradient. For samples taken from the tireshred filled trench, the levels of metals with a primary standard were below their respectiveregulatory limits. However, the levels of manganese and iron were above their secondary(aesthetic) standards. A few organic compounds were present at detectable levels in the tireshred filled trench. However, after flowing through only 2 ft (0.6 m) of soil to the first downgradient wells, the levels in the groundwater had decreased to below the detection limitexcept for three compounds (benzene, cis-1,2-dichloroethene, and toluene) which werepresent at levels below their respective drinking water standards. 1,1-dichloroethane waspresent in some down-gradient wells at the marine clay and till sites but the highestconcentration was 6.9 parts per billion. Concentrations of 1,1-dichloroethane were belowdetection limit in all down-gradient wells on the most recent sampling date. A drinkingwater standard has not been established for this compound.

These studies show that tire shreds have a negligible impact on groundwater quality andcan be used for most civil engineering applications provided the pH of the groundwater isnear neutral. Further field studies would be needed to establish the effect of tire shreds onwater quality for acidic or basic conditions.

CASE HISTORY – PORTLAND JETPORT INTERCHANGETire shreds were used as lightweight fill for construction of two 32-ft (9.8-m) high

highway embankments in Portland, Maine (Humphrey, et al., 1998). These embankments

1/1/

94

4/1/

94

7/1/

94

10/1

/94

1/1/

95

4/1/

95

7/1/

95

10/1

/95

1/1/

96

4/1/

96

7/1/

96

10/1

/96

1/1/

97

4/1/

97

7/1/

97

10/1

/97

1/1/

98

4/1/

98

7/1/

98

10/1

/98

1/1/

99

4/1/

99

DATE

0.0

2.0

4.0

6.0

8.0

10.0C

ON

CEN

TRAT

ION

(mg/

L) FILTERED

CONTROL

SECTION C

SECTION D

R.A.L. = 0.3 mg/L

.

- 14 -

were the approach fills to a new bridge over the Maine Turnpike. The bridge is part of a newinterchange that will provide better access to the Portland Jetport and Congress Street. Thissite was underlain by about 40 ft (12.2 m) of weak marine clay. Test results indicated that theclay is an overconsolidated, moderately sensitive, inorganic clay of low plasticity.Undrained shear strength varied from approximately 1500 psf (72 kPa) near the top to 400psf (19 kPa) near the center of the layer.

The designers for the project (the Maine offices of HNTB, Inc. and Haley and Aldrich,Inc. and the University of Maine) found that embankments built of conventional soil weretoo heavy resulting in an unacceptably low factor of safety against slope instability. Theylooked at several ways to strengthen the foundation soils but these were too costly.Constructing the embankments of lightweight fill was chosen as the lowest cost alternative.They considered several types of lightweight fill including tire shreds, expanded polystyreneinsulation boards, and expanded shale. Tire shreds were chosen because they were $300,000cheaper than the other alternatives. Moreover, the project would put some 1.2 million tires toa beneficial end use. Wick drains were also used to accelerate consolidation of thefoundation soils.

Project Layout and Construction

Several steps were taken to comply with the guidelines to limit heating of thick tireshred fills (Ad Hoc Civil Engineering Committee, 1997; ASTM, 1998). The guidelinesrequired that a single tire shred layer be no thicker than 10 ft (3 m), so the tire shred layerwas broken up into two layers, each up to 10 ft (3 m) thick, separated by 3 ft (0.9 m) of soilas shown in Fig. 9. Low-permeability soil with a minimum of 30% passing the no. 200 sievewas placed on the outside and top of the fill to limit inflow of air and water. The finalprecaution to limit heating was to use large shreds with a minimum of fines. The shreds hadless than 25% passing the 1½-in. (38-mm) sieve and less than 1% passing the No. 4 sieve.The shreds had a maximum size measured in any direction of 12 in. (300 mm) to ensure thatthey could be easily placed with conventional construction equipment. The embankment wastopped with 4 ft (1.22 m) of granular soil plus 4 ft (1.22 m) of temporary surcharge. Thepurpose of the surcharge was to increase the rate of consolidation of the soft clay foundationsoils and was unrelated to the tire shred fill.

Figure 9. Cross section through embankment constructed on soft marine clay for thePortland Jetport Interchange (Humphrey, et al., 1998).

- 15 -

The tire shreds were placed with conventional construction techniques. First geotextilewas placed on the prepared base to act as a separator between the tire shreds and surroundingsoil. Then the tire shreds were spread in 12-in. (300-mm) thick lifts using a Caterpillar D-4dozer as shown in Fig. 10. Each lift was compacted with six passes of a vibratory roller witha minimum 10-ton (9.1-metric ton) operating weight. After placing the shreds, the contractorplaced a geotextile separator on the sides and top of the tire shred zone. Finally, thesurrounding soil cover was placed.

Construction Settlement and In-Place Unit Weight

Settlement plates were installed at the top and bottom of each tire shred layer to monitorsettlement. Compression of each tire shred layer at the end of fill placement is summarizedin Table 2. The compression predicted based on laboratory compression tests on 3-in. (75-mm) maximum size tire shreds is also shown. It is seen that the predicted compression issignificantly greater than the measured value. Thus, the compressibility of shreds with a 12-in. (300-mm) maximum size appears to be less than for 3-in. (75-mm) maximum size shreds.This was one factor that lead to overpredicting the final in-place unit weight. The final in-place unit weight was predicted to be 58 pcf (0.93 Mg/m3) compared to an actual value of 49pcf (0.79 Mg/m3), a difference of 18%. This difference cannot be entirely accounted for bythe difference in compressibility. Thus, it is likely that the initial (uncompressed) unit weightof these larger shreds is less than for 3-in. (75-mm) maximum size shreds.

Figure 10. Catipillar D-4 spreading tire shreds for lightweight embankment fill at PortlandJetport Interchange.

- 16 -

Table 2. Measured compressibility of tire shred layer for Portland Jetport Interchangeproject.

Settlement Location Lower tire shred layer Upper tire shred layerPlate No. Measured Predicted Measured Predicted

SW1 25+00,C/L 12.6% 22% 8.3% 14%SW4 26+00, C/L 13.4% 21% 11.2% 14%SE1 30+00, C/L 19.1% 22% 10.9% 14%SE4 31+00, C/L 17.3% 23% 9.3% 14%

Avg. C/L Plates 15.6% 22% 9.9% 14%

Temperature Measurements

Monitoring the temperatures of the tire shred fill was of great interest because of pastproblems with heating of thick tire shred fills (Humphrey, 1996). The warmest temperatureswere measured at the time of placement when the black tire shreds were heated by exposureto direct sunlight. Initial temperatures ranged from 75 to 100°F (24 to 38°C). After beingcovered with the first few lifts of fill, the temperatures began dropping with time.Temperatures were still dropping when monitoring was discontinued in April, 1998. Typicaltemperature measurements are shown on Fig. 11. From these results it can been seen thatthere was no evidence of self-heating.

6/30/97 9/28/97 12/27/97 3/27/98 6/25/9850

55

60

65

70

75

80

85

90

95

100

Tem

pera

ture

(D

eg. F

)

Embankment 2Lower Tire Shred Layer

TH23

TH25

TH27

TH33

Figure 11. Temperatures in lower tire shed layer of lightweight embankment fill at PortlandJetport Interchange.

- 17 -

CASE HISTORY - NORTH ABUTMENT APPROACH FILLThe key element of the Topsham Brunswick Bypass Project was the 984-ft (300-m) long

Merrymeeting Bridge over the Androscoggin River. The subsurface profile at the location ofthe North Abutment consisted of 10 to 20 ft (3 to 6 m) of marine silty sand overlying 45 to 50ft (14 to 15 m) of marine silty clay. The clay is underlain by glacial till and then bedrock.The existing riverbank had a factor of safety against a deep seated slope failure that was nearone. Moreover, the design called for an approach fill leading up to the bridge abutment thatwould have further lowered the factor of safety. Thus, it was necessary to devise a strategyto both improve the existing factor of safety and allow construction of the approach fill. Thebest solution was to excavate some of the existing riverbank and replace it with a 14-ft (4.3-m) thick layer of tire shreds. Tire shreds had the added advantage of reducing lateralpressures against the abutment wall. Other types of lightweight fill were consideredincluding geofoam and expanded shale aggregate. However, tire shreds proved to be thelowest cost solution. The project used some 400,000 scrap tires (Whetten, et al., 1997).

Project Layout and Construction

The surficial marine sand was excavated to elevation 17 ft (5.2 m) and then the H-pilesupported abutment wall was constructed. A 14 ft (4.3-m) thick zone of tire shreds wasplaced from station 175+50 ft (53+50.6 m) to the face of the abutment wall at station 176+20ft (53+72.0 m). The fill tapers from a thickness of 14 ft (4.3 m) at station 175+50 ft (53+50.6m) to zero thickness at station 175+00 ft (53+35.4 m) to provide a gradual transition betweenthe tire shred layer and the conventional fill. It was estimated that the tire shred layer wouldcompress 18 in. (460 mm) due to the weight of overlying soil layers. As a result, the layerwas built up an additional 18 in. (460 mm) so that the final compressed thickness would be14 ft (4.3 m). The tire shred layer was enclosed in a woven geotextile (Niolon Mirafi 500X)to prevent infiltration of surrounding soil. The tire shreds were spread with front end loadersand bulldozers and then compacted by six passes of a smooth drum vibratory roller (BomagBW201AD) with a static weight of 10.4 tons (9,432 kg). The thickness of a compacted liftwas limited to 12 in. (305 mm). It was determined that to obtain a compacted thickness of 12in. (305 mm), approximately 15 in. (381 mm) of loose tire shreds needed to be initiallyplaced. Tire shred placement began on September 25, 1996 and was completed on October3, 1996. A longitudinal section of the completed abutment and embankment is shown in Fig.12.

This project was designed and built prior to development of the guidelines to limit self-heating of tire shred fills. However, the project did include some design features to limitself-heating. The first was to use larger size shreds (called Type B shreds) in the lowerportion of the fill from elevation 17 ft (5.2 m) to elevation 27 ft (8.2 m). The Type B shredswere specified to have a maximum dimension measured in any direction, of 12 in. (305 mm);a minimum of 75% (by weight) passing the 8-in. (203-mm) square mesh sieve, a maximumof 25% (by weight) passing the 1½-in. (38-mm) square mesh sieve, and a maximum of 5%(by weight) passing the No. 4 (4.75-mm) sieve. Gradation tests showed that the shredsgenerally had a maximum dimension smaller than 6 in. (150 mm). Type A shreds, with amaximum size of 3 in. (75 mm), were placed from elevation 27 ft (8.2 m) to the top of thetire shred fill. It would have been preferable to use the larger Type B shreds for the entire

- 18 -

el. 9.4 mClay

el. 5.2 m

el. 8.2 m

Type B Tire Shreds

NativeSoil

Type ATire Shreds

229 mm BituminousConcrete Pavement

AggregateSubbase

el. 11.3 m

el. 10.1 mel. 10.7 m

Station 53+35.4

CommonBorrow Granular

Borrow

AggregateSubbase

Geotextile

Piles

Station53+72.0

@ Center LineStation53+50.6

Concrete Approach Slab

Figure 12. Cross section through North Abutment tire shred fill.

thickness, however, a significant quantity of Type A shreds had already been stockpiled nearthe project prior to the decision to use larger shreds. It was judged that it would beacceptable to use the smaller Type A shreds in the upper portion of the fill. Moreover, itwould have been preferable to limit the total thickness of the tire shred layer to 10 ft (3 m) asrecommended by the guidelines to limit self-heating.

As an additional step to reduce the possibility of self-heating, the tire shreds are overlainby a layer of compacted clayey soil with a minimum of 30% passing the No. 200 (0.075 mm)sieve. The purpose of the clay layer is to minimize the flow of water and air though the tireshreds. The clay layer is approximately 2 ft (0.61 m) thick and is built up in the center topromote drainage toward the side slopes. A 2-ft (0.61-mm) thick layer of common borrowwas placed over the clay layer. Overlying the common borrow is 2.5 ft (0.76 m) of aggregatesubbase.

Tire shreds undergo a small amount of time dependent settlement. For this project athick tire shred fill adjoined a pile supported bridge abutment. This lead to concerns thatthere could be differential settlement at the junction with the abutment. However, Tweedie,et al. (1997) showed that most of the time dependent settlement occurs within the first 60days. To accommodate the time dependant settlement prior to paving, the contractor wasrequired to place an additional 1 ft (0.3 m) of subbase aggregate as a surcharge to be left inplace for a minimum of 60 days. In fact, the overall construction schedule allowed thecontractor to leave the surcharge in place from October, 1996 through October, 1997. Thesurcharge was removed in October, 1997 and the roadway was topped with 9 in. (229 mm) ofbituminous pavement. The highway was opened to traffic on November 11, 1997.Additional construction information is given in Cosgrove and Humphrey (1998).

- 19 -

Instrumentation

Four types of instruments were installed: pressure cells cast into the back face of theabutment wall; and vibrating wire settlement gauges, settlement plates and temperaturesensors placed in the tire shred fill. Vibrating wire pressure cells were installed to monitorlateral earth pressure against the abutment wall. Three Roctest model TPC pressure cells(PC1-1, PC1-2, PC1-3) were installed on the face of the abutment wall 13 ft (4 m) right ofcenterline at elevations 22, 25.5, and 29 ft (6.7, 7.8, and 8.8 m). Three Roctest model EPCpressure cells (PC2-1, PC2-2, PC2-3) were installed 13 ft (4 m) left of centerline at the sameelevations. Tire shreds were placed against all the cells.

Measured Horizontal Pressure and Settlement

The lateral pressure at the completion of tire shred placement (10/3/96) and completionof soil cover and surcharge placement (10/9/96) is summarized in Table 3. Lateral pressureson 10/31/96 are also shown. It is seen that at completion of tire shred placement, thepressures increased with depth. However, at completion of soil cover and surchargeplacement, the pressures recorded by cells PC1-1, PC1-2, and PC1-3 were nearly constantwith depth and ranged between 356 and 410 psf (17.05 and 19.61 kPa). These findings areconsistent with at-rest conditions measured on an earlier project (Tweedie, et al., 1997;1998a). Cells PC2-1, PC2-2, and PC2-3 showed different behavior. On 10/9/96, cell PC2-2showed a pressure of 631psf (30.22 kPa) while cell PC2-1, located only 3.5 ft (1.07 m)lower, was 418 psf (20.04 kPa) and cell PC2-3, located 3.5 ft (1.07 m) above PC2-2, was 257psf (12.31 kPa). These cells were the less stiff EPC cells. Large scatter has been observedwith EPC cells on an earlier tire shred project (Tweedie, et al., 1997, 1998a,b). This isthought to be due, at least in part, to large tire shreds creating a nonuniform stress distributionon the face of the pressure cell. The average pressure recorded by the three PC2 cells was435 psf (20.85 kPa), which is slightly higher than the PC1 cells. Between 10/9/96 and10/31/96 the lateral pressure increased by 20 to 40 psf (1 to 2 kPa). The pressures have beenapproximately constant since that time.

The tire shred fill compressed about 14.6 in. (370 mm) during placement of theoverlying soil cover. In the next 60 days the fill settled an additional 5.3 in. (135 mm).Between December 15, 1996 and December 31, 1997 the fill underwent an additional 0.6 in.(15 mm) of time dependent settlement. The rate of settlement had decreased to a negligible

Table 3. Summary of Lateral Pressures on Abutment Wall.

PC1-1 PC2-1 PC1-2 PC2-2 PC1-3 PC2-3Date Cell elev. = 6.70 m Cell elev. = 7.77m Cell elev. = 8.84 m10/3/962 7.841 7.41 6.04 7.27 2.62 1.4110/9/963 17.04 20.04 19.61 30.22 17.05 10.9110/31/96 18.27 21.05 20.98 32.84 20.24 12.311Horizontal pressure in kPa.2Date tire shred placement completed.3Date soil cover and surcharge placement completed.

- 20 -

level by late 1997. The total compression of the tire shred fill was (20.4 in.) 520 mm whichwas 13% greater than the 18 in. (460 mm) that was anticipated based on laboratorycompression tests. The difference is due, at least in part, to time dependant settlement that isnot accounted for in the short term laboratory tests. The final compressed density of the tireshreds was about 57 pcf (0.9 Mg/m3).

Temperature of Tire Shred Layer

A small amount of self heating of the tire shreds occurred. Five out of the 12thermistors in Type A shreds experienced a peak temperature of between 30 and 40°C (86and 104°F). In contrast, only two of the 18 thermistors in the larger Type B shredsexperienced a peak in this range and these two sensors may have been influenced by warmeroverlying Type A shreds. This suggests that larger shreds are less susceptible to heating. Inany case, the peak temperatures were too low to be of concern. Since early 1997, the overalltrend has been one of decreasing temperature, however, the temperature of the shreds doappear to be slightly influenced by seasonal temperature changes.

CONCLUSIONSThe low unit weight, widespread availability, and low cost of tire shreds has lead to their

being used as lightweight fill for embankments constructed on weak foundation soils. Theengineering properties of tire shreds are known including gradation, unit weight,compressibility and shear strength. When the special properties of tire shreds are needed fora project they are often the lowest cost alternative. Thus, civil engineers are choosing tireshreds because they offer both the properties needed to solve special problems and lowercosts to satisfy the demands of their clients for the most economical project possible. In thenext few years, major increases in the number of scrap tires used for civil engineeringapplications is possible because of their growing record of successful performance combinedwith guidelines to limit self-heating of thick fills, recently published ASTM guidelinespecifications, and groundwater data showing that they have a negligible environmentalimpact.

ACKNOWLEDGEMENTSThis paper presents the results from several projects. It took many dedicated people to

make these projects happen. Special thanks go to Nate Whetten, Jim Weaver, and KenRecker of Haley and Aldrich, Inc. of South Portland, Maine, who were instrumental indesigning the Portland Jetport Interchange and north abutment projects. Jeff McEwen was akey player of in the north abutment project when he worked for the Portland office of T.Y.Lin International and more recently for the Portland Jetport Project with his new employer,HNTB, Inc. of Portland, Maine.

Several University of Maine students put 110% effort into these projects. Will Manionand Michelle Cribbs are thanked for their laboratory work to determine the engineeringproperties of tire shreds. Tricia Cosgrove is thanked for her hard work on the north abutmentproject. Aaron Smart and Lisa Downs are thanked for performing most of the water quality

- 21 -

tests. The Maine Turnpike Authority, Maine Department of Transportation, and NewEngland Transportation are thanked for funding these projects.

REFERENCESAd Hoc Civil Engineering Committee (1997), “Design Guidelines to Minimize Internal

Heating of Tire Shred Fills,” Scrap Tire Management Council, Washington, DC., 4 pp.Ahmed, I. (1993), "Laboratory Study on Properties of Rubber Soils," Report No.

FHWA/IN/JHRP-93/4, School of Civil Engineering, Purdue University, W Lafayette, IN.ASTM (1998), “Standard Practice for Use of Scrap Tires in Civil Engineering Applications,”

ASTM D6270-98, Am. Soc. Testing & Mat., W. Conshohocken, PA.Benda, C.C. (1995), "Engineering Properties of Scrap Tires Used in Geotechnical

Applications," Report 95-1, Materials and Research Division, Vermont Agency ofTransportation, Montpelier, VT.

Bressette, T. (1984), "Used Tire Material as an Alternative Permeable Aggregate," ReportNo. FHWA/CA/TL-84/07, Office of Transportation Laboratory, California Departmentof Transportation, Sacramento, CA, 1984.

Cosgrove, T.A. (1995), "Interface Strength Between Tire Chips and Geomembrane for Useas a Drainage Layer in a Landfill Cover," Proceedings of Geosynthetics'95, IndustrialFabrics Association, St. Paul, MN, Vol. 3, pp. 1157-1168.

Cosgrove, T.A., and Humphrey, D.N. (1999), “Field Performance of Two Tire Shred Fills inTopsham, Maine,” a report for the Maine Department of Transportation, by Dept. of Civiland Environmental Engineering, University of Maine, Orono, Maine.

Downs, L.A., Humphrey, D.N., Katz, L.E., and Rock, C.A. (1996), “Water Quality Effects ofUsing Tire Chips Below the Groundwater Table,” Technical Services Division, MaineDepartment of Transportation, Augusta, Maine, 324 pp.

Gebhardt, M.A., Kjartanson, B.H., and Lohnes, R.A. (1998), “Shear Strength of Large SizeShredded Scrap Tires as Applied to the Design and Construction of Ravine Crossings,”Proceedings of the 4th International Symposium on Environmental Geotechnology andGlobal Sustainable Development, Danvers, MA.

Humphrey, D.N. (1996), “Investigation of Exothermic Reaction in Tire Shred Fill Located onSR 100 in Ilwaco, Washington,” Prepared for the FHWA, Washington, D.C., 60 pp.

Humphrey, D.N. (1999a), “Water Quality Results for Whitter Farm Road Tire Shred FieldTrial,” Dept. of Civil and Env. Eng., University of Maine, Orono, Maine, 6 pp.

Humphrey, D.N. (1999b), “Water Quality Effects of Using Tire Chips Below theGroundwater Table – Final Report,” Maine DOT, Augusta, Maine.

Humphrey, D.N., and Eaton, R.A. (1995), “Field Performance of Tire Chips as SubgradeInsulation for Rural Roads,” Proceedings of the Sixth International Conference on Low-Volume Roads, Transportation Research Board, Washington, D.C., Vol. 2, pp. 77-86.

Humphrey, D.N., Katz, L.E., and Blumenthal, M. (1997), “Water Quality Effects of TireChip Fills Placed Above the Groundwater Table,” Testing Soil Mixed with Waste orRecycled Materials, ASTM STP 1275, Mark A. Wasemiller and Keith B. Hoddinott,Eds., American Society for Testing and Materials, pp. 299-313.

Humphrey, D.N., and Manion, W.P. (1992), "Properties of Tire Chips for Lightweight Fill,"Grouting, Soil Improvement, and Geosynthetics, ASCE, Vol. 2, pp. 1344-1355.

- 22 -

Humphrey, D.N., and Nickels, W.L., Jr. (1997), “Effect of Tire Shreds as Lightweight Fill onPavement Performance,” Proceedings of the Fourteenth International Conference on SoilMechanics and Foundation Engineering, Vol. 3, pp. 1617-1620.

Humphrey, D.N., and Sandford, T.C. (1993), "Tire Chips as Lightweight Subgrade Fill andRetaining Wall Backfill," Proceedings of the Symposium on Recovery and EffectiveReuse of Discarded Materials and By-Products for Construction of Highway Facilities,Federal Highway Administration, Washington, D.C., pp. 5-87 to 5-99.

Humphrey, D.N., Sandford, T.C., Cribbs, M.M., Gharegrat, H., and Manion, W.P. (1992),"Tire Chips as Lightweight Backfill for Retaining Walls - Phase I," A Study for the NewEngland Transportation Consortium, Dep. of Civil Eng., Univ. of Maine, Orono, ME.

Humphrey, D.N., Sandford, T.C., Cribbs, M.M., Gharegrat, H., and Manion, W.P., "ShearStrength and Compressibility of Tire Chips for Use as Retaining Wall Backfill,"Transportation Research Record No. 1422, TRB, 1993, pp. 29-35.

Humphrey, D.N., Whetten, N., Weaver, J., Recker, K., and Cosgrove, T.A. (1998), “TireShreds as Lightweight Fill for Embankments and Retaining Walls,” Proceedings of theConference on Recycled Materials in Geotechnical Applications, C. Vipulanandan and D.Elton, eds., ASCE, pp. 51-65.

Jesionek, K.S., Humphrey, D.N., and Dunn, R.J. (1998), “Overview of Shredded TireApplications in Landfills,” Proceedings of the Tire Industry Conference, ClemsonUniversity, March 4-6, 12 p.

Lawrence, B.K., Chen, L.H., and Humphrey, D.N. (1998), “Use of Tire Chip/Soil Mixturesto Limit Frost Heave and Pavement Damage of Paved Roads,” A Study for the NewEngland Transportation Consortium, by Dept. of Civil and Environmental Engineering,University of Maine, Orono, Maine, 316 pp.

Manion, W.P., and Humphrey, D.N., "Use of Tire Chips as Lightweight and ConventionalEmbankment Fill, Phase I - Laboratory," Technical Paper 91-1, Technical ServicesDivision, Maine Department of Transportation, Augusta, ME, 1992.

Nickels, W.L., Jr. (1995), “The Effect of Tire Chips as Subgrade Fill on Paved Roads,” M.S.Thesis, Department of Civil Engineering, University of Maine, Orono, Maine, 215 pp.

Reid, R.A., and Soupir, S.P. (1998), “Mitigation of Void Development Under BridgeApproach Slabs Using Rubber Tire Chips,” Proceedings of the Conference on RecycledMaterials in Geotechnical Applications, ASCE, pp. 37-50.

STMC (1997), “Scrap Tire Use/Disposal Study – 1996 Update,” Scrap Tire ManagementCouncil, Washington, D.C., April, 1997, 57 pp.

Tweedie, J.J., Humphrey, D.N., and Sandford, T.C. (1997), “Tire Chips as LightweightBackfill for Retaining Walls - Phase II,” A Study for the New England TransportationConsortium, Dept. of Civil and Env.Eng., Univ of Maine, Orono, Maine, 291 pp.

Tweedie, J.J., Humphrey, D.N., and Sandford, T.C. (1998a), “Full Scale Field Trials of TireChips as Lightweight Retaining Wall Backfill, At-Rest Conditions”, TransportationResearch Record No. 1619, TRB, Washington, D.C., pp. 64-71.

Tweedie, J.J., Humphrey, D.N., and Sandford, T.C. (1998b), “Tire Shreds as Retaining WallBackfill, Active Conditions”, Journal of Geotechnical and GeoenvironmentalEngineering, ASCE, Vol. 124, No. 11, pp. 1061-1070.

Whetten, N., Weaver, J. Humphrey, D., and Sandford, T. (1997), “Rubber Meets the Road inMaine,” Civil Engineering, Vol. 67, No. 9, September, pp. 60-63.

DANA N. HUMPHREYProfessor of Civil Engineering

University of Maine

Dana N. Humphrey joined the University of Maine in 1986 after receiving his Ph.D. inCivil Engineering from Purdue University. His Ph.D. dissertation emphasizedconstruction of reinforced embankments on soft ground. Since 1990, he has focused hisresearch on using tire shreds as lightweight fill, retaining wall backfill, thermalinsulation, and landfill drainage layers. He has constructed twelve full-scale field trialsand has authored 28 papers and technical reports in this area. In addition, he hasconducted three research projects investigating the effects of tire shreds on groundwaterquality. Dr. Humphrey has made over 100 presentations on the use of tire shreds toprofessional societies, engineers, solid waste regulators, and waste management tradegroups. The International Tire and Rubber Association honored him with their 1997Friend of the Industry Award. Maine’s governor awarded him the 1997 SpecialTeamwork Award for his part in the tire shred fill constructed for the new PortlandJetport Interchange. Dr. Humphrey worked for the Denver office of Woodward-ClydeConsultants from 1980 to 1983.

VERTTM: A New Development in Deep Mixing TechnologyBy Eric W. Bahner1, P.E, M.ASCE

ABSTRACT: Deep mixing technology was first introduced in the mid 1980’s on theJackson Lake Dam Project as a means of groundwater cutoff and liquefaction mitigation.Since its introduction in the United States, the Japanese developed the technology into amultimillion-dollar business. At present, deep mixing technology is being usedextensively on the Central Artery project in Boston. In the last several years, URSGreiner Woodward Clyde and specialty contractor Geo-Con designed and constructed apermanent earth retention system using deep mixing for the Lake Parkway Freeway inMilwaukee, and developed the proprietary ground improvement system VERTTM VerticalEarth Reinforcement Technology. As part of the development of VERTTM, a test wallwas designed, constructed and monitored at the National Experimentation Site at TexasA&M University. The background of this important technology, general design criteriaand the results of the test wall program are presented.

INTRODUCTION

Deep mixing technology has been used to construct cutoff walls, improve ground belowfoundations, and for mitigation of liquefaction-susceptible soil. One of the early deepmixing projects undertaken in the United States in the mid 1980’s was the Jackson LakeDam where deep mixing was used to construct a new cutoff wall and confine liquifiablesoils below the dam. Over the past 10 to 12 years, the technology was further developedin Asia, principally Japan, until it all but replaced more traditional earth retention andground stabilization methods. In the 1990s, deep mixing has been used extensively onthe Central Artery project in Boston, and in Milwaukee for the construction of adepressed roadway as part of the extension of I-794, Lake Parkway. An earth retentionsystem constructed with deep mixing methods resembles a water-proof soldier pile andlagging wall, where the soldier piles are inserted into the overlapping plastic soil-cementcolumns, and the cured soil-cement acts as the lagging. A permanent wall is constructedby casting or shotcreteing a permanent concrete face directly connected to the soldierbeams by means of Nelson studs(Figure 1). As a next step, Geo-Con and Woodward-Clyde along with the geotechnical engineering department of Virginia Tech developed agravity wall concept somewhat akin to vertical soil nailing. The approach creates agravity mass of soil-cement columns and untreated soils which requires no bracing oranchors for lateral support.

1 Principal Geotechnical Engineer, URS Greiner Woodward Clyde, Waukesha, Wisconsin,414.513.0577, email: [email protected]

This paper presents an overview of the VERTTM system, a brief summary of the finiteelement modeling done as a part of its development, an overview of the design approachand the results of the monitoring for the test wall constructed at Texas A&M.

HISTORY OF GRAVITY WALLS

Gravity walls are a commonly used civil engineering structure where basic designconcepts are well understood. Examples of gravity walls range from the clay and brickziggurats of Roman Times to gravity walls constructed of concrete, rock and rubble.More recently, such structures have been constructed using steel or geotextiles withsegmented block and a compacted backfill(mechanically stabilized earth), and by soilnailing. Both MSE and soil nail structures operate on the principle that closely spacedreinforcing elements interact with the ground creating a gravity block which is resistantto sliding, overturning and slope stability failure.

Gravity walls have been instructed using soil mixing since 1990. In the early cases, ablock of soil with a width of approximately 0.6 to 0.8 times the wall height was 100%treated using soil mixing. In 1991, such a wall was used for temporary and permanentretention along a riverfront in Columbus, Georgia. After the soil-cement block hadhardened, the riverbank was excavated and a permanent concrete facing was attached tothe treated block(Figures 2 & 3).

The VERTTM method of gravity wall construction was developed over the last couple ofyears beginning on the I-15 project in Salt Lake City. Based on the needs of that project,the team of Geo-Con and Woodward-Clyde, along with the geotechnical engineeringdepartment of Virginia Tech University developed a deep mixing system whichemployed deep mixing technology to construct a composite block of soil-cement columnsand untreated ground to support the lateral and vertical expansion of a highwayembankment on soft ground(Figure 4).

SOIL-CEMENT COLUMN CONSTRUCTION AND LAYOUT

In the Geo-Con approach to deep mixing, soil-cement columns are formed by mixing acement-based slurry with the existing soils, which can vary from fine-grained clays tocoarse-grained sand and gravels. In this process, single or multiple stem shafts, or shaftswith bottom augers and paddles along the shafts are rotated into the ground. As a tool topenetrate the ground, a mixture of cement and water slurry is pumped down the hollowcenter of the stems. The rotation of the auger and mixing paddles blends the cementslurry with the existing soil. This mixture acts as a drilling fluid as the augers areadvanced. After the desired depth is reached, the rotation is reversed and the tools areremoved while additional cement slurry is added. The resulting column of soil-cementhas the properties of a very lean 345 to 3450 kPa(50 to 500 psi) concrete, and similar tothat of soft rock. A staggered array of such columns, 0.5 to 3 m in diameter installed intothe ground to an appropriate depth is used to construct the composite gravity wall knownas VERTTM (Figure 5).

A VERTTM gravity wall is constructed by constructing a front row of tangent or secantcolumns along the intended line of the proposed excavation. Additional vertical soil-cement columns are added in pattern that will ensure composite action of the soil massencompassed by the columns. In a typical installation, The contiguous first row ofcolumns along with 3 to 4 rows of staggered soil-cement columns form a gravitystructure that typically has a width of 0.6 to 0.8 times the exposed wall height, similar tomost gravity structures. The soil-cement columns are capped by a 1-meter thick layer ofsoil-cement spoil from the construction of the columns. This cap is used to tie the tops ofthese individual elements together, and acts as a relieving platform for surcharge loads.

RESULTS OF FINITE ELEMENT STUDIES

Woodward Clyde and Virginia Tech completed finite element studies using FLAC,SOILSTRUC and SAGE to evaluate internal stability of the VERTTM structure. Theintent of the modeling was to confirm what geotechnical engineering intuition suggestedbut could not confirmed with simple had calculations: That closely spaced soil-cementelements will behave compositely with the surrounding untreated soil. At present, thedesign concept assumes a column layout such that the edge to edge spacing of thecolumns is about 1 to 1.2 times the column diameter. A contiguous first row of columns,and 3 to 4 rows of staggered columns results in a replacement ratio(soil-cement columnsto untreated soil) of about 30%. These studies also indicated that tensile forces due tobending of individual soil-cement columns would likely govern internal stability, and thatthe safety factor against bending-induced cracking could be 15% less than safety factorsderived using conventional slope stability analysis and assuming a failure surface throughthe VERTTM gravity block. These studies also showed the development of tensile forcesequal to approximately 1/3 of the tensile strength of the soil-cement column at highsurcharge loads.

DESIGN APPROACH

The design of a VERTTM structure involves analyzing both the external and internalstability of the structure. The external stability of a VERTTM wall can be analyzed in asimilar fashion to other gravity structures. The key modes of external stability failurethat must be analyzed include:

• Sliding: FS > 1.5• Overturning: FS >3• Global Stability: FS> 1.5• Bearing Capacity: FS > 3

The internal stability of a VERTTM structure has been researched with finite elementmodeling principally by Mitchell and Filz (Virginia Tech), most recently as of March,1999. However, no definitive simplified internal stability analysis approach has beendeveloped from this work. At present, the internal stability, and composite action can beassumed with edge to edge column spacings of 1 to 1.2 times the diameter of the columnsin a wide variety of soil conditions. This is similar in concept to soil nailing where

numerous studies shown composite action is achieved when the nail spacings are no morethan 2 meters. Assuming this type of column spacing and a replacement ratio of about30%, internal stability is presently analyzed by:

• Checking horizontal shear resistance through the composite block versus toresultant of the applied horizontal load.

• Using a slope stability program, forcing trial surfaces through the compositeblock.

As discussed earlier, finite element modeling suggests that the factor of safety againstbending failure of the soil-cement columns could be critical and roughly 15% less thanthe factor of safety derived from conventional slope stability analysis.

From the developmental design and analysis completed thus far, the position of the watertable is a big consideration in design. A high water table requires a larger block width,and can result in the front row of contiguous soil columns approaching the width of theentire wall. Consequently, design applications have been limited to waterfrontapplications, or application where the water table is located in the lower 1/3 of the wall.

TEST WALL AT TEXAS A&M

To evaluate the early analyses of the VERTTM system, Geo-Con with Woodward Clydeassistance developed a prototype design and constructed an 8 meter test wall at theNational Geotechnical Experimentation Site at Texas A&M University. Prior toconstruction, three distinguished professors of geotechnical engineering: Mitchell atVirginia Tech; O’Rourke at Cornell, and Briaud at Texas A&M were asked to predict thebehavior of the wall. The test wall was heavily instrumented with inclinometers andvertical and horizontal tall tales mounted within the soil-cement columns and untreatedsoil between the columns to assess the behavior of the wall, and confirm compositebehavior between the treated and untreated ground. Table 1 and attached Figures 6through 12 summarize those predictions verses performance of the test wall. Based onthe data collected thus far, the wall appears to behave similarly to other well-establishedsystems. More in depth discussions concerning the test wall program are discussed inNicholson, et.al(1998) and Nicholson(1999).

GAPS IN OUR UNDERSTANDING

At this point, the internal stability of the VERTTM wall requires further study. However,similar to soil nailing, our experience suggests that a set edge to edge column spacing of1.0 to 1.2 times the diameter of the columns seems satisfactory. Based on early fineelement modeling done as a part of the design/build proposals completed for I-15, itappears that the one key mechanisms to internal stability of such a structure is bending ofthe individual columns. Ongoing analysis at Virginia Tech should hopefully shed somemore light on this important issue, and practical hand calculation methods to evaluateinternal stability.

Another issue associated with the VERTTM wall is the depth of the groundwater table andits impact on the width of the front row of contiguous columns. A high groundwatertable forces close to a 100% replacement ratio to address the stability of the front row ofthe columns. One possible way to overcome this could include tying the front row ofcolumns to the relieving platform. This issue continues to receive further attention. Atpresent, the application of VERTTM in an earth retention mode should be limited tosituations where the groundwater table is located below the wall, in the lower 1/3 of thewall, or in a balanced groundwater table condition.

CONCLUSION

The development of VERTTM opens an important new area of ground improvement bydeep mixing in the United States. This system is applicable in a wide variety of groundconditions, and can be used as a foundation treatment scheme or earth retention system.This type of deep mixing technology may also be well-suited to liquefaction mitigation.As more understanding is gained, the use of deep mixing will enjoy an increase inpopularity as a ground improvement method in the United States.

REFERENCES

Bahner, E.W. and A.M. Naguib. (1998). Design and Construction of a Deep Soil MixRetaining Wall for the Lake Parkway Freeway Extension. Soil Improvement for BigDigs, American Society of Civil Engineers, Geotechnical Specialty Publication No. 81,Boston, MA, October, pp. 41-58.

Federal Highway Administration. (1998). Introduction to the Deep Mixing Methods usedin Geotechncial Applications”, Draft Report, prepared by ECO Geosystems, Inc.,November.

Filz, G.M and J.K. Mitchell. (1997). “Analyses of Deep Soil Mix Alternatives forEmbankment Support-I-15 Reconstruction, Salt Lake City, UT,” Report submitted toGeo-Con, Inc., September 18.

Geo-Con, Inc., VERTTM Technology HITEC Application- Part 2, March 30, 1999

Mitchell J.K. and G.M. Filz (1998). “Analyses of Deep Soil Mix Systems forEmbankment Support and Gravity Wall Applications,” Phase II, Report submittal to Geo-Con, Inc., January 26.

Mitchell, J.K., and G.M. Filz. (1999). “Composite Action and Internal StabilityConsiderations in VERT Wall Systems.” A Report to Geo-Con., March 17.

Moriwaki, Y., Personnel Communication Regarding Finite Element Modeling ofVERTTM, October 1997.

Nicholson, P.J. and B.H. Jasperse.(1998). “Hydraulic and Mechanical Cement SoilMixing,” Presented at the University of Wisconsin Milwaukee Seminar, Deep MixingMethods, Milwaukee, WI, August.

Nicholson, P.J., J.K. Mitchell, E.W. Bahner, and Y. Moriwaki, (1998). “Design of aComposite Gravity Wall Constructed by Soil Mixing”, Soil Improvement for Big Digs,American Society of Civil Engineers, Geotechnical Specialty Publication No. 81, Boston,MA, October, pp. 27-40.

Woodward Clyde, (1997) “Evaluation of DSM System for I-15 Project.” Reportsubmitted to Geo-Con, Inc. October.

FIGURE 2

FIGURE 3

FIGU

RE 5

FIG

UR

E 6

FIG

UR

E 7

FIG

UR

E 8

FIGURE 9

FIGURE 10

FIGURE 11

FIGU

RE 12

TAB

LE 1

EMBANKMENT CONSTRUCTION OVERSOFT GROUND

Overview DamSmart and ADAS

Presented by:Jim Hummert - Maryland Heights, MO314-429-0100 or [email protected]

June 6, 1999


DamSmart• DamSmart - was designed for both long term

performance and construction monitoring ofdams, tunnels, highways and other civilstructures.

• Manages instrumentation data and relatedinformation (eg., fill height, excavation depth, etc)– “Observational Approach”– Output includes detailed analytical plots and data reports


DamSmart Custom IntegrationDamSmart

Geotechnical/Environmental

InstrumentationDatabase,

Graphics andReportingSystem

GraphicalQuery

System/GIS

Dam SafetyEngineering

CharacteristicsDBMS

Dam SafetyInspection

Scheduling andManagement

DBMS

Dam FeaturesImaging, Audio

and Video DBMS

Hand Held Data Loggers

Automated Data AcquisitionSystems (ADAS)

ManualData Entry

Data Sources

Satellite dish

Radio Tower

Email/Intranet/Internet

NotificationSystem

GeotechnicalSoftware

Applications

Phase I and IIInspection

Reports

Design/As-Built

Drawings

Expert SystemShells

RemoteControl and

SCADAInterfaces

ScannedImages

Video

Applications

DamRehabilitationPrioritization

SystemFinancialLiability

Long TermPerformanceMonitoring

FERC Reporting

Municipal/StateReporting

CommunityRelations

State/CountryDam SafetyPrograms

Operations &Management

RiskManagement

(C) URS Greiner Woodward Clyde 1999 Note: Blue Text IndicatesClient Specific Custom Extensions to DamSmart

Instrumentation

EngineeringStudies

InspectionReports

ConstructionRecords/Visual

Surveys

URS Greiner Woodward ClydeDam Safety Management and Reporting/

Tracking System (DamSmart)


DamSmart Technical Information• Uses Client-Server, Windows based technology

(specifically PowerBuilder/Sybase)• Uses a combination of PC based data management

tools that are inexpensive, work well together and arequick to implement, including:

• Excel 5.0c, 7.0 and 8.0 (Excel 97)– Visio 4.+/5+– Surfer (custom)– Crystal Reports (Ver 5+)

• Provide training and support


DamSmart - Instrument Types• User defined instrument types

– Piezometers– Weirs– Survey monuments, GPS– Settlement Plates

• User defined variable names and constants• User defined field conditions• Calibration constants are time dependent


Instrument Type Definition Screen

Define your own valuenames, reductionequations and units


DamSmart Instrument Definition

• User defined instruments• User defined equations• User defined thresholds and

limits• Stored reference information• User defined spatial

definitionsDefine allowablemin/max values for oneor more instrumentreading values


Data Entry/Editing

• Manual data entry• ADAS data importing

(Geomation, CampbellScientific, etc.)

• Spreadsheet dataimporting

• Custom file formatimporting

• Automatic calculationsand reductions

• Alarm Limits andThreshold annunciationthrough email or internet


DamSmart Reporting• User-defined reports• Pre-defined reports (FERC)• Select Percent Change/Rate

of Change• Report Masked

Data/Statistics• Output to Printer/Excel

Spreadsheet/Lotus


DamSmart - Plot Definitions• Time history Plots

(Single and Dual Axis)• Position Plots (eg.,

Phreatic Surface Plots)• Correlation Plots• Contour Plots (with 3rd

party app, eg., Surfer)• Batch Plots• Merged Plots (Visio)• Custom Graphics


DamSmart-Plotting

Use all of Excel’sgraphic formattingfeatures to create yourown custom plottemplates

Assign custom templatesto any number of plotsfor automated batchplotting


DamSmart Clients• Duke Power Company (17 dams)• Alabama Power Company (15)• Georgia Power Company (15)• City of Colorado Springs (1)• LA Co. Dept. of Public Works (15)• New York City - Freshkills Landfill• Utah Dept. of Transportation (I-15)• Ontario Hydro (48 dams)• Kennecott Utah Copper (1)• Coeur Gold Mine, Waihi, NZ• US Army Corps of Engineers (50+)• Atlantic City Expressway Project• Public Service Electric and Gas (1)• British Columbia Hydro (BCHydro)• Portland General Electric (9)

• Wisconsin Electric Power Company (13)• American Electric Power Company (34)• Contra Costa Water District (1)• Stickney/Tyler Landfill• Charleston, SC Port Authority• Illinois Dept of Transportation (Rte 66)


ADAS/DamSmart Case History• 200 ft high tailings dam

• Impoundment area over 5,000 acres

• 50 plus years old

• Undergoing major expansion at time of failure


View of Failure Area

• Construction occurring onnortheast corner

• High rate of fill placement(midway up side-slope)

• Cut being made near toe totie-in extension of newembankment

• Increasing Pool levels


Portable Remote Monitoring Unit (RMU)

Typical Remote Monitoring Unit(RMU) - Solar Powered withCellular Communications--Automating 50 Vibrating wirepiezometers.


ADAS Remote Monitoring Unit• Campbell- Scientific CR-

10x Remote Dataloggers• 80 - Geokon 4500S

vibrating wire pressuretransducers

• Cellular PhoneCommunication linksbetween RemoteMonitoring Units (RMUs)and site office


Pore Pressures Before/After Failure

Pore pressure dropimmediately followingfailure


Pore Pressure

Increased readingfrequency followingautomation


Pore Pressure Dissipation w/ Wick Drains


RMU Diagnostics


Additional Information• For more information on DamSmart or

Automated Data Acquisition Systems(ADAS):

– Call 1.800.788.7627 or 314.429.0100

– Send email to [email protected]

JIM HUMMERTVice President, Information Solutions Group

Education: B.S. Geological EngineeringRegistration: Professional Engineer (Missouri)

Related Experience: Mr. Hummert is a registered professional engineer with over 20 yearsexperience in the application of computer technologies to geotechnical and environmental practiceareas. As manager of the Information Solutions Group in St. Louis, he is directly involved indesign and implementation of automated data acquisition and control systems (ADAS) and thedevelopment and integration of software systems. Jim has been a leader in the field of ADAS overthe past 15 years. He routinely gives technical presentations to ASDSO, Transportation ResearchBoard and the U.S. Army Corps of Engineers. Key ADAS projects he has managed include:Clarence Cannon Dam ADAS (St. Louis District Corps of Engineers), Bonneville Lock and DamADAS (Portland District Corps of Engineers) and Freshkills Landfill ADAS (City of New York).As the originator of DamSmart, Mr. Hummert has played a role in advancing the standard-of-practice in geotechnical instrumentation data management.

1

USERS MANUAL FOR WOODROW WILSON BRIDGE SPREADSHEET(WOODROW.XLS)

This spreadsheet routine has been set up for the Woodrow Wilson Bridge projectto assist in the calculations for assessing the foundation deformations associated withpotential ground stabilization treatments. This spreadsheet is intended to give reasonableestimates of single-point settlements using a 2-D stress distribution approximation. Thedrainage conditions can be identified, including vertical drains, to allow calculations ofthe time for primary consolidation. The amount of secondary compression is calculatedwith an option to address the effect of overconsolidation due to surcharge removal. Theuser can choose to calculate a factor of safety against bearing capacity failure for MSEwalls or a factor of safety against punching shear failure for embankments reinforcedwith geosynthetic materials. Numerous cross sections and subsurface profiles can bedefined and entered in the spreadsheet’s database. The spreadsheet allows individual soilprofiles and embankment geometry conditions to be combined and/or modified. The‘Main’ sheet allows the user to assemble the study sections and to summarize thecalculations. Individual tabs within the ‘Main’ sheet provide access to specificcalculations and present a summary of these calculations. Included is an overview ofwhat the user is expected to input in the Main sheet and what results will be displayed, adescription of what input is entered in the database sheets and a description of thecalculations performed in the individual calculations sheets.

DESCRIPTION OF “MAIN” (Figure 1):

INPUT INFORMATION:The majority of the user-defined input is entered in the “Main”, “Subsurface

Profiles” and “Typical Sections” sheets. Blue font is an indication of user input. Theuser is restricted to input in the blue font cells. Equations and variables are highly linkedthroughout the spreadsheet and modifications of any of these equations or variables couldcause errors in other portions of the spreadsheet. All inputs are entered and all results arereturned using the SI unit system. The following section describes the variables enteredby the user in the Input Information section on the “Main” sheet.

Design Life Including Construction Period: This time period, entered in days, defines thelength of time for secondary settlement calculations. It combines the amount of timeexpected to construct the embankment and surcharge and the subsequent design life ofthe pavement.

Subsurface Information: The user can pick one of the subsurface profiles, listed anddescribed in the Key at the bottom of “Main”. The name of the desired subsurface profilemust be entered exactly as it appears in the Key. This inputs a layered profile of soilcharacteristics that the spreadsheet will use for all calculations. Inputs of these soilprofiles are described in a later section.

2

Cross Section Information: Similar to the subsurface profiles, the user can pick one of thecross sections listed in the Key at the bottom of “Main”. The name of the desired crosssection to analyze must be entered exactly as it appears in the Key. The geometry of thechosen cross section will be plotted in the adjacent chart.

Ground Improvement Information: The ground improvement technique being analyzed isreturned by the spreadsheet based on the cross section chosen. The unit weight of theembankment and surcharge fill is considered equal and is entered by the user. Toevaluate effects of PV drains the user enters the spacing and geometry (triangle or square)in this section. If the embankment is being constructed in an undrained condition, cellC21 should read “n”.

SUMMARY OF CALCULATIONS:The section titled Summary of Calculations on the “Main” sheet summarizes

results from the “Surcharged Settlement Calcs”, “NC Settlement Calcs”, “TimerateCalculations” and “MSEstability” sheets. There are also user-defined variables entered inthis section.

Settlement Calculation:The user defines the point along the transverse axis of the embankment cross

section (x-axis of the adjacent chart) to calculate settlement. The total settlement at thatpoint is returned from the “Surcharged Settlement Calcs” sheet based for the chosengeometry and subsurface profile. The total settlement is broken into normallyconsolidated primary and secondary settlement occurring during construction (whilesurcharge is in place) and a reduced-rate secondary compression, which will occur overthe design life after the surcharge is removed. For a comparison of the surcharge effects,the value of normally consolidated secondary, which can be expected to occur over thedesign life without surcharging is returned from the “NC Settlement Calcs” sheet.

The user can define a percent consolidation, for which the time to reach thatpercentage is returned from the “Timerate Calculations” sheet. The time to achieve thegiven percent of consolidation is calculated for different drainage conditions: vertical,horizontal and an estimated combined drainage. If no prefabricated vertical drains areinstalled, vertical drainage defines the consolidation time.

Bearing Capacity and Punching Shear Calculations:The user determines whether the spreadsheet will return a bearing capacity factor

of safety for a vertical wall or a punching shear factor of safety for a sloped embankmentby entering an X in cell B37 or C37 respectively. The user enters the wall orembankment height for either computation, which can be read off of the adjacent chart.For a bearing capacity calculation, the unit weight of the reinforced soil and the slope ofthe surcharge in degrees are entered. If a vertical surcharge is used the slope is 90. Theuser does not need to enter a slope angle if no surcharge is used. For a punching shearcomputation, the user defines the length of the reinforcement beneath the embankment,the strength of the soft, clay layer and the thickness of the soft layer. The spreadsheetwill return which of the following foundation cases applies to the subsurface profilechosen: (1) Single Layer, (2) Stiff Clay over Soft Clay or (3) Dense Cohesionless Sand

3

over Soft Clay. The surcharge height defined in the Ground Improvement Section is usedfor calculations.

If a bearing capacity computation is chosen, three values will be returned from theMSEstability sheet. The first is the ultimate bearing capacity, which is calculated for theexisting soils based on a two layered foundation and reported in kPa. The second is theconstruction-phase factor of safety, which is calculated based on the maximum height ofthe wall (i.e. with any surcharge in place) and using the ultimate bearing capacity. Thethird is the post-improvement factor of safety, which is calculated based on the finalheight of the wall (after removal of surcharge) and a single-layered improved foundation.The user must enter these improved soil parameters in the MSEStability sheet. If apunching shear computation is chosen one factor of safety value is returned. Details ofthese computations and the required inputs are given in the MSEstability section of thispaper.

Slope Stability Results From UTEXAS 3:A section is set for the user to display the results of slope stability calculations,

which are run independent of the spreadsheet.

DATABASE SHEETS

SUBSURFACE PROFILES (Figure 2):Parameters that are applicable for the entire project are entered in the section

labeled “Project Parameters”. Values to calculate aging effects for normally consolidatedsoil profiles include the length of time (in days) since the completion of the existinggeometry and the length of time (in days) for the original primary consolidation. Theratio of these values is used to calculate an aged preconsolidation stress. If the userwishes to neglect any aging effects, this ratio should be set to 1 by entering the sameamount of days in both cells. Values used to calculate secondary compressions areentered in this section. The time to the end of the design life is read from the user inputin the Main sheet. The logarithmic relationship for reduction of secondary compressionrate with surcharging is chosen. The effective radius of all vertical drains used on theproject is entered here and used as input in the time rate calculations.

The project is broken into numerous design segments based on similar foundationprofiles. Characterization of these profiles is based on in situ testing (cone penetrationsoundings and dilatometer readings), borings and lab testing. Two characterizations ofeach profile are created. One is a detailed, layered profile in which all values needed tocompute settlement, time rate of consolidation and undrained strength are entered. Thesecond is a simplified two-layer system used for bearing capacity calculations.

All of the available subsurface profiles are summarized in the key on the Mainsheet. One profile is reserved for the user’s customization of any of the general profiles.If the user wishes to change any parameters of a given foundation profile, the values ofthat profile can be copied into the “Custom” profile section at the bottom of the page.Once copied, the values can then be altered and saved. The name can be changed toanything other than an existing profile name. This is done so no permanent modificationsare inadvertently done to the general profiles.

4

TYPICAL SECTIONS (Figure 3):Numerous cross sections can be identified for the project. There is no specified

limitation beside the fact that more cross sections yield a larger spreadsheet requiringmore memory space. These cross sections are created for various new constructiongeometries. Each cross section is identified with a name, description and groundimprovement technique, if any. The available cross sections are summarized in the keyon the Main sheet. Similar to the Subsurface Profiles, one cross section is reserved forthe user to customize any of the general cross sections. If the user wishes to modify across section, the values of that cross section can be copied into the “Custom” section atthe bottom of the page. Once copied, the values can then be altered and saved. Thename can be changed to anything other than an existing cross section name. This is doneso no permanent modifications are inadvertently done to the general cross sections.

DESCRIPTION OF INDIVIDUAL CALCULATION SHEETS:

SURCHARGED SETTLEMENT CALCS (Figure 4):These calculations assume the surcharge is left in place for a minimum of 98% of

the consolidation time. This spreadsheet is not intended to, nor will it accuratelycalculate settlements for any earlier time of surcharge removal. The time for 98% ofprimary consolidation, t98, is assumed equal to the total time for primary, tp. T98 iscalculated for each layer in the “Timerate Calculations” sheet given the user-defined PVdrain information. If PV drains are installed, t98 based on horizontal drainage is used.Otherwise, the calculated t98 based on vertical drainage is used.

The inputs for the settlement calculations are read from the “Subsurface Profile”sheet. The soil characteristics of the chosen subsurface profile are automatically read intothe settlement calculation sheet. Aging effects are estimated by taking the time since thecompletion of the existing geometry into account. The spreadsheet uses the standardBoussinesq stress distribution to calculate the effects of the new embankment at the pointof interest. These stress distribution calculations are performed using influence factorsand superposition of linearly increasing loads in the sheets labeled “Exist”, “Final +Surcharge” and “Final”. These sheets have been protected to prevent any inadvertentchanges to the equations.

Elastic and primary consolidation and normally consolidated secondarycompression settlements are calculated for each layer while the surcharge is in place.The time to the end of the design life has been defined by the user in “Main” and is usedto calculate the amount of reduced rate secondary compression after the removal ofsurcharge. The analysis uses Ng’s (1998) logarithmic relationship for reduction ofsecondary compression rate with surcharging. A maximum, minimum or mean reductionis selected by the user in the “Subsurface Profiles” sheet to reflect the expected soilbehavior.

5

NC SETTLEMENT CALCS (Figure 5):For a comparison of surcharge effects on secondary compression after

construction (i.e. after pavement is placed), this sheet will calculate the amount ofnormally consolidated secondary compression which can be expected to occur over thedesign life. This value can be compared to the reduced rate, or overconsolidated rate, ofsecondary compression, which will occur over the design life after a surcharge isremoved.

TIMERATE CALCULATIONS (Figure 6):All soils are assumed to begin virgin compression once construction begins. For

this reason no recompression parameters are used in this spreadsheet. An estimatedeffective coefficient of horizontal consolidation (ch(e)) and an estimated coefficient ofvertical consolidation (cv) are entered for each layer of each foundation profile in‘Subsurface Profiles’. The soil foundation information is automatically read from the‘Subsurface Profile’ sheet for the foundation profile of interest.

Timerates of consolidation are calculated for each layer for the three drainageconditions: horizontal, vertical and combined. The combined timerate calculation ismerely an estimate of the effects from both vertical and horizontal drainage and should beused with caution.

The controlling layers for each drainage condition are found by identifying themaximum time to reach 98% consolidation. The time to reach 90%, 95% and 98%consolidation are then reported for the identified controlling layer.

MSEStability (Figure 7):Bearing Capacity:

Two factors of safety are returned for a bearing capacity calculation. The first iscalculated during construction with existing soil conditions. This construction phasebearing capacity uses a two-layered soil foundation after Vesic (1970). The bearingpressure is calculated with the surcharge in place as described in Figure 8 and equated toa uniform load at the base of the wall. The spreadsheet assumes the surcharge has eithera vertical face or the shoulder of the surcharge occurs within the lateral limits of thereinforcement. The length of reinforcement is assumed to be a standard 70% of the wallheight. This value can be changed in the ‘MSEstability’ sheet.

The post-construction or post-improvement bearing capacity calculation assumesa one-layered foundation with improved soil parameters. These improved soil parametersneed to be input by the user in the ‘MSEstability’ sheet. The weight of the surcharge issubtracted from the maximum bearing pressure at the base of the wall for this calculation.

Punching Shear (See Figure 9):For a reinforced, sloped embankment, a punching shear calculation is appropriate.

The user enters all the necessary input parameters for this computation on the ‘Main’sheet.

6

Limitations:

First, the results of the spreadsheet calculations can be no better than the accuracyof the input by the user and the site characterization in the “Subsurface Profiles”database. Second, the results are limited by the accuracy and appropriateness of thetheories and methods employed in the spreadsheet. See each calculation sheet forreferences of methodology and theories used. The limitations of these theories andmethods are implicit in the results. Third, familiarity of these theories and of spreadsheetfunctionality is required to assure appropriate application and results. The spreadsheet isonly a tool and makes no assessment of the quality of the results. The user should makethis quality assessment. The user is restricted to input in the blue font cells. Equationsand variables are highly linked throughout the spreadsheet and modifications of any ofthese equations or variables could cause errors in other portions of the spreadsheet.

Limitations in the settlement calculations include: 2-D strain conditions apply,1-D consolidation theory is assumed, soil layers are thick enough to preventmathematical breakdown in settlement calculations but thin enough to permit reasonablyconstant strain within individual layers, vertical walls are modeled as “nearly-vertical”,and the existing ground is level.

Project Name/ LocationElevation 1289 = Height 100 = Depth 0

Surcharge Height (m):Unit weight of road & surch. (kN/m3):

PV Drain Spacing (m):PV Drain Spacing Geometry

SUMMARY OF CALCULATIONS forCross Section: Road 1, Subsurface: A1

Point of Interest, Distance (m):Consider Aging Effects of Exisinting Embankment?

Total Settlement (cm):Primary + Elastic Consolidation (m):

NC Secondary During Construction (cm):OC Secondary After Surch. Removal (cm): 26 after 12 years

NC Secondary If No Surcharge is Used (cm): 48 after 12 yearsVariable % for Time of Consolidation

Time for 90% ConsolidationNo Wick DrainsVertical Only:

1648

Horizontal Only:126

Combined Drainage:

115

WALL BEARING CAPACITY CALCULATION

Put an X only in thebox that applies: X

Wall Height (m):Unit Weight of Reinforced Soil in kN/m3 =

Slope of Surcharge (degrees):Subsurface Case (1, 2, or 3):

Surcharge Height (m): Name Description Name Description Slope GI TechUltimate Bearing Capacity (kPa): A1 sand, clay, interbeds Road 1 20m widening, 10m fill 2H:1V surcharge

Construction Phase FS (Wall + Surch)= A2 muck, clay Road2 30m wide, 10m fill 2H:1V surchargePost Construction FS = South Temple Wall 6S-26 South Temple Wall6S26 vertical surcharge & PV Drains

SLOPE STABILITY RESULTS FROM UTEXAS3 North Temple STA 34+200 North Temple STA 34+200 2H:1V surcharge & PV DrainsFactor of Safety: Wall 6S30 Wall 6S30 vertical surcharge & PV Drains

Description of Failure Surface:

1 Single Layer2 Stiff Clay over Soft Clay3 Dense Cohesionless Sand over Soft Clay

1.208.96

65

Cross Section: 20m widening, 10m fillSubsurface Profile: sand, clay, interbeds

INPUT INFORMATION

I-15

PROJECT INFORMATION

Key to Typical Structures

1.5

SETTLEMENT CALCULATION

y13389

390

Key to Subsurface Profiles

10.0

Design Life Including Construction Period (days4380

SUBSURFACE INFORMATION

GI Technique: surcharge

A1sand, clay, interbeds

Embankment Slope:

Depth to Water Table: 2.0CROSS SECTION INFORMATION

2H:1V

Subsurface Profile:Subsurface Description

Road 120m widening, 10m fil

Are PV Drains Present? (y/n) y

GROUND IMPROVEMENT INFORMATION

Cross Section Number:Cross Section Description

Subsurface Case for Bearing Capacity

17.60

90

6.021.2

triangle

20.4

6.0343

98

100

102

104

106

108

110

112

0 10 20 30 40 50 60 70 80 90 100

Distance (m)

Hei

ght (

m)

Final + Surcharge

Existing

FinalPoint of Interest

Bearing Capacity Punching Shear None

Library of Typical Cross Sections and Subsurface Profiles for the user to choose from. Pick one of each

to analyze and enter the name exactly as it appears in here.

X-Section Chosen is Graphed Here

Values output from Timerate Calculations sheet for the %

consolidation chosen

Entered by user and used as input for MSEStability sheet for bearing capacity or punching shear calc.

Results output from MSEStability for Bearing Capaicty or Punching Shear calculation depending onwhich one was chosen.

The user can enter results of slope stability computations from UTexas3

Values output from Surcharged Settlement Calcs sheet for the point of interest chosen.

Value output from NC Settlement Calcs sheet for comparison of surcharge effects.

User enters values which are used as input for Timerate Calculations sheet.

Value is read off of chart and entered by user for an input to MSEStability sheet.

Value is entered by the user and used for input to both Settlement Calcs sheets.

Value is entered by the user and used as input for secondary compression

calculations in both Settlement Calcs sheets.

Value entered by user to equate height value with an elevation. This value is also used as an input in both UTexas

Set Up sheets.

User enters y or n to turn aging effects on or off.

User defines the horizontal distance at which to calculate

settlement

Figure 1: MAIN

t, Time Since Completion of Existing = 10950 days >= tp t, Time to End of Design Life = 7300 days >= ts

tp, Time for Original Primary Settlement = 1095 days Surcharge Relationship Used = Mean (Min, Mean, Max,)

Radius of Vertical Drain = 0.034 mNOTE: Disturbance effects must be included in ch and cv inputs

Profile Name: 1CProfile Description: Profile 1-1, Center Line of I-95/495 Main Line GI Technique:Depth to WT (m): 1.0 Subsurface Case: 3

CR/ RR 8.0

Bottom Average j, Janbu's σ'p = cv ch(e) Soil Soil Soil Layer Angle internal Cohesion Moist unit Sat unit

Soil Soil Soil of Layer Unit Wt. Stress σ'vo + __ (cm2/min) (cm2/min) cα/CR Layer Description Class Thickness friction c weight weightLayer Description Class (m) (kN/m3) Exponent Clay CR (kPa) Comp. Comp. (m) φ (kPa) (kN/m3) (kN/m3)

1 Clay A1 0.50 15.0 0.0 0.380 200 0.1 0.20 0.045 1 Clay A1 3.5 0.0 19.7 16.5 20.02 Clay A1 1.00 15.0 0.0 0.380 200 0.1 0.20 0.045 2 Clay/Sand A1/A2 2.5 0.0 20.9 16.0 20.03 Sand A2 1.50 18.0 0.5 0.010 500 10 10.00 0.0004 Sand A2 2.50 18.0 0.5 0.010 500 10 10.00 0.0005 Clay A1 3.00 15.0 0.0 0.380 150 0.015 0.15 0.0456 Clay A1 3.50 15.0 0.0 0.380 150 0.015 0.15 0.0457 Clay/Sand A1/A2 4.00 17.0 0.0 0.200 200 0.1 0.20 0.0308 Clay/Sand A1/A2 5.00 17.0 0.0 0.200 200 0.1 0.20 0.0309 Clay A1 5.50 15.0 0.5 0.380 80 0.015 0.15 0.04510 Clay A1 6.00 15.0 0.5 0.380 80 0.015 0.15 0.045

Profile Name: 1SProfile Description: Profile 1-1, South of I-95/I495 Main LineGI Technique:Depth to WT (m): 0.5 Subsurface Case: 2

CR/ RR 8.0

Bottom Average j, Janbu's σ'p = cv ch(e) Soil Soil Soil Layer Angle internal Cohesion Moist unit Sat unit

Soil Soil Soil of Layer Unit Wt. Stress σ'vo + __ (cm2/min) (cm2/min) cα/CR Layer Description Class Thickness friction c weight weightLayer Description Class (m) (kN/m3) Exponent Clay CR (kPa) Comp. Comp. (m) φ (kPa) (kN/m3) (kN/m3)

1 Clay A1 0.50 17.0 0.0 0.220 300 0.1 0.20 0.030 1 Clay/Sand A1/A2 2.5 20.0 19.7 17.5 20.02 Clay A1 1.50 17.0 0.0 0.220 300 0.1 0.20 0.030 2 Clay A1 5.0 0.0 20.9 18.0 20.03 Sand A2 2.00 18.0 0.5 0.010 500 10 10.00 0.0304 Sand A2 2.50 18.0 0.5 0.010 500 10 10.00 0.0305 Clay A1 3.50 15.0 0.0 0.380 80 0.015 0.15 0.0456 Clay A1 4.50 15.0 0.0 0.380 80 0.015 0.15 0.0457 Clay A1 5.00 15.0 0.0 0.380 80 0.015 0.15 0.0458 Clay A1 6.00 15.0 0.0 0.380 80 0.015 0.15 0.0459 Sand A2 6.50 18.0 0.5 0.010 80 10 10.00 0.03010 Clay A1 7.50 15.0 0.0 0.380 80 0.015 0.15 0.045

Project Parameters:Aging Effects Secondary Calculations

Free Field Soil Profile Simplified Soil Profile for Retaining Wall Bearing Capacity

Free Field Soil Profile Simplified Soil Profile for Retaining Wall Bearing Capacity

Figure 2: Subsurface Profiles (shown for two layers)

Note: POINTS MUST HAVE UNIQUE, INCREASING POSITIVE X COORDINATES & SURCHARGE Y >= FINAL DESIGN Y >= EXISTING Y >= GROUND ELEVATION >= 100

Cross Section Name: CS-I-L-1H:1VCross Section Description: Cross Section I-I, Left, 1:1 SlopeNote: X=20=CenterlineSurcharge Slope: 1.5 H:1VEmbankment Slope: 1H:1VElevation Reference: 1.2 = Height 100

Point Existing Final+Surcharge Final (Design)X (m) Y (m) X (m) Y (m) X (m) Y (m)

1 0.0 100.0 0.0 100.0 0.0 100.02 0.1 103.1 0.1 103.4 0.1 103.43 10.0 103.1 10.0 103.4 10.0 103.44 20.0 103.1 33.5 103.4 20.0 103.45 30.0 103.1 35.0 104.4 35.0 103.46 41.3 103.1 41.9 104.4 41.9 103.47 43.8 102.5 53.9 104.4 52.9 103.48 51.4 100.0 60.5 100.0 56.3 100.09 66.6 100.0 66.6 100.0 66.6 100.0

10 69.4 101.2 69.4 101.2 69.4 101.211 76.1 102.5 76.1 102.5 76.1 102.512 90.1 102.8 90.1 102.8 90.1 102.813 90.7 102.8 90.7 102.8 90.7 102.814 91.3 102.8 91.3 102.8 91.3 102.815 91.9 102.8 91.9 102.8 91.9 102.816 93.8 102.8 93.8 102.8 93.8 102.817 94.4 102.8 94.4 102.8 94.4 102.818 95.0 102.8 95.0 102.8 95.0 102.819 95.6 102.8 95.6 102.8 95.6 102.820 96.2 102.8 96.2 102.8 96.2 102.821 99.9 102.8 99.9 102.8 99.9 102.822 100.0 100.0 100.0 100.0 100.0 100.0

Cross Section Name: CS-I-L-2H:1Cross Section Description: Cross Section I-I, Left, 2:1 SlopeCenterline: X=20=CenterlineSurcharge Slope: 1.5 H:1VEmbankment Slope: 2H:1VElevation Reference: 1.2 = Height 100

PointX (m) Y (m) X (m) Y (m) X (m) Y (m)

1 0 100 0 100 0 1002 0.1 103.1 0.1 103.4 0.1 103.43 10.0 103.1 10.0 103.4 10.0 103.44 20.0 103.1 33.5 103.4 20.0 103.45 30.0 103.1 35.0 104.4 30.0 103.46 41.3 103.1 41.9 104.4 41.9 103.47 43.8 102.5 53.9 104.4 52.9 103.48 51.4 100.0 60.5 100.0 59.6 100.09 66.6 100.0 66.6 100.0 66.6 100.0

10 69.4 101.2 69.4 101.2 69.4 101.211 76.1 102.5 76.1 102.5 76.1 102.512 90.1 102.8 90.1 102.8 90.1 102.813 90.7 102.8 90.7 102.8 90.7 102.814 91.3 102.8 91.3 102.8 91.3 102.815 91.9 102.8 91.9 102.8 91.9 102.816 93.8 102.8 93.8 102.8 93.8 102.817 94.4 102.8 94.4 102.8 94.4 102.818 95.0 102.8 95.0 102.8 95.0 102.819 95.6 102.8 95.6 102.8 95.6 102.820 96.2 102.8 96.2 102.8 96.2 102.821 99.9 102.8 99.9 102.8 99.9 102.822 100.0 100.0 100.0 100.0 100.0 100.0

Existing Final+Surcharge Final (Design)

100

100

101

101

102

102

103

103

104

104

105

105

0 10 20 30 40 50 60 70 80 90 100

Distance (m)

Hei

ght (

m)

Final + SurchargeExistingFinal

99.5

100

100.5

101

101.5

102

102.5

103

103.5

104

104.5

105

0 10 20 30 40 50 60 70 80 90 100

Distance (m)

Hei

ght (

m)

Final + SurchargeExistingFinal

Figure 3: Typical Sections (shown for two sections)

INPUT PARAMETERS FOR SETTLEMENT CALCULATIONS (SURCHARGED STRUCTURES)

Location of Settlement Point as 100 40 AGING EFFECTS:as Shown on Main Tab 70 40 t, Time Since Completion of Existing = 10950 days >= tp

Depth to watertable = 0.5 m tp, Time for Original Primary Settlement = 1095 daysUnit weight of water = 9.81 kN/m3 (Cα/Cc) / ma = 0.0000 NOTES:

Note: Set t = tp to eliminate effects of aging (1) Spreadsheet assumes the surcharge is taken off when all layers have reached 98% consolidation with horizontal drainageRR/ CR = 8 (2) This t98 is considered to be equal to tp.

Measuring Time Since Completion of Surcharge: O.K. (3) T98 is calculated for each layer on the 'Timerate Calculations' Sheet given the following PV Drain information:Measuring Time Since Completion of Surcharge: t, Time to End of Design Life = 7300 days >= ts PV Drains are spaced at 1.5m in a triangle patternt98 max, Max Time End of Primary = 135 Include Rebound? (Y/N) = n (4) Analysis uses standard Boussinesq stress distributiontr, Time to Removal of Surcharge = 136 days >= tp Surcharge Relationship Used = Mean (Min, Mean, Max,) (5) Analysis uses Janbu's modulus method to calculate elastic & primary consolidation settlement.

(6) Analysis uses Ng's (1998) relationship for reduction of secondary compression rate with surcharging.SUMMARY OF SETTLEMENT RESULTS FOR PROFILE 1S AT A DISTANCE OF 40 METERS

Settlement at the time of surcharge removal = 0.27 m (Elastic + Primary + NC Secondary)OC secondary at the end of 20 years = 0.11 m

Primary + Secondary settlement at the end of the design life of 20 years = 0.38 m

SUBSURFACE INFORMATION FOR 1S

Top of Bottom Average Average j, Janbu's Recomp Free-Field Conditions Effect of Existing Embankment at Point of Interest Effect of Final Embankment w/ Surcharge At Point of InterestSoil Soil Layer of Layer Depth Unit Wt. Stress Modulus Modulus σ'vo σ'p ∆ σ've σ've σ'p Aged σ'p Apparent ∆ σ'v ∆ σ'v σ'vs σ'p Equiv σ'p

Layer Classification (m) (m) (m) kN/m3 Exponent Clay CR Number Number Clay Cα (kPa) (kPa) OCR (kPa) (kPa) (kPa) OCR (kPa) OCR (kPa) (%) (kPa) (kPa) OCR (kPa)0 Fill 0.00 0.00 0.00 21.2 n/a n/a n/a n/a n/a 0 n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a1 Clay 0.00 0.5 0.25 17.0 0.0 0.22 10.5 83.7 0.007 4 304 71.59 148.7 153.0 304 1.99 304 1.99 93.0 60.8 245.9 304 1.24 3042 Clay 0.50 1.5 1.00 17.0 0.0 0.22 10.5 83.7 0.007 12 312 25.80 148.8 160.9 312 1.94 312 1.94 92.6 57.6 253.5 312 1.23 3123 Sand 1.50 2.0 1.75 18.0 0.5 0.01 230.3 1842.1 n/a 18 518 29.19 149.0 166.7 518 3.11 518 3.11 91.3 54.8 258.0 518 2.01 n/a4 Sand 2.00 2.5 2.25 18.0 0.5 0.01 230.3 1842.1 n/a 22 522 23.90 149.2 171.0 522 3.05 522 3.05 89.8 52.5 260.8 522 2.00 n/a5 Clay 2.50 3.5 3.00 15.0 0.0 0.38 6.1 48.5 0.017 26 106 4.02 149.3 175.8 176 1.00 176 1.00 86.9 49.4 262.7 263 1.00 2636 Clay 3.50 4.5 4.00 15.0 0.0 0.38 6.1 48.5 0.017 32 112 3.53 149.4 181.0 181 1.00 181 1.00 81.9 45.3 263.0 263 1.00 2637 Clay 4.50 5.0 4.75 15.0 0.0 0.38 6.1 48.5 0.017 36 116 3.25 149.2 184.7 185 1.00 185 1.00 77.9 42.2 262.7 263 1.00 2638 Clay 5.00 6.0 5.50 15.0 0.0 0.38 6.1 48.5 0.017 39 119 3.03 148.8 188.3 188 1.00 188 1.00 73.9 39.3 262.2 262 1.00 2629 Sand 6.00 6.5 6.25 18.0 0.5 0.01 230.3 1842.1 n/a 44 124 2.81 148.3 192.4 192 1.00 192 1.00 70.0 36.4 262.4 262 1.00 n/a

10 Clay 6.50 7.5 7.00 15.0 0.0 0.38 6.1 48.5 0.017 49 129 2.64 147.7 196.4 196 1.00 196 1.00 66.3 33.8 262.8 263 1.00 263

SUGGESTION: Add increments to bottom of profile until the stress increase in the last layer is 10% of max load pressure and settlement in last layer is minimal.SUGGESTION: Turn off spreadsheet calculation while first entering in profile geometry and soil layer data - this will prevent calculations from being performed for each new data entry and increase the speed of use.

Cases:I Final w/ Surcharge stress <= Existing Aged Preconsolidation stress

II Final w/ Surcharge stress > Existing Aged Preconsolidation & Apparent OCR = 1III Final w/ Surcharge stress > Existing Aged Preconsolidation & Apparent OCR > 1

Reference Stress = 100 kPa

SETTLEMENT CALCULATIONSElastic & Primary Consolidation Settlement Secondary Compression Settlement

Top of Bottom Average Layer Cum. Reduced Rate Secondary Primary +Soil Soil Layer of Layer Depth t98 Settlement Settlement Will it tr/t98 Strain Settlement − ∆ σ'v σ'vf ts t/ts Settlement Secondary

Layer Classification (m) (m) (m) (days) Case I Case II Case III (m) (m) Occur? Cα Cα (m) (kPa) (kPa) AAOS C'α (days) - Rebound * C'α Cα' (m) (m)0 Fill 0.00 0.00 0.00 n/a 0.000 0.269 n/a n/a n/a 0.000 n/a n/a n/a n/a n/a n/a n/a 0.108 0.3771 Clay 0.00 0.5 0.25 101 0.00567 0.003 0.269 O.C. n/a 0.000 -21.2 224.7 n/a n/a n/a n/a 0.000 0.0032 Clay 0.50 1.5 1.00 101 0.00543 0.005 0.266 No - O.C. n/a 0.000 -21.1 232.4 n/a n/a n/a n/a 0.000 0.0053 Sand 1.50 2.0 1.75 2 0.00034 0.000 0.261 No-Sandy n/a 0.000 -20.9 237.1 n/a n/a n/a n/a 0.000 0.0004 Sand 2.00 2.5 2.25 2 0.00033 0.000 0.261 No-Sandy n/a 0.000 -20.7 240.2 n/a n/a n/a n/a 0.000 0.0005 Clay 2.50 3.5 3.00 135 0.06626 0.066 0.261 Yes 1.01 0.00005 0.000 -20.2 242.5 0.08 0.0145172 199 36.62 0.02270 0.023 0.0896 Clay 3.50 4.5 4.00 135 0.06163 0.062 0.194 Yes 1.01 0.00005 0.000 -19.3 243.6 0.08 0.0148815 196 37.25 0.02338 0.023 0.0857 Clay 4.50 5.0 4.75 135 0.05809 0.029 0.133 Yes 1.01 0.00005 0.000 -18.7 243.9 0.08 0.0151614 194 37.72 0.02390 0.012 0.0418 Clay 5.00 6.0 5.50 135 0.05465 0.055 0.104 Yes 1.01 0.00005 0.000 -18.1 244.1 0.07 0.0154400 191 38.18 0.02442 0.024 0.0799 Sand 6.00 6.5 6.25 2 0.00202 0.001 0.049 No-Sandy n/a 0.000 -17.5 244.9 n/a n/a n/a n/a 0.000 0.00110 Clay 6.50 7.5 7.00 135 0.04800 0.048 0.048 Yes 1.01 0.00005 0.000 -16.9 245.8 0.07 0.0160344 187 39.12 0.02553 0.026 0.074

Strain

1S

StrainEffect of Removing SurchargeNC Secondary

Figure 4: Surcharged Settlement Calculations

INPUT PARAMETERS FOR SETTLEMENT CALCULATIONS (NORMALLY CONSOLIDATED)

Location of Settlement Point as 100 40 AGING EFFECTS:as Shown on Main Tab 90 40 t, Time Since Completion of Existing = 10950 days >= tp

Depth to watertable = 0.5 m tp, Time for Original Primary Settlement = 1095 daysUnit weight of water = 9.81 kN/m3 (Cα/Cc) / ma = 0.0000

Note: Set t = tp to eliminate effects of aging NOTES:RR/ CR = 8 (1) This t98 is considered to be equal to tp.

Measuring Time Since Completion of Surcharge: (2) T98 is calculated for each layer on the 'Timerate Calculations' Sheet given the following PV Drain information:Measuring Time Since Completion of Surcharge: t, Time to End of Design Life = 7300 days >= ts WARNING! Design life less than ts PV Drains are spaced at 1.5m in a triangle patternt98 max, Max Time End of Primary = 135 (3) Analysis uses standard Boussinesq stress distribution

(4) Analysis uses Janbu's modulus method to calculate elastic & primary consolidation settlement

SUMMARY OF SETTLEMENT RESULTS FOR 1S AT A DISTANCE OF 40 METERS

Elastic + Primary Consolidation = 0.21 m (Elastic + Primary + NC Secondary)NC secondary at the end of 20 years = 0.13 m

Primary + Secondary settlement at the end of the design life of 20 years = 0.35 m

SUBSURFACE INFORMATION FOR 1S

Top of Bottom Average Average j, Janbu's Recomp Free-Field Conditions Effect of Existing Embankment at Point of Interest Effect of Final Embankment At Point of InterestSoil Soil Layer of Layer Depth Unit Wt. Stress Modulus Modulus σ'vo σ'p ∆ σ've σ've σ'p Aged σ'p Apparent ∆ σ'v ∆ σ'v σ'vs σ'p Equiv σ'p

Layer Classification (m) (m) (m) kN/m3 Exponent Clay CR Number Number Clay Cα (kPa) (kPa) OCR (kPa) (kPa) (kPa) OCR (kPa) OCR (kPa) (%) (kPa) (kPa) OCR (kPa)0 Fill 0.00 0.00 0.00 21.2 n/a n/a n/a n/a n/a 0 n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a1 Clay 0.00 0.5 0.25 17.0 0.0 0.22 10.5 83.7 0.007 4 304 71.59 148.7 153.0 304 1.99 304 1.99 71.8 46.9 224.7 304 1.35 3042 Clay 0.50 1.5 1.00 17.0 0.0 0.22 10.5 83.7 0.007 12 312 25.80 148.8 160.9 312 1.94 312 1.94 71.5 44.4 232.4 312 1.34 3123 Sand 1.50 2.0 1.75 18.0 0.5 0.01 230.3 1842.1 n/a 18 518 29.19 149.0 166.7 518 3.11 518 3.11 70.4 42.2 237.1 518 2.18 n/a4 Sand 2.00 2.5 2.25 18.0 0.5 0.01 230.3 1842.1 n/a 22 522 23.90 149.2 171.0 522 3.05 522 3.05 69.2 40.5 240.2 522 2.17 n/a5 Clay 2.50 3.5 3.00 15.0 0.0 0.38 6.1 48.5 0.017 26 106 4.02 149.3 175.8 176 1.00 176 1.00 66.7 37.9 242.5 243 1.00 2906 Clay 3.50 4.5 4.00 15.0 0.0 0.38 6.1 48.5 0.017 32 112 3.53 149.4 181.0 181 1.00 181 1.00 62.6 34.6 243.6 244 1.00 2927 Clay 4.50 5.0 4.75 15.0 0.0 0.38 6.1 48.5 0.017 36 116 3.25 149.2 184.7 185 1.00 185 1.00 59.2 32.1 243.9 244 1.00 2928 Clay 5.00 6.0 5.50 15.0 0.0 0.38 6.1 48.5 0.017 39 119 3.03 148.8 188.3 188 1.00 188 1.00 55.8 29.7 244.1 244 1.00 2929 Sand 6.00 6.5 6.25 18.0 0.5 0.01 230.3 1842.1 n/a 44 124 2.81 148.3 192.4 192 1.00 192 1.00 52.5 27.3 244.9 245 1.00 n/a

10 Clay 6.50 7.5 7.00 15.0 0.0 0.38 6.1 48.5 0.017 49 129 2.64 147.7 196.4 196 1.00 196 1.00 49.4 25.1 245.8 246 1.00 294

SUGGESTION: Add increments to bottom of profile until the stress increase in the last layer is 10% of max load pressure and settlement in last layer is minimal.SUGGESTION: Turn off spreadsheet calculation while first entering in profile geometry and soil layer data - this will prevent calculations from being performed for each new data entry and increase the speed of use.

Cases:I Final w/ Surcharge stress <= Existing Aged Preconsolidation stress

II Final w/ Surcharge stress > Existing Aged Preconsolidation & Apparent OCR = 1III Final w/ Surcharge stress > Existing Aged Preconsolidation & Apparent OCR > 1

Reference Stress = 100 kPa

SETTLEMENT CALCULATIONS

Elastic & Primary Consolidation Settlement

Top of Bottom Average Layer Cum. Primary +Soil Soil Layer of Layer Depth t98 Settlement Settlement Will it t/t98 Strain Settlement Secondary

Layer Classification (m) (m) (m) (days) Case I Case II Case III (m) (m) Occur? Cα Cα (m) (m)0 Fill 0.00 0.00 0.00 n/a 0.000 0.213 n/a n/a n/a 0.133 0.3461 Clay 0.00 0.5 0.25 101 0.00459 0.002 0.213 O.C. n/a 0.000 0.0022 Clay 0.50 1.5 1.00 101 0.00439 0.004 0.210 No - O.C. n/a 0.000 0.0043 Sand 1.50 2.0 1.75 2 0.00027 0.000 0.206 No-Sandy n/a 0.000 0.0004 Sand 2.00 2.5 2.25 2 0.00026 0.000 0.206 No-Sandy n/a 0.000 0.0005 Clay 2.50 3.5 3.00 135 0.05309 0.053 0.206 Yes 54.19 0.02965 0.030 0.0836 Clay 3.50 4.5 4.00 135 0.04901 0.049 0.153 Yes 54.19 0.02965 0.030 0.0797 Clay 4.50 5.0 4.75 135 0.04589 0.023 0.104 Yes 54.19 0.02965 0.015 0.0388 Clay 5.00 6.0 5.50 135 0.04285 0.043 0.081 Yes 54.19 0.02965 0.030 0.0739 Sand 6.00 6.5 6.25 2 0.00155 0.001 0.038 No-Sandy n/a 0.000 0.00110 Clay 6.50 7.5 7.00 135 0.03702 0.037 0.037 Yes 54.19 0.02965 0.030 0.067

1S

Strain

NC Secondary Compression

Figure 5: Normally Consolidated Settlement Calculations

INPUT PARAMETERS FOR TIMERATE CALULATIONSoil Profile: 1SDepth to Watertable = 0.5 meters

Average Unit Weight of Soils = 16.3 kN/m3 Horizontal Vertical CombinedUnit Weight of Emb. Soils = 21.2 kN/m3 Layer T98 T98 Avg T98Radius of Vertical Drain = 0.034 meters 1 101 59 79.8Spacing pattern for drains = triangle 2 101 59 79.8

3 2 0 1.1NOTE: Disturbance effects must be included in ch and cv inputs 4 2 0 1.1

Vertical Vertical Effective 5 135 2127 1130.8

Layer Mid-depth Drainage Drain V. Drain ch(e) cv Modified 6 135 2127 1130.8

Thickness of Layer Length, Dv Spacing, S Spacing, de (m2/day) (m2/day) Soil Drained/ Layer 7 135 2127 1130.8Layer (m) (m) (m) (m) (m) Comp. Comp. Type Undrained Thickness 8 135 2127 1130.8

1 0.50 0.25 0.75 1.50 1.575 0.0288 0.014 Clay u 0.50 9 2 0 1.12 1.00 1.00 0.75 1.50 1.575 0.0288 0.014 Clay u 1.50 10 135 174 154.23 0.50 1.75 0.5 1.50 1.575 1.4400 1.440 Sand d 0.50 Controlling Times: 135 2127 1130.84 0.50 2.25 0.5 1.50 1.575 1.4400 1.440 Sand d 0.50 98 135 2127 1255 1.00 3.00 1.75 1.50 1.575 0.0216 0.002 Clay u 1.006 1.00 4.00 1.75 1.50 1.575 0.0216 0.002 Clay u 2.007 0.50 4.75 1.75 1.50 1.575 0.0216 0.002 Clay u 2.50 Horizontal Vertical Combined8 1.00 5.50 1.75 1.50 1.575 0.0216 0.002 Clay u 3.50 Controlling Layer: 5 5 59 0.50 6.25 0.5 1.50 1.575 1.4400 1.440 Sand d 0.50 T90 79 1202 72

10 1.00 7.00 0.5 1.50 1.575 0.0216 0.002 Clay u 1.00 T95 103 1601 94

Assumed: SAND d T98 135 2127 125

TIMERATE CALCULATION FOR EACH LAYER

Layer 1 Layer 2 LayerCombined Horizontal and Vertical Flow Combined Horizontal and Vertical Flow Combined

t UH UV UCOMB t UH UV UCOMB t(days) (%) n F(n) TH TV (Terz.) (%) (%) (days) (%) n F(n) TH TV (Terz.) (%) (%) (days)

2.7 10 23.1617647 2.40 0.032 0.070 29.8 36.8 2.7 10 23.161765 2.40 0.032 0.070 29.8 36.8 0.15.8 20 23.1617647 2.40 0.067 0.148 43.3 54.6 5.8 20 23.161765 2.40 0.067 0.148 43.3 54.6 0.19.2 30 23.1617647 2.40 0.107 0.236 54.5 68.1 9.2 30 23.161765 2.40 0.107 0.236 54.5 68.1 0.2

13.2 40 23.1617647 2.40 0.153 0.338 64.5 78.7 13.2 40 23.161765 2.40 0.153 0.338 64.5 78.7 0.317.9 50 23.1617647 2.40 0.208 0.458 73.7 86.9 17.9 50 23.161765 2.40 0.208 0.458 73.7 86.9 0.423.7 60 23.1617647 2.40 0.275 0.606 81.8 92.7 23.7 60 23.161765 2.40 0.275 0.606 81.8 92.7 0.531.1 70 23.1617647 2.40 0.361 0.796 88.6 96.6 31.1 70 23.161765 2.40 0.361 0.796 88.6 96.6 0.641.6 80 23.1617647 2.40 0.483 1.064 93.8 98.8 41.6 80 23.161765 2.40 0.483 1.064 93.8 98.8 0.859.5 90 23.1617647 2.40 0.690 1.522 97.4 99.7 59.5 90 23.161765 2.40 0.690 1.522 97.4 99.7 1.277.4 95 23.1617647 2.40 0.898 1.981 98.6 99.9 77.4 95 23.161765 2.40 0.898 1.981 98.6 99.9 1.5101.0 98 23.1617647 2.40 1.173 2.587 99.2 100.0 101.0 98 23.161765 2.40 1.173 2.587 99.2 100.0 2.0

Vertical Flow Only Vertical Flow Only Vertical Flt UV t UV t

(days) (%) TV (Terz.) (days) (%) TV (Terz.) (days)1 20 0.031 1 20 0.031 03 30 0.071 3 30 0.071 05 40 0.126 5 40 0.126 08 50 0.196 8 50 0.196 0

11 60 0.286 11 60 0.286 016 70 0.403 16 70 0.403 022 80 0.567 22 80 0.567 033 90 0.848 33 90 0.848 044 95 1.129 44 95 1.129 059 98 1.500 59 98 1.500 0

Finding Controlling Layers

SUMMARY OF TIMERATE RESULTS

Effective Drainage

Figure 6: Timerate Calculations

Wall and Reinforced Soil Parameters Surcharge PropertiesExternal wall height (m) = 6.00 19.68 ft surcharge height (m)= 1.00 3.28 ftLength of reinforcement (m) = 4.20 13.78 ft unit wt. (N/m3)= 21,200 134.95 pcfUnit wt. reinforced soil (N/m3) = 20,400 129.85 pcf *slope (degrees)= 90Depth of embedment (m) = 0.86 2.81 ft *Assumes surcharge has either a vertical face (90) or the shoulder of the slope occurs within the length of the reinforcement

*Surcharge slope must = 0 for 0 surcharge height

Subsurface Profile: 1SInitial Foundation Parameters Improved Foundation Parameters

Layer 1 2 cohesion (N/m2) = 0 0.00 psfLayer Thickness, h (m) = 2.5 5.0 friction angle (degrees) = 34Cohesion, c (kPa) = 19.7 20.9 unit weight (N/m3) = 18,500 117.76 pcfAngle of internal friction , φ = 20.0 0.0 Depth of gravel in meters = 0.00 0.00 ftMoist unit weight (kN/m3) = 17.5 18.0Saturated unit weight (kN/m3) = 20.0 20.0 Drained Backfill Soil ParametersLength of wall base , L (m) = 250.0 cohesion (N/m2) = 0.00 0.00 psfDepth to base of wall, D (m) = 0.86 must be < 2.5 O.K. friction angle (degrees) = 36 0.6283 radiansUnit Wt of Water (kN/m 3) = 9.81 unit weight (N/m3) = 21,200 134.95 pcfDepth to Water Table (m) = 0.5Which Case ? (1, 2, 3) = 2 1 - Single Layer

2 - Stiff Clay over Soft Clay3 - Dense Sand over Soft Clay

Construction Phase Factor of Safety = 2.33Post-Construction Phase Factor of Safety = 8.96

earth pressure inclination angle, l= 21.15 degrees surcharge earth pressure(N/m2)= 21,200.00= 0.37 radians lateral earth pressure coefficient, ka = 0.24

Depth from top active earth total earth surcharge thrust (N)= 34,180.19 (1)of wall (m) pressure N/m2 pressure N/m2 surcharge resultant height(m)= 3.43

0.00 0.00 4,984.610.69 3,418.02 8,402.63 backfill thrust (N)= 117,189.21 (2)1.37 6,836.04 11,820.65 backfill resultant height(m)= 2.292.06 10,254.06 15,238.672.74 13,672.07 18,656.68 Total earth thrust (N)= 151,369.39 (1) + (2)3.43 17,090.09 22,074.70 earth thrust resultant height(m)= 2.544.11 20,508.11 25,492.724.80 23,926.13 28,910.745.49 27,344.15 32,328.766.17 30,762.17 35,746.786.86 34,180.19 39,164.80

FT, total earth thrust (N) = 151,369 eccentricity of the resulting force on the base (m) = 0.33weight of surcharge (N) = 89,040 equivalent uniform vertical stress on the base (N/m2) = 207,048surcharge resultant (m) = 2.10 eccentricity of resulting force on base after surcharge removal (m) = 0.26

weight of reinforced earth (N) = 587,520 post construction bearing pressure at base (N/m2) = 170,741Total Vertical Load, Q (N) = 676,560

CALCULATION OF INITIAL BEARING CAPACITY (Two Layer Bearing Capacity Calculation (after Vesic, 1970 & '75)) CALCULATION OF POST-CONSTRUCTION F.S.

Analysis uses the general equation: qb = (c x Nc x sc x bc x ic x gc) + (q x Nq x sq x bq x iq x gq) + (0.5 x γ x B x Nγ x sγ x bγ x iγ x gγ) Post-Construction analysis uses the general equation: Note that depth factors are not used, per Vesic, 1975). qb = (c x Nc) + (q x Nq) + (0.5 x γ x B' x Nγ),Also note that this equation is for general shear only; for local shear, Terzaghi recommends: This equation uses the improved foundation parameters c local = 2/3 x cgeneral & tan(φlocal) = 2/3 x tan(φgeneral).This procedure is suitable for cases with overburden, and conservative for near-surface loadings (per Ismael & Vesic, 1981). Nc= 42.16

Nγ= 31.15Base Width, B (m) = 4.20 Calculated Parameters Nq= 29.44

Layer 1 2 Bearing Capacity, qult(kPa) = 1,530Max. Width Eccent. e (m) = 0.70 φ (radians) = 0.34907 0.00001 Bearing Pressure (kPa) = 170.74Min Effective Width, B' (m) = 2.80 Cohesion, c (kPa) = 19.7 20.88 Post-Construction FS = 8.96Max. Length Eccent. e (m) = 41.67 Nc = 14.83 5.14Min Effective Length, L' (m) = 166.67 Nq = 6.40 1.00mb = 1.983 Nγ = 5.39 0.00

Factors for Layer 1 2 Footing in Layer 1: Base Incline bc = 1.000 1.000

Shape sc = 1.007 Base Incline bq = 1.000 1.000Shape sq = 1.006 Base Incline bγ = 1.000 1.000Shape sγ = 0.993 Ground Slope gc = 1.000 1.000Eccentricity ic = 0.986 Ground Slope gq = 1.000 1.000Eccentricity iq = 0.988 Ground Slope gγ = 1.000 1.000Eccentricity iγ = 0.983 Angle Base Incline, α (rad) = 0.00000

Angle Ground Slope, i (rad) = 0.00000

Single Layer Punching Shear Bearing Capacity CalculationEff. Stress, q (kPa) = 12.4 Thickness of Layer 1, h (m) = 2.50Eff. Wt at Base, γ (kN/m3) = 10.2 Depth to base of wall, D (m) = 0.86 FS = (cu*Nc)/(γH)Bearing Capacity, qb (kPa) = 482 Base Width, B (m) = 4.20

Stiff Clay over Soft Clay Single Layer Controls? NO Nc (rough) = 4.14 + 0.5*(B/D) #DIV/0!

Punching Index, β = 1.3 Ult. Bearing Capacity, qb (kPa) = 482 cu = Undrained strength of soft layer (kPa) #N/AShear Strength Ratio, k = 1.1E+00 Max Bearing Pressure (kPa) = 207 γ = Unit weight of soft layer (kN/m3) 18.50Modified Bear Factor, Nm = 14.94 Construction Phase FS = 2.33 H = Height of embankment + Surcharge (m) 7.00Bearing Capacity, qb (kPa) = 482 B = Length of reinforcement beneath embankment (m) 4.20Dense Cohesionless Sand over Soft Clay D = Thickness of soft layer (m) 0.00

Mirror Footing at Layer 2: Shape sc = 1.003 Factor of Safety = #N/AShape sq = 1.000Shape sγ = 0.993Eccentricity ic = 0.994Eccentricity iq = 1.000Eccentricity iγ = 1.000Eff. Stress, q (kPa) = 29.1Eff. Wt at Base, γ (kN/m3) = 10.2Bearing Capacity, q''b (kPa) = 136Bearing Capacity, qb (kPa) = 178

Subsurface Case

Calculations of lateral earth pressures

Summary of Bearing Capacity Results for Cross Section: CS-IV-R-RW

Summary of Initial Bearing Capacity CalculationUltimate Bearing Capacity Calculation:

Bearing Capacity Calculation

Calculation of Vertical Stresses at Base of Wall

100

102

104

106

108

110

112

0 20 40 60 80 100

100

102

104

106

108

110

112

0 20 40 60 80 100

Figure 7: Bearing Capacity Calculations

Figure 8: Earth Pressure Diagram

S

H

E

VW

VS

FT

B’ = B-2e

B = 0.7He

Ground ImprovementStudy

URS Greiner Woodward ClydeFederal Highway AdministrationVirginia Department of Transportation

• Preliminary Site Characterization• Ground Improvement Techniques• Areas of Constraints and Special Attention• Cost and Schedule Impacts

• Two-Phase Subsurface InvestigationProgram– 35 CPTUs, 2 borings– 21 CPTUs, 13 borings, 23 DMTs

• Five Special Borings– Osterberg Piston Sampler– Correlations with CPTUs and DMTs– Laboratory Testing

• Common Geotechnical Zones• Typical Cross Sections

• Spreadsheet Development - GroundImprovement Evaluation Tool– Typical Sections and subsurface Profiles– Engineering Analyses– Training

• Evaluate Alternatives

Project Name / Location:Design Life Includ Construction (days):

Subsurface Profile Name:Subsurface Profile Description:

Base Ground Elevation (m):Depth to Water Table (m):

Cross Section Name/Number:Cross Section Description:Embankment Slope (H:V):

Ground Improvement Technique:Fill Surcharge Height (m):

Unit weight of road & surch. (kN/m3):Are PV Drains Present? (y/n):

Vertical Drain Spacing (m):Vertical Drain Spacing Geometry:

South TempleWall6S26

21.2y

1.5triangle


2.0

7300

1289

INPUT INFORMATION

Wilson Bridge

PROJECT INFORMATION

GROUND IMPROVEMENT INFORMATION/Surcharge/Wick drains/

1.0

vertical

CROSS SECTION INFORMATION


NOTE: Disturbance effects must be included in ch and cv inputsProfile Name: 1CProfile Description: Profile 1-1, Center Line of I-95/495 Main Line GI Technique:Depth to WT (m): 1.0

CR/ RR 8.0

Bottom Average j, Janbu's σ'p = cv ch(e)

Soil Soil of Layer Unit Wt. Stress σ'vo + __ (cm2/min) (cm2/min) cα/CRLayer Description (m) (kN/m3) Exponent Clay CR (kPa) Comp. Comp.

1 Clay 0.50 15.0 0.0 0.380 200 0.1 0.20 0.0452 Clay 1.00 15.0 0.0 0.380 200 0.1 0.20 0.0453 Sand 1.50 18.0 0.5 0.010 500 10 10.00 0.0004 Sand 2.50 18.0 0.5 0.010 500 10 10.00 0.0005 Clay 3.00 15.0 0.0 0.380 150 0.015 0.15 0.0456 Clay 3.50 15.0 0.0 0.380 150 0.015 0.15 0.0457 Clay/Sand 4.00 17.0 0.0 0.200 200 0.1 0.20 0.0308 Clay/Sand 5.00 17.0 0.0 0.200 200 0.1 0.20 0.0309 Clay 5.50 15.0 0.5 0.380 80 0.015 0.15 0.045

10 Clay 6.00 15.0 0.5 0.380 80 0.015 0.15 0.045

Free Field Soil Profile

7

6

5

4

3

2

1

014 15 16 17

Lab Data

0 0.2 0.4 0 40 80 120

Unit Weight CR Yield Stress

CL-CH

CH

SAND

Dep

th (m

)

Soil Profile

Project Name / Location:Design Life Includ Construction (days):

Subsurface Profile Name:Subsurface Profile Description:

Base Ground Elevation (m):Depth to Water Table (m):

Cross Section Name/Number:Cross Section Description:Embankment Slope (H:V):

Ground Improvement Technique:Fill Surcharge Height (m):

Unit weight of road & surch. (kN/m3):Are PV Drains Present? (y/n):

Vertical Drain Spacing (m):Vertical Drain Spacing Geometry:

South TempleWall6S26

21.2y

1.5triangle


2.0

7300

1289

INPUT INFORMATION

Wilson Bridge

PROJECT INFORMATION

GROUND IMPROVEMENT INFORMATION/Surcharge/Wick drains/

1.0

vertical

CROSS SECTION INFORMATION


Distance (m)

Hei

ght (

m)

80

90

100

110

120

130

0 20 40 60 80 100

ExistingFinal+SurchargeFinal (Design)

Typical Section

Point of Interest, Distance (m):Total Settlement (cm):

Primary + Elastic Consolidation (cm):NC Secondary During Construction (cm):

OC Secondary After Surch. Removal (cm): 27 after 20 yearsNC Secondary If No Surcharge Used (cm): 32 after 20 years

Variable % for Time of Consolidation:

Time for 98% Consolidation (days) Vertical Only:160

Horiz Only:130

Bearing Punching Nonex

Structural Wall Height (m):Slope of Surcharge (degrees):

Subsurface Condition (1, 2, or 3):Ultimate Bearing Capacity (kPa):

Construction Phase FS: Post Construction Phase FS:

Factor of Safety:Description of Failure Surface:

Put an X only in the box that applies:

5626

98

3906.0

2

SETTLEMENT CALCULATION

SUMMARY OF CALCULATIONS FORCross Section: South Temple, Subsurface: A1

WALL BEARING CAPACITY CALCULATION

40

SLOPE STABILITY RESULTS

TBD

4512.18

TBD

8.96

• Analysis uses standard Boussinesqstress distribution

60

70

80

90

100

110

120

0 20 40 60 80 100

10

5

0

5

10

15

20

Distance (m)

Dep

th (m

)

Hei

ght (

m)

Stress Distribution Calculations atMid-Depth of Each Layer

Layer 2

Layer 4

Layer 6

• Analysis uses Janbu's modulusmethod to calculate elastic &primary consolidation settlement.

Primary Settlement CalculationsWith Surcharge

Soil SoilLayer Classification

0 Fill1 sand2 clay3 interbeds4 clay5 interbeds6 clay7 interbeds8 sand9 very dense

10 very dense

Elastic & Primary Consolidation SettlementLayer Cum.

Settlement SettlementCase I Case II Case III (m) (m)

0.000 0.2620.003 0.003 0.262

0.005 0.013 0.2600.006 0.021 0.2460.014 0.061 0.2260.009 0.036 0.1640.012 0.053 0.1280.006 0.028 0.075

0.003 0.016 0.0460.003 0.016 0.0310.003 0.015 0.015

Strain

60

70

80

90

100

110

120

130

0 20 40 60 80 100-200

-150

-100

-50

0

50

100

Distance (m)

Hei

ght (

m)

Settl

emen

t (cm

)

Primary Settlement Calculations

• Analysis uses Ng's (1998)relationship for reduction ofsecondary compression rate withsurcharging.

ε

σ

σ

σ

σ

ε

BASIC CONCEPTS FOR EVALUATING THE EFFECTS OF SURCHARGEON SECONDARY COMPRESSION FROM LADD

σ σ σ

σ σ σ

REDUCTION IN RATEOF SECONDARYCOMPRESSIONDUE TO SURCHARGE

1.0

AAOS=[σ’p - σ’vf]/σ’vf (%)LO

G(t s

/t r)

10

Secondary Compression CalcsPrior to Surcharge Removal


0 Fill1 sand2 clay3 interbeds4 clay5 interbeds6 clay7 interbeds8 sand9 very dense10 very dense

Will it tr/t98 Strain SettlementOccur? Cα Cα (m)

n/a n/a n/a 0.024No-Sandy n/a 0.000

Yes 1.00 0.00000 0.000Yes 2.00 0.00141 0.005Yes 1.13 0.00055 0.002Yes 1.67 0.00151 0.006Yes 1.20 0.00074 0.003Yes 2.00 0.00154 0.008

No-Sandy n/a 0.000No-Sandy n/a 0.000No-Sandy n/a 0.000

NC Secondary

OC Secondary Compression CalcsAfter Surcharge Removal(Reduced Rate)


0 Fill1 sand2 clay3 interbeds4 clay5 interbeds6 clay7 interbeds8 sand9 very dense

10 very dense

ts t/ts SettlementAAOS C'α (days) - Rebound * C'α Cα ' (m)

n/a n/a n/a n/a n/a 0.271n/a n/a n/a n/a 0.000

0.08 0.00468 198 36.94 0.00733 0.0180.10 0.00468 216 33.84 0.00715 0.0250.06 0.01020 179 40.85 0.01643 0.0740.07 0.00680 184 39.58 0.01086 0.0430.05 0.00935 167 43.84 0.01535 0.0690.06 0.00510 180 40.63 0.00821 0.041n/a n/a n/a n/a 0.000n/a n/a n/a n/a 0.000n/a n/a n/a n/a 0.000

Strain

INPUT PARAMETERS FOR TIMERATE CALCSSoil Profile: A1Depth to Watertable = 2 meters

Average Unit Weight of Soils = 18.7 kN/m3

Unit Weight of Emb. Soils = 21.2 kN/m3

Radius of Vertical Drain = 0.034 metersSpacing pattern for drains = triangle

NOTE: Disturbance effects must be included in ch and cv inputsVertical Vertical Effective

Layer Mid-depth Drainage Drain V. Drain ch(e) cv

Thickness of Layer Length, Dv Spacing, S Spacing, de (m2/day) (m2/day)Layer (m) (m) (m) (m) (m) Comp. Comp.

1 1.00 0.50 0.5 1.50 1.575 1.1520 0.772 2.50 2.25 1.25 1.50 1.575 0.0216 0.013 3.50 5.25 1.75 1.50 1.575 0.0432 0.034 4.50 9.25 2.25 1.50 1.575 0.0245 0.025 4.00 13.50 2 1.50 1.575 0.0360 0.026 4.50 17.75 2.25 1.50 1.575 0.0259 0.027 5.00 22.50 2.5 1.50 1.575 0.0432 0.038 5.00 27.50 2.5 1.50 1.575 1.1520 0.779 0.00 0.00 0 1.50 1.575 1.1520 0.7710 5.00 37.50 2.5 1.50 1.575 1.1520 0.77

Horizontal Vertical Combined

Layer T98 T98 Avg T981 3 0 1.52 135 163 148.73 67 160 113.44 119 465 292.15 81 250 165.4

6 112 439 275.9

7 67 326 196.5

8 3 12 7.49 3 0 1.3

10 3 12 7.4Controlling Times: 135 465 292.1

98 135 163 91

Horizontal Vertical CombinedControlling Layer: 2 4 4

T90 79 92 52

T95 103 122 69

T98 135 163 91

Finding Controlling Layers

SUMMARY OF TIMERATE RESULTS

Effective Drainage

Wall and Reinforced Soil ParametersExternal wall height (m) = 6.00Length of reinforcement (m) = 4.20Unit wt. reinforced soil (N/m3) = 20,400Depth of embedment (m) = 0.86

1 - Single Layer2 - Stiff Clay over Soft Clay3 - Dense Sand over Soft Clay

Subsurface Case

Initial Foundation ParametersLayer 1 2

Layer Thickness, h (m) = 4.0 15.0Cohesion, c (kPa) = 0.0 39.0Angle of internal friction , φ = 34.0 0.0Moist unit weight (kN/m3) = 21.2 19.0Saturated unit weight (kN/m3) = 21.2 19.0Length of wall base , L (m) = 250.0Depth to base of wall, D (m) = 0.86Unit Wt of Water (kN/m3) = 9.81Depth to Water Table (m) = 2.0Which Case ? (1, 2, 3) = 3

Case 1: Single Layer

Case 2: Stiff ClayOver Soft Clay

Case 3: Dense SandOver Soft Clay

su = 1.0 tsf

su = 0.3 tsf

φ = 34o, c=0

su = 0.3 tsf

su = 0.3 tsf

S

H

E

VW

VS

FT

B’ = B-2e

B = 0.7H

e

Single LayerEff. Stress, q (kPa) = 18.2Eff. Wt at Base, γ (kN/m3) = 14.1

Bearing Capacity, qb (kPa) = 796

Stiff Clay over Soft ClayPunching Index, β = 0.7Shear Strength Ratio, k = 3.9E+06Modified Bear Factor, Nm = 42.66Bearing Capacity, qb (kPa) = 796

Dense Cohesionless Sand over S Mirror Footing at Layer 2:

Shape sc = 1.003Shape sq = 1.000Shape sγ = 0.993Eccentricity ic = 0.995Eccentricity iq = 1.000Eccentricity iγ = 1.000Eff. Stress, q (kPa) = 65.2Eff. Wt at Base, γ (kN/m3) = 11.4Bearing Capacity, q''b (kPa) = 265Bearing Capacity, qb (kPa) = 442

Dense Cohesionless Sand Over Clay

Bearing Capacity Calcs

Thickness of Layer 1, h (m) = 4.00Depth to base of wall, D (m) = 0.86

Base Width, B (m) = 4.20

Single Layer Controls? NO

Ult. Bearing Capacity, qb (kPa) = 442Max Bearing Pressure (kPa) = 281Construction Phase FS = 1.57

Summary of Initial Bearing Capacity Calculation

•Equation is for GENERAL shear only

Nc= 42.16Nγ= 31.15Nq= 29.44

Bearing Capacity, qult(kPa) = 1,530Bearing Pressure (kPa) = 170.74

Post-Construction FS = 8.96

• After Surcharge Removal• Uses improved foundation parameters

Ground ImprovementStudy

URS Greiner Woodward ClydeFederal Highway AdministrationVirginia Department of Transportation

Reference Materialsfor

Soft Ground Stabilization – Recent Advances inMechanical and Chemical Techniques

Presentation for Embankment Construction Over Soft Ground

By Jim MitchellUniversity Distinguished Professor

Virginia Tech, Blacksburg, VA

FOCUSOverview of the current status of methods for soft ground improvement, including liquefaction riskmitigation, exclusive of preloading and drainage, and their practical applications for embankmentconstruction over soft and unstable ground.

REFERENCESThe primary reference for Professor Mitchell’s presentation at the seminar follows this page,entitled Engineering and Design Guidelines on Ground Improvement for Structures andFacilities, by Jim Mitchell and Patricia M. Gallagher, for the Army Corps of Engineers.Other references that contributed to his presentation at the seminar are:

Ten papers on Deep Soil Mixing in Soil Improvement for Big Digs, A.S.C.E.Geotechnical Special Publication No. 81 (A. Maher and D.S. Wang eds.), 1998.

State of the Art in Deep Mixing Technology: Part I. Basic Concepts and Overview(1998) by A. Porhaba, Ground Improvement, Vol. 2 Number 2 pp.81-92.

State of the Art in Deep Mixing Technology: Part II. Applications (1998) by A.Porhaba, H. Tanaka, and M. Kobayashi, Ground Improvement, Vol. 2 Number 3,pp. 125-139.

Performance of Improved Ground During Earthquakes, by James K. Mitchell,Christopher D.P. Baxter, and Travis C. Munson (1995), in Soil Improvement forEarthquake Hazard Mitigation, (R. D. Hryciw, ed.), A.S.C.E. Geotechnical SpecialPublication No. 49, pp. 1-36

Design Considerations in Ground Improvement for Seismic Risk Mitigation, byJames K. Mitchell, Harry G. Cooke, and Jennifer A. Schaeffer (1998), Emerging Art Paper,Geotechnical Earthquake Engineering and Soil Dynamics III, A.S.C.E. Special GeotechnicalPublication No. 75 (P. Dakoulas, M. Yegian, R.D> Holtz, eds.), Vol. 1, pp.580-613.

Engineering and Design Guidelines on Ground Improvementfor Structures and Facilities

byJim K. Mitchell and Patricia M. Gallagher

Prepared for the U.S. Army Corps of EngineersPublication No. ETL 1110-1-185

February 1st, 1999

To view this document, please click here:http://www.usace.army.mil/inet/usace-docs/eng-tech-ltrs/et11110-1-185/toc.htm

http://www.usace.army.mil/inet/usace-docs/eng-tech-ltrs/et11110-1-185/toc.htm

Embankment Construction

Documents

Transcript of Embankment Construction