AGENCY OF TRANSPORTATION OFFICE MEMORANDUM Robert Young… · To: Robert Young, P.E., Structures...

AGENCY OF TRANSPORTATION OFFICE MEMORANDUM To: Robert Young, P.E., Structures Project Manager

From: Callie Ewald, P. E., Geotechnical Engineering Manager Date: August 30th, 2019 Subject: Georgia BF 023-1(7) – Geotechnical Recommendations Report 1.0 INTRODUCTION

We have completed our geological and geotechnical investigation for the replacement of Bridge No. 1 on VT 104A in Georgia, VT. The bridge is located approximately 1.1 miles east of the intersection of VT Route 104A and US Route 7. The proposed project includes replacement of the bridge on new abutments as well as related approach and channel work. This report documents our subsurface investigation, foundation analyses, and geotechnical recommendations for the proposed project. Contained herein are the results of field sampling and testing, laboratory analyses of soil samples, and geotechnical design recommendations, as determined using the 2017 AASHTO LRFD Bridge Design Specifications. 2.0 FIELD INVESTIGATION The field investigation was completed between May 20th and 23rd, 2019. Two (2) standard penetration borings were drilled to evaluate the subsurface profile to aid in design and construction of abutment foundations. In order to maximize efforts during the temporary bridge closure, VTrans performed Boring B-101 at the same time as Terracon Consultants performed Boring B-102. Eight (8) solid stem auger probes were also performed along the shoulder in both lanes of the roadway to verify the subsurface conditions of the embankment in the vicinity of the proposed guardrail installations.

A summary of the location of each boring and probe and corresponding ground surface elevation can be found in Table 2.1. The borings were located by the VTrans Survey Section and the values for the Northings and Eastings and elevations are based on the Vermont State Plane Grid Coordinate System NAD 83, and the North American Datum, NAVD 88, respectively. The locations and elevations of the borings should be considered accurate only to the degree implied by the method used to determine them.

Table 2.1 Boring Locations Boring

Number Station Offset (ft) Northing (ft) Easting (ft)

Ground Surface Elevation (ft)

B-101 61+91 3.6 LT 796337.2 1486298.0 293.9

B-102 62+73 2.9 RT 796309.8 1486378.8 294.0

P-1 60+35 5.9 RT 796362.73 1486144.55 294.9

P-2 60+71 9.8 LT 796368.94 1486183.08 294.0

P-3 61+40 9.0 LT 796352.12 1486249.13 294.1

GEORGIA BF 023-1(7) of 8

Boring Number

Station Offset (ft) Northing (ft) Easting (ft) Ground Surface

Elevation (ft)

P-4 61+83 5.1 RT 796333.58 1486263.88 293.9

P-5 63+06 6.7 LT 796309.70 1486410.26 294.1

P-6 63+14 5.5 RT 796296.16 1486415.34 294.2

P-7 63+42 8.8 LT 796303.54 1486445.14 294.4

P-8 63+55 4.6 RT 796286.36 1486454.65 294.5

Boring B-102 was performed by Terracon Consultants. The investigation and general site characterization was summarized in a Geotechnical Data Report dated July 16th, 2019 and can be found attached to this report. Boring B-101 was performed in general accordance with AASHTO T206, Standard Method of Test for Penetration Test and Split-Barrel Sampling of Soils. During boring operations, split spoon samples and standard penetration tests (SPT) were taken continuously to 21 feet (ft) below ground surface, then at 5 ft intervals to 40 ft, and then at 10 ft intervals to a depth of 140.0 feet. Bedrock was not encountered. Soil samples were visually identified in the field and SPT blow counts were recorded on the boring logs where applicable. Soil samples were preserved and returned to the Construction and Materials Bureau Central Laboratory for testing and further evaluation. The solid stem auger probes were performed in general accordance with AASHTO test method T306, Processing Auger Borings for Geotechnical Exploration. At each probe location, a pavement core was taken and then a 4-inch solid stem auger flight was rotary drilled to a depth of 10 ft below the top of the roadway. Drilling resistance was noted by the driller to identify any stone fill or material that would present as an obstruction, and soil cuttings were identified and descriptions noted on the field log. 3.0 FIELD AND LABORATORY TESTING

The standard penetration resistance of the in-situ soil is calculated as the number of blows required to drive a 2-inch outside diameter (OD) split-barrel sampler 24 inches into the soil by a 140-pound hammer dropped from a height of 30 inches, in accordance with procedures specified in AASHTO T206. The number of blows required to drive the sampler each 6-inch increment is recorded and the Standard Penetration Resistance (N-Value) is calculated as the sum of the blows over the second and third 6-inch intervals. The SPT N-value is commonly used with established correlations to estimate several soil parameters, particularly the shear strength and density of cohesionless soils. The N-values provided on the boring logs are raw values and have not been corrected for energy, borehole diameter, rod length, or overburden pressure. The VT Agency of Transportation has determined a hammer correction value, CE, to account for the efficiency of the SPT hammers on its drill rigs. For boring B-101, a CME 55 track rig was used, with a hammer energy correction factor of 1.52. A hammer correction value was assumed in calculations for Boring B-102 which was performed by Terracon. These values, included on the boring logs, should be used in calculations to estimate soil parameters.


Geotechnical laboratory tests were performed on samples to assist with soil classification and estimation of engineering properties of the soil. Grain size analyses were performed on soil samples in accordance with AASHTO T 88, Standard Method of Test for Particle Size Analysis of Soils. On soils exhibiting plastic behavior, Liquid and Plastic Limits were evaluated using AASHTO T 89, Standard Method of Test for Determining the Liquid Limit of Soils, and AASHTO T 90, Standard Method of Test for Determining the Plastic Limit and Plasticity Index of Soils, respectively. Results from this testing can be found on the attached boring logs. Auger probe notes with field notes can also be found attached. 4.0 SOIL PROFILE The following soil strata have been identified based on our review of the boring logs and laboratory testing. It should be noted that groundwater elevations are subject to change given the fact that boreholes were generally left open for a short period of time. Because groundwater elevations can fluctuate seasonally and are affected by temperature and precipitation, groundwater may be encountered during construction when not previously noted on the logs.

Abutment No. 1 (B-101): The ground surface elevation at B-101 was approximately 293.9 feet. Groundwater was measured at depths ranging from 1 ft to 15 ft below ground surface during drilling. We theorize this range of depths was caused by the drilling fluid being used coupled with the materials encountered at the bottom of the hole. These depths should not be considered accurate for use in design.

Elevation (ft) Soil Profile

293.9 – 292.4 Asphalt Pavement

292.4 – 281 Medium Dense Silty Sand and Gravel

281 – 275 Very Loose Sand

275 – 214 Dense Silty Sand

214 – 174 Soft Clayey Silt and Clay

174 – 154 Very Dense Silty Sand and Gravelly Silt Abutment No. 2 (B-102): The ground surface elevation at B-102 was approximately 294.0 feet. Groundwater was encountered at an elevation of 288.9 feet during drilling on May 20th, 2019.

Elevation (ft) Soil Profile

294 – 293.2 Asphalt Pavement

293.2 – 287 Medium Dense Silty Sand

287 – 282 Loose Silty Sand

282 – 277 Very Loose Silty Sand

277 – 249 Medium Dense Silty Sand and Sandy Silt

249 – 199 Medium Stiff Clay

199 – 179 Very Soft Clay

179 – 129 Very Dense Gravelly Sandy Silt


5.0 ANALYSIS

5.1 Shallow Foundation Analysis AASHTO’s LRFD Bridge Design Specifications Manual (2017) was used as the reference for settlement and bearing resistance equations. Section 10.6.3.1.2 contains the equation used for bearing resistance. Neither depth factors nor load inclination factors were used in the analysis as they were not considered pertinent. Hough’s Method, used to calculate settlement in normally consolidated cohesionless soils, can be found in section 10.6.2.4.2.

As per section 10.5.5.1 of the 2017 AASHTO LRFD Bridge Design Specifications, a resistance factor of 1.0 should be applied to the unfactored bearing resistance for use in service limit state design. Service limit state design includes, but is not limited to, settlement and scour. Section 10.5.5.2.2 specifies that a resistance factor of 0.45 should be applied to the unfactored bearing resistance for use in strength limit state design for spread footings on soil and rock. Strength limit state design includes, but is not limited to, checks for bearing resistance, sliding and constructability. Table 5.1 summarizes the appropriate resistance factors for various design states.

Table 5.1: Summary of Resistance Factors Design State Resistance Factor, φ

Settlement 1.0

Scour 1.0

Bearing Resistance 0.45

Sliding 0.80

Potential for overturning is limited by controlling the location of the resultant of the reaction forces (eccentricity). Per AASHTO Section 10.6.3.3, eccentricity, e, shall be limited as follows:

Foundations on soil: |e| < b/3 Foundations on rock: |e| < 0.45b

Eccentricity should be considered for settlement and bearing resistance design of spread footings by using effective footing widths based on AASHTO Section 10.6.1.3. All footing widths presented in this report are effective footing widths.

5.1.1 Abutments No. 1 and No. 2 – Bearing Resistance The bottom of footing elevation used for design was 285 feet for Abutment No. 1 and No. 2 based on email correspondence with David Kull of McFarland Johnson on August 6th, 2019. Based on an iterative process of determining bearing resistances with various footing widths and undercut depths, the final analysis and results herein assume a footing length of 34 feet, a footing width of 9 feet, and an undercut depth of 15 inches. With the addition of the undercut, an embedment depth of 5.25 feet was used in both the strength and service limit state design calculations. Based on the soil profiles and empirical relationships, soil friction angles and unit weights were calculated. Table 5.2 includes the assumptions used in design and resulting bearing resistances for strength limit state for each abutment.


Table 5.2 Bearing Resistance Analysis

Abutment No. 1

Abutment No. 2

Design Assumptions

Friction Angle 32 deg 30 deg Unit Weight 115 pcf 105 pcf Undercut Depth 15 in 15 in Footing Width 9 ft 9 ft

Results Factored Bearing Resistance 6.8 ksf 4.8 ksf

This analysis assumed the foundation will be undercut 15 inches and backfilled with a granular material. A geotextile should be used to separate the in-situ soil from the granular fill. An undercut influences the design by effectively reducing the bearing pressure on the in-situ material through a 1H:1.5V load distribution. Therefore, the effective footing width increases resulting in a decreased bearing pressure. The soil profile at each abutment includes a very loose silty sand layer a few feet below the bearing layer. AASHTO specifically addresses this scenario and includes calculations that can be performed to check the bearing resistance assuming a two-layered soil system, or when a firmer layer overlays a loose layer. Calculations were performed according to AASHTO 10.6.3.1.2f to determine if the loose layer is within the critical depth as well as to calculate a new bearing resistance in a two-layered drained loading condition. 5.1.2 Abutments No. 1 and No. 2 - Settlement For the service limit state, soil settlement values were calculated according to AASHTO 10.6.2.4.2 based on a footing width of 9 feet and provided applied bearing pressures. The applied bearing pressures were provided by David Kull in an email dated August 2nd, 2019 and are summarized below in Table 5.3, as well as the calculated bearing pressures reduced due to the 15-inch undercut. Factored bearing pressure values were provided assuming a construction condition when the dead load only is applied as well as a post construction condition when all loads are applied. The loading was provided this way to be able to differentiate between the settlement anticipated during construction and in service and to be able to design for any anticipated settlement as needed. The corresponding anticipated settlement values for each condition can be found below in Table 5.4.

Table 5.3 Bearing Pressures

Bearing Pressure Bottom of Footing (285 ft)

Bottom of Undercut

(283.75 ft) Strength

Limit State Total Load 5.60 ksf 4.75 ksf

Service Limit State

DL Only 2.50 ksf 2.20 ksf Total Load 3.80 ksf 3.20 ksf


Table 5.4 Anticipated Settlements Anticipated Settlement Abutment No. 1 Abutment No. 2 Service

Limit State DL Only 1.98 in. 2.07 in.

Total Load 2.50 in. 2.61 in. Due to the granular nature of the foundation soils, settlement is expected to occur during or immediately after construction, however due to the magnitude of the settlement this should be considered in design and sequencing of construction. Additional calculations were performed to determine the potential for and magnitude of differential settlement across each abutment. Because only one boring was performed at each foundation location, sensitivity analyses were completed using a range of soil parameters to represent varying soil conditions across the abutment. When utilizing extreme values, a maximum differential settlement of 1.4 inches was calculated under the total applied loading condition. Given the consistency of what was encountered in the engineered materials over the native soils in both borings, we don’t anticipate encountering the extreme case that was modeled, and this maximum settlement should be considered a very conservative maximum.

6.0 RECOMMENDATIONS

Shallow foundations appear to be feasible for both Abutment No. 1 and No. 2. Factored bearing resistances were calculated for a footing width of 9 feet and a footing elevation of 285 feet and can be found above in Table 5.2. Both abutments will require a 15-inch undercut using VTrans Item 704.08 Granular Backfill for Structures or similar. The settlement is expected to occur during or immediately after construction and anticipated settlement values for each abutment are provided above in Table 5.4. These calculations are based on the geometric and geotechnical assumptions outlined in Section 5.0. The auger probes that were completed along the edge of the roadway did not encounter any difficult drilling or materials that were interpreted as stone fill. We anticipate that the embankment is largely made up of granular materials and lined with a blanket of stone fill along the slope of the embankments. As the roadway and embankments are getting slightly widened, the stone fill layering the slope at the crest will likely need to be removed and replaced so that it is not an obstruction in the driving of new guardrail posts. Based on the materials expected to be encountered and the importance of the footing elevation and undercut thickness, we recommend having a geotechnical engineer on site during the subgrade preparation activities. This will be to both verify the assumptions made in design and ensure appropriate measures are taken in the field if conditions are different than anticipated.

6.1 Construction Considerations

6.1.1 Cofferdams/Temporary Earthwork Support: Cofferdams or temporary earthwork support may be necessary during construction of the abutments based on the proposed footing elevation. If required, the Contractor should be reminded that Section 208.06 of VTrans’ 2018 Standard Specifications for Construction indicates that “The Contractor shall prepare detailed plans and a schedule of operation for each cofferdam specified in the


Contract”. The design and structural details of the cofferdam shall be signed, stamped, and dated by a Professional Engineer (Structural or Civil) registered in the State of Vermont.

6.1.2 Construction Dewatering: Temporary construction dewatering will likely be necessary during construction of the abutments based on the proposed footing elevation. Temporary dewatering may also be necessary to limit disturbance to and maintain the integrity of the bearing surface. Temporary dewatering can likely be accomplished by open pumping from shallow sumps, temporary ditches, and trenches within and around the excavation limits. Sumps should be provided with filters suitable to prevent pumping of fine-grained soil particles. The water trapped by the temporary dewatering controls should be discharged to settling basins or an approved filter “sock” so that the fine particles suspended in the discharge have adequate time to “settle out” prior to discharge. All effluent water, or discharge, should comply with all applicable permits and regulations.

6.1.3 Placement and Compaction of Soils: Fills should be placed systematically in horizontal layers no more than 12 inches thick prior to compaction. Cobbles larger than 8 inches should be removed from the fill prior to placement. Compaction equipment should preferably consist of large, self-propelled vibratory rollers. Where hand-guided equipment is used, such as a small vibratory plate compactor, the loose lift thickness shall not exceed 6 inches. Cobbles larger than 4 inches should be removed from the fill prior to placement.

Embankment fills should be compacted to a dry density of at least 95% of the maximum dry density determined in accordance with AASHTO T-99 per section 203.11 of the 2018 VTrans Standard Specifications for Construction. Granular Backfill for Structures, or other select materials placed within the roadway base section shall be compacted to a dry density of 95% of the maximum dry density determined in accordance with AASHTO T-99.

6.2 Design Parameters: Table 6.1 highlights the geotechnical design parameters of the regularly specified aggregates. These values should be used when designing the substructure units. It is recommended that values of Ko be used for calculating earth pressures where the structure is not allowed to deflect longitudinally, away from or into the retained soil mass. Values for Ka should be utilized for an active earth pressure condition where the structure is moving away from the soil mass and Kp where the structure is moving toward the soil mass. The design earth pressure coefficients are based on horizontal surfaces (non-sloping backfill) and a vertical wall face.


Table 6.1: Engineering Properties of Construction Materials

703.01A

Granular Borrow

704.08 Granular Backfill

for Structures

Density, γ (lbs/ft3): 130 140

Internal Friction Angle, ϕ (degrees): 32 34

Coefficient of Friction, f

- soil/rock against mass concrete: 0.50 0.55

- soil against precast/formed concrete: 0.40 0.45

Active Earth Pressure Coefficient., Ka: 0.31 0.28

Passive Earth Pressure Coefficient., Kp: 3.25 3.54

At-Rest Earth Pressure Coefficient., Ko: 0.47 0.44

7.0 CONCLUSION The recommendations in this report are directly based on assumptions provided above. If the design is adjusted, the calculations will need to be revised to reflect such adjustments. If you have any questions, would like to discuss this report, or require anything further, please contact me at (802) 595-4589 or at [email protected].

Attachments: Boring Logs (7 Pages) Auger Probe Notes (1 Page) Terracon’s Geotechnical Data Report (20 Pages)

cc: David Kull, McFarland Johnson Project Engineer Electronic Read File/MG

Project File/CEE Z:\Highways\CMB\GeotechEngineering\Projects\Georgia BF 023-1(7)\REPORTS

8.3

12.7

11.3

12.1

22.4

21.1

21.3

26.4

23.3

25.3

24.1

45.5

31.6

29.8

47.9

1.8

12.7

14.3

11.4

8.4

2.9

40.3

53.6

57.7

42.4

65.3

67.7

69.3

61.7

16.2

75.2

76.1

14.2

14.8

12.5

9.7

32.9

19.6

16.4

26.9

75.4

24.8

21.0

Field Note, Asphalt 0.0-1.5'

A-1-b, SaGr, brn, Moist, Rec. = 1.1 ft, Field Note, broken rock was within sampleCleanout NXDC 2.1'-3.0'A-1-b, GrSa, brn, Moist, Rec. = 1.1 ft, Cleanout NXDC 4.4'-5.0'

A-1-b, GrSa, brn, Moist, Rec. = 0.6 ft, Cleanout NXDC 6.2'-7.0'

A-1-b, SaGr, brn, MTW, Rec. = 0.8 ft, Cleanout NXDC 8.6'-9.0'

A-2-4, SiSa, gry, MTW, Rec. = 1.0 ft

Field Note, No Recovery

A-2-4, Sa, gry, MTW, Rec. = 0.6 ft

Field Note, No Recovery

A-2-4, Sa, brn, MTW, Rec. = 0.3 ft

A-2-4, SiSa, gry, MTW, Rec. = 1.2 ft, Field Note: wood was within samplecleanout rollercone 24.4'-25.0'

Field Note, No Recovery, Cleanout rollercone 29.5'-30.0'

A-4, Si, gry, MTW, Rec. = 0.8 ft

A-2-4, SiSa, gry, MTW, Rec. = 1.3 ft

A-2-4, SiSa, gry, Moist, Rec. = 1.0 ft, Field Note, started using bentonite, artesiancondition encountered

12-22-17(39)

8-10-11-11

(21)7-5-6-4

(11)

6-4-3-4(7)

4-2-2-2(4)

3-2-3-2(5)

1-1-WoH-WoH(1)

1-1-1-1(2)

WoH-1-1-WoR

(2)9-6-7-7

(13)

3-2-3-2(5)

3-2-2-2(4)

9-8-9-9(17)

6-6-6-6(12)

BORING LOG

GeorgiaBF 023-1(7)

Dep

th(f

t)

5

10

15

20

25

30

35

40

45

Bridge 1 VT Route 104A

Boring Crew: Judkins, Emerson, Brochu, Gonyaw

Date Started: 5/20/19 Date Finished: 5/23/19

VTSPG NAD83: N 796337.20 ft E 1486298.00 ft

Ground Elevation: 293.9 ft

Boring No.: B-101

Page No.: 1 of 3

Pin No.: 18b265

Checked By: END

Date Depth(ft)

Notes

Notes:

Hammer Fall:Hammer Wt:I.D.:Type:

05/20/19 2.2 W.T. during drilling

05/21/19 1.1 W.T. before drilling

05/23/19 15.2 W/ casing in holeCE = 1.52

Moi

stur

eC

onte

nt %

Rig: CME 55 TRACKHammer/Rod Type: Auto/AWJ

SS1.5 in140 lb.30 in.

WB4 inN.A.N.A.

Casing Sampler

Offset: -3.60

Gra

vel %

San

d %

Fin

es %

Groundwater Observations

CLASSIFICATION OF MATERIALS(Description)

Str

ata

(1)

Station: 61+91

1. Stratification lines represent approximate boundary between material types. Transition may be gradual.2. N Values have not been corrected for hammer energy. CE is the hammer energy correction factor.3. Water level readings have been made at times and under conditions stated. Fluctuations may occur due to other factors than those present at the time measurements were made.

STATE OF VERMONTAGENCY OF TRANSPORTATION

CONSTRUCTION ANDMATERIALS BUREAU

CENTRAL LABORATORY

Blo

ws/

6"(N

Val

ue)

BO

RIN

G L

OG

GE

OR

GIA

BF

023

-1(7

).G

PJ

VE

RM

ON

T A

OT

.GD

T 8

/28

/19

LL %

PI %

23.7

26.2

29.7

33.4

43.2

0.1

0.1

78.9

91.3

67.0

21.0

8.7

32.9

100.0

100.0

A-2-4, SiSa, gry, Moist, Rec. = 1.0 ft

A-3, Sa, gry, Moist, Rec. = 1.3 ft, Cleanout rollercone 69.1'-70.0'

A-2-4, SiSa, gry, MTW, Rec. = 1.2 ft, Cleanout rollercone 76.0'-80.0'

A-4, ClSi, gry, Moist, Rec. = 2.0 ft

A-6, Cl Field Note, Pushed shelby tube

Field Note, Pushed shelby tube, Appears to be Clay

A-4, ClSi, gry, Moist, Rec. = 2.0 ft, Cleanout rollercone 86.8'-90.0'

4-5-7-8(12)

4-7-7-9(14)

7-10-9-10

(19)

WoH-5-4-4(9)

WoH-WoH-2-5

(2)

29

33

30

8

12

10

BORING LOG

GeorgiaBF 023-1(7)

Dep

th(f

t)

55

60

65

70

75

80

85

90

95




VTSPG NAD83: N 796337.20 ft E 1486298.00 ft


Boring No.: B-101

Page No.: 2 of 3

Pin No.: 18b265

Checked By: END

Date Depth(ft)

Notes

Notes:





Moi

stur

eC

onte

nt %


SS1.5 in140 lb.30 in.

WB4 inN.A.N.A.

Casing Sampler

Offset: -3.60

Gra

vel %

San

d %

Fin

es %



Str

ata

(1)

Station: 61+91




CENTRAL LABORATORY

Blo

ws/

6"(N

Val

ue)

BO

RIN

G L

OG

GE

OR

GIA

BF

023

-1(7

).G

PJ

VE

RM

ON

T A

OT

.GD

T 8

/28

/19

LL %

PI %

26.8

24.58.1

8.6

1.4

8.564.0

27.5

66.524.3

26.3

98.6

25.011.7

46.2

A-6, Cl, gry, Moist, Rec. = 2.0 ft, Cleanout NXDC 118.2'-120.0'

A-2-4, SiSa, gry, MTW, Rec. = 0.8 ft, Lab Note: Split sampleA-1-b, SaGr, gry, Moist, Field Note, broken rock was within sample. CleanoutBXDC 129.7'-130.0'

A-4, SaGrSi, gry, Moist, Rec. = 1.1 ft, Cleanout BXDC 139.5'-140.0'

Hole stopped @ 140.0 ft

WoH-WoH-

WoH-5(0)

17-R@5"(R)

9-19-27-R@11"

(46)

Remarks:1. Switched to 3" casing at 120'2. Artesian condition encountered at 40'

32 14

BORING LOG

GeorgiaBF 023-1(7)

Dep

th(f

t)

105

110

115

120

125

130

135

140

145




VTSPG NAD83: N 796337.20 ft E 1486298.00 ft


Boring No.: B-101

Page No.: 3 of 3

Pin No.: 18b265

Checked By: END

Date Depth(ft)

Notes

Notes:





Moi

stur

eC

onte

nt %


SS1.5 in140 lb.30 in.

WB4 inN.A.N.A.

Casing Sampler

Offset: -3.60

Gra

vel %

San

d %

Fin

es %



Str

ata

(1)

Station: 61+91




CENTRAL LABORATORY

Blo

ws/

6"(N

Val

ue)

BO

RIN

G L

OG

GE

OR

GIA

BF

023

-1(7

).G

PJ

VE

RM

ON

T A

OT

.GD

T 8

/28

/19

LL %

PI %

10 inches of bituminous concrete

SiSa, brown, Rec. = 1.0 ft, (FILL)

A-2-4, SiSa, brown, Rec. = 1.83 ft, (FILL)

SiSa, brown, Rec. = 1.0 ft, (ALLUVIUM)

SiSa, brown, Rec. = 0.33 ft, (ALLUVIUM)

A-2-4, SiSa, brown, Rec. = 0.33 ft, (ALLUVIUM)

SiSa, gray brown, Rec. = 1.75 ft, (ALLUVIUM)

A-2-4, SiSa, gray brown, Rec. = 1.75 ft, (ALLUVIUM)


A-2-4, SiSa, gray brown, Rec. = 1.42 ft, (ALLUVIUM)


A-2-4, Sa, dark gray, Rec. = 1.5 ft, (ALLUVIUM)

A-4, SaSi, dark gray, Rec. = 1.75 ft, (ALLUVIUM)

SiSa, dark gray, Rec. = 1.83 ft, (ALLUVIUM)

A-2-4, SiSa, dark gray, Rec. = 2.0 ft, (ALLUVIUM)

9-12-14-11

(26)10-7-5-6

(12)

15-15-7-5

(22)3-2-2-2

(4)

2-2-2-2(4)

1-WOH-WOH-1

1-WOH-1-1(1)

1-WOH-WOH-WOH

2-2-2-3(4)

3-3-2-4(5)

7-7-10-13

(17)

5-4-5-7(9)

6-8-8-10(16)

7-8-7-6(15)

NP NP

BORING LOG

GeorgiaBF 023-1(7)

Dep

th(f

t)

5

10

15

20

25

30

35

40

VT-104A Br. #1

Boring Crew: Terracon/C. Johnston, M. Rooney


VTSPG NAD83: N 796309.80 ft E 1486378.80 ft


Boring No.: B-102

Page No.: 1 of 4

Pin No.: 18b265

Checked By: MAF

Date Depth(ft)

Notes

Notes:


05/20/19 5.0 while drilling

CE =

Moi

stur

eC

onte

nt %

Rig: Mobile B-57Hammer/Rod Type: Auto/N

SS2 in

140 lb.30 in.

Casing4 inN.A.N.A.

Casing Sampler

Offset: 2.9 ft

Gra

vel %

San

d %

Fin

es %



Str

ata

(1)

Station: 62+73




CENTRAL LABORATORY

Blo

ws/

6"(N

Val

ue)

BO

RIN

G L

OG

J11

851

42 G

EO

RG

IA V

TR

AN

S V

ER

SIO

N.G

PJ

VE

RM

ON

T A

OT

.GD

T 8

/26

/19

LL %

PI %

Cl, gray, Rec. = 2.0 ft, (GLACIOLACUSTRINE)

A-4, Cl, gray, Rec. = 2.0 ft, (GLACIOLACUSTRINE)

Shelby tube taken at 55 feet, Rec. = 2.0 ft, (GLACIOLACUSTRINE)




A-7-6, Cl, gray, Rec. = 2.0 ft, (GLACIOLACUSTRINE)

2-4-4-5(8)

3-4-4-5(8)

3-5-5-5(10)

WOH-3-5-5(8)

4-3-5-5(8)

8-5-5-7(10)

31

28

53

9

8

36

BORING LOG

GeorgiaBF 023-1(7)

Dep

th(f

t)

45

50

55

60

65

70

75

80

VT-104A Br. #1



VTSPG NAD83: N 796309.80 ft E 1486378.80 ft


Boring No.: B-102

Page No.: 2 of 4

Pin No.: 18b265

Checked By: MAF

Date Depth(ft)

Notes

Notes:



CE =

Moi

stur

eC

onte

nt %


SS2 in

140 lb.30 in.

Casing4 inN.A.N.A.

Casing Sampler

Offset: 2.9 ft

Gra

vel %

San

d %

Fin

es %



Str

ata

(1)

Station: 62+73




CENTRAL LABORATORY

Blo

ws/

6"(N

Val

ue)

BO

RIN

G L

OG

J11

851

42 G

EO

RG

IA V

TR

AN

S V

ER

SIO

N.G

PJ

VE

RM

ON

T A

OT

.GD

T 8

/26

/19

LL %

PI %




Roller bit resistance indicating a strata change at 114 feet

A-4, GrSaSi, dark gray, Rec. = 1.0 ft, (GLACIAL TILL)

A-4, SaSi, dark gray, Rec. = 1.33 ft, (GLACIAL TILL)

WOH-2-4-4(6)

WOH/24"

WOH/12"-3-4(3)

47-45-50/5"(95+)

49-50-

39

17

17

23

5

4

BORING LOG

GeorgiaBF 023-1(7)

Dep

th(f

t)

85

90

95

100

105

110

115

120

125

VT-104A Br. #1



VTSPG NAD83: N 796309.80 ft E 1486378.80 ft


Boring No.: B-102

Page No.: 3 of 4

Pin No.: 18b265

Checked By: MAF

Date Depth(ft)

Notes

Notes:



CE =

Moi

stur

eC

onte

nt %


SS2 in

140 lb.30 in.

Casing4 inN.A.N.A.

Casing Sampler

Offset: 2.9 ft

Gra

vel %

San

d %

Fin

es %



Str

ata

(1)

Station: 62+73




CENTRAL LABORATORY

Blo

ws/

6"(N

Val

ue)

BO

RIN

G L

OG

J11

851

42 G

EO

RG

IA V

TR

AN

S V

ER

SIO

N.G

PJ

VE

RM

ON

T A

OT

.GD

T 8

/26

/19

LL %

PI %

GrSaSi, dark gray, Rec. = 0.08 ft, (GLACIAL TILL)

Advanced roller bit without sampling past 135 feet

Roller bit resistance indicating a strata change at 145, wash cuttings indicatepossible weathered rock

Boring terminated in possible weathered rock at 165 feet

Hole stopped @ 165.0 ft

50/4"(100+)

50/1"

BORING LOG

GeorgiaBF 023-1(7)

Dep

th(f

t)

130

135

140

145

150

155

160

165

VT-104A Br. #1



VTSPG NAD83: N 796309.80 ft E 1486378.80 ft


Boring No.: B-102

Page No.: 4 of 4

Pin No.: 18b265

Checked By: MAF

Date Depth(ft)

Notes

Notes:



CE =

Moi

stur

eC

onte

nt %


SS2 in

140 lb.30 in.

Casing4 inN.A.N.A.

Casing Sampler

Offset: 2.9 ft

Gra

vel %

San

d %

Fin

es %



Str

ata

(1)

Station: 62+73




CENTRAL LABORATORY

Blo

ws/

6"(N

Val

ue)

BO

RIN

G L

OG

J11

851

42 G

EO

RG

IA V

TR

AN

S V

ER

SIO

N.G

PJ

VE

RM

ON

T A

OT

.GD

T 8

/26

/19

LL %

PI %

SHEET 1 OF 1 .

FEET

PROBE / HAND STEEL NOTES METERS

PROJECT: EA No.

DRILLERS: CHECKED BY: Whitlock

ELEVATION

P‐1 5/21/19 60+35 5.9 10.0' SSAPavement 0.95'

Gr, Si, Sa

P‐2 5/21/19 60+71 ‐9.8 10.0' SSAPavement 0.90'

Si, Sa

P‐3 5/21/19 61+40 ‐9.0 10.0' SSAPavement 1.00'

Gr, Si, Sa

Sample turned Moist to wet at 4.0'

P‐4 5/21/19 61+83 5.1 10.0' SSAPavement 0.80'

Si, Sa

P‐5 5/21/19 63+06 ‐6.7 10.0' SSAPavement 0.90'

Gr, Si, Sa


P‐6 5/21/19 63+14 5.5 10.0' SSAPavement 1.10'

Gr, Si, Sa

5.0'‐ 10.0' soft,

P‐7 5/21/19 63+42 ‐8.8 10.0' SSAPavement 1.30'

Gr, Si, Sa


P‐8 5/21/19 63+55 4.6 10.0' SSAPavement 1.00'

Si, Sa

7.0' 10.0' soft advanced auger without rotation

BORING No.

SAMPLE

StationDate

Drilled

Depth

(Feet)OFFSET FIELD Notes

VERMONT AGENCY OF TRANSPORTATION

CONSTRUCTION & MATERIALS BUREAU

GEOTECHNICAL ENGINEERING SECTION

GEORGIA BF 023‐1(7)

Brochu, Whitlock

0231007‐100

REPORT COVER PAGE

Geotechnical Data Report__________________________________________________________________________

VT-104A, Bridge No. 1Georgia, Vermont

VTrans Project Name & Number: Georgia BF 023-1(7)EA Number: 0231007-100

July 16, 2019Terracon Project No. J1185142

Prepared for:Vermont Agency of Transportation

Berlin, Vermont

Prepared by:Terracon Consultants, Inc.

Manchester, New Hampshire

Terracon Consultants, Inc. 77 Sundia l Ave. , Suite 401W Manchester, New Hampshire 03103P (603) 647 9700 F (603) 647 4432 terracon.com

REPORT COVER LET TER T O SIGN

July 16, 2019

Vermont Agency of TransportationConstruction and Materials Bureau2178 Airport Road Unit BBerlin, VT 05641

Attn: Ms. Callie Ewald, P.E.P: (802) 828-1235E: [email protected]

Re: Geotechnical Data ReportVT-104A, Bridge No. 1Georgia, VermontVTrans Project Name & Number: Georgia BF 021-1(7)EA Number: 0231007-100Terracon Project No. J1185142

Dear Ms. Ewald:

We have completed the Geotechnical Data Report for the above referenced project. This studywas performed in general accordance with Terracon Proposal No. PJ1185142 dated November16, 2018. This report presents the findings of the subsurface exploration for the proposed project.

We appreciate the opportunity to be of service to you on this project. If you have questionsconcerning this report or if we may be of further service, please contact us.

Sincerely,Terracon Consultants, Inc.

Marc A. Gullison, P.E. (NH) Carl W. Thunberg, P.E.Senior Staff Engineer Geotechnical Department Manager

Reviewed by Michele A. Fiorillo, P.E. (NY), Approved Project Reviewer (APR)

Responsive Resourceful Reliable i

REPORT TOPICS

INTRODUCTION ............................................................................................................. 1

SITE CONDITIONS ......................................................................................................... 1

PROJECT DESCRIPTION .............................................................................................. 2

GEOTECHNICAL CHARACTERIZATION ...................................................................... 2

GENERAL COMMENTS ................................................................................................. 3

Note: This report was originally delivered in a web-based format. For more interactive features, please view your projectonline at client.terracon.com.

ATTACHMENTS

EXPLORATION AND TESTING PROCEDURESSITE LOCATION AND EXPLORATION PLANSEXPLORATION RESULTS

Note: Refer to each individual Attachment for a listing of contents.

Responsive Resourceful Reliable 1

INTRODUC TION

Geotechnical Data ReportVT-104A, Bridge No. 1

Georgia, VermontVTrans Project Name & Number: Georgia BF 023-1(7)

Terracon Project No. J1185142July 16, 2019

INTRODUCTION

This report presents the results of our subsurface exploration for the proposed bridge replacementalong VT-104A in Georgia, Vermont. The purpose of these services is to provide informationrelative to:

■ Subsurface soil and rock conditions ■ Groundwater conditions

The geotechnical engineering scope of services for this project included the advancement of onetest boring to a depth of 165 feet below existing site grades near the east abutment of the bridge.VTrans performed an additional boring near the west abutment of the bridge, as well as eightprobes for proposed guardrails.

Maps showing the site and boring location are shown on the Site Location and ExplorationPlan, respectively. The results of the laboratory testing performed on soil samples obtained fromthe site during the field exploration are included on the boring log and as separate graphs in theExploration Results section.

SITE CONDITIONS

The following description of site conditions is derived from our site visit in association with thefield exploration and our review of publicly available geologic and topographic maps.

Item Description

Location

The bridge, designated as Bridge No. 1, is located on Vermont Route 104Aapproximately 1.1 miles east of the intersection with U.S. Route 7 in Georgia,Vermont. The bridge crosses the north end of Arrowhead Mountain Lake. SeeSite Location

ExistingImprovements

Existing approximate 75-feet, single-span, deck bridge. It is reported to beconstructed in 1937. A September 1933 design drawing indicates theabutments are supported on a shallow spread footing, 5.5 feet wide, howeverit is not confirmed.

Bridge DeckPaved roadway with bituminous concrete and cast-in-place concrete bridgedeck with concrete abutments.

Geotechnical Data ReportVT-104A, Bridge No. 1 Georgia, VermontJuly 16, 2019 Terracon Project No. J1185142


Item Description

Existing Topography

The roadway is generally level across the span, with a ground surfaceelevation (USGS topographic plan) estimated at approximately elevation (El)290 feet. The channel bottom, based on available photographs, appears to beabout 6 feet below the bridge deck.

Geology

NRCS SSURGO mapping indicates the overburden soil consists of sand andgravel alluvium. The test boring encountered granular alluvium over fine-grained glaciolacustrine deposits, over glacial till. USGS geologic mappingindicates the bedrock is dolostone of the Dunham Dolostone Formation.

PROJECT DESCRIPTION

Our initial understanding of the project was provided in our proposal and was discussed duringproject planning. Our final understanding of the project conditions is as follows:

Item Description

Proposed Structure

The proposed structure will likely consist of a precast or steel arch bridgesupported on spread footings on soil. As an option, the bridge could consistof a concrete rigid frame supported on H-piles, micro-piles, or spreadfootings. Integral abutments supported on a single row of H-piles may alsobe considered.

Finished GradeElevation

Match existing roadway grades.

GEOTECHNICAL CHARACTERIZATION

Based upon our review of the subsurface exploration, laboratory data, and geologic setting,subsurface conditions can be generalized in the following table. Conditions encountered at eachexploration point are indicated on the boring log which can be found in the Exploration Resultssection.

StratumApproximate Depth to

Bottom of Stratum (feet)Material Description

Relative Density/Consistency

Pavement 0.8 Bituminous concrete N/AFill 5.0 Silty sand, brown Medium dense

Alluvium 45.0 Silty sand; silt with sand, brownto gray

Very loose tomedium dense

GlaciolacustrineDeposits

114.0 Lean clay; Fat clay; gray Very soft tomedium stiff



StratumApproximate Depth to

Bottom of Stratum (feet)Material Description

Relative Density/Consistency

Glacial Till 145.0 Silty-clayey sand with gravel,dark gray

Very dense

Weathered rock Roller bit was advanced from 145 to 165 feet in possible weathered rock.

As noted on the boring log in the Exploration Results section, groundwater was encountered ata depth of 5.0 feet while drilling B-102. Groundwater level fluctuations occur due to seasonalvariations in the amount of rainfall, runoff and other factors not evident at the time the boring wasperformed. Therefore, groundwater levels during construction or at other times in the life of thestructure may be higher or lower than the levels indicated on the boring log. The possibility ofgroundwater level fluctuations should be considered when developing the design and constructionplans for the project.

GENERAL COMMENTS

Natural variations will occur between exploration point locations or due to the modifying effects ofconstruction or weather. The nature and extent of such variations may not become evident untilduring or after construction.

Our scope of services does not include either specifically or by implication any environmental orbiological (e.g., mold, fungi, bacteria) assessment of the site or identification or prevention ofpollutants, hazardous materials or conditions. If the owner is concerned about the potential forsuch contamination or pollution, other studies should be undertaken.

Our services and any correspondence or collaboration are intended for the sole benefit andexclusive use of our client for specific application to the project discussed and are accomplishedin accordance with generally accepted geotechnical engineering practices with no third partybeneficiaries intended. Any third party access to services or correspondence is solely forinformation purposes to support the services provided by Terracon to our client. Reliance uponthe services and any work product is limited to our client, and is not intended for third parties. Anyuse or reliance of the provided information by third parties is done solely at their own risk. Nowarranties, either express or implied, are intended or made.

Site characteristics as provided are for design purposes and not to estimate excavation cost. Anyuse of our report in that regard is done at the sole risk of the excavating cost estimator as theremay be variations on the site that are not apparent in the data that could significantly impactexcavation cost. Any parties charged with estimating excavation costs should seek their own sitecharacterization for specific purposes to obtain the specific level of detail necessary for costing.Site safety, and cost estimating including, excavation support, and dewateringrequirements/design are the responsibility of others.

Responsive Resourceful Reliable

ATTACHMENTS


Responsive Resourceful Reliable EXPLORATION AND TESTING PROCEDURES 1 of 2

EXPLORATION AND TESTING PROCEDURES

Field Exploration

Boring No. Boring Depth (feet) Location

B-102 165.0 East of bridge

Boring Layout and Elevations: Unless otherwise noted, Terracon personnel provided the boringlayout. As-drilled boring coordinates and elevation were provided by VTrans, and were surveyedon June 11, 2019 by VTrans personnel.

Subsurface Exploration Procedures: We advanced the boring with a truck-mounted drill rigusing flush-joint casing. Continuous samples were obtained in the upper 19 feet of B-102,otherwise at intervals of 5 feet. Soil sampling was generally performed using split-barrel samplingprocedures. A thin-wall tube was advanced from a depth of 55 to 57 feet. Below a depth of 135feet the borehole was advanced using the roller bit without sampling.

In the split-barrel sampling procedure, a standard 2-inch outer diameter split-barrel sampling spoonwas driven into the ground by a 140-pound automatic hammer falling a distance of 30 inches. Thenumber of blows required to advance the sampling spoon the middle 12 inches of a 24-inchpenetration is recorded as the Standard Penetration Test (SPT) resistance value. The SPTresistance values, also referred to as N-values, are indicated on the boring log at the test depths. Inthe thin-walled tube sampling procedure, a thin-walled, seamless steel tube with a sharp cuttingedge was pushed hydraulically into the soil to obtain a relatively undisturbed sample. Weobserved and recorded groundwater levels while drilling and sampling. For safety purposes, theboring was backfilled with cuttings upon completion. Pavement was patched with pre-mixedconcrete.

The sampling depths, penetration distances, and other sampling information was recorded on thefield boring log. The samples were placed in appropriate containers and taken to our soil laboratoryfor testing and classification by a Geotechnical Engineer. Our exploration team prepared a fieldboring log as part of the drilling operations. The field log included visual classifications of thematerials encountered during drilling and our interpretation of the subsurface conditions betweensamples. A final boring log was prepared from the field log. The final boring log represents theGeotechnical Engineer's interpretation of the field log and include modifications based onobservations and tests of the samples in our laboratory.

Laboratory Testing

The project engineer reviewed the field data and assigned laboratory tests to understand theengineering properties of the various soil strata, as necessary, for this project. Procedural


Responsive Resourceful Reliable EXPLORATION AND TESTING PROCEDURES 2 of 2

standards noted below are for reference to methodology in general. In some cases, variations tomethods were applied because of local practice or professional judgment. Standards noted belowinclude reference to other, related standards. Such references are not necessarily applicable todescribe the specific test performed.

■ ASTM D2216 Standard Test Methods for Laboratory Determination of Water (Moisture)Content of Soil and Rock by Mass

■ ASTM D4318 Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index ofSoils

■ AASHTO T88 Standard Method of Test for Particle Size Analysis of Soils

The laboratory testing program included examination of soil samples by an engineer. Based onthe material’s texture and plasticity, we described and classified the soil samples in accordancewith AASHTO.


SITE LOCATION AND EXPLORATION PLANS

Contents:

Site Location PlanExploration Location Plan

Note: All attachments are one page unless noted above.

SITE LOCATION VT-104A, Bridge No. 1 ■ Georgia, Vermont July 16, 2019 ■ Terracon Project No. J1185142

TOPOGRAPHIC MAP IMAGE COURTESY OF THE U.S. GEOLOGICAL SURVEY QUADRANGLES INCLUDE: MILTON, VT (1/1/1987).

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES

SITE SITE

EXPLORATION PLAN VT-104A, Bridge No. 1 ■ Georgia, Vermont July 16, 2019 ■ Terracon Project No. J1185142

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES

AERIAL PHOTOGRAPHY PROVIDED BY MICROSOFT BING MAPS


EXPLORATION RESULTS

Contents:

Boring Log (B-102)Grain Size Distribution (2 pages)Atterberg Limits

Note: All attachments are one page unless noted above.

AGENCY OF TRANSPORTATION OFFICE MEMORANDUM Robert Young… · To: Robert Young, P.E., Structures...

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Transcript of AGENCY OF TRANSPORTATION OFFICE MEMORANDUM Robert Young… · To: Robert Young, P.E., Structures...