Assignment 1 Solution

COURSEWORK ON GROUND INVESTIGATION AND SOIL TESTING

CIVL 6077

ASSIGNMENT1

S.I. INTERPRETATION REPORT

Document No. CIVL6077/REP/001

Prepared for:

Department of Civil Engineering

Faculty of Engineering

The University of Hong Kong

Issued: November 2014

Prepared by:

Hamza Nadeem

UID:2010539786

7/F Prosperity Millennia Plaza

663 Kings Road

North Point, Hong Kong

Tel: +852 53749093

Fax: +852 2527 6364

1. GEOLOGICAL CROSS SECTIONS

The following table summarized the soil strata encountered in Boreholes BH1 through BH8

Borehole No.

Top of Stratum (mPD)

Ground Level (mPD)

Concrete Slab

Fill MD Alluvium CDT/HDT

(Grade V/IV)

MDT/SDT (Grade III/II)

End of Borehole

BH1 +4.58 +4.58 +4.48 -10.72 -16.22 -33.72 -37.24 -42.37

BH2 +4.58 +4.58 +4.48 -9.92 -16.88 -31.92 -42.05 -47.24 BH3 +4.53 +4.53 +4.43 -9.07 -17.17 -31.72 -41.29 -46.35

BH4 +4.5 +4.50 +4.40 -9.70 -15.80 -34.50 -44.25 -49.35

BH5 +4.48 +4.48 +4.38 -13.37 -16.44 -34.15 -45.00 -50.18 BH6 +4.47 - +4.47 -11.68 -16.73 -33.83 -37.10 -42.24

BH7 +4.53 +4.53 +4.43 -8.97 -16.23 -33.97 -44.55 -49.70 BH8 +4.57 +4.57 +4.47 -13.53 -16.36 -32.59 -42.51 -47.81

Table 1. Summary of Strata Levels

Key:

MD Marine Deposits

CDT Completely Decomposed Tuff

HDT Highly decomposed Tuff

MDT Moderately Decomposed Tuff

SDT Slightly Decomposed Tuff

Figure 1. Geological Section A-A

hamza_nadeemText BoxScale: 1:400

2. ROCKHEAD CONTOURS

The following table summarized the data relevant to the bedrock contours

Borehole No.

Easting Northing Rockhead Level

(mPD)

BH1 842807.650 814237.110 -37.24

BH2 842834.820 814257.220 -42.05

BH3 842848.450 814280.040 -41.29

BH4 842827.560 814217.570 -44.25

BH5 842844.960 814231.280 -45.00

BH6 842857.160 814255.470 -37.10

BH7 842873.230 814225.450 -44.55

BH8 842877.070 814241.190 -42.51 Table 2. Relavent Data for formulation of Rockhead Contours

Note:

1. Rockhead is defined as 5m continuous vertical thickness of Grade III or better rock with a Total Core Recovery of greater than 85%. 2. The contours shown have been produced using site specific boreholes. 3. The contours have been generated using Krigging Method of interpolation between boreholes. Actual site conditions may vary.

The data summarized in Table 2 above has been used to develop the Rochead Contours for the site area (Figure 2). Commercially available software Surfer 12 has been used to generate the contours.

4.

Figure 2. Rockhead Contours Generated using Surfer

The Rockhead contours developed using surfer have been overlaid on the site area and are shown in Figure 3.

842760 842780 842800 842820 842840842860 842880 842900 842920 842940814150

814200

814250

814300

814350

814400

NOTES:

1. ROCKHEAD IS DEFINED AS 5M CONTINUOUS VERTICAL THICKNESS OF GRADE III OR BETTER ROCK WITH A TOTAL CORE RECOVERY OF GREATER THAN 85%.

2. THE CONTOURS SHOWN HAVE BEEN PRODUCED USING SITE SPECIFIC BOREHOLES.

3. THE CONTOURS HAVE BEEN GENERATED USING KRIGGING METHOD OF INTERPOLATION BETWEEN BOREHOLES. ACTUAL SITE CONDITIONS MAY VARY.

3. SOIL PROPERTIES

Soil Strata

Soil Properties

Bulk Density Cohesion c

(kN/m2)

Friction Angle

(Deg)

Moisture Content (%)

Particle Size Distribution(%)

(kN/m3) Gravel Sand Silt Clay

FILL 18.3 5.14 34.06 31 0 14 68 18

MD 15.9 10.17 24.83 52 2 18 60 20

ALL 18.8-19.4 5.32- 45.80 29.34-32.01

28-31 7-11 24-36 53-69 53-69

CDT/HDT 17.3-18.2 25.44-32.54 22.33-

27.39 29-41 1-10 16-23 74-76 74-76

(Grade V/IV)

MDT/SDT - - - - - - - -

(Grade III/II)

4. SOIL CLASSIFICATION

Following a review of Borehole Drilling data on site, it is my opinion that the following soil layers define the geology of the site. These soil layers can be further classified as follows:

a. Fill: The fill layer is the upper most soil layer identified in all the Drilling Record. The fill is can be classified as coarse grained material and is generally composed mainly of sand, gravels, cobbles and boulders. The thickness varies 13.4m to 18.0m and the material generally comprises loose to medium dense sand (with some silt), gravel, cobbles, and boulders. In addition these is presence of fragments of brick, wood and volcanic tuff.

b. Marine Deposit: A layer of Marine Deposits is presents beneath the Fill layer with thickness ranging from 3.1m to 7.5m. In general, the marine deposit comprises of fine grained material

which predominantly clay with shell fragments. In addition a localized lens of loose sand within the Marine Deposits layer has also been identified.

c. Alluvium: The Alluvium layer underlies the Marine Deposits with thickness varying from 14.6m to 18.7m. In general, the alluvium comprises a coarse grained material predominantly gravels and cobbles of moderately decomposed volcanic tuff (and slightly decomposed Granite) together with medium dense to dense sand. Localized lens of with a thickness ranging from approximately 1m to 3m have also been identified in this layer.

d. Tuff: The Tuff layer underlies the Alluvium layer and is present in different degrees of decomposition with decomposition decreasing as the depth increases. The thickness of the tuff

layer Beneath the alluvium is tuff at different stages of decomposition. For the layer of Completely Decomposed Tuff and Highly Decomposed Tuff (Grade V/IV), the thickness varies from 3.3m to 10.9m.

The bedrock is composed of tuff andhas been defined as atleast 5m of Grade II or better rock with more than 85% core recovery, it vares from -37.10mPD to -45 mPD across the site. It can be classified as Moderately to Slightly Decomposed Rock with close to very close joint spacing. The joints have been described from narrow to extremely narrow and there roughness varies from rough to smooth planar joints.

5. AVERAGE GEOLOGICAL PROFILE The average geological profile has been summarized in the following sections:

5.1. Standard Penetration Tests (SPT) Profiles

SPT Profile

SPT Profile

Borehole No. Ground Level

(mPD) Depth

(m) Level (mPD)

SPT Value

Borehole No.

Ground Level (mPD)

Depth (m)

Level (mPD)

SPT Value

BH1 4.58 2.45 2.13 16

BH5 4.48 2.95 1.53 10

BH1 4.58 16.45 -11.87 2

BH5 4.48 20.45 -15.97 5

BH1 4.58 19.45 -14.87 2

BH5 4.48 26.45 -21.97 53

BH2 4.58 2.45 2.13 10

BH5 4.48 29.45 -24.97 80

BH2 4.58 9.45 -4.87 12

BH5 4.48 34.45 -29.97 34

BH2 4.58 13.5 -8.92 9

BH5 4.48 39.45 -34.97 10

BH2 4.58 14.95 -10.37 6

BH5 4.48 42.45 -37.97 50

BH2 4.58 17.95 -13.37 6

BH5 4.48 45.45 -40.97 69

BH2 4.58 20.95 -16.37 10

BH6 4.47 17.45 -12.98 2

BH2 4.58 25.45 -20.87 34

BH6 4.47 20.45 -15.98 2

BH2 4.58 28.45 -23.87 17

BH6 4.47 28.45 -23.98 30

BH2 4.58 31.95 -27.37 29

BH6 4.47 41.3 -36.83 200

BH2 4.58 35.95 -31.37 80

BH7 4.53 10.45 -5.92 10

BH2 4.58 38.95 -34.37 11

BH7 4.53 13.95 -9.42 5

BH2 4.58 41.95 -37.37 14

BH7 4.53 16.95 -12.42 6

BH2 4.58 45.95 -41.37 80

BH7 4.53 19.95 -15.42 7

BH3 4.53 9.45 -4.92 7

BH7 4.53 26.45 -21.92 27

BH3 4.53 16.43 -11.9 3

BH7 4.53 30.45 -25.92 10

BH3 4.53 19.45 -14.92 9

BH7 4.53 35.45 -30.92 33

BH3 4.53 37.45 -32.92 11

BH7 4.53 38.45 -33.92 5

BH3 4.53 40.45 -35.92 12

BH7 4.53 41.45 -36.92 21

BH3 4.53 43.45 -38.92 136

BH7 4.53 44.45 -39.92 62

BH4 4.5 2.45 2.05 19

BH7 4.53 47.45 -42.92 83

BH4 4.5 15.45 -10.95 2

BH8 4.57 2.45 2.12 6

BH4 4.5 18.45 -13.95 3

BH8 4.57 7.45 -2.88 10

BH4 4.5 34.45 -29.95 43

BH8 4.57 9.95 -5.38 9

BH4 4.5 41.45 -36.95 11

BH8 4.57 14.95 -10.38 8

BH4 4.5 44.45 -39.95 77

BH8 4.57 18.95 -14.38 10

BH4 4.5 47 -42.5 200 BH8 4.57 23.95 -19.38 10

BH8 4.57 27.45 -22.88 27

BH8 4.57 30.45 -25.88 15

BH8 4.57 33.45 -28.88 19

BH8 4.57 36.45 -31.88 50

BH8 4.57 39.45 -34.88 12

BH8 4.57 42.45 -37.88 23

BH8 4.57 45.45 -40.88 89

SPT Profile

-50.00

-45.00

-40.00

-35.00

-30.00

-25.00

-20.00

-15.00

-10.00

-5.00

0.00

5.00

0 50 100 150 200

SPT Value

Le

ve

l (m

PD

)

5.2. Undrained Shear Strength

Undrained Shear Strength

-14.00

-12.00

-10.00

-8.00

-6.00

-4.00

-2.00

0.00

0 2 4 6 8 10 12

Strength (kN/m2)

Le

ve

l (m

PD

)Undrained Shear Strengths


(mPD) Depth (m) Level (mPD)

Undrained Shear Strength

(kN/m2) BH1 4.58 17.5 -12.92 31

BH3 4.53 14.5 -9.97 20

5.3. Total Unit Weight

Total Unit Weight



Total Unit Weight (kN/m3)

BH1 4.58 17.5 -12.92 15.9

BH2 4.58 26.5 -21.92 19.4

BH2 4.58 37 -32.42 18.2

BH3 4.53 14.5 -9.97 18.3

BH6 4.47 39.5 -35.03 17.3

BH7 4.53 31 -26.47 18.8

Total Unit Weight

-40.00

-35.00

-30.00

-25.00

-20.00

-15.00

-10.00

-5.00

0.00

0 5 10 15 20 25

Total Unit Weight (kN/m3)

Le

ve

l (m

PD

)

5.4. Water Content and Atterberg Limits

Water Content and Atterberg Limits



Water Content(%)

Atterberg Limits Liquid Limit (%)

Plastic Limit (%)

BH1 4.58 17.5 -12.92 52 56 25

BH2 4.58 26.5 -21.92 28 - -

BH2 4.58 37 -32.42 29 - -

BH3 4.53 14.5 -9.97 31 41 21

BH6 4.47 39.5 -35.03 41 - -

BH7 4.53 31 -26.47 31 - -

Water Content and Atterberg Limits

-40.00

-35.00

-30.00

-25.00

-20.00

-15.00

-10.00

-5.00

0.00

0.00 10.00 20.00 30.00 40.00 50.00 60.00

Water Content, Atterberg Limits (%)

Le

ve

l (m

PD

)

Water Content

Atterberg Limit -

Plastic Limit

"Atterberg Limit -

Liquid Limit"

5.5. Plasticity Index

Plasticity Index


(mPD) Depth

(m) Level (mPD)

Plasticity Index (%)

BH1 4.58 17.5 -12.92 31

BH3 4.53 14.5 -9.97 20

Plasticity Index

-40.00

-35.00

-30.00

-25.00

-20.00

-15.00

-10.00

-5.00

0.00

0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00

Plasticity Index (%)

Le

ve

l (m

PD

)

5.6. Liquidity Index

Liquidity Index


(mPD) Depth

(m) Level (mPD)

Liquidity Index (%)

BH1 4.58 17.5 -12.92 87

BH3 4.53 14.5 -9.97 50

Liquiditiy Index

-40.00

-35.00

-30.00

-25.00

-20.00

-15.00

-10.00

-5.00

0.00

0.00 20.00 40.00 60.00 80.00 100.00

Liquidity Index (%)

Le

ve

l (m

PD

)

5.7. Hydraulic Conductivity

Hydraulic Conductivity


(mPD) Depth

(m) Level (mPD)

Coefficient of Permeability

(m/sec)

BH1 4.58 17.5 -12.92 1.05E-09

BH3 4.53 14.5 -9.97 9.78E-10

Hydraulic Conductivity

-14.00

-12.00

-10.00

-8.00

-6.00

-4.00

-2.00

0.00

0.00E+00 5.00E-01 1.00E+00 1.50E+00 2.00E+00 2.50E+00

Coefficient of Permeability (m/sec)

Le

ve

l (m

PD

)

5.8. Hydrostatic Pressure Line and in-situ Pore Water Pressures

Hydrostatic Pressure Line and in-situ Pore Water Pressures

Borehole No. Ground

Level (mPD) Depth

(m) Level (mPD)

Hydrostatic Pressure Line

(kN/m2)

In-situ pore water

pressures (kN/m2)

BH1 4.58 17 -12.42 167 95

BH1 4.58 17.5 -12.92 172 95

BH1 4.58 18 -13.42 177 95

BH2 4.58 26 -21.42 255 195

BH2 4.58 26.5 -21.92 260 195

BH2 4.58 27 -22.42 265 195

BH2 4.58 36.5 -31.92 358 145

BH2 4.58 37 -32.42 363 145

BH2 4.58 37.5 -32.92 368 145

BH3 4.53 14 -9.47 137 95

BH3 4.53 14.5 -9.97 142 95

BH3 4.53 15 -10.47 147 95

BH6 4.47 39 -34.53 383 195

BH6 4.47 39.5 -35.03 387 195

BH6 4.47 40 -35.53 392 195

BH7 4.53 30.93 -26.4 303 195

BH7 4.53 31 -26.47 304 195

BH7 4.53 31.5 -26.97 309 195

Hydrostatic Pressure Line and

In-situ Pore Water Pressure

-40.00

-35.00

-30.00

-25.00

-20.00

-15.00

-10.00

-5.00

0.00

0 500 1000 1500

Pressure (kN/m2)

Le

ve

l (m

PD

)

Hydrostatic

Pressure Line

in situ pore

Water

PressureLinear

(Hydrostatic

Pressure Line)

5.9. Total and Effective in-situ Stresses

Total and Effective in-situ vertical stresses

Borehole No. Ground

Level (mPD) Depth

(m) Level (mPD)

p(kN/m2) q(kN/m2)

In-situ pore water

pressures (kN/m2)

Effective in-situ vertical stresses (kN/m2)

Total in-situ

vertical stresses (kN/m2)

BH1 4.58 17.00 -12.42 65.20 35.20 95.00 100.40 195.40

BH1 4.58 17.50 -12.92 124.20 64.20 95.00 188.40 283.40

BH1 4.58 18.00 -13.42 238.00 109.00 95.00 347.00 442.00

BH2 4.58 26.00 -21.42 268.40 176.40 195.00 444.80 639.80

BH2 4.58 26.50 -21.92 474.80 294.80 195.00 769.60 964.60

BH2 4.58 27.00 -22.42 822.90 469.90 195.00 1292.80 1487.80

BH2 4.58 36.50 -31.92 178.60 89.60 145.00 268.20 413.20

BH2 4.58 37.00 -32.42 315.30 143.30 145.00 458.60 603.60

BH2 4.58 37.50 -32.92 590.90 244.90 145.00 835.80 980.80

BH3 4.53 14.00 -9.47 57.00 37.00 95.00 94.00 189.00

BH3 4.53 14.50 -9.97 156.80 91.80 95.00 248.60 343.60

BH3 4.53 15.00 -10.47 324.90 187.90 95.00 512.80 607.80

BH6 4.47 39.00 -34.53 212.80 122.80 195.00 335.60 530.60

BH6 4.47 39.50 -35.03 405.80 225.80 195.00 631.60 826.60

BH6 4.47 40.00 -35.53 701.80 351.80 195.00 1053.60 1248.60

BH7 4.53 30.93 -26.40 175.70 82.70 195.00 258.40 453.40

BH7 4.53 31.00 -26.47 372.00 197.00 195.00 569.00 764.00

BH7 4.53 31.50 -26.97 700.60 340.60 195.00 1041.20 1236.20

Total and Effective in-situ Vertical Stresses

-40.00

-35.00

-30.00

-25.00

-20.00

-15.00

-10.00

-5.00

0.00

0.00 500.00 1000.00 1500.00

In-situ Vertical Stresses (kN/m2)

Le

ve

l (m

PD

) Total in-situvertical stresses

Effective in-situ

vertical stresses

5.10. Preconsolidation Pressures

Preconsolidation Pressures


(mPD) Depth

(m) Level (mPD)

Preconsolidation Pressure (kN/m2)

BH1 4.58 17.5 -12.92 87

BH3 4.53 14.5 -9.97 50

Preconsolidation Pressures

-14.00

-12.00

-10.00

-8.00

-6.00

-4.00

-2.00

0.00

0 2 4 6 8 10 12

Pressure (KN/m2)

Le

ve

l (m

PD

)

6. AVERAGE GEOLOGICAL PROFILE

The project site under discussion is location in the Chai Wan district of Hong Kong Island. Based on the geographic location of the site obtained from the CEDD website, it is quite likely that the site is located on reclaimed land. A review of the history of the site using Aerial Photographs may confirm whether or not the site is indeed located on reclaimed land however based on the available Site Investigation data for the project, it can be seen that up to 18m thick layer of fill material is present on site which indicated reclamation was carried on site at some point in time. Figure 1: The development of reclamation in Hong Kong to 2000 (CEDD Website)

Approximate Location of the Site

In terms of formation history, our site is located at the Che Kwu Shan formation near the Cape Collinson as shown on the figure below. Figure 2: Distribution of the volcanic rocks in Hong Kong (Sewell et al., 2000)

Based on the geological maps for The Che Kwu Shan Formation near the Cape Collinson Correctional Institution, it can be seen that the rock present on site comprises mainly dark grey to black rhyolitic crystal tuff, with a weak streaked appearance, and grey tuff-breccia. The former was generated by welding of very hot crystal ash particles. The clasts within the tuff-breccia are composed mainly of angular to subangular crystal tuff, and vary in size from a few centimetres up to about 8 cm. The tuff-breccia was probably formed by a flow of block and ash that resulted from the collapse of a growing lava dome. In contrast, the rhyolitic crystal tuff probably formed by a volcanic ash flow (GEO, 2007).

According to the site investigation fieldwork report of our project, the bedrock layer mainly consists of fine ash tuff with very closely spaced to extremely narrow joints. This result is in general consistent with the geological characteristics of the Che Kwu Shan Formation.

Based on a desk study of the project site the following observations and conclusions can be made about the soil layers and ground water conditions:

a. Fill: The fill on the project site matches quite well with typical cohessionless fills used in Hong Kong. The thickness of fill in our case is around 15m. Where older reclamations were extended, the later works may incorporate earlier structures such as concrete or masonry sea walls. There is sometimes seawall debris found in the boreholes which further support the evidence that this is indeed reclamation fill.

b. Marine Deposit: Generally in Hong Kong coastal areas, superficial marine deposits overly older alluvial deposits and the pre-Holocene eroded rock surface. In our case, particle size distribution results show that the marine deposit on site has a high percentage (80%) of silt/clay composition. It is also reasonable that the layout has a relatively high percentage of water content (52%).

c. Alluvium: Alluvium is defined as a detrital material of any grain size transported and deposited during comparatively recent geological time by a river or stream. Borehole logs show the shape of the layer is usually sub-rounded. The result is also foreseeable as soil carried by the medium of water usually has a rounded and uniformed shape.

Approximate location of the Site

d. Tuff: Beneath the alluvium is tuff at different stages of decomposition. For the layer of Completely Decomposed Tuff and Highly Decomposed Tuff (Grade V/IV), the thickness varies from 3.3m to 10.9m. For the Rockhead level, which is defined as the elevation below which there is at least 5m of Grade II or better rock with more than 85% core recovery, it vary from -37.10mPD to -45.00mPD across the site.

e. Ground water conditions: The ground water levels measured by standpipe are tabulated as follows.

Borehole No. BH1 BH3 BH8

Date Sept 1994 Oct 1994 Oct 1994 Ground Water Level +2.70 +2.61 +2.60

The values of 2.60mPD to 2.70mPD are relatively higher than that suggested by the Port Works Design Manual (CEDD 2002) in the Quarry Bay/ North Point location as shown below.

Location Period of Data Mean Sea Level

(mPD) Quarry Bay/ North Point 1981-1999 +1.30

Extra care should be paid for adopting the suitable values of ground water tables for design purposes.

7. ENGINEERING IMPLICATIONS ON DESIGN

a) Excavation Stability: Since the excavation is 11m deep it is quite likely that most of the retained soil will be the fill layer. Due to the cohessionless nature of the fill layer, there may be stability issues when designing for the Excavation and Lateral Support Works (ELS). Due to the low stiffness of the Fill layer, lateral deflection of the retaining wall might be an issue hence suitable lateral support measures will need to be provided in order to limit lateral movement of the wall and subsequent vertical ground settlement. Furthermore the retaining walls used will need a relatively large embedment depth in order to ensure the overall stability of the system.

b) Foundation: A shallow foundation may not be suitable for the current site since the building will consist of a 3-level underground parking structure and if a shallow foundation is used it is most likely to be footed on the fill layer. Hence a bearing capacity problem may arise hence it is recommended to adopt pile foundations. Pile foundation would penetrate through the Sand Fill and low strength MD and be founded in the underlying Alluvial Sand, CDG orRock depending on the load and form of piling.

c) Bearing Capacity of Frictional Pile: If frictional piles are adopted as the foundation, one of the potential problems that may arise is significant secondary consolidation settlement due to the presence of the Clay and Silt layers within the Marine deposit layer which has a maximum thickness of approximately 8m. If it is assumed that future secondary consolidation settlement will be significant, there is a potential of significant negative skin friction to be induced on the frictional piles which will reduce their capacity and make them less efficient. A 1-D consolidation test can be used to better estimate the current degree of consolidation of the clays to better predict whether future settlement will be significant or not.

d) Bearing Capacity of End-Bearing Pile: The bedrock is composed primarily of Grade II/II tuff which is generally much stronger and abrasive than granite with a UCS of up to 400MPa. From personal experience, it can be said that the ultimate bearing capacity values suggested in the Code of Practice of Foundations are normally on a very conservative side. In addition these values have been prescribed for granite rather than tuff. If end bearing piles are adopted and designed based on the Code of Practice for Foundations, it is quite likely that the required size and number of piles will be overestimated.

8. ADDITIONAL INVESTIGATION

8.1 Determination of Properties of Marine Clay

In order to determine the strength properties of the MD layer the following testing is recommended to ascertain the undrained shear strength of the Clay layer

1. SPTs may be carried out within the MD layer to get an idea of the consistency of the Clays (e.g Soft/ Firm/ Stiff). The SPt N Value may also be correlated to the undrained shear strength of the Marine Deposit layer, however this alone should not be used and should be supplemented with lab/field test results.

2. Field Vane Shear Testing: Vane Shear testing on site can be used to determine the undrained shear strength of the MD Clay layer since it does not cause disturbance of the soil layer. Vane shear test has an advantage that it is relatively quick and easy to perform. Also it has been used quite commonly in the industry and due to the marine nature of the MD layer; it will generally give reliable results.

3. In order to supplement the Vane Shear Tests results, Triaxial CU Lab tests using the total stress approach may be used to determine the Undrained Shear Strength. Guideline for such testing are prescribed in Geoguide 3.

4. As discussed earlier, the consolidation state of the MD layer may influence the choice of foundation hence a 1D oedometer lab test is suggested to determine the compressibility parameters of the MD layer and predict potential future settlement. The oedometer test can provide us with parameters such as the coefficient of consolidation, coefficient of volume compressibility and the compression index.

8.2 Determination of Parameters for Seepage Analysis

The following field/lab testing is proposed for the seepage analysis

1. Standpipes are proposed to be install din drill holes to ascertain the height of the water table 2. Constant Head Permeability Test is recommended on site to determine the permeability of the coarser layers such as the Fill and Alluvium 3. Falling Head Permeability test is recommended in low permeability soil such as the Marine Deposits that comprises mainly of clay.

9. INSTRUMNETATION AND MONITORING

The following appropriate instrumentation may be installed and monitored during the Excavation and Lateral Support Works:

1. Inclinometers in the retained soil outside the cofferdam 2. Settlement markers are recommended in the ground and existing structures and utilities if any 3. Porewater Pressure will be monitored by piezometers installed in observation wells outside the sheet pile cofferdam. 4. Survey/Tilt meters installed on the sheet piles to measure sheet pile deflection 5. Strain Gauges installed on struts.

Based on adopted design (Type of Sheet Pile/Size of Lateral Members, etc), an instrumentation and monitoring regime should be developed with suitable AAA values.

hamzanTypewritten Text6. Observation Wells with standpipes within the cofferdam to measure the level of ground water

hamzanTypewritten Text7. If sensitive structures or utilities are present nearby vibration points should be installed near these structures/utilities to measure the vibration in terms of peak particle velocity (ppv). It should be recorded at every meter length of penetration of pile, at final set and at levels where obstructions are encountered.

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