P964 01 15 00.12 10 EXHIBIT A Exploration Data.pdf

JACOBS

Shore to Ship Utilities, Naval Support Activity in Bahrain

Geotechnical Interpretive Report

ACTS-Q-11168/Rev.01

17/12/2019

EXHIBIT A - SECTION 01 15 00.12 10

For Information Only

Document Control

Client Name: JACOBS

Project Name: Shore to Ship Utilities, Naval Support Activity in Bahrain

Report Title: Geotechnical Interpretive Report

Report Ref.: ACTS-Q-11168/Rev.01

Details of Issue: Initial Report – For Information

Date: 17/12/2019

File Location: X:\2019\KSA\Q11168 - Shore to Ship Utilities, Naval Support Activity in

Bahrain\02 Reports\Q11168 - Shore to Ship Utilities, Naval Support

Activity in Bahrain - Rev01.docx

Document Checking:

Revision Date Prepared By: Checked By: Approved By:

00 26.11.2019 Charbel Matta Michel Saad Elie Khairallah

01 17.12.2019 Charbel Matta Michel Saad Elie Khairallah

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Geotechnical Interpretive Report

ACTS-Q-11168/Rev.01 Table of Content

Contents

1. INTRODUCTION

1.1. General

1.2. Site Description

2. FIELD WORKS

2.1. Summary of Field Works

2.2. Project Resources and Organization

2.3. Surveying – Setting Out

2.3.1. Drilling of Boreholes

2.4. Sampling

2.5. Logging Procedure

2.6. In-Situ Tests

2.6.1. Standard Penetration Test

2.7. Electrical Resistivity Tests

2.8. Backfilling of the boreholes

3. LABORATORY TESTING

3.1. General

4. REGIONAL GEOLOGY

5. GROUND MODEL

5.1. General

5.2. Characteristic and Design Values

5.3. Direct Shear Test Results

5.4. Geotechnical Parameters

5.5. Karst Features / Cavities

6. SHALLOW FOUNDATION ANALYSIS

6.1.1. General – Shallow Foundations

6.2. Bearing Capacity Criterion

6.3. Settlement Criterion – Burland and Burbidge (1985)

6.4. Results

6.4.1. Subgrade Reaction Modulus

7. PILE FOUNDATION ANALYSIS

7.1. Pile Foundations – General

7.2. Pile Foundations – Lateral Capacity

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7.3. Pile Foundations – Settlements

7.4. Analysis Results - Piles

7.5. Group Efficiency

8. RECOMMENDATIONS

8.1. Shallow Foundations

8.2. Pile Foundations

8.3. Ground Water

8.4. Excavation and Monitoring

8.5. Backfill

8.5.1. Suitable Material

8.5.2. Lateral earth Pressure

8.6. Seismic Parameters

8.7. Protection Against Concrete Deterioration

9. GENERAL NOTES

10. REFERENCES & DEFINITIONS

Tables Table 1: Borehole Details

Table 2: Standard Penetration Test Results

Table 3: Soil Resistivity Test Results Summary

Table 4: List of Laboratory Tests

Table 5: Idealized Subsurface Profile

Table 6: Summary of In-Situ and Lab Test Results for the Soil Layers

Table 7: Design Parameters for Analysis of Foundations

Table 8: General Recommendations for Bearing Capacities (B.O.F = 0.5m bEGL)

Table 9: Bearing Capacity for the Structure’s Foundations (B.O.F=0.5m bEGL)

Table 10: Recommendations for the Slab on Grade

Table 11: Recommendation for the Modulus of Subgrade Reaction

Table 12: Recommendations for the Unit Skin Friction and End Bearing

Table 13: Recommendations for the Lateral Modulus of Subgrade Reaction

Table 14: Pile Recommendations

Table 15: Pile Recommendations - Cont'd

Figures Figure 1: Project Site Location from Google Earth

Figure 2: General Geology of Bahrain

Figure 3: Detailed Stratigraphy of Bahrain

Figure 4: SPT Plot and Design Values

Figure 5: RQD Plot and Design Value

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Figure 6: UCS Plot and Design Value

Figure 7: Young Modulus of Intact Rock Ei Plot and Design Value

Figure 8: Plot of Angle of Friction (Direct Shear) vs. Elevation

Figure 9: Bearing Capacity Plot vs. Foundation Width (B.O.F = 0.5m bEGL)

Figure 10: Extract from ASCE7-10 Chapter 20

Appendices

Appendix A: Project Layout and Drawings Appendix B: Borehole Logs Appendix C: SPT Test Results Plot Appendix D: Electrical Resistivity Test Results Appendix E: Laboratory Test Results

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1. INTRODUCTION

1.1. General

At the request of JACOBS, Advanced Construction Technology Services (ACTS) have carried out a ground investigation campaign at the “Shore to Ship Utilities, Naval Support Activity in Bahrain”.

The field works commenced on September 18, 2019 and were completed on September 24, 2019.

This geotechnical report covers the factual data collected from the site works and the laboratory tests, the details of which are presented in the subsequent sections. The purpose of this investigation is to obtain detailed information about the surface and subsurface conditions. In addition, it provides the necessary recommendations on the most suitable foundation design for the proposed structure.

It should be noted that a previous ground investigation campaign was carried out for this site mentioned above and is presented in the following report:

GIR Ref. No. G/3144/HM April 2013 The results from the boreholes of this investigation campaign were taken into consideration for the data analysis in this report.

1.2. Site Description

The project comprises the construction of comprehensive utility distribution systems and an operational facility to provide dedicated quayside shore-to-ship utility for homeported and deployed ship berthed on NSA II in Bahrain. The ground elevations varied between +2.806m MSL and +3.898m MSL approximately. Figure 1 below represents an aerial view of the project site location from Google Earth.

Figure 1: Project Site Location from Google Earth

The drawings showing the project layout and structures are presented in Appendix A.

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2. FIELD WORKS

The field works for the proposed project comprised of drilling boreholes, performing in-situ testing and laboratory testing. The list of exploratory holes along with their respective depths, as-built coordinates and elevations are presented in Table 1.

Table 1: Borehole Details

BH

No.

Start Date End Date Easting

[UTM84-39R]

Northing

[UTM84-39R]

El.

[m MSL] Depth

[m]

BH-02 9/21/2019 9/21/2019 462,225.848 2,898,781.017 2.806 6

BH-04 9/22/2019 9/22/2019 461,974.364 2,898,531.121 2.857 6

BH-07 9/23/2019 9/23/2019 461,820.074 2,898,467.592 3.898 6

BH-08 9/24/2019 9/24/2019 461,889.763 2,898,502.395 3.738 6

BH-09 9/24/2019 9/24/2019 461,870.372 2,898,485.045 3.794 6

BH-10 9/23/2019 9/23/2019 461,852.429 2,898,503.916 3.753 6

BH-11 9/23/2019 9/23/2019 461,871.458 2,898,521.607 3.808 6

BH-12 9/19/2019 9/19/2019 461,706.116 2,898,805.207 3.487 6

BH-13 9/18/2019 9/19/2019 461,701.927 2,898,809.908 3.453 6

BH-14 9/18/2019 9/18/2019 461,680.165 2,898,823.310 3.536 6

BH-15 9/18/2019 9/18/2019 461,673.609 2,898,829.765 3.319 6

BH-16 9/18/2019 9/18/2019 461,677.966 2,898,839.758 3.227 6

2.1. Summary of Field Works

The site works completed on the project site are summarized as follows:

A. Drilling twelve (12) Nos of boreholes using rotary flushing techniques down to a depth of

6.0m each below the existing ground level with soil and rock sampling.

B. Soil sampling in boreholes using a split spoon sampler (SPT).

C. Carrying out in-situ Standard penetration tests (SPT) in drilled boreholes.

D. Carrying out two (02) Nos of Electrical Resistivity Tests.

2.2. Project Resources and Organization

In order to complete the above scope, ACTS mobilized one (01) drilling rig to the project site along with the necessary tools and competent personnel in order to supervise, coordinate the site activities and to carry out the required in‐situ tests, if any. The rig selected for this operation was equipped with an automatic SPT hammer and a wire‐line system for rock core and soil samples retrieval.

2.3. Surveying – Setting Out

The coordinates of the exploratory holes were provided and specified by the client JACOBS.

Setting out of each borehole was carried out by ACTS in accordance with ASTM D420-18 using a DGPS system with an accuracy less than 30 cm did setting out at each location.

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The above survey is in accordance with UTM84-39R grid for the reported horizontal coordinates and Mean Sea Level MSL (EGM96) for the reported elevations.

2.3.1. Drilling of Boreholes

Regular sampling using Standard penetration test (SPT) were carried out in Soils. Fresh non-saline water was used as a flushing medium. Casing was used to support the walls of the boreholes. The final borehole depth was measured and verified during and at the end of each boring using a dip meter.

2.4. Sampling

Sampling of soil, and groundwater was carried out in accordance with ASTM D420-18. The project number, borehole number, depth of sample, and the date of sampling labeled the retrieved samples. The retrieved samples were transferred to ACTS Warehouse in Riyadh upon completion of each borehole.

Standard penetration test (SPT) was carried out in accordance with ASTM D 1586 – 18. The disturbed soil samples retrieved from the split spoon were placed immediately in airtight plastic bags for classification purposes. The weight of these samples was varying depending on the length penetrated and the quantity retrieved from the split spoon.

2.5. Logging Procedure

The logging and description of soil samples was carried out in accordance with ASTM D420-18 - Standard Guide for Site Characterization for Engineering Design and Construction Purposes. The borehole logs are presented in Appendix B.

2.6. In-Situ Tests

2.6.1. Standard Penetration Test

Standard Penetration Tests (SPT) were carried out at 1.0m intervals along the full length of the borehole. The test was carried out in accordance with ASTM D 1586 – 18 to assess the relative densities of the ground materials.

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The SPT’s were corrected for the hammer efficiency based on the equation below:

𝑁60 =

𝑁.Ƞ𝐻.Ƞ𝐵.Ƞ𝑆.Ƞ𝑅

(Equation 1)

Where:

N SPT blows for the 300mm, N field ȠH Hammer Efficiency = 45% (Donut Hammer) ȠB Correction for Borehole Diameter, equals to 1 ȠS Sampler Correction, equals to 1 ȠR Correction for Rod length, varies with depth.

The standard penetration tests along with the corrected values are presented in the table below.

A plot of the SPT Test results is presented in Appendix C.

Table 2: Standard Penetration Test Results

BH No. Depth (m) El. (m MSL) ηR N N60

BH-02 0.4 2.41 0.75 29 16

BH-02 0.9 1.91 0.75 15 8

BH-02 1.4 1.41 0.75 14 8

BH-02 1.9 0.91 0.75 11 6

BH-02 2.4 0.41 0.85 17 11

BH-02 3.0 -0.19 0.85 22 14

BH-02 3.5 -0.69 0.85 25 16

BH-02 4.0 -1.19 0.95 29 21

BH-02 5.0 -2.19 0.95 32 23

BH-04 0.3 2.60 0.75 30 17

BH-04 0.8 2.11 0.75 41 23

BH-04 1.3 1.61 0.75 12 7

BH-04 1.8 1.11 0.75 5 3

BH-04 2.3 0.61 0.85 10 6

BH-04 3.0 -0.14 0.85 13 8

BH-04 4.0 -1.14 0.95 33 24

BH-04 5.0 -2.14 0.95 24 17

BH-07 2.0 1.90 0.85 9 6

BH-07 2.5 1.40 0.85 28 18

BH-07 3.0 0.90 0.85 24 15

BH-07 4.0 -0.10 0.95 19 14

BH-07 5.0 -1.10 0.95 10 7

BH-08 2.0 1.74 0.85 6 4

BH-08 2.5 1.24 0.85 4 3

BH-08 3.0 0.74 0.85 4 3

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BH No. Depth (m) El. (m MSL) ηR N N60

BH-08 4.0 -0.26 0.95 4 3

BH-08 5.0 -1.26 0.95 5 4

BH-09 2.0 1.79 0.85 6 4

BH-09 2.5 1.29 0.85 2 1

BH-09 3.0 0.79 0.85 6 4

BH-09 4.0 -0.21 0.95 13 9

BH-09 5.0 -1.21 0.95 12 9

BH-10 2.0 1.75 0.85 5 3

BH-10 2.5 1.25 0.85 4 3

BH-10 3.0 0.75 0.85 2 1

BH-10 4.0 -0.25 0.95 5 4

BH-10 5.0 -1.25 0.95 6 4

BH-11 2.0 1.81 0.85 12 8

BH-11 2.5 1.31 0.85 32 20

BH-11 3.0 0.81 0.85 21 13

BH-11 4.0 -0.19 0.95 19 14

BH-11 5.0 -1.19 0.95 9 6

BH-12 2.5 0.99 0.85 7 4

BH-12 3.0 0.49 0.85 4 3

BH-12 3.5 -0.01 0.85 2 1

BH-12 4.0 -0.51 0.95 2 1

BH-12 5.0 -1.51 0.95 13 9

BH-12 5.5 -2.01 0.95 7 5

BH-13 2.3 1.15 0.85 8 5

BH-13 2.8 0.65 0.85 9 6

BH-13 4.2 -0.75 0.95 >50 50

BH-13 5.2 -1.75 0.95 9 6

BH-14 2.0 1.54 0.85 43 27

BH-14 3.0 0.54 0.85 9 6

BH-14 4.0 -0.46 0.95 3 2

BH-14 5.0 -1.46 0.95 7 5

BH-15 2.0 1.32 0.85 29 18

BH-15 2.5 0.82 0.85 7 4

BH-15 3.0 0.32 0.85 6 4

BH-15 4.0 -0.68 0.95 3 2

BH-15 5.0 -1.68 0.95 4 3

BH-16 2.0 1.23 0.85 13 8

BH-16 2.5 0.73 0.85 5 3

BH-16 3.0 0.23 0.85 2 1

BH-16 4.0 -0.77 0.95 5 4

BH-16 5.0 -1.77 0.95 49 35

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2.7. Electrical Resistivity Tests

The electrical resistivity tests were carried out at the specified locations in accordance with IEEE Std 81-1983 using Wenner’s Four-Electrode Method. In Wenner electrode configuration, four electrodes are inserted into the ground at equal distance apart in a straight line. The outer electrodes are used as current electrodes while the inner ones act as potential electrodes. The ground is energized with the help of a battery pack. The current passing through the two current electrodes and the resulting difference between the two potential electrodes are recorded from the instrument. The natural or stray currents in the ground are nullified by the instrument. When the null detector is balanced, using the range switch and the dial, the resistance in ohms between potential electrodes is measured. The resistivity of the ground is calculated as follows:

ρ = R × K (Equation 2)

Where:

R = Resistance (Ohm)

K = 2 Π a (Wenner’s configuration shape factor) a = Electrode spacing (meter)

As the depth of measurement is dependent upon electrode spacing, the readings was taken starting from smaller electrode spacing and increased symmetrically with respect to center of electrode configuration. Readings at electrode spacing of 1.5m, 3.0m and 4.5m (common standard electrode spacing used for the soil resistivity test) were taken in two directions at all ERT locations. For each electrode spacing apparent electrical resistivity values were calculated using the above-mentioned formula.

Table 3: Soil Resistivity Test Results Summary

Test # Location Electrode Spacing

[cm]

Resistivity [Ω.m]

Longitudinal Direction Transverse Direction

ERT-1 Area 2 - SFUS

150 9.90 9.80

300 5.09 8.48

450 3.68 4.81

ERT-2 Area 2 - 1B

150* 13.00 15.27

300* 51.27 57.30

450* 42.98 47.22

*It is suspected that a cable might be passing in the vicinity and might be the reason for the unusual reading.

The soil resistivity results above can be adopted during the design of the grounding system or taken into account for any pipeline or other material that could be subject to corrosion.

Detailed results are presented in Appendix D.

2.8. Backfilling of the boreholes

Upon completion of the field works, the boreholes were grouted immediately as per the client instructions.

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3. LABORATORY TESTING

3.1. General

Upon completion of the site works, laboratory testing programs were prepared in accordance with the project specifications and the approved Bill of Quantities. Afterwards, the testing programs were provided to the laboratory along with the selected samples. All necessary geotechnical laboratory testing was carried out on selected soil and groundwater samples recovered from the boreholes in order to determine the physical, chemical and strength properties of the ground materials. The scope of laboratory testing with the used standard test methods are summarized in Table 4 below.

Table 4: List of Laboratory Tests Type Test Standard Test Method Qty

Soil

Sieve Analysis ASTM D422 29

Moisture Content ASTM D2216 29

Atterberg Limits ASTM D4318-17 29

Material Finer Than 75μm ASTM D1140 29

Unit Weight D7263 29

CBR ASTM D1883 9

Modified Proctor ASTM D1557-12e1 9

Direct Shear ASTM D3080/D3080M-11 6

Chemical

Gypsum Content BS1377-3:1990 Clause 5 16

Organic Matter Content ASTM D2974-14 16

Chloride ASTM C1580 / ASTM D1411 / BS1377-3:1990 Clause 5 16

Sulfate ASTM C1580 / ASTM D1411 / BS1377-3:1990 Clause 5 16

The laboratory test results along with their summaries are presented in Appendix E.

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4. REGIONAL GEOLOGY

Situated in the west central part of the Arabian Gulf, the Kingdom of Bahrain is an archipelago of more than 36 islands, shoals and small islets (Bahrain’s second national communication, 2012). It consists of a group of low-lying islands between the Qatar Peninsula and Saudi Arabia at approximately lat 26° N., long 50°30' E. The main island of Bahrain is about 48.3 kilometers long and 16.1 kilometers wide and reaches a maximum altitude of 134.1 meters at Jabal al Dukhan near its geographical center (R. P. WILLIS, 1963).

The Bahrain anticlinal axis is oriented in a north-south direction and the structure is fairly simple with no faults visible at the surface. Most faults observed in the subsurface have displacements of less than 15.2m and all are classified as normal tension faults.

The principal outcropping rocks on Bahrain Island are of early and middle Eocene age, with Miocene and younger rocks evident along the periphery (Figure 2). Recent deposits are concentrated in the southern and southwestern parts of the island in the Ra's al Barr and Ra's al Jaza'ir areas.

Eocene and Miocene rocks are also exposed in the Huwar Islands to the southeast, but the other small islands of the Bahrain Group are limited to Pleistocene and Recent deposits, with the exception of Umm Na'san, which appears to have some Miocene deposits. The dominant rock types within the Eocene and Miocene of Bahrain are limestone, dolomitic limestone, and chalk, with subsidiary marls and shales as observed in (Figure 3), (Ziegler, 2001).

Evidence of wind sculpturing can be seen throughout the islands, erosional remnants and striations have a predominant NNW orientation. A prominent topographic feature of Bahrain is the rimrock of Eocene limestone which forms a complete ring around the central part of the island. This rimrock is some places support a cliff face in excess of 30.5m.

An angular unconformity is indicated between middle Eocene and younger rocks by variations in thickness of the uppermost Eocene unit and by a change in lithology of the Miocene rocks to a sandier appearance.

Recent beach sands are found on all islands of Bahrain, but the most noteworthy deposits occur on Bahrain Island in the Ra's al Jaza'ir and Ra's al Barr areas. In these areas extensive salt flats and marshes (Sabkha deposits). There is also much evidence of Recent limestone and calcareous-mud deposition in the shallow near-shore water of Bahrain (Mahmoud et al., 1992).

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Figure 2: General Geology of Bahrain

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Figure 3: Detailed Stratigraphy of Bahrain

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5. GROUND MODEL

5.1. General

The information obtained from field works and laboratory testing indicates that the subsurface stratigraphy generally consists of a fine to medium silty Sand having variable densities and strength. Thin layers of sandy silts or gravels were also encountered occasionally throughout the borehole depth. Inclusions of very weak to weak sandstone or limestone embedded with silt, shells and voids at a depth around 4.50m and 5.0m bEGL in BH-12-13-14-15 & 16. The particle size distribution tests classify mainly the soil as poorly graded sand with silts, and the Atterberg limits, when applicable, showed generally low PI values.

Given the inconsistency in the material density and strength throughout the boreholes and even in the same borehole, a conservative approach was adopted to assign the geo-mechanical parameters for the upper soil layers.

Furthermore, since the borehole depth of the current investigation campaign is limited to 6.0m, the findings from the GIR Ref. G/3144/HM April 2013 will be incorporated within this report, especially for the analysis of the deeper soil layers. Accordingly, the subsurface stratigraphy was found to be consisting of two (02) geologic units:

Sand / Gravel / Silt (1a & 1b): The topmost unit, having a thickness between 10m and 12m approximately consists of interbedded layers of silty sands, gravels, or sandy silts with presence of shells and highly weathered fragments of sandstone, limestone or calcarenite. The upper part of this unit, extending down until a depth of 8.0 m bEGL approximately, presented the presence of very weak inclusions along with a high variation in the SPT results and therefore this formation was subdivided into two separate layers 1a & 1b.

Weathered Calcisiltite / Calcisitite / Calcilutite (2a & 2b): Layers 1a & 1B are followed by a highly weathered Calcisiltite formation (2a) having a thickness of 2.0m approximately and showing high SPT values. Following 2a is the Calcisiltite and Calcilutite layers extending down until the end of the borehole exploratory depth. These formations were recovered as very weak to weak and moderately weathered material with fractures closely to medium spaced, and on few occurrences they were recovered as non-intact core of fractured weak rock. The Calcisitite and Calcilutite layers showed similar properties and are treated therefore as a single unit (1b).

The idealized sub-surface profile along with the summary of the lab and in-situ test results are presented in the table below.

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Table 5: Idealized Subsurface Profile

Layer No. Unit Description Top El.

[m bEGL] Bottom El.

[m bEGL]

Layer Thick. [m]

1a Silty Sand 0.0 8.0 8.0

1b Sand / Gravel 8.0 12.0 4.0

2a Weath. Calcisiltite 12.0 14.0 2.0

2b Calcisiltite/Calcilutite 14.0 Undet* Undet*

*Undetermined

Table 6: Summary of In-Situ and Lab Test Results for the Soil Layers

Test Unit No. of Tests Min. Max. Average St. Dev.

Layer 1a

PSD – Gravel % 29 2.40 56.90 25.16 17.66

PSD – Fines % 29 5.40 51.20 16.44 11.69

PSD – Sand % 29 30.10 91.10 58.41 19.73

Material Finer than 75µm (%)

% 29 4.00 57.00 16.86 13.21

Unit Weight Wet kN/m3 29 13.95 19.55 16.62 1.11

Dry kN/m3 29 12.03 17.92 15.57 1.38

PI % 9 6.00 40.00 13.22 10.22

Mod. Proctor MDD kg/m3 9 1,782 2,160 1,980 135

OMC % 9 7.00 20.66 10.77 3.96

CBR (at 95% MDD) % 9 22.00 94.50 48.12 20.81

Direct Shear Phi deg 6 13.61 34.86 26.39 7.45 c kPa 6 33.30 43.30 39.38 3.32

SPT Nfield - 66 2 50 14 11.99

The results from the previous ground investigation campaign are not included in the table above.

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5.2. Characteristic and Design Values

In accordance with Eurocode 7 Geotechnical Design-General Rules (EN 1997-1), the characteristic values will be at 95% level of confidence for a data collected from test results.

XDesign = �̅� − 1.96 × 𝜎

√𝑛 (Equation 3) x̅ = Average Value σ = Standard Deviation N = Number of Data Points

However, the design value will be taken as the minimum between the values computed using Equation 3 and the following:

XDesign = �̅� − 0.5 × 𝜎 (Equation 4)

Using the above methods, the design value of each parameter was derived. The plots for the SPT, RQD, UCS and Ei are presented in the figures below.

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Figure 4: SPT Plot and Design Values

5, 2.6

5, -5.5 24, -5.5

24, -9.5 50, -9.5

50, -11.5-11.5

-10.5

-9.5

-8.5

-7.5

-6.5

-5.5

-4.5

-3.5

-2.5

-1.5

-0.5

0.5

1.5

2.5

3.5

0 5 10 15 20 25 30 35 40 45 50

El ev at io n m M

SL

SPT N60

BH-02 BH-04 BH-07 BH-08 BH-09

BH-10 BH-11 BH-12 BH-13 BH-14

BH-15 BH-16 Previous BH Design Line

1a - Sand / Silt

1b - Sand / Gravel

2a - Weathered Calcisiltite

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Figure 5: RQD Plot and Design Value

32, -11.5

32, -22.0 -22

-21

-20

-19

-18

-17

-16

-15

-14

-13

-12

-11

-10

-9

-8

0 10 20 30 40 50 60 70 80 90 100

El ev at io n m M

SL

RQD [%]

Previous BH Design Line

2b - Calcisiltite / Calcilutite

2a - Weathered Calcisiltite

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Figure 6: UCS Plot and Design Value

1.50, -11.50

1.50, -20.00-20.00

-19.00

-18.00

-17.00

-16.00

-15.00

-14.00

-13.00

-12.00

-11.00

-10.00

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00

El ev at io n m M

SL

UCS [MPa]

Previous BH Design Line

2a - Weathered Calcisiltite

2b - Calcisiltite / Calcilutite

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Figure 7: Young Modulus of Intact Rock Ei Plot and Design Value

210, -11.50

210, -20.00 -20.00

-19.00

-18.00

-17.00

-16.00

-15.00

-14.00

-13.00

-12.00

-11.00

-10.00

150 175 200 225 250 275 300 325 350 375 400

El ev at io n m M

SL

Ei [MPa]

Previous BH Design Line

2a - Weathered Calcisiltite

2b - Calcisiltite / Calcilutite

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5.3. Direct Shear Test Results

The direct shear tests carried out indicate that the angle of friction varies between 33.30 and 43.30, and the cohesion varies between 13.61kPa and 34.86kPa. The cohesion was conservatively neglected in the analyses. On the other hand, the angle of friction was solely derived based on the results of the SPT’s. This is due to the fact that usually the sand specimen tested are disturbed and will not correctly represent the actual in-situ conditions. However, prior to carrying out the direct shear test, the sample was handled in such manner to represent as much as possible the initial in-situ conditions and keeping the disturbance to a minimum. A plot of angle of friction from the direct shear test versus depth is provided below.

Figure 8: Plot of Angle of Friction (Direct Shear) vs. Elevation

It should be also noted that the direct shear tests were carried out at fairly shallow samples and SPT tests were not carried out on the same. The results of the direct shear tests indicate that the top 2.0m below existing grade indicate fairly competent material with angles of friction varying between 33 and 43 approximately, and cohesion varying between 13 and 34kPa.

5.4. Geotechnical Parameters

In light of the above, the strength and stiffness properties of the soil are estimated based on the recommendations and provisions provided in CIRIA R143. The method of Peck Hanson and Thornburn (1974) and that of Burland and Burbidge (1982) was used to determine the angle of friction (Φ) and the Young’s Modulus (E) respectively.

1.50

2.00

2.50

3.00

3.50

4.00

30 32 34 36 38 40 42 44

El ev at io n m M

SL

Angle of Friction φ [Deg]

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ACTS-Q-11168/Rev.01 Page | 22

The strength and stiffness properties of rock mass are estimated based on Hoek‐Brown generalized criterion (2002) which was established to derive the equivalent Mohr-Coulomb strength parameters for the rock mass.

The main input parameters of this criterion, for a given rock mass, are as follow:

UCS (Unconfined Compressive Strength): The adopted values for each rock layer, in our calculations, are shown below. The value was chosen based on the criteria set out above

GSI (Geological Strength Index): The adopted values for each rock layer, in our calculations, are shown below. This was calculated based on the recommendations of Bieniawski (1979) and assuming that GSI = RMR – 5.0 mi (material constant): based on type of rock (assumed based on Hoek-brown generalized criterion)

D (disturbance factor) = 0.0

The elastic modulus for weak rock are estimated based on the recommendation provided by Boyd in CIRIA R181 as follows (with RMR = rating number before adjustment for joints):

𝐸𝑚 = 3.5 (𝑅𝑀𝑅)3.75/1000 (𝑀𝑃𝑎) (Equation 5)

The design parameters of sub-strata, presented below in Table 7, are valid only for foundation design.

Table 7: Design Parameters for Analysis of Foundations

Layer No.

N60

RQD

UCS

[MPa]

Ei [MPa]

GSI

ɣ

[kN/m3] c

[kPa] ɸ

[deg] E

[MPa] ν K0 Ka Kp

1a 5 - - - - 16.0 - 30 5 0.30 0.50 0.33 3.00

1b 24 - - - - 17.0 - 34 24 0.30 0.44 0.28 3.54

2a 50 - - - - 18.0 - 41 50 0.30 0.34 0.21 4.81

2b - 32 1.50 210 38 19.0 69 26 90 0.30 0.70 0.39 2.56

5.5. Karst Features / Cavities

Open karst features/ cavities were not encountered within the drilled depths at the time of the investigation. Nevertheless, it should be noted that cavities could be encountered within the project site since the boreholes logs and related information represent the subsurface conditions only at the specified boreholes locations and the time at which the investigation was carried out.

We would like to point out that the low total core recoveries recorded during the investigation are due to presence of silt matrix material mostly washed out during drilling.

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ACTS-Q-11168/Rev.01 Page | 23

6. SHALLOW FOUNDATION ANALYSIS

6.1.1. General – Shallow Foundations

With little knowledge about the embedment depth and footing dimensions, the analysis will be carried out with an assumed depth of 0.5m bEGL as the bottom of foundations. The calculations will be carried out for the given dimensions of the structures’ foundations as well as for generic foundation dimensions. The allowable bearing capacity will comply with the following:

ULS Criteria: The foundation has adequate factor of safety against ultimate failure.

SLS Criteria: The foundation does not exhibit excessive settlement, which could cause damage to the super-structures. It was assumed that the maximum allowable settlement is 25mm for spread footings and 50mm for raft foundations.

The ultimate bearing capacity shall be determined using the general bearing capacity equation corresponding to the maximum pressure associated with the foundation general shear mode of failure (ULS Criteria). The settlement calculations are calculated using the equations defined below.

It should be noted that the allowable bearing capacity for foundations on granular soils are usually governed by the SLS criteria. If this is the case, the allowable bearing capacity will be the load resulting in a settlement of 25mm for isolated footings and 40mm for raft foundations. This is reflected in the calculations below.

6.2. Bearing Capacity Criterion

Referring to Principle of Foundation Engineering (2014), the allowable bearing capacity can be calculated using the Meyerhoff’s Euqation as:

qu = c′𝑁𝑐𝐹𝑐𝑠𝐹𝑐𝑑𝐹𝑐𝑖 + 𝑞𝑁𝑞𝐹𝑞𝑠𝐹𝑞𝑑𝐹𝑞𝑖 + 0.5𝛾′𝐵𝑁𝛾𝐹𝛾𝑠𝐹𝛾𝑑𝐹𝛾𝑖 (Equation 6) qu = Ultimate bearing capacity (kPa) c’ = Cohesion of soil (kPa) q = Effective stress at the level of the bottom of foundation (kPa)

B = Foundation width (m)

FcsFqsFγs = Shape factors

FcdFqdFγd = Depth factor

FciFqiFγi = Load inclination factor γ = Unit weight of soil (kN/m3)

Nc, Nq, Nϒ = Bearing capacity factors orm ati on

ACTS-Q-11168/Rev.01 Page | 24

6.3. Settlement Criterion – Burland and Burbidge (1985)

The settlement of shallow foundations on granular soils can be calculated using Burland and Burbidge’s (1985) SPT based method which relies on a regression analysis of 100 case records of settlement gathered by Burbidge (1982).

For normally consolidated sand the average settlement, ρ, at the end of construction, for a surface foundation is:

𝜌 = 𝑞′. 𝐵0.7. 𝐼𝑐 (Equation 7)

Where:

𝜌 = Settlement (mm) q’ = Average effective foundation pressure (q-u)

B = Breadth of loaded area

Ic = Compression Index = 1.71/N1.4

In deriving the compression index, Ic, too many cases may require the use of corrected N values:

(i) For very fine, silty sand, below the water table: N = 15+0.5 (Nmeasured - 15)

(ii) for gravel or sandy gravel: N = 1.25 Nmeasured

The following influence factors should be used whenever the influence from L/B ratio, thickness of the compressible layer below the foundation and time should be included:

(i) for L/B>1 𝑓𝑠 = ( 1.25𝐿/𝐵

𝐿

𝐵 )+0.25

)2 For which fs 1.56 as L/B ∞

(ii) for limited thickness of compressible material (Hs) below the foundation 𝑓1 = 𝐻𝑠

𝑍1 (2 −

𝐻𝑠

𝑍1

(iii) for estimating settlements more than three years after the end of construction 𝑓𝑡 = (1 + 𝑅3 + 𝑅𝑡 𝑙𝑜𝑔 𝑡

Where:

R3=proportion of end-of-construction time-dependent settlement occurring in the three-year period following construction

Rt=the proportion of end-of=construction settlements taking place during each log cycle of time after three years.

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ACTS-Q-11168/Rev.01 Page | 25

6.4. Results

Based on the above, the recommendations for the bearing capacities and subgrade reaction modulus are provided below. It should be noted that the Modulus of Subgrade Reaction (ks) was calculated by dividing the allowable bearing capacity by the settlement.

Table 8: General Recommendations for Bearing Capacities (B.O.F = 0.5m bEGL)

B [m] L/B = 1 L/B = 2 L/B = 3 L/B = 5 qall [kPa] Se [mm] qall [kPa] Se [mm] qall [kPa] Se [mm] qall [kPa] Se [mm]

1 95 25.0 78 25.0 72 25.0 68 25.0

2 60 25.0 50 25.0 46 25.0 44 25.0

3 46 25.0 39 25.0 36 25.0 34 25.0

5 34 25.0 28 25.0 27 25.0 25 25.0 qall : Allowable Bearing Capacity

Se: Settlement Below the Foundation

Figure 9: Bearing Capacity Plot vs. Foundation Width (B.O.F = 0.5m bEGL)

0 1 2 3 4 5 6 q al l [k

P a]

Foundation Width B [m]

L/B = 1 L/B = 2 L/B = 3 L/B = 5

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ACTS-Q-11168/Rev.01 Page | 26

The bearing capacity and settlements for the foundations of the Electrical Hotel Station and the 150kW Generator based on the provided dimensions are presented in the table below.

Table 9: Bearing Capacity for the Structure’s Foundations (B.O.F=0.5m bEGL)

Structure

Foundation Dimensions

Embedment Depth

Max. Allowable load Estimated Service Load

B [m] L [m] D [m] qall [kPa] S0[mm] Q [kPa] Se[mm]

Electrical Hotel Station 2.0 9.0 0.5 44 24.4 16.8 7.1

150kW Generator 1.2 4.8 0.5 62 24.7 24.0 7.6

A slab on grade is proposed as well for CMU and/or other structures. The bearing capacity for a slab on grade with generic dimensions is provided in the following table:

Table 10: Recommendations for the Slab on Grade Dimensions [m x m] Embedment Depth [m] qall [kpa] Se[mm]

10 x 10 0.3 150 40.0

15 x 15 0.3 115 40.0

6.4.1. Subgrade Reaction Modulus

The value of the subgrade reaction modulus k is generally not constant for a given soil, but rather depends on several factors, such as the dimensions of the foundation and the embedment depth.

However many methods are available in the literature to estimate the coefficient subgrade reaction, which three of them are presented below:

Method 1:

𝑘 = 𝑘0.3( 𝐵+0.3

2𝐵 )2 (DAS, 2015) (Equation 8) k0.3 = Coefficient of subgrade reaction of foundations measuring 0.3m x 0.3m, kN/m3 k = Coefficient of subgrade reaction of foundations measuring B (m) x B (m), kN/m3

Method 2:

𝑘 = 0.65 × √ 𝐸𝑠×𝐵4

𝐸𝑏×𝐼

𝐸𝑠

𝐵×(1−𝜈2) (Vesic, 1961) (Equation 9)

Where:

K = Modulus of Subgrade Reaction Es = Elastic Modulus of Founding Strata Eb = Elastic Modulus of Concrete νs = Poisson Ratio I = Moment of Inertia of the Foundation orm ati on

ACTS-Q-11168/Rev.01 Page | 27

Method 3:

𝑘 = 40 (𝑆𝐹)𝑞𝑎 (Bowles) (Equation 10)

Where:

K = Modulus of Subgrade Reaction, kN/m3 SF = Safety Factor qa = Allowable Bearing Capacity of the foundation, kPa

Based on the above, the estimated values for the modulus subgrade reaction for a slab on grade with dimension B = L = 10.0 m are presented in the table below:

Table 11: Recommendation for the Modulus of Subgrade Reaction Slab on Grade Dimensions

[m x m]

Modulus of Subgrade Reaction k [MPa/m]

Method 1 Method 2 Method 3

10 x 10 5.5 7.5 18.0 orm ati on

ACTS-Q-11168/Rev.01 Page | 28

7. PILE FOUNDATION ANALYSIS

7.1. Pile Foundations – General

Pile foundations are proposed for the CUB and/or other structures of the project. We have assumed that the cut-off levels of the pile foundations are at a depth of 0.50m below existing grade.

The recommendations provided in CIRIA 143 and CIRIA 181 will be used to compute the allowable pile capacities. Given the granular nature of the sub-surface, the pile will derive its capacity from skin friction and end bearing. This is shown in the equation below:

Qp,u = Qb,u + Qs,u = qb x Ab + fs x As (Equation 11)

Where:

Qp,u = Ultimate Pile Compression Capacity, kN

Qb,u = Ultimate End Bearing Capacity, kN

Qs,u = Ultimate Skin Friction Capacity, kN qb = Ultimate Unit End Bearing Resistance, kPa

Ab = Area of Pile Base = π / 4 x D2, m2 fs = Ultimate Unit Side Friction Resistance, kPa

As = Shaft Area = π x D x L, m2

The equations used for the calculation of the skin friction and end-bearing capacities in sands are presented below:

Ultimate Unit Skin Friction in Soil layers:

fs = β x σ’v (O’Neill and Hassan 1994) (Equation 12)

Where:

fs = Ultimate Unit Shaft Resistance, kPa β = (NSPT/15) x (1.5 – 0.245 z0.5) for N <15 (z in meters) or = 1.5 – 0.245 z0.5 for N >15 (z in meters) σ’v = Effective stress, kPa

Ultimate Unit Skin Friction in Weak Rock layers:

fs = 0.33 x (σc)0.5

(Horvath1978) (Equation 13)

Where:

fs = Ultimate Unit Shaft Resistance, MPa σc = Uniaxial Compressive Strength, MPa orm ati on

ACTS-Q-11168/Rev.01 Page | 29

Ultimate End Bearing Resistance in Weak Rock:

qb = 2.5 σc (Rowe and Armitage 1987b) (Equation 14)

Where:

fs = Ultimate Unit Shaft Resistance, MPa σc = Uniaxial Compressive Strength, MPa

Based on the above, the following values for the unit skin friction and end bearing can be computed:

Table 12: Recommendations for the Unit Skin Friction and End Bearing

Layer Ultimate Skin Friction, fs,u [kPa] Ultimate End Bearing, qb,u [kPa]

1a - -

1b 45 -

2a 100 -

2b 400 3,750

1) The skin friction in Layer 1a was conservatively neglected during the analysis, given the inconsistency throughout the material and the presence of inclusions of very loose strata.

2) The end bearing capacity is only provided for layer 2b as the piles will be embedded in the rock formation.

It should be noted that the allowable skin friction and end bearing capacities were calculated as follows:

Qs,a = Qs,u / FoSskin friction (Allowable Skin Friction Capacity)

Qb,a = Qb,u / FoSend bearing (Allowable End Bearing Capacity)

In accordance with BS8004, an appropriate factor of safety for a single pile would be between two and three. Low values within this range may be applied where the ultimate bearing capacity has been determined by a sufficient number of loading tests or where they may be justified by local experience; higher values should be used when there is less certainty of the value of the ultimate bearing capacity. As such, the following factors of safety were used:

FoSskin friction= Skin Friction FoS = 2.5

FoSend bearing= End Bearing FoS = 3.0

7.2. Pile Foundations – Lateral Capacity

The ultimate lateral pile capacity was calculated in accordance with the recommendations provided in Broms (1964) for piles in cohesionless soils according to the equation below:

PL,u = 3 D kp σ’v (Equation 15)

Where:

D = Diameter of the Pile Kp = Passive Earth Pressure Coefficient σ’v = Average Effective Stress orm ati on

ACTS-Q-11168/Rev.01 Page | 30

The horizontal soil stiffness will be calculated using an approximation proposed by Joseph E.

Bowles, by doubling the value of vertical subgrade reaction modulus, since the soil surrounds the pile, producing a considerable side shear resistance:

Kh = 2 x Kv (Equation 8)

Based on the above the estimation of the lateral modulus of subgrade reaction for each layer as presented below:

Table 13: Recommendations for the Lateral Modulus of Subgrade Reaction

Layer No. Lateral Modulus of Subgrade Reaction, kh [MPa/m]

1a 6

1b 30

2a 70

2b 130

A detailed lateral pile analysis should be carried out using software such as LPILE, ALP, WALLAP, etc… Based on the analysis the lateral capacity might be increased. Furthermore, it should be noted that the above values are independent of the structural capacity of the pile.

7.3. Pile Foundations – Settlements

The settlement of the pile foundations was estimated using the method suggested by W.G.K.

Fleming (1992). The method presents the analysis and prediction of single pile behavior under maintained loading, based on the use of hyperbolic functions to describe individual shaft and base performance. When these functions are combined, and elastic pile shortening is added by a relatively simple procedure, an accurate model is obtained. Extensive use of the procedure has confirmed its validity for maintained load tests in a wide range of soils. The analysis procedure can be summarized by the following equations:

∆t= −g ± √(g2−4fh)

2f (Equation 16)

∆𝑡 = Total Load Settlement (mm) g = d.PT + e.c.PT – a.d – b.c f = e.PT – a.e – b h = c.d.PT a = US b = DB x EB x UB c = MS x DB d = 0.6 x UB e = DB x EB

UB = Ultimate End Bearing (kN)

EB = Soil Elatic Modulus (kPa)

DB = Pile Diameter (m)

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ACTS-Q-11168/Rev.01 Page | 31

MS = Shaft Flexibility Factor Depending on Soil Type

PT = Pile Working Load (kN)

US = Ultimate Skin Friction (kN)

The elastic shortening of the pile shaft under load is added to the settlement calculated above, and depends on the relative development of load transfer between the pile and soil along its length, as well as on any free length or near friction-free length at the pile head, and on the load being transferred at the pile base. The elastic shortening is calculated using one of the two equations below:

If PT < US : ∆E=

Π

PT(L0+KELF)

Ds

2EC

(Equation 17)

If PT > US : ∆E=

Π

Ds

2EC

. (PT(L0 + LF) − LFUS(1 − KE)) (Equation 18)

Where:

ΔE = Elastic Shortening (mm)

L0 = Friction Free or Low Friction Zone Length (m)

LF = Frictional Load Transfer Length (m)

KE = Centroid of Friction Transfer

EC = Elastic Modulus of Concrete (kPa)

7.4. Analysis Results - Piles

Based on the sections above, the recommendations for the piles are provided below in Table 14 and Table 15.

The following should be noted:

Qs,u = Ultimate Skin Friction Capacity - Compression

Qp,u = Ultimate End Bearing Capacity – Compression

Qt,u = Total Ultimate Capacity - Compression

Qs,a = Allowable Skin Friction Capacity - Compression

Qp,a = Allowable End Bearing Capacity – Compression

Qt,a = Total Allowable Capacity - Compression

Qtens,a = Total Allowable Capacity - Tension

Se = Pile Settlement kv = Equivalent Spring Constant

Pl,u = Ultimate Lateral Pile Resistance

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ACTS-Q-11168/Rev.01 Page | 32

Table 14: Pile Recommendations

Dia. Length Qs,u Qp,u Qt,u Qs,a Qp,a Qt,a Qtesn,a [mm] [m] [kN] [kN] [kN] [kN] [kN] [kN] [kN]

15.0 1,772 1,060 2,832 709 353 1,062 591

15.5 2,149 1,060 3,209 860 353 1,213 716

16.0 2,526 1,060 3,586 1,010 353 1,364 842

16.5 2,903 1,060 3,963 1,161 353 1,515 968

17.0 3,280 1,060 4,340 1,312 353 1,665 1,093

17.5 3,657 1,060 4,717 1,463 353 1,816 1,219

18.0 4,034 1,060 5,094 1,614 353 1,967 1,345

15.0 2,362 1,885 4,247 945 628 1,573 787

15.5 2,865 1,885 4,750 1,146 628 1,774 955

16.0 3,368 1,885 5,253 1,347 628 1,975 1,123

16.5 3,870 1,885 5,755 1,548 628 2,176 1,290

17.0 4,373 1,885 6,258 1,749 628 2,378 1,458

17.5 4,876 1,885 6,761 1,950 628 2,579 1,625

18.0 5,378 1,885 7,263 2,151 628 2,780 1,793

Table 15: Pile Recommendations - Cont'd

Dia. [mm] Length [m] Qt,a [kN] Se [mm] kv [kN/mm] PLU [kN]

15.0 1,062 2.60 408.0

15.5 1,213 2.78 436.4

16.0 1,364 3.00 454.5

16.5 1,515 3.25 465.5

17.0 1,665 3.53 471.4

17.5 1,816 3.83 473.7

18.0 1,967 4.16 473.4

15.0 1,573 2.97 530.2

15.5 1,774 3.00 591.9

16.0 1,975 3.10 638.2

16.5 2,176 3.24 672.3

17.0 2,378 3.41 696.9

17.5 2,579 3.61 714.1

18.0 2,780 3.83 725.5

The pile calculations correspond to a cut-off level of 0.5m bEGL.

It should be noted that the values above are based on the findings provided in the report Ref.

G/3144/HM April 2013, and are to be verified through an in-sity pile load test, given that the exploratory depth of the boreholes in the current investigation campaign is limited to 6.0 m bEGL.

7.5. Group Efficiency

When the piles are placed close to each other, the stresses transmitted by the piles to the soil will overlap, reducing the load-bearing capacity of the piles. In practice, the minimum center-to-

For Inf orm ati on

ACTS-Q-11168/Rev.01 Page | 33 center pile spacing is 2.5D and, in ordinary situations, is actually 3.0 to 3.5D (Braja M. Das). The efficiency of the load-bearing capacity of a group of pile is defined as:

ƞ = Qg(u)

ΣQu

2(𝑛1+𝑛2−2)𝑑+4𝐷 𝑝𝑛1𝑛2 (Equation 19) ƞ = Group Efficiency

Qg(u) = Ultimate load-bearing capacity of the group pile

Qu = Ultimate load-bearing capacity of each pile without the group effect n1, n2 = Number of piles in each row width or length of the group of piles d = Center-to-center pile spacing

D = Pile diameter p = Perimeter of the cross section of each pile

If the center to center spacing d is large enough, ƞ >1. In that case, the piles will behave as individual piles. Otherwise, if ƞ < 1, then Qg(u) = ƞ x ΣQu.

In general, the settlement of a group pile under a similar working load per pile increases with the width of the group and the center-to-center spacing of the piles. Several investigations relating to the settlement of group piles have been reported in the literature, with widely varying results.

However, it is preferred that the settlement of a group pile be computed using a proper 3D analysis.

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ACTS-Q-11168/Rev.01 Page | 34

8. RECOMMENDATIONS

8.1. Shallow Foundations

The allowable bearing capacities of the shallow foundation are presented in Table 8, Table 9 & Table 10. The same was calculated assuming that foundation level is at 0.50m below existing grade for the isolated footings and 0.30m for the slab on grade. Bearing capacities were calculated based on the minimum between the actual bearing capacity (ULS Criteria) and the serviceability limitation for a load resulting in a maximum settlement of 2.5cm for isolated footings and 5.0 for the slab on grade.

Furthermore the horizontal bearing pressures for the design of the thrust blocks are dependent of the size of the thrust blocks and the required depth. However this value can be computed using the geotechnical parameters and the passive earth pressure coefficient of the material presented in Table 7.

8.2. Pile Foundations

The recommendations for the piles provided in Table 14 & Table 15 are based on the analysis carried out using the methods presented in Section 7. The calculations provided do not include the effect of using a drilling fluid, if the same will be used, the axial capacity should be reduced by 25% approximately. Furthermore, a factor of safety of 2.5 for skin friction and 3.0 for end bearing were used. The estimated pile settlements, spring constants and lateral pile capacities were also provided.

It should be noted that the axial pile capacities should not exceed the maximum allowable permissible structural stresses of the concrete which are in the order of 25% of characteristic compressive strength as per British Standards (Clause 7.4.4.3.1 of BS 8004:1986).

In addition to the above, the below should be taken into consideration for pile groups:

The settlement of the pile groups might exceed the settlements of the individual piles.

Consequently, it is necessary to calculate the pile group effects in terms of load capacity and corresponding settlements.

It is recommended to maintain a center-to-center spacing of 2.50D to 3.0D between two adjacent piles, and to incorporate the effect of construction tolerances (eccentricity and out of plumb) in the design of the piles.

Furthermore, in accordance with Section 14.5 of the FHWA Drilled Shafts: Construction Procedures and LRFD Design Methods, if the pile spacing is less than 5.0 to 6.0 Diameter, the bending stresses in the piles should be magnified. This will be done by reducing the lateral resistance of the ground using a P-Multiplier (Pm) which are dependent on the Center to Center spacing, and the location of the pile.

It should be noted that the results of the pile load tests will almost always provide higher capacities than those calculated theoretically. This is mainly due to the conservative approaches

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ACTS-Q-11168/Rev.01 Page | 35 usually used to derive the capacities. Referring to Section 17 of FHWA’s Drilled Shafts:

Construction Procedures and LRFD Design Methods, the following is mentioned:

“In spite of the most thorough efforts to correlate drilled shaft performance to geomaterial properties, the behavior of drilled shafts is highly dependent upon the local geology and details of construction procedures. This makes it difficult to accurately predict strength and serviceability limits from standardized design methods”. Furthermore, the following is noted:

Projects of significant size can benefit from field load tests in the following ways:

The test(s) provide a direct measure of resistance in the specific geologic formation in which the shafts will be founded.

The test(s) provide a direct measure of performance using the actual construction means and methods planned for the project.

The test(s) provide a means by which the design methodology can be refined in the local geologic conditions.

As such, it is recommended to carry out fully instrumented pile load tests, in order to establish the actual load settlement behavior of the piles. These tests should be ideally loaded to failure.

The results can be then used to derive the actual pile capacities.

8.3. Ground Water

The groundwater table level was measured at an elevation of +1.24m MSL (2.3m bEGL). However, the groundwater table might vary depending on the seasons, nearby dewatering activities, and will be affected by changes in tides given the proximity to the sea. As such, it is recommended to use the highest astronomical tide as the design groundwater table.

8.4. Excavation and Monitoring

The excavation from ground level down to foundation levels will be carried out in the sand strata using a recommended slope of 1V:2H. The reported slope angles are suggested based on our local experience acquired. Given the presence of a high water table, loose granular deposits, and the presence of nearby utilities and structures, it is recommended to reduce as much as possible the drawdowns in the vicinity of the excavations. Drawdowns in the groundwater table might induce settlements in the soils.

Depending on the depth of excavations, and the type of shoring system used (if any) a suitable dewatering system should be installed. In general, well points can be used for shallow excavation depths (maximum 5.0m) and a more robust system of deep wells or sump pumping could be used for deeper excavations.

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ACTS-Q-11168/Rev.01 Page | 36

8.5. Backfill

8.5.1. Suitable Material

It is important to note that the fill material used shall be conforming to local and international norms and standards. Therefore, the fine particles (material passing 0.075mm sieve) and the fill material plasticity shall be kept at a minimum.

In general, the backfill material used for structural applications should be classified as GW (well-graded gravel - as per the unified classification system). For general purpose of backfilling works, backfill material classified as GP or GM (poorly graded gravel or silty gravel) can be used.

Moreover, the following measures shall be adopted:

Compaction of the backfill to minimum 95% of maximum dry density of the modified proctor test at near optimum moisture conditions.

Prohibiting the segregation of the backfill material and the development of heterogeneous and loose pockets.

8.5.2. Lateral earth Pressure

Lateral earth pressure developed by compacted backfill can be calculated using an angle of internal friction of 33, and the corresponding at rest, active, and passive pressure coefficients are calculated to be 0.45, 0.29, and 3.39, respectively. The coefficient of friction between compacted granular backfill and formed concrete is recommended to be 0.4. Bulk and submerged unit weight values of 18kN/m3 and 10kN/m3 respectively, can be used.

Furthermore the material encountered on site is in general suitable for backfilling. However the materials extending between a depth of 2.0m and 4.5m bEGL, cannot be used due to the presence of high percentage of…