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5351REP2011 20th

Dec 2011

GEOTECHNICAL SITE INVESTIGATION

FOR THE PROPOSED VILLA OF

MR SAEED ATIK SAEED AL HUMAIRI

& MUZA MATAR KHALIFA

PLOT NO-61, SECTOR: SE-42

KHAILFA CITY (A)

ABU DHABI

Consultant:

Al H iwar Engineer ing Consul tants

Abu Dhabi -UAE

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Preface

This report is directed towards the evaluation of the

Geotechnical situation of the proposed site. Our

evaluations are based upon findings of field investigations

and lab testing.

Site investigations are carried out on 17th Dec 2011 upon

the request of our client Messers.MR SAEED ATIK SAEED AL HUMAIRI& MUZA MATAR KHALIFA..

Data of engineering interest, which are gathered during our

course of investigation, are completely considered in

developing our recommendations.

Eng. Fayez Shadid

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Abstract

During the period from 17th Dec 2011 to 18th Dec 2011,

three boreholes were drilled to a depth of 25 meters each.

Drilling revealed the presence of cohesionless soil

underlain by bedrock. Water table is met from (1.5-1.7)

meter below the present ground level (0.00) assumed

center of the asphalt pavement level. Water level may besubjected to tidal and seasonal variations or by induced arti f icial

effects.)

According to information supplied by our client and in the

light of our findings, deep foundation system is proposed.

End bearing bored piles are suggested to support the

projected Villa and to be erected at depth of 11.5 meters

below the present ground level (0.00) assumed center of

the asphalt pavement level. With allowable pile bearingcapacity of 1.21*10 KN & pile diameter of 500mm.

Total sulfate contents are considerably high in soils along

pile perimeter. Therefore, Salt resistant Portland cement is

recommended in pile construction.

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Contents Page

* Preface ii

* Abstract iii

* Contents iv

1. Introduction 1

2. Scope of investigation 1

3. Borehole Drilling 1

4. In situ Testing 2

5. General Geology 2

6. Subsurface Materials 3

7. Laboratory Tests 3

8. Type and Depth of Foundation 4

9. Pile Bearing Capacity 4

10. Settlement 4

11. Findings 5

12. Recommendations 5

13. Precautionary Measures 6

AppendicesBorehole log sheetsTest result tables

Grain size distribution curves

Calculation sheets

Borehole correlation cross section

Borehole location map

Legend to boring logs

Key to subsurface material tests

Abbreviations & Notations

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1. Introduction

Purpose of the investigations conducted at the request of our client is

to determine the values of the geotechnical parameters needed for the

design of a safe and economic foundation for his projected villa.

We commenced work on the 17

th

Dec 2011. Work was completed onthe 18th Dec 2011. Our trained drillers and technicians under the

supervision of our qualified engineers carried out Works. The

projected villa is proposed to be constructed at Plot No 61. Sector SE-

42, Khalifa City A- Abu Dhabi.

2. Scope of Investigation

Investigations were performed in situ and in the laboratory. These are

consisting of:

Borehole drillings and sampling at various levels of theboreholes carried out according to BS 5930, section 4,

18 & 19.

Survey of geotechnical features. Standard penetration tests were performed according to

BS 1377 test 19 and BS 5930, section 4 (21.2).

Unconfined compression tests were done according toBS 1377 test 20.

Grain size analysis was conducted according to BS1377 test 7.

Chemical Analysis was conducted according to BS1377 test 8.

Bulk densities were determined according to BS 812part 2.

3. Borehole Drilling

Drilling operations include three boreholes were drilled at the site at

the locations shown on the enclosed location map. They were

numbered BH1 through BH3 inclusive. Drilling depths are 25 meterseach below the present ground level (0.00) assumed center of the

asphalt pavement level.. Drilling equipment used was Boyles rotary

drilling rig utilizing water flush method. Drilling in overburden is

performed by the means of non-coring bits and casing of HX size.

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Continuous coring utilizing T-86 size double tube core barrels carries

out drilling in bedrock.

Tube samplers obtained disturbed samples. Samples were packed in

plastic bags labeled and brought to the laboratory.

Extracted core samples are also labeled and placed in wooden boxesand delivered to the laboratory.

Lithologic descriptions of subsurface sediments are presented in the

attached borehole log sheets:

Borehole 1-3 Sheets 1&2

4. In Situ Testing

Standard penetration tests using the standard penetration test (SPT)

equipment were carried out. Penetration tests were advanced by the

use of the split spoon sampler, due to the nature of the encountered

formation. The SPT apparatus is in accordance with British Standard

1377 test 19 (5.4.2.4), and utilizing automatically dropping weight of

65.0 kg. With free fall distance of 760 mm.

SPT results are shown at the attached borehole log sheets, and

tabulated in the attached table 1.

5 . General Geology

United Arab Emirates lie within the Arabian platform that is

characterized by thick sediments continued from the early Cambrianto recent age. Structural developments of The Arabian Platform had

influenced the sedimentary pattern in the UAE. Sedimentation

conditions had been changed considerably after the tectonic events

(Hersenien Movement) that formed mountains at the end of the

carboniferous epoch. Sedimentary rocks were altered from detrital

deposits to calcareous deposits that had been deposited in shallow

marine water and continued to Holocene age. Sandy sediments mainly

cover UAE.

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The exposed rocks are limited to certain areas at Alain, Jabal

Dhannah, Das, Delma, Arzanah, Zirkoh, Jabal Alqamar Aljanubi,

Jabal Alqamar Alshamali, Khor fakan Alfujairah and Ras Alkhaimah.

Sandy sediments form chains of hills and dunes separated by flat

gravely areas. Evaporate flats (Sabkha) are widely spread at coastalplains. In general most of rocks in UAE are sedimentary rocks except

some exposed igneous rock intrusions and metamorphic rocks at Jabal

Hafeet and at north east of the northern emirates. Our site in particular

lies within an area of calcareous sand of marine origin, calcareous

rocks with coastal gravel, platform gravel, detritus, terrestrial silty

clayey sand and evaporates, underlain by intercalated layers of

anhydrite, shale, marl and calcareous rocks which may be related to

the early Miocene or younger. Fossil rich calcareous rocks deposited

in shallow marine water underlie the most predominant superficial

sediments. These fossiliferous calcarenites may be related to

Oligocene age.

6. Subsurface Materials

Borehole drilling revealed that subsurface strata are mainly composed

of Sandstone & MudStone and Gypsum, overlain by an overburden of

recent marine deposits consists of loose to dense silty sand. Ground

water level is encountered at depth from (1.5-1.7) meter below thepresent ground level (0.00) assumed center of the asphalt pavement

level The attached correlated cross section reflects the subsurfacedeposition pattern of the site.

7. Laboratory Tests

Laboratory tests were restricted to mechanical, physical and chemical

properties of sub soil useful in safe foundation design.

Tests carried out in our laboratory are:

Unconfined compression tests were carried out on coresamples extracted from bedrock to determine their

compressive strength, which is necessary to certain, theallowable bearing capacity of the subsurface strata.

Results of the above mentioned tests are tabulated in the

attached table 3.

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Chemical Analysis of subsurface soil and ground water inorder to determine the pH-Value, Sulfate and Chloride

contents. This is helpful in choosing the type of cement

suitable for concrete mix design to protect foundations

from unfavorable chemical reactions. Analysis results arepresented in table 2, attached to this report.

Core sample bulk densities are determined and fixed intable 3 of the unconfined compression test results.

Grain size analysis results are presented in curves attachedto this report.

8. Type & Depth of Foundation

Due to the considerably heavy load of the proposed structure, the

most adequate bearing strata is at depth of 11.5 meters below the

present ground level (0.00) assumed center of the asphalt pavement

level. Therefore pile foundations are the most suitable.

9. Pile Load Capacity

Calculations of bored piles bearing loads are presented in the attached

calculation sheets. Formulas used in calculations assume that pile

load capacity is derived from both point resistance and from the bond

between concrete and rock along surface perimeter of the socket in

addition to skin friction of the cohesionless soil along the pile shaftsurface. Final pressure on rock is determined from the analysis of the

core samples extracted from the foundation bearing strata. Allowable

bearing pressure as a function of pile diameter for rock strata with

favorable characteristics is calculated in the calculation sheets

attached to this report.

10. Settlement

Settlement analysis of piles setting on rock is difficult and frequently

unreliable because of discontinuities inherent in bedrockstratification.

In general settlements in sound rocks are minimal and many times it

is negligible due to their high elasticity modules. An attempt to

calculate maximum total immediate settlement is presented in the

attached calculation sheet 3. Calculations based upon the assumption

that the bearing strata are behaving as an elastic body.

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11. Findings

Drilling proved that water table is encountered from (1.5-1.7)meter below the present ground level (0.00) assumedcenter of the asphalt pavement level.

Overburden deposits are composed of cohesionless soilwith thickness of (10.5) meters.Cohesionless soil deposits are not adequate to bear theproposed load.

Bedrock strata that exist at 11.5 meter deep below thepresent ground level (0.00) assumed center of the asphalt

pavement level. form an adequate bearing foundation.

Chemical tests proved that site materials are within class2 of the British Building Research Establishment

12. Recommendations

The followings are recommended in the light of our findings:

Piles are of cast in place board piles.Piles are to be erected at depth of 11.5 meters below thepresent ground level (0.00) assumed center of the asphalt

pavement level

Pile socket length in bedrock is 1.0 meter.The boundary wall foundation & the connected one story

buildings (Guard & Electric rooms) are to be erected as stripshallow foundation at depth of 1.0 m below the present ground

level (0.00) assumed center of the asphalt pavement level with

allowable bearing capacity of not more than 0.5 kg/cm

Or simply attached to adjacent piles

Values of the allowable safe pile load in KN versus pilediameter in meters are shown in tables and curves at the

attached calculation sheets.

Sulfate resisting Portland cement (SRPC) should be usedin pile concrete.

Pile load tests should be carried out to ensure the above-mentioned parameters.

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13. General Precautionary Measures

The following precautionary measures should be considered duringbored pile construction.

Inspection of the bottom of each pile shaft to eliminate thepresence of debris between the bottom of the concrete

shaft and rock surface.

Borehole bottom should be properly cleaned to preventoccurrence of large settlement during bearing capacity

mobilization, due to the compression of the remain mud in

the bottom of the socket.

Controlling ground water flow during pile shaft boring toavoid loss of ground and potential long term undermining

of floor areas.

Ready mix concrete discharge pipe should not be pulledout of the concrete during placing, so that some of the

concrete flows through water. These form a layer or a

pocket of sand and gravel and a concentration of cement

or laitance at cut-off level.

The temporary liner should not be withdrawn too fastcausing soil to intrude in the concrete section (necking).

The temporary liner should not be allowed to becomestuck and to be withdrawn after partial set of concrete has

taken place, causing cracking of the shaft.