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SOIL INVESTIGATION

FOR

Nergiz Project

(Sulaimany \ IRAQ) ôäbáïÝ�@õŠb’@óÜ@��‹Žïä@ôØŠbq@@

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February 2014

KHAK ENGINEERING CONSULTING Bureau

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Mobile : 07701467000 ; 07701574821 e.mail : khakengineering@yahoo.com

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CONTENTS

1- INTRODUCTION 2 1.1 – Authorization and Scope 2 1.2 – Site location 2 1.3 – Report Layout 2

2 – SEISMICITY OF THE AREA 3 3 – FIELD WORKS 4

3.1 – Boring 4 3.2 – Recovery of Samples 3.3 - In-situ Test

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4- LABORATORY TESTING 7 5- SUB-SOIL CONDITION 7

5.1 – Sub-soil profile 7 5.2 – Under- ground Water Condition 7

6- EVALUATION OF RESULTS 8

6.1 – Atterberge Limits 8 6.2 – Unconfined Compression Test 8 6.3 – Consolidation Test 9 6.4 – Soil Texture 9

7 – STRUCTURAL DESIGN INFORMATION 10 8 - RECOMMENDATIONS 10

8.1 – Type of Foundation 10 8.2 – Depth of Footing 10 8.3 – Allowable Bearing Capacity 10 8.4 – Groundwater 11 8.5 – Expansive Soil 11 8.6 – Type of Cement 11

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Nergiz Project

1- INTRODUCTION

1.1 Authorization and Scope

The Balla Company requested from KHAK Engineering Consulting Bureau to undertake the geotechnical investigation for the new building inside the proposed Nergiz Park project.

This report includes the results of soil investigation for the proposed building. Also it incorporates the results of subsurface exploration, laboratory testing, discussion of test results and recommendations about requirements for foundation designing.

1.2 Site Location

The site is located at Sulaimany City, especially at the corner of the Sarchenar Intersection, near to the Pak City Project. The Balla Company is the investor of the project.

1.3 Report Layout

The soil investigation for the new building includes digging of 3 bore-holes by using drilling machines. The boreholes were dug form the existing ground surface, and taking disturbed and undisturbed samples for laboratory testing.

This report presents and discusses the laboratory test results as well as recommendations for the foundations of the proposed building.

3 2. SEISMICITY OF THE AREA

According to Iraqi seismic code (No. 2/1997), the ordinary structure may be designed by the equivalent static method using conventional liner elastic analysis. The seismic analysis of structures shall take the dynamic properties of the structure into consideration by equivalent static analysis. In this analysis the seismic hazard and zoning coefficient (Z) are required. The evaluation of seismic hazard in different seismic areas for the design of buildings and structures shall be performed according to the seismic zoning map of Iraq, (Fig. 1). The value of coefficient (Z) can be taken as follows;

Zone Z I 0.05 II 0.07 III 0.09

The site of the building is located in Zone II, so the value of the coefficient (Z) equals to 0.07 should be used in the design. According to (UBC / 1997), the recommended value can be considered as (Seismic zone factor = 0.3).

Fig. (1) Seismic zoning map of Iraq

Building site

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3. FIELD WORK

3.1 Boring

Three boreholes were drilled to a depth of 20.0 m. Figure (2) shows a site plan with locations of the building and also location of the bore-holes. The boreholes were advanced by using power drilling machine. The applied method for drilling was continuous flight auger method (Photo No. 1).

3.2 Recovery of Samples

Representative samples were generally taken at appropriate intervals ranging from (1 to 2) meters depth or where the stratum was changed. The disturbed samples (D) were collected from the cutting of the auger.

Undisturbed samples (U) were obtained from the boreholes by installing 100 mm diameter, thin – walled Shelby tubes into the stratum.

3.3 In-situ Tests

Bowels (1995) stated that, 90 percent of conventional foundation design in America is made using the SPT. This test is also widely used in other parts of the world.

During the sub-soil investigation, the only in-situ test conducted was the Standard Penetration Test (SPT). The test consists of driving standard 50-mm diameter split spoon sampler of 450-mm length into soil stratum by means of a 63.6-kg weight hammer falling freely 760-mm height. The number of blows for every 150-mm of penetration are recorded, the total number of blows required to drive the second and third 150-mm of penetration is called the standard penetration resistance “N-value” which represents the number of blows per 300-mm of penetration.

The test is halted if more than 50 blows are required for 150-mm increment. When the full test depth of (300 mm) cannot be obtained, the boring log will show a result of SPT as (SS > 50).

The N-values obtained are shown in the “Bore log” sheets appended. Photo (2) shows all parts of the standard split spoon used in this test.

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Figure (2) Master plan of the park showing locations of the proposed building and locations of the boreholes.

BH 2

BH 3 BH 1

Soil investigation carried out for this Building

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Photo (1) power drilling machine using continuous flight auger method for drilling.

Photo (2) Standard Split spoon used for testing SPT.

7 4-LABORATORY TESTING 4.1 Type of Tests 4.1.1 Tests on undisturbed & disturbed soil samples i) Liquid & Plastic Limits. ii) Grain Size Distribution Test. 4.1.2 Tests on undisturbed soil samples iii) Natural dry density and moisture content. iv) Unconfined Compression Test. v) Consolidation Test. 4.2 Method of Testing

Undisturbed samples were used for strength and compressibility tests. Disturbed or undisturbed samples available were used for classification tests. All the tests were carried out according to the recommendations and procedures called for by ASTM and B.S as appropriate or applicable for any given case.

4.3 Presentation of Results All the test results are summarized in tables, as shown in the latter sections.

5- SUB-SOIL CONDITION:

5.1- Sub-soil Profile:

The sub-soil stratification is shown in the boreloges, from which the sub-soil condition can be summarized as follows:

(a) A backfill layer consists of brown clay with rock fragments was found from the existing ground surface. Thickness of this layer is varying between 2.0 to 4.0 m.

(b) The upper mentioned backfill layer is underlained by four different types of soil layers, which are (Brown clay, light brown sandy clay with small gravels, greenish clay with rock fragments, and Greenish clay). The mentioned layers were encountered at different depths and have different thicknesses.

5.2 Underground Water Condition

The groundwater table was encountered inside the boreholes at a different depths varying between 8.0 to 11.50 m, during the time of the soil investigation (January 2014).

Borehole No. Elevation of GL Depth of Groundwater Table (m)

Elevation of Groundwater Table

BH 1 765.5 8.0 757.5 BH 2 765.8 11.0 754.8 BH 3 764.4 11.5 752.9

8 6- EVALUATION AND DISCUSSION OF RESULTS: 6.1 Atterberg Limits:

The values of liquid limit ( LL ), Plastic limit ( PL ), and plasticity index ( PI ), for the cohesive layer at different depths are shown in Table ( 1 ) below:

Table (1) Atterberg limits tests results

Borehole No.

Depth ( m )

Liquid Limit % ( LL )

Plastic Limit % ( PL )

Plasticity Index (PI) %

BH 1

2.0-2.5 52.2 25.7 26.5 6.0-7.5 38.1 16.6 21.5

14.5-15.0 53.3 25.4 27.9 16.5-17.0 52.1 25.5 26.6

BH 2 2.0-3.5 41.9 19.6 22.3

11.0-14.0 42.1 18.3 23.8 19.5-20.0 51.6 22.6 29.0

BH 3 8.0-10.5 42.0 18.4 23.6 11.0-14.0 41.9 16.9 25.0 14.0-14.5 44.6 21.6 23.0

From this table it can be obtained that the cohesive soil layer can be classified as a low to high expansive soil.

6.2- Unconfined Compression Test Results:

Undisturbed soil sample is collected by small diameter of thin wall tube (38 mm), which is suitable for conducting unconfined compression test.

Table (2) shows the result of (qu) value of unconfined compression test, and also shows natural moisture content, bulk and dry unit weight.

Table (2) Unconfined compression test results

Borehole

No.

Depth ( m )

Natural moisture content

(%)

γwet (gm/cm3)

γdry (gm/cm3)

Unconfined compression

strength ( qu ) ( kN/m2 )

BH 2 3.50 – 4.0 19.58 1.8751 1.5680 293.52

9 6.3 Consolidation Properties

Consolidation test is performed on undisturbed cohesive sample by using consolidation ring 50-mm diameter by 19-mm thick. The applied pressure used is in the range of 25 to 800 kN/m2.

The results of consolidation test are shown in consolidation graph appended on the form of (e-log p) curve. Casagrande’s method is used to determine preconsolidation pressure (Pc).

The results of overburden, preconsolidation pressure and consolidation parameters are shown in Table (3). This table indicates that the cohesive layer is overconsolidated soil. These results indicate that the anticipated settlement for the suggested structures will be tolerable.

Table (3) Overburden, preconsolidation pressure & consolidation parameters with depth

Borehole

No.

Depth

(m)

Overburden

pressure

(Po) (kN/m2)

Preconsolidation

pressure(Pc)

(kN/m2)

Initial

void ratio

(eo)

Compression

Index

(Cc)

Expansion

Index

(Ce)

BH 2 3.5 – 4.0 75 115 0.5764 0.1929 0.0320

6.4 Soil Texture:

The grain size analysis test was carried out for the granular samples and the texture of the tested samples are shown in Table (4) below:

Table (4) Soil Texture

Borehole No. Depth ( m )

Gravel %

Sand %

Clay + Silt %

BH 1

4.0 – 4.5 52.7 24.7 22.6

5.5 – 6.0 21.4 44.6 34.0

8.0 – 10.5 14.6 29.9 55.5

11.0 – 14.5 4.1 13.8 82.1

BH 2 5.5 – 6.0 24.5 36.4 39.1

7.5 – 8.0 26.7 40.5 32.8

BH 3

4.0 – 5.5 52.2 30.7 17.1

6.0 – 7.5 34.8 29.5 35.7

10.5 – 11.0 31.9 33.8 34.3

14.5 – 17.0 45.1 22.2 32.7

17.0 – 17.5 46.6 30.8 22.6

10 7- STRUCTURAL DESIGN INFORMATION

The client has provided the following information to us; -

1. It is suggested to construct seven story building (i.e. two basements + five stories). The building will be constructed as a framed structural building.

2. According to the client information there are two stories as a basement under the building.

8. RECOMMENDATIONS

8.1 Type of footings

According to the proposed building type, which is five-story building with two stories as a basement, and depending on the loading condition and recommended value of the allowable bearing capacity, suitable types of foundations can be selected, which may be single column footing, combined footings, or mat foundation. Since there are two stories as a basement under the building, so it is highly recommended to use mat or raft foundation.

8.2. Depth of Footings

Since there are two stories as a basement under the building, so it is recommended to place the foundation at the depth of 5.0 m or more. But it should be ensured that all parts of the upper backfill layer to be excavated and removed before placing the foundation.

8.3 Allowable Bearing Capacity

According to the laboratory test results and Standard Penetration Test (SPT) with a sub-soil condition, the allowable bearing capacity of 140 kN/m2 (14.0 ton/m2) (2.93 ksf) can be considered in designing of the raft or mat foundation. The Modulus of Sub-grade Reaction of 16800 kN/m3 can be used in the designing of the foundation.

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8.4 Groundwater

Groundwater table was encountered inside the boreholes at different depths varying between (8.0 to 11.50 m). So in case of placing the raft foundation at a depth less than 7.0 m, no construction problems due to groundwater will be anticipated. But the basements should be constructed as watertight structures.

8.5. Expansive Soil

The cohesive soil in this site is classified as a low to high expansive soil. Therefore, problem of swelling is anticipated. The following precautions are suitable for the situation of this site and needed to be taken during construction of the foundations:

1- The foundation soil should be protected from wetting, especially if the construction is done during the winter. In this case the foundation structure should be cast as soon as possible after excavation of the soil, because increasing moisture content of the foundation soil before casting the foundation will cause heave of the soil, which causes the soil to be more compressible.

2- As recommended before the depth of the footings should be at a depth of 5.0 m or more, so that the moisture content of the foundation soil will be invariable during the seasonal fluctuation of the moisture content.

3- During the construction, if filling process is required, sub-base materials or granular soil should be used, and the available cohesive soil in the site should not be used as fill materials.

8.6 Type of Cement

Ordinary Portland cement can be used in foundations.

Dr. Kamal A. Rashed

Geotechnical Consultant

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References

1. American Society for Testing and Material “ Annual Book of ASTM Standard”

2. Bowels, E. Joseph (1995) “ Foundation Analysis and Design” Mc Graw-Hill

Companies

3. British Standards Code of Practice (BS)

4. Craig, R. F. (1997) “Soil Mechanics” E & FN Spon , London.

5. Das, B. M. (1983) “Advanced Soil Mechanics” Mc Graw-Hill Book Companies.

6. Das, B. M. (1990) “Principles of Geotechnical Engineering” Pws-kent Publishing

Company – Boston.

7. Das, B. M. (1999) “Principle of Foundation Engineering” Pws-kent Publishing

Company – Boston.

8. Day, R. W. (2001) “Soil Testing Manual” Mc Graw- Hill Inc.

9. Head, K. H. (1981) “ Manual of Soil Laboratory Testing” Vol. 1, Vol. 2 & Vol. 3 ,

Pentch press , London

10. Mc Carthy, D. F. (1998) “Essentials of Soil Mechanics and Foundations” Prentice

Hall company.

11. Uni Budhui (2000) “Soil Mechanics & Foundation” John Wiley & Sons, Inc ,

Newyork.

12. Tomlinson, M. J. (1996) “Foundation Design & Construction” Longman Company.

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BORELOGS

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