The Islamic University of Gaza
‫ غزة‬- ‫الجامعة اإلسالمية‬
Material & Soil Laboratories
Telephone: ++ 972 8 2860700 x 1320
‫مختبرات المواد والتربة‬
Fax: ++ 972 8 2827366
SOIL INVESTIGATION REPORT
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1- INTRODUCTION:
The Material & Soil Laboratories (MSL) of the Islamic University of
GAZA (IUG) has conducted a soil investigation study on the site of the
proposed project of a project at GAZA CITY.
The purpose of this study is to investigate the surface and subsurface
soil conditions on the site and to determine the physical and mechanical
properties of the soil layers to provide a complete technical report with all
recommendations for foundation design and construction.
The scope of the works consists of the drilling of three (3) boreholes
at a specified location to a depth of (10-15 ) meters below the existing
ground surface, performing standard penetration tests (SPT) at one (1)
boring from ground surface up to (9.0) meter depth at 1.50-m intervals,
sampling and testing of both disturbed and undisturbed samples.
The report depends on the analysis of the results of both field and
laboratory tests conducted on a representative samples from all layers and
boreholes. Soil stratification and their mechanical characteristics, the
allowable bearing capacity and the suggestions and recommendations related
to the foundation design and construction are provided.
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2. SITE GEOLOGICAL AND GEOTECHNICAL DESCRIPTION:
The site is at located Al-Nasser St. at Gaza city.
The soil profile below excavated level at site is composed of a a deep
dune sand layer over silty sand layer of low plasticity soft to medium stiff
overlying deep calcareous sand with fragments of sandstones (Kurkar).
Isolated foundation is a suitable foundation system for this area.
The ground water table is expected at –30 m depth at that area below
excavated level.
3- FIELD STUDY:
The field study includes drilling of Three (3) boreholes up to a depth
of (10-15) meters below the existing ground level using a rotary air drilling
machine provided with auger of 40-cm diameter.
The drilling has been made under the supervision of the engineer of
(MSL) laboratory. Samples representing different soil layers were collected,
examined, labeled and sealed at the site then sent to the Material & Soil
laboratory. The soil logs of each bore hole and the water table were
recorded.
Also one standard penetration test (SPT) test was performed
according to ASTM D1586-67(1974)”Penetration Test & Split Barrel
sampling of Soil” up to (9.0) m depth at 1.50m intervals. The SPT test
consists of a split spoon barrel at the end of expanding rods. The split spoon
barrel is driven 45 cm into the soil by free falling of a 63 kg hammer from
76cm height. The number of blows required for each 15 cm penetration is
recorded and the number of the last 30 cm is summarized and named (N30).
Other properties such as relative density, angle of internal friction and
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unconfined compressive strength are estimated from the test. The
consistency of the cohesive soil was measured using the Pocket Pentrometer
on site.
4-LABORATORY TESTS:
Representative samples of the soil layers were tested to
determine the physical, mechanical and chemical properties of the ground
materials. The following tests were performed according to the American
Society for testing and Materials (ASTM) and the British Standards (B.S.):
1- Natural Water Content Test.
ASTM D 2216-92
2- Grain Size Analysis by Sieves.
ASTM D 422-92.
3-Liquid and Plastic Limits and Plasticity Index.
4- Field unit weight.
ASTM D 4318-93
ASTM D2937
5- Unconfined Compressive Strength.
5- ANALYSIS RESULT OF FIELD AND LAB. TESTINGS:
5.1- SOIL STRATIFICATION:
The subsoil in the site can be generally classified into the following
layers. The layers below the existing excavated level encountered and their
engineering characteristics are described below.
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FIRST LAYER: SAND
Yellowish fine to medium dune clean Quartizite sand (SP),wet,
medium dense to dense and non plastic. The fines percent is (0.7-2.0) % and
the gravel (0.0) and the remain is sand. The natural water content is (2.4-4.2)
%. The dry unit weight is (1.66-1.78)gm/cm3. The Angle of internal friction
is 30 degrees. The layer thickness is (9.0-10m) m.
SECOND LAYER: SILTY SAND
Brown silty sand (SM), non-plastic, little wet with kurkar gravel. The
fine percent is (14.3) %. The gravel is (1.8) %. The other is sand. The
natural water content is (4.8) %. The dry unit weight is (1.92) gm/cm3. The
layer thickness is (0.7-1.0) m. This layer did not appear in BH2.
THIRD LAYER: KURKAR
Yellowish calcareous silty sand with fragments of sandstone, (kurkar)
(SP), non plastic, little wet and dense. The fines percent is (0.4-0.7) % and
the gravel (2.8-4.0) and the other is sand. The natural water content is (2.22.4) %. The dry unit weight is (1.77-1.85)gm/cm3. The Angle of internal
friction is 34 degrees. The layer appears from depth of 10 up to 15m below
excavated level.
Summary of Layers Properties:
Layer
Unified
Thick.
Classif.
(m)
% w.c
 (dry)
%
%
C
g/cm3
gravel
fines
kg/cm

Nf
LL
PI
6-13
NP
NP
SPT
2
1
SP
9-10
2.4-4.2
2
SM
0.7-1.0
4.8
3
SP
>5m
To End
2.2-2.4
1.661.78
1.92
1.771.85
0.7-
0.0
2.0
1.8
14.3
2.8-4.0
WATER TABLE ~ 30m
5
0.40.7
-
30
-
-
12
NP
NP
-
34
-
NP
NP
6- CONCLUSION&RECOMMENDATION:
6.1-
FOOTING
TYPE,
DEPTH
AND
ALLOWABLE
BEARING
CAPACITY:
A suitable foundation of any structure designed in accordance with
recommended safe bearing capacity must satisfy two independent criteria in
respect to the underlying foundation soil. Firstly, the foundation must have
an adequate factor of safety against exceeding the shear strength of the
foundation soils. Secondly, the vertical movements (settlement) of the
foundation soils must be within tolerable limits for the structure.
In view of these two important facts all types of considered or recommended
foundation in report has to satisfy the above general criteria.
The analysis of the field and laboratory tests for the project
indicated that the soil is almost the same at the whole site as there is a wet
dense sand layer overlaying a thin brown silty sand layer overlaying a deep
calcareous (kurkar) layer and the water table is 30m from the of excavation
level.
The excavation should be extended to 1.0m from each side of the
footing. The excavated level should be cleaned from loose material or solid
waste or concrete debris then saturated and compacted.
The coefficient of sub-grade reaction k0.3 for sand is 40.0 MN/m3 .
The total and differential settlements for the foundations designed and
constructed in accordance with the recommendation given above is less than
the allowable limiting values is 25mm and 19mm respectively for isolated
foundation and 40mm /19m for strip foundation.
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6.2- EXCAVATION &BACKFILLING WORKS:
The top soil layer is formed from dune soil, therefore conventional
excavation equipment's such as loader and bulldozers will be sufficient for
the excavation works at site. The side of excavation required to be supported
or excavated at 45 degrees.
For structural back filling on the site, which is the filling below the
foundation or supporting members, a suitable granular soil of class (A-1-a)
or (Kurkar) is required. The fill should be spread in layers not more than 25
cm thick, moisten to its optimum moisture contents and compacted to a dry
density of not less than 98% of the maximum dry density of modified
proctor compaction test (ASTM D-1557).
6.3- FOUNDATION PROTECTION:
It is recommended that the cement type "V" Sulfate Resistant
Cement or Ordinary Portland cement with 10% coal ash (Nisher cement,
locally available) to be used for construction of the foundations, to prevent
corrosive action of the surrounding environments. The concrete mix shall be
designed as dense as possible to prevent chemical attacks due to its low
permeability. Drainage system should be designed and constructed precisely
to prevent any leakage, all water should be diverted away from the site .
In addition, a thin plain concrete layer (5-10 cm) shall be laid below
foundations. The sides of the foundations and other structural members
buried below the ground shall be painted with two coats of bitumen to avoid
any attack due to infiltration of subsurface water. The minimum steel cover
for foundations to be 50 mm.
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Standard Penetration Number for the first layer:
DEPTH
(m)
0.0
0.5
0.8
1.7
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
SOIL DESCRIPTION
LAYER
UCS
Symbol
SPT
N30
Yellowish fine to medium, Dune
Sand
SP
6
Ditto.
SP
9
Ditto.
SP
13
Ditto.
SP
11
Ditto.
SP
13
Ditto.
SP
8