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International Journal of Applied Engineering Research ISSN 0973-4562 Volume 13, Number 2 (2018) pp. 1075-1094
© Research India Publications. http://www.ripublication.com
1075
Mechanical Parameters and Bearing Capacity of Soils Predicted from
Geophysical Data of Shear Wave Velocity
Qassun S. Mohammed Shafiqu a, Erol Güler
b and Ayşe Edinçliler
c
aAssistant Professor, Dr., Civil Engineering Department, Al-Nahrain University, College of Engineering, Baghdad, Iraq. Professor, Dr, Civil Engineering Department, Bogazici University, College of Engineering, Istanbul, Turkey.
Professor, Dr, Earthquake Engineering Department, Bogazici University, College of Engineering, Istanbul, Turkey.
aORCID: 0000-0002-0389-6872
Abstract
The analysis of foundation vibrations and earthquake
problems in geotechnical engineering demands
characterization of dynamic soil properties by geophysical
techniques. Also the dynamic structural analysis of the
superstructures needs knowledge of the dynamic response of
the soil-structure, which, in turn depends on dynamics
properties of soil. The estimation of seismic velocities,
modulus of elasticity and structural properties of soils is not
enough in the design of engineering projects. Therefore, an
ultimate bearing capacity has been predicted using the seismic
shear wave velocity. It is indicated that the allowable bearing
pressure and the coefficient of subgrade reaction together with
many other elasticity parameters may be obtained rapidly and
reliably once the seismic wave velocities are determined in
situ by convenient geophysical survey. In this study, the data
for S and P-waves velocities collected from seismic
investigation reports in the different soil deposits of Iraq. Use
was made of the mathematical correlations connecting several
parameters and wave velocities for studying the layers of soil
presented in Iraqi areas. The soil elastic constants together
with the allowable bearing capacity, and other parameters
were obtained and discussed. It was indicated that for
cohesive and cohesionless soils, up to a shear wave velocity of
300 m/s and 400 m/s respectively, the shear wave velocity
may predicts the bearing capacity relatively well.
Keywords: Bearing capacity, soil parameters, shear wave
velocity, seismic technique, shear modulus.
INTRODUCTION
A footing is the supporting base of a building which forms the
interface across which the loads are transmitted to the
sublayers. Shallow footing represents the foundation were the
structural loads are transmitted to the near-surface soil.
Earthquakes may cause a reduction in bearing capacity and
increase in settlement and tilt of shallow foundations due to
seismic loading. The foundation must be safe both for the
static as well for the dynamic loads imposed by the
earthquakes. Soil-foundation-structure system should work
together in a coherent manner. In particular, if the site is
exposed to high seismic loadings it is highly desirable that the
soil-foundation part of the system should play an appropriate
role in delivering the required overall performance.
In the design of shallow foundation one of the main factors
related to soil is bearing capacity and the other is settlement or
in other words the subgrade reaction. As stated in Grant and
West [1], the seismic "S-wave velocity" is effectiveness
property for estimating the soils capacity. Elastic parameters
are related to shear wave velocity providing allowable bearing
capacity estimating for shallow footings [2].
For the calculation of allowable bearing capacity, the
geophysical methods, utilizing seismic wave velocity
measuring techniques with absolutely no disturbance of
natural site conditions, may yield relatively more realistic
results than those of the geotechnical methods, which are
based primarily on bore hole data and laboratory testing of so-
called undisturbed soil samples [3].
Many researchers have extensively studied to obtain a relation
between the various parameters of soil mechanics and the
seismic wave velocities. Depending upon many experimental
results, Hardin and Black [4], and Hardin and Drnevich [5]
established indispensable relationship between void ratio,
shear rigidity of soils with shear wave velocity. Also, Ohkuba
and Terasaki [6] supplied different expressions relating the
seismic wave velocities to density, permeability, water
content, unconfined compressive strength and modulus of
elasticity. Also the use of geophysical methods in foundation
engineering has been extensively investigated [7, 8, 9, 10, 11
and 12].
Keçeli [10 and 13] indicated that the determination of the
allowable bearing capacity could be obtained by means of the
seismic technique. Tezcan et al. [2]; Kaptan et al. [14] has
defined an allowable bearing capacity and a settlement as
depending on the layer thickness. But, it is well known that
the soil bearing capacity, settlement and modulus of elasticity
cannot be dependent on the layer thickness. Nevertheless, they
obtained also an allowable bearing capacity by changing the
notation of the relations in the article of Keçeli [13].
THEORY
The response of soils to dynamic loading is controlled mostly
by the mechanical properties of the soil. Many types of
geotechnical engineering problems are associated with
dynamic loading, such as: machine vibrations, seismic
loading, liquefaction and cyclic transient loading, etc. The
dynamic soil parameters related with dynamic loading are
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 13, Number 2 (2018) pp. 1075-1094
© Research India Publications. http://www.ripublication.com
1076
shear wave velocity (Vs), damping ratio (D), shear modulus
(G), and Poisson’s ratio (ν), which are also used in many non-
dynamic type problems. The problem of predicting the
bearing capacity of soils from wave propagation properties is
that the soil undergoes only very low strain during the wave
propogation. However when soils are subjected to earthquake
loads or static loads upto failure, they undergo large strains.
The waves S via P velocities have been symbol as Vs and Vp respectively. At the time they are measured, G, K or E, ν, Ec
with other elasticity parameters can be estimated from Eqs (1)
to (8). Using the equations will help in finding the allowable
bearing capacity.
1) Shear modulus (G) connect with Vs by Equation (1):
G = ρ Vs2
(1)
Where ρ is the mass density equal to ρ = γ/g , γ is the unit
weight of the soil and gis the acceleration due to gravity
which isgiven as 9.8g m.s2.
The unit mass density relates with P-wave velocity Vpas
shown in Equation (2)
γ = γ0+ 0.002 Vp (2)
Tezcan et al., [2] shows that γo is reference unit weight and
equal to γo= 16 kN/m3 for loose soils. With respect to [15],
few parameters (i.e., elastic) were given in Eqs (3) to (9):
2) Elasticity modulus (Ed)
E = ρ Vp2
(3)
3) The (Ec) which is Oedometric modulus presented as in
Equation (4)
Ec = E (1-v)/(1+v)(1-2v) (4)
4) Bulk modulus (K) is expressed in Equation (5) as
K =2(1+v)G / 3(1-2v) (5)
5) Poisson’s ratio (ν) is given as in Equation (6) as
ν=(α -2) / 2(α-1) (6)
where α= Ec / G= (Vp / Vs)2 (7)
6) Coefficient of Subgrade ks, bearing capacities qult and qall are obtained by Eqs (8) to (10) as in [16] and [17] by,
ks = 4 γ Vs = 40 qult (8)
7) Ultimate Bearing Capacity (qult)
qult=ks/40= 4 γ Vs/40=0.1 γ Vs (9)
8) As allowable Bearing Capacity (qall)
qall=qult / n =0.1 γVs / n (10)
For soils the safety factor n is (n = 4.0)
Small compressible and large capacities are necessary in
footing construction obtained by the reciprocal amounts of E
and K respectively. G and Vs of a soil deposit is decreased
with enlarging shear strain [18].
MATERIALS AND METHODS OF DATA ANALYSIS
Resources of Geophysical and Geotechnical Data
For many projects in Iraq the engineering parameters of the
different strata from many geophysical and geotechnical
investigation reports are collected [19], and a data base is
prepared for static, shear and compression wave velocities
parameters of different soils for most zones in Iraq as shown
in Table (1) and Figures (1 and 2), where the zones borders
are according to the governorate boundaries. These
parameters are evaluated from field and laboratory tests
results of the available geotechnical and geophysical
investigation reports collected from different resource such
National Center of Construction Laboratories and Research
(NCCLR), engineering consulting bureaus of Baghdad and
Al-Nahrain universities together with some private companies
and laboratories such as Andrea Engineering Test labs, AL-
Ahmed Engineering Test lab and others.
When the seismic wave velocities, Vs and Vp, are obtained,
the elastic parameters are estimated by the Eqs (1) to (7). Also
the subgrade modulus ks, ultimate and allowable bearing
capacities are onbtained depending on the Eqs (8), (9) and
(10) respectively and as will be presented in Table (2).
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 13, Number 2 (2018) pp. 1075-1094
© Research India Publications. http://www.ripublication.com
1077
Figure 1. Map study of seismic zones in Iraq [19] Figure 2. Map study of projects locations in Iraq [19]
Table 1: Iraq seismic zones and sites symbols according to [19]
NO. Zone Governorate Site
symbol
Map
symbol
NO. Zone Governorate Site
symbol
Map
symbol
1
North
Dohuk N1 1 26 Middle Babylon M10 26
2 Dohuk N2 2 27
East
Diyala E1 27
3 Irbil N3 3 28 Diyala E2 28
4 Irbil N4 4 29 West Anbar W2 30
5
Eastern
North
Sulaymaniyah EN1 5 30
Western
south
Karbala WS1 31
6 Sulaymaniyah EN2 6 31 Karbala WS2 32
7 Kirkuk EN3 7 32 Karbala WS3 33
8 Kirkuk EN4 8 33 Karbala WS4 34
9 Kirkuk EN5 9 34 Najaf WS5 35
10 Kirkuk EN6 10 35 Najaf WS6 36
11 Kirkuk EN7 11 36 Eastern Missan ES1 37
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 13, Number 2 (2018) pp. 1075-1094
© Research India Publications. http://www.ripublication.com
1078
12
Western
North
Mosul WN1 12 37 South Missan ES2 38
13 Mosul WN2 13 38 Missan ES3 39
14 Mosul WN3 14 39 Missan ES4 40
15 Salah Al-den WN4 15 40
South
Al Dewaniya S1 41
16 Salah Al-den WN5 16 41 Al Dewaniya S2 42
17 Baghdad M1 17 42 Al Nasiriya S3 43
18
Middle
Baghdad M2 18 43 Al Nasiriya S4 44
19 Baghdad M3 19 44 Al Nasiriya S5 45
20 Baghdad M4 20 45 Al Basrah S6 46
21 Baghdad M5 21 46 Al Basrah S7 47
22 Baghdad M6 22 47 Al Basrah S8 48
23 Baghdad M7 23 48 Al Basrah S9 49
24 Baghdad M8 24 49 Al Basrah S10 50
25 Babylon M9 25
Investigated Soil Parameters
The data for soil parameters investigated were taken from
geotechnical and geophysical investigation reports for most
Iraqi soil. Soil parameters such as; γwet ,γdry, c and ϕ which are
given in the geotechnical reports had evaluated by the field or
laboratory tests, also the depth of the water table and
description of the soil types according to borehole logs were
presented in these reports. While the seismic wave velocities
Vs, Vp values are listed in the geophysical reports that been
evaluated from the cross hole and down hole tests. The
geotechnical bore hole should be the same for the geophysical
bore hole or might be different bore hole but they should be
near to each other or collected either from the same borehole
or two adjacent ones which have the same soil layers profile.
The soil strength parameters (c or ϕ ) were evaluated by the
correlations from N value (SPT) according to the type of soil
when their values are not mentioned or evaluated in some of
the soil investigation reports.
Soil Parameters Evaluation
As mentioned earlier the soil parameters γwet ,γdry , c, ϕ
determined from field and laboratory tests results are
presented in the geotechnical investigation reports, and the
dynamic parameters Vs and Vp are prepared from geophysical
investigations reports. Once seismic wave velocities, Vp and
Vs , together with the density are measured, many parameters
of elasticity, such as shear modulus G, oedometric modulus of
elasticity Ec , modulus of elasticity E (Young’s modulus),
bulk modulus K, and Poisson’s ratio ν may be obtained from
the Eqs (1) to (7). Also the subgrade modulus ks, ultimate and
allowable bearing capacities are obtained depending on the
Eqs (8), (9) and (10) respectively.
able (2) presents the geotechnical and geophysical parameters
collected and evaluated together with the values of ks, qult and
qall estimated.
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 13, Number 2 (2018) pp. 1075-1094
© Research India Publications. http://www.ripublication.com
1079
Table 2: Soil properties and bearing capacity in different locations and zones of Iraq.
no. site
depth soil type W.T γwet γdry c ϕ Vp Vs E×103 G×103 ν K×106 Ks×108 qult
1×102 qall
1×102 qult
2×102 qall
2×102 qall
2×102
m m kN/m3 kN/m3 kN/m2 (o) m/s m/s kN/m2 kN/m2 kN/m2 N/m2.s kN/m2 kN/m2 kN/m2 n=4 n=3
1 N1 0-3 Brown silty clay
with little fragment
NO
W.T
18.4 15.3 32 17 992 302 501.95 171.55 0.463 6.62 0.2223 5.56 1.39 4.87 1.22 1.62
3-10 Dense grey gravel
with sand to gravel
with silt and sand
(GP,GP-GM)
19 14.9 0 42 1445 468 1233.6 422.46 0.46 5.14 0.3557 8.89 2.22 16.34 4.08 5.45
2 N2 0-7.5 Reddish brown rock
fragment of
limestone with silty
sand
>25 19.6 16.8 0 39 1623 832 3642.64 1354.1 0.345 39.17 0.6523 16.31 4.08 9.31 2.33 3.1
3 N3 4-10 Brown silt/clay with
few sand & trace of
gravel,(CL-ML)
No
W.T
21.3 18.1 49 28 807 354 706.4 248.56 0.421 1.5 0.3016 7.54 1.89 16.95 4.24 5.65
4. N4 0-6 Brown silt/clay with
few sand,(CL)
21.4 18.1 43 21 988 296 517.13 178.32 0.45 1.72 0.2534 6.33 1.58 8.6 2.15 2.87
6-10 Brown silt/clay with
little sand& few
gravel,(CL-ML)
21.2 17.8 35 34 1460 462 1204.83 413.75 0.456 4.56 0.3918 9.79 2.45 22.45 5.61 7.48
5. EN1 0-4 Unknown 19.9 16.6 94 0 1745 262 419.05 144 0.486 5.13 0.2086 5.21 1.30 5.36 1.34 1.79
4-15 Unknown 20.9 18.4 0 44 2606 576 1963.11 670.6 0.463 8.84 0.4815 12.04 3.01 27.33 6.83 9.11
6 EN2 0-5 Unknown 19.4 17.6 81 3 1485 233 336.53 113.62 0.481 2.95 0.1808 4.52 1.13 4.62 1.16 1.54
5-10 Unknown 21.6 18.1 4 42 2313 384 932.18 283.48 0.467 4.2 0.3318 8.29 2.07 18.57 4.64 6.19
7 EN3 0-4 Brown (CH, CL) 3.9 19.7 16.8 55 0 535 219 253.86 90.6 0.401 0.43 0.1726 4.31 1.08 3.14 0.79 1.05
4-6 Medium brown silty
Sand (SM)
19.6 17.2 21 33 679 301 477.75 172.47 0.385 0.69 0.2359 5.9 1.48 3.13 0.78 1.04
6-12 Dense grey gravel
with sand to gravel
with silt and
sand(GP, ,GP-GM)
19.5 16.8 0 42 1384 733 2760.89 991.7 0.392 4.26 0.5717 14.29 3.57 16.77 4.19 5.59
8
EN4
0-2 Brown silt with
(ML)
2.9 19.4 17.7 5 37 360 145 124.2 44.25 0.403 0.21 0.1125 2.81 0.7 6.33 1.58 2.11
2-6 Stiff brown lean clay
(CL)
17.3 15.8 80 0 514 212 284.06 98.44 0.392 0.42 0.1467 3.67 0.92 4.56 1.14 1.52
6-15 Stiff brown to grey
lean clay (CL)
19.4 17.5 21 39 1065 323 663.2 229.3 0.424 1.43 0.2506 6.27 1.57 9.22 2.3 3.07
9
EN5 2.5 (ML) being Stiff >25 19 16.8 0 32 1125 225 290.15 98.09 0.479 2.3 0.1710 4.28 1.07 2.55 0.63 0.85
2.5-15 (CH, CL) with
consistency very stiff
to hard
20.6 18.2 227 0 1250 321 634.86 216.38 0.467 3.21 0.2645 6.61 1.65 12.94 3.24 4.31
15-20 Very dense silty
gravel with sand
(GM)
20.6 18.2 0 42 2500 476 1409.8 475.9 0.481 12.37 0.3922 9.81 2.45 17.71 4.43 5.9
1seismic method [15]
2conventional method [16]
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 13, Number 2 (2018) pp. 1075-1094
© Research India Publications. http://www.ripublication.com
1080
Table (2): Continue
no. site
depth soil type W.T γwet γdry c ϕ Vp Vs E×103 G×103 ν K×106 Ks×108 qult1×102
qall1×102
qult2×102
qall2×102
qall2×102
m m kN/m3 kN/m3 kN/m2 (o) m/s m/s kN/m2 kN/m2 kN/m2 N/m2.s kN/m2 kN/m2 kN/m2 n=4 n=3
10 EN6 0-10 (CL,CH) very stiff
brown to stiff
2.6 21.0 18.1 120 0 1541 304 585.82 197.91 0.48 4.88 0.2554 6.39 1.6 6.84 1.71 2.28
11 EN7 0-10 Very stiff to hard
brown lean clay (CL)
3.8 20.1 17 130 0 1250 312 585.43 199.53 0.467 2.96 0.2508 6.27 1.57 7.41 1.85 2.47
12 WN1 0-15 moderately gypseous
(CL,CH)
2.8 19 17.3 65 0 1330 459 1069.8 378.56 0.413 2.05 0.3488 8.72 2.18 3.71 0.93 1.24
13 WN2 0-7.5 Dark brown sand silt
with rock fragments
>25 18.3 16 0 37 773 319 542.6 189.3 0.432 1.33 0.2335 5.84 1.46 5.97 1.49 1.99
7.5-20 Brown sand gravel 17.8 15.3 0 42 1113 348 600.3 202.5 0.416 1.14 0.2478 6.2 1.55 15.3 3.83 5.1
14 WN3 4-15 (GM,GP) medium to
very dense
2.3 19.4 16.3 0 38 1057 362 584.6 217.2 0.424 1.36 0.2809 7.02 1.76 7.63 1.91 2.54
15 WN4 0-2 Grey gravel with silt
sometimes with
sand(GM)
No
W.t
18.3 16.8 0 36 714 292 445.39 160.21 0.39 0.67 0.2137 5.34 1.34 4.57 1.14 1.52
2-5 Medium stiff to hard
brown lean clay
sometimes with sand
and gravel to
silt(CL,ML)
20.1 15.3 46 34 1055 346 676.62 238.08 0.421 1.43
0.2782
6.96
1.74
28.03 7.0 9.34
5-10 Dense to very dense
grey gravel with silt
and sand to gravel
17.8 16.1 0 43 1335 606 2009.1 714.45 0.406 3.56 0.4315 10.79 2.7 18.83 4.71 6.28
16 WN5 0-4 Highly gypseoussilty
sand to sandy silt
with little gravel
16 18.4 15.9 0 37 942 451 1030.4 374.97 0.374 1.36 0.3319 8.3 2.07 6 1.5 2
4-20 Silty sand with
gravel to sand with
gravel
19 14.8 0 41 1373 701 2559.4 916.7 0.396 4.1 0.5328 13.32 3.33 13.35 3.34 4.45
17 M1 0-10 slightly
gypseousmarly (CH,
CL,CL-ML)
2.1 18.7 14.8 76 12 544 186 187.1 64.84 0.446 0.578 0.1391 3.48 0.87 4.33 1.08 1.44
10-16 Loose to medium
grey to green silty
sand (SM)
20 16.3 0 36 736 258 381.9 140.42 0.433 1.0 0.2064 5.16 1.29 5.44 1.36 1.81
18
M2 0-8 (CL) stiff to medium
consistency
2.65 20.1 17 125 0 820 265 414.42 144.1 0.438 1.11 0.2131 5.33 1.33 6.42 1.61 2.14
8-15 clayey silty sand to
silty sand loose to
dense
19.1 15.5 0 36 1150 395 815.79 283.26 0.44 2.27 0.3018 7.55 1.89 5.19 1.3 1.73
19 M3 0-10 Soft to stiff brown
lean or fat clay or silt
sometimes lean clay
with sand to sandy
silt (CL,CH,ML)
0.8 18.7 14.9 52 12 443 153 146.53 45.52 0.43 0.31
0.1144 2.86 0.72 2.67 0.67 0.89
10-18 Medium to very
dense grey silt sand
or clayey sand
(SM,SC)
19 14 0 39 769 215 263.34 91.12 0.445 0.8 0.1634 4.1 1.02 9.03 2.26 3
20
M4
0-10 Lean clay stiff to
very stiff
1.55 19.78 17.43 180 0 761 298 538.8 191.5 0.408 0.98 0.2358 5.9 1.47 9.25 2.31 3.08
10-15 Stiff to very stiff
grey to brown to
black lean clay
sometimes with sand
1.55 20.2 17.1 68 16 1113 428 995.34 373.2 0.415 2.1 0.3458 8.65 2.16 9.48 2.37 3.16
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 13, Number 2 (2018) pp. 1075-1094
© Research India Publications. http://www.ripublication.com
1081
(CL)
15-20 Medium grey silty
sand (SM)
20.89 17.02 0 34 1351 507 1388.6 511.6 0.417 2.9 0.4236 10.59 2.65 3.97 0.99 1.32
21 M5 10-15 Loose to medium
grey silty sand (SM)
3.1 18.4 15.6 0 38 1191 430 977.68 336.2 0.454 3.5 0.3165 7.91 1.98 7.23 1.81 2.41
22 M6 0-1 (ML) with filling
materials
1.3 19.00 15.8 28.7 0 322 140 251.99 91.1 0.383 0.36 0.1064 2.66 0.67 1.48
0.37 0.49
1-15 Brown to grey silty
clay to clayey silt
(ML,CL,CH)
18.88 14.7 31.5 0 776 219 403.34 138.51 0.456 1.53 0.1654 4.14 1.03 1.62 0.41 0.54
15-20 (SM,GP) 22.31 17.04 0 38 1504 408 941.3 321.92 0.462 4.13 0.3641 9.10 2.28 8.77 2.19 2.92
23 M7 0-6 (CH) which is stiff
to medium stiff
0.6 19.8 15.8 50 0 641 189 209.16 72.13 0.45 0.7 0.1497 3.74 0.94 2.57 0.64 0.86
6-12 Very stiff brown lean
clay (CL)
19.0 14.5 100 0 675 248 338.44 119.17 0.42 0.71 0.1885 4.71 1.18 5.14 1.29 1.71
12-15 (SM) to Silty Sand
with gravel, medium
stiff to stiff
19.0 15.0 0 37 750 225 284.46 98.09 0.45 0.95 0.1710 4.28 1.07 6.2 1.55 2.07
24 M8 (CH) stiff to very
stiff
19.8 17.1 65 10 841 165 162.7 54.97 0.48 1.36 0.1307 3.27 0.82 6.3 2.1
0-7.5 1.58
7.5-12 (SM) being medium
dense to very dense
2.2 19.0 16.5 0 38 1025 279 440.3 150.8 0.46 1.83 0.2120 5.3 1.33 7.47 1.87 2.49
25 M9 0-5 (CL,CH) sometimes
with sand
1.41 21.26 17.85 90 0 735 260 406.11 145.35 0.397 0.66 0.2211 5.53 1.38 4.63 1.16 1.54
5-15 Losse to dense grey
silty SAND(SM)
18.6 15.4 0 38 1503 369 682.46 242.5 0.403 1.17 0.2745 6.86 1.72 7.31 1.83 2.44
26 M10 0-2.4 Grayish sandy silty
clay soil, medium
consistency
1.5 16.18 14.5 144 0 306 111 57.9 20.33 0.424 0.13 0.0718 1.8 0.45 7.4 1.85 2.47
2.4-15 Grayish medium
silty sand
18.44 16.5 0 38 450 183 176.33 62.98 0.4 0.29 0.1350 3.38 0.84 7.25 1.81 2.42
27 E1 0-10 Very stiff to hard
brown to grisg
brown marl lean clay
(CL)
1.72 21.1 18.3 83 0 976 372 835.49 298.82 0.398 1.37 0.3140 7.85 1.96 4.27 1.07 1.42
28 E2 0-15 Stiff brown clay
(CL)
1.46 20.3 17.1 76 0 1076 398 945.39 331.95 0.424 2.07 0.3232 8.08 2.02 3.9 0.98 1.3
29 W2 0-5 (CL) of very stiff to
stiff consistency
1.75 20.4 17.07 120 0 730 257 386.09 135.85 0.421 0.81 0.2097 5.24 1.31 6.17 1.54 2.06
5-10 Loose to dense grey
to dark grey silty
sand and clayey silty
sand sometimes with
gravel (SM,SC-SM)
18.2 15.2 0 33 1513 379 809.19 282.34 0.433 2.01 0.2759 6.9 1.72 2.91 0.73 0.97
30 WS1 0-5 Stiff brown to green
lean clay
1.2 19.5 15.6 77 0 688 198 223.14 72.87 0.458 0.84 0.1544 3.86 0.97 3.96 0.99 1.32
5-9 Loose to medium
brown to grey silty
sand (SW-SM)
18.4 14.8 0 33 948 265 401.85 137.62 0.46 1.67 0.1950 4.88 1.22 2.94 0.73 0.98
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 13, Number 2 (2018) pp. 1075-1094
© Research India Publications. http://www.ripublication.com
1082
9-15 Very dense grey silty
sand
19.1 15.3 0 36 1370 497 1329.6 463.92 0.433 2.29 0.3797 9.49 2.37 5.19 1.3 1.73
31 WS2 0-18 Loose to very dense
off white yellow,
light brown to grey
sometimes
moderately
gypseoussilty sand or
sand with silt or sand
(SM,SP-SM,SP)
NO
W.T
19.6 17.93 0 38 986 417 958.17 340.98 0.405 1.68 0.3270 8.18 2.04 7.7
1.93 2.57
32 WS3 0-10.5 (CH) gypseous stiff 1.5 18.5 14.7 100 0 1416 312 541.76 183.65 0.475 3.61 0.2309 5.77 1.44 5.14 1.29 1.71
33 WS4 0- 4.5 (SP,SM) yellow to
white dense slightly
to moderately
gypseous sand
0.8 18.8 18 0 37 1433 284 457.0 154.6 0.478 3.46 0.2136 5.34 1.34 6.14 1.53 2.05
4.5-12 (SP,SM) dense to
very dense
19.4 18 0 35 1733 550 1727.2 598.46 0.443 5.05 0.4268 10.67 2.67 4.4 1.1 1.47
12-22 (SP,SM) which is
very dense
19.4 18 0 35 1650 563 1801 627.1 0.436 3.71 0.4369 10.92 2.73 4.4 1.1 1.47
34 WS5 0-10 Very loose grading
to very dense slightly
to moderately
gypseous sand (sm)
or sand with silt (SP-
SM)
2.1 17.5 14.9 0 41 1613 618 1975.9 696.75 0.4185 4.04 0.4326 10.82 2.70 12.29 3.07 4.1
35 WS6 0-1.2 (SM) slightly
gypseous silty sand
0.9 19.1 17 0 43 805 268 412.33 143.37 0.438 1.11 0.2048 5.12 1.28 20.15 5.03 6.71
1.2-7 Medium- dense to
very dense light
brown sand (SP)
19.5 18 0 40 1450 557 1743.5 616.95 0.413 3.34 0.4345 10.86 2.72 11.24 2.81 3.75
7-10 (SM) very dense 19.6 18 0 39 1812 659 2472.2 868.03 0.424 5.42 0.5167 12.92 3.23 9.31 2.33 3.1
36 ES1 0-6 (CL,CH) being stiff
to very stiff
0.41 19.2 14.8 53 4 451 111 69.32 23.67 0.464 0.32 0.08525 2.13 0.53 3.7 0.93 1.23
6-14 Loose grey silty sand
(SM)
20.45 17.8 0 36 605 152 167.53 57.49 0.457 0.65 0.1243 3.11 0.78 5.56 1.39 1.85
14-20 (CH) stiff to very
stiff
19.9 15.6 63 0 690 211 254.57 89.07 0.429 0.61 0.1680 4.2 1.05 3.24 0.81 1.08
37
ES2 0-5 (CL,CH) as stiff to
medium stiff
0.6 18.0 14.6 65 0 377 131 90.15 31.5 0.431 0.22 0.0943 2.36 0.59 3.34 0.84 1.11
5-8
(CL,CH) stiff 19.5 15.8 60 0 604 250 347.98 124.28 0.4 0.58 0.1950 4.88 1.22 3.08 0.77 1.03
8-17 (CL) stiff 20.8 15.9 60 8 1362 420 1082.8 374.17 0.447 3.41 0.3494 8.74 2.18 5.2 1.3 1.73
38 ES3 0-9 (CL,CH) medium
stiff to stiff
0.6 19.7 15.7 80 0 696 179 188.5 64.37 0.464 0.87 0.1411 3.53 0.88 4.11 1.03 1.37
9-18 (CL) stiff 20.9 16.1 60 0 1167 380 886.78 307.76 0.44 2.46 0.3177 7.94 1.99 3.08 0.77 1.03
39 ES4 0-7.5 (CL,CH) stiff to
medium stiff
0.6 19.5 15.1 80 0 500 176 175.96 61.57 0.429 0.41 0.1373 3.43 0.86 4.11 1.03 1.37
7.5-9 Loose grey silty sand 19.5 15.7 0 29 600 200 228.51 79.51 0.437 0.6 0.1560 3.9 0.98 1.58 0.39 0.53
9-10 (CL) stiff 19.5 15.7 60 8 600 250 346.6 124.23 0.395 0.55 0.1950 4.88 1.22 5.2 1.3 1.73
40 S1 0-5 (CL,CH) very stiff
to stiff
0.3 19.6 15 42 8 685 225 281.99 99.02 0.424 0.62 0.1764 4.41 1.10 3.64 0.91 1.21
5-6.5 Loose grey silty sand
(SM)
20.7 17.2 0 33 814 243 340.53 117.34 0.451 1.16 0.2012 5.03 1.26 3.31 0.83 1.1
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 13, Number 2 (2018) pp. 1075-1094
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1083
6.5-10 (CH) very stiff to
stiff
19.3 14.9 65 0 1224 333 645.63 220.2 0.466 3.16 0.2571 6.43 1.61 3.34 0.84 1.11
41 S2 0-1.5 Brown lean clay(CL) 0.3 18.5 14.4 94 0 625 188 193.28 66.65 0.450 0.64 0.1391 3.48 0.87 4.83 1.21 1.61
1.5-2 (SM) loose 20.0 15.0 0 30 909 185 213.45 72.21 0.478 1.62 0.1480 3.7 0.93 1.91 0.48 0.64
2-10 (CL,CH) very stiff
to stiff
19.3 14.7 60 5 909 200 232.17 78.73 0.475 1.55 0.1544 3.86 0.97 4.41 1.1 1.47
42 S3 0-8 Medium stiff to hard
brown or grey or
dark grey lean to fat
clay sometimes with
sand to sandy lean
clay or silt or sandy
silt(CL,CH,ML)
1.2 19.1 15.8 78 0 646 185 198.82 68.72 0.458 0.79 0.1413 3.53 0.88 4.0 1.0 1.33
8-15 Dense to very dense
grey or dark grey or
brown silty sand
otsilty clayey sand or
sand with silt
(SM,SC-SM,SP-SM)
17.7 14.6 0 40 1094 321 562.51 198.94 0.464 2.7 0.2273 5.68 1.42 10.2 2.55 3.4
43 S4 0-12 (CL,CH) medium to
soft
1.7 19.5 15.2 90 3 434 110 70.54 24.06 0.466 0.35 0.0858 2.15 0.54 5.96 1.49 1.99
12-14 Loose grey silty sand
(SM)
20.8 18 0 41 500 145 129.7 44.6 0.454 0.47 0.1206 3.02 0.75 14.61 3.65 4.87
14-15 (CL) very stiff
20.8 17 191 0 600 166 170.56 58.45 0.459 0.69 0.1381 3.45 0.86 9.82 2.46 3.27
44 S5 0-4 (CL) very stiff 4 19.07 15.1 34 0 600 200 223.45 77.75 0.437 1.7 0.1526 3.82 0.95 1.75 0.44 0.58
4-10 (CL,CH) stiff to
hard
19.93 15 112 0 750 240 337.6 117.1 0.442 0.97 0.1913 4.78 1.2 5.76 1.44 1.92
45 S6 0-3 Medium light brown
gypseous soil
1.6 20.3 16.8 0 35 803 329 780.35 258.63 0.397 1.17 0.2671 6.68 1.67 4.61 1.15 1.54
3-10 Medium to very
dense light brown to
grey slightly to
highly gypseoussilty
sand or sand with silt
or sand (SM,SP)
18.9 16.01 0 34 1811 627 1797.46 737.98 0.446 6.59 0.4740 11.85 2.96 3.59 0.89 1.19
46 S7 0-3.7 Grey gypseous
sand (SM)
1.8
18.18 16.1 5.33 39 566 230 269.05 96.012 0.401 0.45 0.1673 4.18 1.05 8.63 2.16 2.88
3.7-15 Grey gypseous silty
sand (SM)
19.16 15.3 8.4 40 1404 365 750.38 256.45 0.463 3.38 0.2797 6.99 1.75 11.04 2.76 3.68
47 S8 0-6 Very soft to stiff
brown lean clay (CL)
5 21.1 16.4 60 0 434 166 168.06 59.47 0.412 0.32 0.1401 3.50 0.88 3.08 0.77 1.03
6-15 Very loose grey
clayey silty sand
(SC-SM)
19 15.3 0 37 510 194 250.53 88.4 0.417 0.50 0.1474 3.69 0.92 6.2 1.55 2.07
48 S9 0-6 (CL,CH) stiff to
medium
1.1 19.7 15.7 80 0 294 117 82.58 29.47 0.401 0.14 0.0922 2.31 0.58 4.11 1.03 1.37
6-12 (CL) stiff 20.9 16.1 60 0 381 198 239.08 83.77 0.427 0.55 0.1655 4.14 1.03 3.08 0.77 1.03
49 S10 0-10 (CL,CH) very soft
to stiff
1.0 18.37 13.92 40 0 550 138 104.6 35.7 0.466 0.51 0.1014 2.54 0.63 2.06 0.52 0.69
10-13 Grey silty sand (SM) 19.63 15.54 0 37 334 103 61.8 21.23 0.455 0.23 0.0801 2 0.5 6.4 1.6 2.13
13-15 (CL) very soft to
stiff
20.02 16.03 48 0 450 102 62.57 21.24 0.473 0.39 0.0817 2.04 0.51 2.47 0.62 0.82
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© Research India Publications. http://www.ripublication.com
1084
RESULTS AND DISCUSSION
Evaluation of the Allowable Bearing Capacity
In this research, and for each layer of the areas of study the
elastic parameters, were calculated from Eqs (1) to (8). The
relations also provide obtaining of the bearing capacities both
ultimate and allowable according to the Eqs (9) and (10)
respectively. The results obtained are presented in Table (2).
Also, following the classical procedure of [16], the ultimate
and allowable bearing capacities were determined, by
assuming the factor of safety equal to n=3 and 4 and as given
in Table (2) for the purpose of comparison. The numerical
values of the ultimate and allowable bearing capacities
determined in accordance with the conventional Terzaghi
theory and seismic technique (Tezcan et al., 2006) for
cohesive soils are plotted in Figures (3 and 4 respectively).
And the results of ultimate and allowable bearing capacities
estimated from both methods for cohesionless soils are plotted
in Figures (5 and 6 respectively).
Two separate linear regression lines were also shown in the
Figures (3 and 5), for the purpose of indicating the average
values of ultimate bearing pressure determined by ‘seismic’
and ‘conventional’ methods. For cohesive and cohesionless
soils it can be indicated that up to a shear wave velocity of
300 m/s and 400 m/s respectively, the shear wave velocity
predicts the bearing capacity relatively well. Above 300 m/s
and 400 m/s the scatter is large and it looks like there are quite
many points that are falling below the bearing capacity
estimated by the shear wave velocity. The linear regression
line indicates for Vs values smaller than 300 m/s and 400 m/s
a narrow band, which should be regarded as quite acceptable.
The ‘seismic’ method proposed herein yields allowable
bearing cabacities (on the order of 10 to 20%) greater than
those of the ‘conventional’ method for Vs values smaller than
400 m/s. In fact, the ‘conventional’ method fails to produce
reliable and consistent results for relatively strong soils,
because it is difficult to determine the appropriate soil
parameters c and ϕ for use in the ‘conventional’ method [20].
Therefore, from the results the use of ‘seismic’ method can
give an order of magnitude for such strong soils with Vs > 300
m/s for cohesive soils and >400 m/s for cohesionless soils.
The allowable bearing capacity has been obtained at different
sites in various regions of Iraq as shown in Table (2) and
Figures (4 and 6) for cohesive and cohesionless soils
respectively. Factor of safety used for allowable bearing
capacity estimated from shear wave velocity is 4 (Tezcan,
2006), and allowable bearing capacity is estimated from
Terzaghi equation using factor of safety, n=3 and 4, it can be
indicated that values from shear wave velocity are close to
that from conventional method till Vs=300 m/s for cohesive
soils and 400 m/s for cohesionless soils and above these
velocities the scatter is large. It can be concluded from these
graphs that allowable bearing capacity estimated from shear
wave velocity may be obtained for n less than 4 for soils that
have Vs less and equal than 400 m/s. Table (3) shows the
range of values for seismic wave velocities and allowable
bearing capacity for different types of soil with various
description. In order to demonstrate that the technique used
covers all soils types, the values of seismic velocities and
allowable bearing capacity given in Table (3) are compared
with the values for foundation materials given in building
codes with entire seismic velocities covering all soils and
rocks types and with the values calculated by using seismic
velocities of soils and rocks [21] which has been obtained at
thousands of construction sites in various regions of Turkey
since 1990. The comparison shows that the allowable bearing
capacity values obtained from hard through loose soils were in
agreement with the building codes and Keçeli [21] values.
Thus, allowable bearing capacity values obtained by the
technique proposed here are evaluated for accuracy. Table (3)
also demonstrated awide range for soil types description.
Allowable bearing capacity for cohesive and cohesionless
soils is drawn via shear wave velocity for each of the layers as
given in Figures (4 and 6 respectively) which shows linear
empirical relationships between qall and Vs. This is clarified in
Eqs (11 and 12):
For Cohesive Soils qall (kN/m2) =(0.0053Vs - 0.073)×10
2
(11)
For Cohesionless Soils qall(kN/m2)=(0.0048Vs + 4.0E-6)×10
2
(12)
Expressions give slopes which are dimensionless constant
predicting elastic deformability coefficient of shallow footing
caused by load on the considered footings. The slopes of qall
and Vs plots considering impulse/driving load gives
deformability of layers over m3 of foundation layers which is
about 0.5 kNs·m−3
. From Eqs (11 and 12), sublayers are
considered less susceptible to deformation than that near
surface depending on the magnitudes of qall and shear
modulus G which is plotted against Vs for cohesive and
cohesionless soils as shown in Figures (7 and 8 respectively).
As it increases, the degree of elastic deformation decreases.
Although through depth and because of compaction which
cause increasing subsurface consolidation, other tectonically
induced secondary structures like divide, fault lineament and
fold within the sedimentary facies could cause voids in the
subsurface thereby leading to elastic deformation of
subsurface.
The layers also show polynomial relationships between qall and G as shown in Figures (7 and 8) for cohesive and
cohesioless soils respectively. The soil layer density and thus
unit weight provides determination shear wave velocity and
the shear modulus in Equation (1) explaining the influential
variation shown in the relation between allowable bearing
capacity qall and shear modulus G in the layers which is given
by Eqs (13 and 14):
For Cohesive Soils qall (kN/m2) =(-4E-06G2 + 0.0061G + 0.4843)×102
(13)
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© Research India Publications. http://www.ripublication.com
1085
For Cohesionless Soils qall (kN/m2) = (-1E-06G2 + 0.0043G + 0.6675)×102
(14)
The highest value of qall for sublayers is seen on north zone
and reduces through middle and south of Iraq. In the zones
that are greatly undrained with water the behavior shows less
allowable bearing capacity while higher bearing capacity is
related to unsaturated zones. The higher allowable bearing
capacity value with depth is due to cementation/compaction
which increases with depth.
The larger value of the allowable bearing capacity is obtained
in North of Iraq (i.e., N1) with a value of about 408 kN/m2 and
the lowest is at Middle and South regions (i.e., M10 and S10
respectively) with avalue of about 50 kN/m2. According to the
depths of investigation and soil descriptions shown in Table
(2), three layers with approximate depths can be considered
for investigation, layer one extends to about 6m from the
ground surface, while layer two extends for a depth 6m to
10m and third one for depth between 10m to 15m. qall value
has an average value of about 142 kN/m2 for layer one, while
the average bearing capacity for layer two is about 176
kN/m2and about 162 kN/m
2 for layer three. With respect to
cohesive and non-cohesive soils, the results of the minimum,
maximum and average values of shear modulus, G, and
allowable bearing capacity, qall appears for the layers to a
depth of about 15m from ground surface in the study areas are
as shown in Table (4).
Table 3: Allowable bearing capacity for different soil descriptions.
Soil type Vp -range (m/s) Vs -range
(m/s)
qall ×102
(kN/ m2)
Rock Fragment of Limestone with Silty Sand to Gravel
with Sand or Gravel with Silt and Sand
Silty Sand (Loose)
Silty Sand (Medium)
Silty Sand (Dense)
Gypseous Sand to Silty Sand
Clay (Very Soft to Soft)
Clay (Medium)
Clay (Stiff)
Clay (Very Stiff to Hard)
714-2500
334-909
450-1191
1025-1733
803-1811
294-550
377-820
381-1076
675-1541
292-733
103-243
183-507
279-659
268-627
102-153
131-265
198-398
248-459
1.34-4.08
0.5-1.26
0.84-2.65
1.33-3.23
1.28-2.96
0.5-0.88
0.59-1.33
0.97-2.02
1.18-2.18
Table 4: Shear modulus and allowable bearing capacity for different depths in cohesive and cohesionless soils.
Soil type
Depth
Approx.
(m)
G×103 –value
(kN/m2)
qall×102-value
(kN/m2)
Min. Avg. Max. Min. Avg. Max.
Cohesive
soil
0-6 21.24 105.5 374.17 0.45 1.06 1.96
6-10 83.77 206 413.75 1.03 1.54 2.45
10-15 21.24 207.6 374.17 0.51 1.47 2.18
Cohesionless soil 0-6 44.25 387.76 1354.1 0.7 1.78 4.08
6-10 57.49 693.8 4142.8 0.78 1.97 3.57
10-15 21.23 464.1 3370 0.5 1.76 3.33
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 13, Number 2 (2018) pp. 1075-1094
© Research India Publications. http://www.ripublication.com
1086
Figure 3: Ultimate bearing capacity against shear wave velocity for cohesive soils.
Figure 4: Allowable bearing capacity against shear wave velocity for cohesive soils.
0
5
10
15
20
25
30
0 50 100 150 200 250 300 350 400 450 500
qult(×
10
2 kP
a)
Vs(m/sec)
conventional method [16]
seismic method [15]
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
0 50 100 150 200 250 300 350 400 450 500
qal
l (×1
02 k
Pa)
Vs (m/sec)
seismic method-n=4 [15]
conventional method-n=3 [16]
conventional method-n=4 [16]
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 13, Number 2 (2018) pp. 1075-1094
© Research India Publications. http://www.ripublication.com
1087
Figure 5: Ultimate bearing capacity against shear wave velocity for cohesionless soils.
Figure 6: Allowable bearing capacity against shear wave velocity for cohesionless soils.
0
10
20
30
40
50
60
70
0 100 200 300 400 500 600 700 800 900
Vs (m/sec)
seismic method [15]
conventional method [16]
qal
l(×10
2kP
a)
0
5
10
15
20
25
30
0 100 200 300 400 500 600 700 800 900
qall
(×10
2 k
Pa)
Vs (m/sec)
2.22
4.08
5.45
seismic method-n=4 [15]
conventional method-n=3 [16]
conventional method-n=4 [16]
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 13, Number 2 (2018) pp. 1075-1094
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1088
Figure 7: Allowable bearing capacity against shear modulus for cohesive soils.
Figure 8: Allowable bearing capacity against shear modulus for cohesionless soils.
Evaluation of the Soil Parameters
This study aimed also at obtaining model equations from the
correlations of the shear wave velocities and the different
geotechnical parameters studied. This was to obtain direct
relationships between the S-wave velocity and the
geotechnical parameters. These equations can be used for a
quick evaluation and inexpensive estimation of the various
soil parameters.
The graphs of the parameters were plotted against the shear
wave velocities. Also, the relations and correlations have been
investigated between seismic velocities and geotechnical
parameters using the best fit curve. The relations give obvious
variations in the geotechnical properties affecting the
velocities differently in different parts of the velocity ranges.
The graphs of modulus of elasticity, E, bulk modulus, K, and
subgrade modulus, ks, against the S-wave velocity (Figures 9,
11 and 13 respectively) gave the empirical equations defined
0
0.5
1
1.5
2
2.5
3
0 50 100 150 200 250 300 350 400 450
qal
l (×
10
2 k
N/m
2 )
G(×103 kPa)
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0 200 400 600 800 1000 1200 1400 1600
qal
l (×
10
2 k
N/m
2)
G(×103 kPa)
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 13, Number 2 (2018) pp. 1075-1094
© Research India Publications. http://www.ripublication.com
1089
in Eqs (15, 16 and 17) for cohesive soils. And the plots of
modulus of elasticity, E, bulk modulus, K, and subgrade
modulus, ks, against the S-wave velocity (Figures 10, 12 and
14 respectively) gave the empirical equations defined in Eqs
(18, 19 and 20) for cohesionless soils. The equations shows
polynomial relationships between E with Vs and exponential
relationship between K and Vs and linear relationship between
ks with Vs. The minimum, maximum, and average values of
modulus of elasticity, E, bulk modulus, K, and subgrade
modulus, ks for the cohesive and cohesionless soils estimated
to a depth of about 15m from ground surface in the study
areas are given in Table (4).
This result shows that the lower layers are more compressed
than the first layer. This may be as a result of the geologic
formation of these layers, their level of saturation and the
level of cementation of the geomaterial. It was also indicated
that the Young modulus of the subsurface increased in direct
proportion with the seismic wave velocity and the two
parameters generally increased with depth. This also shows
that the second layer has more strength than the other layers.
The results also shows that the first layer would deform more
easily under shear stress than the lower layers. The bulk
modulus results further confirmed that the second geologic
layer to be more competent than the first layer. The subgrade
modulus ranges also reveals that the second geologic layer is
more competent than the first layer.
For Cohesive Soils
E (kN/m2) = (0.0047Vs
2 + 0.5284Vs-47.13) ×10
3 (15)
K (kN/m2) = (0.1566e
0.0074Vs) ×10
6 (16)
ks (N/m2.s)= (0.0008Vs - 0.0119) ×10
8 (17)
For Cohesionless Soils
E (kN/m2) = (0.0047 Vs
2 – 0.4619Vs
-50.866) ×10
3 (18)
K (kN/m2) = (0.2789e
0.005Vs) ×10
6 (19)
ks (N/m2.s) = (0.0008Vs - 0.0002) ×10
8 (20)
Table 4: Soil parameters for different depths in cohesive and cohesionless soils in the study areas.
Soil type
Depth
Approx.
(m)
E×103 -value
(kN/m2)
K×106-value
(kN/m2)
ks ×108-value
(N/m2.s)
Min. Avg. Max. Min. Avg. Max. Min. Avg. Max.
Cohesive
soil
0-6 57.9 304.14 835.5 0.13 1.34 6.62 0.072 0.169 0.314
6-10 239.1 592.7 1204.8 0.55 1.88 4.56 0.165 0.247 0.392
10-15 62.57 588 1082.8 1.58 1.58 3.41 0.082 0.236 0.35
Cohesionless
soil
0-6 124.2 1057.6 3642.6 0.21 2.28 5.14 0.113 0.303 0.65
6-10 167.5 1926.5 11343 0.29 3.64 14.43 0.124 0.39 1.191
10-15 61.8 1313 9397 0.23 3.43 14.62 0.08 0.316 0.953
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 13, Number 2 (2018) pp. 1075-1094
© Research India Publications. http://www.ripublication.com
1090
Figure 9: Young’s modulus against shear wave velocity for cohesive soils.
Figure 10: Young’s modulus against shear wave velocity for cohesionless soils.
0
200
400
600
800
1000
1200
1400
0 50 100 150 200 250 300 350 400 450 500
E(×
10
3 k
Pa)
Vs(m/sec)
0
500
1000
1500
2000
2500
3000
3500
4000
0 100 200 300 400 500 600 700 800 900
E(×
10
3 k
Pa)
Vs(m/sec)
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 13, Number 2 (2018) pp. 1075-1094
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1091
Figure 11: Bulk modulus against shear wave velocity for cohesive soils.
Figure 12: Bulk modulus against shear wave velocity for cohesionless soils.
0
1
2
3
4
5
6
7
8
9
10
0 50 100 150 200 250 300 350 400 450 500
K(×
10
6 k
Pa)
Vs(m/sec)
0
5
10
15
20
25
30
35
40
0 100 200 300 400 500 600 700 800 900
K(×
10
6 k
Pa)
Vs(m/sec)
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 13, Number 2 (2018) pp. 1075-1094
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1092
Figure 13: Subgrade modulus against shear wave velocity for cohesive soils.
Figure 14: Subgrade modulus against shear wave velocity for cohesionless soils.
CONCLUSION
The conclusions that can be drawn from this study can be
summarized as follows:
1. Ranges for values of seismic wave velocities and
allowable bearing capacity for different types of soil
with various description are presented, extending the
knowledge for the limit of theses values. Also the
values of qall determined for hard through loose soil
types were found to be in agreement with references
values and the building codes.
2. Correlations between seismic velocity Vs and
allowable bearing capacity has been obtained. This
relationship show direct proportionalities between Vs
with qall. The results show that the range of bearing
capacity for the study area was between 50 and 408
kN/m2, being highest at north regions and reduces
through middle and south regions of Iraq.
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0 50 100 150 200 250 300 350 400 450 500
k s(×
10
8 N
/m2.s
ec)
Vs(m/sec)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 100 200 300 400 500 600 700 800 900
k s(×
10
8 N
/m2.s
ec)
Vs(m/sec)
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© Research India Publications. http://www.ripublication.com
1093
3. The cross and down hole tests results revealed three
geologic layers with the second layer being more
competent. qall value has an average value of about
142 kN/m2 for layer one, while the average bearing
capacity for layer two is about 176 kN/m2and about
162 kN/m2 for layer three.
4. As the bearing capacity is a mechanism where large
shear strains develop and the measured shear wave
velocity is based on very small strains, thus the
bearing capacity estimated from the shear wave
velocity may be used to check the values calculated
by other means.
5. The obtained empirical expressions may be taken
into consideration when evaluating and predicting
the parameters of the study area.
6. For wide range of ground conditions, empirical
expressions estimated for the qall using Vs measured
at small shear strains, are appropriate to give reliable
results.
7. Allowable bearing capacity being larger with higher
shear modulus improved by higher shear wave
velocity. For cohesive and cohesionless soils it was
indicated that up to a shear wave velocity of 300 m/s
and 400 m/s respectively, the shear wave velocity
may predicts the bearing capacity relatively well.
8. Based on the empirical formulations obtained from
the data of the sites, top layer show less bearing
capacity comparing with layers two and three
depending on the elastic deformability coefficients of
shallow foundation from the graphs of qall against G.
Also the layers show relationships of seconed order
between qall and G.
9. Correlations between seismic velocity Vs and
geotechnical properties have been derived. These
relations show polynomial relationships between E
with Vs and exponential relationship between K and
Vs and linear relationship between ks with Vs.
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