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International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308

(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 6, November – December (2013), © IAEME

252

CHARACTERISTICS OF SOME GEOTECHNICAL PROPERTIES OF PILA

SPI AND INJANA SEDIMENTARY FORMATIONS, AT SHAQLAWA AREA,

NORTH IRAQ

Ahmed Shehab Al-Banna, Dhahir Khalil Ali, Hamed Hassan Abdullah

ABSTRACT

The Geotechnical properties are an import aspect of civil engineering projects. So many

construction and mining companies interest with such studies. In the present study, 18 limestone

samples from Pila Spi formation and another 19 sandstones samples from Injana formation were

collected from two limbs of a syncline situated northeast Shaqlawa city, north Iraq. The vp and vs

velocities with some geotechnical properties of these samples were investigated. It is concluded that

the geotechnical properties of the samples are varied depending on many significant factors include

water saturation, the relative location of the sample within the syncline limbs and lithology as well.

Each syncline limb has different geotechnical properties than the other due to the nature and degree

of stresses influencing each limb.

Keywords: Poisson's Ratio, Material Index, Pila Spi Formation, Injana Formation.

INTRODUCTION

Many studies discuss the direct relations of longitudinal and transverse wave velocities with

elastic modulus (Wyllie, 1954 and Dobrin, 1976). Other studies deal with the relation of wave

velocities with the geotechnical properties, that are required for civil engineering purpose (Al-Salihi,

1999; Keary et al. , 2002; Al-Banna et al., 2006; Ezdin et al., 2007; Al-khafaji, 2010; Al-kharsan et

al., 2011;Yagin , 2011; Al-Awsi, 2012; and Tezcan and Ozdemir, 2012).

The present study is an attempt to investigate the characteristic of samples of Pila Spi and

Injana Formations, that exposed at Shaqlawa area, northern Iraq with respect to geotechnical

properties (Figure -1 ). Such this study is use to encourage the engineer to design a suitable building

structure, through definition the proper basement rock which eventually leads to select a better

building material for constructions. It also gives an idea of the environmental impact (water

saturation) on the geotechnical parameters of rocks.

INTERNATIONAL JOURNAL OF CIVIL ENGINEERING AND

TECHNOLOGY (IJCIET)

ISSN 0976 – 6308 (Print)

ISSN 0976 – 6316(Online)

Volume 4, Issue 6, November – December, pp. 252-260

© IAEME: www.iaeme.com/ijciet.asp

Journal Impact Factor (2013): 5.3277 (Calculated by GISI)

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IJCIET

©IAEME

International Journal of Civil Engineering and Technology (IJ

(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 6, November

Figure

International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976

6316(Online) Volume 4, Issue 6, November – December (2013), © IAEME

253

Figure -1: Location map of the study area

CIET), ISSN 0976 – 6308

December (2013), © IAEME



254

TECTOINC AND GEOLOGY

Tectonically, the study area belongs to the low folded zone according to the tectoinc divisions

of Iraq. This zone contains many formations exposed to the surface of Neogene sedimentary rocks.

The core of most anticlines in the folded zone include a sedimentary rocks of upper Cretaceous and

Eocene.

Pila Spi Formation is lagoonal facies belongs to the late lower Eocene –upper Eocene. The

upper part of the formation is well bedded crystalline limestone, while the lower part shows well

bedded hard, porous, limestone (Buday, 1980).

Injana (formally upper Fars) formation is accepted as upper Miocene in age. This formation

is variable from silty marlstone or claystone, medium to coarse grained sandstone (Jassime and Goof,

2006).

SAMPLE COLLECTION AND PROCESSING

Samples were collected from two limbs of the syncline which is situated at the northeastern

side of Shaqlawa city (Figure-1). The number of samples have been collected from the two

formations within the syncline are shown in table- 1.

Table-1: Number of Collected Samples in the Study Area, Northeast of Shaqlawa City

Location Pila Spi Formation Injana Formation

Northeastern limb 9 11

Southwestern limb 9 8

All the samples were processed to measure the physical properties. A cylindrical samples are

introduced with diameter of 7.6 cm and length range (8-16) cm. The surface of the two sides of each

cylindrical sample is smoothed using a special Grinder, according to ASTM 1987, in order to

measure the seismic wave velocity.

Ultrasonic device (New sonic viewer model- 5217A) is used to measure the P-wave and S-

wave in the laboratories of the Department of Geology in the University of Baghdad. The

longitudinal velocity (Vp) and transverse velocity (Vs) for all the samples are measured in two stages.

The first stage where the samples are dry, whereas the second where they are fully saturated with

water. The samples were considered fully saturated after they immersed in water for more than 48

hours.

The theoretical relations of considered parameters The theoretical relations between the seismic velocity of longitudinal and transverse waves

and some geotechnical properties are modified to obtain the average value of the considered

formations.

The present study focuses on the determining of Poisson's ratio (σ), Material index (Im), and

the effective angle of internal friction (ϕ ). Poisson's ratio (σ) is the ratio of frictional transverse contraction to the fractional extension

(Bowles, 1984). The parameters calculated using the following equation:

Poisson's ratio (σ) =�.�� ⁄ ^�� ⁄ ^�� (Dominco, 1984)



255

The equation above is a graph of Vs2 (x-axis ) and Vp

2 (y- axes) ,for each case was plotted

the modified as below to obtain the average values of Poisson's ratio (σ).

Poisson's ratio (σ) =�.��

Material index (Im): It respect the degree of material efficiency . It is influenc by material

content , degree of the consolidation , joints, fracture and existence of liquid in pore, which influence

the elasticity of materials. (Abdel Rahman et al, 1994).

Material index (Im)= �� ⁄ ^�� ⁄ ^��

The slope of the graph of Vp2/Vs

2 was used to modified the equation above in another

form(as below ) To obtain the average value of material index (Im).

Im =��

The effective angle of internal friction (ϕ )

Is an important geotechnical properties. It is possible to measure this angle in the laboratory

by using Mohr's circles in triaxial test . This angle is use for evaluat the engineering properties of soil

and rocks.

Sin ϕ = 1 � �� ⁄ ^�� ⁄ ^� �

Thus

Sin ϕ = ��

�� ⁄ ^�

As the slope of the plotted graph between Vp2 and Vs

2 represent Vp

2/Vs

2 the Sin ϕ was calculated

according to the following equation .

Sin ϕ = ��

��

RESULT AND DISCUSSION

The longitudinal and transverse wave velocities of the considered samples were measured

and plotted for Vp2 versus Vs

2 for both case dry and fully saturated samples . The results of the dry

and saturated sample of Pila Spi formation on both limb are illustrat in figures- 2, Figure- 3 show the

results of sandstone samples collected from Injana formation in case of dry and saturated samples on

both side of the syncline.

The mean values of all the studied cases were computed and summarized in Table- 2.



256

Figure -2: Relationship between Vp2/Vs

2 for Pila Spi formation of the syncline (east of Shaqlawa)

displays the average values of the Geotechnical properties .

3000000 3500000 4000000 4500000 5000000 5500000 6000000

Vs^2 (m/sec)^2

8000000

10000000

12000000

14000000

16000000

Vp

^2

(m

/se

c)^

2

4000000 5000000 6000000 7000000 8000000

Vs^2 (m/sec)^2

8000000

12000000

16000000

20000000

24000000

Vp

^2

(m

/se

c)^

2

PilaspiFn Pilaspi Fn.

Dry case Dry case

Southwestern limb Northeastern limb

Slope= Vp2 = 3.00667952 * Vs

2 - 2816826.024 Slope=Vp

2 = 2.785257566 * Vs

2 - 772244.5231

Corr. Coeff. = 0.95 Corr. Coeff.= 0.98

2000000 3000000 4000000 5000000 6000000

Vs^2 (m/sec)^2

6000000

8000000

10000000

12000000

14000000

16000000

18000000

Vp

^2

(m

/se

c)^

2

2000000 2400000 2800000 3200000 3600000 4000000

Vs^2 (m/sec )^2

8000000

9000000

10000000

11000000

12000000

13000000

Vp

^2

(m

/se

c )

^2

PilaspiFn PilaspiFn

Saturated case Saturated case


Slope=Vp2 = 2.881541654 * Vs

2 + 942619.3444 Slope=Vp

2 = 2.785722779 * Vs

2 + 2167125.688

Corr. Coeff. =0.96 Corr. Coeff. =0.97



257

Figure -3: Relationship between Vp2/Vs

2 for Injana formation of the syncline (east of Shaqlawa

displys the average values of the Geotechnical properties)

400000 800000 1200000 1600000 2000000

Vs^2 ( m/sec)^2

2000000

4000000

6000000

8000000

Vp

^2

(

m/s

ec

)^2

400000 800000 1200000 1600000 2000000

Vs^2 ( m/sec)^2

0

2000000

4000000

6000000

8000000

Vp

^2

(

m/s

ec

)^2

InjanaFn Injana Fn.

Dry case Dry case


Slope= Vp2 = 3.941537118 * Vs

2 - 2769.435304 Slope=Vp

2 = 4.405610867 * Vs

2- 426360.3182

Corr. Coeff. = 0.99 Corr. Coeff.= 0.98

0 200000 400000 600000 800000

Vs^2 ( m/sec)^2

0

500000

1000000

1500000

2000000

2500000

Vp

^2

(

m/s

ec

)^2

100000 200000 300000 400000 500000 600000

Vs^2 (m/sec)^2

400000

800000

1200000

1600000

2000000

Vp

^2

(m

/se

c)^

2

InjanaFn InjanaFn

Saturated case Saturated case


Slope=Vp2 = 3.605746746 * Vs

2 - 15912. Slope=Vp

2 = 3.819683643 * Vs

2 - 55488.2537

Corr. Coeff. =0.99 Corr. Coeff. =0.98



258

Table -2: Summary of the ratio of Vp2/Vs

2 and mean values of the considered Geotechnical

properties for limestone samples of Pila Spi formation and sandstone samples of Injana formation,

northeast of Shaqlawa city

Parameters

Mean

values

Sample

Type

Location

and station

Vp2/Vs

2

Poisson's

ratio (σ)

Material

index (Im)

The effective

angle of

internal friction

(ϕ )

Pilaspi (Lst.)

NE, dry

2.8266 0.226 +0.094 45°

Pilaspi (Lst.)

SW, dry

3.0066 0.251 - 0.0032 42°

Pilaspi (Lst.)

NE, saturate

2.7857 0.2199 +0.120 45.9°

Pilaspi (Lst.)

SW, saturate

2.8815 0.234 +0.0629 44°

Injana (S.st.)

NE, dry

4.4056 0.3431 - 0.412 27°

Injana (S.st.)

SW, dry

3.9415 0.3299 - 0.3199 30°

Injana (S.st.)

NE, saturate

3.81968 0.3226 - 0.2905 31.6°

Injana (S.st.)

SW, saturate

3.6057 0.3081 - 0.2324 33.7°

The results shown in table-2 were interpreted, then the conclusions can be conclude as follows:

1- Generally the mean values of the ratio Vp2/Vs

2 in limestone samples of Pila Spi formation is

lower than that value in sandstone samples of Injana Formation

2- The Poisson's ratio of limestone of Pila Spi formation is lower than that of sandstone of Injana

formation which indicat that the limestone rocks is stronger than sandstone rocks in the study

site.

3- The mean value of Material index (Im) of sandstone samples of Injana formation were

classified within the category (I) according to Abdel Rahman (1989) classification , which

indicates relatively weak rocks. The mean values of Material index (Im) of limestone Pila Spi

formation were considered within the category (III) according to Abdel Rahman (1989) that

indicat relatively hard rocks.



259

4- The effective angle of internal friction of limestone of Pila Spi formation is greater than that

of sandstone of Injana formation indicating relative weakness of sandstone comparing with the

limestone.

5- The mean values of Vp2/Vs

2 and Poisson's ratio (σ) decrease in the saturated samples relative to

the dry samples for both formations.

6- The mean values of Material index (Im) and the effective angle of internal friction (ϕ) increase

with the saturated samples relative to the dry samples for both formations.

7- The samples on the two limbs of Syncline shows a slight variation in the Geotechnical

properties. Generally, limestone samples of Pila Spi formation shows an increase in the values

of Vp2/Vs

2and Poisson's ratio (σ) at the southwestern limb relative to the northeastern limb. The

Material index (Im) and the effective angle of internal friction (ϕ) decrease in the southwestern

limb of syncline.

On the other side, the mean value of Vp2/Vs

2 , Poisson's ratio and Material index (Im) for

sandstone samples of Injana formation decreases at the southwestern limb of the syncline relative to

the other limb. The effective angle of internal friction (ϕ) shows increase values at the southwestern

limb relative to the northeastern limb of the study syncline northeast of Shaqlawa city.

Finally, it is easily concluded that the geotechnical properties are varied relative to the

lithology and saturation.

The important conclusion obtained from the present study is the variance of Geotechnical

values on the opposite side of the syncline. The last conclusion may be related to the relative stresses

which effect to the structure.

In the present study, the stresses cause the syncline structure effecting the northeast side more

than the southwest side, considering the line of collision of Arabian and Iranian plates at the

northeastern side of the studied area.

So, It is recommended to carried out an individual study for each site on the field, in order to

obtain the actual physical or Geotechnical properties rather than using theoretical values which

concealed many effective parameters. The authors believe that the physical properties actually

changed from one meter to another, relative to the lithology, saturation, stresses and other unknown

factors.

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