Empirical Relationship between Three Geotechnical Properties Obtained in Three Sites in Kerbala City, Iraq

Abstract


Introduction
The researches and studies show the calculation of the acoustic waves from inside the wells, and it enables the calculation of the compressional (longitudinal) and shear (inverse) wave velocity for different layers, and then calculate various elastic moduli (Telford et al., 1981).This is a very important step in different civil engineering applications to obtain information in the geological properties and specifications of the layers between the wells, which is important in theoretical and applied studies to determine the soil physical and mechanical properties to treat the soil affected by environmental or physical influences (Khorshid and Al-Awsi, 2020).The seismic wave velocity of the rocks depends on the elasticity and density coefficients, and the velocity values can be calculated by measuring the elasticity coefficient of the rock samples (Al-Banna et al., 2014) and (Sharma, 1986).
Where the density of the elastic medium in which seismic energy progresses is one of the direct influencing factors on the seismic velocity (Michel, 1989) and (Alkafeel Center, 2020).The equations show that the relationship between seismic velocity and density is inverse, but any increase in density leads to increase the velocity (Nafe andDracke, 1957, Al-Fahdawi, 2000).This increase in the elasticity of this ratio as a result will increase the velocity.During the seismic wave is transmitted any error in measuring the density of the elastic medium leads to a doubling of this percentage of error in the values of the elastic coefficients.The error percentage in measuring the density of subsurface soil models increases as we approach the surface of the earth (Bowles, 1984).The high accurate density, longitudin,al and transverse seismiwavees measurements are very important to obtain accurate geotechnical property values (Hunt, 1986 andKhorshid, 1994).
To obtain information on the properties of geological characteristics and layers between wells (Mc Cann et al., 1975), which are important in theoretical and applied studies to determine the properties of physical and mechanical soil and to find scientific means to treat the soil affected by environmental and physiological effects (Holtz et al., 1981).The seismic velocity of the rocks depends on the elasticity and density coefficients, and it is possible to calculate this velocity through the elasticity parameters of the rock samples (Grainger et al., 1977) .
The relationship between the velocity of compressional and shear waves Vp/Vs , Vs/Vp was used proportionately and some geotechnical characteristics of the soil were calculated for geometrical purposes based on this ratio (Mosa, 2003).

Study Area
The study areas are located in the province of Kerbala, Iraq, where three engineering sites were chosen in which the seismic cross-hole method was used to calculate the values of the geotechnical properties of the soil layers, the first one is the Al-Abbas holy shrine, second is Al-Khiam hotel, these sites are located in the center of the city of Kerbala, and the third site is the pure water project located at distance about 3 km towards the south of the city (Table 1 and Fig. 1).
Table 1.The boreholes and seismic cross hole profiles and coordinates for three projects in study area

Project name. Coordinate
Al-Abbas holy shrine

Fieldwork
Fieldwork was carried out at several engineering sites in the Kerbala governorate, the three sites are Al-Abbas Holy Shrine, the Al-Khiam hotel, and the pure water project.The field work ( processing, and calculating of the geotechnical properties for the three projects) were completed in 2014, 2017, and 2021respectivily.Excavation works were carried out for some boreholes and casing for them by plastic pipes to be high-pressure vertical compression PVC, then filling the cavity between the outer surface of the pipes and the wall of the boreholes with cementing material.After that, a cross hole seismic survey was used, from the natural ground surface to 15 m.depth.
The fieldwork included a geophysical survey using the cross hole seismic method of the site of Al Abbas holy shrine (Fig. 2), where the work volume consisted of 32 profiles.The total inspection points were 2034 examination points of depth, starting from the earth surface to depth of 15 meters.

Drilling
After the boreholes significant on the ground surface of the study area through cutting and fracturing the concrete bed by a jackhammer, and the pure water project.Fourty eight boreholes were drilled in the study area by a normal auger using Acker type of drilling rig.The drilling as: Twenty seven boreholes were drilled inside and outside the holy shrine, with a depth ranging between (15-17) m. below the surface of the earth.164 Six boreholes were drilled around the Al-Khiam hotel project, with a depth 12 m.below the ground surface.
Fivteen boreholes were drilled around the filter hall in a pure water project, with a depth of 9 m.below the ground surface.
Then casing by plastic pipes to bear high-pressure vertical compression (PVC) and cement material around the pipe, The locations of these boreholes are shown in Fig. 2 3.1.2.Seismic cross-hole survey Crosshole Seismic is a suitable main geophysical method that was used in the study area to calculate elastic moduli and another geotechnical property, underneath the foundation.For this reason, selected thirty-two profiles were surveyed (Table 2).The profile of a cross hole has a number and consists of two or three boreholes one of them used as a source to generate seismic waves and the other to receiver its (Fig. 3).The twenty five profiles have covered the project of Al-Abbas holy shrine and two profiles are coverd the site of Al-Mukhiam hotel, and there are five profiles cover the pure water project.The cross hole seismic method is the best technique used to calculate the geotechnical properties of soil.The study area was covered by 32 seismic cross-hole profiles (Table 2).

Sites of study area seismic Crosshole profiles
Al-Abbas holy shrine 25 Pure water 5 Al-Khiam Hotel 2 In this paper, selected one profile for each project as example.

Instrumentation
Fig. 4, shows the geophysical instruments and drilling machines that were used in fieldwork.
Drilling machine Mode; MEGA TRUCK (235 PSCRDI ), BEM Terraloc Mark 6 seismic system made in Sweden As well boreholes pickup is a seismic downhole, cross hole, up hole receiver designed to measure P and S wave velocities in a borehole.It consists of three components geophone.

Material Index (Im)
It is one of the most important geotechnical indexes,it refers to the degree of material efficiency due to its dependence on anumber of elastic coefficients depending on the two ratios G/B and λ/B (Palmer, 1991).
This index is affected by the components of the material, the degree of adhesion (consolidation), fractures, water content, joints, , and the presence of fluids in the void, which affect the elasticity of the materials and seismic wave velocities were (Abedel Rahman, 1989).
The values of this coefficient are between (-1) when the shear modulus equal zero for liquid materials to (1) when Lame's Constant equal zero for rocks (Abedel Rahman, 1991).

Coefficient of lateral earth pressure at rest (Ko)
This coefficient is one of the most common in the civil engineering is and very important coefficient in geotechnical engineering (Al-Khafaji, 2004).K o is the ratio of the lateral (horizontal) to vertical stress in the ground as: Where: H =Lateral stress.V=Vertical stress.Ko may be calculated from seismic compressional and shear wave velocity ratio (vp/vs), (vs/vp) (Al-Salihi, 1999, Al-Awsi, 2012). (5)

Concentration Index (Ic)
The concentration index is specially used to measure the qualification of foundations and other engineering objects.The concentration index is soil depend (Bell, 1980).
ko =1 and Ic = 3.It would appear that the range of Ic is 3 < Ic < 6 (Cernica, 1995).Near the ground surface some experimental evidence indicates that Ic < 3 but may well approach 3 at depths in the ground where the soil is denser, stiffer, and substantially " confined ".I c is more than 6 for solid rocks (Al-Khafaji, 2010).
For the relationship between the shear and compressional wave velocities we can define Ic:

Results
The longitudinal and shear wave velocities (Vp and VS) are known by using the previous equations 2,3,5 and 7 of (Khorshid and Al-Awsil, 2020). .
The results of the seismic cross hole survey included the recording, processing(Davis and Schulthesis, 1980) (Fig. 5).The calculation of the longitudinal (compressional) and transverse (shear) seismic wave velocities of the soil from the earth's natural ground surface up to 15 meters.
The values of these velocities have been used to calculate the geotechnical properties such as

Discussion
Al-Abbasia holy shrie, pur water project and Al-Khiam hotel project, where the results of geophysical and geotechnical surveys from the surface of the earth and to a depth of 15 meters to the soil of three sites, were adopted for the sites of the study and using the equations 2,3,5 and 7, and then in this study using the following geotechnical AlKafeel equations: The results are mostly the same only different by about 1% -2%, which percentage success in the use of these equations approximately 99%.
Tables of the results of the seismic cross-hole velocity and geotechnical properties showed that the Material Index( Im), Concentration Index (Ic) ,and Coefficient of Lateral Earth Pressure at Rest (Ko) have approximately the same values in the case of the use of the universally adopted equations and the ones we reached.
Only one of them denotes the other quickly and accurately so we have saved time, speed, and accuracy.These equations can be applied as follows: First, the longitudinal and transverse seismic wave velocity is recorded through the seismic cross hole survey and the values of these velocities are calculated, and then these values of velocities are used in calculating the geotechnical properties by equation 5. Then used new equations 8, 9, and 10 to calculates the material index, and concentration index or may be used the equation 2 or 3 to calculates the material index.Then new equations 8, 9, and 10 are applied in calculating the coefficient of lateral earth pressure at rest and concentration index.Or may be used the equation 10 to calculate the concentration index and then new equations are applied in calculating the material index and coefficient of lateral earth pressure at rest.
But it is preferable to obtain speed and shorten the time and effort in calculating these parameters to use equation 5 in calculating the coefficient of lateral earth pressure at rest and then new equations are applied in calculating the material index and concentration index.
The obtaind relations are empirical relation may be good in study sites that is due to: 1.The values of each properties used in this study are mostly the same only different by about 1% -2%.
2. The new relations can be used to calculate the Material Index ( Im), Concentration Index (Ic) ,and Coefficient of Lateral Earth Pressure at Rest (Ko), for any geological sites especially in engineering sites, which gave very excellent and accurate results by approximately 99%.

Conclusions
An attempt were used to obtain some relations between three geotechnical properties Material Index ( Im), Concentration Index (Ic) ,and Coefficient of Lateral Earth Pressure at Rest (Ko) ) from the result of three sites of kerbala city.The obtaine empirical relation shows an acceptable and accurate results in the study sites.

Fig. 1 .
Fig.1.Location of study area, a) Al-Abbas Holy shrine b) Al-Khiam hotel,c.Pure water project

Fig. 2 .
Fig. 2. Shows field work boring and seismic cross hole survey profiles in study area a) for Al-Abbas holy shrine project b) Al-Khiam hotel c) in the pure water project

Fig. 4 .
Fig. 4. Instrumentations are used in fieldwork, a) Drilling machine b) ABEM Terraloc Mark 6 seismic system, c) Boreholes pickup Poisson's Ration ( ), Material Index (Im), Concentration Index (Ic), and Coefficient of lateral earth pressure at rest (Ko),( Al-Banna et al., 2013).The values of Longitudinal, shear wave velocities and geotechnical properties are illustrated in tables 3 through 8 and the relation between the depths and their properties been shown in Figs. 6 to 8.

Fig. 5 .
Fig. 5. Seismic cross hole recording in study area

Fig. 6 .
Fig. 6.The relationship between seismic wave velocities and geotechnical properties with depth in Al-Abbas Holy Shrine in 2010

Fig. 7 .
Fig.7.The relationship between seismic wave velocities and geotechnical properties with in Pur water project

Fig. 8 .
Fig.8.The relationship between seismic wave velocities and geotechnical properties with depth in Al-Khiam hotel project

Table 3 .
The results of Seismic wave velocities and geotechnical properties in Al-Abbas Holy Shrine in 2010

Table 5 .
The results of Seismic wave velocities and geotechnical properties in Pur water project The results of Seismic wave velocities and geotechnical properties in Al-Khiam hotel project I

Table 8 .
The results of Seismic wave velocities and geotechnical properties in Al-Khiam hotel project