Determination of Elastic Moduli for the Geotechnical Site Characterization Using Compressional and Shear Seismic Refraction Tomography at the Proposed Site for Baba Gur-Gur University, Northeastern Kirkuk, Iraq

Seismic refraction tomography is carried out at a proposed site for the University of Baba Gur-Gur, Kirkuk, Iraq. Four parallel compressional and shear-wave refraction profiles are accomplished to evaluate the dynamic and elastic moduli of the underlying soil and rocks by analyzing the compressional wave (Vp) and shear wave (Vs) velocities. The Vp and Vs are obtained using two refraction tomography (P and SH) acquisitions along each line. In addition, based on these seismic wave velocities and field density values, empirical and theoretical equations are used to evaluate the dynamic and elastic moduli. The results of velocity models agree with available borehole and outcrop information and show the transition from unconsolidated sediment (topsoil) at the surface to consolidated sedimentary rocks at depth. The results indicate that the study area has four layers with fairly velocity increasing with depth. The first layer with Vp (300-310 m/s) and Vs (110 -115 m/s) predominantly consists of topsoil and forms overburden (competent and sometimes loose soil) and has a thickness (<1 m). The second layer has Vp (830-870 m/s), and Vs (310- 325 m/s) with a thickness range from (3 to 4) m. This layer is suggested to be clayey siltstone belonging to the Mukdadiya Formation. The third layer represented by relatively high Vp (1560-1580 m/s) and Vs (675-685 m/s) with a thickness range from (3 to 7 m) is suggested to be relatively denser clayey siltstone. The bedrock represented by the fourth layer with Vp > 2400 m/s and Vs >1100 m/s is considered the sandstone of the Mukdadiya Formation. According to the information provided, the 3rd and 4th layers are appropriate for the engineering project. The resulting geotechnical properties in the area can be used for the preliminary foundation design of any engineering construction.