Utilizing Shear Wave Velocity Techniques for Identifying Engineering Challenges in 6th October City, Egypt

In Egypt, geophysical surveys are now more critical, especially following the significant impact of the October 1992 earthquake on structures in Greater Cairo. Engineering site investigations aim to determine the depth and lithological composition of the bedrock, groundwater depth, and lateral lithological variations, and to identify faults or fissures. To meet these objectives, shallow seismic refraction surveys were conducted in a selected area within 6th October City, Egypt, to assess subsurface characteristics before commencing construction activities. The first step was taken to identify the underlying geological structure by acquiring fifteen seismic refraction profiles over the research region. The primary wave velocity distribution analysis identified the existence of three separate geoseismic strata characterized by velocity ranges of (685 to 835 m/s), (680 to 1030 m/s), and (1340 to 1525 m/s). The sediment layers exhibit shear wave velocities ranging from 356 to 440 m/s, 360 to 536 m/s, and 690 to 790 m/s, respectively. These findings indicate that the first layer has low velocity values, which reflect a sediment composition consisting of sandy gravel. On the other hand, the second layer consists of coarse gravelly sand, while the third layer consists of clayey limestone. The sediment layers were analyzed using a basic equation to derive geophysical characteristics, which include the velocity of the shear wave, the density of the rock, and material indices (including material index, Poisson's ratio, N-value, and stress ratio). According to these data, the sediment layers beneath the surface in this area have a moderate to high level of competence.