Application of seismic refraction and MASW geophysical techniques to characterize the subsoil structure under damaged buildings in Qeft city, Upper Egypt

The shallow seismic methods, including seismic refraction and 1D MASW, were used to investigate the shallow soil in the vicinity of five damaged building blocks in the village of El-Kalaheen. These building blocks exhibited structural problems including cracks, fissures and displacements between neighboring buildings. The results of both methods show that the shallow subsurface consists of two layers: a surface layer of loose sands, gravels, silts and clays and a compacted sandy clay layer that forms the bedrock in the area. The resulting seismic velocities were used to calculate the geotechnical parameters of the two layers, including Poisson’s ratio, shear modulus, Young’s modulus, material index and N-value. In addition, the shear wave velocities resulting from the 1D MASW method were used to calculate the average Vs30 in the site. The calculated values of the geotechnical parameters show a gradual increase in the competence of the upper layer from fairly competent and loose in the south of the area to competent and denser in the north. The geotechnical parameters of the bedrock also show an increase from moderately competent in the south to denser and more competent in the north. Possible zones of weakness are also observed in the southern part of the site. The calculated Vs30 indicates a site with stiff soil classification.