Near-surface foundation level assessment from seismic measurements: a case study of north Jeddah City, Saudi Arabia

Near-surface seismic measurements, along with relevant geotechnical methods, have become important techniques for delineating the elastic coefficients and geotechnical parameters of shallow foundations. In the north Jeddah expansion zone, shallow seismic measurements at 76 sites have been carried out to estimate both the P- and S-wave velocities for near-surface sediments. These data have been processed where the results revealed a three-layered ground model that reaches to 30 m depth with varying velocities and thicknesses. Then, the elastic coefficients such as Young's modulus, bulk modulus, shear modulus, ultimate bearing capacity, and allowable bearing capacity have been assessed based on the estimated seismic wave velocities. It can be concluded that bearing capacity is closely related to shear wave velocity and shear modulus. Comparing our results with the published safe ranges of allowable bearing capacities, it is recommended that the first layer in the western zone as well as the second layer is the most suitable areas for constructing safe engineering foundations in the area of interest. Additionally, the best locations of these foundations can be easily identified from contouring maps.