Using Shallow Seismic Method for Evaluation of the Foundation Beds of New Cairo Extension (Andalus Area), Egypt.

Abstract

Shallow Seismic Refraction Method (SSR) in engineering investigation is growing interest after the October 1992 earthquake in Egypt. In the present study, eight shallow seismic refraction (SSR) profiles were acquired along the Al-Andalus area, which located at the southeastern part of new Cairo extension, Egypt, in order to identify the shallow subsurface geological features of the near-surface section. Both Primary (VP)-wave and Secondary (VS)-wave velocities that were picking and computed during processing and interpretation. The seismic compressional wave velocity (Vp) distribution indicates that there are three geoseismic layers ranging between (420 and 680 m/s), (1040 and 1680 m/s) and (2170 and 3100 m/s), for first, second and third layers, respectively. The first shear wave velocity (VS) is ranging between (240 – 390 m/s), the second VS layer ranging between (570 - 980 m/s), and the third VS layer is ranging between (1240 - 1800 m /s). The thickness of the first layer varies from 1.8 to 2.6 m and the second layer ranges between 7.6 and 10.5 m. The geoseismic cross sections are interpreted geologically as the first low velocity values which indicate weathered sediments fine sands change to sandy gravels sometimes. However, the second geoseismic layer is represented by consolidated sands with clay intercalations and the third layer reflected sandstones. The geotechnical parameters (elastic modulus, material competence and bearing capacities) are estimated. The distribution of these parameters noticed that the areas can be carried heavy loads at the central, east central and north central parts of the study area.