Geophysical Study of the Soil Surrounding Designed Submerged Concrete Tank Using Seismic Refraction Technique

Abstract

A shallow geophysical investigation using seismic refraction technique was conducted to specify soil layers quality surrounded a designed water storage tank as well as to detect whether any subsurface structural features like (weak zones, cavities or faults) present or not, if it is present, it will create a risk after constructing the project. For this purpose four profiles were conducted around the tank using seismic refraction technique. Interpretation results indicate the presence of three layers. The top soil layer has a velocity ranges between  (200 to 665 m/sec), it refers to unconsolidated weathered layer submerged by a drift sediments along profiles No.(1) and (2), and the second layer with the velocity ranges between (800 to 1550 m/sec), which indicates of moderately cohesive soil layer. However, the third layer with the velocity ranges between (2930 to 4425 m/sec), which reveals to the highly compacted soil layer, these ranges of velocity will reflect increasing of density as well as strength of the soil layers with increasing depths.  The depth section under profile No.(1) from the first to the second layer from geophones No.(6) to (18) as well as for profile No.(2) from geophones No.(8) to (12) are revealed by the presence of the weak zone results from the submerged drift sediments including fissures and fractures.  Processing of the weak zone can be done by removing of the first layer then constructing by a thick concrete foundation on the second layer as well as the supported concrete wall is necessary to avoid future risk, which may result from hydrostatic pressure on the tank.