Numerical Analysis of the Effect of Cavity Location on Settlement Behavior

Abstract

The cavity exists in soil mass leads to a serious problem to the structures found on it. This issue rises as dynamic load imposes on soil such as earthquake. The current study investigated numerically the effect of seismic load on behavior of structure placed on the soil media with a cavity. The study comprises the effect of cavity locations on foundation settlement and building deflection. The horizontal distance from foundation center to center of cavity (X) taken as ratio to foundation width (B) (X/B=0, 0.5, 1 and 2), while depth of cavity taken as ratio between vertical distance between foundation base and cavity crown (H) to foundation width (B) of (H/B= 0.067, 0.2, 0.4, 0.8, 1.33 and 2). The results indicated that in case of no-cavity, the settlement increases substantially in presence of cavity under the seismic load to 142 mm compared to 62 mm under static load, and the differential settlement increases from zero to 11 mm due to seismic load. The most critical case appeared when the cavity presented under the edge of foundation (X/B=0.5), where the maximum total and differential settlements under seismic load were148 mm and 38 mm, which they 1.04 and 3.5 times more than the case of no-cavity. Nevertheless, the effect of cavity on settlement was diminished as the cavity offset to location (X≥B) and the effective depth of cavity extended to (H=0.8B). The perturbation of deformation pattern occurred at the crown of cavity especially when cavity closed to foundation. The maximum deflection of building floors exhibited when cavity sited under the edge of foundation (X/B=0).