Liquefaction Potential of Pilani Soil

Abstract

Liquefaction takes place when seismic shear waves pass through a saturated granular soil layer. These shear waves distort its granular structure, and cause some of its pore spaces to collapse. This collapse increases pore water pressure and decreases soil's shear strength. If pore space water pressure increases to the point where the soil's shear strength can no longer support the weight of the overlying soil, liquefaction results. In simplified procedure, cyclic stress ratio and cyclic resistance ratio at required depth is determined. These are used to find out factor of safety against liquefaction. It has been suggested that this factor should be more than 2 to ensure safety with respect to liquefaction, excess pore pressure development and ground settlement. Pilani soil is sand till substantial depth below ground surface. Normally water table is at substantial depth. Only during rainfall, soil from ground surface momentarily gets saturated and is below water table. Although this condition of saturation from ground surface with soil below water table is not very likely during earthquake, factor of safety against liquefaction for Pilani soil has been determined for these conditions using simplified procedure. Results have been analyzed and its practical significance has been explained.