EFFECT OF FINES ON LIQUEFACTION POTENTIAL

Abstract

Earthquake induced liquefaction is a major cause of loss in soil strength and consequent damage to soil-structure systems. Although, loose, saturated cohesionless soils are most susceptible to loss of strength, there are strong evidence suggesting that soils containing fines such as silty sands are also prone to liquefaction during earthquakes. The liquefaction of silty sands has been observed in a number of recent case studies. In fact, the literature contains what appears to be contradictory evidence. There is a need to clarify the effects of fines content on the liquefaction resistance of sandy soils, and to determine methods for accounting for these effects in engineering practice. The goal of the present research work is to evaluate the effect of fine silts in stabilizing or destabilizing a potentially liquefiable sand deposit. During the lab investigations, locally available Solani Sand and Dhanauri Silt have been used. The soil samples has been prepared by the varied silt content from 0% to 25 % and varying the initial relative density. For measuring the pore water pressure generations the vibration table tests at three different accelerations i.e. 0.30 g, 0.40 g and 0.60 g had been performed, keeping the frequency of vibration fixed at 5 cps. The results of the study performed are used to clarify the effects of non-plastic fines content and resolve the majority of the inconsistencies in the literature. As the silt content increases, the no. of cycles requires to produce maximum pore water pressure increases. Rate of maximum pore water pressure generation is maximum at critical silt content for a particular level of excitation and it decreases as percentage of silt content increase. It is also found that critical silt content is different for different accelerations to generate maximum pore water pressure.