Liquefaction Behavior of Low to Medium Plasticity Sand-Fines Mixtures

Abstract

During earthquake, soil deposits are subjected to cyclic loading. Under undrained conditions, cyclic shear stress causes transient disturbance and gives rise to an increase in excess pore water pressure leading to loss of shear strength in saturated soil deposits, there will be excessive strains with continued loss of shear strength resulting in liquefaction. Researchers have identified a significant number of cases where ground failure took place during earthquake in soil deposits containing fines leading to considerable damage to buildings. Some studies show a decrease in liquefaction resistance and others show an increase in liquefaction resistance with an increase in fines content in soil deposit. There is no clarity regarding the effect of fines. In view of this, an experimental investigation has been carried out to evaluate the liquefaction potential of sand-clay mixtures. A series of undrained stress-controlled cyclic triaxial shear tests were performed on reconstituted samples obtained from Cauvery River sand and sand mixtures containing different percentages of plastic fines up to 30%. This paper reports the results of stress-controlled cyclic triaxial shear tests under undrained conditions at 100 kPa confining pressure at a frequency of 0.1 Hz. The results show that the cyclic strength decrease with an increase in fines content upto 20% beyond which it increases. In the present investigation, the limiting fines content is 20%. The results of CRR were analyzed in terms of relative density, fines content, and plasticity characteristics. The results indicate that flow liquefaction depends on the acceleration (CSR) and initial state (void ratio).