LIQUEFACTION POTENTIAL ALONG WITH PORE WATER PRESSURE GENERATION OF COASTAL SAND OF DIGHA IN WEST BENGAL, INDIA.

Stress controlled cyclic triaxial tests have been done on coastal sand of Digha, West Bengal, India, at different frequencies, confining pressures, and relative densities and cyclic stress ratios. Number of cycles for initial liquefaction (NL) has been determined for that number of cycle when excess pore pressure ratio has become equal to 1. Significant influences of density of sand, confining pressure and number of cycles for initial liquefaction on coastal Digha sand have been found. The test results have shown that increasing density of sand increases liquefaction potential, whereas cyclic strength of sand decreases with increase of confining pressure. An empirical correlation has been developed on cyclic strength of sand based on these parameters and this correlation fits quite well with the observed experimental results. Bender Element tests have been performed to determine maximum shear modulus (Gmax) of Digha sand at different densities and confining pressures. A high correlation coefficient between cyclic strength and Gmax of Digha sand at any NL has been found. A new pore water pressure generation model has been introduced for this sand along with upper bound and lower bound curves to predict excess pore water pressure build up due to seismic loads. [ABSTRACT FROM AUTHOR]