CHARACTERISTICS OF LIQUEFIED SILTY SANDS FROMMEIZOSEISMAL REGION OF SHILLONG PLATEAU, ASSAM ANDBHUJ IN INDIA

摘要

This paper describes the results of an experimental study on the undrained behavior of liquefied siltysands collected from the two regions of earthquake affected areas namely Beltaghat in Assam state andBhuj in Gujarat State in India. In the present study both static and dynamic testing of soil was carried outby employing a servo-controlled electro hydraulic closed loop test system. Stress - controlled cyclictriaxial undrained shear tests were carried out on soil specimens from Bhuj area and Strain – controlledcyclic triaxial undrained shear tests were carried out on soil specimens from Assam area. In all the tests asinusoidal loading with a frequency of 1Hz was maintained. The potential for liquefaction of both soilswas evaluated for the range of relative densities from 20% to 75% under an effective confining pressure of100 kPa. Also, undrained triaxial shear tests under monotonic loading were conducted on soil specimensfrom Bhuj area to establish steady-state and quasi-steady state lines for the range of relative densities20% to 80% and confining pressures 25 kPa to 450 kPa to estimate the residual strength of liquefied siltysands. By examining the laboratory test data, the liquefied silty sand from Bhuj consisting of appreciableamount of fines showed the residual strength to be a function of effective confining pressure and voidratio. Further, cyclic triaxial test results clearly explain that there is a consistent relationship betweencyclic shear strain and pore pressure generation in silty sand.