Cyclic Strength of Undisturbed Sands Obtained by a Piston Sampler

Abstract

Undisturbed sand samples were taken from two adjacent sites in Niigata, Japan, using an Osterberg piston sampler. One site showed serious signs of liquefaction during the 1964 Niigata earthquake and the other site showed no surface signs of liquefaction. Laboratory cyclic triaxial shear tests were performed on these specimens to determine cyclic strengths of the soils in their undisturbed insitu condition. It was found as a result of these tests that the cyclic strengths of insitu soils in Niigata were not high. Cyclic stress ratios required to cause 5% double amplitude axial strain for 20 stress cycles were on the order of 0.2 for specimens at an average relative density of 65% and on the order of 0.15 for specimens at an average relative density of 35%. There was no distinct difference in cyclic strength values between the two sites where there was and was not surface evidence of liquefaction during the 1964 earthquake.