Influence of Sample Disturbance on Sand Response to Cyclic Loading

The factors influencing the cyclic liquefaction characteristics of saturated sands are reviewed and shown to be profoundly influenced by the relative density, the sand structure, a prolonged period of pressure application, the past seismic history, and the effects of overconsolidation. A study is described in which the cyclic liquefaction characteristics of samples extracted carefully from a bed of sand having a prior seismic history are determined and compared with the characteristics from an otherwise identical bed having no seismic history. Although the sand beds had characteristics differing by 50%, the characteristics of samples taken from both beds were essentially the same. It is suggested that the effects of many factors affecting the stability of natural deposits of dense clean sand lost during the sampling process and that special care is required to arrive at a reasonable evaluation of the cyclic liquefaction characteristics of such soils.