SHEAR-WAVE VELOCITY TO EVALUATE IN-SITU STATE OF OTTAWA SAND

The initial state of a sand, defined by the void ratio and effective m ean normal stress, can be used to predict its large-strain response. L aboratory studies have shown that the shear-wave velocity of a sand is controlled primarily by the effective confining stresses and void rat io. Since shear-wave velocity can be measured both in the field and in the laboratory, there is an increasing interest in using shear-wave v elocity to define the state of a sand. This paper presents an experime ntal study of shear-wave velocity interpretation for clean Ottawa sand based on steady/critical state concepts. The results show that the la rge-strain behavior of Ottawa sand can be estimated using shear-wave v elocity measurements combined with a knowledge of the in-situ effectiv e stress. Knowledge of the state of a sand makes it possible to estima te the boundary between either a contractant or dilatant sand at large strains. Based on these findings, a preliminary method to evaluate th e potential for flow liquefaction using shear-wave velocity measuremen ts is presented.