Undrained behavior of sand under low cell pressure

Undrained behaviour of sand under low cell pressure was studied in static and cyclic triaxial tests. It was found that very loose sand liquefies under static loading, with the relative density being a key parameter for the undrained behaviour of sand. In the cyclic triaxial tests, pore water pressures built up during the cyclic loading and exceeded the confining cell pressure. This was accompanied by a large sudden increase in axial deformation. The necessary number of cycles to obtain liquefaction was related to the confining cell pressure, the amplitude of cyclic loading and the relative density of sand. In addition, patterns of pore water pressure response are different for sand samples with different relative densities. The test results are very useful for expounding scour mechanism around coastal structures since they relate to the low stress behaviour of the sand.