Effect of Initial Principal Stress Direction on the Dynamic Characteristics of Carbonate Sand

The dynamic characteristics of carbonate sand under wave loads are very important for constructions on the ocean floor.The initial principal stress direction has been known to exert some in-fluence on the dynamic characteristics of sand during cyclic loading.In an effort to investigate this aspect of the problem, several series of cyclic undrained tests were carried out on a saturated and loose sample of carbonate sand using a geotechnical static and dynamic universal triaxial shear apparatus.In this test apparatus, a hollow cylindrical sand specimen is subjected to a simultaneous application of both triaxial and torsional modes of shear stresses, which brings about the continuous rotation of principal stress axes. The test results indicated that the initial principal stress direction has a considerable influence on the dy- namic strength of loose carbonate sand and with the increase of initial orientation of principal stress, dy- namic strength will be reduced, the cyclic pore pressure increased, but the residual pore pressure reduced.