digilib@itb.ac.id +62 812 2508 8800

1990_TS_PP_JITNO_1.pdf
PUBLIC Irwan Sofiyan

An important consideration in the design of clay foundation for seismic or wave loading is the undrained response of clay during and after cyclic loading . Cyclic loading of clays causes, in general, a reduction in both stiffness and undrained strength on subsequent static loading. No systematic study has been carried out to assess this loss in stiffness, and there are conflicting conclusions as to the magnitude of strength reduction 7n studies reported in the literature. This thesis presents a study of the influence of cyclic loading on the post-cyclic uadra t.ed stress-strain characteristics of a marine clay. The influence of factors, such as, cyclic stress level. number of cycles, amplitude of maximum axial strain during cyclic loading, residual pore pressure and residual strain at the conclusion of cyclic loading is systematically investigated. In addition, the influence of initiating cyclic loading with the type of loading pulse (compression and extension) and the sense of residual strain in relation to the sense of strain during post-cyclic monotonic loading is studied. It is shown that the loss in undrained stiffness and undrained strength of the undisturbed clay as a consequence of cyclic loading are not uniquely related to the amplitude of strain during cyclic loading, as commonly assumed. Nor can they be explained in terms of overconsolidation induced as a result of pore pressure generated due to cyclic loading. A rational explanation and correlation of both the changes in post-cyclic stress-strain and strength of clay is provided in terms of hysteretic work absorbed by the clay during cyclic loading.