Consolidation Theory For Non-Monotonic Compression Of Subsoil Under Periodic Loading

The non-monotonic compression and consolidation under periodic loading is mainly caused by the factor that the compressibility of soil for loading differs from that for unloading. Although consolidation theory has been developed for more than eighty years, in normal consolidation analyses, the compressibility of soil is still just taken as a constant in the process of loading, unloading and reloading, which is obviously not consistent with the truth of practical engineering. In this thesis, one-dimensional consolidation theory for non-monotonic compression of subsoil under periodic loading is studied and the consolidation behavior is investigated.Firstly, based on the same assumptions as in Terzaghi's theory except for loading type, an analytical solution for one-dimensional linear consolidation of saturated soil under periodic loading is derived by using laplace transform and Heaciside formula.Secondly, based on semi-analytical method, computer code ODLCASUPL for non-monotonic compression and consolidation of saturated soil is developed by Fortran programming. To verify the reasonability of the code, comparisons are made between the semi-analytical solution and Terzaghi's theory, as well as the analytical solution for one-dimensional linear consolidation under periodic loading given by the author.Finally, by using the computer code, a great amount of computation is made through typical numerical examples, and the behavior of one-dimensional non-monotonic compression and consolidation of saturated soil is illustrated.It has been shown that once the effect of non-monotonic compression factor is taken into account, the consolidation behavior of soil differs greatly from that described by Terzaghi's theory. The non-monotonic compression factors such as compression coefficient ratio a_e/a_v, load ratio q_l/q_u, rate of loading and that of unloading, all have significant influence on the consolidation behavior.