A Study On One-dimensional Nonlinear Consolidation Of Soft Soil Under Cyclic Loading

On the basis of the work so far available, this paper makes a further study of non-linear (the well-known empirical e~lgσ' and e~lgkv relations) one-dimensional consolidation problems of soft clayey soils under cyclic loadings.Firstly, by the method of Laplace transform, at cc/ck=1(permeability index kv changes synchronously with volume compression index mv, and Cv is constant), one dimensional consolidation of one-layer soil under any cyclic loadings is studied and the analytical solutions in frequency domain are obtained. On the basis of the solutions obtained and the computation through programming, the influence of some parameters and loading conditions on the non-linear one-dimensional consolidation behaviors under suddenly-imposed, sin, trapezoidal, triangular and rectangular cyclic loading, are investigated. At last, the results are compared with Terzaghi's consolidation theory and linear consolidation theory under cyclic loadings.Secondly, at cc/ck is any constant K, and the more common situation, which permeability index kv changes non-synchronously with volume compression index mv, at this time, Cv is not constant, non-linear one-dimensional consolidation of one-layered soil with semi-pervious boundaries under any cyclic loadings are studied. In this paper, according to numerical examples, some characteristics of non-linear consolidation behavior of soil are deeply discussed.Then, by the method of Laplace transform and matrix transform, at cc/ck=1 and cc/ck=K respectively, non-linear one-dimensional consolidation of layered soils under arbitrary cyclic loadings is studied and the analytic solutions in frequency domain are obtained. According to the numerical examples, the characteristics of non-linear consolidation of multi-layered soils are found.Finally, when considering the self-weight of soils, non-linear consolidation behaviors of under-consolidated soil under cyclic loadings are investigated. On thebasis of Gibson consolidation theory and by the method of Laplace transform, the analytic solutions in frequency domain are obtained. According to numerical examples, some characteristics of non-linear consolidation behaviors of under-consolidated soil under cyclic loadings are compared with those of normal consolidated soil.From this study, the following conclusions may be obtained: on the assumption of permeability index kv changes linearly with volume compression index mv, consolidation of soil is different from Terzaghi's consolidation theory. And under cyclic loading, the effective stress in soil is not synchronously changed with loading but is developed in a delayed way; the scope of effective stress is related with the parameters of loading and with cc/ck when considering the self-weight of soil, this portion of settlement must be calculated in the under-consolidated soil, if the result is obtained according to the normal consolidated soil, it will be far less than the actual result.