分段循环荷载作用下非饱和土轴对称固结特性研究

Axisymmetric consolidation characteristics for unsaturated soils under piece-wise cyclic load

基于Fredlund等提出的非饱和土轴对称固结理论,采用傅里叶级数展开法和拉普拉斯变换法提出了等应变条件下分段循环荷载作用下同时考虑径向(r方向)和竖向(z方向)渗透的非饱和土轴对称固结半解析解。基于等应变假设和径向边界条件,给出了等应变条件下的超孔隙气压力u_(a)和超孔隙水压力u_(w)的控制方程。然后利用级数展开与Laplace变换求解并给出了超孔隙压力及平均固结度的半解析解。此外,通过退化法以及有限差分法验证了所提解和相应结果的正确性。引入3种具体的分段循环荷载,研究了渗透系数之比k_(a)/k_(w)、模型尺寸N和荷载特征参数a对非饱和土轴对称固结特性的影响,所得结论更加符合实际,可为非饱和土地基处理提供理论指导。

Based on the consolidation theory of unsaturated soils proposed by Fredlund and his co-workers(1984),by using Fourier series expansion and Laplace transform technique,semi-analytical solutions are proposed for the axisymmetric consolidation of the unsaturated foundation under the piece-wise cyclic load with the equal strain hypothesis in this paper.Firstly,based on the radial boundary conditions and equal strain hypothesis,the governing equations of axisymmetric unsaturated soil consolidation under piece-wise cyclic load are established.Afterward,the governing equations are solved by applying series expansion and Laplace transform,and the semi-analytical solutions of excess pore-air and pore-water pressures and the average degree of consolidation are given.Then,the correctness of the solutions and their results is verified by the degradation method and finite difference method.Finally,three specific segmental cyclic loads are introduced as the typical cases,the consolidation properties of unsaturated soil ground with the change of permeability coefficient ratio(k_(a)/k_(w)),model size(N),and load characteristic parameter(a)are analyzed.The conclusions drawn in this paper can give a strong theoretical support for the treatment of unsaturated soil ground.