考虑变荷载和变边界的软土大应变非线性固结分析

Analysis for large-strain nonlinear consolidation of soft soils considering time-dependent loading and drainage boundary

摘要:

为了准确预测实际土层的固结速率,在Gibson大应变固结理论基础之上,考虑土体的非线性压缩渗透特性和土层表面随时间改变的变排水边界条件,建立考虑变荷载和变边界的软土大应变非线性固结模型。在此基础上,获得单级加载和多级加载条件下大应变非线性固结模型的显式解析解,利用获得的解析解开展计算以分析界面参数、荷载取值对土层固结性状的影响。结果表明:外荷载对土体内部超静孔压消散的影响表现为随着荷载的增大,超静孔压消散得越快,但其不会影响土体最终完成固结的时间；参数Ic(α－2)取值对土体固结性状的影响表现为固结速率随着参数Ic(α－2)取值的变化而变化。值得注意的是,描述土体非线性特性的参数取值对固结性状的影响在变边界下显现的固结性状会出现延迟现象,不同参数下的变边界更能反映土体边界的真实透水性情况,在实际工程中可以根据超静孔压实际的消散速率反演界面参数,以便能准确预估土层的固结进程。

Abstract:

In order to accurately predict the actual consolidation rate of soil layer, based on Gibson′s large-stain consolidation theory, a model for the large-strain nonlinear consolidation of soft soils has been developed with consideration of the nonlinear compressibility and permeability characteristics and the time-dependent drainage boundary condition of soils. On this basis, explicit analytical solutions for the large strain nonlinear consolidation model under single-stage and multi-stage loading can be derived. By using the obtained analytical solutions, the influence of interface parameters on consolidation behavior are analyzed. The results indicate that the influence of external loading on the dissipation of excess pore water pressure in soil is that the excess pore water pressure dissipates faster with increasing the loading, but the value of loading has no influence on the final dissipation time of excess pore water pressure. Besides, the influence of parameter Ic(α－2) on soil consolidation behavior is that the consolidation rate changes with the change of parameter values. It is worth noting that the influence of parameter values describing nonlinear behavior of soil on consolidation behavior is delayed under the time-dependent drainage boundary. The time-dependent drainage boundary under different values of interface parameter reflects the actual permeability of soil boundary better. In practical engineering, the corresponding interface parameters can be inversely investigated according to the actual dissipation rate of excess pore water pressure, so as to accurately predict the consolidation process of soil layer.