中文摘要：

软黏土中渗流存在起始水力坡降的现象已逐渐为人们所认识,但变荷载下考虑起始坡降的软土大变形非线性固结理论还很鲜见。考虑土中渗流存在的起始水力坡降及非线性压缩渗透特性,在拉格朗日坐标系中建立变荷载下以超静孔压为变量的软土大变形非线性固结模型并给出其有限差分解。在此基础上,通过与达西定律下大变形固结半解析解对比分析,验证了解的可靠性。最后着重分析起始水力坡降对软土大、小变形固结性状影响的差异。结果表明,无论采用小变形假定还是采用大变形假定,考虑起始坡降后超静孔压的消散速率及最终沉降量均比达西定律下小。大、小变形假定下起始坡降均会引起超静孔压不能完全消散的现象,且大变形假定下超静孔压残留值要小于其小变形假定下的残留值,致使大变形假定下土层最终沉降量要比其小变形假定下大。起始水力坡降和几何变形假定均会影响固结性状,且起始坡降值无疑影响更明显,故在软黏土中渗流存在的起始水力坡降在固结计算中不容忽视。

英文摘要：

It has been gradually recognized that threshold hydraulic gradient of seepage exists in soft clay. However, nonlinear large-strain consolidation of soft clay with threshold gradient, which takes time-dependent load into account, has rarely been reported in the literature so far. By employing the excess pore water pressure as variable, and considering both threshold hydraulic gradient and characteristics of nonlinear compression and permeability, a model for large-strain consolidation is developed in Lagrangian coordinate system. On that basis, the corresponding finite difference solutions for this model are provided. Meanwhile, compared with the semi-analytical solutions of large-strain consolidation under Darcy＇s law, the numerical solutions for the proposed consolidation model are verified. Finally, the differences in the influence of threshold hydraulic gradient on consolidation behaviors of clay between large- and small-strain conditions are emphatically investigated. The results show that, no matter large- or small-strain condition is considered, both the dissipation rate of excess pore water pressure and the settlement of clay layer become smaller than that under condition of Darcy＇s law when considering the influence of threshold hydraulic gradient. The excess pore water pressure in clay with threshold hydraulic gradient is not completely dissipated under both large- and small-strain conditions, moreover, the residual value of excess pore water pressure under large-strain condition is smaller than that under small-strain condition, which leads to a larger settlement of clay layer under large-strain condition than that under small-strain condition. Both threshold hydraulic gradient and different deformation conditions have influences on the consolidation behavior, while the influence of threshold hydraulic gradient is more evident. Therefore, the threshold hydraulic gradient of seepage in soft clay cannot be ignored during the consolidation calculation of soft clay layer.