Study on development in reinforced soil systems effective for prevention of large deformation and progressive failure in ground

本文采用土-水耦合弹塑性变形分析方法，对可能导致建筑工程致命性破坏的地面大变形防治体系进行了研究。主要针对桩筏体系和挡土体系的研究成果如下：研究了桩筏基础体系在不同地基和荷载条件下的变形特性。在平面应变条件下，在速度场上引入线性约束条件，对桩筏体系进行了数值模拟。该系统大大减少了最终的结算量。这种减少是由于荷载通过桩的剪切传递到更深的土层中，从而分散了诱导应力，而不是仅仅通过筏板。此外，即使在偏心荷载作用下，桩筏体系也会产生均匀的沉降。此外，还研究了砂土地基中该体系在液化作用下的行为。研究了超固结状态下开挖边坡的渐进性破坏。对开挖过程中土体性状的认识，使得对挡土结构的土压力进行了真实的评估。有围护结构的地基表现出稳定性，轴力、弯矩等表现出孔隙水迁移的时变特性。

In this study, some preventive/reductive systems of large deformation in ground that may lead to fatal damages in construction projects are investigated using soil-water coupled elasto-plastic deformation analysis. The findings of the study mainly for a piled raft system and earth retaining system are summarized as follows :Deformation characteristics of a piled raft foundation system under different ground and loading conditions are studied. The pile-raft system is simulated introducing some linear constraint conditions over the velocity field in plane strain condition. The system reduces the final settlement significantly. This reduction is due to the load transfer through shear by piles into deeper soil layers that disperse the induced stresses compared with only the raft. Further, the pile-raft system induces homogeneous settlement even with eccentric loading. In addition, behavior of the system under liquefaction in a sandy ground is studied. It also diminishes the liquefaction of the sandy ground, and prevents inhomogeneous settlement under the liquefaction of ground.Progressive failure of the excavated slopes in overconsolidated state is studied. The recognition of the soil behavior in excavation leads to realistic evaluation of earth pressure on retaining structures. The ground with retaining structures exhibits stability and the axial forces and bending moment etc. show the time-dependent behavior due to pore water migration.