支护压力控制下隧道周围砂土变形破坏物质点法模拟

为了探究隧道周围砂土地层在支护压力减小过程中的变形破坏机理，利用能够进行岩土大变形分析的物质点法（MPM）对该过程进行数值模拟. 研究隧道周围土体的剪切带特征、土拱效应、MPM地面沉降槽形态以及支护压力与地层位移间的关系；验证该数值方法研究隧道诱发变形的可靠性. 对比预测结果与已有试验和理论表明，MPM能够准确预测出隧道支护压力降低引起的地层变形和极限支护压力，并且可以得到地层整体失稳及坍塌后的变形行为. 在此基础上，分析隧道埋深比和砂土内摩擦角对变形过程中土拱效应强弱、极限支护压力和地层变形的影响.

Material point method simulations of sand deformation and failure around tunnel controlled by support pressure

To explore the deformation and failure mechanism of sand foundation induced by the decrease of tunnel support pressure, the material point method (MPM), a large deformation analyzing method in geotechnical engineering was used to simulate the whole process. The characteristics of localized shear bands, the arching effect, the settlement trough shape, and the relationship between support pressure and ground movement were investigated. The reliability of MPM in analyzing tunnel-induced soil deformation was verified. By comparing the simulated results with experimental and theoretical data, it is shown that MPM can accurately predict the ground deformation caused by the reduction of tunnel support pressure and the ultimate support pressure, and obtain the overall deformation behavior before and after tunnel collapse. On this basis, the influence of cover depth-to-diameter ratios and friction angles on the arching effect, the limiting support pressure and the strata deformation were investigated.