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考虑浅埋暗挖法施工矩形隧道,由于隧道埋深浅,一般会受到建、构筑物等地表荷载的影响,采用极限分析上限法推导出受地表荷载和孔隙水等荷载作用下的围岩压力表达式。结合序列优化法和Matlab优化工具,计算得到围岩压力的上限解。考虑土体参数以及荷载的离散性,运用可靠度方法对支护力进行失效概率分析。分析了侧压力系数、黏聚力、内摩擦角、埋深、孔隙水压力及地表荷载对围岩压力的影响,通过计算表明,侧压力系数对拱顶、边墙的围岩压力有较大的影响,并且差异性很大,建议区别计算拱顶和边墙的围岩压力。此外,参数的统计特征对浅埋矩形隧道支护力也有较大的影响,特别是变异系数,应提前做好勘测、统计工作。并针对3种不同的安全等级,给出了浅埋矩形隧道的最小安全系数和最小支护力,为其支护设计提供参考。
Considering the shallow tunneling construction of rectangular tunnel, due to the shallow depth of the tunnel, it is generally affected by the surface loads such as the construction and structures. The upper bound method is used to derive the expression of surrounding rock pressure under the load of surface and pore water . Combined with sequence optimization and Matlab optimization tools, the upper bound solution of surrounding rock pressure is calculated. Considering the soil parameters and the discreteness of loads, the failure probability of support force is analyzed by the reliability method. The influence of lateral pressure coefficient, cohesion, internal friction angle, buried depth, pore water pressure and surface load on the surrounding rock pressure is analyzed. The calculation results show that the lateral pressure coefficient has a great pressure on the surrounding rock of the vault and side wall The difference is very large. It is suggested that the pressure difference between the surrounding rock of the vault and the side wall should be calculated separately. In addition, the statistical characteristics of the parameters of shallow rectangular tunnel support force also have a greater impact, especially the coefficient of variation, survey and statistics should be done ahead of schedule. The minimum safety factor and the minimum support force of shallow rectangular tunnel are given for three different safety levels to provide reference for the support design.