黄土隧道设计与施工中的几个问题

通过总结分析黄土地层的饱和、固结、湿陷、可灌性与降排水性等对黄土隧道稳定性的影响,提出了黄土隧道工程中应注意的问题;对黄土隧道衬砌结构设计中需要考虑的侧压力系数、变形模量取值问题,围岩压力计算及围岩与衬砌结构相互作用等问题进行深入剖析,并提出了设计中应注意的问题;对于浅埋黄土隧道,建议采取“拟塌落拱有限元方法”进行分析;以某饱和黄土隧道工程为依托进行了几种常用施工方案的数值对比分析,表明NATM施工、掏槽施工或压桩施工均难以满足成洞条件,且先行降、排水措施和初期喷浆支护难度较大,应采取超前管棚注浆等新工艺才能满足饱和黄土隧洞的成洞要求;针对黄土地层盾构隧道施工,建议采用控制“地层刚度”和修正“盾构工艺参数”的方法来控制地表隆沉。

Some Issues of Loess Tunnel in Design and Construction

Some engineering problems about the stability of loess tunnel were proposed by analyzing the factors including saturation, consolidation, collapsibility, and grouting and drainage capacity of loess. Deep analysis has been conducted to resolve some issues on the design of lining such as lateral pressure coefficient, deformation modulus parameters, the calculation of pressure of the surrounding rock and interaction between rock and lining, and problems should be paid attention to are proposed. As to the shallow buried loess tunnel, the ground arch simulation with FEM proposed by author is more properly to solve the problem than the traditional FEM. Three common tunneling methods in saturated loess are numerically tested and the results demonstrate that the NATM, the traditional tunneling methods and the precast lining techniques are hard to keep the surrounding soil safe except that making good use of the pipe-shield support grouting techniques. The methods of controlling the rigid of ground surface and modified shield tunnel parameters are suggested to control the ground settlement or rising