层状软岩隧道非对称大变形控制解耦方法

Study on the decoupling method for the asymmetric large deformation control of layered rock mass tunnel

层状软岩各向异性特征导致的衬砌结构非对称大变形是隧道建设过程中常见的问题。针对该问题,本文建立了能考虑锚杆拉伸断裂及钢支撑压弯破坏的数值计算模型,并以汶马高速鹧鸪山隧道为对象,对层状软岩隧道大变形控制的解耦技术进行了研究,结果表明:①考虑锚杆及钢拱架断裂的数值模型可以较好地反映初期支护在围岩大变形作用下的断裂失效,能更加准确表征支护结构的实际力学行为。②对于隧道大变形而言,若仅强化支护结构或减小台阶开挖长度,可以减小围岩的位移,但多数情况下,支护结构依然会产生断裂破坏。③对于挤压因子较大的不明显挤压工况,采用常规支护+双台阶(短台阶)施工方法可以较好地控制围岩大变形;对于挤压因子较大的轻微挤压或挤压因子较小的不明显挤压工况,采用常规支护+三台阶可以较好地控制围岩大变形;对于挤压因子较小的轻微挤压工况,采用非对称锚杆支护+三台阶可以较好地控制围岩大变形。

Large asymmetric deformation of lining structure caused by anisotropy of layered soft rock is a common problem in tunnel construction.In this paper,a numerical model based on tensile fracture of anchor bolt and compression and bending failure of steel support is established,and the decoupling technology of large deformation control of layered soft rock tunnel is studied by taking Zhegushan tunnel of Wenma Expressway as the object.The results show that:(1)The numerical model considering the fracture of anchor bolt and steel arch can better reflect the fracture failure of initial support under the action of large deformation of surrounding rock,and can more accurately characterize the actual mechanical behavior of support structure.(2)For large deformation of tunnel,the displacement of surrounding rock can be reduced by strengthening the supporting structure or reducing the excavation length of bench,but in most cases,the supporting structure will still produce fracture failure.(3)For the non-obvious squeezing condition with large squeezing factor,the large deformation of surrounding rock can be well controlled by the construction method of conventional support and double bench(short bench).For slight squeezing with large squeezing factor or insignificant squeezing with small squeezing factor,the large deformation of surrounding rock can be well controlled by conventional support plus three benches.For the slight squeezing condition with small squeezing factor,the large deformation of surrounding rock can be well controlled by using asymmetric bolt support plus three benches.