隧道斜交穿越地裂缝的模型试验研究

西安地区由北向南间隔分布有十多条近东西走向的地裂缝,建设中的多条地铁线路与地裂缝呈斜交状态。为了揭示地铁隧道斜交穿越地裂缝时受地裂缝活动而产生的力学性状变化,采用50:1几何相似比尺的物理模型试验仪,在合理模拟围岩地层、衬砌结构、应力条件、地裂缝与洞轴线交角及其错动位移基础上,开展了斜交地裂缝活动条件下隧道衬砌结构与围岩相互作用的物理模型试验研究,并与正交地裂缝活动下的测试结果进行了对比分析。表明斜交地裂缝活动对地铁隧道的影响范围更大,各变形缝均有明显的沉降差发展;邻近斜交地裂缝的衬砌结构易处于"悬臂梁"受力状态,衬砌结构不均匀沉降使其产生旋转位移,围岩土压力变化使衬砌结构内力产生显著变化;随着地裂缝错动位移的发展,上盘内拱顶和下盘拱顶、拱底出现围岩作用的加强,而上盘拱底出现围岩作用的松弛。与隧道正交穿越地裂缝的情况比较,斜交穿越地裂缝时围岩土压力和衬砌结构内力变化更大,易出现拉裂破坏。

Research on physical model experiment of tunnel obliquely crossing a ground fissure

Because of the upper soil mass relative moving to the lower soil mass beside the ground fissure, there is the complicated action mechanism between lining structure and wall rock of soil with fissures. For investigating the engineering behaviors of Xi’an metro tunnel crossing ground fissures widely distributing the Xi’an zone, the physical model experiment with geometric proportion of 50:1 is carried out by reasonably simulating the wall rock stratum with a oblique ground fissure, lining structure, stress conditions and dislocation displacement of ground fissures. In the physical model experiment, the angle between axial of tunnel and direction of fissure equals to 450, the additional vertical stress of wall rock soil equals to 50 kPa, 100 kPa and 150 kPa respectively; and the tunnel is simulated with the similar material. The pressure of wall rock, settlement and internal stress of lining structure are measured by the new earth pressure sensor, displacement transducer and strain sensor in the processor of movement of ground fissure, so that the mechanical characteristics of wall rock and lining structure are analyzed well and truly. Test results show that the oblique ground fissure gets a larger sphere of influence on metro tunnel; and the settlement of deformation joints is developing significantly. In addition, the lining obliquely crossing ground fissures is in a force state similar to "beam", which will produce a rotating shift with the uniform settlement of tunnel lining. As to the development of ground fissures’ dislocation displacement, internal forces of lining are changed significantly with the changing of wall rock pressure; and both of the wall rock pressure in the foot wall and the wall rock pressure at the top of lining in the hanging wall increase, while the wall rock pressure at the bottom of lining in the hanging wall decrease. Comparing with the situation of the tunnel orthogonally cross ground fissures, the wall rock pressure and the internal force of lining structure changed larger when the tunnel obliquely crossing the movement ground fissure; and the lining structure is more prone to tensile failure.