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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。
A total of more than ten ground fissures near the east and west are distributed in the Xi’an area from north to south. A number of subway lines under construction are inclined to the ground fissures. In order to reveal the changes of mechanical properties caused by ground fissures when the subway tunnel crosses over the ground fissures, a physical model tester with a 50: 1 geometric similarity scale is used to simulate the surrounding rock stratum, lining structure, stress conditions, Based on the intersecting angle with the hole axis and its dislocation displacement, the physical model test on the interaction between tunnel lining structure and surrounding rock under inclined ground motion was carried out. The results were compared with the test results under the action of orthogonal ground-cleft fracture . The results show that the influence of oblique ground fissures on the subway tunnel is more extensive and the deformation joints all have obvious differential settlement. The lining structure near the diagonal intersection cracks is prone to “cantilever ” stress and the lining structure is not uniform As the settlement of ground motion causes a rotational displacement, the change of surrounding rock pressure causes the internal force of lining to change significantly. With the development of the dislocation displacement of ground fissures, The hanging wall at the bottom of the plate appears the role of relaxation. Compared with the case where the tunnel passes through the ground fissure orthogonally, the earth pressure and the internal force of the lining structure change more greatly when crossing the ground fissure diagonally, and the failure of the fissure is apt to occur.