地裂缝对地铁明挖整体式衬砌隧道影响机制的模型试验研究

 以西安地铁2号线穿越地裂缝带为研究背景，采用几何缩比1∶5的大比例尺地裂缝与地铁隧道结构模型试验，研究了地裂缝活动对地铁明挖隧道整体式衬砌结构的影响机制。试验结果表明：随地裂缝位错量的增加，隧道顶部土与结构接触压力上盘明显增大，下盘减小，底部接触压力上盘减小直至为0，下盘则明显增大；当地裂缝位错量达到20 cm时，位于地裂缝上盘的隧道结构底部出现脱空现象，下盘2.5 m处衬砌出现开裂，对隧道底部脱空区应及时进行注浆等地基处理；隧道底板基本处于受压状态，而顶板受力较复杂，下盘受拉，上盘则先受拉后受压。地裂缝作用下隧道变形破坏模式为拉张破坏，且隧道衬砌开裂主要出现在下盘距地裂缝14.0 m范围内，而位于上盘的隧道衬砌基本完好，这与地裂缝活动引起土体和地表建(构)筑物的变形破坏主要发生在上盘刚好相反。研究结果可为西安地铁穿越地裂缝的隧道结构设计与防治措施制定提供一定参考。

MODEL TEST STUDY ON EFFECT OF GROUND FISSURE ON OPEN-CUT METRO TUNNEL WITH INTEGRAL LINING

Based on the Xi¢an metro line No.2 passing through ground fissure active zones，the effect of ground fissure movement on open-cut metro tunnel with rectangular integral lining was studied by a large-scale structural model test with geometric proportion of 1∶5. The test results show that with settlement of the hanging wall of ground fissure increasing，the contact pressure of tunnel top increases in the hanging wall but decreases in the footwall；the contact pressure of tunnel bottom increases in the foot wall but reduces to zero in the hanging wall. When the settlement of hanging wall of ground fissure reaches 20 cm，the tunnel bottom in the hanging wall comes apart from soil，and tunnel lining within 2.5 m from ground fissure in the footwall firstly is found with cracks，so the foundation treatments such as grouting are needed in time. At the meantime，tunnel bottom is basically in compression；tunnel top is in tension in the footwall and initially in tension then in compression in the hanging wall. The deformation and failure model of tunnel induced by ground fissure is tensile failure，and tunnel cracks mainly appear in the footwall of ground fissure，but tunnel located in the hanging wall is basically good，which is just adverse to that the damage of buildings or structures on the ground surface caused by the ground fissure mainly in the hanging wall. The conclusions can be presented as the reference to structural design and prevention measures of metro tunnel passing through the ground fissure active zone.