分段柔性接头地铁隧道适应地裂缝大变形的模型试验研究

西安地裂缝是一种特殊的城市地质灾害,地铁隧道穿越地裂缝带时必须分段设特殊变形缝。以西安地铁隧道正交穿越地裂缝带为工程背景,采用几何比1:5的大比例尺模型试验,研究分段设缝柔性接头隧道穿越地裂缝带的适应性。试验结果表明:地裂缝活动环境下隧道设置特殊变形缝的柔性接头避免了衬砌结构应力集中,对结构起到保护作用,分段柔性接头隧道具有较强的适应地裂缝大变形的能力。设置与地裂缝倾角一致的斜变形缝对围岩压力与位移有一定影响,而对衬砌结构安全性影响较小。正交条件下斜变形缝能消耗20%以上的地裂缝位移量,在地裂缝影响区隧道可通过多段设变形缝串联的方式最大限度地消除地裂缝大变形对隧道的影响。接头处顶底部止水带基本完好,而两侧止水带因地裂缝垂直位移作用出现撕裂现象,防水设计应重点考虑接头两侧壁的防水。研究结果可为地裂缝活动环境下地铁隧道结构与防水设计提供重要参考。

MODEL TEST STUDY OF SECTIONAL METRO TUNNEL WITH FLEXIBLE JOINTS ADAPTING LARGE DEFORMATION OF GROUND FISSURES

Ground fissure is a special urban geological hazard in Xi¢an；and metro tunnels should be divided by special deformation joints and connected with flexible joints to adapt the large deformation of active ground fissures. Based on the Xi¢an metro tunnel orthogonally passing through active ground fissures，by means of large-scale model tests with a geometric proportion of 1∶5，the adaptability of sectional metro tunnel with flexible joints to active ground fissures is studied. The test results show that the flexible joints prevent tunnel from stress concentration and protect tunnel structures under the influence of active ground fissures；and the sectional tunnel with flexible joints can adapt the large deformation of active ground fissures. To some extent，the special deformation joint with the same dip angle as active ground fissure has certain effect on pressure and displacement of surrounding rock，but affects the safety of tunnel lining structure less. Meanwhile，the oblique special deformation joint can absorb over 20% of the total displacement of active ground fissure. In active ground fissure zones，tunnel can be divided into a few sections and connected in series to eliminate the influence of large deformation of active ground fissure on tunnel lining to the maximum. The watertight belts are undamaged at the top and bottom of lining and mangled on the bilateral wall affected by the vertical displacement of ground fissure，so the bilateral wall of flexible joint should be intensified in waterproof design. The conclusions provide an important reference for structure and waterproof designs of metro tunnel under the influence of active ground fissures.