大角度斜交地裂缝带盾构隧道变形破坏机制的模型试验研究

Model test on deformation and failure mechanism of shield tunnel intersecting ground fissure with large angle

地裂缝是西安市最典型的城市地质灾害,其活动对城市地铁建设具有严重威胁,盾构隧道能否应用于地裂缝场地一直是工程界关注的问题。为揭示地裂缝活动对地铁盾构隧道的影响机制,文章以在建西安地铁8号线大角度(θ=75°)穿越地裂缝带为工程背景,基于1∶12几何比尺的物理模型试验并结合数值模拟,对大角度斜交地裂缝带的盾构隧道结构的变形破坏规律进行研究。结果表明:地裂缝错动作用下,大角度穿越地裂缝带的盾构隧道上盘管片拱顶受压、拱底受拉,下盘管片拱顶受拉、拱底受压;盾构隧道纵向整体表现为弯曲-扭动变形,管片衬砌在地裂缝上盘以拱顶内凹变形为主,在下盘以牵引变形为主,地裂缝位置及其附近的管片表现出竖向错动、轴向拉张与挤压以及水平扭转的三向变形特征;当地裂缝位错量达到s=24cm时,盾构隧道出现破坏,其破坏模式以剪切破坏为主,局部存在偏压破坏,且破坏大部分首先出现在螺栓附近;基于盾构隧道的破坏模式和范围提出隧道大角度穿越地裂缝带时的应对措施建议,对于未来100年内地裂缝累积活动量超过s=24cm的场地,地铁建设不宜采用盾构法通过。

Ground fissure is a typical geological disaster in Xi’an, its activity may seriously threaten the city metro construction.Whether the shield tunnel can be constructed in the site with ground fissure has always been a concern in engineering field.To reveal the influence mechanism of the ground fissure activities on metro shield tunnel, the Xi’an metro line 8 under construction crossing ground fissure with a large intersection angle(θ=75°) was taken as an example, the structural deformation and failure mechanism of shield tunnel intersecting ground fissure with large angle was studied based on the physical model test with 1∶12 geometric scale and numerical simulation.The results show that due to the ground fissure dislocation, when the shield tunnel intersects ground fissure with large angle, the crown of arch and the inverted arch of hanging wall are in compression and tension, respectively, while the crown of arch and the inverted arch of footwall are in tension and compression, respectively;the shield tunnel shows flexural-torsional deformation in longitudinal direction, the crown of arch of the segmental lining in hanging wall deforms concavely in most cases, the counterpart in footwall shows traction deformation in most cases, and those segments near ground fissure arecharacterized by deformations in three directions, including vertical dislocation, axial opening and closing, and horizontal torsion;damages occur in shield tunnel when the dislocation of ground fissure is about s=24 cm, the structural failure modes are mainly shear failure and local failure in bias compression, and most of the damages firstly occur near the bolt;based on the deformation and failure characteristics of segmental lining, some countermeasures shall be proposed for shield tunnels intersecting ground fissures with large angle, and shield tunnelling should not be applied to metro project in site with ground fissure dislocation exceeding s=24 cm in 100 years.