深埋隧道软硬交替复合顶板岩体变形破坏分析

Analysis of deformation-failure for soft and hard multilayer roof of deeply buried tunnel

为了解隧道开挖后顶板岩层活动范围及其对隧道支护体的影响,对埋深为700m的隧道多层状顶板岩体,采用两种方式对其顶板围岩破坏形式进行了数值模拟研究和理论分析。一种方式是将顶板112m至地表的588m范围内的岩层视为均布荷载,模拟计算隧道顶板112m范围内岩层的应力、位移及塑性区范围;另一种对隧道至地表岩层进行全断面模拟。模拟计算分析表明,对于隧道顶板112m范围内相应位置的压应力σy、竖向位移Uy及剪应力τxy,两种方式计算结果基本相同,说明在距隧道中心一定高度处的岩层出现离层现象;复合顶板中的两层及两层以上的硬岩层与其间的软岩层构成了若干个组合板结构,隧道支护体所受的载荷主要来源于第一个组合板以下的岩体,并将第一个组合板以下的高度定义为支护体关键荷载圈。由数值模拟分析和理论计算所得到的隧道支护体关键荷载圈高度均在75m左右,相对误差不超过5%。

In order to inquire into the activities of roof rocks and their influence on tunnel support, two methods are used to analyze the failure forms of multilayer roof rocks of a tunnel which is buried in depth of 700 m. One method is considering the roof rocks which are in the fields from above 112 m to surface as the uniformly distributed loads; and another method is to analyze the all roof rocks from tunnel roof to surface. The simulating results show that: the results of compression σy, displacement Uy and shear stress τxy which are calculated by the first method are identical with them calculated by the second method. It is showed that the roof rocks separate from each other at the certain height to tunnel center, and two or more hard rocks and soft rocks composite the combined strata. The stress of tunnel support comes from the first combined strata mainly; and we define this height as the key support stress circle. The heights of the key support stress circle calculated with theory and simulation is about 75 m, and the error is 5.2%.