深埋软岩隧洞中的软弱带效应分析

Impact of the Weak Rock Zones on the Excavation of a Deeply Buried Tunnel

采用考虑围压效应的大理岩弹塑性耦合力学模型和基于Mohr-Coulomb准则的绿泥石片岩理想弹塑性模型,对深埋夹软弱带隧洞的围岩稳定性进行了数值模拟和理论分析,主要结论有:(1)当掌子面开挖至软弱带时,掌子面上的软弱岩体突出并不断塌落,掌子面后性质较好的围岩内产生了较大的塑性区,而掌子面前方围岩稳定性较好;(2)软弱带厚度对掌子面软弱带的塑性区影响较大,而对掌子面后方和前方围岩的稳定性影响不大;(3)岩体存在多软弱带时,当掌子面开挖至软弱带时,掌子面处软弱带内的塑性区与单软弱带时相同,而性质较好的围岩内产生了一定范围的塑性区。

This paper presents the numerical analysis as well as theoretical analysis results of stability of a tunnel in the rock mass with weak rock interlayer.The coupled elastic-plastic model of marble considering confining pressure effect and the perfect elasto-plastic model of the chlorite schist based on Mohr-Coulomb criterion are adopted in the analysis.The major results are：1）when the excavation reaches the rock mass containing weak zones,the weak rock will be intruded in a progressive failure mode and a large plastic zone is formed immediately behind the excavation face,whereas,the stability of the rock mass in front of the excavated face is not significantly affected;2）the thickness of the weak zone has a large influence on the plastic zone of the weak zone but it has limited impact on the stability of the rock mass behind as well as in front of the excavation;3）If multiple weak rock zones are encountered in the tunnel excavation,the time required to reach the plastic zones in the weak rock zones will be the same as the time needed in a single weak zone is encountered.The plastic zone can also be found in surrounding rock mass with better engineering properties.