跨活断层深埋隧道轴线错动位移模式试验研究

Experimental study of axis displacement mode of deep buried tunnel across active faults

活断层蠕滑错动会导致穿越其中的隧道轴线方向岩体发生变形,引起轴线弯曲甚至岩体破坏,沿轴向岩体的位移模式是隧道结构设计与安全运行的重要依据,特别是深埋隧道段,穿越活断层地质分区、错动方式及破碎带内的三维应力场是决定隧道沿轴线岩体变形破坏的关键因素,而现有物理模拟试验多用于研究浅埋隧道、地铁等工程受断层错动的影响,不适于深埋隧道条件的模拟。为此,考虑上述关键因素,采用自主研发的一套用于模拟三维应力作用下断层蠕滑错动的试验装置,以跨活断层凤凰山隧道为依托,通过模型试验研究了不同蠕滑错动量级下深埋隧洞轴线的位移模式,结果表明:断层蠕滑错动位移模式呈"S"形;小错动量下变形由错动盘向破碎带连续传递,而大错动量下错动盘与破碎带交界面发生滑动;破碎带内变形曲线呈"坡面线"形,带内错动位移传播宽度约为20 m。研究成果为穿断层隧道结构设计提供了重要依据。

The creep slippage of active fault leads to shearing of rock mass along the tunnel axis,causing axis bending and even destruction of rock mass.The nonlinear distribution of creep slippage displacement in rock mass plays an important role in structural design and operation safety of tunnels.In deep buried area,the three-dimensional in-situ stress and the structure of fault strips are the key factors to be considered,which are evidently different from geological conditions in shallow buried tunnel or subway project.However,the existing physical simulation tests are mostly used to study faults in shallow buried tunnels,subways and other projects,and are not suitable for the simulation of deep tunnel conditions.In this paper,a new experimental setup for physical modelling of deep buried tunnel crossing active fault is developed and utilized to simulate fault creep slippage under three-dimensional in-situ stress.Based on the Fenghuangshan tunnel that crosses active fault,the axis displacement mode along the tunnel under different slippages is obtained through physical model test.The results show that the displacement mode along the tunnel axis is S-shaped.The shear deformation is continuously transmitted from slippage plane to crushed zone under small slippage,while the slippage occurs between slip plane and crushed zone under large slippage.The deformation curve within the crushed zone is‘slope line’shape,and the transmission width within the zone is around 20 m.This result could provide important knowledge for the structural design of fault crossing tunnels.