Study On Collapse Mechanism And Optimization Construction And Supporting Program Of Tunnel With Phyllite Surrounding Rock And Rich-Water

Great losses of the development of transportation and the safety of people's lives and property will be caused by tunnel collapse,and the geological condition of tunnel engineering is complex and unknown.Therefore,the analysis of tunnel collapse is of great significance.Phyllite will be softened by water,so the large deformation of tunnel with phyllite surrounding rock and rich-water is easily occurs,and landslides have even occurred.Therefore,it is necessary to study the collapse mechanism of tunnel with phyllite surrounding rock and rich-water.Based on the collapse accidents of Huangtuliang tunnel,collapse classification is divided by the characteristics and causes of collapse.Collapse mechanism is studied,and the optimized construction supporting scheme of tunnel under the geological condition is put forward.The conclusions are as follows.1)Huangtuliang tunnel is with phyllite surrounding rock and rich-water,many collapses accidents occurred during construction.The simulation results show that:After excavating by step method,the tunnel deformation of surrounding rock has been increased uniformly.While the deformation rate suddenly increase when the load release rate is 20%.And the plastic zone of lower step is transfixion,and the simulation is not convergent.Therefore,the instability of the system is due to the instability of the surround rock of lower step.2)According to the force characteristics and collapse mechanism of collapse section of Huangtuliang tunnel,the following optimizations of thickness of reinforcing ring of Full-face Curtain Grouting Technology,construction method,load ratio of two lining,are proposed by the view of improving its mechanical characteristics.3)The reinforcement effect of Full-face Curtain Grouting Technology shows that,the bearing capacity of surrounding rock is improve continuously with the increase of the thickness of reinforcement ring.While the increase rate of the bearing capacity is slow down after the thickness of reinforcement ring is more than 4.5m.Therefore,the best thickness of reinforcement ring is 4.5m.4)Through the comparison of bench method,CD method,double side drift of up step construction method and double side drift construction method,double side drift construction method is most applicable to limit the deformation of the surrounding rock,And the load sharing ratio of the initial support and temporary support is greater thanother methods.So the best construction method is double side drift construction method.5)The overall stability of the tunnel system can be properly improved by maximizing the supporting role within the two lining bearable range,the simulation result shows that the best load sharing ratio of two lining is 45%.6)Deformation results of tunnel construction shows that,perfect results were obtained after the optimization program is apply to the construction of Huangtuliang tunnel.