The Deformation Regularity And Stability Evaluation Of Surrounding Rock Of Large Buried Diversion Tunnel Crossing Fault Zone

As our country attaches more importance to the sustainable development and utilization of water resources,the water conservancy and hydropower engineering project construction is rapidly developing.As an important means in long-distance water diversion project,the large buried deep diversion tunnel often encounters various complex and changeable adverse geological conditions in the actual construction and excavation process,which is characterized by high construction risk and difficulty.Fault zone is a typical adverse geological phenomenon,which is easy to cause geological disasters such as large deformation or even collapse.So,it is of great theoretical significance and engineering application value to study the deformation law and influencing factors of surrounding rock with large buried diversion tunnel crossing fault zone,and to carry out the stability evaluation of surrounding rock of tunnel crossing fault zone.In this paper,Xianglushan Tunnel of central Yunnan diversion Project is taken as the engineering background.The geological conditions of the engineering site through deformation monitoring and geological detection is comprehensively analyzed,and the deformation regularity of surrounding rock of the tunnel through the fault zone and its influencing factors is studied by combining with three-dimensional discrete element numerical simulation method.Based on extension matter element method and fuzzy comprehensive evaluation method,the stability grade of surrounding rock of tunnel crossing fault zone is studied.The main research work and conclusions of this paper are as follows:(1)According to the engineering geological data of the construction site,the engineering geological conditions and the adverse geological conditions in the study area are analyzed.Combined with the field monitoring and measurement,the comprehensive advanced geological prediction method which combines the advanced drilling method,the geological radar method,the tunnel seismic wave method and the excitation polarization method is adopted.The deformation monitoring and geological detection are carried out on the tunnel crossing the fault zone in the study area,and the geological condition of the tunnel crossing the fault zone is analyzed.The results show that the surrounding rock in the tunnel fracture zone is loose and broken,with poor integrity,structural plane development,low strength of surrounding rock,and easy to occur large deformation or even collapse during excavation.The construction is difficult and the safety risk is high.(2)By establishing the numerical model of tunnel excavation through the fault zone,the deformation law of surrounding rock on both sides of the arch,arch bottom and arch waist of the tunnel is studied,and the influence of the tunnel on the deformation of surrounding rock under different conditions of the tunnel crossing different fault zone widths,dip angles,strike angles and buried depths is further analyzed.The results show that the vertical displacement and horizontal displacement of surrounding rock change obviously due to the existence of the fault zone.The closer the tunnel is to the core of the fault zone,the greater the deformation of the surrounding rock on both sides of the tunnel arch,arch bottom and arch waist.The deformation of the surrounding rock near the central zone of the fault zone reaches the maximum value.Among the factors affecting the deformation of surrounding rock through the fault zone,the vertical displacement and horizontal displacement of surrounding rock increase with the increase of the width of the fault zone and the buried depth of the tunnel.With the increase of the dip Angle of the fault zone,the vertical displacement and horizontal displacement of surrounding rock become smaller,and two extreme values are obtained when the dip Angle is 45°and 90°.With the increase of the strike of the fault zone,there is little difference between the vertical displacement and horizontal displacement of the surrounding rock.The influence degree of comprehensive factors from small to large is fault zone strike,fault zone dip angle,fault zone width and tunnel buried depth for vault settlement.(3)According to the results of three-dimensional discrete element numerical simulation,combined with the actual situation of the project site,the extension matter element method and fuzzy comprehensive evaluation method are used to study the stability evaluation of the surrounding rock of the tunnel crossing the fault zone.Five evaluation indicators including the width of the fault zone,the dip Angle of the fault zone,the strike of the fault zone,the depth of the tunnel and the distance from the center of the fault zone are selected.The weight of each evaluation indicator is determined by the combination weighting method of analytic hierarchy process and entropy method.The stability evaluation models of surrounding rock of tunnel crossing fault zone is established based on the extension matter element method and the fuzzy comprehensive evaluation method.Ten groups of sample data of the stability degree of surrounding rock of Xianglushan Tunnel crossing fault zone are selected for evaluation and prediction.The results show that the evaluation model based on fuzzy comprehensive evaluation method is more safe,and the evaluation model based on extension matter-element method is more in line with the engineering practice,which has better application effect and higher accuracy.