Study On The Stability Analysis And Management Measures Of The Surrounding Rocks Of The Yiliang Tunnel Through The Heilaolin Fault Fracture Zone

With the development of transportation,tunnel engineering across mountainous areas has become inevitable.The terrain and geological conditions in mountainous areas are relatively complex,and there are various adverse geological phenomena.The fault fracture zones have a significant impact on the safety of tunnel construction,which can easily lead to various geological disasters during tunnel construction.This thesis takes the Heilaolin fault fracture zone of Yiliang Tunnel as the research object.Through a combination of theoretical analysis,engineering case study,numerical simulation,and on-site monitoring,the influence of different influencing factors on the stability of surrounding rock in the fault fracture zone is analyzed.The excavation of the tunnel passing through the Heilaolin fault fracture zone with different displacement and treatment measures are studied,providing reference for subsequent engineering construction.The specific content and achievements are as follows:(1)By collecting general information on the Yiliang Tunnel project and analyzing the nature of the Heilaolin fault fracture zone,it can be inferred from its trajectory characteristics that the fault is a tensile fault.The crustal stress around the Heilaolin fault fracture zone is analyzed by geomechanics method and measured data,and the pressure coefficient along and perpendicular to the tunnel axis is obtained.The geological model of the Heilaolin fault fracture zone disaster is established,and it is pointed out that the existence of the fault fracture zone is the main reason for the occurrence of geological disasters.(2)Through a large number of relevant engineering investigations,the influence factors of surrounding rock damage caused by fault fracture zone are analyzed,and it is concluded that the dip angle and width of different fault fracture zones and the pressure coefficient of surrounding rock side will cause different damage to surrounding rock.Prepare for numerical simulation analysis of tunnel excavation under different fault factors based on this project in the following text.(3)By using FLAC 3D numerical simulation software and relying on the Heilaolin fault fracture zone of Yiliang Tunnel,a three-dimensional model of different fault fracture zone shapes is established.Through the distribution of displacement field and plastic zone,the laws of the dip angle,width and lateral pressure coefficient of different fault fracture zones on the stability of surrounding rock are studied to maximize the impact of various factors on the stability of surrounding rock.(4)Considering the influence of three factors of fault dip angle,width and lateral pressure coefficient on the stability of surrounding rock,the construction simulation of the actual project is carried out according to the fact that the angle of the Heilaolin fault fracture zone is 75 °,the width is 10 m,and the lateral pressure coefficient along and perpendicular to the tunnel axis is 0.53 and 0.43 respectively.The Yiliang Tunnel is a double hole tunnel.When constructing through the Heilaolin fault fracture zone,the mutual influence between the left and right tunnels should be considered.Due to the symmetrical distribution of the left and right tunnels in the Yiliang Tunnel,the excavation sequence of the left and right tunnels does not affect the stability of the surrounding rock.Only a reasonable selection of the distance between the left and right tunnel faces is needed.Through numerical analysis,it can be concluded that the construction is most reasonable when the face distance is 24 meters.(5)Propose governance measures for the Heilaolin fault fracture zone.Through analysis and comparison,select a pre grouting reinforcement scheme for numerical simulation.After reinforcement,the vertical displacement of the tunnel arch top decreases by 45.08%,the vertical displacement of the tunnel arch bottom decreases by55.34%,and the horizontal displacement of the tunnel decreases by 86.71%,verifying the effectiveness of pre grouting reinforcement.Reasonable optimization was conducted on the thickness of the advanced grouting reinforcement area.The influence of different thicknesses of the advanced grouting reinforcement area on the vertical displacement of the arch crown and arch bottom,as well as the horizontal displacement of the arch waist,was analyzed.Combined with monitoring measurements and numerical simulation,it was verified that the advanced grouting reinforcement area with a width of 2.0 meters has a significant support effect.