Study On Engineering Geological Problems Of Rock Burst In Deep Tunnel In Northwestern Yunnan

Based on the existing research results,this paper uses a variety of theoretical methods to select a specific tunnel for research,and has made the following progress and understanding for the rockburst problem of deep tunnels in northwestern Yunnan:1.Based on the geological background and stability analysis of the northwestern Yunnan region,the engineering geological conditions of the tunnel area are mainly studied,and the geological conditions of the area are divided into relatively unfavorable geological conditions that are not conducive to the stability of the tunnel,and the engineering rocks of the area are The group was divided into several parts,and the limestone and basalt areas were sampled and studied,and the physical and mechanical properties of the regional rocks were obtained.2.In the absence of the measured data of regional geostress,the ground displacement field of the tunnel area is reversed by GPS displacement data,which indicates that the direction of the stress field in the northwestern Yunnan is NNW direction(about 335°),which is basically consistent with most tunnels.The ground stress in the tunnel area is relatively high,which is mainly affected by the topography of the area.On the surface of the ground stress simulation results,the principal stress along the tunnel changes greatly,the stress value in the middle section is larger and more stable,and the stress in the inlet and outlet areas changes greatly.3.Based on the analysis of the related factors of rockburst,this paper uses the rockburst tendency criterion and the stress criterion,and uses the rock mechanics test and the numerical simulation of the stress field to analyze and calculate the elastic energy index of the surrounding rock of the tunnel.Various rockburst indicators such as brittleness index,maximum storage strain energy index and Barton stress index.Combined with the engineering geological conditions of the tunnel area,the danger of tunnel rockburst is predicted.The results show that moderate-strong rockburst can occur in thick layered limestone and massive basalt,with a length of about 4,500 m,accounting for 75% of the total length of the tunnel.Among them,about 2,000 m may cause serious rockburst;In the debris section,rockburst may occur only in thelocalized weathering part,and the intensity is slight-medium;the possibility of rockburst in the tunnel entrance and exit section is relatively small,and there may be a slight rockburst in the local area.4.Numerical simulation results show that different stress concentration phenomena appear after tunnel excavation on the tunnel section,so there are different rockburst possibilities,and the possibility of rockburst on both sides of the tunnel is higher,but at the bottom and bottom.The stress value is relatively low and the probability of rockburst is low.5.Summarizing the law,it is concluded that due to the existence of high ground stress,the rockburst may occur in the area of the northwestern Yunnan where the lithology is more than 400 m.Therefore,special prevention and treatment are needed in the tunnel construction stage.