Study On The Tendency Prediction And Control Techniques Of Rock Burst In Laobi Mountain Tunnel Of Chengdu To Kunming Railway

Rock burst is one of the common engineering geological disaster in the course of deep buried hard rock tunnel construction.The occurrence of Rock burstnot only influence the progress of the project,but also seriously threaten constructors' safety.There are still a lot of shortcomings in the study of rock burst because of the complexity of rock burst and the diversity of engineering geological environment.Study on the tendency prediction and disposal measures of rock burst for rock engineering have an important theoretical and engineering significance to tunnel design and construction.Rock burst is likely to happen in Laobi mountain tunnel of Chengdu to Kunming railway because of its long line,large buried depth and high ground stress.In this paper,the influence factors of rock burst are preliminarily analyzed with the background of tunnel construction.The rockburst tendency is predicted by using a variety of rock burst prediction methods,and the effect of advance stress release pilot and Anchor and Shotcrete support on rock burst disposal is focused on the analysis.The main research contents are as follows:(1)The variation curve of the ground stress value with the buried depth is obtained by the method of regression analysis on the basis of the collation of the geostress measurement data of Laobi mountain tunnel site.The rock samples from tunnel site are tested,including uniaxial compression strength,complete stress-strain curve experiments and stress-strain curve experiments of loading and unloading.Based on the experimental data,the stress criterion(Russeneses criterion,Bartoncriterion and Tao zhenyu criterion),the energy criterion and the impact criterion are used to predict the rockburst tendency of Laobi mountain tunnel.The prediction result is medium rock burst.(2)The Russenes and Turchaninov criteria are used to simulate the influence of the variation of the ground stress field on the rockburst tendency of the tunnel.The influence of lateral pressure coefficient,depth of tunnel,The angle between the maximum horizontal principal stress and the axis of the tunnel,angle between vertical stress and middle axis of tunnel on rock burst is discussed.The influence of the construction factors such as tunnel excavation method,tunnel step length and tunnel excavation footage on the rockburst tendency is studied.(3)Combined with the engineering practice of Laobi mountain tunnel,the control effect of advance stress release pilot on rock burst is analyzed numerically.Taking the circumferential shear stress of tunnel as the target,the parameters of section form,aperture size,position and excavation length of pilot were optimized.Taking the control effect of bolting and shotcrete support on rock burst as the target,the construction parameters such as lining thickness,volume content of steel fiber in lining,anchor spacing and anchor length were optimized.