Study On Rockburst Prediction Of Single-track Railway Tunnel Under High Ground Stress

With the rapid development of infrastructure construction in china,railway engineering constantly extends to western region.Deep-lying tunnels appear widely.Due to the high ground stress and hard rock,the rockburst in excavation process brings great challenges to the safety of tunnel construction.Therefore,the studies on rockburst prediction under high ground stress are of great significance.This thesis takes Sang Zhuling tunnel in sichuan-tibet railway Lasa-Linzhi line as engineering background to research the rockburst prediction of single-track railway tunnel under high ground stress.First,the back analysis of initial geostress in tunnel zone: Based on the previous measured results of in-situ stress by hydraulic fracturing,the finite element numerical model of Sang Zhuling tunnel can be formulated on the basis of three dimensions FEM regression analysis.The method takes 6 geostress fundamental states into consideration.The distribution law of initial geostress in Sang Zhuling tunnel zone can be finally found out with the regression equation of initial stress in tunnel zone determined.Secondary,general study on rockburst prediction in full-lengh range of tunnel: Based on the results of the back analysis of initial geostress,the numerical calculation model can be set up with several typical computed section picked in full lenghth range of Sang Zhuling tunnel.To analyze the stress change of surrounding rock in different stages,increasing stress release ratios were adopted to simulate the releasing progress of surrounding rock stress.The full-lengh range rockburst prediction of Sang Zhuling tunnel in different releasing ratios and different rockburst criteria can be generally summed up combined with the rock parameter such as uniaxial compressive strength in geological exploration data and rockburst stress-strengh ratio criteria raised by many experts from home or abroad.Third,study on rockburst prediction in sections during construction term: With the aid of finite element numerical calculation software,the study was combined with the rockburst prediction methods such as stress criterion method and analogy method.And the secondary correction analysis of initial geostress was developed with field data in the front of tunnel face.At the same time,a real-time rockburst prediction for unexcavated segment was carried out.