Long-Term Stability Analysis of Surrounding Rock in Excavation Sequence of Deep Hard Rock Group Tunnels

摘要

The delayed rockburst will cause great damage to the deep rock mass engineering,and the long-term stability of the surrounding rock of the deep hard rock tunnel is closely related to the occurrence of the delayed rockburst.In order to study the influence of the excavation sequence of deep hard rock multi-tunnel on the long-term stability of surrounding rock,this paper takes the diversion tunnel of Jinping II Hydropower Station as the engineering background,and establishes a numerical model to analyze the impact of delayed rockburst in three different excavation conditions The three working conditions are:simultaneous excavation,interval excavation and sequential excavation.The results show that the surrounding rock stress shifts to the outside after tunnel excavation.The stress concentration of the first principal stress occurs about 2m from both sides of the tunnel.Under the condition of simultaneous excavation,the stress concentration range is the largest,and the first principal stress value at the stress concentration is also the largest.The interval excavation working condition is second,and the sequential excavation working condition is the smallest;the analysis of the plastic zone range shows that it has the largest plastic zone volume according to the working condition 1,the working condition 2 is second,and the working condition 3 is the smallest.Combined with the numerical analysis results and the actual construction speed on site,it is recommended to use the interval excavation method for multi-tunnel excavation,which is beneficial to reduce the risk of delayed rockburst while increasing the construction speed.At present,the research on the time effect of rock mass mainly focuses on the weak rock with significant rheological properties.This paper studies the time-dependent deformation and failure of surrounding rock in deep hard rock tunnel,which has certain significance for the support design of deep rock mass engineering and the study of diverticulum stability.