Study On The Influence Of Slope Excavation On The Stability Of Existing Tunnel In Shanxi Province

In slope excavation engineering,one of the key issues is how to evaluate and guarantee the stability of the mountain and adjacent infrastructure.This article is based on an engineering example of the stability study of an existing tunnel in Shanxi.In order to ensure the smooth progress of the project,the stability of the slope and the safety and normal use of the tunnel are not affected.The effects were studied.According to the engineering geological conditions,the principle of strength reduction and other relevant data,the large-scale finite difference software FLAC3 D was used to carry out three-dimensional numerical simulation of the slope and the mountain after excavation.The specific research content is as follows:(1)Select appropriate calculation range,modeling and analysis software according to the actual engineering requirements,and carry out 3D numerical simulation analysis of the mountain and tunnel in the excavation section of the slope.Using FLAC3 D software,the stability of slopes,mountains and tunnels under natural conditions were analyzed from the perspective of plastic area distribution,stress field and displacement.The research results show that,under Condition 1(the natural state is the normal use state),the excavation slope is in a stable state,and the excavation of the slope has little effect on the adjacent existing tunnel,and does not affect the safety and normal use of the tunnel.(2)Based on the strength reduction method,study the stability of slopes,mountains and tunnels under heavy rain conditions(saturated soil).The research results show that the current excavation slope of the second condition(saturated state of soil)is in an unstable state.The current slope will be partially unstable and the mountain will undergo creep.Does not affect the safety and normal use of the tunnel.However,over time(timeliness),the trend of increasing influence cannot be ruled out.(3)In order to analyze the stability of slopes and tunnels more comprehensively,seismic factors(saturated soil + earthquake)are added on the basis of heavy rain conditions.Combined with the seismic conditions in the study area,a seismic wave similar to the actual situation in the study area was synthesized using seismic wave generation software;then FLAC3 D software was imported for calculation and analysis.The research results show that in the third condition(saturated soil + earthquake),that is,under the condition of continuous heavy rain and simultaneous earthquakes,the slope,mountain and tunnel have undergone large displacement and deformation,and the mountain and slope have undergone instability and damage;The stress curve generated by the excavation of the slope in the front exit section develops to the top of the left tunnel,which reduces the safety of the tunnel;the excavation of the slope has a greater impact on the adjacent existing left tunnel,and the left tunnel in the middle and rear sections which are less affected by slope excavation.(4)In the criterion of tunnel instability,the convergence of numerical calculation can be used as the basis for instability.Therefore,the analysis of the convergence of the maximum imbalance force curve has a great effect on the judgment of rock mass stability.The maximum unbalanced force curve is used to analyze the three working conditions.The results show that under natural conditions,the unbalanced force curve gradually converges from the peak to zero,and the slope,mountain and tunnel are in a stable state;under heavy rain conditions The maximum imbalance force curve gradually decreases after reaching the peak value,the curve is relatively balanced but does not tend to 0,the mountain body creeps but is basically in a stable state;it can be clearly seen in the maximum imbalance force curve of rainstorm and earthquake conditions The curve does not converge after the peak,the curve fluctuates greatly and still shows an upward trend,the mountain body has not reached the state of force equilibrium,and is in a state of complete destruction;the maximum imbalance curve under three conditions and the stress field of each condition,The analysis results of the plastic zone and displacement agree well.