Research On The Sensitivity And Stability Of The Supporting Parameters Of The Advance Small Conduit In The Tunnel

As the country vigorously builds highways,railways and other tunnel projects,more and more construction safety problems are gradually emerging.In order to avoid the occurrence of unfavorable geological disasters such as unstable landslides during tunnel excavation,it is necessary to adopt reinforcement measures for advance support according to local conditions.In this paper,the Jinzhou Xituanshanzi tunnel is used as the engineering support to establish the stress model of the small lead pipe at different stages during tunnel excavation.Through FLAC^3Dnumerical simulation software,study the deformation law of surrounding rock and palm face under the condition of advanced small duct and the condition of no advanced small duct calculation of sensitivity.Through the on-site monitoring data,the rationality of the numerical simulation model is verified.（1）Through the introduction of Pasternak（Pasternak）two-parameter model,during the tunnel excavation process,the stress state of the leading small pipe at different stages is established,and the mechanical behavior curve of the small pipe is drawn.According to the curve equation,the maximum deflection,rotation angle,bending moment and shear force near the palm face are obtained,that is,the unsupported area has been excavated,and the small pipe is in the most unfavorable stress stage.（2）The FLAC^3Dsimulates the tunneling effect of the leading small pipe under the real tunnel excavation environment.Under the condition of whether there is a small lead pipe support,study the influence of the small lead pipe on the surrounding rock excavation trend,the displacement characteristics of the surrounding rock and the stability of the palm face,and compare the theoretical calculated value with the simulated calculated value.The overall change trend is consistent,which verifies the correctness of the mechanical model.Introduce the sensitivity parameter and take the settlement of the surrounding rock vault as the evaluation standard to quantitatively study the sensitivity of the influence parameters of the small pipe and the influence parameters of the grouting circle on the reinforcement effect of the surrounding rock.（3）It is concluded that the sensitivity of the grouting ring to the parameters is better than the sensitivity of the small catheter to the parameters.On this basis,carry out correlation studies of influencing parameters.（4）According to the monitoring data of the ground surface,arch top,arch shoulder and arch foot,the deformation law of surrounding rock during tunnel excavation is obtained.And carry out regression analysis on the monitoring data to predict the final deformation of the surrounding rock.Comparing and analyzing the on-site monitoring data with the numerical simulation data,it can be concluded that the displacement law of numerically simulated surrounding rock displacement is basically consistent with the displacement law of on-site monitoring displacement,which can verify the rationality of the numerical model.The paper has a figure of 61,table 29,references 71.