Analysis On Surrounding Rock Monitoring And Supporting Mechanical Characteristics Of Huianpu Loess Tunnel

Loess is widely distributed in northwest and north China,with the rapid development trend of various traffic infrastructure construction,loess tunnel,as a key part of road engineering,its mechanical properties and safety evaluation are particularly important in the construction engineering passing through loess geological structure.Taking Huianpu tunnel in yxzq-8 bid section of Ganning section of Yinxi railway as the engineering background,this paper studies the following aspects by using the methods of field monitoring,theoretical calculation and numerical simulation:(1)Based on the on-site monitoring of Huianpu tunnel,the monitoring data of peripheral convergence and vault settlement are sorted and analyzed,and the deformation characteristics of surrounding rock of loess tunnel are summarized.The peripheral convergence law of surrounding rock is basically the same as that of vault settlement,which conforms to the deformation law characteristics of rapid subsidence-gentle subsidence-basically stable.The excavation deformation of tunnel is mainly vertical displacement,peripheral convergence takes the second place.After a certain period of time,the vault subsidence and peripheral convergence are almost zero,so it is concluded that the construction time of secondary lining should be the 16th day after excavation.(2)On the basis of summarizing and sorting out the calculation methods of surrounding rock pressure,the calculated values of each basic theoretical formula are compared and analyzed with the field measured values,so as to verify the applicab ility of each calculation basic theory,connect the field measured values of surrounding rock pressure of Huianpu tunnel,study the distribution law of surrounding rock pressure,and draw the conclusions:Xie Jiaxiu basic theory,Terzaghi theory The change trend of bill Bowman’s basic theory and field measurement values are similar,and Terzaghi theory is the most in line with the specific actual situation.Therefore,it is proposed that Terzaghi theory is the recommended formula for the calculation of surrounding rock pressure in tunnel construction under shallow burial.(3)The three-dimensional model is established through the numerical simulation software to simulate the tunnel under different shotcrete thickness at the initial support and different secondary lining thickness and inverted arch thickness.Through the displacement and stress diagram of the overall support,the stability of the tunnel surrounding rock under different support conditions is studied.(4)The three-dimensional model is established through the numerical simulation software to simulate the three engineering construction methods of loess tunnel,the simulation results after excavation are compared and analyzed,the horizontal displacement of surrounding rock and foundation settlement of each process after excavation are simulated by three construction technologies,and the applicability of three-step seven step excavation method is demonstrated.