Application Research Of Safety Monitoring Technology In A Chongqing Rail Transit Tunnel

With the development of economy and technology in our country, the investment of infrastructure is increasing, and the number of tunnels construction is the same, The area of Chongqing rail transit is facing a large number of tunnel construction due to the special topography. Tunnel excavation will destroy the original balance of rock mass and lead to safety accidents such as land subsidence, collapsing, building cracking, tunnel collapsing, etc. Safety monitoring mainly monitor the surrounding rock and supporting structure after excavation by a variety of measuring methods and instruments, and determine the stability state of surrounding rock and supporting structure to provide the relevant units timely analysis data and direct tunnel construction, which has very important significance to ensure the safety of the tunnel construction.The paper analyzed and studied the stability of surrounding rock and initial support structure which are based on tunnel engineering of Chongqing rail transit line 4(hereafter referred to as Beixia section) by theoretical analyzing, field testing and numerical simulating. Main work of the paper are listed as following:(1)Based on the summary of common tunnel safety monitoring technique, the field safety monitoring plan is designed by combing with Beixia section geological conditions and construction requirements and the relevant technical specifications.(2)Crown subsidence and horizontal convergence of K16+688 section and the left line K16+701 section were taken as examples. The regression analysis is performed by applying single variable linear function、logarithmic function and exponential function. By comparing the correlation coefficients of the three regression functions, it is proved that the logarithmic function is more suitable for the prediction of the deformation of surrounding rocks.(3)The law of the change of surrounding rock with time in the process of tunnel construction is analyzed by drawing time-displacement curve of crown subsidence and horizontal convergence of K16+688 section and the left line K16+701 section, and the conclusion was drawn that the surrounding rock is almost stable after excavating for 2 weeks, and then secondary lining constructing should be considered.(4)We established the model of tunnel construction process by using Midas GTS software and the stress and deformation of surrounding rock and initial support structure after calculating, after that, the stability of surrounding rock and initial support structure were analyzed based on the results of calculation., It is found that both of them are consistent and the deformation trend is nearly the same by comparing the simulation results to the field measured data. The simulation results can provide guidance for the construction.According to the measuring and numerical simulation of the tunnel construction process, the safety of the tunnel construction can be insured by technical supporting and theoretical certifying. What is more, the results can be provided for similar projects.