Research On Reasonable Supporting Time For The Highway Tunnel Secondary Lining

With the development of traffic and transportation in China,great progress has been made in infrastructure projects,especially in mountains and highway tunnels.As a result of the tunnel construction is mostly in the field,the complex topography bring great difficulty to construction,especially for weak surrounding rock or poor engineering geological conditions of the tunnel support,Therefore,it is very important for us to clarify the reasonable support time of the secondary lining for timely feedback of the stress state of the tunnel surrounding rock and the supporting structure,and to ensure the safety and stability of the tunnel excavation.relying on the Cha-Zhen tunnel,The MATLAB software is used to do regression analysis on the monitoring data of the Cha-Zhen tunnel,and it is compared with the numerical simulation results,so as to study the secondary lining time of weak surrounding rock tunnel.The main research contents and conclusions are as follows:(1)By checking the related research paper data,A summary of the development course of reasonable supporting time for the highway tunnel secondary Lining.(2)According to the Hanzhoung Xixiang county Cha-Zhen tunnel,introduces the main contents of the project monitoring and measuring point arrangement,the use of chazhen tunnel monitoring measurement data regression analysis software MATLAB,variation of settlement and tunnel vault of different section under-the condition of tunnel convergence,the stress of the lining,and obtained the regression equation of displacement.The results show that the overall trend of the three measured sections is fast increasing and then gradually slowing down until finally tends to relatively stable.On the basis of secondary lining support time discrimination method and principle of comparative analysis to determine the reasonable time of the excavation to about 24?26 days,from the face of 48?52m.(3)Determine the calculation range and boundary conditions,establish the corresponding engineering model,using MIDAS GTS to simulate the tunnel model,analysis of the change regularity of tunnel vault settlement,tunnel convergence,the stress of the lining,and the results of the simulation and monitoring measurement data were compared and analyzed,the results showed that the monitoring data and the results of calculation error in a reasonable range,and the stress distribution of Cha-Zhen tunnel line layout position consistent with the reliability calculation model of tunnel excavation in twenty-sixth days,can begin to do the secondary lining.(4)by adding different surrounding rock load release coefficient method,we choose multiple working conditions to study the influence of initial lining and secondary lining on the stress and variation of tunnel vault settlement and tunnel convergence value and surrounding rock and supporting structure under different load proportions.Then,the working conditions of different load release coefficients and the proportion of the secondary lining distribution are analyzed,and the reasonable support time is determined when the load release coefficient is 60%and the secondary lining bears 15%load ratio.