| In order to meet the economic and social development of the western region,infrastructure construction such as railways,highways and pipeline transportation in the western region are showing a rapid development trend,especially with the construction of the Sichuan-Tibet Railway in my country,the demand for deep buried tunnel construction is increasing.Deep buried tunnels can overcome terrain obstacles such as hills,mountains and valleys,shorten the distance between the two places,make the running routes of railways,highways and pipelines more smooth,and improve the quality of traffic and transportation safety.The western region has high mountains and deep valleys,well-developed stratums,rich in rock and soil types,and rich in hydropower resources.Various geological disasters will be encountered during the construction of deep buried tunnels.Among them,large squeezing deformations occur under the conditions of high ground stress and weak surrounding rocks.It has become one of the urgent problems to be solved.This paper takes Zhongwei-Lanzhou Passenger Special Line Jianshan Tunnel as the supporting project,combined with the test section monitoring and initial in-situ stress test results,based on theoretical analysis and numerical simulation,the mechanical mechanism and influencing factors of large squeezing deformation of deep buried tunnel are analyzed,and the grading standard is established by analytic hierarchy process and fuzzy comprehensive evaluation method,The corresponding technical measures to control the large squeezing deformation of deep buried tunnel extrusion should be put forward.The main contents and achievements of this paper are as follows:(1)The definition and mechanical mechanism of large squeezing deformation of deep buried tunnel are systematically discussed,and the main influencing factors of large squeezing deformation are obtained: Physical and mechanical indexes of surrounding rock,tunnel section form,initial in-situ stress state,groundwater state and main structural plane occurrence.(2)The characteristics of finite difference software FLAC3 D and the ubiquitous-joint model are briefly described,the numerical model was established,and the main influencing factors were simulated through single variable principle.The deformation characteristics of the tunnel are compared comprehensively,and the law of influence of various influencing factors on the deformation of the tunnel were obtained.(3)By summing up the deformation classification of similar engineering and combining with the engineering practice,the large squeezing deformation of deep buried tunnel is classified into: Severe large deformation,moderate large deformation,slight large deformation,no large deformation.By using analytic hierarchy process(AHP)and fuzzy comprehensive evaluation method,a grading standard evaluation system for deformation of large squeezing deformation tunnel were established,and a comparison matrix of various factors were established through MATLAB software,and the weight value of each influencing factor were obtained.(4)The control concept and supporting principle of large squeezing deformation of deep buried tunnel are researched,using finite difference software FLAC3 D,the tunnel section shape,the length of rock bolt,the Angle of the rock bolt,the application of temporary invert and transverse bracing,and the installation of expanded arch foot support technology were optimized,established large squeezing deformation control technical measures that matched the deformation classification,and applied them to the DK113+635～DK113+735 section of Zhongwei-Lanzhou Passenger Special Line Jianshan Tunnel,and achieved good results on site. |
