Mechanism Study Of Deformation And Failure On Prefabricated Underground Utility Tunnel Crossing Active Ground Fissures

Xi’an is the pilot city of the national underground utility tunnel and almost the city with the most serious ground fissute disaster in China even all over the world.All the newly planned urban underground utility tunnel almost intersect with ground fissures in Xi ’an,which are facing serious threat of ground fissure disaster.The research of ground fissure and engineering disaster has not been involved in the field of urban underground utility tunnel in the past,which is a new subject.Therefore,how to select the structural form and construction method in the ground fissure site,is an urgent engineering problem,to reduce the influence of ground fissure activities on the underground utility tunnels.This study takes the ground fissure disaster in Xi ’an as the background,selected a construction project of an underground utility tunnel in Xincheng district as the research engineering background and support,adopted the physical model test and numerical simulation methods to establish the mechanical model on the failure of the prefabricated underground utility tunnel crossing active ground fissures,which considered the nonlinear interaction between structual and soil.This study researched the structure disaster mechanism of and waterproof failure of prefabricated underground utility tunnel crossing active ground fissures,quantified the optimal working condition settings for the structure design of underground utility tunnel crossing ground fissures,which can provide the theoretical and technical guidance for the structure design of Xi ’an and enrich the research content of the disaster of ground fissure in China.The main achievements are as follows:(1)Based on the prototype of an underground utility tunnel project in Xincheng District,XI’an,a physical model test of the prefabricated utility tunnel crossing active ground fissures was established.Soil pressure change,structure displacement,reinforcement strain and joint displacement was taken to research the deformation and failure mechanism of the prefabricated utility tunnel.(2)Based on the finite element software,taking underground utility tunnel project in Xincheng District as the prototype,a three-dimensional numerical calculation model of strata-ground fractures-utility tunnel was established.The influence mechanism of different settlement(50mm,100 mm,150mm,200 mm,250mm and 300mm)and different crossing angles(45°,60°,75° and 90°)on mechanical response and rubber waterproof ability of prefabricated utility tunnel was researched.(3)Construction optimization schemes were proposed based on the stress and deformation law of underground utility tunnel crossing active ground fissures.Numerical simulation software was used to confirm the huge advantages of prefabricated utility tunnels in resistance to deformation compared with the traditional cast-in-place utility tunnel,and the structural stress and deformation characteristics of prefabricated utility tunnel under different crossing positions and different initial interface stress conditions of rubber were compared and analyzed.The feasibility of optimizing the construction method of the utility tunnel is verified and the optimal scheme is proposed.