Study On The Mechanism Of Surface Subsidence Caused By Urban Tunnel Construction

Urban tunnel construction will inevitably cause some degree of surfacesubsidence, and serious surface subsidence accident will threat the safety of people’slife and property, so the mechanism of surface subsidence caused by urban tunnelconstruction has drawn more and more concerns. Meanwhile， with the fastdevelopment of subway construction, the accidents of surface subsidence caused byurban tunnel construction take place more and more frequently, so it carry bothacademic value and practical significance to study the mechanism of surfacesubsidence caused by urban tunnel construction.Using the combination research methods of theoretical analysis, numericalsimulation and field project analysis, this thesis studied the mechanism of surfacesubsidence caused by urban tunnel construction from the pressure arch perspective.The main researching work was as follows：(1) The whole process of subsidence caused by urban tunnel construction wasstudied by UDEC numerical simulation, concluding that if the pressure arch innerboundary move outside to the near-surface, the surface collapse integrally, and if thepressure arch inner boundary stop moving outside, the surface only appear somedegree subsidence.(2) Through a orthogonal experiment, the influence factors of subsidencecaused by urban tunnel construction were analyzed, concluding that rock conditionhad the greatest effects on subsidence maximum and subsidence area. Besides, jointspacing had the greatest effects on tunnel collapse area.(3) The influence of bolting support, bolting-shotcrete combined support andcomposite lining support on subsidence was studied, concluding that support couldlimit the outward movement of pressure arch inner boundary to varying degrees,thereby reducing subsidence.(4) The influence of full-section method and step method on subsidence wasstudied, concluding that step method could effectively limit the outward movement ofpressure arch inner boundary, thereby reducing subsidence.(5) A practical project was compared and verified. The results showed themeasured value was basic consistent with the simulation value.