Research On The Stability And Ground Subsidence Of Shallow Embedded Tunnels In Water-Rich Soft Soil Stratum

In the construction of urban rail traffic,shallow metro tunnel will usually pass through tunnel construction in watery and weak stratum,which will bring about the difficulty of tunnel construction,deform the surrounding strata and have a bad influence on the buildings and underground buried objects.In the background of Guan,hui inter-city railways GHZ-5part bored tunnels project,this paper has carried out mainly the following aspects of work to analyze shallow-buried tunnel in watery and weak stratum.1. Choose the test section in the mined tunnel with shallow cover and monitor the tunnel surface settlement、vault crown settlement、hole convergence、pressure of surrounding rock、steal arch frame internal force、internal force in lining.Then get the mechanical deformation law of strata and tunnel support structure.2. The three dimensional numerical analysis of test section by finite element software ABAQUS,analyze the regularity of stress and strain of tunnel,the influence of seepage on tunnel and strata deformation.If there is seepage in test section,hydrostatic stress field change obviously after the excavation,around the surface of tunnel excavation from pore water pressure areas in funnel-form.Tunnel vault settlement convergence and ground subsidence mainly take place at the excavation phase of the left side of tunnel section.3. Choose the typical section of the test section and analyze the value of tunnel excavation by means of CD method,CRD method and double-side-drift method,analyze the influence of Construction method on tunnel stability and strata deformation.Comparing the result of analysis, Guan,hui inter-city railways GHZ-5part should adopt CD method.4. Take the calculation of coupling effect of seepage rock deformation into consideration, and analyze the law of the influence of seepage on tunnel and the stress of stratum. Vault sedimentation and ground settlement value and its influence scope of the tunnel which has seepage after excavating is much bigger. Seepage may cause deformation of rock and soil mass easily. The upheaval of the bottom of arch increases linearly according to underground water level decrease, tunnel vault settlement, convergence, ground surface settlement.5. By two-dimensional finite calculation analysis, analyze two strategies of double parallel tunnel excavation and single tunnel excavation separately and the influence of the tunnel spacing on tunnel stability and deformation.Compared with single-track tunnel, small spacing double-track tunnel cause the increase of vault crown settlement、hole convergence、 ground surface settlement after completion, the increase of bending moment、axial force and sheer force, but steel arch and Initial concrete stress distribution rule is invariant.