Analysis Of The Wall Rock Stability Of Soil Tunnel

Underground engineering on our country land is highly processedof level in the word. Highway tunnel and railway tunnel are totally oflength of 3000km , that is the longest in the world. Dayao hill double lineelectrification railway tunnel is 14.3km, processing the tenth Place oflength in world. Recently, there were Many successful engineering intraffic tunnel under river and sea .many tunnel under river areprogramming in our country. tunnel under river ,superior to bridge , hasadvantages of being access to life all weather and not changingenvironment condition in existence, when defending against war andnatural disaster. In order to lighten heavy traffic condition over Songhuariver in Harbin City , government have decided to invest to engineertunnel under river. One of important Problem in excavation under river isthe study of tunnel wall rock stability, that has direct influence onengineering cost, construction difficulty and safe work in future.In this paper, the studying objection is tunnel crossing Songhuariver in Harbin City , and ANSYS is used to digitally simulate excavationof tunnel, based on exploration data. On the basis of it, the paperstudy the displacement and the stress redistribution behavior in soil,and analyze the wall rock stability .Factors influencing wall rock stability are sorted to be twocategories, geological factor and man-made factor. Soil structurecondition, groundwater condition and wall rock initialization stresscondition are contained to the first categories. The second factor is tosay engineering and construction factor, containing depth of tunnel,construction method, timbering method and time, tunnel shape anddimension. The first is basic and the later is work based on the first. Thepaper suggestes that it be possible to use shield method for excavationof tunnel crossing Songhua river in Harbin City, considering geologicalenvironment and specialty of shield method. Under special geologicalcondition and excavation method, strata over tunnel and constructionpressure are important factors influencing the wall rock stability. Thework of the paper is mainly discusses influence that strata over tunnelhave on the wall rock stability and influence strata and constructionpressure together have on the wall rock stability.The paper apply Plane42 element to simulate elastic Plane strain, anduse element birth and death technique to simulate tunnel excavationand analyse the displacement and stress redistribution.The content of the paper:(1)Introduce the finite element numerical analysis and elastic planestrain finite element numerical analysis. And also introduce thefunction of ANSYS and the technical possibility to realize numericalsimulation tunnel excavation.(2)Based on geologic condition of tunnel crossing SongHua river,applying shield method, the paper use ANSYS to simulate tunnelexcavation, and analyse the displacement and stress redistributionbehavior in soil under different depth of strata over tunnel.(3)Based on geologic condition of the tunnel crossing Songhua river,applying shield method, the paper use ANSYS to simulate tunnelexcavation, and analyse the stress redistribution behavior in soilunder different construction pressure, finally get the criticalconstruction pressure under different depth of strata over tunnel.(4)Based on numerical simulation above, the paper applied regressanalysis method ,and analysed the wall rock stability under differentstrata over tunnel,and finally get the relation between strata overtunnel and factor of wall rock stability when there is not pull stress atthe top and bottom of tunnel.