Stress Analysis Of Deep-buried Tunnel Under The Load Of High-rise Ground-buildings

The new high-rise buildings will have an unfavorable effect on the nearby tunnel's structure.Indicated by the practical monitoring results,the tunnel structure close to the high-rise buildings whose under-lying foundation will produce certain additional loads in surrounding soils can be displaced in one direction,or can else show some deformations on its outer surface.In this paper,the mechanical response of the deep-tunnel lining in its cross section,the vertical displacement along its axial direction and the bending moment have been analyzed theoretically due to the forces transformed from the above-buildings.The main works of this paper are:(1)Firstly,by simplifying the soil around the tunnel as a semi-infinite elastic solid and the forces made by the foundations(piles-type and box-type foundation)under the high-rise building as easily settled forms,and by using the Mindlin stress expressions of the vertical pointed force in the semi-infinite elasticity,the analyzed expressions of the loads around the tunnel-lining sections are derived.(2)Secondly,the stresses in the tunnel-lining cross sections are obtained by decomposing the loads around the lining as pure pressure and shear force.And in the shear-force part,the stress in the tunnel lining are gotten by simplifying the tunnel-lining and its surrounding soil as the fiber two-phase composites and using the general displacement expressions applied to determine the shear modulus of the fiber composites.And then the influences on the stress from the depths,the widths the relative distances between the center of the tunnel-lining and the center of foundation and the thickness of the lining are discussed while the final results are also compared with that caused only by soil weight.(3)Finally,the analytical expression of the vertical displacement w along the tunnel's axial direction and the bending moment M are gotten by seeing the deep tunnel with a certain length as an infinite Euler-Bernoulli beam on elastic foundation and then using the Pasternak elastic-foundation model considering the shear effects from nearby soil;the effects from the tunnel depth are also discussed,and the results gotten from Winkler elastic foundation model and results caused only by the soil weight are compared with that from Pasternak foundation.The stress and displacement analytical expressions derived in this paper can be directly applied into evaluating the structural effects of existing tunnels lead by the loads of above new-buildings,or can be applied into the tunnel-deformation analyzing cases with simple soil conditions.