Research on consolidation settlement of ground surface caused by shield tunnelling

Regarding the soil around the tunnel as homogeneous,continuous,isotropic,saturated and elastic medium,the conformal mapping method is applied to transform the considered region in the physical plane into concentric ring region in the image.The control equation for dissipation of excess pore water pressure is established based on Terzaghi-Rendulic theory of two-dimensional consolidation when the lining is impermeable.The analytical solution for dissipation of excess pore water pressure is obtained using separation variables method;and the formula for consolidation settlement is got according to the theory of elasticity.Combined with an example,consolidation settlement of ground surface is discussed considering disturbance degree of soil,soil's coefficient of permeability,soil's modulus of elasticity and the depth of tunnel.The results show that there is a proportional relationship between the added value of consolidation settlement and the variation of initial excess pore water pressure in the outside of tunnel.And the greater the disturbance degree is,the larger the consolidation settlement is.The greater the coefficient of permeability is,the faster the consolidation settlement is.There is no relationship between the coefficient of permeability and the final value of consolidation settlement.The larger the modulus of elasticity is,the larger the final value of consolidation settlement is.The deeper the tunnel is,the longer the time of consolidation settlement is,and the larger the final value of consolidation settlement is.