Research on diaphragm wall mechanism and effect of deformation control in soft soil

On the basis of measured data from 20 subway station foundation pits in Tianjin, a normalized model is established and the affection of the distance between diaphragm wall and retaining structure（L）, the stiffness（E）and the depth of diaphragm wall（H） which may influence the internal forces (M_D) and horizontal displacement (δ_hm) of the containment structure and the surface subsidence (δ_vm), are studied by using the finite element method and orthogonal test. And it turns out that the three factors influence the deformation control of foundation pit in varying degrees. L primarily affects M_D and δ_vm, and the maximum settlement can be reduced by more than 60%. And H mainly controls δ_hm, to the greatest extent, the lateral displacement can be reduced by about 50%. But the impact of E is not obvious within the range of normal variation. Then according to the computation theory for the similar structure of double row pile, the quantitative relationship of internal forces between diaphragm wall and containment structure is established. Finally, the applicability of the above conclusions to the deformation control and prediction of foundation pit in soft soil is verified by using the deformation prediction of Kung et al. to analyses the control effect of diaphragm wall in soft soil area, and by comparing with the measured value with the result of the finite element calculation.