Abstract: Researching the deformation characteristics of diaphragm wall foundation pit in water-rich sandy stratum is of important significance for engineering practice. The deformation characteristics and influence factors of a diaphragm wall foundation pit induced by deep excavation in water-rich sandy stratum were studied via numerical simulation and field monitoring. The horizontal displacement curve of diaphragm wall developed from an “oblique line” shape to that of a “bow” and then to an “inverted-V” shape with the deepening of excavation. The relation of maximum horizontal displacement U_x, max and its location H_x, max with excavation depth he could be described by linear function. U_x, max was about (0.048%~0.082%)h_e, and H_x, max was about (0.60~1.20)h_e. The vertical displacement of ground surface behaved as a groove-shaped curve with the increase of transverse horizontal distance. Such settlement groove grew wider and deeper with the deepening of excavation depth. The sensitive range of settlement deformation was about (1.0-1.5)h_e, and the maximum ground surface settlement occurred in (1/3~1/2)h_e from the foundation pit wall. The foundation pit deformation in consideration of the combined effect of diaphragm wall and impervious curtain in water-rich sandy stratum is consistent with observations. The waterproof and retaining function of impervious curtain has a significant effect on foundation pit deformation. The increment of both underground water level and sandy stratum thickness helped augment the horizontal displacement and ground surface's vertical displacement. The rising of permeability coefficient had a more significant impact on ground surface's vertical displacement than on the horizontal displacement of wall if the permeability coefficient is large. Reasonable depth and spacing of impervious curtain are conducive to control the deformation and stability of foundation pit.

Key words: deep foundation pit, water-rich sandy stratum, diaphragm wall, impervious curtain, seepage, deformation behavior, numerical simulation