Anti-seepage Curtain Stability And Seepage Analysis Of Deep Foundation Pit Near Lake Or River

With the development of national economy and social increasing needs, the deep foundation pit engineering near lakes or rivers are increasing gradually, this kind of deep foundation pit engineering have close hydraulic contact with neighboring rivers and lakes, which have riched groundwater and complicated seepage field, bringing many difficulties to the project.In order to guaranteeing the smooth construction, needing to install anti-seepage curtain to block the seepage of the groundwater to the foundation pit when the bottom elevation of foundation pit under groundwater’s level. The existence of the anti-seepage curtain will reduce water inflow intto the foundation pit and working hours of the draining equipment; For another, it will reduce head drop and settlement of surrounding buildings outside of curtain, thus, it will reduce effect to surrounding environment greatly.But the existence of the anti-seepage curtain also lead to the head difference between inside and outside of curtain, resulting in the increase of curtain stress and deformation and threatening stability of curtain. On the other hand, increasing head difference make the ground water outside flowing into foundation pit bypass the bottom of structure, when the seepage force greater than the buoyant unit weight of soil, quicksand and piping will be appeared, and it will bring safty problem to surrounding structure.This paper based on the deep foundation pit engineering of south-to-north water diversion project in Baliwan pump station, and researched key technology of deep foundation pit near lakers or rivers combining theoretical analysis, numerical simulation and field test.Firstly, by three-dimensional seepage theory and finite element method, the dewatering scheme and construction parameters was determined, and characteristics of foundation pit seepage field was gotten. Then, relationship between anti-seepage curtain depth and groundwater level was analyzed, and foundation pit seepage law was revealed, and dewatering result of curtain was evaluated quantificationally. In addition, optimized drainage mothod was suggested, it reduced the construction costs and get a good effect.According to curtain characteristics of the deep foundation pit near lakers or rivers, the effect to curtain in different modulus of elasticity, thickness, drawdown of groundwater, excavating depth and distance between curtain and edge of foundation pit was analysed. Furthermore, throughing analyse bearing capacity, engineering cost and construction and so on of different structure form, best structure form of the curtain was obtained, and construction methods to the critical site of curtain was given.