| Steel sheet pile cofferdam have advantage of high strength, easy to break into hard soil layer, construction in deep water, many kinds of shape according to the need, using repeatedly, etc. So the steel sheet pile cofferdam uses a very wide range. As science and technology progressed, steel sheet pile cofferdam construction technology are also constantly improve and mature. And according to the different water depth, different geographical conditions, different flow conditions, the mechanical problem of steel sheet pile cofferdam shown are not the same.This paper takes the double steel sheet-pile cofferdam engineering which is on the basis of silt as the project background. In the middle of the cofferdam is filled earth and the both sides are the steel sheet piles. The two rows of steel sheet piles by the steel tie bar are connected into a whole. After pumping within the cofferdam, the double steel sheet-pile cofferdam has become a temporary maintenance structure of retaining water. This paper uses the FLAC 3D finite difference software to simulate the pumping process in cofferdam. The stress and displacement of cofferdam has been analyzed in three different conditions. One is taking the width of 8 meters weir core soil(Project One), one is taking the width of 9 meters weir core soil(Project Two), the last one is taking the width of 8 meters weir core soil and a stack back(Project Three). Through this study, draws the following conclusions:1. The displacement velocity of cofferdam which based in the silt increases sharply during the pumping process. The settlement of upstream and dorsal surface of steel sheet pile is obvious. Increasing the width of the weir core soil is not effective to prevent displacement of the steel sheet pile cofferdam. But taking stack back pressure emergency measure, the displacement velocity and displacement are got good controlled. Then the cofferdam will gradually stabilized;2. The pumping process like an unloading process for the soil in the cofferdam. The soil gradually uplift with the water level decrease. The weir core soil have obvious settlement and steel tie bar exposed. Increasing the width of the weir core soil, the soil subsidence and uplift have eased, but did not change the plastic area of the soil. The soil near the steel sheet pile and the bulge region soil have occurred plastic deformation, and the sliding surface as a whole. After taking stack back pressure emergency measure, it can have a good control of the inhibition of weir core soil subsidence and uplift of inner soil, and greatly reduce soil plastic sabotage;3. When the distance between steel sheet pile cofferdam and foundation pit is far, the excavation of foundation pit have little impact on the steel sheet pile cofferdam;4. Calculation model of the value is generally consistent with the actual monitoring results and they have same change trend suggesting that simplified model for improving the speed of computation and the value of the parameters are feasible. |
