The Treatment Of Mucky Soft Foundation At Xiaogushan Hydropower Station

Xiaogushan hydropower station, which is in the Sunan Yugur Autonomous County in Gansu province, is the sixth cascade hydropower station consisted of hubs,diversion tunnels and workshops in Heihe mainstream. The hydropower station hub is made as the type of gate dam,and the basic parts of the riverbed is covered with quarternary loose sediments including alluvial-diluvial silty clay layer with the thickness of5-18m. Since the soil is judged as the silty soil by the physical and mechanical properties and the geological conditions, the ground treatment is needed in order to guarantee the safety of the operation of the project.In consideration of the engineering characteristics and the geological conditions of the project area, the design uses treatment measures of bored concrete pile of pile group foundation. Here identifies the arrangement and the structure form according to the specification, calculates the vertical and horizontal bearing capacity and the displacement of the pile foundation, and then forecasts the deformation of pile foundation under the multiple load cases based on the Biot consolidation theory with the finite element method. The results of the calculate shows that the selected foundation treatment scheme is feasible to content the regulatory requirements.A large number of deformations monitoring data has been obtained by monitoring the3row for a total of15monitoring points on the upper, middle, and lower reaches after the hub project. By analyzing these data and then comparing with the prior forecast data, we can say that Xiaogushan hydropower station is operating normally. And the hub deformation monitoring data is basically consistent with the preliminary forecast data to content the requirements of safe operation. The foundation treatment program is also reasonable and effective.After analyzing the whole process of the previous survey and the completion monitoring of this project, Xiaogushan hydropower station hub foundation treatment uses the way called concrete filling pile to enhance the bearing capacity and stability of the foundation, improve the deformation features of the soft clay, prevent the shear failure of the soil mass, reduce the shear deformation and the uneven settlement, and also provide a guarantee for the safe operation of the project. This typical case has a reference value which can provide a reference for the basic processing design of hydraulic structures under similar geological conditions.