Sham Dam Plain Reservoir Construction Geological Studies On Soft Ground

In the downriver area of Yellow River and the seaside delta area, the main source of the water for industry and living use is Yellow River. Many reservoirs have been built in the plain. These reservoirs in the plain are built by all sides dam in the flat, which are restrained by the soft and weak groundwork. The dams are normally low in height and shallow in sluice of 4-6m, which result in large occupied areas and loss due to evaporation. To increase the depth of the sluice of the reservoir can not only improve the technical and economical index of the reservoir but also make rational use of the local water and land resources. It is of special significance to build the reservoirs in plains in our country due to serious lack of the land resources. The soil distribution of the alluvium in embouchure of Yellow River and the sea facies sedimentary soil layer are normally light powder soil and/or powdery sand soil, powdery clay and/or clay interlayer. It has very poor engineering geologic condition and the mechanical characteristics. For the above reasons, this article aims at deep research on the feasibility, geological and engineering measures to be taken while building the "Deep Water with High Dam" reservoir on such kind of groundwork in the plain, taking the example of Chunha reservoir.Firstly, the static and dynamic stress triaxes experiment was done on the soil of groundwork of the dam in order to study the deformation characteristics under the static and dynamic stresses. Simulation on static and dynamic forces was done on the typical dam cross section, applying the non-linear static and dynamic limited component analysis program. By using this program, the stress, deformation and stress horizontal distribution of the dam body in the different periods of dam building, operation with sluice and occurrence of 7°earthquake and the response of dynamic force to the earthquake and the extra-static pore water pressure distribution were calculated in order to make analysis and judgment on possibility of occurrence of plastic section, cracks and fluidifying due to earthquake. After construction of the example dam, actual measurements have been taken to verify the stress and deformation of the dam body and groundwork, applying the simulated model observation system. It was proved that the calculation theory and methodology adopted and the analysis made in this research are correct and highly referential to construction of other reservoirs in the plain.Secondly, the experiment on the permeability characteristics of the soil under the dam body and the groundwork and analysis on limited permeable components with different permeable-proof techniques were done to determine the reasonable proposals for permeable-proof of the dam of reservoir. As for analysis on stability, the simplified Bishop method was adopted to make the analysis on the anti-sliding stability of the dam body and groundwork in completion period, stable permeable period and earthquake intensity of 7°, which was verified through the experiment by centrifugal model. In order to assure realization of the design idea, the permeable-proof technique and operation control techniques were adopted in this research. It is observed and proved that the wholly enclosed permeable-proof system by combined civil membrane permeable-proof glacis, vertical plastic permeable-catch and two (2) layers clay in the groundwork can not only prevent the dam body failure due to permeability of the dam body but also reduce the permeability and fluidity of the dam of reservoir and the pickled impact on the surrounding soil. This technique has the advantage of low cost, easy construction and it is the priorable permeable-proof technique for building the reservoir in the plain.In addition, the new technology of groundwork treatment through combination of pre-compacting stack and deep mixing powder spraying piling, "grate plate＋prefabricated concrete plate" complex protection structure and soil backfilling for d ditches along the ground work, were adopted in this research to solve various technical problems in building reservoir in the soft ground in the plain. The feasibility and effectiveness of the above methods have been verified by construction of the example dam.The research shows that the depth of the sluice can be increased by 10m without enforcing the dam groundwork in whole, while building reservoir in the soft and weak groundwork of the alluvium in embouchure of Yellow River and the sea facies sedimentary soil layer. It was proved that, by applying the technology described in this paper, the control on the stress, deformation, stability and the permeability and fluidity of the enclosed dam could be guaranteed, and obtained remarkable social, economical and environmental benefit. This research could be referential to construction of similar reservoir in the plain. Those existing reservoirs with low dam and shallow sluice could be expanded by applying this technology in order to improve the operation efficiency of the reservoir.