| Shandong Province, located downstream of Yellow River, has built large amounts of plain reservoirs to solve the unbalance between supply and demand for water resources. Most of reservoirs lie in the alluvial plain of Yellow River, the type of dams is usually uniform earth dam, its foundation is usually composed of sandy silt or sandy clay with high permeability, and the impervious stratum is buried deeply. Both the body of earth dam and the foundation of dam are of high permeability, so the amounts of seepage of reservoir are large. According to the imperfect statistics, in the plain reservoirs which have not taken any anti-seepage measures, the amount of seepage per year accounts for 20%～30% of its adjusting storage capacity. Viewing the performance of plain reservoirs, many of them have a leakage problem, and seepage deformations, such as flowing sand, spring, occurred behind some dams. A combined measure of paving compound film on the upstream surface of dam and setting up vertical anti-seepage in dam foundation is adopted to treat leakage.The vertical anti-seepage means that a vertical curtain is set up in the pervious stratum to prevent percolation. The depth, thickness and materials of anti-seepage have an effect on its permeability and structural stability. According to the principle of its formation, the vertical anti-seepage can be classified into two types, one is replacement of anti-seepage material and the other is introduction of anti-seepage material. The type of replacement means that the foundation materials are replaced with anti-seepage materials, such as thin wall of anti-seepage concrete, paving plastics in vertical direction. This measure needs machines to form a trough, then to construct anti-seepage body. So, this measure requires a high stability for trough. The type of introduction means that the original foundation material is directly transformed with anti-seepage material such as high-pressure jet sheet pile, anti-seepage... |
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