Seepage Characteristics Of Rock-Soil Mediums And Finite Element Analyzing On Three-Dimensional Seepage Flow In Heihe Water Conservancy Project

The stability of the seepage flow is the key technique in construction of a earth-rock dam. In this paper, pointing to Jinpen Hydro Project of Heihe Water Consevvancy Project and based on detailed analyses of the condition of the engineering geology and hydrogeology in site and the structure of the earth-rock dam for water retaining, the seepage characteristic parameters of rock-soil materials for the dam body are determined rationally through a large number of the seepage tests about the filled earth, reversed filter and contact face; the range of seepage area in the dam site is determined rationally through the evaluation for geologic structure and strata distribution of both banks; the numerical calculations about three-dimensional seepage flow with in the range of 1.2×1.2 km² in dam area are performeed by using the calculating programs for three-dimensional seepage flow. The analyses of the tests and calculation show such the conclusions as follows: â‘  The soil material filled in core wall, with all the seepage coefficients being little than 10^-5 cm/s under the condition of controlled dry density, can meet with the demands of the seepage control of the dam core; â‘¡The graded sands from Weihe sands with the down-envelope curve, up-envelope curve and average envelope curve and the different sediment percentage sand with the up-envelope curve, and the graded sands from the sands in stacking site and the compound filter materials with down-envelope curve and up-envelope curve can all meet the demands of the design with the allowed gradient of piping being 0.642⁰.937 under the condition of controlled dry density; â‘¢ The critical gradient of the contact losing for the graded materials from the filter sands with up-envelope curve and the compound filter materials withdown-envelope curve is 11.37, the critical gradient of the contact losing for the graded materials from the compound filter materials with up-envelope curve and the dam shell materials with down-envelope curve is 2.007; ?The critical gradient of the contact scouring of earth material filled in core wall with Weihe sand is 1.13-4.94, it is 1.13-4.94 with filter sand and 80-152 with concrete; ?The reverse osmosis system constituted with the seepage control walls and grouting curtains in two banks of the dam body and dam abutment as well as in the thin hills and secondary dam body is modeled by using the calculated model for three-dimensional seepage flow, and the crushed zone, fissure growth and the central seepage flow from right bank to left bank along the east to west direction are also modeled by using the above model; ?The bedrock below the dam, the thin hills on left bank and north ridges are the main seepage passages, the annual seepage quantity of which is about 4780000m3. The maximum seepage gradient in core wall is 3.846, the maximum seepage gradient in reversed filter is 2.55, so there is no seepage failure under the condition of filter protection.The studies in this paper have a important directing function for construction of Jinpen Hydro Project of Heihe Water Conservancy Project.