Research On The Permeability Rule And The Seepage Control Effects Of Concrete Gravity Dam On Complex Batholith

For concrete gravity dam, appropriate seepage control measures to reduce the upliftpressure of dam foundation are essential for the safe operation of the dam. For thegravity dam located in complex batholith, the existence of complex geologicalstructures and the staggered distribution of different rock groups increase thecomplexity of the seepage field, using the finite element method to create a model thatcontains the special geological structure, rock groups and dam structures for seepagecalculation can more truly simulate the seepage field distribution. In this thesis,two-dimensional and three-dimensional finite element models of Xiangjiabahydropower station and Longhuakou hydropower station were established whichcontain the anti-seepage system, drainage system, structures of the dam and rock layerzones. Based on the equivalent continuum model theory, considering the differences ofthe permeability of strata division, the typical dam monolith’s two-dimensional andoverall three-dimensional finite element seepage calculations were completed.Combined with practical engineering problems, contrasting calculation results of avariety of conditions to evaluate the seepage control effects of single anti-seepagesystem, drainage system, and the combination of both systems. The influence of thepermeability of flexural fracture zone on dam foundation and consolidation groutingarea on seepage field was analysised. The sensitivity analyses of drainage system wouldprovide a basis for the optimization and adjustment of drain holes.Seepage calculation and analysis show that the seepage control systems of bothXiangjiaba project and Longhuakou project are effective. Anti-seepage curtain caneffectively block the upstream flow and reduce the dam foundation seepage flow, butmake small contribution to reduce uplift pressure, the decrease of uplift pressure mainlyrelies on drainage measures. The influence of consolidation grouting on seepage field ischiefly reflected on the variation of seepage discharge. Changes of permeabilitycoefficient of the flexural fracture zone on the dam foundation principally affect its ownhydraulic gradient distribution and the dam foundation seepage discharge, drain holesthat pass through this zone will increase the hydraulic gradient of the fractured rockmass, by adjusting the depth or opening degree of these drain holes can banlance the value of hydraulic gradient and uplift pressure. In the case of multi-row drain holes, theclosure of part of drain holes will decrease the hydraulic gradient of their surroundingrock masses, reduce the dam foundation uplift pressure, increase the discharge ofadjacent drain holes, bring down the total discharge of drainage system. As the waterlevel rises, the discharge of each row drain holes increases, but the growth degree varieswith the locations of each row drain holes. In this thesis, the calculation results haveprovided a basis for the optimal adjustment of the dams’ seepage control system and thedams’ safety evaluation. The permeability rule summarized in this thesis can alsoprovide a reference for similar projects.