Research On Seepage Field Characteristics Of RCC Dam Based On Finite Volume Method

Seepage is an important factor affecting the safety of dams.The unique pouring method of thin-layer rolling compaction of roller compacted concrete dams causes its seepage characteristics to be very different from conventional concrete.Due to the existence of this special layer,it is of great significance for the safety and stability of the dam to consider the layer seepage problem in the RCC seepage analysis.In view of the shortcomings such as poor calculation convergence and low calculation efficiency of the current research methods for the seepage analysis of RCC dams,this paper adopts the finite volume method and the fluid volume function method to construct the dam seepage calculation model,and uses the equivalent method for the dam level.Expansion treatment to highlight layer seepage characteristics.Combined with the actual project,taking a roller compacted concrete dam as an example,the seepage field of its seepage field is studied in many aspects,and the conclusions are as follows:(1)Based on the finite volume method,the paper uses the VOF method and the porous medium model to construct the seepage calculation model of the dam,and the VOF method and the porous medium model are verified by two examples of the homogeneous earth dam and the roller compacted concrete dam.Reliability for seepage analysis in dams.(2)Combined with the actual project,the established seepage calculation model is used to numerically simulate the seepage situation at the surface of the roller compacted concrete dam.By analyzing the results of the dam pore water pressure,infiltration line,seepage flow and overflow point,it is found that when the layer seepage is not considered,the infiltration line of the dam body and the seepage overflow point are at a lower position,and the seepage resistance of the dam body is relatively low.it is good.When considering layer seepage,the seepage capacity in the horizontal direction of the layer is much greater than that in the vertical direction,resulting in poor anti-seepage performance inside the dam body.Compared with the downstream overflow point,the infiltration line inside the dam body will increase without considering the existence of the layer.The seepage flow of the downstream dam surface will also increase;especially when the upstream anti-seepage layer has a weak surface,the wetting line inside the dam body will be further raised,and the seepage flow of the downstream surface will also increase greatly,indicating that the level seepage flow affects the stability of the dam body It is an important factor,so attention should be paid to the cementation quality of the control layer during construction.(3)Numerical simulation of the unsteady seepage field during the water storage period of RCC shows that it takes a long time for the seepage field of the dam to reach the stable seepage state from unsteady seepage during the water storage stage.In the stage of reservoir water level change,the hydraulic gradient of the dam will gradually increase as the reservoir water level rises,and the dam body infiltration line extends upward along the upstream face.When the steady seepage is achieved.the position of the wetting line inside the dam body continues to rise upwards.However,due to the good anti-seepage performance of the metamorphic concrete upstream of the dam body,the wetting line changes slowly inward,and the water head at the bottom of the dam is large,so the bottom wetting line is upward.The change is fast,making the wetting line appear as a concave distribution.(4)Analyze the influence of different seepage control measures on the seepage field of the dam.It is found that increasing the thickness of the metamorphic concrete and reducing the permeability coefficient of the metamorphic concrete can enhance the seepage resistance of the dam,but when the thickness of the metamorphic concrete is 1.5m,the effect of increasing the thickness on improving the seepage resistance of the dam is small;The value of the permeability coefficient of metamorphic concrete is more sensitive.When the permeability coefficient increases by one order of magnitude,the seepage flow of the dam increases by 22.81%,and when it increases by two orders of magnitude,the seepage flow increases by 82.44%;The antiseepage effect of the dam is better.Analysis of the influence of dam foundation anti-seepage on dam seepage.When the anti-seepage performance of the dam foundation is poor,the pore water pressure inside the dam is relatively high,and the position of the wetting line is relatively high.When the dam is equipped with horizontal anti-seepage facilities and vertical anti-seepage facilities,the anti-seepage capacity of the dam is improved,and with the increase of the length of the vertical curtain and the horizontal anti-seepage body,the anti-seepage performance of the dam foundation will be further improved,and the seepage flow of the dam foundation will be further improved.The height of the wetting line and the overflow point of the dam body decreases continuously,indicating that the vertical anti-seepage curtain and the horizontal antiseepage body of the dam foundation have good anti-seepage effects on the dam.Therefore,in the design and construction of the dam,reasonable anti-seepage measures can be arranged for the dam foundation according to the actual situation,which can save the project investment while ensuring the safety and stability of the project.