Optimization Design Principle And Application Of Impervious Curtain For Super High Rockfill Dam

Concrete faced rockfill dam has the advantages of excellent seismic stability and strong deformation adaptability,but the construction technology of ultra-high faced rockfill dam over200 m is not yet mature,and the safety and stability of seepage and stress and strain are faced with great challenges,among which anti-seepage works are crucial to ensure that the project can play the expected benefits.Therefore,the key of concrete face rockfill dam is to establish a reliable anti-seepage system.Anti-seepage curtain is an important part of the anti-seepage control structure of face rockfill dam,and the optimal design of anti-seepage curtain is an important research topic in the construction of face rockfill dam.In this paper,the optimal design of the anti-seepage curtain of a certain ultra-high rockfill dam is studied.Firstly,the calculation theory of the optimal design of the anti-seepage curtain and the finite element analysis software Seep-3d are introduced.Secondly,the design conditions of the curtain with different lengths,depths and thickens are analyzed through the finite element analysis software Seep-3d,and the optimal design scheme of the anti-seepage curtain is proposed.The main conclusions of this study are as follows:(1)By using the control variable method for the different length of the left bank curtain,the different depth of the riverbed impervious curtain and the different thickness of the riverbed impervious curtain,the influence of the size change of the impervious curtain on the seepage flow,seepage velocity,hydraulic slope and head height of each part of the dam is studied.The optimal anti-seepage curtain size scheme is selected as the length of the left bank curtain 250 m,the depth of the riverbed curtain 100 m and the thickness of the riverbed curtain 5m.Because the permeability coefficient of the curtain is large,and the permeability coefficient of the mountain on both sides is not much different,so it is suggested to improve the construction quality of the curtain,in order to achieve better seepage control.Through the comparative study,it is found that the optimal design of the anti-seepage curtain depends on the seepage flow,and the size change of the anti-seepage curtain has little influence on the seepage velocity,hydraulic slope and head height.(2)Based on parameter sensitivity analysis of anti-seepage curtain and overlay parameters,the influence of calculation parameters on optimal design of anti-seepage curtain for ultra-high rockfill dam is studied.It is found that the length,depth and thickness of the anti-seepage curtain decrease when the permeability coefficient of the curtain and the permeability coefficient of the micro-permeable layer change.On the contrary,when the permeability coefficient increases,the length,depth and thickness of the anti-seepage curtain increase.(3)This paper introduces the principle of "balanced anti-seepage method" in the optimization design of anti-seepage curtain structure,and according to the principle,the optimization design of anti-seepage structure in the hub area of ultra-high rockfill dam,including the thickness and depth of the anti-seepage curtain of riverbed and the horizontal length of the curtain on both sides is studied.The analytical solution calculated by "balanced anti-seepage method" is compared with the optimal design scheme calculated by the finite element method.Verify the safety rationality of the optimized design scheme.Some necessary suggestions are put forward for the construction scheme of anti-seepage curtain: first,improve the construction quality of the river bed and the curtain on both sides,reduce the permeability coefficient of the curtain.It is suggested that the second grouting should be carried out after the first grouting.The second is to increase the thickness of the riverbed and the curtain on both sides,and the curtain of the riverbed is designed according to 4～5 rows of curtains.The theoretical part of this method takes the optimization design of dam anti-seepage curtain structure as an example.The optimization principle is also applicable to the design of similar hydraulic structures such as antiseepage wall.