Impermeable Wall Research Of Earth-Rock Dam On Deep Overburden Layer

In recent years,building the dam over the deep overburden has been quite common.In terms of the seepage,due to the loose structure of deep overburden layer and the large value of permeability coefficient,deep overburden becomes the main seepage way of the whole dam project,in view of this situation,a large number of scholars study the seepage control structure of deep overburden dam foundation.At present,the concrete cut-off wall is the widely used way in impervious structures,and according to the actual engineering needs,a variety of combination forms have appeared,among them,two anti-seepage walls are widely used in the deep overburden of high earth-rock dams.Using the Midas GTS software to analysis the seepage and stress distribution of the Pubugou core dam when the distance between the main and secondary impervious walls is 10m?12m?14m?16m?18m,by analysing and comparing the head value,the horizontal displacement,the vertical displacement and the vertical stress of 5 conditions,the following conclusions can be drawn:(1)Both the core wall and the composition of anti-seepageand grout curtain bellows it play important roles in the dam seepage control,the calculation results of two direction and three direction seepage show that the former is better than the latter,but the latter is closer to the reality;(2)The reduction of water head in dam foundation and dam mainly occurs in the vicinity of anti-seepage structure,keep the main impervious wall in the dam axis,with the increase of the distance between the secondary wall and the main wall,the head of both the dam and the foundation is gradually reduced(3)The maximum horizontal displacement of the dam appears in the structures which locate at upstream and dowmstream sides,owing to the arch effect of core wall,horizontal displacement appears in the upstream and downstream sides bottom the core wall,the movement of the upstream impervious wall towards upstream has little influence on the horizontal displacement of the dam;(4)The maximum vertical displacement of the dam appears in the core wall at the dam height of 1/3,the settlement of the dam has little vary when the distance of two anti-seepage walls changes,in the covering layer between the bottom of the core wall and the two antiseepage wall,with the increase of the distance between two walls,the settlement also increases;(5)For the vertical stress of the dam,because of the arch effect of the core wall,the value of the core wall is smaller than the value of two sides which in the same elevation,there is no tensile stress in the core wall,so there will be no horizontal cracks appear,The change in the vertical cut-off wall spacing has little effect on the vertical stress of the dam crest and downstream sides;(6)In the high plastic clay area,with the increase of the distance between the impervious walls,the stress gradually decreases and then increases gradually,when the spacing is 14 m,the stress value of the cutoff wall and corridor is the smallest.