EFFECT OF VARIOUS SEEPAGE PREVENTIVE MEASURES ON SEEPAGE DISCHARGE THROUGH EARTH DAM

Dams are built across rivers for impounding water which is further utilized for various purposes. Earth dams are most common type of dams. One of the major problem earth dams might face is seepage through dam body and foundation. To minimize seepage through dam body and foundation, various measures are adopted such as Cut off Trench, upstream slope lining, impervious blanket on upstream side, cut-off wall in foundation, etc. Owing to site specific characteristics every problem of earth dam seepage is unique and requires design of optimum remedial measures. Analysis using numerical modelling proves to be a great tool for designing the most effective seepage control measure. In the present paper, results of seepage analyses for a zoned earth dam using various seepage control measures are presented. Seepage analysis is carried using finite element based numerical modelling software with following remedial measures: (i) varying length of horizontal blanket (10 m to 50 m) from upstream toe, (ii) cut-off wall below COT up to three different depths in foundation, (iii) combination of upstream blanket of various lengths and cut-off wall below COT up to two different depths in foundation and (iv) cut-off wall at 5 different locations from upstream to downstream toe. Analysis indicated that, combined provision of upstream blanket and cut-off wall below COT up to bottom amygdaloidal basalt layer in foundation proved to be most effective by reducing seepage discharge by 77 % as compared to that of design dam section. Provision of cut-off wall below COT up to bottom amygdaloidal basalt layer, reduced seepage by 76 %. It is observed that, provision of upstream blanket does not affect seepage quantity considerably