Author(s): Xie Xinghua; Lu Jun; Tan Yefei; Zhao Jianjun
Linked Author(s): Xinghua Xie
Keywords: Deep overburden; Anti-seepage in dam base; Suspended impervious wall; Identified value
Abstract: There are plenty of rivers with prolific water energy in west China. These rivers are located in high mountains with river bed of sands and gravels that is called deep overburden. Anti-seepage structures in basement are needed to cut-off the seepage as earth dams are built on river bed with deep overburden. In China, concrete impervious wall is used as this kind of anti-seepage structures. Concrete impervious wall is built to cut-off the seepage path in river bed when the overburden is in a depth of no more than 80m. But in other scenarios such as the depth of overburden is more than 90m, for instance it is more than 140m in depth in the dam base of Yele hydropower station, it is difficult to build the cut-off style imperious wall because its qualification is out of control in such deep overburden. So it is necessary to study the effectiveness of suspended imperious wall in deep overburden dam base and to find the best depth considering the anti-seepage demand and its economical. The best depth of impervious wall is studied following the basic principles of seepage. It shown that the deeper the impervious wall, the smaller of the average seepage gradient in the seepage path, and the smaller of the uplift pressure to the dam base. The relation curve iss not linear between depth of impervious wall and its effectiveness. There iss an identified depth of the impervious wall. The effectiveness is significantly when the depth of the impervious wall is lower than the identified depth. When it goes upper than the identified depth, the affecting becomes smaller, and a most economical depth of the suspended impervious wall in deep overburden. As the seepage gradient is kept in the safe range, the most economical depth would be the best depth of the suspended impervious wall. And it is clear that the best depth is affected by the overburden composition and the water head pressure.
Year: 2013