Structural measures for preventing reservoir water penetrating into dam-foundation interface of high gravity darns

摘要

In planning of high concrete gravity dams, a problem frequently encountered is that tension exists on the upstream face of dam heel area and in the immediate vicinity of foundation rock. In this case the dam-foundation interface may be detached due to its low bearing capacity of tensile stresses, and thus the high pressure reservoir water may penetrate into the interface. The interface crack feeds reservoir pressure as full uplift along the open interface and the uplift pressure in the crack would in turn assist propagation of the interface cracking, which will aggravate the working state of the dam, or even may render the dam unsafe. To cope with this difficult situation, various transit structures in the vicinity of dam heel, such as concrete plinths/platforms, concrete dragging plates, base joints and synthetic geomembrane sealing systems etc., may be considered as appropriate solutions used in practice to prevent water ingress. In the present paper, such structural measures are summarised and discussed on basis of the application experiences. An analysis for an ongoing high gravity dam is performed and observation results from an existing dam are presented. The results demonstrate that the transit structures mentioned above are suitable for solving this problem. These transit structures are easy to be constructed and can effectively relieve and solve the problem of water ingress into the dam-foundation interface after cracking to maintain the dam stability.