Research For The Effect Of Toe Weight On The Static And Dynamic Characteristics Of The Earth-rockfiil Dam

The reservoirs have exhibited great performance on flood control and drought relief. Since most of medium and small reservoirs were built from the early1950s to late1970s, not maintained for many years, their capability to flood control is jeopardized and the normal performance is inhibited. Of the dilapidated reservoirs in China, great numbers of the reservoirs are made of the clay core wall and coarse sand-gravel shell. The density of the shell sand backfill is low, not meeting the code requirements that the relative density should not be less than0.8. Since most of the dam foundation is composed of the gravel, it’s density can meet the seismic requirement and liquefies code, posing great hazards to the safety of the dams.Of all reinforcement measures on the sand-shell foundation, using rock riprap as kentledge is a more effective and economical way, the most used reinforcement measures by the designers. However, the length and height of the toe weight block are not regulated in codes and the manuals. The study on the theory for the toe weight needs to be carried on further. The reasonable dimensions of weight block are imperative to clarify.Firstly the basic principles for toe weight on the dam were introduced. Secondly small and medium sized earth-rock dam, the Yangzhuang reservoir, was chose as the typical subject. The effects of toe weight on the static and dynamic characteristics of the dam were analyzed via the theoretical analysis and numerical analysis. The result is showed as follows. Toe weight can effectively improve the stability of the clay core wall and coarse sand-gravel shell dam; Toe weight block length should be0.45-0.55times the length of the dam; Toe weight block height should be larger than0.19times the dam height; The larger is toe weight block height, the more the safety coefficient is; But the toe weight block height should not be larger than0.3times the dam height. Toe weight can effectively augment initial stress of the foundation soil; The further from the toe weight block, the less significant its effect is; Stress near the dam axis is the largest, basically the x-axis symmetry, diminishing along the direction of upstream and downstream; Based on the finite element analysis their sphere of influence ranges from100m to the toe weight; Pressure weight can effectively mitigate the displacement of the nodes, the stress of the dam during the earthquake, improving the stability of the dam; After the reinforcement of the dam, the displacement was significantly reduced, with the amplitude lowed1%, and the stress curves become more smooth than before; Inferred from time history curves, the displacement of the top of the dam larger than that of its foundation, and the whipping effect of the dam in the event of earthquake was verified.