Research Of Gravelly Soil With Spreading Gradation For Being Used In Soil Core Rockfill Dam

The spreading gradation gravelly soil is a kind of clayey coarse-grained soil. It's also a soil-rock mixtures. It's often divided into fine material and coarse material by the save of 5mm and the granutometric composition affects its project characteristics directly.The gravelly soil is a better kind of damming material. It's usually used as impervious core and also as dam shell. The soil in the impervious core of Mania Rockfi.ll Dam in Tibet belongs to gravelly light loam. It has better compaction degree, higher shear strength and lower comperssibility. But it has more nonuniform gravel content, lower clay content, larger permeability coefficient. Lower natural moisture content and worse plasticity. In this article the conclusion was got from some experiments and researches that the crux of the matter is to solve the seepage stability of the soil and it is possible that gravelly soil is made into impervious core with the protection of filter. The wider soil core and wider filter has been used in design to solve the seepage stability question and the good seepage prevention result has been got.