A study of improvement of physical property on decomposed granite soil depended on the difference of weathering

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In this study, we evaluated the shear strength, permeability and soil moisture on decomposed granite soil (Masa soil) depended on the difference of weathering. And, we also evaluated the improvement of these characteristics on Masa soil mixture of bentonite or bark.The conclusions were summarized as follows ;(1) The water content was used for an indication of soil moisture. The water contents appeared peak cohesion (C_p) and changes of internal friction angle (phi) were difference among the weathering. Index of pF was used for the indication of soil moisture. The values of pF appeared C_p and changes of phi were similar among the weathering, and the values of pF were appeared approximately 2.5. Cohesion and internal friction angle with soil moisture used index of pF exhibited similar characteristic depending on degree of weathering.In case the water content was lower than optimum water content, Masa soil mixture of bentonite enabled to be increased Cohesion. The shear strength of Masa soil mixture of bentonite exhibited similar characteristic on Masa soil without mixture, and values of pF appeared C_p and changes of phi were also 2.5.(2) Permeability changed remarkably with weathering. In case 2-3% of bentonite was miscible with Masa soil, sandy-loam classified by triangle coordinate on U.S.P.R.A.was satisfy with standard of permeability for core soil of earth dam (1*10^<-5>cm/s). For sand classified by U.S.P.R.A., 7-8% of bentonite was miscible with Masa soil was satisfy with standard of it. On the other hand, for sandyclay-loam classified by U.S.P.R.A., no requirement of bentonite was satisfy with standard of it. These results corresponded the field tests. Then, sandy Masa soil mixture of bentonite was possible to use the material for construction of earth dam in case of satisfying the standard of compaction.(3) Soil moisture changed remarkable with weathering. In case 3% of bark was miscible with Masa soil, it was possible to improve the soil moisture.