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

本研究以风化花岗岩风化土为研究对象，探讨风化花岗岩风化土之抗剪强度、渗透性及土壤含水量之差异。研究结果表明：（1）土壤含水量可以作为土壤含水量的指示指标;（2）土壤含水量可以作为土壤含水量的指示指标;含水量出现峰值凝聚力（C_p），内摩擦角（φ）的变化随风化程度的不同而不同。pF指数用于指示土壤水分。pF值出现在C_p值和φ值的变化趋势相似，pF值出现在2.5左右。粘聚力和内摩擦角随土壤含水量pF的变化表现出类似的风化程度特征，当含水量低于最佳含水量时，膨润土的混合物能够提高粘聚力。混合土的抗剪强度与未混合土的抗剪强度相似，pF值出现C_p，phi值变化也为2.5。(2)渗透率随着风化而发生显着变化。在膨润土与粉砂土混溶2-3%的情况下，按美国P.R.A.三角坐标分类的砂壤土满足土坝心墙土渗透性标准（1 × 10 ~（-3）<-5>cm/s）。对于U.S.P.R.A.分类的沙子，7-8%的膨润土与粉土混溶，符合粉土混溶标准，而对于美国P.R.A.分类的砂质粘壤土，试验结果与现场试验结果相吻合。因此，在满足压实度要求的情况下，桑迪粉土与膨润土混合料可用于土坝的筑坝。(3)土壤水分随风化程度变化显著。在3%的树皮与Masa土壤混溶的情况下，有可能改善土壤水分。

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.