| We studied slope disintegration's different layers soil, which was developed from granite in south China. After analyzed 8 layers'soil physical property (including mineral component,chemical component, bulk density, porosity, particle analysis, microaggregate, disintegration, anti-shear strength, and soil infiltration), we illustrated the characteristics of slope disintegration's different soil layer. The results showed that:In red soil layer, we can't found out damourite and feldspar in BG-1 and BG-2, but the kaolinite content were 37% and 55% respectively, and the quartz content were 51% and 45% respectively. In sandy soil layer, BG-3's content of damourite, kaolinite and quartz were 7%, 55% and 34% respectively, and BG-5's content of damourite, kaolinite and quartz were 4%, 42% and 46% respectively. In detritus layer, BG-6's content of damourite, kaolinite, quartz, and feldspar were 3%, 38%, 28% and 31% respectively, So, from red soil layer to detritus layer, the chemical composition of Al2O3, K2O and Na2O increased with increasing deepth, While there are no obvious rules in other seven kinds of chemical components. After calculated coefficient of alkali,,we found out the degree of weathering sequence in different soil lays were red soil layer >the sandy soil layer>the detritus layer.The variation of bulk density in different layers is detritus layer> red soil layer> sandy soil layer, and total porosity have same changed trend. But non-capillary porosity have reverse result. Follwed the increasd of sampling deepth, the content of 0.05-1mm particle fraction increases gradually. So, in BG-7 and BG-8 sampling points, 0.05-0.005mm particle fraction were lower than other sampling points. The content of micro-aggregate, which was more than 0.25mm, varied form 20.82% to～54.53% in each layers. The sequence of different layers'micro-aggreaggte, which was more than 0.05mm, was detritus layer> sandy soil layer> red soil layer. And the sequence of different layers'micro-aggreaggte, which was less than 0.05mm,was red soil layer> sandy soil layer> detritus layer. The rank of structure coefficient in different sampling point is BG-1>BG-2>BG-3>BG-4>BG-5>BG-6>BG-7>BG-8. It worth to notice that the characteristics of soil disintegration were total different. BG-1's soil only 2.00% particle disintegrated within 90 seconds, but BG-2 and BG-3's particle disintegration reached 33.33% and 63.33%, respectively. BG-4's soil was completely disintegrated within 30 seconds, and BG-6, BG-7 and BG-8's soil were totaly disintegrated within 20 seconds.Soil infiltration experiment results showed that soil infiltration rate of red soil layer was better than other two layers. And the accumulative infiltration volume in red soil layer also higher than other two layers. The linear regression formula of accumulative infiltration and time was F=a1*t + b1 (F: cumulative infiltration, t:permeation time), where the value of constant al of the red soil layer is much larger than other two layers, and the value of constant b1 got same result. The initial infiltration rate and stable infiltration rate of red soil layer was 9.86 mm/min and 6.96mm/min, respectively. Sandy soil layer were 2.56mm/min and 1.25mm/min, respectively. And detritus layer were 1.39mm/min and 0.75mm/min, respectively. The linear regression formula of inflitration rate and time was power function f=a2t-k, where the sequence of constant a2 was red soil layer> sandy soil layer> detritus layer, and the sequence of power exponent K was detritus layer> red soil layer> sandy soil layer.The analysis of shear strength showed that the shear strength of red soil layer's BG-1 and BG-2 were consisted of cohesive force and internal friction angle. When water content of BG-1 increased from 18.26% to 22.56%, the cohesive force increased from 9.07KPa to 11.52KPa. However, following the increased of water content, the cohesive force began to decreased. When water content reach 27.38%, the cohesive force only have 1.67KPa. We also found same phenomenon in BG-2's soil .When water content of BG-2 was 13.84%, the cohesive force was 40.31KPa, but followed the increases of water contnet (about 30.04%), the cohesive force rapid decreased (only 1.87Kpa). Because of shear strength in sandy soil layer and detritus layer only consisted of internal friction angle, so soil water content can't effect sheat strength. The internal friction angle of sandy soil layer's were 35°in BG-3,BG-4 and BG-5, and the angle of the detritus layer's were about 40°in BG-6,BG-7 and BG-8 . Because sheat strength of sandy soil layer was the weakest in all layers, so sandy soil layer are prone to disintegrate.
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