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Abstract Lots of intact sliding zone soil samples are collected from Huangtupo landslide，Badong town. CT scanning technique is used to get the grain distribution of the intact soil samples. 30 scanning samples are selected，and according to the statistics result，the average percentage of gravel(particle size more than 2mm) is about 30%；so the intact sliding zone soil should be treated as soil-rock mixture. Typical CT scanning images are rasterized；and then triaxial numerical tests on the rasterized soil samples are conducted. The mechanical parameters of granule part (particle size less than 2 mm) in intact soil are obtained by direct shear tests；while the mechanical parameters of granule part in intact soil depend on that of sliding bedrock. According to numerical calculation results，the deformation and failure mechanism of intact sliding zone soil is analyzed including distinguish between mechanical parameters of intact soil and that of only granule soil part. The results show that comparing with the shear strength parameters of granule part，the internal friction angle of intact sliding zone soil doesn?t increase obviously；meanwhile，the cohesion increases at least 80%. It?s because the percentage of gravel in soil-rock mixture is only about 30%，which still keeps the granule soil part to be framework of soil-rock mixture. During the shear deformation process，the motion velocity of gravel is lower than that of soil，combining with the activity of normal stress，it supports an effective resistance to granule soil，just as similar as the external friction angle between retaining wall and backfill soil. In the Mohr circle，this action can be reflected by the increasing of cohesion of soil-rock mixture. By analyzing the mechanical traces on the surface of a rock block，the evidence is found. This research method can provide a new method to obtain reliable shear strength parameters of intact sliding zone soil.
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Received: 13 December 2010
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2011, Vol. 30 
