Fractal characteristics of shear failure surface and mechanism of strength generation of soil-rock aggregate#br#
LIU Xinrong1，2，TU Yiliang1，2，WANG Linfeng1，2，FENG Hao1，2，ZHONG Zuliang1，2，LEI Xiaodan1，2，WANG Lei1，2
(1. School of Civil Engineering，Chongqing University，Chongqing 400045，China；2. Key Laboratory of New Technology for Construction of Cities in Mountain Area，Ministry of Education，Chongqing University，Chongqing 400045，China)
Abstract：The large-scale direct shear test was conducted to soil-rock aggregate with different rock contents，water contents，rock lithology，initial void ratios and normal pressures. The shear strength mechanism of soil-rock aggregate was analyzed through the statistical analysis of fractal geometry of shear surface and the numerical simulation of particle interactions in the direct shear test with the particle flow code. The results indicate that the irregular topography of the shear failure surfaces of soil-rock aggregate are closely related to the existence of rock blocks and presents the fractal characteristics. The fractal dimension increases gradually with the decreasing of water content and normal pressure and the increasing of rock content and strength. If the rock content is more than 40%，the cohesion will be less than 30 kPa. The internal friction angle increases with the increasing of rock content and strength，the decreasing of water content，initial void ratio and normal pressure，and it has a positive correlation with the fractal dimension. The stress concentration happens near the rock particles. In the process of shearing，the contact force between the particles transfer mainly through the surface in the direction of shearing，but the contact surfaces back to the shear direction does not appear to transfer force. The internal friction angle is equal to the sum of and ，where is the internal friction angle of the contact surface of particles on the shear plane related to the particle?s properties and is the dip angle of the contact surfaces of particles related to the fractal dimension on the shear surface. The variation of shear strength parameters in the shear test can be explained with this mechanism.
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2017, Vol. 36 
