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Abstract The stress effect on friction angles of structural planes of rocks was considered. In order to obtain the relationship between peak friction angle and normal stress，modeling materials for rock similar to calcareous slate in physico-mechanical properties were obtained through studying the ratios of raw materials such as the medium sand，the cement，the silica powder，the naphthalene super-plasticizer of non-air entraining. Ten groups of rock structural planes with different waviness and roughness were made. Friction angles of the rock structural planes under different normal stresses were determined with the direct shear apparatus. Results show that the peak friction angle and its rate of variation of rock joints are decreased with the increasing of normal stress instead of a constant value generally considered. The residual friction angles of structural planes changed little with the increasing of normal stresses. The peak friction angles under the same normal stress are different for each rock model due to the differences of surface waviness and roughness of structural planes. The stress effect on peak friction angles of rock joints are the same with the variation of friction angles determined with the failure criterion of joint roughness coefficient-joint wall compressive strength(JRC-JCS)，the larger the JRC is，the more significant the stress effect on peak friction angle is.
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Received: 30 September 2013
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2014, Vol. 33 
