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Abstract Simulated rock joint samples with different first-order and second-order asperity heights are casted by high strength gypsum material. A series of CNL(constant normal load) shear tests are carried out to study the shear strength characteristics of joints with different first-order and second-order asperity heights under different normal stresses. The influences of first-order and second-order asperity heights and normal stress on shear strength are analyzed. Based on the experimental results，it can be found that the joint samples with second-order asperity have multi-peak shear stresses，while the joint samples only with first-order asperity have not apparent peak shear stress. The shear strength increases with the increasing first-order and second-order asperity heights and normal stress. With the increasing ratio of second-order asperity height to first-order asperity height，shear strength first increases and then decreases. Finally，an empirical formula is proposed by regression analysis of experimental data to predict the shear strength. The formula can reflect the influences of first-order and second-order asperity heights and normal stress on shear strength.
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Received: 05 January 2011
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2011, Vol. 30 
