Abstract：For the interface of the weak structural plane and the rock mass，the shear strength is an important parameter to affect the fissured rocks stability. The two-material mechanical model and direct shear test are employed to study the fissured rocks? mechanical properties of the interface. According to the famous Barton?s rough description method (JRC value)，five different JRC curves are chosen to make a series of two-material mechanical model specimens. Each specimen is casted with the mortar and concrete on the both sides of the interface. Besides，the interface is rough along one direction(shear direction)，but un-rough along another. The rough degree of interface is also described with the modified fractal index Rd and shape factor λ. The Rd-λ description system can not only describe the roughness of the interface，but also explain the experimental phenomenon that the same rough surface shows different mechanical behaviors if the shear stress direction on the surface is changed. Through the direct shear tests，the failure patterns of the interface in fissured rock mass and their shear stress-shear displacement curves are obtained. The main influence factors，such as the material strength ratio k，the surface appearance，the normal stress σ and the cohesional strength C，are determined and analyzed. Based on the analysis，a shear strength formula，in which the main influence factors are included and the rough interface appearance is expressed with Rd-? system is proposed. Finally，the formula calculating result is compared with test results provided by other researcher and its validity is testified.
2011, Vol. 30 
