Abstract: To make a better understanding of the meso-mechanism of composing the long-term shear strength of fractured rocks, an experimental study of the micro-contact and damage evolution of fracture surfaces in rocks is carried out. Two types of fractured rocks are made by compressive shear and Brazilian tests respectively. Under a constant normal load, the fractured rock samples are tested by stepwise increasing creep shear forces. The fractured rocks are scanned using CT and laser scanner before, in the middle and after the creep shear test respectively. The meso-contact and the damage states in the fractured rocks are observed in different loading stages; and then the shear strength of the fractured rocks are obtained. The experimental results show that the long-term shear strength of fractured rocks is composed mainly by two mechanisms, one is the anti-shear ability of interlocked meso-asperities; the other is the anti-friction ability of contacted asperities. The tensile fractured rocks preset a relatively higher roughness and the shear strength is mainly from the first mechanism. The shear fractured rock gives rise to a relatively higher roughness; and the shear strength is mainly from the second mechanism. During creep shear, the two mechanisms are interacted and changed their roles with the development of time and shear displacement.

Key words: fractured rocks, meso-contact, creep shear, CT scanning, shear strength