Experimental study on mechanical properties of fractured rock mass under different anchoring modes

To study the toughening effect and the anchoring mechanism of rock bolts, fractured rock specimens with different crack angles and different crack lengths are made of cement mortar. The prefabricated specimens are applied with different anchoring modes for reinforcement, containing no-anchoring, full-length bonded anchoring and pre-stressed anchoring. The uniaxial compression tests of fractured rock specimens under different anchoring modes are carried out, and then the mechanical properties and the failure modes of fractured rock specimens before and after anchoring are analysed. The 'Cavity Damage Effect' is defined and the test results show that the peak strength of the fractured specimens are roughly proportional to the crack inclination angle due to the 'Cavity Damage Effect', the crack is equivalent to a 'cavity damage' inside the prefabricated specimen if the opening of the crack is larger. The crack length can significantly affect the strength and deformation characteristics of no-anchoring specimens, while has little influence on the anchoring specimens. The full-length bonded anchoring and the pre-stressed anchoring can both significantly increase the mechanical parameters (the peak strength, residual strength and elastic modulus) of the specimens, enhance the resistance to deformation of fractured rock mass, and inhibit the expansion and coalescence of cracks.