Effect of fracture number and aperture on mechanical properties and failure modes of low-strength rock mass

Conventional uniaxial compression test on low-strength fractured specimens with different fracture numbers and fracture apertures are carried out by using the MTS815 electro-hydraulic servo control test machine. The stress- strain curves,strength,deformation parameters and failure modes of various types of low-strength fractured specimens are analyzed based on the experimental results. The main conclusions are drawn as follows:① The fracture number can make the post-peak failure stage of the stress-strain curve change from a rapid decline to a step down,and finally to a slow decline in horizontal extension,showing an approximate plastic flow deformation failure. In contrast,the effect of fracture aperture on the stress-strain curves of specimens is very small;② Influenced by the structural effect,the peak strength of specimens decreases with the increase of fracture number only under the condition of horizontal and in- clined fracture. However,the fracture aperture has little effect on the peak-strength of specimens,and there is the wea- kest influence value;③ The fracture number has a great influence on the deformation characteristics of specimens un- der different fracture angles. However,the fracture aperture only has obvious influence on the deformation characteris- tics of the inclined fracture specimen;④ The effect of fracture number on the failure mode of the inclined and vertical fracture specimens is more obvious than that of the horizontal fracture specimen,but the influence law is not clear. Fracture aperture can completely change the failure mode of vertical fracture specimen and make it change from pure tensile failure to single shear failure,but it has little effect on the failure mode of horizontal and inclined fracture speci- mens.