Three-dimensional surface fracture is set in specimens composed of rock similar material. In order to get the effect of bolts on strength and propagation mode of the pre-existing fracture

uniaxial compression tests are carried out on specimens with different anchorage modes. The results show that

comparing with the specimens without bolts

compressive strength and compression modulus of reinforced specimens increase in different degrees. Compression modulus of reinforced specimen is enhanced more significantly than compressive strength. Residual strengths of four types of reinforced specimens are approaching to each other with the value being about 3 to 3.5 times that of specimen without bolt. The failure process of anchored specimen is divided into four phases: ① initial fracture compression phase; ② micro-fractures developing phase; ③ unsteady failure phase; ④ post-failure phase. And the surface macro-fractures all appear in the post-failure phase. Due to the reinforced and crack arresting effect of bolts the mode of crack propagation changes. Curved fracture plane and low-shear-strength plane are found in the reinforced specimens. Three types of cracks are found in test

namely tensile crack

shear crack and tensile-shear mixed crack.