Experimental Study On Reinforcement And Crack Arrest Effect Of Bolt On Three-Dimensional Fractured Rock Mass

Due to constant motion and change of the earth's curst, apparent discontinuity is present in rock medium, which contains plenty of discontinuous surfaces such as joints, crack and so on. Mechanics property of rock mass is influenced by discontinuous surface. For instance, rock strength is weaken and rock mass can be regarded as anisotropy material.In engineering practice, strengthening measures are usually used to ensure the engineering reliable and safe. As an important strengthening component in underground and rock slope project, it has obvious strengthening effects on fractured rock mass. It is a kind of safe, reliable and economic anchoring technology with small disturbance on original rock. Besides, anchor bolt can improve the integrity of rocks. The strengthening measure can not only improve the integrity of the rock mass, but also play its self-supporting role.Although anchoring technology has been widely used in construction for almost one century, anchoring mechanism is not studied clearly certainly and research on this aspect is laggard. So it is very necessary to study anchoring deeply to direct engineering.Based on the previous study, the main results and conclusions of this thesis are listed as follows:(1) Based on cement mortar, add some rubber powder as additive. Measured physical and mechanical properties of the modified cement mortar for different water cement ratio and rubber powder substituted ratio. Get the conclusion that this modified cement mortar satisfies well the rules of similar material and can be used as a perfect type of rock similar material. Choose GFRP to simulate the real anchor bolt.(2) A type of new mould which can pinpoint preset-fracture and bolt is designed. The direct tensile test technology is improved and efficiency and precision is improved by avoiding eccentric tension.(3) Many specimens with different preset-fracture (different throughout or fracture angles) and different anchorage mode (different anchorage angles or anchorage positions) are made. Uniaxial tension and compression tests are done to study strengthening effects of bolts on fractures by analysing the stress-strain, strength changes and elasticity moduli changes.(4) 3D AE location is used to study the AE characteristics and failure mode for full throughout single bolt specimen under uniaxial tensile test.By the above works, reinforcing effects of anchor bolt on fractured rock mass is studied and the extended mode and of 3-D fracture is summarized, which has guiding significance to practical engineering.