Abstract: In order to analyze the deterioration effect of mechanical properties of the fractured rocks strengthened by grouting in a long-term immersion in pressurized water, the long-term immersion tests of reinforced fractured rock samples considering the influence of water pressure. These tests are based on the earlier research of strengthening the fractured rock mass using carbon fiber reinforced cement-based composites mixed with grouting materials. Besides, the shear tests were also carried out in different immersion periods. The results show that: (1) a significant change trend of the shear stress-shear displacement occurs for the fractured rock samples reinforced by grouting and immersed in the pressure water in the long-term, with the shear stiffness gradually decreases, and the shear displacement gradually increases when the shear strength reaches to its peak. (2) With the longer immersion period, shear strength of reinforced fractured rock mass shows a sharp degradation trend at first, and then a gentle degradation. After 6 cycles of soak periods (i.e. 150 days), the degradation rate of the maximum shear strength under different normal stresses is in the range of 32.6%-39.9%. It means that the internal friction angle and cohesion is reduced by 19.3% and 39.4%, respectively. The shear strength parameters in the first four soaking periods (0-90 d) account for about 90% of the total deterioration range. (3) Dissolution, corrosion, lubrication, softening of the fractured rocks occurs in the pressurized water. Besides, the gel in the slurry is softened by the water molecules entering into the interior of the slurry, which result in a gradually deterioration in mechanical properties of fractured rocks and grouting. Meanwhile, cementation between the slurry and fracture surface, and bond performance between the slurry and carbon fiber are gradually weakened. As a result, shear performance of grouting reinforced fractured rocks gradually deteriorates, and shear failure surface gradually developed to cementation surface between the slurry and fracture surface. The experimental results in this paper can provide reference for the long-term evaluation on stability analysis of fractured rock mass reinforced by grouting method.

Key words: grouting reinforcement, fractured rock mass, carbon fiber, water pressure, long-term immersion, degradation effect