Abstract: The gateway with complex granular roof surrounding rock fails seriously with large deformation and difficult support. The paper analyzed the deformation damage characteristics and failure causes of surrounding rock with complex granular roof,studied the characteristics of slurry density,water extraction rate and fluidity of similar-paste grouting materials with different proportions,explored the influence mechanism of different ash-sand ratio and coal ash content on the strength of similar- paste grouting materials,and determined the optimal ratio of similar-paste grouting materials and reasonable grouting reinforcement support scheme. The results showed that gateway roof of complex granular surrounding rock was damaged seriously with mesh pocket sinking,overall intrusion and "concave" expansion deformation at high and low sides respectively. The main causes for the instability of gateway surrounding rock were granular block,weak cementation,high stress,soft coal and support failure. With the increase of ash-sand ratio and coal ash content,the water extraction rate and fluidity of slurry increased,while the slurry density decreased,and the influence of ash-sand ratio on slurry fluidity was greater than coal ash content. With the increase of ash-sand ratio and coal ash content,the failure strength of slurry grouts showed accelerated attenuation and sharp decline-slow increase-slow decline trend. The optimum ratio on the ash-sand ratio and coal ash content of similar-paste grouting materials were 0. 6∶1 and 80% respectively. After adopting the technical scheme of anchor (cables) + paste grouting control for 30 days,the maximum subsidence of the roof was less than 80 mm,the maximum convergence of two sides was less than 70 mm,and the gateway surrounding rock was stable.

Key words: complex granular,gateway,coal ash,similar-paste slurry,mechanical property,stability