Experimental study on the influence of grouting diffusion in fissure aquifer at the top Ordovician limestone

In order to explore the influence of slurry viscosity，dissolution fracture surfaces and karst cavities on slurry diffusion and filling in fractures during grouting reinforcement and reconstruction，a set of dynamic water grouting model testbed for fractured rock mass was developed，and the fracture distribution，dynamic confined water and grouting technology factors can be considered during experiment. First，the device was used to simulate the diffusion process of three kinds of viscosity slurries in four types of confined aquifers with karst fissures and holes distribution. Then the laws of slurry diffusion and filling were summarized. Combined with numerical simulation，the stress distribution and variation law of fractured rock mass were obtained from 11 sets of grouting tests during the filling process of grouting. At last，the changing rule of rock elastic modulus after slurry transformation under different conditions was analyzed by ultrasonic detection. The results demonstrated that ① the slurry diffusion pattern after considering different conditions shows a non-standard arc shape. Specifically，the slurry diffusion pattern in uniformly distributed fissures is close to the “∩” shape. The dominant fissure containing karst is “Λ” shape and the apex angle is smaller with the increase of the fracture opening. In the fissure zone containing karst cavities is “M” shape with transition form of “︹” shaped; ② The fractured rock after grouting transformation has zoning characteristics，which can be divided into four areas:full filling (FF)，partial filling (PF)，fracture development filling (DeF) and original rock fracture (OF); ③ After grouting，the elastic modulus of karst fractures and karst pores was significantly enhanced，and the distribution of slurry pressure in fractures presented a nonlinear decline. Moreover，the effect of stress and action time on the matrix of fractured rock mass were directly proportional to the dynamic modulus of rock mass after grouting.