# A State-of-the-Art Review on the Study of the Diffusion Mechanism of Fissure Grouting
## 5 Current Status of Experimental Research on Grouting Modeling of Fissured Rock Bodies  
Research, Development, and Testing of Spatiotemporal Diffusion Modeling Systems for the Cement Slurry Grouting of Fissures  
Generally, in theoretical analysis and numerical computation, it is necessary to establish an appropriate fissure model to systematically observe the grouting parameters, mainly to obtain important physical parameters that are difficult to observe intuitively in practical engineering. A crucial prerequisite for conducting these experimental studies is to ensure that the environment constructed at the experimental site is similar to the actual engineering project so that the experimental results have practical engineering significance. [PERSON] et al. [77] conducted a study on the temporal and spatial diffusion patterns of cement particles in porous media under varying hydraulic conditions, as depicted in Figure 3. They used a self-developed diffusion test device to investigate changes in filtrate viscosity, receiving medium porosity, and slurry diffusion pressure at different testing points during a specific period. The study successfully determined the temporal and spatial diffusion patterns of slurry in porous media while considering the filtration effect. Wuhan Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, has developed an experimental device that can achieve visualized injection grouting in fissures with dynamic water [78]. The principle of the experimental device is shown in Figure 4. The experimental device is equipped with a high-definition camera, which can visualize the grouting diffusion process by changing different experimental conditions. It then obtains a clear and intuitive understanding of the influence of dynamic water velocity, fluid characteristics of the slurry, and structural characteristics of the fissures on the diffusion law of the slurry. Figure 3: Diffusion test set-up diagram [77]. Shandong University has developed a grouting experimental platform that can change the inclination angle of fissures, as shown in Figure 5[79]. The experimental platform can adjust the distance between two glass plates to vary the width of the fissure. It can also simulate a fissure by filling it with porous media, simulating the diffusion morphology and distribution law under the conditions of receiving different media. In addition, [PERSON] et al. [80] first used pre-made templates to pour single fissures and fissure network rock masses and then conducted slurry diffusion experiments with given grouting pressures and water-cement ratios in rock fissures with different apertures. Their study found that under the conditions of large apertures and a slurry with a high water-cement ratio, the diffusion law of the slurry conforms to the fluid characteristics of a Newtonian fluid, while under the conditions of small apertures and a slurry with a low water-cement ratio, the seepage characteristics of the slurry are consistent with the characteristics of a non-Newtonian fluid. The aperture opening, the angle (bending degree) between the fissures, and the viscosity of the slurry have a significant impact on the distribution of slurry diffusion pressure in fissures. Figure 4: Schematic diagram of the visualized cross-fissure dynamic water grouting experimental set-up. 1—slurry collection device; 2—experimental platform for cross-fissure; 3—support frame; 4—laboratory; 5—fissure; 6—sensor flow rate; 7—sensor pressure; 8—kinetic water storage device; 9—slurry pressure supply device; 10—monitoring camera; 11—image information acquisition system; 12—upper unit; 13—data signal acquisition device [78]. Figure 5: Schematic diagram of the variable fissure grouting simulation test bench. 1—simulated fissure; 2—pressure stabilization tank; 3—liftable support; 4—supply tank; 5—grouting pump; 6—supply pipe; 7—grouting pipe [79]. Groundwater environments generally exist in dynamic and static water conditions.