# 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
Due to the relative simplicity of grouting diffusion in a static water environment, there are more studies on the diffusion of slurry in different fissures in dynamic water conditions. In order to intuitively explore the diffusion of slurry in multiple fissures or even fissure networks, many current researchers have mainly focused on flat fissure models or models similar to them. These models include single-flat fissure model experiments, approximate single-flat fissure model experiments, and multi-fissure, intersecting, branching fissure, and fissure network model experiments. Currently, research on grouting reinforcement technology for groundwater environment control is somewhat limited to simulating experiments on single fissures or uniformly distributed fissures. Research, Development, and Testing of Spatiotemporal Diffusion Modeling Systems for the Polymer Grouting of Fissures  
High-polymer slurry, in contrast to non-expansive slurry, utilizes its own foaming reaction to generate secondary pressure, enhancing flow within a fissure after injection with a high-pressure gun. As the foaming process of high-polymer slurry gradually stops, it solidifies due to gel, resulting in an increase in dynamic viscosity and the formation of rigid polyurethane foam. [PERSON] et al. [81] categorized the grouting process of fissures using high-polymer slurry into the following three stages: static pressure grouting, expansion and diffusion, and gel solidification. Their research provides insights into the temporal and spatial evolution of foaming-type high-polymer slurry diffusion, as illustrated in Figure 6.  
Figure 6 shows a schematic diagram of the grouting model test system. The data monitoring module in this test system mainly consists of a strain acquisition system and a high-definition camera. The scale is marked along the direction of slurry flow from the grouting hole on the fissure model so that the spatiotemporal diffusion law of the slurry can be observed using a high-definition camera. In a study by [PERSON] et al. [82], a center combination design (CCD) experiment was conducted using a self-made visual diffusion device with pressure and water-blocking rate monitoring functions to study the spatiotemporal diffusion law (diffusion morphology,  
Figure 6: Schematic diagram of the grouting model test system [81]. diffusion pressure, and water-blocking rate) of the slurry in receiving media. Their study revealed the influence of grouting parameters (dynamic water pump pressure, grouting volume, and mass fractal dimensions) on the spatiotemporal distribution of the diffusion morphology, diffusion dynamic response, and water-blocking rate of high-polymer slurry, as shown in Figure 7. The expansive nature of high-polymer slurry makes its diffusion mechanism more complex in the water-rich gravel layer. The main influencing factors, including dynamic water pump pressure, grouting volume, and mass fractal dimensions, were investigated to explore the diffusion law and grouting effect of high-polymer slurry in water-rich gravel layers. Water flow direction  
Due to the control of stress and characteristics on the cavity structure inside real rough fissures, it is difficult to directly observe internal seepage. Currently, there is a lack of high-precision numerical analysis and experimental verification of the displacement law of the slurry-water two-phase flow in rough fissures. [PERSON] et al. [83] conducted research on the displacement seepage law of slurry-water two-phase flow and developed a visualization displacement test system and method based on particle image velocimetry (PIV) technology. They obtained the flow field distribution and the relationship between flow rate and pressure drop inside a transparent 3D-printed rough fissure. As shown in Figure 8, the 3D-printed model is fixed on a test bench with the smooth side facing up and the rough side facing down. Before the experiment, the model is filled with water, and bubbles are removed to ensure that the fissure is in a saturated state.