# Theoretical Approach to Predicting the Diffusion Radius of Fracture Grouting in Soil-Rock Mixtures
## 4 Results and Discussion  
### Mechanism of Slurry Diffusion of Indoor Grouting Tests  
The #10 group of test concretions had irregularly oblate slice shapes and could not be obtained by toppling them as a whole to prevent them from breaking up during the toppling process, so they were measured using the \"stratification method,\" and a diffusion radius value of 21 cm was obtained. Images of each stratum were taken, as shown in Figure 10.  
Figure 10: The concretion sections of Group #10. Figure 9: Grouting system: (**a**) slurry agitator; (**b**) reserve pit; (**c**) grouting pump; (**d**) slurry flow meter. The layer-by-layer dissection of the concretion revealed that the concretion in the pure soil was oblate slice shape, and the diffusion path of the slurry in the pure soil was in one direction in the radial direction, thus forming an oblate slice shape concretion. A closer look at the cementation relationship between the slurry and the soil reveals that the slurry and the soil grains were not embedded in each other but had a demarcation line, as shown in Figure 11.  
This means that the diffusion path of the slurry was not the soil pores, the slurry fractured the soil under pressure to create a new fracture, and the slurry diffused into the fracture. Therefore, the form of slurry diffusion in pure soil is fracture diffusion. The stratified measurement method measured the shape parameters of the test concretions in groups #1-3. The dumping method removed the test concretions in groups #4-9, and the shape parameters were measured by the \"multiangle measurement method\". The concretions in groups #7-9 were taken out entirely, and their morphology was well preserved, as shown in Figure 12g-i. Among them, the concretions of groups #4-6 were not completely removed, and the concretions were damaged in the removal process. Only representative parts were preserved, and other broken parts were small in size and difficult to recover, as shown in Figure 12d-f. Groups #1-3 were measured by the stratified measurement method through active destruction, so the concretions were not retained, but the photos of each section were retained, among which the profile of the slurry outlet is shown in Figure 12a-c. According to the diffusion form of the slurry in the indoor test of groups #1-9, analyzed by the morphology of the concretions, the morphology of the concretions in groups #1-3 was branching and scattering, and there were clear fracture paths in the images. The slurry and soil boundaries were clearly defined, showing the typical characteristics of fracture grouting. However, during the process of chiseling the concretions for filming, it was found that there were areas in the concretions where the slurry and soil were embedded and uniformly mixed, as shown in Figure 13. In Figure 13, from left to right, there are some blocks of concretions in groups #1, #2, and #3. The light-colored strip in the middle of the block shows the fracture surface of the slurry, and on both sides of the fracture surface are stone bodies mixed with soil, stone, and slurry, indicating that in groups #1-3 tests, permeation grouting was accompanied by fracture grouting, and the slurry took fracture cracks as the main circulation channel for fracture grouting. At the same time, the slurry penetrated the two walls of the crack under the action of grouting pressure. According  
Figure 11: Part of the concretion of Group #10.  
to the average permeation depth of the samples, the relationship between the size of the permeation grouting radius of the three groups of tests can be determined as #3 > #2 > #1. In addition, permeation diffusion processes also exist around the grouting pipe, as shown in Figure 14, which shows the enlarged profile of the concretion at the grouting outlet of group #3. There was a small scope of permeable grouting concretion near the outlet of the grouting pipe, and the permeation area surrounded the grouting outlet, which was close to a pair of concentric circles. Figure 12: Concretion shape of Groups #1–9.