# Theoretical Approach to Predicting the Diffusion Radius of Fracture Grouting in Soil-Rock Mixtures
## 3 Validation Tests of the Calculation Theory of Grout Diffusion in Soil-Rock Mixtures
### Indoor Grouting Tests
#### 3.1.2 Test Device and Process  
(1) Test Device  
The core device of the grouting test is a self-designed grouting system, which can satisfactorily meet the test requirements of adjustable and monitorable grouting pressure, monitorable grouting volume, determinable grouting time, and removable grouted stone body. The grouting system includes four parts: pressurized equipment, slurry storage bucket, grouting bucket, and connecting device (air pipe and grouting pipe), as shown in Figure 3. The grouting bucket is a stainless steel bucket with a diameter of 55 cm, height of 63 cm, and thickness of 2.8 mm. The test cement materials in this paper were 42.5R ordinary silicate cement (a hydraulic cementitious material made of silicate cement linker, 5-20% of mixed materials, and appropriate amount of gypsum finely ground) produced by Chongqing Xiaonanhai Cement Plant. The grouting slurry in this paper was pure cement slurry, which is a mixture of cement and water and does not contain gravel. The composition of the soil-rock mixture was clay and sandstone. (2) Test process  
The indoor test process is as follows:  
(a) Control particle grading: soil-rock mixture sampling was carried out from the construction site to determine the particle gradation (shown in Figure 4), and the soil-rock mixture samples were configured in the room. (a) (b) (c) (d) Figure 4. Particle grading test procedure. (a) Drying the samples; (b) hammering the fine-grained soil; (c) sieving the samples; (d) separating each particle size and weighing. * (b) Control water content: The dried soil-rock mixture sample was mixed evenly one day in advance and laid flat in the aluminum box, sprinkled evenly with water, and mixed thoroughly to ensure that the water content was equal to the natural water content of the original soil-rock mixture, covered with plastic film for 24 h, and then taken, as shown in Figure 5. (c) Soil-rock mixture specimen: In the grouting bucket against the wall set of plastic bags, the soil-rock mixture was added to the mold in 4 layers. Each layer was 150 mm thick, and the height was controlled in layers. The soil-rock mixture layer was compacted with a wooden compaction hammer according to the principle of light hammering and multi-striking to ensure that the dry density of the configured specimen was equal to the dry density of the original soil-stone mixture, as shown in Figure 6. To prevent the appearance of a preset weak surface between layers, surface chiseling treatment was carried out after each layer was compacted before adding soil samples. Figure 5: Control water content. Figure 6: Tap and compact. Buried pipe: After the soil-rock mixture sample was added to 3 layers, the grouting pipe was buried, and the position of the grouting pipe mouth was fixed. To prevent the soil-rock mixture in the mouth of the pipe from blocking the pipe, a layer of gravel was placed under the pipe mouth so that it was wrapped by gravel, and then the position of the grouting pipe was fixed, as shown in Figure 7. Then, the fourth layer of the soil-rock mixture was buried, compacted, and sealed with a cover. Safety check: After connecting the device, we opened the inlet valve, closed the outlet valve, opened the main valve of the nitrogen tank, and adjusted the output pressure to 0.2 MPa. Then, we closed the main valve after the air pressure in the slurry storage barrel was stable. If the pressure value of the pressure gauge on the slurry storage barrel remained unchanged for 5 min, we considered the sealing gaskets, valves, and pipes as gas-tight at these critical connection locations and the device as safe. Slurry making: First, we poured a specific mass of cement and water into the mixing barrel according to the water-cement ratio.