## 4 Experimental Results
### Grout Diffusion Characteristics  
The characteristics of the grout bulbs obtained at increasing grouting pressure for different grout volumes are compared in Table 6 in terms of digital photos, dimensions, and description of the main features (at the same unloading condition of 100-25 kPa). Table 6 shows that the grouting pressure and grout volume affect both the grout bulb shapes and the grout diffusion patterns. When the grout volume is 200 mL, the grout bulb shape gradually transitions from a half-droplet shape to a long and narrow strip shape with increasing grouting pressure, indicating that the grout diffusion mode transitions from perfect compaction grouting to compaction dominant. When the grout volume is 300 mL, the grout bulb shape gradually transitions from a half-droplet shape to a flat shape and exists thick and short grout veins in the horizontal and lateral directions with increasing grouting pressure, indicating that the grout diffusion mode transitions from a perfectly compaction grouting to compaction dominant and thick and short pulp veins in the horizontal and lateral directions. When the grout volume is 400 mL, the grout bulb shape gradually transitions from a combination of a semi-cylindrical body and a semi-cone body to an obvious grout bulb shell and a cracked surface morphology existed with increasing grouting pressure, indicating that the grout diffusion mode transitions from compaction grouting to fracture grouting dominant. Figure 10: Grout diffusion distance-applied normal stress curves under loading and unloading conditions: (**a**) horizontal grout diffusion; (**b**) vertical grout diffusion. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Grout Volume** **(mL)** & **Grouting Pressure** **(kPa)** & **Digital Photos** & **Horizontal Diffusion Grout Distance (cm)** & **Vertical Diffusion** **Grout Distance (cm)** & **Main Features** \\ \hline
**Grout Volume** **(mL)** & **Grouting Pressure** **(kPa)** & **Digital Photos** & **Diffusion Grout Distance (cm)** & **Vertical Diffusion** **Grout Distance (cm)** & **Main Features \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Grout Volume** **(mL)** & **Grouting Pressure** **(kPa)** & **Digital Photos** & **Horizontal** **Diffusion Grout** **Distance (cm)** & **Vertical Diffusion** **Grout Distance (cm)** & **Main Features** \\ \hline
300 & & & & & Compaction dominant; Thick and short grout veins in the horizontal and lateral directions \\ \hline
400 & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 6: _Cont._Table 7 exhibits the compared characteristics of the grout bulbs obtained at increasing grouting pressure for different grout volumes and the soil stress history with loading conditions at 100-100 kPa in terms of digital photos, dimensions, and description of the main features. Table 7 shows when the grout volume is 200 mL, the grout bulb shape gradually transitions from a half-droplet shape to a long and narrow half-ellipsoidal shape with increasing grouting pressure, indicating that the grout diffusion mode is perfectly compaction grouting. When the grout volume is 300 mL, the grout bulb shape gradually transitions from a wide and short half-ellipsoidal shape to the half-spherical shape closing to the grouting hole, and thick and short grout veins away from the grouting hole with increasing grouting pressure, indicating that the grout diffusion mode transitions from a perfectly compaction grouting to compaction grouting dominant and fracture grouting coexistence grout diffusion mode. When the grouting volume is 400 mL, the grout bulb shape gradually transitions from the initial grout bulb gathered on the grouting hole liked ancient bell and sheet shape away from the grouting hole to the shape of the \"ball snout\" at the bottom of the ship and obvious grout bulb shell and cracked surface morphology existed with increasing grouting pressure, indicating that the grout diffusion mode transitions from a compaction grouting dominant to fracture grouting dominant.