## 3 Results and Discussion
### The Change in Uplift Displacement in Two Kinds of Soil  
The relationship between grout diffusion and grouting pressure variation, as shown in Figure 4, was obtained by comparing the measurement of grouting pressure and observation of grout diffusion on the same time during the experiment, resulting in the curves and images depicted in Figure 4. The grouting pressure curve indicates that, when compaction diffusion predominates, the grouting pressure variation curve exhibits a smooth characteristic. However, during low-pressure infiltration, the grouting pressure curve is non-smooth. This may be due to the presence of pore water pressure in the sand soil pores (caused by the existence of excess pore water pressure during soil filling), which varies in size. Consequently, during each infiltration and crack occurrence, there is a significant drop in grouting pressure. Subsequently, the increase rate of grouting pressure after the sharp drop exceeds the increase rate before the drop, as can be directly observed from the average slope of the tangent lines of each segment of the grouting pressure curve. The starting and ending points of each segment exhibit distinct features in the graph, presenting a convex tip at the end of the pressure curve. Figure 4 further verifies the previous analysis regarding the formation of the stone structure. When the grouting pressure is relatively low, the diffusion of grout in the soil is mainly dominated by infiltration, with compaction as a secondary process. As the grouting pressure gradually increases, after the first minor fracturing, grout diffusion is primarily dominated by compaction, with infiltration as a secondary process. This continues until the occurrence of the second fracturing. Due to the compaction effect of the grout around the bubble, the permeability decreases, and, thus, infiltration mainly occurs around the fracturing grout veins at this point. After the second major fracturing, the higher grouting pressure reaches the surrounding soil's resistance to fracturing. At this point, the grout diffusion is primarily dominated by fracturing, with compaction and infiltration around the grout veins as secondary processes. Consequently,continuous minor fracturing occurs. From the second fracturing to the third major fracturing stage, the pressure curve is no longer smooth, showing more concave endpoint characteristics. This further illustrates that grout diffusion in the soil is primarily dominated by fracturing, which is more visually observable in transparent sand, emphasizing the fracturing phenomenon. While observing the temporal variations in the grouting pressure curve, significant characteristics are also evident in the changes in surface displacement caused by grouting, as shown in Figure 5. Both the grouting pressure and surface displacement exhibit good consistency in their temporal variations, showing a gradual increase followed by rapid growth with increasing grouting time. After the completion of grouting, the final surface displacement shows a larger displacement at the center (central measuring point) compared to the edges (fourth measuring point). In this experiment, the difference in displacement between the central point and the second and third points is relatively small, because these three points are located within the horizontal range of the grout bulb. The fourth measuring  
Figure 3: Consolidated body after grouting test. (**a**) Ordinary sand; (**b**) Transparent sand. point, however, is located outside the horizontal range of the grout bulb, indicating that the grout is more effective in lifting the surface within the range of the grout bulb, while the lifting effect outside the grout bulb range is relatively smaller. The surface uplift displacement curves for the four measuring points (from the center to the fourth measuring point) exhibit similar characteristics. There is a nearly horizontal displacement-time development segment in the grouting displacement curve corresponding to the peak of grouting pressure (grouting fracture).