## 3 Results and Discussion
### Self-Bearing Mechanism of Gangue Slurry  
Based on the variation characteristics of various parameters in the experiment, the self-bearing mechanism of the gangue slurry is obtained, as shown in Figure 12.  
As shown in Figure 12, the self-bearing and deformation process of gangue slurry can be divided into three stages.  
Stage I: rapid compression and drainage stage. The water in the gangue slurry mainly exists in the form of free water, and the relative position of the gangue particles is loose, with large pores in the slurry. When subjected to pressure, the vast majority of supersaturated water is quickly discharged, and the gangue particles are not yet compressed at this time. The pore water in the slurry plays a main role in load-bearing, and the slurry has poor stability under loading. At this stage, the fast water bleeding and compression deformation rate of the slurry are the main features.  
Stage II: pore compaction and water bleeding stage. After the first loading stage, the bearing effect of the gangue particles is affected by water, and the pores of the slurry are continuously compacted with water bleeding. Water forms a water film on the surface of gangue particles under pressure, which has a lubricating effect, reduces the frictional resistance between particles, and facilitates the sliding and backfilling of gangue particles. Since the main components of gangue are sandstone and mudstone, the strength of gangue particles is degraded under the action of water wedge, dissolution, and softening, accelerating particle fragmentation and further densifying pores. The water bleeding in this stage is mainly the combined water discharged under pressure. Compared with the first stage, the growth rate of the bleeding rate and compression rate in this stage gradually decrease.  
Stage III: particle crushing and elastic-plastic deformation stage. After the loading stress of the gangue slurry reaches the threshold, the bleeding rate and porosity tend to extreme value with minimal changes. The backfilling material almost transforms from a slurry to a compacted solid with a stable solid-water ratio, and the water retained in the compacted solid plays a bearing role with the crushed gangue particles in the form of bound water. As the stress continues to increase within a certain range, compression occurs between gangue particles, and gangue is tightly connected through point contact or mutual meshing. Point contact generates stress concentration, leading to elastic-plastic failure of particles. Broken small particles fill the pores, gradually reducing the porosity and significantly enhancing the resistance to deformation. The contact points increase with the increase in external load, and the number of contact points increases. It leads to an increase in the pressure increment necessary for the relative deformation to continue. Additionally, the contact between particles evolves from sharp angle contact to obtuse  
Figure 12: Self–bearing mechanism of gangue slurry.  
angle contact, spherical contact, or meshing contact. The average stress between particles decreases, the particle bearing capacity gradually increases, and the gangue transforms into a continuous medium, resulting in the hardening phenomenon.