# Study of the Internal Rebreaking Characteristics of Crushed Gangue in Mine Goal during Compression
## 3 Results
### AE Characteristics and Analysis of Crushed Gagnee Compaction
#### 3.2.2 Analysis of AE of Crushed Gangue Compaction Deformation  
The number of AE ringing counts and energy can represent the number of crushed gangue samples. The AE characteristic curves of the sandstone, sandy mudstone and sandstone-sandy mudstone combination are shown in Figure 12.  
The following can be seen from Figure 12:  
(a) In the sliding flow deformation stage (which corresponded to the rapid compaction stage), the particles overcame the friction between them under the axial pressure to produce a wide range of dislocations and sliding. The pores between the blocks were compressed, the blocks and the crushed ones showed the adjustment of the contact state and the rapid closure of the interspace between them, the contact was relatively dense, the deformation speed was fast, the ringing count showed a significant increase, and the cumulative ringing count increased sharply. With the increase in axial stress, the gap between the crushed blocks continued to be filled and closed, and the blocks continued to rotate and move. During this period, the crushed gangue sample blocks formed a relatively dense skeleton as edges and corners met. The ring count decreased sharply, and the cumulative ring count increased slowly. Throughout the whole stage, there were crushed AE signals caused by a small number of irregular block corner breakages as well as friction AE signals caused by rotation, friction, and dislocation between the particles. Overall, the AE counts in this stage were relatively small.  
(b) In the fracturing deformation filling stage (which corresponded to the slow compaction stage), the crushed blocks formed a combination with a relatively dense skeleton structure compared to that in the previous stage, with a slightly improved deformation resistance. Compared to the slip flow deformation stage, with the increase in stress, the AE count and energy generated by fracturing and crushing between the blocks, as well as the frictional AE count and energy caused by the denser skeleton, all gradually increased. At the initial stage of gangue block fracturing deformation and filling, the growth trend of the AE count was gentle, and as the axial stress increased, the cumulative AE count and energy curves showed a \"convex\" growth trend before being flattened.  
Figure 11: AE parameter curves of crushed sandstone and sandy mudstone. (**a**) AE ring count–cumulative ring count–strain-time. (**b**) AE energy–cumulative energy–strain-time.  
(c) In the compaction elastic deformation stage (which corresponded to the stable consolidation stage), the crushed sandstone ganguue sample block assembly had a \"strain enhanced\" skeleton structure, with relatively stronger deformation resistance than before, due to the stress in the early fracturing, deformation, and filling stages. In this stage, the work performed by the universal servo machine was converted into particle crushing and friction energy consumption, and the total amount of energy consumption decreased as the axial stress increased. Therefore, the whole AE cumulative count curve presented a convergent growth trend, as did the strain curve.  
In conclusion, as the stress increased, the evolution characteristics of the AE of singular and combined crushed ganguues in the caved zone showed a stage change and similar evolution laws. The evolution process of AE corresponded to the compaction process of the same samples.  
Figure 12: AE characteristics of sandstone, sandy mudstone, and sandstone–sandy mudstone crushed ganguue samples during confined compression. (a) Sandstone. (b) AE energy–cumulative energy–strain-time. (c) Sandstone–sandy mudstone.