## 4 Results
### Parameters of the Shear Strength  
The shear strength is the most important parameter for analyzing the stability of SRM slopes. The Mohr-Coulomb model was adopted to calculate the shear strength parameters of SRM in terms of total stresses, as shown in Table 2. All the vertical and horizontal stresses were average values. Four groups of vertical pressures and shear stresses for each test were calculated by linear fitting to obtain the friction angle and cohesion. Figure 12 gives the relationships between shear stress, vertical displacement, and horizontal displacement. The shear stresses of specimens with an \(L3\) stone content of 50% gradually increased with the horizontal displacement increasing. Furthermore, the specimens showed shear shrinkage characteristics, as shown in Figure 12a. At this point, the stones staggered each other and gradually compacted. The shear stresses of specimens with \(L3\) stone content of 70% gradually increased with the horizontal displacement increasing. However, the specimens showed the characteristic of first shrinking and then expanding, as shown in Figure 12b. At this point, due to more blocks, there was not enough space for compaction. Thus, with the increase of shear displacement, the block stone gradually occluded and climbed, and the dilatancy gradually increased. When the block stones staggered with each other, the shear stress suddenly decreased and shear shrinkage occurred. The friction angle increased linearly with the change of stone content for different stone sizes in the SRM specimens. The larger the stone size in the SRM was, the larger the friction angle of the specimen was, as shown in Figure 13a. This was mainly because the occlusal friction of the block increased with stone content and block size increasing. The cohesion was directly proportional to the change of the stone content for different stone sizes, as shown in Figure 13b. The cohesion of the specimens with block stones of the \(L3\) group was greater than that with stones of groups \(L1\) or \(L2\). For a sample with larger stone content, the shearing of grain itself was measured. This is the reason the larger values of cohesion were obtained. The cohesions of SRM depended on the unique fabric composed of pores, fine particles, and coarse particles with different spatial distribution and content.  
Figure 11: Comparison of the deformation characteristics of Al wires in samples after shear tests. (**a**) \(L1\) stone size with a stone content of 30% and vertical pressure of 200 kPa; (**b**) \(L2\) stone size with a stone content of 30% and vertical pressure of 200 kPa; (**c**) \(L3\) stone size with a stone content of 30% and vertical pressure of 200 kPa; (**d**) \(L1\) stone size with a stone content of 50% and vertical pressure of 400 kPa; (**f**) \(L2\) stone size with a stone content of 50% and vertical pressure of 400 kPa; (**f**) \(L3\) stone size with a stone content of 50% and vertical pressure of 400 kPa.  
Figure 12: Shear stress and vertical displacement versus horizontal displacement. (**a**) \(L3\) stone content of 50%; (**b**) \(L3\) stone content of 70%.  
Figure 13: Parameters of shear strength versus the stone content of SRM. (**a**) Friction angle versus stone content; (**b**) cohesion versus stone content.