## 6 Conclusions  
1. The uniaxial compressive strength of the specimens with different grain size quartz sand as the aggregate showed significant differences, with a smaller surface area for the smaller grain size quartz sand aggregate, a smaller contact surface for gypsum, which formed smaller size structural surfaces inside the specimen and had a smaller degree of fragmentation, whereas the larger grain size quartz sand aggregate formed larger size structural surfaces inside the specimen and a higher degree of fragmentation. The uniaxial compressive strength and modulus of elasticity of the specimens showed the following pattern: small-size aggregate specimen > medium-size aggregate specimen > large-size aggregate specimen. 2. Compared with the specimen without the anchor, the residual strength value of the anchored specimen in the late stage of damage had a greater increase, but the residual strength value was higher than that of the large aggregate specimen in the compression process of the small aggregate specimen, and the trend of the stress-strain curve close to the horizontal direction was more obvious in the specimen of the larger aggregate size. This shows that under uniaxial compression, the anchor can not only improve the compressive strength and elastic modulus of the rock mass but it can also improve the residual strength of the rock mass. However, with the increase in specimen crushing degree, the ability of the anchor to improve the residual strength of the rock mass gradually decreased. 3. The anchoring effect of the anchors on the specimens with different grain sizes varies was crucial. When different anchoring methods are used for the specimens with the different grain sizes of the aggregates, the uniaxial compressive strength and elastic modulus of the specimens follow the following pattern: no anchor<single anchor<double anchor. With the increase in the specimen aggregate size, the degree of improvement of the mechanical properties of the specimens by the anchors decreases gradually. Figure 13: Schematic diagram of the reinforcing effect of anchors. \(\Sigma_{b}\) represents maximum tensile stress. Numerical tests on the uniaxial compression of the rock containing cohesive units were carried out. It was found that under the no-anchor condition, the specimen showed typical oblique shear damage characteristics, and under the single-anchor action, the deformation of the specimen near the anchor bar was obviously reduced. By contrast, the main rupture surface was blocked, and an obvious reinforcement zone was formed near the anchor bar. Under the double-anchor condition, the anchor tension stress was more obvious, the reinforcement zone was wider, and the rock rupture surface was strongly blocked, all of which made its reinforcement effect the more obvious. 5. The anchoring effect of the anchor on the specimen was reflected in the two aspects of reinforcement and crack stopping. Under the prestressing effect of the anchor, when the crack developed to the range of the anchor's action, the anchor played the role of stopping the crack from developing or changing its direction. After the specimen rupture, an obvious conical reinforcement zone was formed at the anchor reinforcement, and this extrusion reinforcement effect improved the integrity and bearing capacity of the rock mass. Moreover, the denser the anchors, the wider the reinforcement zone, and the superposition effect occurred, which better utilized the supporting role of the anchors and played a key role in stabilizing the rock. Conceptualization, L.W. ; methodology, Z.L. ; software, Z.L. and C.J. ; validation, B.R. ; formal analysis, B.R. and S.W. ; investigation, S.W., K.D. and J.G. ; resources, F.T. ; data curation, S.W. and K.D. ; writing--original draft preparation, S.W. ; writing--review and editing, S.W. ; visualization, C.J. ; supervision, F.T. and J.G. ; project administration, F.T. ; funding acquisition, L.W. All authors have read and agreed to the published version of the manuscript. Not applicable.