## 5 Conclusions  
The development of fractures in the rock can be judged by intermittent zonal fracturing via the discrete element method. The damage to roadway-surrounding rocks can be subdivided into distinct fractured and intact zones. The zonal disintegration characteristics were obtained in this study by numerical simulation using the FLAC\({}^{\text{2D}}\) software. The development of fractured zones and the appearance of intact ones exhibited a certain regularity. The main conclusions were drawn as follows:  
1. Under high-stress conditions, the damage to a rectangular roadway started at its four corners. The fractured zones extended towards the deeper parts of surrounding rocks in a compression-shear conjugate fracture mode, forming a nearly rectangular fracture loop, whereas the four edges (the roof, the floor, and two sides) served as free surfaces. The rock masses within the fracture loop were extruded and loosened into the roadway, and the boundary stress of the fracture loop dropped, thereby forming a new free surface. Under high stress, the fractures developed toward the deep parts of the surrounding rocks in a compression-shear conjugate fracture mode along various sides of the fracture loop to form a new fracture loop. For a circular roadway, the loosening failure first appeared near the two shoulders and footings, accompanied by the formation of a nearly rectangular failure boundary. Next, zonal disintegration evolved and developed in the surrounding rocks. Thus, the rectangular and circular roadways showed similar development patterns of zonal disintegration.
2. Rock strength is a crucial factor in influencing zonal disintegration. Under fixed stress conditions, significantly fractured zones appeared only in shallow surrounding rocks and could not develop deep when rock strength was high. According to the Mohr-Coulomb model, the main factors controlling the development of zonal disintegration could be ranked in decreasing order as follows: cohesive force, internal friction angle, and tensile strength.
3. The stressed state is a key factor controlling the development of zonal disintegration. At low vertical and horizontal stresses, significantly fractured zones appeared only near the roadway perimeter surfaces. At high vertical stresses and low horizontal ones, zonal disintegration appeared on the roadway's two sides. At high horizontal stresses and low vertical ones, zonal disintegration developed only in the roof and the floor. When both vertical and horizontal stresses increased, the extension range of the fractured zone grew steadily, while its structure became increasingly complex.
4. The fractured zones in the surrounding rocks formed under the compression-shear conjugate fracture mode originated from the roadway surface. Various layers of fracture loops were interconnected, forming a network, which was consistent with the elastoplastic slip line theory prediction.
5. In anchor-supported roadways undergoing zonal disintegration processes, the intact zone blocks slide relatively along the fracture surface during the process of loosening and deformation of the surrounding rock, making the anchor rods susceptible to tensile, shear, and bending actions.  
**Author Contributions:** Conceptualization, P.Y. and C.L.; methodology, P.Y.; software, P.Y. and S.Z.; validation, P.Y. and C.L.; formal analysis, C.L.; investigation, P.Y. and S.Z.; resources, P.Y.; data curation, P.Y.; writing--original draft preparation, P.Y.; writing--review and editing, P.Y. and S.Z.; visualization, S.Z.; supervision, C.L.; project administration, C.L.; funding acquisition, C.L. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by the National Natural Science Foundation of China, grant number 52074267.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Data are contained within the article.  
**Conflicts of Interest:** The authors declare no conflicts of interest.