The performance of resin anchoring agents in deep coal mine roadways is significantly compromised by water-bearing and chemically aggressive conditions, posing a major threat to support system reliability. This study aims to systematically quantify this performance deterioration and develop a more resilient material solution for these challenging environments. A comprehensive experimental program was conducted, including uniaxial compression, pull-out, and interface shear tests, accompanied by the systematic improvement of the resin formulation and microstructural analysis via Scanning Electron Microscopy (SEM). The results showed that increasing borehole water content to 30% reduced the compressive strength of conventional resin by over 40%, while acidic environments (pH = 5) caused a 70% drop in its interfacial shear strength. In contrast, an improved formulation incorporating hydroxypropyl acrylate and a super absorbent polymer (SAP) exhibited a 20% higher initial strength, maintained over 85% of its strength under water saturation, and retained functional residual strength in acidic conditions. SEM analysis confirmed that the improved resin’s denser microstructure suppressed interfacial microcrack formation. The findings demonstrate that the improved formulation provides a robust material basis for enhancing the long-term durability and safety of anchorage support systems in extreme underground engineering environments.

Optimizing the mechanical behavior of the bolt-grout interface is paramount for the performance of fully-grouted rock bolts, with the bolt’s rib geometry being a critical design parameter. However, the mechanism by which rib geometry governs the interfacial failure mode remains unclear. To this end, this study employs a multi-scale approach, combining laboratory pull-out tests with Particle Flow Code (PFC) numerical simulations to systematically reveal the dominant role of bolt rib geometry on the interfacial failure mode from both macroscopic and microscopic scales. Experimental results reveal that as the bolt’s rib spacing-to-height ratio increases, the macroscopic failure mode of the interface undergoes a significant transition from brittle shear failure to highly ductile shear-dilation failure. The experimentally-calibrated PFC model reveals the underlying micro-mechanical mechanism of this transition: (1) in terms of force transmission, a larger rib spacing-to-height ratio causes the force chains to shift from a sub-horizontal orientation to a steeply inclined one, transferring the load more effectively into the deep-seated grout; and (2) in terms of damage mode, the crack propagation path correspondingly shifts from pure shear failure along the interface to a tensile-shear composite failure propagating into the grout. This study establishes that the rib spacing-to-height ratio is a key design parameter for regulating the ductility and post-peak mechanical behavior of the anchored system, offering a clear mechanical pathway for the optimal design of high-performance rock bolts intended for complex conditions such as large deformations or rock bursts.