Structural deterioration and instability in grouted reinforcement crushed rock masses subjected to increasing-amplitude fatigue loading

Abstract

To investigate the influence of different Talbot grading indices (n-values) on the fatigue damage deterioration and instability behavior of grouted reinforcement body, an increasing-amplitude fatigue loading test was conducted on grouted reinforcement specimens with different n-values using the multi-functional electro-hydraulic servo-controlled rigidity test system (MTS-815). Acoustic emission (AE) technology was employed to monitor the entire testing process. The fatigue mechanical response mechanism, AE characteristic parameters, and damage modes were analyzed. The results demonstrate that as n-value increases, the mechanical characteristics of the specimens initially increase and then decrease. AE parameters, including the cumulative AE ring counts and energy counts, follow the same trend, and spectral characteristics exhibit a strong correlation with crack evolution. The cumulative AE ring counts damage model reveals a three-phase behavior for the specimens under different n-values. The b-value, which characterizes the scale distribution of cracking events, correlates with the volumetric strain growth rate, showing a more sensitive response. Differences in n-values directly affect the distribution of RA/AF signals and damage modes. The findings provide valuable insights into predicting the destabilization of grouted reinforcement specimens under fatigue disturbance and offer necessary theoretical support for the design and stability control of excavation in fragmented surrounding rock.

1. Introduction

With the gradual depletion of shallow mineral resources, the exploitation of deep mineral resources has become a focal point. However, the geological conditions of deep strata are extremely complex, involving numerous discontinuous structural planes and fractured rock masses as unfavorable geological bodies [1−3]. At the same time, some resource-scarce mines are under increasing pressure for resource succession, and there is an urgent need to make breakthroughs in recoverable reserves. The Dongfeng mining area in the Linglong Gold Mine has been mined to great depths. However, due to the long-term extraction of high-grade ore and the impact of private mining, some relatively low-grade ore has been left unmined. With the continuous advancement of stoping operations, a large volume of fragmented rock mass has gradually accumulated in the hanging wall, leading to the emerging problem of excessive ore stacking and difficult ore extraction.

Fragmented rock masses are typically characterized by weak cementation, low strength, loose structure, high porosity, and uneven deformation under stress. Meanwhile, during underground construction, in addition to static loading, the rock mass is frequently subjected to dynamic loads, such as frequent blasting vibrations, mechanical excavation, and heavy vehicle loads, which result in strong disturbances [4−7]. Under such conditions, the deformation and failure of the rock mass typically exhibit characteristics such as being difficult to detect, hard to predict, and highly destructive [8−11]. Fragmented rock masses, when subjected to repeated cyclic loading, are prone to inducing hazards such as roof falls, collapses, floor heave, and significant structural deformations, which can lead to construction delays as well as losses of personnel and property [12−14].

Grouting technology, due to its strong applicability and significant reinforcement effect, has been widely used to address safety issues caused by the instability of fragmented rock masses [15, 16]. It can directly enhance the cementation strength, reduce porosity, and improve the mechanical properties and overall stability of the crushed rock mass, thereby increasing the overall bearing capacity of the surrounding rock and preventing the occurrence of engineering geological disasters [17−19]. Currently, scholars have conducted extensive research on the physical and mechanical properties of grouting materials [20−22], grouting reinforcement effects and evaluations [23−26]. In terms of the mechanical ...