# Mechanical Behaviour of Rock Samples with Burst Liability Under Different Pre-Cycling Thresholds
## 4 Discussion  
In deep mining, the periodic failure of the main roof will cause loading and unloading impact on rock pillars. It directly affects mechanical behaviour and long-term stability of rock mass. Pre-cycling loading experiments can simulate actual conditions and reflect the mechanical response of rocks under the complex stress path. By setting different pre-cycling thresholds, the mechanical behaviour characteristics of rocks under different pre-cycling thresholds were studied. Meanwhile, during the process from microstructural changes to macroscopic failure, the evolution mechanism was revealed.  
Burst liability is an inherent property of rocks during instantaneous energy releasing under disturbance. It is a necessary condition to induce rock burst. Pre-cycling loading can improve compressive properties of rocks through closing primary pores and enhancing the intergranular bonding force. However, this also causes an increasing in elastic energy storage. When the loading stress exceeds the pre-cycling threshold, energy storage is released rapidly. Meanwhile, shear failure occurs in rocks. This phenomenon is consistent with the failure process of deep rock mass under periodic pressure. It indicates that pre-cycling loading experiments can effectively simulate the rock burst evolution process. Unconfined pre-cycling loading was used because it simplified experimental conditions. It focused on the independent influence of the pre-cycling threshold on the mechanical response. Although the actual deep rock mass was in a confined condition, in this experimental design, the confining pressure variable was removed based on uniaxial loading conditions. Meanwhile, the direct correlation between pre-cycling threshold parameters and rock strength was clarified. It provided a theoretical foundation for the subsequent triaxial loading experiment and in-situ stress field coupling analysis [48]. Based on this study, further research will be conducted with triaxial tests to evaluate the performance of rocks under confined conditions. It simulates in situ confined stress conditions. [PERSON] et al. [49] suggested analytical graphic techniques ensure consistency in compressive strength and elastic modulus parameters for rocks with burst liability. [PERSON] et al. [50] utilised uniaxial compression analytical solutions to study the transverse isotropic parameter impact on elastic strain distribution. [PERSON] et al. [51] linked goat collapses to abutment load increases and burst risks. It emphasised the understanding of mechanical performance for disaster prevention. The bending energy index may be influenced by mineral composition, such as quartz content and cement type. It evaluated sandstone burst liability, with rock brittleness, tensile strength and energy storage capacity affecting instantaneous energy release. Although the dynamic loading effect was not studied, it theoretically accelerated crack propagation and energy outburst. Therefore, further dynamic experiments and mineral analysis will be conducted. Three pre-cycling thresholds (6 MPa, 12 MPa and 18 MPa) revealed peak strength evolution with negative exponential growth. It indicated a diminishing strengthening effect. No clear critical threshold for mechanical degradation was observed. Therefore, further intensive experiments should be conducted. Moreover, further research will be performed to correlate critical thresholds with sample properties based on experimental tests and numerical simulations [52]. This study addressed previous limitations by analysing multiple thresholds, characterising shear failure via the _AF-RA_ distribution and identifying the Kaiser effect disappearance during continuous loading. It offered a theoretical foundation for threshold warning systems.