Energy release and related sensitivity analysis of anisotropic CJBs under compression conditions without and with lateral pressure

The cumulative energy released by micro-cracks when columnar jointed basalts (CJBs) attain peak strength (micro-crack energy index (MCEI)) under compression is a crucial foundation for understanding the mechanical behavior of CJBs and informing engineering strategies for monitoring and reinforcement. Beginning with the construction of detailed CJB images owning varied settings, the meso-scale damage mechanics, stochastic strength principle, and continuum mechanics are integrated. Employing the rock failure process analysis method improved by digital image correlation, the related heterogeneity numerical models are established using the generated images, facilitating a comprehensive scrutiny of the force–deformation features, fracture process, and energy change of CJBs exposed to compression conditions without and with lateral pressure (CCWOLP and CCWLP). Then, the effects of different factors on the micro-crack quantity index (MCQI) and MCEI are investigated, and the sensitivity analysis is conducted to clarify the impact relationships and recognize pivotal variables. The results show that under the CCWOLP and CCWLP, the increased rock homogeneity and larger column diameter lead to the intensified stress concentration at joints and accelerate the occurrence of the MCEI. Conversely, the higher residual strength coefficient of joints can delay the MCEI. The specimen, with the greater joint elastic modulus / no secondary joint set, may release MCEI later, and the MCEI value may be lower, hinging on the specific column dip angle. Under the CCWOLP, the dominant sensitive variables for the MCEI comprise joint constitutive correlation, column diameter, column irregularity degree. However, under the CCWLP, the primary sensitive variables regarding the MCEI contain rock mass restraint state, column irregularity degree, joint mechanical property. Additionally, the corresponding fitting models provide theoretical underpinnings for guiding the monitoring, enhancement, functioning, and servicing of CJB project undertakings.