Study on the mechanical traits, failure mechanisms, energy responses, and influencing factors of columnar jointed basalts under direct and indirect tensile conditions

Dan Liang H Q Yang Zekang Ping Yongyi Wang ^* Kanglei Song Chiwei Chen Hao Li Xingyue Li Lixin Peng Anhua Ju

• Chongqing University, Chongqing, China

In this study, via merging mesoscopic damage mechanics, probabilistic strength principle, and continuous mechanics, the visuals of columnar jointed basalts (CJBs) featuring various joint arrangement patterns are converted into inhomogeneous numerical models utilizing the digital visual analysis of the DIC-upgraded RFPA. The strength-deformation traits, rupture features, and energy progression trends of CJBs subjected to direct tension and indirect tension (Brazilian splitting) are explored and compared. The acoustic emission (AE) energy buildup linked to the specimen peak stress is defined as the micro-crack energy index (MCEI), and the impact of multiple factors on the MCEI is analyzed. Factor sensitivity analysis is conducted. The study reveals that compared to the Brazilian splitting condition (BSC), under the direct tensile condition (DTC), the tensile strength (TS) and equivalent deformation modulus (EDM) of specimens in the directions I and II perpendicular to column axis are greater. For the direction parallel to column axis, compared to the DTC, the specimen TS under the BSC is smaller at the column tilt angle β = 0°-60°, and larger at β = 75°-90°. Under the BSC, damage and fracture occur to the joints and columns within a localized area along the longitudinal centerline of the specimen. Considering diverse influencing factors and compared to the DTC, the MCEI for the β=30° specimens appears later and exhibits a reduced magnitude in the BSC. When subjected to the DTC, the sensitivity of the MCEI to diverse factors ranks in diminishing order as follows: joint strength, the secondary joint set, joint constitutive behavior, meso-rock strength, and rock homogeneity index. However, when undergoing the BSC, the sensitivity of the MCEI to the joint constitutive behavior is higher than that to the secondary joint set. The above discoveries can function as an academic basis for understanding the emergence series and magnitude differences of the MCEIs in CJBs under tensile conditions, thus supplying scientific underpinning for corresponding rock mass engineering monitoring, reinforcement, and operational maintenance.