Experimental study on strength and deformation anisotropy of columnar jointed rock mass under triaxial compression

To investigate the mechanical properties and energy evolution of columnar jointed rock mass (CJRM) during tunnel excavation, uniaxial and triaxial compression tests were conducted. The effects of confining pressure, dip angle, and irregularity on strength, deformation, energy evolution, failure modes, and anisotropy were analyzed. Results indicate that increasing confining pressure enhances peak stress, deformation modulus, and dissipation energy while reducing brittleness. Peak stress and deformation modulus exhibit a U-shaped variation with dip angle, while total energy and elastic strain energy show an M-shaped trend. Irregularity has a complex influence on strength and deformation, with total and elastic energy increasing first and then decreasing. Failure modes are categorized into splitting, slip, and fracturing. Confining pressure and dip angle significantly affect deformation modulus anisotropy. A modified Ramamurthy nonlinear failure criterion incorporating dip angle effectively describes the strength behavior of CJRM. This study provides insights into CJRM behavior and supports safe design in tunnel engineering.