Cyclic shear test device for rock: an add-on for a uniaxial compression test rig

Rock discontinuities play a crucial role for the mechanical behavior of surface and subsurface formations, significantly affecting the stability of slopes, underground mines, geoenergy systems, including geothermal reservoirs, carbon sequestration sites, and underground energy storage. This study introduces an innovative cyclic shear test device, designed as an add-on to existing uniaxial compressive testing rigs, providing a cost-effective and versatile alternative to conventional shear box devices. The developed apparatus enables biaxial loading, adjustable shear angles (15°–75°), and cyclic shear testing, thereby facilitating a more comprehensive evaluation of rock joint behavior under complex stress conditions. The system utilizes pneumatic actuators to generate a counterforce, allowing precise simulation of cyclic loading scenarios. We demonstrate the effectiveness of this device through experimental investigations on artificial rock joints, assessing shear strength, deformation characteristics, and shear-induced dilation under varying loading conditions. Results indicate that shear resistance and joint damage evolution are strongly influenced by cyclic loading, providing valuable insights into rock mechanics essential for optimizing geoengineering applications. This novel testing approach enhances the understanding of rock discontinuity behavior and supports the development of safer and more efficient surface and subsurface solutions for geoengineering projects.