The　shear　resistance　of　multi-joint　rock　masses　significantly　affects　the　stability　of　underground　engineering　structures.　In　this　work,　using　3D　printing　technology,　rock-like　samples　containing　two　joints　with　varying　joint　spacings　and　roughness　values　are　prepared　and　subjected　to　direct　shear　tests　under　different　normal　stress　conditions.　The　results　demonstrate　that　the　shear　stress-shear　displacement　curve　is　influenced　by　the　joint　roughness　coefficient　(JRC)　and　normal　stress.　Peak　shear　stress　increases　with　increasing　JRC　and　normal　stress　but　decreases　with　increasing　joint　spacing.　Increases　in　JRC　and　normal　stress　increase　the　shear　stress　softening.　The　primary　failure　mode　of　the　double-joint　samples　involves　rock　interlayer　fracturing,　the　joint　spacing　has　a　smaller　impact　on　shear　failure　mode　than　the　JRC　and　normal　stress.　The　shear　failure　behaviour　and　microcracking　mechanism　of　a　double-joint　sample　are　revealed　based　on　the　developed　cohesive　zone　model　(CZM)　method.　Numerical　tests　revealed　that　the　number　of　cracks　in　the　double-joint　model　increases　with　increasing　JRC　and　normal　stress　but　decreases　with　increasing　joint　spacing.　The　model　results　in　significantly　more　tensile　cracks　than　shear　cracks,　tensile　cracks　are　predominantly　located　in　the　rock　interlayer　of　the　double-joint　model,　whereas　shear　cracks　are　concentrated　near　the　joint　surfaces.　This　study　explores　the　shear　mechanical　characteristics　and　microdamage　behaviour　of　double-joint　rock　masses　and　offers　foundational　insights　into　the　shear　failure　mechanisms　of　complex　multi-joint　rock　masses.　©　2024　Elsevier　Ltd