Mechanical behavior of rock-like specimens with 3D nonpenetrating and nonpersistent rough joints under uniaxial compression: experimental study

This study employs 3D printing and Digital Image Correlation technology to investigate rock-like specimens with nonpenetrating and nonpersistent rough joints under uniaxial compression. It analyzes crack propagation and elucidates the mechanical mechanisms by summarizing surface displacement features. Findings reveal the influence of nonpenetrating joint number, penetration depth, and arrangement on mechanical performance. The displacement X field exhibits high sensitivity to both the arrangement type and penetration depth of nonpenetrating joints, while the displacement Z field is particularly sensitive to the arrangement type. Nonpenetrating joints locally inhibit discontinuity of displacement X, globally inhibit attenuation of displacement Y, and overall promote displacement Z. Pre-existing joints are categorized into main and subordinate joints. The distribution of displacement X is influenced by the relative penetration depth of horizontally adjacent joints, both main and subordinate. Consequently, under the control of subordinate joints, this leads to the development of wing extension cracks characterized by a pure tensile mechanism and obliquely parallel cracks exhibiting a tensile-shear mechanism. As a result, four distinct failure modes are manifest on the frontal face. Nonpenetrating joints, which form the significant spalling surface, induce noncoplanar extension cracks on the lateral face, exacerbating surface spalling on the back face. The presence of nonpenetrating joints in symmetric specimens effectively enhances the strength, while weakening the strength in asymmetric specimens. The defined joint parameter, including penetration rate and type, exhibits a monotonic decreasing relationship with the peak strength. The study provides compelling evidence that specimens with nonpenetrating joints reproduce layered step path failure surfaces.