Exploring the shear behavior and local roughness degradation of rock fractures with laterally composite dentate profiles

Shear response and spatial evolution of roughness degradation in rock fracture surfaces with heterogeneously distributed multi-angle asperities

The simplified characterization of rough rock fracture morphology is fundamental to understanding shear mechanical behavior. This study presents a method for constructing fracture surfaces by integrating profiles with varied inclined dentate asperities. The resulting five surfaces (D_1 to D_5) were quantitatively validated using the roughness index θ * max /(C+1) , demonstrating distinct roughness gradients. Utilizing three-dimensional (3D) printing technology, these fracture types were cast into mortar specimens for direct shear testing under varying normal loads. Experimental results allowed for a detailed analysis of shear stress, normal displacement, and their correlation with initial roughness and normal stress. Post-test 3D scanning revealed significant spatial variations in macroscopic surface damage. Investigation into the reduction and residual values of surface roughness indicates that degradation is closely linked to initial topography. Specifically, the roughest regions sustain the most significant damage and contribute most substantially to shear resistance. This research offers a feasible and novel approach to evaluating the mechanical properties of rock fractures.

A JRC3D shear strength model considering failure surface spatial anisotropy of soft rock

Fracture behavior and constitutive modeling of rock-concrete contact surfaces with different roughness under freeze–thaw cycles

Investigation of Compressive–Shear Fracture in Rock Considering Flaw Distribution and Interaction via an Improved Energy-Stress-Based Peridynamics Model

Predicting compressive–shear fracture in rock masses containing complex flaw distributions remains a major challenge in rock engineering. We propose an improved non-ordinary state-based peridynamics (NOSB-PD) model to simulate rock fracture behavior in this work. A stabilized NOSB-PD formulation is developed by incorporating a bond-level deformation gradient strategy to effectively suppress the zero-energy mode inherent in conventional NOSB-PD formulations, thereby ensuring deformation compatibility and numerical robustness. More importantly, the triple-shear energy criterion is introduced into the PD framework for the first time, enabling a more accurate characterization of shear fracture in rocks under complex stress states. The proposed NOSB-PD model is validated using two examples, demonstrating its excellent capability in suppressing the zero-energy mode and capturing fracture behavior in rock under compressive–shear conditions. Subsequently, the proposed model is used to systematically investigate the influence of flaw distribution on crack propagation and failure modes in rocks. The results indicate that variations in flaw distribution alter the local stress field, leading to a change in the rock fracture mode. Consequently, the rock bridge failure mode transitions from shear-dominated direct coalescence to mixed tensile-shear failure, and finally to tension-dominated indirect failure. The overall rock specimen is more prone to tensile–shear-mixed failure under conditions of shorter rock bridges with larger inclinations, or longer rock bridges with smaller inclinations. These findings provide new insights into the role of flaw distribution on rock fracture behavior.

Influence of discontinuous gradation and surface morphology on the shear behavior of soil rock mixtures-bedrock interface

Anisotropic progressive shear damage and fracture mechanisms of fractured shale based on acoustic-optical-mechanical methods

Bedding planes and natural fractures are key factors controlling the anisotropic mechanical properties of shale reservoirs, exerting a critical influence on underground engineering. However, their shear deformation and fracture evolution mechanisms remain poorly understood. In this study, synthetic shales containing bedding planes and fractures were prepared using a natural mineral reduction−stepwise compaction−mechanical similarity method. Subsequently, the evolution characteristics of macroscopic mechanical behavior, acoustic emission (AE) signals, and strain fields during the shear process of fractured shale were explored using acoustic-optical-mechanical multiphysics monitoring. Finally, the anisotropy of damage deformation, failure modes, and fracture mechanisms in shale were revealed. The test results indicate (1) synthetic shales exhibit strong similarity to natural shale, making them suitable for investigating variations in mechanical behavior; (2) cohesion and peak shear strength reach their maximum and minimum values at bedding angles (α) of 45° and 0°, respectively, while the friction coefficient and residual strength reach the two at α = 90° and 0°, respectively; (3) as α increases, a localized high-strain zone forms along the bedding planes and shear plane, leading to irregular shear fracture zones with jagged surfaces; (4) the shear fracture mechanisms in artificial shale include bedding shear fracture, bedding tensile fracture, matrix shear fracture, and matrix tensile fracture; at α = 45°, the bedding direction aligns with the σ1 direction, causing shear fracturing jointly controlled by the matrix and bedding planes; and (5) the shear failure process of fractured shale exhibits a well-coupled acoustic-optical-mechanical effect. The deformation energy density, in particular, demonstrates a strong response to the energy accumulation and release patterns. This study provides a novel experimental framework and mechanistic insights that are critical for the efficient development of deep shale gas resources, as well as for the prediction and mitigation of geological hazards.