Search

Long-term wave loading is the main cause of destabilization and damage to shallow coral reef near the coast. In this study, the fine-scale damage mechanism and fracture characteristics of reef at a scoured structural surface were analyzed based on fracture and fine-scale mechanics principles to investigate the effect of the number of wave loading cycles on fracture damage to coral reefs. Through indoor hollow torsional shear and Brazilian splitting tests, the deterioration effects of the tensile strength and fracture toughness of reef rock were investigated. Finally, the reliability of the model for simulating the fracture toughness degradation of reef rock was verified by conducting a comparative analysis between the experimental and theoretical results. The results showed that with an increase in the number of wave loading cycles, the fracture control coefficient Qn of the coral reef first decreased, then decreased more slowly, and finally, tended to stabilize. When fracture propagation in the scouring structural plane occurred, the deterioration effect of the wave loading on the fracture toughness of the coral reef limestone was more significant than that of the tip stress intensity factor. Under the same number of wave loading cycles, Qn showed a decelerating decreasing trend with an increase in the effective wave height, and a decreasing and then increasing trend with an increase in the wave period, and the increasing phase is almost linear. The final extension length of the rock at the scouring structural plane of the coral reef is positively correlated with the wave height and has a V-shaped correlation with the wave period. [ABSTRACT FROM AUTHOR]

Rock masses characterized by X‐type joints are prevalent in cold region rock engineering projects. A precise understanding of the mechanical mechanisms governing the fracture initiation strength of these jointed rock masses after experiencing freeze–thaw damage is paramount for ensuring the safety and stability of associated engineering structures. Leveraging the mutual constraint relationship between the displacements at the tips of intersecting joints under compressive shear conditions, a computational approach has been developed to determine the stress intensity factor at the tip of the main joint, taking into account the interference effects arising from both main and subjoints. Furthermore, the fine‐grained defects within the rock mass are abstracted as elliptical microcracks, and deterioration equations for rock cohesion and fracture toughness under freeze–thaw cycling are derived using frost heave theory. Taking into account the mutual interference effects between main and subjoints, as well as the degradation of rock mechanical properties caused by freeze–thaw cycles, a computational approach for determining the initiation strength of X‐type jointed rock masses has been developed. The validity of this method has been confirmed through rigorous model testing. The findings reveal that the wing cracks in X‐type jointed rock masses predominantly propagate along the tips of the main joints, while the extension of subjoints is constrained. When the X‐joints have the same inclination, the initiation strength of the subjoint exceeds that of the single‐joint rock mass when its inclination is less than the main joint's but is lower when the subjoint's inclination exceeds that of the main joint. The interference effect between oppositely inclined intersecting joints enhances the initiation strength of the rock mass, with the maximum occurring when the subjoint is at an inclination of 120°. When the freezing time is less than 18 h and the temperature is below −16°C, variations in both time and temperature are more sensitive in affecting the initiation strength of the X‐jointed rock mass. Rocks with a high elastic modulus and low tensile strength experience a greater rate of freeze–thaw damage, and brittle rocks are more susceptible to frost heaving failure. [ABSTRACT FROM AUTHOR]

The shear strength and resistance of granular materials are critical indicators in geotechnical engineering and infrastructure construction. Both sliding and rotation influence the energy evolution of soil granular motion during shear. To examine the effects of particle rotation on shear damage and energy evolution in granular systems, we first describe the transformation of irregularly shaped particles into regular shapes via geometrical parameters, ensuring the invariance of energy density and density. We then analyze the impact of particle rotation on shear-stress variation and energy dissipation through a shear energy evolution equation. Additionally, we establish the relationship between the shear-stress ratio and normal stress, considering particle rotation. Finally, we verify the influence of particle rotation on energy evolution and shear damage through shear tests on irregular calcareous sand and regular silica-bead particles. The results indicate that granular materials do not fully comply with the Coulomb strength criterion. In the initial shear stage, most of the external work is converted into granular rotational-shear energy, whereas in the later stage, it primarily shifts to granular sliding-shear energy. Notably, the sensitivity of the granular rotational energy to a vertical load is significantly greater than that of the granular sliding energy. [ABSTRACT FROM AUTHOR]