AE responses, energy evolution, and damage constitutive model of jointed rock-like material subjected to unilaterally confined compression.

Failure evolution and strength modeling of H-jointed layered sandstone under compression

H-shaped joints, which consist of tensile and shear parts, are common in layered rocks and substantially affect rock failure and instability. To explore the mechanical performances of the H-jointed sandstone under different loading conditions. Uniaxial and confined compressive tests were carried out on H-jointed sandstone samples. The samples’ stress-strain responses, failure modes, AE activities, and strength were analyzed. The results show that the stress-strain curve has four phases: crack closing, elastic phase, elastic-plastic phase, and residual stages. The failure patterns of the H-jointed samples change from tension to shear as the joint dip angle increases. Tensile failure is dominant at lower inclination angles, whereas shear slip failure occurs along the joint surfaces at higher angles. Sliding along the joint surfaces with tensile cracking is observed at moderate angles. The joint roughness coefficient (JRC) significantly influences the samples’ mechanical behavior. A modified Hoek-Brown criterion that considers the joint dip angle and JRC is suggested for evaluating the strength of H-jointed rock samples under compression. This study provides a better understanding of the mechanical performance of H-jointed sandstone and a method to evaluate the strength.

Research on the Stability of Arc-Fractured Rock–Concrete Composites: Mechanical Response and Energy Evolution

To mitigate the violent movement of overlying strata in goaf areas, rock–concrete composite support systems are widely utilized. However, the mechanical behavior of such systems under the influence of complex pre-existing defects, such as arc-shaped fractures, remains insufficiently understood. This study aims to clarify the failure mechanisms and the evolution of stability in these composites by evaluating the influence of fracture inclination angles. A synergistic methodology was adopted, combining laboratory uniaxial compression tests with discrete-element method simulations. Based on energy dissipation theory and the strain equivalence hypothesis, a statistical damage constitutive model was established to bridge the gap between microscopic damage and macroscopic mechanical response. The results demonstrate that fracture inclination significantly dictates the energy partitioning and crack propagation patterns within the composite. The established constitutive model, validated by numerical results ( R 2 > 0.999), effectively quantifies how increasing inclination angles enhance energy absorption efficiency and retard structural damage progression. Due to the high toughness of the concrete component, the composite maintains substantial residual bearing capacity, preventing instantaneous failure. These findings provide a robust theoretical framework and practical guidance for optimizing support designs in deep underground excavations with intricate geological defects.

Dynamic response and local buckling behavior of offshore tubular T-joints under drop-weight impact loading

Dynamic tensile failure of CFRP/aluminum bolted joints: Experimental and numerical investigation

The dynamic tensile failure of composite/metal bolted joints is governed by the coupled effects of stress concentration, local contact deformation, and rate-dependent damage evolution. In this study, single-bolt CFRP (Carbon Fiber Reinforced Polymer)/7075 aluminum joints are found to exhibit a pronounced strain-rate strengthening effect, with the peak stress increasing from 438.18 MPa at 1000 s −1 to 579.29 MPa at 3000 s −1 . Using split Hopkinson tension bar tests with high-speed imaging, damage was consistently observed to initiate around the composite bolt hole and became increasingly localized as the strain rate increased. More importantly, the combined high-speed observations and numerical results suggest that the local failure morphology under high-strain-rate loading is closely associated with transient secondary bending and bolt tilting, which intensify compressive damage in the region perpendicular to the loading direction and thus influence the evolution of hole-edge damage. An Abaqus/Explicit model based on the three-dimensional Hashin failure criterion was developed. The model predicted the peak stress with an error of 4.08% and successfully reproduced the main damage evolution features. These results provide new insight into the rate-dependent local failure mechanism of composite/metal bolted joints and offer a useful basis for the design and assessment of impact-resistant hybrid joint structures.

Experimental Study on Seismic Performance of Through-Tenon Joints with Different Degrees of Looseness

This study investigated the impact of joint looseness on the seismic performance of through-tenon joints in traditional timber structures. The through-tenon joint from the fourth floor of Guangyue Tower served as the research prototype. Five specimens, including one intact joint and four joints with varying looseness levels, were fabricated at a geometric scaling ratio of 1:2. Low-cycle reversed cyclic loading tests were conducted to characterize the mechanical behaviors of all specimens. Evaluation parameters included failure modes, moment–rotation hysteretic curves, skeleton curves, strength degradation curves, stiffness degradation curves, energy dissipation capacity, and ductility performance. The test results revealed that increasing joint looseness transformed the hysteretic curve from an anti-Z shape to an arch shape. This transformation involved aggravated pinching behaviour and evident slippage. All test specimens showed strength degradation coefficients below unity. Loosened joints exhibited lower stiffness and energy dissipation capacity than the intact joint. These properties declined monotonically with increasing looseness levels. Ductility performance revealed a remarkable directional discrepancy under bidirectional loading. Deformation responses diverged notably under positive and negative cyclic loads. All specimens possessed favorable global deformability. Ultimate rotation angles and loading displacements correlated positively with the degree of looseness. Tenon withdrawal deformation continuously accumulated with an increasing rotation angle.

Study on the macroscopic deformation characteristics and failure mechanisms of rock bridge specimens under compressive shear stress state

Rock bridges play a critical role in the initiation and evolution of tectonic earthquakes and locked-type landslides. However, existing laboratory methods have limitations in reproducing compressive-shear stress conditions and capturing the deformation evolution of rock bridges, restricting a comprehensive understanding of their failure mechanisms. To address these issues, this study proposes a uniaxial compression testing method for rock bridge specimens containing discontinuous cracks. Specimens with different rock bridge angles were designed to induce compressive-shear-dominated stress states within the rock bridge region under uniaxial loading. The deformation and failure processes were investigated by integrating mechanical response analysis, acoustic emission monitoring, and digital image correlation measurements. The results demonstrate that the proposed testing method effectively reproduces the macroscopic deformation characteristics and failure modes of rock bridges under compressive-shear conditions. Specimens with different rock bridge angles exhibited a characteristic valley-shaped evolution of AE activity, while the distributions of average frequency and rise angle parameters indicated that failure was predominantly governed by shear cracking. In addition, DIC measurements revealed the development of a nearly circular vertical displacement field immediately before failure, providing experimental evidence for the formation of circular slip surfaces in homogeneous three-stage locked-type landslides. These findings improve the experimental characterization of rock bridge shear failure and provide new insights into the mechanisms governing circular slip surface formation, offering a useful experimental basis for investigating rock bridge failure and related geological hazards.