Large-scale hydropower projects in Southwest China typically encounter challenges in maintaining the stability of high-steep rock slopes, with their inherent complexity and associated risks directly affecting construction and operational safety. This study takes the engineered slopes of the Wudongde Hydropower Station as a representative case to systematically investigate the geological characteristics and key factors influencing the stability control of high-steep engineered slopes. Based on this analysis, a systematic treatment concept is proposed, integrating full-process, full-element, and full-level control, leading to the establishment of a comprehensive safety-oriented treatment system for high-steep engineered slopes. Additionally, technical methods for the stability control of both natural and artificial slopes are developed. A coordinated control strategy is formulated to facilitate the synchronous advancement of natural slope treatment and artificial slope excavation, thereby achieving an effective coordination between safety and the construction schedule. Finally, standardized management procedures and supporting documentation for the systematic treatment of high-steep slopes in large-scale hydropower projects are summarized and formalized. The monitoring results indicate that the proposed treatment system effectively ensures the overall stability of high-steep engineered slopes, providing safety and controllability throughout the slope excavation and treatment processes. These findings provide a useful reference for the management of high-steep slopes in major hydropower projects across Southwest China and other regions with similar geological conditions.

The reinforcement of anti-dip rock slopes under seismic waves is an urgent issue that requires attention. Shaking table tests were conducted on anti-dip rock slopes, both with and without anchor cables. The deformation and failure patterns of the slopes were analyzed. The Hilbert-Huang Transform(HHT) time-frequency analysis method was utilized to investigate the seismic damage characteristics of the slopes, while the dynamic response of cable axial forces was examined. The results indicate that the deformation and failure of cable-anchored anti-dip rock slopes under seismic action occur in four distinct stages: elastic deformation, crack initiation, fracture surface development, and failure. The inclusion of cable reinforcement significantly enhances the dynamic stability of anti-dip rock slopes. The critical seismic wave amplitude for slope instability increased from 0.9 g to 1.3 g following reinforcement, resulting in an overall stability increase of approximately 44.4%. The Hilbert spectrum and Hilbert marginal spectrum reveal that anchor cables effectively absorb seismic energy and reduce dynamic response. Prior to seismic damage in cable-anchored anti-dip rock slopes, the seismic energy is relatively small and concentrated in the low-frequency range of 15–22 Hz. After seismic damage occurs, the seismic energy across the entire slope increases abruptly, and due to crack development in the upper damaged area, the seismic energy shifts to higher frequencies (39–42 Hz). Compared to unreinforced anti-dip rock slopes, the seismic damage in cable-anchored slopes is characterized by abruptness. As the seismic damage intensifies, the anchoring effectiveness of prestressed cables in the upper part of the slope diminishes, while their effectiveness in the middle and lower sections correspondingly strengthens. When designing seismic support for anti-dip rock slopes, it is essential to consider the influence of cable reinforcement on the potential failure surface locations. These research findings can serve as a reference for the stability evaluation and support design of cable-anchored rock slopes in high-intensity seismic regions.

To elucidate the failure evolution mechanism and multi-parameter precursor characteristics of rock slopes controlled by a locked segment with anti-dip weak planes, a physical model test was conducted using a stepwise creep loading system based on a self-balanced loading apparatus. The Chana landslide served as the geological prototype for constructing an idealized conceptual model. Conventional prestressed anchors, constant-resistance large-deformation (NPR) anchors, acoustic emission (AE) sensors and vibration sensors were installed, while digital image correlation (DIC) technology was employed to monitor and integrate the mechanical response, microseismic activity, and deformation evolution throughout the loading process. The results indicate that: (1) the DIC displacement field and AE localization reveal the spatiotemporal evolution of the developing slip zone, exhibiting a pronounced staged behavior characterized by a progressive transition from localized deformation to global sliding. (2) A sudden drop in Newton force occurs prior to failure. (3) The microseismic duration parameter demonstrates significant critical slowing down. (4) The improved tangential angle model of displacement enters a warning stage before global instability. While all three monitoring parameters exhibit clear precursory characteristics, their response sequences differ: microseismic signals display the earliest anomaly, followed by the drop in Newton force, with displacement responding last. This temporal sequence reflects a hierarchical failure evolution process, transitioning from microcrack accumulation to structural unloading and ultimately macroscopic sliding. The findings provide experimental evidence and theoretical support for the development of a multi-parameter graded early warning approach based on integrated force-seismic-deformation monitoring for rock slopes controlled by locked segments.

To address the challenges of ambiguous physical meanings and the difficulty in quantitatively characterizing driving factors in existing slope displacement decomposition methods, a model- and data-driven displacement decomposition approach was proposed. This method first constructs a displacement model that considers the influencing factors of rainfall, blasting, excavation, and creep. It integrates numerical simulation results into the objective function, thereby establishing dual optimization objectives that ensure consistency between monitoring data and numerical simulations. The Adam optimization algorithm is utilized for parameter optimization, allowing for the quantitative separation of displacement contributions from various influencing factors by minimizing the objective function. The proposed method was applied to the slope of the material yard at the Yebatan Hydropower Station. Results indicate that the displacements induced by rainfall, blasting, excavation, and creep accounted for approximately 7.7%, 5.9%, 35.1%, and 51.3% of the total displacement, respectively. Initially, the early deformation of the slope was predominantly influenced by excavation. However, the contribution of creep gradually increased over time, ultimately becoming the dominant factor. In contrast, the effects of rainfall and blasting became significantly more pronounced during the later stages of excavation. The proposed method effectively reveals the temporal variation patterns of individual displacement components, contributing to a deeper understanding of the mechanisms of deformation evolution and the instability behavior of slopes.

The dissolution process in rock fractures is jointly controlled by advection, reaction, and diffusion, leading to the formation of compact dissolution, wormhole dissolution, and uniform dissolution patterns. Wormhole dissolution can create localized preferential flow channels, significantly altering the permeability of rock masses and accelerating reservoir leakage or dam foundation instability. Therefore, understanding these pattern transitions is crucial. Using rough rock fractures as a case study, a visual experimental platform for fracture dissolution was developed to conduct flow-dissolution tests under varying flow velocities and reaction rates. This platform successfully reproduced the co-evolution of dissolution morphology, aperture changes, and pattern transitions in rough fractures, aiming to investigate the underlying mechanisms. The results indicate that as flow velocity increases, the dissolution pattern transitions first from compact to wormhole dissolution, and then from wormhole to uniform dissolution. An increase in the reaction rate raises the critical Péclet number (Pe) required for the transitions from compact to wormhole dissolution and from wormhole to uniform dissolution. Considering that the solute concentration field is primarily influenced by the relationship between longitudinal (horizontal) and transverse mass transfer, a condition number for dissolution pattern transition was defined as the ratio of the longitudinal to transverse mass transfer coefficients. The critical values of this condition number were identified as 350 for the transition from compact to wormhole dissolution and 7 for the transition from wormhole to uniform dissolution. The findings of this research elucidate the dissolution processes and pattern transitions in fractures within soluble rock areas, providing a scientific basis for evaluating seepage stability and optimizing seepage control measures for reservoir banks and dam foundations in hydropower engineering projects.

To accurately elucidate the evolution of hydrogen migration and the sealing integrity of bedded rock salt formations for hydrogen storage in China, a unified gas flow equation that encompasses all flow regimes was proposed, based on the microstructural characteristics of the rock and multi-scale hydrogen flow behavior. A fluid-solid coupled seepage model that accounts for real gas compressibility has been established and applied to analyze hydrogen seepage dynamics under cyclic injection and production. The results indicate that hydrogen flow in the surrounding strata is predominantly influenced by slip and transitional regimes. Driven by periodic operating pressures, a significant dynamic competition mechanism between leakage and backflow emerges. Nevertheless, a long-term net mass loss is observed, with an average daily leakage rate of 3.07 kg/d and an annual leakage rate of 0.035%. The range of hydrogen leakage exhibits a power-law growth over time, with average annual expansion rates of 2.26 m/a in interlayers and 0.77 m/a in rock salt layers, identifying interlayers as the primary leakage pathways. Comparative analysis reveals that after 50 years of operation under identical geological conditions and working parameters, the extent of hydrogen leakage is approximately 1.38 times that of natural gas. Therefore, it is recommended that design parameters such as safety pillar width and protective roof thickness be increased by 40% beyond the current standards for salt cavern natural gas storage to ensure the long-term sealing safety of salt cavern hydrogen storage.

To investigate the effects of fracture width and grouting reinforcement on the dynamic mechanical properties of sandstone under blast loading, the split Hopkinson pressure bar(SHPB) impact test, combined with high-speed photography, can be utilized to investigate the dynamic mechanical properties of intact sandstone, fractured sandstone with varying crack widths, and grout-reinforced fractured sandstone under blast loading. Based on fracture mechanics theory, the stress intensity factors of various rock specimens were evaluated, and a dynamic constitutive model was established. The results indicate that: (1) fractured sandstone exhibit a failure mode primarily characterized by shear, supplemented by tensile failure. Following grouting, the failure pattern transitions to predominantly axial tension, accompanied by secondary radial tension, with a significantly reduced degree of damage. As the grout absorbs and reflects a substantial portion of the stress waves, the failure becomes concentrated within the grout itself, considerably enhancing the deformation resistance of the rock mass. Furthermore, this reinforcement effect is progressively amplified with an increase in grout width. (2) The absolute strength degradation coefficient Rs and the absolute strength restoration coefficient Rx were defined. It was observed that both Rs and Rx decrease linearly as fracture width increases. Similarly, the dynamic compressive strength exhibits a linear decline with increasing fracture width, while the peak strain demonstrates a linear upward trend. Grouting significantly enhances the dynamic compressive strength of fractured rock masses and effectively suppresses their peak strain. (3) An increase in fracture width results in a rise in the energy reflection coefficient and a decline in the transmission coefficient. The energy dissipation ratio exhibits a non-monotonic trend—initially increasing and then decreasing—reaching its maximum at a critical width of 5.83 mm. After grouting, the curves for transmitted and reflected energy tend to stabilize, indicating improved energy transmission efficiency. The grout substantially optimizes the energy absorption efficiency of the rock mass, and the dissipated energy increases monotonically with fracture width. (4) Calculated stress intensity factors increase with fracture width but decrease post-grouting. The dynamic constitutive model, which incorporates strain equivalence, Weibull distribution, and the TCK model, demonstrates good agreement with experimental curves.

To meet the safety requirements for the operation of underground caverns utilized in compressed air energy storage under high internal pressure and complex in-situ stress conditions, this study investigates the cracking and instability mechanisms of concrete lining structures subjected to cyclic loading. A true triaxial testing method was employed to fabricate concrete lining specimens featuring circular openings. Combined with acoustic emission (AE) monitoring, three-dimensional localization, and RA-AF parameter analysis, the mechanical response characteristics, crack evolution behavior, and failure mechanisms of cavern models with varying lining thicknesses were systematically examined. The results indicate that during the true triaxial compression process, specimens with different lining thicknesses undergo four distinct stages: compaction, elastic deformation, plastic deformation, and instability failure. Macroscopically, V-shaped crushed zones and through-going shear bands are formed on both sides of the opening. The lining thickness exhibits a dual regulatory effect on the failure mode: excessively thin linings provide insufficient confinement, leading to rapid crack penetration, while overly thick linings tend to accumulate elastic strain energy, resulting in sudden failure. In contrast, a moderate lining thickness achieves an optimal balance among load-bearing capacity, crack control, and energy release. AE monitoring results reveal that crack evolution follows a staged pattern of “compaction–stable crack propagation–accelerated crack growth–instability failure”, with AE events evolving from “low-energy and sparse” to “high-energy and dense”, concentrating during the failure stage. Furthermore, based on three-dimensional localization and RA-AF parameter analysis, the crack types evolve from initially scattered tensile cracks in localized weak zones to tensile-shear composite cracks concentrated around the opening. Correspondingly, the failure mode transitions from tensile failure to tensile-shear composite failure, ultimately culminating in shear-dominated failure. Quantitative analysis shows that the lining thickness exerts a significant influence on the peak strength and crack evolution. The peak strength of specimens increases by approximately 12.5% as the lining thickness rises. Moreover, when the proportion of shear cracks exceeds 58.05%, the structure transitions from tensile?shear composite failure to shear?dominated failure.

The key to accurately predicting the macro-mechanical behavior of rock materials lies in a profound understanding of the evolution laws and mechanisms governing microcracks at the mineral scale. This paper proposes a high-precision multi-scale modeling framework that integrates advanced X-ray computed tomography (CT) technology, nanoindentation techniques, and the Smoothed Particle Hydrodynamics (SPH) numerical method. Utilizing this modeling framework, an SPH-GBM numerical model that accurately represents the spatial distribution of mineral crystals (quartz, feldspar, and mica) and grain boundaries within granite was successfully developed. The simulation results indicate that the failure of granite under uniaxial loading is primarily driven by tensile damage. Microcracks initially emerge as tensile intragranular cracks at grain boundaries, where stress concentrations are likely to occur. As the load increases, these cracks propagate and converge along the grain boundaries and subsequently penetrate the interior of the crystals, forming grain boundary cracks. The crack propagation path exhibits distinct mineral selectivity, with microcracks preferentially forming within feldspar, followed by quartz, while mica particles, which possess the lowest stiffness, tend to fracture near peak strength. This study confirms that SPH-GBM is a robust tool for linking high-precision microstructural characteristics with macroscopic failure behavior in rocks, offering significant potential for advancing research in rock mesomechanics.

To thoroughly analyze the three-dimensional (3D) fracture evolution characteristics and transformation effects of coal under CO2 phase-change fracturing (CO2-PTF), experiments were conducted on CO2-PTF coal at fracturing pressures of 120 MPa and 185 MPa. By integrating computed tomography (CT) scanning with 3D fracture reconstruction techniques, both single fractal and multifractal theories were employed to systematically investigate the geometric and fractal parameter evolution of the 3D fracture structure in coal following CO2-PTF, thereby elucidating the 3D transformation effects of CO2-PTF coal. The results demonstrate that CO2-PTF significantly enhances the fracture volume, porosity, surface area, and maximum fracture length of coal. The fracturing pressure has a considerable positive influence on fracture evolution; as the fracturing pressure increases, the effects on fracture volume, porosity, surface area, and fracture length become more pronounced. The relationship between the evolution of 3D fracture volume and surface area with fracture length further indicates that CO2-PTF coal exhibits both fracture generation and expansion transformation effects. Analysis of the single fractal and multifractal characteristics of the fracture structure reveals that the fractal dimension for fracture volume in coal increases post-CO2-PTF, suggesting greater complexity in the fracture structure. Additionally, the heterogeneity within the low probability, high probability, and overall regions of fracture structure distribution increases, demonstrating significant local concentration and enhanced singularity. Although notable differences exist within the fracture structure, the predominant influence of the low probability region in controlling its heterogeneity diminishes. Further analysis indicates that during the CO2-PTF process, the dynamic high-pressure gas jet stage primarily corresponds to the fracture generation effect, resulting in an increased fractal dimension for fracture volume and greater enhancement of heterogeneity in the low probability, high probability, and overall fracture distribution. Conversely, the subsequent quasi-static high-pressure gas stage predominantly induces the fracture expansion transformation effect, leading to a substantial reduction in the volume and surface area of small-scale fractures, causing the fracture structure to become locally concentrated in high probability regions, thereby exacerbating internal disparities and weakening the low probability region's dominance in controlling fracture structure heterogeneity. These research findings provide a theoretical basis for optimizing CO2-PTF device parameters and enhancing fracturing and permeability improvement in low-permeability coal seams.

Microcrack growth induced by water imbibition and hydration in hard-brittle shale has consistently posed a challenge to wellbore stability during drilling. While most current studies rely on modeling assumptions of constant crack width and hydration driving force, as well as semi-quantitative experimental characterizations, they fail to sufficiently reveal the chemical fracture mechanisms underlying hydration cracking in hard-brittle shale. To address these limitations, this work establishes a mathematical model applicable to the nucleation and subcritical crack growth (SCG) of hydration cracking in illite-rich hard-brittle shale, based on the principles of physical equivalence and the framework of linear elastic fracture mechanics (LEFM). The asymptotic solutions of stress fields near the tips of hydration microcracks, under variable crack width and nonlinear hydration stress conditions, were derived, and the long-term stability was also evaluated, clarifying the evolution mode of SCG dominated by intrinsic multi-processes. Additionally, an innovative indoor double torsion test was developed for the first time, wherein water was instantaneously introduced to the tip of a stress-loaded crack to simulate water-rock interactions after wellbore formation. The dynamic behavior of hydration cracking evolution in hard-brittle shale from the Gulong Qingshankou formation was quantitatively characterized. Furthermore, a critical criterion for the transition time from hydration cracking to sudden instability failure was proposed. Results indicate that the double torsion program, which incorporates instantaneous water introduction to the crack tip, is reliable and repeatable. The hydration of illite crystal layers in hard-brittle shale can significantly enhance the rate of SCG by 1 to 2 orders of magnitude, reaching rates of μm/s, and increase the length of SCG to 4 to 13 times that of the original length. Moreover, the model predictions provided by the iterative algorithm align well with experimental results, exhibiting a maximum mean relative error not exceeding 8.2% and achieving rapid convergence under varying initial stress levels, thereby confirming the reliability and robustness of the proposed model. This study clarifies the microscopic origins and progressive evolution behaviors of hydration cracking in illite-rich hard-brittle shale from the perspective of chemical fracture mechanics, highlighting a hierarchical regulation strategy that enhances blockage at the crack mouth, obstructs flow within the crack, and inhibits growth at the crack tip, thereby ensuring overall wellbore stability. The experimental results and theoretical model offer methodological references and data for both indoor expanded tests and on-site engineering practices.

Fluidized mining of deep solid resources represents an innovative approach to mining; however, the evolution of mining-induced stress under this method remains inadequately understood. To elucidate the mechanism of stress evolution and establish its relationship with laboratory testing conditions, this study employs FLAC3D numerical simulations to investigate the characteristics of the mining-induced stress field, the variations in the stress concentration coefficient, and the stress disturbance path under the looped mining layout of fluidized mining. The findings reveal that the evolution of mining-induced stress in looped mining exhibits stage-dependent behavior, leading to the development of a spatially non-uniform stress field ahead of the excavation face, which may result in long-term eccentric loading of mining equipment. The evolution trend of the stress concentration coefficient aligns with that observed in longwall mining. However, under the filling conditions considered in this study, the asymptotic value (2.0–2.4) is approximately 20% lower than that observed in longwall mining, indicating that filling can effectively mitigate peak stress and enhance mining safety. Based on these numerical results, a mapping scheme for the  stress disturbance path for laboratory testing has been established, providing a preliminary foundation for the experimental investigation of the mechanical response of coal-rock under looped fluidized mining conditions.

Uniaxial compression experiments were conducted to investigate granite slabbing failure with and without anchor cables. Transverse and longitudinal wave sensors were employed to synchronously collect acoustic emission (AE) signals throughout the entire loading process of the specimens, aiming to explore the differences in time-frequency characteristics of AE transverse and longitudinal waves during granite slabbing failure influenced by anchor cables. The results indicate that at peak stress in the time domain, unanchored specimens displayed abrupt increases followed by sharp decreases in both P-wave and S-wave event rates, accompanied by single-peak energy rate evolutions. In contrast, anchored specimens maintained stable low P-wave event rates, while S-wave event rates surged and then gradually declined, with both wave energy rates exhibiting multi-peak patterns. Anchored specimens showed increases of 12.33% and 11.41% in average peak S-wave and P-wave event rates, respectively, but experienced reductions of 77.22% and 23.94% in average peak energy rates. In the frequency domain, anchored specimens exhibited narrower P-wave dominant frequency ranges (30–110 kHz compared to 10–155 kHz for unanchored specimens) and simplified frequency bands (4 versus 6). They also demonstrated lower S-wave signal density, with low-frequency components (0–128 kHz) decreasing by 6.05% and high-frequency components (256–500 kHz) increasing by 6.37%. Additionally, the entropy ranges of S-wave and P-wave dominant frequencies narrowed, showing gentler fluctuations. The lateral presence of anchor cables significantly inhibited the propagation and coalescence of tensile cracks during the plastic and post-peak stages of the slabbing specimens, transforming the failure mode from instantaneous tensile splitting to progressive tensile-shear composite failure. This transition is the fundamental reason for the observed differences in AE P-wave and S-wave time-frequency characteristics between anchored and unanchored specimens. This study further elucidates the influence of anchor cables on the AE P-wave and S-wave time-frequency characteristics during the slabbing failure of surrounding rock, providing a theoretical basis for dynamic damage assessment of anchored rock masses and control of surrounding rock slabbing failure.

Acidic wastewater circulation from coal mines leads to the degradation of surrounding rock strength, which is a key factor contributing to the long-term stability failure of closed coal mines. Currently, there is a substantial amount of research on the fracture behavior and microscopic mechanisms of limestone under single-factor conditions. However, the relevant mechanisms under the combined influence of an acidic environment and dry-wet cycles still require further investigation. To explore the fracture behavior and microscopic mechanisms of limestone under acidic wastewater circulation, this study employed Brazilian splitting tests in conjunction with acoustic emission and digital image correlation techniques to analyze the effects on tensile strength, fracture characteristics, and crack propagation. Nuclear magnetic resonance and scanning electron microscopy was utilized to reveal mineral corrosion patterns and microscopic pore responses. The results indicate that: (1) with increasing circulation cycles, the tensile strength of limestone decreases significantly, tensile crack propagation becomes more pronounced, and the number of surface cracks increases during the fracture stage; (2) acidic wastewater circulation reduces acoustic emission (AE) ringing counts and high-energy events during failure, while both the a- and b-values derived from AE event statistics increase; (3) at the microscopic level, calcite dissolution reduces the surface calcium (Ca) content of limestone. Concurrently, due to the influence of metal ions in the acidic wastewater, the surface contents of iron (Fe) and magnesium (Mg) elements increase. The combined action of acidic wastewater and dry-wet cycles exacerbates internal microstructural damage in limestone, promoting pore evolution from micropores to mesopores and macropores, ultimately resulting in the deterioration of tensile properties. This study provides valuable insights into the fracture behavior and microscopic mechanisms of limestone under acidic wastewater circulation, offering a reference for understanding the degradation processes of related underground structures.

Based on the stress characteristics, geometric shape, and deformation behavior of cantilever rock masses in the goaf of longwall working faces, an independently developed non-uniform loading experimental system for cantilever rock masses has been established. This experimental system comprises a main frame, a non-uniform loading device, a variable-sized controllable pressure airbag, a uniform pressure variable angle loading system, a hydraulic power system, and a data acquisition system. It enables uniform pressure confining pressure variable angle loading, non-uniform pressure variable rate loading, and non-uniform pressure controllable constant pressure loading for large-sized cantilever rock mass samples. The system simulates the extrusion of adjacent fractured rock blocks in the goaf of longwall working faces, accounting for upper non-uniform loading and the residual bearing capacity of the lower foundation. The effects of sidewall inclination angle, confining pressure strength, non-uniform loading coefficient, and non-uniform support coefficient on the fracture characteristic parameters (peak load, peak displacement, and elastic deformation energy) of the cantilever rock mass are analyzed. Test results indicate that as the sidewall inclination angle increases, the peak load, peak displacement, and elastic deformation energy of the cantilever rock mass exhibit an asymmetric “W”, “V” and “U” type change trend. With increasing confining pressure strength, all three parameters show a pattern of slow increase followed by rapid increase. As the non-uniform loading coefficient increases, these parameters display an asymmetric “M” type change trend. Moreover, with an increase in the non-uniform support coefficient, the parameters show an asymmetric “Λ” pattern, initially increasing and then decreasing. The sensitivity of the factors affecting the elastic deformation energy accumulated prior to the fracture of the sample is ranked as follows: confining pressure strength＞non-uniform support coefficient＞sidewall inclination angle＞non-uniform loading coefficient. These test results validate the reliability of the experimental system and provide a method for studying the fracture behavior of cantilever rock masses in goaf.

 Two-dimensional contour lines play a crucial role in the rapid assessment of rock joint characteristics and shear strength. The challenge of accurately and portably acquiring the contour features of field rock joints, along with the efficient completion of joint roughness coefficient (JRC) evaluation, remains a significant technical hurdle in the development of contemporary contour measuring instruments. This study develops and integrates four key modules: contour feature parallel measurement, information acquisition and operation control, human-computer interaction and remote communication, and high-efficiency JRC evaluation for rock joints, based on the mechanical structures, measurement methods, and JRC evaluation approaches of existing instruments. A portable JRC rapid measuring instrument suitable for field use has been created, and its accuracy has been validated through assessments of specimen material, profile inclination, and illumination intensity. Both the instrument and a laser scanner were utilized to measure the same rock joint in the field. Results indicate that the profile curves obtained from the instrument align closely with those captured by laser scanning, demonstrating the instrument's high efficiency and strong adaptability to various environmental conditions. Direct shear tests were conducted on specimens prepared using the measured rock joint data, and the JRC values back-calculated from these tests were compared with those obtained from the instrument. This verification confirms that the JRC evaluation method based on the proposed instrument exhibits high accuracy. This research provides essential technical support for the development of contour measuring instruments for rock joints and advances the study of JRC measurement.

To investigate the impact of train-induced dynamic loading on the migration characteristics of fine particles, this study conducts a series of internal erosion tests on sandy gravel with a representative continuous gradation under dynamic loading conditions. Additionally, a coupled computational fluid dynamics-discrete element method (CFD-DEM) is employed to simulate the internal erosion processes induced by dynamic loading, aiming to reveal the hydraulic and dynamic responses, as well as the underlying mechanisms from both macro and micro perspectives. The results indicate that the application of dynamic loading disrupts the stable structural configuration established under static seepage conditions. However, the system quickly evolves towards a new equilibrium state. Under high-disturbance-intensity dynamic loading, the hydraulic gradient increases instantaneously by approximately 32%, and the time required for the specimen to achieve a new stable state is reduced by about 40% compared to medium-disturbance conditions. During the static stage, the particle size distribution curve of the migrated particles is dominated by fine sand and exhibits a unimodal pattern. Upon the introduction of dynamic loading, the distribution curve gradually transforms into a bimodal form, with the particle size at the second curve peak extending into the coarse-sand range, resulting in a maximum particle size increase of 884.3%. Under static conditions, the overall structure of the specimen remains dense and stable. Low-disturbance-intensity dynamic loading only causes localized contact weakening, promoting a more uniform porosity distribution. As disturbance intensity increases, structural loosening and fluidization of fine particles occur beneath the vibration source, with migrated particles predominantly redepositing in the upstream and downstream regions along the seepage path relative to the vibration source. Under low-disturbance-intensity dynamic loading, particle migration is primarily restricted to localized disturbances of fine particles, while the overall force-chain structure remains relatively stable. As disturbance intensity escalates, dominant force chains gradually align with the vibration direction and undergo continuous breakage and reorganization, leading to the loosening of the granular skeleton and cooperative migration of particles ranging from fine sand to fine gravel. These findings elucidate the macro-micro mechanisms governing fine-particle migration and internal erosion in sandy gravel strata under coupled dynamic loading-seepage conditions, providing theoretical support and experimental evidence for the stability analysis and prevention of seepage erosion in sandy gravel strata subjected to train-induced dynamic loading in rail transit engineering.

To elucidate the mechanisms of wave transmission and reflection and the associated energy-partitioning characteristics at the interface between saturated frozen soil and saturated unfrozen soil under plane shear-wave incidence, an interfacial wave-propagation model is developed within a Biot-type poroelastic framework. The continuity conditions for interfacial stresses and displacements are derived, and a plane-wave potential method is used to determine the amplitude ratios and energy-flux coefficients of all transmitted and reflected modes. A deterministic sensitivity analysis is then conducted to investigate the effects of key parameters, including the angle and frequency of incidence, porosity, Poissons ratio and temperature. The computational implementation is validated by comparing a limiting case with published results and by verifying energy conservation. The results show that the angle of incidence governs the transmission and reflection responses. Pronounced peaks or discontinuities in the amplitude ratios and energy-flux coefficients generally occur near the critical angles, indicating the high sensitivity of interfacial mode conversion and energy redistribution. The incident frequency primarily modulates the magnitude of energy partitioning, while the critical angles remain largely unchanged. Furthermore, variations in porosity, Poissons ratio and temperature substantially affect slow-wave-related modes, demonstrating that the slow-wave channel is the principal carrier of parameter sensitivity. Parameters associated with the frozen medium exert a particularly strong influence on energy redistribution. These findings provide a theoretical basis for assessing the dynamic response of layered interfaces and identifying freeze-thaw states in cold-region engineering.

The demand for a risk assessment method for sand liquefaction based on shear wave velocity is increasingly strong. However, progress has been hindered by the long-standing dilemma between deterministic and probabilistic models. This paper presents a new univariate-based probability analysis model that facilitates a seamless integration of deterministic and probabilistic approaches. Building on this model, we establish a novel formula for the probabilistic evaluation of sand liquefaction based on shear wave velocity. The research indicates that while the fundamental models for deterministic liquefaction discrimination methods based on shear wave velocity differ between China and other countries, the outcomes are generally consistent. Existing probabilistic evaluation methods for sand liquefaction based on shear wave velocity exhibit systematic deviations from deterministic methods, which have led to skepticism within the engineering community. The new formula proposed in this paper addresses this issue, enabling a comprehensive and effective integration with advanced deterministic methods utilized in China. It fully leverages the dual advantages of wave velocity testing and probability analysis, thus providing direct technical support for the revision of seismic code and engineering practices. Additionally, the univariate-based probability calculation model introduced in this paper offers fresh perspectives for tackling binary probability analysis challenges across various fields.