Search Results (1,669)

To reveal the mechanism of the load transfer of drilling shaft lining under the influence of filter cake, this study establishes a mechanical interaction model that integrates the surrounding rock, filter cake, backfill layer, and shaft lining system based on elastoplastic theory. The analytical solution of this system was derived; this was followed by the systematic examination of the impact of the key parameters (thickness of filter cake, elastic modulus of surrounding rock, cohesion, and internal friction angle) on stress field evolution and load distribution. The operational mechanisms of filter cake and load formation principles in drilling shaft linings were elucidated. The results show that the filter cake induces stress concentration in surrounding rock by delaying stress transmission, effectively mobilizing the bearing capacity of surrounding rock and improving the stress state of the lining. An increase in the elastic modulus of the surrounding rock enhances the load-bearing proportion of the surrounding rock, thereby reducing the load transferred to the backfill layer and shaft lining. Higher cohesion and a higher internal friction angle of the surrounding rock strengthen the bearing capacity of the surrounding rock, which decreases the load transmitted to the backfill layer and shaft lining. The increased stiffness of the backfill layer raises the load-bearing proportion of the backfill layer, while diminishing loads on both the shaft lining and surrounding rock. The above research provides a theoretical basis for promoting the application of drilling technology in deep, water-rich, and weakly cemented bedrock formations in western China. Full article

This study investigates CO₂–brine–rock interactions in Entrada Sandstone from the San Juan Basin under reservoir-relevant pressure and temperature conditions. A core plug from 8313 to 8315 ft was exposed to CO₂-saturated synthetic formation brine with a salinity of 16,601 ppm, followed by static aging. Pre- and post-experiment analyses included porosity and permeability measurements, ICP-MS, SEM-EDS, XRD, CT imaging, and petrographic thin-section analysis. Permeability decreased from 4.22 to 1.60 mD, corresponding to a 62.08% reduction, whereas porosity decreased from 12.37% to 11.75%, a change interpreted as within experimental uncertainty. Effluent chemistry showed increases in Ca²⁺, Mg²⁺, K⁺, Si, Sr, and Mn, consistent with carbonate cement dissolution and feldspar/silicate alteration under CO₂-acidified brine conditions. XRD analysis of suspended effluent solids identified quartz, montmorillonite, and illite–montmorillonite mixed-layer clays, indicating fines mobilization. These results suggest that permeability impairment was governed primarily by pore–throat blockage from mobilized clay particles, with possible contribution from secondary carbonate redistribution. The findings emphasize the importance of cement composition and clay mineralogy in evaluating injectivity risks for CO₂ storage in clay-bearing sandstone reservoirs. Full article

Instrumented rock-bolt monitoring requires strain records that retain integrity and asset context after local processing and wireless transmission. An Internet of Things (IoT) strain-sensing system with LoRa telemetry and asset metadata was evaluated on a cantilever fixture. The node converted tare-referenced bridge counts to apparent strain, applied temperature compensation using a lagged temperature term, evaluated alarms locally, and buffered summaries for LoRa transfer. Histories were assessed using sequence continuity and a 32-bit cyclic redundancy check (CRC-32). Ten monotonic loading runs showed linear responses to nominal screw advance (R² > 0.9997); fitted slopes had a coefficient of variation of 0.55%. Across three fixed-setting tests spanning 5.1–8.0 °C, unchanged embedded compensation reduced the magnitude of fitted apparent thermal sensitivity by 89.1–95.5%. In all 45 operator-controlled alarm trials, trigger or non-trigger outcomes matched expectations recorded before dashboard inspection. Of 60 planned application-layer history transfers, 50 passed; the remaining ten comprised four failures, three interruptions, and three invalid or contaminated trials. Passed transfers included exact reconstruction of a 1024-record circular buffer. Retrieved metadata passed CRC-32 verification and matched the registered laboratory asset. These results characterize a one-asset laboratory workflow before packaged-bolt, underground, and multi-asset validation. Full article

Rock glaciers are important geomorphic indicators of mountain permafrost conditions, yet the mechanisms controlling spatially heterogeneous deformation within individual rock glaciers remain poorly understood. This study investigates the Baishuigou Rock Glacier (BRG) in the Qilian Mountains by integrating multi-year InSAR observations, borehole stratigraphic data, and ground-temperature measurements to characterize its deformation and explore its relationship with permafrost degradation. The results reveal pronounced spatial heterogeneity in surface displacement. The main body of the rock glacier exhibits persistent displacement, with mean annual LOS displacement rates ranging from −6.93 to 13.19 mm yr⁻¹, corresponding to relatively well-preserved ice-rich frozen ground. The frontal zone shows stronger and more variable displacement under more degraded subsurface conditions, whereas the relict rock glacier area exhibits relatively weak displacement dominated by seasonal thermal responses. Comparisons among the borehole sites further indicate that spatial differences in surface displacement correspond to variations in active-layer thickness, ground-ice conditions, and thermal state. The integrated observations suggest a possible spatial transition from relatively well-preserved ice-rich frozen ground in the upper part of the rock glacier toward more degraded conditions downstream. This study demonstrates that integrating surface deformation with subsurface structural and thermal observations provides stronger physical constraints for understanding spatially heterogeneous rock glacier deformation and its relationship with frozen-ground conditions. Full article

Large deformation is one of the most critical hazards in tunnels excavated under complex geological conditions. It often causes significant economic losses and threatens construction safety. For layered soft rock tunnels subjected to high in situ stress, the deformation and failure mechanisms are largely governed by the bedding dip angle. To clarify these mechanisms and optimize the corresponding construction control measures, this study investigates a carbonaceous slate section of a railway tunnel in the Western Sichuan Plateau. Field monitoring and FLAC3D numerical modelling are coupled. The influence of the bedding dip angle on the plastic-zone evolution and the failure modes of the surrounding rock is analysed. The micro-bench, three-bench, and reserved core soil methods, together with the rock bolt length, are comparatively evaluated. On this basis, a differentiated reinforcement strategy is proposed for bedding-induced asymmetric loading. The results indicate that: (1) The bedding dip angle governs the failure mode of the surrounding rock. Under the micro-bench method, the plastic zone in subvertically bedded rock masses exhibits a quasi-symmetrical distribution along the normal direction of the bedding planes. The sidewalls predominantly undergo flexural failure. In contrast, under bedding-induced asymmetric loading, the plastic zone concentrates at the left springline and right shoulder. An asymmetric composite failure mode is formed, characterized by shallow flexural–tensile cracking and deep-seated interlayer shear. (2) Under the subvertical bedding condition (89°), the reserved core soil method mitigates the excavation-induced unloading disturbance most effectively. It achieves the lowest peak stress and the smallest tunnel convergence, which is 15.7% and 33.0% lower than those of the micro-bench and three-bench methods, respectively. Its plastic zone reaches full numerical convergence. The reserved core soil method is therefore identified as the optimal excavation Scenario under this condition. (3) The rock bolt length exhibits a threshold effect on deformation control. The most substantial improvement occurs when the bolt length is increased from 4 m to 6 m, beyond which the benefit tends to plateau. A bolt length of 6 m is therefore recommended as the best-performing Scenario among the tested values (4, 6, 8, and 10 m) for the investigated geological and support conditions. For surrounding rock subjected to bedding-induced asymmetric loading, a differentiated reinforcement strategy targeting the vulnerable zones reduces the maximum deformation by 18.8% and 28.3% compared with the uniform reinforcement Scenario and the baseline Scenario, respectively. These findings provide practical insights into excavation-method selection and support optimization for layered soft rock tunnels under similar conditions. Full article

In the subsequent backfilling mining method, the composite structure formed by the ore pillar and the backfill is the key element in ensuring the stability of the working face. Its mechanical behaviour directly affects mining safety and ore recovery rates. In order to elucidate the mechanical response and failure mechanisms of rock-like backfill composite structures (RLBCS) under biaxial loading, specimens with different water-to-cement (W/C) ratios (0.5, 0.6, 0.7 and 0.8) for the rock-like backfill were prepared in this study. Biaxial loading tests were conducted, with digital image correlation (DIC) technology employed simultaneously to monitor the evolution of strain and displacement on the specimen surface. The results indicate that the biaxial strength of RLBCS decreases exponentially as the W/C increases. When the W/C exceeds 0.7, the strength reaches a plateau. The strength contribution of the backfill increases relatively. The axial stress–strain curve exhibits four distinct phases. A pronounced bimodal distribution is observed when the W/C exceeds 0.5. The evolution of lateral strain exhibits a transition point where compression is followed by expansion. The threshold for lateral expansion stress exhibits a non-monotonic variation. The modulus of elasticity decreases as the W/C increases. The apparent structural strain ratio exhibits a non-monotonic variation. The failure pattern exhibits marked asymmetry. The rock-like side shows tensile failure. Where the interface is present, this manifests as localised crushing at the top of the rock-like layer, cracking along the interface, and bulging of the backfill. The W/C ratio of the rock-like material governs the failure mechanism of RLBCS. The strain localisation modes in backfill materials are classified into two types: post-peak abrupt and pre-peak gradual. The evolution of interface strain exhibits four distinct stages: an initial abrupt change, cooperative deformation, crack initiation, and post-peak instability. The spatiotemporal evolution of interfacial delamination and the deformation of the backfill was quantified through displacement field analysis. The research findings provide a theoretical basis for the design of underground mining operations. Full article

Advanced manufacturing and cutting machinery often operate under variable material properties and uncertain load conditions, making real-time process optimization difficult when high-fidelity simulations and physical experiments are costly. To address this problem, this study proposes a physics-guided surrogate-assisted reinforcement learning framework for multi-objective speed regulation of coal–rock cutting machinery. The haulage speed and drum rotational speed are jointly optimized to balance production rate, cutting specific energy consumption, current load, vibration impact, and speed-regulation stability. First, an EDEM–RecurDyn–Simulink co-simulation model was established to obtain cutting current and vibration response data under different coal–rock structures and speed combinations. Similar-material cutting experiments were conducted to validate the vibration response, with root mean square (RMS) relative errors of 3.38%, 4.21%, 5.75%, and 5.03% under full-coal, single-gangue-layer, double-gangue-layer, and full-rock conditions, respectively. Based on these data, an improved physics-informed neural network (PINN) surrogate model was developed by embedding an equivalent coal–rock difficulty factor, a speed-matching factor, a semi-empirical current prior, and a vibration residual calibration mechanism. The surrogate model achieved R² values of 0.9623 and 0.9147 for cutting current and vibration kurtosis, respectively. It was then integrated into a Soft Actor–Critic (SAC) control environment to learn continuous dual-variable speed-regulation policies. Across five independent SAC training seeds, the improved SAC achieved an average theoretical productivity of 207.8033 ± 6.5641 t·h⁻¹ and a cutting specific energy consumption of 0.3387 ± 0.0114 kW·h·t⁻¹. Compared with the fixed-speed, empirical speed-regulation, and conventional SAC strategies, the proposed method increased the average theoretical productivity by 2.65%, 5.01%, and 1.77%, respectively, while reducing the corresponding specific cutting energy consumption by 1.37%, 4.05%, and 2.22%. These results demonstrate that the proposed framework provides an efficient intelligent optimization method for condition-aware speed regulation in complex industrial cutting processes. Full article

Vertical hydraulic-fracture propagation controls the effective stimulated thickness of deep layered shale, yet conventional fracability indices omit this response. Coupled hydromechanical cohesive-zone models were built for nine sublayers in the northern and southern Yongchuan sub-blocks, Sichuan Basin, using rock-mechanics tests, well logs, in situ stress evaluation, and measured layer thicknesses. Increasing bedding dip from 0° to 10° raised fracture height by 19.8% in northern Yongchuan and 41.7% in southern Yongchuan, whereas reducing tensile strength from 8.0 to 6.4 MPa raised it by 31.3% and 33.2%, respectively. These results indicate that, within the investigated parameter ranges, fracture height responded more strongly to tensile-strength variation than to bedding-dip variation, whereas the southern sub-block was more sensitive to bedding orientation. For northern Yongchuan, a 30-case full-factorial dataset was used to train a Gaussian process regression model of fracture height (leave-one-out R² = 0.932, MAE = 0.77 m, RMSE = 0.97 m), and 12 additional off-grid simulations yielded an R² of 0.864, an MAE of 0.93 m, and an RMSE of 1.06 m. The normalized vertical fracture-propagation response was then combined with a baseline fracability index through a weighted geometric mean. At the selected wells, the integrated index showed better agreement with average monthly gas production than the baseline index. The resulting evaluation framework provides a basis for fracturing feasibility screening in the Yongchuan area. Full article

During the service life of karst tunnels, groundwater containing Ca²⁺ and CO₃²⁻ can migrate along the shotcrete–surrounding rock interface and induce calcite deposition, thereby changing the interfacial material composition and load transfer path. To clarify the effect of this process on interfacial bonding performance, this study used molecular dynamics simulations to construct CSH–SiO₂, SiO₂–calcite, CSH–calcite, and CSH–calcite–SiO₂ interface models. The interfacial density distribution, radial distribution function, number of hydrogen bonds, interaction energy, and normal tensile failure behavior were analyzed. The results show that all four models reached stable energy plateaus after relaxation, and clear atomic density overlap and short-range RDF peaks appeared in the interfacial regions. These descriptors indicate short-range contact and possible Ca–O electrostatic attraction, hydroxyl-related hydrogen bonding, and carbonate-associated interactions between calcite and both SiO₂ and CSH surfaces. Approximately 80 hydrogen bonds were formed at the SiO₂–calcite interface, approximately 32 at the CSH–calcite interface, and approximately 59 in total for the two hydrogen bond subtypes at the SiO₂–CSH interface, indicating that the hydroxyl state of different substrate surfaces controls the interfacial hydrogen bond network. Interaction energy analysis shows that the single CSH–calcite interface has the strongest interaction (−51,753.6 kcal/mol), approximately 1.90 times that of the SiO₂–CSH interface and 16.43 times that of the SiO₂–calcite interface. However, in the three-layer composite model, the interaction energy on the CSH–calcite side is only approximately 28.0% of that on the SiO₂–calcite side, suggesting that a continuous calcite interlayer introduces asymmetric interfacial constraints. Tensile simulations further show that the SiO₂–calcite model has the highest peak stress (approximately 3.23 GPa) and exhibits brittle failure, whereas failure in CSH-containing systems is more likely to transfer into the CSH layer or weakly connected regions. These results indicate that calcite deposition does not simply strengthen or weaken the interface. Instead, within the two idealized endpoint configurations tested here, its effect depends on deposition continuity, the surface chemistry of the two substrates, and the weak links within the serial interface. This study provides a nanoscale theoretical basis for evaluating relative trends in the long-term service performance of shotcrete–surrounding rock interfaces, and for guiding future multiscale validations of drainage and waterproofing measures in karst tunnels. Full article

Road alignment creates unequal shortwave-radiation inputs on opposite embankment slopes, whereas the way in which overlying fill height redistributes this contrast among embankment layers remains unclear. This study aimed to quantify how road-axis azimuth controls transverse heat input and how upper fill height redistributes this input among the upper fill, rock-filled target layer, and permafrost foundation of a representative G219 rock-filled ventilated embankment. A two-dimensional transient enthalpy-based heat-transfer model, incorporating a smoothed phase-change treatment and coupled convection–shortwave boundary conditions, was used to compare three azimuths ($0^{\circ }$, ${45}^{\circ }$, and ${90}^{\circ }$), three upper fill heights (0.5, 1.5, and 3.5 m), and cold-year, reference-climate, and warm-year boundaries. Three counterfactual scenarios were used to separate the effects of target-layer equivalent thermal properties and exposed-surface optical conditions, while continuous simulations over $0^{\circ }$–${165}^{\circ }$ verified the representativeness of the formal azimuths. The common-domain response at ${45}^{\circ }$ reached 67.9–70.1% of that at ${90}^{\circ }$, indicating a continuous transition from near-symmetric to strong transverse heating input. Under the thermal–optical scenario at ${90}^{\circ }$, increasing fill height increased common-domain asymmetry by factors of 2.69–2.89; however, the target-layer response consistently peaked at 1.5 m, whereas the foundation-layer response decreased. The upper-fill-to-target-layer peak lag also increased with fill height. These patterns persisted across climate boundaries and prescribed thermal–optical–conductivity perturbations. Within the controlled scenarios, road alignment set the transverse heat input, whereas fill height regulated its within-profile transfer and layer-specific thermal response. The results support comparative thermal assessment of embankments with a similar upper-fill–rock-filled-target-layer–permafrost-foundation sequence, rather than design of an optimum fill height for a specific site. Full article

Blocky-rock masses are prone to dynamic slip along sand-filled joints under impact disturbance. The constraint normal to the joint and the size of the infill particles jointly influence their stability. To determine how axial load and particle-size affect dynamic slip, this study uses a custom-developed dynamic slip testing system for blocky-rock masses. Impact-disturbance tests are conducted under a constant lateral shear load with different axial load values and quartz-sand particle sizes. The block displacement evolves through three stages: stationary incubation, rapid slip, and deceleration to a stable state. When the axial load increases from 100 N to 400 N, residual slip displacement decreases by 87.52% to 90.12% across the particle size conditions. Residual slip displacement also follows an exponential decay with increasing axial load. Reducing particle size decreases both slip velocity and residual slip displacement, but its influence gradually weakens as the axial load increases. The difference in residual slip displacement between the coarse and fine particle conditions narrows from 0.460 mm to 0.030 mm. Strengthening the normal constraint compacts the granular layer and restricts particle movement, causing the dynamic slippage at sand-containing structural interfaces to gradually shift from being significantly influenced by the particle scale to being primarily controlled by the normal constraint. Full article

The Waliguan–Duohemao tectonic belt on the northeastern Tibetan Plateau hosts Qinghai’s highest-temperature hot springs (Zhacanggou 98 °C, Qunaihai 97 °C) and deep hot dry rock resources in the Gonghe Basin. However, the mechanisms governing hydrothermal circulation in this region remain poorly understood, limiting the assessment of its sustainable geothermal development potential. Through integrated fluid geochemistry, borehole temperature logging, and crustal thermal structure analyses, this study reveals the dual “water–heat” control exerted by the fault zone. The fault acts as a dominant pathway for deep meteoric water circulation, controlling mixing between deep hydrothermal fluids and shallow cold water, as evidenced by continuous hydrochemical and isotopic trends. Heat flow analysis indicates surface heat flow values up to 134.66 mW/m² in the Gonghe Basin (with a 78.6% crustal contribution), decreasing to 57.4% in the Guinan area. A deep intra-crustal partial melting layer provides additional heat in the Gonghe Basin, whereas the Guide and Tongren areas rely primarily on radiogenic heat generation. The systematic increase in crustal heat flow from southwest to northeast confirms the fault zone as an efficient conduit for deep thermal transport, highlighting the region’s substantial deep geothermal energy potential. To overcome the “heat without water” exploration bottleneck and promote sustainable resource development, we propose differentiated exploration strategies tailored to the structural heterogeneity of the belt: (1) in the western Gonghe Basin, prioritize heat source characterization and enhanced geothermal system (EGS) feasibility assessment; (2) in the central Guide area, employ high-resolution geophysical methods to detect water-conducting fault zones; and (3) in the eastern Tongren area, evaluate water source conditions and fault connectivity with recharge areas. These strategies collectively minimize exploration risks and support the long-term, sustainable utilization of geothermal resources in this high-altitude region. Full article

The coal–roof/floor combination system is a special geological structure consisting of both coal and roof/floor materials, which often leads to the occurrence of impact failure. The instability and failure of the coal seam are not caused by a single disturbance, but often occur under repeated loading and unloading processes under the action of mining stress. Thus, research on the impact failure, especially the energy evaluation of coal–rock combination materials under cyclic loading and unloading, is of great significance for understanding the rock burst mechanisms of deep coal mines. This paper focuses on the combination material formed by coal seam and roof and floor rock. Taking the #9 coal seam and roof and floor sandstone from the Zhangshuanglou Coal Mine as the test subjects, conventional triaxial compression and cyclic loading and unloading tests were conducted on sandstone, coal, and coal–rock combination material, respectively. Based on the strain energy evolution characteristics, the failure behavior of the coal–rock combination materials throughout the entire process of energy accumulation, dissipation, and release during cyclic loading and unloading are discussed. The research finds that the macroscopic failure behavior of the tested coal–rock combination specimens is dominated by the weaker coal component, and there are marked differences between the tested sandstone and coal components in their respective energy storage capacities, release characteristics, and dissipation behavior. On the basis of these measured differences and of CT-confirmed failure localization within the coal layer, it is inferred—as a mechanistic working hypothesis rather than a directly demonstrated result—that the main driving energy for the impact failure of the coal component may originate from the elastic strain energy stored in the roof/floor sandstone components, released preferentially toward the coal through their interfaces. For mining and excavation at high-in-situ-stress mining areas, the essence of the impact failure of surrounding rock is the non-coordination of energy storage and release between the roof and floor rock materials and the coal seam. The key to preventing impact failure is to eliminate the differences in energy storage and release between different rock materials in the coal seam. Full article

Argillaceous siltstone forms water-sensitive weak layers in red-bed slopes, but its multiscale deterioration under wet–dry cycling remains incompletely understood. Specimens subjected to 0, 1, 3, 5, 7, and 9 cycles were examined through uniaxial compression, energy analysis, digital image correlation (DIC), and microstructural and mineralogical characterization. The mean unconfined compressive strength (UCS) decreased by 36.0% after the first cycle and then remained broadly stable, with modest fluctuations, from 1 to 5 cycles. At five cycles, the elastic modulus remained substantially below the natural-state value, and although total strain energy approached the natural-state level, elastic strain energy remained lower and the dissipated energy ratio more than doubled, indicating continued irreversible damage. The characteristic calcite diffraction peak was no longer detected in the X-ray diffraction (XRD) patterns, while microstructural observations showed redistributed fines within pores together with a temporary decrease in face porosity. With further cycling, the UCS declined again and was 59.0% below its initial level after nine cycles. Meanwhile, strain fields and failure patterns evolved from localized deformation and splitting to distributed cracking and surface spalling, while particle detachment reopened pores and increased face porosity to 14.37%. These observations are consistent with a dissolution–filling–detachment mechanism and suggest that the intermediate UCS stabilization reflected temporary maintenance of load-bearing capacity rather than recovery of the original rock skeleton. Full article

Digital rock technology is essential for characterizing the petrophysical properties of tight reservoirs. However, conventional construction methods often yield models with insufficient pore connectivity due to low porosity and complex nanopore structures. To address this limitation, we propose a novel connectivity algorithm for isolated pore systems. First, a digital rock model is constructed using a random particle packing algorithm that integrates high-resolution SEM parameters, including kaolinite particle morphologies and randomly distributed microfractures. Subsequently, the connectivity algorithm sequentially links isolated pore clusters to the largest continuous pore system, forming an interconnected channel. Pore network extraction reveals that the algorithm produces significantly denser and more continuous structures, with pore–throat size distributions aligning well with experimental observations. Single-phase flow simulations demonstrate that the enhanced model yields porosity and permeability values consistent with laboratory measurements, whereas unenhanced models deviate substantially. To further advance microscale flow characterization, we derive explicit fitting formulas for the dimensionless conductivity of canonical pore cross-sections (equilateral triangle, square, and circle) considering water film boundary layer (WFBL) effects. These formulations are based on a comprehensive parametric study using the ab initio finite element method, followed by regression analysis to yield closed-form expressions. Two-phase flow simulations reveal that the WFBL increases residual saturations, reduces relative permeabilities, and decreases waterflooding displacement efficiency, with effects being more pronounced during secondary imbibition. This integrated approach provides a robust framework for constructing representative digital rock models of tight reservoirs and offers essential theoretical support for accurately modeling nanoscale flow behaviors in complex subsurface systems. Full article