Increase In Shear Stress Research Articles

Prediction model of PTO shaft fatigue damage considering sandy loam and loam in rotary-tillage operation

In this study, the fatigue damage to a power takeoff (PTO) shaft was evaluated under various operating conditions in rotary-tillage operations, considering soil strength and texture. Pearson correlation analysis was conducted to identify the significant variables influencing PTO shaft fatigue damage, and a prediction formula was derived through regression analysis using these variables. The PTO shaft exhibited increased shear stress with higher transmission gear stages, PTO gear stages, or soil properties, including strength and texture. The fatigue damage increased with higher transmission gear stages and soil strength while decreasing with higher PTO gear stages. Notably, as the PTO gear stage increased, the mean stress increased; however, the stress amplitude and equivalent completely reversed stress significantly reduced fatigue damage. Statistical analyses revealed a strong correlation between PTO shaft fatigue damage and factors such as tractor travel speed, PTO shaft power consumption, PTO shaft rotational speed properties, including strength and texture. The developed prediction equation, incorporating all significant variables, demonstrated, with a coefficient of determination (R²) of 0.93 and a root mean square error (RMSE) of 2.94×10-9. This equation effectively identifies trends in PTO shaft fatigue damage based on key operational variables. Furthermore, the findings emphasize the critical role of soil texture in assessing PTO shaft fatigue damage.

Mechanical properties and macro–micro failure mechanisms of granite under thermal treatment and inclination

The coupling effects of inclination angle (θ) and high temperature (T) on rock degradation present significant construction challenges for underground engineering projects, such as underground coal gasification, inclined mining pillars, and nuclear waste repositories. This study is built on a novel combined compression and shear test system, investigating granite’s physical and mechanical properties and macroscopic failure characteristics under varying temperatures and inclination angles. Additionally, acoustic emission technology was used to analyze the impact of inclination and temperature on the micro-failure behavior of the specimens. The experimental results indicate that as the inclination angle increases, the specimens’ peak compressive strength and elastic modulus decrease linearly. In contrast, the shear stress increases non-linearly, suggesting that additional shear stress accelerates the initiation and propagation of cracks. Furthermore, these mechanical parameters initially increase with rising temperatures before decreasing, with a temperature threshold identified at 400 °C. The effect of inclination angle on the failure mode of the specimens is more pronounced than that of temperature; as the inclination angle increases, the failure mode transitions from splitting failure to shear failure at any given temperature. Acoustic emission results reveal that the specimens’ microcrack initiation (CI) and damage (CD) thresholds reduce with increasing inclination, while the corresponding shear stress increases. As temperature rises, the CI and CD thresholds exhibit an initial increase attended by a decrease. Finally, founded on the experimental findings, a multivariate equation was established to accurately predict the peak compressive strength and elastic modulus about θ and T. The results of this study provide valuable insights and references for the construction of underground thermal engineering under complex conditions.

Comparative analysis of airflow dynamics and sputum expulsion during cough in healthy and bronchial stenosis respiratory tract

Bronchial stenosis impacts cough mechanisms and respiratory function. This study used MIMICS and Fluent to construct and simulate a 3D airway model of an elderly female patient with bronchial stenosis. Utilizing dynamic mesh and fluid-structure interaction, airflow during coughing was analyzed, including velocity, wall shear stress, and deformation. The Eulerian wall film model quantified sputum dynamics, revealing that stenosis increases shear stress, exacerbates deformation, and reduces sputum expulsion efficiency, particularly for medium to high viscosity sputum. These findings deepen understanding of bronchial stenosis pathophysiology and offer insights for improving diagnosis, treatment, and prevention of respiratory diseases.

Numerical analysis of the hydraulic fracture propagation behavior encountering gravel in conglomerate reservoirs

Hydraulic fracturing, which forms complex fracture networks, is a common technique for efficiently exploiting low-permeability conglomerate reservoirs. However, the presence of gravel makes conglomerate highly heterogeneous, endowing the deformation, failure, and internal micro-scale fracture expansion mechanisms with uniqueness. The mechanism of fracture expansion when encountering gravel in conglomerate reservoirs remains unclear, challenging the design and effective implementation of hydraulic fracturing. This paper utilizes the Abaqus platform and adopts the maximum circumferential strain fracture criterion to establish a two-dimensional fluid-solid-structure coupled fracture expansion model. The study investigates the impact of permeability, Young’s modulus, in-situ stress difference, and incidence angle on the fracture expansion behavior in the presence of gravel. The results indicate that low-permeability gravel induces pressure changes near the fracture tip, like 13% pore pressure increase and stress reductions. Shear stress on the gravel surface rises by 28.3%, and choosing layers with a smaller permeability gap between matrix and gravel can reduce complex near-well fractures. High Young’s modulus gravel has a stress shielding effect around fractures, which is direction-dependent, with over tenfold stress variations. It causes a 60.7% increase in peak shear stress on the gravel surface, exacerbating fracture complexity and reducing extension distance, and a greater strength disparity between gravel and matrix enhances this effect. A high in-situ stress difference (over 8 MPa) weakens gravel-caused stress shielding, leading to stable fracture propagation with a single morphology and increased extension distance, though not favoring complex network formation. As the incidence angle rises, the gravel’s impact on stress and seepage fields weakens, but the risk of shear failure on the cementation interface increases. The findings provide a basis for optimizing operations in such reservoirs considering the various properties of gravel and their effects on fluid flow and fracture behavior.

Comparative investigation of the energy consumption and heat transfer characteristics of Uni-modal and Bi-modal slurry flow through a straight pipe

Slurry transport via pipelines is a widely used method across various industries globally. While extensive research exists on optimizing parameters for efficient slurry pipeline systems, studies on the optimal combination of two mixtures to maximize efficiency in bi-modal slurry transport remain limited. This research addresses the gap by developing a three-dimensional computational model to examine the energy, transport, and thermal characteristics of mono-dispersed and bi-modal slurries. The model compares these characteristics with the behavior of pure water flowing through a straight pipe, providing insights into how slurry composition affects flow dynamics and heat transfer. The study investigates slurry flow through a round straight pipe at Reynolds numbers ranging from 128,035 to 320,000 and volumetric concentrations (Cvf = 10–40 %). The bi-modal slurry consists of silica sand and fly ash mixtures in proportions of 85:15 and 65:35, while the uni-modal slurry has proportions of 100:0 and 0:100. Computational results indicate that the 65:35 mixture, flowing at Re = 128035 and Cvf = 10–20 % achieves the lowest pressure drop and specific energy consumption (SEC), enhancing transport efficiency. Furthermore, wall shear stress (WSS) and energy consumption increase with higher Reynolds numbers and volumetric concentrations. Notably, the 100:0 mixture achieves the highest convective heat transfer coefficient, which increases with Reynolds number and volumetric concentration.

Increasing the operating time of hollow fiber membrane bundles used for water ultrafiltration

In order to increase the interval between cleanings of a hollow fiber membrane bundle (HFMB) used for water ultrafiltration, a numerical study and an experimental test were conducted. The relation between the water flow rate and shear stress along the hollow fiber membrane wires (HFMW) was studied for three geometries. Three angles (α = 900,450,00) for the intake flow pipe (di = 25 mm) against the horizontal axis of a cylinder (Dc = 100 mm; L = 600 mm) containing one hollow fiber membrane wire (dw = 1 mm) were chosen for the numerical investigation; five different water flow rates (Q = 8…16 l/min) were considered. The values for the shear stresses along one membrane wire placed along the cylinder's central axis were computed. The findings show that the best geome1try for enhanced shear stress is obtained for α = 00. For this geometry a mean value of 1.1 Pa for the shear stress was obtain along the first 1/3 of the membrane wire at a minimum flow rate of Q = 8 l/min. Higher values for water flow rates do raise shear stress but increased energy consumption is needed. The tests were carried out on a HFMB with molecular weight cut-off (MWCO) of 0.097 μm, that was put in a glass cylinder with a horizontal axis, for μ = 900, μ = 00, and Q = 8 l/min. The results confirmed the conclusions of the numerical study i.e. the filtering capacity of the membrane was maintained higher by 6-6.5% for α = 00 comparing to α = 900 due to shear stress increase. For the flow rate of Q = 12 l/min the filtering capacity of the membrane did not increased. The study confirmed the hypothesis that for certain geometries there could be settle down optimum flow rates to minimize energy consumption during membrane operation but comprehensive research is needed.

Role of TGF-β1/Smad3 signalling pathway in renal tubulointerstitial fibrosis and renal damage in elderly rats with isolated systolic hypertension induced by increased pulse pressure

Objective Elevated systolic blood pressure and increased pulse pressure are closely associated with renal damage; however, the exact mechanism remains unclear. Therefore, we investigated the effects of increased pulse pressure on tubulointerstitial fibrosis and renal damage in elderly rats with isolated systolic hypertension (ISH). Additionally, the role of renal tubular epithelial-mesenchymal transition (EMT) and its upstream signalling pathways were elucidated. Methods Ten-month-old male rats were randomly divided into control and ISH groups, with seven rats in each group administered warfarin and vitamin K1 for 6 weeks. Blood pressure, renal function, mean blood flow in the common iliac artery, and diastolic vessel diameter were assessed, and the rat kidney medulla was collected for histological, genetic, and protein level analysis. Results Increased pulse pressure, abnormal renal function, and increased shear stress were detected in rats with ISH. Histology assessments revealed fibrosis in the interstitium of ISH rats. Epithelial marker E-cadherin protein expression was decreased, while the protein expression of interstitial markers α-SMA and Vimentin was increased, and transforming growth factor (TGF)-β1/Smad3 signalling was upregulated in the kidney tissue of ISH rats. Conclusions Increased pulse pressure in elderly rats with ISH caused an increase in shear stress. These effects led to the development of EMT and the activation of its upstream TGF-β1/Smad3 signalling pathway, ultimately leading to renal tubular interstitial fibrosis causing renal injury.

Shear stress controls prokaryotic and eukaryotic biofilm communities together with EPS and metabolomic expression in a semi-controlled coastal environment in the NW Mediterranean Sea

While waves, swells and currents are important drivers of the ocean, their specific influence on the biocolonization of marine surfaces has been little studied. The aim of this study was to determine how hydrodynamics influence the dynamics of microbial communities, metabolic production, macrofoulers and the associated vagile fauna. Using a field device simulating a shear stress gradient, a multi-scale characterization of attached communities (metabarcoding, LC–MS, biochemical tests, microscopy) was carried out for one month each season in Toulon Bay (northwestern Mediterranean). Shear stress appeared to be the primary factor influencing biomass, EPS production and community structure and composition. Especially, the transition from static to dynamic conditions, characterized by varying shear stress intensities, had a more pronounced effect on prokaryotic and eukaryotic beta-diversity than changes in shear stress intensity or seasonal physico-chemical parameters. In static samples, mobile microbe feeders such as arthropods and nematodes were predominant, whereas shear stress favored the colonization of sessile organisms and heterotrophic protists using the protective structure of biofilms for growth. The increase in shear stress resulted in a decrease in biomass but an overproduction of EPS, specifically exopolysaccharides, suggesting an adaptive response to withstand shear forces. Metabolite analysis highlighted the influence of shear stress on community dynamics. Specific metabolites associated with static conditions correlated positively with certain bacterial and algal groups, indirectly indicating reduced grazer control with increasing shear stress.

Developing a Flow-Resistance Module for Elucidating Cell Mechanotransduction on Multiple Shear Stresses.

Fluid shear stress plays a pivotal role in regulating cellular behaviors, maintaining tissue homeostasis, and driving disease progression. Cells in various tissues are specifically adapted to physiological levels of shear stress and exhibit sensitivity to variations in its magnitude, highlighting the requirement for a comprehensive understanding of cellular responses to both physiologically and pathologically relevant levels of shear stress. In this study, we developed an independent upstream flow-resistance module with high fluidic resistances comprising three microchannels. The validity of the flow-resistance module was confirmed via computational fluid dynamics (CFD) simulations and flow calibration experiments, resulting in the generation of steady wall shear stresses ranging from 0.06 to 11.57 dyn/cm2 within the interconnected cell culture chips. Gene expression profiles, cytoskeletal remodeling, and morphological changes, as well as Yes-associated protein (YAP) nuclear translocation, were investigated in response to various shear stresses to authenticate the reliability of our experimental platform, indicating an increasing trend as the shear stress increases, reaching its maximum at various shear stresses. Our findings suggest that this flow-resistance module can be readily employed for precise characterization of cellular responses under various shear stresses.

Hybrid Modeling for In Situ Artificial Fish Spawning Ground Stabilization

ABSTRACTErosion generally reduces the resilience of replenished gravel in rivers. As a result, structures are sometimes added to modify the upstream flow and stabilize artificial spawning grounds. In particular, rows of boulders can be placed around the replenishment area to limit the transport of replenished gravel during flood events. This study aims to optimize the arrangement of these rows, based on field experiments as well as physical and numerical models. A combined hydro‐sedimentary numerical model is calibrated and validated by comparing simulated and measured morphological evolutions in nine laboratory experiments. The results show that boulders positioned downstream of the replenishment slow down the flow above the replenishment, decreasing shear stress over the gravel. The stabilization efficiency depends on both the positioning of the boulders and the arrangement of the replenished surface. To achieve sustainable spawning, prospective scenarios using the numerical model highlight the need to limit the width of the replenishment area. Experiments demonstrated that when the replenishment area spans the entire width flume, the erosion rate is significantly higher compared to a narrower replenishment area placed close to the edges. This effect is attributed to increased flow velocities in the center of the channel, leading to increased shear stress and gravel erosion.

Analysis of MHD slip blood flow through a constricted artery filled with a porous medium of variable permeability: Applications in Biomedical Engineering

The primary goal of this research is to investigate the impact of partial slip and variable permeability on the dynamics of blood flow in a constricted artery filled with a porous medium, and to assess the influence of an externally applied magnetic field on the blood flow. The blood is modeled as an incompressible Newtonian fluid. By employing a stream function formulation, the coupled nonlinear flow equations are transformed into a single dimensionless equation, which is solved using the Adomian decomposition method (ADM). Key parameters such as the slip parameter, permeability parameter, Hartmann number, and Reynolds number are examined in relation to their effects on the flow field. The results reveal significant changes in blood flow dynamics within the stenosed section of the artery, particularly due to the incorporation of variable permeability in the porous medium and the partial slip condition along the arterial wall in the presence of the magnetic field. Notable outcomes include the escalation in axial velocity with increasing permeability and slip, as well as the formation of flow separation and recirculation zones in regions of high stenosis height. Additionally, the magnetic field was found to suppress axial velocity while increasing shear stress, particularly near the throat of the stenosis. These findings provide deeper insights into how variable permeability and slip conditions influence blood flow in clinical scenarios such as magnetic resonance imaging (MRI). Importantly, the results in specific cases align with established findings from existing literature, validating the approach and offering new contributions to the understanding of MHD flow in constricted arteries.

Interaction of a Taylor bubble with the liquid–liquid interface in a notched tube

Injection of air into stratified liquids for improved mixing and for the removal of oil droplets from water is some well-established applications for augmentation of heat and mass transfer and purification of water. The present study investigates the dynamics of a Taylor bubble passing through the liquid–liquid interface in a vertical tube provided with rounded notch of different radii using the Eulerian approach-based volume of fluid method. The complete bypass of the Taylor bubble across the liquid–liquid interface and the notch is observed for dimensionless notch radius, r* = 0.0388, whereas the Taylor bubble has bypassed in the form of smaller volumes periodically pinched-off near the notch for higher notch radius. The drag coefficient has significantly increased during the bypass of the bubble across the liquid–liquid interface, its peak has an order of magnitude ≅102 for r* = 0.0388, and it is ≅ 103 for a larger notch radius. This increase in the drag coefficient is also manifested in terms of significant increase in the wall shear stress and capillary pressure drop across the notch. The increase in liquid viscosity ratio has resulted in a slight increase in pinched-off bubble volumes and their surface oscillations.

The importance of hemodynamics in stented vessels: A conceptual model for predicting restenosis using the time-averaged shear stress

The role of hemodynamics has often been overlooked in mathematical modeling aimed at replicating the restenosis process in stented arteries. This study seeks to address this gap by proposing a simplified model of tissue growth driven by the distribution of mean shear stress acting on the vessel wall. Using an iterative sequence of three-dimensional Computational Fluid Dynamics simulations applied to idealized coronary and femoral arteries, combined with a semi-empirical parametrization of endothelium growth, we demonstrated that the progression of restenosis can be effectively modeled and differentiated according to the intensity of time-varying flow velocities. Notably, restenosis develops faster in the femoral artery (approximately 17 days) compared to the coronary artery (approximately 25 days). The progress of tissue accretion is well defined by the evolution of time-averaged wall shear stress. After an initial decrease (triggering phase), significant increases in wall shear stress are observed during the main accretion phase until the shear stress eventually recovers a sufficient level to arrest the process (stabilization phase). This process, attributed to varying hemodynamic conditions within the stent, highlights the significant influence of local flow dynamics and emphasizes the necessity of accurately modeling both the anatomical structure and the corresponding hemodynamics of arteries when predicting in-stent restenosis.

Evaluation of the effect of hemodynamic factors on retinal microcirculation by using 3D confocal image-based computational fluid dynamics.

To investigate local hemodynamic changes resulting from elevated intraocular pressure (IOP) in different vasculature networks using a computational fluid dynamics model based on 3D reconstructed confocal microscopic images. Three-dimensional rat retinal vasculature was reconstructed from confocal microscopy images using a 3D U-Net-based labeling technique, followed by manual correction. We conducted a computational fluid dynamics (CFD) analysis on different retinal vasculature networks derived from a single rat. Various venule and arteriole pressures were applied to mimic the effects of elevated intraocular pressure (IOP), a major glaucoma risk factor. An increase in IOP typically correlates with a decrease in venous pressure. We also varied the percentage of capillary dropout, simulating the loss of blood vessels within the capillary network, by reducing the volume of the normal capillary network by 10%, 30%, and 50%. Based on the output of the CFD analysis, we calculated velocity, wall shear stress (WSS), and pressure gradient for different vasculature densities. Arteriolar pressure, venular pressure, and capillary dropout appear to be important factors influencing wall shear stress in the rat capillary network. Our study revealed that the pressure gradient between arterioles and venules strongly affects the local wall shear stress distribution across the 3D retinal vasculature. Specifically, under a pressure gradient of 3,250Pa, the wall shear stress was found to vary between 0 and 20Pa, with the highest shear stress observed in the region of the superficial layer. Additionally, capillary dropout led to a 25% increase or decrease in wall shear stress in affected areas. The hemodynamic differences under various arteriole and venule pressures, along with different capillary dropout conditions, could help explain the development of various optic disorders, such as glaucoma, diabetic retinopathy, and retinal vein occlusion.

Failure characteristics and stress field distribution law of roadway in downward mining of deep close distance coal seam

Deep close distance coal seam mining is affected by the goaf of upper coal and remaining coal pillar, and the roadway of lower coal is difficult to maintain stability. By means of theoretical analysis, physical simulation test and numerical simulation, this paper analyzes the failure characteristics of roadway in deep close distance coal seam and the evolution law of stress field, and optimizes the reasonable layout of lower coal roadway. The results show that: (1) The analytical formula of the evolution of the floor principal stress difference with depth is derived theoretically, and the distribution law of the shear stress of the rock mass in the floor of the coal seam is obtained. (2) The airway below the goaf can maintain good stability. High stress accumulation phenomenon occurs in the transport roadway below the coal pillar, which can not keep stable. (3) Due to the stress difference under the goaf and the coal pillar, the shear stress increases and the rock mass is damaged, and the left gang of the transport roadway is prone to instability destruction. (4) By comparing the distribution characteristics of plastic zones of transport roadway at different locations, it is determined that the transport roadway is more appropriate to be arranged 45 m below the coal pillar from the goaf.

Turbulent features of nearshore wave–current flow

Abstract. Waves and currents influence nearly all nearshore physical processes. Their complex interaction gives birth to complex turbulence features that are far from being completely understood. In this regard, previous studies mainly focused on mean flow or inferred turbulent features from averaged velocities, seldom examining turbulent fluctuations. Moreover, the dynamics of wave–current flow have mostly been replicated in experimental channel setups, i.e., overlooking the natural occurrence of waves and longshore currents intersecting at a near-orthogonal angle. In the present work, the hydrodynamics of near-orthogonal wave–current interaction are investigated through a physical model study. Experiments were carried out in a laboratory basin in the presence of fixed sand and gravel beds, where current-only, wave-only, and combined flow tests were performed. Flow velocities were measured by means of acoustic Doppler velocimeters, through which time-averaged, phase-averaged, and turbulent velocities were obtained. Results revealed two main features of the wave–current flow. First, we observed that the superposition of waves does not necessarily induce an increase in the current bed shear stresses. Indeed, depending on bed roughness, current freestream velocity and wave orbital velocity, enhancements or reductions of the current bed shear were observed. Moreover, application of quadrant analysis revealed a periodic evolution of the current turbulent bursts. Specifically, the number of current turbulent ejections and sweeps is reduced or increased as the wave phase progresses from antinodes to nodes and from nodes to antinodes, respectively.

A Century of Deformation and Stress Change on Kīlauea's Décollement

AbstractKīlauea Volcano on Hawai'i Island is host to a complex volcanic and interwoven fault system. Over the last ∼120 years, a range of seismic events, including large earthquakes such as the 1975 7.7 Kalapana earthquake, creep, and slow slip events, have occurred along the décollement underlying Kilauea's south flank. We explore both the deformation and stress changes of Kīlauea from 1896 to 2018 by collating six geodetic data sets and creating an analytical model to determine the dominant deformation sources (i.e., fault planes, rifts, magma chambers) driving this system at different times. The 1975 Kalapana earthquake significantly altered the region's state of stress and deformation; we find the average slip along the décollement was reduced from 10 cm/yr prior, to 4 cm/yr after the rupture. Prior to 1975 no slip is resolved along the décollement where the earthquake nucleated, suggesting that this portion may have been locked leading up to the rupture. After 1975, décollement slip overall is smaller and more irregular, suggesting increased control by spatial variation of mechanical properties. We find increases in shear stress along the Kīlauea décollement and a decrease in normal compressive stress within the East Rift Zone prior to the Kalapana earthquake, creating favorable conditions for failure of the décollement and subsequent magmatic intrusion.

Structure and formation of mud volcanoes in the South Caspian Basin according to seismic data

The South Caspian Basin (SCB) constitutes a classic province to study mud volcanoes and their associated processes. Approximately 280 active mud volcanoes have been documented in the offshore and the onshore areas of Azerbaijan, emitting water, hydrocarbons (oil and mainly methane), and fluidized muds that transport solid fragments from deep sedimentary sequences. Seismic characteristics of mud volcano systems in the Azerbaijan area of the SCB are used to address (1) the nature of the mud volcano source layer; (2) the internal geometry of the feeder systems; and (3) the processes associated with shale mobilization and extrusion. We confirm that the source layer is mainly the Maykop Suite (Oligocene-Lower Miocene), which is a thick (≤3 km) and deep (>10 km) clayey sequence rich in organic matter. This layer was quickly buried due to basin subsidence and the rapid deposition (since the Middle Miocene) of thick fluvio-lacustrine sediments of the Productive Series (PS) (Upper Miocene-Upper Pliocene), which contributed to the creation of high pore pressures and the transformation of organic matter into methane (through thermal cracking). Since the Middle Miocene and more important, during the Upper Pliocene, the Maykop shales mobilized due to an increase in shear stresses and pore pressures, which promoted a decrease in effective stresses and, as a consequence, facilitated the achievement of critical state conditions in the shales that began to flow. This process, repeated over time, allowed multiple pulses of shale mobilization to originate (as in a loading piston system). Shale piercing transporting deep-sourced fluids (and hydrocarbons) was carried out through fractures in the outer arc of anticlines, forming subvertical feeder systems. The mobilized hydrocarbons and fluids also recharged some of the younger and more permeable layers of the PS, creating shallower reservoirs in the vicinities of the mud volcano structures.

Evaluating drinking water treatment residuals as an in-situ capping material for metal-contaminated sediments

This study evaluated drinking water treatment residuals (DWTR) as an in-situ capping material for metal-contaminated sediments using Gust-chamber experiments. Metal release from non-capped and DWTR-capped sediments was measured under increasing shear stress (τ) from 0.05 to 0.4 Pa. Fathead minnow (FHM) juveniles (Pimephales promelas) were exposed to water from these sediments in 96-h bioassays to assess DWTR's efficacy in reducing metal toxicity. Sand was used as an inert capping material for comparison. Diffusive gradients in thin films (DGT) assessed DWTR's impact on vertical metal concentration profiles in sediment pore water and overlying water, with concentrations determined by ICP-MS. Without capping, increasing τ raised metal concentrations in the overlying water from 45 to 95 mg/L for Cd and Zn, 4–10 mg/L for Cu, and 2–4 mg/L for Pb. Sand capping reduced these levels, with Cd and Zn ranging from 4 to 21 mg/L, Cu from 0.26 to 0.63 mg/L, and Pb from 0.051 to 0.23 mg/L. DWTR capping significantly lowered metal concentrations in the overlying water, with Cd ranging from 1 to 8 μg/L, Zn from 30 to 40 μg/L, Cu from 2.5 to 5 μg/L, and Pb from 1 to 2 μg/L. Therefore, beyond the physical barrier effect, the DWTR cap immobilizes metals through other mechanisms such as sorption and precipitation. Bioassays showed that DWTR significantly decreased metal toxicity to FHM, while sand-capped and non-capped sediments caused 100% mortality. DGT confirmed DWTR reduced metal fluxes at the sediment-water interface by up to two orders of magnitude.

Uncovering the Fracturing Mechanism of Granite Under Compressive–Shear Loads for Sustainable Hot Dry Rock Geothermal Exploitation

Shear-dominated hazards, such as induced earthquakes, pose an escalating threat to the sustainability and safety of the geothermal exploitation. Variations in fault orientations and compression–shear stress ratios exert a profound influence on the failure processes underlying these disasters. To better understand these effects on the shear failure mechanisms of hot dry rocks, mode-II fracturing tests on granites were conducted at varying loading angles (specifically, 55°, 60°, 65°, and 70°). These tests were accompanied by a comprehensive analysis of the mechanical properties, energy dissipation behavior, acoustic emission (AE) responses, and digital image correlation (DIC)-extracted displacement fields. The tensile–shear properties of stress-induced microcracks were discerned via AE characteristic parameter analysis and DIC displacement decomposition, and the mode-II fracture energy release rate was quantitatively characterized. The results reveal that with increasing compression–shear loading angles, the mechanical properties of granites are weakened, and the elastic strain energy at peak stress gradually decreases, while the slip-related dissipated energy increases. Throughout the fracturing process, the AE count progressively climbs and reaches a peak near catastrophic failure, with an upsurge in low-frequency and high-amplitude AE events. Microcrack distribution concentrates aggregation along the shear plane, reflecting the emergent displacement discontinuities evident in DIC contours. Both the AE characteristic parameter analysis and DIC displacement decomposition demonstrate that shear-sliding constitutes the paramount mechanism, and the fraction of shear-oriented microcracks and the ratio of tangential versus normal displacement escalate with increases in shear stress. This analysis is supported by the heightened propensity for transgranular microcracking events observed through scanning electron microscopy. As the shear-to-compression stress increases, the energy concentration along the shear band intensifies, with the gradient of the fitting line between cumulative AE energy and slip displacement steepening, indicative of a heightened mode-II energy release rate. These results contribute to a deeper understanding of the mode-II fracture mechanism of rocks, thereby providing a foundational basis for early warnings of shear-dominant geomechanical disasters, and improving the safety and sustainability of subsurface rock engineering.