Search Results (510)

Accurate differentiation between microseismic signals induced by hydraulic fracturing and those from roof fracturing is vital for optimizing fracturing efficiency, assessing roof stability, and mitigating mining-induced hazards in coal mining operations. We propose an automatic identification method for microseismic signals generated by hydraulic fracturing in coal seam roofs. This method first transforms the microseismic signals induced by hydraulic fracturing and roof fracturing into time-frequency feature images using the Frequency Slice Wavelet Transform (FSWT) technique, and then employs a sliding window (Swin) Transformer network to automatically identify and classify these two types of time-frequency feature maps. A comparative analysis is conducted on the performance of three methods—including the signal energy distribution method, Residual Network (ResNet) model, and VGG Network (VGGNet) model—in identifying microseismic signals from hydraulic fracturing in coal seam roofs. The results demonstrate that the Swin Transformer recognition model combined with FSWT achieves an accuracy of 92.49% and an F1-score of 92.96% on the test set of field-acquired microseismic signals from hydraulic fracturing and roof fracturing. These performance metrics are significantly superior to those of the signal energy distribution method (accuracy: 64.70%, F1-score: 64.70%), ResNet model (accuracy: 88.04%, F1-score: 89.24%), and VGGNet model (accuracy: 88.47%, F1-score: 89.52%). This advancement provides a reliable technical approach for monitoring hydraulic fracturing effects and ensuring roof safety in coal mines. Full article

Tight conglomerate reservoirs are characterized by dense lithology, significant compositional contrasts between cement and gravel, strong stress gravel content, strong heterogeneity, and uneven spatial distribution, which collectively result in low porosity, complex pore–throat structures, and low permeability. After hydraulic fracturing, the stress sensitivity of tight conglomerate reservoirs is jointly governed by the rock matrix and induced fractures. In this study, the Mahu tight conglomerate reservoir in the Xinjiang Oilfield was selected as the research target. Stress sensitivity experiments were conducted on conglomerate matrix cores and on cores with varying fracture conditions. After stress loading, the degrees of permeability damage of the matrix, through-fracture, double short-fracture, and microfracture cores were 41%, 69%, 93%, and 97%, respectively. The matrix exhibited moderate-to-weak stress sensitivity, the through-fracture cores showed moderate-to-strong stress sensitivity, while the double short-fracture and microfracture cores exhibited strong stress sensitivity. Experimental results indicate that when fractures are present, the stress sensitivity of the core is primarily controlled by fracture closure and matrix compression. As fracture development increases, core permeability is significantly enhanced; however, stress sensitivity also increases accordingly. Under net stress, gravel protrusions embed into fracture surfaces, reducing surface roughness, while irreversible alteration of fracture geometry becomes the dominant factor driving stress sensitivity in fractured cores. These findings provide a scientific basis for predicting stress-sensitivity-induced damage in tight conglomerate reservoirs. Full article

This article presents the results of an experimental study on the hydrodynamics of the coolant at the inlet of the fuel assembly in the RITM reactor core. The importance of these studies stems from the significant impact that inlet flow conditions have on the flow structure within a fuel assembly. A significant variation in axial velocity and local flow rates can greatly affect the heat exchange processes within the fuel assembly, potentially compromising the safety of the core operation. The aim of this work was to investigate the effect of different designs of orifice inlet devices and integrated absorber grids on the flow pattern of the coolant in the rod bundle of the fuel assembly. To achieve this goal, experiments were conducted on a scaled model of the inlet section of the fuel assembly, which included all the structural components of the actual fuel assembly, from the orifice inlet device to the second spacer grids. The test model was scaled down by a factor of 5.8 from the original fuel assembly. Two methods were used to study the hydrodynamics: dynamic pressure probe measurements and the tracer injection technique. The studies were conducted in several sections along the length of the test model, covering its entire cross-section. The choice of measurement locations was determined by the design features of the test model. The loss coefficient (K) of the orifice inlet device in fully open and maximally closed positions was experimentally determined. The features of the coolant flow at the inlet of the fuel assembly were visualized using axial velocity plots in cross-sections, as well as concentration distribution plots for the injected tracer. The geometry of the inlet orifice device at the fuel assembly has a significant impact on the pattern of axial flow velocity up to the center of the fuel bundle, between the first and second spacing grids. Two zones of low axial velocity are created at the edges of the fuel element cover, parallel to the mounting plates, at the entrance to the fuel bundle. These unevennesses in the axial speed are evened out before reaching the second grid. The attachment plates of the fuel elements to the diffuser greatly influence the intensity and direction of flow mixing. A comparative analysis of the effectiveness of two types of integrated absorber grids was performed. The experimental results were used to justify design modifications of individual elements of the fuel assembly and to validate the hydraulic performance of new core designs. Additionally, the experimental data can be used to validate CFD codes. Full article

This study aims to investigate the sedimentary facies characteristics of the coal seam roof in the Qinglong and Longfeng coal mines and their control over water abundance. By collecting core samples and well logging data from both mining areas, multiple methods were employed, including core observation, thin-section analysis, sedimentary microfacies distribution mapping, nitrogen adsorption tests, and nuclear magnetic resonance analysis, to systematically analyze the depositional environments, types of sedimentary microfacies, and their distribution patterns. Results indicate that the roof of Qinglong Coal Mine is predominantly composed of sandy microfacies with well-developed faults, which not only increase fracture porosity but also provide water-conducting pathways between surface water and aquifers, significantly enhancing water abundance. In contrast, Longfeng Coal Mine is characterized mainly by muddy microfacies, with small-scale faults exhibiting weak water-conducting capacity and relatively low water abundance. Hydrochemical analysis indicates that consistent water quality between Qinglong’s working face, karst water, and goaf water confirms fault-induced aquifer–surface water connectivity, whereas Longfeng’s water quality suggests weak aquifer–coal seam hydraulic connectivity. The difference in water hazard threats between the two mining areas primarily stems from variations in sedimentary microfacies and fault structures. Full article

In response to the problems encountered during the pressure-driven oil recovery process in low-permeability oil reservoirs, such as slow pressure transmission, poor liquid supply, vulnerability of the reservoir to damage, and difficulties in injection and production, in order to achieve the goal of high-quality water injection development, based on the theories of rock mechanics and seepage mechanics, combined with large-scale physical model experiments, acoustic emission crack monitoring, and microscopic scanning technology, an oil reservoir and fracture model was established to conduct a feasibility analysis of pressure-driven assisted pressure reduction and enhanced injection, and it was successfully applied in the exploration and development practice of the Shengli Oilfield. The research shows the following: (1) During the pressure-driven process, the distribution of the fracture network system is relatively limited. In the early stages of the process, there will be minor fractures, but they do not communicate or activate effectively. The improvement of physical properties and pore-throat structure is negligible. As the injection flow rate increases, the effective fracture network system begins to be established, and the range of fluid coverage begins to expand. With the progress of the pressure-driven process, the hydraulic fractures gradually extend, the number of activated original fractures gradually increases, the communication area between hydraulic fractures and original fractures gradually increases, and the reservoir modification effect gradually improves. (2) Based on the compression cracking experiment of large object molds, it is concluded that generating effective micro-cracks and activating them to form efficient diversion channels is the key to pressure flooding injection. Combining the mechanical characteristics of the rock in the target layer to precisely control the injection speed and injection pressure can maximize the fracture network, thereby improving the reservoir to achieve the purpose of pressure reduction and injection increase. (3) Different pressure flooding injection parameters were set for the low-permeability oil reservoirs in the study area to simulate the fracture network expansion. Finally, it was concluded that the optimal injection speed for fracture expansion was 1.2 m³/min and the optimal total injection volume was 20,000 m³. Through research, the mechanism of pressure-driven injection and the extent of reservoir modification caused by this pressure-driven process have been enhanced in terms of understanding. Full article

Landslides are a major natural hazard capable of causing severe damage to infrastructure, ecosystems, and human life. They result from complex interactions of geological, hydrological, and environmental factors, with soil properties playing a crucial role by influencing the mechanical behavior and moisture dynamics of slope materials that drive initiation and progression. In South Africa, few studies have examined soil influences on landslide susceptibility, and none have been conducted in the Eastern Cape Province. This study investigated the role of soil physical and chemical properties in landslide susceptibility by comparing profiles from landslide scars and stable sites in the Port St. Johns and Lusikisiki region. Samples from topsoil and subsoil horizons were analyzed for soil organic matter (SOM), cation exchange capacity (CEC), saturated hydraulic conductivity (Ksat), exchangeable sodium adsorption ratio (SARexc), and texture. Statistical analyses included the Shapiro–Wilk test to evaluate data normality. For inter-profile comparisons, Welch’s t-test was applied to normally distributed data, while the Mann–Whitney U test was used for non-normal distributions. Intra-profile differences across more than two groups were assessed using the Kruskal–Wallis test for the non-normally distributed data. Results showed that landslide-prone soils had higher SOM, CEC, and Ksat in topsoil, promoting moisture retention and rapid infiltration, which favor pore pressure build-up and slope failure. Non-landslide soils displayed higher sodium-related indices and finer textures, suggesting more uniform water retention and resilience. Vertical variation in landslide soils indicated hydraulic discontinuities, fostering perched saturation zones. Findings highlight landslide initiation as a product of interactions between hydromechanical gradients and chemical dynamics. Full article

The water retention and permeability characteristics of loess are core factors governing geological disaster prevention and engineering stability in the loess regions of northwest China. This study focuses on Yangling loess, systematically conducting soil water characteristic curve (SWCC) measurements and saturated permeability tests under different initial compaction degrees and water contents using a pressure plate apparatus and a TST-55 permeameter. By combining fitting analyses of the Gardner, Fredlund–Xing, and Van Genuchten SWCC models, the study reveals the influence mechanism of initial conditions on the water retention properties of Yangling loess. Furthermore, the unsaturated hydraulic conductivity of loess was predicted using the Van Genuchten–Mualem model. Finally, a quantitative relationship model between hydraulic conductivity and multiple factors (initial compaction degree, water content, and matric suction) was constructed using the response surface methodology. The results indicate the following: (1) A higher initial compaction degree and water content lead to a higher air entry value of loess, resulting in stronger water retention capacity. Among the three models, the Van Genuchten model exhibits the optimal fitting effect for the SWCC of Yangling loess. Its parameter a (related to the air entry value) decreases significantly with increasing compaction degree, while parameter n (pore size distribution index) increases linearly. The SWCC model, considering compaction degree, established based on these findings, can accurately predict the water retention characteristics in the high suction range (0~1200 kPa). This model’s precision in the high-suction segment is particularly valuable, as it addresses a critical range for engineering applications where soil behavior transitions from near-saturated to highly unsaturated states. (2) When loess transitions from a saturated to an unsaturated state, the hydraulic conductivity decreases up to 10⁴ times. Both increased initial compaction degree and water content lead to a significant reduction in hydraulic conductivity. This drastic reduction highlights the sensitivity of loess permeability to saturation changes, which is attributed to the rapid reduction in interconnected pore channels as soil suction increases and pore spaces are filled or compressed under higher compaction. (3) The response surface prediction model quantitatively reveals the influence weights of various factors on hydraulic conductivity in the order of matric suction > initial compaction degree > initial water content. The model exhibits a high coefficient of determination (R² = 0.9861), enabling rapid and accurate prediction of the hydraulic conductivity of Yangling loess. This high precision confirms that the model effectively captures the complex interactions between the factors, providing a reliable tool for practical engineering calculations. This study provides a new model and experimental basis for the accurate prediction of unsaturated loess hydraulic properties. The proposed SWCC model, considering compaction degree and the response surface model for hydraulic conductivity, offers practical tools for engineers and researchers, facilitating more precise design and risk assessment in collapsible loess areas. Full article

Sediment buildup in storage tanks over extended operation periods may compromise their efficiency. To prevent pollutant deposition in storage tanks and enhance their hydraulic self-cleaning efficiency, this study addressed the unique structural configuration of lateral flow in storage tanks. Conducting numerical simulations to investigate the hydraulic characteristics within storage tanks, an integrated approach combining physical experiments and response surface methodology (RSM) was employed to optimize flow distribution. Key findings reveal that tangential and normal velocity differences lead to flow distribution nonuniformity, exacerbated by increased inflow Froude number (F_r) and reduced relative weir height (h_i). Based on the flow-splitting mechanism, an optimized “combined raised baffle” was proposed. Through single-factor experiments, Plackett–Burman (PB) screening, and RSM experiments, the optimal combination for maximal flow uniformity was determined as h₁ = 1.27, h₂ = 1.23, and h₃ = 1.24, achieving an 87.18% improvement in Q_y compared to the initial design. After optimization, the incoming flow pattern of the inlet channel of the storage pond was improved, and the difference between tangential and normal flow velocity in the flow field was significantly reduced. This research provides a novel approach and methodological paradigm for optimizing storage tanks and other hydraulic structures, demonstrating significant academic and engineering value. Full article

Water management in arid regions, such as Arizona, is critical due to increasing demands from the urban, agricultural, and recreational sectors. In this study, Finite element analysis software COMSOL Multiphysics (COMSOL 6.3) is used to quantify water demands in Chandler, Arizona. Evapotranspiration from vegetation and pools is studied. Factors are divided into environmental (temperature, humidity, wind speed) and soil-related properties (moisture content, hydraulic conductivity), which are modeled and used to estimate annual water losses. This study represents the first comprehensive investigation of the usage across several main categories at Arizona. Results indicate that pools contribute 61% of surface water evaporation. Annual water demand in Chandler for 2024 peaks at 425,000 m³ in June, with irrigation for vegetation dominating consumption. Validation against experimental data confirms model accuracy. This simulation work aims to provide scalable insights for water management in arid urban environments. Based on the simulation, various solutions were proposed to reduce water consumption and minimize water loss. Some active measures include the optimization of irrigation time and frequency based on dynamic and real-time environmental conditions. The proposed solution can help minimize the water consumption while maintaining the water demands for plant life sustenance. Other passive measures include the modification of localized environmental conditions to reduce water evaporation. In particular, it was found that fence installation can significantly change the water vapor flow and distribution close to the water surface and suppress the water evaporation by simply lowering the wind speed right above the water surface. A logical takeaway is that evaporation would also decrease when pools are built with deeper water surfaces. Full article

To address the difficulty in eliminating low-frequency vibrations in the hydraulic pipelines of large marine vessels, this study first investigates the vibration characteristics of hydraulic pipelines. The research is conducted based on the stress states of pipelines under external excitations—specifically axial (X-direction), radial (Y-direction), and combined radial–axial (X + Y) excitations and integrates theoretical derivation, simulation, and experimental validation. Firstly, a multidimensional directional vibration equation for the pipeline was derived based on its stress distribution, yielding a more accurate vibration model for marine pipelines. Subsequently, simulations were performed to analyze the effects of fluid velocity, pipeline layout, and support distribution on the pipeline’s vibration characteristics. Finally, experiments were designed to verify the simulation results and examine the impact of external interference on pipeline vibration. The experimental results indicate the following: the influence of flow velocity variations on pipeline modes is generally negligible; increasing the number of pipeline circuits effectively reduces its natural frequencies; increasing the number of supports not only lowers the overall vibration intensity of the pipeline but also achieves peak shaving, thereby effectively reducing the maximum vibration amplitude; and the impact of external environmental interference on the pipeline’s vibration characteristics is complex, as it not only enhances vibration intensity but also weakens vibrations in specific directions. This study lays a theoretical foundation for subsequent vibration reduction efforts for marine hydraulic pipelines. Full article

The hyporheic zone functions as a critical interface mediating hydrological and biogeochemical exchanges between stream water and streambed. Within shallow streambed layers, sediment transport and biofilm colonization can induce dynamic layered clogging, alter hydraulic conductivity, and foster physical stratification that significantly modulates hyporheic exchange patterns. This study develops a coupled hydrodynamic–mass transport model for a representative streambed bedform to examine the impacts of biofilm-driven dynamic clogging on hyporheic exchange dynamics. Results reveal that dynamic layered clogging reduces pore water velocity and total water flux, causing a 45.1% decline in the total inflow to the hyporheic zone. The transport of non-absorbable solutes exhibits a biphasic pattern: initial rapid penetration transitions to gradual deceleration over time, with dynamic clogging extending the penetration time of the solute center of mass distribution (CMD). Notably, when hydraulic conductivity falls below a threshold (K* < 0.25), CMD penetration time exhibits a positive correlation with hydraulic conductivity, attributed to porosity-induced changes in actual flow velocity. When considering the anaerobic growth in deeper layers, the penetration time become longer because of the clogging present there. This research clarifies the mechanistic connections between biofilm-induced clogging and hyporheic exchange, providing valuable insights for the management of hyporheic ecosystems and the modeling of biogeochemical processes. Full article

The precise and accurate use of aquifer hydraulic parameters for assessing local and regional recharge potential for enhancing groundwater allocation planning is vital for many hydrogeological studies. The conventional approach for allocating groundwater presents a challenging scenario, as it remains uncertain whether the applied recharge estimate is local or regional recharge. The approach does not account for the extent of the aquifer recharge in terms of local and regional scale; instead, it assumes that recharge is distributed across the catchment. This study aimed to demonstrate the use of aquifer hydraulic parameters (transmissivity and storativity) to explain areas of potential recharge (local and regional) for enhancing groundwater allocation planning with a specific case study of De Aar, Northern Cape, South Africa. It argues that not integrating local and regional recharge potentials in planning for groundwater allocations can result in over- or under-allocation of groundwater resources to users. A constant discharge pumping test and recovery test matching the duration of pumping were conducted for data collection. The Flow Characteristics method was used as a diagnostic tool to understand the different aquifer flow regimes in the study area. To develop an integrated understanding of the groundwater system, a hydrogeological conceptual model was used to visualize areas with higher or lower recharge potential across local and regional scales. Results showed significant variability in transmissivity, ranging from 213 to 596 m²/d, and storativity, ranging from 0.0000297 to 0.000185. The transmissivity values suggest that groundwater moves faster; meanwhile, the storativity values suggest that the aquifer system has high water storage capacity. These results will assist water resource planners in making informed decisions on how to allocate groundwater to users. This study demonstrated that aquifer hydraulic parameters are a valuable tool for improving groundwater allocations, thereby highlighting the importance of considering areas for potential recharge, both local and regional, in planning groundwater allocation. Full article

To address frost heave in winter-lined canals and sediment accumulation in the Hetao Irrigation District of Inner Mongolia Autonomous Region, while reducing long-term maintenance costs of canal linings and relocating sediment as solid waste, this study proposes the use of low-toxicity, environmentally friendly octadecyltrichlorosilane (OTS) to modify channel sediment. This approach aims to improve the frost heave resistance of canal sediment and investigate optimal modification conditions and their impact on frost heave phenomena, aligning with sustainable development goals of low energy consumption and economic efficiency. Water Droplet Penetration Time (WDPT) tests and unidirectional freezing experiments were conducted to analyze frost heave magnitude, temperature distribution, and moisture variation in modified sediment. A coupled thermal–hydraulic–mechanical (THM) model established using COMSOL Multiphysics 6.2 software was employed for numerical simulations. Experimental results demonstrate that the hydrophobicity of channel sediment increases with higher OTS concentrations. The optimal modification effect is achieved at 50 °C with a silane-to-sediment mass ratio of 0.001, aligning with the economic efficiency of sustainable development. The unidirectional freezing test results indicate that compared to the 0% modified sediment content, the 40% modified sediment proportion reduces frost heave magnitude by 71.3% and decreases water accumulation at the freezing front by 21.1%. The comparison between numerical simulation results and experimental data demonstrates that the model can accurately simulate the frost heave behavior of modified sediment, with the error margin maintained within 15%. In conclusion, OTS-modified channel sediment demonstrates significant advantages in enhancing frost heave resistance while aligning with the economic and environmental sustainability requirements. Furthermore, the coupled thermal–hydraulic–mechanical (THM) model provides a reliable tool to guide sustainable infrastructure development for hydraulic engineering in the cold and arid regions of Inner Mongolia, effectively reducing long-term maintenance energy consumption. Full article

Soil moisture is one of the key hydrologic components indicating the performance of landfill final covers. Conventional compacted clay (CC) covers and evapotranspiration (ET) covers often suffer from moisture-induced stresses, such as desiccation cracking and irreversible hydraulic conductivity. Engineered turf (EnT) cover systems have been introduced recently as an alternative; however, their field-scale moisture distribution behavior remains unexplored. This study investigates and compares the soil moisture distribution characteristics of EnT, ET, and CC landfill covers at a shallow depth using one year of field-monitored data in a humid subtropical region. Three full-scale test Sections (3 m × 3 m × 1.2 m) were constructed side by side and instrumented with moisture sensors at a depth of 0.3 m. Distributional characteristics of moisture were evaluated with descriptive statistics, goodness-of-fit tests such as Shapiro–Wilk (SW) and Anderson–Darling (AD), Gaussian probability density functions, Q–Q plots, and standard-normal transformations. Results revealed that Shapiro–Wilk (W = 0.75–0.92, p < 0.001) and Anderson–Darling $(A^2=1.63\times {10}^3\mathrm{to}6.31\times {10}^3,p<0.001)$ tests rejected normality for every cover, while Levene’s test showed unequal variances between EnT and the other covers $(F>5.4\times {10}^4,$$p<0.001)$ but equivalence between CC and ET (F = 0.23, p = 0.628). EnT cover exhibited the narrowest moisture envelope $(95\%\mathrm{range}=0.156\mathrm{to}0.240{\mathrm{m}}^3/{\mathrm{m}}^3;\mathrm{CV}=10.6\%)$, whereas ET and CC covers showed markedly broader distributions (CV = 38.6 % and 33.3 %, respectively). These findings demonstrated that EnT cover maintains a more stable shallow soil moisture profile under dynamic weather conditions. Full article

Hydrological modeling is essential for the sustainable management of watershed systems. Physically based models like MOHID-Land simulate soil water dynamics using Richards’ equation, parameterized through the van Genuchten–Mualem (VGM) model. Although the sensitivity of individual VGM parameters—residual water content (${\theta }_r$), saturated water content (${\theta }_s$), pore size distribution ($n$), inverse of air entry pressure ($\alpha$), and saturated hydraulic conductivity ($K_{sat}$)—is well documented, their combined effects remain underexplored. This study assessed both isolated and joint impacts of these parameters through a deterministic ±10% perturbation scheme, resulting in 31 unique parameter combinations. Model performance was evaluated using the Nash–Sutcliffe Efficiency (NSE) and Percent Bias (PBIAS). Full-parameter interaction achieved the best results (NSE = 0.50, PBIAS = 25.32), compared to the uncalibrated baseline (NSE = 0.01, PBIAS = 34.06). The pair ${\theta }_s$ and $n$ emerged as the most influential. Adding secondary parameters to this core pair yielded only marginal performance gains, while removing them from the full set caused similarly marginal declines. These findings reveal a hierarchical sensitivity structure, emphasizing ${\theta }_s$ and $n$ as key targets for calibration. Prioritizing this pair enables a more efficient soil calibration process, preserving model accuracy while reducing computational cost by limiting parameter space exploration. Full article