Search Results (71)

Rectangular aqueducts are critical building structures in large-scale water conveyance systems used worldwide. Liquid sloshing can produce hydrodynamic forces that threaten structural safety and long-term performance. This study analytically investigates the vibration characteristics of two-dimensional rectangular cantilever aqueduct systems while accounting for soil–structure interaction (SSI). To reduce sloshing and enhance the performance of the mechanical system, a bottom-mounted vertical baffle is proposed as a hydrodynamic damping solution. Through subdomain analysis, mathematical expressions for liquid potential fields are derived. The continuous liquid is represented through discrete mass–spring elements for dynamic analysis. Horizontal soil impedance is characterized by using Chebyshev orthogonal polynomial approximations with optimized least squares fitting techniques. A dynamic mechanical model for the soil–aqueduct–liquid–baffle coupling system is developed by using the substructure method. Convergence and comparative studies are conducted to validate the reliability of the proposed method. Between the current results and those reported previously, the variation in the first-order sloshing frequency is less than 1.10%. Parametric analyses evaluate how baffle size, baffle position, and soil properties influence sloshing behavior. The presentation of an equivalent analytical model is the novelty of this research. The results can provide the theoretical basis for optimizing anti-sloshing designs in hydraulic building structures, thereby supporting safer and more sustainable engineering practices. 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

Pulse width modulation (PWM) allows for the real-time flow rate adjustment of spray nozzles without changing system pressure, indicating that PWM is a promising technology for improving the quality of pesticide applications. However, its effect on the droplet formation process is not yet fully understood. In this study, the effects of a PWM system on the droplet spectrum and velocity generated by different flat fan hydraulic nozzles were evaluated. The experiment was conducted via a spray simulator to test the impact of PWM technology under various operational conditions and flat fan nozzle types (standard, pre-orifice, and air inclusion). With the aid of a real-time particle analyzer and high-resolution imaging, the following variables were analyzed: volume median diameter (VMD), relative span, droplet velocity, and the percentage of volume composed of droplets with a diameter smaller than 100 µm. Four simulated working speeds (1.1, 1.7, 2.8, and 3.9 m s⁻¹), which were equivalent to four PWM valve duty cycles (35%, 42%, 71%, and 100%), respectively, were evaluated. The PWM system altered the droplet size, generally reducing the VMD in comparison to the conventional system. The relative span was not influenced by the PWM system’s duty cycle, although system activation increased droplet size heterogeneity in some nozzle types. The droplet velocity was generally slower using the PWM system in comparison with the conventional system, but higher duty cycles increased this parameter. Overall, the results of this study suggest that spray patterns are altered by PWM activation, and the traits of this behaviour depend on the spray nozzle type. Full article

The proper development of groundwater resources is very important in many parts of the world. Its planning requires mathematical simulation of groundwater flows. Simulation can be either analytical or numerical. Analytical tools, when available, require fewer computational resources, but they are usually based on more assumptions, at the conceptual level, which restrict their applicability. In this paper, we aim to check the applicability of one-dimensional analytical solutions for groundwater flows through non-homogeneous aquifers, which are bound by two constant head and two impermeable boundaries and bear many zones of different transmissivities. These solutions are based on the stepwise inclusion of neighboring zones to larger ones, with equivalent transmissivity coefficients. We compare analytical results with numerical ones, obtained from a two-dimensional numerical model. We have selected the boundary element method (BEM) for this task. BEM is very versatile in solving steady-state groundwater flow problems, since discretization is restricted to external and internal field boundaries only. This feature fits perfectly with our research, which requires flow velocities at the boundaries only. Our research shows that analytical results can serve as upper and lower limits of total inflow. If the differences between the transmissivities of adjacent zones are small, they can be used in preliminary calculations too. Full article

In modern shock absorber development, the fatigue durability of shim-based clamped valve systems remains a critical factor influencing both performance and operational safety. In this study, the authors extend their previous research achievements by developing a fatigue life prediction methodology that integrates an established finite element framework with a strength-based fatigue model incorporating experimentally derived and validated Wöhler characteristics of the metal alloy used in the valve shims. The focus of this work is the validation of the proposed methodology for hydraulic shock absorbers equipped with shim stack valve systems, supporting the virtual pre-selection of valve configurations during the OEM design process. This approach enables substantial reductions in experimental testing and facilitates cost-effective development under realistic operating conditions. To address random-amplitude loading scenarios, the rainflow-counting algorithm was employed to convert complex load histories into equivalent constant-amplitude cycles, thereby accurately capturing material memory effects associated with stress–strain hysteresis. Experimental validation was conducted using a high-performance servo-hydraulic load frame tester. The validated model demonstrated a prediction uncertainty of 46% for random-amplitude lifetime estimation. Full article

The non-Darcy seepage characteristics of broken rock mass is important for analyzing the seepage and stability of rock and soil mass. At present, the research on non-Darcy seepage models considering hydraulic conditions and medium void structures has considerable room for improvement. In this study, non-Darcy seepage tests were conducted on broken rock mass under the influence of different hydraulic pressures, sample gradations, and porosities. The influence of sample gradation and porosity on the linear and nonlinear term coefficients of Forchheimer’s law, the critical criterion of non-Darcy seepage, and the seepage flow regime was clarified. The influence of hydraulic gradient on the value of traditional hydraulic conductivity was revealed. A non-Darcy equivalent hydraulic conductivity, which changed with pressure gradient, was defined, then Forchheimer’s law and Darcy’s law were modified. Results showed that the relationship between pressure gradient and flow rate highly obeyed Forchheimer’s law. The minimum value of Forchheimer number was 9.4 times the critical value. Owing to the influence of inertial force and variable seepage channels, the linear and nonlinear term coefficients of Forchheimer’s law decreased while the Forchheimer number increased with the increase of pressure gradient, sample gradation, and porosity. With high hydraulic gradient, the non-Darcy equivalent hydraulic conductivity decreased nonlinearly, causing Darcy’s law to overestimate the seepage flow in this study by 2.47–13.40 times. Finally, Forchheimer’s law and Darcy’s law were modified to consider the influence of hydraulic gradient, sample gradation, and porosity. The modified Darcy’s law does not require the determination of the seepage flow regime and can accommodate the mutual transformation and coexistence between Darcy and non-Darcy seepage. Full article

To address the hydrogeological parameters of polluted sites at the site scale, a series of physical and numerical simulation experiments were conducted to investigate seepage and solute transport under the influence of various physical fields. These experiments utilized an experimental platform designed for the acquisition of pollutant transport and transformation data, which incorporated three-dimensional multifield coupling, alongside a numerical model that also accounted for multiphysical field interactions. The numerical simulations employed Darcy’s law, the heat conduction equation, and convective–dispersive equations to analyze the seepage field, heat transfer, and solute transport processes, respectively. The findings from both physical and numerical tests indicate that variations in groundwater temperature and solute concentration significantly influence solute transport dynamics. Specifically, an increase in groundwater temperature correlates with an accelerated migration rate of sodium chloride (NaCl) solute, resulting in a reduced time for the solute to achieve equivalent concentrations in observation wells. Conversely, when the concentration of NaCl in groundwater rises, the temperature of the groundwater also increases when the solute reaches the same concentration in the observation wells. This phenomenon can be attributed to the decrease in the specific heat capacity of groundwater with higher solute concentrations. Moreover, as the concentration of sodium chloride in groundwater increases, the rate of temperature elevation in the groundwater accelerates due to a decrease in specific heat capacity associated with higher solute concentrations, thereby requiring less thermal energy for the groundwater to attain the same temperature. The results further reveal that the hydraulic conductivity of the target aquifer, specifically the pulverized clay layer, ranges from 6.72 to 8.52 × 10⁻⁶ m/s, with an effective thermal conductivity of 2.2 W/(m·K), a longitudinal dispersion of 0.554 m, and a transverse dispersion of 0.05 m. Full article

To address the challenges in predicting roof water hazards in weakly cemented strata of Northwest China, this study pioneers an integrated CNN-BiLSTM model for aquifer water abundance prediction. Focusing on the 1301E working face in the Yili No. 1 Coal Mine, we employed kriging interpolation to process sparse hydrological datasets (mean relative error: 8.7%), identifying five dominant controlling factors—aquifer burial depth, hydraulic conductivity, core recovery rate, sandstone–mudstone interbedded layer count, and sandstone equivalent thickness. The proposed bidirectional architecture synergizes CNN-based spatial feature extraction with BiLSTM-driven nonlinear temporal modeling, optimized via Bayesian algorithms to determine hyperparameters (32-channel convolutional kernels and 64-unit BiLSTM hidden layers). This framework achieves the comprehensive characterization of multifactorial synergistic effects. The experimental results demonstrate: (1) that the test set root mean square error (1.57 × 10⁻³) shows 65.3% and 85.9% reductions compared to the GA-BP and standalone CNN models, respectively; (2) that the coefficient of determination (R² = 0.9966) significantly outperforms the conventional fuzzy analytic hierarchy process (FAHP, error: 0.071 L/(s·m)) and BP-based neural networks; (3) that water abundance zoning reveals predominantly weak water-rich zones (q = 0.05–0.1 L/(s·m)), with 93.3% spatial consistency between predictions and pumping test data. Full article

In the field of marine resource development, conventional axial-flow adjustable-blade pumps rely on the monolithic rotation of rigid blades for operational condition regulation, a mechanism constrained by simplistic angular adjustments that inadequately adapt to the dynamic and complex marine operational environment. To address this limitation, this study proposes a novel angle-adjustment scheme utilizing flexible variable-twist blades, where operational condition regulation is achieved through active blade twisting, enabling refined and adaptive angle modulation. Four typical blade profiles were selected for the variable-twist blades at distinct angular positions (−1°, +1°, −2°, and +2°), corresponding to the four conventional angle-adjustment positions of axial-flow adjustable-blade pumps. Numerical simulations were conducted to investigate the hydraulic performance impacts of the proposed flexible variable-twist blades compared to traditional rigid blades under identical angular configurations. The results demonstrate that under high-flow conditions (1.2 Q), the torsion-based angle-adjustment strategy exhibits superior efficiency across all four angular positions: −1° configuration: 11.1% efficiency improvement; +1° configuration: comparable efficiency; −2° configuration: 78% efficiency improvement; and +2° configuration: 3.2% efficiency improvement. Moreover, at equivalent angular settings, the variable-twist blades significantly enhance hydraulic performance and expand the high-efficiency operating range of the pump compared to conventional rigid blades. The implementation of flexible variable-twist blade technology not only advances the performance of axial-flow pumps in marine engineering applications but also provides a new approach for high-efficiency research on axial-flow pumps. Full article

As part of this study, mechanical property tests were carried out at different stages with different curing temperatures to elucidate the effect of temperature on the mechanical properties of concrete. The curing temperatures were laboratory curing temperature (standard curing at 20 °C) and variable temperature curing (simulated site ambient temperature curing) according to the actual temperature of previous construction sites. The compressive strength, split tensile strength, axial tensile strength, and modulus of elasticity values were tested, and the growth rates were calculated. According to previous experiments, the maturity indexes under two kinds of maintenance conditions were calculated based on the N-S maturity formula, F-P equivalent age calculation formula, and D-L equivalent age calculation formula proposed by the maturity theory. Moreover, logarithmic function, exponential function, and hyperbolic function fitting were carried out using the fitting software to study the developmental relationship between strength and maturity. The physical phase analysis of low-heat cement was performed using XRD and simultaneous thermal analysis, and pore structure analysis was conducted using the mercuric pressure method (MIP). We also conducted an SEM analysis of hydration products and the micromorphology of low-heat cement with 25% fly ash. Energetic spectroscopy analyzed the elemental content. In this study, it was found that temperature has a significant effect on the mechanical properties of concrete, with temperature having the greatest effect on splitting tensile strength. The strength of low-heat silicate cement concrete increases with maturity. The highest correlation coefficient was based on the hyperbolic function fit in the F-P equivalent age. The improved development of concrete strength in the later stages of the two curing conditions in this test indicates that low-heat cement is suitable for use in hydraulic tunnels. The low-heat cement generates a large number of C-S-H gels via C₂S in the late stage, filling the internal pores, strengthening the concrete densification to make the structure more stable, guaranteeing the late development of concrete strength, and imparting a micro-expansive effect, which is effective for long-term crack resistance in hydraulic lining structures. Full article

Optimizing well spacing is crucial for enhancing the production efficiency and economic returns of tight oil development. The limited understanding of hydraulic fracture geometry and properties poses significant challenges in designing well spacing for tight oil reservoirs. In this study, we proposed an integrated workflow for optimizing well spacing in tight oil reservoirs. Geological and geomechanical models were established to form the basis for numerical reservoir simulation and dynamic fracture modeling. A multi-staged, multi-clustered fracture propagation simulation of horizontal wells was conducted by a hydraulic fracturing simulator with matched actual field pumping schedules. The differences between fracture propagation simulation results and field monitoring results, including micro-seismic testing and distributed temperature sensing (DTS) monitoring, were analyzed. The geological model and fracture propagation simulation results were integrated into an efficient numerical reservoir simulator. A material balance method for fracturing fluids leak-off was proposed and utilized to equivalently calculate the actual oil–water distribution after fracturing and to complete the historical matching water cuts of all wells. Subsequently, the inter-well drainage area and pressure interference were evaluated. By employing this integrated workflow, the production performance of six wells (three well pairs) at different well spacings was simulated over a 15-year period, and their estimated ultimate recoveries (EURs) were predicted. When well spacing was less than the optimal distance, oil production dropped significantly. Ultimately, it was determined that reasonable well spacing for this block was 250 m. In future well pattern designs, well spacing smaller than the current value should be used. Full article

In order to study the influence of split blades on the turbine force characteristics and fluid–structure coupling characteristics of pumps, this paper selected the IS 80-50-315 centrifugal pump, used as a reverse-acting hydraulic turbine, as the research object, optimized the original pump-acting turbine impeller, and adopted different combinations of long and short blades. Based on the SIMPLE algorithm and RNG k–ε turbulence model, a complete three-dimensional unsteady numerical simulation was conducted on the internal flow field of the pump-turbine. The results show that the split blades reduce the radial and axial forces. The deformation patterns of rotor components in the two pump types used as turbine models were similar, with deformation gradually decreasing from the inlet to the outlet of the impeller. The equivalent stress distribution law of the rotor components of the two pump turbine models has also been found to be similar, with the maximum stress occurring at the connection between the blades and the front and rear cover plates and the minimum stress occurring at the outlet area of the impeller and the maximum shaft diameter of the pump shaft. The maximum deformation and stress of the rotor components in the split blade impeller model were smaller than those in the original impeller model. Full article

Affected by discontinuities, the hydraulic properties of rock masses are characterized by significant scale dependency and anisotropy. Sampling a rock mass at any scale smaller than the representative elementary volume (REV) size may result in incorrect characterization and property upscaling. Here, a three-dimensional discrete fracture network (DFN) model was built using the joint data obtained from a dam site in southwest China. A total of 504 two-dimensional sub-models with sizes ranging from 1 m × 1 m to 42 m × 42 m were extracted from the DFN model and then used as geometric models for equivalent permeability tensor calculations. A series of steady-state seepage numerical simulations were conducted for these models using the finite element method. We propose a new method for estimating the REV size of fractured rock masses based on permeability. This method provides a reliable estimate of the REV size by analyzing the tensor characteristic of the directional permeability, as well as its constant characteristic beyond the REV size. We find that the hydraulic REV sizes in different directions vary from 6 to 36 m, with the maximum size aligning with the average orientation of joint sets and the minimum along the angle bisector of intersecting joints. Additionally, the REV size is negatively correlated with the average trace length of the two intersecting joint sets. We find that the geometric REV size, determined by the joint connectivity and density, falls into the range of the hydraulic REV size. The findings could provide guidance for determining the threshold values of numerical rock mass models. Full article

Hydraulic fracturing changes the stress state of the coal body, and the residual water within the coal body after fracturing affects its permeability characteristics. To examine the impact of hydraulic measures on the permeability of coal under varying water contents and radial stress distributions, permeability tests were conducted using the improved LFTD1812 triaxial permeameter. The flow rate of coal under different water content combinations was measured, and the permeability, pressure gradient, and seepage velocity of the samples were calculated. The relationships among porosity, permeability, pressure gradient, and seepage velocity were analyzed. The effect of water content on permeability was evaluated, and the directional behavior of permeability was identified. The results showed that the porosity of the samples with water contents of 25%, 17.5%, and 10% decreased by 48.5%, 23.9%, and 17.6%, respectively, during the loading process. The permeability of all samples ranged from 1.91 × 10⁻¹³ m² to 76.91 × 10⁻¹³ m². As the absolute value of the pressure gradient increased, the downward trend of permeability was categorized into three stages: rapid, slow, and stable. Higher water content corresponded to lower initial permeability, with the permeability–pressure gradient curve shifting downward. Additionally, the slow decline zone moved to the right, and the absolute value of the pressure gradient required to enter this zone decreased. Seepage velocity consistently decreased with increasing water content across all osmotic pressure levels, although the rate of decline progressively weakened. The maximum permeability difference between the forward and reverse samples was 10.48 × 10⁻¹³ m². Permeability directionality decreased with increasing equivalent water content and osmotic pressure, with water content identified as the primary influencing factor. Permeability variations caused by axial compression were divided into three phases: the weak influence of the polarization effect, the transition phase, and the strong influence phase. These findings confirm that water content has the most significant impact on permeability, demonstrating that gas flow primarily follows the principle of distance priority toward the nearest borehole. Boreholes closer to the source exhibit higher extraction volumes. These results provide theoretical support for improving coal permeability, enhancing gas drainage efficiency, and preventing gas accidents through hydraulic measures. Full article

Concrete stress is a key factor influencing the operational safety of concrete dams, and understanding the true distribution and variation of stress is a major research focus in the field of dam engineering. In the heel region of the dam, internal voids in the concrete may allow external water infiltration under high hydraulic head, leading to changes in the concrete’s elastic modulus and Biot coefficient. These changes, in turn, affect the effective stress experienced by the concrete. Consequently, the measured stress in the heel and toe regions may differ from conventional understanding and standard calculation methods for dam stresses. This is particularly evident in the following aspects: after water impoundment, compressive stress in the dam heel is higher than in the dam toe, with the heel stress exceeding the calculated value by a significant margin, and the variation in stress during the impoundment process being smaller than the calculated value. To address these issues, this paper proposes a theoretical method for measuring the Biot coefficient of concrete through experimental testing and innovatively develops the corresponding experimental equipment. This equipment can accurately simulate the conditions of the dam under different water depths (confining pressures) and measure the deformation of concrete caused by changes in water depth. Based on this equipment, tests were conducted on the elastic modulus and Biot coefficient of dry and saturated concrete specimens under different confining pressures. The Voigt–Reuss–Hill mixed average modulus formula was applied to calculate the elastic modulus of the concrete matrix, exploring the influence of pore water on the mechanical properties of the concrete. The results indicate that the pore water inside the concrete increases its equivalent elastic modulus during the testing process. In numerical simulations of the dam, this increased modulus due to pore water is often overlooked, leading to an underestimation of the results. This partially explains why the measured compressive stress in the dam heel consistently exceeds the calculated values. According to the Biot coefficient calculation theory proposed in this paper, the Biot coefficient of concrete varies with its water content. The Biot coefficient is lower in specimens with high water content compared to those with low water content. Using the Voigt–Reuss–Hill mixed average modulus formula, the elastic modulus of the concrete matrix obtained from the tests was found to be 28 $\mathrm{G}\mathrm{P}\mathrm{a}$, which is in good agreement with the results from regression analysis. These findings are of significant importance for the safe operation of concrete dam engineering. Full article