Water Pressure Research Articles

Analysis of seepage behavior of porous asphalt pavement based on scale test and three-dimensional simulation

This study implemented indoor scaled drainage testing and three-dimensional (3D) finite element simulations to analyze the seepage behavior of ultra-wide cross-section porous asphalt concrete (PAC) pavement with voids of 18 %, 20 % and 22 %. The seepage water level curves under the rainfall intensity of 0.5, 1, 2, 10, 50 and 100 years recurrence intervals were obtained by scaled test. The Seep3D software was used to analyze the seepage state of the ultra-wide cross-section porous pavement. Results indicated that void ratio was the paramount factor affecting the drainage capacity, which decreasing porosity significantly intensifies roadway surface water depth over 25 %. Water level curves obtained in scaled test showed similar trends to pore water pressure curves in 3D simulation. According to the theory of non-uniform gradual seepage, the pore water pressure can be used to effectively characterize the seepage state inside the porous pavement. Implementing cross drain with 10 m spacing maximally alleviated inundation by 23 %. Spacing intervals of 50 m, 30 m, and 20 m proportionately mitigated peak value by 4 %, 7 % and 12 % respectively.

Multi-scale variations of subglacial hydro-mechanical conditions at Kongsvegen glacier, Svalbard

Abstract. The flow of glaciers is largely controlled by changes at the ice–bed interface, where basal slip and sediment deformation drive basal glacier motion. Determining subglacial conditions and their responses to hydraulic forcing remains challenging due to the difficulty of accessing the glacier bed. Here, we monitor the interplay between surface runoff and hydro-mechanical conditions at the base of the Kongsvegen glacier in Svalbard. From July 2021 to August 2022, we measured both subglacial water pressure and till strength. Additionally, we derived median values of subglacial hydraulic gradient and radius of channelized subglacial drainage system from seismic power, recorded at the glacier surface. To characterize the variations in the subglacial conditions caused by changes in surface runoff, we investigate the variations of the following hydro-mechanical properties: measured water pressure, measured sediment ploughing forces, and derived hydraulic gradient and radius, over seasonal, multi-day, and diurnal timescales. We discuss our results in light of existing theories of subglacial hydrology and till mechanics to describe subglacial conditions. We find that during the short, low-melt-rate season in 2021, the subglacial drainage system evolved at equilibrium with runoff, increasing its capacity as the melt season progressed. In contrast, during the long and high-melt-rate season in 2022, the subglacial drainage system evolved transiently to respond to the abrupt and large water supply. We suggest that in the latter configuration, the drainage capacity of the preferential drainage axis was exceeded, promoting the expansion of hydraulically connected regions and local weakening of ice–bed coupling and, hence, enhanced sliding.

Quantification of SCC mechanisms in austenitic alloys under PWR primary water conditions

Abstract In order to achieve a full mechanistic understanding of stress corrosion cracking (SCC), the key operating mechanisms need to be identified but also quantified. In this study, we summarize and rationalize key findings from the last 15 years of high-resolution characterization of SCC in our group. A comprehensive characterization of a set of austenitic alloys with different Ni content and constant Cr level, tested under simulated pressurized water reactor (PWR) primary water conditions at various temperatures, has revealed evidence for at least two operating mechanisms: one diffusion-related and the other deformation-related. For their relevance to the nuclear industry, two additional alloys with increased Cr content were also studied (A800 and A690). Key precursors for SCC initiation and propagation are identified and their effect on alloy degradation discussed. A list of key materials’ properties that ensure low SCC susceptibility is proposed.

Robust Rain-Repellency and Droplet Bouncing Properties of Bauhinia Fresh and Aged Leaves Up to 6 Months.

Robust rain-repellent surfaces are useful in roofs, solar panels, windshields, etc. Herein, excellent rain-repellency and droplet bouncing properties of Bauhinia Variegata leaves are presented. They possess surface microbumps (l ∼ 13 μm, w ∼ 8 μm, h ∼ 3 μm), which in turn comprise nanoplatelets (l ∼ 741 nm, t ∼ 59 nm) and Wenzel roughness (r w) of ∼2.2. The leaf's surface energy was estimated to be 9.47 ± 0.03 mJ·m-2 by incorporating rw into the van Oss-Good-Chaudhary theory. The leaves exhibited static contact angle of 157 ± 1°, roll-off angle of 9 ± 1°, and contact angle hysteresis of 12 ± 4°, which retained as they aged up to 186 days in the natural weather and laboratory conditions. The water droplets (10 μL, 40 μL) bounced off for free-fall heights from 5 cm to ∼13 m (Weber no. 36 to ∼2990) and displayed robust rain-repellency (Weber no. ∼4500), similar to that of a lotus leaf. Also, Bauhinia leaves survived pressurized water jets (Weber no. ∼4240). Nevertheless, underwater hydrophobicity has been persistent only for up to 3 h when submerged in 20 cm (∼1.96 kPa gauge pressure) deep water, while lotus leaves retained for >7 h. Such robust Bauhinia leaf's nanoplatelets and wax chemistries can be replicated onto glass/metals for preparing rain-repellent surfaces.

Water Injection Into Coal Seams for Outburst Prevention: The Coupling Effect of Gas Displacement and Desorption Inhibition.

Gassy coal seams generally have low permeability and dry coal bodies, which are susceptible to coal and gas outburst hazards in the process of mining. Water injection into coal seams can significantly alter the gas release rate and flow behavior. However, water has dual effects on coal seams: gas displacement and water-locking, and the coupling mechanism of these two effects is not clear in the whole process of coal seam water injection. By measuring high-pressure gas adsorption isotherms and gas diffusion initial velocity, it was found that both the Langmuir adsorption constant a and gas diffusion initial velocity ΔP decrease with the increase of water content, which would reduce outburst risks. Through the self-developed integrated experimental device of "gas adsorption + water injection displacement + gas desorption″, the changing rules of gas displacement amount, desorption amount, and water lock amount under different water injection conditions were studied. The results show that when the water injection ratio increases from 6 to 25%, the gas displacement would increase from 0.62 to 1.16 mL/g, with an increase of 87.09%. Also, at the same time, the gas desorption capacity would decrease from 4.86 to 4.05 mL/g after pressure relief, with a decrease of 16.67%. The amount of water-locking increased from 0.11 to 0.38 mL/g. The effect of water injection to control coal and gas outburst occurs in two different water injection stages. In the process of water injection, water plays a major role in gas displacement, which is conducive to reducing the gas content of the coal seam. After the completion of water injection, the static water pressure remaining in the coal seam can reduce the gas emission rate. The combination of these two effects can effectively reduce the risk of outbursts.

Prediction of Excess Pore Water Pressure Generation in Sand–Silt Mixtures During Cyclic Loading: A Dissipated Energy-Based Model

Prediction of Excess Pore Water Pressure Generation in Sand–Silt Mixtures During Cyclic Loading: A Dissipated Energy-Based Model

Numerical research on disastrous mechanism of seepage instability of karst collapse column considering variable mass effect

In order to reveal the disastrous mechanism of seepage instability of karst collapse column considering variable mass effect, a variable mass fluid–solid coupling mechanical model of water inrush is established, by considering the random distribution characteristics of a collapse column. Taking Qianjin coal mine as the research background, based on the Weibull distribution theory, the heterogeneous distribution characteristics of rock mass is described, and COMSOL Multiphysics numerical simulation software is employed to simulate the seepage characteristics and inrush water changes in collapse columns under different conditions of homogeneity, water pressure, and initial porosity. The research results show that the greater the homogeneity is, the more water conduction channels are formed, and the porosity increases accordingly, when considering the influence of different homogeneity on the seepage characteristics of broken rock mass, which eventually leads to water inrush accidents and a sharp increase in water inflow. Besides, when studying the seepage evolution law of different water pressures on a broken rock mass, an elevation of water pressure dramatically increases the porosity and seepage rate of the water. Over time, the broken rock particles gradually migrate and the fine particles are transported and eroded by the water flow, resulting in changes in the seepage characteristics and the formation of potential water diversion channels. Finally, when taking into account the effect of different initial porosity on the fractured rock mass seepage characteristics, the greater the original porosity is, the higher the seepage velocity is, and the particle migration increases the permeability. This leads to a more pronounced conductive water passage formation, which reveals the disastrous mechanism of seepage instability of karst collapse column considering variable mass effect.

Investigation on the Effects of Volute Geometric Parameters on the Performance of Pico Francis Turbines Used in Water Pipes

The development of new hydro turbines or the optimization of traditional hydro turbines is one of the research directions that scholars have been interested in to broaden the source of hydropower and improve energy efficiency. In our previous work, a Francis turbine was used in the water supply systems of high-rise buildings to properly control water pressure inside the pipeline and recover excess water energy. In this paper, an optimization study of the volute for the sectional shape, design method, inlet parameters, outlet width, and tongue was conducted using numerical simulations to improve the hydro turbine performance. The simulated results show that a circular section could better enhance the flow velocity inside the volute and make the flow velocity distribution more uniform at the volute outlet, and the equal mean velocity method is a more suitable volute design method in this special condition. The results of range analysis show that the water head reduction increases significantly with the increase in the inlet height, and both inlet height and outlet width have a significant effect on the efficiency. In addition, in the tongue optimization, a larger tilt angle corresponds to smaller output power and water head reduction; a larger stretch length in the limited angle range corresponds to larger output power and lower efficiency. Ultimately, the output power of the hydro turbine was increased by 18.65% and the efficiency by 2.1% through the volute optimization.

Effect of loading frequency and cyclic stress ratio on undrained cyclic behaviors of clay-structure interface with various overconsolidation ratios

The widely used suction caissons in offshore engineering are commonly subject to cyclic loads including the wind, wave, and current. For proper design and sustainable maintenance of the suction caisson foundations, it is essential to investigate the dynamic response of the clay-structure interface. This research conducted a series of clay-structure interface cyclic shear tests under constant volume equivalent undrained state using a modified direct simple shear device to fully investigate the effects of cyclic stress ratio (CSR), loading frequency, and overconsolidation ratio (OCR) on the dynamic response of the interface. The interface shear strength, relative shear displacement, the number of cycles to failure (Nf), and interface pore water pressure were analyzed. Results show that the Nf is strongly affected by CSR and loading frequency. A model is proposed to describe the decrease in the Nf with increasing CSR under a given loading frequency and OCR. The Nf increases approximately linearly with loading frequency on a double-logarithmic scale. Additionally, the contour diagrams, defining the Nf as a function of interface average and cyclic shear stress under various OCRs, are proposed to predict the failure behaviors of clay-structure interface subjected to various loading combinations. Besides, the development models are established respectively to describe the evolutions of accumulated interface pore pressure (Uia) against the number of cycles (N) and cyclic relative shear displacement (Wcy), presenting better capability to describe the development of Uia. The findings in this study hold potential implications for determining whether the failure occurs under corresponding loading conditions and predicting interface pore pressure development.

Determination of Constrained Modulus of Granular Soil from In Situ Tests—Part 2 Application

The paper demonstrates how the concepts presented in the companion paper: “Determination of Constrained Modulus of Granular Soil from In Situ Tests—Part 1 Analyses” can be applied in practice. A settlement design based on the tangent modulus method is described. Extensive in situ tests were performed on a well-documented test site consisting of sand with silt and clay layers. The field tests comprised different types of penetration tests, such as the cone penetration test, the flat dilatometer, and the seismic down-hole test. The modulus number and the constrained tangent modulus were derived from the cone penetration test with pore water pressure measurement and the flat dilatometer test. In addition, the shear wave speed was determined from two seismic down-hole tests, from which the small-strain shear modulus could be evaluated. The constrained modulus obtained from the cone penetration test with pore water pressure measurement (CPTU) and the flat dilatometer (DMT) was compared with that from the seismic down-hole tests. The importance of the stress history on the constrained modulus was demonstrated. The range of modulus numbers, derived from different in situ tests, compares favorably with empirical values reported in the literature.

Thermal safety characteristics analysis of helium xenon gas cooled small reactor system under LOCA accidents

The thermal safety characteristics of the system after a small break loss of coolant accident (SB-LOCA) in a helium xenon gas-cooled small reactor will determine whether the reactor will experience a meltdown and the duration of the meltdown. At present, research on SB-LOCA both domestically and internationally is mostly focused on water-cooled reactors, lacking relevant research on helium xenon gas-cooled reactors (He-Xe GCR). Therefore, it is of great significance to research the thermal safety characteristics of He-Xe GCR after a breach loss of coolant accident. This article improves the gas turbine model based on the original SB-LOCA analysis program for pressurized water reactors. And added a calculation model for the characteristics of helium xenon mixed gas, a heat transfer model for helium xenon mixed airflow, and a compressor model. Finally, a Brayton Cycle Reactor System Analysis program (BRESA) was developed for SB-LOCA analysis of He-Xe GCR. Explore the impact of the size and location of fractures on the thermal safety characteristics of the system using BRESA. Research has found that as the size of the rupture gradually increases, the decrease in reactor core power is greater, and the reactor power is shut down earlier. Comparative analysis of the impact of different breach positions on the residual heat removal characteristics reveals that a breach accident on the high-pressure side of the system poses a greater threat to system safety. Therefore, when setting the safety threshold for the Brayton cycle system, the focus should be on the hazards of high-voltage side breaches. This research achievement assists with the safe operation strategy of He-Xe GCR in the future.

Extraction of Bioactive Secondary Metabolites from Citrus Maxima Peel Via Pressurized Hot Water Extractor for the Synthesis of Iron Oxide Nanoparticles

Using bioactive secondary metabolites (BSM) from Citrus maxima peel extract, this work investigated a green method of synthesizing magnetite iron oxide (Fe3O4) nanoparticles (NPs). The BSM acts as a reducing cum stabilizing agent in the process. The optimization of the BSM parameters were conducted through response surface methodology (RSM). The optimal condition obtained in this study for pressurized hot water extractor (PHWE) extraction was temperature of 94.96 °C, solvent-to-solid ratio of 29.7 ml/g and extraction time of 27.6 min. BSM Yield of 49.31 % could be obtained based on this condition. The formation of Fe3O4 NPs were detected using the FTIR analysis with the absorption peaks observed at around 590 and 580 cm−1. X-ray diffraction results matched standard magnetite Fe3O4 patterns with planes at (220), (311), (400), (511) and (440). Field emission scanning electron microscopy (FESEM) results showed that the magnetite Fe3O4 NPs synthesized in this study predominantly appeared in spherical shape. The extraction process's kinetics were examined using various empirical models, including the Elovich’s model, Peleg’s model, Power law and parabolic diffusion model. All applied models were found to be well fitted with the measured data from experiment, with R2 values exceeding 0.9. Notably, the Peleg’s model exhibited the highest R2, the smallest RMSD, and the least significant p-values, indicating its superior performance.

Study on the Seepage Mechanism of Gaskets at the Joints of Shield Segments Based on Coupled Euler-Lagrangian Method

In the construction and operation stage of urban shield tunnels, joint leakage of shield is always an urgent problem to be solved. In order to further explore the waterproof performance of elastic rubber gaskets at segment joints, the finite element software ABAQUS (2022) was used to establish a fluid-solid coupling calculation model. The dynamic simulation of the leakage process at the segment joints under water pressure revealed the whole process of leakage at the segment joints and the instant water pressure value when the waterproof system failed. The results show that during the whole process from segment assembly to joint leakage, the elastic rubber gasket has experienced four key stages: gasket compression, confined water pushing, water wedge and final leakage. When the opening amount of the gasket is 6 mm and 10 mm, the contact stress between the gasket shows a “W” symmetrical distribution of high at both ends and low in the middle, and the peak of the contact stress at both ends of the interface is about twice as much as that in the middle. The waterproof threshold of the gasket is closely related to the opening amount of the gasket, and the waterproof threshold has the same trend with the initial contact stress between the gaskets.

Rapid prediction of water hammer characteristics in liquid hydrogen storage and transportation systems: A theoretical model

A renewable energy liquid hydrogen storage and transportation system is a very complex system, so water hammering due to valve closure cannot be ignored. A theoretical model for the rapid prediction of the water hammer effect in liquid hydrogen pipeline valves was developed in this work. The impact of valve closure characteristics and subcooling on the peak pressure water hammer was analyzed. The results indicate that as the subcooling temperature of liquid hydrogen decreases, the density of subcooled liquid hydrogen increases, leading to larger peak pressures in the water hammer transient. At subcooling temperatures of 14, 16, 18, and 20 K, the maximum instantaneous pressures for the water hammer fluctuation are 51563.02, 50846.76, 50082.40, and 48510.70 Pa, respectively. Under identical boundary conditions, the density of subcooled liquid hydrogen emerges as the primary factor influencing the peak pressure of water hammer. The theoretical model exhibits a significant advantage in terms of computational time cost, saving approximately 9.99 h. However, the accuracy of the theoretical model is slightly inferior to that of the CFD model. The results of the study are expected to provide a technical basis for the design of refueling systems for storage and transportation, as well as densification technology of supercooled renewable liquid hydrogen and safety protection.

Leakage detection applied to the Da Hedong Reservoir dam (China) based on the flow-field fitting method

Detecting leakage in concrete gravity dams presents a formidable challenge. The flow-field fitting (FFF) method is used to identify leaks in China’s Da Hedong Reservoir dam. We develop vertical- and horizontal-gradient approaches based on the transmitted signal electrical field. A plastic frame is developed to allow the probe to measure horizontal gradients. We determine the exact location of leaks at the reservoir’s bottom and upstream face, respectively, assuming that current leakages are located in hydraulic leakage zones. Numerical experiments and water pressure tests reveal that the conductive silt layer beneath the reservoir can lower the response of the potential values at the leakage inlet, and the effect of the silt layer should be considered and not ignored when interpreting measured data. In addition, with regard to the principle of superposition, the contribution associated with metal pipes in the dam body can be roughly determined by subtracting it from the original potential field data, thereby aiding in locating leaks around the metal pipes. In addition, the FFF measurements from the reservoir’s bottom also confirm the position of existing faults in the substratum at the reservoir site. Last, the results of the FFF method are tested against supporting evidence, such as ground penetrating radar and water pressure tests. In conclusion, these independent data confirm the effectiveness of the FFF method for leakage localization in the concrete gravity dam.

Excess pore water pressure response of soil inside the mini bucket embedded in saturated soil under seismic loading

This study investigates the behavior of suction bucket foundations during seismic loading induced soil liquefaction through shaking table experiments using both steel and 3D printed mini buckets. The pore water pressure response of the soil inside and around the mini buckets was monitored, and the results show that excess pore water pressure ratios greater than 1.0, indicating liquefaction occurred inside and around the buckets. In order to verify whether the soil plug liquefies under seismic loading, a floating ball experiments was specifically designed. The findings suggest that behavior of suction bucket foundations may differ from that of gravity-based foundations when experiencing soil liquefaction, owing to their unique semi-enclosed geometric structure and suction installation method. The appropriately weighted steel mini bucket has the advantage of being less prone settlement in the liquefied soil, making it suitable as a monitoring platform for soil liquefaction.

Repair of undersea concrete using biopolymer-assisted plant urease

Concrete repair in marine environments is influenced by various factors, particularly underwater pressure and dynamic water flow. Traditional materials used for underwater concrete repair suffer from issues such as dilution, dispersion, susceptibility to erosion by moving water, and poor grout retention. In this study, a novel biopolymer-based undersea crack repair material composed of quaternized chitosan (Hydroxypropyl trimethyl ammonium chloride chitosan, HACC), sodium alginate (SA), urease, and aggregates was developed. It investigated the impact of biopolymers on urease's physiological and biochemical properties, as well as its mineralization capacity. Additionally, It conducted a comprehensive evaluation of the fluidity, rheological behavior, grout retention, mechanical properties, and anti-permeability rate of the bio-grouting material. The results showed that the optimized bio-grouting material exhibited suitable viscosity and fluidity. After injection, it rapidly formed a cohesive seal, with a grout retention rate exceeding 90 % at 48 days. The water resistance of the repaired concrete reached 93 %. Microstructural analysis using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) revealed strong electrostatic interactions between HACC and SA molecular chains. These interactions encapsulated mineralization products and sand particles, resulting in a denser microstructure.

Numerical investigate on the heat transfer performance and mechanical analysis of a water sublimator

Water sublimators play a critical role in efficiently managing the high thermal load of spacecraft in a vacuum environment, ensuring their proper functioning. This article focuses on a novel cold plate water sublimator driven by a porous sublimation tube structure, which is still in the theoretical research stage. Numerical methods are employed to study the evaporation, freezing, and sublimation processes, with validation against experimental data. The average absolute error of the four operating conditions is 1.33 K, and the ice layer thickness error is 8.33 %. Additionally, a method to calculate the effective thermal conductivity of porous aluminum foam is proposed, with a model error of 9 %. The sublimator's heat transfer characteristics are significantly influenced by the porosity of the aluminum foam and sublimation tubes. The impacts on temperature behavior, ice thickness, feed water pressure, and stress are carefully examined. Results reveal aluminum foam porosity of 0.7 and sublimation tube porosity of 0.3. Moreover, the study explores how different heat loads affect the sublimator's operation mode. Heat loads above 2 W/cm2 cause evaporation and dryness within the sublimation tube, while excessively small heat loads lead to ice formation and increased stress on the aluminum foam structure. These findings provide valuable insights for water sublimator design.

On the influence of the shearing rate on the monotonic and cyclic response of Malaysian kaolin

This article experimentally evaluates the influence of shearing rate on the monotonic and cyclic response of isotropically-consolidated samples of Malaysian kaolin. On the one hand, a series of undrained monotonic triaxial tests were performed with varying shearing displacement rate. On the other hand, undrained cyclic triaxial tests were conducted considering different deviatoric stress amplitudes and loading frequencies. The well-known soil rate-dependency under monotonic loading was confirmed up to a displacement rate threshold. The experimental results under cyclic loading suggest that for the given loading frequency, the variation of the deviatoric stress amplitude remarkably influences the strains and pore water pressure accumulation rates. In addition, the results suggest that depending on the loading frequency different shapes of mobilized effective stress loops are obtained. Larger loading frequencies lead to banana-shaped effective stress loops, while smaller frequencies reproduce eight-shaped effective stress loops. Furthermore, higher loading frequencies result in a larger number of cycles required to reach failure conditions. The reasons for the observed differences in the behavior are thoroughly analyzed and discussed.

Impact of nuclear heating distribution on the structural behavior of ITER first wall panel 11

The ITER blanket system safeguards the Tokamak's Vacuum Vessel and ex-vessel components from thermal and nuclear loads induced by the plasma. It comprises two parts: the First Wall panel facing the plasma and the Shield Block that provides the bulk of the shielding. The First Wall panels consist of Beryllium tiles on a CuCrZr layer, supported by stainless-steel structures which are cooled using a pressurized water circuit at 40 bar with an inlet temperature of 70 °C.Fusion for Energy has updated the thermal and mechanical analyses of ITER First Wall Panel 11 in preparation for the serial manufacturing. The panel will face heat flux up to 2 MW/m2 from plasma radiation, in addition to the volumetric nuclear heating, and the electromagnetic loads. A model with an enhanced detailed 3D geometry and heterogeneous materials indicates a 25% reduction of the deposited heating compared to the previous 2D model, from 625.4 kW (2D) to 455.4 kW (3D).The study embraces numerous thermal and mechanical analyses using Ansys software v19.2, incorporating 2D and 3D nuclear heating data. Responses are then compared and thus the possible impact of the two distributions on the thermal and mechanical behavior of the Fist Wall Panel 11 is assessed.