Water Pressure Research Articles

A sensitivity study on the PDFs treating uncertainties in severe accidents for pressurized heavy water reactors

This research article introduces a study regarding the uncertainties treatment during severe accidents for Pressurized Heavy Water Reactors (PHWRs). The present study is focused upon the unmitigated Station BlackOut (SBO) accident analysis for a CANada Deuterium Uranium (CANDU) type reactor emphasizing the impact of the uncertainties treatment on the relevant key timings of the SBO accident progression through different approaches for the uncertainty parameters’ Probabilistic Distribution Functions (PDFs). A comparison between the sensitivity analysis results is provided in the present research study.The uncertainty analysis is performed with the RELAP/SCDAPSIM code with the Integrated Uncertainty Analysis (IUA) package from the code.Results from the research would support the advancements on the best-practices for uncertainty analyses with respect to the parameter's uncertainties distribution functions. Data dispersion is a key element for the realistic quantification of uncertainties in nuclear power plant safety analyses, including severe accidents.

High-temperature water vapor sensors based on rare-earth-doped barium cerate

In this novel study, BaCe0.9Y0.1O3–δ, BaCe0.9Eu0.1O3–δ, BaCe0.9Nd0.1O3–δ, and BaCe0.9Dy0.1O3–δ powders were synthesized by the self-combustion method and processed into thick porous films (60–70 % porosity) to investigate the water vapor sensing properties in the 400–700 °C temperature range. All samples showed a stable response value to water vapor in the whole temperature range, expressed as impedance ratio in dry and wet argon (ZdryAr/ZwetAr), and were able to detect 0.03 vol% of water vapor at 550 °C within the impedance range of 103 Ω at 100 Hz. The response values increased with the partial pressure of water and decreased with the temperature, whereas the maximal value of 3.41 reached the BaCe0.9Eu0.1O3–δ sample at 550 °C and p(H2O) = 4.28 kPa. The average response time was several seconds and only slightly changed with the material type and experimental conditions. The recovery time depended on temperature and the ZdryAr/ZwetAr ratio, whereas the increase in the gas flow rate from 100 cm3/min to 200 cm3/min significantly reduced the recovery time for the BaCe0.9Eu0.1O3–δ sample from 230 s to 55 s at 550 °C and p(H2O) = 2.14 kPa. All the samples exhibited stability and a high degree of reversibility after multiple exchanges of wet and dry atmospheres at different temperatures. Yet, their tendency to deteriorate in the presence of CO2 might challenge a potential application in aggressive environments.

Prediction of the axial strain development curve of soft clay under dynamic triaxial conditions based on LSTM

The dynamic triaxial test results of soft clay show that a long-term cyclic traffic load lead to significant deformation of soft clay. Considering that the dynamic triaxial test data of soft clay under cyclic loading have apparent time series characteristics, the long short-term memory (LSTM) model can be used to predict the deformation law of soft clay. Through a dynamic triaxial test of Shanghai soft clay, time series data, such as axial stress, pore water pressure, and axial strain were obtained to establish the sample data of the LSTM model. The LSTM model is then used to predict the axial strain development curve. The results showed that the LSTM model had a good fitting precision for the sample data under different dynamic stresses and frequencies, and its accuracy was above 97% in all conditions. The prediction results can reproduce the fluctuation law of the axial strain under cyclic loads and can be used to study elastic and plastic strains. The research results can provide technical support for disaster prevention and control in soft clay.

Modeling the Seepage-induced Damage in Water-Rich Fault Zones at Tunnel Faces by Double Point Material Point Methods

During tunnel construction, crossing water-rich fault fracture zones leads to water influx hazards at the tunnel face. Excavation exposes the fault, causing disturbances and changes in the hydraulic gradient. Thus, the tunnel face becomes a low hydraulic head surface. The naturally high permeability of the fracture zone provides a pathway for groundwater flow, resulting in water seepage along the fracture zone and subsequent water influx at the tunnel face. To investigate this interaction, a two-phase double-point material point method was employed aimed at developing a coupled fluid-solid numerical model for excavating submarine fault tunnels. The model incorporates solid-liquid phase interaction, including rock mass permeability, water viscosity, and tunnel geometry. It analyzes the changes in the liquid-phase flow velocity, pore water pressure, and particle trajectories in the fractured zone ahead of the working face after the fracture zone is exposed, revealing the dynamic evolution of water influx following excavation. Additionally, this study discusses the impact of the solid-liquid phase permeability coefficients on the range of water influx hazards. The research findings demonstrate that the two-phase double-point material point method effectively captures the seepage and water influx processes, offering valuable insights into the mechanisms of sudden water influx in tunnel engineering.

Inrushing failure characteristics of deep shaft structures in soft soils based on material point method simulation

In areas with soft soil, inrushing may occur during the construction of deep shaft structures under high water pressures, causing destructive accidents. Most studies on inrushing have used the finite element method. However, it is difficult to achieve a large deformation simulation because of mesh limitations. The material point method is not constrained by the mesh, and the material properties and motion information of the material are stored at the material points. Therefore, it can be used to effectively simulate large soil deformations. In this study, a numerical model for a deep shaft structure in Shanghai was formulated using the material point method to simulate the evolution of inrushing failure. The likelihood of inrushing damage at different excavation depths was analyzed. Soil heave at the bottom of the pit in the absence of inrushing was examined. The structural and environmental factors affecting the inrushing process are discussed. Strategies have been proposed from different perspectives, such as structure, environment, and construction methods, to reduce the damage caused by inrushing, thereby providing a reference for the safer construction of deep shaft structures.

Research on Reduction Coefficients of Water Pressure on Outer Surfaces of Linings of Inclined Shaft Tunnels in Deep Embedment

Research on Reduction Coefficients of Water Pressure on Outer Surfaces of Linings of Inclined Shaft Tunnels in Deep Embedment

Analysis of the Influence of Groundwater Level on Slope Stability at Highwall PT. X, South Kalimantan

Mine slope design is an important part of mining operations because it is used to determine the balance between mine economy and operational safety. In the mine slope design there will also be a groundwater level design, the groundwater level is one of the triggers for a slide to occur. Therefore, this study aims to determine the effect of the groundwater level on the stability of the highwall slope cross section A-A’ as well as to determine the factor of safety value and probability of slope failure under various conditions of high groundwater levels. This research method uses quantitative methods because there are numerical data that will be used to calculate the value of slope stability. Slope stability analysis uses the “morgenstern-price” boundary equilibrium and the “monte-carlo” landslide probability. From the research results it is known that the higher the groundwater level, the lower the safety factor value because the presence of groundwater can reduce slope stability causing a decrease in soil shear strength due to increased pore water pressure. In addition, the weight of the material will increase due to the presence of groundwater, which causes the driving force on the slope to also increase. In addition, the movement of air in the soil can cause seepage forces which can affect slope stability. The lowest safety factor value is at the groundwater level 100% of the overall slope height, in conditions of 100% of the overall slope height, the deterministic safety factor value is 1.337, the mean safety factor is 1.358, and 0% hazard susceptibility.

Analytical model for calculating the soil pressure on inclined shield tunnels during construction phase

As a new tunneling technology for shallowly buried tunnels, ground penetration shield tunneling (GPST) penetrates the ground directly without launching or receiving shafts, thereby improving the construction efficiency and land-occupation economics. Unlike traditional shield tunnels, which have a leveled or approximately leveled route, the entrance and exit sections of GPST tunnels are inclined, and the external soil and water pressures acting on the latter vary along the route. This study proposes a new loading calculation model for the GPST during the construction phase, considering the dynamically varying stress state along the route. First, a comparison was conducted to delineate the advantages of the proposed model in contrast to the modified conventional method, followed by an analysis of the potential underlying reasons. Subsequently, a parametric study is conducted to evaluate the influence of the excavation slope on the soil pressures acting on the tunnel. The results indicate that the proposed method is better suited for calculating loads at shallow burial depths in GPST.

Numerical Evaluation of Pile Group Behavior Subject to Earthquake Loads

The seismic design of pile foundations mainly relies on analyzing the seismic response of layered, liquefiable locations. Two design scenarios are taken into consideration from the case histories; the first is how pile foundations react to the stresses and lateral displacements brought on by the lateral dispersion of liquefied soil. The second is how to piles reaction to seismic activity that occurs with the development of high pore water pressures. The PLAXIS 3D software is utilized in this research with a non-linear soil constitutive model (hypoplastic model) for both dry and saturated loose sandy soils under the impact of two earthquakes and the motion of different features to give a complete understanding of the dynamic piled foundation response. The findings from this study show that the site profile, pile diameter, pile length, and excitation of ground motion significantly affect the dynamic response of the layered liquefied site. So, in the saturated case, the increase in the piles length to (L/D = 55) in comparison to the original length (L/D = 35) decreased the peak acceleration at the raft foundation by about (24.4 and 41.9) % under the effect of Kobe and Upland earthquake motion, respectively, while in the dry case, the reduction in peak acceleration was about (22.8 and 40.9) % under the effect of Kobe and Upland earthquake motion, respectively.

Mechanical mechanism of soft soil foundation improved by geosynthetic-reinforced pile-supported technology based on field experiment

Geosynthetic-reinforced pile-supported (GRPS) technology is an effective method for improving soft soil foundations. Conducting field tests is crucial for accurately assessing the mechanical behavior of GRPS technology. Based on the fourth expansion project at Pudong Airport, field tests were conducted to investigate the effects of GRPS technology on soft-foundation treatment. Specifically, the tests examined the changes in the pile and soil settlement, pore water pressure, and pile and soil stress. The results showed that the settlement of the GRPS foundation mainly occurred during the loading period, accounting for approximately 65% of the total foundation settlement. Increasing the pile modulus and reducing the pile spacing decreased the total foundation settlement. The filling load was mainly transferred to the piles through the soil arching effect, resulting in a large excess pore water pressure in the soil layer near the pile tip. In addition, when the filling height was low, the load transfer relied predominantly on the tensile membrane effect of the geogrid, which was more pronounced near the piles. However, as the filling height increased, the soil arching effect surpassed the tensile membrane effect and played a key role in load transfer.

Formulation and numerical realization of anisotropic permeability coefficient for fluid-solid coupling in underground engineering

Underground engineering soil functions as a typical porous medium wherein groundwater flow and alterations in pore water pressure can influence the medium’s porosity, thereby affecting soil permeability. Moreover, changes in porosity (volumetric strain) result in anisotropy in the permeability coefficient, complicating the accurate depiction of the entire fluid-solid coupling process using a uniform permeability coefficient. Fluid–solid coupling is achieved by establishing a connection between soil and fluid parameters in response to changes in the permeability coefficient during soil deformation. Considering the limitations of the deformation mode described by volumetric strain, this paper proposes different influencing factors of anisotropic principal strains (εx, εy , and εz ) on the anisotropic permeability coefficient k i, based on the Kozeny–Carman semi-empirical equation for the permeability of porous media. Additionally, a numerical simulation method for the fluid-solid interaction effect in underground engineering is implemented by incorporating variations in the permeability coefficient with strain, using a fish-parameterized programming language within the FLAC 3D software. The coupling effect of the seepage field with the strain-dependent permeability coefficient on the mechanical field is validated using a specific calculation example. This methodology presents a novel approach for expressing fluid-solid coupling processes.

Effect of parameter optimization on the flow characteristics of venturi-self-excited oscillation mixer based on response surface model and multi-island genetic algorithm

Effect of parameter optimization on the flow characteristics of venturi-self-excited oscillation mixer based on response surface model and multi-island genetic algorithm

FAGSO-BP neural network model for settlement prediction of soft soil foundation

To address the problem of difficulty in theoretical formulas and numerical analysis methods to consider the prediction of foundation settlement in the case of multiparameter coupling, the fireworks algorithm (FWA) with a gravity search operator (FAGSO) is introduced into the back propagation (BP) neural network model, and the weight and threshold processes in the neural network are improved by the FAGSO algorithm. A soft soil foundation settlement prediction model based on a FWA optimized BP neural network (FAGSO-BP) with a gravity search operator is proposed. Based on the second phase of the soft foundation treatment project of the Shatian Port Area, Humen City, and Dongguan City, the parameters of pile load height, pore water pressure, and groundwater level were collected and tested. The results indicate that the average relative error of the predicted cumulative settlement value of the soft soil foundation was 0.06%, root mean square error was 7.68, mean absolute error was 4.30, mean absolute percentage error was 1.40%, and mean square error was 59.98. Compared with the BP neural network, GA-BP neural network, and FWA-BP neural network, the error was smaller and the model stability was higher.

The impact of initial fabric anisotropy on cyclic liquefaction behavior with polygonal particles using the discrete element method (DEM)

Liquefaction is one of the most significant phenomena that can occur in soil during an earthquake. The destructive effects of this phenomenon on earth structures have captured the attention of many geotechnical engineers. Additionally, the gradual increase in pore water pressure during the cyclic loading induced by the propagation of earthquake waves, known as cyclic liquefaction, is a crucial factor that might lead to the complete loss of shear strength in soils. A better understanding of cyclic liquefaction is essential for improving earthquake hazard analysis and mitigating structural damage. Factors influencing liquefaction behavior include particle size, particle grading, and soil fabric. By “soil fabric,” we refer to the arrangement and positioning of particles with each other, particle shape, and the shape of voids among particles. This research aims to focus on the effects of fabric anisotropy on cyclic liquefaction of granular soils with angular particles. To carry out this investigation, the discrete element method has been employed. In the discrete element method, the geometry of particles and, generally, the soil fabric can be considered. In this research, specimens with varying particle orientation angles were produced and subjected to cyclic loading tests under undrained conditions. By examining the stress paths of specimens during cyclic loading, it is observed that the initial fabric and inherent anisotropy significantly influence the behavior of the specimens. Inherent anisotropy leads to varying numbers of cycles required for the initial liquefaction of each specimen. Furthermore, it is observed that as the particle orientation angle increases, the localization of axial strains shifts from tensile to compressive directions. The effect of inherent anisotropy plays a substantial role in the initial liquefaction (ru = 1). If the liquefaction of specimens is of interest at lower values of ru, the effect of inherent anisotropy can be disregarded.

Experimental study of the dynamic characteristics of deep silty clay in Shanghai

To investigate the dynamic properties of deep silty clay, a comprehensive set of cyclic triaxial and resonant column tests were performed on undisturbed samples of silty clay containing sand from depths reaching 54.5 m in Shanghai. This study aimed to characterize the influence of confining pressure on the stress–strain behavior, pore water pressure, and dynamic modulus of the soil. The present findings revealed that the confining pressure, which is correlated with the depth of burial, significantly influenced the soil deformation. Moreover, elevated confining pressures resulted in increased stress within the hysteresis loops, a higher initial shear modulus, and a diminished ratio of excess pore water pressure. Based on the empirical data, a refined model was formulated for the shear modulus and damping ratio as functions of the shear strain for deep silty clay in Shanghai. These insights are intended to offer a robust reference point, facilitating calibration and guiding subsequent investigations into structures situated in the deep subterranean environments of Shanghai.

Investigations of the Effect of Artificial Rainfall on the Pore Water Pressure and Slope Surface Displacement of Loess Slopes

Investigations of the Effect of Artificial Rainfall on the Pore Water Pressure and Slope Surface Displacement of Loess Slopes

Effects of computational domain in underwater explosion numerical simulation on bubble pulsation

To clarify the influence of the computational domain size on the underwater explosion bubble pulsation, a one-dimensional axisymmetric model of the underwater explosion was established. The computational model was verified using empirical formulas. Further research was conducted on the variation patterns of the bubble pulsation period and maximum radius with changes in the proportional computational domain radius. The results indicate that as the proportional computational domain radius increases, the maximum radius of the bubble and the bubble pulsation period gradually increase and stabilize. The proportional computational domain radius required to achieve stability is related to the static water pressure of the computational domain. Increasing static water pressure makes the required computational domain size for achieving high numerical accuracy smaller. When the proportional computational domain radius reaches around 1600, the calculation results are highly accurate under different static water pressures at different depths of explosion.

Experimental study on the influence of principal stress axes rotation on sand mechanical behavior and non-coaxiality effects

The soil around the foundations of offshore engineering experienced the principal stress axes rotation caused by the wave loadings. To investigate the influence of the principal stress axes rotation on the soil stress-strain relationship, a series of pure principal stress axes rotation tests under drained/undrained conditions were carried out with a hollow cylinder apparatus. The undrained test results show that the deviatoric stress, relative density, and starting point of rotation affect the mechanical properties of sand. Through the analysis of pore water pressure accumulation in the 1st cycle, it was observed that more pore pressure accumulates in Quadrants II and III, while relatively less accumulates in Quadrants I and IV. Under drained and undrained conditions, the non-coaxial behavior of the soil differs. The non-coaxiality can be significantly observed in the drained test, and the direction of strain increment tends to the stress increment direction when the cycle number increases.

Physical model test on rainfall-induced instability of silty slope

In the context of ecological conservation and high-quality development in the Yellow River Basin, extensive silty slopes have emerged in the downstream alluvial plain regions owing to engineering construction. These slopes are susceptible to rainfall infiltration-induced instability, resulting in geological hazards, such as landslides and mudslides. This study explored the hydrodynamic characteristics and spatiotemporal evolution patterns of silty slopes under rainfall conditions, focusing on the alluvial silty slopes of the Yellow River. Experiments were performed to monitor variations in soil water content, soil water potential, and pore water pressure at various locations on the slope. Slope instability and failure under rainfall were monitored using high-frequency photography technology. The results indicated the development of layered vertical collapses along the surface of the slope, starting from the base and accumulating below the failure point. With increasing rainfall intensity, soil water content, soil water potential, and pore water pressure increased earlier at various points on the slope. These findings provide crucial experimental data and a theoretical foundation for exploring the instability mechanisms within silty slopes in the lower Yellow River’s alluvial and siltation plain areas during rainfall events. Moreover, they are significant for formulating more effective strategies for geological disaster warning and prevention.

Numerical simulation study on noise pollution of the pressurized gas system in pumped storage power station

To Investigate the noise pollution caused by pneumatic whistling during the blowdown operation of a pressurized gas storage system in a pumped storage power station, the flow field and sound field distribution of the gas storage tank under blowdown operation are analyzed in detail through full-channel unsteady numerical simulation of the gas storage tank and its supporting facilities. Subsequently, a comprehensive analysis of the noise issue in the gas cylinder was conducted. While investigating the mechanism of noise generation based on the distribution of noise intensity, the precise location of the noise source was pinpointed, providing a reference for the stability research of the exhaust pressurized water system.