Effect Of Seepage Research Articles

Surface Plasmon Effect Dominated High-Performance Triboelectric Nanogenerator for Traditional Chinese Medicine Acupuncture.

Available, effectively converting low-frequency vibration into available electricity, triboelectric nanogenerator (TENG) is always research hot nowadays. However, the enhancing effect of the existing methods for the output have all sorts of drawbacks, i.e., low efficiency and unstable, and its practical applications still need to be further explored. Here, leveraging core-shell nanoparticles Ag@SiO2 doping into tribo-materials generates the surface plasmon effect to boost the output performance of the TENG. On one hand, the shell alleviated the seepage effect from conventional nanoparticles; on the other hand, the surface plasmon effect enabled the core-shell nanoparticles to further boost the output performance of TENG. We circumvent the limitations and present a TENG whose output power density can be up to 4.375 mW/cm2. Points is that this article novelty investigate the high-performance TENG applicating for traditional Chinese medicine and develop a pratical self-powered acupuncture system. This technology enables rapid, routine regulation of human health at any age, which has potential applications in nearly any setting across healthcare platforms alike.

Water Field Distribution Characteristics under Slope Runoff and Seepage Coupled Effect Based on the Finite Element Method

The unsaturated seepage field coupled with heavy rainfall-induced surface flow mainly accounts for the slope instability. If the slope contains macropores, the coupled model and solution process significantly differ from the traditional one (without macropores). Most of the studies on the variation of the water field under the coupled effect of runoff and seepage on the slope did not consider the macropore structure. In this paper, two coupled Richards equations were used to describe the MF (Macropore Flow), and along with the kinematic wave equation, they were applied to establish a coupled model of SR (Slope Runoff) and MF. The numerical solving of the coupled model was realized by the COMSOL PDE finite element method, and an innovative laboratory test was conducted to verify the numerical results. The effects of different factors (i.e., rainfall intensity, rainfall duration, saturated conductivity, and slope roughness coefficient) on water content and ponding depth with and without macropores were compared and analyzed. The results show that infiltration is more likely to happen in MF than UF (Unsaturated Flow, without macropore). The depths of the saturation zone and the wetting front of MF are obviously greater than those of UF. When SR occurs, rainfall duration has the most significant influence on infiltration. When macropores are considered, the ponding depth is smaller at the beginning of rainfall, while the effects are not obvious in the later period. Rain intensity and roughness coefficient have significant influences on the ponding depth. Therefore, macropores should not be ignored in the analysis of the slope seepage field.

Optimal pumping scheduling for municipal water storage systems

In this paper, bulk water abstractions and a purification process in terms of water pumped energy consumption, is modelled and simulated. The study proposes an optimal energy consumption-rate management system, using real-time data. The aim is to achieve the goal of obtaining potable water by scheduling the pumping process, to obtain the cheapest energy-rate at any given load demand. Considering the loss due to the effect of evaporation, the effect of precipitation (or rainfall) and seepage losses.As a baseline, an electronic timer switching system for the powering of electrical pumps, used to pump water from one level to another, is incorporated. An optimal control system is included that looks at the energy cost before scheduling the pumping sequence in such a way that pumping occurs during the more affordable energy costing period and ensures that the water demand from consumers matches the water pump level in the storage reservoir.The configuration involved the time of use (TOU) tariff; in the context of the South African electricity tariff. The optimal control output, compared to an electronic timer switching system, shows an end-of-day cost reduction of 1994 ZAR in water-pumped energy consumption from the grid. This reduction in energy consumption is therefore a direct reflection of the reduction in the cost of water supply to consumers.

Fracturing of granite rock with supercritical water for superhot geothermal resources

Fracture patterns induced by supercritical-water fracturing show complex fracture networks with branched and isolated fractures. Such fracture patterns are expected to effectively increase permeability and significantly improve the heat exchange surface area. We clarify the mechanism of complex fracture induced by supercritical water using a coupled model and discuss the performance of the supercritical-water fracturing under geothermal environments. The numerical approaches to the coupled model are the pore-scale network method and finite element method with cohesive elements. Supercritical-water fracturing in granite at the laboratory scale was simulated and compared with the experimental results. The simulation results of fracture patterns are in good agreement with the experimental results.The results suggest that low viscosity of supercritical water leads to a strong seepage effect in granite, which reduces the effective stress over a wide area and makes it easier for shear failures to occur. We also found that differential stress and large confining stress induce more complex cloud-fracture networks. Our results clearly show that fracturing with supercritical water is effective not only for the geothermal resources that are considered so far but also for the development of the area at even deeper depths, which can contribute a leap forward in geothermal development.

Numerical Simulation of Soil Displacement and Settlement in Deep Foundation Pit Excavations Near Water

Advancing urbanization in China requires large-scale high-rise construction and underground transportation projects. Consequently, there is an increasing number of deep foundation pits adjacent to water bodies, and accidents occur frequently. This study uses a numerical simulation method to study the stability of the deep foundation pit near water based on the Biot three-dimensional seepage-stress coupling model, with the open-cut section on the south bank of the Jinan Yellow River Tunnel Project as the engineering field test. This indicates the following: (1) the maximum horizontal displacement of the diaphragm wall occurred in the fifth excavation stage, and a horizontal brace effectively controlled the inward horizontal displacement of the foundation pit; (2) considering the effect of seepage in the soft soil foundation, the maximum vertical displacement of the ground surface at each excavation stage occurred adjacent to the underground continuous wall. As the depth of the foundation pit increased, the vertical surface settlement decreases gradually in the direction away from the excavation face; (3) considering the seepage conditions, within each interval of excavation of the foundation pit, the horizontal displacement of the continuous underground wall and ground settlement declined; and (4) the numerical simulation and field monitoring data were in good agreement. Under the conditions of accurate model simplification and parameter selection, numerical simulations can adequately forecast conditions of the actual project.

Study on interactive effect of waste seepage and chemical reaction on changes in properties of silty clay

Study on interactive effect of waste seepage and chemical reaction on changes in properties of silty clay

Discussion on the optimal spacing of water curtain holes in cavern reservoir

Vertical and horizontal water curtain holes can be effectively used to seal underground oil storage caverns. However, the density of hole spacing affects the water sealing effect of the water curtain system. Based on the basic theory of Darcy’s law, this study established a three-dimensional model involving a main oil storage cavern, water curtain tunnel, water curtain hole, and surrounding rock mass. Different seepage effects on water curtain holes under different spacing are calculated and analyzed using a numerical analysis method. The optimal water curtain hole layout is finally determined by comparing the recommended spacing with the minimum water head difference.

Stability analysis of surrounding rock of high-pressure cavern tunnel under coupled stress-damage-seepage

The high-pressure cavern is located below the diversion tunnel, which will produce a large seepage force during the excavation process. Consider the effect of seepage field on the stress field with the seepage force, consider the effect of stress and damage on the seepage field through the improved Louis formula, and establish the stress-damage-permeability coefficient equation to consider the effect of stress and damage on the seepage field. The three-dimensional elastoplastic damage finite element analysis of rock mass structure has established a stress-damage-seepage calculation model for surrounding rock excavation of a diversion tunnel with high-pressure cavities. A sequential iteration method is proposed to summarize the above factors and then iteratively solve them in a certain order. Based on a water diversion project, the relevant calculation examples are appropriately simplified. The results show that the seepage effect has a greater impact on the stability of the surrounding rock of the diversion tunnel, and it can be seen that the coupling effect cannot be ignored in the analysis of the stability of the surrounding rock of the excavation of the diversion tunnel.

Research on water migration and deformation characteristics of coastal composite strata under artificial ground freezing affected by seepage

When the artificial ground freezing (AGF) method is used to construct underground structures in the coastal composite strata, the differences between characteristics of soft clay and silty sand under seepage often increase the risk of freezing construction and the difficulty of deformation control. In order to find out water migration and deformation characteristics of costal composite strata under seepage condition in freezing process, a series of unidirectional freezing tests of silty sand and soft clay in Shanghai and AGF model experiments on composite strata of soft clay and underlying silty sand were carried out under seepage condition. The results of unidirectional freezing tests of single soil type showed that the layered deformation curve of silty sand and soft clay can be divided into two types that steep mode of silty sand and gradual mode of soft clay. It also indicates that the water migration is fully developed within soft clay during freezing; but most of water inside silty sand froze quickly, thus water migration was not developed as that much in soft clay. In AGF model experiments, the seepage contributed to the development of water migration inside composite strata. However, the deformation characteristics of composite strata under seepage condition were evidently different from that of unidirectional freezing tests. The frost heave force development of the lower silt sand in the area directly affected by seepage was gradual mode, while that of the upper soft clay in the area indirectly affected by seepage was steep mode. The above results demonstrated that influence on freezing process of seepage is greater than that of soil properties in freezing process. Through research results, some optimization strategies can be made for the relevant measures to deal with the adverse effects of seepage and frost heave in the practice of the freezing method for coastal composite strata.

Effect of non-Darcy seepage on productivity of tight gas reservoir

In the process of gas reservoir development, with the production of formation fluid, the effective overburden pressure on the rock skeleton of the reservoir increases, and the rock is deformed under compression, which changes the physical properties of the rock (porosity, permeability, etc.), especially the influence on permeability. Stress sensitivity and threshold pressure gradient are important factors for non-linear seepage in tight gas reservoirs. This paper establishes an empirical prediction model through experimental tests and uses numerical simulation to analyze the effects on productivity. The experimental results show that the relationship between stress sensitivity and permeability is exponential, and there is a strong hysteresis effect. The starting pressure gradient of gas presents a power function relationship with water saturation and permeability respectively, and an empirical relationship is established to predict the starting pressure gradient by comprehensively considering the influence of permeability and water saturation. The single well productivity simulation shows that: The effect of starting pressure gradient on gas well development is greater than stress sensitivity. When starting pressure gradient or stress sensitivity is taken into account, the formation average pressure increases relative to each other and the stable production period decreases obviously.

Seepage and Heat Transfer Characteristics of Gas Leakage under the Condition of CAES Air Reservoir Cracking

The contradiction between supply and demand of energy leads to more and more attention on the large-scale energy storage technology; Compressed Air Energy Storage (CAES) technology is a new energy storage technology that is widely concerned in the world. The research of coupled heat transfer and seepage in fractured surrounding rocks is the necessary basis to evaluate the operation safety and effectiveness of CAES. Current studies point to the possibility of cracking in concrete liner seals, but the thermodynamic processes and leakage characteristics of compressed air in the presence of cracking and the heat transfer characteristics of seepage have not been addressed and reported. In order to investigate the leakage, the gas seepage and heat transfer law in fractured rock when the hard rock CAES gas reservoir seal cracks, the COMSOL fracture Darcy module, and the non-Darcy Forchheimer model are used as the constitutive seepage. The global ODE is used to calculate the thermodynamic process of compressed air in gas storage with coupled seepage and heat transfer process. The pressure and temperature of compressed air are obtained as the unsteady boundary of the seepage heat transfer model. A program for calculating the seepage and heat transfer characteristics of fractured surrounding rock in the CAES gas reservoir is established. On this basis, with the proposed Suichang CAES cavern as the background, the seepage and heat transfer characteristics of the fractured surrounding rock of the gas storage are studied. The results showed that when there are fewer cracks in the lining and surrounding rock of the air reservoir, the air pressure decreases due to a small amount of air leakage after 30 operation cycles, and the leakage rate of each cycle is 0.7% of the gas storage capacity, but it still meets the engineering requirements. If the plant is operating under these conditions, the charging rate will need to be increased by 1.2 kg/s per cycle charging stage. In the discharging and power generation phase, the high-pressure air that previously percolated into the rock mass cracks could flow back into the air storage through the lining cracks. Therefore, it is incorrect and unreliable to consider the gas which flows out from the inner surface of the lining as unusable. When the lining crack width is less than 0.3 mm, the seepage flow is Darcy flow and the non-Darcy effect can be ignored; when the lining crack width is greater than 0.5 mm, the non-Darcy effect of seepage cannot be ignored. The gas velocity in the surrounding rock fracture medium is on the order of 0.01 m/s with an influence range of over 100 m, and the gas velocity in the pore medium is on the order of 10-6 m/s with an influence range of 50 m. The findings of this study contribute to a better understanding of the interaction between the thermodynamic properties of compressed air and the seepage heat transfer process in compressed air storage underground reservoirs, as well as the gas leakage process in the event of liner seal cracking.

Numerical Investigation to the Effect of Suction-Induced Seepage on the Settlement in the Underwater Vacuum Preloading with Prefabricated Vertical Drains

Vacuum preloading combined with prefabricated vertical drains (PVDs) has the potential to improve the soft sediments under water, however, its development is partly limited by the unclear understanding of the mechanism. This paper aims to extend the comprehension of the influential mechanism of overlapping water in the scenario of underwater vacuum preloading with PVDs. The systematic investigations were conducted by small strain finite element drained analyses, with the separated analysis schemes considering suction-induced consolidation, seepage and their combination. The development of settlement in the improved soil region and the evolution of seepage flow from the overlapping water through the non-improved soil region into improved zone are examined in terms of the build-up of excess pore pressure. Based on the results of numerical analyses, a theoretical approach was set out. It was capable to estimate the time-dependent non-uniform settlement along the improved soil surface in response to the combined effects of suction-induced consolidation and seepage. The difference of underwater and onshore vacuum preloading with PVDs is discussed with some practical implication and suggestion provided.

Study of the slope deformation characteristics and landslide mechanisms under alternating excavation and rainfall disturbance

To investigate slope stability under alternating excavation and rainfall disturbance and to reveal the intrinsic mechanism of the slope stress diffusion process caused by stress-seepage coupling, a method consisting of separate simulation of the excavation stress field and rainfall seepage field and superposition analysis is proposed. Meanwhile, the distribution of the pore water pressure and transient saturation zone in the AK2 + 210 ~ AK2 + 610 section slope of a highway in Guangdong Province, China, is comprehensively analysed by calculating the rainfall seepage field during the excavation process. The effects of the rainfall seepage and slope stresses are further studied by applying the changing natural/saturated physical and mechanical parameters and pore water pressure values obtained by physical testing and parameter inversion. Moreover, the safety and stability of the highway slope during each stage is computed numerically using the strength reduction method, and the slope failure process, instability-inducing factors and failure mechanism are discussed in detail. The results indicate that the proposed separate simulation and superposition analysis method is effective and of considerable practical value in slope engineering. Additionally, a comprehensive slope stability treatment is suggested, which can be used as a reference for other slope projects experiencing alternating excavation and rainfall disturbance.

Theoretical Analysis on Safety Thickness of the Water-Resistant Rock Mass of Karst Tunnel Face Taking Into Account Seepage Effect

We took into account the adverse influence of the karst water seepage effect on the water-resistant rock mass of karst tunnel face. Based on the upper-bound theorem of limit analysis and the Hoek–Brown failure criterion, we obtained the calculation method of the critical safety thickness of the water-resistant rock mass. We carried out a feasibility analysis, an analysis of influencing factors and a comparative analysis with previous related research achievements of this method. The results showed that: (1) With the decrease of surrounding rock grade, the safety thickness of water-resistant rock mass gradually increased, and the safety thickness of surrounding rock at all grades remained within a reasonable range. (2) The safety thickness decreased as the compressive strength, the tensile strength and parameter A increased, and it increased as the karst water pressure, the tunnel excavation height, and parameter B increased. (3) The change trend of the safety thickness with the influencing factors was completely consistent under the two conditions of considering and without considering the seepage effect, and the safety thickness with considering the seepage force was greater than that without considering the seepage force. Taking the Yunwushan Tunnel of Yiwan railway as an example, the critical safety thickness of the water-resistant rock mass was calculated and the calculated value was in good coincidence with the safety thickness adopted in the actual project. The research results are of great significance to prevent the occurrence of high pressure filling karst geological disasters such as water inrush in tunnels.

Modeling Seepage Flow and Spatial Variability of Soil Thermal Conductivity during Artificial Ground Freezing for Tunnel Excavation

Artificial ground freezing (AGF) technology has been commonly applied in tunnel construction. Its primary goal is to create a frozen wall around the tunnel profile as a hydraulic barrier and temporary support, but it is inevitably affected by two natural factors. Firstly, seepage flows provide large and continuous heat energy to prevent the soil from freezing. Secondly, as a key soil parameter in heat transfer, the soil thermal conductivity shows inherent spatial variability, binging uncertainties in freezing effects and efficiency. However, few studies have explored the influence of spatially varied soil thermal conductivity on AGF. In this study, a coupled hydro-thermal numerical model was developed to examine the effects of seepage on the formation of frozen wall. The soil thermal conductivity is simulated as a lognormal random field and analyzed by groups of Monte-Carlo simulations. The results confirmed the adverse effect of groundwater flow on the formation of frozen wall, including the uneven development of frozen body towards the downstream side and the higher risk of water leakage on the upstream face of the tunnel. Based on random finite element analysis, this study quantitively tabulated the required additional freezing time above the deterministic scenario. Two levels of the additional freezing time are provided, namely the average level and conservative level, which aim to facilitate practitioners in making a rule-of-thumb estimation in the design of comparable situations. The findings can offer practitioners a rule of thumb for estimating the additional freezing times needed in artificial ground freezing, accounting for the seepage flow and spatial variation in soil thermal conductivity.

Landslide stability analysis using mathematical approach

Landslide is a commonly occurring natural disaster and also a societal hazard in the world. Rainfall is considered as one of the major triggering factors for cause of landslide slope failures. In the present study, a constitutive model is proposed and analyzed using mathematical theory, which deals better with geomorphic changes causing landslides. The constitutive behavior of soil is characterized along the planar shear plane and comprised of different soil properties with different strength parameters. The stiffness parameter of the soil along the shearing plane is analyzed to study the effect of infiltration and seepage of rainfall. The impact of water seepage on the stability analysis of landslide were discussed with importance. The present study shows the results that rainfall infiltration on the slope and the difference in the water level can tremendously influence the stability of landslide.

Enhancing the leaching effect of an ion-absorbed rare earth ore by ameliorating the seepage effect with sodium dodecyl sulfate surfactant

Ameliorating the problem of low leaching efficiency, long leaching period, and high agent consumption should be studied to efficiently exploit ion-absorbed rare earth ore resources. In this study, the surfactant sodium dodecyl sulfate (SDS) is used to enhance the leaching effect of an ion-absorbed rare earth ore by ameliorating the seepage effect for the first time. The effects of surfactant concentration, leaching agent dosage, solution flow velocity, and solution pH on the leaching rate were explored, and the mechanism of SDS was discussed. Under the optimum conditions, the addition of a small amount of SDS (mass fraction 0.04%) can increase the leaching rate by about 5%, shorten the leaching period, and reduce the consumption of the leaching agent. SDS significantly ameliorates the seepage effect of the ore body by reducing the surface tension of the leaching agent and ameliorating the wettability of the mineral surface. This effect is the main factor that improves the leaching efficiency. DFT (density functional theory) calculation results show that SDS can react with rare earth ions, which reduces the adsorption strength on clay mineral surfaces. Hence, rare earth ions are easily exchanged by ammonium ions, and mass transfer is enhanced.

The effect of leachate seepage on the mechanical properties and microstructure of solidified sludge when used as a landfill temporary cover material.

In this study, the effect of leachate seepage on the strength properties of a landfill temporary cover material: sewage sludge solidified with soda residue, ground granulated blast furnace slag, and quicklime, was investigated using small-scale column tests. The strength of the solidified sludge was reflected by penetration resistance with a micro penetrometer. The results showed that the penetration resistance increased at first, but then decreased with the increase in duration. The peak value for penetration resistance appeared at around the 75th day under the effect of leachate seepage. In contrast, without leachate seepage, penetration resistance increased at first as duration increased and then remained stable. The main hydration products were calcium silicate hydrate, ettringite and hydrocalumite. Some pollutants, such as copper, chromium, and arsenic, were also stabilized by the solidified sludge. The nuclear magnetic resonance results showed that the sample with highest penetration resistance had a reduced pore volume, especially macropore volume. Furthermore, leachate corrosion and the removal of some substances contributed to the decrease in penetration resistance after long-term seepage. The strength performance of temporary cover in laboratory short-term seepage and leachate soaking environments might be different from that in a landfill leachate seepage environment. This study improves understanding about the performance of temporary cover materials in landfill.

Mechanical characteristics of karst tunnel lining structure under the action of groundwater from rainfall seepage

Heavy rainfall in areas with developed karst depressions will cause the water pressure behind the tunnel lining structure to rise rapidly, which brings about high safety risk of the lining structure. In order to determine the stress characteristics of the karst tunnel lining structure under the effect of rainfall seepage, a load-structure numerical model was established to analyze the changes in axial force, bending moment and safety factor under different water load conditions. The calculation results show that the single-point (small range) water pressure often leads to the damage of the arch and invert of the lining structure. When the pressure-bearing range increases, the damage of the foot and side wall of the lining structure tends to occur. When the overall range of the invert is subjected to water pressure, the damage of the lining structure from the invert to the side wall is likely to occur. Among them, the increasing pressure-bearing range is the most unfavorable water load state, and the safety factor of each part of the lining structure is significantly smaller than that in other three water load states. The research results can provide reference for the design of the lining structure section in similar conditions.

The Analysis of Tunnel Collapse Mechanism and Grouting Reinforcement Measures Under the Unsaturated Seepage Effect

Based on the unsaturated seepage and strength theory, the influence of seepage on tunnel deformation and stability is studied, the mechanism of tunnel collapse under seepage is deeply analyzed, and the grouting reinforcement measures are put forward. The analysis results show that the strength attenuation of unsaturated soil caused by seepage is the main inducement of tunnel collapse. The development of tunnel collapse is controlled by conducting the backpressure of surcharge, improving the softening condition of soil, and grouting reinforcement of soil with weakened strength. Finally, the risk of collapse is effectively solved.