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In this paper, a homogenized multiphase lattice Boltzmann (LB) model is established for parallelly simulating immiscible two-phase flow in both solid-free regions (pore scale) and porous areas (continuum scale). It combines the color-gradient multiphase model with the Darcy–Brinkman–Stokes method by adding a term that includes surface force and drag force of porous matrix to multiple-relaxation-time LB equation in moment space. Moreover, an improved algorithm is proposed to characterize and implement the apparent wettability in the locally homogenized porosity field. Validations and test cases are given to demonstrate the accuracy and robustness of this new model, as well as its applicability for trans-scale fluid simulation of transport and sorption behavior from porous (Darcy flow) area to free (Stokes flow) area. For practicality, the two-phase seepage flow in a composite rock structure with multiscale pores is simulated by this new model, and the effects of viscosity ratio and wettability on the displacement process are discussed. [ABSTRACT FROM AUTHOR]

With reference to earth pressure balance (EPB) shield tunnelling, the pressure infiltration of foam into saturated sand is investigated through model study. The model accounts for the companion liquid flow during the foam spurt that was experimentally measured in a previous paper. A micro-stability model is established to predict the maximum foam penetration depth that is based on the minimum pressure difference over an individual foam bubble through the pore throats. From tests on three different sands, the micro-stability model compared well with two sands but underestimated the maximum penetration depth for the third. This is attributed to a case where many bubbles are small enough to flow through the larger pore throats unhindered. Further results from numerical simulation are in accordance with the measured discharge behaviour during the foam spurt. The general agreement suggests that the model could explain the foam infiltration behaviour and can be used to describe the foam spurt during foam infiltration that can be expected in EPB shield tunnelling. [ABSTRACT FROM AUTHOR]

Unlike the hydrodynamic model used in the current popular numerical simulation of buried gas pipeline leakage, this paper adopts the Darcy equation of underground seepage, mass balance equation, and equation of state of gas to establish a buried gas pipeline leakage model. Geometrically, the established model is a soil cylinder with the ground as the top surface and the vertical line through the pipeline leakage point as the axis. Due to the axial symmetry, the three-dimensional buried pipeline leakage model is expressed as a two-dimensional mathematical problem. A series of key concepts about the hydrodynamic model of buried pipeline leakage and its solution are presented. A comprehensive description of the physical process (pressure and flow rate) of buried gas pipeline leakage is provided through numerical examples. Quantitative analysis was conducted on the relevant structural parameters of the model and relations of leakage flow rate with related factors of leakage. By providing a comprehensive and quantitative understanding of buried gas pipeline leakage, this paper proposes a flow rate formula and an estimation formula of leak orifice equivalent diameter of leaking buried pipelines, and provides a theoretical and data processing framework for experimental study of buried gas pipeline leakage. [ABSTRACT FROM AUTHOR]

Reservoir heterogeneity, water-oil mobility ratio, cementation degree, and strong injection and production significantly influence long-term waterflooding and polymer flooding processes in oil reservoir development, leading to the formation of low-resistance dominant seepage channels in the lower part of thick oil layers without internal laminations. Understanding the spatial distribution and evolution of dominant seepage channels in oil reservoirs during waterflooding and polymer flooding is crucial for improving reservoir development and recovery rates. It uses a streamlined numerical simulation method to quantitatively show the spatial and temporal distribution of dominant seepage channels in the oil reservoir. A model and chart were created to demonstrate the relationship between permeability and throat radius, capturing changes in reservoir permeabilities over time. The study developed a comprehensive mathematical model to identify dominant seepage channels, considering parameters such as inter-well flow ratio, injection efficiency, permeability change value, and water saturation. Research findings indicate a 14.8 % increase in reservoir permeability after polymer flooding, with slight changes in porosity and a 20.3 % decrease in clay content. The established mathematical model and identification criteria were used to comprehensively quantitatively evaluate flow channels, describing the distribution characteristics and evolution process of dominant seepage channels in the experimental area over four periods: pre-polymer flooding, low water-saturation period during polymer flooding, post-polymer injection, and subsequent 10 years of water flooding. Both polymer flooding and subsequent water flooding have significantly altered the distribution pattern of predominant fluid pathways: 254 well layers now demonstrate robust predominant fluid pathways (19 %); another 272 well layers feature moderately predominant fluid pathways (22 %); while an additional 440 well layers display weaker predominant fluid pathways (approximately 35 %). There has been a noticeable increase in both weak and moderate predominant fluid pathways, which are now more widespread in the area. However, localized occurrences of strong predominant fluid pathways persist with no significant change in their distribution characteristics. Analysis at four different time points shows a clear trend of increasing intensity as we move from polymer to subsequent water flooding in this decade. Additionally, examination along an axis from upper left to lower right reveals a linear progression that indicates clear connections among different categories of dominant seepage channel. The verification results show a strong correlation between the calculated dominant seepage channel distribution and actual water-injection profile test results, indicating that the method effectively identifies dominant seepage channels in oil reservoirs after polymer flooding and has the potential to enhance oil recovery further. [ABSTRACT FROM AUTHOR]

This study investigates the diffusion characteristics and optimization of borehole water injection in the 3# coal seam of Licun Coal Mine under mining influence. The distribution of stress and permeability ahead of working face using FLAC3D combined COMSOL Multiphysics. The influence of distances between the borehole along with the diameters of the boreholes on the stress distribution around the borehole is studied. Additionally, the diffusion characteristics of coal seam water injection are analyzed under various parameters. The study found that borehole proximity to the working face significantly enhances stress relief and permeability, while borehole diameter has a minor impact. Simulation results from COMSOL Multiphysics indicated that increasing injection pressure significantly improves seepage velocity and wetting range, though borehole diameter effects remain negligible. Optimal water injection parameters were identified, suggesting that the most effective water injection occurs at a borehole 3 m from the working face, with a diameter of 0.11 m and an injection pressure of 10 MPa, achieving saturation within 48 h. This research contributes to the theoretical and practical understanding of optimizing borehole water injection in complex geological settings and thick coal seams. [ABSTRACT FROM AUTHOR]

This study investigates the intricate interplay of hydraulic coupling, creep damage, and permeability evolution mechanisms in phyllite, focusing on their relevance to tunnel engineering design and long-term stability in soft rock formations. To achieve this, conventional triaxial tests were conducted on saturated phyllite specimens under creep-seepage acoustic emission conditions. The results were systematically analyzed to unveil the inherent characteristics of creep deformation, seepage rate evolution, and damage progression in phyllite when subjected to stress–seepage coupling. Furthermore, a permeability model for representative volume element (RVE) was developed based on meso-mechanics principles, considering the distinctive attributes of low-permeability non-Darcy's flow in rock. Consequently, a novel relationship between effective damage and permeability was established. We determined that seepage pressure induces three key effects on the creep damage mechanism of phyllite samples: (1) It adds to the existing stress through the superposition of osmotic pressure and axial load, (2) it induces tensile expansion stress because of pore water pressure, and (3) it softens the fracture surfaces to some extent. More importantly, this study validates the relationship between effective damage and permeability through the fitting of creep and damage parameters, which were obtained from the test results, and it reveals a square relationship between subsequent damage and permeability under stress conditions. The findings of this study provide a robust theoretical foundation for comprehending the evolution of damage and permeability characteristics during the creep process of rock under seepage conditions. We obtained essential insights and quantitative analyses for comprehending the damage mechanisms in rock creep under hydraulic coupling, which has significant implications for tunnel engineering and long-term rock stability assessments in soft rock environments. Highlights: Model developed for RVE element based on meso-mechanics to consider low-permeability non-Darcy seepage in rock. Relationships between effective damage and permeability analyzed. Creep damage mechanism of phyllite under stress–seepage coupling investigated. Evolution law of damage and permeability properties of phyllite under seepage condition clarified. [ABSTRACT FROM AUTHOR]

The water repellency of soil occurs when organic matter coats the soil particle surface; this can either happen naturally due to wildfire and fungal growth or be induced by chemical treatments. The internal stability of water-repellent soils subjected to seepage has not been explored in the literature. In this study, the mechanical responses to internal erosion in three synthetic water-repellent soils, treated by different organic matters, were first investigated using a modified stress-controlled triaxial apparatus. The degree of hydrophobicity of the test soils was assessed through the measurement of apparent water contact angle. In each internal erosion test, the cumulative particle loss, deformation and hydraulic conductivity were evaluated. The water-repellent coatings efficiently suppressed the progression of internal erosion at practical hydraulic gradients because of their smaller fluid–solid adhesion. Continuously increasing the hydraulic gradient would finally result in a breakthrough of internal erosion due to the saturation of the hydrophobic soils under high pore-water pressures. Post-erosion contact angle measurements and scanning electron microscopy images confirmed the durability of the three water-repellent coatings against seepage erosion. The findings of this study confirm the potential of applying hydrophobic soils to mitigate internal erosion under normal hydraulic loading conditions. [ABSTRACT FROM AUTHOR]

Accurately assessing the erodibility of geomaterials is of great significance for the design of earthen structures and the prevention of the associated failure induced by seepage force. Recently, the un-resolved Computational Fluid Dynamics–Discrete Element Method (CFD–DEM) has been widely used to investigate internal erosion. However, due to the use of wall boundary and the fact that the fixed CFD domain cannot be changed with the soil sample's volume contraction during the erosion test, a larger porosity at the boundary of the CFD domain is commonly formed, resulting in sidewall preferential flow (i.e., relatively more fine particles migrate along the boundary of the DEM domain) and thereby overestimating the soil erodibility. In this study, a new method based on particle boundary is developed to tackle this problem. The newly proposed particle boundary can prevent its particles from erosion via inter-particle bonding and transfer stress from servo walls to the simulated sample. An optimal particle boundary thickness is determined by considering sample contraction and computational efficiency. The performance of the new method was compared with the conventional method and also verified using experimental results. The results show that the newly proposed method has significantly improved the uniformity of fluid velocity distribution. Furthermore, the cumulative eroded mass of fine particles in the new model is approximately 15% lower than in the conventional model. It is convincingly demonstrated that the new method can simulate internal erosion better and give a more accurate assessment of geomaterial erodibility. [ABSTRACT FROM AUTHOR]

In order to truly describe the dynamic characteristics of bottom-hole pressure in the reservoir, in this paper, the elastic outer boundary condition is introduced to replace the three kinds of traditional outer boundary conditions (infinity, constant pressure, closed), and a spherical nonlinear seepage model is established for the dual-porosity reservoir, which takes into account wellbore storage, effective well diameter and quadratic gradient term. The solution of the model in the Laplace space is found, and the similar structural formula of the solution is obtained by combining the Laplace transformation with the similarity construction method. Subsequently, by the Stehfest numerical inversion method, the well test curve is drawn, and the influence of main reservoir parameters on bottom-hole pressure dynamics is analyzed. The introduction of the elastic outer boundary not only breaks the traditional fixed form of the ideal outer boundary condition, but also improves the interpretation accuracy of the reservoir boundary. At the same time, a more general representation of the model is put forward, which provides a more effective theoretical basis for further exploration of the seepage law of the reservoir. Simultaneously, the similarity construction method simplifies the complex calculation process of solving the model and provides a new idea for solving the more complicated percolation model of oil and gas reservoirs. The similar construction method simplifies the complicated calculation process of solving the model and provides a new idea for solving the more complicated percolation model of oil and gas reservoirs. [ABSTRACT FROM AUTHOR]

Water conservation in arid and semi-arid regions faces significant challenges due to low and irregular rainfall, worsened by climate change, which negatively affects rain-fed crop productivity. Various techniques, including supplemental irrigation using runoff harvesting ponds, aim to address these issues but often suffer from water loss due to infiltration, influenced by the pond liner type. This study uses a factorial analysis to assess the farmers' perceptions of four pond sealing techniques. Using the Waso-2 method, a survey conducted in 2022 among 41 rainwater harvesting pond owners across three regions of Burkina Faso revealed that farmers prioritized impermeability and ease of maintenance over cost and availability. Concrete, scoring 16/20, was the most preferred, chosen by over 75% of farmers for its durability and resistance to weathering, despite its high cost. Geomembrane, with a score of 12/20, was valued for its waterproofing properties but had durability concerns. Clay, although cheap and available, scored 8/20 due to poor waterproofing on unstable ground. Bitumen, the least favored with a score of 6/20, was hindered by scarcity and lack of familiarity. To enhance supplemental irrigation in Burkina Faso and similar regions, waterproof concrete or durable geomembrane liners are recommended. Further research into improving bitumen and clay liners is also suggested. These findings provide key insights into farmers' preferences, offering guidance for developing effective water conservation strategies to boost agricultural productivity and address food security challenges in the context of climate change. [ABSTRACT FROM AUTHOR]

The problem of seepage control is faced in the construction of large underground powerhouse cavern systems. To reduce leakage and improve the permeability stability of the surrounding rock, a complex seepage control system, including drainage hole arrays, drainage tunnels, and grouting curtains, was designed for the Wunonglong underground powerhouse caverns. In this study, we performed a seepage field numerical analysis of the Wunonglong underground powerhouse caverns system to optimize the seepage control system. A three-dimensional numerical model was established considering the complex seepage control system and the geological conditions. A steady seepage analysis method, with a variational inequality formulation, was adopted in order to calculate the long-term seepage field. A drainage substructure method was used to simulate the seepage behavior of the densely arranged drainage hole arrays. The seepage control effects of single and double grouting curtains were compared to determine a reasonable curtain layout scheme. The effect of the drainage system on the seepage control of the powerhouse caverns is further discussed. The findings offer reliable insights into the seepage behavior of underground powerhouse caverns and provide a reference for the design and construction of similar underground powerhouse cavern systems. [ABSTRACT FROM AUTHOR]

Evaluating groundwater inflow is greatly significant for ensuring the safety and economy during foundation pit dewatering with suspended waterproof curtains. However, there are limited applicable methods to predict the groundwater inflow of circle foundation pit with waterproof curtains in deep unconfined aquifers. In this study, based on Darcy's law and the continuity of water flow, the impact of suspended waterproof curtains on groundwater seepage was initially analyzed during circle foundation pit dewatering in deep unconfined aquifers. Furthermore, an analytical solution was proposed for groundwater inflow of circle foundation pit with suspended waterproof curtains in the unconfined aquifers. The effect of suspended waterproof curtains on seepage area, seepage direction, and seepage path were respectively considered by introducing the buried depth of waterproof curtain, the anisotropy coefficient, and the seepage path reduction coefficient. Finally, based on the self-conducted indoor seepage experiment and other cases (an indoor seepage experiment and two actual engineering projects), this proposed method was applied to conduct a comparative analysis with the existing methods. Results indicated that the proposed method can more reasonably evaluate the groundwater inflow of circle foundation pit with waterproof curtains in the unconfined aquifer, which can provide a better guidance for the groundwater inflow control in the practical dewatering projects. [ABSTRACT FROM AUTHOR]

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The seepage field of a suspended waterproof curtain strip foundation pit in a deep phreatic aquifer is theoretically analyzed, and a calculation method for the foundation pit water inflow and water level outside the curtain is derived. In this paper, it is assumed that the horizontal hydraulic gradient of the seepage field above the aquiclude below the bottom of the waterproof curtain decreases linearly. The separation variable method is used to solve the seepage field in the regular area inside the foundation pit, and the hydraulic head distribution function inside the foundation pit is obtained. According to the hydraulic head distribution function inside the foundation pit, the calculation expression of the water inflow of the foundation pit is further deduced theoretically. On this basis, the improved resistance coefficient method is applied to link the water level outside the pit with the solved hydraulic head inside the pit and solved. In addition, the calculation results presented in this study are compared with the calculation results of the existing model and the measured data of the foundation pit project of Yangwan Station, which proves that the analytical method can effectively meet the requirements of engineering applications. [ABSTRACT FROM AUTHOR]

Rigid-wall permeameter testing of two potentially unstable gradations established that the critical hydraulic gradient to trigger instability is smaller for upward flow than for downward flow. The experimental finding is explained with reference to the Skempton-Brogan stress reduction factor α in the finer fraction content of the soil. Theory uses the α-factor to define a hydro-mechanical envelope in gradient-stress space that is independent of flow direction, and the experimental results are found to be in good agreement with the theory. Testing with upward flow is recommended to determine the value of α for an internally unstable gradation because, in contrast to downward flow, there is no requirement for an outflow boundary. [ABSTRACT FROM AUTHOR]

To investigate the influence of uniaxial tension on the permeation characteristics of the Geotextile-sand system under different water flows, a self-developed multifunctional gradient ratio permeameter was used to conduct relevant permeation tests on three commonly used geotextiles in engineering. The study, respectively, explores the variations in seepage velocity and gradient ratio of the Geotextile-sand system under different uniaxial tension strains with unidirectional water flow and reciprocating water flow, as well as the effects of different water flows on the system under the same uniaxial tension strain. The test results indicate that the trends of gradient ratio and seepage velocity in geotextiles are consistent under different water flows; however, the gradient ratio under reciprocating flow is smaller, while the seepage velocity is greater compared to unidirectional flow. [ABSTRACT FROM AUTHOR]

Abstract Excessive seepage significantly affects the stability of levees during flood seasons. Recently, infrared thermal imaging technology has been proposed to detect the seepage leakage of levees for its simplicity, high efficiency and non-contact. However, previous studies mainly focused on theoretical and laboratory tests to verify its effect, which involve many assumptions and simplification. This paper aims to study the practical application effects of infrared thermal imaging technology on levee leakage detection. A typical embankment in Xiangyin County, Hunan Province is selected as the studied area, where a specific point containing water is considered as the potential leakage point. Then, DJI M300RTK UAV equipped with Zenith H20T gimbal is adopted to collect the visible and infrared images of the embankment’s leaking point. The visible and infrared image data collected at different times and at different measurement heights are analyzed to investigate the detection accuracy of infrared thermal imaging technology. Results show that the infrared thermal imaging technology can accurately identify the potential seepage leakage point of levees. Compared with the visible light recognition method, the infrared thermal imaging technology can identify the location and scope of leakage hazards more clearly and accurately at night. During the daytime, infrared detection is less effective than visible light method. Moreover, the measurement altitude between the drone and the target leakage points significantly affects the detection accuracy of infrared thermal imaging technology.

Environmental factors (such as temperature and water) and their coupling effects will change the unloading creep properties of surrounding rock after tunnel excavation, threatening the stability of surrounding rock and the safety maintenance of construction sites. To analyze the effects of temperature, seepage flow, and their coupling on the creep characteristics of sandstone unloading, the triaxial unloading creep test was carried out on the sandstone specimen (φ50 mm×100 mm) by using the self-designed temperature control system and the improved pore water conduction specimen sealing device. The results show that during the creep time of 300 min after unloading the confining stress, the axial compression and radial expansion creep speed increase gradually and then slow down. The strain is mainly radial creep. The decrease in temperature leads to the increase in axial creep deformation and the decrease in radial creep deformation of the dry and saturated specimens. With the increase in seepage water pressure, the axial strain reduces, and the seepage water pressure suppresses the axial creep deformation, while the radial strain increases significantly, and the expansion phenomenon is obvious. Seepage water pressure promotes radial creep deformation. With the increase of seepage water pressure, the axial unloading creep rate decreases and the radial unloading creep rate increases. Under the coupling effect of temperature and seepage, the creep rate curve of unloading is divided into the attenuation stage and the stable stage, and the deformation in the attenuation stage is dominant. The radial creep rate is higher than the axial creep rate, and the fluctuation amplitude of the radial creep rate is small, which reaches stability fast. This study can provide scientific information for the stability evaluation of surrounding rock in deep underground engineering.

Vacuum preloading via prefabricated horizontal drains (PHDs) is an efficient technique to accelerate the consolidation of dredged soft soils. However, this technique lacks a clear and concise theoretical solution to the PHD vacuum consolidation analysis for slurry. To address this issue, this study proposes a novel analytical solution based on a mathematical logical procedure. The governing equations are first derived based on square PHD consolidation unit cells given the assumption of equal strain, taking into account various drainage conditions at the boundaries and the horizontal and vertical spacings of PHD. A seepage direction coefficient, directly determined through PHD spacing without additional identification, is further introduced into the derived formulation to enhance the solution to be more consistent with the results of free strain consolidation analysis. Then, the proposed analytical solution is validated based on three laboratory and field tests. The proposed solution is successfully applied to estimate the consolidation behavior at a site in Aomori Prefecture, Japan, involving PHD vacuum preloading. All results demonstrate that the proposed analytical solution is applicable for the design and management of PHD vacuum preloading construction projects and practically useful for engineers. Furthermore, the influences of the large strain effect, variable hydraulic conductivity, and variable compressibility on the consolidation analysis are discussed. [ABSTRACT FROM AUTHOR]

The rheological properties and seepage laws of fractured rock masses have a highly significant impact on the long-term stability of engineering rock masses. To study the rheological properties and seepage laws, rheological experiments under different loading paths were designed and conducted on sandstone samples with pre-fabricated single fractures. The results indicated that (1) as the axial stress or pore pressure increases, or the confining pressure decreases, the creep strain (both axial and radial directions) during the creep tests increases, and their stain rate decreases; (2) compared to the pore pressure, the axial stress and confining pressure have a more significant influence on the flow rate during the creep process. As the axial stress increases or the confining pressure decreases, the flow rate shows an increasing trend; (3) the higher connectivity results in higher final flow in an exponential function, indicating that the connectivity ratios can well reflect the permeability of the fractures; (4) the changes in the stress field may lead to the transition of the surrounding rock from a stable state to an unstable state, i.e., the occurrence of creep failure, or water inrush. Therefore, when the state of the surrounding rock changes, strengthened monitoring and proper preventive measures should be implemented.

Background: Special attention should be given to the seepage in dams since it may cause failure. Seepage is not considered in the total risk factor calculated using the International Commission of Large Dams (ICOLD), the United States Bureau Reclamation (USBR) while the description of the dam seepage condition is given a weightage in the Brazilian method. Methods: Haditha Dam, Iraq, was constructed on varying degrees of limestone beds of the Euphrates and Ana formations. Therefore, seepage from the dam should be continuously monitored and accurately measured. In the present study, a methodology was proposed to overcome the problem of inconsistent seepage data. The inconsistent seepage rates can be replaced by the predicted seepage rates obtained from SEEP/W model. Results: The predicted seepage rates for different water levels in the reservoir of Haditha Dam were found in association (R2 = 0.96). In addition, the value of mean absolute error (MAE) for the model accuracy was found to be 0.0106. According to the Brazilian index, the weightage for the seepage condition of Haditha dam was in the second category and equal to 3. Conclusion: For Haditha Dam, the seepage data cannot be used in the dam risk assessment since it was inconsistent with gaps, and it can be replaced by the consistent predicted seepage rates predicted by SEEP/W model. Generally, the aging and other dam problems result in increasing seepage rate. This highlights the importance of efficient management that follows resilient monitoring and surveillance programs that ensure dam safety.

Abstract Background Seepage control measures are essential in earth dams to enhance their safety against seepage and slope failures. A diaphragm is a thin impervious wall that is used in the core area of the dam to prevent the seepage of water. Any crack in the diaphragm can reduce its efficiency and threaten the safety and stability of the dam. Extensive evaluation of the influence of diaphragm fracturing on dam safety is required to establish a safe design and offer the appropriate measures. This study investigates the effect of diaphragm cracking on the safety of the dam for seepage and slope stability. A permeability tank is first used to validate the numerical model; then, different scenarios for cracked diaphragm walls are studied numerically. The crack’s height, width, direction, and number are all investigated. The effect of having a downstream horizontal blanket drain with cracked internal diaphragms is also evaluated. Results The results showed that the internal diaphragm enhances the safety of earth dams as it reduced the seepage discharge by 98% and increased the downstream slope safety by 34%. Considering the development of a crack in the internal diaphragm, the most critical location was at the base of the dam, wider cracks were more destructive, and the most critical direction was the horizontal crack. The fracturing of the diaphragm at multiple locations proved to be detrimental to the safety of the dam. Having three cracks caused the seepage discharge to reach 74% of its value for no diaphragm, the pore water pressure to raise drastically, and the downstream critical factor of safety to be higher than the case of no diaphragm by 8% only. Conclusions According to the findings, it is advised to continuously monitor the components of diaphragm-type earth dams and perform the necessary maintenance works whenever any sign of damage or water seepage appears. Furthermore, using a well-graded horizontal drain of sufficient length and high permeability with the internal diaphragm is highly recommended as a mitigation measure if diaphragm fracturing occurs. This helps to quickly release the seeping water and keep the phreatic line away from the downstream slope. Graphical abstract

This research article focuses on achieving water security in hilly terrains through the identification of suitable sites for rainwater harvesting reservoirs near habitations. The study was conducted in the planned geological park (PGP) location within Sikkim University (SU) campus, utilizing a multi-faceted approach that combined geological, geophysical, and geotechnical methodologies. The analysis of ALOS-P DEM revealed the absence of streamflow within SU campus, ruling out direct water recharge options. However, the planned geological park (PGP) location exhibited a gentle slope and receives an annual average precipitation (ERA) of 1215 mm indicating potential for rainwater harvesting. Geological fieldwork excluded densely fractured areas, involving data collection on soil and rock types, joint analysis, soil sampling, and Schmidt hammer tests. Geophysical fieldwork provided insights into fracture zones, layer depth, and fracture orientation. Incorporating data into a non-linear finite element model allowed to assess shear, deformation, and safety factors, identifying Site A as most suitable due to higher stability compared to Sites B and C. The key innovation lies in the integration of scientific methodologies. The combination of geological, geophysical, and geotechnical data, in the study has presented a holistic approach to site identification, ensuring a comprehensive understanding of the terrain’s hydrological characteristics.

The seepage-stress coupling characteristics of fractured rock mass were studied theoretically in this paper. Based on the cubic law and the equivalent circuit principle, a modified multi-parallel plate equivalent model (MPPEM) for seepage analysis of a rough single-fracture and a modified equivalent seepage resistance model (ESRM) for seepage analysis of a fracture networks consisting of rough single-fracture combined in series and parallel were proposed. On this basis, the equation for the variation of fracture aperture of fractured rock masses under the action of the three-direction principal stresses and pore water pressure was derived, and the discrete element calculations of the seepage-stress coupling of the two-dimensional fractured rock mass were carried out under different ground stress coefficients. The results show that the error of the modified MPPEM characterizing the seepage in a rough single-fracture in a rock mass does not exceed 7%. The modified ESRM can better characterize the seepage in T-shaped combined fracture and × -shaped combined fracture. With the increase of normal stress applied to the fracture surface, the fracture aperture and seepage flow rate of the fractured rock mass decrease. The above study is of great theoretical significance for the analysis of the seepage evolution law of the fractured rock mass under the action of geostress. [ABSTRACT FROM AUTHOR]

Archive data (1970–2024) on the results of monitoring the tritium content of surface liquid radioactive waste (LRW) storage reservoirs (special radioactive waste repositories) and of groundwater in the vicinity of the Mayak Production Association are analyzed. The tritium contamination existing today was formed before the 1970s and was initially accumulated (a) in V-2 reservoir (Kyzyl-Tash), which operated as a reservoir for recirculating direct-cooling of industrial uranium–graphite reactors (PUGRs) in case of failure of uranium slug cladding; (b) in V-9 (Karachay) and V-17 (Staroye Boloto) reservoirs, which were used for storage of intermediate-level tritium-containing liquid waste; (c) in groundwater as a result of tritium seepage from the reservoirs. After putting into operation the RT-1 radiochemical plant (1977), the major fraction of tritium was accumulated in a new LRW type, tritium condensate, which was stored in V-17 reservoir. The contaminated groundwater filtering from V-17 reservoir was discharged only into an inlet of V-10 reservoir of the Techa Cascade of Reservoirs (TCR). The maximal rate of tritium discharge was estimated at 0.11 TBq/year, and the specific activity of tritium in the TCR water, at 2 Bq/L. In the 2020s, the tritium discharge into the atmosphere from the RT-1 plant was ~34 TBq, which was ~2800 times lower than the maximum permissible discharge prescribed for the whole enterprise. The mean value of the annual effective dose from all the pathways of tritium intake by Ozyorsk inhabitants was 0.26 μSv, and the maximal value was 0.49 μSv, which is ~2000 times lower than the dose limit of 1 mSv for the population. The tritium emissions and discharges from the RT-1 plant are negligible and exert virtually no radiation impact on the population. [ABSTRACT FROM AUTHOR]

A new type of small, dry-filled geotextile tubes is introduced, that, in a stacked formation, can be used as dike cores. Dikes made out of these tubes consist of great potential regarding more resilient flood protection. The geotextile protects the fill from erosion, enabling steeper slopes along with reduced material and less land consumption. The behavior and potential failure mechanisms of such dikes were investigated first by literature research and second by full-scale hydraulic model tests under systematic variation of tube number, number of textile layers, filling ratio, and fill material. The tubes were exposed to the loads of seepage and overflow. Most relevant failure mechanisms were seepage-induced sagging, lateral displacement, and overturning of the upper tube due to overflow. During seepage, the tube height was reduced by up to 22.8 % due to sagging. Overflow led to a lateral displacement of up to 13 cm and, at overflow heights of 23.1 cm and 26.8 cm, to overturning of the upper tube. The present results give new insights into the behavior of innovatively constructed geotextile tubes under hydraulic loads and serve as basis for the development of design rules. • Dry-filled geotextile tubes represent a promising way towards resilient river dikes • Tube behavior is investigated experimentally under parameter variation • Sagging and lateral deformation must be considered in design rules • The tubes withstand overflow heights of >20 cm • Compacting the tubes increases the stability [ABSTRACT FROM AUTHOR]

Permeation grouting – injections at low-pressure values of either microfine cements or chemical products – is frequently adopted to increase the mechanical/hydraulic properties of soils, and standard design approaches are currently either empirical or based on simplified analytical solutions. In this paper, some fundamental hypotheses of these analytical solutions are discussed by carrying out a campaign of finite-element numerical analyses, in which the injection phase in a water-saturated soil is analysed, a Newtonian rheology for the grout is implemented and the hypothesis of immiscibility for the two liquids is assumed. The effect of injection source geometry is discussed, as well as the role of gravity and capillarity. The authors analyse the conditions, in terms of injection flow rate, grout viscosity, soil intrinsic permeability and retention curve, under which the analytical solutions provide reliable results. The numerical results have been compared with the simplified analytical solution herein derived for a one-dimensional spherical geometry, in terms of the 'characteristic curves' for the system: the relationship between injection pressure/grout front advancement and injection time. [ABSTRACT FROM AUTHOR]

High-pressure groundwater brings great challenges to the construction of mountain tunnels. Hence, controlling and discharging groundwater are two key problems that must be addressed before constructing tunnels in high-pressure and water-rich region. Fluid–solid coupling seepage analysis method is used to analyze the variation of displacement, stress and pore water pressure of the tunnel. A waterproof and drainage method suitable for tunnels in high-pressure and water-rich region is proposed. Curtain grouting plays a dual role in waterproof and reinforcing surrounding rock. Decompression drainage holes are designed in order to further reduce the pore water pressure acting on the initial lining. The thickness of grouting circle, the permeability coefficient ratio and the decompression drainage holes distribution rate of the initial lining are the main factors that affect the waterproof and drainage effect of tunnels in high-pressure and water-rich region. Suggested parameters on waterproof and drainage measures for tunnels in high-pressure and water-rich region are given after comprehensive analysis, which can provide basis for the technology on high-pressure groundwater treatments and constructions of underground engineering under complex geological conditions. [ABSTRACT FROM AUTHOR]

Safety conditions in geotechnical structures require the investigation of the phenomena responsible for the loss of their stability. When combined with commonly used direct investigations, geophysical methods add greater efficiency to geotechnical investigations, since their application allows the acquisition of a large amount of data in a short period of time, and at a relatively low cost. In this context, the present study aimed to evaluate percolation through the massif of a small earth dam, based on an integrated interpretation of results obtained with the application of the geophysical methods of Electroresistivity and Self Potential, in addition to results from geotechnical investigations previously carried out on the structure. The results proved the efficiency of the proposed methodology, allowing the confirmation of hypotheses formulated by other authors in previous studies of the same dam. Also, the results allowed the evaluation of the efficiency of correction works carried out in the dam massif to solve the problems caused by a piping process. Among the identified geotechnical properties, a preferential flow path, which indicates the occurrence of a water loss process through the dam foundation layer, was detected and can be linked to the occurrence of a landslide on the downstream slope of the embankment. It can be concluded that the geophysical survey effectively evaluated the geotechnical conditions and seepage within the massif and its foundations, meeting the study's objectives. Both shallow and deep flow paths in the study area were delineated, pinpointing the factors contributing to their occurrence. [ABSTRACT FROM AUTHOR]

This study investigated active and passive lateral earth pressure in the presence of anisotropic seepage conditions. The soil was assumed to be granular and fully saturated. Three methods were used to solve the problem: (1) the upper bound limit analysis method (UBM); (2) upper and lower bound solutions of finite-element limit analysis (FELA); and (3) the stress characteristic method (SCM). The proposed analytical solution for the UBM employed the logarithmic spiral slip surface. The lateral earth pressure coefficients for the active and passive cases were calculated and presented, considering variations in the vertical-to-horizontal hydraulic conductivity ratio, friction angle, and soil–wall interface friction angle. The obtained results for the active and passive cases agree with those of previous studies. The results of the SCM showed that in the presence of seepage, the distribution of stress on the soil–wall interface is nonlinear. In addition, the failure zone obtained from different methods was compared and examined. The failure patterns obtained from the SCM and FELA were almost identical. [ABSTRACT FROM AUTHOR]

To understand the fluid hydraulic behavior change in a fracture under different shear displacements, fluid flow simulations at different flow velocities are carried out based on the Navier–Stokes equation. We characterized and conducted statistics on the change and distribution of the fracture aperture under different shear displacements, especially the measurement of the contact area under shear displacement, which was helpful for accurately studying the effect of shear displacement on fracture fluid flow. The results showed that the shear displacement of a fracture could be regarded as dislocation between the upper and lower fracture surfaces. The fluid flow velocity became larger near the contact sites and the streamlines became denser. The resulting hydraulic aperture exhibited a negative correlation with the contact area. The relationship between the volumetric flow rate and pressure gradient during the flow field simulation could be well-fitted by the Forchheimer equation, and the steepness of the curves was related to the contact area. The linear coefficient a and the nonlinear coefficient b in the Forchheimer equation were positively correlated with the contact area. Based on the measured flow velocity, the mechanical aperture was usually an order of magnitude larger than the hydraulic aperture. The linear relationship between the mechanical aperture and hydraulic aperture was described. The positive correlation between the permeability and mechanical aperture profiled during shear explained the hydraulic behavior in the flow field. [ABSTRACT FROM AUTHOR]

Existing methods for calculating the ultimate support pressure of tunnel faces do not consider the control of seepage flow. Therefore, a model for calculating the ultimate support pressure under seepage conditions was established based on a two-dimensional water head distribution model and the upper bound theorem of limit analysis. The reliability of this method was verified through comparisons with other studies. Subsequently, the influence of water level and tunnel face water pressure coefficient on stability was analyzed. The results indicate that the ultimate support pressure is linearly positively correlated with the water level and tunnel face water pressure coefficient; as the water level increases and the water pressure coefficient decreases, the failure area extends and enlarges. Finally, an existing seepage flow calculation formula was introduced, and a method for calculating the ultimate support pressure based on seepage control was proposed. The appropriate tunnel face water pressure coefficient is determined through the seepage flow calculation formula, and the corresponding ultimate support pressure is then calculated. The results demonstrate that this method can provide better theoretical guidance for seepage control in tunnel faces in practical engineering. [ABSTRACT FROM AUTHOR]

In this paper, the research progress made in the methods used for assessing the internal stability of landslide dam soils was reviewed. Influence factors such as the gradation of soil and the stress state in the soil in different analysis methods were discussed, as these can provide a reference for the development of more accurate methods to analyze the internal stability of landslide dam soils. It focuses on the evaluation of internal stability based on the characteristic particle size and fine particle content, hydraulic conditions such as the critical hydraulic gradient and critical seepage velocity, and the stress state such as lateral confinement, isotropic compression, and triaxial compression. The characteristic particle size and fine particle content are parameters commonly used to distinguish the types of seepage failure. The critical hydraulic gradient or seepage failure velocity are necessary for a further assessment of the occurrence of seepage failure. The stress state in the soil is a significant influence factor for the internal stability of natural deposited soils. Although various analysis methods are available, the applicability of each method is limited and an analysis method for complex stress states is lacking. Therefore, the further validation and development of existing methods are necessary for landslide dam soils. [ABSTRACT FROM AUTHOR]

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In the last decade, Brazil witnessed disasters relating to tailings dams. This led to changes in the National Dam Safety Policy, which regulates a set of measures to improve dam safety management. In this context, this paper presents a case study of the Ribeirão João Leite dam. The dam consists of a concrete gravity structure with embankment fill at both abutments, placed on a foundation composed of gneiss with quartzite veins. The study aims to investigate its seepage behavior and assess the performance of the seepage control system in the concrete and embankment cross-sections at the right abutment. Two-dimensional seepage analyses under steady-state and transient conditions were performed using the finite element method. A straightforward approach based on monitoring data was proposed to validate seepage analyses and estimate the efficiency of the seepage control system. It was concluded that the foundation of the dam has a significant influence on the pore water pressures and seepage flow behavior due to the presence of markedly fractured materials. The analyses indicated that the efficiency of the grout curtain in the right abutment foundation is not noticeable. On the other hand, the foundation drains play an important role in controlling pore water pressures throughout the dam foundation, even in unfavorable geological conditions. The efficiency of these drains was 28% at the drainage line of Block 2, preventing pressure increases of 36% in the foundation of Block 2 and 160% in the horizontal filter drain. [ABSTRACT FROM AUTHOR]

The post-construction improvement technology of bored pile tips has been widely used in the construction of gravel pebble layers, but the diffusion law of the grouting slurry remains to be revealed. To study the diffusion law of the grouting slurry at the tip of bored piles in gravel pebble layers, an equivalent relationship between the seepage continuity equation and the mass diffusion continuity equation was established based on an in-depth comparative analysis; further relying on the Diluted Species Transport Module in Porous Media of Comsol Multiphysics, a three-dimensional numerical model of slurry diffusion was established to systematically study the impact of key factors such as different porosities, grouting times, grouting pressures, slurry diffusion coefficients, and the ratio of vertical to horizontal slurry diffusion coefficients on the diffusion radius of the slurry. The calculation results show that with the continuation of grouting, the increase in porosity, grouting pressure, and slurry diffusion coefficient, or the decrease in the ratio of vertical to horizontal slurry diffusion coefficients, the diffusion range of the slurry increases accordingly. Furthermore, comparatively speaking, the impact of porosity is the smallest, while the impact of the slurry diffusion coefficient is the greatest. The research findings reflect the diffusion trend of the slurry in the gravel pebble layer, which has guiding significance for the quality control of the actual design and construction of grouting. [ABSTRACT FROM AUTHOR]

Due to tectonic uplift in the Cenozoic and numerous shelf-wide glaciations during the Quaternary, -1-2.5 km of sedimentary overburden has been eroded from the Barents Sea shelf, leading to the exhumation and partial uncapping of hydrocarbon accumulations. Widespread natural gas and oil leakage from the glacially eroded middle-upper Triassic reservoir directly into the water column has been documented at the Sentralbanken high in the northern Norwegian Barents Sea. However, it remains unclear whether the hydrocarbon leakage occurs only from the middle-upper Triassic reservoir units in geological settings exceptionally conducive to hydrocarbon leakage, or if other reservoir formations contributed to the release of hydrocarbons into the water column. It is also not clear whether complete erosion of the caprock is a prerequisite for widespread liberation of natural gas and oil from glacially eroded reservoirs across Arctic continental shelves. Here we analyze multibeam echosounder data covering -5,000 km2 and a suite of high-resolution P-cable seismic lines from a range of geological structures across the northern Norwegian Barents Sea. Our analyses reveal that -21,700 natural gas seeps originate from exhumed, faulted and variably eroded structural highs bearing a range of Mesozoic reservoir formations. All investigated structural highs fuel seabed methane release hotspots with no exception. Evident from observations of seismic anomalies, fluid accumulations are pervasive in the subsurface and likely to continue fuelling seabed gas seepage into the future. We also document that gas seepage through faults piercing overburden, caprocks and reaching potential reservoir levels is pervasive at all investigated structural highs. On the Storbanken high and the Kong Karl platform, such fault-controlled seepage is more prevalent than seepage from reservoir formations subcropping below the seafloor. Using a simple parametrization approach, we estimate that seeps identified within our multibeam data coverage produce a seabed methane flux of 61 x 107 mol/yr (9,803 ton/yr), which is one to two orders of magnitude higher than other globally known submarine methane seepage provinces. Fluxes of methane from sea water to the air above the thermogenic gas seep provinces in the northern Norwegian Barents Sea remain to be determined. [ABSTRACT FROM AUTHOR]

AbstractThe geological environment of deep coal seam is complex, and the failure mechanism of coal seam under the action of seepage pressure and disturbance stress is unclear, which restricts the development of deep ground engineering. In this study, triaxial compression test of sandstone under seepage-creep-disturbance loading (SCD) was carried out to analyze the characteristics of disturbance deformation, creep rate and permeability. The focus was on the energy evolution law of sandstone under SCD, and the damage creep model was constructed based on the energy proportion. The results show that the creep increment of sandstone under disturbed load was significantly higher than that under undisturbed load, and the stress level can promote the expansion and development of microcracks, in which the creep increment under high stress level showed a jump increase. The total energy and elastic energy of sandstone showed a step change with time. The damage factor under disturbance load was defined in the form of energy dissipation ratio, and the corresponding coupling damage factor was determined by considering the seepage factor and creep factor, which can reflect the coupled damage deformation of sandstone under SCD. Based on fractional order theory, a nonlinear damage creep model describing sandstone deformation under SCD was established by connecting the acceleration element in series with the Nishihara model and introducing the coupling damage factor. This study can provide research ideas for water inrush of coal seam rock mass. [ABSTRACT FROM AUTHOR]

Background: Seepage control measures are essential in earth dams to enhance their safety against seepage and slope failures. A diaphragm is a thin impervious wall that is used in the core area of the dam to prevent the seepage of water. Any crack in the diaphragm can reduce its efficiency and threaten the safety and stability of the dam. Extensive evaluation of the influence of diaphragm fracturing on dam safety is required to establish a safe design and offer the appropriate measures. This study investigates the effect of diaphragm cracking on the safety of the dam for seepage and slope stability. A permeability tank is first used to validate the numerical model; then, different scenarios for cracked diaphragm walls are studied numerically. The crack's height, width, direction, and number are all investigated. The effect of having a downstream horizontal blanket drain with cracked internal diaphragms is also evaluated. Results: The results showed that the internal diaphragm enhances the safety of earth dams as it reduced the seepage discharge by 98% and increased the downstream slope safety by 34%. Considering the development of a crack in the internal diaphragm, the most critical location was at the base of the dam, wider cracks were more destructive, and the most critical direction was the horizontal crack. The fracturing of the diaphragm at multiple locations proved to be detrimental to the safety of the dam. Having three cracks caused the seepage discharge to reach 74% of its value for no diaphragm, the pore water pressure to raise drastically, and the downstream critical factor of safety to be higher than the case of no diaphragm by 8% only. Conclusions: According to the findings, it is advised to continuously monitor the components of diaphragm-type earth dams and perform the necessary maintenance works whenever any sign of damage or water seepage appears. Furthermore, using a well-graded horizontal drain of sufficient length and high permeability with the internal diaphragm is highly recommended as a mitigation measure if diaphragm fracturing occurs. This helps to quickly release the seeping water and keep the phreatic line away from the downstream slope. [ABSTRACT FROM AUTHOR]

This paper describes a simple methodology to calculate the two-dimensional seepage across an infinite unsaturated slope using models of one-dimensional infiltration through horizontal ground. The methodology decomposes the seepage across the infinite slope into antisymmetric and symmetric parts, whose respective solutions are combined to calculate the actual flow regime. The antisymmetric solution is trivial and does not even require integration of the governing continuity equation, while the symmetric solution, albeit non-trivial, reduces to the case of one-dimensional flow through horizontal ground, for which solutions already exist. The methodology is generally applicable to the calculation of distinct seepage regimes across unsaturated slopes with different hydraulic properties under both stationary and transient conditions. The paper also defines the gradient of the piezometric head parallel to the slope, which is the Neumann boundary condition to be imposed on slope sections perpendicular to the ground surface. The rigorous definition of this gradient overcomes the need of imposing arbitrary boundary conditions in finite-element models. Finally, the paper demonstrates that all infiltrated water crosses the slope along the shortest path – namely, the path normal to the surface – while the flow parallel to the slope is entirely fed by an upstream source at infinite distance. [ABSTRACT FROM AUTHOR]

Seawalls are constructed by covering and protecting the sloping seashore ground with concrete plates or blocks. Their purpose is to sustain high waves induced by strong winds and prevent ground erosion, but they often collapse, mobilising different modes of failure, including that of the ground. Nevertheless, limited research has been conducted on ground failure caused by high waves. In this study, a series of novel centrifuge model tests was first conducted to investigate the failure mechanisms of seawalls due to wave propagation, focusing on the failure of the ground. Finite-element analyses were subsequently conducted to explore the failures observed in the model tests and to provide further insight as to the state of the ground leading to failure. Two failure modes were demonstrated to prevail: floating of the covering panel and sliding failure of the ground. In addition, of the possible causes of failure, the following three were identified in the current study: increased unit weight and reduced suction from wetting; enhanced seepage force under the panel and around the toe block during backwash; water pressure on the back of the panel and the landward side of the toe block during backwash. [ABSTRACT FROM AUTHOR]

Grouting has been commonly used for structure controlling in mining engineering. To investigate the mechanism of fracturing grouting, an experiment was conducted under constant flowing conditions. Through the real-time gathering of main parameters and reconstruction of the slurry distribution, the complete grouting process and pressure spread of the high-pressure slurry were revealed. An identification method of fracturing diffusion based on acoustic emission (AE) signals was proposed and verified. The results indicated that the intact rock showed fracturing response with a mutated pressure in a short time. For fractured ones, the grouting process can be divided into five stages: seepage flow, pressure holding, fracturing diffusion, steady flow, and pressure relief. Influenced by the hydraulic fracture and slurry infiltration, there were three states: cement diffusion, water seepage, and the unaffected zone. A calculation method of whole stages for the grouting pressure was proposed based on the Hoek–Brown strength criterion and flow model in a fracture. In addition, AE ring counting occurred during the entire slurry process but was relatively concentrated in pressure holding and fracturing diffusion stages. Considering the zonal distribution characteristics, the AE method was used to characterize the slurry diffusion range and flow paths. The slurry distribution was obtained by the three-dimensional cutting and reconstruction method to verify its feasibility. This study is expected to further clarify the grouting mechanism, and guide engineering practices. Highlights: High-pressure grouting experiment of fractured rock based on acoustic emission was carried out. The whole process of fracturing grouting shows five responses in fractured rock. The pressure calculation model for revealed whole injection process was established in inclined fracture. AE monitoring can be used to identify the splitting-diffusion range and path for fracturing grouting. [ABSTRACT FROM AUTHOR]

Earth-fill dams should be monitored during the first filling of the reservoir to avoid several potential risks. Following the completion of dam construction, the primary safety check is monitoring the dam behavior during the first interaction of the earth material with water. The presented work fills the gap in the literature on the determination of intermediary hold durations of multistage filling schedule and provides insights into the first-filling process. The study investigated the behavior of a 20 m high earth-fill dam model subjected to staged reservoir filling. The durations of the intermediary holds were determined based on coupled stress and pore water pressure analyses using the finite-element method, with a particular emphasis on the transient behavior of the filling process. Hydraulic fracturing and internal erosion possibilities were evaluated based on minimum principal stress and seepage quantities at critical sections. It was observed that the minimum principal stress reaches a local minimum and tends to increase, leading to significant convergence for longer hold alternatives. In addition, seepage quantities exhibited similar behavior of decreasing with longer hold durations. A specific hold duration was recommended for the low-pool level, which resulted in a hold-to-height ratio of 2.35. At the high-pool level, it was found that further waiting has a positive effect in mitigating the risk of hydraulic fracturing and internal erosion initiation. The presented practical methodology is proposed to be used for the design of filling schedules of new dams. Practical Applications: This study provides practical insights for design engineers to determine the first-filling schedule of earth-fill dams. The stress–pore pressure coupled finite-element model information obtained from this study can be helpful for onsite engineers who have access to instrumentation data during the first filling. These data can be used to predict the convergence of key parameters. For intermediary holds at low-pool levels, monitoring minimum principal stress and effective stress behavior over time is crucial to prevent cracking which can lead to hydraulic fracturing if filling continues. Specifically, the initially decreasing principal stress at the upstream face of the core should be closely monitored until an increasing trend is observed, to ensure that sufficient time is allowed before the dam is subjected to higher loads. [ABSTRACT FROM AUTHOR]

This study examines the influence of preferential flow (PF) on seepage under different rainfall infiltration scenarios, addressing a critical gap in current modeling practices, which often overlook the interactive dynamics between matrix flow (MF) and PF domains within soil environments. In this study, an integrated saturated and unsaturated subsurface flow of dual-permeability (DP) model is developed to calculate seepage and slope stability using pore water pressure. This study aims to conduct numerical experiments of shallow landslides induced by rainfall to quantify the temporal and spatial impact of preferential flow on hydrological mechanisms and slope stability. For low-rainfall intensity, the variation in pore water pressure is greater in the MF domain than in the PF domain. 90 % of rainwater infiltrates downward through the MF domain. Water exchange predominantly occurs in the PF domain, as opposed to the MF domain. The factor of safety decreases from 1.61 to 1.55 when comparing before and after rainfall, which reduces by 3.73%. For high-rainfall intensity, the pore water pressure variation in the PF domain is more pronounced than in the MF domain. The entirety of precipitation infiltration downwards through the PF domain. Water exchange mainly flows from the PF domain to the MF domain. The factor of safety decreases from 1.61 to 1.45 when comparing before and after rainfall, resulting in a reduction of 9.94%. [ABSTRACT FROM AUTHOR]

Purpose: Geotechnical mat has good water collection and drainage functions. However, after long-term operation of tailings pond, geotechnical mat is often failed due to clogging, which will lead to insufficient drainage inside the dam body and an increase in the infiltration surface, thereby increasing the possibility of seepage damage. Therefore, it is proposed to add drainage walls to solve the drainage safety problem caused by the failure of geotechnical mat. Method: Taking a tailings pond project as an example, the saturated-unsaturated seepage calculation theory was used to calculate and analyze the changes in the seepage field under different degrees of failure of the geotechnical mat and after the addition of the drainage wall. Result: The results show that as the geotechnical mat failure gradually deepens, the infiltration line inside the tailings dam will gradually increase until it cannot meet the seepage control requirements. Conclusion: After adding drainage wall, the burial depth of the infiltration line in the dam body can be effectively controlled, the drainage capacity of the dam body can be improved, and the safety requirements can be met. [ABSTRACT FROM AUTHOR]

The study of rough fissure seepage and grouting diffusion, slurry consolidation and filling, as well as the seepage reduction law is of great significance for the detection of grouting effect and water damage prevention and control in fissured rock bodies. To this end, a new technology combining three-dimensional scanning and 3D printing was used to batch prepare a visualization test model based on the morphology of real rock fissures, and carry out visualization tests of seepage in rough single fissure, grouting with different water-cement ratios, and seepage after grouting and consolidation filling of fissures. The test results show that: Rough single fissure seepage in the seepage path and seepage law are non-linear characteristics, for the laminar and turbulent flow of the composite flow form; in the equal flow conditions, the water-cement ratio of small slurry has a pre-diffusion of slow in the middle and late fast, the total time instead of the characteristics of the less; slurries with different water-cement ratios fill and consolidate extremely unevenly in the cracks, and the cross-sectional void ratio gradually decreases from the entrance to the end, while the overall filling rate can be increased by up to 20% in slurries with small water-cement ratios; the seepage coefficient of the fissure before and after slurry filling decreased by a factor of 100–1000, and the seepage flow was along the connected gap network and conformed to the nonlinear characteristics of Forchheimer's equation, and with the decrease of water-cement ratio, the coefficients of the nonlinear term and the coefficients of the linear term increased and decreased, respectively, and the ratio of both of them could reach a maximum value of 102. [ABSTRACT FROM AUTHOR]

Fluctuations in reservoir water levels have a significant impact on the seepage and slope stability of earth dams. The varying rate of the water level and soil–water characteristic curve (SWCC) hysteresis are the main factors affecting the seepage and the stability of dam slopes; however, they are not adequately considered in engineering practices. In this study, the SEEP/W module and the SLOPE/W module of Geo-studio were employed to analyze the seepage features and the stability of downstream slopes, taking into account the water level fluctuation rate and the SWCC hysteresis. The results reveal that the pore water pressure of the representative point forms a hysteresis loop when the water level fluctuates, which becomes smaller as the water level variation rate increases. Within the loop, the pore water pressure with a rising water level is greater than the value when the water level is dropping, and the desorption SWCC derives greater pore water pressures than the adsorption SWCC. Similarly, the safety factor (Fs) curves under the condition of water level fluctuations also form a hysteresis loop, which becomes smaller as the variation rate of the water level increases. When the water level fluctuation rate increases to 4 m/d, the two curves are tangent, meaning that the Fs with a rising water level is always greater than the value when the water level is dropping. The desorption SWCC derives a lower Fs value than the adsorption SWCC as the water level draws up, but this initiates no evident difference in the Fs value when the water level draws down. These findings can be used to inform the design and operation of earth dams under fluctuating water levels. [ABSTRACT FROM AUTHOR]

High‐resolution modeling of the flow dynamics in fractured soils is highly complex and computationally demanding as it requires precise geometrical description of the fractures in addition to resolving a multiphase free‐flow problem inside the fractures. In this paper, we present an idealized model for saturated–unsaturated flow in fractured soils that preserves the core aspects of fractured flow dynamics using an explicit representation of the fractures. The model is based on Richards' equation in the matrix and hydrostatic equilibrium in the fractures. While the first modeling choice is standard, the latter is motivated by the difference in flow regimes between matrix and fractures, that is, the water velocity inside the fractures is considerably larger than in the soil even under saturated conditions. On matrix/fracture interfaces, the model permits water exchange between matrix and fractures only when the capillary barrier offered by the presence of air inside the fractures is overcome. Thus, depending on the wetting conditions, fractures can either act as impervious barriers or as paths for rapid water flow. Since in numerical simulations each fracture face in the computational grid is a potential seepage face, solving the resulting system of nonlinear equations is a nontrivial task. Here, we propose a general framework based on a discrete‐fracture matrix approach, a finite volume discretization of the equations, and a practical iterative technique to solve the conditional flow at the interfaces. Numerical examples support the mathematical validity and the physical applicability of the model. Core Ideas: Due to the presence of air in dry fractured soils, fractures of large aperture act as capillary barriers.If the capillary barriers are overcome, fractures become fast‐flowing paths for water to travel downward.A flow model based on Richards' equation in the soil and instantaneous ponding in the fractures is proposed.The model is numerically consistent and its physical applicability is showcased in two‐dimensional simulations. [ABSTRACT FROM AUTHOR]