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The large deformation and strong rheological characteristics of the underground rock body under complex geological conditions have led to the failure of the support system and even the instability of tunnels from time to time. Based on the theory of groundwater seepage, the elastic solution of the mechanical model of the tunnel anchorage support system under seepage is solved, which reveals the influence of seepage on the peripheral rock and the support parameters of the anchorage support system; the viscoelastic solution is solved according to the corresponding principle of elasticity—viscoelasticity, which analyses the influence of seepage on the rheological process of the anchorage support system; and the model is simulated with the help of finite element software, which analyses the agreement and discrepancy of the numerical solution and the theoretical solution. The results show that the analytical and numerical solutions are basically consistent. This study can provide important guidance for controlling long-term stability of water-rich tunnel rocks. [ABSTRACT FROM AUTHOR]

In the process of development and utilization of mine resources, the damp-heat environment has always been a difficult problem for mining. An enormous amount of research effort has gone into analyzing the underground operating environment. By summarizing the existing research theories on the damp-heat environment in the mine, this paper analyzed the influence of the wall rock, wind flow parameters, groundwater seepage, and other factors on the damp-heat environment and summarizes the determination of heat transfer coefficient (h) and mass transfer coefficient (m), which provided the theoretical basis for the improved technology of the damp-heat environment of mines. The field synergy theory (FST) reveals the essence of enhancing heat transfer performance and mass transfer performance and has been widely applied in engineering practice; based on the commonality between the research model of the FST and the damp-heat environment of the mine, we put forward a novel approach by using the FST to study the mine's damp-heat problem and gave the research models based on the FST under the form of bifurcation and turning wall rock, which can be used to guide the design and layout of the mine wind flow deflector. Finally, considering the actual economic benefits of mine engineering, the FST and ventilation system power consumption are used as comprehensive evaluation indicators to guide the design of ventilation systems, which provided fresh concepts and approaches for improving the subterranean damp-heat environment. [ABSTRACT FROM AUTHOR]

The occurrence of water inrush accidents in most mines is related to geological structures, especially faults. The influence of mining and confined water on floor fault activation and aquitard stability was analyzed theoretically using mechanical models to study the mechanism of water inrushes caused by mining above confined water under a fault structure. In addition, the stress distribution and seepage characteristics of the floor during mining were simulated and studied by COMSOL Multiphysics. We found that a fault is easier to activate when its dip angle is closer to 45° plus half of the fault's internal friction angle. Fault activation becomes more likely with decreased fault cohesion, friction angle, and minimal principal stress. The instability and failure of the key aquitard occur when: the maximum failure depth of the floor exceeds the distance to the aquitard, and the actual confined water pressure exceeds the critical water inrush pressure. A water inrush point occurred at the floor of the working face 35 m from the fault during mining, where the peak seepage velocity reached 0.22 m/s. The seepage velocity within the fault positively correlated with the initial confined water pressure. This study provides a criterion for fault activation and aquitard failure and improves our ability to predict fault-induced mine water inrushes. [ABSTRACT FROM AUTHOR]

Sediment incipient motion is the first step in sediment resuspension. Previous studies ignored the effect of seepage flow on the mobility of sediment particles and simplified the seabed surface as a rigid boundary. A flume experiment was designed to innovatively divide the seabed into two parts to control the dynamic response of the seabed and control the seepage conditions. In the experiment, the seabed sediments and the amplitude of internal solitary waves (ISWs) were changed to compare and analyze the impact of seepage flow on the sediment resuspension by shoaling ISWs. Moreover, parametric research and verification were carried out. Results indicate that seepage flow can greatly influence fine sand, promote sediment resuspension, and increase the amount of suspension by two times on average. However, seepage flow had a little effect on the suspension of clayey silt and sandy silt. Besides, seepage force was added to the traditional gravity, drag force, and uplift force, and the parameterization of threshold starting shear stress of coarse-grained sediments was developed. The results of this parameterization were verified, and seepage force was critical to parameterization. The threshold starting shear stress was reduced by 54.6% after increasing the seepage force. The physical mechanism of this process corresponded to the vertical reciprocating transient seepage in and out the seabed interface caused by the wave-induced transient excess pore water pressure. This quantitative study on seepage flow for shear stress of coarse-grained sediments induced by ISWs is critical to geohazard assessment. [ABSTRACT FROM AUTHOR]

In the present study, three machine learning methods were applied for predicting seepage flow through embankment dams, namely (i) support vector regression (SVR), relevance vector machine (RVM), and Gaussian process regression (GPR). The three models were developed using seepage flow (Q: L/mn) and piezometer level (Z:m) measured at several piezometers placed in the corps body of the dam. The proposed models were calibrated and validated using a separate subset. Models evaluation and comparison was successfully achieved using various performances metrics, i.e., coefficient of correlation (R), Nash-Sutcliffe efficiency (NSE), root mean square error (RMSE), and mean absolute error (MAE). Experimental results showed that the proposed models are a good alternative to the in situ measured and contributed significantly in overcoming the case of missing measured seepage flow. The best performances were obtained using the RVM model with R and NSE values of ≈0.909 and ≈0.823, followed by the GPR model with R and NSE values of ≈0.891 and ≈0.767, while the SVR model was ranked as the poorest one exhibiting R and NSE values of ≈0.780 and ≈0.600, respectively. While, a growing number of investigations have focused on testing machine learning in terms of their feasibilities to accurately describe seepage flow, as well as providing important support to our understanding of the factors affecting its fluctuation, the present work was demonstrated that the combination of a wide range of variables can help in simulating seepage flow, and enhance their sensitivity which has help in developing new algorithms. [ABSTRACT FROM AUTHOR]

This work is motivated to study the face stability of earth pressure balance shield tunnels excavated in the semi-open mode and supported by non-uniform chamber pressure under seepage conditions. Within the kinematic approach of limit analysis, an analytical framework incorporating the seepage effect and linear chamber pressure distribution is developed. The pore pressure distributions are numerically simulated and imported into the three-dimensional (3D) discrete rotational failure mechanism. The work rates caused by the pore pressure and non-uniform support in the semi-open mode are introduced into the work rate balance equation to optimize the critical support pressure. Then, a parametric analysis of three typical soils, including the sand, silt, and clay, is performed to investigate the difference between the semi-open mode and closed mode under seepage conditions. The effects of the muck height and pressure gradient in the chamber, the groundwater levels, and anisotropic permeability are also studied. Finally, several design charts of the normalized critical support are presented. The results show that the difference between considering a linear pressure distribution and a uniform distribution in the semi-open mode is small, with a maximum difference of 3%. Compared to the closed mode, the instability of the tunnel face is significantly higher in the semi-open mode under seepage conditions. [ABSTRACT FROM AUTHOR]

In open channel flow, the velocity distribution is required to analyze the flow parameters such as discharge, energy and momentum correction factors, and scour depth. Though the existing technique can simulate the velocity distribution practically sound, the hypothesis on the cumulative distribution function of velocity is difficult to track and restricted by several factors that it holds. The paper aims to extend the entropy-based 1-D velocity distribution to rectangular seepage channels, considering the cumulative distribution function based on channel geometry. The present work developed a Tsallis and Shannon entropy-based model for proposing 1-D velocity distributions in seepage-affected alluvial channels. The velocity distributions were evaluated with laboratory observations and were compared with Shannon and Tsallis entropy-based velocity distributions equation. The Shannon and Tsallis entropy-based 1D velocity distributions agreed with experimental data satisfactorily and compared well. However, based on the regression analysis, Tsallis-based velocity distribution performed better than the Shannon-based entropy model. [ABSTRACT FROM AUTHOR]

Seepage analysis plays a key role in geotechnical engineering and contributes significantly to the success of its infrastructure projects. Several engineers consider the Finite element (FE) method basics when executing calculations for designing hydraulic structures and dams. Numerical methods are used herein to solve the problem of seepage flow of water under concrete dams. The FE method is applied to model the dam structure and water level. The seepage velocity distribution in the porous soil is determined, and the effects of varying multiple parameters on the velocity are studied. The different parameters investigated are the dam dimensions (i.e., width (4,8,10,15 m) and depth (0,2,4,8 m)), upstream water head level (10, 15, 20 m), soil permeability (10, 15, 20 m day−1) and ambient temperature (5 °C and 50 °C). The developed FE models were validated by carrying out comparisons with analytical solutions that showed that they were in good agreement. It was found that the dam width is inversely proportional to the seepage rate and is independent of the water head level where increasing the dam by 1 unit width drops the seepage by 3.7% regardless of the water head levels. The depth of the dam is exponentially related to the distance away from the toe and independent of both the dam's width and water head level. Increasing the dam depth reduces the seepage flow by 73% at shallower depths and the effect minimizes as we increase the depth to 1% reduction in seepage simulating an exponential behavior. Such behavior is typical for the dam depth factor regardless of the dam width and water head level variations used in the study. The water head level was also found to be linearly proportional to the seepage flow rate with an increased effect of about 10% per additional 1-m head level. In addition, the soil permeability is linearly proportional to the seepage rate, and the same increment is obtained regardless of the dam's dimensions and water head level. The effects of ambient temperature on the seepage flow were introduced in this paper and will be further studied in detail in our future simulations. Our study concludes that the developed FE model can predict the seepage flow of water under concrete dams with a reasonable level of accuracy. [ABSTRACT FROM AUTHOR]

This paper proposed a calculation method for bolts reinforcement of tunnel face under the seepage condition. The existence of seepage in tunnel engineering may greatly reduce the stability of tunnel face, and bolts reinforcement technology is widely used in traditional tunnel engineering. In this paper, a 3D rotational failure mechanism is proposed by the kinematics method combined with the discretization technique. The pore water pressure was added in the energy calculation based on the empirical distribution formula of water head. The interaction between soil and bolts is simulated by using a finite thickness interaction region. The method was compared with the published works in order to verify the effectiveness. The influence of the bolt length, the bolt strength, the hydraulic head size, the face height and the soil parameters are given in the form of some graph. [ABSTRACT FROM AUTHOR]

The paper is devoted to the simulation of oil displacement by water and the formation of the Saffman–Taylor instability. The problem is solved in two-dimensional formulation. A circular domain with one injection well and eight production wells located along the contour around the injection well is considered as geometry. To study the patterns of oil displacement by water, hydrostatic pressure, oil and water seepage rates, and oil saturation are calculated. The graphical analysis considers mainly the oil saturation field. The hydrostatic pressure field is calculated by solving the steady-state piezoconductivity equation; the field of the oil-water seepage rate is calculated using the linear Darcy filtration law; and the oil saturation field is calculated from the solution of the advection transport equation. The two-phase nature of the flow considered in the problem lies in the fact that the oil and water phases have their own relative phase permeabilities calculated using the Brooks–Corey model. The equations are solved numerically using the finite volume method. An irregular triangular grid is used to discretize the computational domain. As a result of the simulation, it is established that the type of the Saffman–Taylor instability, due to its randomness, strongly depends on the computational grid. After the production wells are flooded, the displacement front stabilizes. The instability increases as the ratio of dynamic viscosities of oil and water increases. [ABSTRACT FROM AUTHOR]

Solid backfill coal mining technology can be safely and efficiently used to exploit coal resources under aquifers, without causing harm to the water resources and the environment. Nevertheless, the mechanism of fracture development and seepage channel or pathway control in the key aquiclude strata (KAS) in backfill coal mining under fluid–solid coupling have not been studied. Based on the similarity theory of fluid–solid coupling physical simulation, this study involves experimental evaluation of similar materials and characteristics of composite KAS, backfill body, and aquifer. Subsequently, we designed and employed three experimental models for physical simulation, corresponding to backfill materials' compaction ratios (BMCRs) of 0%, 65%, and 80% using the geological conditions of mining face No. 101 under the aquifer in the Wugou coal mine. Fracture evolution laws, mining-induced deformation, and stress distribution characteristics of composite KAS with different BMCRs are studied. The backfill body can effectively weaken the influence of mining stress, such as the maximum subsidence, sinking speed, initial or periodic fracture damage area of the composite KAS, inhibiting the formation of seepage cracks and water inrush channels. The increase in the BMCR plays an important role in the closure and repair of developed fractures. [ABSTRACT FROM AUTHOR]

Field observations of the foundations of high-head dams established the high sensitivity of the fluid to the crack opening and changes in the stress field, which is used for prediction purposes. [ABSTRACT FROM AUTHOR]

The deep-seated failure caused by inadequate shear resistance against the weight of the surrounding soils is often the more probable mode of failure prior to other types of failure. In this research, stability of flexible supported vertical cuts in granular soils against the deep-seated failure, in the presence of the seepage flow, is investigated. First of all, the flow field is computed by the traditional finite elements method. It is then assumed that the soil in the proximity of the bottom of the cut is at the verge of the limiting equilibrium. Once the flow field solution is known as a steady-state solution, i.e., the background solution, the stress field at the limiting equilibrium subjected to this flow field has been calculated. The method of stress characteristics was used to solve the stress field. It is, therefore, possible to estimate the factor of safety against the deep-seated failure and to assess the overall stability of the system. Results reveal that in spite of quite good margin of safety in the absence of the seepage flow, the deep-seated failure becomes most likely to initiate when the seepage flow exists. [ABSTRACT FROM AUTHOR]

Soil arching effect, which relates to the load transfer and stress redistribution in a soil mass, exists commonly in various geotechnical situations. Many researchers have conducted trapdoor tests and theoretical analyses to study the soil arching and its development in recent years. However, little attention has been paid to the interaction between soil arching and seepage flow, both occurring during the tunnelling of a seabed tunnel. To study the influence of the seepage flow on soil arching, a series of two-dimensional trapdoor tests were carried out considering different fill heights and water level heights. Two subvertical slip surfaces were observed during the tests using the PIV technique. It was found that seepage flow increased the displacement of the particles and the effective vertical stress acting at the top of the trapdoor. However, there was little difference in the development of slip surfaces between the seepage condition and the saturated/no-seepage condition. In addition, a nonuniform distribution of vertical stresses at the top of the trapdoor was observed. The effective earth pressure measured along the centreline of the trapdoor was larger than that on the two edges of the trapdoor. But this nonuniformity decreased with an increasing water level height in the test chamber. [ABSTRACT FROM AUTHOR]

The face stability of tunnel may be decreased significantly due to the presence of seepage flow. In order to investigate effects of seepage flow, an original procedure is presented for face stability of a circular tunnel excavated by a pressurized shied, based on the discretization technique and the nonlinear failure criterion. A discretization technique is utilized to generate the latent failure mechanism by making use of point to point method. The collapsed blocks are decomposed into infinitesimal triangular elements. Each element is consisted of discretized points and adjacent radial to simplify the computed process. The upper bound solutions of retaining force are derived by equating the total rate of external work to the rate of internal energy dissipation. Pore water pressure is incorporated into energy calculation, according to the empirical distribution formula of hydraulic head which is derived by trial and error. The validity of the proposed method has been proved by making comparison with the published works. Agreement shows that the proposed method is effective. A parametric analysis is implemented to discuss the effects of seepage flow and soil nonlinearity on stability of tunnel face, and the concrete results are illustrated for practical use in engineering. [ABSTRACT FROM AUTHOR]

Behaviour of granular soils subjected to internal erosion involves complex coupling between solid–fluid interaction, skeleton deformation and microstructural evolutions. This paper presents a micro–macro investigation on suffusion in idealized gap-graded and well-graded soils using the coupled computational fluid dynamics and discrete element method. The interaction between soil particles and seepage flow is modelled via momentum exchange between two phases. The progressive loss of fine particles subjected to upward seepage flow at various hydraulic gradients is investigated. The fines content, volumetric contraction and void ratio are monitored to identify the changes of macroscopic states of the soil skeleton. In addition, the microstructural evolution is tracked via particle-scale descriptors such as coordination numbers and force chain statistics. Several clogging–unclogging events which are responsible for the sudden changes of fines content and skeleton response are observed during suffusion. A parametric study indicates that the initial fines content and the hydraulic gradient significantly affect the kinetics of suffusion. Microstructural analyses reveal that the removal of fines is accompanied by the reduction in weak contact pairs and particles with low connectivity. [ABSTRACT FROM AUTHOR]

Underestimation of raw material reserves contained in gold mining waste dumps results in tense socio-economic situation in gold mining regions. Efficient management of gold mine waste is only possible with the new and sound technologies of waste preparation and deep conversion with a view to recovering valuable components. Aimed at creation of such technology, the large-scale theoretical and experimental research has been undertaken in order to study the nature and rate of influence exerted by basic process factors on migration and concentration of gold particles in gold mine waste. [ABSTRACT FROM AUTHOR]

The stepped spillway design has been used for more than 3,300 years. A simple structure is the gabion stepped weir. A laboratory study was performed herein in a large size facility. Three gabion stepped weirs were tested with and without capping, as well as a flat impervious stepped configuration. For each configuration, detailed air-water flow measurements were conducted systematically for a range of discharges. The observations highlighted the seepage flow through the gabions and the interactions between seepage and overflow. The air-water flow properties showed that the air concentration, bubble count rate and specific interface data presented lower quantitative values in the gabion stepped weir, compared to those on the impervious stepped chute, while higher velocities were measured at the downstream end of the gabion stepped chute. The re-oxygenation rate was deduced from the integration of the mass transfer equation using air-water interfacial area and velocity measurements. The aeration performances of the gabion stepped weir were lesser than on the flat impervious stepped chute, but for the lowest discharge. For the two configurations with step capping, the resulting flow properties were close to those on the impervious stepped configuration. [ABSTRACT FROM AUTHOR]

Flood and sediment disasters caused by glacial lake outbursts have occurred frequently in recent years in the Himalayas of Nepal. Glacial lake outburst floods (GLOFs) can cause catastrophic flooding in downstream areas with serious damage to lives and property. It is thus important to investigate outburst floods from potentially dangerous glacial lakes. In this study, the characteristics of potential outburst floods from the Tsho Rolpa glacial lake due to two types of moraine dam failure caused by seepage flow or water overtopping were analyzed with various scenarios by using integrated modeling system of three numerical models: (1) the flow and bed-surface erosion model, (2) the seepage model and (3) the slope stability model. Flood inundation areas were also identified by using the numerical model of the flow and moraine dam failure and geographical information system tools. Possible threats and damages due to the potential GLOF events from the lake were also analyzed based on numerical results, flood inundation maps and field investigations. [ABSTRACT FROM AUTHOR]

The structure of fractures in nature rock appears irregular and induces complicated seepage flow behavior. The mechanism and quantitative description of fluid flow through rock fractures is a difficult subject that has been greatly concerned in the fields of geotechnical, mining, geological, and petroleum engineering. In order to probe the mechanism of fluid flow and the effects of rough structures, we conducted a few laboratory tests of fluid flow through single rough fractures, in which the Weierstrass-Mandelbrot fractal function and PMMA material were employed to produce the fracture models with various fractal roughnesses. A high-speed video camera was employed to record the fluid flow through the entire single rough fracture with a constant hydraulic pressure. The properties of fluid flow varying with the fracture roughness and the influences of the rough structure were analyzed. The components of flow resistance of a single rough fracture were discussed. A fractal model was proposed to relate the fluid resistance to the fracture roughness. A fractal equivalent permeability coefficient of a single rough fracture was formulated. This study aims to provide an experimental basis and reference for better understanding and quantitatively relating the fluid flow properties to the structures of rock fractures. [ABSTRACT FROM AUTHOR]

The space block search technology is used to determine a connected three-dimensional fracture network in polygonal shapes, i.e., seepage paths. After triangulation on these polygons, a finite element mesh for 3D fracture network seepage is obtained. Through introduction of the generalized Darcy's law, conservative equations for both fracture surface and fracture interactions are established. Combined with the boundary condition of Signorini's type, a partial differential equation (PDE) formulation is presented for the whole domain concerned. To solve this problem efficiently, an equivalent variational inequality (VI) formulation is given. With the penalized Heaviside function, a finite element procedure for unconfined seepage problem in 3D fracture network is developed. Through an example in a homogeneous rectangular dam, validity of the algorithm is verified. The analysis of an unconfined seepage problem in a complex fracture network shows that the proposed algorithm is very applicable to complex three-dimensional problems, and is effective in describing some interesting phenomenon usually encountered in practice, such as 'preferential flow'. [ABSTRACT FROM AUTHOR]

Darcy's law only applying to the flow domain is extended to the entire fracture network domain including the dry domain. The partial differential equation (PDE) formulation for unconfined seepage flow problems for discrete fracture network is established, in which a boundary condition of Signorini's type is prescribed over the potential seepage surfaces. In order to reduce the difficulty in selecting trial functions, a new variational inequality formulation is presented and mathematically proved to be equivalent to the PDE formulation. The numerical procedure based on the VI formulation is proposed and the corresponding algorithm has been developed. Since a continuous penalized Heaviside function is introduced to replace a jump function in finite element analysis, oscillation of numerical integration for facture elements cut by the free surface is eliminated and stability of numerical solution is assured. The numerical results from two typical examples demonstrate, on the one hand the effectiveness and robustness of the proposed method, and on the other hand the capability of predicting main seepage pathways in fractured rocks and flow rates out of the drainage system, which is very important for performance assessments and design optimization of complex drainage system. [ABSTRACT FROM AUTHOR]

On the basis of the generalized physical model of the riverbank, the experiments were conducted to study the mechanisms of riverbank failure under the coupling effect of seepage flow and river flow. The experimental setup was specially designed, as well as test point location, parameters and procedures, and the main influencing factors were analyzed affecting riverbank failure based on the failure types, the variations of pore water pressure and soil displacement. The results indicated that the coupling effect has different influences on the bank failure in three aspects: the failure type, the process and the extent. In addition, the river flow played a more important role than the seepage flow in the coupling effect on the bank failure. [ABSTRACT FROM AUTHOR]

The standing column well for ground source heat pump systems is a promising technology with high efficiency and environmental benefit, where groundwater is drawn from the bottom of a well and then re-injected to its top after transferring heat with heat pumps. Heat transfer analysis of great significance and aquifer involves complex problems. Determining the groundwater seepage flow is a precondition to solve the energy equation describing the heat transfer of the system. Only when piezometric head is obtained, the seepage velocity can be determined according to Darcy’s law. In this article the groundwater seepage flow in an axial symmetrical geometry was studied under the assumption that gross groundwater flow is neglected. An analytical solution of the groundwater seepage flow for a confined aquifer was acquired by using the integral transform method, which may provide a foundation for heat transfer analysis of the standing column well system. [ABSTRACT FROM AUTHOR]

Based on the theory of the pumping well test, the transient injection well test was suggested in this paper. The design method and the scope of application are discussed in detail. The mathematical models are developed for the short-time and long-time transient injection test respectively. A double logarithm type curve matching method was introduced for analyzing the field transient injection test data. A set of methods for the transient injection test design, experiment performance and data analysis were established. Some field tests were analyzed, and the results show that the test model and method are suitable for the transient injection test and can be used to deal with the real engineering problems. [ABSTRACT FROM AUTHOR]

In the second-order perturbation theory approximation, the longitudinal and transverse components of the velocity variance tensor are calculated for a plane flow through a randomly heterogeneous porous medium with a log-normal conductivity distribution. [ABSTRACT FROM AUTHOR]

A systematic summary is presented describing the application of isotope tracer method in detecting seepage flow in a single borehole. In a single borehole, many hydraulic coefficients, such as flow velocity, direction of flow, vertical flow etc., Can be obtained by using isotope tracer method. There are three conditions if a fissure intersects a borehole: vertical, parallel and tilt. According to each different condition, the formulation of flow velocity deduced by isotope dilution method is different. At the same time, well theory of blended borehole about fissure groups including single fissure group and multi-fissure groups, has also been discussed. [ABSTRACT FROM AUTHOR]