Seepage Stability Research Articles

Simulation Parameter Selection and Steady Seepage Analysis of Binary Structure Slope

The selection of calculation parameters for slope excavation support design and the analysis of seepage stability is a significant challenge. This difficulty also hinders the development of slope support engineering. This study examined the right binary structure slope engineering of the K5 + 220–K5 + 770 section of the TJ1A mark of the Jiangkou-Weng’an Highway in Guizhou province. In this study, we propose and use the deep displacement monitoring data and p value test method to check the simulation parameters. Furthermore, the superposition calculation method for steady-state seepage analysis of slope geotechnical structure is proposed. A comparative analysis of the displacement, strain, stress, and safety factor of the slope after the application of pore water pressure was carried out for three slope conditions. The analysis showed that steady-state seepage has a significant effect on the displacement of the slope during the completion of excavation. As a result, a continuous distribution of strain arises on the slope along the interface between the potential sliding surface and the rock–soil layer, and then forms a continuous sliding zone. Additionally, steady-state seepage has a significant effect on the position of the displacement distribution during the initial support of the slope, leading to a significant increase in the extreme value of the shear outlet displacement of the potential slip surface of the slope and in the extreme value of equivalent strain. Finally, steady-state seepage reduces the displacement and equivalent strain upon construction of the secondary slope support. The steady-state seepage has a limited effect on the stress concentration, but reduces the safety factor calculated using the strength reduction method, in all three stages of slope excavation and support. This study enriches the analysis methods for determining the stability of a dual-structure slope during the rainy season, and provides new ideas for the safety and control of slope support projects.

Application of gallium oxide-based UV detector in complex topography and geological exploration

In order to overcome the problem that the current geological exploration cannot detect complex geology effectively, a method of complex topographic geological exploration based on gallium oxide-based ultraviolet detector is proposed. On the surface of gallium oxide thin film, the dispersed aluminum nanoparticles are formed by a rapid thermal annealing method to prepare gallium oxide-based UV detector. The prepared UV detector is applied in the exploration of complex topography and geology, and the calibration conditions of geological exploration are determined. The appropriate UV detector probe is selected according to the calibration conditions. After the calibration conditions and probe are determined, the complex terrain is corrected by 3Mnnaert correction model, and the complex terrain is classified by multi-UV spectral band to realize the complex terrain geological exploration. The Maliba Reservoir in Yunnan Province with complex topography is selected as the experimental object. The experimental results show that the method can effectively explore the geological problems such as seepage, seepage stability, soil liquefaction, and uneven settlement of dam foundation in the experimental area.

Research on seepage field of concrete dam foundation based on artificial neural network

Reservoir dams have varying degrees of damage and hidden dangers under long-term and complex operating conditions, engineering problems mainly focus on the gradual decrease of seepage stability and guarantee rate of deformation and stability of dam foundation. However, due to the complexity of the dam foundation structure and the surrounding environment, the performance degradation of the dam foundation caused by the aging of the impervious structure lacks a systematic study of the process and its mechanism, In particular, the determination of relevant seepage parameters is complicated, moreover the simulation accuracy of its inversion model is not enough to meet the needs of long-term stability evaluation of the dam foundation. In order to study the seepage stability of the dam foundation of the reservoir during operation, a three-dimensional finite element model of complex geological bodies is combined with artificial neural network to establish a model of inversion of seepage field in the dam foundation, According to the 22 groups of predicted grouting schemes, five groups of representative grouting schemes were selected and the seepage characteristics of the same location were analyzed. The conclusions as below: (1) the inversion predicted that when the permeability coefficient was in the range of 3.0 × 10−6 cm/s to 5.0 × 10−6 cm/s, the change range was small, and the curtain's anti-seepage effect was more obvious. (2) The analysis of the dam base surface and the bottom of the grouting area shows that the difference between the water head and seepage gradient of the dam base surface and the bottom of the grouting area under the GZ7 and GZ3 schemes vary significantly with the grouting effect. Among them, especially in the GZ3 scheme, the key parts of the dam foundation surface F2 ~ F4: the seepage gradient value gradually increases, and all reach the maximum value in the GZ3 scheme; For G6 ~ G15 at the bottom of the grouting area, the water head value under the GZ3 scheme is gradually smaller than the three grouting schemes of GZ11, GD3 and GD7, as the water head value gradually decreases, the anti-seepage effect becomes more and more obvious. The above results show that the inversion prediction range is in good agreement with the actual law, when the permeability coefficient is within the predicted range, the anti-seepage effect is optimal. (3) The difference of the water head and seepage gradient difference between the dam foundation and the grouting area near the curtain changes significantly with the grouting effect. Characteristics of seepage field in key parts of the dam foundation under the six curtain grouting coefficients, the water head value F1-F2 decreased by 75%, F3-F13 decreased by 28%, the seepage gradient value F1-F2 decreased by 88%, and F3-F13 decreased by 29%, namely the grouting effect of the dam foundation and the grouting area gradually weakens as the distance between the characteristic part and the curtain increases. The research in this paper can provide a theoretical reference for the analysis and evaluation of dam seepage conditions.

Analysis of Impacts of Crossing Bridges on Flood Control and Dike Safety

The construction of bridges across rivers mostly involves occupying river sections and dike sections, which will adversely affect flood control of rivers and the safety and stability of dikes. Taking an actual project for example, this paper puts forward some ideas and methods for the analysis of impacts of crossing bridges on flood control and dike safety, analyses and evaluates effects of raising of water level, dike foot erosion, seepage stability and anti-sliding stability. Finally, suggestions and measures for bridge construction and dike protection are raised.

Investigation of gap-graded soils' seepage internal stability with the concept of void filling ratio.

Gap-graded soils from mountain areas are often used as subgrade filling materials, but problems associated with the gap-graded soils such as large permeability, poor uniformity, and poor seepage stability have to be solved. This article proposes a new terminology “void filling ratio” to study the seepage internal stability of gap-graded soils as subgrade filling materials. Laboratory seepage tests were performed to investigate the effects of compaction degrees of coarse grains, void filling ratios, and clay contents on the internal stability. Laboratory model tests were also performed to verify the findings from the laboratory seepage tests. It was found that the internal stability increased with increase of the void filling ratios, confirmed by both laboratory seepage tests and slope model tests. The increases of both void filling ratio and the clay content were able to change the type of internal instability from piping to the transitional type of internal instability. In laboratory model tests, surface areas lost more fine particles than the deeper area did in the models, but when the void filling ratio was increased, the amount of lost fine particles was significantly reduced. Finally, it was confirmed that void filling ratio was able to effectively describe the internal stability of gap-graded soils subject to different levels of hydraulic gradient.

Topographic Effects on Three-Dimensional Slope Stability for Fluctuating Water Conditions Using Numerical Analysis

With recent advances in calculation methods, the external factors that affect slope stability, such as water content fluctuations and self-configuration, can be more easily assessed. In this study, a three-dimensional finite element strength reduction method was used to analyze the stability of three-dimensional slopes under fluctuating water conditions. Based on soil parameter variations in engineering practice, the calculation models were established using heterogeneous layers, including a cover layer with inferior properties. An analysis of seepage, deformation and slope stability was carried out with 27 different models, including three different slope gradients and nine different corner angles under five different hydraulic conditions. The failure mechanism has been shown to be closely related to the change in matric suction of unsaturated soils and the geometric slope configuration. Finally, the effect of geometry (surface shape, turning corner and slope gradient) and water (fluctuations) on slope stability are discussed in detail. Emphasis is given to comparing safety factors obtained considering or ignoring matric suction.

The variation of grain size distribution in rock granular material in seepage process considering the mechanical-hydrological-chemical coupling effect: an experimental research.

As a common solid waste in geotechnical engineering, rock granular material should be properly treated and recycled. Rock granular material often coexists with water when it is used as the filling material in geotechnical engineering. Water flowing in rock granular materials is a complex progress with the mechanical–hydrological–chemical (MHC) coupling effect, i.e. the water scours in the gaps and spaces in the rock granular material structure, produces chemical reactions with rock grains, rock grains squeeze each other under the water pressure and compression leading to re-breakage and producing secondary rock grains, and the fine rock grains are migrated with water and rushed out. In this process, rock grain size distribution (GSD) changes, it affects the physical and mechanical characteristics of the rock granular materials, and even influences the seepage stability of the rock granular materials. To study the variation of GSD in the rock granular material considering the MHC coupling effect after the seepage process, seepage experiments of rock grain samples are carried out and analysed in this paper. The result is expected to have a positive impact on further studies of the properties of the rock granular material.

Determining the Seepage Stability of Fractured Coal Rock in the Karst Collapse Pillar

The karst collapse pillar (KCP) is a common geological structure in the coal mines of northern China. KCPs contain many fractured coal rocks, which can easily migrate under the action of high‐pressure water. The destruction or instability of the cementation structure between the rocks can directly induce coalmine water‐inrush accidents. To study the seepage stability of cemented and fractured coal rock under triaxial pressures, a self‐designed triaxial seepage testing system was used and the permeability k and non‐Darcy factor β of the cemented and fractured coal rock were tested. Furthermore, the 1D non‐Darcy seepage equations were used to calculate the evolution criteria of the seepage loss stability. The results show the following: (1) The cemented structure in the KCP under the triaxial pressures can be easily destroyed. The damaged coal and rock body mainly exists in bulk form, and the permeability depends mainly on the effective stress of the particles. (2) The seepage process in the KCP structure is a combination of pore flow, fracture flow, and pipe flow, and the transition of the seepage state is closely related to the change in the magnitude of β. (3) Under the long‐term effect of confined underground water, the migration of small fractured particles in the KCP will increase the structural porosity. If the parameter βk2 reaches the threshold value, the seepage system will evolve into a pipeline flow state, eventually causing a water‐inrush accident.

Reliability Analysis for Bypass Seepage Stability of Complex Reinforced Earth-Rockfill Dam with High-Order Practical Stochastic Response Surface Method

Practical stochastic response surface method (SRSM) using ordinary high-order polynomials with mixed terms to approximate the true limit state function (LSF) is proposed to analyze the reliability of bypass seepage stability of earth-rockfill dam. Firstly, the orders of random variable are determined with a univariate fitting. Secondly, nonessential variables are excluded to identify possible mixed terms. Thirdly, orthogonal table is used to arrange additional samples, and stepwise regression is conducted to achieve a specific high-order response surface polynomial (RSP). Fourthly, Monte Carlo simulation (MCS) is used to calculate the failure probability, and RSP is updated by arranging several additional samplings around the design point. At last, the Bantou complex reinforced earth-rockfill dam was taken as an example. There are 6 random variables, that is, the upper water level and 5 hydraulic conductivities (HCs). The result shows that a third-order RSP can ensure good precision, and the failure probability of bypass seepage stability is3.680×10−5within an acceptable risk range. The HC of concrete cut-off wall and the HC of rockfill are unimportant random variables. Maximum failure probability at the bank slope has positive correlation with the HC of curtain and the upper water level, negative correlation with the HC of alluvial deposits, and less significance with the HC of filled soil. With the increase of coefficient of variation (Cov) of the HC of curtain, the bypass seepage failure probability increases dramatically. Practical SRSM adopts a nonintrusive form. The reliability analysis and the bypass seepage analysis were conducted separately; therefore, it has a high computational efficiency. Compared with the existing SRSM, the RSP of practical SRSM is simpler and the procedure of the reliability analysis is easier. This paper provides a further evidence for readily application of the high-order practical SRSM to engineering.

The behavior of mass migration and loss in fractured rock during seepage

Mass migration and loss in fractured rock during seepage processes are considered to cause seepage instabilities, which can lead to seepage catastrophes. In this study, the migration and loss of fine particles in fractured rock during seepage are theoretically and experimentally investigated. We analyze the characteristics of lost and migrated mass obtained from the experiments over time, as well as the effect of initial compression. A linear relationship is found to best describe the difference of migrated versus lost mass and Talbot power exponent (TPE), with the slope and intercept related to initial compression. The lost and migrated mass are described mathematically based on the TPE and initial compression. We quantify the behavior of mass migration and loss, which allows calculation of the possibility of seepage instability and water inrush. A seepage instability occurs if the lost mass ratio is greater than 4.90%. The results presented here provide important insight into the water inrush mechanism in geotechnical engineering applications.

Analysis of the coal seam spalling-failure mechanism based on the seepage instability theory.

Coal and gas outburst is a common coal-rock dynamic disaster. Such accidents frequently occur, and the mechanism underlying the occurrence of these outbursts is complex. As a typical failure mode of a gas-filled and pressure-relieved coal body, the spallation mechanism should be investigated to reveal the mechanism of coal and gas outburst and guide outburst-prevention strategies. In this paper, a fluid-solid coupling model for coal seam gas flow is established. This model considers the adsorption characteristics of coal. Numerical calculations are used to simulate the stress field distribution and evolution of gas-filled coal bodies under different boundary conditions. The mechanical mechanism of the spallation occurrence after the pressure relief of coal is explained from the perspective of seepage breaking coal. The control of the flow and stress state of the gas to the spallation failure is analyzed. The mechanical-quantitative conditions for the initial failure of the coal body under seepage and the mechanical-qualitative conditions for the continuous advancement and termination of spallation are studied based on numerical solution results. The numerical calculation results show that the formation of a flow field after pressure relief will apply a drag force (tensile stress) on the porous media of coal. The presence of this force plays a crucial role in promoting the spallation and cracking of coal and, thus, the promotion of spallation. The tensile strength, initial adsorption pressure, and pressure relief rate of the coal body jointly control whether the initial failure can occur and the thickness of the fracture layer cracks. Spallation propulsion is mainly determined by the pressure relief conditions of the undestroyed coal body and pressure changes in the spallation space; the former can be quantitatively obtained by numerical calculations, whereas the latter is related to the thickness of the spalled layer and the degree of the layer-crack structure.

The Mining-Induced Seepage Effect and Reconstruction of Key Aquiclude Strata During Backfill Mining

When mining coal below aquifers, the height of the water-conducting zone above the mine panel is widely used as one of the main criteria in assessing mine safety. However, its direct application to backfill mining is quite problematic, and alternative approaches have to be used to more accurately reflect the relevant processes. The compaction characteristics and seepage behavior in crushed key aquiclude strata were experimentally investigated by analyzing the hydrogeological characters of aquiclude strata and aquifers in the Wugou coal mine. The results explained the mechanism of the backfill mining-induced seepage and indicated the feasibility of reconstructing the key aquiclude strata to protect regional water resources. Based on the regional geology and hydrogeological characteristics of the aquiclude strata, various reconstruction forms were analyzed, with the approbation of structural and seepage stability criteria of aquiclude strata. The research results were corroborated by field measurements and provide new theoretical guidance for protecting water resources during mining in China.

Geotechnical characteristics of unburnt colliery spoils after coal-recovery

The aim of the study was to determine the geotechnical characteristics of the unburnt colliery spoils after coal-recovery from the dumping site of one of the mines of the Upper Silesian Coal Basin in Poland. Due to grain-size distribution of tested spoils their geotechnical properties were determined using medium-sized apparatuses. In order to verify the suitability of the studied spoils for the construction of hydraulic embankments, the seepage and stability calculations were conducted for models of hydraulic embankments including the effect of flood wave passage on stress conditions within the construction and their slope stability. The test results revealed, that the studied colliery spoils are characterized by favourable values of geotechnical parameters and they fulfil the requirements for soil materials used in the analysed type of constructions. The spoils are characterized by good compactibility, relatively low water permeability and average susceptibility to mechanical disintegration, which in the case of using this material for the construction of hydraulic embankments and using proper compaction technology, should reduce their susceptibility to weathering. The results of seepage and slope stability calculations for hydraulic embankments built of the studied spoils confirmed their suitability for that type of constructions, retaining the proper inclination of slopes, whereas the variant of embankment without sealing is safer from the stability viewpoint.

Non-Darcian seepage stability analysis of non-Newtonian fluid

In this paper, the two-phase fluid composed of fine geologic particles and water is considered to be a non-Newtonian fluid, and the seepage dynamics model of the two-phase medium in the rock-soil structure is constructed. Based on the hypothesis, the boundary conditions and solving methods of the model are given and the critical conditions of the model instability are also discussed in detail. It is shown that the existence of the equilibrium state of the kinetic model is determined by the power exponent, the effective fluidity and the non-Darcian flow factor.

Seepage test by HCA for remolded kaolin

Permeability is an import character of soil, especially in excavation and tunnelling. Hollow cylindrical apparatus (HCA) is often used to determine soil anisotropy, particularly soil strength and stiffness under different directions of major principal stress, so complex stress paths can be simulated and the corresponding soil properties can be examined. It can also be used to determine the permeability coefficient if a special mode is added, therefore the seepage test can be expected. Owing to no seepage test has been conducted by HCA before, the complete procedure of HCA seepage tests after static and dynamic loading are respectively studied. And the seepage stability stage is discussed since only data in this stage are valid and reliable for permeability calculation. The results show that:1) when the difference in average permeability coefficient within unit time (3600 seconds) less than 2% in 24h, it is reliable to take the average permeability coefficient in this period as the ultimate permeability in static seepage test; 2) for dynamic test, if the average permeability in 3600 seconds varies with 5% in 24h, the average permeability coefficient in this period can be taken as the ultimate value. Research in this paper provides a solid foundation for HCA seepage test under complex stress paths.

The Seepage and Stability Performance Assessment of a New Drainage System to Increase the Height of a Tailings Dam

Effective methods for extending the storage capacity of tailings for a mining company include expanding and increasing the height of the tailings dam. However, this change could lead to an uplift in the phreatic line and a decrease in the slope stability. In this paper, a new drainage system combining a horizontal drainage pipe with an upward bending slotted pipe was proposed and applied to the design of a seepage-proof system for the Xigou tailings dam with an increased height. To accurately simulate the performance of the seepage control system, a three-dimensional finite element model was established on the basis of a geological investigation of the site conditions. In this work, a substructure technique was used to model the drainage pipe with a small radius and dense spacing to reduce the difficulty in mesh generation, and a back-analysis method called MPSO-BP (modified particle swarm optimization algorithm and a back propagation neural network) was used to correct the measured permeability coefficients. The results show that the new drainage system can effectively dissipate the seepage pressure, decrease the phreatic surface, and improve the safety factors of the slope stability. The proposed drainage system can also meet the seepage stability requirements of the higher tailings dam. Additionally, this system can be widely deployed in similar projects.

Seepage problems on fractured rock accompanying with mass loss during excavation in coal mines with karst collapse columns

Under the background of China as a big coal-hungry country lasting till 2050, deep mining becomes more and more significant. However, deep coal seams usually have a very complex geological structure like Karst collapse columns, and excavation is often accompanied with water-inrush accidents, restricting the development of the coal industry. In order to study on seepage problems on fractured rock accompanying with mass loss during excavation in coal mines with karst collapse columns, researchers studied on water-inrush mechanism in karst collapse columns directly, researched on seepage behavior of fractured rock with pressure as the basis of studying on water-inrush mechanism indirectly, studied the fluid flow change in fractured rock regarding the change of liquid flow type in fractured rock as seepage instability, and observed and studied the phenomenon of mass loss during seepage in succession. In the following research, (1) the cementation, lithology, and match rate of testing samples, which are the foundation of the simulation study, need to be determined in more detail; (2) migrated particles in fractured rock should be distributed which are from migration, corrosion, erosion, and abrasion; (3) multi-permeate agents in the fractured geological structure, their diffusion and convection, and the related chemical reactions should be involved; (4) more and more contemporary mathematical methods will be introduced to help us to study the complex dynamic system; and (5) experimental equipment needs to be designed and improved. What we did before, do now, and will do later is to penetrate the mysteries of seepage problems on fractured rock accompanying with mass loss during excavation in coal mines with karst collapse columns.

Experimental Investigation on Seepage Stability of Filling Material of Karst Collapse Pillar in Mining Engineering

In northern China, groundwater inrush of Karst collapse pillar (KCP) often affects the coal mining process. Current studies rarely consider the seepage stability of filling materials of KCP, especially through experimental investigations. This study is to quantify the impacts of variable initial porosity and cementing strength on the seepage properties of filling material. For this purpose, we designed and fabricated a test system. This system can offer high water pressure and abundant water flow rate. We tested three types of specimens which were cemented by clay, gypsum, and cement, respectively. The seepage properties were obtained under the initial porosity of 0.11, 0.13, 0.15, and 0.17, respectively. The change mechanism of seepage properties was measured through the comparison between mass loss and mass gain. The results showed the followings findings: (1) The permeability-time curves have two types: the first type is that permeability gradually increases up to the occurrence of seepage instability and the second type is that permeability gradually decreases and approaches to a stable value. No seepage instability is observed. (2) Initial porosity and cementing material significantly affect the water flow properties of filling material. In general, larger initial porosity has larger permeability. For clay as cementing material, seepage instability occurs soon and higher initial porosity has shorter time to reach seepage instability. For gypsum, seepage instability occurs after a period of time when initial porosity is large enough. For cement, the permeability decreases gradually and approaches to a stable value. The permeability-time curves have rapid decrease and slow decrease. (3) The permeability has a magnitude of 10−15–10−13 m2 and varies with initial porosity and cementing materials. The permeability is the largest for clay cementing and is the smallest for cement cementing.

An Investigation of PSO Algorithm-Based Back Analysis on the Three-Dimensional Seepage Characteristics of an Earth Dam

In view of the problem of seepage safety and the character of dangerous reservoir earth dam, the 3D seepage of FEM back analysis was studied. Based on a reservoir project, the rationality of prototype observation data in recent years is analyzed, and the effective monitoring point and its observation data are selected for back analysis. The simulation calculation model is built, and the permeability coefficient of key materials and seepage characteristics of calculation area of earth dam are obtained after using particle swarm optimization (PSO) algorithm as the inversion algorithm and using FEM as the seepage field algorithm method of improved nodal virtual flux. The results shows that the PSO, which has high efficiency with back analyzing the permeability coefficient of materials in the dam and satisfactory accuracy, can meet the requirements of engineering, and a large seepage gradient in overflow point and boundary of earth dam, which is unfavorable for dam seepage stability, is produced when the problem of contact erosion is also existed in connection part of earth dam section and masonry dam section.

Numerical 3D simulations of seepage and the seepage stability of the right-bank dam of the Dry Flood Control Reservoir in Racibórz

Abstract This article presents the results of numerical simulations of seepage through the body of the dam and the reservoir bed. The purpose of this study was to analyse the seepage stability during a flood as well as the impact on seepage stability of the diaphragm wall and gravel columns, on which the dam body is founded in selected segments. Simulations were conducted for three different locations, and the following 3D models of the dum were prepared: – a model containing the front and right-bank part of the dam, for which no diaphragm wall, gravel columns and drainage ditch were provided for – a model of a segment of the right-bank dam including a diaphragm wall, drainage ditch and gravel columns under the dam (two variants with differing diaphragm wall lengths) – a model of the water dam segment accounting for gravel columns and a drainage ditch, but without a diaphragm wall. In the case of founding on gravel columns, the base was modelled as an anisotropic medium in terms of seepage properties, macroscopically equivalent to the actual soil medium. The numerical model utilises the finite element method. The geometry of the dam and geological substrate was defined in the GIS tools in the form of a 3D model of the terrain and geology of the substrate.