Stability Analysis Of Tailings Dam Research Articles

Numerical Investigation of Saturated-Unsaturated Flow and Stability Analysis of Tailings Dams Considering the Influence of Saline Solutions

A tailings dam is normally constructed through self-consolidation with minimum compaction effort. Accordingly, special attention to the ultimate limit design in assessing the tailings dam instability condition is of primary importance. Furthermore, the existence of pore fluid chemical contaminants with high concentrations makes soil hydraulic and shear resistance properties subject to considerable changes.Therefore, this study aims to investigate the stability of a tailing dam using saturated-unsaturated flow analysis under 0.2 and 0.6 M sodium chloride solutions and pure water as a benchmark. To make the analyses as realistic as possible, recently developed solute-dependent hydraulic conductivity and water retention models are embedded into the numerical software. The results show that the saline-based model has higher pore water pressure than the pure water model due to more rainfall penetration by increasing the pore fluid salt concentration. Furthermore, increasing salt solution concentration enhances the tailing dam's drainagecondition, which leads to an increase in the dam's shear strength and, consequently, the factor of safety. Therefore, the stability of the tailings dam is improved by the combined impact of salt on both the flow and strength.

Determination of the critical state of a silty sand iron tailings in triaxial extension tests using photographic correction

Determination of the critical state of tailings is essential to the stability analysis of tailings dams, especially to assess the susceptibility to flow liquefaction failures. In contrast to the peak resistance, which can be determined in triaxial tests at relatively small strains, the critical state is often reached at higher strains. Therefore, determining the critical state in triaxial extension tests is more difficult than in compression tests because the concentration of stresses and strains in extension tests is more severe and usually inevitable, resulting in necking that may greatly affect the computed deviatoric stress and void ratio (if the test is drained). This paper presents a simple and cost-effective method of necking correction using photography. The method was used in the determination of the critical state in drained triaxial extension tests. A sample of silty sand tailings obtained from the reservoir of the Fundão dam two years prior to its collapse was used. The critical state friction angle was approximately the same in compression and extension, showing that the proposed method is promising as many authors consider that the critical state friction angle is the same in these two conditions.

Seepage field characteristic and stability analysis of tailings dam under action of chemical solution

As one of the important influencing factors of tailings dam stability, seepage field distribution within the dam is often affected by the tailings mineral characteristics. While the alkalinity or acidity of reservoir water and long term immersion will partially change the physical and mechanical properties of tailings. This study carried out permeability tests of tailings under the action of chemical solution. On this basis, a three dimensional (3D) model was constructed to analyze the velocity field and effective saturation within the tailings dam. Moreover, the dam section along the valley bottom was selected as the basic section in calculation, so as to analyze the changes in infiltration point and buried depth of the phreatic line under different permeability coefficient ratios. The results suggest that, under the action of acid-alkaline solution, the permeability coefficients of tailings reduced, and the stronger solution acidity-alkalinity resulted in the longer action time and more obvious change; under the action of chemical solution, the fluid flow velocity in the dam gradually decreased, and the drat beach length in the reservoir gradually shortened. Besides, when the upper layer permeability coefficients of tailings was lower than that of the lower layer, the dam phreatic line had a shallow buried depth and a high infiltration point.

Ageing deformation of tailings dams in seasonally frozen soil areas under freeze-thaw cycles

The freeze-thaw cycle is one of the important factors in inducing a dam-break in the permafrost region, so it is of great practical significance to study the mechanism of the failure deformation of tailings dams under freeze-thaw cycles. In this paper, the water-heat-force coupling model of a tailings dam considering frost-thaw damage is established, and the freeze-thaw cyclic ageing deformation of a tailings dam in a seasonally frozen soil area is studied. The correctness of the model is validated by numerical calculation. The research shows under the same water content, the compressive strength and modulus of deformation decrease with an increase in the number of freeze-thaw cycles, the cohesion and internal friction angle decrease, and the amplitude gradually decreases before becoming stable. In the process of cooling, the pore water pressure first increases and then decreases, and the pore water pressure first decreases and then increases during the heating process. The research results can provide a theoretical basis and reference values for the stability analysis of tailings dams in seasonally frozen soil areas.

Finite element-based probabilistic stability analysis of rock-fill tailing dam considering regional seismicity

The recent tailing dam failure in Brazil has again emphasized the need of performing robust stability analysis prior to construction. This paper demonstrates the probabilistic dynamic stability analysis of tailing dams considering an existing rock-fill tailing dam in India. The stability analysis was performed using 2D finite element-based package RS2. In the probabilistic analysis, the strength parameters such as cohesion (c) and the friction angle (φ) were considered as random variables. In total, 3000 numbers of samples were generated assuming a normal distribution. Monte Carlo simulation was used to evaluate the probability of failure (PoF) and reliability index. Strength reduction method was used for the finite element analyses. A pseudo-static seismic loading was incorporated in the strength reduction analysis to check the seismic stability of the dam. A factor of safety (FoS) of 1.15 was observed from the deterministic analysis for downstream slope. For the same case, the probabilistic analysis provided a mean FoS of 1.19 with 5.46% probability of failure. The FoS values and the locations of the critical failure surface obtained by the limit equilibrium method and finite element method were compared. The observed FoS values were found to be higher than the values specified in the IS 7894-1975 (reaffirmed in 1997) and ANCOLD (1999). In the case of pseudo-static approach, the maximum displacement of 0.53 m was observed in the slope. Furthermore, nonlinear dynamic stability analysis was performed to simulate a true earthquake event. The permanent deformation of the slope after the earthquake was found to be 0.40 m. The zone of failure observed in both pseudo-static and nonlinear dynamic stability analyses was found to be the same. Overall, the results revealed that the spatial variability of the soil significantly influences the FoS values.

Stability Analysis of Tailings Dam based on the Combination of Seepage and Stress

According to an example of a tailings dam, a numerical model is established by finite difference software FLAC3D, and a tailings dam is calculated and analyzed by the combination of fluid-solid coupling and strength subtraction method. The distribution of seepage field and flow rate of tailings dam and the approximate position of saturation line are determined. The coupling effect of stress field and seepage field under different dry beach length is analyzed. The result shows that with the decrease of dry beach length, the shear strain region gradually becomes wider and forms a through area, and the area with large shear strain appears at the top of the dam in the initial stage. The seepage flow of the tailings dam increases gradually, the saturation line rises and the safety factor of the tailings dam is reduced, so it is necessary to ensure the length of the tailings dam to be large enough in order to stabilize the tailings dam.

Dynamic response of Zelazny Most tailings dam to mining induced extreme seismic event occurred in 2016

The paper deals with the stability analysis of tailings dam subjected to dynamic loading induced by mining shocks which occurred in neighbouring copper mine. The main goal of the paper was to model the dynamic response of the dam during two extreme paraseismic events which occurred in 2016 based on accelerograms recorded at the dam toe. Dynamic response of the tailings dam was calculated using finite element method and the implicit time-integration method implemented in commercial codes. The boundary condition corresponding to dynamic loading was determined by deconvolution procedure. The error analysis showed that most precise signal reproduction is achieved while using target signal with peak value reduced by 40% as a test signal. Both acceleration and displacement time-series were successfully reproduced. Moreover, the stability analysis was conducted for five independent signals with design peak horizontal acceleration and showed that no permanent displacements should occur. The temporary horizontal displacement of the dam crest should not exceed 13 mm, assuming equivalent linear material model.

Investigation of a fluid–solid coupling model for a tailings dam with infiltration of suspended particles

The study of the migration and deposition characteristics of suspended particles in porous media is significant in petroleum exploitation, groundwater recharge, filter design, nuclear waste disposal, and migration of underground pollutants. In recent years, researchers have tended to neglect the influence of tailings particle movement on seepage action in stability analysis of tailings dams. They have focused on analyzing the influence of tailings particle movement and deposition on tailings dams’ physical parameters. Based on the effective stress principle, the suspended-particle deposition equation is incorporated into the model of the fluid–solid coupling seepage field and combined with the stress field equation. Then, the particle deposition fluid–solid coupling model is established and gives the proper solution conditions for simplification. Based on a calculation program developed in-house, the stability of a tailings dam is analyzed while taking into account suspended particles. This approach aims to gradually reduce variation in percolation time growth of the coefficients of permeability and porosity. On this basis, we monitor the horizontal displacement and sedimentation values of the primary dam crest and of all levels of the sub-dam. We explore preliminarily the distribution law for tailings pore pressure to validate the correctness of the proposed mathematical model. Numerical analysis results show that in the process of deposition, the porosity, permeability coefficient, and flow rate become progressively smaller. The displacement of the primary dam is minimal and displacement of the third sub-dam is the largest, with displacement size displaying a relationship with dam height. The vertical displacement of the dam top gradually increases with increasing grades of sub-dams, and the difference is nearly 0.5 cm between the displacement of the primary and third dam crest-monitoring points. The results provide a theoretical basis for stability analysis of tailings dams undergoing tailings particle infiltration. Moreover, they provide reference material for studying migration and deposition characteristics of suspended particles in porous media.

Dynamic Response Analysis of Tailings Dam under Seismic Action

A finite element model of tailiings dam was used to analyze the dynamic responses of the stress field, displacement and acceleration of the dam with the dynamic time-history response analysis method in this paper. The time-history curves of different responses were obtained. And an evaluation for dynamic stability of the tailings dam was also discussed. The analysis result shows that this case can provide a certain reference value for the dynamic calculation and the dynamic stability analysis of tailings dam under seismic load.

Anisotropic shear strength characteristics of a tailings sand

The deposition process of tailings in a tailings dam may lead to the anisotropy of mechanical properties of tailings. To investigate the anisotropic shear strength characteristics of a tailings sand, samples deposited under gravity were sheared in a modified direct shear apparatus along different orientations of the shear planes relative to the bedding plane. The experimental results reveal that the anisotropy has a substantial effect on the peak shear strength of the tailings sand, leading to a variation in peak friction angle of 10°. It is found that the effect of anisotropy on the peak shear strength of the tailings sand is mainly attributed to the effect of anisotropy on soil dilatancy. On the other hand, the effect of anisotropy on the residual friction angle of the tailing sand is relatively smaller, likely due to the partial erasure of anisotropy at large shear deformation. The degree of anisotropy is reduced by an increase in normal stress. To achieve more accurate stability analysis of tailings dams, it is suggested to take into account the shear strength anisotropy of tailings soils.

The Analysis of Stability of Mine's Tailing Dam Based on the FLAC<sup>3D</sup>

Tailings dam is an important part of engineering construction of tailings pond. Stability analysis of tailing dam is of great significance, because it is the significant security risk of the project of tailings. FLAC3D program which based on Lagrange algorithm is especially suitable for solving the nonlinear large deformation problems in rock and soil mechanics engineering. After the adequate mastery of the soil layer structure, the physical and mechanical properties and the determination of the calculation parameters, the engineering software of FLAC3D and the numerical analysis method are utilized to analyze the integral stability of the tailing dam of Guangxi Xinfa Aluminum Company in Jingxi county. It can provide a scientific basis for the stability analysis of engineering construction of another tailing pond.

Pseudo-Static and Pseudo-Dynamic Stability Analysis of Tailings Dam Under Seismic Conditions

In this paper the seismic slope stability analyses are performed for a typical section of 44 m high water retention type tailings earthen dam located in the eastern part of India, using both the conventional pseudo-static and recent pseudo-dynamic methods. The tailings earthen dam is analyzed for different upstream conditions of reservoir like filled up with compacted and non-compacted dumped waste materials with different water levels of the pond tailings portion. Phreatic surface is generated using seepage analysis in geotechnical software SEEP/W and that same is used in the pseudo-static and pseudo-dynamic analyses to make the approach more realistic. The minimum values of factor of safety using pseudo-static and pseudo-dynamic method are obtained as 1.18 and 1.09 respectively for the chosen seismic zone in India. These values of factor of safety show clearly the demerits of conventional pseudo-static analysis compared to recent pseudo-dynamic analysis, where in addition to the seismic accelerations, duration, frequency of earthquake, body waves traveling during earthquake and amplification effects are considered.

Seepage-Stability Analysis of a Mine Tailings Dam in Yunnan Province Based on ANSYS

As a major hazard installation in mine the safe and effective running of a tailings dam is very important, therefore the stability analysis of tailings dam is necessary. In order to evaluate the effect of seepage on stability of mine tailings dam, in this paper, a numerical model of a tailings dam in Yunnan province was established by using ANSYS software. It was focused on the dam seepage field analysis and the seepage-stability analysis, and on using the strength reduction method to derive the safety coefficient of the tailings dam. The results were proved reasonable and could be used to provide helpful guidance of dam safety.

The Stability Analysis of Tailings Dam under the Fluid-Solid Coupled Interaction

Numerical simulation method is adopted to analysis the stability of tailings dam under the fluid-solid coupled interaction. Using the full-coupled analysis function, stress field 、seepage field and their coupled model are studied in this paper. Finally, the critical sliding surface of the tailings dam is searched. Results show that the safety factor after coupling is smaller than before. It illustrates that the fluid-solid coupling analysis has an important practical significance for the stability analysis of tailings dam.

Strength Anisotropy of a Tailings Sand and its Effect on Stability of a Tailing Dam

In current engineering practice, the effect of strength anisotropy on stability analysis of tailings dam is often ignored. This paper presents direct shear test results on a tailing sand with different angles between shear direction and bedding plane. It is found that shear strength of this soil is significantly directional dependent. The variations in peak friction angle are about 11o, which is approximately 28.3% of the minimum value. The effect of strength anisotropy on stability of a tailings dam is also investigated. The analysis considering anisotropic strength shows a smaller factor of safety and shallower most critical slip surface as compared with isotropic strength model that is used in current engineering practice. To achieve more accurate stability analysis of tailings dams, it is suggested to take into account shear strength anisotropy of tailings soils.

Stability analysis of a copper tailings dam via laboratory model tests: A Chinese case study

The upstream method is a popular method for raising tailings dams. Currently in China there are more than 12,000 tailings impoundments and almost 95% of them use the upstream method for the construction of the dam. Statistical data has shown that the tailings impoundment is one of the main sources of risk in the mining industry. Failures of tailings impoundments have resulted in the loss of many lives, considerable property damage, and irreversible pollution in downstream areas. Therefore, the safety of tailings management facilities has been of increasing concern to governments and local communities. The management of a conventional tailings storage facility requires the maintenance of a high level of structural stability. Therefore, according to the relevant mine Acts, the mine operators are required to conduct stability analyses for all types of tailings facilities, whether they are new, active, or decommissioned. For the stability analysis of tailings dams, the accurate profile of the tailings dam is very important. The profiles are easily obtained for both active and decommissioned tailings facilities because their data can be collected through field investigations. However, collecting basic data from newly constructed tailings facilities is difficult. In this paper, a laboratory physical model test has been performed. The construction process for new tailings impoundment has been physically simulated in the laboratory, where the tailings particle composition and distribution below a beach, the change of phreatic surface of the dam, and the engineering properties of the tailings of the dam profiles have been measured. A new tailings facility, Yangtianqin tailings impoundment, owned by Tongchang copper mine of Yuxi Mine Co., was used as a case study to illustrate the physical modeling of the tailings dam. In the model test, the geometrical model of pond area was constructed according to the scale factor, λL, of 1:200 (model:prototype), and the tailings discharge system was also established, the tailings slurry then being discharged based on the design data. Finally, on the basis of the model test results on profiles, the stability analysis of the tailings dam at different heights was conducted under different conditions. The model test results and stability analysis show that the height of the tailings dam should be less than that originally planned. The original design of Yangtianqing tailings impoundment should therefore be revised for the safety of the tailings impoundment.

Effects of Nonhomogenity of Permeability on Tailings Dams

This paper has the objective of showing the influence of the permeability gradient during the construction of tailings dams, built by the upstream method, using the hydraulic fill technique. During the hydraulic disposition, two mechanisms affect the tailings permeability: the hydraulic segregation and the consolidation due the staged construction procedure. These mechanisms influence considerably the permeability distribution along the fill and, consequently, the behaviour of the dam. Results show that the pore pressure immediately after deposition may reach quite high values (532 kPa), but dissipates in a short period of time (1 to 10 days). Then, this effect should be taken into account in a short-term stability analysis of tailings dams. On the other hand, after pore pressure dissipation, there is a gain in the shear strength (13 %), which should also be considered, but in a long-term stability analysis of tailings dams.

97/03517 Industrial use of technologies potentially applicable to the cleaning of slurry pond fines

The upstream method is a popular method for raising tailings dams. Currently in China there are more than 12,000 tailings impoundments and almost 95% of them use the upstream method for the construction of the dam. Statistical data has shown that the tailings impoundment is one of the main sources of risk in the mining industry. Failures of tailings impoundments have resulted in the loss of many lives, considerable property damage, and irreversible pollution in downstream areas. Therefore, the safety of tailings management facilities has been of increasing concern to governments and local communities. The management of a conventional tailings storage facility requires the maintenance of a high level of structural stability. Therefore, according to the relevant mine Acts, the mine operators are required to conduct stability analyses for all types of tailings facilities, whether they are new, active, or decommissioned. For the stability analysis of tailings dams, the accurate profile of the tailings dam is very important. The profiles are easily obtained for both active and decommissioned tailings facilities because their data can be collected through field investigations. However, collecting basic data from newly constructed tailings facilities is difficult. In this paper, a laboratory physical model test has been performed. The construction process for new tailings impoundment has been physically simulated in the laboratory, where the tailings particle composition and distribution below a beach, the change of phreatic surface of the dam, and the engineering properties of the tailings of the dam profiles have been measured. A new tailings facility, Yangtianqin tailings impoundment, owned by Tongchang copper mine of Yuxi Mine Co., was used as a case study to illustrate the physical modeling of the tailings dam. In the model test, the geometrical model of pond area was constructed according to the scale factor, λL, of 1:200 (model:prototype), and the tailings discharge system was also established, the tailings slurry then being discharged based on the design data. Finally, on the basis of the model test results on profiles, the stability analysis of the tailings dam at different heights was conducted under different conditions. The model test results and stability analysis show that the height of the tailings dam should be less than that originally planned. The original design of Yangtianqing tailings impoundment should therefore be revised for the safety of the tailings impoundment.