Abstract
Earthquakes are one of the primary causes of instability in tailings storage facilities (TSFs), highlighting the necessity of studying dynamic responses and stability analysis under seismic wave action. This paper investigates the dynamic characteristics of a TSF proposed for decommissioning under seismic loading using the finite element time-history method. The study comprehensively analyzes dynamic deformation, seismic-induced permanent deformation, and pore water pressure changes, while identifying potential liquefaction zones and slope safety factors after seismic events. Results show that stress levels in the tailings dam remain low under applied dynamic loads, indicating a significant safety margin. Liquefaction zones are mainly concentrated in the shallow surface layers of the tailings beach, particularly in the fine sand and silt layers, with no liquefaction observed in the dam slope. The dam body’s deformation accumulates over the duration of seismic shaking, reaching a final value of 11.95 cm. The minimum slope safety factors during seismic events meet regulatory requirements, confirming dam slope stability. The findings provide a scientific basis for the design of TSF decommissioning projects.
Keywords
Introduction
Tailings storage facilities (TSFs) are sites used to store tailings discharged after ore processing in metal and non-metal mines. 1 The number and height of TSFs have been rapidly increasing to accommodate the growing demand for mineral resources and the resulting rise in tailings production. Among various hazards, earthquakes are one of the primary causes of tailings dam instability.2,3 Due to the fine particle size and high specific gravity of tailings dam materials, these structures may appear stable under normal conditions but are highly sensitive to external disturbances. 4 This sensitivity is particularly pronounced during high-intensity seismic events, which may trigger liquefaction and destructive deformation. For instance, the 2011 Tōhoku Earthquake in Japan (magnitude 9.0 on the Richter scale) caused structural instability in several tailings storage facilities, leading to tailings leaks that contaminated nearby farmland and water resources.5–7
The dynamic response of tailings dams under seismic wave action is highly complex. It involves changes in acceleration, displacement, and stress, all of which directly impact their stability. Therefore, research on the dynamic response and stability of TSFs under seismic loading is essential. 8 Scholars worldwide have extensively studied this issue using methods such as numerical simulation, physical modeling, and field monitoring.9–11 Among these, numerical simulation has gained widespread application in the stability analysis of tailings dams due to its cost-effectiveness, efficiency, and high reproducibility. Numerical simulation methods primarily include the traditional pseudo-static method and the time-history analysis method.12,13 The latter offers distinct advantages by accounting for seismic wave characteristics and integrating the dynamic properties of tailings materials (e.g., dynamic strength, pore pressure, shear modulus, and damping ratio), ensuring more representative simulation results.14,15 Yin analyzed the permanent deformation and dynamic stability of a high tailings dam using the time-history analysis method, the global deformation analysis method, and the limit equilibrium method, with Xiaodae tailings pond as an example. 16 Focusing on the Dashawo Tailings Reservoir heightening and expansion project, Wang adopted the time-course power analysis method to systematically study and comprehensively evaluate the dam’s dynamic response and stability before and after the expansion. 14
Therefore, this study focuses on a proposed decommissioned tailings storage facility as the research object and employs the finite element time-history method to investigate the dynamic characteristics of the dam under seismic wave action. A comprehensive analysis is conducted on the dynamic deformation characteristics of the dam body, seismic-induced permanent deformation, and dynamic pore water pressure. Additionally, the study identifies potential seismic liquefaction zones and evaluates post-seismic slope safety factors, offering a scientific basis for designing TSF decommissioning projects.
Engineering overview
The tailings storage facility of a certain iron mine, which was designed in 1992 and put into operation in 1994, has now ceased operation. It is a valley-type tailings storage facility, surrounded by mountains on three sides. The surrounding mountainous terrain, characterized by dense vegetation and simple geological structures, is stable. No major faults, landslides, or debris flows have been identified in the area.
Geotechnical surveys and engineering assessments indicate that the dam crest has reached its highest elevation of 336 meters. This corresponds to a maximum dam height of 86 meters. The reservoir’s total storage capacity is 4.62 million cubic meters. With an effective storage coefficient of 0.75, this equates to an effective capacity of 3.465 million cubic meters. This capacity classifies the reservoir as a third-class facility.
The original structure was a permeable rock-fill dam, measuring 27 meters in height and 135 meters in crest length, with an outer slope ratio of approximately 1:1.75 and a crest width of 3.5 meters. The dam’s expansion utilized upstream tailings embankment methods, with sub-dam slope ratios ranging from 1:4.0 to 1:4.3. The extended dam section has an average outer slope ratio of 1:4.5 and a final crest length of 301 meters. The layout and design of the tailings pond are illustrated in Figure 1. Plan layout of the tailings storage facility.
Dynamic finite element calculation theory
Dynamic constitutive model
The Hardin-Drnevich model is employed to calculate the dynamic shear modulus and damping ratio, which serve as the foundation for dynamic analysis in finite element calculations. 17
The model includes the following relationships: a. Dynamic Modulus: b. Damping Ratio: c. Maximum Shear Modulus:
These equations provide the relationships needed to model the stress-strain behavior of materials under dynamic loading conditions. The Hardin-Drnevich model is particularly suitable for representing soil behavior in seismic analyses, as it captures the nonlinear stress-strain response and energy dissipation through damping.
Dynamic control equation and solution steps
The dynamic control equation is expressed as:
The damping matrix
To solve the dynamic control equation, the Wilson-θ method is applied. The main calculation steps are as follows:
Perform static nonlinear calculations to determine the static stress distribution of each element before the earthquake.
Divide the seismic process into multiple intervals based on the amplitude of seismic waves; assume that the dynamic parameters of each element, specifically the shear modulus
Use a time step
Based on the calculated average shear strain
Repeat Steps 3 and 4 for each interval until the end of the seismic process is reached; obtain the required dynamic response quantities for the entire earthquake.
Calculation method of dynamic pore water pressure
The calculation formula for dynamic pore water pressure is as follows:
Isotropic Pressure Consolidation:
Anisotropic Pressure Consolidation:
Differentiating equation (7) gives the incremental calculation formula for pore water pressure:
Calculation method for seismic permanent deformation
The assessment of seismic permanent deformation on slopes is conducted using the Newmark methodology,18,19 as shown in Figure 2. In scenarios where the potential sliding plane forms a circular arc, the sliding moment caused by the mass under static conditions is calculated using the following formula: Newmark sliding block method.
Under dynamic conditions, the sliding moment of the mass must take into account the effect of seismic loads. The sliding moment in this case is expressed as:
From equations (9) and (10), the following can be derived:
At a specific moment during an earthquake, when
Throughout the earthquake event, the state of the sliding mass can be categorized based on the value of
The mass reaches a limit equilibrium state when
The mass remains stable when
The mass initiates sliding when
Assuming the rotational angular acceleration of the sliding mass is
From equation (13), the angular acceleration
Once the rotational angular displacement of the sliding mass is determined, multiplying it by the radius of the sliding arc gives the rotational arc length at any given point along the sliding surface. By applying the geometric principles of circular motion, the corresponding horizontal and vertical displacements for any point on the sliding arc can then be accurately calculated.
Calculation conditions and parameters
Dam body calculation section and finite element division
Based on the engineering survey report, the cross-sectional configuration and tailings zoning of the main dam at its final elevation of 336 meters were determined, as shown in Figure 3. The finite element mesh for the tailings dam cross-section was primarily generated using four-node quadrilateral elements, with triangular elements used locally for smooth transitions. The finite element computational mesh is shown in Figure 4, consisting of 3452 nodes and 3284 elements. Tailings dam calculation section diagram. Finite element calculation grid of tailings dam.

Static calculation parameters
Duncan E-B model calculation parameters.
Seismic acceleration time history curve
At the project site, the peak ground acceleration is recorded as 0.15 g, corresponding to a seismic fortification intensity of VII degrees and a characteristic seismic response spectrum period of 0.45 s. Three groups of artificially fitted seismic waves are used in the calculation, with all amplitudes taken as 0.15 g. When calculating the dynamics of the tailings dam, both horizontal and vertical acceleration curves are input simultaneously, with the peak value of the vertical acceleration curve taken as 2/3 of the peak value in the horizontal direction. The calculation results show that the contour distribution of the different seismic waves is similar, with only a slight difference in the extremes of the physical quantities. Due to space limitations, this paper only presents the results of analyzing and calculating a group of seismic waves with larger extreme values of physical quantities.
Figures 5 and 6 display the synthesized seismic waves, the standard spectrum curve, and the seismic acceleration time history curves. Artificially synthesized seismic waves and standard spectrum curve. Artificially synthesized seismic acceleration time history curve. (a) Horizontal, (b) vertical.

Dynamic calculation parameters
Maximum dynamic shear modulus
Maximum dynamic shear modulus relationship with confining pressure.
Relationship between dynamic shear modulus ratio, damping ratio, and dynamic shear strain
According to the dynamic test report, the test results of the dynamic shear modulus ratio Relationship between dynamic shear modulus ratio, damping ratio, and dynamic shear strain. (a) Relationship curve between 
Finite element result analysis
Static calculation results
Figure 8 presents the isocontour map showing the static stress and stress levels within the tailings dam. The pattern of stress distribution and the stress level isocontours under static conditions appears logical and consistent. The dam body’s maximum vertical stress is recorded as 998.39 kPa, excluding the foundation. These stress isocontours, largely parallel to the dam’s slope, indicate that the dam body’s vertical stress predominantly results from the weight, or height, of the “soil column.” At the base of the upstream side of the dam, the highest shear stress is observed at 130.12 kPa, again excluding the foundation. With the maximum stress level in the dam body at 0.83, there is no indication of a risk of shear failure or plastic deformation. Notably, areas with extreme values are primarily located near the dam’s bottom, away from the external slope, suggesting that the slope stability of the dam is not compromised. Isocontour map of static stress and stress level in tailings dam (stress unit: kPa). (a) Vertical stress, (b) shear stress, (c) stress level.
Dynamic calculation results
Typically, the seismic acceleration time history curve reflects the surface conditions of the dam bedrock or the site itself. When directly applied to dynamic analyses of the dam grid, including the bedrock, this can lead to an overestimation of the dam’s seismic response due to the amplification effect of the bedrock. Additionally, it is observed that during seismic events, the deformation experienced by the dam body significantly exceeds that of the bedrock. Consequently, the seismic response analysis model is designed to focus exclusively on the area encompassing the tailings dam.
Dynamic displacement response
Figure 9 shows the isocontour map of dynamic displacement of the tailings dam under seismic dynamic loads. Isocontour map of dynamic displacement in tailings dam (unit: cm). (a) Horizontal, (b) vertical.
Figure 10 shows the locations of typical nodes at elevations 227 m (Point A), 312.1 m (Point B), and 336.3 m (Point C). Figure 11 presents the corresponding time history curves of dynamic displacement at these nodes under seismic dynamic load. Typical node locations of the dam cross-section. Time history curves of dynamic displacement at typical nodes. (a) Horizontal dynamic displacement at Point A, (b) vertical dynamic displacement at Point A, (c) horizontal dynamic displacement at Point B, (d) vertical dynamic displacement at Point B, (e) horizontal dynamic displacement at Point C, (f) vertical dynamic displacement at Point C.

In the context of seismic activity, the tailings dam exhibits a pattern in the distribution of dynamic displacement isocontours, with dynamic displacement values gradually increasing from the dam’s base to its apex. The analysis also reveals that horizontal displacement predominates over vertical displacement. Specifically, the peak values of horizontal and vertical dynamic displacements recorded for the entire structure are 6.40 cm and 1.06 cm, respectively, under the influence of seismic waves.
Acceleration response
Figure 12 shows the acceleration isocontour map of the dam body, representing the maximum absolute value of acceleration throughout the entire seismic duration. Acceleration isocontour map of tailings dam (unit: m/s2). (a) Horizontal, (b) vertical.
Depicted in Figure 13 are the acceleration time history curves for selected nodes at various elevations: 277.0 m (Point A), 312.1 m (Point B), and 336.3 m (Point C), under seismic dynamic loading. The precise locations of these nodes are shown in Figure 10. Time history curves of acceleration at typical nodes. (a) Horizontal acceleration at Point A, (b) vertical acceleration at Point A, (c) horizontal acceleration at Point B, (d) vertical acceleration at Point B, (e) horizontal acceleration at Point C, (f) vertical acceleration at Point C.
During seismic activity, the tailings dam exhibits a logical distribution of acceleration isocontours under various conditions, with the highest values predominantly near the dam’s crest. The dam experiences a maximum horizontal seismic acceleration of 4.06 m/s2, with an amplification factor of 2.71. The maximum vertical acceleration is 2.64 m/s2, with an amplification factor of 2.64.
Analysis of liquefaction potential
Figure 14 shows the distribution of dynamic pore pressure and liquefaction zones in the tailings dam under seismic action, with liquefaction areas highlighted in red. Isocontour map of dynamic pore pressure and liquefaction zones (pore pressure unit: kPa). (a) Dynamic pore pressure, (b) liquefaction zones.
During seismic wave activity, the peak dynamic pore pressure in the dam reaches 92.25 kPa. Liquefaction primarily occurs in the shallow layers of the beach area (consisting of fine sand and silt) within the tailings dam, with no liquefaction observed on the slope. This indicates that the overall structure of the tailings dam remains secure.23–25
Permanent deformation
Figure 15 shows the distribution of cumulative permanent deformation in the tailings dam under seismic wave action. Cumulative curve of seismic permanent deformation of tailings dam.
During seismic events, the tailings dam experiences cumulative permanent deformation. When the acceleration of soil elements exceeds the yield acceleration, incremental residual deformations accumulate, reaching their peak by the end of the earthquake. Under seismic wave activity, the tailings dam undergoes permanent deformation of 11.95 cm.
Post-earthquake analysis of the dam body’s anti-slide stability
Figure 16 illustrates the change in the anti-slide stability safety factor of the tailings dam slope over the course of the earthquake, influenced by seismic wave action. Safety factor for anti-slide stability of tailings dam slope.
The sliding safety factor is calculated using the Bishop method, as expressed by the following formula:
During seismic wave activity, the minimum safety factor of the dam slope remains at 1.09. This value meets regulatory standards throughout the earthquake, indicating that the dam slope remains stable and resistant to sliding under seismic conditions.26,27
Conclusions and recommendations
The nonlinear finite element static and dynamic analyses of the tailings dam project lead to the following conclusions:
Static conditions: Stress patterns and levels in the dam exhibit a generally rational distribution. The highest vertical stress reaches 998.39 kPa, with isocontours aligned parallel to the slope. The maximum shear stress, located near the upstream dam bottom, is 130.12 kPa. The stress level peak of 0.83 in the dam body suggests a low risk of shear failure, with high-stress regions primarily at the dam’s base and away from the outer slope, ensuring slope safety.
Seismic events: During seismic activity, the tailings dam exhibits a progressive increase in dynamic displacement from the base to the crest. Specifically, under an earthquake with a peak acceleration of 0.15 g, the dam experiences maximum horizontal and vertical dynamic displacements of 6.40 cm and 1.06 cm, respectively. The acceleration isocontours within the dam show a logical pattern, peaking near the crest. The highest horizontal and vertical accelerations are 4.06 m/s2 and 2.64 m/s2, respectively, with amplification factors of 2.71 and 2.64. The peak dynamic pore pressure reaches 92.25 kPa. Liquefaction primarily occurs in the shallow layers of the beach area (comprising fine sand and silt), but not on the slope, highlighting the dam’s overall safety. The cumulative permanent deformation due to seismic activity is 11.95 cm, and the lowest safety factor of the slope complies with regulatory standards, confirming the dam’s stability.
Despite seismic activity, the tailings dam remains stable. Liquefaction is confined to the shallow surface layers of the beach areas, specifically in fine sand and silt zones. To further enhance safety, seismic reinforcement in these specific areas is recommended.
Statements and declarations
Footnotes
Conflicting interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The authors acknowledge the General Project of the Science and Technology Plan of the Beijing Municipal Commission of Education (KM202310009005), the National Natural Science Foundation of China (No. 52309131, No. 52304202), the Guizhou Science and Technology Plan Project (Qianke Science Support [2023] General 122), the Yuxiu Innovation Project of NCUT (No. 2024NCUTYXCX209), and the Open Project of the Key Laboratory of Xinjiang Coal Resources Green Mining (No. KLXGY-KB2409).
