Dam Failure Research Articles

Restrictions in water treatment by conventional processes (coagulation, flocculation, and sand-filtration) following scenarios of dam failure

Dam failure events can result in a high suspended solids concentration in surface waters. To understand the impact of high suspended solids concentration on the treatment process of water treatment plants, this study investigated coagulation-flocculation stages using different coagulants (ferric chloride and a polymeric coagulant – CAT-FLOC 8799 Plus) and solids concentrations (2000–46,000 mg/L), and how they impacted on the mean diameter (d50), density (ρs), and settling velocity (vs) of the agglomerates formed. After the sedimentation process, the turbidity values varied between 201–26 NTU when FeCl3 was used as a coagulant, and 36–11 NTU when using the organic coagulant. The study reinforces the effect of particle diameter on sedimentation velocity, which is lower for cases involving smaller average diameters. Even so, solids removal was high regardless of the initial conditions and characteristics of the agglomerated particles, starting early in flocculators with removals >80 %. The results point to the need for frequent maintenance of these units to remove the sludge settled, which could compromise the operation of water treatment plants. In this sense, two alternatives were proposed as pre- and post-treatment. Under high total solids concentration (>20,000 mg/L), pre-treatment with thickeners becomes mandatory, and ultrafiltration comes as an additional barrier that will prevent high turbidity values in drinking water. In this study, the use of ultrafiltration membranes in partial or total replacement of sand filters showed stable performance (permeate flow: 130–136 L/m2h) with no tendency to fouling and guaranteeing a residual turbidity value <0.3 NTU. Future studies should prove the technical and operational feasibility of the strategies proposed, which until then showed promising results to guarantee the operation of water treatment plants in adverse scenarios.

Gravity dams under blast loading: A Review

Hi-tech wars, accidental explosions, and subversive bombing attacks have alarmingly increased throughout the globe in recent times. Destructive Beirut explosion that occurred recently is the witness of this fact. Thus, it is increasingly realized that blast loading is a potential threat to the structures of higher importance. With the rapid development of precision and transmission techniques, the accuracy to blast the target and destruction potential of guided or controlled blasts have increased the vulnerability of important structures from subversive attacks in strategic border areas. Consequently, important infrastructure has become susceptible to such harsh blast loadings. Notwithstanding this prevailing belief that risk to water facilities from blast loading is small, yet dam operators and engineers are aware of 9/11 kind of threat [6]. The failure of dams with large reservoirs as a result of blast loads will cause serious economic loss by damaging the structure, hit agricultural sector of the area and also inundate downstream populated area. Modern dams are designed considering conventional loads, including hydrostatic pressure, gravity, sediment pressure, uplift pressure and seismic loads. Seismic performance evaluation of dam-reservoir-foundation systems under strong earthquakes has been widely studied [1, 10, 17, 18, 28, 29]. The effects of explosions on dams are not very well understood because not many investigations have been done on blast performance of dams. This is why most dam engineers lack the understanding of response of dams under blast loading. This review presents the studies conducted on gravity dams subjected to various kinds of impulsive loadings. Also, numerical investigations done on concrete gravity dams (CGD) subjected to blast loading have been comprehensively reviewed. Probable research gap on underwater explosive loading to dams is also presented.

A source tracking framework for attribution of reservoir fluxes in multi-reservoir systems

Reservoir water balance models are required to analyze the impact of alternative designs and operations on the performance of water infrastructure projects spanning multiple basins. However, the impact of such projects on instream ecology and water quality of participating basins remains relatively less explored quantitatively from a design perspective. This is due to the requirement of the complex systems model to simulate processes, which require additional data for parameterization while also increasing simulation time, which affects the performance of optimization algorithms. Here, we propose a conceptual framework to quantify the contribution of water from different basins to various reservoir-related fluxes in a multi-reservoir system. These include water released for demand satisfaction, maintaining minimum environmental flows, and preventing dam failure. For a given reservoir, we quantify the time-varying proportions of water supplied from other reservoirs and from the reservoir’s inflows for each release. We apply this framework to a proposed water transfer project in southern India that caters to the diminishing water supply of the Nagarjuna Sagar (NS) reservoir in the Krishna river basin by transferring water from the Godavari river basin. Our results show that the transferred water majorly caters to the additional demands on the NS reservoir to transfer water further south. We also find that, in general, the transferred water has little to no contribution to satisfying environmental flows downstream of the recipient. However, we do note a very high (up to 50%) contribution of transferred water to environmental flows at the NS reservoir for a few selected realizations of inflows in the monsoon season. Based on prior literature, these releases are concerning given the substantial differences in the ecological composition of fish species in both basins and may lead to invasive species downstream of the NS reservoir. We show how the proposed framework can be used to attribute recipient reservoir releases to donor and recipient inflows and shed light on failure dynamics by identifying fluxes that contribute to failures.

Potential use of iron ore tailings for binder production: A life cycle assessment

Iron ore tailings (IOT) are generated in large-scale around the world and are stored in its slurry form generating risks of dam failure. The stabilization of this tailings by cementing agent provides a better mechanical capacity for stockpiling. Alkali-activated cement (AAC) can be used due to its versatility in the use of waste for its production, thus reducing environmental impacts. In this context, the present work brings the use of iron ore mining waste for an alternative production of a binder. The IOT Binder uses a differentiated production of sodium silicate with tailings (from flotation process) and production of metakaolin with mining overburden. To evaluate the environmental efficiency of IOT Binder product, an environmental Life Cycle Assessment (LCA) is performed and compared with a conventional production of alkali-activated cement, using commercial products, for mining tailings stabilization. Eleven environmental impact categories are used for the evaluation of the IOT Binder and conventional AAC production inputs and their application for tailings stabilization. Preliminary compressive strength tests were performed with IOT Binder in the stabilization of iron ore tailings from Brazil. LCA results indicate that IOT Binder is more environmentally sustainable than conventional alkali-activated cement due to its lower energy consumption and avoidance of natural resource use. In addition, it is effective in cementing and stabilizing iron ore tailings for possible use in dry stacking.

Assessment of resource potential from mine tailings using geostatistical modeling for compositions: A methodology and application to Katherine Mine site, Arizona, USA

The mining industry, in most cases, targets a specific valuable commodity that is present in small quantities within large volumes of extracted material. After milling and processing, most of the extracted material and the effluents are stored as waste (tailings) in impoundments, such as dams or waste dumps, or are backfilled into underground mines. In time, tailing materials may become an issue of environmental and health concern due to the hazardous elements, ions, and oxides contained within the waste material. In addition, handling and storage of such waste in dams may pose the risk of dam failure with catastrophic consequences to nature and nearby communities. On the other hand, tailings may offer potential as secondary sources of critical elements (CEs), including rare earth elements (REEs), which may have been overlooked during primary production and processing. Therefore, treating mine tailings as a resource has economic and environmental benefits by reducing the waste from new and historical mine sites through remining. One of the critical steps for taking advantage of these benefits is to spatially quantify the resources and the pollutants, which require the application of adequate data analysis and modeling methods, often to compositional geochemical data. Utilizing adequate methods is especially important for correctly quantifying resource potential, as the quantities will often be at low concentrations.This work presents quantification of resource potential (Au, Ag, Cu, Zn, Pb) and elements of environmental concern (Hg and As) from the tailings of a historic mine site, Katherine Mine, AZ, USA. Data reported by the U.S. Bureau of Mines (USBM) after extensive field campaigns in the 1990s, including sampling from tailing impoundment and surrounding areas for geochemical characterization and geophysical surveys, were used. First, compositional data (CoDa) analysis was employed to explore associations of sampling locations, geochemical parts, and the clustering of samples. Next, sequential Gaussian simulation (SGSIM) was applied to samples that showed a genetic link to tailing material after isometric log-ratio transformation (ilr) and mix/max autocorrelation factor (MAF) transformation for spatial modeling and uncertainty evaluation. Geostatistical results revealed spatial variability of concentrations within the tailing area. Uncertainty evaluation based on realizations indicated that Cu (14.27–20.01 t), Zn (44.23–76.23 t), and Pb (22.56–38.28 t) are the most abundant elements within a 5 %–95 % interval, followed by Ag and Au (~5.3 and 0.18 t, at 50th percentile), respectively. Of the elements of health concern, As was found to be ~4.8 t (50th percentile) in the tailing area. The work also showed that ~0.51 t As, 0.005 t Hg, 0.020 t of Au, and 0.62 t of Ag were carried to Lake Mohave by an ephemeral stream called Katherine Wash, which transects the tailings.

Health risk assessment and cost-benefit analysis of agricultural soil remediation for tailing dam failure in Jinding mining area, SW China.

The impact of the tailing dams and the economic feasibility of the remediation process is significant for future risk management for tailing dams. In this research, we develop a hypothetical failure scenario for a tailing dam in the Jinding mining area, Southwest China. We assess the exposure with the Geo-Environmental Risk Assessment System, tier-1 model, and health impact with Disability-Adjusted Life Years (DALY). Cost and benefit are also analyzed for the following clean-up process. The result shows that the exposure dose (mg/kg-BW/d) of As, Cd, and Pb right after the dam failure is 1.07 × 10-2 for As, 1.76 × 10-4 for Cd, and 5.68 × 10-3 for Pb, respectively. The DALY caused by heavy metal exposure is 2.63 × 10-2 DALY per year, which significantly exceeds the tolerable level. This indicates that the tailing dam failure will pose a high health risk to the residents, and remediation is necessary. After remediation, the DALY is 1.24 × 10-8 DALY per year, indicating the clean-up process effectively reduces the resident's health impact. From the financial point of view, the net present value of the clean-up is $- 1.02 × 107. This indicates that the clean-up process is not economically feasible. Sensitivity analysis shows that the amount of released tailing influences the output result. The time span for benefit estimation is also an important issue. This research shows that the impact of a tailing dam failure will be severe, and remediation may be effective but economically infeasible. Therefore, preventing tailing dam failure is the most crucial task for the local government.

Predictive explicit expressions from data-driven models for estimation of scour depth below ski-jump bucket spillways

Abstract Scour depth estimation is an essential factor in water-related engineering problems. Scouring below spillways may endanger a dam's stability and even lead to dam destruction. As a result, it has undesirable environmental effects due to dam failure. Hence, reliable and accurate scour depth estimation below spillways is an exciting topic for researchers. For this purpose, the published and reliable prototype data related to scour depth below ski jump bucket spillways (Ds) was used to develop data-driven models. This study employed two widely used decision tree (DT) methods, including the M5 model tree (M5MT) and the classification and regression tree (CART), and also multivariate adaptive regression splines (MARS) for the estimation of (Ds). The proposed methods provided explicit and clear equations with straightforward applications for estimating scour depth. For the quantitative assessments of the developed formulas, three common statistical metrics, namely root mean square error (RMSE), mean absolute error (MAE), and correlation coefficient (CC), were used. Moreover, comparison results with previous approaches existing in the literature indicated the efficacy of the suggested methods. The obtained results revealed that the MARS technique was the best approach for the estimation of scour depth.

An Investigation of Instability on Constant Shear Drained (CSD) Path under the CSSM Framework: A DEM Study

Soil liquefaction or instability, one of the most catastrophic phenomena, has attracted significant research attention in recent years. The main cause of soil liquefaction or instability is the reduction in the effective stress in the soil due to the build-up of pore water pressure. Such a phenomenon has often been thought to be related to the undrained shearing of saturated or nearly saturated sandy soils. Notwithstanding, many researchers also reported soil instability under a drained condition due to the reduction in lateral stress. This condition is often referred to as the constant shear drained (CSD) condition, and it is not uncommon in nature, especially in a soil slope. Even though several catastrophic dam failures have been attributed to CSD failure, the failure mechanisms in CSD conditions are not well understood, e.g., how the volumetric strain or effective stress changes at the triggering of flow deformation. Researchers often consider the soil fabric to be one of the contributors to soil behaviour and use this parameter to explain the failure mechanism of soil. However, the soil fabric is difficult to measure in conventional laboratory tests. Due to that reason, a numerical approach capable of capturing the soil fabric, the discrete element method (DEM), is used to investigate the CSD shearing mechanism. A series of simulations on 3D assemblies of ellipsoid particles was conducted. The DEM specimens exhibited instability behaviour when the effective stress paths nearly reached the critical state line. It can be clearly observed that the axial and volumetric strains changed suddenly when the stress states were close to the critical state line. Alongside these micromechanical observations, the study also presents deeper insights into soil behaviour by relating the macro-observations to the micromechanical aspect of the soil.

Structural Failure of the Cohesive Core of Rockfill Dams: An Experimental Research Using Sand-Bentonite Mixtures

This article presents experimental research focusing on the structural failure of the central core of a rockfill dam using sand-bentonite mixtures. It comprised an extensive geotechnical characterization of soil materials and mixtures, including compaction and strength tests, as well as the construction of 1 m high and 1.5 m wide physical models. The displacements of the cohesive cores were recorded using a tailored measuring system, based on a laser pointer and a mirror, designed to amplify the real displacements. The cohesive cores were extremely sensitive to small oscillations and behaved as rigid bodies, similar to concrete slabs with three fixed sides and another free. The shape and dimensions of the breach formed on the cohesive cores had roughly the same shape and dimensions as the unprotected area. This experimental research has the potential to be used as validation tool for several models available in the literature to predict the failure of embankment dams.

Determining the construction areas of the retaining wall in order to reduce the flooding of the lands of Mehrgerd village due to the flood flow caused by the failure of the earth dam of Ghare Aghach

Determining the construction areas of the retaining wall in order to reduce the flooding of the lands of Mehrgerd village due to the flood flow caused by the failure of the earth dam of Ghare Aghach

Impacts of Climate Change on the Environment, Increase in Reservoir Levels, and Safety Threats to Earthen Dams: Post Failure Case Study of Two Cascading Dams in Michigan

Abstract Climate change has received significant attention lately as it has adverse environmental impacts. Among them, rising water levels in the reservoirs are of key concern for infrastructures such as dams. Dam officials are compelled to reconsider dam safety with the increment in catastrophic floods and accelerated dam failure issues. Relatedly, there are numerous earthen dams in the US that may not be up to the current design standards as these dams are aging. They possess a higher risk of failure due to various factors such as defects in design geometry, geologic materials, and hydrologic deficiency due to extreme storms associated with changing climate. Hence, this study focuses on evaluating the impacts of climate change on earthen dams and spillways by conducting a post-failure analysis of the two cascading dams, Edenville Dam and Sanford Dam, located in Michigan, USA, that failed in series in May 2020. The study aims to accomplish three main objectives: 1) to identify the role of climate change on recent dam failures of Edenville and Sanford, 2) to perform a Windows Dam Analysis Modules (WinDAM) C simulation for the failure analysis of the two dams, and 3) to perform Hydrologic Engineering Center - River Analysis System (HEC-RAS) simulation for the failure analysis of both dams by observing downstream propagation of flood with the detailed evaluation of depth and velocity. The overall results show that extreme storms and flooding are associated with the increase in temperature and precipitation rates, impacting overall dam safety. Careful precautions should be undertaken before any of these catastrophic dam events occur. The analysis is useful for the dam agencies as they reconsider their guidelines and policies for future updates.

Study on fracture development and progressive failure characteristics of downstream dam-type expansion tailings reservoir

With the economic development and industrialization, the increasingly accumulated tailings ponds in China have become a great risk. Due to the difficulty of selecting proper site for a new reservoir in Yunnan, a sub-dam was built at the downstream original reservoir. This study explored the fracture development and progressive failure characteristics of the tailings reservoir area after capacity expansion based on a similarity experiment and the numerical simulation. The results showed that the primary cracks in the reservoir area were more than those at the top of the sub-dam. With the increase of the upper load, the primary cracks further developed and penetrated the whole sub-dam top, and the sub-cracks were then produced under the concentrate stress of the primary cracks. After the further development of the sub-cracks, the secondary cracks parallel to the primary cracks were formed on the outer slope of the sub-dam. The progressive failure of a tailings dam can be summarized as: the maximum shear stress was firstly generated at the toe of the slope or the top of the dam which then extended to the top of the sub-dam in the form of a curve and finally formed the failure surface by connecting with the primary fracture of the tensile plastic zone at the top of the dam. The study also found that in the process of tailings accumulation in the new reservoir area, tailings would form "back pressure slope protection" at the initial dam of the original reservoir, which not only effectively delayed the occurrence of shear failure, but also inhibited the generation and penetration of tensile plastic zone.

Acoustic identification and classification of four dolphin species in the Brazilian marine area affected by the largest tailings dam failure disaster.

Passive acoustic monitoring (PAM) is an increasingly used technique to access the occurrence, distribution, and abundance of cetaceans that may be visually unavailable most of the time. The largest tailings dam failure disaster occurred on 5 November 2015, when the Fundão dam collapsed, releasing over 50 million cubic meters of tailings into the Doce River basin; 14 days later, the tailings plume reached the Atlantic Ocean. PAM was implemented in the concerned area and cetacean species were acoustically identified. Whistles and clicks of visual and acoustic matches were used to predict and classify exclusive acoustic records through random forest models. The identified species were Guiana, rough-toothed, and bottlenose dolphins. Additionally, the franciscana, the most threatened cetacean in the western South Atlantic Ocean, was also acoustically identified. The whistle classifier had 86.9% accuracy with final frequency, duration, and maximum frequency ranked as the most important parameters. The clicks classifier had 86.7% accuracy with peak frequency and 3 dB bandwidth as the most important parameters for classifying species. Considering the potential effect of the increase in turbidity on sound transmission, such as attenuation, the presented classifier should be continuously improved with novel data collected from long-term acoustic monitoring.

Mosul dam issues: analysis of the problem based on several studies

Mosul Dam is the Middle East’s second-largest dam in terms of reservoir capacity. Since its inception in 1986, this dam has been plagued by seepage difficulties in its base caused by the breakdown of gypsum. Underneath the foundation, there are strata of anhydrite. This occurrence has sparked worry the dam’s stability. This paper presents a survey of studies conducted by several researchers on concerns related to the stability and safety of the Mosul Dam in Iraq. Additionally, the implications of the dam breach scenarios are to be presented and discussed. In another word, the Mosul Dam issues are assessed with different references to geologic challenges of the abutments and foundation, dissolution of gypsum and formation of sinkholes, dissolution of gypsum and seepage, and the probable scenarios for concerns of dam failure. After the ISIS conflict, maintenance has been disrupted and signs at the dam have triggered renewed concerns. Consequently, the Iraqi government have contracted the Italian engineering company Trevi to start remedial work on the dam. This work was in 2016. Therefore, the present state of Mosul Dam was declared as safe and stable.

Flood Modelling due to Dam Failure Using HEC-RAS 2D with GIS Overlay: Case Study of Karalloe Dam in South Sulawesi Province Indonesia

A dam is one of the water structures that have many benefits for humans. However, flood disasters caused by dam break may have a very bad impact on human life. This study specifically analyzed the impact of flooding caused by the failure of the Karalloe dam in Bone Regency, South Sulawesi Province, Indonesia. For the first time, the selected flood discharge used in the dam break analysis was verified using the Creager graph by comparing the calculated discharge from several synthetic unit hydrograph methods (HSS) with the flood discharge measured on the automatic water level recorder (AWLR) at the monitoring point. The impact of flooding due to dam break was simulated using HEC-RAS 2D combined with ArcGIS for mapping. The calculation results of the design flood discharge based on rainfall data using the methods of HSS Nakayasu, HSS ITB I, HSS ITB II, and HSS SCS (HEC-HMS) as well as the calculation of the designed flood discharge based on the discharge data showed that the design flood discharge value which is closest to the measured discharge value and Q1000 Creager was the HSS SCS method. The flood discharge values obtained based on the HSS SCS method for Tr (return period) 2 years, Tr 5 years, Tr 10 years, Tr 20 years, Tr 25 years, Tr 50 years, Tr 100 years, and Tr 1000 years were 322.70 m³/s, 464.10 m³/s, 560.40 m³/s, 658.40 m³/s, 682.70 m³/s, 787.00 m³/s, 885.70 m³/s, and 1202.60 m³/s, respectively. The simulation results showed that 22 villages will be affected by flooding due to the failure of the Karalloe dam and the fastest standby time of the flood is 12 minutes, namely at Lookout Point 7 in Paitana Village. This result suggests that early warning system should be installed at the downstream of the dam and flood disaster mitigation should be adopted and applied to these threatened area.

Advanced monitoring of tailings dam performance using seismic noise and stress models

Tailings dams retain the waste by-products of mining operations and are among the world’s largest engineered structures. Recent tailings dam failures highlight important gaps in current monitoring methods. Here we demonstrate how ambient noise interferometry can be applied to monitor dam performance at an active tailings dam using a geophone array. Seismic velocity changes of less than 1% correlate strongly with water level changes at the adjacent tailings pond. We implement a power-law relationship between effective stress and shear wave velocity, using the pond level recordings with shear wave velocity profiles obtained from cone penetration tests to model changes in shear wave velocities. The resulting one-dimensional model shows good agreement with the seismic velocity changes. As shear wave velocity provides a direct measure of soil stiffness and can be used to infer numerous other geotechnical design parameters, this method provides important advances in understanding changes in dam performance over time.

Retrospective analysis and hazard assessment of Gega glacial lake in the eastern Himalayan syntaxis

The frequency of glacier related hazards like Glacial Lake Outburst Flood (GLOF) is increasing in the High Mountain Asia due to global climate warming. The extreme floods generated by glacial lake outburst aggravate the risk to people, towns and infrastructure in downstream regions. However, little attention is paid to the destructive potential of the lakes in the southeastern margin of the Tibet in spite of recent rapid increases in population, infrastructure, and economic investment. With retrospective investigation of the Gega lake, we found historical overtopping flood(s) impacted by landslides based on the lake dam consists of landslide deposits on both sides and bedrock in the middle, manifesting the GLOF risk in future. BRCH-J model is used to simulate the flow hydrographs after dam break, then, the HEC-RAS software is used to simulate the propagation of outburst floods. Finally, the GLOF risk is evaluated with a semi-quantitative approach considering overtopping and piping failure scenarios. The peak discharge after dam failure would reach up to 17,000 ​m3 ​s−1 (at dam site), which is about two times greater than the average seasonal flood peak near Gega village in the trunk river. Piping failure attains a larger peak discharge and quicker peak time (∼0.13 ​h) compared to the overtopping failure (∼0.5 ​h). The sensitivity analysis of materials properties (like internal friction angle and porosity etc.) shows geotechnical properties of the dam material affect the magnitude of peak discharge. The 1D steady flood routing of the peak flow indicates the flow depth is larger than 35 ​m at the Yarlung Tsangpo - Gega confluence. The extreme flow through narrow and steep terrain could even trigger debris flow along the Gega stream. The results can be useful for mitigating risk of GLOFs in the eastern Himalayan syntaxis and neighboring alpine areas.

A Systematic Investigation of Historical Churches in Michigan, USA

Michigan is very rich with an abundance of historical churches listed in the National Register of Historic Places including the second oldest Catholic parish in the nation. These historical churches reflect the city’s multicultural nature with their alluring architecture and offer a crucial socio-cultural involvement in extreme events as broadly observed during the pandemic period. On the other hand, Michigan is also prone to disasters such as hurricanes, tornadoes, and fires. The last flood in May 2020 resulted in dam failures and caused severe damage in Midland, Michigan. Therefore, preservation planning is urgently needed to be prepared for such extreme events including climate-related flooding. The research work investigates the historical churches in Michigan and their structural resistance to a possible natural disaster. In the research, a rapid visual inspection approach and FEMA methodology were used in combination to ensure the safety of historical churches for disaster preparedness. A structural investigation procedure was carried out for eighteen historical churches in Michigan to understand the current structural status of the historical churches. The churches were selected based on their historical characteristics. Selected churches are also the famous ones in Michigan. As a result of the carried investigation process, structural capacities, structural responses, damage risks, and hazard risks of the historical churches were defined. Structural capacities were defined with the target to increase resilience for the recovery, rebuild, and preparation for possible future disasters.

Hydro-mechanical coupling effect on water permeability of intensely weathered sandstone

The combined effect of stress and seepage is an important reason of engineering geological problems such as landslides, dam failures, and tunnel collapse. However, due to the limitations of the test apparatus, the existing studies rarely consider the stress effect in the seepage process. In this study, a soil column apparatus based on the wetting front advancing method was developed to explore the permeability properties of intensely weathered sandstone in a wide range of suction (10∼106 kPa). The results suggest that the wetting front advancing velocity decreased as the vertical stress increased during infiltration, which indicates that the stress changes the infiltration channel and affects the infiltration rate. On the other hand, due to the water sensitivity of intensely weathered sandstone, the soil column deformation before and after wetting is significantly different, indicating that water infiltration further exacerbates the deformation. When vertical stress is applied to the soil column, the permeability coefficient–suction curves at different sections are paralleled in general, which is affected by the variation in dry density and the non-uniform distribution of stresses inside the soil column. Moreover, as the initial dry density increases, the influence of the vertical stress on the permeability coefficient gradually decreases.

Static Liquefaction Causes the Flow Failure of a Tailings Dam: A Case Study of El Descargador, Cartagena–La Unión Mining Region, SE Spain (October 1963)

The aim of this work is to investigate the causes of the El Descargador tailings dam failure, at the mine district Cartagena–La Unión (SE Spain), in October 1963. Dam stability back analyses have been carried out by applying a geotechnical and geophysical approach. The failure occurred in the form of several landslides in five different points along the dam structure. The rise in the pore pressure and the steeped slopes of the tails, scaling up to 40° in some sectors, were the main causal preparatory factors. Here we propose that static liquefaction is the most plausible cause of the tailings dam flow failure. The presence of sand dikes and sand volcanoes with atypical stratigraphic architecture, both in the lagoon and at the surfaces exposed in the landslide areas, as well as the evidence of conspicuous sand fraction on the surface support the occurrence of the liquefaction processes. Major landslides were located near the drainage pipe and the flow directions were controlled by its position. Our results reveal that the liquefaction processes were triggered and aggravated by the poor drainage capability of the tailings dam structure.