Tailings Disposal Research Articles

Evaluation of short-term strength development of cemented backfill with varying sulphide contents and the use of additives

The disposal of sulphide tailings and control of strength deterioration of sulphide cemented backfills are of both environmental and financial interest. The uniaxial compressive strength (UCS) of samples with varying sulphide contents (6–25 wt%) was evaluated over a short-term period. A severe strength loss occurred after 14 days on those with low sulphide and the sulphide-rich samples keep increasing over 28 days. With SEM and XRD, it was inferred that the expansive phases were presumably responsible for the strength failure and the mechanical performance is closely in relation to the microstructure. They are deemed to present a positive to negative turn of effects on the strength. Initially, the precipitation in voids and micropores contributes to strength development until the already hardened structure cannot bear the inner pressure, microcracks begin to occur. For sulphide-rich cemented backfills, two kinds of additives, set retarder and accelerator, were adopted to measure their effects on the mechanical strength and setting time as the hardening process of cemented backfills was varied, and the results show that the accelerator gave rise to a rapid gain of strength while followed by a sharp deterioration after 14 days. In contrast, the retarder contributes to the continuous strength growth. From the economic perspective, the use of set retarder or accelerator involves 6.25% and 9.5% of binder cost respectively.

Optimization of tailings disposal method using fuzzy analytic hierarchy process

Abstract Due to the increasing demand for metals, the extractable grade of metal deposits has been decreasing and caused an increase in the amount of tailings. Increase in the volume of tailings requires proper attention to tailings disposal, the establishment of tailings dams, water consumption and prevention of environmental and groundwater pollution. Since tailings disposal consists of many stages such as discharge, thickening technology and location, and transportation, selection of the best disposal method is a complicated task. Nowadays, decision-making methods are widely used and they are very reliable and efficient. Therefore, a model based on fuzzy analytic hierarchy process (AHP) has been developed in this study to optimize tailings disposal method selection. In the model, 21 criteria and a wide range of alternatives have been introduced. The model has been applied to the Sangan Iron Ore Project (SIOP). The concentrator plant of SIOP will produce 75 million tons of tailings during the mine lifetime. Since the current disposal method wastes 1.5 million cubic metres of water annually and the project is located in a dry region, the proposed model has been used to investigate other options and the results show the filtered technique is the best alternative.

Evaluation of the impact of karst depression-type impoundments on the underlying karst water systems in the Gejiu mining district, southern Yunnan, China

The influence of mining activities on groundwater quality is a growing concern due to highly toxic metals in the tailings. Carbonate rocks are common in the surrounding rocks of ore deposits. But such mining districts generally do not have the conditions to construct traditional tailings impoundments due to the different degrees of karstification. This paper utilises field investigations, chemical analyses, and permeability tests, etc. to study the effect of tailings impoundments on the underlying karst water systems in the Gejiu world-class Sn-polymetallic mine located in a typical karst region in southern China, with samples collected from both karst springs deriving from the mining area and tailings porewater. Because of the abundance of sulphide minerals in the ores, acid mine drainage is expected to pose a high risk. However, the results indicate that the tailings porewater is moderately neutral and is characterized by the SO4–Ca–Mg hydrochemical type. This can be attributed to the substantial buffering capacity of carbonate minerals. Pollution elements in the tailings porewater mainly include SO42− and toxic metals including As, Cd, Mn, Pb, and Hg. The type of pollution factors and the degree of contamination are not consistent in the different tailings impoundments. The hydrochemical classification of four karst springs distributed in the south of the mining area is HCO3–Ca–Mg. The concentrations of SO42− and the toxic constituents in the springs are far below the national standards for drinking water. The spring water not being contaminated may be attributed to the operation mode of the tailings impoundments (peripheral discharge and reuse of ponded water), the residual clay between the tailings impoundments and the carbonate bedrocks and the sufficient buffering capacity of the underlying karst systems. The tailings disposal at the Gejiu tin mine within the natural karst depressions is able to provide a reference for the operation of karst mines in China and elsewhere.

Mn concentration and mycorrhizal colonization in understory native species grown at areas of manganese mine tailings disposal

Revegetation of areas with mine tailings should consider not only the best technique but also the choice of species adapted to this condition. This study aimed to analyze the occurrence of plant species, their Mn concentrations, and mycorrhizal colonization after implementation of two revegetation techniques (replacement of topsoil with natural seed bank and planting of seedlings) in an area of disposal of tailings from Mn processing compared to a native forest area as well as to a place that was not revegetated. Plant samples (at least three individuals/species) were collected from the understory at revegetated locations and forest. The established plant species and their Mn concentrations, mycorrhizal colonization, and forms of Mn in the soil were analyzed. The use of topsoil led to greater plant diversity. The high concentrations of Mn in the substrates did not affect the occurrence of vegetation in the understory and mycorrhizal colonization. The plant species established in the revegetated areas differed in relation to Mn concentration (471–27,842 mg kg−1 in leaves), Mn translocation factor (0.2–125.3) and mycorrhizal colonization rates (1–35%). Four potential Mn hyperaccumulators species were identified: Aparisthmium cordatum, Clidemia hirta, Socratea exorrhiza, and Vismia latifolia.

A case study on utilizing geotextile tubes for tailings dams construction in China

This research presents a successful case, in which geotextile tubes have been used to construct a tailings dam for fine tailings disposal since 2008. Up to the end of 2016, the tailings dam raise has reached 9 m in height. The total height of the dam including the starter dike was 61 m. In order to ensure that the tailings reservoir is safe in its current condition and during future construction, the comprehensive geotechnical investigation and stability analyses of the tailings embankment are conducted in this study. The results show that the application of geotextile tubes in the construction of tailings dam is a good alternative for fine tailings disposal.

Stability of the dam "Prevoj Šaška" of the flotation tailing dump "Valja Fundata" in Majdanpek

The existing dam "Prevoj Šaška" is located on the active flotation tailing dump "Valja Fundata" in Majdanpek. Since there is no valid documentation for the current maximum height of dam K+538 m, and disposal of tailings into this landfill is continued, the stability of dam has been carried out. Stability is calculated with the software SLIDE v6.0.

Research on the Dynamic Characteristics in the Flocculation Process of Mineral Processing Tailings

Abandoned mineral management has become an important global issue, and the collection, recycling, and disposal of mineral processing tailings (MPT) is critical in both mining engineering and environmental protection. In this study, flocculation sedimentation experiments and slurry rheological tests were carried out with unclassified tailings, and the flocculation sedimentation behaviour of the tailings under different conditions was investigated. The experimental results showed the followings: (1) Under close sedimentation effect conditions, different flocculants showed different effects on the fluidity of the slurry underflow, which was used as an important basis for optimization of the flocculation effect. (2) A tailings solid mass concentration of 40% and a flocculant dosage of 25 g/t were obtained as preferable sedimentation conditions. (3) Based on a microparticle agglomeration characteristics tests at the initial stage of flocculation, a flocculation concentration kinetic model was established that conformed to the fractal characteristics of the particles, which improved the applicability and accuracy of the concentration kinetic equation and the characteristic variables. In this study, an objective method for determining the parameters of full tailings flocculation sedimentation was realized. The results of an industrial trial operation also verified the reliability of the preferred parameters, which provided an effective basis for refined control of an efficient tailings recycling process.

Utilization of sulphidic mine tailings in alkali-activated materials

Disposal of mine tailings is one of the most important environmental issues during the mining lifetime. Especially sulphidic tailings can cause environmental and ecological risks because of their tendency to oxidize in the presence of water or air. Because of small particle size and harmful chemical properties, utilization possibilities of sulphidic mine tailings are limited. The aim of the present study was to develop technologies to utilize sulphidic mine tailings in alkali activated materials. Alkali-activated materials also known as geopolymers are nanosized zeolite type or slightly amorphous materials comparable to traditional Portland cement concrete, which can physically encapsulate or chemically stabilize the hazardous elements such as heavy metals into the 3D structure. Mine tailing based geopolymer aggregates were successfully produced from sulphidic mine tailings with good physical properties. The geopolymer aggregates performed as a concrete aggregate comparable to commercial lightweight aggregates. In addition, geopolymer mortars were prepared from mine tailings. In mortar application, there is a need to add some co-binder such as blast furnace slag in order to achieve high strength for the material. The mine tailing based geopolymer structure has an ability to stabilize a large number of cationic species into the structure while some anionic species were not able to immobilize by alkaline activation.

Bi-level depth assessment of an abandoned tailings dam aiming its reprocessing for recovery of valuable metals

The present work was developed in the scope of ERA-MIN/0007/2015 REMinE project, aiming recover of valuable metals through reprocessing of abandoned mine waste deposits. Cabeço do Pião site, the Portuguese case study in this project, is an old tailings disposal whose property was transferred from Panasqueira Mine to the Municipality of Fundão. The material deposited in the dam constitutes a risk to the environment, in particular to Zézere’s river that flows close to the bottom of the tailings pile and is a relevant contributor for the supply of drinking water. The study area was sampled at two different depths according to a regular grid. About fifty samples were collected and analyzed by X-ray fluorescence. The multivariate analysis of the chemical and the particle size data, allowed to establish mineralogical associations, proving to be a useful planning tool in a future selective re-mining of the tailings pile. Information extracted from the results of the principal component analysis was corroborated by the results of the geostatistical techniques applied to the analytical data.

Effect of sulfide on the long-term strength of lead-zinc tailings cemented paste backfill

With the production of a large amount of metal tailings, backfill is one of the best models for waste management and has been widely used in many mines. Metal deposit, especially lead-zinc mines, usually contain sulfide minerals, mainly pyrite. Sulfide attack would cause the strength degradation of cemented materials and decrease the structural stability. This study aimed to understand the effect of sulfide on the long-term strength of lead-zinc tailings cemented paste backfill (CPB). CPB specimens with four sulfur contents (2 wt%, 5 wt%, 10 wt%, 15 wt%) were prepared to investigate their physicochemical characteristics in 28–360 days. Scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) analyses of the CPB specimens were also conducted to obtain valuable information. The results showed that the highest strength of CPB was achieved at curing 90 days. Sulfide showed early strength agent property and the early strength of CPB with sulfur content of 5 wt% was improved. The internal system of CPB was alkaline, and sulfate mainly involved in cement hydration reaction. SEM observed that CPB specimens had compact structures, and calcium silicate hydrate (C-S-H) was produced. After 90 days, under the influence of sulfide, the strength of all the CPB specimens decreased, and the strength of CPB specimen with the highest sulfur content decreased the most. The pH value of the solution continuously decreased and eventually became acidic. A large amount of sulfate accumulated. The hydrated calcium silicate decomposed in the acidic environment. The number of expansive ettringite and gypsum products increased, and the number of large pores increased. Sulfide reactivity includes sulfate and acid attack. Large internal defects lead the strength and stability deterioration. This study compared the differences between sulfide erosion and sulfate attack, then provided some advice for the disposal of high sulfide tailings.

Environmental Impact Assessment (EIA) of a gold mine tailing through the multi-criteria decision making tool

Gold mine tailings dams are a high risk part of mining as they contain hazardous materials such as cyanide, mercury and arsenic from processing operations which present a risk to the public and to the environment. When tailing dams fail, the impact is disastrous for humans and the natural environment. The International Commission on Large Dams (ICOLD) collected 221 case records of tailing facility failure incidents worldwide to determine the causes of these incidents. The main causes of these incidents and reported cases of failure were found to be lack of control during the construction, lack of control of the water balance and a general lack of understanding of the features that control safe operations. The important elements to improve the safety and stability of tailings disposal facilities are geotechnical investigation, engineered design, construction, operation and monitoring of the tailings storage facility.

An evolutive bounding surface plasticity model for early-age cemented tailings backfill under cyclic loading

Cemented tailings backfill (CTB), an evolutive man-made soil or porous medium, is extensively utilized in underground mines as a sustainable solution for the disposal of tailings (mine waste) and/or ground control. At the early stages of curing, CTB is commonly saturated and weakly cemented, and thus subjected to the risk of seismically-induced liquefaction caused by mine blasts, rock bursts and earthquakes. The resulting intrusion of liquefied backfill mass into the mine tunnels may give rise to significant casualties and loss of production. In the present study, an evolutive bounding surface plasticity model is developed to capture the hydro-mechanical response of hydrating CTB under cyclic loading. Specifically, the changes of model components (yield and plastic potential functions, etc.) due to evolution of material properties are incorporated into the prototype bounding surface model. Then, the material property changes induced by binder hydration are determined and coupled to a binder hydration model that quantifies the curing process of CTB. Therefore, the developed model can be employed to assess the cyclic response of hydrating CTB at any given time of interest during its early age of curing when seismically induced liquefaction is of primary concern. The simulated results show good agreement with the experimental data for both monotonic and cyclic loadings. The proposed model can therefore provide more insight into the behavior of early-age CTB under seismic loading, and contribute to designing cost-effective CTB structures and assessing the risk of liquefaction.

Marine mine tailings disposal at Lillebukt, Stjernsundet, North Norway: distribution, sedimentary processes and depositional impacts

Marine mine tailings disposal at Lillebukt, Stjernsundet, North Norway: distribution, sedimentary processes and depositional impacts

In situ evaluation of performance of reclamation measures implemented on abandoned reactive tailings disposal site

The abandoned Manitou mine site produced acid mine drainage for decades. One of the site’s tailings storage facilities (TSF 2) was reclaimed in 2009 using an elevated water table combined with a monolayer cover made of low-sulphur tailings. A field investigation was undertaken from 2012 to 2015 to verify the performance of the reclamation technique in stemming the production of contaminants. This verification is based on two main criteria, i.e., the minimum water table level and maximum oxygen flux reaching the Manitou tailings. Thirteen monitoring stations were installed in TSF 2. The hydrogeological behavior and oxygen migration were investigated at each station by measuring volumetric water content, suction, water table level, gaseous pore oxygen concentration, and oxygen consumption. Analyses of field data showed that the minimum water table level criterion was reached with the exception of a portion of TSF 2 during the summer months. Oxygen fluxes reaching the Manitou tailings were determined using numerical simulations and analytical solutions; their yearly mean was many times lower than maximum targets generally used on reclaimed tailings disposal areas. The current system met the targeted performance criteria over the studied period.

Cu, Pb and Fe release from sulfide-containing tailings in seawater: Results from laboratory simulation of submarine tailings disposal

Metal release from the deposition of sulfide-containing tailings in seawater was investigated using a batch reaction experiment inside a temperature and dissolved oxygen-controlled chamber. Two hundred grams of tailings from a porphyry Cu-Au and a sediment-hosted Cu deposit were submerged in 1.8 L synthetic seawater. The sulfides present in the porphyry Cu-Au tailings are pyrite (FeS2), chalcopyrite (CuFeS2) and bornite (Cu5FeS4) while in the sediment-hosted Cu tailings are bornite, chalcocite (Cu2S) and covellite (CuS). Galena occurs as a minor sulfide in both tailings. Pore water and overlying seawater samples were collected and analyzed for pH, redox potential and trace metals (Cu, Pb and Fe) concentration. Results show that there is very low Cu (10–40 μg/L), Pb (1–10 μg/L) and Fe (5–50 μg/L) released into solution throughout the course of 87 days. Long-term trace metal release from tailings in seawater is therefore theorized to be low and is a slow process.

Prediction of Mechanical Performance of Cemented Paste Backfill by the Electrical Resistivity Measurement

Abstract Cemented Paste Backfill (CPB) has become a useful practice in many modern operations around the world. This method is an innovative tailings disposal and underground mine backfilling scheme that returns much of this material to the underground stope field. Thus, it is of great interest for financial and security reasons to fully comprehend the mechanical performance of such underground CPB. Uniaxial compressive strength (UCS) is one of the most commonly used parameters for evaluating the mechanical performance of CPB. Electrical resistivity (ER) measurement, which is a method of nondestructive testing, can also be used to determine the mechanical properties of CPB. This study was undertaken to suggest a nondestructive testing method that would permit prediction of the UCS of a CPB within 90 days. Five CPB samples were prepared at different cement-to-tailing ratios (1/4, 1/6, and 1/8 by weight) and solid content (65 and 70 wt. %), and a curing period of 3–90 days was used for ER measurement. Seventy-five CPB samples were prepared with the same cement content as those used in the pastes for UCS tests cured for 3, 7, 28, 56, and 90 days. The results of the ER measurement show that the ER versus curing periods of 3–90 days first drop to a minimum value and then gradually increase with time. The greater ER values of CPB are reached when the greater cement-to-tailing ratio and solid content is used. A logarithmic relationship is established between the UCS and the ER of CPB at 90 days. It is possible that a nondestructive method could be developed to evaluate the strength of underground CPB based on the obtained logarithmic relationship with ER at 90 days.

Application of a Rapid and Simple UV-Spectrophotometric Method for the Study of Desorption of Esterquat Collectors in Tailings–Seawater Systems

The growing demand for mineral resources followed by the steady increase in mining activity result in the need for the disposal of large amount of tailings. Submarine tailings placements (STPs) is a viable option to land-based waste disposal. However, disposal of tailings with accumulated chemicals continues to contribute to the degradation of the marine environment. Replacement of chemicals towards more environmentally friendly alternatives is a good initiative aimed at preservation and protection of the marine ecosystem. Among the cationic surfactants esterquats-containing reagents have attracted particular attention due to their specific ability to degrade rapidly into non-surface-active and environmentally friendly fragments followed by inorganic end products. The important decomposition reaction is the hydrolysis in the presence of water. In this study the rate of esterquats-containing reagent FLOT 2015 desorption by seawater and the probable mechanism of its chemical degradation in aqueous mediums were investigated with the aid of a simple and adequate UV-spectrophotometric technique. By investigating the desorption characteristics of the adsorbed collector FLOT 2015 on mineral samples, important information regarding its mobility and stability was obtained that would be valuable for environmental impact assessment.

The effects of cement on some physical and chemical behavior for surface paste disposal method

Environmental impacts resulting from conventional tailings disposal such as tailings dam accidents are a common problem for base metal mines around the world. In this context, laboratory-scale studies have been carried out on the Surface Paste Disposal (SPD) method, which is one of the alternative surface storage methods. In this study, three different SPD designs were tested; and volumetric water content, oxygen consumption, and matric suction sensors in first, fifth and 10th paste layers plus pH- electric conductivity (EC) values were all measured. Specifically, it was determined that the amount of oxygen in the environment required for the oxidation of sulfur minerals is reduced in the cemented layers in Design 3. In addition, the cement additive keeps the pH values of the seepage in an alkaline environment (over 7) so that it minimizes the risks of Acid Mine Drainage (AMD) and heavy metals mobilization at low pH values. Also, the EC values started a downward trend and ion dissolution decreased in designs with cemented layers. As a result, it was understood from the sensor measurements that the cemented layers act like a barrier.

Into the deep: science, politics and law in conflicts over marine dumping of mine waste

AbstractNational and international deliberations about whether the global mining industry should be permitted to use the earth's seas as mine waste dumps are not decided on the basis of independent scientific data from past or existing sites. Nor is a critical lack of scientific knowledge about the deep sea environment and about the long‐term consequences of marine dumping triggering the precautionary principle for proposed projects. Rather, governments make decisions on submarine tailings disposal (STD) on a mine‐by‐mine basis, in a context of contested scientific claims, considerable political and economic pressure, and, sometimes, contravening or amending existing legislation to allow a project to proceed. These decisions provoke complex social processes that commonly involve: local opposition; political conflict; regulatory and legal challenges; powerful industry lobbies; international financial institutions, and resource‐hungry states. STD projects engender controversy in developing countries, such as Papua New Guinea (Divecha 2002; Shearman 2002a), Indonesia (Edinger 2012; Glynn 2002) and the Philippines (Coumans et al. 2002; Coumans and MaCEC 2002), but also in Canada (Cultural Survival 1982) and Norway (Kvassness et al. 2009). This paper examines cases drawn from the Philippines, Canada and Papua New Guinea to illustrate common themes that arise in conflicts surrounding STD mine projects.

Flocculation of flotation tailings in presence of silicate gel and polymer

Flotation tailings were successfully flocculated in the presence of cationic polyacrylamide and silica gel. The effects of various parameters such as polymer weight, charge density, and pH on the rate of flocculation were also investigated in the current study. The flocculation mechanism of the flocculant on tailings was investigated using zeta potential and Fourier transform infrared (FTIR) measurements. The results obtained reveal that 1) sodium silicate gel, used as a binder for the consolidation of tailings form primary flocs, acts as an anchor and the adsorption of polymer flocculant on these anchors results in the formation of larger flocs and, consequently, enhanced settling rate; 2) flocculation in the presence of silica gel and polymer has a faster settling rate than single-polymer flocculation owing to the mechanisms of charge neutralization and bridging as identified using zeta potential and FTIR measurements. A pilot level study was conducted to investigate the influence of processed water on the flotation of scheelite. The results show that the proposed tailing disposal method could improve scheelite recovery by 2% (approximately) and could reduce the daily operation costs of the plant by approximately 108.57 USD.