Waste Rock Piles Research Articles

Physical and Numerical Modeling of a Flow Control Layer Made with a Sludge and Slag Mixture for Use in Waste Rock Pile Reclamation

Physical and Numerical Modeling of a Flow Control Layer Made with a Sludge and Slag Mixture for Use in Waste Rock Pile Reclamation

Geochemical and mineralogical characterization and resource potential of the Namib Pb-Zn tailings (Erongo Region, Namibia)

In Southern Africa, historic mining and mineral processing of base metal deposits have almost exclusively focussed on the extraction of major metals, leading to the loss of remaining valuable raw materials into tailings dumps and waste rock piles. At the Namib Pb-Zn mine (Erongo Region, Namibia), historic base metal tailings deposits are present as unreclaimed exposed waste piles. The tailings comprise silt- (fraction A: d50 = 25 to 48 μm) to sand-sized (fraction B: d50 = 86 to 185 μm; fraction C: d5o = 210 to 230 μm) material and contain major concentrations of base metals (Pb av. 1.15 mass%, Zn av. 3.20 mass%), S (av. 9.95 mass%), as well as lower values of other metals (Cu av. 490 μg/g, Cd av. 133 μg/g, Ag av. 22 μg/g), and critical elements like Sb (av. 14.7 μg/g) and In (14.3 μg/g). Former mineral processing only targeted the extraction of galena and sphalerite. As a consequence, qualitative mineralogical composition of the tailings is similar to that of the primary ore. Ca-Fe-Mg(-Mn) carbonates, quartz, micas, chlorite, minor graphite, magnetite, and rare parisite relate to the former host rock and gangue matrix, whereas Fe-rich sphalerite, galena, magnetite, pyrite with minor pyrrhotite, rare arsenopyrite, marcasite, cassiterite, and accessory scheelite are original constituents of the primary ore. Reprocessing of such a material would be challenging, but a mixed Pb-Zn concentrate enriched in Cd and Ag might be obtained. In future, possible reprocessing of Namib tailings and associated disposal of wastes into an appropriately designed repository would not only generate valuable metal commodities, but such activities would also eliminate a major metal pollution source from the local environment.

Grading scalping and sample size effects on critical shear strength of mine waste rock through laboratory and in-situ testing

Geotechnical stability analyses of mine waste rock (WR) piles require the critical friction angle (ϕcr) of the coarse blasted rock. However, due to the presence of oversized rock clasts, shear strength can only be characterized on small samples prepared using grading scaling techniques, such as scalping. Thus, considering a testing device able to handle samples of characteristic size D, the material should be scaled down to a maximum particle size dmax given by the minimum sample aspect ratio α = D/dmax. However, a practical concern about how far the size scale can be reduced while keeping representative results remains a matter of debate in the geotechnical community. International standards do not agree on the minimum recommended α, and its effects on the mechanical behavior remain poorly understood. This paper aims to investigate the grading effects and sample size effects on ϕcr of WR materials using the scalping technique, to provide insights on the minimum recommended α. Triaxial tests were conducted on loose and dense samples of diameters D = 150 and 300 mm. Samples were scalped from field material having dmax = 75 mm, to allow a range of α from 4 to 30. Additionally, one of the world largest in-situ direct shear boxes (120 × 120 × 38 cm3) was developed to test the same WR material. The results show that scalping is an appropriate technique to assess the critical shear strength of WR. The minimum α for ϕcr assessment in triaxial testing is not sensitive to grading nor sample size, but it is affected by sample density. The aspect ratio was found to be α ≥ 12 and α ≥ 16 for loose and dense samples, respectively. This finding advocates that α values recommended by worldwide standards, such as ASTM D7181-20, might be too low and should be revisited after comprehensive testing.

Scale and suction effects on compressibility and time-dependent deformation of mine waste rock material

Designing high mine waste rock piles for long-term behavior requires material mechanical characterization over a large range of stresses and variable environmental conditions. However, representative coarse samples cannot be handled by standard testing devices and the common approach is to test small-scaled samples at the laboratory, which might be affected by particle size effects when compared to the field material. Several reported results indicate that coarser samples present higher amount of particle crushing than small-scaled samples, thus lower dilatancy and higher compressibility. However, specific studies of size effects on time-dependent deformation are lacking. The aim of this paper is to identify the effects of particle size and suction on stress-deformation mechanism of partially saturated mine waste rock. Oedometric compression tests on two parallel graded samples are presented: the gravelly fraction (dmax=50 mm) and the sandy fraction (dmax=2.36 mm). Each stress increment triggers « instantaneous » and delayed strains. The results reveal the combined effects of particle size and humidity on the mechanical behavior. Coarser samples exhibit higher total compressibility and creep deformation, which also increases with the material humidity. The results give empirical support for the development of scaling laws and suggest that total deformation can be decoupled considering a suction dependent index for creep deformation.

Effect of construction method and bench height on particle size segregation during waste rock disposal

ABSTRACT Waste rock segregation and heterogeneity can increase the hydrogeotechnical and geochemical instability of waste rock piles, but characterising segregation quantitatively in the field is difficult because of the large dimensions of these structures. In this study, a discrete element model (PFC3D) was calibrated on two real cases and used to simulate the flow behaviour of waste rock during disposal. The effect of the construction method, the bench height, and additional factors (e.g. mine truck payloads and push velocities) on particle segregation was investigated. Segregation degree and relative particle diameters of waste rock at different locations in the pile were compared to propose practical solutions and reduce segregation and heterogeneity during deposition. Results indicated that simulated bench heights and mine truck payloads had limited effect on segregation. A smaller proportion of large particles in the original waste rock can increase segregation. Lateral disposal and increasing the push velocity tend to reduce segregation.

Simulation Study on the Influence of Chimney Structure on the Efficiency of Gravity Heat Pipes for Controlling Spontaneous Combustion in Coal Waste Rock Piles

ABSTRACT Heat pipe is an efficient heat transfer element. Using heat pipes to control spontaneous combustion of coal gangue piles is a simple and effective method. However, the heat conducted by the heat pipe is usually directly released into the atmosphere, causing waste of resources. In order to utilize this part of the heat, this paper studied the method of enhancing the heat dissipation of the heat pipe. Based on the chimney effect, a chimney that utilizes the heat conducted by the heat pipe to enhance its heat dissipation efficiency was designed. The effects of five different parameters, including the distance between the chimney and the ground, the length of the chimney expansion section, the radius of the chimney inlet, the distance between the heat pipe and the inner wall of the chimney, and the height of the chimney, on the enhancement of heat dissipation of the chimney effect by the heat pipe were mainly studied. A large number of numerical simulation studies were carried out for chimneys with different structural sizes. The results show that all of the above five parameters have certain effects on the enhancement of heat dissipation of the chimney by the heat pipe, and each parameter has an optimal value to achieve the best enhancement effect of the chimney on the heat dissipation of the heat pipe. The response surface analysis was used to optimize the parameter values. The final designed chimney can increase the heat dissipation efficiency of the heat pipe by three times, providing a new direction for heat dissipation of heat pipes and the utilization of waste energy.

Design and Implementation of Sampling Wells in Phosphate Mine Waste Rock Piles: Towards an Enhanced Composition Understanding and Sustainable Reclamation

Establishing a circular economy in mining begins with a dedicated sampling strategy as its fundamental phase. This specific approach is crucial for enhancing resource retrieval and isolating essential minerals from mining residues. By carefully examining and defining the makeup of waste materials, mining activities can discover overlooked possibilities, promoting sustainability. A thoughtfully planned sampling strategy not only reduces environmental harm but also sets the stage for the effective use of resources. In doing so, the mining industry can shift towards a circular model, adhering to the principles of waste reduction, material reuse, and ultimately promoting a more environmentally conscious and economically viable industry. In the phosphate industry and during the pre-concentration process of phosphate ore through screening, significant amounts of mining waste, consisting of various lithologies including indurated and fine phosphate, coarse-grained silicified phosphate, limestone, and marls, are deposited in waste rock stockpiles. Collecting representative samples from these heterogeneous materials presents challenges in accurately characterizing the entire stockpile. To overcome this issue, circular mining wells were implemented as a novel sampling method in waste rock stockpiles, enabling the collection of intact representative samples. This paper shares a successful experience in constructing three concrete-lined wells within a phosphate mine waste rock stockpile measuring 662 m in length, 240 m in width, and ranging in height from 0 to 65 m. The wells were dug at various depths, ranging from 20 m to 55 m, with a circular section and a diameter of 1.5 m. An integrated method utilizing analytical techniques in conjunction with numerical modeling via Robot Structural Analysis software (version of 2020) was utilized to assess the stress on the well supports and confirm their stability. This methodology serves as a valuable tool for evaluating the stability of similar wells, ensuring the safety of operators. The structural model yielded a stress level of 1 MPa, which aligned with the values obtained from the analytical model. Sensitivity analysis was performed on various parameters (friction angle, Poisson Ratio, and gravity), and the safety factor consistently remained above 1.5 for all scenarios investigated up to a depth of 60 m. Consequently, this study demonstrates that concrete-lined wells can be utilized safely for intact sampling in waste rock stockpiles. This sampling operation will allow the pursuit of optimizing resource utilization and enhancing environmental sustainability, by studying phosphate distribution in the Phosphate Mine Waste Rock (PMWR) for better recovery.

Antimony mobility in soil near historical waste rock at the world's largest Sb mine, Central China

Soil near waste rock often contains high concentrations of antimony (Sb), but the mechanisms that mobilize Sb in a soil closely impacted by the waste rock piles are not well understood. We investigated these mobility mechanisms in soils near historical waste rock at the world's largest Sb mine. The sequential extraction (BCR) of soil reveal that over 95 % Sb is present in the residual fraction. The leached Sb concentration is related to the surface protonation and deprotonation of soil minerals. SEM-EDS shows Sb in the soil is associated with Fe and Ca. Moreover, X-ray absorption spectroscopy (XAS) results show Sb is predominantly present as Sb(V) and is associated with Fe in the form of tripuhyite (FeSbO4) as well as edge- and corner-sharing complexes on ferrihydrite and goethite. Thus, Fe in soils is important in controlling the mobility of Sb via surface complexation and co-precipitation of Sb by Fe oxides. The initially surface-adsorbed Sb(V) or co-precipitation is likely to undergo a phase transformation as the Fe oxides age. In addition, Sb mobility may be controlled by small amounts of calcium antimonate. These results further the understanding of the effect of secondary minerals in soils on the fate of Sb from waste rock weathering and inform source treatment for Sb-contaminated soils.

Hydrogeochemical modelling of pyrite oxidation ion mobility in unsaturated mine waste rock piles

Hydrogeochemical modelling of pyrite oxidation ion mobility in unsaturated mine waste rock piles

Complex electrical measurements of waste rock during acid mine drainage generation and release: Kinetic column tests

Acid mine drainage (AMD) emanating from waste rock piles (WRPs) at mining sites is a global concern. Successful rehabilitation of these sites requires effective characterization and monitoring of the waste rock during AMD generation/release. Traditional approaches involve ex-situ analysis of waste rock and porewater samples collected via corings and monitoring wells; however, this is highly disruptive, costly, and provides sparsely distributed point information across enormous volumes typical of WRPs. Geoelectrical techniques are a promising approach for non-invasive continuous imaging; however, their application has been limited to ‘one-off’ imaging with few studies on monitoring waste rock evolution. The objective of this study is to assess the geoelectrical signatures of changing waste rock during AMD generation/release. Field waste rock samples were extracted from three mine WRPs and first characterized for mineralogy and acid generation potential. Kinetic tests were then performed on each sample using leaching columns and humidity cells, with simultaneous measurements of effluent quality and complex electrical conductivity (real and imaginary components measure conduction and polarization, respectively). Results show that real conductivity was highly sensitive to changes associated with AMD leachate quality (e.g., 28,800 to 68 mg/L acidity) and surface of the waste material. Imaginary conductivity measurements identified changes in the waste mineralogy over time, though these signatures were not very distinct, which is likely due to low sulfide contents and limited oxidation (e.g., 0.59 wt% sulfide and 33% air saturation). This study improves our understanding of geoelectrical signatures associated with real waste rock, demonstrating the potential application of the electrical resistivity tomography and induced polarization techniques for mine waste investigations.

Indium use, resource, market and ore deposit type

With the continuous advancement of science and technology, rare dispersed elements that have long been dormant in rocks and ignored by humans have become increasingly important. Indium is one of these rare dispersed elements, although most people know little or nothing about it. In fact, indium has a wide range of important uses in many aspects. Given the unique physical and chemical properties of indium, some uses are even irreplaceable. Therefore, many countries have included some rare elements, including indium, in the list of national strategic resources or critical metals for protection. This article not only popularizes the main uses of indium in modern society, briefly describes the distribution and current status of natural indium ore resources around the world, but also explores its market status in the past 10 years and future development trends. Finally, the main genesis types of associated or symbiotic indium ores around the world are summarized and briefly discussed. Because indium does not exist as an independent deposit and can only exist as a by-product of non-ferrous metals such as copper, lead, zinc and tin, it is very important to research and develop new sources of indium, including recycling and reuse. These new sources include but are not limited to waste rock piles and tailings from related abandoned old mines, etc.

Characterization of particle size segregation and heterogeneity along the slopes of a waste rock pile using image analysis

Large amounts of waste rock are produced during mining operations and often disposed of in large piles. Particle size segregation usually occurs during waste rock disposal, which can lead to high variations of particle size distribution (PSD) along the pile slope, increasing the risk for hydrogeotechnical instabilities. Determining segregation in situ is, therefore, critical to implement control measures and optimize deposition plans. However, characterizing PSD at field scale remains challenging because of the large dimensions of the pile, the instability of the blocks and the steep slopes. In this study, images, covering a 1400 m wide and 10 m high section of a waste rock pile, were taken and analyzed using image analysis to characterize segregation along the slope of the pile. PSD curves in different sections along the slope were determined and the segregation degree and characteristic diameters (e.g., D10, D50, D80,D95) were quantitatively compared. Results allowed to quantify segregation along the vertical direction of the pile, showing that segregation degree increased from − 0.77 ± 0.39 in the top (finer zone) to + 0.4 ± 0.14 in the bottom (coarser zone). Significant lateral heterogeneity was also observed with maximum diameters varying between 80 and 180 cm in the bottom section. Such segregation and lateral heterogeneity could induce significant variations of waste rock properties, with, for example, hydraulic conductivities varying by more than 2 orders of magnitude within the pile.

Assessing water dynamics and net percolation rates within engineered cover systems for mine waste rock piles: A long-term field monitoring study

Mine waste rock piles (WRPs) typically contain trace sulfidic minerals that can react with the atmosphere and produce toxic acid mine drainage (AMD) leachate. Water flow through the waste rock affects both the chemistry and transport of the leachate, and a common remedial solution is the installation of engineered cover systems over the WRP to control net percolation (NP) into the waste rock. As NP is mainly controlled by meteorological conditions and the hydrological properties of cover materials, the water balance (WB) method can be employed to investigate NP and water dynamics within cover systems. However, studies on comprehensive WBs at full-scale WRPs have been limited, and most NP studies have relied on controlled, small-scale laboratory and field tests. This unique study contains the long-term field monitoring data at multiple WRPs needed to comprehensively assess NP rates within cover systems. Field monitoring data with high temporal resolution (hourly) was collected from 2012 to 2018 at four covered WRPs located within the Sydney Coalfield (Nova Scotia, Canada), consisting of one simple soil cover and three multi-layer covers lined with the same geomembrane but differing drainage layer materials. Each WB component – precipitation (PPT), evapotranspiration (ET), water/snow storage, surface runoff, and interflow – was determined, with the residual inferred to be NP into the waste rock. The simple soil cover was not very effective, only reducing NP from the pre-cover 34% PPT to 30% PPT. In contrast, the geomembrane-lined cover systems reduced NP to 4% PPT (no drainage layer), 1.6% PPT (thick gravel drainage), and 1.8% PPT (geocomposite drainage net). While ET and water/snow storage changes at all WRPs were similar, the biggest influence on NP was runoff and interflow. This study provides new field information on the performance of cover systems for controlling NP and water dynamics at full-scale WRPs.

Short-Term Predictions of Evaporation Using SoilCover at the Near-Surface of a Mine Waste Pile following Heavy Rainfall Events

Accurate measurements and predictions of near-surface soil drying and evaporation following heavy rainfall events are often needed for research in agriculture and hydrology. However, such measurements and predictions at mine waste pile and tailing settings are limited. The prediction of evaporation at mine waste piles is essential for many problems in geotechnical engineering, including the design of soil cover systems for the long-term closure of hazardous waste sites, and thus mitigates, for example, the generation of acid mine drainage (AMD) and metal leaching. AMD is one of mining’s most serious threats to the environment. This study investigated the short-term (8 days) and medium-term (27 days) drying rates and evaporative fluxes at the surface and near-surface of the Deilmann South waste-rock (DSWR) pile at the Key Lake uranium mine, northern Saskatchewan, using the gravimetric (GV) method and SoilCover (SC) model, respectively, during and following heavy rainfall events for the environment. The SC simulation results showed that during the weather-controlled stage (Stage I) of the first 5-day period of rainfall events, while the surface was wet, the potential evaporation (PE) was equal to the actual evaporation (AE) (i.e., AE/PE = 1). As the surface became drier on Day 6, the cumulative PE began to separate from the cumulative AE and the surface’s drying rate rapidly diverged from those at the deeper depths. This occurrence signaled the onset of the soil profile property-controlled stage (Stage II). As the drying continued, the surface became desiccated and the slow-rate drying stage (Stage III) was established from Day 7 onward. The SC-simulated AE results were compared to those measured using the eddy covariance (EC) method for the same test period at the DSWR pile in a different study. The comparison showed that the two methods yielded similar AE results, with 18% relative errors. The results of this study provided the opportunity to validate the SC model using actual data gathered under field conditions and to ascertain its ability to accurately predict the PE and AE at the surfaces of mine waste piles.

Coupled CFD-DEM simulation and experimental study of particle distribution and accumulation during tailings seepage process

The movement of tailings particles in waste rock systems under different flow rates was studied using experimental and numerical methods, aiming to provide theoretical guidance for preventing particle infiltration. The research results established a calculation relationship between pressure drop, porosity, and waste rock thickness. They also revealed the self-similarity of blockage accumulation within the waste rock. The overall study indicates that smaller particles can pass through the waste rock, but larger particles face greater difficulties. It becomes highly challenging for particles to pass through when they exceed the pore spaces between the largest waste rock particles. The distribution pattern of blockage decreases gradually from the upper part to the lower part of the waste rock pile, with proportions of blockages at different depths being 35.2%, 22.7%, 15.5%, 15%, and 11.6%. The study also examined the cumulative distribution of tailings particles passing through the waste rock under varying flow velocities (0.2 m/s, 0.3 m/s), showing that the quantity of tailings particles passing through the waste rock at 0.3 m/s is approximately 1.15 times that at 0.2 m/s. Additionally, the effectiveness of using geotextile for sealing was investigated, providing theoretical support for determining the application of waste rock particle size, thickness, and geotextile in sealing tailings particles. Moreover, understanding the self-similarity and velocity variation patterns of particles helps in selecting suitable waste rock characteristics.

Geological and Geomechanical Characterization of Phosphate Mine Waste Rock in View of Their Potential Civil Applications: A Case Study of the Benguerir Mine Site, Morocco

Sedimentary phosphate extraction in open-pit operations generates large volumes of waste rock (WR), which are mainly overburdens and interburdens. Traditionally, the WR is mixed and stored on the surface in waste rock piles (WRPs). This paper presents a case study of the Benguerir mine site in Morocco. It investigates the potential valorization of each WR lithology based on the geological and geomechanical properties to reduce their environmental footprint and create added value to “waste.” The WR samples (soils and rocks) were collected from drill cores and mining trenches in the Benguerir mine. The geological characterization results using petrographic descriptions indicate the presence of nine phosphate layers and, in addition to the overburdens, eight interburdens. Four types of WR are identified: carbonate, siliceous, marly clay, and phosphate. The geomechanical characterization of soil-like samples showed an average plasticity index (PI) of 50% according to the methylene blue value (MBV) of 7.1, classifying them in the A3–A4 categories as plastic and clayey marl soils. The hard rock samples have excellent mechanical properties in terms of their uniaxial compressive strength (UCS), Los Angeles abrasion value (LA), and micro-Deval value (MD). The average compressive strength is 104 MPa for the flint, 35 MPa for the phosphate flint, 32 MPa for the silexite, 26 MPa for the limestone, 11 MPa for the indurated phosphate, and 8 MPa for the marly limestone. Based on the obtained results, these WRs can be considered as an excellent alternative secondary raw material for use in civil engineering applications, ceramics, and cement industries.

Geochemical and mineralogical aspects of acid mine drainage associated with 100 years of coal mining in the arctic, Svalbard (78°N)

Acid mine drainage (AMD) is a pressing issue due to increasing mining activities in arctic climate zones. Over 100 years of coal mining in Svalbard presents an ideal study case for the development of AMD in arctic regions.The mined coal (low liptinite type oil prone coal) has less than 1.1 wt% sulphur with micro inclusions of pyrite but the contacting silt and sandstones contain pyrite nodules of centimeter size. These forms of pyrite are left to oxidize on multiple large waste rock piles. Simple accounting of the acid producing and neutralizing potential reveals that all studied lithologies are prone to produce acid waters despite a relatively low pyrite content but with an almost absent neutralization potential.During spring and summer, there are small streams draining the waste rock piles with a pH of 2.5 to 3.7, buffered by an iron hydroxide assemblage. The sulphate concentration of the water samples correlates well with the sum of the cations, indicating that pyrite oxidation is the dominant weathering process. There is no correlation between the age of the waste rock piles and the acidity of the effluents and the system might be controlled by the geometry of the waste rock piles combined with the local hydrology.Mass balance calculations for one of the mine sites estimates that AMD will continue for another 150 years. The sole operating mine site to date is likely to face a similar prospect once lime buffering measures seize.

Geochemical Behavior of Lanthanides and Actinides in an Old Uranium Mine, Portugal

New insights about the geochemical behavior of actinides and lanthanides in an old uranium mine are provided for the first time in this work. Fifteen samples (water, soil, and sediments) were collected inside and outside the Quinta do Bispo old mine (Portugal) in order to better understand the lanthanide and actinide behavior in the soil–water system. The chemical and mineralogical composition was obtained via ICP-MS, INAA, and XRD. The water sample from the open pit exhibits a higher U and REE dissolved concentration when compared to the other water samples. A positive Eu anomaly is found in this sample. The soil samples collected inside the mine area, including mine waste rocks and the minesoils surrounding the open pit, show uranium mineral phases, higher U contents, an enrichment of LREE relative to HREE, and a lower Th/U. This heterogeneity may be due to the open pit extraction and ore processes, as well as the percolation and water infiltration through the waste rock piles. Soils from outside the mine area have a similar mineralogical and chemical composition, despite their different geological context, which could be related to the influence of the granitic geological unit during the alluvial unit deposition. The sediments have similar REE patterns, negative Eu anomaly, and a high (La/Yb)N.

Mechanical Characterization of Coarse-Grained Waste Rocks Using Large-Scale Triaxial Tests and Neuroevolution of Augmenting Topologies

Mining operations produce large quantities of waste rocks, which are usually disposed of in waste rock piles, but can also be valorized in mine haul roads. The engineering performance of these haul roads significantly depends on the mechanical characteristics of the materials used for the construction. However, available experimental studies on coarse-grained waste rocks are relatively limited, mainly because of their large grain size and the scarcity of adapted testing equipment. In this study, a series of repeated load and monotonic triaxial tests (specimens 300 mm in diameter and 600 mm in height) were carried out to evaluate the resilient modulus, permanent deformation, and shear strength of coarse-grained waste rocks (up to 60 mm in diameter) with different gradations. Results showed that an increasing in maximum particle size and compaction effort resulted in a larger resilient modulus and shear strength and smaller permanent deformation. The optimal gravel-to-sand ratio to maximize resilient modulus and shear strength was around 5. Permanent strain was relatively constant when the gravel-to-sand ratio was between 1 and 5, but it decreased significantly when the ratio increased to 8. The impact of fines content and water content on the mechanical properties was relatively limited. Also, the MR-θ model and Rahman and Erlingsson model showed good fitting performance for resilient modulus and permanent strain, respectively. Finally, neuroevolution of augmenting topologies (NEAT) was used to develop a machine learning model for predicting the resilient modulus of waste rocks, based on 265 data sets. The model showed reliable accuracy, simple topology, and high generalizability capacity. The findings described in this article should be beneficial for the valorization of waste rocks in pavement engineering.

Influence of competition on root architecture and root anchorage of young hybrid poplar plantations on waste rock slopes

ABSTRACT Root systems are crucial to tree and soil stability in terms of mechanical support, but are rarely considered in revegetation studies. This study aimed at determining the effect of planting density and herbaceous hydroseeding on the root architecture and mechanical resistance to uprooting of planted hybrid poplars on waste rock piles. The study took place at an open pit gold mine in the Canadian boreal zone where a hybrid poplar plantation was established in 2013 on soil-covered waste rock slopes (33%). Four treatments were randomly distributed in three replicated blocks: 4 × 4 m, 2 × 2 m, 1 × 1 m between trees and 2 × 2 m + h, corresponding to trees spaced at 2 × 2 m with hydroseeding. Lateral uprooting tests of four-year-old hybrid poplars were conducted in the direction of the slope. Maximum resistance to the uprooting force was observed in the 2 × 2 m treatment. Root systems were more symmetrical, deep, branched, and had higher root diameters in the 2 × 2 m and 4 × 4 m treatments. In contrast, the treatments with greater intra- or interspecific competition showed shallower, asymmetrical root systems with smaller roots. Therefore, competition significantly reduced tree anchorage.