This study investigates tunnel stability within sedimentary rock masses characterized by multiple joint sets and challenging geological conditions. The behavior of stratified rock masses around an excavation depends on both the intact rock and the combination of dominant and bedding joints. The main objective of this study is to highlight the convergence and deformation in rock masses around horseshoe-shaped tunnels using an integrated methodology that combines field investigations, finite element modeling, and pull-out test results. Statistical analysis confirmed the robustness of the 3D modeling approach for reproducing in situ behavior and creating realistic models of heterogeneous, anisotropic rock masses. The numerical results indicate that the highest displacement ratio is concentrated at the intersection of the bedding and dominant joints with dip angles ranging from 0 degrees to 45 degrees, which should be considered as critical dip angles for mining progress. Indeed, wedge and sliding failure zones developed on the roofs and left rib, respectively. Increasing depth reduced the influence of rock mass quality, particularly for GSIchart values ranging between 35 and 40, resulting in significant convergence around the excavation. The support system emphasizes the effectiveness of systematic bolting in competent rock masses. Moreover, the pull-out tests revealed that the load-bearing capacity of the split-set bolts increased substantially when the bedding approached vertical orientations theta = 90 degrees, and the compressive strength exceeded 39.6 MPa, conditions that promote safer tunneling through vertical stratum orientations. These findings enhance the understanding of tunneling stability mechanisms in stratified rock masses with multiple joint sets under various geological conditions.

In order to limit the production of acid mine drainage, different techniques can be used for mine site rehabilitation. Among of these techniques, one find oxygen barriers such as covers with capillary barrier effects (CCBE). A CCBE is made of different layers, the most important of which is the moisture-retaining layer (MRL). This layer can be made using optimized mixtures of till and sludge produced from AMD treatment using carbonate materials. Indeed, laboratory studies showed that material mix (MM) of a till and sludge at an optimal ratio can achieve the required hydraulic properties for an efficient MRL. To evaluate the performance of three MMs as MRLs, instrumented columns simulating CCBEs placed over sulfide-rich tailings were used. Each column was subjected to wetting-drying cycles where matric suctions were measured. Leaching water was also collected and chemically analyzed at the end of each cycle. Results of these investigations showed that the suctions measured in the MRL were below the air entry value (AEV) for the three tested MM, and the leachate quality did not show production of AMD. According to these results, the MM tested could be used as MRLs in CCBEs. However, it is recommended to test their behavior at a field scale in order to integrate mine site climatic conditions.

Low-saturated hydraulic conductivity covers (LSHCC) or hydraulic barriers are one of the reclamation techniques used to control the acid mine drainage generation (AMD). These covers are intended to limit the infiltration of water into reactive tailings. Compacted clays are among the materials used as LSHCC. The performance of clay-based hydraulic barriers can be affected by their geotechnical and hydrogeological properties. Freeze-thaw cycles can increase their saturated hydraulic conductivity (ksat). However, these effects can be minimized by adding amendments. To evaluate the performance of these clay-based covers, four field experimental cells were built. The first one simulates a cover composed entirely of clay, the second a clay-silt mixture, the third a clay-sand mixture and the last two layers of clay with an intermediate layer of silt. Each cell has been equipped with a monitoring station with continuous measurements of volumetric water content, suction and temperature. In situ permeability tests were also conducted to assess field hydraulic conductivity. Numerical simulations were also conducted to evaluate the water balance for each cover scenario. The laboratory results showed low-saturated hydraulic conductivity values meeting waterproofing criteria, whereas field measurements and calibrated model values were consistently higher and exceeded the waterproofing criteria. Infiltration monitoring indicated that 15 to 40% of precipitation infiltrated the covers, with possible overestimation due to preferential flow. Discrepancies between laboratory and field-saturated hydraulic conductivity values were mainly attributed to inadequate compaction, unfavorable weather conditions, and excessive water content during cover installation. Variations in saturated hydraulic conductivity over time were generally within statistical variability, although differences among cells and responses to wetting-drying cycles highlight the influence of construction conditions on field performance.

Quantifying time-dependent rock mass degradation is critical for assessing long-term slope stability during open-pit mine closure. This study evaluates the geotechnical evolution of Paleoproterozoic arenites and argillites in the semi-arid Essakane Main Zone (Burkina Faso) over a 0–9-year atmospheric exposure period. Field characterization across 32 sampling stations included density measurements, point load testing (Is(50)), determination of the Geological Strength Index (GSI), and petrographic analysis. The results demonstrate a time-dependent reduction in physico-mechanical properties, modeled with a high correlation (R2 = 0.80–0.99). While density exhibited minor reductions, structural degradation was pronounced; the GSI decreased by 10 points for both lithologies, and Is(50) dropped significantly, particularly in argillites (4.1 to 2.3 MPa) relative to arenites (4.0 to 3.6 MPa). Petrographic evidence indicates negligible chemical weathering and mineral neoformation. Consequently, the degradation was attributed primarily to physical processes, specifically microcracking and discontinuity deterioration driven by thermal cycling and phyllosilicate sensitivity in argillites. These empirical relationships provide essential quantitative input for numerical slope stability modeling in semi-arid mine closure scenarios.

Natural lateral particle segregation commonly occurs during the hydraulic deposition of slurry and thickened tailings in surface tailings storage facilities (TSFs), producing spatial heterogeneity in physical, hydrogeotechnical, and mineralogical properties, as well as in the water table. In sulfide-rich tailings, such heterogeneity complicates the design of reclamation cover systems, which are themselves affected by it. This study investigates the impact of physical and rheological properties of hard-rock mine tailings slurries on their segregation under hydrodynamic conditions. It proposes a multiparametric equation for the segregation index (SI) based on Buckingham's pi theorem. For this purpose, six flume experiments were conducted using tailings with initial solid mass concentrations of 63%, 66%, and 69% at slopes of 0.5% and 1%. Results revealed strong exponential correlations (R-2 > 0.95) between SI and tailings' physical properties (solid concentration, bulk density) as well as rheological parameters (Herschel-Bulkley yield stress and flow index, Cross infinite dynamic viscosity). The SI equation was developed using MATLAB R2025b nonlinear least-squares optimization with a trust-region reflective algorithm. Using an SI threshold of 0.05 to define non-segregating behavior, the proposed model can predict segregation tendencies as a function of tailings properties and slope conditions. Further laboratory and field investigations are needed to validate and generalize the criterion.

The presence of free muscovite in tailings can negatively affect the mechanical strength and rheological properties of cemented paste backfill, as has been observed for several cementitious materials. The aim of this study is to evaluate the influence of free muscovite content in tailings on the consistency and rheology of cemented paste backfill. For this purpose, cemented paste backfill mixtures were prepared from two different tailings. The mixtures were prepared at solids contents between 70% and 74% and with the addition of 5% GU (general use Portland cement)/slag binder. In addition, the influence of muscovite was studied by varying the muscovite content of the tailings from about 14% to 25%. Abrams cone slump tests and rheological analyses were carried out for each recipe. The results show a decrease in slump height and an increase in yield stress, Herschel–Bulkley flow index, and infinite shear rate Cross viscosity with increasing muscovite content for a given solids content. Therefore, water should be added to maintain the required flowability of cemented paste backfill, which increases the water/binder ratio and may affect the mechanical strength. A method is presented for determining the amount of binder to be incorporated to maintain the water/binder ratio of the original cemented paste backfill recipe.

Several techniques are commonly employed to treat AMD, including raising the pH by adding alkaline materials, precipitating dissolved metals by introducing sulfide reagents, and using biological processes. Superabsorbent polymers (SAPs), known for their high water absorption and retention capacity, offer a promising alternative for treating mining effluents due to their unique properties. In this study, synthetic metal solutions were used to assess the effectiveness of SAPs in effluent treatment using artificial solution. Investigation results demonstrate the effectiveness of SAPs in sequestering metal ions. The sequestration capacity of metals is influenced by pH, the ionic radius of the element, and the availability of binding sites in the SAPs. To better understand the relationship between absorption rates, metal and metalloid sequestration and these chemical factors, equations have been proposed that consider both ionic radii and the concentrations of the elements analyzed. These equations provide highly accurate predictions of the metallic ion absorption rate.

The performance of the cover system, used in the reclamation of a mine site, is primarily assessed through hydraulic properties, including volumetric water content, suction, and saturated hydraulic conductivity ( k sat ). However, these properties may be influenced by factors such as soil mineralization (which refers to the process by which organic materials are converted into inorganic substances through natural processes), temperature (by the viscosity of water and the activity of microorganisms in the soil), and organic matter content (OMC), which complicate the accurate assessment of cover system performance. To better understand the impact of OMC on hydraulic properties, this study was initiated with two objectives: (i) evaluating the effect of OMC on the water retention curve (WRC) and k sat of a sandy material amended with peat and (ii) proposing equations to predict the WRC of sand amended with organic matter using the Fredlund and Xing model. This was accomplished through laboratory tests that determined the WRC and k sat of sand and sand amended with varying concentrations of peat (0%, 1%, 3%, 5%, 7.5%, 10%, 12.5%, and 15%). The investigation results indicate the air entry value (the suction at which the material begins to desaturate) evaluated using the sand mixture WRC did not show any notable variation. The k sat of the sand mixtures decreases with increasing peat concentration. In terms of prediction, the results obtained for the six mixtures tested in the laboratory showed an excellent agreement between predicted and experimental values, demonstrating the high accuracy with which the WRC s were predicted.

As a secondary support material, cemented paste backfill (CPB) is widely used in underground mining operations. CPB is a mixture of mine tailings, water, and a small amount of a binder agent. In the Abitibi region of Canada, the standard binder typically contains 20 % general-use Portland cement (GU) and 80 % ground granulated blast-furnace slag (GGBFS). This binder combination reliably ensures that CPB meets the required unconfined compressive strength (UCS) targets. However, the rising cost of binders, the environmental impact of GU, and the limited availability of GGBFS have created a need for alternative materials. Efforts are underway to replace GU and identify substitutes for GGBFS in CPB formulations. This study explores the potential of ground granulated ladle furnace slag (GGLFS) as a partial replacement for both GU and GGBFS in CPB. Raw ladle furnace slag (LFS) was first quenched under pressurized water and ground to produce GGLFS. The GGLFS was then incorporated into various CPB formulations and pure cement pastes for testing. The results demonstrate that GGLFS enhances the reactivity of GU/GGBFS blends in CPB, achieving satisfactory UCS after 7 and 28 days of curing. Additionally, GGLFS accelerates the initial reaction and modifies the hydration products in GU/GGBFS formulations. These findings highlight the promising potential of GGLFS as a supplementary cementitious material in CPB applications.

Many countries employ mining and ore processing techniques to concentrate and extract precious natural resources. However, the slow leaching of numerous dissolved elements and compounds from large quantities of waste rock and mine tailings can significantly threaten groundwater quality in the affected region. When exposed to oxygen and water, sulfide minerals in mine tailing oxidize, potentially forming acid mine drainage (AMD). Various reclamation techniques can inhibit AMD generation, including monolayer cover combined with an elevated water table (EWT), hydraulic barrier, and cover with capillary barrier effect (CCBE). Selecting the most suitable technique requires consideration of site-specific hydrogeological conditions (e.g., water table depth) and available cover materials. Numerical modeling tools such as PHT3D and MT3D can help identify optimal reclamation methods during preliminary planning stages. The 119-hectare Quémont 2 mine site near Rouyn-Noranda city will undergo reclamation following the closure of its tailings storage facilities (TSF). A three-dimensional numerical groundwater and solute-transport model were constructed and calibrated to simulate the site’s hydrogeological behavior post-closure, enabling selection of the most effective AMD control technique. Subsequently, a three-dimensional multicomponent reactive transport model incorporating various cover designs was developed, with simulations considering climate change impacts. The PHT3D model code, which integrates the PHREEQC geochemical model with the MT3D three-dimensional transport simulator, was employed to evaluate cover performance on the Quémont 2 TSF. Four reclamation configurations were tested: Cell #1 (80 cm single-layer clay cover), Cell #2 (60 cm single-layer clay-sand cover), Cell #3 (60 cm single-layer clay-silt cover), and Cell #4 (120 cm multilayer clay-sand-clay sequence). Simulations were conducted under various climate change scenarios (Representative Concentration Pathways—RCPs 2.6, 4.5, and 8.5). This paper describes the numerical model, cover materials, and modeling results both with and without covers. Results indicate that Cells #1 and #4, completely reduced sulfate in groundwater, suggesting these configurations would provide the most effective reclamation solutions for the Quémont 2 mine site.

Directed energy deposition (DED), a form of additive manufacturing (AM), is gaining traction for its ability to produce complex metal parts with precise geometries. However, defects like distortion, residual stresses, and porosity can compromise part quality, leading to rejection. This research addresses this challenge by emphasizing the importance of monitoring process parameters (overlayer distance, powder feed rate, and laser path/power/spot size) to achieve desired mechanical properties. To improve DED quality and reliability, a numerical approach is presented and compared with an experimental work. The parametric finite element model and predictive methods are used to quantify and control material behavior, focusing on minimizing residual stresses and distortions. Numerical simulations using the Abaqus software 2022 are validated against experimental results to predict distortion and residual stresses. A coupled thermomechanical analysis model is employed to understand the impact of thermal distribution on the mechanical responses of the parts. Finally, new strategies based on laser scan trajectory and power are proposed to reduce residual stresses and distortions, ultimately enhancing the quality and reliability of DED-manufactured parts.

Ladle furnace slag (LFS), a by-product of steel refining, shows a promising reuse pathway as an alternative additive or substitute for Portland cement due to its high alkalinity and similar chemical composition to clinkers. However, LFS is often stored in large, open surface areas, leading to many environmental issues. To tackle waste management challenges, LFS can be recycled as supplementary cementitious material (SCM) in many cementitious composites. However, LFS contains some mineral phases that hinder its reactivity (dicalcium silicate (γ-C2S)) and pose long-term durability issues in the cured cemented final product (free lime (f-CaO) and free magnesia (f-MgO)). Therefore, LFS needs to be adequately treated to enhance its reactivity and ensure long-term durability in the structures of the cementitious materials. This literature review assesses possible LFS treatments to enhance its suitability for valorization. Traditional reviews are often multidisciplinary and explore all types of iron and steel slags, sometimes including the recycling of LFS in the steel industry. As the reuse of industrial by-products requires a knowledge of their characteristics, this paper focuses first on LFS characterization, then on the obstacles to its use, and finally compiles an exhaustive inventory of previously investigated treatments. The main parameters for treatment evaluation are the mineralogical composition of treated LFS and the unconfined compressive strength (UCS) of the final geo-composite in the short and long term. This review indicates that the treatment of LFS using rapid air/water quenching at the end-of-refining process is most appropriate, allowing a nearly amorphous slag to be obtained, which is therefore suitable for use as a SCM. Moreover, the open-air watering treatment leads to an optimal content of treated LFS. Recycling LFS in this manner can reduce OPC consumption, solve the problem of limited availability of blast furnace slag (GGBFS) by partially replacing this material, conserve natural resources, and reduce the carbon footprint of cementitious material operations.

This paper highlights an issue that has not received much attention which is the use of phosphate waste rock (PWR) in road embankments. This study focuses on the valorization of marly clay and marly limestone lithologies, which are abundant but often unused or undervalued, being simply deposited around mine sites. Investigating the potential use of these materials in road embankments requires a combination of experimentation, stability analysis, and economic evaluation. The materials were collected from mining trenches in the Benguerir mine (Morocco). The samples were subjected to i) chemical and mineralogical characterization; ii) environmental characterization; and iii) geotechnical characterization. The results of the characterization show that the samples are chemically dominated by CaO (12–33 wt%), SiO2 (23–38 wt%), and MgO (7 – 9 wt%); mineralogically, the main phases are quartz, calcite, dolomite, apatite, and clay minerals. The environmental characterization classified the studied materials as non-hazardous waste. In terms of geotechnical characterization, the marly limestone and marly clay belong to the A3 and R33 categories, which means that they can be successfully used as a sustainable alternative material for the embankment. This finding supports their safe utilization. The stability analysis reveals that embankments up to 10 m in height can be constructed with marly clay without significant physical instability risks. Satisfactory safety factors (SF) were found (SF=1.97 for H=5 m and SF=1.54 for H=10 m). For marly limestone, the height limit is less than 10 m (SF=1.74 for H=5 m and SF=1.33 for H=10 m), but it can be increased to 10 m by adding a bench of rock fill with a safety factor of 1.64. Finally, an economic evaluation demonstrates that PWR can be used as embankment materials within a radius of 28 km around the mine site. It appears to be a cost-effective alternative compared to conventional materials.

Phosphate mines produce large quantities of waste rock. These waste rocks are mixed and managed on the surface as large unrestored piles, which makes them difficult to rehabilitate. They primarily comprise carbonates, clays, marls, and cherts (flints). In many cases, the unrestored mine sites, when exposed to normal climatic conditions, could frequently produce toxic environmental pollution, and significant ecological disruptions. This research aims to assess the phosphate waste rock's (PWR) geochemistry and environmental behavior upstream of the extraction process. For this purpose, different core drilling specimens and data were collected from different lithologies and depths in the interlayers of the Benguerir mine to forecast the environmental profile and determine the mobility of the analyzed chemical species. These samples were analyzed for their petrographical, chemical, and mineralogical compositions, static leaching tests, and semi-dynamic test. The mineralogy results showed that the PWR mainly consists of calcite, dolomite, apatite, and quartz, with minor phases such as clay minerals. Chemically, the PWRs are dominated by the following major oxides: CaO and MgO, followed by SiO2 and P2O5. Trace elements can be classified into three groups based on their concentrations: group of Sr, Zn and Cr (> 150 ppm), group of Ba, V, Ni, Zr, Y, U, Cu, Cd, Co (10–150 ppm), and group of trace elements with relatively low concentrations (< 10 ppm): Rb, Pb, As, Mo, Se, Sc, Ga, Nb, Th, Hf, Sb and Cs. Environmentally, the pH of the leachates was neutral to alkaline (6 ± 0.6–9.3) for all the samples, which have a high neutralizing potential (38–991 kg CaCO3/t). The release of major and trace elements in the leaching test remains below international standard limits. Consequently, the leaching test results confirm the non-hazardous nature of the PWR. Therefore, the studied PWR could be considered a natural raw material and can be used in various applications in different sectors, such as civil engineering, cement industry, phosphate recovery, and acid mine drainage treatment through neutralization.

Pipelines play a pivotal role in transporting large volumes of oil and gas within refineries. However, over time, they are susceptible to deterioration, leading to potential failures. Effective monitoring is imperative to maintain their optimal performance and safety. This research introduces a machine learning (ML) approach to pinpoint failure sources in oil and gas pipelines. Analysing an industrial dataset, we compared six ML models to predict failures in refinery pipelines. Leakage sources are predicted based on three operational parameters: transported fluid, temperature, and pressure. The models are evaluated and compared in terms of precision, recall, F1-score, accuracy, and the ROC-AUC. Remarkably, the XGBoost classifier exhibited a 99.7% accuracy, outperforming other algorithms in predicting the failure source. Emphasizing the value of Industry 4.0 solutions, this study underscores the potential of advanced ML in enhancing pipeline monitoring. Such predictions empower operators to pre-empt failures, reinforcing industry safety and sustainability.