Engineering

Abstract: Background: The blasting gallery (BG) method extracts thick coal seams in a single lift through floor-level development, long-hole ring blasting, remote load-haul-dump loading, and controlled caving. Its Indian record contains local successes but uncertain and sustained scalability. Methods: A retrospective multi-case synthesis examined seven Indian applications using 75 sources available until August 14, 2026. The evidence was classified as complete-cycle execution (L1), panel success (L2), sustained performance (L3), or cross-coalfield scalability (L4). Five coupled control functions and five interruption pathways were assessed. Results: All seven applications supported L1, and four supported stronger L2 evidence. L3 was limited or localised in four cases, uncertain in one case, and not located in two; L4 was not established. Three interacting pathways were identified: drilling and charging variability impairing fragmentation and remote loading, delayed caving increasing unsupported span and dynamic demand, and leakage-promoting self-heating. This interruption amplified all three. Conclusions: BG evidence demonstrates technical feasibility and selected panel success, but not comparable cross-site scalability. Assessment should prioritise full-cycle availability, retreat momentum, interruption tolerance, verified goaf control and remote resolution of abnormal states. The detailed methods, case matrices, and evidence audit trails are provided in the Supplementary Material.

Abstract: The growing adoption of sensor-based Particle Ore Sorting (POS) across mineral processing operations increases the need for an objective and repeatable method to assess whether and how an ore can be upgraded. Standardised POS testwork methods have recently been proposed but no universally accepted framework yet provides cross-comparable measures of material, classification and mechanical contributions. This review excludes sensor-based Batch Bulk Ore Sorting and Belt Bulk Ore Sorting and structures the POS literature into three analytical categories: Intrinsic Sortability, Sensor Amenability and Sensor Sortability. Intrinsic Sortability is represented by Sorter Feed Heterogeneity (SFH) and describes the theoretical upgrading potential under ideal separation. Sensor Amenability addresses Detection Effectiveness (DE) and Image Processing Effectiveness (IPE), which together determine Classification Effectiveness (CE). Sensor Sortability evaluates the POS process result under dynamic conditions, including CE, material presentation and Mechanical Effectiveness (ME). The review identifies inconsistent terminology and frequent overlap between these categories. The recently defined Single Particle Test (SPT), Bench Scale Test (BST), Cascade Test (CT) and Process Test (PT) clarify which combinations of SFH, CE and ME are assessed but cross-study comparability remains limited by project-lot heterogeneity, sensor configuration and operating conditions. A universal framework must retain clear system boundaries, standardise performance metrics and use Process Tests as the final validation and feasibility stage. Simulation based on SFH and CE data, supported by open reference datasets and cross-laboratory benchmarks, offers a route towards scalable and vendor-independent assessment.

Abstract: With the continuous expansion of the depth and scale of mining, the mined-out area poses a major threat to the safety of mine production, the surrounding environment, and the lives of residents. Because of the potential safety hazards caused by the large-scale collapse of the mined-out area of metal mines, a treatment plan was formulated in combination with the actual geological conditions of the mined-out area under a metal mine in Henan Province. Through the comparative analysis of the treatment scheme, the blasting caving method is preliminarily selected to control the mined-out area. Considering that the roof of the mined-out area of the mine is strong and the area of the mined-out area is large, an optimized blasting caving method—Underground induced caving and roof cutting technique scheme. Considering the influence of geological conditions and surrounding rock, Flac3D was used for numerical simulation calculation, and the design of the Underground induced caving and roof cutting technique scheme and blasting operation was formulated. By canceling the pressure relief skylight project, unnecessary engineering expenditure is avoided, and the investment structure of the project is optimized. Through the on-site blasting practice, the roof of the mined-out area gradually collapses, and the precise damage induction of the roof of the mined-out area is realized. Finally, a stable waste rock overburden is formed, which effectively prevents the occurrence of sudden roof caving and significantly reduces the risk of mine safety production. It provides technical ideas and practical experience for the treatment of mined-out areas under similar geological conditions.

Abstract: Granite-hosted uranium ores commonly exhibit complex mineral assemblages and heterogeneous pore structures, which may restrict lixiviant accessibility and uranium dissolution during acid leaching. In this study, a mixed nonionic surfactant system consisting of OP-10 and Tween 80 was investigated for enhancing uranium recovery from a granite-hosted uranium ore containing approximately 787.5 ppm U. Mineralogical and pore-structure characterization, surface tension measurements, stirring leaching, column leaching, and kinetic analyses were conducted to evaluate the effects of the mixed surfactants on uranium leaching. The ore was composed mainly of quartz and aluminosilicate minerals and exhibited a heterogeneous multiscale pore structure. OP-10 showed a greater ability to reduce surface tension than Tween 80, while the OP-10/Tween 80 mixture at a volume ratio of 3:1 maintained relatively low surface tension under the acidic conditions investigated. In stirring leaching at 30 °C with 20 g·L⁻¹ H₂SO₄, the addition of the mixed surfactants increased uranium recovery after 10 h from approximately 72.4% to 87.8%. In a separate kinetic experiment conducted at 20 °C, the apparent rate constant obtained from the chemical-reaction-controlled model for the mixed-surfactant system was 0.20266 h⁻¹. The comparable fitting quality of the internal-diffusion and chemical-reaction models suggested that both processes contributed to the overall leaching kinetics. In column leaching, the mixed surfactants increased the cumulative uranium recovery after 31 d from approximately 74.0% to 92.6%, while the apparent first-order rate constant increased from 0.0418 to 0.0648 d⁻¹. Shrinking-core-model analysis of the column experiments gave the highest fitting quality for the interfacial chemical-reaction model in both systems, although mass-transfer effects remained appreciable. These results indicate that the OP-10/Tween 80 system can enhance uranium recovery and accelerate the apparent leaching kinetics of heterogeneous granite-hosted uranium ore, providing a potential approach for improving sulfuric acid leaching of low-permeability hard-rock uranium resources.

Abstract: Thick and ultra-thick coal seams contain large resources; however, greater extraction heights amplify strata movement, coal wall instability, support demand, gas and fire hazards, dilution, and interruption risk. This review develops and foregrounds a conceptual six-gate, non-compensatory “study-to-assurance” framework that turns thick-seam method selection, demonstration, replication, and cross-mine transfer into an explicit evidence-to-decision pathway rather than a one-off design event. The framework specifies minimum evidence sets, auditable artifacts, and pass/conditional-hold/stop outcomes at six stages, from resource screening and geotechnical characterization to integrated design, instrumented demonstration, second-panel replication, and transfer to new blocks or mines. To support and bound this architecture, a structured critical review of literature and grey sources from 1950 to 2025 identified 300 records; 190 were screened, 145 full texts were assessed, and 120 sources were included across ten extraction or boundary option systems. Continuous miners have emerged as India’s most scalable mechanized underground system within a bounded cutting envelope, whereas high-reach single-pass longwalls deliver high outputs only within narrow geomechanical and operational windows. Although longwall top coal caving appears to address the residual height problem, it remains undeveloped in India. Historical blasting galleries, multislice, sublevel-caving, hydraulic, and descending-shield experiences are therefore not used as templates to revive but as engineering evidence that shapes the gate thresholds and failure tests. The proposed six-gate framework integrates evidence quality, geomechanical compatibility, coupled hazards, operational continuity, lifecycle economics, responsibility, and energy transition reporting. Its quantitative thresholds are demonstration minima, not statutory limits or design guarantees, and require field validation and mine-specific recalibration to be effective.

Abstract: To address the issues of significant brittleness and susceptibility to catastrophic failure in traditional gangue-based cemented backfill, this study designed and prepared steel fiber and fly ash reinforced gangue backfill (FGB). Through macroscopic mechanical testing and Discrete Element Method (DEM) numerical simulation, the synergistic effects of steel fiber (VSF=0.0~2.0%) and fly ash (ωFA=5~15%) content on the mechanical properties, energy evolution, and failure modes of the FGB were systematically investigated. The results indicate that steel fibers and fly ash significantly improve the mechanical properties and failure modes of the backfill. The steel fiber content exhibits a linear positive correlation with the strength of the backfill, while the fly ash content shows a negative correlation with strength. The incorporation of fly ash enhances energy dissipation, and steel fibers effectively regulate the distribution ratio between elastic energy and dissipated energy. The addition of steel fibers and fly ash caused the crack type in the backfill to shift from a predominantly S-type to a composite S, T, and ST failure mode, and the failure mechanism transformed from a brittle mode controlled by a single dominant crack to a ductile mode characterized by multi-crack propagation. The fibers restructured the three-dimensional stress chain network, altering stress transfer pathways, increasing horizontal contact forces and the density of stress chains, and enabling the gradual transfer of stress from localized failure zones to the entire structure. This study provides a reference for the development of high-toughness, high-performance mine backfill materials.

Abstract: A polymer transport and kinetic adsorption model is developed and applied to assist in the understanding of some recent results in polymer flow though porous media. The coupled equations in dimensionless form show that the system is governed by 3 dimensionless numbers, 2 of which are important, the Adsorption number (N_Ad) and the adsorption Damköhler number (N_Da-A). This leads to a wide range of behaviours in terms of the polymer effluent profiles which are in broad qualitative agreement with experimental observations. The hypothesis is that it is the kinetics of the system (principally N_Da-A) that is strongly controlling the experimental observations. The model also predicts that the way to establish if this is true, is to conduct polymer core flood including “shut-in” stages where flow is stopped, then resumed after some period of time, depending on the kinetic adsorption timescale. Preliminary experiments support this and a following paper will present these experimental results directly simulated using our model.

Abstract: This study investigates the effect of preliminary ultrasonic treatment on the flotation re-covery of copper from aged tailings of copper-porphyry ores. The initial sample was char-acterized by a low copper content of 0.17%, a high proportion of oxidized copper forms of 53.84%, and fine dissemination of copper-bearing minerals, which complicates their re-covery by conventional flotation. Ultrasonic treatment was applied after grinding as a physical method of surface activation. The pulp was treated at a power of 30 W and a fre-quency of 22 kHz, while the treatment duration varied from 0 to 25 min. The effects of ul-trasonic treatment on concentrate yield, copper grade, copper recovery, and enrichment efficiency were evaluated. One-way analysis of variance (ANOVA) was used to assess the statistical significance of the results, and SEM analysis was performed to examine changes in particle surface morphology. The best flotation performance was obtained after 15 min of preliminary ultrasonic treatment. Under these conditions, the copper grade in the con-centrate was 1.79 ± 0.06%, copper recovery was 44.37 ± 0.21%, and enrichment efficiency was 40.06 ± 0.38%. Longer treatment times did not improve the results. SEM observations indicated particle disaggregation and partial removal of slime coatings. The results con-firm that preliminary ultrasonic treatment can improve copper flotation from aged tailings.

Abstract: Poland is the largest hard coal producer in the European Union. Economic decarbonization, undertaken to slow climate change, is reducing demand for fossil fuels. The restructuring of the hard coal mining industry in Poland is adapting the sector to new market, environmental, and social challenges. Currently, the Polish energy sector is not prepared to phase out the combustion of thermal coal. A transition period is necessary, during which the Polish hard coal mining industry must provide sufficient coal to stabilize the power grid through coal-fired power plants. Coal extraction occurs in extraction excavations, but to enable their operation, mining companies must conduct a certain amount of preparatory roadway excavations. The article analyzes the changes occurring in the basic technical parameters of excavated preparatory excavations and the difficulties affecting the length and number of excavated preparatory roadway excavations. Selected reasons for the temporary suspension of excavated preparatory roadway excavations are also analyzed. An attempt is made to identify the most important causes of these limitations and proposes recommendations. The obtained results of the statistical review of difficulties in preparatory exploitation will be used to present a picture of the current condition of the sector and to forecast possible directions of transformation of the hard coal mining sector in Poland and can potentially be used in other countries conducting similar decarbonization processes.

Abstract: For nearly a century, flotation kinetics has relied on deterministic first-order rate equations treating the cell as a homogeneous reactor, a paradigm that inherently fails for heterogeneous ores, especially coal, whose organic macerals, porosity, and oxidation susceptibility defy a single rate constant. Breaking from chronological cataloguing, this review proposes a three-dimensional taxonomy based on physical scale, inherent material heterogeneity, and epistemic certainty. We demonstrate that critical industrial prediction failures arise from structural mismatches between model physics and particle surface chemistry, notably time-dependent oxidation deactivation and selective maceral recovery. Six fundamental failure modes are identified, from neglected time-dependence of rate constants to the absence of a thermodynamic deactivation term, corroborated by experimental evidence from coal and base-metal flotation. Advanced microfluidic, automated mineralogical, surface-sensitive spectromicroscopic, CFD-DEM, and physics-informed machine learning tools are dismantling the black box of the flotation rate constant “k”. We introduce the Distributed Reactive Surface Kinetics (DRSK) framework, which embeds particle-scale heterogeneity into a population balance via an adaptive surface-sensitive selection function and treats kinetic uncertainty through stochastic differential equations. A comprehensive comparison table facilitates the transition from conventional models to the DRSK paradigm. We conclude with a roadmap for flotation kinetics 4.0, where digital twins, real-time froth analytics, and self-calibrating hybrid models transform this empirical discipline into a truly predictive engineering science. The framework is elaborated for coal and conventional minerals, underscoring why coal demands its own dedicated kinetic theory and how these lessons can revolutionize the processing of increasingly complex, low-grade ores and secondary resources.

Abstract: Wellbore attitude and trajectory are critical parameters for complex oil and gas drilling and geosteering. As global energy exploration extends to deep earth, deep water, and unconventional resources, higher demands are imposed on downhole navigation accuracy and real-time performance. This paper reviews the development status and future trends of wellbore attitude and trajectory measurement technologies. Attitude measurement mechanisms based on magnetometers and gyroscopes are comparatively analyzed, along with their respective research focuses. Recent advances in magnetic interference compensation and accuracy enhancement for magnetometer-based schemes are summarized. Differences in attitude determination algorithms between reduced and full gyroscopes configurations are compared, and the common issue of performance degradation in near-vertical sections due to reduced accelerometer SNR is examined via numerical simulation. For trajectory measurement, traditional discrete reconstruction methods and their station-interval-induced accuracy limitations are evaluated, highlighting the urgent need for a transition from static discrete to dynamic continuous measurement. Strapdown inertial navigation based real-time estimation methods are discussed, with error propagation characteristics analyzed. Kinematic constraints such as depth increments and zero-velocity updates are identified as effective means to mitigate inertial error divergence. Finally, future prospects are outlined, emphasizing that an integrated “underground positioning system” leveraging AI, quantum sensing, and multi-sensor fusion will be key to enabling intelligent drilling measurement and control.

Abstract: Elevated salinity can significantly affect the rheological behavior, thickening time, and early strength development of API Class G cement slurries. This study experimentally investigated the effect of NaCl additions of 0, 4, and 8 wt.% BWOC on cement slurries with densities of 1.5 and 1.9 g/cm³ at temperatures of 25, 50, 75, and 90 °C. Rheological parameters, the time required to reach a consistency of 30 Bc under atmospheric pressure, the times required to attain selected compressive strength thresholds, and the ultrasonic cement analyzer (UCA)-estimated compressive strength after 12 and 24 h were evaluated.The results demonstrated that the effect of NaCl was not pro-portional to its concentration but depended on slurry density, temperature, and the property being evaluated. NaCl generally reduced plastic viscosity and yield stress, whereas gel strength exhibited a non-uniform response with a pronounced dependence on temperature. Its influence on thickening time and early strength development was likewise non-monotonic. Under certain test conditions, higher NaCl concentrations accelerated the attainment of the initial strength thresholds; however, they did not consistently increase the UCA-estimated compressive strength after 24 h or improve all evaluated operational properties. Among the investigated salinity levels, the slurry containing 4 wt.% NaCl exhibited the most balanced overall performance in terms of rheological behavior, thickening time, and early mechanical properties across both slurry densities and the investigated temperature range. Nevertheless, this concentration did not provide the best performance for every individual parameter or under all test conditions. The findings provide a basis for the further op-timization of cement slurry formulations intended for use in high-salinity environments. Since the experimental program did not include independent repetitions, the observed differences should be interpreted as descriptive trends that require statistical validation in future studies.

Abstract: Extended-reach and highly deviated wells often adopt a double build-up trajectory. This profile contains two curvature transition zones: the build-to-tangent transition and the tangent-to-build transition. The annular flow undergoes severe restructuring in these zones. They are potential bottlenecks for cuttings transport. This work uses a 215.9 mm wellbore with 127.0 mm drill pipe as the reference case. Analytical expressions for the cuttings accumulation ratio in both transition zones are developed based on the three-layer transport model. For power-law drilling fluids, a generalized Reynolds number is introduced to reformulate the Dean number. A dynamic disturbance coefficient is constructed from the along-hole Dean number gradient. This coefficient captures the contrasting behavior of secondary flow. In one transition zone, the secondary flow decays. In the other, it suddenly emerges. The results show that when the two curvature radii are equal, the accumulation ratio in the tangent-to-build transition is roughly 1.15 times that in the build-to-tangent transition. Reducing the curvature radius from 250 m to 100 m increases the accumulation ratio by about 2.5 times. The ratio rises with inclination angle. The disturbance coefficient increases monotonically with build rate. After accounting for drill pipe eccentricity, the recommended minimum curvature radii are 160 m for the first build section and 220 m for the second. These findings offer a theoretical basis for trajectory design in sections with abrupt curvature changes.

Abstract: Designing interlevel pillars for deep, structurally complex vein deposits requires balancing rock mass stability against ore recovery. This study evaluates the geomechanical response of the Kenzhem area of the Akbakay gold deposit using a three-dimensional finite-element model that reproduces the lithological structure, irregular ore-body geometry, underground workings, and mined-out stopes. Four extraction scenarios were analyzed: complete extraction without pillars and mining with 10, 15, and 20 m inter-stope pillars. Stability was assessed using maximum total displacement, the extent and connectivity of yielded zones predicted by the generalized Hoek–Brown criterion, and numerical convergence. Pillarless extraction produced displacements of 2.6–3.0 m, a continuous yielded zone extending toward the surface, and loss of numerical convergence. A 10 m pillar reduced displacements to 0.50–0.66 m but did not provide a stable equilibrium state. Increasing the pillar thickness to 15 m reduced the maximum displacement to approximately 0.08 m, localized the yielded zones near excavation boundaries, and ensured convergence. A 20 m pillar produced only a minor additional reduction to 0.065–0.070 m without materially changing the failure pattern. Therefore, a 15 m inter-stope pillar provides the most rational balance between geomechanical safety and ore recovery under the investigated conditions.

Abstract: The transition from open pit to underground mining is becoming increasingly important as near-surface ore is depleted and operations seek to extend mine life. However, its environmental effects are still often discussed in separate technical areas rather than as one connected planning problem. This review examines the environmental impacts reported during the transition stage and proposes an integrated framework to support mine planning. Following a PRISMA-guided approach, peer-reviewed studies published between 2010 and 2026 were screened, and 68 studies were included in the final review. The findings show that the transition does not simply reduce environmental impacts; instead, it redistributes them across water, ground stability, air quality, energy use, land disturbance, and nearby communities. The main reported concerns include groundwater rebound and inflow, slope instability and subsidence, underground dust exposure, and higher ventilation-related energy demand, while some surface impacts, such as land clearing, dust, and blasting noise, may decline as open pit activity decreases. Overall, the transition should be treated as a distinct planning stage, and the proposed framework helps mine planners address these impacts together rather than separately.

Abstract: Mine drainage containing manganese (Mn) and zinc (Zn) poses a major environmental challenge. In Japan, Mn-rich mine drainage frequently exceeds the discharge standards of 10 mg/L for Mn and 2 mg/L for Zn. This study evaluated laboratory-scale continuous-flow constructed wetlands (CWs) for the treatment of both synthetic and actual mine drainage without external carbon addition. Two limestone-filled CWs (2 L), one planted with Phragmites australis and the other unplanted, were operated at hydraulic retention times of 1–2 d. The influent mine drainage contained approximately 66 mg/L Mn and 10–15 mg/L Zn together with Fe, Cu, Cd, and Pb. During 170 days of continuous operation, the planted CW consistently achieved lower effluent Mn and Zn concentrations than the unplanted CW under both synthetic and actual mine drainage conditions. Effluent Mn concentrations in the planted CW ranged from 5.5 to 20.0 mg/L, compared with 46.1–54.2 mg/L in the unplanted CW. Likewise, effluent Zn concentrations ranged from 0.21 to 3.0 mg/L in the planted CW and from 2.4 to 10.1 mg/L in the unplanted CW. The superior performance of the planted CW was associated with enhanced limestone dissolution, elevated pH, and favorable rhizosphere conditions that likely promoted biologically mediated Mn(II) oxidation and the formation of Mn oxides, while Mn carbonate precipitation may also have contributed to Mn removal. These findings demonstrate that limestone-based planted CWs can effectively treat Mn-rich mine drainage without external carbon addition and highlight their potential as sustainable, low-energy passive treatment systems for the long-term management of abandoned mine drainage.

Abstract: This study investigates the direct and indirect effects of mining activity on the Human Development Index (HDI) at the district level in Peru during 2009–2024. The research addresses whether mining activity contributes to local human development and whether its benefits extend beyond mining-producing districts through spatial spillover effects. Using a balanced panel dataset of 13,118 observations from 1,874 Peruvian districts, a spatial random-effects model based on a Spatial Durbin Model (SDM) specification is estimated. The empirical model incorporates the effects of mining activity, the State Density Index (IDE), and education, while controlling for spatial dependence among neighboring districts. The results provide strong evidence that mining activity has both local and spatial effects on human development. The direct effect of mining activity is positive and statistically significant (0.0231; p< 0.001)), indicating that districts with mining activity tend to achieve higher HDI levels. Furthermore, the indirect spatial effect is also positive and significant (0.0428; p=0.001), demonstrating that mining generates benefits that extend to neighboring districts through regional economic linkages, infrastructure development, labor markets, and public investment channels. The model also reveals a strong spatial dependence of human development (0.811; p< 0.001), confirming that district-level development outcomes are geographically interconnected. Additionally, state presence and education emerge as important determinants of human development. The State Density Index has a positive and significant effect on HDI (0.0418; p< 0.001)), while education presents the largest estimated effect ((0.2429; p< 0.001)). These findings indicate that mining activity contributes to human development, but its impact depends on the institutional capacity of the State and investments in human capital. The study concludes that mining should be understood as a territorial development factor whose benefits can spread beyond administrative boundaries, highlighting the importance of spatially coordinated public policies to transform natural resource revenues into sustainable improvements in human well-being.

Abstract: Flocculation-sedimentation is a widely used solid-liquid separation process in mineral processing and wastewater treatment, yet its optimization remains challenging due to nonlinear interactions among reagents, solids, and operating conditions. This study presents a statistically rigorous multi-response optimization framework combining HuberT robust regression, canonical analysis, and the Derringer desirability function, and demonstrates its application to coal slurry water treatment as a case study. Coal slurry concentration, polyacrylamide (PAM) dosage, and CaCl₂ concentration were used as factors, with supernatant turbidity and initial settling velocity as responses. A central composite design (20 runs) was employed, and second-order models were fitted via HuberT M-estimation to mitigate the influence of potential outliers. Both the ln-transformed turbidity model (R² = 0.9887) and settling velocity model (R² = 0.9908) showed high significance and predictive capability. Canonical analysis confirmed that the turbidity response surface exhibits a true minimum within the design space, while the settling velocity surface has a saddle-point structure. HuberT weight diagnostics identified no downweighted runs for turbidity and two mildly influential runs for settling velocity, confirming overall data consistency. Multi-response optimization via the Derringer desirability function yielded a combined optimum (coal slurry 25.27 g/L, PAM 5.19 mg/L, CaCl₂ 2.07 g/L; desirability D = 0.8981) with predicted turbidity of 29.21 NTU and settling velocity of 13.26 mm/s. The proposed framework is generalizable to other flocculation-sedimentation systems requiring simultaneous improvement of multiple, often conflicting, process responses.

Abstract: Poorly governed geoscience databases introduce subtle but systematic biases that propagate through mineral resource estimation workflows, distorting grade continuity and resource classification. While the importance of data quality in mining is widely acknowledged, quantitative demonstrations of how specific data-management decisions translate into downstream technical and economic impacts remain limited. This study addresses that gap through three case studies derived from real-world industry examples. The first case study quantifies operator-dependent data extraction bias by comparing two independently generated datasets sourced from the same database on the same day. Despite nominal equivalence, the datasets differed materially in record counts and grade distributions, producing only negligible global volumetric differences (~0.1%) but up to ~5% local geometric variability and a 19.5% difference in estimated copper grade, resulting in a ~36% divergence in projected revenue. The second case study evaluates analytical uncertainty near detection limits using duplicate assay pairs, demonstrating that relative error increases markedly at low concentrations and that this behavior reflects inherent analytical limitations rather than laboratory non-compliance. The third case study examines the common practice of assigning detection-limit placeholder values to un-assayed intervals, showing that such substitutions can artificially generate ore in barren domains, whereas retaining null values and applying assignments during post-processing yields geologically and statistically coherent results. Collectively, these case studies demonstrate that hidden data biases can exert a stronger influence on resource outcomes than estimation methodology alone. The results highlight the need for standardized extraction workflows, explicit treatment of low-grade uncertainty, and validation practices that extend beyond global reconciliation metrics. Robust data governance and transparent, reproducible workflows are essential to reducing compounding uncertainty and improving confidence in mineral resource models. All datasets have been anonymized, scaled, or modified to prevent identification of any specific project, company, or operation. No confidential or propriety datasets are disclosed.

Abstract: Downhole vibrations are a primary cause of premature wear and failure of rock-cutting elements (RCEs) during well drilling, yet existing models often treat axial and torsional vibrations separately and neglect the feedback between wear flat growth and dynamic loading. This study develops an integrated finite element model that couples all three vibration modes (axial, torsional, lateral) with the evolution of the wear flat, friction, and temperature. The model is validated against laboratory experiments on a drilling stand using MEMS accelerometers. Two types of tungsten-cobalt (WC-Co) inserts were compared: uncoated and coated with a 3–5 nm titanium nitride (TiN) layer. Thirty tests were performed on granite and sandstone under varying weight on bit (WOB = 1.0–2.2 kN single-RCE) and rotation speed (RPM = 80–120). The TiN coating reduced axial RMS acceleration by 18%, torsional amplitude by 24%, and wear rate by 27% (from 0.154 to 0.112 mm/h) in granite. Frequency spectra revealed a resonant torsional peak at 55 Hz when RPM exceeded 120, with torque fluctuations increasing by 240%. A safe operating chart was constructed, defining green (WOB 1.0–1.6 kN, RPM 80–110), yellow, and red zones. The recommended regime (WOB = 1.7 kN, RPM = 105) gives 94% of maximum rate of penetration while reducing predicted wear by 35% compared to the red zone. The model prediction errors are 8–12% for axial and 10–15% for torsional vibrations. This work demonstrates that nanoscale TiN coatings and low-cost MEMS sensors can substantially improve vibration control and wear resistance, providing practical operating charts for drilling optimization.