Search Results (83)

For the metal deposits exploited by the open-stope subsequent filling method, the goaf roof is prone to large-scale caving when the stope ore is not fully mined. This further results in the accumulation of a thick layer of waste rock on the goaf floor due to the caving of surrounding rocks. In the treatment using cemented filling, it is essential to ensure that the filling slurry fully permeates into the granular pile, and that the granular-cemented backfill possesses sufficient strength to guarantee the production safety of adjacent stopes. Taking the caving goaf of Shirengou Iron Mine as the engineering background, the effects of slurry concentration, cement–tailing ratio, height of the granular pile, and particle size of the granular rock on seepage laws are investigated by means of a self-developed simplified filling test device. The filling slurry concentration that meets the on-site requirements for fluidity and permeability is thereby determined. Meanwhile, by prefabricating the granular-cemented backfill, the characteristics of the self-supporting capacity and strength of the backfill are studied, considering factors such as different slurry concentrations, cement–tailing ratios, and curing ages. The results indicate that the cement–tailing ratio exerts the least influence on the seepage law, yet it has the most significant impact on the strength of the granular-cemented backfill. When the cement–tailing ratio of the filling slurry ranges from 1:8 to 1:4 with a concentration of 68%, the filling slurry can completely seep and cement the waste rock layer. At this point, the granular-cemented backfill strength can reach 1~2 MPa, which satisfies the seepage and cementation requirements for the waste rock inside the caving goaf of Shirengou Iron Mine. Full article

This study tackles the critical challenges of stress evolution and pillar optimization in underground potash mining, with a focus on the 351-stope of Kaiyuan Mining in Laos. Integrating theoretical calculations, large-scale 3D numerical modeling, and an AHP-Fuzzy comprehensive evaluation, we systematically analyze the complex mechanical behaviors of the mining environment. Applying key stratum theory, we reveal the unique mechanism by which overlying hard rock bends without fracturing in carnallite layers under room-and-pillar conditions. Comparative numerical simulations of four pillar-width schemes—involving 8 m rooms with 10 m, 8 m, 6 m, and 4 m pillars—show that reducing pillar width markedly increases vertical stress, triggers exponential roof subsidence, and expands pillar failure zones. Using an AHP-Fuzzy method that incorporates safety, technical, and economic factors, the Simultaneous Backfilling with 8 m Mining and 6 m Pillar Retention is identified as the optimal scheme. This configuration demonstrates superior stability, exhibiting an average pillar stress of 9.3 MPa and only limited plastic failure zones at pillar ends. These findings offer a robust scientific and technical foundation for enhancing the safety, efficiency, and sustainability of underground potash mining operations. Full article

Cemented paste backfill (CPB) is widely used in mining operations to enhance underground stope stability, production, and safety. Accurately predicting paste flow behaviours in backfill reticulation circuits is crucial for efficient delivery control and asset longevity. However, the predictions remain challenging due to complex rheology and flow-induced particle heterogeneities of CPB. This study develops a computational fluid dynamics (CFD)-based analysis framework to investigate flow dynamics of the CPB and the wear conditions of the pipes, considering slip layer and shear-induced particle migration. Experimental loop tests are conducted to measure pressure drops of CPB at different velocities, providing data for validating the developed CFD model. Simulation results are in good agreement with the measured pressure drops and wear rates of the internal pipeline wall. Furthermore, comparisons with existing models indicate that the developed model provides more accurate predictions. Microscopical analyses reveal that shear-induced particle migration leads to the formation of a distinct plug flow region, with particles accumulating near the unyielded boundary. Meanwhile, a low particle concentration near the pipe wall reduces local viscosity and pressure drop. Parametric studies reveal that increased flow velocity and reduced pipe diameter significantly elevate both pressure drop and wear rate, while higher solid concentrations induce nonlinear rheological effects. Full article

This study investigates the settlement characteristics of overlying strata in backfilled stopes at the Sanshandao Gold Mine, focusing on the compaction behavior of backfill materials. Integrating laboratory tests, numerical modeling, and field monitoring, we analyzed the particle size distribution and fractal dimensions of tailings (2.1525) and C material (2.1994), with tailings showing better gradation. Systematic compaction tests examined the effects of mix ratio, water content, and curing time. Results indicate that compression follows a viscous sliding model with exponential curves, progressing through three stages—pore compaction, structural deformation, and elastic/plastic deformation—with energy dissipation ratios of 1:5:18. Water content was the most influential factor, with optimal compaction occurring at 5~8%. Coupled Midas-Flac3D simulations estimated a theoretical compaction rate of 0~2% in filled stopes, excluding seepage and equipment effects. Field monitoring at the −480 m level revealed non-uniform settlement, with maximum subsidence of 63.75 mm above stopes and initial settlement rates of 12~20 mm/month. At the −520 m mining level, the backfill compaction rate reached 0.31%, with minor future increases expected. These findings offer valuable guidance for backfill mixture design and strata control in mining engineering. Full article

Engineering unloading activities during deep mineral resource extraction subject the backfill materials to complex true triaxial stress conditions, where their mechanical behavior and damage mechanisms are critical to stope stability. In this article, a true triaxial testing system was employed to conduct unloading tests under different initial intermediate principal stress (σ₂) conditions, aiming to elucidate the influence mechanism of σ₂ on strength, deformation, failure modes, and acoustic emission (AE) characteristics of the backfill, and to establish a corresponding damage constitutive model. The results demonstrate that the σ₂ governs the mechanical response and failure mode of the filling material. Within the tested range, σ₂ nonlinearly enhances both the peak stress, indicating improved load-bearing. As σ₂ increases, acoustic emission activity changes from intermittent to continuous high-intensity ringing counts. The transition from brittle to ductile fracture. Model predictions showed high agreement with experimental data, validating its applicability. This study provides a critical theoretical foundation and modeling framework for assessing the stability of backfill structures under deep well mining conditions and guiding engineering design. Full article

The mining industry faces the critical challenge of balancing economic profitability with environmental responsibility. Traditional mine planning models often prioritise financial gains, particularly Net Present Value (NPV), while placing less emphasis on environmental impacts, such as carbon emissions. This research presents a comprehensive multi-objective optimisation model for production scheduling in sublevel stoping operations. The model simultaneously aims to maximise NPV and minimise carbon emissions, providing a more sustainable framework for decision-making. The carbon emission objective comprehensively accounts for energy consumption across all key mining activities, including drilling, blasting, ventilation, transportation, crushing, and backfilling, using a “top-down” accounting method. The multi-objective problem is solved using the Non-dominated Sorting Genetic Algorithm II (NSGA-II), which generates a set of Pareto-optimal solutions representing the trade-off between the two conflicting goals. The model is applied to a conceptual copper deposit with 200 stopes. The results demonstrate a clear trade-off: schedules with higher NPV inevitably lead to higher carbon emissions, and vice versa. For instance, one solution yields a high NPV of $312.94 million but with 23,602 tonnes of CO₂ emissions. In contrast, another, more environmentally friendly solution reduces emissions by 26.5% to 18,647 tonnes, resulting in only a 1.21% reduction in NPV. This research concludes that integrating environmental objectives into mine planning is not only feasible but essential for promoting sustainable mining practices, offering a practical tool for operators to make informed, balanced decisions. Full article

Understanding the shear behavior of the interface between surrounding rock and backfill is of significant engineering importance for enhancing stope stability in cemented tailings backfill mining. However, the evolutionary mechanisms of shear properties and damage under varying mechanical conditions remain insufficiently studied. This investigation employed tailings and surrounding rock from a Guangdong tailings pond, with basic mechanical parameters determined through laboratory tests. Numerical models of the rock-backfill composite were developed using PFC2D, considering different shear rates (0.3, 0.6, and 0.9 mm/min), lateral confinement levels (0.5, 1.0, and 1.5 MPa), and roughness coefficients. The analysis compared the interface’s peak and residual shear strengths, revealed crack evolution patterns, and explored damage mechanisms using acoustic emission monitoring and energy dissipation theory. Key findings include the following: (1) Shear stress–displacement curves under all conditions exhibited three stages, ascending, shearing-off, and sliding, with distinct peak and residual strengths. (2) Increasing lateral confinement, shear rate, and roughness transformed failure from localized to global sliding, with cracks occurring at the interface and propagating into the backfill. (3) Cumulative acoustic emission events increased with all three factors, with lateral confinement showing the most substantial effect on interface energy accumulation (83% increase). These results provide theoretical support for assessing interface stability in deep backfilled stopes. Full article

Globally, the open-stope method is used in over 60% of small- and medium-sized mines because of its low cost and high initial efficiency, but it has issues like high ore loss and a great goaf-collapse risk, becoming a core bottleneck for mines’ green and sustainable development. Thus, accelerating its transition to the green backfilling method is an urgent industry need. This study focuses on Shishudi Gold Mine, Xingan Fluorite Mine, and Suichang Gold Mine, adopting a “problem diagnosis–scheme design–case verification–experience extraction” framework to analyze their economic and ecological indicators pre- and post-transition. Our results show remarkable effects: Shishudi’s ore recovery rose from 75% to 88.5%, with 300,000 tons of residual ore recovered and 100% tailing utilization; Xingan’s ore loss dropped by 12%, annual output increased by 60,000 tons, and 200,000 tons of tailings was consumed to achieve a “tailless mine”; and Suichang’s mining capacity rose from 30 tons per day (t/d) to 120 t/d, using 150,000 tons of cyanide-free tailings yearly. In this paper, the key problems of open-stope mining are identified and a transition path of “process innovation–system construction–tailing utilization–mechanization support” is summarized. Our results provide promotable technical solutions and practical references for global small- and medium-sized mines that are of great significance for driving their green and sustainable development. Full article

In underground mining, the stage pillar (SP) is essential for maintaining stope stability, acting as a load-bearing structure between stages. Determining the minimum safe SP thickness is critical to balancing mineral recovery and operational safety. This study investigates the design and mechanical stability of SP under substantial backfill loads, using a representative Iron ore mine as a case study. Based on the geometry of the overlying backfill and core sampling data, extreme loading conditions were identified, with the stope measuring 85 m in height, 72 m in length, and 18 m in width. A mathematical model incorporating the pressure arch effect and triangular pillar geometry was developed to estimate the backfill-induced load. Safety factors for various SP thicknesses were calculated using thin plate and elastic beam theories. Considering sequential excavation of the first- and second-step stopes, the minimum safe SP thickness was determined to be 6.0 m. This design was evaluated using FLAC^3D numerical simulations. The results reveal that during the first step, stress concentrations occurred mainly at the pillar base, with a maximum displacement of approximately 2.0 cm and peak tensile stress of 0.36 MPa—both within acceptable limits. These findings support improved pillar design for safe, efficient ore recovery in underground metal mining. Full article

In order to improve the poor prediction effect of current filling body strength design, a support vector machine (SVM) and Lib Toolbox were used to build an optimal match model or strength index of unclassified tailings filling body. Eight main factors were analyzed and screened as condition attributes, and backfill strength as a decision attribute. Next, we selected 72 groups of training samples and 6 groups of calibration samples. Our model adopts a radial basis function (RBF) as the kernel function and uses a grid search method to optimize parameters; it then tests the combination of optimal parameters by cross-validation. Results show that the mean error of regression prediction and verified predictions made by the SVM match model were 1.01%, which were more accurate than the BP neural network model’s predictions. On the premise that stope stability is ensured, the SVM match model may decrease cement consumption and the cost of backfill more effectively, and improve economic efficiency. Full article

To address the challenges associated with deep ground pressure control at the Sanshandao Gold Mine, a pre-controlled top-to-middle and deep-hole upper and lower-wall goaf subsequent filling mining method was proposed. Three distinct downward mining schemes were designed, the excavation procedure is systematically designed with 18 steps, and the temporal and spatial evolution characteristics of stress and displacement were analyzed using FLAC3D. The results revealed that stress concentration occurred during excavation steps 1–3. As excavation progressed to steps 4–9, the stress concentration area shifted primarily to the filling zones of partially excavated and filled sections. By steps 10–12, the stress concentration in these areas was alleviated. Upon completion of all excavation and filling steps, a small plastic zone was observed, accompanied by an alternating distribution of high and low stress within the backfill. Throughout the excavation process, vertical displacement ranged from 4.42 to 22.73 mm, while horizontal displacement ranged from 1.72 to 3.69 mm, indicating that vertical displacement had a more significant impact on stope stability than horizontal displacement. Furthermore, the fuzzy comprehensive evaluation method was applied to optimize the selection among the three schemes, with Scheme 2 identified as the optimal. Field industrial trials subsequently confirmed the technical rationality and practical applicability of Scheme 2 under actual mining conditions. Full article

This study investigates the stability risks associated with a substandard-thickness (42 m) backfill isolation layer in the open-underground coordinated mining system of the Yongping Copper Mine’s eastern panel at the −150 m level. A numerical simulation based on FLAC3D 3.00 was conducted to evaluate the impacts of four mining sequences (south-to-north, north-to-south, center-to-flank, and flank-to-center) on stress redistribution and displacement evolution. A three-dimensional geomechanical model incorporating lithological parameters was established, with 23 monitoring points tracking stress and displacement dynamics. Results indicate that the mining sequence significantly influences the stability of both the isolation layer and the slope. No abrupt displacement occurred during mining, with incremental isolation layer settlement controlled within 3 mm. Post-mining maximum displacement increased to 10–12 mm. The “north-to-south” sequence emerged as the theoretically optimal solution, reducing cumulative displacements in pillars and stopes by 9.1% and 7.8%, respectively, compared to the suboptimal scheme. However, considering the engineering continuity of the existing “south-to-north” sequence at the −100 m level, maintaining consistent directional mining at the −150 m level is recommended to ensure synergistic disturbance control, ventilation system stability, and operational management coherence. Full article

To explore the influence of the arching effect on stress distribution in jointed backfill structures, this study employs three-dimensional numerical modeling to systematically analyze the mechanical behavior of backfill materials. A finite-difference approach was adopted to establish a representative stope model incorporating interface elements to simulate rock–backfill interactions. The methodology involved parametric studies examining key material properties (internal friction angle, cohesion, elastic modulus, Poisson’s ratio) and geometric configurations, with boundary conditions derived from typical mining scenarios. The results demonstrate that stress distribution follows nonlinear relationships with all investigated parameters. Increasing the internal friction angle and the cohesion reduce internal stresses, though the arch effect exhibits a distinct upper limit. Mechanical properties significantly influence stress transfer characteristics, with the elastic modulus governing stiffness response and the Poisson’s ratio affecting lateral stress development. Geometric parameters control the spatial extent of arching, with larger dimensions modifying the stress redistribution pattern. This research quantitatively establishes the operational limits of arching in backfill structures, providing crucial thresholds to prevent stability risks from overestimating its benefits. The findings offer practical guidelines for optimizing backfill design in deep mining and paste filling applications, contributing both technical solutions for mine safety and fundamental insights for geomechanical theory. The developed methodology serves as a robust framework for future studies on complex backfill behavior under various loading conditions. Full article

The width of the pillar is an important factor in the stability of the underground space and the efficiency of resource recovery. This study aims to model the performance of retained walls in panel barrier pillar stopes. By simplifying the three-dimensional problem based on the mining operation, a two-dimensional mechanical model of non-equal-width retained walls was established, and the stress and deflection were solved analytically. The calculated deformation characteristics of equal-width and non-equal-width retained walls were analyzed and compared with numerical simulations. The results indicated that the deformation of retained walls is mainly influenced by the roof loads, the uniaxial compressive strength, and the internal friction angle of backfill materials. For equal-width retained wall design, corresponding to the areas of pillar stopes where the uniaxial compressive strength and internal friction angle of backfill materials are low, great lateral pressure will be created on the retained walls. This results in significant flexural wall deformations in this area, increasing the risk of wall collapses. In comparison, for non-equal-width retained walls, the width is defined based on the surrounding backfill materials, which could greatly reduce the risk of potential damage. For the mining operation at the actual mine, the non-equal-width design with 2.5 m and 4.0 m intervals was adopted for the panel barrier pillar stopes, and the final displacement of the roof of the stope after the completion of the mining is 34 mm, and the two sides of the mine wall remain in good integrity with no significant peeling or cracking identified. This design improves the recovery rate of mineral resources and the stability of mining. Full article

A comprehensive understanding of the mechanical behavior of backfill under compression is crucial for optimizing its design, improving stope stability and enhancing resource recovery. Laboratory testing and numerical simulation were conducted to study the mechanical properties and damage mechanism of cemented tailings backfill (CTB) with different cement-to-tailings (c/t) ratios under uniaxial compression. Laboratory testing was used to investigate the strength and deformation characteristics, macroscopic failure modes, and energy evolution patterns of CTB, while simulation with Particle Flow Code (PFC) was employed to explore the distribution of microcracks and mesoscopic damage mechanisms. A constitutive model accounting for the initial compaction stage was proposed, validated, and applied to practical engineering. The results show that as the c/t ratio decreases, the failure mode of CTB transforms from shear failure to combined tensile–shear failure, and tensile failure. Mesoscopically, a higher c/t ratio leads to more bond contacts, which increases the bearing capacity and consequently causes more cracks to damage CTB. From an energy standpoint, the damage mechanism of CTB is further analyzed and the development of energy is characterized by four stages. Moreover, to explore the failure mechanism of CTB, an innovative constitutive model was proposed and verified through experiments. The matching coefficients, based on the novel constitutive model, indicate that CTB with a c/t ratio of 1:6 is qualified for all current mining depths, and a c/t ratio of 1:10 is sufficient to depths below 300 m. Full article