Ziling Song

Coal-based solid waste (CBSW; fly ash, weathered coal, coal gangue) from open-pit coal mining in extremely cold regions differentially releases salinity/alkalinity, heavy metals and acids, altering surrounding black-soil properties and reshaping its bacterial communities. We compared healthy farmland black soil (CK) with three dumping treatments—fly ash (FA), weathered coal (WC) and coal gangue (CG) (six replicates each; n = 24)—using full-length 16S rRNA sequencing (PacBio CCS), physicochemical, phospholipid fatty acid and enzyme-activity analyses. The wastes showed contrasting stress regimes: fly ash was slightly alkaline, saline and heavy-metal-enriched; weathered coal was strongly acidic and saline; and coal gangue was acidic–sulfidic. Dumping significantly altered soil pH, salinity and metal speciation, reducing organic matter by 36–61% and microbial biomass carbon by 45–74%. Alpha diversity responded in a type-specific manner: WC had the lowest Shannon index (4.72, −55.1%) and was dominated by Pseudomonadota (80.6%) with methylotrophy being enriched; FA retained the highest diversity (11.23); and CG was dominated by Actinobacteriota (45.1%). PERMANOVA and ANOSIM confirmed significant community separation. Nitrification was nearly lost under WC, while sulfate respiration was enriched under CG and sulfur respiration under FA, indicating type-specific restructuring of nitrogen and sulfur cycling. These results show that CBSW dumping drives restructuring and nitrogen–sulfur functional degradation of black-soil bacterial communities through type-specific environmental filtering, with weathered coal causing the most severe degradation, informing classified remediation.

Abandoned open-pit coal mine slopes are compacted, infertile and water-limited, hindering vegetation restoration. This study evaluated the combined use of two waste materials—coal gangue (an alkaline, mineral-rich mining residue) and decomposed straw (a nutrient-rich agricultural residue)—as a composite substrate for restoring degraded slope soil. In a 60-day greenhouse pot experiment, slope soil from the Haizhou Open-Pit Coal Mine (Fuxin, China) was amended with coal gangue (5%, 10% or 15% by dry mass), decomposed straw (1%, 3% or 5%), or their nine full-factorial combinations (16 treatments in total, including an unamended control, each with three replicates), and sown with three herbaceous species (ryegrass, alfalfa and tall fescue). Soil physical and chemical properties and plant growth traits were measured. Relative to the unamended control, the composite substrates improved soil structure and fertility: soil water content and field water-holding capacity were highest under the 10% gangue + 5% straw treatment (25.6% and 25.89%, increases of 28.0% and 29.5%), bulk density was lowest, with the correspondingly highest total porosity, under the 15% gangue + 3% straw treatment (1.35 g/cm³, a 14.9% decrease). Organic matter (9.42 g/kg), total nitrogen (0.71 g/kg, +65.1%), available nitrogen (45.3 mg/kg, +33.0%) and available potassium (106.44 mg/kg, +26.2%) were highest under the 5% gangue + 5% straw treatment, which also gave the best growth of ryegrass and alfalfa (alfalfa aboveground and underground dry weight increased by 221% and 188%, respectively), whereas tall fescue grew best under the 5% gangue + 3% straw treatment. These results indicate that a 5% coal gangue + 5% decomposed straw composite substrate is a promising amendment for revegetating degraded open-pit slopes, although field validation is still required.

Internal dump slopes in cold-region open-pit coal mines are subjected to moisture variation, freezing temperatures, rainfall infiltration, and groundwater seepage. This study developed an integrated experimental-numerical-field framework to evaluate these effects for the Chaoyang open-pit coal mine in Heilongjiang Province, China. Unconfined compression and direct shear tests were conducted under four moisture contents of 14.0%, 17.6%, 23.0%, and 26.0% and three temperatures of 23 ± 2°C, −5°C, and −15°C. The measured elastic modulus, cohesion, and internal friction angle were incorporated into a three-dimensional GTS NX model to assess slope responses before and after 72 h of rainfall.At room temperature, increasing moisture content reduced the elastic modulus from 1802.4 to 1003.6 MPa and cohesion from 18 to 10 kPa, while the pre-rainfall factor of safety decreased from 1.405 to 1.176. Under subzero conditions, stiffness and cohesion increased because of pore-ice bonding, whereas the internal friction angle varied only modestly and non-monotonically. At −15°C, the post-rainfall factor of safety ranged from 1.478 to 1.537, and rainfall-induced reductions under all subzero conditions remained below 0.60%. Under the room-temperature natural-moisture condition, drainage pipes increased the factors of safety before and after rainfall from 1.221 and 1.184 to 1.413 and 1.384, respectively. Field monitoring recorded an average drainage discharge of 2.51 × 10 ⁴ m ³ /day and groundwater-level drawdowns of 12.19 and 9.94 m in the upper and middle aquifers.The results demonstrate that moisture weakens unfrozen dump materials but can enhance frozen-state strength through ice bonding. The integration of laboratory-derived temperature-moisture parameters, three-dimensional rainfall analysis, and field hydraulic validation provides a practical framework for stability assessment and drainage control of cold-region internal dump slopes.

Rainfall-induced seepage instability is a major concern for internal waste dump slopes in cold-region open-pit coal mines, where slope performance is influenced by groundwater conditions, moisture state, and seasonal temperature variations. This study investigates the internal waste dump slope of the Chaoyang open-pit coal mine and evaluates its seepage and stability responses under prescribed moisture and temperature states before and after rainfall, together with the effectiveness of drainage control. Soil specimens with moisture contents of 14%, 17.6% (natural), 23%, and 26% were tested at ambient temperature, −5 °C, and −15 °C by uniaxial compression and direct shear tests. The mechanical parameters measured under the prescribed moisture and temperature states were assigned to a GTS NX seepage–stability model. Twenty-four parametric cases, comprising four moisture contents, three temperature states, and pre- and post-rainfall conditions, were evaluated using the strength-reduction method, and an HDPE perforated drainage scheme was subsequently assessed. Under the ambient-temperature parameter state, increasing specimen moisture content from 14% to 26% reduced the pre-rainfall factor of safety from 1.41 to 1.18 and the post-rainfall value from 1.38 to 1.17. Parameter sets obtained from low-temperature-conditioned specimens produced higher calculated factors of safety; however, these cases represent prescribed mechanical states rather than the actual winter condition of the full-scale slope. Under the idealized drainage boundary, the pre- and post-rainfall factors of safety increased from 1.22 and 1.18 to 1.40 and 1.39, respectively. The results demonstrate the relative effects of laboratory-derived mechanical parameters, rainfall-induced seepage, and idealized drainage under the prescribed scenarios.

Spontaneous combustion in fire-affected coal seams can degrade coal quality, alter rock mechanical parameters and reduce mining profitability. Traditional pit limit optimization methods ignore coal fire-induced quality degradation, ignore the coupling effect of economic fluctuation and slope stability, and lack quantitative optimization for fire-affected open-pit mines. Here, we optimize loss-reducing mining boundaries for the southern fire-affected highwall in the first mining district of the Dananhu No. 2 Mine, Hami, Xinjiang. The aim is to move beyond binary decisions that either sterilize or fully extract fire-affected reserves. We instead integrate economic return, slope stability and coal-price uncertainty into a single boundary-optimization framework. First, we established a three-dimensional Cartesian coordinate system for the study area. We then modeled and fitted the coal-seam roof and floor using MATLAB-based multiple integration, reducing edge errors in solid surfaces. Laboratory analyses of borehole coal samples defined how calorific value varied with advance distance. These data were used to derive the coal-quality curve. Net mining profit was then formulated as the objective function, replacing the conventional stripping-ratio criterion. Profit was calculated across advance distances to identify the economically optimal boundary. Mechanical parameters of thermally altered rocks were obtained from laboratory deformation tests. Rhino and FLAC3D 6.0 were then used to evaluate three-dimensional slope stability at critical locations. Coal-price perturbation scenarios were finally introduced to test the sensitivity of net profit and optimal advance distance. Under the baseline coal price, the slope remained stable at an advance distance of 193 m. At this boundary, net profit reached a maximum of RMB 676.608 million. The southern surface boundary contracted by 47 m relative to the initial boundary, reducing unnecessary land disturbance. Sensitivity analysis showed that lower coal prices sharply reduced both the optimal advance distance and maximum net profit. When coal price decreased by 30%, the optimal advance distance contracted to approximately 116.9 m. Maximum net profit fell to approximately RMB 248.239 million. Higher coal prices expanded the optimal boundary outward. Once coal price reached approximately 128.7 yuan/t, or 18.5% above baseline, the optimum reached the upper constraint of 240 m. Net profit then increased substantially with further price growth. These results provide a quantitative basis for dynamic boundary optimization and disturbance-reducing extraction in fire-affected open-pit coal mines.

To address dust diffusion in deep concave open-pit coal mines, this study examined Fushun East open-pit coal mine in Liaoning Province, a deep concave open-pit coal mine. Employing theoretical analyses, field testing, numerical simulation, and experimental validation, we comprehensively investigated the mechanisms of dust generation, migration, and effective control strategies, revealing the mine dust migration patterns and providing practical foundations for dust control systems. Based on field measurements, road transportation was identified as the primary source of dust emissions. Atmospheric flow within the deep concave open-pit mine follows a complex recirculation pattern. Using COMSOL numerical simulation software, a fluid-solid coupling dust dispersion model was established based on the scale conditions of deep concave open-pit mines, revealing the formation mechanism of negative pressure dust accumulation zones induced by the inclination angle of the pit’s lateral slopes, while the pit’s shape illustrated dust migration trajectories. The air flow inside the pit was vortex-induced, primarily concentrated near the intake air areas of the pit. The study simulated air flow and dust particle trajectories in the flow field around mining vehicles, determining that the air disturbance range during vehicle movement extends to 1.5 times the vehicle’s volume. It is found that under low-speed driving conditions, dust dispersion behavior is mainly controlled by external wind speed and direction, with relative speed playing a dominant role in affecting the dust dispersion rate around mining vehicles. This in-depth study of dust sources, generation mechanisms, dispersion patterns, and precise control measures in deep concave open-pit coal mines has significant implications for achieving coordinated development between economic benefits and environmental protection.

Respirable coal dust remains a major occupational hazard in informal mining operations in Pakistan, where high-ash, low-moisture bituminous coals are handled without engineered dust-control systems. This study evaluates how particle size distribution (PSD), moisture content, and surface wettability influence dust-generation potential in coal from the Darra Adam Khel coalfield. Laboratory analyses were conducted on three particle-size fractions (> 75 μm, 45–75 μm, and < 45 μm) to measure moisture retention, slurry pH, and contact-angle–based wettability under ambient conditions. Results show a size-dependent response, with ultrafine particles (< 45 μm) retaining the highest moisture (up to 6.60%) and exhibiting near-neutral pH (6.7), indicating increased carbonate dissolution. Contact angles ranged from 72° to 109°, confirming moderate–strong hydrophobicity that intensified upon compaction. Because dust-generation chamber tests were not available, respirable dust-suppression efficiency (35–58%) was estimated from established Pakistani benchmarks rather than measured directly. The study also acknowledges that the hypothesized 8% moisture threshold for optimal suppression could not be experimentally validated, as the maximum achievable sample moisture was 6.60%. High-pressure gas-atmosphere wettability trends (He, N₂, CO₂) referenced in the discussion represent conceptual mechanisms from published literature, not in-house experimental data. Overall, the findings indicate that Darra Adam Khel coal exhibits limited natural wettability and low moisture-holding capacity, providing a physicochemical basis for enhanced dust-control strategies such as pH conditioning and nonionic surfactants to address hydrophobic surface behavior in semi-arid mining environments.

To address key challenges during the capacity expansion of the Baoqing Chaoyang Open-Pit Coal Mine from 7 to 11 Mt/a—such as insufficient working-line length, excessive advancing intensity, poor coordination between mining zones, elevated internal dump slope risks, and constrained dumping capacity—this study develops a zoning optimization method based on Unascertained Measure Theory (UMT). A working-line optimization model, constructed from coal seam thickness, density, production targets, and advancing dynamics, indicates a rational length range of 1350–2050 m at 11 Mt/a. Guided by coal seam occurrence and the original layout, the initial longitudinal-mining area is reorganized into four transverse primary zones. An eight-dimensional evaluation index system is established, covering geological, geotechnical, hydrogeological, topographic, engineering, economic, environmental, and social factors. Combined weighting using the Analytic Hierarchy Process and the Entropy Weight Method, together with multiplicative normalization, yields a hybrid subjective–objective weighting set. On this basis, four-level UMT evaluation functions and an evaluation matrix are constructed, and comprehensive assessments are performed using a confidence recognition criterion. The results show that Scheme II achieves the best overall performance in terms of economic efficiency, transportation, safety, and resource utilization, with a V₁-level confidence of 0.7058, significantly higher than the other schemes. Under Scheme II, the four zones provide 971.2 Mt of recoverable raw coal, an average stripping ratio of 5.8, and a maximum service life of 34.3 years. The proposed integrated framework of working-line design, mining-zone zoning, and uncertainty-based evaluation offers a practical decision-support tool for capacity expansion planning in large-scale open-pit coal mines.

In response to the problems of developed rock fractures and unsatisfactory bench blasting effects in open-pit coal mines in Xinjiang, China, By using on-site research, theoretical analysis, numerical simulation and other methods, the main influencing factors of burnt rock blasting are analyzed, and the impact of joint cracks in burnt rock on its blastability is quantitatively evaluated and graded. Research shows: the main influencing factors on the blastability of burnt rock are the density of original rock joint fractures, the length of original rock joint fractures, the radius of crack propagation after blasting, and the peak blasting stress. We have established quantitative mathematical models for various influencing factors, established a classification evaluation model and evaluation standards for the blastability of burnt rocks in Xinjiang region. The comprehensive evaluation index G of blastability is divided into five levels: Level I (G > 20.7) extremely easy to blast, Level II (G = 16.7–20.7) easy to blast, Level III (G = 12.7–16.6) difficult to blast, Level IV (G = 8.7–12.6) difficult to blast, and Level V (G < 8.7) extremely difficult to blast. And a study was conducted on the blastability evaluation and classification of burnt rocks in six open-pit coal mines in Xinjiang region, and the results of blastability classification were obtained: open-pit mine 1: G = 13.3 is level III difficult to blast, open-pit mine 2: G = 13.0 is level III difficult to blast, open-pit mine 3: G = 13.3 is level III difficult to blast, open-pit mine 4: G = 13.1 is level III difficult to blast, open-pit mine 5: G = 12.8 is level III difficult to blast, and open-pit mine 6: G = 12.5 is level IV difficult to blast.

The ore mining sites commonly experience slope instability, which is causing concern for the workers’ safety and the operation’s stability. Considering the Ziluoyi iron ore mining site as a case study, uniaxial compression strength and shear tests are performed on the lower disk peripheral rock, ore body, and upper disk peripheral rock, leading to the extraction of compressive strength and elastic modulus (lower disk: 77.7 MPa–9.093 GPa; ore body: 19.6 MPa–4.619 GPa; upper disk: 55.47 MPa–5.573 GPa). Further, using the Hoek–Brown criterion in conjunction with the Moher–Columb criterion, the cohesion and internal friction angle of various samples are appropriately determined (lower disk: 21.124 MPa–35.614°; ore body: 21.66 MPa–26.5°; upper disk: 42.916 MPa–25.743°). By employing an appropriate rock mass reduction model, its constants (m and s) and RMR score for the consisting layers (schist layer and ore body) of the three understudy slopes (Slope#1–Slope#3) are evaluated. An effective algorithm based on the Morgenstern–Price method is employed and its effectiveness is also proved by comparing its factor of safety results with those of Geo-Slope for various slope structures subjected to different loads. Subsequently, the stability analyses of various slopes are methodically examined by predicting the factor of safety values under multiple types of loading (i.e., self-weight + groundwater, slope self-weight + groundwater + blasting vibration force, and self-weight + groundwater + seismic force). The factor of safety values of the slopes pertinent to Slope#1/Slope#2/Slope#3 subjected to the above loading conditions are obtained as 1.354/1.273/1.188, 1.326/1.239/1.169, and 1.321/1.232/1.162, respectively. Upon comparing these results with those of a valid homeland specification, it becomes clear that the results are able to meet safety standards and ensure efficient mine operation.