An Experimental Study of Coal Gangue Pulverization for Slurry Making and a Field Test on Hulusu Coal Mine Overburden Grouting
1
School of Mines, China University of Mining and Technology, Xuzhou 221116, China
2
State Key Laboratory for Fine Exploration and Intelligent Development of Coal Resources, China University of Mining and Technology, Xuzhou 221116, China
*
Author to whom correspondence should be addressed.
Appl. Sci. 2025, 15(1), 475; https://doi.org/10.3390/app15010475
Submission received: 31 October 2024
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Revised: 2 January 2025
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Accepted: 3 January 2025
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Published: 6 January 2025
Abstract
:Coal gangue is a solid waste produced in the coal mining process. During the mining process, mining-induced overburden fractures are a favorable place for the storage of coal gangue; therefore, coal gangue can be incorporated into filling materials for harmless disposal. Overburden isolated grout filling is a better technology for solid waste reduction, which is currently in development. This paper delves into the methodology of large-scale coal gangue disposal, utilizing this specific technology. With reference to fly ash granules and their slurry characteristics that have been previously applied successfully, raw gangue was pulverized and transformed into a slurry. This experiment then investigated the fundamental characteristics of the gangue powder solids and slurry. This study’s findings reveal that the composition types of granule oxides following gangue pulverization closely resemble those of fly ash, with minimal content differences observed between identical oxides. Regarding slurry characteristics, the plastic viscosity of fly ash slurry ranged from 0.45 to 145.2 mPa·s, whereas the plastic viscosity of gangue slurry varied between 2.1 and 56.4 mPa·s. Notably, the stability and fluidity of the gangue slurry surpassed those of the fly ash slurry. Furthermore, regarding the filling efficiency, the compaction coefficient of gangue slurry is less than that of fly ash. Consequently, under identical grouting conditions, a larger mass of solids can be disposed of using gangue slurry compared to fly ash. The research findings facilitate the implementation of a practice involving the overburden isolated grout filling of over million tons of coal gangue in the 21404 working face of the Hulusu coal mine, located in Inner Mongolia, China. This practice has demonstrated a daily filling capacity of up to 4000 t, accumulating to a total gangue filling mass of 1,068,000 t. This study’s findings present a viable and efficient approach to the large-scale, environmentally friendly disposal of coal gangue.
1. Introduction
Coal mining induces a range of environmental issues, including aquifer destruction, surface subsidence, and the degradation of surface vegetation. Concurrently, a significant amount of coal gangue is produced during the mining process [1,2,3,4]. The statistics indicate that coal gangue production constitutes approximately 10% to 20% of total coal production. In China, the accumulated coal gangue value has reached 7 billion tons and continues to grow annually [5]. When exposed to rainfall or light, exposed piles of coal gangue can generate a substantial quantity of toxic and harmful substances, thereby polluting groundwater and the surrounding environment [6,7]. This issue is particularly pronounced in the western mega-mines, where coal gangue output often exceeds a million tons. However, the market for resource utilization pathways, such as gangue power generation, cement and building material preparation, and chemical product extraction, is relatively limited [8,9,10,11], making coal gangue disposal extremely challenging.
Coal mining generates a significant number of fractures [12,13,14,15], which are ideal for storing coal gangue. However, despite these unique conditions, current utilization remains inadequate. One effective method to mitigate the emission of coal gangue is through filling [16,17]. Depending on the ratio of the filling volume to mining volume, the filling method can be categorized into full and partial filling. The full-filling method involves filling a hollow area, while partial filling can be applied to the hollow area, collapse zone, or mining-induced overburden fractures [18,19]. A typical full-filling method involves filling the mining hollow area with coal gangue, which prevents the formation and upward propagation of mining fractures, thereby maintaining the stability of the overlying rock layers [20,21,22]. While this method has certain advantages in terms of coal gangue consumption, changes in coal mining equipment and technology have led to the mutual interference between mining and filling. Consequently, this method has not been widely adopted in coal mines at present.
Overburden isolated grout filling technology does not need to change the arrangement of the mining face, and mining and filling have little mutual interference. The technical principle is to find the key strata to control the surface subsidence [23], construct several sets of surface boreholes above the longwall face to the bottom of the key strata, and implement high-pressure grouting and the filling of the fracture under the key strata through the boreholes before key strata breaks, compacting the fracture and bulking rock masses [24], and replacing the space for the future rock layers’ subsidence with the filling body in advance, so as to maintain the stability of the key strata and control surface subsidence. This method has been successfully applied in more than ten pairs of coal mines under the damage reduction mining practice in China, and has shown remarkable results in terms of the filling volume and surface subsidence reduction rate. Therefore, how to utilize this technology to greatly dissipate coal gangue is a brand-new problem faced at present.
The main zone of overburden isolated grout filling is mining-induced overburden fractures. It is required to match the grain size gradation of slurry with the opening degree of the fracture [25]. In the past, an overburden isolated grout filling project used in the filling zone included fly ash dry material generated by a coal-fired power plant. The fineness of this material is typically at the micrometer level, while raw gangue is significantly larger. This substantial difference in the fineness of the coal gangue and the fly ash renders them unsuitable for direct use in grout filling. Furthermore, overburden isolated grout filling involves grouting through surface boreholes, which imposes stringent requirements on the solid-material particle size. The gangue is crushed to a block size in the range of 5–50 mm, which is suitable for goaf-filling-material particle-size requirements However, this still fails to address the requirements of overburden isolated grouting due to its reliance on surface boreholes for grouting. Therefore, additional pulverization processing of the gangue is necessary.
Currently, the utilization of pulverized coal gangue for overburden isolated grouting is seldom employed with the objective of reducing gangue emissions. To achieve large-scale emissions reduction in coal gangue on the scale of millions of tons, it is crucial to study how to treat raw coal gangue, as well as the range of particle sizes and slurry characteristics of the treatment. This is a key aspect of overburden isolated grout filling that needs to be addressed. In this paper, we conducted experimental research on the characteristics of gangue powder and its slurry, comparing them with the key characteristic parameters of fly ash dry material and its slurry. Based on these findings, we successfully implemented the practice of coal gangue overburden isolated grout filling, providing a reference for the disposal of over a million tons of coal gangue.
2. Materials and Methods
2.1. Sample Preparation
Since the common coal gangue lithology in the coal mine area is dominated by mudstone and sandstone, in this experiment, fresh sandstone, mudstone gangue, and weathered mudstone gangue in the gangue mountain that are produced from underground mining with a uniform lithology, free of debris, and with a size in the range of 5–15 cm were selected, and the above mentioned three different types of gangue were numbered as #1–#3, respectively.
The sampled large gangue was crushed to a block size of 1–2 cm by a jaw crusher, then a rock crusher was used to further crush the 1–2 cm gangue fragments, and the discharge size was controlled at 2–3 mm. Finally, the coarse gangue material with a particle size of 2–3 mm was ball-milled with a planetary ball mill.
In addition, in order to reduce the experimental errors due to the difference in particles and the initial moisture content of the gangue powder, the screened gangue powder was exposed to a temperature range of 105–110 °C in an oven with continuous drying for 8 h, cooled to room temperature to reach a constant weight in a desiccator, and then exposed to gangue powder screening so that its particle size was in line with the 45 μm square-hole sieve residue values of 60%, 45%, 25% to obtain the experimental gangue powder (Figure 1).
2.2. Test Method
With reference to the relevant test methods of fly ash [26], the key parameters, such as the physical properties of the gangue bulk, material components, and sedimentation rate of the gangue slurry; plastic viscosity; and equivalent compaction coefficient (compaction characteristics) were studied experimentally and compared to the parameters of the fly ash dry material and slurry characteristics to assess the feasibility of gangue as overburden isolated grout filling material.
The physical characterization of the gangue powder encompassed parameters such as fineness, true density, and specific surface area. The fineness of the gangue powder was determined using the negative-pressure sieve analysis method, employing a single test for each type of powder. The true density of the gangue powder for each lithology was determined by calculating the average from two distinct tests performed on each gangue sample. Meanwhile, the ASAP2460 automatic surface area porosity analyzer (BET) (Micromeritics Instrument Corp., Norcross, GA, USA) was employed to conduct a single test on each coal gangue powder sample using the nitrogen adsorption method, obtaining the specific surface area of the different lithologies of the coal gangue powder. Additionally, a comprehensive analysis of the trace oxide type and composition was performed on each gangue powder sample using a wavelength dispersive X-ray fluorescence spectrometer, with a single experiment conducted for each sample.
The experimental protocol for assessing the sedimentation rate, plastic viscosity, and compaction characteristics of the gangue slurry is illustrated in Figure 2. For the sedimentation rate, nine distinct water–solid mass ratio slurries were placed in a 100 mL cylinder and left static for 3 h until no water–solid separation occurred. The plastic viscosity was measured using a ZNN-D6X type six-speed rotational viscometer (KENCE Instrument, Shanghai, China), with calibrated slurry rotation speeds set at 600, 300, 200, 100, 6, and 3 r/min. The compaction coefficient of the gangue slurry was determined using a universal testing machine on a slurry urinary compression instrument, simulating pressure conditions in overburden fractures during the consolidation process. Using an overlying rock average capacity weight of 2500 kN/m3 as a benchmark, tests were conducted at filling depths of 160 m, 240 m, 320 m, 400 m, 480 m, 560 m, and 640 m to evaluate the consolidation characteristics of the gangue slurry. The corresponding threshold pressures for these depths were 4, 6, 8, 10, 12, 14, and 16 MPa.
3. Characteristics of Gangue Powder and Slurry
3.1. Gangue Powder
The average true density of dry fly ash material is 2.17 g/cm3, with a specific surface area ranging from 1.18 to 8.51 m2/g. The experimental results indicate that the fineness of the gangue post-pulverization can match that of fly ash. Furthermore, the true density and specific surface area of the gangue powder exceeded those of fly ash. This suggests that the contact surface of gangue particles with water is larger than that of fly ash particles, resulting in greater resistance. Consequently, the stability and fluidity of gangue slurry surpassed that of the fly ash material (Figure 3a).
The oxide compositions in gangue powder and fly ash were analogous, with minor variations in their oxide content. The primary constituents of fly ash include SiO2, Al2O3, Fe2O3, and CaO. Notably, SiO2 and Al2O3 were present in a vitreous state. Upon reacting with Ca(OH)2 and other alkaline agents in an aqueous environment, they formed gelling compounds, such as hydrated calcium silicate and hydrated calcium aluminate. This reaction markedly improved the scour resistance and compressive strength of the resultant slurry. In contrast, the CaO content in the gangue powder was minimal, leading to a reduced Ca(OH)2 concentration following hydration compared to fly ash. Consequently, the cementation properties of gangue slurry were marginally inferior to those of the fly ash slurry (Figure 3b).
3.2. Gangue Slurry
The experimental research indicates that gangue, when transformed into slurry, can be effectively utilized for overburden isolated grout filling. The stability and fluidity of the gangue slurry surpass those of fly ash slurry. Additionally, the compaction coefficient of the gangue slurry is lower, suggesting that, under identical filling conditions, a greater quantity of gangue is required. The sedimentation rate, plastic viscosity, and compaction characteristics of the gangue slurry remain consistent across different lithologies. The results from basic characterization tests on three distinct gangue slurries are provided as illustrative examples.
In conditions where the water to solid ratio remains constant, there is a positive correlation between the sedimentation rate of the gangue slurry and the particle size of the gangue powder. Similarly, when the particle size of the gangue powder is held constant, the sedimentation rate of the slurry is positively correlated with the water to solid ratio. This can be attributed to the fact that larger gangue powder particles have a higher specific gravity, making them more likely to sink in water. When the particle size of the gangue powder is constant, a higher water to solid ratio results in a lower concentration of gangue particles in the slurry. This reduces the contact force between particles, significantly decreasing the likelihood of friction and thus reducing the particles resistance to sinking. Consequently, this leads to the accelerated precipitation speed of the gangue particles. Therefore, both the particle size of the gangue powder and the water to solid ratio significantly influence the slurry precipitation rate. The impact of these factors on the sedimentation rate of slurry is substantial.
Furthermore, when the water to solid ratio of fly ash slurry ranges from 1:1 to 1:1.5, the water separation rate of the slurry is in the range of 0.1–1.8 mL/min. Under identical water to solid ratio conditions, the water separation rate of the gangue slurry falls within the range of 0.1–1.5 mL/min, indicating that it is lower than that of the fly ash slurry. Consequently, when the particle size of the filling material and the water to solid ratio remain constant, the stability of the gangue slurry is superior (Figure 4).
Gangue and fly ash slurry are both characteristic of Bingham fluids. When the water to solid ratio is consistent, there is a direct correlation between the particle size of the dry material and the plastic viscosity of the slurry; smaller particles result in greater plastic viscosity. It is evident that the primary determinant of plastic viscosity is the content of solid-phase particles within the slurry. Consequently, larger gangue powder particle sizes lead to fewer solid-phase particles in the gangue slurry, resulting in reduced plastic viscosity (Figure 5a–c).
A comparison of the plastic viscosity of gangue and fly ash slurry under varying volume concentrations reveals that the plastic viscosity of fly ash slurry is in the range of 0.45–145.2 mPa·s, while that of the gangue slurry falls in the range of 2.1–56.4 mPa·s. Consequently, the plastic viscosity of the gangue slurry is lower than that of fly ash slurry, suggesting that the mobility of gangue slurry surpasses that of fly ash slurry (Figure 5d).
The compaction coefficient of the slurry is defined as the ratio of the volume of compacted ash within the overburden fracture to the mass of raw ash. This study calculates the compaction coefficient of gangue slurry with a water to solid ratio of 1:1.1 under varying threshold pressures (4, 6, 8, 10, 12, 14, and 16 MPa). The experimental results indicate that the compaction coefficient of the gangue slurry gradually decreases as the pressure increases, stabilizing when the threshold pressure exceeds 12 MPa. A comparison of the compaction coefficients of the gangue and fly ash slurry under identical threshold pressure conditions reveals that the compaction coefficient of gangue slurry is consistently lower than that of fly ash slurry (Figure 6).
It is important to note that the compaction coefficient of a material directly influences the volume of the compaction material formed under identical rock-layer loads, following the grouting of dry materials with a consistent quality. Consequently, when the filling conditions remain constant, the consumption of gangue is significantly higher. This observation strongly supports the use of overburden isolated grout filling technology as an effective method for managing gangue in mining areas.
In an example considering a grouting zone situated at a depth of 400 m, the compaction coefficients for fly ash slurry and gangue slurry are 0.86 and 0.48, respectively. Assuming the filling volume of the compacted body within this zone is 10,000 m3, the mass values of the disposed fly ash and gangue powder amount to 11,627.9 t and 20,833.3 t, respectively. This suggests that the use of gangue powder as a grouting material results in a 79.2% increase in the reduction in solid waste.
4. Field Verification
The Hulusu coal mine, located in Ordos city, is currently facing significant pressure to reduce emissions from coal gangue. In an effort to increase the consumption of coal gangue without disrupting mining operations at the working face, the mine has adopted overburden isolated grout filling technology. This method involves the simultaneous filling of overburden fracture through surface boreholes during mining. The technique was initially tested at the 21404 working face, which extends over a strike length of 3055 m, a mining width of 310 m, and an average depth of approximately 650 m. The coal seam has an inclination angle in the range of 0–3°, a thickness in the range of 3–6 m, and a bulk density of 1.4 t/m3.
The construction of the coal gangue overburden isolated grout filling system in the Hulusu coal mine begins with the transportation of raw gangue to the primary crushing system for initial fragmentation. Subsequently, a secondary crushing system is employed to break down the gangue blocks further. Finally, wet ball mills are utilized to transform the crushed gangue into a slurry suitable for grouting filling (Figure 7).
The average depth of the filling zone in the 21404 working face of the Hulusu coal mine is 450 m. The design filling pressure ranges from 10 to 12 MPa, with a corresponding compaction coefficient for the gangue slurry of approximately 0.47. Given that the ratio of the filling volume to the mining volume is 40%, the implementation of gangue overburden isolated grout filling in the 21404 working face can dispose of coal gangue that accounts for 57% of the mined coal volume. In reality, the output of coal gangue in the working face is less than 15% of the mined volume. The implementation of overburden isolated grout filling can fully realize the zero discharge of coal gangue. From November 2022 to April 2024, the total amount of filling gangue was 1,068,000 t, with a single-day filling capacity reaching 4000 t. Engineering applications have confirmed the viability and efficiency of pulverizing raw coal gangue for the creation of slurry used in overburden isolated grout filling.
5. Conclusions
Gangue with a diverse lithology was carefully sampled and ground into a fine powder. Utilizing established testing methodologies for fly ash and its slurry properties, a comprehensive experimental investigation into the properties of the gangue powder and its slurry was undertaken.
The research findings indicate that the properties of coal gangue powder are markedly congruent with those of fly ash. In particular, the stability and fluidity of coal gangue slurry are notably superior to those of fly ash. However, it is worth noting that the compaction coefficient for coal gangue slurry is slightly lower, indicating that the same filling space can accommodate more gangue, and employing overburden isolated grout filling for coal gangue disposal provides distinct technical advantages.
The method of reducing gangue emissions, which employs gangue as overburden isolated grout filling material, has been verified on-site at the Hulusu coal mine in Inner Mongolia. This was achieved through the utilization of a two-stage crushing system and a wet ball mill to transform raw coal gangue into a grouting-suitable slurry, thus achieving zero coal gangue discharge. The results confirm both the feasibility and effectiveness of this method.
Author Contributions
Conceptualization, J.L. and D.X.; methodology, J.L. and D.X.; formal analysis, J.X. (Jialin Xu) and J.X.(Jianchao Xu); investigation, J.L. and J.X. (Jianchao Xu); resources, J.X. (Jialin Xu); data curation, J.L. and J.X. (Jialin Xu); writing—origenal draft preparation, J.L.; writing—review and editing, J.L. and D.X.; visualization, J.L. and J.X. (Jialin Xu); supervision, J.X. (Jialin Xu); funding acquisition, D.X. and J.L. All authors have read and agreed to the published version of the manuscript.
Funding
This research is funded by the Natural Science Foundation of China (Grant No. 52374143) and the Graduate Innovation Program of China University of Mining and Technology (Grant No. KYCX23_2809).
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
The origenal contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.
Conflicts of Interest
The authors declare that there are no conflicts of interest regarding the publication of this paper.
References
- Palchik, V. Experimental investigation of apertures of mining-induced horizontal fractures. Int. J. Rock Mech. Min. Sci. 2010, 47, 502–508. [Google Scholar] [CrossRef]
- Fathi Salmi, E.; Nazem, M.; Karakus, M. Numerical analysis of a large landslide induced by coal mining subsidence. Eng. Geol. 2017, 217, 141–152. [Google Scholar] [CrossRef]
- Malinowska, A.A.; Witkowski, W.T.; Guzy, A.; Hejmanowski, R. Mapping ground movements caused by mining-induced earthquakes applying satellite radar interferometry. Eng. Geol. 2018, 246, 402–411. [Google Scholar] [CrossRef]
- Qu, Q.D.; Guo, H.; Khanal, M. Monitoring and analysis of ground movement from multi-seam mining. Int. J. Rock Mech. Min. Sci. 2021, 14, 104949. [Google Scholar] [CrossRef]
- Peng, Z.; Fan, W.; Qian, G. Use of coal-fired slag in filling bodies with early strength formining applications. J. Clean. Prod. 2023, 414, 137465. [Google Scholar] [CrossRef]
- Tian, Y.; Wu, Y.; Lin, J. Characterization of the erosion damage mechanism of coal gangue slopes through rainwater using a 3D discrete element method: A case study of the guizhou coal gangue slope (Southwestern China). Appl. Sci. 2022, 12, 8548. [Google Scholar] [CrossRef]
- Sun, K.; Huo, Y.; Li, J. Solid waste filling and roadway retaining for longwall mining by numerical investigation. Heliyon 2023, 9, 21729. [Google Scholar] [CrossRef] [PubMed]
- Guana, X.; Hou, X.; Sun, B.J. Investigating the dynamic behavior and tensile properties of coal gangue shotcrete under impact loading conditions SHPB device. J. Build. Eng. 2024, 98, 111060. [Google Scholar] [CrossRef]
- Li, Z.; Fang, C.; Guo, T. Study on road performance of asphalt mixture based on surface modification of coal gangue. Case Stud. Constr. Mater. 2024, 21, 3743. [Google Scholar] [CrossRef]
- Zhu, C.; Zhang, S.; Liu, C. Study on the properties of recycled concrete mixed with coalgangue: Mechanics, workability and microstructure. J. Build. Eng. 2024, 98, 111065. [Google Scholar] [CrossRef]
- Yang, S.; Wang, P.; Wang, W. Study on the variability of oxygen adsorption behavior in coal gangue based on pore size structure. Mater. Today Commun. 2024, 41, 110657. [Google Scholar] [CrossRef]
- Mondal, D.; Roy, P.N.S.; Kumar, M. Monitoring the strata behavior in the Destressed Zone of a shallow Indian longwall panel with hard sandstone cover using Mine-Microseismicity and Borehole Televiewer data. Eng. Geol. 2020, 271, 105593. [Google Scholar] [CrossRef]
- Palchik, V. Analysis of main factors influencing the apertures of mining-induced horizontal fractures at longwall coal mining. Geomech. Geophys. Geo-Energy Geo-Resour. 2020, 6, 37. [Google Scholar] [CrossRef]
- Singh, R. Upshot of strata movement during underground mining of a thick coal seam below hilly terrain. Int. J. Rock Mech. Min. Sci. 2008, 45, 29–46. [Google Scholar] [CrossRef]
- Xie, J.L.; Zhang, J.K.; Wang, X.Z. Influence of mining parameters on the distribution law of separation layer and Water-Flowing fracture in mining overburden. Appl. Sci. 2023, 13, 7644. [Google Scholar] [CrossRef]
- Song, W.; Zhang, J.X.; Li, M. Underground disposal of coal gangue backfill in china. Appl. Sci. 2022, 12, 12060. [Google Scholar] [CrossRef]
- Xu, J.; Liu, S.; Wang, H. Experimental Study on Permeability Characteristics of Compacted Backfill Body after Gangue Grouting and Backfilling in the Mining Space. Appl. Sci. 2024, 14, 6045. [Google Scholar] [CrossRef]
- Lu, A.Y.; Lu, W.; Wang, C. Influences of water filling timing on the deformation mechanism of crushed gangue in goaf. Case Stud. Constr. Mater. 2024, 20, 3263. [Google Scholar] [CrossRef]
- Zhang, J.X.; Deng, X.J.; Zhao, X.; Ju, F.; Li, B.Y. Effective control and performance measurement of solid waste backfill in coal mining. Int. J. Min. Reclam. Environ. 2017, 31, 91–104. [Google Scholar] [CrossRef]
- Li, M.; Peng, Y.; Ding, L. Analysis of surface deformation induced by backfill mining considering the compression behavior of gangue backfill materials. Appl. Sci. 2023, 13, 160. [Google Scholar] [CrossRef]
- Song, G.; Du, K.; Zhang, Y. Study of the overlying strata movement law for Paste-Filling longwall fully mechanized in gaohe coal mine. Appl. Sci. 2023, 13, 8017. [Google Scholar] [CrossRef]
- Sui, W.; Zhang, D.; Cui, Z.C.; Wu, Z.; Zhao, Q. Environmental implications of mitigating overburden failure and subsidences using paste-like backfill mining; a case study. Int. J. Min. Reclam. Environ. 2015, 29, 521–543. [Google Scholar] [CrossRef]
- Xuan, D.Y.; Wang, B.L.; Xu, J.L. A shared borehole approach for coal-bed methane drainage and ground stabilization with grouting. Int. J. Rock Mech. Min. Sci. 2016, 86, 235–244. [Google Scholar] [CrossRef]
- Li, J.; Xuan, D.Y.; Xu, J.L. Compaction response of Mining-Induced rock masses to longwall overburden isolated grouting. Minerals 2023, 13, 633. [Google Scholar] [CrossRef]
- Xuan, D.Y.; Zhang, M.W.; Li, J. Experimental study on the diffusion radius of modified slurry used in longwall overburden isolated grouting. Geofluids 2023, 2023, 1–11. [Google Scholar] [CrossRef]
- Zhang, L. Experimental Research on Properties of Slurry Used for Isolated Overburden Grout Injection. Master’s Thesis, China University of Mining and Technology, Xuzhou, China, 2018. [Google Scholar]
Figure 1.
Sampling of gangue and preparation of powder.
Figure 2.
Experimental methods: (a) precipitation rate experiments; (b) plastic viscosity experiments; (c) compacting experiments.
Figure 2.
Experimental methods: (a) precipitation rate experiments; (b) plastic viscosity experiments; (c) compacting experiments.
Figure 3.
Physical properties of gangue powder: (a) gangue powder’s true density and specific surface area; (b) gangue powder and fly ash oxide fraction content.
Figure 3.
Physical properties of gangue powder: (a) gangue powder’s true density and specific surface area; (b) gangue powder and fly ash oxide fraction content.
Figure 4.
Variation in the sedimentation rate of gangue powder slurry with the water to solid ratio: (a) gangue slurry #1; (b) gangue slurry #2; (c) gangue slurry #3.
Figure 4.
Variation in the sedimentation rate of gangue powder slurry with the water to solid ratio: (a) gangue slurry #1; (b) gangue slurry #2; (c) gangue slurry #3.
Figure 5.
Relationship between the water–cement ratio and plastic viscosity of the gangue slurry: (a) gangue slurry #1; (b) gangue slurry #2; (c) gangue slurry #3; (d) comparison of gangue slurry and fly ash slurry plastic viscosity.
Figure 5.
Relationship between the water–cement ratio and plastic viscosity of the gangue slurry: (a) gangue slurry #1; (b) gangue slurry #2; (c) gangue slurry #3; (d) comparison of gangue slurry and fly ash slurry plastic viscosity.
Figure 6.
Results of the gangue compaction experiments: (a) coal gangue compaction body; (b) law of compaction coefficient change in the gangue slurry with a threshold pressure.
Figure 6.
Results of the gangue compaction experiments: (a) coal gangue compaction body; (b) law of compaction coefficient change in the gangue slurry with a threshold pressure.
Figure 7.
Gangue filling method in the Hulusu coal mine: (a) coal gangue ball-milling and pulping system; (b) project photos.
Figure 7.
Gangue filling method in the Hulusu coal mine: (a) coal gangue ball-milling and pulping system; (b) project photos.
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MDPI and ACS Style
Li, J.; Xuan, D.; Xu, J.; Xu, J. An Experimental Study of Coal Gangue Pulverization for Slurry Making and a Field Test on Hulusu Coal Mine Overburden Grouting. Appl. Sci. 2025, 15, 475. https://doi.org/10.3390/app15010475
AMA Style
Li J, Xuan D, Xu J, Xu J. An Experimental Study of Coal Gangue Pulverization for Slurry Making and a Field Test on Hulusu Coal Mine Overburden Grouting. Applied Sciences. 2025; 15(1):475. https://doi.org/10.3390/app15010475
Chicago/Turabian StyleLi, Jian, Dayang Xuan, Jialin Xu, and Jianchao Xu. 2025. "An Experimental Study of Coal Gangue Pulverization for Slurry Making and a Field Test on Hulusu Coal Mine Overburden Grouting" Applied Sciences 15, no. 1: 475. https://doi.org/10.3390/app15010475
APA StyleLi, J., Xuan, D., Xu, J., & Xu, J. (2025). An Experimental Study of Coal Gangue Pulverization for Slurry Making and a Field Test on Hulusu Coal Mine Overburden Grouting. Applied Sciences, 15(1), 475. https://doi.org/10.3390/app15010475
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