Coal Water Research Articles

Chemical Evolution Process and Quality Assessment of Seepage Groundwater in Tunnel Crossing Gas-Bearing Coal Seams

The chemical characteristics of groundwater in the gas coal seam section of the tunnel have rich geological significance. To study the chemical evolution process and controlling factors of groundwater in the gas-bearing coal seam section of the tunnel, and the influence of tunnel coal removal on the groundwater quality, field investigations and laboratory experiments were carried out on the groundwater in the coal measure strata and the high-gaseous section and surrounding aquifers. Through hydrochemical analysis, correlation analysis, hydrochemical simulation, and other methods, the chemical origin of groundwater in coal measure strata and other aquifers was revealed. The water quality of groundwater was analyzed by water quality index (WQI), sodium adsorption rate (SAR), percentage of soluble sodium (Na+%), and participation of sodium carbonate (RSC). The results show that the water samples of each aquifer are weakly alkaline. Influenced by formation lithology and mineral redox reactions, the genesis of coal formation water is more complex than that of natural karst groundwater. The water chemistry characteristics show obvious differences among aquifer groups, with low correlation of HCO3-, Ca2+, and Mg2+. The central drainage ditch is dominated by dolomite dissolution, and the sloping shaft side ditch is dominated by calcite dissolution, and ion exchange effects are prevalent in different water sources. In terms of irrigation water quality, the permeability index (PI), magnesium hazard (MH), and Kelly index (KI) calculations show that 45.8% of the water samples are in the “unsuitable” condition. This study helps to fully understand the quality of coal seam water in tunnels and can provide a reference for groundwater utilization.

Nuclear Magnetic Resonance Experiment on the Influence of Confining Pressure on Spontaneous Imbibition of Water in Coal

Nuclear Magnetic Resonance Experiment on the Influence of Confining Pressure on Spontaneous Imbibition of Water in Coal

Study on Hydraulic Connection and Seepage Law of Goaf Groups in Coal Mine Underground Reservoir

A coal mine underground reservoir, composed of a large number of goaf groups, is effective in achieving the protective utilization of coal mine water. Mastering the hydraulic connection between the goaf groups and the law of seepage is the key to the design and safe operation of coal mine underground reservoirs. Coal/rock sample seepage tests were conducted in Wanli No. 1 Mine in the Shendong mining area according to the evolution law of the lateral supporting pressure of the coal pillars. From the tests, the function of vertical stress in relation to the permeability of coal/rock samples was obtained and the distribution law of permeability of porous media in the goaf was revealed. On this basis, the computational fluid dynamics (CFD) numerical calculation of seepage properties of the coal/rock pillars was conducted. The results show that with the decrease of water level in the goaf and the increase of coal pillar width, the flow range and flow velocity keep decreasing. At the water level of 18.65, 28.65, and 38.65 m, the critical coal pillar widths for the goaf water to penetrate into the adjacent goaf are 30, 50, and 70 m, respectively. When the coal pillar width is less than 10 m, the water can bypass the elastic core area at the bottom coal seam to the adjacent goaf area; when the width exceeds 20 m, the water cannot enter the adjacent goaf area through the bottom coal pillar. On the basis of CFD simulation study on seepage properties of coal/rock pillars between goafs, this paper conducts calculations for all the goafs in the 4-2 coal-panel block of Wanli No. 1 Mine and reveals the seepage path and seepage law in the underground reservoir of this mine.

Dynamic Prediction Method of 3D Spatial Information of Coal Mining Subsidence Water Area Integrated with Landsat Remote Sensing and Knothe Time Function

Subsidence water disaster has become a major problem to the ecological environment because of the submerged villages, farmland destruction, and ecological destructive changes in the mining subsidence area of high-water level. Taking the 1031 working face of Wugou Coal Mine in Huaibei, Anhui, China, as the research subject, (1) a three-dimensional (3D) spatial information dynamic prediction method was proposed for high-water-level coal mining subsidence areas by combining the Knothe time function based on the probability integration method (PIM) and the principle of water balance. (2) The dynamic evolution law of the water accumulation area in the high-water-level coal mining subsidence area was studied. (3) The applicability of the dynamic prediction model of the water accumulation range in the high-water-level coal mining subsidence area was verified. The results showed that the dynamic prediction of the 3D spatial information of the high diving area is highly accurate and can be suitable for the dynamic prediction by comparison with the results of remote sensing monitoring and field measurement. As a result, technical reference and theoretical basis for the comprehensive assessment and remediation of the ecological environment of the high diving mining subsidence area were proposed.

Evaluating water-yield property of karst aquifer based on the AHP and CV

In order to ensure the safety of mine production, it is of great practical significance to make a reasonable evaluation of the water-yield property (WYP) of a karst aquifer. In this paper, we selected fault-lines distribution, fault-scale index, aquifer thickness, water pressure, consumption of rinsing liquid, and hydraulic conductivity as the evaluation indexes to analyze the WYP of a karst aquifer. Meanwhile, the analytic hierarchy process (AHP) is used to calculate the subjective weight of indexes, and the coefficient of variation (CV) is used to calculate the objective weight of indexes. Combined with GIS, a multi-factor composite superposition is carried out to evaluate the WYP of a karst aquifer. The reliability of the research results is verified by the specific yield. Besides, for improving the reliability of evaluation results, the chemical composition of karst water was discussed. The results show that the selection of indexes is reasonable and the AHP–CV method is effective to evaluate the WYP of a karst aquifer. Therefore, on the premise of reasonable index selection, the evaluation models of AHP and CV can be used to evaluate the WYP of a karst aquifer and provide reference for coal mine water control measures.

Catalytic Ozonation for Effective Degradation of Coal Chemical Biochemical Tail Water by Mn/Ce@RM Catalyst

An Mn/Ce@red mud (RM) catalyst was prepared from RM via a doping–calcination method. Scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were used to characterize the surface morphology, crystal morphology, and elemental composition of the Mn/Ce@RM catalyst, respectively. In addition, preparation and catalytic ozonation conditions were optimized, and the mechanism of catalytic ozonation was discussed. Lastly, a fuzzy analytic hierarchy process (FAHP) was adopted to evaluate the degradation of coal chemical biochemical tail water. The best preparation conditions for the Mn/Ce@RM catalyst were found to be as follows: (1) active component loading of 3%, (2) Mn/Ce doping ratio of 2:1, (3) calcination temperature of 550 °C, (4) calcination time of 240 min, and (5) fly ash floating bead doping of 10%. The chemical oxygen demand (COD) removal rate was 76.58% under this preparation condition. The characterization results suggested that the pore structure of the optimized Mn/Ce@RM catalyst was significantly improved. Mn and Ce were successfully loaded on the catalyst in the form of MnO2 and CeO2. The best operating conditions in the study were as follows: (1) reaction time of 80 min, (2) initial pH of 9, (3) ozone dosage of 2.0 g/h, (4) catalyst dosage of 62.5 g/L, and (5) COD removal rate of 84.96%. Mechanism analysis results showed that hydroxyl radicals (•OH) played a leading role in degrading organics in the biochemical tail water, and adsorption of RM and direct oxidation of ozone played a secondary role. FAHP was established on the basis of environmental impact, economic benefit, and energy consumption. Comprehensive evaluation by FAHP demonstrated that D3 (with an ozone dosage of 2.0 g/H, a catalyst dosage of 62.5 g/L, initial pH of 9, reaction time of 80 min, and a COD removal rate of 84.96%) was the best operating condition.

Spontaneous imbibition in coal with in-situ dynamic micro-CT imaging

The gas/fluid flowing behavior and fluid distribution under capillary forces in porous media are essential for evaluating the pore-fracture characteristics of coal. Capillary force is crucial for flow-back efficiency after hydraulic fracturing during enhanced coalbed methane (CBM) production. In this work, in situ dynamic X-ray micro-computed tomography (X-ray μ-CT), field emission scanning electron microscopy (FE-SEM) combined with mercury intrusion porosimetry (MIP) were used on two coal samples of different wettability to explore the behavior of spontaneous imbibition. The results show that both pore-fracture and mineral content could affect the imbibition behavior of coal, which the former has played a major role. The spontaneous imbibition process can be divided into 4 stages to reveal fluid flow characteristics by the fluid distribution at different time steps. The gas relative permeability of coal attenuates exponentially with imbibition time result for capillary force based on fractal theory (the gas relative permeability reduces its value from 0.72 mD to 0.01 mD for WD, 0.5 mD to 0.08 mD for WZX). A low flow-back rate of fracturing fluid would lead to severe permeability damage. The longer the return drainage time, the more severe the permeability damage. • IEffect of pore-fracture and mineral on spontaneous imbibition was studied. • Spontaneous imbibition process was divided into four stages by studying the change of water in coal. • The gas relative permeability of coal attenuates exponentially with imbibition time result for capillary force.

Influence of coal mechanical properties and water content on generation characteristics of coal particles

Influence of coal mechanical properties and water content on generation characteristics of coal particles

Study on the effect of CO2–alkaline water two phase displacing gas and wetting coal

ABSTRACT To solve the deficiencies in the techniques of coal seam water injection and gas displacement, the new measure of CO2–alkaline water two-phase displacing gas and wetting coal was developed. A variety of corresponding experiments were conducted to investigate the effects and action mechanism of this method. The results showed that in comparison to the conventional coal seam water injection, after adopting this new measure, the fluid pressure in coal samples increased obviously and the pressure hysteresis phenomenon appeared. The water injection effects were improved distinctly. The water injection volume of DL, ZX, and XT coal samples increased 262%, 204%, and 356%, respectively. The increments of moisture content at 60 mm in three coal samples were 394%, 532%, and 461%, respectively. The wetting radius in three coal samples increased all more than 50%. The ground stress restrained the effect of water injection, while increasing the diameter of water injection borehole can effectively improve the water injection effect. Hence, this measure can significantly enhance the effects of water injection and better prevent the risk of gas outburst.

Effect of the Polymerized Titanium Ferric Sulfate (PTFS) Coagulant on Sedimentation of Coal Slime Water

High efficiency slime water settlement is very important for ensuring washing water recycling in coal preparation plants. In order to improve the sedimentation of coal slime water, an iron ion-based coagulant was prepared by titanium ion complexation action using titanium sulfate as a main raw material, Fe3+ and NaH2PO3 as a stabilizer and NaHCO3 as an alkalizing agent. The particle size distribution of coal slime was measured, and the sedimentation test for coal slime water was carried out with PAM, polyaluminum chloride and polymerized titanium ferric sulfate (PTFS), respectively. Then, coal slime water sedimentation was investigated at different PAM dosages and polyaluminum chloride or coal slime water of PTFS with various molar ratios of PAM and ferrotitanium. The results showed that PAM and polyaluminum chloride could not make coal slime settle down, and PTFS showed a poor settlement effect. When polyaluminum chloride and PTFS were used together with PAM, it produced a molecular weight of 3 million respectively. Polyaluminum chloride needs 6.66 × 10−10 mol of PAM, PTFS needs 0.66 × 10−10 mol of PAM and the effect of sedimentation is improved. When the molar ratio of PTFS was 1:7, polymerization performance was effective. The sedimentation effect of PTFS was better than that of polymeric aluminum chloride coagulant usually used in coal preparation plants, especially when combined with flocculant, and high efficiency was reached. The surface potential and surface free energy of coal slime particles before and after adding coagulant were measured and analyzed by XDLVO theory to explain the action mechanism of PTFS coagulant. Experimental results demonstrated that PTFS can significantly improve the sedimentation of coal slime water, save the dosage of PAM and increase economic benefit.

Effect of Cone-Plate Clarifier Structure Parameters on Flocculation Efficiency

In this study, a coal mine water flocculation system was established. A series of flocculation tests were carried out at different structural parameters (cylinder height, cone-plate insertion depth and cone-plate spacing) to better investigate the effect of the cone-plate clarifier on coal mine water treatment performance. Sixteen sampling points were set up in the system for data monitoring to generate the required data. The cone-plate clarifier was divided into five zones for flocculation analysis. The increased cylinder height facilitated the flocculation of particles in the micro flocculation zone and the settling of particles in the settlement zone. The chemicals used are polyaluminum chloride (PACl), Fe3O4 and polyacrylamide (PAM), corresponding to doses of 60 mg/L, 40 mg/L and 6 mg/L, respectively. Insufficient insertion depth of the cone-plate will cause the small flocs that have not been fully flocculated to enter the exit pipe zone directly through the cone-plate, while too much insertion depth will cause the large floc in the settlement zone to re-enter the exit pipe zone. The flocculation effect of small flocs increased as the cone-plate spacing decreased, which is consistent with the shallow pool theory. When the cone plate spacing was too narrow, the amount of fluid was reduced and the increase in fluid velocity reduced the flocculation effect. Curve fitting was conducted for Suspended solids(SS) and turbidity removal efficiency under each structural parameter to derive the variation of SS and turbidity removal efficiency under different structural parameters. The regression models of SS and turbidity removal efficiency on the cylinder height, cone-plate insertion depth and cone-plate spacing were established based on the curve fitting results, and the regression models were verified to be well fitted based on the comparison of experimental results. Finally, the optimal values of SS and turbidity removal efficiency were found based on the regression model. The flow rate of the cone-plate clarifier is 0.6 m3/h. The SS removal efficiency reached 96.82% when the cylinder height was 708 mm, the cone-plate insertion depth was 367 mm and the cone-plate spacing was 26 mm. The turbidity removal efficiency reached 86.75% when the cylinder height was 709 mm, the cone-plate insertion depth was 369 mm and the cone-plate spacing was 26 mm.

Experimental research on increasing effect of water injection in coal seam with chelating agent

ABSTRACT Coal seam water injection has a significant effect on the prevention and control of coal mine rock burst, and the pore characteristics of the coal seam is an important factor affecting the effect of coal seam water injection. With the deep mining of coal mine, the physical and mechanical properties of coal body change, the porosity of the coal seam decreases, and the injectability of the coal seam becomes worse. With the passage of time the minerals and CO2 in coal makes it more difficult to inject water. In order to obtain the reason why the water injection in coal seam becomes worse, the water injection additive with excellent performance is found, and a series of experiments on the impact tendency of coal body are carried out. The results show that the mine water used for coal seam water injection was liable to precipitate more ions, which may react with CO2 dissolved in water to form precipitates, plug coal pore and reduce the fluidity of water in the coal seam, resulting in poor water injection effect. Adding chelating agent IDS in aqueous solution can effectively prevent precipitation formed by the combination of easily precipitated ions and carbonate ions in it. At the same time, the chelating agent IDS can decompose precipitated ions from the surface of coal particles, change from insoluble to soluble, promote pore development, increase the effect of water injection and the pore diameter of the coal, and reduce hydrophobic groups on the coal surface. IDS can reduce the impact tendency of coal, and it is an environmental protection additive that can increase permeability. It can provide reference for prevention and control of composite power disasters by coal seam water injection.

Green strength properties of waterjet abrasive waste as potential composition in green mould by Taguchi and ANOVA approach

The sand casting process still continues today due to the cost-effectiveness of materials and processes. There is a wide variety of castings related to composition and size, but silica sand is widely available from coastal line mining and has a negative impact on the environment. Moreover, waste from waterjet cutting of non-ferrous and ferrous metals is practically unhazardous and may potentially be used in sand casting mould. The aim of this paper is to optimize the proportion of coal dust, water and bentonite added to the silica sand mixture and the waterjet cutting abrasive waste as a new way of handling waste with the potential to be used in sand casting manufacturing. The method used was L9 orthogonal array optimization and the composition was qualitatively measured using a green compression strength test and a green shear strength test. Factors were evaluated using the analysis of variance (ANOVA) to find the the critical factors while confirmation test was conducted for the optimal material proportion. The study concluded that the ideal ratio for silica sand mixture with waterjet abrasive waste is bentonite-12%, coal dust-5%, and water-7% for green compression strength while bentonite-12%, coal dust-6%, water-7% for green shear strength. With proper selection, the incorporation of waterjet abrasive waste into the green sand mixture is promising to potentially be used in green sand mould casting without undermine the quality of mould.

STUDY ON SEEPAGE CHARACTERISTICS OF FRACTAL-LIKE TREE NETWORK STRUCTURE IN WATER-INJECTED COAL FRACTURE UNDER STRESS

The study of water seepage characteristics in coal fracture networks is the key for accurately guiding the development of coal seam water injection technology. Based on the fractal geometry theory, we represented the shape of a fracture network in a water-injected coal body through a tree branch network; furthermore, we established a seepage model for the fracture network, determined the relationship between permeability, overburden pressure, and water pressure according to the relationship between fractal dimension and effective stress, and verified the applicability of the proposed model through a self-developed experimental system. This model was developed based on the “penny-shaped” single-fracture seepage model and did not contain any empirical constants. The results showed that the influence weight of the fracture diameter ratio ([Formula: see text] on permeability was the highest: when [Formula: see text], the permeability was almost 0, but when [Formula: see text], the permeability increased rapidly. Notably, the local and overall permeabilities of the fracture network decreased with the increase of the radial distance; when the radial distance was constant, however, the permeability of the fracture network decreased with the increase of the bifurcation series (m) and of the fracture radius. Lastly, the ratio of gap depth to length increased with the increase of the ratio of fracture depth to length ([Formula: see text]. Overall, our research results provide a theoretical basis for defining the seepage law of high-pressure water in coal bodies, as well as the relationship between permeability and several environmental parameters.

Combined Treatments of Underground Coal Slurry: Laboratory Testing and Field Application

During the coal mining process, underground water is generated from the longwall face. In the meantime, the coal cutting process would produce coal particles. Coal slurry is generated in the underground working site, especially for water abundant coal mines. The generated coal slurry is treated to prevent water pollution. Due to the extensively existing of the suspended solid, the traditional process method would often introduce new problems. In this study, laboratory testing was conducted to investigate the characteristics, including the particle size distribution of the coal sludge, coal slurry compositions, slurry viscosity and coal mine water quality. In order to improve the coal slurry treatment efficiency, based on the laboratory results, a novel combined treatment of underground coal slurry is proposed. First, the coarse grained coal slurry is process by a vibrating screening machine. Then, the coal slurry containing fine coal powders is processed through a settling pond. The sedimentation results of the coal solid materials are analyzed. The polymer flocculant is also added into the coal slurry to improve the sedimentation. These combined treats of the coal slurry significantly remove the suspended solid and improve the quality of the coal mine water. Based on the laboratory testing, the specific details of the field applications are designed. The key novelty of this paper is the underground background. All of these treatments are based on the underground environment and are capable of being applied in underground workings. From field applications and observations, these novel combined treatments of coal slurry in the underground site are effective. This study provides a novel method to treat the coal slurry, which has innovations from engineering aspect. These procedures are useful for the underground coal slurry treatment, especially for water-abundant coal mines. The normal coal production is guaranteed and less affected by the coal slurry discharge process. Meanwhile, the water pollution problem is much addressed and the damage of coal slurry to the environment is reduced.

Effects of water on pyridine pyrolysis: A reactive force field molecular dynamics study

The emission of nitrogen oxides (NOx) from coal combustion causes serious environmental problems. Fuel splitting and staging is a promising method for NOx control by combustion modification. In this process, nitrogen-containing compounds generated from pyrolysis gas play an important role in regulating NOx generation. Water from coal could potentially change reactions during the coal pyrolysis process. Adjusting the content of water in coal may be an effective way to control coal pyrolysis reactions. This work aims to investigate the effects of water on pyridine (a main nitrogen-containing compound in coal) pyrolysis via reactive force field (ReaxFF) molecular dynamics (MD) simulations. Results indicate that the addition of water during the pyridine pyrolysis process increases the number of OH radicals in the system and accelerates the consumption of pyridine at the initial stage. However, at a later stage, water inhibits the consumption of pyridine as it impedes the condensation reaction of pyridine molecules. Common and unique intermediates are identified and quantified under various water-content conditions. Results suggest that water also reduces the proportion of nitrogen atoms in the polycondensation product. Furthermore, ring opening processes of pyridine molecules are reproduced at the atomic level. The changes in reaction pathways due to the presence of water are also revealed. The new insights into the mechanisms of pyridine pyrolysis under water and water-free conditions provide a possibility to control nitrogen migration during the pyrolysis process, which is of great significance to emission reduction from coal combustion.

Study on the reactivity of oxygen-containing functional groups in coal with and without adsorbed water in low-temperature oxidation

The form of water adsorbed in coal was analyzed, and the effect of adsorbed water on the low-temperature oxidation of coal was investigated. A dynamic vapor sorption analyzer and a specific surface and pore analyzer was used to analyze water diffusion/sorption processes and oxygen adsorption, respectively. Quantum chemical calculations were carried out to analyze H abstraction from oxygen-containing functional groups by O2. With increasing relative pressure, the manifestations of adsorbed water in coal are as follows: sequential adsorption at primary sites (44%), adsorption at secondary sites (34%), the formation of water clusters (5%), and micropore filling (17%). The moisture content in coal reaches a critical value with the maximum adsorption of oxygen when the air humidity is approximately 55%. Reactions of hydroxyl, carbonyl, and carboxyl groups with oxygen need to overcome energies of 70.89, 68.26, and 84.02 kJ/mol, have associated heat releases of 86.64, 128.65, and 170.66 kJ/mol, and rate constants of 4.622 × 104, 1.924 × 103, and 3.334 s−1m−1, respectively. When water participates in these reactions, the energies to overcome are increased to 97.14, 76.14, and 120.77 kJ/mol, the associated heat releases are 154.91, 123.40, and 322.94 kJ/mol, and the rate constants are 6.668 × 102, 6.641 × 10−4, and 4.169 × 10−7s−1m−1, respectively. The respective functional groups show lower reactivity with adsorbed water. Therefore, the adsorption of water increases the reaction of aliphatic structures/carbon free radicals with oxygen to promote free radical chain reactions, and also plays a role through the heat of wetting in the initial stage of the spontaneous combustion of coal.

Analysis on Rock Burst Risks and Prevention of a 54 m-Wide Coal Pillar for Roadway Protection in a Fully Mechanized Top-Coal Caving Face

A case study based on the 401103 fully mechanized caving face in the Hujiahe Coal Mine was carried out in this research to analyze the rock burst risks in a 54 m-wide coal pillar for roadway protection. Influencing factors of rock burst risks on the working face were analyzed. Stress distribution characteristics on the working face of the wide coal pillar for roadway protection were discussed using FLAC3D numerical simulation software. Spatial distribution characteristics of historical impact events on the working face were also investigated using the microseismic monitoring method. Results show that mining depth, geological structure, outburst proneness of coal strata, roof strata structure, adjacent mining area, and mining influence of the current working face are the main influencing factors of rock burst on the working face. Owing to the collaborative effects of front abutment pressure of the working face and lateral abutment pressure in the goaf, the coal pillar is in the ultimate equilibrium state and microseismic events mainly concentrate in places surrounding the coal pillars. Hence, wide coal pillars become the regions with rock burst risks on the working face. The working face adopts some local prevention technologies, such as pressure relief through presplitting blasting in roof, pressure relief through large-diameter pores in coal seam, coal seam water injection, pressure relief through large-diameter pores at bottom corners, and pressure relief through blasting at bottom corners. Moreover, some regional prevention technologies were proposed for narrow coal pillar for roadway protection, including gob-side entry, layer mining, and fully mechanized top-coal caving face with premining top layer.

Adsorption of Ca(II) and K(I) on the kaolinite surface: a DFT study with an experimental verification

The clay minerals have a negative influence on the settlement of coal tailings, and the addition of metal cations has a positive effect on treating coal tailings water. Microscopic adsorption mechanism of Ca(II) and K(I) on kaolinite surface was investigated by means of density functional theory (DFT) calculations and Monte Carlo method. The structures of Ca(II) and K(I) adsorption on kaolinite (001) and (00−1) was obtained, with Mulliken bond populations and binding energies calculated. Ca(II) adsorbed on kaolinite (001) surface and K(I) adsorbed on (00−1) surface are their main products, respectively, and the binding energies of all the adsorption products of Ca(II) are higher than those of K(I). Partial density of states projections combining with Mulliken bond charge and populations indicate that Ca−O and K−O bonds of the adsorption products are dominated by ionic interaction. Cation hydration can make the adsorption occurs more easily and enhance the covalent interaction of the bonds. The adsorption experiment verifies that Ca(II) is easier to adsorb on kaolinite than K(I).

Experimental Study of Hysteresis Characteristics of Water-Sediment Mixture Seepage in Rock Fractures

The hysteresis of water-sediment mixture seepage in rock fractures is one of the critical factors which affect the determination of the timing of coal mine water inrush disasters prevention and control. In this paper, a mechanical model was established to study the hysteresis whose criteria were also put forward. The area of the hysteresis loop and the maximum pressure gradient were selected as characterization parameters of hysteresis. On this basis, an experimental system was established to study influences of different sand particle size, sand mass concentration, and fracture opening on water-sediment mixture seepage in rock fractures. The results indicated that the increase in the sand particle size and sand mass concentration could effectively enhance hysteresis characteristics of specimen fractures. While hysteresis characteristics decreased significantly with the increase of fracture opening. The research results are useful to prevent and control water inrush disasters of coal mine.