Study on the two-phase coupling migration mechanism of deceleration aggregate and water in coal mine water inrush channel | Scientific Reports

Apr 06, 2025

Scientific Reports volume 15, Article number: 11702 (2025) Cite this article

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Currently, perfusing deceleration aggregate is the most effective way to create water-blocking sections for controlling coal mine water inrush disasters. Clarifying the two-phase coupling migration mechanism of deceleration aggregate and water in coal mine water inrush channels is the key to quantitatively determining the deposition and migration distance of aggregate after entering the water inrush channel from the perfusion hole. Based on fluid mechanics, slurry pipeline transportation theory and sediment dynamics, this paper categories the entire migration process of aggregate entering the water inrush channel from the perfusion hole into three motion stages: free fall, curved-throwing, and sliding. The motion and force characteristics of each stage are analyzed, and a theoretical model for single-aggregate sedimentary migration is established. The CFD-DEM method is used to establish a transient bidirectional coupling numerical calculation model of aggregate-water to verify the theoretical model (overall error not exceeding 10%). Finally, based on this research, reasonable suggestions are proposed for the actual engineering of plugging by perfusing deceleration aggregate.

In recent years, affected by the depth of coal mining1,2, complex hydrogeological conditions have led to an increasingly frequent occurrence of coal mine disasters3,4, especially the water inrush disasters5. When water inrush occurs in the roof and floor or working face of a coal mine6,7,8,9, the nearby low-lying channels are completely flooded10, and the parts through which water flows are prone to roof fall or collapse11,12,13. If emergency rescue and disaster relief are not carried out in a timely manner, the mine work safety will be seriously affected.

In the traditional coal mine water inrush disaster management: Although underground drainage14 can handle routine water flow, it often fails to respond promptly to emergency water inrush situations due to limited drainage capacity. This kind of method has the disadvantages of high energy consumption in drainage and secondary disasters easily induced by long-term operation15,16, so it can only play a part of mitigation role in actual projects, which belongs to passive response17. In recent years, the newly developed water-blocking materials such as Polyurethane18 and Nano-adhesive19 have the characteristics of rapid curing and active water plugging, but they are rarely used in emergency engineering because of their high economic cost and the defects that they are easy to be eroded and invalid under high flow rate20. By comparison, the physical method of using local materials to perfusion deceleration rock aggregate to establish “water-blocking section” to turn the pipeline flow into seepage flow21,22, and then grouting to complete the plugging is the fastest response23, the lowest economic cost, and the most effective velocity-reduction and flow-interception control method for such disasters. Among them, clarifying the migration mechanism of aggregate in the water inrush channel is the foundation for efficiently establishing a water-blocking section24. Scholars at home and abroad have conducted extensive research in this area: Yu Wang et al.25 simulated the water-inrush prevention and control of the 1841 working face of Desheng Coal Mine and drew the fundamental conclusion that when a large number of aggregate enters and accumulates in the water inrush channel, the pipeline flow in the water inrush channel would be transformed into seepage flow. Ravelet et al.26 conducted visualization experiments on the hydraulic conveying of spherical aggregate in horizontal pipes and the influence law of aggregate size and mass on its movement process under the action of horizontal dynamic water was obtained. Lei Zhang et al.27 summarized the correlations of 24 drag coefficients in granular flow, established a calculation formula for the critical velocity in particle transitional flow, and analysed the effects of particle density and size as well as fluid density and viscosity on its critical velocity. Yingchao Wang et al.28 investigated the migration process of small particles in rock faults under water inrush conditions. The Discrete Element Method (DEM) was used to analyse the characteristics of the movement of particles of different sizes under different dynamic water conditions. Gailing Zhang et al.29 conducted model experiments on reducing the flow velocity in water-inrush channels by perfusing aggregate, and determined through data analysis that the factors affecting the aggregate deposition process were aggregate diameter, dynamic water velocity, and solid-water mass ratio in order. Lin Mou et al.30 established a numerical model (CFD-DEM) for the process of aggregate interception and water-blocking, summarizing the general accumulation laws of aggregate entering the water-inrush channel through perfusion holes, including “early-stage sequencing”, “post stacking”, and “reverse growth”. Shang Hui et al.31 conducted experimental research on various working conditions of water shutoff with porous combined perfusing aggregate for decelerating and water-blocking in mine water inrush channels, and determined the basic criteria for perfusing aggregate to plug horizontal and inclined water inrush channels. Kangwei Lai et al.32 carried out physical experiments on the sedimentary movement state of coarse aggregate in horizontal water inrush channels and expounded on the relationship between their movement state and the instantaneous pressure, average pressure, and fluctuating pressure of the pipeline. Peili Su et al.33 investigated the mechanism of aggregate accumulation and growth during downhole dynamic water plugging construction, proposing an analytical calculation method that divides the process of aggregate settlement and accumulation into a stacking process of granular layers with a certain thickness.

In summary, current research on the two-phase coupling migration mechanism of deceleration aggregate and water in coal mine water inrush channels mainly focuses on indoor model experiments and numerical simulations to qualitatively describe the aggregate migration process and evaluate the water-blocking effect of the water-blocking section. There are limited researches on quantitative analysis of the full spatiotemporal migration law of aggregate after they enter the water inrush channel from the perfusion hole, and the internal migration mechanism of aggregate and water is unclear. In view of this, this paper employs fluid mechanics34, slurry pipeline transportation theory35, and mechanics of sediment transport36 to analyse the force characteristics and migration mechanism of aggregate under dynamic water condition. Theoretical calculation models for the deposition and migration of a single aggregate in water inrush channels are established in stages. Finally, a two-way coupling numerical calculation model of aggregate and water is established by using CFD-DEM to verify the applicability of the theoretical model37, aiming to provide a scientific basis for the construction of perfusing deceleration aggregate in coal mine water inrush disasters.

After a large-scale water inrush disaster occurs in the coal mine, through the directional Roadway Drilling of the ground construction, the aggregate is rapidly perfused into the water inrush channel to reduce the flow velocity. When the aggregate can be effectively retained to form a water blocking section, grouting can be carried out to complete the water plugging. In order to clarify the two-phase coupling migration mechanism of deceleration aggregate and water, this chapter selects a section of the water inrush channel with relatively stable flow velocity when water inrush occurs in the coal mine, and sets up a perfusion hole above it. Through the stress analysis of the complete migration process of the perfused aggregate under dynamic water conditions, the theoretical migration model in the water inrush channel is established.

Under dynamic water condition, the entire movement process of aggregate in water inrush channel in coal-rock masses can be divided into three stages: in stage I, aggregate undergo free fall motion within the perfusion hole and enter the water inrush channel of coal-rock mass until they contact the water; in stage II, after the aggregate comes into contact with the water flow, it undergoes curve throwing motion and settling from the water inrush surface to the bottom of the channel; in stage III, the aggregate in the bottom of water inrush channel will remain stationary after sliding for a certain distance under the joint action of its own gravity, water thrust and friction resistance.

Considering the complexity and randomness of the deceleration aggregate migration and force in water inrush channel under dynamic water condition, in order to simplify the theoretical calculation and analysis of the entire movement process, the following basic assumptions are made regarding various influencing factors: the movement of aggregate in the water inrush channel belongs to the problem of solid-liquid two-phase pipe flow; negligible infiltration of water inside the water inrush channel to the outside of the channel; the water within the water inrush channel is isotropic and incompressible; compared to the water inrush channel, the width of the perfusion hole is extremely small and can be neglected, and it is assumed that water will not come out of the perfusion hole; the aggregate to be perfused can be regarded as spheres with uniform mass; before the aggregate enters the perfusion hole but has not come into contact with the water, it undergoes free fall motion (ignoring the influence of air resistance and the mutual collision between aggregate); the dynamic water velocity in the channel is relatively fast and the flow regime is turbulence (Reynolds number Re > 4000)38; after the aggregate entering water inrush channel to form a water-blocking section, the dynamic water velocity in the channel decreases, the viscosity increases, and the flow regime transitions between laminar flow and turbulent flow (Reynolds number 2100 < Re < 4000); the interior of the water inrush channel is regarded as a uniform plane with the same friction coefficient everywhere.

Under dynamic water condition, the entire migration process of the deceleration aggregate entering water inrush channel through the perfusion hole until it is deposited at the bottom is shown in Fig. 1.

Schematic diagram of the entire migration process of aggregate in water inrush channel.

Stage I: aggregate moves in free fall motion inside the perfusion hole. The detailed movement and force conditions of aggregate are shown in Fig. 2.

Schematic diagram of the movement and force of aggregate in stage I.

The self-gravity Gs of spherical aggregate is shown in Eq. (1) as follows:

In the equation: ρs is the density of aggregate, kg/m3; Vs is the volume of spherical aggregate, m3; g is the acceleration due to gravity, 9.8 m/s2; ds is diameter of spherical aggregate, m.

The distance for the aggregate to fall freely in stage I is hI(D), the time is \(t_{{{\text{I(D)}}}} {\text{ = }}\sqrt {2h_{{I(D)}} /g}\), and the instantaneous velocity when it contacts water at the end of free fall motion is \(v_{{{\text{I(S)}}}} {\text{ = }}\sqrt {2gh_{{{\text{I(S)}}}} }\).

Stage II: aggregate enters the water inrush channel at a certain initial velocity and comes into contact with the water, it undergoes curved-throwing motion under the dynamic water conditions. The detailed movement and force conditions of aggregate are shown in Fig. 3.

Schematic diagram of the movement and force of aggregate in stage II.

Drag force of water flow FD39 is shown in Eq. (2):

In the equation: CD40 is the water resistance coefficient (a function related to Reynolds number = ωds/v); ρw is the density of water, kg/m3; µrx is the relative horizontal velocity between the water flow and the aggregate in the x-direction, m/s; S is the water-facing area of aggregate m2; vwx is the horizontal velocity of water in the x-direction, m/s; vsx is the horizontal velocity of aggregate in the x-direction, m/s.

The additional mass force Fm41 is shown in Eq. (3):

In the equation: tII(D) is the movement time of aggregate in stage II.

The Basset force is FB42 is shown in Eq. (4):

In the equation: µ is the dynamic viscosity of water flow, with the unit of Pa s.

Effective gravity Ge is shown in Eq. (5):

The lifting force FL43 is shown in Eq. (6):

In the equation: µry is the relative vertical velocity between the water flow and the aggregate in the y-direction, m/s; vwy is the vertical velocity of water flow in the y-direction, m/s; vsy is the vertical velocity of aggregate moving in the y-direction, m/s.

The Magnus force FM44, is shown in Eq. (7):

In the equation: ω is the rotational angular velocity of the aggregate, in rad/s.

The Saffman shear lift force FS45 is shown in Eq. (8):

In the equation: ∂vwyH/∂y is the velocity gradient of water flow at the cross-section it flows through.

When the aggregate is initially in contact with the water flow, the direction of the resultant force changes under the action of water flow. The specific situation is shown in Fig. 4.

Schematic diagram of velocity and resultant force when aggregate is initially contact with water.

Under ideal conditions, the water flow direction in the water inrush channel is the same everywhere. When the aggregate is initially in contact with the water flow, its motion should be a concave curved-throwing motion. The direction of this motion is within the angle range between the vertical downward velocity v(D) and inclined downward force FJ, and tends to the direction of the combined force FJ. With the direction of motion changes, the subsequent type of motion is changed into a convex curve throwing motion. The motion trajectory is shown in Fig. 5.

Schematic diagram of aggregate motion trajectory under ideal condition in stage II.

However, due to the connection between the perfusion hole and the water inrush channel, and under the influence of high-water pressure in the dynamic water conditions at the connection point, the flow field at the orifice is relatively complex. It does not flow directly from one side to the other; instead, a concentrated surging phenomenon occurs. The specific situation is shown in Fig. 6.

Schematic diagram of concentrated surging of water flow at the connection between the perfusion hole and the water inrush channel.

In actual situations, due to the fast flow velocity in the water inrush channel and concentrated surging of water flow at the connection point, the velocity direction of aggregate changes rapidly. There is no small-distance concave curved throwing motion in the ideal state as shown in Fig. 5. Instead, it directly enters the convex curved throwing motion stage. Therefore, to be closer to the actual situation and facilitate subsequent analysis, the overall motion of aggregate in stage II is regarded as convex curved throwing motion.

Establish the relevant B.B.O balance equation: The vector sum of the forces on a single aggregate is equal to its mass multiplied by acceleration, as follows:

Substituting the horizontal force FD, Fm, and FB in Eqs. (2–4) into Eq. (9) and ignoring the extremely small force acting on the aggregate in the x-direction, it can be obtained that:

Substituting the boundary condition \(v_{{sx}} |_{{tII\left( D \right) = 0}} = 0\) into the above equation, integrating and solving gives the horizontal migration velocity vsx of the aggregate along the x-direction in stage II as:

Let vsx=dXII/dtII(D), and substitute the boundary condition XII|tII(D)=0 = 0 into Eq. (11). Integrate and resolve to obtain the expression for the horizontal migration distance XII of the aggregate in stage II as:

Establish the vertical-direction mechanical equilibrium equation:

Substituting the force Ge, FL, FMH, and FSH in Eqs. (5–8) into Eq. (13) and ignoring the extremely small force acting on the aggregate in the vertical direction, it can be obtained that:

Substituting the boundary condition \(v_{{sy}} {\text{|}}_{{{\text{tII(D)}}}} \;{\text{ = }}\;{\text{0}}\;{\text{ = }}\;\sqrt {2gh_{{{\text{I(D)}}}} }\) into the above equation, integrating and simplifying, the vertical migration velocity of aggregate along the y-direction in stage II can be obtained. To simplify the expression, let \(A = \sqrt {4d_{s} g(\rho _{s} - \rho _{w} )/3C_{D} \rho w}\), and the expression of vsy can be obtained that:

The vertical movement velocity of water along the y-direction is extremely small compared to the horizontal movement velocity of water along the x-direction and can be ignored. Let vsy = dYII/dtII(D), and substitute the boundary condition YII|tII(D)=0 = 0 into Eq. (15). After arranging and integrating, the expression for the vertical migration distance YII of aggregate along the y-direction in stage II can be obtained as:

Equation (16) yields the expression for migration distance YII of aggregate in y-direction and movement time tII(D) in stage II. Combining the height H of water inrush channel obtained by actual condition measurement46, it can be substituted into equation to find the movement time tII(D) of aggregate in stage II. Then substituting tII(D) into Eq. (12), the migration distance of aggregate in x-direction can be calculated.

The migration distances of the aggregate in the horizontal and vertical directions in stage II in the water inrush channel are respectively:

Stage III: the aggregate at the bottom of water inrush channel is affected by friction, and their velocities gradually decreases until they come to a standstill, with a straight trajectory. The detailed migration and force conditions are shown in Fig. 7.

Schematic diagram of the movement and force of aggregate in stage III.

According to the of kinetic-energy theorem, the equilibrium equation is listed as follows:

In the equation, \(\bar{F}_{{\text{D}}}\) and \(\bar{F}_{{\text{L}}}\) are respectively the mean values of the water flow drag force FDH and the upward force FLH, where:

The vertical movement velocity vsy of the aggregate is extremely small and can be ignored. Therefore, Eq. (18) can be simplified to Eq. (21):

vsx1, the initial velocity of the aggregate in the horizontal direction in stage III, is equal to vsx, its velocity in the horizontal direction in stage II, that is:

Substituting Eqs. (19 and 22) into Eq. (21), the displacement XIII of aggregate in the horizontal direction in stage III can be obtained that:

The migration distances of the aggregate in the horizontal and vertical directions in stage III in the water inrush channel under dynamic water conditions are respectively:

Utilize variance and range analysis methods to conduct a parametric analysis of the parameters included in the calculation formulas Eqs. (17) and (24) for the horizontal and vertical migration distances of decelerated aggregates in the water inrush channel in stage II and III.

Among them: the water inrush channel height did not show significance, and it would not have a differential influence on migration distance XII and XIII in stage II and III; the aggregate density, diameter and the dynamic water flow velocity showed significance, and they would have a differential influence on migration distance XII and XIII in stage II and III. The primary and secondary order of factors influencing the aggregate’s migration distance in stage II in the water inrush channel is: dynamic water flow velocity > aggregate density > aggregate diameter > water inrush channel height. In stage III is: dynamic water flow velocity > aggregate density > aggregate diameter > water inrush channel height. The water inrush channel height and dynamic water flow velocity are positively correlated with the migration distances XII and XIII in stage II and III, while the aggregate density and diameter are negatively correlated with migration distances XII and XIII of stage II and III.

The computational method of transient bidirectional coupling simulation of CFD-DEM is used47. Firstly, Fluent is used to calculate the flow field of the fluid at a certain time state until it is stable (Eulerian method). Secondly, the flow field information is converted into the external forces acting on each solid particle in DEM (Lagrange method). Finally, the migration (force, velocity, and position) of the calculated aggregate is updated, and a numerical model of the migration of deceleration aggregate in water inrush channel is established to verify the results obtained from the theoretical calculation models in previous text.

In conjunction with the parameter analysis approach, a numerical model is established to simulate the entire migration process of the deceleration aggregate within the water inrush channel in the theoretical model. The cross sectional size of the rectangular channel of the coal-rock mass is generally 5 m×4 m. Based on the actual engineering situation and the theoretical calculation results, the numerical simulation experiment takes three times the width of the perfusion hole (0.6 m) as one calculation unit and sets the fluid calculation domain in a 1:1 ratio. The detailed dimensions are shown in Fig. 8. The fluid calculation domain is divided by using unstructured cubic meshes, and the mesh size is 40 mm.

Numerical model of deceleration aggregate perfusion in water inrush channel.

The previous text has proposed the ideal assumption that the aggregate enters the water inrush channel through free fall motion in the perfusion hole. Therefore, in order to avoid the complex calculations of solid-liquid-gas three-phase coupling, the perfusion hole is set as a virtual particle factory (0.2 m × 0.2 m) that can automatically generate aggregate in the simulation process. This paper focuses on the research of the motion trajectory of a single aggregate. During the simulation experiment, the particle factory is set to generate 100 spherical aggregate with an initial velocity of – 1 m/s (in the Z-direction) per second to ensure that the simulation results are statistically significant.

In DEM, the Hertz-Mindlin (no slip) “soft-sphere” model is selected for the contact and collision between aggregate48, and the Gidaspow model, which is suitable for multiphase flow and can capture dynamic characteristics more accurately, is used for drag force calculation49. In Fluent, the dynamic water flow velocity is set to 0.5 m/s; the material parameters of aggregate are set according to Table 1.

In actual engineering, the dynamic water flow velocity and the height of water inrush channel as objective conditions cannot be changed, and the aggregate density and diameter can be controlled mutually. Therefore, in the simulation, only the density with a higher degree of influence is used to verify the control process of the migration of aggregate in the water inrush channel.

The aggregate with three densities from small to large is provided in the above material parameter table. The calculation results of the migration numerical model of the aggregate with the intermediate density of 2600 kg/m3 in the water inrush channel is shown in Fig. 9.

The simulation calculation results of the migration and accumulation of deceleration aggregate.

The calculation result of numerical simulation is used to verify the theoretical model: (1) In stage II, the aggregate enters the water inrush channel at a speed of – 1 m/s, which is consistent with the analysis of their motion trajectory under the ideal condition in the previous text. They accelerate in the horizontal x-direction and decelerate in the vertical y-direction. Overall, they first perform a concave curved-throwing motion and then a convex curved-throwing motion, and sink to the bottom after 6.4s. The aggregate that subsequently enter the water inrush channel is affected by the sedimentation of the previous aggregate on the flow field, and they perform convex curved-throwing motion as a whole. (2) After the aggregate completes the paving of the first layer, the front section particles decelerate under the influence of frictional resistance, slide for a certain distance and then tend to become stationary. The subsequently newly-settled aggregate forms the second layer, which is not in direct contact with the water inrush channel, and there are gaps between the particles, resulting in less resistance and relatively slow deceleration. Eventually, an accumulation body with a compact front section and a rear section is formed as a whole.

The comparison of the migration distances in the horizontal direction in stage II of aggregate with densities of 2200 kg/m3, 2600 kg/m3, and 3000 kg/m3 and the same diameter (15 mm) under the same engineering conditions is shown in Fig. 10.

A comparison diagram of throwing distances of aggregate with three densities in stage II.

In the stage II: aggregate with a density of 2600 kg/m3 moves horizontally for a distance of 1.14 m (Eq. 17) the theoretical calculation result is 1.23 m, with an error of 7.3%); aggregate with a density of 2200 kg/m3 moves horizontally for the distance of 1.49 m (Eq. 17) the theoretical calculation result is 1.58 m, with an error of 5.7%) is farther than that of aggregate with a density of 2600 kg/m3; aggregate with a density of 3000 kg/m3 moves horizontally for the distance of 0.86 m (Eq. 17) the theoretical calculation result is 0.94 m, with an error of 8.5%) is closer than that of aggregate with a density of 2600 kg/m3. The errors between the above three groups of numerical simulation experiments and the theoretical calculation results do not exceed 10%. In addition, by comparing three experimental groups, it can be found that when the diameter of aggregate and other engineering conditions remains unchanged, as the density increases, the horizontal migration distance of aggregate in stage II also increases.

The comparison of migration and accumulation distances in stage III of aggregate with densities of 2200 kg/m3, 2600 kg/m3, and 3000 kg/m3 and the same diameter (15 mm) under the same engineering conditions is shown in Fig. 11. In stage III: the sliding distance of aggregate with a density of 2600 kg/m3 is 0.72 m (Eq. 24) the theoretical calculation result is 0.76 m, with an error of 5.3%); the sliding distance of aggregate with a density of 2200 kg/m3 is farther than that of aggregate with a density of 2600 kg/m3, is 1.09 m (Eq. 24) the theoretical calculation result is 1.14 m, with an error of 4.4%); the sliding distance of aggregate with a density of 3000 kg/m3 is closer than that of aggregate with a density of 2600 kg/m3, is 0.38 m (Eq. 24) the theoretical calculation result is 0.41 m, with an error of 7.3%). The errors between above three groups of numerical simulation experiments and the theoretical calculation results do not exceed 10%. In addition, by comparing three experimental groups, it can be found that when diameter of aggregate and other engineering conditions remains unchanged, as the density increases, the sliding distance of aggregate in stage III also increases.

A comparison diagram of migration distances of aggregate with three densities in stage III.

The calculation of the migration distance of aggregate by the theoretical model (Eqs. 18 and 25) can be used to preliminarily estimate the throwing distance of aggregate in stage II and the effective length of the water-blocking section in stage III in actual engineering.

Based on the theoretical calculation models of the deposition and migration of aggregate in the water inrush channel, combined with the numerical simulation results, relevant discussions are put forward for the construction methods of the deceleration aggregate perfusing and plugging project:

When the dynamic water flow velocity and the water inrush channel height are big (the condition of high flow velocity and large cross-section), the migration state of aggregate entering the water inrush channel is mainly dominated by the stage II. For this working condition, in order to ensure that the perfused aggregate do not block the holes, it is recommended to first perfuse aggregate with larger aggregate diameters and densities at a low speed. After the water flow around the perfusion holes is decelerated for a short time, then perfuse aggregate with smaller diameters and densities at a high speed to achieve rapid capping, providing basic conditions for plugging by later grouting.

When the dynamic water flow velocity is big and the water inrush channel height is small (the condition of high flow velocity and small cross-section), since the flow velocity is the mainly influencing factor for the horizontal migration in the stage II, the entire movement process is still dominated by the migration in the stage II. The relevant analysis is the same as before and will not be repeated.

When the dynamic water flow velocity is small and the water inrush channel height is big (the condition of low flow velocity and large cross-section), after the aggregate enter the water inrush channel, their migration is predominantly characterized by Stage III movement. For this working condition, the perfusion plan focuses on ensuring the density of aggregate, and the aggregate diameter can be determined according to the specific construction requirements. If rapid plugging is required, it is recommended to select aggregate with smaller diameters. Although it is impossible to minimize stage III migration distance, which partially loses the water blocking efficiency in a disguised form, the aggregate can be perfused at a higher speed, enabling them to quickly accumulate at the bottom of channel to form water-blocking framework and provide conditions for grouting.

When both the dynamic water flow velocity and the water inrush channel height are small (the condition of low flow velocity and small cross-section), it is necessary to discuss whether it is necessary to perfuse aggregate before grouting. If it is still necessary to perfuse aggregate to improve the water-blocking efficiency, large particle size and high-density aggregate are still preferred. However, the danger and construction difficulty of this condition are relatively low, and local materials can be used.

Using fluid mechanics, slurry pipeline transportation theory, and sediment movement mechanics, respectively study the movement and force characteristics of deceleration aggregate in the water inrush channel: the entire migration process is divided into three stages, which are free fall, curved throwing, and sliding. Based on this, establish the deposition and migration theoretical model of a single aggregate in the water inrush channel in stages, and obtain the calculation formulas of the migration distances in the horizontal x and vertical y directions in each stage.

Using CFD-DEM transient two-way coupling calculation method to simulate the migration process of deceleration aggregate: the overall migration processes of aggregate in water inrush channel including free fall, curve throwing, and sliding stages, are consistent with the theoretical model; the simulated migration distance of the aggregate is slightly smaller than that of theoretical calculation results, however, the overall error does not exceed 10%, the theoretical model has a certain degree of accuracy, in practical engineering, the formulas obtained in this paper can be used to preliminarily estimate the migration distance of aggregate.

Relevant discussions are put forward for the construction methods of the actual aggregate perfusing and plugging project: the conditions of high flow velocity-large cross-section and the condition of high flow velocity-small cross-section, it is recommended to adopt the aggregate perfusing concept of using large (large diameter and density) first and then small (small diameter and density); the condition of low flow velocity-large cross-section, it is recommended to select aggregate with smaller diameters, although the part of the water-blocking efficiency is lost in a disguised form, the perfusing rate is increased; the condition of low flow velocity and small cross-section, local materials can be used.

Building upon the existing research on the two-phase coupling migration mechanism of aggregate and water, it is possible to investigate the deposition and migration of aggregate in complex water inrush channel types (inclined upward, downward, and curved) and analyze the morphology of water-blocking sections formed by aggregate accumulation. On the basis of the CFD-DEM transient two-way coupling calculation method, the Discrete Fracture Network (DFN) can be introduced to achieve a full-process simulation from fracture development to water inrush disaster and then to aggregate water-blocking.

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College of Architecture and Civil Engineering, Xi’an University of Science and Technology, Xi’an, 710054, China

Jiahao Wen, Shuancheng Gu, Peili Su & Jinhua Li

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Conceptualization, J.W. and P.S.; methodology, J.W. and S.G. ; sofware, J.W. and J.L.; validation, J.W., S.G., P.S. and J.L.; formal analysis, J.W.; investigation, J.W. and S.G.; resources S.G. and P.S.; data curation, J.W.; wrote the main manuscript text, J.W. and S.G; visualization, J.W. and J.L.; supervision S.G. and P.S.; project administration J.W. and S.G.; funding acquisition, S.G. and P.S.All authors have read and agreed to the published version of the manuscript.

Correspondence to Jiahao Wen.

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Wen, J., Gu, S., Su, P. et al. Study on the two-phase coupling migration mechanism of deceleration aggregate and water in coal mine water inrush channel. Sci Rep 15, 11702 (2025). https://doi.org/10.1038/s41598-025-95575-w

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Received: 22 January 2025

Accepted: 21 March 2025

Published: 05 April 2025

DOI: https://doi.org/10.1038/s41598-025-95575-w

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