Numerical Simulation of Diffusion Regularity and Parameter Optimization of Shaft Grouting Slurry

Abstract

Increase in downhole mining prompts the need to develop effective methods for maintenance of shafts. Currently, grouting behind the shaft wall is the main approach used for prevention of water seepage into the shaft. Several factors determine the grouting effect, and grouting often fails during field applications due to use of ineffective parameters. In the present study, numerical simulation was performed to evaluate slurry diffusion regularity under different grouting parameters based on the factors that affect shaft grouting. The simulation results showed that the overall diffusion radius of the slurry increased with increase in grouting time and stabilized toward the end of the simulation, under different grouting parameters. Porosity of the surrounding rock near the grouting hole gradually became denser with an increase in time, which is not conducive for diffusion of the slurry. The amount of water gushing at 146 m below the secondary shaft of Zhundong No. 2 mine decreased by 81% after optimizing the grouting parameters for application at the actual site. This decrease in amount of water had a significant anti-seepage effect, and it reduced grouting costs. The findings of the present study provide a basis for conducting subsequent shaft grouting projects.

1. Introduction

Flooding is a common disaster in mining areas and is commonly referred to as the phenomenon of water penetration [1,2,3]. Surface water and water from underground aquifers gush into the mine shaft or tunnel through pores, fissures, and faults in the rock body during mining. Flood water corrodes the mining equipment, shortens the service life of the mining equipment, blocks the tunnel space, and causes casualties. Therefore, flooding significantly limits effective harvesting of minerals. Therefore, it is imperative to explore the mechanism of water damage under different geological conditions, and corresponding anti-seepage measures should be adopted to improve safety during mining [4,5,6,7].

Grouting seepage control technology has advanced from previous clay grouting strategies to modern techniques characterized by the full range of theory, advanced technology, and new materials [8,9,10,11]. A modern grouting method involves mixing of grouting materials to form slurry, which is injected into the rock under a certain pressure using pressurized slurry equipment. The slurry solidifies after it penetrates the pores and cracks of the rock for a certain distance. As a result, it blocks the voids of the surrounding rock and increases the mechanical strength of the surrounding rock to achieve reinforcement [12]. Infiltration grouting theory is widely used in the establishment of grouting theory. In the theory of infiltration grouting, the rock and soil body are presumed to be a porous uniform medium. The injected slurry fills the pores of the rock body and displaces the water in the original rock body. Moreover, it increases the strength of the rock body by combining with the soil particles. The slurry–rock coupling that diffuses into the slurry does not damage the original rock body in the stratum at the end of grouting, and hydraulic splitting does not occur. Slurry diffusion of the infiltration grouting method is classified into spherical diffusion and columnar diffusion [13]. Zhou et al. introduced the “variable viscosity” parameter to optimize the equation for solving the Maag grouting theory [14]. Yang et al. optimized the equation of motion of slurry percolation by considering the self-weight of slurry [15]. Several studies have explored diffusion of slurry under different geological conditions to determine diffusion regularity of the slurry. Saada et al. conducted simulation experiments, and the findings showed that sandy rock layers filter cement particles in the slurry, revealing the mode of slurry transport in sandy rock layers [16]. Zhou et al. explored slurry diffusion regularity for characteristics of sandy formations and proposed a quantitative relationship between multiple grouting parameters. The results showed that the form of slurry diffusion is correlated with multiple forms of compound action [17]. Li et al. evaluated the grouting regularity of medium and coarse sandstone pile end using a PFC numerical simulation technique, and the findings indicated that slurry diffusion radius and grouting pressure exhibit a non-linear relationship [18]. Moreover, Chen et al. explored the relationship between slurry diffusion regularity in porous media and microstructural changes, and the results showed that higher porosity was correlated with more complex slurry diffusion [19]. Zhang et al. evaluated the slurry–rock coupling effect, in which slurry diffusion was gradual, and the coupling effect was significant when the fracture width was small [20]. Zhang et al. conducted simulation tests considering soil permeability and explored slurry diffusion regularity under different diffusion paths [21]. Zhou et al. reported that two strategies can be used to control water influx in the shaft, namely, reducing permeability of the surrounding rock and increasing the thickness of the slurry curtain [22]. Zhang et al. performed similar simulation experiments as Zhou et al. to determine diffusion regularity of the slurry under different water–cement ratios [23]. Notably, these studies did not fully explore slurry diffusion regularity, and slurry diffusion behind the wall of the shaft through the aquifer has not been elucidated. The principles of most research methods are similar to simulation experiments; however, numerical simulation experiments are not commonly used to evaluate slurry diffusion regularity. Therefore, the slurry section of the secondary shaft of Zhundong No. 2 mine was used as the research object in the present study. In addition, factors affecting the diffusion range of slurry behind the wall of the shaft were explored to minimize excessive water gushing in the shaft. A numerical simulation method was used to study diffusion regularity of the slurry under different slurry parameters. Slurry parameters were optimized to effectively control the amount of water gushing in the shaft. The research results of the present study provide a basis for slurry injection behind the wall of the shaft to minimize water gushing in the field.

2. Shaft Grouting Mechanism

2.1. Project Overview

The present study was conducted in Zhundong No. 2 mine, which is located in Jimsar County, Xinjiang China. The secondary shaft of Zhundong No. 2 mine is a vertical shaft with a net diameter of 9.5 m and a depth of 545 m. The shaft wall is supported by grade C40 concrete. The length of the shaft comprises three sections. The first section is about 5 to 90 m deep, with a double-layer reinforced concrete wall material and a thickness of 0.65 m. The middle section is approximately 90 to 496.4 m deep. This section has a single-layer concrete wall structure with an average thickness of 0.7 m. The last section is approximately 496.4 to 545 m deep and is characterized by a reinforced concrete wall material with 0.8 m thickness. The rate of flow of water from the secondary shaft in 2020 was approximately 5.2 m³/h. Notably, the total amount of water gushing from this shaft met the production requirements. However, flow of water from the shaft wall in the middle section of the shaft, about 146 m from the surface, exhibited multi-point emanation. Water flows into the middle of the shaft in the form of rainfall after confluence, and the shaft materials undergo long-term corrosion owing to the highly mineralized water (Figure 1). The system should have several grouting holes behind the shaft wall to alleviate corrosion of the shaft. The slurry and the surrounding rock behind the wall are cemented after grouting, and the strength is increased to effectively plug water and prevent leakage. The area around the shaft where grouting is performed (referred to as the grouting section in this paper) and the layout of grouting holes are shown in Figure 2.

2.2. Factors Affecting Grout Diffusion

The single-hole grouting test was conducted to explore whether the equipment capacity met the test requirements. In addition, this test was performed to evaluate the grouting difficulty, grouting volume, and grouting pressure parameters. Hydrostatic pressure of the surrounding rock was approximately 1 Mpa, which was the same as that for the multiple grouting holes drilled in the grouting section at a depth of 146 m. Therefore, one grouting hole was used to evaluate slurry diffusion. The grouting section was represented as a single-hole grouting model behind the wall (Figure 3).

The post-wall grouting hole presented in Figure 3 was generally deeper. The grouting orifice was equivalent to a point source, and the slurry diffused outward in a spherical shape at the orifice [12]. In the present study, the assumption was that the soil behind the wall was an isotropic porous medium, the slurry was permeable and diffusive in the soil, and the slurry was an incompressible fluid. The slurry volume Q can be expressed as shown below [24]:

$$Q=\frac{2\pi K_{\mathrm{w}}{\mu }_{\mathrm{w}}(\mathrm{P}-{\mathrm{P}}_r)(1-e^{-\alpha t})}{\alpha {\mu }_{\mathrm{g}}(\frac{1}{r_0}-\frac{1}{r})}$$

(1)

where K_w represents the permeability coefficient of water to the surrounding rock and soil. P indicates the initial grouting pressure of the slurry for single-hole injection, expressed in MPa. P_r represents the final pressure of the slurry after diffusion in the soil (this generally refers to the hydrostatic pressure of the surrounding rock behind the wall near the orifice), expressed in MPa. α indicates the coefficient related to the inherent properties of the slurry. t represents the grouting time in min. r₀ indicates the radius of the grouting hole in m. μ_g represents the viscosity of the slurry. r represents the grouting radius in m. The slurry exhibits spherical diffusion in single-hole grouting. The total grouting volume is expressed as Q = 4φπr³/3, which can be obtained by substituting this expression into Equation (1) and then simplifying the equation to obtain the diffusion radius of the slurry as follows:

$$r=\sqrt[3]{\frac{3r_0{K}_{\mathrm{w}}{\mu }_{\mathrm{w}}(\mathrm{P}-{\mathrm{P}}_r)(1-e^{-\alpha t})}{2\alpha {\mu }_{\mathrm{g}}\phi }}$$

(2)

where φ represents the porosity of the soil. Equation (2) indicates that the size of the diffusion radius of the slurry is correlated with the grouting pressure P, slurry viscosity μ_g, grouting time t, and porosity φ of the soil. This relationship among the grouting parameters behind the shaft wall provides a theoretical basis for establishing a numerical model.

3. Numerical Simulation

3.1. Numerical Calculation Principle

COMSOL Multiphysics is a multi-physics coupled numerical simulation software based on a finite element algorithm. This tool is used for numerical simulation of physical phenomena through the solving of partial differential equations or systems of partial differential equations. The most important feature of this tool is that material properties and boundary conditions of each module can be set individually. In addition, the function or logical expression of any variable can be customized [15,25]. Diffusion of the slurry behind the shaft wall exhibits Darcy’s regularity; therefore, the process of diffusion of the slurry is simulated using the Darcy interface in COMSOL software. The process is expressed as shown below:

$$\nabla \left[\rho \left(-\frac{K}{{\mu }_{\mathrm{g}}}\nabla \mathrm{P}\right)\right]=Q_m$$

(3)

where ρ indicates the density of the fluid material, K represents permeability of the porous media material, and Q_m represents the mass source term.

Equation (3) shows that the density ρ and the dynamic viscosity μ of the slurry, the permeability K and porosity φ of the porous medium, as well as the various boundary conditions and initial conditions of the domain of action, are the inputs in the interface of Darcy’s regularity model in the COMSOL software. The density ρ of the slurry represents the sum of two parts with different percentages, namely: density of the slurry solids and density of the water in the slurry [26]. The density ρ is expressed as follows:

$$\rho ={\rho }_c\delta +(1-\delta ){\rho }_w$$

(4)

where δ indicates the volume fraction of solid slurry particles. Calculated expressions for the volume fraction of solid slurry particles and expressions for porosity of the surrounding rock behind the wall with the grouting time t are presented as follows [26]:

$$\delta (t)=\frac{1}{1+(\frac{1}{{\delta }_0}-1)\exp \left[\frac{\alpha }{r_0{}^2{v}_0}(\frac{r_0{}^2{v}_0}{{\phi }_0}t-\frac{2r_0{}^3}{3})\right]}$$

(5)

$$\phi (r,t)={\phi }_0-\frac{\alpha \left[t-\frac{{\phi }_0(r^3-r_0{}^3)}{3r_0{}^2{v}_0}\right]}{1+(\frac{1}{{\delta }_0}-1)\exp \left[\frac{\alpha }{r_0{}^2{v}_0}(\frac{r^3}{3}-\frac{r_0{}^3}{3})\right]}$$

(6)

where δ₀ represents the initial slurry solids mass fraction, and v₀ indicates the initial radial velocity of grout injection, expressed in m/s.

Permeability coefficient K of the slurry in the surrounding rock behind the shaft wall is expressed as follows:

$$K=\frac{K_0{\mu }_{\mathrm{w}}}{{\mu }_{\mathrm{g}}}$$

(7)

where K₀ indicates the initial permeability coefficient of the shaft envelope in m/s. μ_w represents the viscosity of groundwater at room temperature; in this case, it is considered as 1.005 × 10⁻³ Pa·s. μ_g represents the initial viscosity of the slurry. Notably, the initial viscosity of the slurry(μ_g) is obtained by using the unified equation for the variation in slurry viscosity with time [27], as follows:

$${\mu }_{\mathrm{g}}={\mu }_0{e}^{-at}$$

(8)

The permeability coefficient K is obtained by combining Equations (7) and (8) as shown below:

$$K=\frac{K_0{\mu }_{\mathrm{w}}}{{\mu }_0{e}^{-at}}$$

(9)

3.2. Construction of a Numerical Model

A 3D cubic geometry model was constructed by intercepting a part of the shaft wall and its surrounding rock based on the single-hole grouting model behind the shaft wall established in Section 2.2. The 3D cubic geometry model was used to simulate and explore the diffusion process of single-hole grouting. The overall size of the model shaft was set as 22 × 22 × 22 m, and the shaft diameter was set to 0.95 m. The grouting hole was located near the center of the model shaft wall with a diameter of 0.038 m and a length of 2 m. The geometric model was covered with a free-dissecting triangular mesh generated using the COMSOL Multiphysics software. The number of triangular elements in the constructed grid was 366,355, the maximum cell size of the grid was 0.77 m, and the minimum cell size of the grid was 0.0011 m. The maximum cell growth rate of the elements was 1.2, and the curvature factor was 0.25. The results of the geometric model as well as the mesh generation results are presented in Figure 4 and Figure 5.

The definition function sets the model parameters on the left side of the COMSOL Multiphysics software. This includes setting the constant model parameters and variable parameters, whereby the variables are determined by setting the corresponding functions. The constant parameters were defined based on the actual grouting parameters of the Zhundong No. 2 mine (

Table 1. Constant parameters used in the model.

Parameter Name	Numerical Value	Unit	Description
r0	0.038	m	Grouting hole radius
δ0	0.5		Initial slurry solid particle volume fraction
v0	0.4	m/s	Initial injection velocity
φ0	0.5		Initial surrounding rock porosity
α	0.0011	1/s	Permeability coefficient
μw	0.001	Pa·s	Dynamic viscosity of water
ρc	1500	kg/m3	Slurry density
ρw	1000	kg/m3	Density of water
t	6000	s	Slurry injection time
K0	0.00003	m/s	The initial permeability coefficient of surrounding rock and soil

).

Numerical implementation of the post-shaft wall grouting process using Darcy’s regularity principle requires the definition of five variables including density of the slurry ρ, permeability of the surrounding rock K, dynamic viscosity of the slurry μ_g, porosity of the surrounding rock φ and diffusion radius r. Control of the grouting process in the software is achieved using Equation (4) presented in Section 2.2 and expressions of each variable with time t in Section 3.1 as input. The COMSOL Multiphysics software uses Cartesian coordinates as the default coordinate system; thus, the Cartesian coordinate system for the diffusion radius r is converted to a polar coordinate system. Variables used in the modeling process are presented in

Table 2. Model variable setting.

Variable Name	Expression	Unit	Description
r1	sqrt((x−11)^2 + (y−17.75)^2 + (z−11)^2)	m	Diffusion radius
μg	miug	Pa·s	Slurry viscosity
kg	μwK0/miug	m2	Permeability coefficient
ρg	pw1(t) × ρc + (1 − pw1(t)) × ρw	kg/m3	Slurry density
φ	if(r < R,an2(t,r),fai0)		The porosity of surrounding rock

.

The r₁ variable in Table 2 represents the slurry diffusion radius after conversion to polar coordinates. miug represents the viscosity of slurry in Equation (8). pw1 (t) indicates the variation in the slurry solid particle volume fraction with time t. an2(t,r) represents variation in the surrounding rock porosity with time t and diffusion radius r. R represents the maximum radius of slurry diffusion allowed in the software, which is significantly higher relative to the diffusion radius, and was set at 50 m in the simulation test.

3.3. Boundary Conditions

Boundary conditions for the physical field should be set after defining the parameters of the numerical model. Boundary conditions in Darcy’s regularity interface mainly include fluid and basic properties, without flow, initial values, and pressure sections. Density ρ and hydrodynamic viscosity μ of the fluid material are assigned as parameters ρ_g and μ_g in the fluid and basic properties of the column. In addition, porosity φ and permeability K of the porous medium (all homogeneous) are presented as functions φ and parameters k_g. The interfaces (except for the grouting hole) were selected separately during boundary selection of the column without flow. The selected part appears as blue, indicating the boundary of the numerical model as shown in Figure 6 below. The initial grouting pressure P is set at the entrance of the grouting hole.

The solver was selected after setting the boundary conditions. A steady-state solver was used to solve the diffusion process of the slurry. The parametric scan function in the COMSOL Multiphysics software was applied to scan time t where the starting time was set at 0 min, the interval time was set at 10 min, and the termination time was set at 100 min, to explore variation in the slurry diffusion radius r with time.

3.4. Analysis of Simulation Results

The effect of grouting varied with use of the diverse grouting parameters in the actual project, and the slurry diffusion regularity was also different. The COMSOL Multiphysics numerical simulation software allows adjustment of the grouting parameters to control slurry dispersion (mainly by adjusting the size of the slurry dispersion radius r). The simulation experiments were conducted to quantify and evaluate variation in the radius r of the slurry diffusion with change in grouting time t at different grouting pressure P and slurry dynamic viscosity μ_g.

3.4.1. Effects of Grouting Pressure

Grouting behind the shaft wall was dominated by infiltration grouting. The infiltration grouting method aims at not damaging the formation for grouting, and the grouting pressure is generally low. The slurry dynamic viscosity μ₀ and grouting hole diameter r₀ for the constant parameters were set to 10 MPa·s and 0.038 m, respectively. Other parameters were not changed. Variation in pressure P with time t was explored under three gradients of pressure, namely, 2, 3, and 4 MPa considering hydrostatic pressure (Figure 7).

The results showed that the overall diffusion radius r of the slurry increased with increase in grouting time t under varying grouting pressure, in a non-linear manner (Figure 7). The diffusion radius of slurry markedly increased between 0 and 50 min. On the contrary, the growth rate stagnated after 50 min, indicating that a longer grouting time limits slurry diffusion; thus, the grouting time should be controlled in the actual project. The slurry diffusion radius r increased under the same grouting time with an increase in grouting pressure, but the magnitude of the increase varied with change in grouting pressure. The slurry diffusion radius r increased by 25% when the grouting pressure P changed from 2 to 3 MPa under the same period. The slurry diffusion radius increased by about 14% over the same period when the pressure P changed from 3 to 4 MPa. This indicates that the grouting pressure should not be too high, and a limit of grouting pressure should be set for effective infiltration grouting. Therefore, a suitable grouting pressure should be selected for grouting in the actual project.

3.4.2. Effect of Slurry Dynamic Viscosity

Dynamic viscosity of the slurry is a physical parameter reflecting the flow state of the slurry. The level of slurry viscosity affects the ease of spreading of the slurry in the surrounding rock. The pressure was set to 3 MPa based on the slurry pressure test, and other parameters were kept constant. Further, two viscosity gradients at 20 and 30 MPa·s were set for the simulation test. The outcome of 10 MPa·s viscosity was compared with the gradient test result. The effect of viscosity on diffusion regularity of the slurry is presented in Figure 8.

The findings show that a change in slurry diffusion radius r was consistent with the results of the grouting pressure test, whereby both initially increased with time t and then stabilized (Figure 8). Comparison at the same grouting time showed that high viscosity of the slurry was correlated with a smaller diffusion radius. The diffusion radius after two incremental gradients of viscosity decreased by 20% and 12%, respectively. This finding indicates that a higher viscosity of the slurry is associated with more friction between the slurry and the pores of the surrounding rock and soil. This implies that the slurry cannot easily diffuse to the inside of the surrounding rock. Notably, the results show that the stability and impermeability of the consolidated slurry were poor when the slurry viscosity was low. Therefore, a suitable slurry viscosity should be selected for grouting in practical projects to improve slurry infiltration.

3.4.3. Optimization of Grouting Parameters

The optimal parameters, including slurry injection pressure at 3 MPa and slurry dynamic viscosity at 20 MPa·s obtained after simulating and evaluating the effects of different factors on slurry diffusion regularity, were used in the simulation test. The expected slurry injection volume of the project was 30 L/min, which was compared with the variation in slurry diffusion radius with time t after optimization (Figure 9).

The findings showed that the grouting radius r increased with increase in time t and then stabilized at around 40 min (Figure 9). Notably, grouting volume Q increased monotonically with increase in time t. A higher influence range of slurry diffusion under the same construction conditions (i.e., a larger diffusion radius r), was associated with a higher reinforcement effect in the actual project. However, the cost factor should be considered. The results showed that grouting radius reached a peak value of about 3.8 m when time (t) was 60 min, and the grouting quantity Q was 1.8 m³. On the left side, with t = 60 min as the cut-off point, a significant change in diffusion radius r was observed, and the grouting effect was better. The change in diffusion radius r was not significant on the right side of the cut-off point, whereas the grouting volume Q increased with time beyond the cut-off point. This finding indicates that the grouting effect was highest at t = 60 min; thus, grouting should be stopped at this time to save on cost.

A change in slurry concentration allows for visualization of the difference in diffusion radius r. Analysis using the parametric scanning function in the COMSOL numerical simulation software showed that the volume fraction of solid slurry particles extracted at 10 min intervals varied significantly between 0 and 100 min of grouting time (Figure 10).

The results indicated that a longer grouting time t was correlated with a higher spread of the volume fraction δ of solid slurry particles (Figure 10). The area of the peripheral blue circle expanded markedly, and diffusion range of the volume fraction of solid slurry particles δ significantly changed from 0–60 min. This indicates that the slurry diffusion was relatively fast at this period. The area of the peripheral blue circle changed at a significantly slower rate between 60–100 min of injection time t, whereas the diffusion range of the slurry solid particle volume fraction δ did not change markedly at this period. This finding indicates that the slurry diffusion rate was stable from 60–100 min.

A section of the surrounding rock near the quarter grouting hole was selected to explore the process of reinforcing the surrounding rock by grouting behind the wall of the shaft (the section is shown in Figure 11). Porosity φ of the surrounding rock behind the wall showed significant variation at t = 50, 60, and 70 min (Figure 12).

The findings indicated that the porosity φ of the surrounding rock behind the wall was slightly increased with increase in diffusion radius r as the slurry diffused (Figure 12). The porosity of the surrounding rock was lowest at the point adjacent to the grouting hole. This was attributed to filling of the fissures of the surrounding rock around the grouting hole by slurry and reinforcement of the surrounding rock. A higher porosity was observed for regions distant from the grouting hole, which was closer to the original rock porosity.

Analysis of the porosity φ of the surrounding rock at t = 50, 60, and 70 min showed that the value of porosity near the grouting hole reduced with increase in time. This indicates that a longer grouting time is associated with significantly higher fracture filling of the surrounding rock near the grouting hole. This reduces the rate of diffusion of slurry to the depth of the surrounding rock, and the grouting effect was not significant at a longer grouting time. This implies that the diffusion radius r was maximum at t = 60 min, and the reinforcement effect was highest at this point.

4. On-Site Verification of the Optimized Parameters

The optimized grouting parameters including grouting pressure of 3 MPa, slurry viscosity of 20 MPa·s, and grouting time of 60 min were tested in the field after the simulated tests to explore diffusion regularity of the slurry. Grouting was conducted using drilling rod end-hole grouting, key filling, and drilling, as well as intensive grouting to fill the water-bearing layer behind the wall for establishment of grouting and water plugging. The poor-quality area of the shaft wall was reinforced by grouting first, and then the water was re-injected after the cement slurry had solidified. A 2 m depth of grouting hole was used uniformly, and the cracks between the wall and surrounding rock as well as the cracks in the surrounding rock were sealed by grouting in all directions to form a water barrier curtain.

The overall construction process comprised a total of 61 grouting holes and was grouted with 23.8 tons of cement. The slurry plugging construction before the shaft gushing water was approximately 5.2 m³/h, whereas the grouting plugging construction after the shaft gushing water was about 0.98 m³/h. The shaft gushing water decreased by 81%, showing that the grouting plugging effect was significant. Optimization of the parameters after construction increased the service life of the shaft facilities, reduced operation and maintenance costs, and provided a strong guarantee for safety and standardization of the mine. A representation of the shaft before and after slurry injection at 146 m is presented in Figure 13.

5. Conclusions

(1)

In the present study, the diffusion regularity of the slurry was evaluated under different grouting parameters. The findings showed that the overall radius of slurry diffusion increased with increase in grouting time, and then it stabilized. This indicates that there is a limit to the range of slurry diffusion, and appropriate grouting parameters should be chosen for the actual project.

(2)

The porosity of the surrounding rock near the grouting hole was smaller when slurry diffuses behind the shaft wall, whereas the porosity is higher at parts away from the grouting hole. The porosity of the surrounding rock near the hole gradually becomes dense with an increase in time, which is not conducive for diffusion of slurry. Optimal grouting time should be determined when in the field to minimize destruction of the surrounding rock and reduce the grouting effect.

(3)

The engineering conditions of the Zhundong No. 2 mine and the numerical simulation method were used to optimize the grouting parameters. The water gushing in the shaft after optimization of the parameters decreased by 81%. Grouting and water plugging effects were significant, which verified reliability of parameter optimization. The present findings provide a basis for minimizing flooding in mines and for further studies to explore approaches for reducing water gashing in mines to improve harvesting of minerals and to reduce the number of casualties associated with flooding.