Water-blocking body construction method based on FLUENT-EDEM coupling model

Abstract

The application relates to a water-blocking body construction method based on a FLUENT-EDEM coupling model, in which water flow and aggregate particles are respectively modeled by different theories, the motion state of each aggregate particle in the water flow can be efficiently depicted, the running state of the whole aggregate particle group of the water-blocking body can be real-timely presented, quantitative calculation and prediction of the water-blocking body construction process are realized, the method can be used for simulation calculation before water inrush in a mine, various water inrush disaster conditions are analyzed in advance, possible construction schemes are classified and modeled for calculation, and then a water-blocking body construction optimization scheme database is formed, which can be quickly called and used when a water inrush disaster occurs; therefore, the method has the advantages of high calculation precision, low cost, dynamic visualization and the like, key data or evolution rules which cannot be directly obtained by field or indoor tests can be obtained in real time, potential risks of experience-dominant engineering construction are reduced, and the technicality and scientificity of a concealed water disaster treatment engineering construction scheme are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coal mine water disaster control, and particularly relates to a water blocking body construction method based on a FLUENT-EDEM coupling model. BACKGROUND

[0002] After a mine water inrush, the construction of a water blocking body to cut off the hydraulic connection between the water inrush source and the mine system is an important method to realize rescue and mine recovery. The water blocking body construction refers to pouring aggregate of different particle sizes from the ground into the roadway, the aggregate migrating and accumulating in the roadway until the top is reached to form a water blocking effect, and finally the roadway is completely plugged by grouting reinforcement. Due to the complexity and concealment of the site engineering conditions, this construction technology has been mainly based on experience for a long time, especially in the technical optimization of the aggregate pouring process.

[0003] The aggregate pouring process guided by experience judgment often has a lot of invalid pouring situations, the aggregate is continuously washed to the downstream distal end, the roadway system is buried, the mine equipment is submerged, the post-dredging is difficult, leading to a long project duration, high investment cost, and even causing secondary property loss.

[0004] In order to study and optimize the water blocking body construction technology, people have made relevant exploration and research from the perspective of experimental simulation, mainly by establishing a similar simulation test platform, converting various parameters to the design parameters of the platform according to the similarity ratio, and then conducting simulation tests according to the site working conditions. This kind of platform can simulate the main phenomena and basic laws during the aggregate pouring period, and generally belongs to the qualitative research level. However, from the quantitative point of view, this method cannot accurately describe the mechanical behavior between the aggregate particles and the water flow, and many key data related to construction cannot be directly measured or quickly obtained, which restricts the development of the water blocking body construction technology.

[0005] In recent years, with the rapid development of computational fluid dynamics and discrete element method, a new way has been provided to solve the coupling calculation problem between fluid and particle medium. However, there is no relevant report on the numerical simulation of the water blocking body construction technology optimization by numerical simulation means. The numerical simulation calculation research of the water blocking body construction has important significance for the design of its technical scheme and parameter optimization. SUMMARY

[0006] In view of this, in order to solve the problems existing in the quantitative analysis and technical optimization of the existing test technology means in the water blocking body construction process, the present application provides a water blocking body construction method based on a FLUENT-EDEM coupling model, and the specific technical scheme is as follows:

[0007] A water blocking body construction method based on a FLUENT-EDEM coupling model, comprising the following steps:

[0008] (1) Engineering technical condition analysis: After the mine water inrush and flooding accident, the technical analysis of the water inrush process is carried out through the field data, the construction site of the water blocking body is selected, and the feasibility of the water blocking and mine recovery is evaluated;

[0009] (2) Construction of physical model of water blocking body: According to the space-time variation relationship between the water level in the mine during water inrush and the water level of the water inrush source, and the related basic data measured on site, the physical model during the construction of the water blocking body is constructed. The key parameters involved in the model include stable water flow during construction, pressure difference between upstream and downstream of the water blocking body, roadway specification, roadway slope and relief conditions, surrounding rock conditions, etc.;

[0010] (3) Construction parameter estimation: Based on the database constructed according to the past construction experience, considering the water blocking and pressure relief capacity of the water blocking body aggregate, stable water flow during construction, grout solidification conditions during grouting, and water flow velocity variation during pouring, the construction parameters of the water blocking body are estimated, including aggregate accumulation section length, borehole number, aggregate particle size selection, etc.;

[0011] (4) Fluid-structure coupling control equation set: including fluid phase control equation and solid phase control equation, the former includes continuity equation and momentum equation, and the latter includes particle motion control equation;

[0012] (5) Numerical model construction and mesh division: draw the calculation model according to the spatial size of the engineering physical model, and reasonably divide the model into meshes;

[0013] (6) Particle and wall parameter calibration: According to the gradation curve and particle shape of the commonly used aggregate on site, the aggregate particles conforming to the actual working condition are generated by using EDEM software; According to the properties of aggregate and roadway wall, the parameters to be calibrated include Young's modulus, Poisson's ratio, collision restitution coefficient, sliding friction coefficient and motion viscous coefficient;

[0014] (7) Setting solution parameters: According to the engineering physical model, set the upstream inlet pressure and downstream outlet pressure; The solution model adopts Euler-Lagrange model, that is, the fluid behavior is described by computational fluid dynamics method, and the mechanical behavior of particles is described by discrete element method; The calculation time step and solution accuracy should meet the basic law of aggregate motion;

[0015] (8) Reliability verification of numerical model: After establishing the numerical simulation model, the reliability of the model is verified, including the settling velocity of aggregate particles, the angle of repose, the flow field distribution, etc., to determine whether the model can truly describe the motion state and mechanical behavior of aggregate and fluid;

[0016] (9) The fluid-structure coupling calculation in the construction process of the water-blocking body: the flow field before the aggregate is poured is calculated first, and after the flow field is stable, the aggregate pouring simulation calculation is carried out according to the established construction scheme, and the pouring scheme setting includes the aggregate pouring sequence of a single hole, the pouring speed, the cooperation scheme between holes, the number of simultaneously poured holes and the like; the setting of the pouring scheme should be consistent with the actual working condition on site as much as possible, so as to reduce the calculation workload;

[0017] (10) Construction scheme and parameter optimization: the calculation data and experimental phenomena of each construction scheme are analyzed, the water-blocking effect is comprehensively evaluated from the indicators such as the accumulation length, the construction period, the top-joining length, the residual water amount, the upstream pressure recovery condition and the like, and the optimal construction scheme meeting the expectation is selected to guide the on-site construction.

[0018] Compared with the prior art, the advantages of the present application are:

[0019] (1) The water-blocking body construction method based on the FLUENT-EDEM coupling model can efficiently depict the motion state of each aggregate particle in the water flow, and realize the quantitative calculation and prediction of the water-blocking body construction process by modeling the water flow and the aggregate particles respectively with different theories and real-time displaying the motion state of the aggregate particle group of the whole water-blocking body;

[0020] (2) The water-blocking body construction method based on the FLUENT-EDEM coupling model can simulate and calculate before water inrush occurs in a mine, analyze various water inrush disaster conditions in advance, classify and model calculate the possible construction schemes, and then form a water-blocking body construction optimization scheme database, which can be quickly retrieved and used when water inrush disaster occurs;

[0021] (3) The water-blocking body construction method based on the FLUENT-EDEM coupling model has the advantages of high calculation precision, low cost and dynamic visualization, can obtain key data or evolution rules that cannot be directly obtained by on-site or indoor tests, reduces the potential risks of experience-oriented engineering construction, improves the technicality and scientificity of the construction scheme of the concealed water disaster control project, is a new water disaster prevention and control technical concept and method, and has high theoretical significance and engineering application potential. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is the water-blocking body construction technology optimization flowchart based on the FLUENT-EDEM coupling model of the present application;

[0023] Figure 2 is the water-blocking body construction physical model of the present application;

[0024] Figure 3 is the water-blocking body simulation calculation model and mesh division of the present application;

[0025] Figure 4 is a schematic diagram of the method of the present application, wherein (a) is a settling velocity verification curve of the aggregate particles of the present application, (b) is a packing morphology verification diagram of the aggregate particles of the present application, and (c) is a verification diagram of the flow field distribution state in the grouting tunnel of the present application;

[0026] Figure 5 is a packing morphology diagram of the aggregate grouting construction of the present application at different stages. DETAILED DESCRIPTION

[0027] The content of the present application is further illustrated below in combination with the drawings and examples:

[0028] As Figures 1-5 , the specific examples simulate the construction process of the water-blocking body by simulating the process of grouting different particle sizes of aggregate into the tunnel in stages through four ground holes in the submerged horizontal tunnel, the aggregate is carried downstream and accumulated under the action of water flow, and finally the water-blocking body construction process of full-line roof connection is successfully realized; wherein FLUENT is a computational fluid dynamics software, EDEM is a particle medium mechanics analysis software, FLUENT-EDEM coupling simulation is a method based on Euler-Lagrange coordinate system, and the two are simulated by interactive calculation; Figure 1 is a flow chart of the water-blocking body construction technology based on the FLUENT-EDEM coupling model, and the specific process is as follows:

[0029] (1) Analysis of engineering technical conditions: After the mine is flooded by water inrush accident, the technical analysis of the water inrush process is carried out through the field data, the site selection of the water-blocking body construction position is carried out, and the feasibility of implementing the water interception and mine recovery is evaluated; the roadway position is generally selected in the concentrated water passage roadway close to the water inrush point, and multiple roadways are not recommended to be intercepted at the same time, and the site selection section is designed in the straight or water flow uphill section of the roadway to reduce the engineering quantity;

[0030] (2) Construction of physical model of water-blocking body: as Figure 2 shown, according to the space-time variation relationship between the water level in the mine during water inrush and the water level of the water inrush source and the related basic data measured on site, the physical model during the water-blocking body construction is constructed, the key parameters involved in the model include stable water flow during water interception construction, pressure difference between upstream and downstream of the water-blocking body, roadway specification, roadway slope and fluctuation conditions, surrounding rock conditions, etc.;

[0031] The key parameters can be obtained by using the hydrogeological data provided by Party A, combined with the field survey data, and comprehensively analyzed and identified. In the typical examples, the value range of the key parameters is generally: stable water flow 500-10000 m 3The upstream and downstream pressure difference is 0-2 MPa, the roadway size is generally 4-5 m in length and width, the roadway slope is generally 0-20°, and when the surrounding rock condition is an extremely soft rock roadway, the working condition correction coefficient in step (3) should consider the scouring effect.

[0032] (3) Construction parameter estimation: based on the database constructed based on previous construction experience, considering the water blocking and pressure relief capacity of the water blocking body aggregate, the stable water flow during construction, the slurry solidification condition during grouting, and the change of dynamic water flow velocity during grouting, the construction parameters of the water blocking body are estimated, including the aggregate accumulation section length, the number of drill holes, the aggregate particle size selection, etc.

[0033] The aggregate accumulation length L is estimated by the following formula:

[0034]

[0035] Wherein, x is the water flow; A is the roadway cross-sectional area; Δh is the upstream and downstream pressure difference; t0 is the initial setting time of the slurry; k z is the permeability coefficient of the accumulation body; J max is the limit hydraulic gradient of the accumulation section; k is the working condition correction coefficient (1 for simple working condition, 2-3 for medium working condition, and 3-4 for complex working condition);

[0036] The number of drill holes n is estimated by the following formula (generally not less than 3 holes):

[0037]

[0038] Wherein, ξ is the drill hole surplus coefficient; ζ is the time efficiency coefficient; m is the maximum single-hole grouting capacity; T is the predicted roof contact period; ρ' is the bulk accumulation density;

[0039] The aggregate particle size should meet the matching of the aggregate grouting capacity and the water flow carrying capacity when determining the particle size, which can be verified by field test, and the general particle size selection range is 0.2 mm-50 mm.

[0040] (4) Fluid-solid coupling control equation set: including fluid phase control equation and solid phase control equation, the former includes continuity equation and momentum equation, and the latter includes particle motion control equation; the fluid-solid coupling control equation set is the mechanical basis for the numerical model, and is the control equation for describing the fluid and particle motion behavior. Among them:

[0041] The continuity equation is:

[0042]

[0043] The momentum equation is:

[0044]

[0045] Wherein, For Hamiltonian operators; ρ f u f P, η, and η represent fluid velocity, density, pressure, and viscosity, respectively; ε is the liquid volume fraction; g is the acceleration due to gravity; and S is the momentum exchange term between the fluid phase and the solid phase.

[0046] The particle motion control equation is as follows:

[0047]

[0048]

[0049] Where, m i v i Let F be the mass and velocity of the i-th particle; gp F dra These are the pressure gradient force and drag force exerted by the fluid on the i-th particle, respectively; F cont I represents the contact force acting on the particle. i ω i These are the particle's moment of inertia and rotational velocity, respectively; T j For torque; N is the number of particles in contact with the particles.

[0050] (5) Numerical model construction and mesh generation: such as Figure 3 As shown, a numerical mechanical calculation model is designed based on the engineering physical model parameters, construction parameters, and fluid-structure interaction control equations in steps (2) and (3). Considering the roadway slope (the slope is 0° when the roadway is horizontal), multiple symmetrically distributed inlets are used to simulate the water inrush channel. The sum of the water volume of each inlet is equal to the simulated stable flow rate, which facilitates the flow field in the roadway to quickly enter a stable state after the simulation calculation is started. The boreholes are located in the middle of the roadway, with a spacing of 25-30m. The number is set according to the result of the construction parameter estimation in step (3), and is generally no less than 3. Finally, the calculation model is divided into grids using unstructured grids. Among them, the water-blocking body construction physical model in (2) is an actual physical model abstracted from the engineering object. The numerical model constructed in this step is converted into a grid model that can be recognized and run by the machine through computer modeling processing.

[0051] (6) Particle and wall parameter calibration: Based on the gradation curves and particle morphology of commonly used aggregates (particle size 0.2-50mm) on site, aggregate particles conforming to actual working conditions are generated using EDEM software; according to the properties of the aggregates and roadway walls, the parameters to be calibrated include Young's modulus, Poisson's ratio, collision recovery coefficient, sliding friction coefficient, and kinematic viscosity coefficient; the parameter calibration refers to the mechanics of particle media and experimental data of common particle aggregates. In this embodiment, the particle Young's modulus is 5.5×10⁻⁶. 6 N / m 2Poisson's ratio 0.25-0.3, collision restitution coefficient 0.3, sliding friction coefficient 0.1, kinematic viscosity 10 -6 m 2 / s. This step (6) is to calibrate the mechanical action parameters between the aggregate particles in the EDEM software, so that the motion of the aggregate particles conforms to the mechanical behavior of the aggregate in nature;

[0052] (7) Set the solution parameters: interconnect FLUENT and EDEM software through the interface program, set the upstream inlet pressure and downstream outlet pressure in the FLUENT software according to the physical model; the solution model adopts the Euler-Lagrange model, that is, the fluid behavior is described by the computational fluid dynamics method, and the mechanical behavior of the particles is described by the discrete element method; the calculation time step and the solution accuracy should meet the basic requirements of program convergence;

[0053] (8) Numerical model reliability verification: as shown in Figure 4 , the reliability of the numerical model is verified by combining the published test data, including the settling velocity of the aggregate particles, the angle of repose, the flow field distribution, etc., to determine whether the model can truly describe the motion state and mechanical behavior of the aggregate and the fluid; among them, the reliability of the numerical calculation model can be verified by comparing the simulation data with the laboratory measured data from the aspects of the aggregate settling velocity, the angle of repose, the flow field distribution, etc.

[0054] (9) Fluid-structure coupling calculation of water-blocking body construction process: use the established coupled numerical mechanics model to perform fluid-structure coupling calculation under different working conditions. As shown in Figure 5 , run the established FLUENT-EDEM coupled numerical model, first calculate the flow field before the aggregate is poured to a stable state, and then perform simulation calculation according to the established construction scheme, including the aggregate pouring sequence of single hole, pouring speed, cooperation scheme between holes, and the number of simultaneously poured holes; the setting of the pouring scheme should be consistent with the actual working condition as much as possible to reduce the calculation workload;

[0055] (10) Construction scheme and parameter optimization: analyze the calculation data and experimental phenomena of each construction scheme, and comprehensively evaluate the water-blocking effect from the indicators such as the accumulation length, construction period, joint length, residual water quantity, and upstream pressure recovery, etc., to select the optimal construction scheme that meets the expectations to guide the site construction.

[0056] Compared with the prior art, the advantages of the present application are:

[0057] (1) The water-blocking body construction method based on the FLUENT-EDEM coupling model can model water flow and aggregate particles by using different theories respectively, can efficiently depict the motion state of each aggregate particle in the water flow, can show the motion state of the whole aggregate particle group of the water-blocking body in real time, and realizes quantitative calculation and prediction of the water-blocking body construction process.

[0058] (2) The water-blocking body construction method based on the FLUENT-EDEM coupling model can simulate and calculate before water inrush occurs in a mine, can analyze various water inrush disaster conditions in advance, can classify and model calculate possible construction schemes, and can further form a water-blocking body construction optimization scheme database, so that the database can be quickly called and used when water inrush disaster occurs.

[0059] (3) The water-blocking body construction method based on the FLUENT-EDEM coupling model has the advantages of high calculation precision, low cost and dynamic visualization, can obtain key data or evolution rules that cannot be directly obtained by field or indoor tests in real time, reduces potential risks of experience-dominant engineering construction, improves the technicality and scientificity of a concealed water disaster treatment engineering construction scheme, is a new water disaster prevention and treatment technical concept and method, and has high theoretical significance and engineering application potential.

[0060] The embodiments are preferred embodiments of the present application, and are not a limitation on the technical solutions, and any obvious improvements and replacements made by those skilled in the art without departing from the essential content of the present application shall fall within the protection scope of the present application.

Claims

1. A construction method for water-blocking bodies based on the FLUENT-EDEM coupled model, characterized in that, The main steps include: Step 1, Engineering and Technical Conditions Analysis: After a mine flooding accident caused by a sudden water inrush, the water inrush process is technically analyzed based on on-site data, the location of the water-blocking body is selected, and the feasibility of implementing the interception and mine restoration is assessed. Step 2, Construction of the physical model for water-blocking body construction: Based on the spatiotemporal relationship between the mine water level and the water source level during the water inrush and the relevant basic data measured on site, a physical model for the construction of the water-blocking body is constructed. Step 3, Construction Parameter Estimation: Based on a database built from historical construction experience, the construction parameters of the water-blocking body are estimated by considering the water-blocking and pressure-reducing capacity of the aggregate, the stable water flow during construction, the grout solidification conditions during grouting, and the change in dynamic water flow velocity during grouting. Step 4: Construct a fluid-structure interaction control equation set, which includes fluid phase control equations and solid phase control equations. The fluid phase control equations include continuity equations and momentum equations, and the solid phase control equations include particle motion control equations. Step 5, Numerical Mechanics Model Construction and Mesh Generation: Draw the computational model according to the spatial dimensions of the engineering physical model, and perform reasonable mesh generation on the model; Step 6, Particle and wall parameter calibration: Based on the gradation curves and particle morphology of commonly used aggregates on site, use EDEM software to generate aggregate particles that conform to the actual working conditions; according to the properties of aggregates and tunnel walls, the parameters to be calibrated include Young's modulus, Poisson's ratio, collision recovery coefficient, sliding friction coefficient, and kinematic viscosity coefficient. Step 7, Set the solution parameters: Set the upstream inlet pressure and downstream outlet pressure according to the engineering physics model; The solution model adopts the Euler-Lagrange model, that is, the computational fluid dynamics method is used to describe the fluid behavior and the discrete element method is used to describe the mechanical behavior of the particles; The calculation time step and solution accuracy should meet the basic laws of aggregate movement; Step 8, Verification of the reliability of the numerical model: After establishing the numerical simulation model, the reliability of the model is verified, including the settling velocity of aggregate particles, angle of repose, flow field distribution, and whether the model can truly describe the motion state and mechanical behavior of aggregate and fluid. Step 9, Fluid-structure Interaction Calculation during Water Barrier Construction: First, calculate the flow field before aggregate grouting. After the flow field stabilizes, perform aggregate grouting simulation calculations according to the established construction plan. The grouting plan settings include the aggregate grouting sequence and grouting speed for a single hole, the coordination scheme between holes, and the number of holes to be grouted simultaneously. The grouting plan settings should be as consistent as possible with the actual working conditions on site to reduce the workload of calculations. Step 10, Construction Scheme and Parameter Optimization: Analyze the calculation data and experimental phenomena of each construction scheme, comprehensively evaluate the water blocking effect from the indicators of stacking length, construction period, top connection length, residual water volume, and upstream pressure recovery, and select the optimal construction scheme that meets the expectations to guide on-site construction.

2. The construction method for water-blocking bodies based on the FLUENT-EDEM coupled model according to claim 1, characterized in that, In step 1, the tunnel location is selected in a concentrated water passage tunnel that is close to the water inrush point, and the site selection section is designed in a straight tunnel or a section where the water flows uphill.

3. The construction method for water-blocking bodies based on the FLUENT-EDEM coupled model according to claim 1, characterized in that, In step 2, the key parameters involved in the physical model include the stable water flow during construction, the pressure difference between the upstream and downstream of the water-blocking body, the tunnel specifications, the tunnel slope and undulation conditions, and the surrounding rock conditions.

4. The construction method for a water-blocking body based on the FLUENT-EDEM coupled model according to claim 1, characterized in that, In step 3, estimating the water-blocking construction parameters includes estimating the length of the aggregate accumulation section, the number of boreholes, and the aggregate particle size. The aggregate stacking length L is estimated using the following formula: Where x is the flow rate; A is the cross-sectional area of ​​the tunnel; Δh is the pressure difference between upstream and downstream; t0 is the initial setting time of the slurry; k z J is the permeability coefficient of the aggregate; max is the ultimate hydraulic gradient of the deposition section; k is the working condition correction factor (1 for simple working conditions, 2-3 for medium working conditions, and 3-4 for complex working conditions); The number of boreholes, n, is estimated using the following formula (generally no less than 3 holes): Where ξ is the borehole margin coefficient; ζ is the time efficiency coefficient; m is the maximum single-hole injection capacity; T is the expected jacking period; and ρ' is the bulk density of the granular material. The aggregate particle size should be determined so that the aggregate injection capacity matches the water flow carrying capacity. This matching can be verified through field tests.

5. The construction method for a water-blocking body based on the FLUENT-EDEM coupled model according to claim 1, characterized in that, In step 4, the fluid phase control equation includes: The continuity equation is as follows: The momentum equation is as follows: Where, ρ f u f P, η, and η represent the velocity, density, pressure, and viscosity of the fluid, respectively; ε is the liquid volume fraction; g is the gravitational acceleration; and S is the momentum exchange term between the fluid phase and the solid phase.

6. The construction method for a water-blocking body based on the FLUENT-EDEM coupled model according to claim 1, characterized in that, In step 4, the particle motion control equation is: Where, m i v i Let F be the mass and velocity of the i-th particle; gp F dra These are the pressure gradient force and drag force exerted by the fluid on the i-th particle, respectively; F cont I represents the contact force acting on the particle. i ω i These are the particle's moment of inertia and rotational speed, respectively; T j is the torque; N is the number of particles in contact with the particles.

7. The construction method for a water-blocking body based on the FLUENT-EDEM coupled model according to claim 1, characterized in that, In step 5, the simulation of the water inrush channel uses multiple symmetrically distributed inlets, and the sum of the water volume of each inlet is equal to the simulated stable water flow rate; the boreholes are located in the middle of the roadway, with a spacing of 25-30m, and the number is set according to the estimated results of the construction parameters; finally, the model is divided into grids using an unstructured grid.

8. The construction method for a water-blocking body based on the FLUENT-EDEM coupled model according to claim 1, characterized in that, In step 9, aggregate grouting simulation calculations are performed according to the established construction plan. The grouting plan includes the aggregate grouting sequence and grouting speed of a single hole, the coordination scheme between holes, and the number of holes to be grouted simultaneously. The grouting plan should be set as close as possible to the actual working conditions on site to reduce the workload of calculations.

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