A method for constructing a coal rock mass grouting reinforcement model

Abstract

The application discloses a kind of broken coal rock mass grouting reinforcement model construction methods, including geological condition acquisition, model physical field and control equation determination, grouting reinforcement initial model construction, initial and boundary condition loading, representative coal rock mass broken structure determination.This method defines slurry equivalent diffusion radius and diffusion state judgment basis, can be used to represent the representative coal rock mass broken structure and the slurry filling reinforcement effect in coal rock mass model, improve the efficiency and accuracy of slurry diffusion process simulation in broken coal rock mass, provide basis for broken coal rock mass grouting simulation, further promote the development of grouting reinforcement technology in broken coal rock mass.This method is simple in operation, accurate in result, and can study the grouting diffusion law under different conditions by setting different grouting pressure, filling slurry performance parameters and other factors, with wide applicability.

Description

Technical Field

[0001] This invention relates to the field of underground grouting and filling, specifically to a method for constructing a grouting reinforcement model for fractured coal and rock masses. Background Technology

[0002] Coal, as one of my country's most important energy sources, plays a crucial role in the country's economic development, and research indicates that its importance will remain unchanged for a considerable period. However, with the rapid development of the coal industry, my country's shallow coal resources are gradually being depleted, and the focus of coal mining is shifting towards deeper areas, with increasing mining height and intensity. These complex mining conditions exacerbate problems such as roof and floor fracturing and coal face breakage during tunnel excavation, threatening the safety of underground miners and affecting the safe and normal operation of the working face. To address the issue of roof and floor fracturing and coal face breakage, scholars have proposed grouting and filling reinforcement technology. This involves injecting filling grout into the fractured coal and rock mass, allowing the grout to be squeezed or penetrate into the large and small fissures within the coal and rock mass. After reaction and consolidation, a new network skeleton structure is formed within the coal and rock mass, improving the overall cohesion and tensile and shear strength of the coal and rock mass.

[0003] Due to the concealed nature of the grouting process, monitoring the diffusion of grout in fractured coal and rock masses is difficult. The diffusion pattern determines the effectiveness of grouting reinforcement. Therefore, many scholars have conducted numerical simulations of the grout diffusion process in fractured coal and rock masses, leading to more in-depth research on grout diffusion patterns. However, the grout diffusion process exhibits different patterns depending on the fracture state in different coal and rock mass models. Inappropriate fracture characteristic parameters can lead to inaccurate calculation results, making it impossible to accurately simulate the real grout diffusion process. Therefore, it is urgent to develop a method for constructing grouting reinforcement models for fractured coal and rock masses to improve the accuracy and efficiency of grout diffusion process simulation, providing a basis for grouting reinforcement work in fractured coal and rock masses. Summary of the Invention

[0004] To address the aforementioned technical shortcomings, the purpose of this invention is to provide a method for constructing a grouting reinforcement model for fractured coal and rock masses. This method is used to determine the representative fractured structure of coal and rock masses, assess the filling and reinforcement effect of the grout during the grouting process, and determine a model that can accurately simulate the flow of grout in fractured coal and rock masses.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] This invention provides a method for constructing a grouting reinforcement model for fractured coal and rock masses, comprising the following steps:

[0007] (1) First, based on the geological data of the study area, obtain the geometric geological parameters of the rock strata where the tunnel is located, determine the model construction area, obtain the slurry performance parameters through the filling slurry performance experiment, and determine the model physical field and fluid flow control equations;

[0008] (2) Based on the model construction area and the model physical field and fluid flow control equations, an initial fractured coal and rock mass model is constructed in the numerical simulation software, including grouting boreholes and fractured coal and rock mass. The fractured coal and rock mass is constructed through a prefabricated fracture network within the unit.

[0009] (3) Set the initial and boundary conditions for the model according to the actual working conditions, including grouting pressure, grout density and dynamic viscosity, grouting inlet and outlet, and mesh the broken coal and rock mass model.

[0010] (4) After adjusting the research settings, numerical simulation calculations are performed. Based on the defined slurry equivalent diffusion radius and diffusion state judgment criteria, the slurry filling and reinforcement effect in the coal and rock mass model is characterized. By increasing the number of prefabricated fracture networks until the slurry equivalent diffusion radius and diffusion state do not change with the increase of the number of fractures, the prefabricated fracture network can represent the representative coal and rock mass fracture structure, and thus determine the model that can accurately simulate the slurry flow in the fractured coal and rock mass.

[0011] Preferably, the geometric geological parameters of the rock strata mainly include the physical and mechanical parameters and thickness of the coal seam and the roof and floor strata, the roadway layout and support parameters, and the slurry performance parameters mainly include density, dynamic viscosity, Reynolds number, fluid diffusion coefficient and compressibility coefficient.

[0012] Preferably, the slurry diffusion area ratio is defined. As a criterion for determining the diffusion state, it is used to characterize the filling and reinforcement effect of slurry in the coal and rock mass model, and the proportion of slurry diffusion area. The calculation formula is as follows:

[0013]

[0014] Among them, S 模 The area of ​​the fractured coal and rock mass model is in meters. 2 ;

[0015] The slurry diffusion area is determined by simulation software, and the slurry diffusion area ratio is calculated by the above formula. When the slurry diffusion area exceeds 80% of the model area and diffuses to the model boundary, it is considered that the slurry filling effect meets the requirements for grouting and reinforcement of the fractured coal and rock mass, and the grouting work can be stopped.

[0016] Preferably, fractures in the coal and rock mass can guide the diffusion direction of the slurry, thus affecting its diffusion pattern. Therefore, determining the fractured structure of the coal and rock mass is crucial. A pre-fabricated fracture network is used to characterize the representative fractured structure of the coal and rock mass. To determine the representative number of fracture network segments and reduce calculation errors caused by random fracture generation, the equivalent diffusion radius r of the slurry is defined. e Based on the diffusion state determination criteria, the representative number of fracture network segments and the equivalent diffusion radius r of the slurry are determined. e The calculation formula is as follows:

[0017]

[0018] Among them, S l The diffusion area of ​​the slurry is m. 2 ;

[0019] Numerical simulation software was used to randomly generate a fracture network. By increasing the number of fractures, the variation of the equivalent diffusion radius and the proportion of diffusion area of ​​the slurry was studied. When the change of the equivalent diffusion radius and the proportion of diffusion area of ​​the slurry is less than 1% as the number of fractures increases, there is no need to continue to increase the number of fractures. The calculation error caused by the random generation of fractures is minimized. All fractures are spatially interconnected and independent of each other. It is determined that the fracture network at this time can well characterize the actual fracture structure of coal and rock mass.

[0020] Preferably, when the fractured coal and rock mass model is meshed, the mesh distribution is denser in the area near the grouting holes and fractures, while the mesh distribution is relatively coarser in other areas, which can improve the simulation accuracy and computational efficiency.

[0021] The beneficial effects of this invention are as follows: This method defines the equivalent diffusion radius and diffusion state determination criteria for slurry, which can be used to characterize the slurry filling and reinforcement effect in representative coal and rock mass fractured structures and coal and rock mass models. It improves the efficiency and accuracy of slurry diffusion process simulation in fractured coal and rock masses, provides a basis for grouting simulation in fractured coal and rock masses, and further promotes the development of grouting reinforcement technology in fractured coal and rock masses. This method is simple to operate and yields accurate results. By setting different grouting pressures, filling slurry performance parameters, and other factors, the grouting diffusion law under different conditions can be studied, making it widely applicable. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1A flowchart illustrating a method for constructing a grouting reinforcement model for fractured coal and rock masses, as provided in an embodiment of the present invention;

[0024] Figure 2 Numerical models of fractured coal and rock masses with different numbers of fractures provided in embodiments of the present invention;

[0025] Figure 3 The curves showing the variation of slurry diffusion area ratio and equivalent diffusion radius with the number of cracks provided in the embodiments of the present invention;

[0026] Figure 4 The image shows the grouting effect of the fractured coal and rock mass provided in an embodiment of the present invention. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] like Figure 1 As shown, a method for constructing a grouting reinforcement model for fractured coal and rock masses includes obtaining geological conditions, determining the model's physical field and governing equations, constructing an initial grouting reinforcement model, loading initial and boundary conditions, and determining the representative fractured structure of the coal and rock mass. Specifically, grout performance parameters are obtained through grout performance experiments to determine the model's physical field and governing equations. The constructed initial model includes grouting boreholes and fractured coal and rock mass, which is constructed using a pre-fabricated fracture network within units. The determination of the representative fractured structure of the coal and rock mass involves first defining the grout's equivalent diffusion radius and diffusion state as criteria for characterizing the grout's filling and reinforcement effect in the coal and rock mass model. This is achieved by increasing the number of fracture network segments until the grout's equivalent diffusion radius and diffusion state do not change with the increase in the number of fracture segments, thus determining a model that can accurately simulate grout flow in fractured coal and rock masses.

[0029] Taking the surrounding rock of a mine working face roadway as an example, the specific implementation steps are as follows:

[0030] (1) First, based on the geological data of the study area, the geometric and geological parameters of the rock strata where the roadway is located were obtained. The model construction area was determined to be the broken coal seam on both sides of the roadway, and the permeability of the broken coal seam was κ=5×10 -15 m 2 With a porosity of 0.7, the slurry performance parameters were obtained through filling slurry performance experiments. The application of porous media dilute mass transfer (TDS) and Darcy flow (DL) calculation modules was determined to simulate the slurry diffusion process. The slurry migration process was analyzed using porous media dilute mass transfer, and the governing equations were:

[0031]

[0032] In the formula, c i The concentration of grouting material in the liquid phase (mg / L), c p,i c represents the adsorption capacity (mg / kg) of the grouting material adsorbed onto the solid phase. G,i Let θ be the concentration of the grouting material in the gas phase, θ be the volume fraction of the liquid phase, and D be the concentration of the grouting material in the gas phase. D,i D is the mechanical dispersion coefficient. e,i R is the effective diffusion coefficient. i For chemical reaction terms, S i To supplement the source term.

[0033] The Darcy flow module was used to analyze the slurry flow process, and the governing equations were:

[0034]

[0035] In the formula, ρ is the density of the grouting material (kg / m³). 3 ), where ε is porosity, Q m For mass source item (kg / (m 3 .s), k is the permeability of the porous medium (m / s), and ρ is the density of the grouting material (kg / m³). 3 ), p is the pressure (Pa), and ▽D is the unit vector of gravity direction.

[0036] (2) Based on the model construction region and physical field calculation module, a finite element calculation model of the fractured coal and rock mass was established in the numerical simulation software. The model size was 4×4m, with the grouting borehole diameter set to 34mm. The porosity of the coal body was defined as 0.7 using random parameters, and random fractures in the fractured coal body at the fully mechanized mining face were established using the DFN model. Figure 2 As shown, the slurry diffusion area is determined by the surface integral module in the COMSOL simulation software's derived value solution. The number of cracks is gradually increased, and the equivalent diffusion radius and diffusion area ratio of the slurry with different numbers of cracks are compared. Figure 3 As shown, when the number of fractures is 100, 150 and 200, the equivalent diffusion radius and diffusion area of ​​the slurry are stable at 84%, and the variation is less than 1%. Therefore, when the number of fractures exceeds 100, the random error between models is small. At this time, the number of fracture network lines can characterize the fracture structure of the representative coal and rock mass.

[0037] (3) The grouting hole is set as the inlet boundary, and the entire perimeter of the model is the outlet boundary. The density of the filling grout is 0.8 g / cm³. 3 The dynamic viscosity was 1.5 mPa·s, and the grouting pressure was set to a constant pressure of 8 MPa. The fractured coal and rock mass model was meshed, with a denser mesh distribution in the area near the grouting holes and fractures, and a relatively coarser mesh distribution in other areas.

[0038] (4) Run the calculation model to study the grout diffusion law at different grouting times, set the number of cracks, keep the grouting pressure constant at 8MPa, and the grout filling effect is as follows: Figure 4 As shown, when the slurry diffusion area exceeds 80% of the model area and spreads to the model boundary, it is considered that the slurry filling effect meets the requirements for grouting reinforcement of fractured coal and rock mass, and the grouting work can be stopped.

[0039] This method defines the equivalent diffusion radius and diffusion state criteria for grout, which can be used to characterize the grout filling and reinforcement effect in representative fractured coal and rock masses and coal and rock mass models. It improves the efficiency and accuracy of grout diffusion process simulation in fractured coal and rock masses, provides a basis for grouting simulation in fractured coal and rock masses, and further promotes the development of grouting reinforcement technology in fractured coal and rock masses. This method is simple to operate, yields accurate results, and can study the grouting diffusion law under different conditions by setting different grouting pressures, filling grout performance parameters, etc., making it widely applicable.

[0040] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for constructing a grouting reinforcement model for fractured coal and rock masses, characterized in that, Includes the following steps: (1) First, based on the geological data of the study area, obtain the geometric geological parameters of the rock strata where the tunnel is located, determine the model construction area, obtain the slurry performance parameters through the filling slurry performance experiment, and determine the model physical field and fluid flow control equations; (2) Based on the model construction area and the model physical field and fluid flow control equations, an initial fractured coal and rock mass model is constructed in the numerical simulation software, including grouting boreholes and fractured coal and rock mass. The fractured coal and rock mass is constructed through a prefabricated fracture network within the unit. (3) Set the initial and boundary conditions for the model according to the actual working conditions, including grouting pressure, grout density and dynamic viscosity, grouting inlet and outlet, and mesh the broken coal and rock mass model; (4) After adjusting the research settings, numerical simulation calculations are performed. Based on the defined slurry equivalent diffusion radius and diffusion state judgment criteria, the slurry filling and reinforcement effect in the coal and rock mass model is characterized. By increasing the number of prefabricated fracture networks, simulations of different prefabricated fracture network states are performed until the slurry equivalent diffusion radius and diffusion state do not change with the increase of the number of fractures. At this time, the prefabricated fracture network can represent the representative coal and rock mass fractured structure, and thus determine the model that can accurately simulate the slurry flow in the fractured coal and rock mass. In step (4), the slurry diffusion area ratio φ is defined as the criterion for determining the diffusion state, and is used to characterize the slurry filling and reinforcement effect in the coal and rock mass model. The formula for calculating the slurry diffusion area ratio φ is as follows: Among them, S 模 The area of ​​the fractured coal and rock mass model is in meters. 2 ; The slurry diffusion area is determined by simulation software, and the slurry diffusion area ratio is calculated by the above formula. When the slurry diffusion area exceeds 80% of the model area and diffuses to the model boundary, it is considered that the slurry filling effect meets the requirements for grouting and reinforcement of the fractured coal and rock mass, and the grouting work is stopped.

2. The method for constructing a grouting reinforcement model for fractured coal and rock mass as described in claim 1, characterized in that, In step (1), the geometric geological parameters of the rock strata include the physical and mechanical parameters and thickness of each rock stratum in the coal seam and the roof and floor, the roadway layout and support parameters, and the slurry performance parameters include density, dynamic viscosity, Reynolds number, fluid diffusion coefficient and compressibility coefficient.

3. The method for constructing a grouting reinforcement model for fractured coal and rock mass as described in claim 1, characterized in that, In step (4), the fractures in the coal and rock mass can guide the diffusion direction of the slurry, thus affecting the diffusion law of the slurry. A prefabricated fracture network is used to characterize the fractured structure of the representative coal and rock mass. In order to determine the representative number of fracture network lines and reduce the calculation error caused by the random generation of fractures, the equivalent diffusion radius r of the slurry is defined. e Based on the diffusion state determination criteria, the representative number of fracture network segments and the equivalent diffusion radius r of the slurry are determined. e The calculation formula is as follows: Among them, S l The diffusion area of ​​the slurry is m. 2 ; Numerical simulation software was used to randomly generate a fracture network. By increasing the number of fractures, the variation of the equivalent diffusion radius and the proportion of diffusion area of ​​the slurry was studied. When the change of the equivalent diffusion radius and the proportion of diffusion area of ​​the slurry is less than 1% as the number of fractures increases, there is no need to continue to increase the number of fractures. The calculation error caused by the random generation of fractures is minimized. All fractures are spatially interconnected and independent of each other. It is determined that the fracture network at this time can well characterize the actual fracture structure of coal and rock mass.

4. The method for constructing a grouting reinforcement model for fractured coal and rock mass as described in claim 1, characterized in that, When the fractured coal and rock mass model is meshed, the mesh distribution is denser in the area near the grouting holes and fractures, while the mesh distribution is relatively coarser in other areas, which can improve the simulation accuracy and computational efficiency.

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