Grouting water blocking method for coal mining area

Abstract

The present invention relates to the technical field of grouting and water blocking, and in particular to a grouting and water blocking method for coal mining areas, comprising determining the complexity of a crack network based on geological information on the surface of a grouting area; determining the dosage of several components of a grouting material according to the complexity of the crack network; injecting the grouting material into a grouting port using preset grouting parameters; determining a change rate ratio and a comprehensive deviation of grouting process parameters based on preset time intervals and periodically acquired grouting process parameters; determining an abnormality level of the grouting process according to the change rate ratio and the comprehensive deviation; determining a grouting dynamic control strategy according to the abnormality level of the grouting process; and dynamically adjusting the preset grouting parameters and the components of the grouting material according to the grouting dynamic control strategy until the grouting operation is completed. This ensures the effective filling, diffusion, and consolidation of slurry in cracks, improves the water blocking and anti-seepage effect, and avoids slurry waste or water blocking failure caused by mismatch between materials and geological conditions.

Description

Technical Field

[0001] The invention relates to the technical field of grouting and water blocking, and in particular to a grouting and water blocking method used in coal mining areas. Background Art

[0002] In projects such as underground space development, mining, tunnel construction and geological disaster control, grouting technology is a key means to achieve water blocking and anti-seepage, and to strengthen the strata. Its effectiveness directly affects the safety and cost of the project.

[0003] Invention patent CN114198124A discloses a construction method for grouting and blocking water in the roof burst area of ​​a coal mine inclined shaft, comprising the following steps: S1, drilling holes at the water outlet layer of the inclined shaft to detect the range of the cavity and measuring the amount of water gushing from the cavity area; S2, filling the water gushing from the cavity area with filling materials; S3, grouting and blocking water in the roof burst area by drilling holes in alternate rows from top to bottom at the water outlet layer of the inclined shaft, installing grouting pipes, and performing repeated grouting in alternate rows. When water gushes from the roof burst area of ​​a coal mine inclined shaft, the cavity formed in the roof burst area is first filled with filling materials, and then the cavity formed in the roof burst area is quickly grouting and blocking water by drilling holes in alternate rows, installing grouting pipes in alternate rows, and repeating grouting in alternate rows at the water-yielding layer of the inclined shaft, thereby avoiding the formation of larger cavities in the roof burst area of ​​the coal mine inclined shaft. Although this grouting and blocking water construction method has obvious grouting and blocking water effects in the roof burst area of ​​the coal mine inclined shaft, it still suffers from problems such as long slurry gel time, poor permeability, and high cost. Especially in strata with complex fissure development and abundant groundwater, cement slurry is easily diluted and lost by water flow, resulting in poor water blocking effect. Summary of the Invention

[0004] To this end, the present invention provides a grouting water blocking method for coal mining areas, which is used to overcome the problems of long slurry gel time, poor permeability, high cost and the like in the prior art.

[0005] To achieve the above object, the present invention provides a grouting water blocking method for coal mining areas, comprising the following steps:

[0006] Step S1, based on the geological information of the surface of the grouting area, determine the complexity of the fracture network, and according to the complexity of the fracture network, determine the dosage of several components of the grouting material to inject the grouting material into the grouting port using preset grouting parameters, wherein,

[0007] The grouting material is mainly made of silicon-aluminum raw materials, and is mixed with alkaline activator, saline activator, retarder, nano silicon oxide and thickener;

[0008] Step S2, periodically acquiring grouting process parameters, and judging abnormalities in the grouting process according to the grouting process pressure in the grouting process parameters;

[0009] Step S3, when it is determined that the grouting process is abnormal, determining the ratio of the rate of change and the comprehensive deviation of the grouting process parameters to determine the abnormality level of the grouting process;

[0010] Step S4, obtaining a comparison result of the abnormality level of the grouting process and the abnormality level of the standard grouting process, and if it is determined based on the comparison that the pipeline is not blocked, reducing the preset grouting pressure, increasing the retarder, or determining to adjust the grouting mode in the preset grouting parameters to intermittent grouting, and increasing the thickener until the grouting operation is completed;

[0011] The grouting material is mainly made of silicon-aluminum raw materials, and is mixed with alkaline activator, saline activator, retarder, nano-silicon oxide and thickener.

[0012] Furthermore, the process of determining the complexity of the fracture network includes:

[0013] Step S111, obtaining the connected fracture length and the total fracture length of the main fracture based on the three-dimensional model constructed based on the geological information to determine the fracture connectivity index;

[0014] Step S112, obtaining the fluid path length and the straight-line distance of the fluid in the main fracture based on the ultrasonic data to determine the tortuosity of the permeation path;

[0015] Step S113, obtaining the main crack width based on the borehole peek data, and determining the ratio of the standard deviation to the mean of the main crack width as the coefficient of variation of the opening;

[0016] Step S114 : determining the complexity of the fracture network based on the fracture connectivity index, the permeability path tortuosity, and the coefficient of variation of the opening.

[0017] Furthermore, the process of determining the complexity of the fracture network based on the fracture connectivity index, the permeability path tortuosity, and the coefficient of variation of the opening degree includes:

[0018] Normalizing the fracture connectivity index, the permeability path tortuosity, and the coefficient of variation of the opening degree respectively;

[0019] The fracture network complexity is determined by taking a weighted sum of the normalized fracture connectivity index, the permeability path tortuosity, and the coefficient of variation of the opening.

[0020] Furthermore, the dosage of each component of the grouting material is:

[0021] The silicon-alumina raw material is 87.5% to 92.8% fly ash;

[0022] The nano silicon oxide is 3% to 5%;

[0023] The alkaline activator is 3% to 5% caustic soda;

[0024] The salt stimulant is sodium sulfate 0.5% to 1%;

[0025] The retarder is 0.5% to 1% lignin sulfonate;

[0026] The thickener is 0.2% to 0.5% modified cellulose.

[0027] Furthermore, the process of determining the dosage of several components of the grouting material includes:

[0028] Step S121, determining a component parameter adjustment scheme based on a comparison result between the fracture network complexity and a standard fracture network complexity;

[0029] Step S122, determining to adopt a first component parameter adjustment scheme based on the result that the fracture network complexity is less than a first standard fracture network complexity;

[0030] Step S123, or, based on the result that the fracture network complexity is greater than or equal to the first standard fracture network complexity and the fracture network complexity is less than the second standard fracture network complexity, determining to adopt a second component parameter adjustment scheme;

[0031] Step S124 , or, based on the result that the fracture network complexity is greater than the second standard fracture network complexity, it is determined to adopt a third component parameter adjustment scheme.

[0032] Furthermore, the parameter adjustment scheme of the first component is 92.8% fly ash, 3% nano-silicon oxide, 3% caustic soda, 0.5% sodium sulfate, 0.5% lignin sulfonate and 0.2% modified cellulose;

[0033] The parameter adjustment scheme of the second component is fly ash 90.15%, nano-silicon oxide 4%, caustic soda 4%, sodium sulfate 0.75%, lignin sulfonate 0.75% and modified cellulose 0.35%;

[0034] The parameter adjustment scheme of the third component is 87.5% fly ash, 5% nano-silicon oxide, 5% caustic soda, 1% sodium sulfate, 1% lignin sulfonate and 0.5% modified cellulose.

[0035] Furthermore, the process of determining the change rate ratio and comprehensive deviation of the grouting process parameters includes:

[0036] Step S31, periodically obtaining the grouting process pressure and the grouting process flow rate among the grouting process parameters;

[0037] Step S32, determining the pressure change amplitude of the grouting process according to the pressure of the grouting process;

[0038] Step S33, determining the flow rate change amplitude of the grouting process according to the flow rate of the grouting process;

[0039] Step S34, determining the change rate ratio and the comprehensive deviation based on the preset grouting pressure and the preset grouting flow in the preset grouting parameters, as well as the pressure change amplitude and the flow change amplitude of the grouting process.

[0040] Furthermore, the process of determining the abnormality level of the grouting process includes:

[0041] Determining the abnormality level of the grouting process according to a comparison result of the change rate ratio with a standard change rate ratio, and a comparison result of the comprehensive deviation with a standard comprehensive deviation;

[0042] Based on the result that the change rate ratio is less than the first standard change rate ratio, or the change rate ratio is greater than the second standard change rate ratio,

[0043] If the comprehensive deviation is greater than the second standard comprehensive deviation, the abnormality level of the grouting process is determined to be a serious abnormality;

[0044] Otherwise, based on the result that the change rate ratio is greater than the first standard change rate ratio and the change rate ratio is less than the second standard change rate ratio,

[0045] If the comprehensive deviation is greater than the first standard comprehensive deviation, the abnormality level of the grouting process is determined to be moderate abnormality;

[0046] Otherwise, the abnormality level of the grouting process is determined to be normal.

[0047] Furthermore, the process of determining, based on the comparison result, that the pipeline is not blocked, reducing the preset grouting pressure in the preset grouting parameters, adding a retarder, or determining to dynamically adjust the preset grouting parameters and the components of the grouting material includes:

[0048] Based on the result that the change rate ratio in the grouting process abnormality level is serious abnormality is greater than the second standard change rate ratio, determining that the preset grouting pressure in the preset grouting parameters is reduced and the retarder is increased when the pipeline is not blocked;

[0049] Alternatively, based on the result that the change rate ratio in the grouting process abnormality level is severe abnormality and is less than the first standard change rate ratio, it is determined that the grouting method in the preset grouting parameters is adjusted to intermittent grouting, and the thickener is increased.

[0050] Furthermore, it also includes, based on the result that the abnormality level of the grouting process is moderate abnormality, determining to reduce the preset grouting pressure by 10% to 20%.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] The use of fly ash and other silicon-alumina raw materials as the main materials greatly reduces the cost of grouting materials. Compared with traditional cement-based grouting materials, the activity of fly ash is activated by stimulants, which not only ensures the water blocking effect but also reduces the use of high-energy consumption and high-carbon emission materials, and has significant economic and environmental benefits.

[0053] Furthermore, by determining the complexity of the fracture network and adjusting the grouting material dosage based on this complexity, we can precisely match the geological conditions of different fracture development levels in coal mining areas. Whether the fractures are sparse, moderately developed, or densely complex, targeted material ratios ensure the effective filling, diffusion, and consolidation of the slurry within the fractures, improving water plugging and anti-seepage effectiveness while avoiding slurry waste or water plugging failures caused by a mismatch between materials and geological conditions.

[0054] Furthermore, by determining the abnormality level of the grouting process in real time based on the change rate ratio and comprehensive deviation of the grouting process parameters and adopting corresponding dynamic control strategies, refined management of the grouting process is achieved;

[0055] Furthermore, by responding to formation changes and slurry diffusion in real time, problems such as slurry loss and formation uplift caused by unreasonable parameters can be avoided, effectively ensuring the safety and effectiveness of grouting construction and ensuring high-quality completion of grouting operations.

[0056] Furthermore, by using geological information to construct a three-dimensional model and combining multi-source information such as ultrasonic data and borehole peek data, the fracture connectivity index, permeability path tortuosity and opening coefficient of variation are quantitatively evaluated, providing a scientific basis for determining the complexity of the fracture network. Compared with traditional single geological exploration methods, it can more comprehensively and accurately reflect the stratigraphic characteristics of the coal mining area, provide solid data support for the design of grouting schemes, and make decisions more scientific and reasonable.

[0057] Furthermore, by grading the complexity of the crack network and the abnormality level of the grouting process, and formulating corresponding material adjustments and construction strategies, a standardized and process-based operation system is formed, which is convenient for on-site construction personnel to quickly understand and implement. While improving construction efficiency, it reduces the engineering risks caused by human misjudgment and ensures the efficient and orderly progress of grouting and water blocking projects in coal mines. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is a flowchart of the steps of a grouting water blocking method for a coal mine area according to an embodiment of the present invention;

[0059] Figure 2A flowchart of the steps for determining the complexity of a fracture network according to an embodiment of the present invention;

[0060] Figure 3 A flow chart showing the steps for determining the dosage of several components of a grouting material according to an embodiment of the present invention;

[0061] Figure 4 This is a flowchart of the steps for determining the change rate ratio and comprehensive deviation of grouting process parameters in an embodiment of the present invention. DETAILED DESCRIPTION

[0062] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention.

[0063] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0064] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside", and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0065] Furthermore, it should be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0066] See also Figure 1 As shown, Figure 1 The present invention is a flowchart of a grouting water blocking method for coal mining areas according to an embodiment of the present invention.

[0067] A grouting water blocking method for a coal mine according to an embodiment of the present invention comprises the following steps:

[0068] Step S1, based on the geological information of the surface of the grouting area, determine the complexity of the fracture network, determine the dosage of several components of the grouting material according to the complexity of the fracture network, and inject the grouting material into the grouting port using the preset grouting parameters, wherein,

[0069] Grouting materials are mainly made of silicon-aluminum raw materials, with alkaline activator, salt activator, retarder, nano-silicon oxide and thickener;

[0070] Step S2, periodically acquiring grouting process parameters, and judging abnormalities in the grouting process according to the grouting process pressure in the grouting process parameters;

[0071] Step S3, when it is determined that the grouting process is abnormal, determining the ratio of the rate of change and the comprehensive deviation of the grouting process parameters to determine the abnormality level of the grouting process;

[0072] Step S4, obtain the comparison result of the abnormal level of the grouting process and the abnormal level of the standard grouting process, and determine based on the comparison result that when the pipeline is not blocked, reduce the preset grouting pressure in the preset grouting parameters, increase the retarder, or determine to adjust the grouting method in the preset grouting parameters to intermittent grouting, increase the thickener, until the grouting operation is completed.

[0073] In the embodiment of the present invention, the preset time interval is 5 minutes.

[0074] See also Figure 2 As shown, Figure 2 This is a flow chart of the steps for determining the complexity of a fracture network according to an embodiment of the present invention.

[0075] Specifically, the process of determining the complexity of the fracture network includes:

[0076] Step S111, obtaining the connected fracture length and total fracture length of the main fracture based on the three-dimensional model constructed based on geological information to determine the fracture connectivity index;

[0077] Step S112, obtaining the fluid path length and straight-line distance of the main fracture based on the ultrasonic data to determine the tortuosity of the permeation path;

[0078] Step S113, obtaining the main crack width based on the borehole peek data, and determining the ratio of the standard deviation of the main crack width to the mean as the coefficient of variation of the opening;

[0079] Step S114 : determining the complexity of the fracture network based on the fracture connectivity index, the permeability path tortuosity, and the coefficient of variation of the opening.

[0080] In an embodiment of the present invention, the method for constructing a three-dimensional model is:

[0081] Arrange radar survey lines at intervals of 2 to 5 meters to cover the grouting area to form a two-dimensional profile grid. Use software (such as GRED3D) to synthesize a three-dimensional data volume and mark abnormal fracture areas (reflection intensity mutation zones).

[0082] Arrange 1 to 2 boreholes in the radar anomaly area, conduct cross-hole acoustic wave testing, obtain wave velocity data, and establish a "wave velocity-fracture development degree" correspondence (for example, a wave velocity <2000m / s indicates a high fracture area).

[0083] The radar reflection anomaly band is superimposed on the low-velocity acoustic wave zone to define the “skeleton path” of the fracture network, ignoring the secondary microcracks and forming a simplified three-dimensional model consisting of the main fractures.

[0084] Specifically, the fracture connectivity index is used to quantify the degree of interconnection between fractures in a fracture network, which directly determines whether the slurry can effectively diffuse in the fractures and form a continuous plugging structure. Traditional calculation methods require statistics on all-scale fractures, which is labor-intensive and inefficient. In this embodiment of the present invention, a dimensionality reduction strategy is adopted to focus on the main fractures for calculation:

[0085] Specifically, the connectivity rate C is calculated based on the number of intersections and extension length of the main cracks in the three-dimensional model:

[0086]

[0087] The length of connected cracks refers to the sum of the lengths of the main cracks that are interconnected to form an effective channel;

[0088] The total fracture length is the sum of the lengths of all main fractures in the model;

[0089] When the main cracks form a ring or network structure, the slurry diffusion path is rich, and the C value is usually ≥0.7, which is judged to be highly connected. At this time, the slurry is prone to rapid loss, and high-viscosity, fast-setting slurry is required.

[0090] In the embodiment of the present invention, the tortuosity of the permeation path T quantifies the spatial curvature of the main fracture. The larger the ratio, the higher the slurry diffusion resistance. The calculation formula is:

[0091]

[0092] in, is the actual path length of the slurry flowing along the main fracture, is the straight-line distance from the start to the end of the fracture. When T is between 1.5 and 2.0, it indicates that the path is complex and slurry tends to accumulate in the tortuous areas.

[0093] In the embodiment of the present invention, the coefficient of variation (V) of the opening degree measures the degree of dispersion of the main crack width, and the calculation formula is:

[0094]

[0095] Among them, μ represents the mean value of the main crack width. In actual measurement, the width of the main crack in the target area is measured.

[0096] Measure n times, obtain width data x1, x2, ..., xn, and get the average value through the formula;

[0097]

[0098] σ represents the standard deviation of the main crack width, which is calculated based on the mean value and the formula is

[0099]

[0100] That is, first calculate the square of the difference between each measurement value and the mean, then find the average of these square values, and finally take the square root to get the standard deviation. When V>0.5, it indicates that the crack width difference is significant, and the slurry tends to flow quickly in the wide cracks, making it difficult to fill small cracks.

[0101] Specifically, the process of determining the complexity of the fracture network based on the fracture connectivity index, permeability path tortuosity, and the coefficient of variation of the opening degree includes:

[0102] The fracture connectivity index, permeability path tortuosity, and coefficient of variation of opening were normalized respectively;

[0103] The fracture network complexity is determined by taking the weighted sum of the normalized fracture connectivity index, permeability path tortuosity, and coefficient of variation of opening.

[0104] In the embodiment of the present invention, since the dimensions of the parameters are different (for example, the connectivity index is dimensionless, and the coefficient of variation of the opening is the length variation ratio), they need to be mapped to the interval [0, 1] using the normalization formula:

[0105] The normalized connectivity index is denoted as C'. The normalization method is the ratio of the connectivity index C to the theoretical maximum connectivity value. The theoretical maximum connectivity index is 1 when the fracture is fully connected.

[0106] The normalized tortuosity of the infiltration path is recorded as T', and its normalized formula is:

[0107]

[0108] It can be understood that the higher the tortuosity of the permeation path, the smaller the normalized value.

[0109] The normalized coefficient of variation of the opening degree is recorded as , its normalized formula is:

[0110]

[0111] in, It is the maximum value of all the coefficients of variation of the opening degree in the current sample set.

[0112] The weight distribution needs to be combined with the geological requirements of the grouting target (mainly water blocking) and set according to the degree of influence of the parameters on the slurry diffusion:

[0113] Connectivity index (weight 40%): determines whether the slurry can effectively cover the fracture network and has the highest weight.

[0114] Permeation path tortuosity (weight 35%): affects the slurry flow resistance and uniformity, and has the second highest weight.

[0115] Coefficient of variation of opening degree (weight 25%): reflects the uniformity of spatial distribution of cracks and has a great influence on the anti-dispersion requirements of slurry.

[0116] The calculation formula of the crack network complexity K is: .

[0117] Specifically, the dosage of each component of the grouting material is:

[0118] The siliceous and aluminous raw materials are 87.5% to 92.8% fly ash;

[0119] Nano silicon oxide 3% to 5%;

[0120] The alkaline activator is 3% to 5% caustic soda;

[0121] The salt stimulant is sodium sulfate 0.5% to 1%;

[0122] The retarder is lignin sulfonate 0.5% to 1%;

[0123] The thickener is modified cellulose 0.2% to 0.5%.

[0124] See also Figure 3 As shown, Figure 3 The present invention provides a flowchart of the steps for determining the dosage of several components of grouting materials according to an embodiment of the present invention.

[0125] Specifically, the process of determining the dosage of several components of grouting materials includes:

[0126] Step S121, determining a component parameter adjustment plan based on a comparison result between the fracture network complexity and the standard fracture network complexity;

[0127] Step S122, determining to adopt the first component parameter adjustment scheme based on the result that the fracture network complexity is less than the first standard fracture network complexity;

[0128] Step S123, or, based on the result that the fracture network complexity is greater than or equal to the first standard fracture network complexity and the fracture network complexity is less than the second standard fracture network complexity, determining to adopt the second component parameter adjustment scheme;

[0129] Step S124 , or, based on the result that the fracture network complexity is greater than the second standard fracture network complexity, it is determined to adopt the third component parameter adjustment scheme.

[0130] In the embodiment of the present invention, the first standard fracture network complexity is set to 0.3, and the second standard fracture network complexity is set to 0.6.

[0131] It can be understood that when the fracture network complexity is greater than or equal to the first standard fracture network complexity, it indicates that the fractures are sparse and poorly connected, and the slurry is easy to diffuse but may be lost;

[0132] Adjustments include:

[0133] Reduce the thickener (modified cellulose) to 0.2%-0.3% to reduce the slurry viscosity and promote diffusion; due to the low anti-seepage requirements, the nano-silica dosage is limited to 3%;

[0134] The lower limit of alkaline activator (caustic soda) can be 3% to ensure basic gelling properties.

[0135] When the fracture network complexity is greater than or equal to the first standard fracture network complexity, it indicates that the fracture network is moderately connected and the permeation path has a certain degree of tortuosity;

[0136] Adjustments include:

[0137] The thickener is maintained at 0.3% to 0.4% to balance anti-dispersion and fluidity;

[0138] Retarder (lignin sulfonate) is added at 0.5% to 0.8% to prevent the slurry from setting prematurely in a tortuous path;

[0139] The salt activator (sodium sulfate) takes a median value of 0.7% to 0.8% to enhance early gelling properties.

[0140] The result that the complexity of the fracture network is greater than the second standard fracture network complexity determines the use of the third component parameter adjustment scheme, indicating that the fractures are dense and have large width differences, the slurry is easy to leak along the large fractures, and the small fractures are difficult to fill;

[0141] Adjustments include:

[0142] Increase the thickener to 0.4% to 0.5% to increase the viscosity of the slurry and prevent dispersion;

[0143] The content of nano-silicon oxide is increased to 4% to 5% to fill micro cracks and enhance impermeability;

[0144] Increase the retarder to 0.8% to 1% to extend the setting time and ensure sufficient diffusion of the slurry;

[0145] An additional 0.1% to 0.2% expansion agent (such as ettringite) can be added to compensate for shrinkage in large cracks and improve the sealing density.

[0146] In the embodiment of the present invention, the parameter adjustment scheme of the first component is fly ash 92.8%, nano-silicon oxide 3%, caustic soda 3%, sodium sulfate 0.5%, lignin sulfonate 0.5% and modified cellulose 0.2%;

[0147] The parameter adjustment scheme for the second component is fly ash 90.15%, nano-silicon oxide 4%, caustic soda 4%, sodium sulfate 0.75%, lignin sulfonate 0.75% and modified cellulose 0.35%;

[0148] The parameter adjustment plan for the third component is 87.5% fly ash, 5% nano-silicon oxide, 5% caustic soda, 1% sodium sulfate, 1% lignin sulfonate and 0.5% modified cellulose.

[0149] It is understandable that the mechanism of fracture network complexity and component adjustment in the embodiment of the present invention is explained as follows:

[0150] 1. Fracture network complexity hierarchical correlation

[0151] Combining the fracture connectivity index, permeability path tortuosity and opening coefficient of variation, the fracture network complexity is divided into three levels: low, medium and high, corresponding to the first, second and third component parameter adjustment schemes respectively.

[0152] Low complexity: The fracture connectivity index is small (the proportion of connected fractures is low), the permeation path tortuosity is small (the fluid path is close to a straight line), and the coefficient of variation of the opening is small (the difference in fracture width is small). In this case, the first component parameter adjustment scheme is adopted.

[0153] Medium complexity: The fracture connectivity index, permeability path tortuosity, and coefficient of variation of opening are all at a medium level, corresponding to the parameter adjustment scheme of the second component.

[0154] High complexity: large fracture connectivity index (a large number of fractures are interconnected), large permeability path tortuosity (complex fluid flow path), large coefficient of variation of opening (significant differences in fracture width), suitable for the third component parameter adjustment scheme.

[0155] 2. Explanation of the adjustment mechanism of each component

[0156] 2.1 Low complexity corresponds to the first group of solutions

[0157] High Fly Ash Content: Low-complexity crack networks are relatively simple, with a small number of fissures and poor connectivity, requiring less filling and gelling of the grouting material. A high fly ash content (92.8%) ensures basic gelling properties while reducing material costs. As the primary base material, the gelling properties generated by the alkaline activator are sufficient for filling and repairing simple cracks.

[0158] Low dosage of nano-silica (3%): The anti-permeability requirements for low-complexity cracks are not high. A small amount of nano-silica can fill the pores between the fly ash hydration products, slightly improving the density and anti-permeability of the consolidated body, without the need for too high a dosage.

[0159] Low dosage of alkaline activator (3% caustic soda) and salt activator (0.5% sodium sulfate): In a simple crack network, the fly ash has a low activation requirement. A lower dosage of composite activator can make the fly ash produce sufficient gelling properties, avoiding excessive activator that leads to increased material costs and excessive shrinkage.

[0160] Low dosage of retarder (0.5% lignin sulfonate): The construction of low-complexity crack grouting is relatively simple, the slurry flow path is short, and there is no need for an excessively long setting time. Low dosage of retarder can ensure that the slurry sets within a reasonable time, thereby improving construction efficiency.

[0161] Low dosage of environmentally friendly thickener (0.2% modified cellulose): The slurry is not easy to disperse in simple cracks, and a low dosage of thickener can meet the basic anti-dispersion requirements and avoid the slurry viscosity being too high to affect penetration and filling.

[0162] 2.2 Medium complexity corresponds to the second group of solutions

[0163] Moderately reduced fly ash content: The connectivity and number of fissures in the medium-complexity fracture network increased, requiring more cementitious material to fill and cement. The fly ash content was reduced to 90.15%, making room for other functional components while still serving as the primary matrix, providing the basic cementitious framework.

[0164] Increasing the nano-silica content (4%): As crack complexity increases and permeation pathways become more tortuous, the need for water resistance increases. Increasing the nano-silica content further fills pores, refines the pore structure, enhances the permeability of the cement, and prevents water from penetrating through complex pathways.

[0165] Increased activator dosage: Medium-complexity cracks require more cementitious products to fill connected cracks. The dosages of caustic soda and sodium sulfate are increased to 4% and 0.75% respectively, which enhances the composite activation effect on fly ash, promotes more active components to participate in the reaction, and generates more cementitious substances.

[0166] Increasing the retarder dosage (0.75%): The penetration path of moderately complex cracks becomes longer, and the slurry needs longer to fully fill all cracks. Increasing the retarder dosage prolongs the slurry setting time and ensures that the slurry does not solidify prematurely when flowing through complex paths.

[0167] Increasing the thickener dosage (0.35%): The coefficient of variation of crack opening was moderate, with some areas exhibiting larger crack widths, leading to the slurry's tendency to disperse and dissipate. Increasing the modified cellulose dosage increased the slurry's viscosity and anti-dispersion ability, ensuring that the slurry could effectively fill cracks of varying widths.

[0168] 2.3 High complexity corresponds to the third group of solutions

[0169] The fly ash content is further reduced: The highly complex fracture network, characterized by dense and extensive interconnected fissures, requires a large number of functional additives to enhance material performance. The fly ash content has been reduced to 87.5%, providing sufficient room for higher dosages of functional components.

[0170] High Nano-Silica Dosage (5%): Highly complex fractures have extremely tortuous permeation paths, requiring extremely high water resistance. 5% nano-silica can fill pores to the maximum extent, forming a dense structure, significantly improving the permeability of the consolidated structure and effectively blocking water penetration channels.

[0171] High activator dosage: Highly connected fracture networks require a large amount of cementitious products to fill them. High dosages of caustic soda (5%) and sodium sulfate (1%) fully activate fly ash, prompting it to produce a large amount of cementitious hydration products, meeting the needs of filling and cementing complex fractures.

[0172] High retarder dosage (1%): Highly complex cracks have long and complex fluid paths, requiring extended slurry flow. High lignin sulfonate dosage significantly prolongs the setting time, ensuring sufficient time for the slurry to penetrate all crack branches and avoid inadequate filling due to premature setting.

[0173] High thickener dosage (0.5%): A large coefficient of variation in opening indicates significant differences in crack widths, and some wide cracks can easily lead to slurry loss. High dosages of modified cellulose significantly increase the slurry's viscosity and anti-dispersion ability, ensuring that the slurry remains stable and fully fills cracks of various widths.

[0174] By adjusting the components according to the complexity of the crack network, the performance of the grouting material can be precisely matched with the crack characteristics, ensuring the repair effect while achieving reasonable control of material costs.

[0175] See also Figure 4 As shown, Figure 4 This is a flowchart of the steps for determining the change rate ratio and comprehensive deviation of grouting process parameters in an embodiment of the present invention.

[0176] Specifically, the process of determining the change rate ratio and comprehensive deviation of the grouting process parameters includes:

[0177] Step S31, periodically obtaining the grouting process pressure and the grouting process flow rate among the grouting process parameters;

[0178] Step S32, determining the pressure change amplitude during the grouting process according to the pressure during the grouting process;

[0179] Step S33, determining the flow rate change amplitude of the grouting process according to the flow rate of the grouting process;

[0180] Step S34, determining the change rate ratio and the comprehensive deviation based on the preset grouting pressure and the preset grouting flow in the preset grouting parameters, as well as the pressure change amplitude and the flow change amplitude during the grouting process.

[0181] In the embodiment of the present invention, the pressure and flow rate during the grouting process are regarded as interrelated variables, and a comprehensive evaluation index is constructed by the ratio of the change rate of the pressure during the grouting process to the flow rate during the grouting process R and the joint deviation D. The specific calculation is as follows:

[0182] The ratio of the pressure and flow rate change rate during the grouting process R:

[0183] Where ΔP is the pressure change amplitude, is the preset grouting pressure;

[0184] ΔQ is the flow rate change amplitude, The preset grouting flow rate.

[0185] The specific calculation of the joint deviation D is as follows:

[0186]

[0187] Specifically, the process of determining the abnormality level of the grouting process includes:

[0188] The abnormality level of the grouting process is determined based on the comparison results of the change rate ratio and the standard change rate ratio, as well as the comparison results of the comprehensive deviation and the standard comprehensive deviation;

[0189] Based on the result that the rate of change ratio is less than the first standard rate of change ratio, or the rate of change ratio is greater than the second standard rate of change ratio,

[0190] If the comprehensive deviation is greater than the second standard comprehensive deviation, the abnormality level of the grouting process is determined to be severe abnormality;

[0191] Otherwise, based on the result that the change rate ratio is greater than the first standard change rate ratio and the change rate ratio is less than the second standard change rate ratio,

[0192] If the comprehensive deviation degree is greater than the first standard comprehensive deviation degree, determine that the abnormal level of the grouting process is moderately abnormal;

[0193] Otherwise, determine that the abnormal level of the grouting process is normal.

[0194] In the embodiments of the present invention, the first standard change rate is set to 0.5, the second standard change rate is set to 2, the first standard comprehensive deviation degree is set to 0.2, and the second standard comprehensive deviation degree is set to 0.3.

[0195] It can be understood that on the premise that the abnormal level of the grouting process is severely abnormal:

[0196] If R>2 and D>0.3, it indicates that the pressure increases sharply while the flow rate decreases suddenly, which may be pipe blockage or rapid filling of cracks. The control strategy should include:

[0197] Control strategy: Immediately stop grouting and check whether the pipeline is blocked; Add 0.2% - 0.3% retarder (lignosulfonate) and remix the slurry; Use pulsed grouting and test grout at low pressure (60% - 70% of the original pressure) and small flow rate (50% of the original flow rate).

[0198] If R<0.5 and D>0.3, it indicates that the pressure drops suddenly but the flow rate surges, and there is large crack leakage or channeling. The control strategy should include:

[0199] Suspend grouting, increase the dosage of environmental protection thickener (modified cellulose) by 0.3% - 0.5%, and increase nano - silica to 5% to enhance the viscosity and anti - permeability of the slurry; Use intermittent grouting, grout for 3 minutes each time, with an interval of 15 minutes, to force the slurry to solidify and seal in the cracks.

[0200] When the abnormal level of the grouting process is moderately abnormal, that is, 1<R<2 or 0.5<R<1, it indicates that the change trends of pressure and flow rate are inconsistent, and potential risks need to be alerted. The control strategy should include:

[0201] Reduce the grouting speed by 10% - 20% to make the slurry spread evenly; Adjust the grouting sequence and preferentially grout in the low - pressure and high - flow areas; If the abnormality persists, drill detection holes 2 - 3m around the original hole position and re - evaluate the geological conditions.

[0202] Specifically, according to the comparison result, when the pipeline is not blocked, the preset grouting pressure in the preset grouting parameters is reduced, the retarder is added, or the process of dynamically adjusting the preset grouting parameters and the components of the grouting material includes:

[0203] Based on the result that the change rate ratio in the severely abnormal grouting process is greater than the second standard change rate ratio, when the pipeline is not blocked, the preset grouting pressure in the preset grouting parameters is reduced, and the retarder is added;

[0204] Alternatively, based on the result that the change rate ratio of the grouting process abnormality level is a severe abnormality and is less than the first standard change rate ratio, it is determined that the preset grouting parameters and the components of the grouting material are dynamically adjusted.

[0205] Specifically, when the pipeline is not blocked, the preset grouting pressure in the preset grouting parameters is reduced. When adding retarder, 0.2% to 0.3% of lignin sulfonate is added to reduce the preset grouting pressure by 60% to 70%;

[0206] When determining to adjust the grouting method in the preset grouting parameters to intermittent grouting and adding the thickener, increase the modified cellulose by 0.3% to 0.5%.

[0207] Specifically, based on the result that the abnormality level of the grouting process is moderate, it is determined to adjust and reduce the preset grouting pressure by 10% to 20%.

[0208] A specific embodiment:

[0209] 1. Project Overview

[0210] Water seepage was observed in the side wall of a tunnel in a coal mine. Preliminary investigation revealed multiple cracks in the wall, requiring grouting to repair the water. The grouting area was approximately 50 square meters, and the wall thickness was 0.8 meters.

[0211] 2. Determining the complexity of the crack network

[0212] Data acquisition: Based on the geological information of the grouting area surface, a three-dimensional model was constructed, and the connected crack length of the main crack was obtained to be 12m, and the total crack length was 15m. Through ultrasonic testing, the fluid path length of the main crack was obtained to be 8m, and the straight-line distance was 5m. Using borehole peek data, the main crack widths were measured to be 1.2mm, 1.5mm, 1.0mm, 1.8mm, and 0.9mm, respectively.

[0213] Calculate the correlation index:

[0214] Fracture connectivity index = connected fracture length / total fracture length = 12 / 15 = 0.8.

[0215] The tortuosity of the permeation path = fluid path length / straight-line distance = 8 / 5 = 1.6.

[0216] The mean of the main crack width = (1.2+1.5+1.0+1.8+0.9) / 5 = 1.28 mm, the standard deviation is calculated to be 0.36 mm, and the coefficient of variation of the opening degree = standard deviation / mean = 0.36 / 1.28≈0.28.

[0217] Normalization processing: Assuming that the value ranges of the fracture connectivity index, permeability path tortuosity, and coefficient of variation of opening are [0, 1], [1, 3], and [0, 1], respectively, after normalization processing, they are 0.8, 0.3, and 0.28, respectively.

[0218] Determine the complexity of the fracture network: use weighted summation with weights set to 0.4, 0.3, and 0.3, respectively. The fracture network complexity = 0.8×0.4+0.3×0.3+0.28×0.3=0.32+0.09+0.084=0.494.

[0219] 3. Determine the dosage of grouting material components

[0220] The first standard fracture network complexity was set at 0.3, and the second standard fracture network complexity was set at 0.6. Since 0.3≤0.494<0.6, the second component parameter adjustment scheme was adopted, namely 90.15% fly ash, 4% nano-silica, 4% caustic soda, 0.75% sodium sulfate, 0.75% lignin sulfonate, and 0.35% modified cellulose.

[0221] 4. Grouting operation and process monitoring

[0222] Preset grouting parameters: the preset grouting pressure is 1.5MPa, and the preset grouting flow rate is 20L / min.

[0223] Acquisition of grouting process parameters: Grouting process parameters are periodically acquired at preset time intervals (every 5 minutes). Some of the data are shown in the following table:

[0224]

[0225] Determine if the grouting process is abnormal:

[0226] Calculate the pressure and flow rate change amplitudes during the grouting process. Taking the data at 15 minutes as an example, the pressure change amplitude = 1.8-1.5 = 0.3 MPa, and the flow rate change amplitude = 20-15.6 = 4.4 L / min.

[0227] The change rate ratio = (pressure change amplitude / preset grouting pressure) / (flow change amplitude / preset grouting flow) = (0.3 / 1.5) / (4.4 / 20) = 0.2 / 0.22≈0.91.

[0228] Comprehensive deviation = √[(pressure change amplitude / preset grouting pressure)²+(flow change amplitude / preset grouting flow)²]=√[0.2²+0.22²]=√[0.04+0.0484]=√0.0884≈0.297.

[0229] Determine the abnormality level of the grouting process: set the first standard change rate ratio to 0.8, and the second standard change rate ratio to 1.2; the first standard comprehensive deviation to 0.2, and the second standard comprehensive deviation to 0.3. At 15 minutes, the change rate ratio of 0.91 is between 0.8-1.2, and the comprehensive deviation of 0.297>0.2, so the abnormality level of the grouting process is determined to be moderate.

[0230] Determine the dynamic grouting control strategy: Since the abnormality level is moderate, the third dynamic grouting control strategy is adopted to reduce the preset grouting pressure by 15%, that is, adjust it to 1.5×(1-15%)=1.275MPa.

[0231] 5. Dynamic adjustment and completion of grouting

[0232] After adjusting the grouting parameters according to the above control strategy, the grouting operation was continued. Subsequent monitoring found that the grouting process parameters tended to be stable until the grouting operation was completed.

[0233] VI. Experimental Verification

[0234] 1. Experimental Purpose

[0235] Verify the water blocking effect and reliability of the grouting water blocking method.

[0236] 2. Experimental Design

[0237] Two experimental areas A and B with similar conditions to those in the above embodiment were selected. Area A adopted the grouting water blocking method of the present invention, and area B adopted the traditional grouting method, while other conditions remained the same.

[0238] 3. Experimental results and analysis

[0239] Water blocking effect: Seven days after the grouting was completed, water seepage tests were conducted in two areas. Area A showed no obvious water seepage points, with a water seepage rate of 0; Area B still had three water seepage points, with a water seepage rate of 6%.

[0240] Material cost: The grouting material cost in area A is 800 yuan / m2, and in area B it is 1,000 yuan / m2. The method of the present invention reduces the material cost while ensuring the water blocking effect.

[0241] Wall damage: Ultrasonic testing revealed no new cracks in the wall of area A, but two new cracks appeared in area B due to excessive holes.

[0242] 4. Experimental Conclusion

[0243] The grouting and water blocking method for coal mining areas provided by the present invention can accurately determine the components of the grouting material according to the complexity of the crack network, effectively ensure the grouting effect through process monitoring and dynamic regulation, reduce material costs, and cause little damage to the wall, and has good practicality and reliability.

[0244] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A grouting water blocking method for coal mining areas, characterized in that: include: Determine the complexity of the fracture network based on geological information of the surface of the grouting area, and determine the dosage of several components of the grouting material based on the complexity of the fracture network; Injecting the grouting material into the grouting port using preset grouting parameters; Based on the grouting process parameters periodically acquired at preset time intervals, determining the grouting process abnormality according to the grouting process pressure in the grouting process parameters; Determine the change rate ratio and comprehensive deviation of the grouting process parameters based on the grouting process pressure and the grouting process flow rate in the grouting process parameters to determine the abnormality level of the grouting process; The dynamic grouting control strategy is determined according to the abnormal level of the grouting process, wherein: The grouting dynamic control strategy includes a first grouting dynamic control strategy and a second grouting dynamic control strategy. The first grouting dynamic control strategy is to reduce the preset grouting pressure in the preset grouting parameters and increase the retarder when it is determined that the pipeline is not blocked. The second grouting dynamic control strategy is to adjust the grouting method to intermittent grouting and add thickener; Dynamically adjusting the preset grouting parameters and the components of the grouting material according to the grouting dynamic control strategy until the grouting operation is completed; The grouting material is mainly composed of silicon-aluminum raw materials, and is mixed with alkaline activator, salt activator, retarder, nano-silicon oxide and thickener; The process of determining the complexity of the fracture network includes: The three-dimensional model constructed based on the geological information obtains the connected fracture length and the total fracture length of the main fracture to determine the fracture connectivity index. Obtain the fluid path length and straight-line distance of the main fracture based on ultrasonic data to determine the tortuosity of the permeation path; The main crack width is obtained based on the borehole peek data, and the ratio of the standard deviation of the main crack width to the mean is determined as the coefficient of variation of the opening degree. Determining the complexity of the fracture network based on the fracture connectivity index, the permeability path tortuosity, and the coefficient of variation of the opening; The process of determining the complexity of the fracture network based on the fracture connectivity index, the permeability path tortuosity, and the coefficient of variation of the opening degree includes: The fracture connectivity index, the permeability path tortuosity and the coefficient of variation of the opening degree are normalized respectively. The fracture network complexity is determined by taking a weighted sum of the normalized fracture connectivity index, the permeability path tortuosity, and the coefficient of variation of the opening.

2. The grouting water blocking method for coal mining area according to claim 1, characterized in that: The dosage of each component of the grouting material is: The silicon-alumina raw material is 87.5% to 92.8% fly ash; The nano silicon oxide is 3% to 5%; The alkaline activator is 3% to 5% caustic soda; The salt stimulant is sodium sulfate 0.5% to 1%; The retarder is 0.5% to 1% lignin sulfonate; The thickener is 0.2% to 0.5% modified cellulose.

3. The grouting water blocking method for coal mining area according to claim 2, characterized in that: The process of determining the dosage of several components of the grouting material includes: Determining a component parameter adjustment scheme based on a comparison result of the fracture network complexity and the standard fracture network complexity; Determining to adopt a first component parameter adjustment scheme based on a result that the fracture network complexity is less than a first standard fracture network complexity; Or, based on the result that the fracture network complexity is greater than or equal to the first standard fracture network complexity and the fracture network complexity is less than the second standard fracture network complexity, it is determined to adopt the second component parameter adjustment scheme; Alternatively, based on the result that the fracture network complexity is greater than the second standard fracture network complexity, it is determined to adopt the third component parameter adjustment scheme.

4. The grouting water blocking method for coal mining area according to claim 3, characterized in that: The parameter adjustment scheme of the first component is fly ash 92.8%, nano-silicon oxide 3%, caustic soda 3%, sodium sulfate 0.5%, lignin sulfonate 0.5% and modified cellulose 0.2%; The parameter adjustment scheme of the second component is fly ash 90.15%, nano-silicon oxide 4%, caustic soda 4%, sodium sulfate 0.75%, lignin sulfonate 0.75% and modified cellulose 0.35%; The parameter adjustment scheme of the third component is 87.5% fly ash, 5% nano-silicon oxide, 5% caustic soda, 1% sodium sulfate, 1% lignin sulfonate and 0.5% modified cellulose.

5. The grouting water blocking method for coal mining area according to claim 4, characterized in that: The process of determining the change rate ratio and comprehensive deviation of the grouting process parameters includes: Periodically obtaining the grouting process pressure and the grouting process flow; Determining the pressure change amplitude of the grouting process according to the pressure of the grouting process; Determining a flow rate change amplitude during the grouting process according to the flow rate during the grouting process; The change rate ratio and the comprehensive deviation are determined based on the preset grouting pressure and the preset grouting flow in the preset grouting parameters, as well as the pressure change amplitude and the flow change amplitude during the grouting process.

6. The grouting water blocking method for coal mining area according to claim 5, characterized in that: The process of determining the abnormality level of the grouting process includes: Determining the abnormality level of the grouting process according to a comparison result of the change rate ratio with a standard change rate ratio, and a comparison result of the comprehensive deviation with a standard comprehensive deviation; Based on the result that the change rate ratio is less than the first standard change rate ratio, or the change rate ratio is greater than the second standard change rate ratio, If the comprehensive deviation is greater than the second standard comprehensive deviation, the abnormality level of the grouting process is determined to be a serious abnormality; Otherwise, based on the result that the change rate ratio is greater than the first standard change rate ratio and the change rate ratio is less than the second standard change rate ratio, If the comprehensive deviation is greater than the first standard comprehensive deviation, the abnormality level of the grouting process is determined to be moderate abnormality; Otherwise, the abnormality level of the grouting process is determined to be normal.

7. The grouting water blocking method for coal mining area according to claim 6, characterized in that: The process of determining the dynamic grouting control strategy according to the abnormality level of the grouting process includes: Based on the result that the change rate ratio in the grouting process abnormality level is severe abnormality is greater than the second standard change rate ratio, determining to adopt the first grouting dynamic control strategy; Or, based on the result that the change rate ratio in the grouting process abnormality level is severe abnormality is less than the first standard change rate ratio, determining to adopt the second grouting dynamic control strategy; The first grouting dynamic control strategy is to add 0.2% to 0.3% of the lignin sulfonate to reduce the preset grouting pressure by 60% to 70% when it is determined that the pipeline is not blocked; The second grouting dynamic control strategy is to adjust the grouting method to intermittent grouting and increase the modified cellulose by 0.3% to 0.5%.

8. The grouting water blocking method for coal mining area according to claim 7, characterized in that: The process of determining the dynamic grouting control strategy according to the abnormality level of the grouting process further includes: Based on the result that the abnormality level of the grouting process is moderate abnormality, determining to adopt the third grouting dynamic control strategy; The third grouting dynamic control strategy is to reduce the preset grouting pressure by 10% to 20%.

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