Method for testing water flow blocking effect under action of mining-induced fracture grouting

Abstract

The invention relates to a method for testing a water flow blocking effect under the action of mining-induced fracture grouting, and belongs to the technical field of mineral engineering and grouting engineering. The method comprises the following steps: acquiring an artificial rock model of a rock sample; wherein the artificial rock model comprises a fracture network; performing grouting treatment on the artificial rock model; and respectively carrying out mechanical seepage test on the artificial rock model before and after grouting, collecting seepage parameters before and after grouting, and quantitatively evaluating the water flow barrier effect of grouting in combination with a water flow migration track. The method can visually, quantitatively and dynamically evaluate the water flow blocking effect of mining-induced fracture grouting, and provides a standardized test method and a reliable evaluation means for engineering practice.

Description

Technical Field

[0001] The present invention relates to the technical fields of mining engineering and grouting engineering, and particularly relates to a test method for the water flow blocking effect under the action of grouting in mining-induced fractures. Background Art

[0002] During the coal mining process, a large number of fractures will be formed in the rock strata due to mining-induced effects. These mining-induced fractures not only affect the safe production of mines, but may also become channels for groundwater flow, causing water inrush or even water bursting disasters in the stope. At the same time, the development of mining-induced fractures will also exacerbate surface subsidence, threatening the safety of ground buildings and structures.

[0003] Grouting is one of the important technical means for dealing with mining-induced fractures. By injecting grout into the fractures, the water flow channels can be effectively blocked and the broken rock mass can be reinforced. However, with the increase of coal mining intensity and mining depth, the development of mining-induced fractures becomes more complex, and the effect of single grouting is difficult to meet the engineering requirements. Especially under complex geological conditions, traditional grouting methods often have problems such as uneven slurry diffusion and incomplete filling, resulting in unsatisfactory grouting effects.

[0004] At present, the evaluation of the grouting effect of mining-induced fractures mainly relies on engineering experience and simple physical and mechanical tests, lacking scientific and quantitative evaluation methods. Especially for the water flow blocking effect of fractures after grouting, the existing technology mainly indirectly evaluates it through the change of water conductivity before and after grouting, and cannot intuitively and accurately reflect the blocking effect of grouting on water flow. At the same time, the existing evaluation methods rarely consider the dynamic development process of mining-induced fractures, resulting in a deviation between the evaluation results of grouting effects and the actual situation.

[0005] Therefore, establishing a test method that can intuitively and quantitatively evaluate the water flow blocking effect of grouting in mining-induced fractures is of great significance for guiding engineering practice and improving grouting effects. Summary of the Invention

[0006] In view of the fact that the existing technical means cannot directly and effectively analyze and evaluate the water flow blocking effect of grouting in mining-induced fractures, resulting in certain uncertainty and blindness in on-site construction. The purpose of the present invention is to provide a test method for the water flow blocking effect under the action of grouting in mining-induced fractures, which is based on real rock samples, uses 3D printing models and dynamically monitors, so as to solve the problem of lacking an intuitive and quantitative grouting effect evaluation method in the existing technology.

[0007] To achieve the above purpose, the present invention provides the following solutions:

[0008] A test method for the water flow blocking effect under the action of grouting in mining-induced fractures, comprising:

[0009] An artificial rock model of a rock sample; wherein, the artificial rock model includes a fracture network;

[0010] Perform grouting treatment on the artificial rock model;

[0011] Perform mechanical seepage tests on the artificial rock model before and after grouting respectively, collect seepage parameters before and after grouting, and quantitatively evaluate the water flow blocking effect of grouting in combination with the water flow migration trajectory.

[0012] Optionally, using 3D printing technology, obtaining an artificial rock model of a rock sample includes:

[0013] Perform 3D digital scanning on the rock sample to obtain a digital fracture network model;

[0014] Based on the digital fracture network model, use 3D printing technology to construct an artificial rock model containing a complex fracture network.

[0015] Optionally, performing 3D digital scanning on the rock sample includes:

[0016] Using scanning technology to obtain the three-dimensional geometric information of the rock fractures; wherein, the three-dimensional geometric information includes: fracture distribution, strike, aperture, and connectivity.

[0017] Optionally, using 3D printing technology to construct an artificial rock model containing a complex fracture network includes:

[0018] Use raw materials similar to the composition of the rock sample, and at the same time add cement and binder, and mix them according to a preset ratio to obtain 3D printing raw materials;

[0019] Set printing parameters, and perform printing based on the 3D printing raw materials; wherein, the printing parameters include: layer thickness, printing speed, nozzle diameter, and the formed size is the same as that of the rock sample;

[0020] Perform surface pretreatment after printing.

[0021] Optionally, performing grouting treatment on the artificial rock model includes:

[0022] Based on Portland cement, use the micro-pressure sectional grouting method to grout the artificial rock model.

[0023] Optionally, performing the mechanical seepage test includes:

[0024] Inject a colored fluorescent tracer into the water, apply preset stress and water pressure conditions, and use visualization observation technology to record the water flow migration trajectory.

[0025] Optionally, quantitatively evaluating the water flow blocking effect of grouting includes:

[0026] Based on the seepage parameters before and after grouting, combined with the water flow migration trajectory, calculate quantitative evaluation indexes; wherein, the quantitative evaluation indexes include: permeability coefficient and water flow blockage rate;

[0027] Analyze the changes of water flow paths and quantitative evaluation indexes before and after grouting under different confining pressure conditions, and evaluate the water flow blockage effect and stress sensitivity of grouting.

[0028] Optionally, the water flow blockage rate is:

[0029] Blockage rate = (1 - permeability coefficient after grouting / permeability coefficient before grouting) × 100%.

[0030] The present invention also provides a multifunctional test system for implementing the mechanical seepage test in the test method for the water flow blockage effect under the action of grouting in mining-induced fractures;

[0031] The system includes:

[0032] A stress loading module for simulating the stress environment under actual mining conditions;

[0033] A water pressure control module for precisely adjusting and controlling the water pressure;

[0034] A tracer injection module for precisely injecting a liquid with specific color and tracer characteristics into the fractures of the rock sample;

[0035] A data acquisition module responsible for recording the data of the entire test process;

[0036] A visualization observation module for real-time recording and observing the water flow migration process through a high-speed camera and an ultraviolet light source.

[0037] The beneficial effects of the present invention are as follows:

[0038] 1. Through the visualization water flow tracing technology and quantitative indexes (such as water flow blockage rate), the present invention realizes the intuitive presentation and precise quantification of the grouting water flow blockage effect, overcomes the deficiencies of subjective and qualitative evaluation results of traditional methods, and makes the evaluation of grouting effect more scientific and credible.

[0039] 2. The present invention uses 3D printing technology to construct a high-precision mining-induced fracture rock model, which maximally restores the complexity of real fractures and can be tested under different stress and water pressure conditions, being closer to the actual engineering environment and making the test results more effective in guiding engineering practice.

[0040] 3. The present invention establishes a set of systematic test procedures with strong operability and repeatable results, provides a standardized technical solution for the evaluation of mining-induced fracture grouting effect, and is convenient for popularization and application and technical communication. Description of the Drawings

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0042] Figure 1 A test method for the water flow blocking effect under the action of grouting in mining-induced fractures according to an embodiment of the present invention. Specific embodiments

[0043] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0044] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0045] As Figure 1 shown, this embodiment proposes a test method for the water flow blocking effect under the action of grouting in mining-induced fractures, including:

[0046] Obtain an artificial rock model of a rock sample; wherein, the artificial rock model includes a fracture network;

[0047] Perform grouting treatment on the artificial rock model;

[0048] Respectively perform mechanical seepage tests on the artificial rock model before and after grouting, collect the seepage parameters before and after grouting, and quantitatively evaluate the water flow blocking effect of grouting in combination with the water flow migration trajectory.

[0049] Specifically, in this embodiment, first, obtain a real rock sample containing natural mining-induced fractures and perform three-dimensional digital scanning on it to obtain a digital fracture network model; secondly, based on the obtained digital fracture network model, use three-dimensional printing technology to construct an artificial rock model containing a complex fracture network; then perform grouting treatment on the constructed artificial rock model to obtain a post-grouting rock model; then place the rock models before and after grouting in a mechanical seepage test system, apply set stress and water pressure conditions, and use a visualization observation system to record the water flow migration trajectory; finally, collect the seepage parameters before and after grouting, and quantitatively evaluate the water flow blocking effect of grouting in combination with the water flow migration trajectory.

[0050] Furthermore, using 3D printing technology, obtaining an artificial rock model of the rock sample includes:

[0051] Performing 3D digital scanning on the rock sample to obtain a digital fracture network model;

[0052] Based on the digital fracture network model, using 3D printing technology to construct an artificial rock model containing a complex fracture network.

[0053] Among them, performing 3D digital scanning on the rock sample includes:

[0054] Using scanning technology to obtain the 3D geometric information of the rock fractures; among them, the 3D geometric information includes: fracture distribution, strike, aperture, and connectivity.

[0055] Using 3D printing technology to construct an artificial rock model containing a complex fracture network includes:

[0056] Using raw materials similar to the composition of the rock sample, and adding cement and binder at the same time, mixing according to a preset ratio to obtain 3D printing raw materials;

[0057] Setting printing parameters, and performing printing based on the 3D printing raw materials; among them, the printing parameters include: layer thickness, printing speed, nozzle diameter, and the forming size is the same as that of the rock sample;

[0058] Performing surface pretreatment after printing.

[0059] Specifically, in this embodiment, 3D digital scanning uses CT scanning or laser scanning technology to obtain the 3D geometric information of the rock fractures, including fracture distribution, strike, aperture, and connectivity parameters.

[0060] The 3D printing technology uses powder bed fusion or material extrusion forming process, and the printing material is a mixed material similar to the composition and mechanical properties of the natural rock sample.

[0061] Furthermore, performing grouting treatment on the artificial rock model includes:

[0062] Based on portland cement, using the micro-pressure sectional grouting method to perform grouting on the artificial rock model.

[0063] Specifically, in this embodiment, the grouting treatment uses the same grouting material and grouting process as in the actual engineering application, and records grouting parameters such as grouting pressure, grouting volume, and slurry ratio.

[0064] Furthermore, performing mechanical seepage testing includes:

[0065] Injecting a colored fluorescent tracer into water, applying preset stress and water pressure conditions, and using visualization observation technology to record the water flow migration trajectory.

[0066] Specifically, in this embodiment, a mechanical seepage test system is used to conduct mechanical seepage tests. The mechanical seepage test system can apply confining pressure and axial pressure simulating in-situ stress, as well as set water pressure, and precisely control stress and water pressure conditions. Among them, the visualization observation system includes a high-speed camera and a light source. The light source is an ultraviolet light source. A colored fluorescent tracer is added to the injected water, and the high-speed camera and the ultraviolet light source are used to record and observe the water flow migration process in real time.

[0067] In this embodiment, the colored fluorescent tracer is sodium fluorescein or rhodamine B.

[0068] Furthermore, the quantitative evaluation of the water flow blocking effect of grouting includes:

[0069] Based on the seepage parameters before and after grouting, combined with the water flow migration trajectory, calculate the quantitative evaluation index; among them, the quantitative evaluation index includes: permeability coefficient and water flow blocking rate;

[0070] Among them, the seepage parameters include: permeability coefficient and permeability, etc.

[0071] Analyze the changes in the water flow path and quantitative evaluation index before and after grouting under different confining pressure conditions, and evaluate the water flow blocking effect and stress sensitivity of grouting.

[0072] The calculation formula for the water flow blocking rate is: blocking rate = (1 - permeability coefficient after grouting / permeability coefficient before grouting) × 100%.

[0073] Use image processing technology to analyze the water flow migration trajectory, extract water flow path and seepage velocity information, and comprehensively evaluate the water flow blocking effect of grouting in combination with seepage parameters.

[0074] The following uses specific data to illustrate the test method of this embodiment:

[0075] S1. Select a representative mining-influenced area at a coal mine site, select the sandstone rock layer located on the coal seam roof as the real test sample, and use a coring bit with a diameter of Φ100mm to collect a core sample with a length of 500mm. Record information such as sample depth, geological structure, and initial stress state.

[0076] S2. Use a CT scanning system to conduct three-dimensional scanning on the core sample with a scanning accuracy of 0.1mm. Through professional image reconstruction software, draw a three-dimensional network distribution map of rock fractures, accurately extract fracture geometric feature data, including fracture density, fractal dimension, average aperture, connectivity rate, etc., and obtain a 3D scan file.

[0077] S3. Use gangue with a composition similar to that of the rock sample as the raw material, and at the same time add cement, binder, etc., and mix them in a certain proportion to obtain the 3D printing raw material. Set the printing parameters, with a layer thickness of 0.1 mm, a printing speed of 50 mm / s, a nozzle diameter of 0.4 mm, and the formed size being exactly the same as that of the original core sample. After printing, perform surface fine processing to ensure a highly restored fracture morphology.

[0078] S4. Use ordinary Portland cement, control the ratio of cement to water at 0.5:1, and add fine silica gel and an expansive agent to improve the permeability and stability of the slurry. Adopt the micro-pressure sectional grouting method, control the grouting pressure at 1.0 MPa, the grouting rate at 25 mL / min, and complete the grouting in 3 working sections. After grouting, place it in a constant temperature and humidity chamber at a temperature of 20±2°C and a relative humidity of 95% for 28 days of curing to make the slurry fully hardened.

[0079] S5. Conduct tests on a multi-functional testing system, set the confining pressure at 3.0 MPa, the water pressure gradient at 0.5 MPa / m, and select sodium fluorescein as the tracer. Use a high-speed camera to record the water flow migration process, with a frame rate of 1500 fps, and perform fluorescence-enhanced imaging in cooperation with an ultraviolet light source.

[0080] S6. Analyze the water flow trajectory through image processing software, calculate the permeability coefficient and the water flow barrier rate, and comprehensively evaluate the water flow barrier effect after grouting. Use image processing software (such as ImageJ) to analyze the water flow migration video, extract the water flow path, and calculate the water flow velocity. Define the calculation formula for the water flow barrier rate as: Barrier rate = (1 - permeability coefficient after grouting / permeability coefficient before grouting) × 100%.

[0081] S7. Analyze the changes in the water flow path, permeability coefficient, and water flow barrier rate before and after grouting under different confining pressure conditions, and evaluate the water flow barrier effect and stress sensitivity of grouting.

[0082] Experimental results: When the confining pressure is 3 MPa, the permeability coefficient of the rock model before grouting is 5.2×10 -5 m / s, and the permeability coefficient after grouting is reduced to 8.7×10 -7 m / s, and the water flow barrier rate reaches 98.3%. The visualization results show that before grouting, the water flow rapidly migrates in the fracture network, and after grouting, the water flow path is significantly reduced and the water flow velocity is significantly decreased. Under different confining pressure conditions, the water flow barrier rate of grouting remains above 95%, indicating that this grouting method has good stress adaptability.

[0083] This embodiment also proposes a multi-functional testing system for implementing the mechanical seepage test in the test method for the water flow barrier effect under the action of goaf fracture grouting;

[0084] Its system includes:

[0085] The stress loading module is used to simulate the stress environment under actual mining conditions. By applying different pressures and stress conditions to rock samples, the change of rock fractures during the mining process can be more realistically reproduced.

[0086] The water pressure control module is used to accurately adjust and control the water pressure. During the test, by controlling the water pressure, the water flow characteristics of fractures under different groundwater pressure conditions can be simulated.

[0087] The tracer injection module is used to accurately inject a liquid with specific color and tracer characteristics into the fractures of rock samples. By using tracers of different colors, the water flow migration path can be visually traced and marked, and the propagation trajectory of the water flow can be clearly presented under ultraviolet light, providing an intuitive visualization solution for studying the grouting effect of mining fractures.

[0088] The data acquisition module is responsible for recording the key data of the entire test process, including the water flow migration trajectory, permeability parameters, and the change of water flow characteristics before and after grouting, providing a detailed data basis for subsequent quantitative analysis.

[0089] The visualization observation system mainly uses a high-speed camera and an ultraviolet light source to record and observe the water flow migration process in real time, converting the abstract water flow propagation into an intuitive image.

[0090] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A test method for the water flow blocking effect under the action of grouting in mining-induced fissures, characterized in that, Comprising: An artificial rock model obtained from a rock sample; wherein, the artificial rock model includes a fracture network; Performing grouting treatment on the artificial rock model; Performing mechanical seepage tests on the artificial rock model before and after grouting respectively, collecting seepage parameters before and after grouting, and combining with the water flow migration trajectory to quantitatively evaluate the water flow blocking effect of grouting.

2. The test method for the water flow blocking effect under the action of grouting in mining-induced fissures according to claim 1, wherein The artificial rock model obtained from a rock sample includes: Performing three-dimensional digital scanning on the rock sample to obtain a digital fracture network model; Based on the digital fracture network model, using three-dimensional printing technology to construct an artificial rock model containing a complex fracture network.

3. The test method for the water flow blocking effect under the action of grouting in mining-induced fissures according to claim 2, wherein Performing three-dimensional digital scanning on the rock sample includes: Using scanning technology to obtain three-dimensional geometric information of rock fractures; wherein, the three-dimensional geometric information includes: fracture distribution, strike, aperture, and connectivity.

4. The test method for the water flow blocking effect under the action of grouting in mining-induced fissures according to claim 2, characterized in that Using three-dimensional printing technology to construct an artificial rock model containing a complex fracture network includes: Using raw materials similar to the composition of the rock sample, adding cement and binder at the same time, and mixing according to a preset ratio to obtain three-dimensional printing raw materials; Setting printing parameters and performing printing based on the three-dimensional printing raw materials; wherein, the printing parameters include: layer thickness, printing speed, nozzle diameter, and the formed size is the same as that of the rock sample; Performing surface pre-treatment after printing.

5. The test method for the water flow blocking effect under the action of grouting in mining-induced fissures according to claim 1, characterized in that, Performing grouting treatment on the artificial rock model includes: Based on Portland cement, using the micro-pressure sectional grouting method to perform grouting on the artificial rock model.

6. The test method for the water flow blocking effect under the action of grouting in mining-induced fissures according to claim 1, wherein Performing the mechanical seepage test includes: Injecting a colored fluorescent tracer into water, applying preset stress and water pressure conditions, and using visualization observation technology to record the water flow migration trajectory.

7. The test method for the water flow blocking effect under the action of grouting in mining-induced fissures according to claim 1, characterized in that, Quantitatively evaluating the water flow blocking effect of grouting includes: Based on the seepage parameters before and after grouting, combining with the water flow migration trajectory, calculating a quantitative evaluation index; wherein, the quantitative evaluation index includes: permeability coefficient and water flow blocking rate; Analyzing the changes in water flow paths and quantitative evaluation indexes before and after grouting under different confining pressure conditions, and evaluating the water flow blocking effect and stress sensitivity of grouting.

8. The test method for the water flow blocking effect under the action of grouting in mining-induced fissures according to claim 7, characterized in that The water flow blocking rate is: Blocking rate = (1 - permeability coefficient after grouting / permeability coefficient before grouting) × 100%.

9. A multi-functional test system, characterized in that, For implementing the mechanical seepage test in the test method for the water flow blocking effect under the action of mining-induced fracture grouting as described in any one of claims 1-8; The system includes: A stress loading module for simulating the stress environment under actual mining conditions; A water pressure control module for precisely adjusting and controlling the water pressure; A tracer injection module for precisely injecting a liquid with a specific color and tracer characteristics into the fractures of the rock sample; A data acquisition module responsible for recording data throughout the test process; A visualization observation module for real-time recording and observing the water flow migration process through a high-speed camera and an ultraviolet light source.

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