Coal seam roof up and down area fracturing physical simulation experiment method

Abstract

The application discloses a kind of coal seam roof well upper and lower area fracturing physical similarity simulation experiment method, comprising the following steps: one, according to the field geological conditions and experimental purpose to build physical similarity model;Two, according to coal seam roof well upper and lower area fracturing engineering practice, thick hard target disaster-causing rock layer is expanded and fractured using static breaking agent;Three, according to the similarity ratio of experimental parameters, excavate area fracturing physical similarity model and carry out data monitoring.The experimental method of the application is mainly based on the similarity of rock mass cracking mechanism and fracture propagation morphology after fracturing, without considering the hydration reaction of rock mass, the target disaster-causing rock layer is expanded and fractured using static breaking agent, and the fracturing weakening effect of fracturing on rock layer is simulated, which has good implementability in laboratory, and the simulation is closer to the real working condition, which improves the accuracy of the experiment.

Description

Technical Field

[0001] This invention relates to the field of coal seam mining similarity simulation technology, specifically to a physical similarity simulation experimental method for fracturing the upper and lower regions of the coal seam roof. Background Technology

[0002] Thick, hard roofs are the main source of static and dynamic loads for the rock bursts that trigger regional rock bursts. Currently, some mines are conducting segmented fracturing of the surface and underground horizontal shafts before mining. By destroying the integrity of the overlying roof in the dangerous area in advance, a certain number of cracks of varying lengths, widths, and heights are formed in the disaster-causing rock strata, thereby changing the physical and mechanical properties of the disaster-causing rock strata and forming an "artificial liberation layer". This can provide a low-stress working environment for underground mining activities.

[0003] Physical similarity simulation experiments are one of the important methods for research and engineering application of coal mining and rock strata control technology in my country. Based on the on-site geological strata columnar section and the physical and mechanical parameters of the rock strata, physical similarity simulation experiments construct experimental models according to similarity theory, based on the geological conditions of the prototype and the experimental objectives. Various engineering works are then excavated on the model. By monitoring the excavation process, the deformation, movement, and failure of the surrounding rock mass can be studied and analyzed.

[0004] The physical similarity experimental model is mainly based on the on-site geological conditions and similarity ratio. It is made by mixing and laying materials such as fine sand, gypsum, and white powder layer by layer. It has low strength and softens when it comes into contact with water. Therefore, it is not possible to directly apply the fracturing technology of the well and the underground area to the laboratory similarity model, which hinders the study of the mining-induced overburden activity law and the pressure relief and anti-shocking mechanism under regional fracturing conditions.

[0005] Secondly, current methods for physical similarity simulation of regional fracturing commonly involve vertically or horizontally embedding iron sheets or polyester films in hard, disaster-causing rock strata to simulate the fractures formed in the hard rock strata after regional fracturing, thereby characterizing the fracturing weakening effect of regional fracturing on hard rock strata. However, this method simplifies the fractures formed by regional fracturing, resulting in a significant difference from the actual fracture propagation morphology. This means that the physical similarity test process and results cannot accurately reflect actual working conditions, reducing the accuracy of the results. Summary of the Invention

[0006] The present invention aims to at least partially solve one of the technical problems in the related art.

[0007] Therefore, this invention proposes a physical similarity simulation experiment method for fracturing the upper and lower regions of a coal seam roof. This method is based on the similarity of rock mass fracturing mechanism and fracture propagation morphology after fracturing, without considering the hydration reaction of the rock mass. It uses a static fracturing agent to expand and fracture the target disaster-causing rock layer and simulates the fracturing weakening effect of fracturing on the rock layer. This method is simple and convenient, has good feasibility in the laboratory, and the simulation is closer to the real working conditions, thus improving the accuracy of the experiment.

[0008] The physical similarity simulation experimental method for fracturing the upper and lower regions of the coal seam roof in this embodiment of the invention includes the following steps:

[0009] A physical similarity model is constructed, which includes a mining layer and a target fracture-inducing layer, and the target fracture-inducing layer contains a plurality of fracture-inducing holes.

[0010] Select a static fracturing agent and determine the water-to-agent ratio and orifice diameter of the static fracturing agent;

[0011] A fracturing slurry is prepared by using the static fracturing agent and determining the water-to-agent ratio;

[0012] The fracturing slurry is loaded into at least a portion of the fracturing pores to induce fracturing of the target fracturing layer of the physical similarity model.

[0013] The cracks generated after the initial cracking are measured. If the cracks do not reach the expected range, a second cracking process is performed.

[0014] The mining layer is mined, and the mining data is recorded.

[0015] The physical similarity simulation experiment method for fracturing the upper and lower regions of the coal seam roof in this embodiment of the invention is based on the similarity of rock mass fracturing mechanism and fracture propagation morphology after fracturing. It does not consider the hydration reaction of the rock mass, but uses a static fracturing agent to expand and fracture the target disaster-causing rock layer and simulates the fracturing weakening effect of fracturing on the rock layer. This method is simple and convenient, has good feasibility in the laboratory, and the simulation is closer to the real working conditions, thus improving the accuracy of the experiment.

[0016] In some embodiments, the construction of the physical similarity model includes the following steps:

[0017] The basic similarity ratios of the physical similarity models are determined, including: geometric similarity ratio, stress similarity ratio, displacement similarity ratio, strength similarity ratio, unit weight similarity ratio, and time similarity ratio.

[0018] Determine the similar experimental parameters for regional hydraulic fracturing, which include: similar average segmented fracturing length, similar average fracture propagation height, and similar rock mass fracturing pressure.

[0019] The layering materials of each layer of the physically similar model are determined, and then each layer is laid from bottom to top, with sensors embedded in the laying process to monitor deformation or displacement.

[0020] In some embodiments, when laying the target fracturing layer of the physical similar model, a plurality of tubes are pre-embedded in the target fracturing layer. The plurality of tubes are arranged at intervals according to similar average segmented fracturing lengths along the laying direction of the target fracturing layer. The tubes are used to be removed later to form the fracturing holes in the target fracturing layer.

[0021] In some embodiments, the tube body has two oppositely arranged grooves. When pre-embedding the tube body, one of the grooves faces upward and the other faces downward. The grooves are used for later fixing and guiding the fracture-inducing holes. In some embodiments, before embedding the tube body into the target fracture-inducing layer, adhesive tape is wrapped around the outer periphery of the tube body.

[0022] In some embodiments, determining the water-to-agent ratio includes the following steps:

[0023] The similar expansion pressure used for the physical similarity model is calculated using the stress similarity ratio;

[0024] The expansion pressure of the fracturing slurry under different water-to-agent ratios and different charge apertures was tested, and the water-to-agent ratio and charge aperture corresponding to the expansion pressure that is consistent with or similar to the similar expansion pressure were selected.

[0025] In some embodiments, the expansion pressure is measured by methods such as resistance strain gauge measurement, axial output measurement, or hydraulic balance pressure gauge measurement.

[0026] In some embodiments, the fracturing slurry is injected into the fracturing hole using a syringe, and the opening of the fracturing hole is sealed after injection.

[0027] Alternatively, the fracturing slurry is placed into a bag, and then the bag, along with the fracturing slurry inside the bag, is placed into the fracturing orifice.

[0028] In some embodiments, the experimental method further includes the following steps: placing the target fracturing layer at different levels to respectively simulate the segmented regional fracturing of a surface horizontal well or the segmented regional fracturing of a downhole top plate ultra-long hole horizontal well.

[0029] In some embodiments, the mining of the mining layer is divided into multiple mining cycles, and after the mining of the mining layer is completed in each mining cycle, the mining data of that mining cycle is recorded, and then the mining of the next mining cycle is carried out. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating the experimental method of an embodiment of the present invention.

[0031] Figure 2 This is a schematic diagram of segmented fracturing of a surface horizontal well (above ground) according to an embodiment of the present invention.

[0032] Figure 3 This is a schematic diagram of horizontal fracturing of the ultra-long hole in the downhole roof according to an embodiment of the present invention.

[0033] Figure 4 This is a three-dimensional schematic diagram of a physical similarity model according to an embodiment of the present invention.

[0034] Figure 5 yes Figure 4 A magnified schematic diagram of a centrally located crack.

[0035] Figure 6 yes Figure 5 Schematic diagram of cross-section at point AA.

[0036] Figure 7 This is a three-dimensional schematic diagram of the tube body according to an embodiment of the present invention.

[0037] Figure 8 This is a schematic diagram of the pipe opening of the pipe body according to an embodiment of the present invention.

[0038] Figure 9 This is a schematic diagram of the testing device for the expansion pressure test according to an embodiment of the present invention.

[0039] Figure 10 yes Figure 9 A schematic diagram of the port of the test device.

[0040] Figure label:

[0041] 1. Mining layer; 2. Cutting hole; 3. Target fracture layer; 4. Fracture hole; 5. Equivalent stress; 6. Groove; 7. Pipe body; 8. Cutting groove; 9. Steel pipe; 10. Strain gauge; 11. Steel plate. Detailed Implementation

[0042] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0043] It should be noted that the physical similarity simulation experimental method for fracturing in the upper and lower regions of the coal seam roof in this embodiment of the invention (hereinafter referred to as the experimental method) can be used to simulate fracturing from the surface area. That is, the fracturing equipment is located on the surface, and during fracturing, fracturing slurry can be transported from the surface to the fracturing rock layer (thick and hard rock layer), specifically as follows: Figure 2As shown. The experimental method of this invention can also be used to simulate fracturing in downhole areas. That is, the fracturing equipment can be located in a roadway or a dedicated drilling site. During fracturing, fracturing slurry can be delivered from the roadway or dedicated drilling site to the fracturing rock formation, specifically as follows. Figure 3 As shown.

[0044] The physical similarity simulation experiment method for fracturing the upper and lower regions of the coal seam roof in this invention can be divided into three main steps, such as... Figure 1 As shown, the three main steps are:

[0045] Step 1: Construct a physical similarity model based on the on-site geological conditions and experimental objectives.

[0046] Step 2: Based on the practical experience of fracturing engineering in the upper and lower areas of the coal seam roof, static fracturing agents are used to expand and fracture the thick and hard target disaster-causing rock strata.

[0047] Step 3: Based on the similarity ratio of experimental parameters, establish a physical similarity model for fracturing in the excavated area and monitor the data.

[0048] like Figure 4 As shown, the experimental method of this invention embodiment based on the above three major steps may specifically include the following steps:

[0049] S1: Construct a physical similarity model, which includes a mining layer 1 and a target fracture-inducing layer 3, with multiple fracture-inducing holes 4 pre-set within the target fracture-inducing layer 3. Specifically, the physical similarity model can be constructed by mixing materials such as sand, gypsum, and white powder with water and laying them layer by layer. During the laying process, the corresponding rock strata form the mining layer 1 and the target fracture-inducing layer 3. The mining layer 1 can be a coal seam, and the target fracture-inducing layer 3 can be a thick, hard rock stratum.

[0050] It should be noted that during the process of laying the target fracture-inducing layer 3, some pre-embedded pipes can be pre-buried. After the physical similarity model is solidified, the pre-embedded pipes can be extracted, thereby forming fracture-inducing holes 4.

[0051] S2: Select a static fracturing agent and determine its water-to-agent ratio and charge aperture. Specifically, the static fracturing agent can be selected based on the laboratory room temperature; based on regional fracturing engineering practice and the physical and mechanical properties of the target fracturing-induced rock strata, the appropriate water-to-agent ratio and charge aperture for the physical similarity model can be determined by testing the expansion pressure under different water-to-agent ratios and charge apertures.

[0052] The selection of static fracturing agents should be based on the laboratory's ambient temperature. Temperature significantly affects the hydration reaction rate of static fracturing agents; high temperatures promote hydration but can cause nozzle formation, while low temperatures hinder the reaction. Static fracturing agents are categorized as follows: Spring / Autumn type (10–30℃), Summer type (25–40℃), and Winter type (-5–15℃).

[0053] The water-to-powder ratio and the charge orifice diameter are the main factors affecting the expansion pressure of static rock fracturing agents. By changing the water-to-powder ratio of the static rock fracturing agent, the degree of hydration reaction can be controlled, thereby controlling the expansion pressure. Under normal use, the water-to-powder ratio of the static rock fracturing agent is between 26% and 35%, which results in the best degree of hydration reaction and optimal expansion pressure, thus enabling rock mass fracturing. In engineering applications, the charge orifice diameter is generally between 30 and 50 mm. The larger the charge orifice diameter, the more static rock fracturing agent is injected into the borehole, and the greater the expansion pressure generated. However, it generally should not exceed 50 mm, otherwise blowouts are likely to occur.

[0054] S3: Prepare fracturing slurry by using a static fracturing agent and determining the water-to-agent ratio. Specifically, the selected static fracturing agent can be weighed according to the water-to-agent ratio of a similar model using an electronic balance, and the appropriate amount of agent and water can be poured into a container and stirred thoroughly. After thorough stirring, the fracturing slurry is formed.

[0055] S4: The fracturing slurry is loaded into at least some of the fracturing pores 4 to achieve fracturing of the target fracturing layer of the physically similar model. Specifically, the prepared fracturing slurry can be loaded into all the fracturing pores 4. After loading, the expansion pressure generated by the hydration reaction of the fracturing slurry can achieve expansion fracturing of the target fracturing layer 3.

[0056] S5: Measure the cracks generated after fracturing. If the cracks do not reach the expected range, perform secondary fracturing. For example, after the static fracturing agent hydration reaction is completed, the cracks formed on the model surface can be measured using measuring tools such as rulers and measuring tapes to determine whether the similar propagation height (expected range) of the regional fracturing crack has been reached. If it has not been reached, the same method can be used to perform secondary fracturing on the target fracturing layer 3.

[0057] S6: Mining of mining layer 1 and recording mining data. For example, the regional fracturing physical similarity model can be excavated based on the similarity ratio of mining distance and time of the coal seam. After each mining cycle is completed, the mining distance, time and other information of the similar model are recorded first, and then data from other monitoring sensors are collected. Only after the data collection is completed can the next mining cycle begin, until the mining is stopped at the stop line.

[0058] It is understood that in some other embodiments, the fracturing hole 4 is first fracturing, and then the mining layer 1 (coal seam) corresponding to the fracturing hole 4 is excavated. The physical similarity simulation experiment method for fracturing in the upper and lower regions of the coal seam roof in this embodiment of the invention is based on the similarity of rock fracturing mechanism and fracture propagation morphology after fracturing. It does not consider the hydration reaction of the rock mass, but uses a static fracturing agent to expand and fracture the target disaster-causing rock layer and simulates the fracturing weakening effect of fracturing on the rock layer. This method is simple and convenient, has good feasibility in the laboratory, and the simulation is closer to the real working conditions, thus improving the accuracy of the experiment.

[0059] In some embodiments, the construction of a physical similarity model includes the following steps:

[0060] A1: Determine the basic similarity ratio of the physical similarity model. The basic similarity ratio of the model includes: geometric similarity ratio, stress similarity ratio, displacement similarity ratio, strength similarity ratio, unit weight similarity ratio, and time similarity ratio.

[0061] Specifically, the geometric similarity ratio of the model can be determined first based on the on-site and experimental conditions. Then, other experimental similarity ratios can be determined based on the geometric similarity ratio and the principle of similarity. Each similarity ratio can be determined using the following formula:

[0062] Geometric similarity ratio: ;

[0063] In the formula, , Let m be the geometric dimensions of the physical prototype and the similar model;

[0064] Displacement similarity ratio: ;

[0065] Time similarity ratio: ;

[0066] Bulk density similarity ratio: ;

[0067] Stress similarity ratio: ;

[0068] Strength similarity ratio: .

[0069] A2: Determine the parameters for the regional fracturing similar experiment. The parameters for the regional fracturing similar experiment include: the similar average segmented fracturing length, the similar average fracture propagation height, and the similar rock mass fracturing pressure.

[0070] Specifically, based on the basic similarity ratio between the surface and surface fracturing field engineering practice and the experimental model, the similarity parameters for regional fracturing experiments can be determined, including: the similar average segmented fracturing length, the similar average fracture propagation height, and the similar rock mass fracturing pressure. The fracture propagation height can be obtained from the combined surface and surface microseismic monitoring system. A schematic diagram of segmented regional fracturing in a surface horizontal well is shown below. Figure 2 As shown; Schematic diagram of horizontal fracturing in the ultra-long borehole area of ​​the downhole roof, as follows. Figure 3 As shown.

[0071] Similar average segmented fracturing length: In the formula, The average segment length in regional fracturing field engineering practice is given in meters (m). This represents the geometric similarity ratio of the physically similar models.

[0072] Similar average crack propagation height: In the formula, The average fracture propagation height, in meters, is the average fracture propagation height in regional fracturing field engineering practice.

[0073] Similar rock mass fracturing pressure: In the formula, Hydraulic fracturing pressure in regional fracturing field engineering practice, MPa: This represents the stress similarity ratio of the physically similar models.

[0074] A3: Determine the layering material for each layer of the physically similar model, and then lay each layer from bottom to top, with sensors embedded during the laying process to monitor deformation or displacement.

[0075] Specifically, river sand, fly ash, and clay can be used as aggregates, gypsum and calcium carbonate as binders, mica powder as a layering material, and water as the mixture. Then, based on the physical and mechanical parameters of the prototype rock strata, a suitable mix ratio can be selected. Following the stratigraphic sequence and mix ratio, various similar materials are mixed evenly, laid flat, and compacted, and the model is constructed layer by layer from bottom to top. Coal seams can be simulated by adding ink during the mixing process according to the calculated ratio.

[0076] It should be noted that during the model laying process, sensors can be deployed to monitor the deformation, damage, and movement of the surrounding rock, depending on the experimental objectives. For example, during the laying of a similar model, stress sensors such as pressure cells can be pre-embedded in the overburden and floor of the coal seam to monitor the stress during the excavation of mining layer 1.

[0077] In some other embodiments, digital speckle technology can be used to monitor and image the deformation and displacement of the model surface. In other embodiments, different numbers of horizontal and vertical optical fibers can be laid in the model to monitor the deformation of the overlying rock, thereby delineating the "three vertical zones and three horizontal areas".

[0078] In some embodiments, when laying the target fracture-inducing layer 3 of the physical similarity model, a plurality of tubes 7 are pre-embedded in the target fracture-inducing layer 3. The plurality of tubes 7 are arranged at intervals along the laying direction of the target fracture-inducing layer. The tubes 7 are used to be removed later to form fracture-inducing holes 4 in the target fracture-inducing layer 3.

[0079] Specifically, when laying the target fracturing layer 3, a PVC pipe (pipe body 7) can be pre-laid and embedded. The specifications of the PVC pipe can be made according to the depth and diameter of the fracturing hole 4, such as... Figure 4 As shown, the target fracturing layer 3 extends roughly in the left-right direction, and multiple PVC pipes are arranged at roughly equal intervals in the left-right direction. The diameter of the PVC pipe holes needs to be determined based on the expansion pressure test results under different charge hole diameter conditions. After the physical similarity model has completely solidified (it can be left to stand for about 5-10 days depending on the indoor temperature), the PVC pipes can be extracted from the target fracturing layer 3. The holes formed after the PVC pipes are extracted are the various fracturing holes 4.

[0080] In some embodiments, the pipe body 7 is provided with two oppositely arranged grooves 8. When the pipe body 7 is pre-embedded, one groove 8 is arranged facing upwards and the other groove 8 is arranged facing downwards. The grooves 8 are used for later fixing and guiding the fracture hole 4. Specifically, as Figure 7 and Figure 8 As shown, the tube 7 can be cylindrical, and both grooves 8 can penetrate the tube wall of the tube 7, and both grooves 8 can extend along the axial direction of the tube 7. It should be noted that one end of the two grooves 8 extends to one end face of the tube 7, while the other end of the two grooves 8 does not extend to the other end face of the tube 7.

[0081] Therefore, once the physically similar model is solidified, the target fracture layer 3 can be cut upwards or downwards from the corresponding groove 8 using tools such as blades or saws. After cutting, as... Figure 5 and Figure 6 As shown, two slots 6 are formed on the upper and lower sides of the fracturing hole 4, communicating with the fracturing hole 4. Free surfaces can be formed within the two slots 6, so that when the fracturing slurry fracturing the fracturing hole 4, the fracture can mainly develop and expand along the vertical direction.

[0082] In some embodiments, before embedding the tube 7 into the target fracturing layer 3, tape is wrapped around the outer periphery of the tube 7. The tape prevents the laying material from entering the tube 7 during model laying and also facilitates the guide slotting 8. In some embodiments, determining the water-to-powder ratio and the charge aperture includes the following steps:

[0083] B1: The similar expansion pressure used in the physical similarity model is calculated through the stress similarity ratio. Specifically, the fracturing expansion force under real working conditions can be obtained through engineering practice, and then the similar expansion pressure of the model can be obtained through the stress similarity ratio.

[0084] B2: Test the expansion pressure of the fracturing slurry under different water-to-material ratios and different charge apertures, and select the water-to-material ratio and charge aperture corresponding to the expansion pressure that is consistent with or close to the similar expansion pressure. Specifically, the expansion pressure can be measured by the following methods: resistance strain gauge method, axial output method, and hydraulic balance pressure gauge.

[0085] Because the resistance strain gauge method 10 is simple to operate and is a commonly used method, the following explanation of the test method is based on the resistance strain gauge method 10 measurement:

[0086] During measurement, such as Figure 9 and Figure 10 As shown, a Q235 seamless steel pipe 9 can be used, with a length of 500 mm, an inner diameter of 30 mm (to be determined according to actual conditions), and a wall thickness of 4 mm. The bottom of the steel pipe 9 is welded with a 4 mm thick steel plate 11 (ensuring no leakage). Strain gauges 10 can be attached laterally and longitudinally to the corresponding positions on the steel pipe 9 using sealant. The resistance strain gauges 10 are connected to the strain gauge instrument via wires. The steel pipe 9 is placed in a plastic bag and then placed in a bucket of water. The fracturing slurry is then mixed and poured into the steel pipe 9. It can then be tamped down with a wooden stick. Measurements are then taken, and finally, the static fracturing agent expansion pressure is calculated using the thin-walled cylinder theory in elasticity mechanics.

[0087]

[0088] In the formula, The static expansion pressure of the fracturing agent is MPa. The elastic modulus of steel pipe 9 is given in GPa. This is the ratio of the outer diameter to the inner diameter of steel pipe 9; Let be the circumferential strain of steel pipe 9; The steel pipe has a Poisson's ratio of 9.

[0089] In some embodiments, the fracturing slurry can be injected into the fracturing hole 4 using a syringe, and the opening of the fracturing hole 4 can be sealed after injection. For example, a sealing device or sealing material can be used to seal the opening of the fracturing hole 4. In other embodiments, the fracturing slurry can be first placed in a bag, and then the bag along with the fracturing slurry inside the bag can be inserted into the fracturing hole 4.

[0090] It should be noted that the interval between the fully stirred fracturing slurry and the start of grouting should not be too long. This is to avoid the fracturing slurry losing some of its expansion force due to hydration reaction or failing to grout due to solidification.

[0091] In some embodiments, the experimental method further includes the following steps: Figure 4 As shown, an equivalent stress 5 is applied above the physically similar model to replace the unpaved overburden portion, and the equivalent stress 5 is determined by the following formula:

[0092]

[0093] In the formula, : Thickness of the overlying rock and soil layer from the coal seam to the surface, in meters;

[0094] : The thickness of the simulated soil and rock layer above the coal seam, in meters;

[0095] Average bulk density of the overlying loose layer, kN / m³ 3 ;

[0096] Bulk density similarity ratio, kN / m 2 ;

[0097] Geometric similarity ratio;

[0098] Model length, in meters;

[0099] Model width, in meters.

[0100] Therefore, the situation where the overlying rock layer of a similar model cannot generate the corresponding stress due to the limited model height and lack of paving can be avoided. That is, by applying equivalent stress 5, the unpaved overlying rock layer can be replaced, making the experiment closer to the real working conditions and ensuring the accuracy of the experimental data.

[0101] In some embodiments, the experimental method further includes the following steps: placing the target fracturing layer 3 at different layers to respectively realize the segmented regional fracturing simulation of a surface horizontal well or the segmented regional fracturing simulation of an ultra-long hole horizontal well in the downhole top plate.

[0102] Specifically, the specific location of the target fracturing layer 3 can be determined first based on engineering practice. Then, when laying the physical test model, it can be laid to the corresponding location of the target fracturing layer 3. This allows the experimental method to achieve similar simulation of fracturing in segmented areas of surface horizontal wells as well as similar simulation of fracturing in segmented areas of downhole ultra-long borehole horizontal wells.

[0103] In some embodiments, the mining of mining layer 1 is divided into multiple mining cycles. After the excavation of mining layer 1 in each mining cycle is completed, the mining data for that mining cycle is recorded before the next mining cycle begins. Specifically, the regional fracturing physical similarity model can be used for excavation based on the coal seam mining distance similarity ratio and time similarity ratio. During excavation, data can be obtained from... Figure 4 The mining begins at the location of the central cut-out 2, and excavation proceeds to the right. After each mining cycle is completed, information such as the mining distance and time of the similar model can be recorded first, followed by data collection from other monitoring sensors. Only after the data collection is completed can the next mining cycle begin, until the mining is stopped at the stop line.

[0104] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0105] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0106] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0107] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0108] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0109] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A coal seam roof up and down area fracturing physical simulation experiment method, characterized in that, The method comprises the following steps: building a physical similar model, which comprises a mining layer and a target fracturing layer, and a plurality of fracturing holes are preset in the target fracturing layer; selecting a static breaker, and determining a water-agent ratio and a charging aperture of the static breaker; preparing a fracturing slurry by using the static breaker and the determined water-agent ratio; loading the fracturing slurry into at least part of the fracturing holes to realize fracturing of the target fracturing layer of the physical similar model; measuring cracks generated after fracturing, and performing secondary fracturing if the cracks do not reach a predetermined range; mining the mining layer, and recording mining data; The building of the physical similar model comprises the following steps: determining a basic similar ratio of the physical similar model, which comprises a geometric similar ratio, a stress similar ratio, a displacement similar ratio, a strength similar ratio, a volume weight similar ratio and a time similar ratio; determining regional fracturing similar experimental parameters, which comprise a similar average segmented fracturing length, a similar average crack propagation height and a similar rock mass fracturing pressure; determining a layer material of each layer of the physical similar model, and then layer by layer from bottom to top, laying each layer, and embedding sensors for monitoring deformation or displacement in the laying process; when laying the target fracturing layer of the physical similar model, embedding a plurality of pipe bodies in the target fracturing layer, the plurality of pipe bodies being arranged at intervals according to the similar average segmented fracturing length along the laying direction of the layering of the target fracturing layer, and the pipe bodies being used to be taken out later to form the fracturing holes in the target fracturing layer.

2. The coal seam roof over-and-under area fracturing physical simulation experiment method according to claim 1, characterized in that, The pipe bodies are provided with two relatively arranged cutting grooves, one of the cutting grooves being arranged upward and the other being arranged downward when the pipe bodies are embedded, and the cutting grooves being used for later fixed guiding cutting of the fracturing holes.

3. The coal seam roof over-and-under area fracturing physical simulation experiment method according to claim 1, characterized in that, Before embedding the pipe bodies in the target fracturing layer, wrapping adhesive tape around the outer circumferential side of the pipe bodies.

4. The coal seam roof uphole and downhole area fracturing physical simulation experiment method according to claim 1, characterized in that, The determination of the water-agent ratio and the charging aperture comprises the following steps: calculating a similar inflation pressure for the physical similar model by using the stress similar ratio; testing inflation pressures of the fracturing slurry under different water-agent ratios and different charging apertures, and selecting a water-agent ratio and a charging aperture corresponding to an inflation pressure consistent with or similar to the similar inflation pressure.

5. The coal seam roof over-and-under area fracturing physical simulation experiment method according to claim 4, characterized in that, The inflation pressure is measured by using an electric resistance strain gauge measurement method, an axial output measurement method or a hydraulic balance pressure gauge measurement method.

6. The coal seam roof uphole and downhole area fracturing physical simulation experiment method according to claim 1, characterized in that, The fracturing slurry is loaded into the fracturing holes by using a syringe, and the hole opening of the fracturing hole is blocked after loading. Or, the fracturing slurry is loaded into a bag, and then the bag and the fracturing slurry in the bag are loaded into the fracturing hole.

7. The coal seam roof over-and-under-area fracturing physical simulation experiment method according to claim 1, characterized in that, The method further comprises the following steps: placing the target fracturing layer at different layer positions to respectively realize ground horizontal well segmented regional fracturing simulation or downhole roof super-long hole horizontal well segmented regional fracturing simulation.

8. The coal seam roof over-and-under area fracturing physical simulation experiment method according to any one of claims 1-7, characterized in that, The mining of the mining layer is divided into multiple mining cycles, and mining data of each mining cycle is recorded after excavation of the mining layer of the mining cycle, and then mining of the next mining cycle is performed.

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