Method for actually measuring top plate two-zone and bottom plate damage zone of working face

Abstract

The invention relates to a method for actually measuring two zones of a top plate and a bottom plate failure zone of a working face. The method comprises the following steps: constructing a water injection drill hole, performing a segmented water pressure test on the water injection drill hole, obtaining segmented water pressure data in the water injection drill hole before and after stoping, and comparing the development degree of a rock stratum fracture before stoping with the development degree of the rock stratum fracture after stoping. The invention has the following beneficial effects: double plugging devices are adopted to carry out segmented hydrostatic test on a single water injection drill hole, test data of the whole segment of the water injection drill hole can be obtained, test positions can be flexibly selected, the number of the water injection drill holes and test equipment are reduced, the test cost is obviously saved, the working efficiency and the equipment utilization rate are improved, and the test data are enriched; and by adopting a depressurization test method, the test pressure is reduced, stable change data can be obtained under the condition that the test equipment is kept static, and the lower test pressure is also beneficial to avoiding deformation of the water injection drill hole.

Description

Technical Field

[0001] The invention relates to the technical field of coal mine safety detection, and in particular to a method for actually measuring "two zones" of a roof and a damaged zone of a bottom plate of a working face. Background Art

[0002] When there are aquifers and near-water bodies above the coal seams in coal mines, and when the destructive effects of mining are transmitted to the roof and floor, the roof collapse zone, the roof water-conducting fracture zone (commonly known as the "two zones" of the roof), the floor mining damage zone, geological structures and other water-conducting channels of the coal seams are very likely to induce water inrush into the mining space, posing a serious threat to the safe mining of coal. Therefore, coal mine safety measures need to identify the height of the "two zones" of the roof and the depth of the floor damage zone, so as to provide basic data support for safety analysis and demonstration of modules, coal pillar retention and other coal mine safety work.

[0003] Article 27 of the "Detailed Rules for Coal Mine Geological Work" stipulates that in the survey of water-conducting fracture zones, actual measurement methods should be used to determine the height of the water-conducting fracture zone in the mining area, and the scope and extent of the impact should be predicted. Mines threatened by bottom water should find out the depth of the water-conducting damage zone caused by bottom mining.

[0004] The testing principles of the roof "two zones" and the floor damage zone are basically the same. The double plug method is generally used to test the leakage volume at equal lengths, and the depth of the floor damage zone is determined by drilling peek (drilling TV). Drilling construction can be carried out on the corresponding ground or in the roadway near the mining face.

[0005] A Chinese invention patent (patent number: CN201710196579) discloses a method for detecting the depth of the working face floor damage zone by drilling holes adjacent to the tunnels. The holes are constructed at different depths, most of which are casingd, and there is no casing at the end of the hole. The boreholes are continuously injected with water and pressurized before and after mining, and the pressure and leakage changes before and after mining are continuously observed. The depth of floor damage is determined based on the borehole pressure and leakage. With this technical solution, each borehole can be tested for water injection at a specific depth. For example, in the embodiment of the patent document, 6 boreholes are set at a test point, and the final hole positions are located at 18m, 20m, 22m, 24m, 26m, and 30m below the working face floor, respectively. In such a technical solution, multiple boreholes need to be drilled at one test point (drilling site), which is labor-intensive and has high test costs. Each borehole can only detect water injection test data at a fixed point, and the center hole position of each borehole is pre-designed, which makes it difficult to flexibly conduct full-depth tests and is not conducive to the discovery of newly developed fractures. In addition, in the prior art, the water pressure test adopts a test method of increasing the pressure to the upper limit of the water pressure, but the pressure-boosting test is easily affected by changes in equipment and test environment, which is not conducive to obtaining accurate data. In addition, the pressure-boosting test will apply higher pressure and larger water flow to the water injection borehole, which can easily cause the water injection borehole to deform. Summary of the invention

[0006] The purpose of the present invention is to propose a method for measuring the "two zones" of the top plate and the damage zone of the bottom plate of the working face, so as to improve the efficiency of the water pressure test and obtain richer and more comprehensive test data.

[0007] In order to achieve the above-mentioned purpose, the technical solution of the present invention is: a method for measuring the "two zones" of the top plate and the damaged zone of the bottom plate of the working face, including constructing a water injection borehole, performing a segmented water pressure test on the water injection borehole, obtaining the segmented water pressure data in the water injection borehole before and after mining, and comparing the degree of development of rock strata fractures before mining and the degree of development of rock strata fractures after mining.

[0008] Furthermore, a preferred length of the segmented water pressure test section is that the segmented water pressure test section of the water injection borehole is 1 m.

[0009] Furthermore, in order to effectively obtain test data, the water pressure test method includes injecting water into the water injection borehole in sections, pressurizing the water in the water injection borehole to a test pressure, and monitoring the time it takes for the water pressure in the water injection borehole to drop to normal pressure.

[0010] Furthermore, a preferred water pressure test pressure is that the test pressure of water in the water injection borehole is not less than 1.0 MPa.

[0011] Furthermore, in order to better determine the impact of mining on the rock formation, one or more segmented water pressure tests are carried out before mining, and the segmented water pressure test results before mining are compared to determine the self-development of the rock formation; a segmented water pressure test is carried out after mining, and the segmented water pressure test results after mining are compared with the segmented water pressure test results before mining to determine the impact of the mining process on the rock formation.

[0012] Furthermore, in order to obtain more complete data, the method also includes peek detection of the water injection borehole and compiling a borehole histogram.

[0013] Furthermore, the orifice of the water injection borehole is reinforced to prevent the orifice from collapsing.

[0014] Furthermore, in order to obtain more comprehensive test data, at least four water injection boreholes are drilled in the test mining area, and the four water injection boreholes are divided into two groups, each group has two water injection boreholes, and the interval between the two groups of water injection boreholes is greater than the periodic pressure step.

[0015] Furthermore, a device for implementing a segmented water pressure test is provided, wherein the segmented water pressure test device comprises a first hole sealer 20 and a second hole sealer 30, wherein the second hole sealer is located on a side close to the orifice 11 of the water injection borehole 10, and the interval space between the first hole sealer 20 and the second hole sealer 30 is a segmented water pressure test section S.

[0016] Furthermore, one end of the first hole sealer 20 is provided with a first expansion pipe interface 21; one end of the second hole sealer 30 is provided with a second expansion pipe interface 31 and a second water injection pipe interface 32, and the other end of the second hole sealer 30 is provided with a second expansion pipe serial interface 33 and a second water injection pipe outlet 34; the first expansion pipe interface 21 and the second expansion pipe serial interface 33 are connected through a connecting pipe 40, the second expansion pipe interface 31 is connected to the expansion pressure pipe 13, the second water injection pipe interface 32 is connected to the test water injection pipe 12, the second water injection pipe outlet 34 is connected to the segmented water pressure test section S, the test water injection pipe 12 and the expansion pressure pipe 13 are connected to the water injection pump 14, a pressure sensor 15 and a timer 16 are provided on the test water injection pipe 12, and control valves are provided on the test water injection pipe 12 and the expansion pressure pipe 13.

[0017] The beneficial effects of the present invention are as follows: by adopting a double plugger, a segmented water pressure test is performed on a single water injection borehole, test data of the entire section of the water injection borehole can be obtained, and the test position can be flexibly selected, thereby reducing the number of water injection boreholes and test equipment, significantly saving test costs, improving work efficiency and equipment utilization, and enriching test data; by adopting a pressure reduction test method, the test pressure is reduced, and stably changing data can be obtained while the test equipment remains stationary, and a lower test pressure is also beneficial to avoiding deformation of the water injection borehole.

[0018] The present invention is described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the water injection drilling system of the present invention; Figure 2 is a structural diagram of the double occluder of the present invention, which is a view observed from the upper side (the second occluder side); Figure 3 yes Figure 2 The A-direction view is a structural diagram of the double occluder, a view observed from the bottom side (the first occluder side); Figure 4 It is the drilling site and design plan diagram of the test case; Figure 5 This is a chart of the main parameters of drilling construction for the test example. Figure 6 It is a data chart comparing the design and actual end hole positions of the test case; Figure 7 It is the borehole peep crack diagram of the test example; Figure 8 is the comprehensive histogram of the boreholes of the test case; Fig. 9It is a comparison chart of the first water injection test curve of the water injection drilling of the test example; Fig.10 It is a chart of the data of the first water injection test of the water injection borehole of the test example; Fig.11 This is a comparison of the crack peeping before and after water injection drilling in the test example; Fig.12 It is the curve diagram of the pressure increase, pressure relief and mean value ratio of the first and second water injection of the water injection borehole of the test example; Fig.13 It is a chart of the first and second water injection test data of the water injection drilling of the test example. DETAILED DESCRIPTION

[0020] Embodiment 1: like Figures 1 to 3 A segmented water pressure test device includes a first hole sealer 20 and a second hole sealer 30, wherein the second hole sealer is arranged on a side of a hole opening 11 close to a water injection borehole 10, and the interval space between the first hole sealer 20 and the second hole sealer 30 is a segmented water pressure test section S.

[0021] The first hole sealer 20 and the second hole sealer 30 are cylindrical with an expansion inner cavity. The diameter of the first hole sealer and the second hole sealer is smaller than the diameter of the water injection borehole 10 under normal pressure. When the expansion inner cavity is pressurized, the first hole sealer and the second hole sealer will expand and squeeze the inner wall of the water injection borehole 10 to seal the water injection borehole.

[0022] One end of the first hole sealer 20 is provided with a first expansion pipe interface 21, and the other end of the first hole sealer 20 is a closed end. The first expansion pipe interface 21 is connected to the expansion inner cavity of the first hole sealer.

[0023] A second expansion pipe interface 31 and a second water injection pipe interface 32 are provided at one end of the second hole sealer 30, and a second expansion pipe serial interface 33 and a second water injection pipe outlet 34 are provided at the other end of the second hole sealer 30. The second expansion pipe interface 31 and the second expansion pipe serial interface 33 are connected to the expansion inner cavity of the second hole sealer, and the second water injection pipe interface 32 is connected to the second water injection pipe outlet 34 through the pipe inside the second hole sealer 30, and the second water injection pipe interface 32 and the second water injection pipe outlet 34 are not connected to the expansion inner cavity of the second hole sealer.

[0024] The first expansion pipe interface 21 is connected to the second expansion pipe serial interface 33 through a connecting pipe 40, the length of the connecting pipe 40 corresponds to the length of the segmented water pressure test section S, so that the interval between the first plugging device 20 and the second plugging device 30 constitutes the segmented water pressure test section S. The connecting pipe 40 is a rigid pipe, such as a steel pipe.

[0025] The second expansion pipe interface 31 is connected to the expansion pressure pipe 13. In order to facilitate the operation of entering and exiting the water injection borehole, the expansion pressure pipe 13 is made of steel pipe. The expansion pressure pipe 13 pressurizes the first hole sealer 20 and the second hole sealer 30, so that the first hole sealer 20 and the second hole sealer 30 expand, thereby sealing the water injection borehole 10 and forming a closed segmented water pressure test section S. After the expansion pressure pipe 13 is depressurized, the first hole sealer 20 and the second hole sealer 30 shrink, and the shrunken first hole sealer 20 and the second hole sealer 30 can move in the water injection borehole. The expansion pressure pipe 13 is connected to the injection pump 14, and a control valve 18 is provided on the expansion pressure pipe 13.

[0026] The second water injection pipe interface 32 is connected to the test water injection pipe 12, and the test water injection pipe 12 is connected to the segmented water pressure test section S through the second water injection pipe interface 32 and the second water injection pipe outlet 34. The test water injection pipe 12 is connected to the water injection pump 14, and the water injection pump can be a fracturing pump. A pressure sensor 15 and a timer 16 are provided on the test water injection pipe 12, and a control valve 17 is also provided on the test water injection pipe 12.

[0027] The segmented hydraulic pressure test device of this embodiment creates a closed segmented hydraulic pressure test section S for the water injection borehole, and can move the segmented hydraulic pressure test section S to any (depth) position of the water injection borehole 10. Through the pressurization of the water injection pump and valve control, hydraulic pressure test conditions are provided for the segmented hydraulic pressure test section S. Through the pressure sensor and timer, the hydraulic pressure test data is obtained.

[0028] Embodiment 2: A method for measuring the "two zones" of the roof of a working face and the damaged zone of the bottom plate adopts the segmented water pressure testing device described in Example 1. The process includes drilling a water injection borehole, performing a segmented water pressure test on the water injection borehole, obtaining segmented water pressure data in the water injection borehole before and after mining, and comparing the development of rock strata fractures before and after mining.

[0029] The process of this method includes: 1. Estimation of the depth of the floor damage zone. Calculate the estimated value of the floor damage depth based on the "Specifications for the Retention and Compressed Coal Mining of Coal Pillars in Buildings, Water Bodies, Railways and Main Wells and Lanes", or the existing measured data on the floor damage depth of working faces in the country, and the empirical formula for the floor damage depth of working faces.

[0030] 2. Drilling design and construction. Drill water injection holes according to the estimated value of the bottom plate damage depth. The water injection drilling design is divided into two or more groups to facilitate control tests, which can be carried out in adjacent tunnels or on the ground. Refer to the KA / T4-2023 standard for drilling design. The vertical depth of the drilling design must be greater than the estimated value of the bottom plate damage depth, and the depth of the drilling into the (overlooking) mining face is greater than 20m. A borehole pipe is set at the orifice of the borehole, and the length of the orifice pipe is determined by the lithology and the degree of fracture development. After the drilling is completed, the orifice 11 of the water injection borehole needs to be reinforced. The reinforcement can be achieved by a borehole pipe, which is made of steel pipe and fixed with cement.

[0031] In order to facilitate the control test, multiple water injection boreholes can be drilled in the experimental mining area. The preferred solution is to drill four water injection boreholes 10 in the experimental mining area. The four water injection boreholes are divided into two groups, with two water injection boreholes in each group. The interval between the two groups of water injection boreholes must be greater than the periodic pressure step. Usually, the interval between the two groups of water injection boreholes can be set to 100m.

[0032] 3. Conduct pre-mining observation of water injection boreholes. After the borehole and orifice pipe are installed, punch the hole repeatedly. Before mining (more than 20 meters away from the mining surface), use a borehole peep to peep at the water injection borehole. The borehole peep (borehole TV) preferably uses an instrument with inclinometer and natural gamma sensor. If not, it is necessary to drill and coring. Use the peep data to complete the compilation of the borehole column chart and the comparison of fracture development before and after mining.

[0033] 4. Carry out a pre-mining water injection test on the water injection borehole. Before mining (more than 20 meters away from the mining surface), conduct multiple segmented water pressure tests. When conducting the segmented water pressure test, the first sealer 20 and the second sealer 30 are inserted into the set position of the water injection borehole 10 and seal with the water injection borehole. Then use the water injection pump 13 to inject water into the segmented water pressure test section S. First, fill the segmented water pressure test section S with water to keep the water in the segmented water pressure test section S at normal pressure (such as 0MPa), and then start to inject water into the segmented water pressure test section S to increase pressure and start timing. When the water injection test pressure is reached, the timer records the pressure increase time. The water injection test pressure should be determined according to the structure of the rock formation and set according to the compressive strength of the regional rock formation to avoid excessive pressure that causes the rock formation structure to break. In order to obtain valid data, the test pressure of water in the water injection borehole is usually not less than 1.0MPa. For example, to conduct a water injection test pressure of 1.5MPa, the water pressure in the segmented water pressure test section S can be pressurized to above 1.5MPa, such as to 1.6MPa, and then the pressurization is stopped, and the control valve 16 is closed to cut off the influence of the tail equipment on the water pressure in the segmented water pressure test section S. Due to the voids and cracks in the rock formation, the water pressure in the segmented water pressure test section S will gradually decrease. The pressure sensor 14 detects the water pressure. When the water pressure is about to reach 1.5MPa, the timer 15 starts timing. When the water pressure drops to normal pressure (such as 0MPa), the timer 15 records the time, that is, the time taken for the water pressure in the water injection borehole to drop from the test pressure to normal pressure is obtained, which is called the pressure relief time.

[0034] The segmented hydraulic pressure test is carried out in multiple steps, and a segmented hydraulic pressure test section S is carried out in each step. Several segmented hydraulic pressure test sections S can be selected as needed, or they can be carried out step by step to carry out a full-segment hydraulic pressure test on the water injection borehole. The length of the segmented hydraulic pressure test section S can be set according to the test requirements. Usually, the length of the segmented hydraulic pressure test section S is 0.8m~2.0m.

[0035] Before mining, it is necessary to conduct multiple segmented hydraulic pressure tests on the same segmented hydraulic pressure test section S. By comparing the segmented hydraulic pressure test results before multiple mining, the self-development of the rock formation can be determined, that is, the natural changes of the rock formation not affected by mining. After mining, at least one segmented hydraulic pressure test is conducted, and the segmented hydraulic pressure test results after mining are compared with those before mining to determine the impact of the mining process on the development of the rock formation.

[0036] 5. Data analysis. The data analysis takes the pressure relief time as the main analysis object, and analyzes the results of water injection drilling peek comprehensively. The boost time is affected by factors such as pumps, operating valve groups, and natural water pressure and is only used as a reference value. In the pressure relief data analysis, the average pressure relief time is calculated for multiple segmented water pressure test sections S (or the entire section), and the average pressure relief time is compared with the pressure relief time of each segmented water pressure test section S. The larger the ratio, the more developed the primary fractures or the larger the porosity. As reference data, the average pressure relief time of multiple segmented water pressure test sections S is also calculated for boost time, and the average pressure relief time is compared with the boost time of each segmented water pressure test section S.

[0037] The destruction of the floor after mining affects the rock structure, and cracks will develop and the porosity will increase or decrease. When the impact of mining is greater than the original primary crack development or porosity before mining, the data before and after mining will be different. When the impact of mining is less than the original primary crack development or porosity before mining, the data before and after mining will show the same trend. When the section is not affected by mining, the data before and after mining will show the same trend (the ratio is not greater than 1 or less than 1 to determine whether it is affected or not).

[0038] Therefore, the impact of the damaged zones of the roof and floor of the working face during mining is analyzed and judged, providing data support for coal mine safety.

[0039] The following is an example of an actual test process. This is an example of a bottom plate mining damage zone test. The same method is also used for the test of the "two zones" of the top plate.

[0040] 1. Drilling site design Based on the principle of reflecting the mining damage law of the floor after coal seam mining in the working face and saving engineering costs, and taking into account the convenient conditions of construction, two drilling sites are designed in the working face. Drilling site 1 and drilling site 2 are located 52 meters to the left and 48 meters to the right of the Y18 conductor point of the 13101 return air chute, respectively. Figure 4 The bottom plate elevations of Drilling Sites 1 and 2 are +868m and +864m respectively, which are higher than the net water level of the Aohui water here (+848m~+849m).

[0041] In order to achieve the goal of one hole for multiple uses and comparative verification, the water pressure test hole also serves as a peep test hole. Two water injection boreholes are arranged in both drilling sites and also serve as drilling peep observation holes. According to the "Specifications for Coal Pillar Retention and Coal Pressure Mining in Buildings, Water Bodies, Railways and Main Wells and Lanes", the maximum floor damage depth is expected to be 26 meters, and considering the error factor to ensure that the measured range is greater than the floor mining damage range, the overall control depth of the four water injection boreholes in the two drilling sites is 35m, and the spacing between the two water injection boreholes in each drilling site is 2m. The drilling construction uses a Φ113mm drill bit to drill 6.3m. In order to avoid the collapse of the orifice, the orifice of the water injection borehole is reinforced, and a φ108mm orifice pipe is inserted for 6m. The orifice pipe uses a seamless steel pipe with a steel grade of D40 and a thickness of 8mm, and a valve is installed. The orifice pipe is fixed with epoxy resin + cement. Then carry out water injection test, the pressure is above 0.5MPa, the pressure is stable for more than 30 minutes, and the water injection drilling hole is qualified without water leakage around it, otherwise the casing is re-fixed. Then use a Ф75mm drill bit to drill to the final hole. The main parameters of drilling construction are shown in Figure 5 .

[0042] 2. Analysis of the results of the pre-mining inspection (taking 1# and 2# boreholes as examples) On March 26, the drilling site No. 2 borehole was peeped, and the recovery face was more than 120m away from the borehole. On March 31, the drilling site No. 1 borehole was peeped, and the recovery face was more than 100m away from the borehole. According to the borehole logging and peeping trajectory, it is inferred that the final borehole of the borehole basically meets the design requirements. Figure 6 .

[0043] The drilling observation revealed that there were many high-angle cracks in the sandstone section, and multi-angle cracks appeared crosswise. In the limestone section, the primary cracks were particularly developed, and huge karst cavities and sulfur-containing nodules were visible. Figure 7 , the comprehensive column chart of drilling holes is shown in Figure 8 .

[0044] 3. Analysis of water injection test results before mining (taking 1# and 2# boreholes as examples) On April 1, a water injection test was conducted on the 1# and 2# water injection boreholes in the first drilling field. At this time, the mining face was more than 80m away from the water injection borehole. The pressure increase time t1 and pressure relief time t2 of each water injection borehole in the first water injection test before mining were obtained. The segmented water pressure test device described in Example 1 was used, with 1.5MPa as the end water pressure, and the segmented water pressure test section S=1m. Without fracturing the surrounding rocks, the automatic pressure monitor automatically monitored the time when the water pressure dropped to 0MPa. Due to the influence of drill cuttings during drilling construction, the water injection test was not conducted on the entire hole.

[0045] Through data analysis and graph comparison, the corresponding sections of the pressure-increasing time t1 and the pressure-releasing time t2 are basically inversely proportional. The comparison graph of the water injection test curve shows that the peak of the pressure-increasing time corresponds to the trough of the pressure-releasing time. In the section with developed fractures, the pressure-increasing time data is large and the pressure-releasing time data is small; in the section with undeveloped fractures, the pressure-increasing time data is small and the pressure-releasing time data is large. Fig. 9 , Fig.10 .

[0046] 4. Post-mining observation and measurement analysis (taking 1# and 2# boreholes as examples) From April 16 to April 18, borehole peep was conducted on the 1# and 2# boreholes in the first drilling site. At this time, the mining face was 24m to 34m past the borehole. By repeatedly comparing the borehole peep videos before and after mining, it was found that in areas where primary fractures were developed, there was an obvious increase in fractures after mining; in areas where primary fractures were not developed, no particularly obvious increase in fractures was found, especially in the coarse sandstone and mudstone sections at the end of the peep, which were almost unchanged. The 1# water injection borehole showed an increase in rock cuttings that blocked the borehole at 30m, indicating that the bottom plate was still significantly affected by mining. The comparison of fracture peep before and after drilling is shown in Fig.11 , 5. Analysis of water injection test results after mining (taking 1# borehole as an example) From April 16 to April 18, the second water injection test was carried out on boreholes 1 and 2 in the first drilling field. At this time, the mining face was 24m to 34m beyond the borehole. The pressure increase time t3 and pressure relief time t4 of each water injection borehole in the second water injection test after mining were obtained.

[0047] The segmented water pressure test device described in Example 1 was used, with 1.5 MPa as the termination water pressure, and each water injection test interval of 1 m. Without fracturing the surrounding rocks, the pressure automatic monitor (pressure sensor 15 and timer 16) automatically monitored the time when the water pressure dropped to 0 MPa. Due to the influence of drilling cuttings during drilling construction, the water injection test was not performed on the entire hole. In order to more intuitively compare the time changes of pressure increase and pressure relief, the mean of each group of time was introduced, and the ratio of the pressure increase time t1, t3 to the mean of each pressure increase time was used to draw a curve graph. The larger the ratio, the more developed the cracks. The mean of each pressure relief time and the pressure relief time t2, t4 were used to draw a curve graph. The larger the ratio, the more developed the cracks.

[0048] The pressure-rising time t1 and t3 are affected by the pump, operating valve group, natural water pressure, etc. and can only be used as reference values. When located in the same lithology, the greater the change in the two curve data, the more uneven the structure development. Combined with the peek results, when the curve data is greater than 1 or close to 1, it is generally a fracture development area or a section with high porosity.

[0049] The larger the ratio of the mean pressure relief time to the pressure relief time t2, the more developed the primary fractures are or the larger the porosity is. The destruction of the bottom plate after mining affects the rock structure, and there will be a phenomenon of fracture development and increased or decreased porosity. When the impact of mining is greater than the original primary fracture development or the large porosity before mining, the two curves will be differentiated; when the impact of mining is less than the original primary fracture development or the large porosity before mining, the two curves will show the same trend; when the section is not affected by mining, the two curves will show the same trend (the ratio is not greater than 1 or less than 1 to determine whether it is affected). The first and second water injection boost, pressure relief, and mean ratio curves are shown in Fig.12 .

[0050] Through analysis, we know that: (1) The ratio of t1 to the average time of the first pressure increase is greater than 1m in the 7m-40m section of the borehole, and less than 1m in the 40m-55m section. It increases rapidly after 55m, that is, the primary fissures in the 7m-40m section are relatively developed, and the fissures are more developed after 55m. The ratio of t3 to the average time of the second pressure increase is greater than 1 in the 10m-11m, 14m, 27m-29m, 33m-34m, and 49m-51m sections of the borehole. It is less than 1m in other sections before 49m, and increases rapidly after 49m, that is, the primary fissures in the 7m-40m section are relatively developed, and the fissures are more developed after 55m. The overall curve trend is the same after 52m, and the curve trend before 52m is partially inconsistent.

[0051] (2) Under the condition of equal pressure and volume, the pressure relief time can accurately reflect the development of cracks. The overall curve trend is the same before 48m and after 52m, but the curve trend is inconsistent before 48m to 52m.

[0052] (3) By comparing the time taken to raise the pressure to equal volume of water injection before and after mining and combining it with the peek results, it can be seen that the cracks are not developed after drilling 52m (coarse sandstone) because of the large porosity. The local inconsistency of the curve trend before drilling 52m is due to the inconsistent development of cracks before and after mining.

[0053] (4) By combining the time of decompression to 0 under the condition of equal pressure and volume before and after mining with the peek results, the curve trends before 48m and after 52m are the same. The porosity is large after 52m (coarse sandstone), and the fracture development section before 48m. 48m to 52m is the boundary of the mining floor damage zone.

[0054] 6. Comprehensive measurement results analysis (1) The results of the peeping show that the lithology of the 13 coal floor has changed to some extent in the adjacent areas, but the overall consistency is consistent, the development of fractures and porosity are also different, and the porosity of the same lithology is also different. The peeping did not find that the areas with developed fractures also had a long pressure increase time and a short pressure release time (mostly in the coarse sandstone section), indicating that the rock stratum has a large porosity, which is reflected in the curve graph being greater than the area affected by mining.

[0055] (2) Mudstone and siltstone are aquicludes. In this experiment, primary fractures are more developed in mudstone and siltstone than in other rock types.

[0056] (3) By repeatedly comparing the pre- and post-mining videos of the boreholes, it was found that in areas where primary fissures were developed, the cracks increased significantly after mining; in areas where primary fissures were not developed, no particularly obvious increase in cracks was found, especially in the coarse sandstone and mudstone sections at the end of the peek, which were almost unchanged. The increase in rock cuttings in the 1# borehole at the site where the borehole was blocked at 30m indicated that the floor was still significantly affected by mining.

[0057] (4) The excavation process of the 13101 working face revealed a simple structure. The calculation formula for the floor damage depth determined that the maximum mining damage depth of the floor was about 26m. In the water injection test, the 48m-52m (vertical depth 26.6m) of boreholes 1# to 2# is the boundary of the mining floor damage zone; the 48m-52m (vertical depth 30m) of borehole 3# is the boundary of the mining floor damage zone; the 52m-57m (vertical depth 32m) of borehole 3# is the boundary of the mining floor damage zone.

[0058] (5) Comprehensive analysis shows that the floor lithology is an interlayer structure of mudstone and sandstone. Affected by mining, the mudstone strata have developed mining cracks with good connectivity and large scale, mainly in the upper and middle parts of the borehole. The sandstone mainly has primary cracks and high porosity. The depth of mining damage to the floor of the No. 13 coal is about 32m.

Claims

1. A method for measuring the "two zones" of the top plate and the damaged zone of the bottom plate of the working face, including construction of water injection drilling, characterized in that: The water injection borehole is subjected to a segmented water pressure test to obtain segmented water pressure data in the water injection borehole before and after mining, and the degree of development of rock strata fissures before and after mining is compared.

2. The method for measuring the "two zones" of the top plate and the damaged zone of the bottom plate of the working face according to claim 1 is characterized in that: The segmented water pressure test section of the water injection borehole is 1m.

3. The method for measuring the "two zones" of the top plate and the damaged zone of the bottom plate of the working face according to claim 1 is characterized in that: The method of the water pressure test comprises injecting water into the water injection borehole in sections, pressurizing the water in the water injection borehole to a test pressure, and monitoring the time taken for the water pressure in the water injection borehole to drop to normal pressure.

4. The method for measuring the "two zones" of the top plate and the damaged zone of the bottom plate of the working face according to claim 3 is characterized in that: The test pressure of water in the water injection borehole is not less than 1.0MPa.

5. The method for measuring the "two zones" of the top plate and the damaged zone of the bottom plate of the working face according to claim 1 is characterized in that: Carry out one or more segmented water pressure tests before mining, compare the segmented water pressure test results before mining, and judge the self-development of the rock formation; carry out one segmented water pressure test after mining, compare the segmented water pressure test results after mining with the segmented water pressure test results before mining, and judge the impact of the mining process on the rock formation.

6. The method for measuring the "two zones" of the top plate and the damaged zone of the bottom plate of the working face according to claim 1 is characterized in that: The method also includes peek detection of the water injection boreholes and preparation of a borehole histogram.

7. The method for measuring the "two zones" of the top plate and the damaged zone of the bottom plate of the working face according to claim 1 is characterized in that: The orifice of the water injection borehole is reinforced to prevent the orifice from collapsing.

8. The method for measuring the "two zones" of the top plate and the damaged zone of the bottom plate of the working face according to claim 1 is characterized in that: At least four water injection boreholes are drilled in the experimental mining area, and the four water injection boreholes are divided into two groups, each group has two water injection boreholes, and the interval between the two groups of water injection boreholes is greater than the periodic pressure step.

9. The method for measuring the "two zones" of the top plate and the damaged zone of the bottom plate of the working face according to claim 1 is characterized in that: The method adopts a segmented water pressure test device, which comprises a first hole sealer (20) and a second hole sealer (30), wherein the second hole sealer is located on a side close to a hole opening (11) of a water injection borehole (10), and the interval space between the first hole sealer (20) and the second hole sealer (30) is a segmented water pressure test section (S).

10. The method for measuring the "two zones" of the top plate and the damaged zone of the bottom plate of the working face according to claim 9 is characterized in that: A first expansion pipe interface (21) is provided at one end of the first hole sealer (20); a second expansion pipe interface (31) and a second water injection pipe interface (32) are provided at one end of the second hole sealer (30); a second expansion pipe serial interface (33) and a second water injection pipe outlet (34) are provided at the other end of the second hole sealer (30); the first expansion pipe interface (21) and the second expansion pipe serial interface (33) are connected via a connecting pipe (40); the second expansion pipe interface (31) is connected to an expansion pressure pipe (13); the second water injection pipe interface (32) is connected to a test water injection pipe (12); the second water injection pipe outlet (34) is connected to the segmented water pressure test section (S); the test water injection pipe (12) and the expansion pressure pipe (13) are connected to a water injection pump (14); a pressure sensor (15) and a timer (16) are provided on the test water injection pipe (12); and control valves are provided on the test water injection pipe (12) and the expansion pressure pipe (13).

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