A method for determining the width of the pressure-relief zone of coal roadway based on surrounding rock stress

Abstract

The present invention discloses a method for measuring the width of the pressure-relief zone of a coal roadway based on surrounding rock stress, comprising the following steps: S1, drilling a plurality of holes with different depths in the roadway rib; S2, sending the in-hole stress induction package and the high-pressure liquid delivery pipeline to the bottom position of the hole; S3, installing a three-way interface at one end of the high-pressure liquid delivery pipeline extending out of the hole, connecting the second port of the three-way interface to a digital stress display, connecting the second port of the three-way interface to a stop valve and connecting a liquid adding gun through the stop valve; S4, opening the stop valve, inputting hydraulic oil into the in-hole stress induction package through the liquid adding gun, and closing the stop valve after the pressure value reading on the digital stress display reaches a certain value and stabilizes; S5, repeating steps S2 to S4, recording the pressure value readings displayed by each digital stress display at high frequency within a certain time period, and determining the range of the width of the pressure-relief zone according to the magnitude and change range of the pressure values in the holes with different depths.

Description

Technical Field

[0001] The present invention relates to the field of coal mining, and particularly to a method for determining the width of the pressure-relief zone of a coal seam roadway based on surrounding rock stress. Background Art

[0002] Coal and gas outburst (hereinafter referred to as outburst) is a dynamic phenomenon caused by the combined action of factors such as gas pressure, in-situ stress, and the physical and mechanical properties of coal. It mostly occurs during the driving process of the roadway in the coal seam. Improper roadway layout or insufficient gas drainage may lead to the accidental mining and driving of outburst-prone coal seams, thereby triggering outburst accidents, causing huge property losses and casualties, affecting the project progress, and severely restricting the mining and excavation succession of the mine. When driving a roadway in an outburst coal seam, how to reduce the gas content in the coal body in front of the driving face and achieve the smooth outburst elimination of the driving roadway has become one of the difficulties restricting the high-efficiency and safe production of coal mines.

[0003] A large number of studies at home and abroad have shown that after the roadway is excavated in the coal seam, the stress balance state of the coal body is broken, and a zonal division appears on both sides of the roadway during the process of tending to a new stress balance, which are the pressure-relief zone, the stress concentration zone, and the original stress zone in sequence. In the pressure-relief zone, the stress is released for a long time, the gas permeability of the coal seam increases, the gas is continuously desorbed and released, and the gas pressure is greatly reduced, gradually losing the kinetic energy of gas disasters. Under the protection of this pressure-relief zone, as long as enough protection width is reserved, the outburst elimination work during the driving of the coal seam roadway can be achieved. At the same time, driving a roadway in the pressure-relief zone can improve the roadway support conditions, increase the recovery of coal resources, reduce the outburst prevention engineering quantity, and achieve safe and efficient driving. Many current outburst prevention measures, such as deep-hole loosening blasting and opening pressure-relief grooves, all achieve the purpose of outburst prevention by increasing the width of the pressure-relief zone. In addition, to improve the drainage effect, the sealing length of the boreholes for drainage along the coal seam should preferably exceed the width of the pressure-relief zone. It can be seen that accurately determining the width of the pressure-relief zone is of great significance for rapid and safe driving and effective gas drainage.

[0004] The previous methods for determining the width of the pressure-relief zone beside the coal seam roadway mainly include the drill cuttings method, the gas content method, the initial gas emission velocity method of boreholes, the gas drainage parameter method, and the gas leakage volume method; the data measured by the above methods are restricted by many influencing factors, and the measurement results have great uncertainty. Therefore, the present invention proposes a method for determining the width of the pressure-relief zone of a coal seam roadway based on surrounding rock stress according to the theory of the distribution law of mine pressure of the coal seam. Summary of the Invention

[0005] The object of the present invention is to provide a method for determining the width of the pressure-relief zone of a coal seam roadway based on surrounding rock stress, which is simple to operate, convenient and fast, in view of the above problems.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] A method for measuring the width of the pressure-relief zone of a coal roadway based on surrounding rock stress, comprising the following steps:

[0008] S1. Drill a number of holes with different depths in the roadway rib in a direction perpendicular to the axial direction of the roadway, and the number of holes are arranged horizontally side by side;

[0009] S2. In the hole, use a push rod to send the in-hole stress induction package and the high-pressure liquid delivery pipeline connecting the in-hole stress induction package to the bottom of the hole;

[0010] S3. Install a three-way interface at one end of the high-pressure liquid delivery pipeline extending out of the hole. The second port of the three-way interface is connected to a digital stress display. The second port of the three-way interface is connected to a stop valve and connected to a liquid adding gun through the stop valve;

[0011] S4. Open the stop valve, input hydraulic oil into the high-pressure liquid delivery pipeline through the liquid adding gun, and the hydraulic oil enters the in-hole stress induction package through the high-pressure liquid delivery pipeline; Observe the pressure value reading displayed on the digital stress display. After the pressure value reading on the digital stress display reaches a certain value and stabilizes, close the stop valve, and read and record the pressure value reading;

[0012] S5. Repeat steps S2 to S4 until the pressure value readings of all holes are read. Then, record the pressure value readings displayed on the digital stress display of each hole at high frequency within a certain period of time, and determine the range of the width of the pressure-relief zone according to the magnitude and change range of the pressure values in the holes with different depths.

[0013] Further, in the step S1, the number of holes are arranged at equal intervals, and the interval between adjacent holes is 1 to 2 m.

[0014] Further, in the step S4, close the stop valve after the pressure value reading on the digital stress display reaches 2 to 4 MPa and stabilizes.

[0015] Further, in the step S5, the duration of a certain period of time is not less than 30 days; the recording frequency of high-frequency recording is that the interval time between two adjacent recordings does not exceed two hours.

[0016] Compared with the prior art, the advantages and positive effects of the present invention are:

[0017] The present invention provides a method for determining the width of the pressure-relief zone in coal roadway based on surrounding rock stress, which is proposed based on the theory of the distribution law of mine pressure. That is, after the coal seam is excavated, due to the change of the support condition, its original equilibrium state is damaged, and different stress distribution regions are formed from the roadway contour line to the deep part in the surrounding rock, namely the stress reduction zone, the stress concentration zone and the virgin rock stress zone. The stress reduction zone is the pressure-relief zone. In the whole determination process of the present invention, there is no need to collect drill cuttings of boreholes, no need to seal the holes, no need to worry about data distortion caused by imperfect hole sealing, no interference with the measurement data due to the leakage of coal seam gas during drilling, and no error caused by the damage to the hole wall during drilling. It only needs to measure the surrounding rock stress at different depths of the borehole to accurately determine the width of the pressure-relief zone beside the roadway near the measuring point. The measurement process is simple and fast, not affected by other factors, effectively improving the measurement accuracy of the width of the pressure-relief zone in coal roadway and bringing convenience to coal mining operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order 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 for the description of the embodiments or the prior art. Obviously, the following drawings 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.

[0019] Figure 1 It is the effect diagram of the measurement operation of a single borehole in the present invention;

[0020] Figure 2 It is the layout diagram of the arrangement of the measurement boreholes in the present invention. EMBODIMENTS

[0021] 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 a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts, any modifications, equivalent replacements, improvements, etc., shall be included in the protection scope of the present invention.

[0022] Such as Figure 1 、 Figure 2As shown in the figure, this embodiment discloses a method for measuring the width of the pressure-relief zone of a coal roadway based on the surrounding rock stress. The tools required in the measurement process include an in-hole stress induction package 2, a high-pressure liquid delivery pipeline 3, a push rod 5, a push rod connecting sleeve 4, a three-way interface 6, a digital stress display 7, a stop valve 8, and a liquid filling gun 9. The two ends of the high-pressure liquid delivery pipeline 3 are respectively connected to the in-hole stress induction package 2 and the three-way interface 6. The other two ports of the three-way interface 6 are respectively connected to the liquid filling gun 9 and the digital stress display 7. The liquid filling gun 9 delivers hydraulic oil into the in-hole stress induction package 2 through the high-pressure liquid delivery pipeline 3. The push rod 5 is used to push the in-hole stress induction package 2 into a specified position in the drill hole and can be taken out after pushing.

[0023] The specific measurement steps of the present invention are as follows:

[0024] A method for measuring the width of the pressure-relief zone of a coal roadway based on the surrounding rock stress includes the following steps:

[0025] S1. Drill a number of drill holes 1 with different depths in the direction perpendicular to the axial direction of the roadway on the roadway sidewall, and the number of drill holes 1 are arranged horizontally side by side. The number of drill holes 1 are arranged at equal intervals, and the distance between adjacent drill holes 1 is 1 m.

[0026] S2. In the drill hole 1, use the push rod 5 to send the in-hole stress induction package 2 and one end of the high-pressure liquid delivery pipeline 3 connected to the in-hole stress induction package 2 to the bottom of the drill hole 1. When the length of the push rod 5 is not enough, the push rod connecting sleeve 4 can be used for connection and extension.

[0027] S3. Install a three-way interface 6 at one end of the high-pressure liquid delivery pipeline 3 extending out of the drill hole 1. The second port of the three-way interface 6 is connected to the digital stress display 7. The second port of the three-way interface 6 is connected to the stop valve 8 and is connected to the liquid filling gun 9 through the stop valve 8.

[0028] S4. Open the stop valve 8, input hydraulic oil into the high-pressure liquid delivery pipeline 3 through the liquid filling gun 9, and the hydraulic oil enters the in-hole stress induction package 2 through the high-pressure liquid delivery pipeline 3. Observe the pressure value reading displayed on the digital stress display 7. After the pressure value reading on the digital stress display 7 reaches 3 MPa and stabilizes, close the stop valve 8, and read and record the pressure value reading.

[0029] S5. Repeat steps S2 to S4 until the pressure value readings of all drill holes 1 are read. Then, within a time period of not less than 30 days, record the pressure value readings displayed on the digital stress display 7 belonging to each drill hole 1 at a recording frequency of once per hour, and determine the range of the width of the pressure-relief zone according to the magnitude and change range of the pressure values in the drill holes 1 with different depths.

[0030] The present invention has the following beneficial effects:

[0031] 1. New measurement method: The direct cause of the pressure-relief zone in the roadway is the stress concentration acting on the roadway. The stress concentration (increase) causes the coal body to break and soften, resulting in coal fragments, fissures, and more drill cuttings. The gas in the coal body also changes accordingly. The previous drill cutting method, gas content method, and gas leakage volume method all measure this indirectly generated result, which is indirect measurement. Indirect measurement is easily interfered by various external factors, such as the damage of the drill bit to the fissures, drilling rate, drilling time, and drill cutting statistical error. However, this method directly measures the surrounding rock stress, is not easily interfered by the outside world, and the measurement is more accurate.

[0032] 2. Wide application range: This method can be used not only in high-gas areas but also in areas with low gas content and low gas pressure. In areas with low gas content, the change value of the gas content may be extremely small and cannot be measured. Since this method does not measure the gas content, it is not affected by the size of the gas content. As long as it is in the pressure-relief zone, the stress will inevitably have a process of rising and falling. Therefore, this method has a wide application range.

[0033] 3. Convenient data collection: This method can continuously collect data automatically without human intervention. Personnel only need to regularly check the on-site equipment and collect data, reducing the frequency of personnel going down the well. It is safer and more convenient than other methods. At the same time, the data measured by other methods is only the instantaneous data at the time of measurement and does not have continuity, which affects the accuracy of the measurement results.

[0034] 4. Simple construction: The boreholes required for this method can utilize the boreholes used in tests such as the gas content method and the drill cutting method, without the need to repeat the construction of boreholes, which can further reduce the measurement cost.

[0035] 5. High measurement accuracy: The final measurement accuracy of the width of the pressure-relief zone by this method can reach 0.1 m, while the measurement accuracy of the width of the pressure-relief zone by other methods can only reach 1.0 - 1.5 m.

Claims

1. A method for determining the width of the pressure-relief zone in a coal roadway based on the surrounding rock stress, characterized in that: It includes the following steps: S1: Drill a number of holes with different depths in the direction perpendicular to the axial direction of the roadway in the roadway rib, and the number of holes are arranged horizontally side by side; S2: In the holes, use the pushing rod to send the in-hole stress induction package and the high-pressure liquid delivery pipeline connecting the in-hole stress induction package to the bottom of the hole; S3: Install a three-way interface at one end of the high-pressure liquid delivery pipeline extending out of the hole. The second port of the three-way interface is connected to the digital stress display, and the second port of the three-way interface is connected to a stop valve and connected to a liquid adding gun through the stop valve; S4: Open the stop valve, input hydraulic oil into the high-pressure liquid delivery pipeline through the liquid adding gun, and the hydraulic oil enters the in-hole stress induction package through the high-pressure liquid delivery pipeline; Observe the pressure value reading displayed on the digital stress display. After the pressure value reading on the digital stress display reaches a certain value and stabilizes, close the stop valve, and read and record the pressure value reading; S5: Repeat steps S2 to S4 until the pressure value readings of all holes are read. Then, record the pressure value readings displayed on the digital stress display belonging to each hole at high frequency within a certain period of time, and determine the range of the width of the pressure relief zone according to the magnitude and change range of the pressure values in the holes with different depths.

2. The method for measuring the width of the pressure-relief zone of the coal roadway based on the surrounding rock stress according to claim 1, wherein: In step S1, a number of holes are arranged at equal intervals, and the interval between adjacent holes is 1 to 2 m.

3. The method for determining the width of the pressure-relief zone of a coal roadway based on surrounding rock stress according to claim 1, wherein: In step S4, close the stop valve after the pressure value reading on the digital stress display reaches 2 to 4 MPa and stabilizes.

4. The method for determining the width of the pressure-relief zone of a coal roadway based on the surrounding rock stress according to claim 1, characterized in that: In step S5, the duration of a certain period of time is not less than 30 days; the recording frequency of high-frequency recording is that the interval time between adjacent recordings does not exceed two hours.

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