A method for monitoring coal mine working face pressure based on self-sensing concrete

Abstract

The present invention discloses a method for monitoring the mine pressure of a coal mine working face based on self-sensing concrete, wherein an advanced stress detection borehole is drilled in a coal seam and self-sensing concrete is cast in situ, and a pre-buried electrode detection device and an external electrical method detector are used to monitor the resistivity change of the cast-in-situ self-sensing concrete in the advanced stress detection borehole in real time, and the relationship between the resistivity of the self-sensing concrete and the pressure it is subjected to is combined to quickly and accurately detect the mine pressure condition in the coal seam in front of the working face, and a borehole monitoring body composed of self-sensing concrete is integrated with a coal rock mass, and the pressure-sensitive characteristics of the self-sensing concrete are utilized to adopt an electrical method to detect the changing characteristics of the pressure of the coal rock mass, and the method has the advantages of simple operation, high sensitivity, and low cost, and has wide practicality in the art.

Description

Technical Field

[0001] The invention relates to the field of coal mining, and in particular to a method for monitoring the mine pressure of a coal mine working face based on self-sensing concrete. Background Art

[0002] As the depth of coal mining continues to increase, the mine pressure faced by the working face is also increasing. In order to ensure the safety of personnel and equipment in the working area, accurate monitoring of the mine pressure data of the working face has become extremely important. However, the method of burying sensors in the advanced stress detection borehole, which is currently widely used, cannot accurately monitor the mine pressure data due to the following two fatal defects. The first defect is that when the coal rock mass at the detection location undergoes irregular or large-scale deformation, the sensor may lose contact with the coal rock mass, resulting in the inability to effectively monitor the mine pressure data. The second defect is that when the coal rock mass around the sensor undergoes only local tensile cracking or horizontal sliding, the sensor may not be able to effectively monitor the mine pressure data due to the inability to undergo effective synchronous deformation. Summary of the invention

[0003] In view of the above-mentioned technical deficiencies, the purpose of the present invention is to provide a method for monitoring mine pressure at a coal mine working face based on self-sensing concrete, which monitors the resistivity changes of the cast-in-place self-sensing concrete in the advance stress detection borehole in real time through a pre-buried electrode detection device and an external electrical detector, and combines the relationship between the resistivity of the self-sensing concrete and the pressure it is subjected to to quickly and accurately detect the mine pressure conditions in the coal seam in front of the working face.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] The present invention provides a method for monitoring the working face pressure of a coal mine based on self-sensing concrete, comprising the following steps:

[0006] Step 1: At the middle of the track tunnel or transport tunnel at a certain distance from the working face, a number of evenly distributed advance stress detection boreholes are drilled in the coal seam along the advancing direction of the working face;

[0007] Step 2: Connect the insulated detection wire to the inner side of the edge of the circular electrode mesh to form a complete electrode detection device; set up two layers of upper and lower electrode detection devices, the upper electrode detection device is installed on the upper support of the special joint, and the lower electrode detection device is installed on the lower support of the special joint; then firmly connect the special joint with the grouting pipe, and push the electrode detection device to the bottom of the advanced stress detection borehole;

[0008] Step 3: Use an electrical detector to detect the connectivity of the electrode detection device placed at the bottom of the advance stress detection borehole and ensure that it is in a good connection state;

[0009] Step 4: Inject the prepared self-sensing concrete slurry into the bottom of the advanced stress detection borehole through a grouting pipe;

[0010] Step 5: Before the self-sensing concrete slurry is about to initially set, the grouting pipe is pulled out of the space occupied by the self-sensing concrete slurry, and ordinary concrete slurry is injected into the remaining space in the advanced stress detection borehole through the grouting pipe;

[0011] Step 6: Use an electrical detector to detect the connectivity of the electrode detection devices buried in the self-sensing concrete slurry and the ordinary concrete slurry, and ensure that they are in a good connection state;

[0012] Step 7: After the self-sensing concrete slurry and the ordinary concrete slurry are completely solidified, an electrical detector is used to initially calibrate the electrical signal and pressure signal of the self-sensing concrete;

[0013] Step 8. When the working face is mined to within 150m of the first advance stress detection borehole, start using an electrical detector to monitor the self-sensing concrete resistivity changes, and convert the resistivity into pressure data to obtain the evolution law of the mine pressure on the working face. Monitor once every 1m until the working face has advanced through all the advance stress detection boreholes.

[0014] Preferably, in step two, the special joint includes an annular base, on which a number of alternating upper and lower supports are evenly distributed in a ring, the base, the upper supports and the lower supports are all made of hard plastic, the base is provided with an upper semicircular wire trough, a lower semicircular wire trough and a reserved grouting port, and the upper and lower supports are provided with rectangular reserved grooves.

[0015] Preferably, when installing the lower electrode detection device on the special joint in step 2, the circular electrode mesh is passed through the upper support of the special joint and stuck in the rectangular reserved groove of the lower support, and the insulation detection line is led out from the lower semicircular wire groove of the special joint; when installing the upper electrode detection device on the special joint, the circular electrode mesh is stuck at the bottom of the rectangular reserved groove of the upper support of the special joint, and the insulation detection line is led out from the upper semicircular wire groove of the special joint; the distance between the upper and lower electrode detection devices is greater than or equal to 30 cm.

[0016] Preferably, in step one, the horizontal distance between the first detection borehole and the working surface is 100m, the distance between two adjacent advance stress detection boreholes is 10-15m, the length of the advance stress detection borehole is 1 / 4-1 / 2 of the width of the working surface, the diameter is 70mm, and the total number is 5.

[0017] Preferably, in step 4, the self-sensing concrete slurry is injected three times, and the self-sensing concrete slurry should completely cover the special joint during the first injection; after the first injection is completed and waiting for 5 minutes, the grouting pipe is pulled out 25 cm, and the second grouting is performed until the special joint is completely covered by the self-sensing concrete slurry again; after the second injection is completed and waiting for 5 minutes, the grouting pipe is pulled out again 25 cm, and the third grouting is performed until the special joint is completely covered by the self-sensing concrete slurry again.

[0018] Preferably, the raw materials required for preparing the self-sensing concrete slurry in step 4 include: 42.5R ordinary Portland cement, silica fume, polyacrylonitrile carbon fiber, water reducer, defoamer and dispersant; the water-cement ratio of the self-sensing concrete slurry is 0.55, and the carbon fiber length is 4 mm; the amount of carbon fiber, water reducer, silica fume, dispersant and defoamer is 0.5%, 1.5%, 15%, 0.7% and 0.08% of the cement mass, respectively; when preparing the self-sensing concrete slurry, the carbon fiber is first placed in an aqueous solution of a water reducer, a dispersant and a defoamer, and then it is fully stirred by a mortar mixer, and finally the silica fume and cement are added in sequence and stirred for 2 minutes.

[0019] The beneficial effects of the present invention are as follows: the monitoring method proposed by the present invention is simple to operate, highly sensitive, and low in cost, and has wide practicability in the art.

[0020] The self-sensing concrete used as the monitoring medium in the present invention does not need to be recycled, thereby reducing corresponding expenses and simplifying the coordination between coal mining operations and mine pressure monitoring procedures.

[0021] 3. The self-sensing concrete used as the monitoring medium in the present invention can be tightly bonded with the coal and rock mass to be measured, and is very sensitive to changes in its own resistivity, thereby ensuring rapid and effective monitoring of complex deformation conditions of the coal and rock mass. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 A schematic diagram of the arrangement of various components in a method for monitoring pressure at a coal mine working face based on self-sensing concrete provided in an embodiment of the present invention.

[0024] Figure 2 A schematic diagram of the structure of a special joint provided in an embodiment of the present invention;

[0025] Figure 3 A top view of the structure schematic diagram of a special joint provided in an embodiment of the present invention;

[0026] Figure 4 A side view of a structural schematic diagram of a special joint provided by an embodiment of the present invention;

[0027] Figure 5 A schematic diagram of pumping concrete slurry provided in an embodiment of the present invention.

[0028] Description of reference numerals:

[0029] 1. Advanced stress detection drilling hole; 2. Insulated detection line; 3. Circular electrode mesh; 4. Electrode detection device; 5. Special joint; 51. Upper support; 52. Lower support; 53. Upper semicircular wire trough; 54. Lower semicircular wire trough; 55. Reserved grouting port; 6. Grouting pipe; 7. Electrical detector; 8. Self-sensing concrete; 9. Ordinary concrete. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] like Figures 1 to 5 As shown, a method for monitoring the working face pressure of a coal mine based on self-sensing concrete comprises the following steps:

[0032] Step 1: At the middle of the track tunnel or transport tunnel 100m away from the working face, drill a horizontal advance stress detection borehole 1 into the coal seam every 10-15m along the advancing direction of the working face. The length of the advance stress detection borehole 1 is 1 / 4-1 / 2 of the width of the working face, the diameter is 70mm, and the total number is 5;

[0033] Step 2: Connect the insulated detection wire 2 to the inner side of the edge of the circular electrode mesh 3 to form a complete electrode detection device 4; the diameter of the circular electrode mesh 3 is 60 mm, the diameter of the mesh wire is 1 mm, and the mesh size is 5 mm×5 mm;

[0034] The upper and lower electrode detection devices 4 are respectively installed on the upper and lower pillars 52 of the special joint 5; the special joint 5 with the electrode detection device 4 installed is firmly connected to the grouting pipe 6 in a threaded connection manner, and the electrode detection device 4 is pushed to the bottom of the advanced stress detection borehole 1 by using the grouting pipe 6;

[0035] The special joint 5 includes an annular base, on which a plurality of alternating upper supports 51 and lower supports 52 are evenly distributed in an annular shape, and there are four upper supports 51 and four lower supports 52. The base, the upper supports 51 and the lower supports 52 are all made of hard plastic. An upper semicircular wire groove 53, a lower semicircular wire groove 54 and a reserved grouting port 55 are provided on the base. A rectangular reserved groove is provided on the upper support 51 and the lower support 52. The diameter of the base is 65 mm, the diameter of the reserved grouting port 55 is 40 mm, the diameter and height of the lower support 52 are 4 mm and 12 mm respectively, the width and depth of the rectangular reserved groove on the lower support 52 are both 2 mm, the diameter and height of the upper support 51 are 4 mm and 50 mm respectively, the width and depth of the rectangular reserved groove on the upper support 51 are 2 mm and 10 mm respectively, and the diameters of the upper semicircular wire groove and the lower semicircular wire groove are both 2 mm.

[0036] When installing the lower electrode detection device 4 on the special joint 5, the circular electrode mesh 3 is passed through the upper support 51 of the special joint and stuck in the rectangular reserved groove of the lower support 52, and the insulation detection line 2 is led out from the lower semicircular wire groove 54 of the special joint 5; when installing the upper electrode detection device 4 on the special joint 5, the circular electrode mesh 3 is stuck at the bottom of the rectangular reserved groove of the upper support 51 of the special joint, and the insulation detection line 2 is led out from the upper semicircular wire groove 53 of the special joint 5; the distance between the upper and lower electrode detection devices 4 is 30cm.

[0037] Step 3: Use the electrical detector 7 to detect the connectivity of the electrode detection device 4 placed at the bottom of the advanced stress detection borehole 1, and ensure that it is in a good connection state;

[0038] Step 4: Inject the prepared self-sensing concrete 8 slurry into the bottom of the advanced stress detection borehole three times using the grouting pipe 6. The first injection should make the self-sensing concrete 8 slurry completely cover the special joint 5; after the first injection is completed and waiting for 5 minutes, pull the grouting pipe 6 outward by 25 cm, and perform the second grouting until the special joint 5 is completely covered by the self-sensing concrete 8 slurry again; after the second injection is completed and waiting for 5 minutes, pull the grouting pipe 6 outward by 25 cm again, and perform the third grouting until the special joint 5 is completely covered by the self-sensing concrete 8 slurry again;

[0039] The raw materials required for preparing self-sensing concrete 8 slurry include: 42.5R ordinary Portland cement, silica fume, polyacrylonitrile carbon fiber, water reducer, defoamer and dispersant; the water-cement ratio of self-sensing concrete 8 slurry is 0.55, and the carbon fiber length is 4 mm; the amount of carbon fiber, water reducer, silica fume, dispersant and defoamer is 0.5%, 1.5%, 15%, 0.7% and 0.08% of the cement mass, respectively; when preparing self-sensing concrete 8 slurry, the carbon fiber is first placed in the aqueous solution of water reducer, dispersant and defoamer, and then it is fully stirred by a mortar mixer, and finally silica fume and cement are added in turn and stirred for 2 min.

[0040] Step 5: before the self-sensing concrete 8 slurry is about to initially set, the grouting pipe 6 is pulled out of the space occupied by the self-sensing concrete 8 slurry, and the grouting pipe 6 is used to inject ordinary concrete 9 slurry into the remaining space in the advanced stress detection borehole 1;

[0041] Step 6: Use the electrical detector 7 to detect the connectivity of the electrode detection device 4 embedded in the self-sensing concrete 8 slurry and the ordinary concrete 9 slurry, and ensure that they are in a good connection state;

[0042] Step 7: After the self-sensing concrete 8 slurry and the ordinary concrete 9 slurry are completely solidified, the electrical detector 7 is used to perform initial calibration on the electrical signal and pressure signal of the self-sensing concrete 8;

[0043] Step 8. When the working face is mined to within 150m of the first advance stress detection borehole, start using the electrical detector 7 to monitor the resistivity change of the self-sensing concrete 8, and convert the resistivity into pressure data to obtain the evolution law of the mine pressure on the working face. Monitor once every 1m until the working face has advanced through all the advance stress detection boreholes 1.

[0044] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for monitoring coal mine working face pressure based on self-sensing concrete, characterized in that: The following steps are involved: Step 1: drilling a number of evenly distributed advance stress detection boreholes (1) in the coal seam in the direction of advancement of the working face at a middle position of a track tunnel or a transport tunnel at a certain distance from the working face; Step 2: Connect the insulating detection wire (2) to the inner side of the edge of the circular electrode mesh (3) to form a complete electrode detection device (4); provide an upper and lower layer of electrode detection devices (4), wherein the upper electrode detection device (4) is installed on the upper support (51) of the special joint (5), and the lower electrode detection device (4) is installed on the lower support (52) of the special joint (5); then firmly connect the special joint (5) to the grouting pipe (6), and push the electrode detection device (4) to the bottom of the advanced stress detection borehole (1); Step 3: Use an electrical detector (7) to detect the connectivity of the electrode detection device (4) placed at the bottom of the advanced stress detection borehole (1) and ensure that it is in a good connection state; Step 4: Inject the prepared self-sensing concrete (8) slurry into the bottom of the advanced stress detection borehole through a grouting pipe (6); Step 5: before the self-sensing concrete (8) slurry is about to initially set, the grouting pipe (6) is pulled out of the space occupied by the self-sensing concrete (8) slurry, and the ordinary concrete (9) slurry is injected into the remaining space in the advanced stress detection borehole (1) through the grouting pipe (6); Step 6: Use an electrical detector (7) to detect the connectivity of the electrode detection device (4) embedded in the self-sensing concrete (8) slurry and the ordinary concrete (9) slurry, and ensure that they are in a good connection state; Step 7: After the slurry of the self-sensing concrete (8) and the slurry of the ordinary concrete (9) are completely solidified, an electrical detector (7) is used to initially calibrate the electrical signal and pressure signal of the self-sensing concrete (8); Step 8: When the working face is mined to within 50 m of the first advance stress detection borehole (1), the electrical detector (7) is used to monitor the resistivity change of the self-sensing concrete (8), and the resistivity is converted into pressure data to obtain the evolution law of the mine pressure at the working face. The monitoring is performed every 1 m until the working face has advanced through all the advance stress detection boreholes (1).

2. A method for monitoring coal mine working face pressure based on self-sensing concrete as claimed in claim 1, characterized in that: In step 2, the special joint (5) includes a ring-shaped base, on which a plurality of upper supports (51) and lower supports (52) are evenly distributed in a ring and arranged alternately. The base, the upper supports (51) and the lower supports (52) are all made of hard plastic. The base is provided with an upper semicircular wire groove (53), a lower semicircular wire groove (54) and a reserved grouting port (55), and the upper supports (51) and the lower supports (52) are both provided with rectangular reserved grooves.

3. A method for monitoring coal mine working face pressure based on self-sensing concrete as claimed in claim 2, characterized in that: In step 2, when installing the lower electrode detection device (4) on the special joint (5), the circular electrode mesh (3) is passed through the upper support (51) of the special joint (5) and is clamped in the rectangular reserved groove of the lower support (52), and the insulation detection line (2) is led out from the lower semicircular wire groove (54) of the special joint (5); when installing the upper electrode detection device (4) on the special joint (5), the circular electrode mesh (3) is clamped at the bottom of the rectangular reserved groove of the upper support (51) of the special joint (5), and the insulation detection line (2) is led out from the upper semicircular wire groove (53) of the special joint (5); The distance between the upper and lower electrode detection devices (4) is greater than or equal to 30 cm.

4. A method for monitoring coal mine working face pressure based on self-sensing concrete as claimed in claim 1, characterized in that: In step 1, the horizontal distance between the first detection borehole (1) and the working surface is 100m, the distance between two adjacent advanced stress detection boreholes (1) is 10-15m, the length of the advanced stress detection boreholes (1) is 1 / 4-1 / 2 of the width of the working surface, the diameter is 70mm, and the total number is 5.

5. A method for monitoring coal mine working face pressure based on self-sensing concrete as claimed in claim 4, characterized in that: In step 4, the self-sensing concrete (8) slurry is injected three times. The first injection should be such that the self-sensing concrete (8) slurry completely covers the special joint (5). After the first injection is completed and 5 minutes are waited, the grouting pipe (6) is pulled outward by 25 cm, and the second grouting is performed until the special joint (5) is again completely covered by the self-sensing concrete (8) slurry. After the second injection is completed and 5 minutes are waited, the grouting pipe (6) is pulled outward by 25 cm again, and the third grouting is performed until the special joint (5) is again completely covered by the self-sensing concrete (8) slurry.

6. A method for monitoring coal mine working face pressure based on self-sensing concrete as claimed in claim 1, characterized in that: The raw materials required for preparing the self-sensing concrete (8) slurry in step 4 include: 42.5R ordinary silicate cement, silica fume, polyacrylonitrile carbon fiber, water reducer, defoamer and dispersant; the water-cement ratio of the self-sensing concrete (8) slurry is 0.55, and the carbon fiber length is 4 mm; the amounts of carbon fiber, water reducer, silica fume, dispersant and defoamer are 0.5%, 1.5%, 15%, 0.7% and 0.08% of the cement mass, respectively; when preparing the self-sensing concrete (8) slurry, the carbon fiber is first placed in an aqueous solution of the water reducer, dispersant and defoamer, and then fully stirred by a mortar mixer, and finally the silica fume and cement are added in sequence and stirred for 2 minutes.

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