Method for testing and evaluating optimal depth of in-situ stress on-line sensor arrangement

Abstract

The application relates to a method for testing and evaluating the optimal arrangement depth of an online stress sensor for rock burst, which comprises the following steps: determining the detection drilling arrangement area according to the on-site equipment arrangement and construction conditions; arranging a coal body blasting hole group and a plurality of stress online sensor installation hole groups in the detection drilling arrangement area; charging, wiring and sealing the holes for each coal body blasting hole; implementing coal body blasting after effective testing of the stress online sensor data monitoring; monitoring the sensor change condition during each coal body blasting construction by the stress online sensor, including stress change value Delta sigma i and stress change time Delta t i ; determining the optimal arrangement position of the sensor and performing effect grade evaluation according to the change condition of the stress sensor arranged at different positions in the same stress online sensor installation hole during the implementation of the coal body blasting. The method can change the stress state of the roadway surrounding rock, evaluate the sensitivity of the sensor at different installation positions, obtain the optimal arrangement position of the sensor and improve the monitoring efficiency.

Description

Technical Field

[0001] This invention relates to a method for verifying and evaluating the optimal placement depth of online rockburst stress sensors, belonging to the field of coal mine safety mining technology. Background Technology

[0002] With the increasing intensity and depth of coal mining, the deterioration of the stress environment in resource storage has led to frequent rockbursts, severely restricting safe production in coal mines. Effective monitoring and early warning technologies have become crucial to effectively curb rockbursts. In recent years, rockburst monitoring and early warning have developed towards regionalization, continuity, and diversification, with various monitoring devices and methods such as microseismic, acoustic emission, and electromagnetic radiation emerging. For stress monitoring in rockburst-prone areas, the current methods mainly include the drill cuttings method and online stress monitoring. The drill cuttings method is primarily used for monitoring stress points within roadways, while online stress monitoring focuses on linear stress monitoring within the leading range of the two roadways in the working face.

[0003] Numerous online stress monitoring devices exist, and their deployment methods vary widely beyond relevant regulations. Many mines, especially those prone to rock bursts and other hazards, have installed online stress monitoring systems. However, due to differences in roadway mining and geological factors, the distribution characteristics of coal and rock stress differ. Therefore, the placement of downhole and deep boreholes for online stress monitoring should also vary depending on the coal pillar or the actual coal conditions at the working face. Consequently, the current use of the same deployment method for monitoring roadways with different conditions needs improvement.

[0004] Given the complex stress environment at the site, existing methods for altering the stress state of the surrounding rock mainly include coal blasting and large-diameter drilling. However, no corresponding detection and evaluation methods have been developed for the optimal installation location of online stress sensors, which prevents the online stress monitoring system from fully utilizing its monitoring capabilities. Summary of the Invention

[0005] This invention provides a method for verifying and evaluating the optimal placement depth of online stress sensors for rockburst. This method can change the stress state of the surrounding rock in the roadway and evaluate the sensitivity of online stress sensors at different installation positions, thereby determining the optimal placement position of the online stress sensors and improving monitoring efficiency.

[0006] To achieve the above objectives, the present invention provides a method for verifying and evaluating the optimal placement depth of online rock pressure stress sensors, comprising the following steps:

[0007] (1) Based on the on-site equipment layout and construction conditions, determine the area for the detection boreholes, that is, arrange stress online sensor installation boreholes and coal blasting boreholes perpendicular to the coal body on the side of the roadway solid coal at a distance a from the advance working face.

[0008] (2) Within the detection borehole layout area determined in step (1), coal body blasting hole groups and multiple stress online sensor installation hole groups are arranged along the roadway direction. Each coal body blasting hole group is equipped with multiple coal body blasting holes. The distance between each coal body blasting hole and the first stress online sensor installation hole that is closest to the roadway direction is not less than 5m. Each stress online sensor installation hole group is equipped with multiple stress online sensor installation holes. The spacing between adjacent stress online sensor installation holes is b. Multiple stress online sensors are installed in each stress online sensor installation hole. The horizontal distance between the location of each stress online sensor and the opening of the stress online sensor installation hole is not less than 8m.

[0009] (3) Load the explosives into each coal body blasting hole laid out in step (2), connect the wires, and seal the holes. At the same time, after effectively testing the data of the stress online sensor laid out in step (2), carry out coal body blasting. The blasting is carried out in the order from farthest to near the stress online sensor.

[0010] (4) Using the online stress sensor tested in step (3), monitor the changes in the online stress sensor during each coal blasting operation, including the stress change value Δσ. i and stress change time Δt i ;

[0011] (5) Based on the changes in stress sensors at different locations within the same online stress sensor mounting hole during coal blasting, the sensitivity of each sensor in monitoring stress changes is determined, thereby identifying the optimal placement of the online stress sensors and evaluating their effectiveness. This involves statistically analyzing the stress change values ​​Δσ at different locations within the same online stress sensor mounting hole during each coal blasting operation. i and stress change time Δt i The ratio of the stress change rate ε is used to obtain the stress change rate ε. i Its expression is: The unit is MPa / min; the optimal placement location is the online stress sensor with the highest stress change rate, and the evaluation criterion for the placement location of the online stress sensor is the stress change rate ε. i <0.01MPa / min、0.01MPa / min≤ε i ≤0.1MPa / min、0.1MPa / min≤ε i ≤1MPa / min, ε i >1MPa / min, corresponding to the location evaluation levels of poor, medium, good, and excellent, respectively.

[0012] Furthermore, in step (1), the distance a from the advanced working face is ≥200m; the area for the detection borehole layout is convenient for drilling construction and is not affected by factors such as conveyor belts and substation equipment.

[0013] Furthermore, in step (2), at least 5 coal blasting holes are arranged in the coal blasting hole group. The distances between each coal blasting hole and the first stress online sensor installation hole that is closest to the roadway direction are 90-100m, 40-50m, 20-30m, 8-10m, and 3-5m, respectively. The hole diameter is 70-80mm, the drilling depth is 13-15m, the distance from the roadway floor is 1-1.2m, the charge length is 2-3m, and the sealing length is 2-3m.

[0014] Each stress online sensor installation hole group shall have at least 3 stress online sensor installation holes, with a spacing b of 20-25m between adjacent stress online sensor installation holes, a hole depth of 25-30m, a distance of 1-1.2m from the roadway floor, and the same horizontal height as the coal blasting hole.

[0015] At least four identical stress sensors are installed in each stress sensor mounting hole. The horizontal distances between each stress sensor and the opening of its mounting hole are 8–10 m, 14–16 m, 20–22 m, and 25–27 m, respectively.

[0016] This invention determines a suitable area for detecting coal seams, facilitating construction and unaffected by equipment limitations. Within this area, multiple coal seam blasting holes and online stress sensor mounting holes are arranged, with multiple identical online stress sensors installed in each hole. The coal seam is blasted sequentially from far to near to alter the stress state. Simultaneously, the corresponding online stress sensors monitor the stress changes and response times before and after blasting. Based on the stress changes and response times monitored by different sensors, the stress change rate is calculated, determining the optimal sensor placement within the same hole for optimal sensitivity. This leads to the determination of the optimal sensor installation location, completing the inspection process. This invention enables the determination of the optimal placement of online stress sensors within the same mounting hole, achieving control over the stress state of the surrounding rock in the roadway and significantly improving the monitoring efficiency of the sensors. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the layout of coal blasting holes and stress online sensor installation holes in an embodiment of the present invention;

[0018] Figure 2 This is a stress change curve after blasting is carried out at a distance of 100m from the stress online sensor installation hole in the coal body in this embodiment of the invention;

[0019] Figure 3 This is a stress change curve after blasting is carried out at a distance of 50m from the stress online sensor installation hole in the coal body in an embodiment of the present invention;

[0020] Figure 4 This is a stress change curve after blasting is carried out at a distance of 30m from the stress online sensor installation hole in the coal body in an embodiment of the present invention;

[0021] Figure 5 This is a stress change curve after blasting is carried out at a distance of 10m from the stress online sensor installation hole in the coal body in an embodiment of the present invention;

[0022] Figure 6 This is a stress change curve after blasting is performed at a distance of 5m from the stress online sensor installation hole in the coal body, as described in this embodiment of the invention. Detailed Implementation

[0023] The invention will now be further described with reference to the accompanying drawings.

[0024] A method for verifying and evaluating the optimal placement depth of online rock pressure stress sensors includes the following steps:

[0025] (1) Based on the on-site equipment layout and construction conditions, determine the area for the detection boreholes, that is, arrange stress online sensor installation boreholes and coal blasting boreholes perpendicular to the coal body on the side of the roadway solid coal at a distance a from the advance working face.

[0026] (2) Within the detection borehole layout area determined in step (1), coal body blasting hole groups and multiple stress online sensor installation hole groups are arranged along the roadway direction. Each coal body blasting hole group is equipped with multiple coal body blasting holes. The distance between each coal body blasting hole and the first stress online sensor installation hole that is closest to the roadway direction is not less than 5m. Each stress online sensor installation hole group is equipped with multiple stress online sensor installation holes. The spacing between adjacent stress online sensor installation holes is b. Multiple stress online sensors are installed in each stress online sensor installation hole. The horizontal distance between the location of each stress online sensor and the opening of the stress online sensor installation hole is not less than 8m.

[0027] (3) Load the explosives into each coal body blasting hole laid out in step (2), connect the wires, and seal the holes. At the same time, after effectively testing the data of the stress online sensor laid out in step (2), carry out coal body blasting. The blasting is carried out in the order from farthest to near the stress online sensor.

[0028] (4) Use the online stress sensor tested in step (3) to monitor the sensor changes during each coal blasting operation, including the stress change value Δσ. i and stress change time Δt i ;

[0029] (5) Based on the changes in stress sensors at different locations within the same online stress sensor mounting hole during coal blasting, the sensitivity of each sensor in monitoring stress changes is determined, thereby identifying the optimal sensor placement location and evaluating the effectiveness. Specifically, the stress change value Δσ of the online stress sensor at different locations within the same online stress sensor mounting hole is statistically analyzed during each coal blasting operation. i and stress change time Δt i The ratio of the stress change rate ε is used to obtain the stress change rate ε. i Its expression is: The unit is MPa / min; the optimal placement position is the sensor location with the highest stress change rate, and the evaluation criterion for the sensor placement position is the stress change rate ε. i <0.01MPa / min、0.01MPa / min≤ε i ≤0.1MPa / min、0.1MPa / min≤ε i ≤1MPa / min, ε i >1MPa / min, corresponding to the location evaluation levels of poor, medium, good, and excellent, respectively.

[0030] In a preferred embodiment, the distance a from the working face in step (1) is ≥200m; the area for the detection borehole layout is convenient for drilling construction and is not affected by factors such as conveyor belts and substation equipment.

[0031] In a preferred embodiment, in step (2), at least 5 coal blasting holes are arranged in the coal blasting hole group. The distances between each coal blasting hole and the first stress online sensor installation hole that is closest to the roadway direction are 90-100m, 40-50m, 20-30m, 8-10m, and 3-5m, respectively. The hole diameter is 70-80mm, the drilling depth is 13-15m, the distance from the roadway floor is 1-1.2m, the charge length is 2-3m, and the sealing length is 2-3m.

[0032] Each stress online sensor installation hole group shall have at least 3 stress online sensor installation holes, with a spacing b of 20-25m between adjacent stress online sensor installation holes, a hole depth of 25-30m, a distance of 1-1.2m from the roadway floor, and the same horizontal height as the coal blasting hole.

[0033] At least four identical stress sensors are installed in each stress sensor mounting hole. The horizontal distances between each stress sensor and the opening of its mounting hole are 8–10 m, 14–16 m, 20–22 m, and 25–27 m, respectively.

[0034] Example:

[0035] This implementation case focuses on the optimal arrangement of online stress sensors at the 3308 working face of a certain mine. The mine has already installed a microseismic monitoring system that can effectively surround the 3308 working face area and has high accuracy in monitoring microseismic events within the area.

[0036] (1) As Figure 1 As shown, the optimal placement of online stress sensors was detected within a range of 200-360m ahead of the return air roadway of the 3308 working face. This area is free from interference from other equipment and is convenient for construction.

[0037] (2) Within the defined borehole detection area, coal blasting hole groups and multiple stress online sensor installation hole groups are set up along the roadway direction. Each coal blasting hole group has at least 5 coal blasting holes, and the distances to the nearest stress online sensor installation hole along the roadway direction are 100m, 50m, 30m, 10m, and 5m, respectively. Each stress online sensor installation hole group has 3 stress online sensor installation holes, with a spacing of 20m between adjacent installation holes. Each stress online sensor installation hole has 4 stress online sensors, and the horizontal distances between the location of each stress online sensor and the opening of the stress online sensor installation hole are 8m, 16m, 20m, and 25m, respectively.

[0038] The coal blasting holes are 75mm in diameter, 13m deep, with a charge length of 2m and a sealing length of 2m, connected in series within the forward-charging holes. After the online stress sensors are deployed and the monitoring data is verified, the coal blasting is carried out, proceeding from the furthest point from the online stress sensors. Figures 2 to 6 As shown;

[0039] (3) Monitor the changes in the stress during each coal blasting operation using the installed and tested online stress sensors, including the stress change value Δσ. i and stress change time Δt i Then, the rate of stress change can be obtained. The unit is MPa / min; the evaluation criterion for the sensor placement is the stress change rate ε. i <0.05MPa / min、0.05MPa / min≤ε i <0.1MPa / min, 0.1MPa / min≤ε i <0.5MPa / min, ε i ≥0.5MPa / min, corresponding to location evaluation levels of poor, medium, good, and excellent respectively. The optimal installation location was ultimately determined to be 16m, as shown in Table 1.

[0040] Table 1. Coal Body Blasting Monitoring and Evaluation Table

[0041]

Claims

1. A method for verifying and evaluating the optimal placement depth of online rockburst stress sensors, characterized in that, Includes the following steps: (1) Based on the on-site equipment layout and construction conditions, determine the area for the detection boreholes, that is, arrange stress online sensor installation boreholes and coal blasting boreholes perpendicular to the coal body on the side of the roadway solid coal at a distance a from the advance working face. (2) Within the detection borehole layout area determined in step (1), coal blasting hole groups and multiple stress online sensor installation hole groups are arranged along the roadway direction. Multiple coal blasting holes are arranged in each coal blasting hole group. The distance between each coal blasting hole and the first stress online sensor installation hole closest to the roadway direction is not less than 5m. Multiple stress online sensor installation holes are arranged in each stress online sensor installation hole group. The spacing between adjacent stress online sensor installation holes is b. Multiple stress online sensors are arranged in each stress online sensor installation hole. The horizontal distance between the location of each stress online sensor and the opening of the stress online sensor installation hole is not less than 8m. (3) Load the explosives into each coal body blasting hole laid out in step (2), connect the wires, and seal the holes. At the same time, after effectively testing the data of the stress online sensor laid out in step (2), carry out coal body blasting. The blasting is carried out in the order from farthest to closest to the stress online sensor. (4) Use the online stress sensor tested in step (3) to monitor the changes in the online stress sensor during each coal blasting operation, including the stress change value. and stress change time ; (5) Based on the changes in stress sensors at different positions within the same stress online sensor mounting hole during coal blasting, the sensitivity of each stress online sensor in monitoring stress changes is determined, thereby determining the optimal placement of the stress online sensors and evaluating the effectiveness level. That is, the stress change values ​​of stress online sensors at different positions within the same stress online sensor mounting hole are statistically analyzed during each coal blasting operation. and stress change time The ratio of the stress changes is used to determine the rate of stress change. Its expression is: The unit is MPa / min; the optimal placement location is the sensor with the highest stress change rate, and the evaluation criterion for the placement of online stress sensors is the stress change rate. 0.05MPa / min≤ <0.1MPa / min, 0.1MPa / min≤ <0.5MPa / min ≥0.5MPa / min corresponds to the evaluation levels of poor, medium, good, and excellent at the location, respectively.

2. The method for verifying and evaluating the optimal placement depth of online rockburst stress sensors according to claim 1, characterized in that, In step (1), the distance a from the advanced working face is ≥200m; the area for the detection borehole layout is convenient for drilling construction and is not affected by factors such as conveyor belts and substation equipment.

3. The method for verifying and evaluating the optimal placement depth of online rockburst stress sensors according to claim 1, characterized in that, In step (2), at least 5 coal blasting holes are arranged in the coal blasting hole group. The distances between each coal blasting hole and the first stress online sensor installation hole that is closest to the roadway direction are 90~100m, 40~50m, 20~30m, 8~10m, and 3~5m, respectively. The hole diameter is 70~80mm, the drilling depth is 13~15m, the distance from the roadway floor is 1~1.2m, the charge length is 2~3m, and the sealing length is 2~3m. Each stress online sensor installation hole group shall be equipped with at least 3 stress online sensor installation holes, with a spacing b of 20~25m between adjacent stress online sensor installation holes, a hole depth of 25~30m, a distance of 1~1.2m from the roadway floor, and the same horizontal height as the coal body blasting hole; At least four identical stress sensors are installed in each stress sensor mounting hole. The horizontal distances between each stress sensor and the opening of its mounting hole are 8~10m, 14~16m, 20~22m, and 25~27m, respectively.

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