Early warning evaluation method for rock burst / rockburst hazard based on temperature gradient

Abstract

The present invention provides a method for early warning and evaluation of rock burst hazard based on temperature gradient. The innovation lies in that by accurately capturing the subtle changes in the temperature field gradient before and during the impact of the mining stress field, the temperature gradient value within the entire length of the borehole and the temperature change rate at a specific position of the borehole are used as impact tendency evaluation indicators, and quantitative qualitative and early warning analysis are carried out accordingly, and four levels of no, weak, medium and strong impact are divided for accurate hazard resolution. Temperature sensors are continuously arranged for monitoring from the borehole surface to the peak area of ​​mining stress, that is, within the range of original rock stress above the elastic zone. The monitoring range covers the entire time period from the formation of deep mining space to the end of mining, especially the initial and periodic pressure periods of the deep mine working face, the period when the working face is squared, and special periods such as across areas with complex geological structures. The method has high sensitivity and strong timeliness, and can accurately predict and forecast the rock burst hazard and its intensity level.

Description

Technical Field

[0001] The invention relates to the technical field of deep coal mine safety and tunnel rock engineering monitoring, and in particular to a method for early warning and evaluation of rock burst danger based on temperature gradient. Background Art

[0002] With the continuous expansion of underground space development, underground space projects continue to extend to deeper areas, and mine impact / tunnel rock burst has become one of the main disasters restricting the development of deep space. Rock burst / rock burst refers to the dynamic phenomenon characterized by violent vibration and explosive destruction caused by the release of large energy when the coal rock mass loses stability and is damaged by external disturbances. In the field of deep mining, rock burst / rock burst will not only affect normal safe and efficient production, but also cause heavy casualties and huge economic losses.

[0003] At present, the main technologies in the field of early warning and evaluation of rock burst / rock burst in my country include microseismic source location monitoring technology, CT inversion monitoring technology, electromagnetic radiation monitoring technology, borehole stress gauge monitoring technology, and drill cuttings monitoring technology. These technologies still have many shortcomings, such as low sensitivity and high cost of online stress monitoring and real-time monitoring system; elastic wave CT inversion technology cannot achieve real-time early warning; microseismic method, acoustic emission technology, and electromagnetic radiation technology have large errors and low accuracy. At present, there are also related technologies for predicting rock burst danger based on temperature change indicators, such as:

[0004] Chinese patent CN104763470A discloses a mine-use multi-indicator intelligent early warning rock burst system, which sequentially determines whether the drill rod torque value, drill cutting thrust value, drill cutting temperature value and drill cutting weight value are greater than their respective early warning values. If they are greater than the early warning value, a direct early warning is issued, otherwise the next indicator is judged. It is undeniable that this step-by-step early warning method can improve the accuracy of the early warning, but this method requires a complex early warning system support, which is obviously unrealistic for the narrow operating space underground in coal mines. In particular, it involves many mechanical structures, such as drilling devices, which generate mechanical vibrations when in use, affecting the accuracy of collected data; this method monitors the temperature of the drilling cuttings at a certain moment in the process, and monitors the temperature change rate of the equipment caused by friction, etc., rather than monitoring the temperature change of the inherent coal rock mass itself; at the same time, the monitoring position changes all the time, and the temperature change rate of a fixed position cannot be continuously observed, and the drilling direction lacks continuity; in addition, when it warns based on the drill cuttings temperature change index of the drill cuttings method, it uses sensors to monitor the temperature change rate near the drill bit. Due to environmental factors such as the heat generated by the drilling rig, the temperature change monitoring has a great influence, which is prone to false alarms, resulting in the drill cuttings temperature index failing to meet the precise requirements of impact ground pressure monitoring; whether the drill cuttings hole depth reaches the energy accumulation zone of the impact source, and the time difference of the drilling cuttings process also has a great influence on the impact prediction.

[0005] Chinese patent publication number CN105158813A discloses a method for monitoring the surface temperature signal of coal body based on a hot red probe, which can reflect the temperature change of coal body to a certain extent, and uses the temperature change rate of rock surface as an early warning indicator to monitor the surface temperature of the excavation free surface. The temperature change rate of the excavation free surface reflects the significant temperature change of a certain free area. It is difficult to provide temperature monitoring data for deep areas where impact / rock burst occurs, and it is impossible to determine the depth of the free surface. When the surface temperature of the free surface far away from the impact source is used as the early warning value, the environmental impact is extremely large, and it is impossible to distinguish the temperature impact of environmental factors and engineering heat source factors, making it difficult to effectively predict the impact danger situation. Because the rock interior involves the burial depth of the rock, how deep it needs to be monitored, how deep the sensor is installed, and how to choose the installation angle are all a series of problems.

[0006] Chinese patent publication number CN111551624A discloses a hydrogen bond fracture prediction coal rock rock burst device and its prediction method, which is an impact warning method using a voltage signal and temperature signal acquisition module, and judges the degree of crushing of coal rocks at different depths by monitoring the temperature change rate of the inner wall of the borehole and the transient voltage value when the inner wall breaks, and uses the degree of crushing of the coal rocks as a warning value to judge the danger of rock burst. This technology provides a new idea for judging rock burst, but because the temperature change rate of different areas of the inner wall of the borehole and the transient voltage value when it breaks are greatly affected by the depth of the monitoring hole, under the premise that the depth and position of the monitoring hole are not quantitatively determined, the monitoring position is not fixed, and the monitoring process is transient, that is, it is impossible to monitor at a fixed point for a long time. How deep the monitoring needs to be and how long the structure is installed in the deep part are all problems to be solved. The technicians can only select the depth of the monitoring hole manually based on experience, and the warning results obtained are more dependent on the empirical method, and the temperature changes in the impact area cannot be truly captured.

[0007] Chinese patent publication number CN207395935U discloses an online monitoring system for rock burst based on fiber optic Bragg grating sensing technology, which belongs to the fiber optic sensor rock burst warning method, and realizes the danger prediction of the rock burst area by monitoring the temperature change rate of anchor bolts and cables at specific positions. The fiber optic Bragg grating sensor is first fixed on the anchor bolt cable, and then implanted into the borehole together with the anchor bolt cable and fixed with mortar. Due to the heat conduction of the sensor carrier itself, the monitored temperature value dissipates greatly. The method mainly monitors the temperature change rate of a specific area in the borehole rather than the entire borehole, and monitors whether the depth of the hole meets the requirements for capturing the rock burst / rock burst temperature signal, and whether the monitoring position of the anchor bolt cable reaches the area where the energy source that induces the rock burst is located. This method has the possibility of missed monitoring or repeated monitoring, and the monitoring has a certain degree of blindness. The continuity, effectiveness and accuracy of the monitoring need to be improved.

[0008] The prior art discloses many rock burst warning methods. The cuttings temperature method analyzes the drilling temperature and drilling volume, the infrared probe free surface monitoring method considers the temperature change rate as the main monitoring factor, the hydrogen bond rupture law combines the temperature change rate with the breaking stress, and the grating anchor monitoring law monitors specific areas with sensors of different spacing. These monitoring and warning methods consider the change of temperature values, but do not provide a clear method for the borehole length that affects the monitoring effect. There is little research on the early warning evaluation of rock burst danger based on the temperature gradient in the borehole length direction and the temperature change rate in the stress peak area. The geological conditions of deep mines are complex and changeable. The occurrence of rock burst is characterized by suddenness and huge destructiveness. It involves the intersection of multiple disciplines such as geology, rock mechanics and nonlinear dynamics, making it difficult to predict rock burst. How to improve the monitoring accuracy and how to determine the location, time and intensity of occurrence are currently urgent research focuses for rock burst warning evaluation. Summary of the invention

[0009] In view of the shortcomings of the above-mentioned technologies in using temperature to warn of rock burst, the present invention provides a rock burst / rock burst hazard warning evaluation method based on temperature gradient.

[0010] To achieve the above-mentioned purpose, the temperature gradient-based rock burst hazard early warning evaluation method provided by the present invention is innovative in that it accurately captures the subtle changes in the temperature field gradient before and during the impact of the mining stress field, and uses the temperature gradient value within the entire length of the borehole and the temperature change rate at a specific position of the borehole as impact tendency evaluation indicators, and conducts quantitative qualitative and early warning analysis accordingly, and divides the four levels of no, weak, medium, and strong impact to accurately resolve the hazard; temperature sensors are continuously arranged for monitoring from the borehole surface to the peak area of ​​mining stress, that is, within the range of original rock stress above the elastic zone, and the monitoring range covers the entire time period from the formation of deep mining space to the end of mining, especially the initial and periodic pressure periods of the deep mine working face, the period when the working face is squared, and special periods such as across complex geological structures. It has high sensitivity and strong timeliness, and can accurately predict and forecast the rock burst hazard and its intensity level.

[0011] A method for early warning and evaluation of rock burst hazard based on temperature gradient, characterized by following the steps:

[0012] Step 1: Preliminary assessment of the risk level of rock burst / rockburst in the area to be monitored

[0013] Evaluate the impact area / rock burst in the monitored area, determine the dangerous area and its danger level in the monitored area according to the evaluation results, and divide the monitored area into no impact danger area, weak impact danger area, medium impact danger area, and strong impact danger area;

[0014] Step 2: Obtain the temperature change rate E of the test block when the rock in the monitored area is damaged

[0015] Take coal and rock samples in the area to be monitored, conduct impact damage test on the coal sample blocks, and record the temperature change rate E when the test blocks are damaged. 阀 , thus serving as the warning threshold;

[0016] Step 3: Arrange temperature sensors in the area to be monitored

[0017] First, mining stress monitoring sensors are arranged in the monitored area in advance to monitor the changing law of mining stress field, so as to determine the high stress area of ​​coal seam or rock formation and the original rock stress range above the elastic area; the arrangement scheme of borehole spacing, row spacing and temperature sensors is designed in the high stress area of ​​coal seam or rock formation and the original rock stress range above the elastic area, requiring the temperature sensors to be arranged continuously from the surface of the borehole to the stress peak area, and the maximum monitoring depth of the temperature sensor should be located in the original rock stress range above the elastic area on the side of the elastic area of ​​the coal seam or rock formation; the arrangement spacing and row spacing of the temperature sensors are designed according to the principle that the higher the danger level, the more sensor groups should be arranged, and the installation position parameters of each temperature sensor (including at least the installation angle and the relationship between the burial depth of the layer, etc.) are recorded, and the management is carried out by listing;

[0018] Further: The arrangement of drilling holes, row spacing and temperature sensors follows the following principles:

[0019] The higher the danger level, the more sensor groups should be arranged. Generally, the borehole spacing in the strong impact danger area is 5m, the borehole spacing in the medium impact danger area is 10m, and the borehole spacing in the weak impact area is 20m. The borehole spacing is 1.5m. In each borehole, a group of sensors is arranged at intervals of 0.2 to 0.5m along the depth.

[0020] In order to ensure the accuracy of the sensor, the temperature sensor is arranged in a protective tube. The specific structure is: a hole is opened on the wall of a protective tube made of non-heat-conducting material, the sensor is placed in the protective tube, the sensor base is stuck on the tube wall, the sensor temperature sensing probe is exposed from the opening and sealed, so that the sensor is fixed in the protective tube, and different groups of temperature sensors are installed in each protective sleeve according to actual conditions.

[0021] Furthermore, in order to facilitate underground installation, the protection pipe is formed by screwing multiple protection pipes together through threads.

[0022] Step 4: Use temperature gradient to preliminarily predict the area where the impact source is located

[0023] 4.1: Collect the temperature of each temperature sensor in real time, and determine the temperature gradient of adjacent sensors at different times based on the temperature difference ΔT and the distance ΔL of adjacent temperature sensors;

[0024]

[0025] Where: M represents the temperature gradient value, in units of ℃ / m; ΔT represents the monitoring temperature change corresponding to the temperature sensor, in units of ℃; ΔL represents the distance between adjacent monitoring sensors, in units of m;

[0026] 4.2: Obtain the temperature gradient warning surface within the drilling length range

[0027] With time as the horizontal axis X-axis, drilling depth as the horizontal axis Y-axis, and the temperature monitoring value corresponding to the temperature sensor as the vertical axis Z-axis, the temperature gradient surface of the area to be monitored at different times is drawn; that is, each adjacent sensor corresponds to a temperature gradient surface over time;

[0028] 4.3: Get the temperature change rate curve at a specific location as a warning curve

[0029] The temperature value monitored by the temperature sensor at a specific position is collected regularly, and then the data is analyzed to obtain the temperature change rate curve of the temperature sensor at the specific position;

[0030] The specific position temperature refers to the area extending from the peak position of the mining stress field to the plastic zone and elastic zone on both sides to the original rock stress position;

[0031] 4.4: Preliminary prediction of energy concentration areas based on temperature gradient and temperature change rate

[0032] During operation, compare the temperature gradient surfaces of all boreholes and combine with the temperature change rate of the temperature sensor at a specific location to find the surfaces and curves where the temperature gradient and temperature change rate change significantly. When the temperature gradient and temperature change rate are large, the corresponding position range is the energy concentration area, and the time range of significant temperature gradient changes corresponds to the process from the beginning to the occurrence of impact damage.

[0033] Step 5: Use the temperature change rate to find the temperature sensor closest to the energy concentration area, and accurately determine the specific location of the energy concentration area based on the installation location parameters of the temperature sensor (including installation angle, layer depth relationship, etc.)

[0034] 5.1: Using the temperature data monitored by the temperature sensor in step 4.3, draw a temperature change rate curve of the temperature sensor in the energy concentration area;

[0035] 5.2: Eliminate invalid temperature change rate curves to eliminate the error value of ambient temperature. During operation, the temperature change rate E obtained in the second step 阀As a threshold value for determining the temperature change rate of the coal seam; then compare the slope of each temperature change rate curve in step 5.1 with the threshold value, when the slope of a certain temperature change rate curve is greater than a certain coefficient of the threshold value, the temperature change rate curve is an invalid temperature change rate curve, otherwise it is a valid temperature change rate curve;

[0036] 5.3: Compare the slopes of all effective temperature change rate curves. The larger the slope of the curve, the greater the temperature change rate and the closer the distance to the energy concentration area. Based on this principle, find the temperature sensor number corresponding to the temperature change rate curve with the largest slope, find its position parameter according to the temperature sensor number, and use the position parameter of the temperature sensor to deduce a more specific location of the energy concentration area;

[0037] Step 6: Determine the danger level of the energy concentration area

[0038] 6.1: According to the more specific location of the impact energy accumulation obtained in step 5.3, and combined with the time range of the area where the temperature gradient changes significantly, the impact damage process is determined, and the monitoring value M corresponding to the temperature gradient surface with significant changes and the monitoring value E corresponding to the temperature change rate curve are calculated, and the temperature gradient warning lower limit value for weak impact is set in advance as M1, and the temperature change rate warning lower limit value is set as E1; the temperature gradient warning lower limit value for medium impact is set as M2, and the temperature change rate warning lower limit value is set as E2; the temperature gradient warning lower limit value for strong impact is set as M3, and the temperature change rate warning lower limit value is set as E3;

[0039] 6.2: Compare the temperature gradient monitoring value M of the energy concentration area with the pre-set temperature gradient warning lower limit M1 of weak impact, and compare the temperature change rate monitoring value E of significant change with the temperature change rate warning lower limit E1 to determine whether the temperature gradient is greater than M1 and whether the temperature change rate is greater than E1; if not, it is determined that there is no impact and no alarm is needed; if so, the alarm is triggered to sound an alarm, and further perform the impact rock pressure hazard level warning determination;

[0040] (1) If M1≤M<M2, E1≤E<E2, it is judged as a weak impact, the display screen flashes green, and a weak impact green warning is issued;

[0041] (2) If M2≤M<M3, E2≤E<E3, it is judged as a medium impact, the display screen flashes yellow, and a medium impact yellow warning is issued;

[0042] (3) If M>M3, E>E3, it is judged as a strong impact, the display screen flashes red, and a strong impact red warning is issued;

[0043] Step 7: Specify measures to prevent and control rock bursts and impact ground pressure according to the specific location and hazard level of the energy concentration area.

[0044] Matters needing attention during the implementation of the present invention:

[0045] (1) The protection tube is preferably made of materials that are corrosion-resistant and have poor heat transfer properties. In order to adapt to the complex and changeable geological environment on site, the protection tube adopts a multi-tube splicing method to meet the needs of monitoring length;

[0046] (2) On-site drilling operation: The drilling operation is carried out in an area with a flat wall, no broken parts, and a safe and intact roof. For coal mine monitoring, the drilling holes are arranged in the coal seam; for tunnel construction areas, the drilling holes are arranged in the rock stratum, and the drilling holes must be arranged along the direction of the rock stratum. A drill bit with a diameter of Φ32mm is used for drilling on site. The hole axis is vertically tilted upward by 5°. The hole depth is determined according to the high stress area of ​​the coal seam or rock stratum and the position of the original rock stress range above the elastic area. The drilling depth should slightly exceed the original rock stress area of ​​the stress peak area.

[0047] (3) When the thickness of the coal seam or rock formation in the monitoring area is less than 3.0m, the monitoring boreholes should be arranged in the middle of the coal seam or rock formation; when the thickness of the coal seam or rock formation is greater than 3.0m, the number of rows of borehole monitoring should be set according to the specific thickness, starting from the bottom plate, the first row of boreholes should be arranged 1.5m away from the bottom plate of the coal seam or rock formation, and then arranged upwards in sequence, with an interval of 1.5m, until it is within 1.5m above the top plate;

[0048] (4) After the temperature monitoring hole is drilled, the excess dust inside the hole needs to be cleaned with an air gun, and the observation point should be marked with spray paint in time;

[0049] (5) When installing the first temperature sensor protection tube, the end of the first temperature sensor protection tube needs to be sealed. Use a sealing nut to seal the end. Apply high-viscosity vaseline on the sealing surface to prevent water and reduce friction between nuts to avoid thread corrosion and deformation. High-viscosity vaseline is also used on other interfaces.

[0050] (6) In order to avoid the impact of on-site construction on the installation of the temperature sensor protection tube, the exposed length of the on-site installation is required to be no more than 5 cm;

[0051] (7) In order to isolate the heat source released artificially inside the chamber and minimize the impact of the external environment on the temperature field inside the coal rock mass, it is necessary to use yellow mud to seal the hole. The sealing depth extends at least 20 cm from the surface of the surrounding rock into the hole, and the sealing hole also plays the role of fixing the protective pipe;

[0052] (8) After the temperature sensor protection tube is installed, it needs to be marked in time, and all temperature sensors in the area need to be installed, and then connected uniformly, powered on and debugged. The power supply adopts an intrinsically safe structure, which can operate reliably in flammable and explosive environments, and can provide real-time protection for online monitoring of mine rock burst pressure.

[0053] The beneficial effects of the present invention are:

[0054] The present invention is based on a temperature gradient rock burst / rock burst hazard early warning evaluation method. This method uses a temperature sensor to accurately capture the subtle changes in the temperature field gradient before and during the impact of the mining stress field. The temperature gradient value within the entire length of the borehole and the temperature change rate at a specific position of the borehole are used as impact tendency evaluation indicators at the same time. Quantitative qualitative and early warning analysis are performed accordingly, and the four levels of no, weak, medium, and strong impact are divided and accurately eliminated. The temperature sensor is continuously arranged for monitoring from the borehole surface to the original rock stress range above the elastic zone. The temperature sensor is used to monitor the temperature field gradient changes in high stress areas, especially the initial and periodic pressure areas of the deep mine working face, the square area of ​​the working face, and the area with complex geological structures. The monitoring can cover the entire time period from the formation of the deep mining space to the end of mining, which greatly improves the accuracy of the prediction of coal and rock dynamic disasters in front of the mining working face, and provides a technical basis for the integration of multiple indicators of coal and rock dynamic disasters. The device involved in the method has a simple structure and is easy to install. The system is practical and easy to use, has good shielding effect and good stability, does not have measurement loss, and is highly practical and economical. Combined with the ground smart mine system, it does not require human intervention and has the ability to automatically analyze and distinguish. Since the temperature measuring component is fixed inside the coal body, it can effectively avoid operating errors and improve test accuracy. The coal and rock temperature measuring component is small in size and easy to operate, and is suitable for areas with impact hazards / rock bursts. It provides a new impact hazard early warning and evaluation method. External interference has little effect on the temperature measuring component deep in the coal body, and has no effect on underground coal mine production. It can warn of dynamic disasters such as mine impacts and tunnel rock bursts and make grade evaluations.

[0055] The temperature gradient-based rock burst / rock burst hazard early warning and evaluation method provided by the present invention monitors the temperature gradient signal changes in the high stress area of ​​the mining stress field based on the temperature sensor, and performs graded and quantitative judgment on the temperature gradient value within the entire length of the borehole and the temperature change rate at a specific position of the borehole. The method adjusts the monitoring area according to the location of the peak mining stress area of ​​the deep mine working face and the change in the thickness of the coal seam strike. The monitoring covers the entire time period from the formation of the deep mining space to the end of mining, especially the initial and periodic pressure periods of the deep mine working face, the period when the working face is squared, and special periods such as across complex geological structures. The early warning and evaluation method quantifies the impact tendency index, and can accurately predict and forecast the risk of coal mine rock burst / rock burst and its intensity level, providing a basis for early warning and evaluation of deep mine impact and tunnel rock burst.

[0056] The present invention firstly uses mining stress monitoring sensors to determine the high stress area of ​​the coal seam or rock formation and the original rock stress range higher than the elastic area. The maximum monitoring depth of the temperature sensor should be located at the position of the original rock stress higher than the elastic area on the side of the elastic area of ​​the coal seam or rock formation; the temperature gradients of all boreholes are compared and combined with the temperature change rate of the stress peak area to find out the position where the temperature gradient and the temperature change rate change significantly. When the temperature gradient and the temperature change rate are large, the corresponding position range is the energy concentration position. The time range in which the temperature gradient changes significantly corresponds to the process from the beginning to the occurrence of impact damage, that is, the range of the energy concentration area and the impact occurrence time are determined; finally, the average temperature gradient of the energy concentration area and the average temperature change rate of the fixed position are used to predict and evaluate the occurrence intensity of rock burst. With the specific position of the energy concentration area and the occurrence intensity of rock burst, more accurate prevention and control measures can be prepared. This step-by-step warning logic method is more in line with the actual situation on site. In addition, the whole process does not require complex systems and mechanical equipment, which is not only simple and easy but also has high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are 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.

[0058] Figure 1 It is a monitoring system diagram of the rock burst hazard early warning evaluation method based on temperature gradient;

[0059] Figure 2 A schematic diagram of the on-site arrangement of an embodiment of the present invention;

[0060] Figure 3 This is a schematic diagram of capturing the temperature field gradient in the high stress area of ​​the present invention;

[0061] Figure 4 Based on Figure 3 Schematic diagram of the evolution characteristic curve of monitoring time and temperature value;

[0062] Figure 5 It is a schematic diagram of the temperature sensor structure;

[0063] Figure 6 Based on Figure 5 Schematic diagram of connection of two single protection pipes;

[0064] Figure 7 This is the overall framework diagram of the rock burst hazard early warning evaluation method based on temperature gradient.

[0065] In the figure: 1-temperature sensor; 2-transmission line; 3-protection tube; 4-protection tube housing; 5-temperature sensor probe; 6-temperature sensor base; 7-end external thread; 8-internal thread pipe stud nut. DETAILED DESCRIPTION

[0066] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings and embodiments, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the invention.

[0067] The rock burst / rockburst hazard early warning evaluation method of the present invention mainly monitors areas including: deep rock engineering, such as the initial and periodic rock burst areas of the mine working face, square areas of the working face, areas with complex geological structures, etc. The monitoring covers the entire time period from the formation of the deep mining space to the end of mining. These are areas prone to rock burst and monitoring must be strengthened. The method of early warning of rock burst in these areas using the method of the present invention is described in detail below.

[0068] like Figure 7 As shown, the rock burst / rockburst hazard early warning evaluation method of the present invention is.

[0069] Step 1: Preliminary assessment of the danger level of rock burst in the area to be monitored

[0070] The dangerous areas are divided according to the existing impact area evaluation method, and the danger level of the impact ground pressure in the monitored area is evaluated, so that the monitored area is divided into no impact danger area, weak impact danger area, medium impact danger area, and strong impact danger area.

[0071] Step 2: Obtain the temperature change rate E of the test block when the rock in the monitored area is damaged

[0072] According to the national standard "GBT 23561.1-2009 Method for Determination of Physical and Mechanical Properties of Coal and Rock", coal and rock samples were collected in the monitored area, processed into coal sample blocks in the laboratory, and the test blocks were cured for 28 days according to the predetermined temperature and humidity. The block size was required to be 100mm×100mm×100mm, and the surface of the block was complete and smooth. The rock testing machine was used to conduct impact damage simulation experiments, and the thermal radiation camera was used to monitor the thermal radiation of the test block throughout the process, recording the temperature change rate E when the test block was damaged, so as to find the precursor law of temperature change of the test block during the impact damage process.

[0073] Step 3: Drill holes and arrange temperature sensors according to the danger level of the area to be monitored

[0074] First, mining stress monitoring sensors are arranged in the monitored area in advance to monitor the change law of mining stress field, so as to determine the high stress area of ​​coal seam or rock layer and the original rock stress range higher than the elastic area; Figure 3 As shown in the figure, the temperature sensor layout scheme is designed according to the high stress area of ​​the coal seam or rock formation and the original rock stress range above the elastic area. The temperature sensors are required to be arranged continuously from the borehole surface to the stress peak area; the key nodes selected include the tunnel wall 0, the original rock stress point A, the stress peak value B, and the original rock stress starting point C. At the same time, other key nodes are further subdivided, including the surrounding rock depth L corresponding to the OA curve A , the surrounding rock depth L corresponding to the stress score in the AC curve B , the surrounding rock depth L corresponding to the original rock stress point in the BC curve C The maximum depth of the temperature tube sensor protection tube 3 should be located on the elastic area side of the coal seam or rock formation and higher than the original rock stress range of the elastic area.

[0075] refer to Figure 2 On-site drilling operations: Select areas with flat walls, no broken parts, and intact and safe roofs for drilling construction. For coal mine monitoring, the boreholes are arranged in the coal seam; for tunnel construction areas, the boreholes are arranged in the rock stratum, and the boreholes must be arranged along the direction of the rock stratum. A Φ32mm diameter drill bit is used for drilling on site. The axis of the hole is vertically tilted up 5°. The hole depth is determined based on the high stress area of ​​the coal seam or rock stratum and the position above the original rock stress range. The drilling depth should slightly exceed the original rock stress area in the stress peak area. After the temperature monitoring hole is drilled, an air gun needs to be used to clean up excess dust inside the hole, and the hole should be sprayed with paint in time for sign management. The spacing between drilling holes, row spacing, and the spacing of temperature sensors should follow the following principles:

[0076] Drill holes and arrange sensors according to the danger level. Generally, the spacing between holes in high impact danger areas is 5m, the spacing between holes in medium impact danger areas is 10m, and the spacing between holes in weak impact areas is 20m. The spacing between holes is 1.5m. In each borehole, a group of sensors is arranged at intervals of 0.2 to 0.5m along the depth.

[0077] Then, the temperature sensor 1 is arranged in the monitoring hole, and the installation position parameters of each temperature sensor (including installation angle, layer depth relationship, etc.) are recorded and managed by the signboard; the temperature affects the signal change of the temperature sensor 1, which is decoded by the decoder, and the photoelectric signal is converted into current change. The temperature gradient signal data is incorporated into the underground sub-base station through the signal line, and then the underground sub-base station signal is uploaded to the underground main transmission signal cable through the ring network switch, and connected to the ground main control server database, see Figure 1 .

[0078] In order to ensure the accuracy of the sensor, the temperature sensor 1 is arranged in the protection tube 3. The specific structure is shown in FIG. Figure 5, a hole is opened on the wall of a protective tube 3 with both ends sealed by a non-conductive material, a temperature sensor 1 is placed in the protective tube 3, the temperature sensors 1 are arranged at intervals of 1m, the temperature sensor base 6 is stuck on the protective tube shell 4, the temperature sensor probe 5 is exposed from the opening, the end of the protective tube and the opening are sealed, the transmission line 2 of the temperature sensor is led out from the inner diameter of the protective tube 3, so that the sensor is sealed and fixed in the protective tube, and each protective sleeve is installed with different groups of temperature sensors according to actual conditions. In order to facilitate underground installation, the protective tube is made of multiple protective tubes screwed together by threads, see Figure 6 During implementation, the two ends of the protection tubes are processed into external threads, and then the internal threaded tube stud nuts 8 are screwed onto the external threads 7 of the two ends of the protection tubes.

[0079] Step 4: Use temperature gradient to preliminarily predict the area where energy concentration is located

[0080] 4.1: The temperature of each temperature sensor 1 is collected in real time, and the temperature gradient of adjacent sensors at different times is determined according to the temperature difference ΔT and the distance ΔL of adjacent temperature sensors 1 .

[0081]

[0082] Where: M represents the temperature gradient value, the unit is ℃ / m; ΔT represents the monitoring temperature change corresponding to the temperature sensor, the unit is ℃; ΔL represents the distance between adjacent monitoring sensors, the unit is m.

[0083] 4.2: Obtain the temperature gradient warning surface within the drilling length range

[0084] With time as the horizontal axis X-axis, drilling depth as the horizontal axis Y-axis, and the temperature monitoring value corresponding to the temperature sensor as the vertical axis Z-axis, the temperature gradient surface of the area to be monitored at different times is plotted; that is, each adjacent sensor corresponds to a temperature gradient surface over time, see Figure 4 .

[0085] 4.3: Get the temperature change rate curve at a specific location as a warning curve

[0086] The temperature value monitored by the temperature sensor at a specific location is collected every 5-10 minutes, and then the data is analyzed to obtain a temperature change rate curve of the temperature sensor at the specific location;

[0087] The specific position temperature refers to the area extending from the peak position of the mining stress field to the plastic zone and elastic zone on both sides to the original rock stress position;

[0088] 4.4: Determine the energy concentration area based on the temperature gradient curve and temperature change rate

[0089] During operation, compare the temperature gradient surface diagrams of all boreholes and combine them with the temperature change rate in the stress peak area to find out the surfaces and curves where the temperature gradient and temperature change rate change significantly. When the temperature gradient and temperature change rate are large, the corresponding position range is the energy concentration area, and the time range of the temperature gradient significant change curve corresponds to the process from the beginning to the occurrence of impact damage.

[0090] Step 5: Use the temperature change rate to find the temperature sensor closest to the energy concentration area, and accurately determine the specific location of the energy concentration area based on the installation location parameters of the temperature sensor (including installation angle, layer depth relationship, etc.). The specific process is as follows:

[0091] 5.1: Using the temperature data monitored by the temperature sensor in step 4.3, draw a temperature change rate curve of the temperature sensor in the energy concentration area;

[0092] 5.2: First, invalid temperature change rate curves are eliminated in order to eliminate the error value of the ambient temperature. During the operation, the temperature change rate E obtained in the second step is used as the threshold for determining the temperature change rate of the coal seam; then the slope of each temperature change rate curve is compared with the threshold. When the slope of a temperature change rate curve is greater than a certain coefficient of the threshold, the temperature change rate curve is an invalid temperature change rate curve, otherwise it is a valid temperature change rate curve.

[0093] 5.3: Compare the slopes of all effective temperature change rate curves. The larger the slope of the curve, the greater the temperature change rate and the closer the distance to the energy concentration area. Based on this principle, find the temperature sensor number corresponding to the temperature change rate curve with the largest slope. Find the location parameters of the temperature sensor according to the temperature sensor number, and further obtain the more accurate location of the energy concentration area. Find the curve where the temperature gradient along the length of the borehole and the temperature change rate of the stress peak area change significantly, that is, the position range corresponding to the temperature change rate is the energy concentration area, and further use the temperature gradient to determine the occurrence process and energy size.

[0094] Step 6: Determine the danger level of the energy concentration area

[0095] 6.1: Based on the temperature change rate curve of the stress peak area

[0096] According to the more accurate location of the energy concentration area and the time range of the area with significant temperature gradient changes, the impact damage process is determined, and the monitoring value M corresponding to the temperature gradient surface with significant changes and the monitoring value E corresponding to the temperature change rate curve are calculated. The temperature gradient warning lower limit value for weak impact is M1, and the temperature change rate warning lower limit value is E1; the temperature gradient warning lower limit value for medium impact is M2, and the temperature change rate warning lower limit value is E2; the temperature gradient warning lower limit value for strong impact is M3, and the temperature change rate warning lower limit value is E3.

[0097] 6.2: Compare the temperature gradient monitoring value M in the energy concentration area with the pre-set weak impact temperature gradient warning lower limit value M1, and compare the temperature change rate monitoring value E with the temperature change rate warning lower limit value E1 to determine whether the temperature gradient is greater than M1 and whether the temperature change rate is greater than E1; if not, it is determined that there is no impact and no alarm is needed; if so, the alarm is triggered to sound an alarm, and further perform impact ground pressure hazard level warning judgment.

[0098] (1) If M1≤M<M2, E1≤E<E2, it is judged as a weak impact, the display screen flashes green, and a weak impact green warning is issued;

[0099] (2) If M2≤M<M3, E2≤E<E3, it is judged as a medium impact, the display screen flashes yellow, and a medium impact yellow warning is issued;

[0100] (3) If M>M3, E>E3, it is judged as a strong impact, the display screen flashes red, and a strong impact red warning is issued.

[0101] Step 7: Formulate specific measures to prevent and control rock burst according to the danger level of the energy concentration area and the specific location of the energy concentration area.

[0102] The measures for preventing and controlling rock burst refer to the related measures in the prior art, such as water injection into coal seams, top cutting and pressure relief, large-diameter pressure relief, etc. These measures are common knowledge in the field and are not within the scope of protection of the present invention. They will not be described in detail.

[0103] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto, and any changes or substitutions that are not conceived through creative work should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope defined in the claims.

Claims

1. A method for early warning and evaluation of rock burst risk based on temperature gradient, characterized in that: The following steps are involved: Step 1: Preliminary assessment of the risk level of rock burst / rockburst in the area to be monitored Evaluate the impact area / rock burst in the monitored area, determine the dangerous area and its danger level in the monitored area according to the evaluation results, and divide the monitored area into no impact danger area, weak impact danger area, medium impact danger area, and strong impact danger area; Step 2: Obtain the temperature change rate E of the test block when the rock in the monitored area is damaged Take coal and rock samples in the area to be monitored, conduct impact damage test on the coal sample blocks, and record the temperature change rate E when the test blocks are damaged. 阀 , thus serving as the warning threshold; Step 3: Arrange temperature sensors in the area to be monitored First, mining stress monitoring sensors are arranged in the area to be monitored in advance to monitor the changing law of the mining stress field, so as to determine the high stress area of ​​the coal seam or rock formation and the original rock stress range above the elastic area; the borehole spacing and temperature sensor arrangement plan are designed in the high stress area of ​​the coal seam or rock formation and the original rock stress range above the elastic area, requiring the temperature sensors to be arranged continuously from the borehole surface to the stress peak area, and the maximum monitoring depth of the temperature sensor should be located in the original rock stress range above the elastic area on the side of the elastic area of ​​the coal seam or rock formation; the arrangement method of the temperature sensors is designed according to the principle that the higher the danger level, the more sensor groups should be arranged, and the installation position parameters of each temperature sensor are recorded, and the registration management is carried out; Step 4: Use temperature gradient to preliminarily predict the area where energy concentration is located 4.1: Collect the temperature of each temperature sensor in real time, and determine the temperature gradient of adjacent sensors at different times based on the temperature difference ΔT and the distance ΔL of adjacent temperature sensors; Where: M represents the temperature gradient value, in units of ℃ / m; ΔT represents the monitoring temperature change corresponding to the temperature sensor, in units of ℃; ΔL represents the distance between adjacent monitoring sensors, in units of m; 4.2: Obtain the temperature gradient warning surface within the drilling length range With time as the horizontal axis X-axis, drilling depth as the horizontal axis Y-axis, and the temperature monitoring value corresponding to the temperature sensor as the vertical axis Z-axis, the temperature gradient surface of the area to be monitored at different times is drawn; that is, each adjacent sensor corresponds to a temperature gradient surface over time; 4.3: Get the temperature change rate curve at a specific location as a warning curve The temperature value monitored by the temperature sensor at a specific position is collected regularly, and then the data is analyzed to obtain the temperature change rate curve of the temperature sensor at the specific position; The specific position refers to: the area extending from the peak position of the mining stress field to the plastic zone and the elastic zone on both sides to the original rock stress position; 4.4: Preliminary prediction of energy concentration areas based on temperature gradient and temperature change rate During operation, compare the temperature gradient surfaces of all boreholes and combine with the temperature change rate of the temperature sensor at a specific location to find the surfaces and curves where the temperature gradient and temperature change rate change significantly. When the temperature gradient and temperature change rate are large, the corresponding position range is the energy concentration area, and the time range of significant temperature gradient changes corresponds to the process from the beginning to the occurrence of impact damage. Step 5: Use the temperature change rate to find the temperature sensor closest to the energy collection and concentration area, and accurately determine the specific location of the energy collection and concentration area based on the installation location parameters of the temperature sensor. 5.1: Using the temperature data monitored by the temperature sensor in step 4.3, draw a temperature change rate curve of the temperature sensor in the energy concentration area; 5.2: Eliminate invalid temperature change rate curves to eliminate the error value of ambient temperature. During operation, the temperature change rate E obtained in the second step 阀 As a threshold value for determining the temperature change rate of the coal seam; then compare the slope of each temperature change rate curve in step 5.1 with the threshold value, when the slope of a certain temperature change rate curve is greater than a certain coefficient of the threshold value, the temperature change rate curve is an invalid temperature change rate curve, otherwise it is a valid temperature change rate curve; 5.3: Compare the slopes of all effective temperature change rate curves. The larger the slope of the curve, the greater the temperature change rate and the closer the distance to the energy concentration area. Based on this principle, find the temperature sensor number corresponding to the temperature change rate curve with the largest slope, find its position parameter according to the temperature sensor number, and use the position parameter of the temperature sensor to deduce a more specific location of the energy concentration area; Step 6: Determine the danger level of the energy concentration area 6.1: According to the more specific location of the impact energy accumulation obtained in step 5.3, and combined with the time range of the area where the temperature gradient changes significantly, the impact damage process is determined, and the monitoring value M corresponding to the temperature gradient surface with significant changes and the monitoring value E corresponding to the temperature change rate curve are calculated, and the temperature gradient warning lower limit value for weak impact is set in advance as M1, and the temperature change rate warning lower limit value is set as E1; the temperature gradient warning lower limit value for medium impact is set as M2, and the temperature change rate warning lower limit value is set as E2; the temperature gradient warning lower limit value for strong impact is set as M3, and the temperature change rate warning lower limit value is set as E3; 6.2: Compare the temperature gradient monitoring value M of the energy concentration area with the pre-set temperature gradient warning lower limit M1 of weak impact, and compare the temperature change rate monitoring value E of significant change with the temperature change rate warning lower limit E1 to determine whether the temperature gradient is greater than M1 and whether the temperature change rate is greater than E1; if not, it is determined that there is no impact and no alarm is needed; if so, the alarm is triggered to sound an alarm, and further perform the impact rock pressure hazard level warning determination; (1) If M1≤M<M2, E1≤E<E2, it is judged as a weak impact, the display screen flashes green, and a weak impact green warning is issued; (2) If M2≤M<M3, E2≤E<E3, it is judged as a medium impact, the display screen flashes yellow, and a medium impact yellow warning is issued; (3) If M>M3, E>E3, it is judged as a strong impact, the display screen flashes red, and a strong impact red warning is issued; Step 7: Specify measures to prevent and control rock bursts and impact ground pressure according to the specific location and hazard level of the energy concentration area.

2. The impact rock pressure / rock burst hazard early warning and evaluation method based on temperature gradient as described in claim 1 is characterized in that the arrangement of the borehole spacing, row spacing and temperature sensors in step 3 follows the following principles: the borehole spacing in the strong impact hazard area is 5m, the borehole spacing in the medium impact hazard area is 10m, the borehole spacing in the weak impact area is 20m, and the borehole row spacing is 1.5m; a group of sensors is arranged in each borehole at intervals of 0.2 to 0.5m along the depth.

3. The impact rock pressure / rock burst hazard early warning and evaluation method based on temperature gradient as described in claim 1 is characterized in that the temperature sensor is arranged in a protective tube, and the specific structure is: a hole is opened on the wall of a protective tube made of non-heat-conducting material, the sensor is placed in the protective tube, the sensor base is stuck on the tube wall, the sensor temperature sensing probe is exposed from the opening and sealed, so as to fix the sensor in the protective tube, and different groups of temperature sensors are installed in each protective sleeve according to actual conditions.

4. The rock burst / burst hazard early warning and evaluation method based on temperature gradient as described in claim 3 is characterized in that the protection tube is formed by screwing multiple protection tubes together.

5. The method for early warning and evaluation of rock burst / rockburst hazard based on temperature gradient according to claim 1, characterized in that: The installation position parameters of each temperature sensor described in step 3 at least include the installation angle and the layer burial depth relationship.

6. The method for early warning and evaluation of rock burst risk based on temperature gradient according to claim 1, characterized in that: The timing described in step 4.3 refers to intervals of 5-10 minutes.

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