Column stability in-situ monitoring system and assessment method

Abstract

The invention discloses an ore pillar stability in-situ monitoring system which comprises a top plate grouting anchoring mechanism, a top plate settlement and weighting monitoring mechanism and an ore pillar circumferential deformation monitoring mechanism, and the system effectively fixes an upper structure on an ore body top plate through an air inflation pipeline, a grouting pipeline, an exhaust pipeline and a serial alarm circuit which are arranged in the system. Furthermore, real-time measurement of the stress variation and the self-degradation deformation of the pillar is realized through comprehensive cooperation of multiple sensors, a jack and a monitoring line, and a foundation is laid for the stability evaluation of the pillar. Based on the system, the invention further provides an in-situ assessment method for the stability of the jamb, the stable state of the jamb is divided into four grades of extremely high, high, medium and low risks according to a deformation-time curve and a stress-time curve of the jamb, multi-index comprehensive grading characterization of the stability of the jamb is realized, and a foundation is laid for differentiated treatment of a goaf jamb group. Reference and guidance are provided for avoiding goaf collapse accidents.

Description

Technical Field

[0001] The present invention relates to the technical field of underground mine disaster risk monitoring and assessment, and in particular to an in-situ monitoring system and assessment method for pillar stability. Background Art

[0002] As one of the main methods of underground mining, open-pit mining has been widely used in underground mining in the past few decades, resulting in an astonishing number of large-scale goafs. After the evolution of time and complex geological environment, these goafs have gradually become unstable factors that induce serious accidents in mines, posing serious safety threats to the ecological restoration of mining areas and the normal production and life of nearby residents.

[0003] As the main bearing structure in the goaf, the stability of the pillar determines the stability of the goaf to a great extent. However, constrained by the complex geological conditions of the goaf and the rheological effect of pillar degradation, the current monitoring and evaluation methods for pillar stability are mainly focused on pillar stress monitoring, surface settlement measurement, theoretical analysis, etc., with problems such as single evaluation index, non-in-situ parameter acquisition and ignoring the geological differences of different mining areas. There is still a lack of in-situ monitoring system and evaluation method for pillar stability based on multiple factors. In fact, the instability and destruction of the pillar is affected by the dual disaster factors of roof pressure (external factors) and self-degradation and deformation (internal factors). Therefore, it is necessary to break through the limitations of traditional single monitoring and evaluation indicators, regard the roof-pillar-floor as a complete system, comprehensively consider the influence of multiple disaster factors on the stability of the pillar, and realize in-situ real-time monitoring and comprehensive evaluation of the stability of the pillar.

[0004] In view of this, in order to solve the above problems, the present invention provides an in-situ monitoring system and evaluation method for pillar stability. Summary of the invention

[0005] The present invention provides an in-situ monitoring system and evaluation method for pillar stability, which aims to realize in-situ real-time monitoring and comprehensive classification characterization of pillar stability through the in-situ monitoring system for pillar stability, thereby helping ground personnel to quickly and accurately grasp the deterioration state of pillars, and guiding ground personnel to take differentiated management measures for pillars with collapse risks in underground goafs, so as to promptly eliminate the hidden dangers of goaf collapse.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A system for monitoring the stability of a mine pillar in situ, characterized in that the system consists of three parts: a roof grouting anchoring mechanism, a roof settlement and pressure monitoring mechanism, and a mine pillar annular deformation monitoring mechanism; the roof grouting anchoring mechanism comprises a cylindrical grouting pipe body, an annular sealing airbag, and an automatic grouting stop valve; a Y-shaped grouting pipeline, an airbag inflation pipeline, and an air exhaust pipeline are arranged inside the grouting pipe body, and the automatic grouting stop valve is installed at the top center of the grouting pipe body, and a series alarm circuit and an air exhaust pipeline are connected below it; the roof settlement and pressure monitoring mechanism is connected below the roof grouting anchoring mechanism, and comprises a roof displacement and pressure detection structure, a power supply, a mechanical jack, and a pressure-bearing bottom plate, the mechanical jack is fixed at the center of the pressure-bearing bottom plate, a level bubble is embedded in the pressure-bearing bottom plate, the roof displacement and pressure detection structure consists of a micro laser ranging sensor, an elastic pressure sensor, a limit kit, and a T-shaped force transmission rod, and a micro laser ranging sensor The sensor and the elastic pressure sensor are installed in the groove at the lower end of the cylindrical grouting pipe, the T-shaped force transmission rod passes through one end of the limit kit and is connected to the elastic pressure sensor, and the other end with the stud is connected to the mechanical jack fixed on the pressure-bearing bottom plate, the limit kit is connected to the groove at the lower end of the grouting pipe through a thread, and its internal structure matches the T-shaped force transmission rod, so that when the top plate settles, the limit kit can sink with the grouting pipe, so that the limit kit can move along the T-shaped force transmission rod; the circumferential deformation monitoring mechanism of the mine pillar includes a line box, a line length monitoring sensor, an annular deformation monitoring line and a line anchor; the line box is installed below the grouting pipe body near the bottom end of the pipe body, the annular deformation monitoring line is received in the line box through the wire wheel, the line length monitoring sensor is installed in the grouting pipe body, connected to the power supply, and connected to the external line box, the line anchor is an independent component arranged on the bottom plate of the goaf, and is used to fix the monitoring line during the monitoring process.

[0008] Furthermore, a conical opening is provided at the top end of the grouting pipe body, and isolation gaskets are arranged at intervals along the outer side of the opening in a circle along the pipe body.

[0009] Furthermore, the automatic grouting stop valve is composed of an arc-shaped pressure-bearing gasket, a micro spring, a waterproof breathable membrane and a connecting rod with a V-shaped head. The micro spring and the waterproof breathable membrane are respectively installed between the arc-shaped pressure-bearing gasket and the conical groove at the top of the grouting tube body, wherein the waterproof breathable membrane is located outside the micro spring. The connecting rod is arranged along the central axis of the micro spring, one end of which is connected to the arc-shaped pressure-bearing gasket, and the other end with a V-shaped head is located in the first hollow chamber in the grouting tube body when there is no pressure from above, and automatically enters the second hollow chamber below and is fixed when subjected to the limit pressure of the pressure-bearing gasket.

[0010] Furthermore, the waterproof and breathable membrane allows air to flow freely during the grouting process and blocks the slurry from entering the lower pipeline; an air exhaust pipeline is opened below the second hollow chamber, and the air in the upper enclosed space in the drilled hole enters the exhaust channel from the waterproof and breathable membrane and is discharged from the exhaust hole on the grouting pipe.

[0011] Furthermore, the series alarm circuit is composed of a conductor, an indicator light with a power supply, and an electrode groove located below the second hollow chamber. The electrode groove is directly opposite to the central axis of the connecting rod, and a conductor is also installed below the V-shaped head of the connecting rod. When the V-shaped head completely enters the second hollow chamber, the conductor enters the electrode groove, the alarm circuit below is connected, and the indicator light on the grouting pipe body lights up, indicating that the grouting is completed.

[0012] Furthermore, a groove is circumferentially arranged on one side of the grouting pipe body near the bottom end, the annular sealing airbag is located in the groove and is connected to the airbag inflation pipeline inside the grouting pipe body, the grouting hole of the Y-shaped grouting pipeline, the exhaust hole of the air exhaust pipeline, the inflation hole of the airbag inflation pipeline, the indicator light of the alarm circuit and the measuring line box are all located below the annular sealing airbag, and only the two slurry outlet holes of the Y-shaped grouting pipeline are located above the annular sealing airbag.

[0013] Furthermore, the elastic pressure sensor, limit kit, T-shaped force transmission rod, mechanical jack and pressure base plate are all located on the central axis of the grouting pipe body, the micro laser ranging sensor is arranged in a mounting hole on one side of the groove inside the lower end of the grouting pipe body, the emitted laser is projected on the end of the T-shaped force transmission rod, and the elastic pressure sensor is arranged in the central mounting hole inside the groove at the lower end of the grouting pipe body.

[0014] Furthermore, the survey line anchor consists of an upper tube body with a vertical guide channel in the center and a lower conical head with a V-shaped guide channel inside. The vertical guide channel and the V-shaped guide channel are connected at the junction of the conical head and the upper tube body. The V-shaped guide channel is connected to the outside world, and two channel outlets are arranged on the cone surface.

[0015] The present invention also provides an in-situ evaluation method for pillar stability, which is implemented by using the above-mentioned in-situ monitoring system for pillar stability, and comprises the following steps:

[0016] 1) Measure the initial vertical ground stress near the pillar, calculate the pillar strength according to the formula, and evaluate the initial stability of the pillar;

[0017] 2) Drill a hole at the junction of the top of the pillar to be tested and the roof of the ore body, and construct a groove at the bottom of the pillar hole to clean up the residual rock debris in the entire hole in advance;

[0018] 3) Place the pillar stability in-situ monitoring system into the borehole, and adjust the height by a mechanical jack to ensure that the annular sealing airbag is located inside the roof borehole and other structures below the airbag are located outside the roof borehole;

[0019] 4) Use the level bubble on the pressure bottom plate to level the overall position of the system, and fix the grouting pipe body and the pressure bottom plate respectively by grouting in the hole;

[0020] 5) After the slurry solidifies, the handle of the mechanical jack is reciprocated to apply pressure until the pressure detected by the elastic pressure sensor is equal to the vertical stress of the rock mass measured in step 1);

[0021] 6) Pull out the monitoring line in the line box, arrange it around the pillar downward and close to the pillar, and fix it on the floor of the goaf with the line anchor;

[0022] 7) Turn on the laser distance measuring sensor and the line length monitoring sensor, record the initial value of the sensor, and start the long-term monitoring mode;

[0023] 8) The stability of the pillars is evaluated in real time based on the changes in the stress-time curve and the circumferential deformation-time curve, and the pillar stability is comprehensively divided into four levels: extremely high risk, high risk, medium risk and low risk.

[0024] Furthermore, the specific operation of using grouting to fix the system components is as follows: inflate the airbag through the inflation hole to seal the upper space in the hole. Then, grout is injected into the enclosed space in the hole through the grouting hole until the indicator light comes on and the grouting is stopped, waiting for the slurry to solidify. After that, grout is injected into the groove at the bottom of the pillar drilling hole to fix the pressure-bearing bottom plate.

[0025] Furthermore, the basis for grading the stability of the pillars is as follows: when the stress-time curve and the circumferential deformation-time curve both fluctuate near the initial value, the stability of the pillar is judged to be low risk; when one of the two curves fluctuates near the initial value and the other shows an upward trend (below the instability threshold), the stability of the pillar is judged to be medium risk; when one of the two curves exceeds the instability threshold and the other does not exceed the instability threshold or both curves show an upward trend (below the instability threshold), the stability of the pillar is judged to be high risk; when both curves exceed the instability threshold, the stability of the pillar is judged to be extremely high risk.

[0026] Beneficial Effects

[0027] The pillar stability in-situ monitoring system and evaluation method proposed in the present invention have the following three main outstanding advantages:

[0028] (1) The solution proposed in the present invention realizes long-term monitoring of pillar stability under in-situ conditions in the goaf, breaking through the limitations of the traditional non-in-situ method of monitoring the risk of goaf collapse through surface settlement;

[0029] (2) The roof-pillar-floor system is regarded as a complete system, and the real-time measurement of three important parameters, namely roof settlement, stress change, and pillar deformation, is achieved. The monitoring results not only lay the foundation for the stability assessment of the corresponding pillars to be tested, but also provide a reference for the stability evolution assessment of the pillar group system in the surrounding area with the pillars as the supporting units;

[0030] (3) An in-situ evaluation method for pillar stability is proposed. Based on the data collected by the pillar stability in-situ monitoring system, the internal and external dual disaster-causing factors of the pillar's own degradation and roof pressure changes are comprehensively considered to achieve a multi-index classification of pillar stability, solving the problem of ignoring the internal / external dual disaster-causing factors in a single evaluation indicator. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the appearance of the in-situ monitoring system for pillar stability according to Example 1 of the present invention;

[0032] Figure 2 It is a schematic diagram of the internal core structure and partial enlarged details of the in-situ monitoring system for pillar stability according to Example 1 of the present invention;

[0033] Figure 3 This is a schematic diagram of the field application of the in-situ monitoring system for pillar stability according to Example 2 of the present invention;

[0034] Figure 4 This is a risk classification diagram of the in-situ assessment method for pillar stability described in Example 2 of the present invention.

[0035] The symbols and corresponding names in the accompanying drawings are as follows:

[0036] 1. Grouting pipe body; 101. Annular isolation gasket; A. Automatic stop valve; 201. Exhaust hole; 202. Exhaust channel; 203. Second hollow chamber; 204. First hollow chamber; 205. Connecting rod movable channel; 3. Indicator light with power supply; 301. Wire; 302. Electrode groove; 401. Grouting hole; 402. Y-shaped grouting channel; 403. Grouting hole; 5. Annular sealing airbag; 501. Inflating hole; 502. Inflating channel; 6. Measuring line box; 601. Monitoring line; 7. Measuring line length monitoring sensor; 8. Power supply circuit; 9. Power supply; B. Top plate displacement and pressure detection structure; 10. T-shaped force transmission rod; 11. Mechanical axle Jack; 111, jack piston rod; 112, jack handle; 12, pressure base plate; 121, level bubble; 131, arc-shaped pressure gasket; 132, micro spring; 133, connecting rod; 134, waterproof breathable membrane; 135, conductor; 14, micro laser ranging sensor; 15, elastic pressure sensor; 161, mounting hole; 162, lower end groove; 17, limit kit; C, measuring line anchor; 18, upper tube body; 181, vertical diversion channel; 19, lower conical head; 191, V-shaped diversion channel; 20, slurry; 21, ore body roof; 211, roof drilling; 22, ore pillar; 221, drilling groove; 23, goaf floor. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only structures and processing steps closely related to the scheme of the present invention are shown in the drawings, while other details that are not closely related to the present invention are omitted.

[0039] Embodiment 1

[0040] like Figures 1 to 3As shown, Embodiment 1 of the present invention provides an in-situ monitoring system for pillar stability, which is composed of three parts: a roof grouting anchoring mechanism, a roof settlement and pressure monitoring mechanism, and a pillar annular deformation monitoring mechanism. The roof grouting anchoring mechanism includes a cylindrical grouting pipe body 1, an annular sealing airbag 5, and an automatic grouting stop valve A. The grouting pipe body 1 is provided with a Y-shaped grouting pipeline (including a grouting hole 401 provided on the grouting pipe body 1, an internal Y-shaped grouting channel 402, and two grouting outlets 403 provided on the grouting pipe body 1), an airbag inflation pipeline (including an inflation hole 501 provided on the grouting pipe body 1 and an internal inflation channel 502), and an air exhaust pipeline (including an exhaust hole 201 provided on the grouting pipe body 1 and an internal exhaust channel 202). The automatic grouting stop valve A is installed at the top center of the grouting pipe body 1, and a series alarm circuit and an air exhaust pipeline are connected below it. The top plate settlement and pressure monitoring mechanism is connected to the bottom of the top plate grouting anchor mechanism, including a top plate displacement and pressure detection structure B, a power supply 9, a mechanical jack 11 and a pressure bottom plate 12. The mechanical jack 11 is fixed at the center of the pressure bottom plate 12, and a level bubble 121 is embedded on the pressure bottom plate 12. The top plate displacement and pressure detection structure B is composed of a micro laser ranging sensor 14, an elastic pressure sensor 15, a limit kit 17 and a T-shaped force transmission rod 10. The micro laser ranging sensor 14 is arranged on one side of the groove 162 at the lower end of the grouting pipe. In the mounting hole 161, the elastic pressure sensor 15 is arranged in the central mounting hole in the groove 162 at the lower end of the grouting pipe, the T-shaped force transmission rod 10 passes through one end of the limit kit and is connected to the elastic pressure sensor 15, and the other end with the stud is connected to the piston rod 111 with a threaded hole on the mechanical jack 11, and the limit kit 17 is connected to the groove 162 at the lower end of the grouting pipe through a thread, and its internal structure matches the T-shaped force transmission rod 10, so that when the top plate 21 settles, the limit kit 17 can sink with the grouting pipe, so that the limit kit 17 can move along the T-shaped force transmission rod 10. The circumferential deformation monitoring mechanism of the mine pillar includes a measuring line box 6, a measuring line length monitoring sensor 7, a circumferential deformation monitoring line 601 and a measuring line anchor C. The measuring line box 6 is installed below the grouting pipe body 1 and close to the bottom end of the pipe body. The annular deformation monitoring line 601 is received inside the measuring line box 6 through a wire wheel (not shown). The measuring line length monitoring sensor 7 is installed inside the grouting pipe body 1, connected to the power supply 9, and connected to the external measuring line box 6. The measuring line anchor C is an independent component arranged on the bottom plate 23 of the goaf, and is used to fix the monitoring line 601 during the monitoring process.

[0041] Furthermore, a conical opening is provided at the top of the grouting pipe body 1 , and isolation gaskets 101 with spaced openings are arranged around the pipe body 1 in a circle outside the opening.

[0042] Furthermore, the automatic grout stop valve A is composed of an arc-shaped pressure-bearing gasket 131, a micro spring 132, a connecting rod 133 with a V-shaped head, and a waterproof breathable membrane 134. The micro spring 132 and the waterproof breathable membrane 134 are respectively installed between the arc-shaped pressure-bearing gasket 131 and the conical groove at the top of the grouting tube body 1, wherein the waterproof breathable membrane 134 is located outside the micro spring 132. The connecting rod 133 is arranged along the central axis of the micro spring 132, one end of which is connected to the arc-shaped pressure-bearing gasket 131, and the other end with a V-shaped head is located in the first hollow chamber 204 in the grouting tube body 1 when there is no pressure from above, and automatically enters the second hollow chamber 203 below and is fixed when subjected to the limit pressure of the pressure-bearing gasket 131.

[0043] Furthermore, the waterproof and breathable membrane 134 allows air to flow freely during the grouting process and blocks the slurry 20 from entering the lower pipeline; an air exhaust pipeline is opened below the second hollow chamber 203, and the air in the upper enclosed space in the drilled hole enters the exhaust channel 202 from the waterproof and breathable membrane 134 and is discharged from the exhaust hole 201 on the grouting pipe.

[0044] Furthermore, the series alarm circuit is composed of a conductor 301, an indicator light 3 with a power supply, and an electrode groove 302 located below the second hollow chamber 203. The electrode groove 302 is directly opposite to the central axis of the connecting rod 133. A conductor 135 is also installed below the V-shaped head of the connecting rod 133. When the V-shaped head of the connecting rod 133 completely enters the second hollow chamber 203, the conductor 135 enters the electrode groove 302, the alarm circuit below is connected, and the indicator light 3 on the grouting pipe body 1 lights up, indicating that the grouting is completed.

[0045] Furthermore, the grouting pipe body 1 is circumferentially provided with a groove on one side near the bottom end, the annular sealing airbag 5 is located in the groove and is connected to the airbag inflation pipeline inside the grouting pipe body, the grouting hole 401 of the Y-shaped grouting pipeline, the exhaust hole 201 of the air exhaust pipeline, the inflation hole 501 of the airbag inflation pipeline, the indicator light 3 of the alarm circuit and the measuring line box 6 are all located below the annular sealing airbag 5, and only the two slurry outlet holes 403 of the Y-shaped grouting pipeline are located above the annular sealing airbag 5.

[0046] Furthermore, the elastic pressure sensor 15, the limit kit 17, the T-shaped force transmission rod 10, the mechanical jack 11 and the pressure-bearing base plate 12 are all located on the central axis of the grouting pipe body 1, and the micro laser ranging sensor 14 is arranged in a mounting hole 161 on one side inside the groove at the lower end of the grouting pipe body, and the emitted laser is projected onto the end of the T-shaped force transmission rod 10.

[0047] Furthermore, the survey line anchor C is composed of an upper tube body 18 with a vertical guide channel 181 opened in the center and a lower conical head 19 with a V-shaped guide channel 191 opened inside. The vertical guide channel 181 is connected to the V-shaped guide channel 191 at the junction of the conical head 19 and the upper tube body 18. The V-shaped guide channel 191 is connected to the outside, and two channel outlets are arranged on the cone surface.

[0048] Specifically, the working process of the present application is as follows: During the installation of the in-situ monitoring system for pillar stability, the system is first leveled by the level bubble 121 on the pressure-bearing bottom plate 12, and then the annular sealing airbag 5 is used to realize the positioning and sealing of the upper structure of the system inside the borehole 211, creating conditions for grouting. The slurry 20 is injected from the grouting hole 401, flows out from the slurry outlet hole 403 through the Y-shaped grouting channel 402, and gradually fills the closed borehole space. During the grouting process, the role of the waterproof and breathable membrane 134 is to allow air to flow freely and block the slurry 20 from entering the lower pipeline. Therefore, the air in the upper enclosed space in the borehole 211 enters the exhaust channel 202 from the waterproof and breathable membrane 134, and is discharged from the exhaust hole 201, thereby ensuring that the slurry 20 completely fills the enclosed space in the borehole. When the enclosed space in the borehole is filled with grout 20, the pressure above the arc-shaped pressure-bearing gasket 131 continues to increase, causing the micro spring 132 to be compressed. When the compression limit is reached, the connecting rod 133 is pushed from the first hollow chamber 204 into the second hollow chamber 203, and the conductor 135 installed on the top of the connecting rod 133 enters the electrode groove 302. The series alarm circuit is connected, and the indicator light 3 on the grouting pipe body 1 lights up, indicating that the grouting is completed. After that, grouting is injected into the groove 221 at the bottom of the borehole 211 to complete the fixing of the pressure-bearing bottom plate 12 on the pillar 22. In addition, by injecting grout into the upper tube body 18 of the survey line anchor C, the slurry 20 is diverted from the vertical diversion channel 181 through the V-shaped diversion channel 191 and flows to the gap between the survey line anchor C and the rock mass of the goaf floor 23. After filling and solidifying, the purpose of firmly fixing the survey line anchor C is achieved, thereby realizing the firm binding of the monitoring line 601 to the goaf floor 23.

[0049] The principle of evaluating the stability of the ore pillar in this application is as follows: during the monitoring process of the system, the grouting pipe body 1 and the ore body top plate 21 form a whole, the grouting pipe body 1 drops as the ore body top plate 21 settles, the elastic pressure sensor 15 produces elastic deformation and monitors the change of the top plate stress, the micro laser ranging sensor 14 measures the deformation of the elastic pressure sensor 15 in real time, and further converts it into the settlement of the ore body top plate 21. As time goes by and the external environment changes, when the ore pillar 22 deteriorates and deforms, the ore on the side wall of the ore pillar 22 will be peeled off, resulting in a change in the length of the monitoring line 601. The line length monitoring sensor 7 located inside the grouting pipe body 1 records the length change of the monitoring line 601 in real time, thereby obtaining the deformation-time curve of the ore pillar 22. Finally, the stability of the ore pillar is evaluated by recording and comprehensively analyzing the ore pillar stress-time curve and the ore pillar deformation-time curve.

[0050] Embodiment 2

[0051] Embodiment 2 of the present invention provides an in-situ evaluation method for pillar stability, such as Figure 4 As shown, it is implemented by using the pillar stability in-situ monitoring system in Example 1, including the following steps:

[0052] 1) Measure the initial vertical stress near the pillar 22 and record the initial vertical stress as σ 0 , calculate the strength of the pillar 22 according to the formula and evaluate the initial stability of the pillar 22;

[0053] 2) constructing a borehole 211 at the junction of the top of the ore pillar 22 to be tested and the ore body roof 21, and constructing a groove 221 at the bottom of the borehole 211, and cleaning the residual rock debris inside the entire borehole 211 in advance;

[0054] 3) Place the pillar stability in-situ monitoring system into the borehole 211, and adjust the height by the mechanical jack 11 to ensure that the annular sealing airbag 5 is located inside the top plate borehole 211, and other structures below the airbag 5 are located outside the top plate borehole 211;

[0055] 4) Use the level bubble 121 on the pressure bottom plate 12 to level the overall position of the system, and fix the grouting pipe body 1 and the pressure bottom plate 12 respectively by grouting in the hole;

[0056] 5) After the slurry 20 solidifies, the handle 112 of the mechanical jack 11 is reciprocated to apply pressure until the pressure detected by the elastic pressure sensor 15 is equal to the vertical stress σ of the rock mass measured in step 1). 0 until;

[0057] 6) Pull out the monitoring line 601 in the line box 6, arrange it around the pillar 22 in a circular manner downward and close to the pillar 22, and fix it on the floor 23 of the goaf through the line anchor C;

[0058] 7) Turn on the laser distance measuring sensor 14 and the line length monitoring sensor 7, record the initial values ​​of the sensors, and start the long-term monitoring mode;

[0059] 8) The stability of the pillar 22 is evaluated in real time based on the changes in the stress-time curve and the circumferential deformation-time curve, and the pillar stability is comprehensively divided into four levels: extremely high risk, high risk, medium risk and low risk.

[0060] Furthermore, the strength calculation formula for selecting the pillar 22 may refer to the following principles:

[0061] ① The uniaxial compressive strength (σ p ) data, the strength of the pillar 22 (S p ) The calculation formula can be selected as:

[0062]

[0063] In the formula, S p is the pillar strength (MPa); w is the pillar width (m); h is the pillar height (m); n is the pillar morphology factor, when the aspect ratio w / h ≥ 5, n is 1.4, and when w / h < 5, n is 1.0; σ p is the uniaxial compressive strength (MPa) of the cubic specimen taken from the pillar.

[0064] ② The uniaxial compressive strength (σ p ) data, then the strength of the pillar 22 (S p ) The calculation formula can be selected as:

[0065]

[0066] It is worth noting that due to the irregularity and randomness of the pillar contour, the pillar width can be replaced by the equivalent width calculated by the hydraulic radius:

[0067]

[0068] In the formula, A p is the cross-sectional area of ​​the pillar (m 2 );C p is the cross-sectional perimeter of the pillar (m).

[0069] Furthermore, according to the pillar instability theory, when the roof rock stress borne by the pillar exceeds the pillar strength limit, the pillar will become unstable. Therefore, the calculated pillar strength S p The stress threshold at which the pillar 22 becomes unstable.

[0070] Furthermore, the overall radial deformation of the pillar 22 due to its own degradation can be monitored by the line length monitoring sensor 7. Since the local degradation deformation of the pillar 22 over time is random, its degradation deformation threshold is difficult to calculate theoretically. Therefore, it is recommended that the value be determined by a large amount of field measured data combined with the geological environmental conditions of the goaf.

[0071] Furthermore, if Figure 4 As shown in the figure, when the pillar stability is graded based on the roof pressure monitoring (pillar stress-time curve) and the pillar's own degradation and deformation (pillar deformation-time curve), the following grading principles are adopted: when the stress-time curve and the circumferential deformation-time curve are both fluctuating near the initial value, the pillar stability is judged to be low risk; when one of the two curves fluctuates near the initial value and the other shows an upward trend (lower than the instability threshold), the pillar stability is judged to be medium risk; when one of the two curves exceeds the instability threshold and the other does not exceed the instability threshold or both curves show an upward trend (lower than the instability threshold), the pillar stability is judged to be high risk; when both curves exceed the instability threshold, the pillar stability is judged to be extremely high risk. According to the stability classification of different pillars, the overall distribution of pillar stability in the goaf is comprehensively considered, and differentiated governance measures can be taken for the pillar group in the goaf, so as to timely avoid the occurrence of goaf collapse disasters.

[0072] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Any equivalent structures or equivalent transformations made using the contents of the present invention's specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. An in-situ monitoring system for pillar stability, characterized in that: The system consists of three parts: a roof grouting anchoring mechanism, a roof settlement and pressure monitoring mechanism, and a pillar annular deformation monitoring mechanism; the roof grouting anchoring mechanism includes a cylindrical grouting pipe body, an annular sealing airbag and an automatic grouting stop valve, a Y-shaped grouting pipeline, an airbag inflation pipeline and an air exhaust pipeline are arranged inside the grouting pipe body, and the automatic grouting stop valve is installed at the top center of the grouting pipe body, and a series alarm circuit and an air exhaust pipeline are connected below it; the roof settlement and pressure monitoring mechanism is connected below the roof grouting anchoring mechanism, and includes a roof displacement and pressure detection structure, a power supply, a mechanical jack and a pressure bottom plate, the mechanical jack is fixed at the center of the pressure bottom plate, and a level bubble is embedded in the pressure bottom plate, the roof displacement and pressure detection structure consists of a micro laser ranging sensor, an elastic pressure sensor, a limit kit and a T-shaped sensor The grouting pipe body is composed of a micro laser ranging sensor and an elastic pressure sensor installed in the groove at the lower end of the cylindrical grouting pipe. The T-shaped force transmission rod passes through one end of the limit kit and is connected to the elastic pressure sensor, and the other end with a stud is connected to a mechanical jack fixed on the pressure-bearing bottom plate. The limit kit is connected to the groove at the lower end of the grouting pipe through a thread, and its internal structure matches the T-shaped force transmission rod; the circumferential deformation monitoring mechanism of the mine pillar includes a measuring line box, a measuring line length monitoring sensor, an annular deformation monitoring line and a measuring line anchor. The measuring line box is installed on the side of the grouting pipe body below the grouting pipe body close to the bottom end of the pipe body, the annular deformation monitoring line is received in the measuring line box through a wire wheel, the measuring line length monitoring sensor is installed in the grouting pipe body, is connected to the power supply, and is connected to the external measuring line box, and the measuring line anchor is an independent component arranged on the bottom plate of the goaf area, and is used to fix the monitoring line during the monitoring process.

2. The in-situ monitoring system for pillar stability according to claim 1, characterized in that: The top end of the grouting pipe body is provided with a conical opening, and the outer side of the opening is provided with isolation gaskets with spaced openings arranged in a circle along the circumference of the pipe body.

3. The in-situ monitoring system for pillar stability according to claim 1, characterized in that: The automatic grouting stop valve is composed of an arc-shaped pressure-bearing gasket, a micro spring, a waterproof breathable membrane and a connecting rod with a V-shaped head. The micro spring and the waterproof breathable membrane are respectively installed between the arc-shaped pressure-bearing gasket and the conical groove at the top of the grouting pipe body, wherein the waterproof breathable membrane is located on the outside of the micro spring, and the connecting rod is arranged along the central axis of the micro spring, with one end connected to the arc-shaped pressure gasket and the other end with the V-shaped head located in the first hollow chamber in the grouting pipe body when there is no pressure from above, and automatically enters the second hollow chamber below and is fixed when subjected to the limit pressure of the pressure gasket.

4. The in-situ monitoring system for pillar stability according to claim 3, characterized in that: The waterproof and breathable membrane allows air to flow freely during the grouting process and blocks the slurry from entering the lower pipeline; an air exhaust pipeline is opened below the second hollow chamber, and the air in the upper enclosed space in the drilled hole enters the exhaust channel from the waterproof and breathable membrane and is discharged from the exhaust hole on the grouting pipe.

5. The in-situ monitoring system for pillar stability according to claim 1, characterized in that: The series alarm circuit consists of a wire, an indicator light with a power supply and an electrode groove located below the second hollow chamber; the electrode groove is directly opposite to the central axis of the connecting rod, and a conductor is also installed below the V-shaped head of the connecting rod. When the V-shaped head completely enters the second hollow chamber, the conductor enters the electrode groove, the alarm circuit below is connected, and the indicator light on the grouting pipe body lights up, indicating that the grouting is completed.

6. The in-situ monitoring system for pillar stability according to claim 1, characterized in that: A groove is circumferentially arranged on one side of the grouting pipe body near the bottom end. The annular sealing airbag is located in the groove and is connected to the airbag inflation pipeline inside the grouting pipe body. The grouting holes of the Y-shaped grouting pipeline, the exhaust holes of the air exhaust pipeline, the inflation holes of the airbag inflation pipeline, the indicator lights of the alarm circuit and the measuring line box are all located below the annular sealing airbag. Only the two grouting holes of the Y-shaped grouting pipeline are located above the annular sealing airbag.

7. The in-situ monitoring system for pillar stability according to claim 1, characterized in that: The survey line anchor consists of an upper tube body with a vertical diversion channel in the center and a lower conical head with a V-shaped diversion channel inside. The vertical diversion channel and the V-shaped diversion channel are connected at the junction of the conical head and the upper tube body. The V-shaped diversion channel is connected to the outside world, and two channel outlets are arranged on the cone surface.

8. A method for in-situ evaluation of pillar stability, which is implemented by using an in-situ monitoring system for pillar stability according to any one of claims 1 to 7, characterized in that: The following steps are involved: 1) Measure the initial vertical ground stress near the pillar, calculate the pillar strength according to the formula, and evaluate the initial stability of the pillar; 2) Drill a hole at the junction of the top of the pillar to be tested and the roof of the ore body, and construct a groove at the bottom of the pillar hole to clean up the residual rock debris in the entire hole in advance; 3) Place the pillar stability in-situ monitoring system into the borehole, and adjust the height by a mechanical jack to ensure that the annular sealing airbag is located inside the roof borehole and other structures below the airbag are located outside the roof borehole; 4) Use the level bubble on the pressure bottom plate to level the overall position of the system, and fix the grouting pipe body and the pressure bottom plate respectively by grouting in the hole; 5) After the slurry solidifies, the handle of the mechanical jack is reciprocated to apply pressure until the pressure detected by the elastic pressure sensor is equal to the vertical stress of the rock mass measured in step 1); 6) Pull out the monitoring line in the line box, arrange it around the pillar downward and close to the pillar, and fix it on the floor of the goaf with the line anchor; 7) Turn on the laser distance measuring sensor and the line length monitoring sensor, record the initial value of the sensor, and start the long-term monitoring mode; 8) The stability of the pillars is evaluated in real time based on the changes in the stress-time curve and the circumferential deformation-time curve, and the pillar stability is comprehensively divided into four levels: extremely high risk, high risk, medium risk and low risk.

9. The in-situ evaluation method for pillar stability according to claim 8, characterized in that: The specific operation of using grouting to fix the system components is as follows: inflate the airbag through the inflation hole to seal the upper space in the hole, then inject grout into the enclosed space in the hole through the grouting hole until the indicator light comes on and stop grouting, wait for the slurry to solidify, and then inject grout into the groove at the bottom of the pillar borehole to fix the pressure bottom plate.

10. The in-situ evaluation method for pillar stability according to claim 8, characterized in that: The basis for grading the pillar stability is as follows: when both the stress-time curve and the circumferential deformation-time curve fluctuate near the initial value, the pillar stability is judged to be low risk; when one of the two curves fluctuates near the initial value and the other shows an upward trend (below the instability threshold), the pillar stability is judged to be medium risk; when one of the two curves exceeds the instability threshold and the other does not exceed the instability threshold or both curves show an upward trend (below the instability threshold), the pillar stability is judged to be high risk; when both curves exceed the instability threshold, the pillar stability is judged to be extremely high risk.

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