A coal fire area fissure active enhancement exploration test system and method

Abstract

The application discloses a coal fire area fissure active enhancement exploration test system and method, and belongs to the technical field of mine safety and geophysical exploration, and comprises: a fissure evolution module, which is used for simulating the thermal-power-gas coupling condition of an underground coal fire area, and inducing the coal rock mass test piece to generate fissures; a fissure exploration module, which is used for collecting the multi-physical field data of the coal rock mass test piece in real time and synchronously; a fissure intervention module, which is used for injecting natural medium simulation objects and enhanced medium foam gel materials into the fissures, so as to simulate a real environment and enhance the detection signal; an intelligent feedback and data fusion module, which is used for controlling the operation parameters of each module, synchronously acquiring the detection data, and performing fusion processing, intelligent inversion and four-dimensional visualization on the detection data, and realizing the whole process monitoring and detection of the fissure evolution. The application provides a scientific method for accurately delineating and target plugging and treating the hidden fissures in the coal fire area, and solves the problems of the multi-solution of traditional fissure exploration and the easy re-ignition of the coal fire treatment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of mine safety and geophysical exploration, and particularly relates to a coal fire zone fissure active enhancement exploration test system and method. BACKGROUND

[0002] Underground coal fire is a major global geological disaster. Due to the complex geological conditions, large burning area, long development time, strong concealment of burning state, and complex air supply channel of underground coal fire, it leads to many new fire zones, rapid development of fire zones, slow extinguishing speed of fire zones, and easy rekindling of fire zones in the early stage of coal fire management. In the early stage of coal fire management, the heat released by the burning center of underground fire bakes the surrounding coal rock, and the coal smolders continuously produce high-temperature gas to circulate and leach the overlying coal rock, resulting in changes in the mechanical properties and pore fissures of the coal rock. In addition, a large number of burned-out areas are formed, which disrupt the original stress balance of the coal rock, thereby breeding new oxygen supply channels. Although the conventional five management technologies can extinguish the fire source, this hidden oxygen supply channel is the root cause of the rekindling and spread of the extinguished fire zone.

[0003] At present, geophysical exploration methods are widely used in the exploration of coal fire sources, providing important support for the delineation of coal fire management target areas, but the precise control of rekindling prevention in extinguished coal fire zones still faces severe challenges. The core bottleneck is the lack of effective exploration means for the spatial distribution, geometric shape, and connectivity of underground hidden fissure systems, which seriously restricts the precise implementation of sealing technology and causes hidden fissures to continue to supply oxygen to extinguished coal bodies, leading to uncontrolled rekindling of extinguished coal bodies and serious harm to the ecological environment and coal resource reserves.

[0004] In view of the above problems in the prior art, it is urgent to propose a coal fire zone fissure active enhancement exploration test system and method. SUMMARY

[0005] To make up for the blank of low precision in exploring hidden fissures in coal fire zones, lack of controllable verification platform, and difficulty in evaluating sealing effect in the prior art, the present application proposes a coal fire zone fissure active enhancement exploration test system and method, in order to accurately locate and quantitatively characterize the spatial distribution, geometric shape, and connectivity of hidden fissures; evaluate the weakening effect of fissure fillers on geophysical signals; improve the detection sensitivity of fissures by actively enhancing the medium; and provide a verifiable theoretical basis and technical support for on-site fissure sealing design and rekindling prevention decision-making.

[0006] To achieve the above-mentioned purpose, the present application provides a coal fire zone fissure active enhancement exploration test system, comprising:

[0007] A fissure evolution module for simulating the thermal-mechanical-gas coupling conditions of an underground coal fire zone to induce fissures in a coal rock test piece;

[0008] A fracture detection module for real-time and synchronous acquisition of multi-physical field data of the coal rock mass specimen;

[0009] A fracture intervention module for injecting natural medium simulators and enhanced medium foam gel materials into the fractures to simulate real environment and enhance the detection signal;

[0010] An intelligent feedback and data fusion module for controlling the operation parameters of each module, synchronously acquiring the detection data, and performing fusion processing, intelligent inversion and four-dimensional visualization on the detection data to realize geometric feature monitoring of the whole process of fracture evolution.

[0011] Optionally, the fracture evolution module comprises:

[0012] A closed rigid cabin for accommodating the cuboid coal rock mass specimen;

[0013] A servo pressurizing unit installed on a bearing frame of the closed rigid cabin for applying independent controlled four-face stress to the specimen to form a force acting part;

[0014] A heating device arranged at the bottom of the closed rigid cabin for providing a heat source from the bottom of the specimen to form a heat acting part;

[0015] A gas injection and control system connected to the closed rigid cabin for injecting gas into the cabin and controlling the cyclic adsorption and release process of the gas to form a gas acting part.

[0016] Optionally, the fracture detection module comprises a sensor array arranged on the closed rigid cabin and the coal rock mass specimen, and the sensor array comprises:

[0017] An array of resistivity probes for high-density resistivity method measurement and resistivity tomography imaging;

[0018] An acoustic emission sensor for monitoring acoustic emission signals in the process of fracture initiation and expansion;

[0019] An acoustic wave emission and receiving transducer for emitting and receiving acoustic wave signals;

[0020] An electrical resistance strain gauge for measuring strain;

[0021] A distributed optical fiber sensing network for measuring temperature and strain;

[0022] A magnetic force sensor for monitoring magnetic signals.

[0023] Optionally, the fracture evolution module comprises a gas injection and control system, and the gas injection and control system comprises:

[0024] Vacuum pump, displacement pump and mass flow controller are used for vacuumizing cabin environment, coal rock cyclic air suction and exhaust and whole process pressure and flow monitoring, and air damage to coal rock specimen under expansion and shrinkage is realized.

[0025] Optionally, in the crack generation module, each servo pressurizing unit corresponding to one side of the long side of the specimen comprises two independently controlled electro-hydraulic servo actuators and one force transmission plate, and each servo pressurizing unit corresponding to one side of the short side of the specimen comprises one independently controlled electro-hydraulic servo actuator and one force transmission plate.

[0026] The force transmission plates are connected to the output ends of the actuators;

[0027] The side of the force transmission plate in contact with the coal rock specimen is integrated with a thin film pressure sensor array for real-time monitoring of the contact stress distribution and constituting a closed-loop feedback control of the servo pressurizing unit.

[0028] Optionally, the crack generation module further comprises an auxiliary heating system, and the auxiliary heating system comprises:

[0029] A closed fluid channel network is integrated in the force transmission plate;

[0030] A constant-temperature liquid circulating device is arranged on the bearing frame of the closed rigid cabin body, connected to the closed fluid channel network through a heat insulation pipeline, used for providing high-temperature heat conducting oil as a heating medium for the coal rock specimen, and controlling the temperature and flow of the heating medium to realize heating of the coal rock specimen.

[0031] Optionally, the crack detection module further comprises one or more groups of vertical comprehensive logging probes pre-buried in the coal rock specimen, and the probes and the resistivity probe array arranged on the force transmission plate work cooperatively to constitute a resistivity-acoustic wave combined three-dimensional detection network.

[0032] Optionally, the vertical comprehensive logging probe comprises a center tube made of insulating material;

[0033] The center tube is internally provided with a sound wave transducer, and the center tube is externally fixedly arranged with a ring electrode, and the ring electrode is electrically connected to the coal rock body through a conductive coupling medium.

[0034] Optionally, the intelligent feedback and data fusion module is used for receiving physical field data fed back by the crack detection module in real time, dynamically adjusting stress field, temperature field, atmosphere environment parameters of the crack generation module and injection parameters of the crack intervention module through a machine learning algorithm, and realizing adaptive intelligent feedback control of the test process.

[0035] The application also provides a coal fire zone crack active enhancement exploration test method based on the system, and the method comprises the following steps:

[0036] According to the preparation of the test piece and the system initialization, the thermal-mechanical-gas coupling crack evolution condition is obtained;

[0037] The thermal-mechanical-gas coupling crack evolution condition is simulated, the crack network of the coal rock mass is induced, and the first physical field data is synchronously collected;

[0038] Natural medium simulation objects are injected into the cracks, the second physical field data obtained by detection after injection is obtained, the first physical field data is compared with the second physical field data, and the physical signal weakening effect evaluation result is obtained;

[0039] Enhanced medium foam gel materials are injected into the cracks, the third physical field data obtained by detection after injection is obtained, the first physical field data, the second physical field data and the third physical field data are compared, and the crack and enhanced medium detection enhancement inversion result is obtained;

[0040] According to the physical signal weakening effect evaluation result and the crack and enhanced medium detection enhancement inversion result, four-dimensional dynamic visualization is carried out, and the whole process of crack evolution and detection is displayed or reproduced in real time.

[0041] Compared with the prior art, the present application has the following advantages and technical effects:

[0042] 1) The crack evolution module simulates the thermal-mechanical-gas coupling condition of the underground coal fire area through airtight rigid cabin, servo pressurizing unit, heating device and gas injection and control system, and induces the crack network of the coal rock mass. The module can accurately control the four-way stress, bottom heating and gas adsorption-desorption cycle, utilize the gas-induced damage effect, simulate the complex environment of the real coal fire area, and provide controllable experimental conditions for crack evolution.

[0043] 2) The crack detection module can realize real-time and synchronous collection of multi-physical field data through the sensor array arranged on the cabin and the coal rock mass test piece, including the resistivity probe array, acoustic emission sensor, acoustic wave emission and receiving transducer, resistance strain gauge, distributed optical fiber sensing network and magnetic force sensor. The module can realize high-precision monitoring of the crack evolution process, capture the initiation, expansion and penetration process of the crack, and provide detailed physical field data support for the detection of the whole process of crack evolution.

[0044] 3) The crack intervention module injects natural medium simulation objects and enhanced medium foam gel materials into the cracks through the fluid injection system. The natural medium simulation objects are used to simulate the complex crack filling environment of the real coal fire area and evaluate the weakening effect of the geophysical signal; the enhanced medium foam gel material is used to enhance the detection signal and improve the sensitivity and accuracy of crack detection. The module can effectively simulate the real environment and optimize the detection conditions, and provide a more reliable signal active enhancement basis for crack detection.

[0045] 4) The intelligent feedback and data fusion module synchronously collects detection data by controlling the operation parameters of each module, and performs fusion processing, intelligent inversion and four-dimensional visualization on the data. The module can real-time feedback the physical field data of the fracture evolution, dynamically adjust the operation parameters of each module, and realize adaptive intelligent feedback control of the test process. Through four-dimensional visualization technology, the fracture development process and channel morphology are intuitively presented, which provides a decision basis for coal fire area treatment.

[0046] The present application provides theoretical insights and technical support for the accurate delineation and targeted plugging of hidden fractures in coal fire areas, and solves the problems of multi-solution of traditional fracture detection and easy re-ignition of coal fire treatment. BRIEF DESCRIPTION OF DRAWINGS

[0047] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application and are incorporated in and constitute a part of this application. The embodiments of this application and its description together with the drawings make an enabling disclosure and those skilled in the art can readily practice the application by reading the disclosure in conjunction with the common general knowledge.

[0048] Figure 1 The structure diagram of the coal fire area fracture active enhancement detection test system of the embodiment of the present application is shown in the figure.

[0049] Figure 2 The flow chart of the coal fire area fracture active enhancement detection method of the embodiment of the present application is shown in the figure.

[0050] Figure 3 The vertical probe embedded in the coal rock mass test piece of the embodiment of the present application is shown in the figure.

[0051] Wherein: 1, sealed rigid cabin; 2, sensor array; 201, resistivity probe array; 202, acoustic emission and receiving transducer; 3, displacement pump; 4, vacuum pump; 5, electro-hydraulic servo actuator; 6, force transmission plate; 7, constant temperature liquid circulating device; 8, central tube; 9, coal tar; 10, flue gas condensate; 11, injection pump; 12, acoustic emission sensor. DETAILED DESCRIPTION

[0052] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0053] It should be noted that the steps shown in the flow chart of the accompanying drawings can be executed in a computer system such as a group of computer executable instructions, and although the logical order is shown in the flow chart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0054] Embodiment one

[0055] AsFigure 1 As shown, the present embodiment provides a coal fire zone fracture active enhancement exploration test system, comprising:

[0056] A fracture evolution module for simulating the heat-force-gas coupling conditions of the underground coal fire zone to induce the coal rock mass to generate fractures;

[0057] A fracture detection module for real-time and synchronous acquisition of multi-physical field data to monitor the evolution process of the fractures;

[0058] A fracture intervention module for injecting natural medium simulators and enhanced medium foam gel materials into the fractures to simulate the real environment and enhance the detection signal;

[0059] An intelligent feedback and data fusion module for controlling the operating parameters of each module, synchronously acquiring the detection data, and performing fusion processing, intelligent inversion, and four-dimensional visualization on the detection data to realize the whole-process monitoring of the fracture evolution.

[0060] The fracture evolution module can be implemented to reconstruct and accurately control the real underground coal fire environment in the laboratory to actively induce the coal rock mass fractures. It comprises a sealed rigid cabin 1 for accommodating a cuboid coal rock mass test piece with a size of 2.0x1.0x1.0m. The cabin is installed on a rigid bearing frame, and independent servo pressurizing units are arranged in the five orthogonal directions except the bottom surface to apply independently controllable four-face stress to the test piece, constituting a force acting part. A heating device is arranged at the bottom of the cabin to provide a heat source from the bottom of the test piece, constituting a heat acting part. The cabin is connected with a gas injection and control system for injecting gases including CH4 and CO2 into the cabin and controlling the adsorption and release process through programming, constituting a gas acting part.

[0061] Further, the rigid bearing frame and the sealed rigid cabin 1 can be preferably arranged as a whole in the underground bedrock slot and coupled with the bedrock through a vibration isolation foundation to further improve the stability and anti-interference ability of the system.

[0062] Further, each servo pressurizing unit corresponding to one side of the long side of the coal rock mass test piece in the fracture evolution module comprises two independently controlled electro-hydraulic servo actuators 5 and a force transmission plate 6, and each servo pressurizing unit corresponding to the short side comprises one independently controlled electro-hydraulic servo actuator 5 and one force transmission plate 6. The output ends of the actuators are connected to the force transmission plate 6.

[0063] Further, the force transmission plate 6 is a flexible plate made of flexible composite material, or a pressure head matrix composed of multiple pressure heads that can independently fine-tune the pressure.

[0064] Further, the force transmission platen 6 is integrated with a thin film pressure sensor array 2 on the side in contact with the coal rock mass specimen, for real-time monitoring of the contact stress distribution and constituting a closed-loop feedback control of the servo-pressurization unit.

[0065] Further, the gas injection and control system in the fracture evolution module is specifically configured to: through programmed control of the pressure of the injected gas and the number of adsorption-discharge cycles, utilize the matrix expansion and contraction effects generated by the repeated adsorption and discharge processes of CH4, CO2 and other gases in the pores and fractures of the coal rock mass, to achieve gas-induced damage to the coal rock mass.

[0066] As an optional implementation, the gas injection and control system includes a mass flow controller, a displacement pump 3 and a vacuum pump 4, which can realize the vacuumization of the cabin environment, gas injection, and pressure and flow monitoring throughout the adsorption / discharge process.

[0067] Further, the fracture evolution module also includes an auxiliary heating system, which includes: a closed fluid channel network integrated inside the force transmission platen 6; a constant temperature liquid circulation device 7 provided on the rigid bearing frame, connected to the fluid channel network through a heat insulation pipeline; the constant temperature liquid circulation device 7 can provide high temperature heat conducting oil as a heating medium and accurately control its temperature and flow, thereby achieving uniform and stable heating of the coal rock mass specimen.

[0068] The fracture detection module can be implemented, including a sensor array 2 distributedly arranged on the cabin and the coal rock mass specimen, the sensor array 2 including: a resistivity probe array 201 arranged on the pressurization unit and embedded in the specimen, for high-density resistivity method measurement and resistivity tomography imaging; acoustic emission sensors 12 arranged on the surface of the specimen, and acoustic emission and reception transducers 202 installed on the pressurization unit and embedded in the fixed device in the specimen; resistance strain gauges arranged on key areas on the surface of the specimen; a distributed optical fiber sensing network arranged inside and on the surface of the specimen; magnetic force sensors arranged on the inner wall of the cabin.

[0069] Further, as shown in Figure 3 The fracture detection module also includes one or more sets of vertical comprehensive logging probes embedded in the interior of the coal rock mass specimen; the comprehensive logging probes are integrated with one or more sets of ring electrodes for resistivity measurement and acoustic wave transducers for acoustic wave measurement arranged along the axial direction of the probes; the probes work cooperatively with the sensor array 2 arranged on the force transmission platen 6 to constitute a resistivity-acoustic wave combined three-dimensional detection network.

[0070] Further, the vertical comprehensive logging probe includes a center tube 8 made of insulating material, and the acoustic transducer is sealingly installed in the center tube 8; the outer portion of the center tube 8 is fixedly arranged with the annular electrode; the probe is integrated with the coal rock body test piece through a layer of conductive coupling medium which is consolidated with the coal rock body, and the annular electrode establishes electrical connection with the coal rock body through the conductive coupling medium.

[0071] Further, the resistivity probe array 201 of the fracture detection module is arranged on each force transfer plate 6 in a two-dimensional grid form, and together with the vertical probes embedded in the coal rock body test piece, forms a three-dimensional detection network; the intelligent feedback and data fusion module is configured to control the three-dimensional network to collect data, and based on the electrical resistivity tomography algorithm, to obtain a three-dimensional distribution image of the internal resistivity of the coal rock body.

[0072] Implementable, the fracture intervention module includes a fluid injection system in communication with the cabin, and the system is configured to be capable of: injecting natural medium simulation objects including residual coal tar 9, flue gas condensate 10, broken coal rock chips, gas or liquid water into the fractures formed by the fracture generation module for simulating real environment; and / or injecting enhanced medium foam gel material for changing geophysical response characteristics into the fractures.

[0073] Further, the enhanced medium foam gel material includes the following components in terms of total mass percentage of base fluid: 0.5% to 10% of conductive material; 5% to 30% of magnetic particles; 0.1% to 5% of foaming agent; 0.05% to 2% of foam stabilizer; the balance being water and water-soluble polymer dispersant; the conductivity of the material after foaming and solidification is not less than 1 S / m, and / or the saturation magnetization is not less than 10 emu / g.

[0074] Further, the fluid injection system of the fracture intervention module includes at least one high-precision servo-driven injection pump 11, capable of performing constant pressure injection, constant current injection and pulse injection modes.

[0075] Implementable, the intelligent feedback and data fusion module is in communication connection with the fracture generation module, the fracture detection module and the fracture intervention module, for controlling the operating parameters of each module, synchronously collecting detection data, and performing fusion processing, intelligent inversion and four-dimensional visualization on the data.

[0076] Further, the intelligent feedback and data fusion module is configured to: based on the physical field data fed back in real time by the fracture detection module, dynamically adjust the stress field, temperature field, atmosphere environment parameters of the fracture generation module and the injection parameters of the fracture intervention module through a machine learning algorithm, to realize adaptive intelligent feedback control of the test process.

[0077] Further, the intelligent feedback and data fusion module includes a four-dimensional visualization unit for mapping the multi-physical field data after fusion processing to a three-dimensional geometric model of the coal rock mass specimen, dynamically displaying the time-space evolution process of crack initiation, expansion, penetration and fluid migration, and forming a digital twin.

[0078] As shown in Figure 2 the same overall inventive concept, the present application also provides a method for coal fire zone crack evolution simulation and active enhancement detection, comprising the following steps:

[0079] (1) Specimen preparation and system initialization: place the 2.0x1.0x1.0m cuboid coal rock mass specimen in the sealed rigid cabin 1, and arrange various sensors of the crack detection module;

[0080] (2) Thermal-mechanical-gas coupling crack initiation: through the crack initiation module, four-face stress and bottom heating are applied in sequence or coupling, and the adsorption-desorption cycle of CH4 and CO2 gas is controlled by program, using gas-induced damage effect, to simulate the thermal-mechanical-gas coupling conditions of underground coal fire zone and induce crack network in coal rock mass;

[0081] (3) In-situ synchronous detection of multiple physical fields: during the whole process of crack initiation, the crack detection module is used to collect real-time and synchronous first physical field data such as resistivity, acoustic emission, ultrasonic wave, temperature, strain and magnetic signal;

[0082] (4) Natural crack environment simulation and weakening effect evaluation: through the crack intervention module, natural medium simulation objects are injected into the crack network formed in step (2) to simulate the complex crack filling environment of real coal fire zone, and based on the comparison of the first physical field data in step (3) and the second physical field data obtained after injection, the weakening effect of geophysical signal is evaluated;

[0083] (5) Active enhancement detection: through the crack intervention module, enhanced medium foam gel material is injected into the crack network;

[0084] (6) Enhanced signal acquisition and comparison inversion: third physical field data are obtained by detection again, and the first, second and third physical field data are compared to quantitatively evaluate the geometric characteristics, spatial distribution of cracks and the detection enhancement effect of the enhanced medium;

[0085] (7) Four-dimensional dynamic visualization: through the intelligent feedback and data fusion module, the four-dimensional dynamic model of the whole process of crack evolution and detection is displayed or reproduced in real time.

[0086] Example Two

[0087] The embodiment provides a coal fire zone fracture active enhancement exploration test system, which comprises the following four core modules: a fracture evolution module, a fracture detection module, a fracture intervention module and an intelligent feedback and data fusion module.

[0088] The fracture evolution module is used for reconstructing and accurately controlling a real underground coal fire environment in a laboratory and actively inducing coal rock mass fractures. The core is a sealed rigid cabin 1 for accommodating a cuboid coal rock mass test piece with a size of 2.0*1.0*1.0 m. The cabin is fixed on a rigid bearing frame through bolts. The module integrates three independent physical and chemical action mechanisms.

[0089] The force acting part is provided with independent servo pressurizing units in five orthogonal directions except the bottom surface of the cabin. The pressurizing unit corresponding to one side of the long edge of the test piece comprises two independently controlled electro-hydraulic servo actuators 5 and a force transmission plate 6. The pressurizing unit corresponding to one side of the short edge comprises an independently controlled electro-hydraulic servo actuator 5 and a force transmission plate 6. The rated output of the actuator is greater than or equal to 500 kN, the stroke is greater than or equal to 200 mm, the control accuracy is ±0.5 % FS, the size of the plate matches the corresponding surface of the cabin, the thickness can be randomly changed, the output end of the actuator is connected to the force transmission plate 6 through a spherical hinge joint, and uniform pressure transmission is ensured. The force transmission plate 6 can be selected as two types: one is a flexible plate made of flexible composite material, which can adapt to the unevenness of the surface of the coal rock mass test piece, and the other is a pressure head matrix composed of multiple pressure heads that can independently adjust the pressure, which can realize accurate application of a non-uniform stress field. The side of the force transmission plate 6 in contact with the coal rock mass test piece is integrated with a thin film pressure sensor array 2 for real-time monitoring of the contact stress distribution and constitutes a closed-loop feedback control of the servo pressurizing unit, so that the deviation of the applied stress from the set value is less than 3 %.

[0090] The heat acting part comprises a main heating device and an auxiliary heating system. The main heating device is arranged at the bottom of the cabin and adopts a present stepped heating type armored electric heating pipe to simulate the burning path of the coal fire from bottom to top. The auxiliary heating system comprises a sealed fluid channel network integrated in the force transmission plate 6 and a constant-temperature liquid circulating device 7 arranged on the rigid bearing frame. The constant-temperature liquid circulating device 7 is connected with the fluid channel network through a high-temperature-resistant heat insulation pipeline and can provide high-temperature heat conducting oil as a heating medium and accurately control the flow through a frequency conversion pump, so as to realize uniform and stable heating of the coal rock mass test piece.

[0091] The gas acting part is connected with the gas injection and control system through the flange interface, and is used for programmed injection of CH4, CO2 and other gases into the cabin and control of the pressure and adsorption-discharge cycle. The gas injection and control system includes a mass flow controller, a displacement pump 3 and a vacuum pump 4, and can realize the vacuumization of the cabin environment, the gas injection and the pressure and flow monitoring of the whole adsorption-discharge process. Through the programmed control of the pressure (0-10 MPa adjustable) of the injected gas and the adsorption-discharge cycle times (0-10 times adjustable, and the single cycle time is 1-72 hours controllable), the matrix expansion and shrinkage effect generated by the repeated adsorption and discharge process of CH4, CO2 and other gases in the pores and fissures of the coal rock body is utilized, the gas-induced damage to the coal rock body is realized, and the long-term effect of the real coal fire area gas on the coal rock is simulated.

[0092] In addition, the rigid bearing frame and the sealed rigid cabin body 1 can be preferably arranged as a whole in the underground bedrock groove (the bedrock groove depth is greater than or equal to 2 m, the periphery is reinforced by pouring C30 concrete, and is coupled with the bedrock through a vibration isolation foundation (the vibration isolation foundation adopts a spring-damping vibration isolation system, the natural frequency is less than or equal to 5 Hz, and the damping ratio is 0.05-0.1), which effectively isolates external vibration interference (the vibration attenuation rate is greater than or equal to 90%), and further improves the stability and anti-interference ability of the system.

[0093] The crack detection module is used for in-situ, real-time and stereoscopic transparent observation of the whole process of crack evolution, and the sampling frequency can be set to 0.1-1000 Hz according to the detection type. The core is a distributed, multi-physical field sensor array 2, which specifically includes:

[0094] The resistivity detection array is arranged in a two-dimensional grid form (grid spacing 20-50 mm) on each force transmission plate 6, and together with the vertical probe (probe material is brass, diameter 2-5 mm, length 100-200 mm, and pre-embedded spacing 50-100 mm) pre-embedded in the coal rock body sample forms a three-dimensional detection network. The resistivity probe array 201 is connected to a high-precision resistivity instrument or a resistivity tomography acquisition module, and is used for high-density resistivity measurement and three-dimensional resistivity tomography. The resistivity probe array 201 can capture the change of the resistivity inside the coal rock body in real time, so as to invert the generation and expansion of the crack.

[0095] Acoustic detection array, including acoustic emission sensor 12 and acoustic transducer. The acoustic emission sensor 12 (resonant frequency 100-300 kHz, sensitivity ≥80 dB, preamplification 40 dB) is pasted on the surface of the test piece through high-temperature coupling agent, and is used for monitoring the micro-fracture events generated in the crack initiation and expansion process of the coal rock mass; the acoustic transducer is divided into two parts, one part is installed on each pressure plate 6 of the pressure unit, and 4-8 pressure plates are arranged on each pressure plate, and the other part is embedded in the fixing device in the test piece, and the fixing device is made of high-temperature-resistant ceramic, and the temperature resistance is ≥500 DEG C, so as to form a multi-channel acoustic emission and receiving network, which is used for actively emitting and receiving acoustic signals, and the development degree of the crack is evaluated through the analysis of the changes of acoustic wave velocity, amplitude and attenuation coefficient, that is, through the acoustic emission combined detection technology.

[0096] The resistance strain gauge is arranged on the surface of the test piece. The distributed optical fiber sensing network is made of high-temperature-resistant quartz optical fiber and is arranged in a pre-embedded or surface-pasted manner, and is connected to a distributed optical fiber strain meter and a distributed optical fiber temperature meter, which is used for continuously and accurately measuring the fine space-time distribution of the internal temperature and strain field of the test piece, and capturing the local strain concentration and temperature anomaly caused by crack expansion.

[0097] Magnetic force sensor, high-sensitivity Hall effect magnetic force sensor is used, which is fixedly arranged on the inner wall of the cabin through a support, 4-8 are arranged on each cabin wall, and the distance from the test piece surface is 50-100 mm), which is used for monitoring the magnetic anomaly signal caused by high temperature and magnetic enhanced medium injection, and realizing double verification of the distribution of the enhanced medium in the crack in combination with the resistivity signal.

[0098] Vertical comprehensive logging probe: the crack detection module further includes one or more groups of vertical comprehensive logging probes embedded in the coal rock test piece; the comprehensive logging probe is integrated with one or more groups of ring electrodes for resistivity measurement and acoustic transducers for acoustic wave measurement arranged along the axial direction of the probe; the probe cooperates with the sensor array 2 arranged on the force transmission plate 6 to form a resistivity-acoustic wave combined three-dimensional detection network. The vertical comprehensive logging probe includes a center pipe 8 made of insulating material, and the acoustic transducer is sealedly installed in the center pipe 8; the ring electrodes are fixedly arranged outside the center pipe 8; the probe is integrated with the coal rock test piece through a layer of conductive coupling medium which is consolidated with the coal rock, and the ring electrodes are electrically connected with the coal rock through the conductive coupling medium.

[0099] The fracture intervention module is used to change the physical properties of the fracture to optimize the detection or simulate the real environment. It includes a set of high-precision fluid injection system, which includes at least one high-precision servo-driven injection pump 11, which can perform constant pressure injection (pressure range 0-15 MPa, control accuracy ±0.1 MPa), constant flow injection (flow range 0.1-100 mL / min, control accuracy ±0.01 mL / min) and pulse injection (pulse frequency 0-10 Hz, pulse pressure difference 0-10 MPa) three modes, the system is configured to be able to perform two function modes:

[0100] The environment simulation mode injects natural medium simulation objects for simulating the real environment into the generated fracture, including: residual coal tar 9 simulation object, using a mixture of residual tar and gas quality condensate tar (mass ratio 1:1-5:1), the viscosity can be adjusted by temperature; flue gas condensate 10 simulation object, made of 5%-15% carbon black, 1%-5% sodium sulfide and water, solid content 10%-30%; broken coal debris, coal particles of the same material and particle size of 0.1-5 mm of the test specimen coal rock, injected by dry mixing or mixed with water, coal debris volume fraction 10%-50%; gas or liquid water, gas uses air or N2, liquid water uses deionized water or rainwater. By injecting the above natural medium, the complex fracture filling environment of the real coal fire area is simulated, and the weakening effect of different filling types, content and distribution on the geophysical signal is quantitatively studied, such as resistivity signal attenuation rate, acoustic signal attenuation coefficient, etc.

[0101] The active enhancement mode injects an enhanced medium foam gel material for changing the geophysical response characteristics into the fracture, which includes the following components by total mass percentage: conductive material (0.5%-10%) can be selected from one or more of graphene, carbon black or carbon fiber mixture, which ensures that the material has excellent conductivity after solidification; magnetic particles (5%-30%) can be selected from one of four iron oxide, neodymium iron boron or carbonyl iron, which gives the material strong magnetic response characteristics; foaming agent (0.1%-5%) uses sodium dodecyl sulfate or fatty alcohol polyoxyethylene ether sulfate to foam by mechanical stirring; foam stabilizer selects guar gum or xanthan gum to prolong the half-life of the foam and avoid the decrease of material density caused by bubble rupture; the rest is water and water-soluble polymer dispersant, which can prevent the agglomeration of conductive material and magnetic particles and ensure the uniformity of material performance. The conductivity of the enhanced medium foam gel material is not less than 1 S / m and / or the saturation magnetization is not less than 10 emu / g after foaming and solidification for 2-8 h, which can significantly amplify the resistivity and magnetic signal response of the target body of the fracture, solving the problem of low signal-to-noise ratio in micro-fracture detection.

[0102] In addition, the fracture intervention module also includes a medium recovery and monitoring subsystem: through the bottom of the cabin equipped with a discharge outlet of the stop valve and filter to recover the unfilled medium, avoiding waste and pollution; at the same time, a pressure sensor and a flow sensor are arranged in the injection pipeline to monitor the pressure fluctuation and flow change of the injection process in real time, to determine the migration state of the medium in the fracture, such as whether the blockage occurs or whether the fracture is full.

[0103] The intelligent feedback and data fusion module, as the central nervous system of the system, is connected with each module through an industrial bus and has the following core functions:

[0104] Multi-module collaborative control, 10-20 typical coal fire zone working condition parameters are preset, which can be directly called or customized parameters; through the PLC controller, control instructions are sent to each module to synchronously control the stress loading rate of the fracture evolution module, the heating temperature, the gas injection pressure, the sampling frequency of the fracture detection module, and the injection mode and injection amount of the fracture intervention module, and the response time of the control instruction is less than 100 ms, ensuring the timing synchronization of each module.

[0105] Adaptive intelligent feedback: based on the multi-physical field data such as resistivity, acoustic emission event number, acoustic wave velocity, and magnetic signal intensity, which are fed back by the fracture detection module in real time, through the built-in machine learning algorithm such as random forest and neural network, the model training sample size is greater than or equal to 1000 groups, the operating parameters are dynamically adjusted: if the fracture detection module monitors that the fracture propagation rate is less than 0.1 mm / h, the heating temperature or the gas injection pressure of the fracture evolution module is automatically increased to accelerate the fracture evolution; if the magnetic signal intensity is increased by less than 3 times after the fracture intervention module injects the enhanced medium, the proportion of magnetic particles in the base fluid is automatically increased (the increase range is 1%-5%) or the injection pressure is increased (the increase range is 0.5-1 MPa), to ensure the enhancement effect; the feedback adjustment period can be set to 1-10 minutes, to realize adaptive optimization of the test process and reduce manual intervention, so that the best experimental working condition can be obtained.

[0106] Data fusion and intelligent inversion: first, the multi-source data collected by the fracture detection module are preprocessed, the resistivity data are denoised, the acoustic emission data are event positioned and parameter extracted, and the acoustic wave data are velocity corrected; then, through the data fusion algorithm (such as D-S evidence theory and Kalman filter), the preprocessed resistivity, acoustic emission, acoustic wave, and magnetic signal data are fused to construct a multi-physical field coupled data set; based on the electrical resistivity tomography algorithm and the acoustic wave tomography algorithm, the three-dimensional spatial distribution, geometric morphology, and connectivity of the fracture inside the coal rock mass are inversed.

[0107] Four-dimensional visualization and digital twin, the integrated four-dimensional visualization unit, associates the multi-physical field data after fusion processing with the three-dimensional geometric model of the coal rock mass specimen (constructed according to a 1:1 scale), and dynamically displays the spatio-temporal evolution process of crack initiation (from micro-pore to micro-crack, pore size 1-100 μm), propagation (crack length from <10 mm to >100 mm), penetration (forming a connected network, with a connected path number ≥3), and fluid migration (medium migration speed in the crack 0.1-10 mm / min, filling range real-time display), with a time step that can be set to 1-60 s. At the same time, the digital twin of the test process is constructed, realizing real-time synchronization of physical testing and digital modeling: the physical field distribution (such as temperature field, stress field, medium concentration field) of any cross section inside the specimen can be viewed through the digital twin, and different working conditions can also be simulated by modifying the digital model parameters (such as increasing the number of cracks, adjusting the medium viscosity), predicting the physical test results, and guiding the optimization of the test scheme.

[0108] A coal fire zone crack active enhancement detection method based on the coal fire zone crack active enhancement test system described above, comprising the following steps:

[0109] (1) Specimen preparation and system initialization: prepare a cubic meter level coal rock mass specimen and place it in the cabin, and simultaneously arrange the integrated internal and external sensor array 2.

[0110] (2) Thermal-mechanical-gas coupled crack evolution: through the crack evolution module, coupled with the application of four-sided non-uniform stress, bottom gradient heating and programmed gas adsorption-desorption cycle, the complex environment of underground coal fire zone is simulated, and the crack network is actively induced.

[0111] (3) In-situ synchronous detection of multiple physical fields: During the entire evolution process, the crack detection module is used to collect real-time, synchronous full-field physical field data such as electricity, sound, heat, magnetism, and strain.

[0112] (4) Natural crack environment simulation and weakening evaluation: The crack intervention module is used to inject natural medium simulation materials into the crack to evaluate the weakening effect of complex filling environment on geophysical signals and establish a background-interference response model.

[0113] (5) Active enhancement detection: The crack intervention module is used to inject enhanced medium foam gel material into the crack.

[0114] (6) Enhanced signal comparison and intelligent inversion: The crack detection module is used again for detection, the intelligent feedback and data fusion module is used for comparative analysis of the data before and after enhancement, and the intelligent inversion algorithm is used to accurately quantify the geometric characteristics and spatial distribution of the crack.

[0115] (7) Four-dimensional dynamic visualization and verification: Through the intelligent feedback and data fusion module, the whole process dynamic model from crack initiation to accurate detection is displayed or reproduced in real time, forming a digital twin body synchronized with the physical test, which is used for result verification and mechanism analysis.

[0116] Compared with the prior art, the embodiment realizes:

[0117] (1) From blind to transparent observation: The observation of coal and rock mass cracks in the prior art is mostly surface monitoring or discrete point measurement, such as single-point acoustic emission, local resistivity testing, which cannot cover the whole life cycle of cracks. The embodiment realizes the in-situ, real-time, three-dimensional and dynamic CT observation of the whole life cycle of crack initiation (micro-pore expansion) - expansion - penetration (forming a connected network) - filling (medium migration) in large rock mass experiments through the built-in, multi-dimensional in-situ sensing network, especially the cooperation of pre-embedded resistivity-acoustic wave joint probe and distributed optical fiber, which provides continuous and refined data support for the crack channel evolution mechanism research in coal fire area which cannot be realized by the prior art.

[0118] (2) Create a new paradigm of active enhancement detection: Traditional geophysical detection relies on the differences in physical properties of coal and rock mass, such as natural resistivity, acoustic impedance, which is seriously weakened in complex coal fire area such as coal tar and smoke condensate, and the signal-to-noise ratio is generally less than 5:1, making it difficult to identify hidden cracks. The embodiment injects specially designed enhanced medium foam gel material into the cracks, converting passive reception of weak signals into active creation of strong anomalies, increasing the amplitude of resistivity signal by 5-100 times and the strength of magnetic signal by 5-50 times, which fundamentally solves the core bottleneck of low detection accuracy of hidden target bodies in complex background.

[0119] (3) Build an integrated research platform of multi-field coupling and multi-module cooperation: Existing coal fire simulation devices can only realize a single physical field, and the detection and intervention modules are independent of each other, requiring multiple devices to be used together, with poor test consistency. The embodiment integrates four-sided gradient stress loading, bottom-circumferential cooperative heating, gas programmed damage, multi-physical field synchronous detection, intelligent fluid injection and closed-loop control for the first time, which can complete the whole chain test of environment simulation - crack initiation - detection verification - intervention optimization in one system, avoiding the error accumulation of multiple device combination, greatly improving the test efficiency compared with the prior art, and can reproduce typical coal fire conditions of different mines, and the platform is significantly better than the existing single-function device in terms of universality.

[0120] (4) Realize the intelligent upgrade of adaptive control-four-dimensional visualization: The existing test device needs to be adjusted frequently by manual, and the data is presented in the form of table, which is difficult to intuitively correlate the fracture evolution process. Through the machine learning algorithm of intelligent feedback and data fusion module, the working condition parameters can be dynamically adjusted based on real-time detection data in this embodiment; at the same time, through four-dimensional digital twinning, the massive data is converted into a dynamic visualization model of fracture initiation and expansion, medium migration, and the temperature field and stress field distribution of any section can be directly observed, which builds a data-application transformation bridge from laboratory mechanism research to field engineering decision (such as optimization of sealing material dosage).

[0121] (5) Wide application value of cross-field expansion-high efficiency transformation: The system and method not only directly solve the problem of fracture detection and accurate sealing in coal fire area, but also have significant ecological benefits; in addition, multi-field coupling simulation, active enhancement detection and digital twinning can be directly expanded to the fields of oil and gas shale gas hydraulic fracturing monitoring, geothermal development reservoir evaluation, CO2 geological storage, radioactive waste disposal, etc., which has high popularization value and potential cross-industry social benefits.

[0122] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any skilled person in the art can easily think of changes or replacements within the technical scope disclosed in the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A coal fire zone fracture active enhancement exploration test system, characterized in that, The system comprises: a fracture evolution module for simulating the thermal-mechanical-gas coupling conditions of an underground coal fire zone to induce fractures in a coal rock specimen; a fracture detection module for real-time and synchronous acquisition of multi-physical field data of the coal rock specimen; a fracture intervention module for injecting natural medium simulators and enhanced medium foam gel materials into the fractures to simulate real environments and enhance detection signals; natural medium simulators for simulating real environments are injected into the fractures formed by the fracture evolution module, including residual coal tar, smoke condensate, broken coal rock debris, gas or liquid water; and / or enhanced medium foam gel materials for changing geophysical response characteristics are injected into the fractures; the enhanced medium foam gel material comprises, in terms of total mass percentage of base fluid, the following components: 0.5%-10% of conductive material; 5%-30% of magnetic particles; 0.1%-5% of foaming agent; 0.05%-2% of foam stabilizer; and the balance of water and water-soluble polymer dispersant; an intelligent feedback and data fusion module for controlling the operating parameters of each module, synchronously acquiring detection data, and performing fusion processing, intelligent inversion and four-dimensional visualization on the detection data to realize geometric characteristic monitoring of the whole process of fracture evolution; the fracture evolution module comprises: a sealed rigid cabin for accommodating a cuboid coal rock specimen; a servo pressurizing unit installed on a load-bearing frame of the sealed rigid cabin for applying independently controlled four-face stress to the specimen to form a force acting part; a heating device arranged at the bottom of the sealed rigid cabin for providing a heat source from the bottom of the specimen to form a heat acting part; a gas injection and control system connected to the sealed rigid cabin for injecting gas into the cabin and controlling the gas circulation adsorption and release process to form a gas acting part.

2. The system according to claim 1, wherein the fracture detection module comprises a sensor array arranged on the sealed rigid cabin and the coal rock specimen, and the sensor array comprises: a resistivity probe array for high-density resistivity method measurement and resistivity tomography imaging; an acoustic emission sensor for monitoring acoustic emission signals in the process of fracture initiation and expansion; an acoustic wave emission and receiving transducer for emitting and receiving acoustic wave signals; an electrical resistance strain gauge for measuring strain; a distributed optical fiber sensing network for measuring temperature and strain; a magnetic force sensor for monitoring magnetic signals.

3. The system according to claim 1, wherein the fracture evolution module comprises a gas injection and control system, and the gas injection and control system comprises: a vacuum pump, a displacement pump and a mass flow controller for vacuumizing the cabin environment, coal rock circulation adsorption and release, and pressure and flow monitoring throughout the process to realize gas-induced damage of the coal rock specimen under expansion and contraction.

4. The coal fire zone fracture active enhancement detection test system according to claim 1, wherein each servo pressurizing unit corresponding to one side of the long edge of the specimen in the fracture evolution module comprises two independently controlled electro-hydraulic servo actuators and one force transmission plate; and each servo pressurizing unit corresponding to one side of the short edge of the specimen comprises one independently controlled electro-hydraulic servo actuator and one force transmission plate. The force transmission platen is connected to the output end of the actuator; The force transmission platen is integrated with a thin film pressure sensor array on the side in contact with the coal rock mass specimen, which is used to monitor the contact stress distribution in real time and constitute a closed-loop feedback control for the servo pressurizing unit.

5. The system of claim 4, wherein, The fracture evolution module further comprises an auxiliary heating system, which comprises: A sealed fluid channel network integrated in the force transmission platen; A constant-temperature liquid circulating device arranged on the load-bearing frame of the sealed rigid cabin, connected to the sealed fluid channel network through a heat insulation pipeline, used to provide high-temperature heat transfer oil as a heating medium for the coal rock mass specimen, and control the temperature and flow of the heating medium to heat the coal rock mass specimen.

6. The system of claim 2, wherein, The fracture detection module further comprises one or more groups of vertical comprehensive logging probes pre-buried in the coal rock mass specimen, which work cooperatively with the resistivity probe array arranged on the force transmission platen to form a resistivity-acoustic combined three-dimensional detection network.

7. The system of claim 6, wherein, The vertical comprehensive logging probe comprises a center tube made of insulating material; The center tube is internally provided with a sound wave transducer, and externally fixed with a ring electrode, which is electrically connected to the coal rock mass through a conductive coupling medium.

8. The system of claim 1, wherein, The intelligent feedback and data fusion module is used to receive the physical field data fed back by the fracture detection module in real time, dynamically adjust the stress field, temperature field, atmosphere environment parameters of the fracture evolution module and the injection parameters of the fracture intervention module through a machine learning algorithm, and realize adaptive intelligent feedback control of the test process.

9. A coal fire zone fracture active enhancement exploration test method, characterized in that, The system based on any one of claims 1-8, the method comprising the following steps: According to the specimen preparation and system initialization, obtain the thermal-mechanical-gas coupling fracture evolution conditions; Simulate the thermal-mechanical-gas coupling fracture evolution conditions to induce the coal rock mass to generate a fracture network, and synchronously collect first physical field data; Inject natural medium simulators into the fractures to obtain second physical field data detected after injection, compare the first physical field data with the second physical field data, and obtain the physical signal weakening effect evaluation results; Inject enhanced medium foam gel materials into the fractures to obtain third physical field data detected after injection, compare the first physical field data, the second physical field data and the third physical field data, and obtain the fracture and enhanced medium detection enhancement inversion results; According to the physical signal weakening effect evaluation results and the fracture and enhanced medium detection enhancement inversion results, perform four-dimensional dynamic visualization to display or reproduce the whole process of fracture evolution and detection in real time.

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