An experimental device and method for the combustion evolution of large-scale coalfield fire areas

Abstract

The present invention relates to the field of prevention and control of coalfield fires, and discloses a large-scale experimental device and method for the combustion evolution of coalfield fire areas. For coalfield fire areas under complex strata outcrop conditions, the device constructs a three-dimensional physical similarity model, sets up a fire source ignition device, a gas flow and pressure control unit, and a multi-factor coupling monitoring module including a temperature sensing device, a humidity monitoring device, a pressure sensor, and a gas sampling port. By collecting real-time multi-dimensional spatio-temporal distribution data of "fire-water-soil-gas", comprehensively analyzing the combustion center temperature, the combustion spread speed, the distribution of overlying rock fractures, the moisture change, and the gas migration law, and then constructing a combustion evolution control prediction model for coalfield fire areas under multi-factor interference, the intelligent prediction of the combustion evolution process of the fire area is realized. The present invention can accurately simulate the real combustion environment of large-scale outcrop coalfield fire areas, reveal the multi-factor interference mechanism of the combustion evolution of typical coalfield fire areas, and provide a scientific basis and technical support for the prevention and control of coalfield fire areas.

Description

Technical Field

[0001] The present invention relates to the fields of prevention and control of coalfield fires, protection of coal resources and their disaster management, and relates to, but is not limited to, a large-size experimental device and method for combustion evolution of coalfield fire areas. Background Art

[0002] In the northwest region of China, the distribution of shallow-buried coal seams and exposed coal seams is relatively concentrated. The external climate is dry and windy, ground fissures are developed, and coalfield fires are prone to occur and are difficult to completely control. In addition, traditional fire-fighting methods such as stripping, covering with loess, water injection and grouting often have limitations in practical applications, and it is difficult to provide a systematic treatment plan for the combustion mechanism under the coupling of multiple factors. Therefore, in-depth study of the combustion evolution law of coalfield fire areas, especially the establishment of a large-size test platform to simulate the process of multi-factor coupling of "fire-water-soil-air", and the proposal of a scientific and perfect self-heating combustion determination criterion are of great significance for guiding the prevention and control of coalfield fires and ensuring the safe utilization of coal resources.

[0003] At present, the research on the combustion evolution process of coalfield fire areas mainly focuses on establishing small-size or medium-size similarity simulation test benches. The core idea is to construct a physical similarity model including an underlying heat-insulating layer, a coal seam and multiple overlying rock layers in a simulation test box, and simulate the real coalfield fire area combustion environment through heating rods. Some research work uses numerical simulation software to conduct numerical analysis on the temperature field, fissure seepage and overlying rock deformation of coalfield fire areas, and analyze the combustion spread law of coalfield fire areas to provide reference for fire control and resource protection. By arranging temperature sensing devices, gas collection equipment and pressure monitoring systems in the coalfield fire area, the location and temperature of the combustion fire source are tracked, and on-site treatment is carried out in combination with measures such as stripping, water injection or covering and isolation. Some research uses technologies such as unmanned aerial vehicle infrared detection to realize the monitoring of the surface temperature field of large-area coalfield fire areas. There are still the following deficiencies:

[0004] (1) Most of the research uses small-size or medium-size experimental models, which cannot completely simulate the large-scale geological structure, fissure network and complex overlying rock movement process of the actual coalfield fire area, and it is difficult to reflect the dynamic evolution of the fire area in the real environment.

[0005] (2) Insufficient multi-factor coupling. Existing test devices usually only simulate single or a few influencing factors, such as air leakage pressure, local moisture content or temperature field distribution, etc. For the actual situation of the comprehensive interference of coalfield fire areas by multiple factors such as air flow, surface water, meteorological environment, fissure channels, and rock layer collapse, there is still a lack of a systematic coupling experimental research platform.

[0006] (3) At present, the research on the combustion characteristics of coalfield fire areas mainly focuses on the low-temperature oxidation process under different oxygen concentrations, with less research on oxygen-deficient oxidation at high temperatures, and insufficient quantitative analysis of combustion characteristics such as oxygen consumption, combustion rate, and gas products during high-temperature combustion. In terms of the pore fissures in the overlying strata of coalfield fire areas, domestic and foreign research mainly focuses on the strength and mechanics during the thermal damage process of coal and rock, with less research on the movement and evolution law of overlying strata during the continuous combustion process of coal seams in fire areas. In existing research, the relevant results of fire spread in fire areas are mainly estimated through surface parameters, lacking research on how air leakage affects the spread of the combustion center, and at the same time, less research on the combustion evolution characteristics of coalfield fire areas under the coupling interference feedback of multiple factors.

[0007] In summary, although the existing technology has accumulated a certain experimental and theoretical basis, it still lacks sufficient originality and comprehensiveness to solve the problems of multi-factor coupling and large-scale simulation in the actual combustion evolution process of coalfield fire areas. Summary of the Invention

[0008] In view of this, the embodiments of the present invention provide a large-scale experimental device and method for the combustion evolution of coalfield fire areas, to study the spatio-temporal distribution characteristics of "fire-water-soil-air" in coalfield fire areas, construct a control prediction model for the combustion evolution of coalfield fire areas under multi-factor interference, reveal the multi-factor interference mechanism of the combustion evolution of typical Xinjiang coalfield fire areas, and provide a theoretical basis and technical support for subsequent fire area control and treatment.

[0009] The technical solutions of the embodiments of the present invention are specifically as follows:

[0010] In the first aspect, the embodiments of the present invention provide a large-scale experimental device for the combustion evolution of coalfield fire areas, including:

[0011] The main body support module, including an experimental box, a bearing frame, transparent acrylic side plates, filled with heat-insulating materials, a movable top plate activity platform, a hydraulic lifting device, and a bottom heat-insulating layer;

[0012] The geological environment simulation module, including a coal seam area, an overlying strata area, a floor area, and support guides, for filling coal seams and simulating surrounding rock materials according to the geological characteristics of actual coalfield fire areas; the coal seam can be laid in an inclined or horizontal manner, and sandstone, mudstone, or other similar materials can be added in layers to form a three-dimensional structure similar to the real geological environment;

[0013] The multi-modal information detection module, including a temperature sensing device, a pressure sensor, a humidity monitoring device, and a gas sampling port, for monitoring the temperature field, pressure field, humidity, fissure development, and gas composition changes during the experiment at multiple points, multiple layers, and multiple time periods, and transmitting the monitoring data to the data acquisition and analysis system in real time;

[0014] The data acquisition and analysis system is used to record multi-dimensional spatiotemporal distribution data in real time, and to construct the temperature field evolution equation, humidity field evolution equation, crack deformation equation, and gas evolution equation respectively, and to establish the four equations in parallel to form a coalfield fire zone combustion evolution control prediction model under multi-factor interference; at the same time, it proposes combustion critical criteria and operable control strategies;

[0015] The environmental control module includes a spray unit, an ignition device, a gas flow and pressure control unit, an exhaust gas treatment device, and an exhaust hole. It is used to control the humidity in the fire area, provide cooling and fire extinguishing means, simulate the fire source of the coal seam, study the combustion and spread mechanism of the fire area, and simulate the air leakage and oxygen supply environment after the formation of cracks. The airflow can be adjusted according to experimental needs.

[0016] In some embodiments, the load-bearing frame is welded with steel sections, and the surface is treated with anti-corrosion and anti-rust. The bottom and sides of the frame are closed with thick steel plates, and adjustable bolts or reinforcing ribs are left at the connection parts to facilitate fine-tuning or maintenance of the device during the experiment or between experiments; transparent acrylic side panels are installed on the outside of the length × height position to facilitate observation of the combustion process and rock formation changes inside the experiment; channel steel is installed and fixed at the width × height position to form a fully enclosed experimental box; safety auxiliary modules for providing on-site safety protection for the experiment are also arranged on both sides and around the experimental device; the auxiliary operation platform is used to assist personnel to enter the operation; the safety auxiliary unit is used to ensure the safety of the experimental operators and the experiment.

[0017] In some embodiments, the experimental box adopts a basic size of 5 meters in length, 3 meters in width and 2 meters in height. Inside the simulated space with this basic size, inclined coal seams or horizontal coal seams are flexibly set according to the geological characteristics of the actual fire zone: when the target fire zone of the study is an inclined coal seam, a support guide plate with an inclination angle of 20° to 45° is set in the coal seam area for angle positioning; when the target fire zone is mainly composed of horizontal coal seams, parallel layering is adopted for filling.

[0018] In some embodiments, the position of the ignition device is dynamically adjusted according to the position of the coal seam, so as to simulate the initial position of the spread of the coal seam fire source; according to the subsequent combustion source position and monitoring requirements, a temperature sensor device and a gas sampling port are inserted into the reserved holes in the corresponding acrylic plate area to obtain temperature and gas information respectively.

[0019] In some embodiments, a movable roof platform and a hydraulic lifting device are assembled on the top of the experimental box, and an openable observation port is set; a spray unit and a humidity monitoring device are arranged under the movable roof platform to simulate the humidity conditions in the coalfield fire area, monitor humidity changes, control the humidity environment, and cool down after the experiment.

[0020] In some embodiments, a temperature sensor device and a pressure sensor matrix are added above the bottom insulation layer of the experimental device to monitor the degree of heat conduction from the coal seam downward and stress changes; temperature sensor devices are installed at multiple points and in layers in the coal seam area, overlying rock area and bottom plate area to achieve three-dimensional dynamic monitoring.

[0021] In a second aspect, an embodiment of the present invention provides a large-scale coalfield fire zone combustion evolution experimental method, characterized in that it is applied to the experimental device described in the first aspect above, comprising:

[0022] The sensor network deployed in the experimental device is used to obtain multi-dimensional spatiotemporal distribution data sets, including three-dimensional temperature distribution data, humidity information and water migration information, stress change and crack extension information, and natural characteristic gas information of coal;

[0023] Based on the three-dimensional temperature distribution data, a temperature field evolution equation consisting of an adaptive thermal diffusion coefficient, a Laplace operator, a combustion gain function, and an environmental heat dissipation term is constructed to capture the dynamic changes in the combustion center position and quantify key indicators;

[0024] Based on the moisture information and moisture migration information, a moisture field evolution equation is established to quantitatively describe the moisture content of the coal body and the water injection / evaporation process, and confirm the dual effect of moisture;

[0025] Based on the stress change and crack extension information, a crack deformation equation is constructed to use the damage variable D and stress tensor σ Coupled description of deformation, crack propagation and collapse risk of coal seams and overlying rock formations;

[0026] Based on the coal spontaneous combustion characteristic gas, a gas evolution equation is constructed to describe the coupling between external air leakage oxygen supply and internal combustion reaction, taking into account porosity, gas flow rate, gas generation / consumption, and air leakage or gas escape correction;

[0027] The temperature field evolution equation, humidity field evolution equation, crack deformation equation and gas evolution equation are combined into a coalfield fire zone combustion evolution control prediction model, and the combustion critical criterion and operational control strategy are proposed.

[0028] In some embodiments, the temperature field evolution equation is expressed as:

[0029] ;

[0030] in, T Represents the temperature field, which is used to represent the coalfield fire area in three-dimensional space ( x, y, z ) and time t Temperature distribution on the is the adaptive thermal diffusivity, which depends on the stress tensor of the rock formationσ With porosity ; is the Laplace operator; is the combustion gain function, which depends at least on the temperature field T , humidity field W , stress tensor σ , gas concentration G four factors; is the environmental heat dissipation term, is the temperature field T gradient vector;

[0031] The evolution equation of the humidity field is expressed as:

[0032] ;

[0033] Wherein, W is the humidity field, which characterizes the moisture content or humidity distribution of the coal body and the interior of the fissures in three-dimensional space ( x, y, z ) and time t ; is the moisture diffusion tensor, which is coupled by the stress tensor and the damage variable ; is the gradient vector of the humidity field; is the evaporation loss term; is the seepage or external moisture supply term, which depends on the water phase pressure gradient and the permeability coefficient C water , which characterizes the process of external spraying, rainfall or aquifer injection of water into the fire area;

[0034] The fissure deformation equation is expressed as:

[0035] ;

[0036] Wherein, σ represents the stress tensor, which describes the stress state of a point in all directions ( x, y, z ); is the stress divergence, which represents the stress distribution of local equilibrium in the rock and soil mass; represents the density of the medium simulated by the model, which is determined according to experimental data; g is the gravitational acceleration vector; D ∈[0,1] is the damage variable, C is the material elastic stiffness matrix, represents the comprehensive strain, reflects the deformation of the material under the action of external or internal forces, reflects the thermal expansion or thermal contraction effect caused by high temperature or temperature gradient; Represents a custom thermoplastic model, further calibrated by the stress-strain-temperature curve from large-scale experiments; Represents the crack propagation rate considering the coupling of temperature, moisture content, and gas pressure;

[0037] The gas evolution equation is expressed as:

[0038] ;

[0039] Wherein, is the porosity, varying with the damage degree and stress field; represents the gas concentration; represents the gas flow rate, described by the modified Darcy's law or the Forchheimer term; , represent the gas generation term and the gas consumption term respectively, given by chemical kinetics or empirical formulas; represents the air leakage or gas escape correction term.

[0040] In some embodiments, the combustion critical criterion includes: obtaining a combustion critical determination function based on a certain weight combination of temperature, moisture content, stress, gas concentration, and damage variable. When the combustion critical determination value calculated at the current moment is greater than a specific threshold, it indicates that the fire area is about to enter an irreversible or high-risk stage of spontaneous combustion and external intervention is required.

[0041] In some embodiments, the method further includes: combining deep learning to quickly approximate or correct the combustion evolution control prediction model of the coalfield fire area to achieve two-way iteration between the model and the data; after predicting the evolution result of the fire area, automatically determining whether the combustion critical determination value exceeds a specific threshold and selecting an intervention plan to form a closed-loop automatic control; wherein, the intervention plan is determined by another reinforcement learning or optimization module and includes at least the water injection volume, air flow regulation, and crack plugging plan.

[0042] The beneficial effects brought by the technical solutions provided in the embodiments of the present invention at least include:

[0043] Based on the large-scale similarity model, the embodiments of the present invention innovatively add a multi-factor coupling simulation function and a self-heating combustion determination method, deeply study the evolution laws of ecological environment problems such as overlying rock movement, groundwater loss, soil heat impoverishment, vegetation degradation, and air pollution during the coal combustion process in the coalfield fire area, and reveal the coupling interference feedback mechanism among "fire-water-soil-air" in the coalfield fire area. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings, where:

[0045] Figure 1 It is the overall structural design drawing of a large-scale coalfield fire area combustion evolution experimental device provided by the embodiments of the present invention;

[0046] Figure 2 It is the structural schematic diagram of the bearing frame provided by the embodiments of the present invention;

[0047] Figure 3 It is the design schematic diagram of the transparent acrylic side plate provided by the embodiments of the present invention;

[0048] Figure 4 It is the schematic diagram of the formation building method provided by the embodiments of the present invention;

[0049] Figure 5 It is the process schematic diagram of a large-scale coalfield fire area combustion evolution experimental method provided by the embodiments of the present invention.

[0050] Reference numerals: 1 - experimental box body; 2 - bearing frame; 3 - transparent acrylic side plate; 4 - filling thermal insulation material; 5 - movable top plate activity platform; 6 - hydraulic lifting device; 7 - spraying unit; 8 - humidity monitoring device; 9 - ignition device; 10 - temperature sensing device; 11 - gas sampling port; 12 - bottom heat insulation layer; 13 - pressure sensor; 14 - data acquisition and analysis system; 15 - coal seam area; 16 - overlying rock layer area; 17 - backing plate; 18 - floor area; 19 - support guide plate; 20 - gas flow and pressure control unit; 21 - auxiliary operation platform; 22 - safety auxiliary unit; 23 - tail gas treatment device; 24 - exhaust hole. Detailed implementation manners

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0052] In the following description, reference is made to "some embodiments", which describe a subset of all possible embodiments. However, it is understood that "some embodiments" may be the same subset or different subsets of all possible embodiments, and may be combined with each other without conflict.

[0053] It should be noted that the terms "first / second / third" involved in the embodiments of the present invention are only used to distinguish similar objects, and do not represent a specific order for the objects. It can be understood that "first / second / third" can be interchanged with a specific order or sequence when permitted, so that the embodiments of the present invention described herein can be implemented in an order other than that illustrated or described herein.

[0054] Those skilled in the art of this technology can understand that, unless otherwise defined, all terms used herein (including technical terms and scientific terms) have the same meaning as the general understanding of those of ordinary skill in the art in the field to which the embodiments of the present invention belong. It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted with an idealized or overly formal meaning unless specifically defined as herein.

[0055] Most existing experiments on coalfield fire areas are mainly based on small and medium scales or simplified two-dimensional platforms, and it is difficult to comprehensively reflect the combustion and spread characteristics of outcrop coalfield fire areas in complex environments. The present invention aims to develop a large-scale three-dimensional physical similarity model experimental device, which can more realistically simulate the multi-stratum structure, fracture development and combustion process of coalfield fire areas.

[0056] The combustion of coalfield fire areas is affected by the coupling of multiple factors such as the coal seam temperature field, moisture content, overlying rock movement, gas migration, and surface wind flow. Existing research often focuses on single or a few factors, and it is difficult to make a systematic quantitative analysis of their comprehensive interference mechanism. The present invention realizes the dynamic monitoring of the combustion center temperature, the range of high-temperature areas, the change of fracture channels, the moisture migration, and the gas composition, etc. in three-dimensional space and at different time periods through a multi-point and stratified monitoring device.

[0057] Figure 1 As shown in the overall structural design drawing of a large-scale experimental device for the combustion evolution of coalfield fire areas provided by the embodiments of the present invention, Figure 1 as shown, the experimental device includes:

[0058] The main body support module includes an experimental box body 1, a bearing frame 2, a transparent acrylic side plate 3, a filling heat-insulating material 4, a movable top plate activity platform 5, a hydraulic lifting device 6, and a bottom heat-insulating layer 12;

[0059] The geological environment simulation module includes a coal seam area 15, an overlying rock layer area 16, a bottom plate area 18, and a support guide plate 19, which are used to fill the coal seam and simulate surrounding rock materials according to the geological characteristics of the actual coalfield fire area; the coal seam can be laid in an inclined or horizontal manner, and sandstone, mudstone or other similar materials can be added in layers to form a three-dimensional structure similar to the real geological environment;

[0060] The multimodal information detection module includes a temperature sensor 10, a pressure sensor 13, a humidity monitoring device 8 and a gas sampling port 11, which is used to monitor the temperature field, pressure field, humidity, crack development, and gas composition changes during the experiment at multiple points, multiple layers, and multiple time periods, and transmit the monitoring data to the data acquisition and analysis system in real time;

[0061] The data acquisition and analysis system 14 is used to record multi-dimensional spatiotemporal distribution data in real time, respectively construct the temperature field evolution equation, humidity field evolution equation, crack deformation equation, and gas evolution equation, and jointly establish the four equations to form a coalfield fire zone combustion evolution control prediction model under multi-factor interference; at the same time, it proposes combustion critical criteria and operable control strategies;

[0062] The environmental control module includes a spray unit 7, an ignition device 9, a gas flow and pressure control unit 20, an exhaust gas treatment device 23, and an exhaust hole 24, which are used to control the humidity of the fire area, provide cooling and fire extinguishing means, simulate the fire source of the coal seam, study the combustion and spread mechanism of the fire area, and simulate the air leakage oxygen supply environment after the formation of the cracks, and can adjust the airflow according to the experimental requirements.

[0063] Here, the main support module is responsible for the structural support and sealing of the entire experimental device; while maintaining visualization, thermal insulation, fire prevention and other measures are used to ensure the safety and operability of the experiment; the movable top plate and hydraulic lifting device facilitate the addition of materials, maintenance and modifications during the experiment.

[0064] The stratum construction method of the geological environment simulation module is as follows Figure 4 As shown, an overlying rock layer area 16 is set above the bottom plate area 18, and coal seams and simulated surrounding rock materials are filled according to the actual geological characteristics of the coalfield fire area; the coal seam area 15 can be laid in an inclined or horizontal manner, and sandstone, mudstone or other similar materials can be added in layers to form a "three-dimensional" structure similar to the real geological environment.

[0065] The multimodal information monitoring and acquisition module realizes multi-point, multi-layer, and multi-period monitoring of the temperature field, pressure field, humidity, crack development, gas composition changes, etc. during the experiment; the monitoring data is transmitted to the data acquisition and analysis system in real time for subsequent processing and analysis.

[0066] The environmental control module can control the humidity in the fire area, provide means for cooling and extinguishing fires; simulate the coal seam fire source, and study the combustion and spread mechanism in the fire area; a gas flow and pressure control unit 20 is arranged on the side of the experimental box body to simulate the air leakage and oxygen supply environment after the formation of fractures, and the air flow can be adjusted according to experimental requirements; at the same time, the gas flow and pressure control unit 20 is connected to the tail gas treatment device 23, which can be connected to the exhaust hole 24, and discharged after filtration or cooling, and the flue gas, heat, etc. generated by combustion can be collected and processed.

[0067] This experimental device can record data such as temperature, gas, stress, humidity, etc. in real time through a multi-modal information detection module. It can be used to study the combustion characteristics, fracture development law, gas flow and diffusion, temperature and stress changes, etc. in the coalfield fire area, providing experimental basis and technical support for the treatment of the coalfield fire area.

[0068] In some embodiments, the bearing frame 2 is welded by section steel, and the surface is treated with anti-corrosion and rust prevention. The bottom and around of the frame are closed with thick steel plates, and adjustable bolts or stiffeners are left at the connection parts to facilitate fine-tuning or maintenance of the device during the experiment or during the experiment interval; transparent acrylic side plates 3 are installed on the outer side of the length×height position to facilitate observing the combustion process and rock formation changes inside the experiment; channels are installed at the width×height position for fixation, forming a fully enclosed experimental box body; safety auxiliary modules for providing on-site safety guarantee for the experiment are also arranged on both sides and around the experimental device, including a safety auxiliary unit 22 and an auxiliary operation platform 21; the auxiliary operation platform 21 is used to assist personnel to enter and operate; the safety auxiliary unit 22 is used to ensure the safety of experimental operators and the experiment.

[0069] Here, the bearing frame is a frame structure welded by section steel (channel steel), as Figure 2 shown. The bottom and around of the frame are made of thick steel plates (for example, 12 mm thick) to ensure that the overall device has sufficient bearing strength and anti-deformation ability. The steel plates and the frame are combined by welding or bolt fastening to ensure tightness and durability. The channels and acrylic side plates are both provided with holes for convenient combination and fixation and insertion of sensors. A buffer gasket or elastic fastener is used between the acrylic side plate and the frame to avoid cracking or loosening of the plate due to thermal expansion and contraction or local stress.

[0070] Furthermore, in order to prevent the heat generated by high temperature or combustion from having too much impact on the external environment of the device, heat-insulating materials 4 such as ceramic fiber felts are added to the outside of the device and the channel steel sandwich for moderate heat insulation, and a backing plate 17 is placed at the bottom.

[0071] The auxiliary operation platform 21 provides a detachable staircase, safety guardrail, material box, etc. to facilitate personnel to enter and operate. The safety auxiliary unit 22 is equipped with a fire extinguisher, fire hose, water bucket and faucet, safety guardrail, etc. to reduce the experimental operation risk.

[0072] In some embodiments, the experimental chamber 1 has a basic size of 5 m × 3 m × 2 m. Inside the simulation space with this basic size, according to the geological characteristics of the actual fire area, an inclined coal seam or a horizontal coal seam is flexibly set: when the target fire area under study is an inclined coal seam, a support guide plate 19 with an inclination angle of 20° to 45° is set in the coal seam area for angle positioning; when the target fire area is mainly a horizontal coal seam, a parallel layering method is used for filling.

[0073] Here, to simulate the geological and combustion environment of the coalfield fire area as realistically as possible, the experimental chamber 1 adopts a scale of 5 m × 3 m × 2 m (meters) as the basic size. This size takes into account the experimental operability and the actual requirements of fully restoring the coal seam thickness, overlying rock structure, etc.

[0074] As Figure 4 shown, if there is a need for an inclined coal seam, the support guide plate 19 is pre-installed in the coal seam area for angle positioning when the coal seam is inclined, and it can also play an auxiliary fixing or interlayer separation role during the layout of the flat coal seam to improve the stability of the coal seam. If it is a flat coal seam, a horizontal layout method can be adopted. The prepared coal seam material is filled in layers. If an inclined coal seam is simulated, it is filled section by section in the inclination direction; if it is a flat coal seam, it can be spread horizontally in layers. The thickness of the coal seam can be controlled according to the actual needs of the target area (0.3 - 1.0 m). During the filling process, it needs to be slightly compacted to ensure the uniformity and stability of the coal body structure.

[0075] In some embodiments, the position of the ignition device 9 is dynamically adjusted according to the position of the coal seam to the position of the reserved holes on the transparent acrylic side plate 3, for simulating the initial position of the spread of the coal seam fire source; according to the subsequent position of the combustion source and the monitoring requirements, a temperature sensing device 10 and a gas sampling port 11 are inserted into the reserved holes in the corresponding acrylic plate area to obtain temperature and gas information respectively.

[0076] Here, the design schematic diagram of the transparent acrylic side plate is as Figure 3 shown. A plurality of holes are reserved on the transparent acrylic side plate 3 for flexibly installing the ignition device 9 to meet the requirements of different experimental scenarios. By adjusting the position of the ignition device 9, the influence of different initial fire source positions on the spread of coal seam combustion can be simulated. The gas sampling port 11 is used to collect the gas components generated during the combustion process and analyze the gas concentration and types. The layout of the sensors and sampling ports can be flexibly adjusted according to the experimental objectives to achieve comprehensive monitoring of the combustion process.

[0077] The dynamic adjustment capabilities of the ignition device and sensors enable the experimental setup to adapt to different experimental scenarios and objectives, enhancing the universality and repeatability of the experiments. Combined with temperature monitoring, gas sampling, and video surveillance, multi-dimensional and dynamic monitoring of the coal seam combustion process is achieved, capable of comprehensively capturing the physical and chemical changes during combustion. The design of the transparent acrylic side plate 3 not only facilitates the installation of sensors but also allows for real-time observation of the internal situation of the experiment, while ensuring the safety of experimental operations.

[0078] This design is applicable to the study of the combustion characteristics, fire spread patterns, fracture development mechanisms, and gas generation and diffusion processes in coalfield fire areas. By flexibly adjusting the layout of the ignition device and sensors, coal seam combustion scenarios under different geological conditions can be simulated, providing a scientific basis for fire prevention and extinguishment strategies in coalfield fire areas.

[0079] In some embodiments, a movable roof activity platform 5 and a hydraulic lifting device 6 are assembled on the top of the experimental box 1. An openable observation port is provided, and a spray unit 7 and a humidity monitoring device 8 are arranged below the movable roof activity platform 5 to simulate the humidity conditions in coalfield fire areas, monitor humidity changes, control the humidity environment, and cool down after the experiment.

[0080] Here, the top of the experimental setup is a movable roof activity platform 5, with an openable observation port and a movable platform reserved on the roof, facilitating operations such as local modification inside and sensor deployment during the experiment. This platform can be adjusted in height through the hydraulic lifting device 6 to flexibly replace experimental components or perform maintenance. At the same time, a spray unit 7 and a humidity monitoring device 8 are arranged below the top, providing the necessary moisture conditions and monitoring devices for the experimental setup.

[0081] In some embodiments, a temperature sensing device 10 and a pressure sensor 13 matrix are added above the bottom insulation layer 12 of the experimental setup to monitor the degree of heat conduction from the coal seam downward and stress changes; temperature sensing devices 10 are installed at multiple points and in layers in the coal seam area 15, overlying rock area 16, and floor area 18 respectively to achieve three-dimensional dynamic monitoring.

[0082] Here, by installing a temperature sensing device matrix above the bottom insulation layer, the degree of heat conduction from the coal seam downward is monitored. By installing a pressure sensor matrix above the bottom insulation layer, stress changes caused by heat conduction and physical changes are monitored. By installing temperature sensing devices at multiple points and in layers in the coal seam area, overlying rock area, and floor area respectively, three-dimensional dynamic temperature monitoring of the experimental area is achieved. This monitoring scheme can provide accurate experimental data for the combustion evolution control prediction model of coalfield fire areas, helping to improve the prediction accuracy and reliability of the model. At the same time, through three-dimensional dynamic monitoring, the combustion process and heat conduction situation in coalfield fire areas can be grasped in real time, providing a scientific basis for fire area governance and fire prevention and extinguishment strategies.

[0083] Figure 5 A large - scale coalfield fire area combustion evolution experimental method provided by an embodiment of the present invention is as follows Figure 5 shown. This method includes:

[0084] Step S510: Obtain a multi - dimensional spatio - temporal distribution data set by using the sensing network deployed in the experimental device, including three - dimensional temperature distribution data, humidity information and moisture migration information, stress change and crack propagation information, and coal spontaneous combustion characteristic gas information.

[0085] Step S520: Based on the three - dimensional temperature distribution data, construct a temperature field evolution equation composed of an adaptive thermal diffusion coefficient, a Laplace operator, a combustion gain function, and an environmental heat dissipation term to capture the dynamic change of the combustion center position and quantify key indicators.

[0086] Here, the constructed temperature field evolution equation is expected to accurately describe the temperature distribution in the large - scale three - dimensional physical similarity simulation of the coalfield fire area T ( x, y, z, t ) and its evolution process. Among them, key indicators such as the combustion center temperature threshold, combustion radius, high - temperature area range, and combustion rate, etc.

[0087] Step S530: Based on the humidity information and moisture migration information, establish a humidity field evolution equation to quantitatively describe the moisture content of the coal body and the water injection / evaporation process, and confirm the dual effects of moisture.

[0088] Here, for the coalfield fire area, water is an inhibitor of combustion, and it may also scour or change the pore structure in some cases. By quantitatively describing the moisture content of the coal body and the water injection / evaporation process through the humidity field evolution equation, confirm the dual effects of moisture in inhibiting or promoting the spread of the fire area and regulating heat transfer.

[0089] Step S540: Based on the stress change and crack propagation information, construct a crack deformation equation to use the damage variable D and stress tensor σ to couple and describe the deformation of the coal seam and overlying strata, crack propagation, and collapse risk.

[0090] Here, the crack deformation equation uses a "heat - water - gas" damage variable D and stress tensor σ to couple and describe the deformation of the coal seam and overlying strata, crack propagation, and collapse risk, and realize the mutual feedback between mechanics, thermotics, and flow.

[0091] Step S550: Based on the coal spontaneous combustion characteristic gas, and considering porosity, gas flow rate, gas generation / consumption, and leakage or gas escape correction at the same time, construct a gas evolution equation to describe the coupling between external leakage of oxygen supply and internal combustion reaction;

[0092] Step S560, the temperature field evolution equation, humidity field evolution equation, crack deformation equation, and gas evolution equation are combined into a coalfield fire zone combustion evolution control prediction model, and combustion critical criteria and operable control strategies are proposed.

[0093] Here, the single-field equations of the first four parts are connected into a multi-field coupling system to form a coupled coalfield fire zone combustion evolution control prediction model, which solves "fire-water-earth-air" synchronously or iteratively in time and space. The combustion critical criterion indicates that the fire zone is about to enter the irreversible or high-risk stage of spontaneous combustion and requires external intervention. Control strategies include but are not limited to water injection, wind pressure reduction, plugging leaks, etc.

[0094] Based on the aforementioned large-scale experimental device, the embodiment of the present invention uses a sensor network to obtain a data set of the spatiotemporal distribution characteristics of the "fire-water-soil-gas" multi-field. Based on the spatiotemporal migration data of "fire-water-soil-gas", a prediction model for the combustion evolution control of coalfield fire areas under multi-factor interference is further constructed to describe the coupling mechanism between the temperature field, the fracture deformation field, the gas field and the moisture field during the self-heating combustion of the coal seam. The promotion or inhibition effect of factors such as different moisture content, wind flow pressure, coal seam inclination and the degree of development of fracture channels on the spread of combustion is further clarified. The judgment criteria for core indicators such as the combustion center temperature threshold, the combustion radius, the high temperature zone range and the combustion rate are proposed, and the corresponding intelligent prediction method is established to provide a scientific basis for the fire prevention and extinguishing strategy of the on-site fire area. The model contains the evolution equations of the four fields, and realizes overall prediction and control through mutual coupling. The model is based on the data collection and verification of large-scale experiments (and actual coalfield on-site monitoring), and can be used to quantitatively analyze and predict the combustion spread, fracture expansion and water-gas migration processes in the coalfield fire area.

[0095] In some embodiments, the temperature field evolution equation is expressed as:

[0096] ;

[0097] in, T Represents the temperature field, which is used to represent the coalfield fire area in three-dimensional space ( x, y, z ) and time t Temperature distribution on the is the adaptive thermal diffusivity, which depends on the stress tensor of the rock formation σ Porosity ; is the Laplace operator; is the combustion gain function, which depends at least on the temperature field T , humidity field W , stress tensor σ , gas concentration G Four factors; is the environmental heat dissipation term, is the temperature field T of the gradient vector.

[0098] Here, by solving the state quantity of the temperature field T ( x, y, z, t ), the position of the combustion center, the range of the high-temperature zone, and the temperature gradient can be judged. When the stress (or damage variable D) increases and the crack expands, the heat transfer channels increase, and the value of the adaptive thermal diffusion coefficient becomes larger accordingly; conversely, when the medium is relatively dense the value is smaller. is used to describe the diffusion process of temperature in the heat conduction equation. If the temperature is high at a certain place and the surrounding temperature is low, heat diffusion will transfer heat to the low-temperature zone. is the adaptive heat source term. When the temperature is high enough, the oxygen is sufficient and the moisture is not much, the combustion heat release intensity is large; if the moisture evaporation takes away heat or the stress causes the crack to enhance oxygen supply, the combustion intensity will be further adjusted. can include convective heat transfer, radiative heat dissipation, and heat exchange with the surrounding medium, etc. If the temperature difference between the fire area and the outside world is large, the value is large, indicating that more heat is dissipated to the external environment.

[0099] Furthermore, define the position of the combustion center X center ( t ) as the temperature extreme point or the point with the strongest oxidation reaction; its spread rate X’ center can be jointly determined by the combustion gain and the thermal gradient to form a dynamic tracking equation:

[0100] ;

[0101] where, is a function fitted based on experimental data, different from the traditional fixed spread speed assumption, and has high adaptability and calibratability.

[0102] In some embodiments, the humidity field evolution equation is expressed as:

[0103] ;

[0104] where, W is the humidity field, characterizing the moisture content or humidity distribution of the coal body and inside the cracks in three-dimensional space ( x, y, z ) and time t ; is the moisture diffusion tensor, coupled by the stress tensor and the damage variable ; is the gradient vector of the humidity field; is the evaporation loss term; is the seepage or external water recharge term, which depends on the water phase pressure gradient and the permeability coefficient C water , which characterizes the process of external spraying, rainfall or aquifer injection of water into the fire area.

[0105] Here, W characterizes the moisture content or humidity distribution inside the coal body and fractures. For a coalfield fire area, water is an inhibitor of combustion and may also scour or change the pore structure in some cases. If the stress increases or the fracture damage expands, the larger it is, the easier it is for water to diffuse and seep in these new fractures. represents that when the temperature reaches a certain threshold, water evaporates and takes away a large amount of latent heat. If the temperature in a certain area is too high and the moisture content is also high, strong evaporation cooling will be formed, which has a negative feedback effect on the temperature field T and plays a negative feedback role.

[0106] In some embodiments, the fracture deformation equation is expressed as:

[0107] ;

[0108] Wherein, σ represents the stress tensor, which describes the stress state of a certain point in all directions ( x, y, z ); is the stress divergence, which represents the stress distribution of local equilibrium in the rock and soil mass; represents the density of the medium simulated by the model, which is determined according to experimental data; g is the gravitational acceleration vector; D ∈[0,1] is the damage variable, C is the material elastic stiffness matrix, represents the comprehensive strain, reflects the deformation of the material under the action of external or internal forces, reflects the thermal expansion or thermal contraction effect caused by high temperature or temperature gradient; represents a user-defined thermo-plastic model, which is further calibrated by the stress-strain-temperature curve of large-scale experiments; represents the fracture propagation rate coupling temperature, moisture content and gas pressure.

[0109] Here, the damage variable D depends on , when high temperature and strong stress coexist, DIt is more likely to increase; when water penetration causes the rock formation to expand or the infiltration strength to increase, local damage may also be induced. The custom thermoplastic model is for the plastic stress term, emphasizing the weakening of the rock mass stiffness by high-temperature softening. When the crack propagation rate reaches the critical threshold, the damaged area grows rapidly, generating large cracks or collapses.

[0110] In some embodiments, the gas evolution equation is expressed as:

[0111] ;

[0112] where is the porosity, which varies with the damage degree and stress field; represents the gas concentration; represents the gas flow rate, which is described by the modified Darcy's law or the Forchheimer term; 、 respectively represent the gas generation term and the gas consumption term, which are given by chemical kinetics or empirical formulas; represents the air leakage or gas escape correction term.

[0113] Here, the transport and diffusion of multi-component gases (O2, CO, CO2, CH4, etc.) in the fracture network are studied through the gas evolution equation, as well as the generation or consumption of different components of gas during the spontaneous combustion / pyrolysis process; the coupling between external air leakage for oxygen supply and internal combustion reactions is described.

[0114] Porosity The larger it is, the more pores and fractures there are, and the smoother the gas channels are. Multiple gas components include oxygen, CO, CO2, methane, etc. The distribution of each component in the fracture network is different, which has a key impact on combustion and spontaneous combustion. The gas flow rate considers the non-linear effect when the fracture has high-speed through-flow. The gas consumption term, such as oxygen being consumed in oxidative combustion, and the gas generation term, such as CO2 and CO being generated in pyrolysis reactions. The coupling reaction rates of different gas components are different and require large-scale experiments for correction. The air leakage or gas escape correction term, when the fracture further expands or penetrates the ground surface, a large amount of external air or air current may enter; conversely, the flue gas generated in the fire area can also be discharged faster.

[0115] In some embodiments, the combustion critical criterion includes: obtaining a combustion critical determination function based on a certain weight combination of temperature, moisture content, stress, gas concentration, and damage variable. When the combustion critical determination value calculated at the current moment is greater than a specific threshold, it indicates that the fire area is about to enter an irreversible or high-risk stage of spontaneous combustion and external intervention is required.

[0116] Here, the combustion critical determination function is expressed as Φ crit ( T, W, σ, G, D ), and the combustion critical determination value calculated at the current momentΦ crit Greater than a specific threshold Φ 0 In this case, corresponding control strategies need to be adopted for intervention.

[0117] In some embodiments, the method further includes: combining deep learning to quickly approximate or correct the combustion evolution control prediction model of the coalfield fire area, realizing two-way iteration between the model and data; after predicting the fire area evolution result, automatically judging whether the combustion critical determination value exceeds a specific threshold and selecting an intervention plan to form a closed-loop automatic control; wherein, the intervention plan is determined by another reinforcement learning or optimization module and at least includes the water injection volume, air flow regulation, and fracture plugging plan.

[0118] Here, deep learning is combined to quickly approximate or correct the above-mentioned coupled combustion evolution control prediction model of the coalfield fire area; two-way iteration of "model + data" is realized under the drive of on-site data (temperature, moisture content, gas concentration, fracture deformation, etc.).

[0119] ;

[0120] Among them, represents a neural network approximator, θ are network parameters (such as weights and biases); given the initial-boundary conditions measured in experiments or on-site, the neural network directly outputs the prediction results of the fire-water-soil-gas-damage state at the next moment. are the predicted values of the neural network for temperature, moisture, pressure, and gas concentration respectively, representing the predicted subsequent temperature field, moisture content, stress damage, and gas distribution of the model under the given current state. If the deviation between the predicted value and the true measurement or numerical solution is too large, the network structure or loss function needs to be adjusted for correction.

[0121] The loss function used for training is as follows:

[0122] ;

[0123] Among them, is the loss value; is the output value of the neural network approximator; is the reference solution obtained by numerical discretization or classical PDE solution; is the real data obtained from the experimental bench or on-site monitoring; represents the physical constraint or conservation law penalty term to prevent the network solution from violating the basic energy balance; , , are weight coefficients respectively.

[0124] After the neural network accurately predicts the next-step evolution of the fire area, it can automatically determine whether the combustion critical determination value exceeds a specific threshold. If it exceeds the specific threshold, intervention schemes such as water injection volume, air flow regulation, and crack plugging are selected through another reinforcement learning (RL) or optimization module to form a closed-loop automatic control and achieve the integration of prediction and decision-making.

[0125] The following describes the above-mentioned large-scale coalfield fire area combustion evolution experimental device in combination with a specific embodiment. However, it should be noted that this specific embodiment is only for better explaining the present invention and does not constitute an improper limitation to the present invention.

[0126] In view of the environmental characteristics of typical Xinjiang coalfield fire areas and combined with on-site investigation data, the present invention systematically designs a large-scale coalfield fire area combustion evolution experimental device, which can more realistically simulate the multi-stratum structure, crack development, and fire area combustion process of coalfield fire areas. The purpose is to study the spatio-temporal distribution characteristics of "fire-water-soil-air" in coalfield fire areas, construct a combustion evolution control prediction model for coalfield fire areas under multi-factor interference, reveal the multi-factor interference mechanism of combustion evolution in typical Xinjiang coalfield fire areas, and provide theoretical basis and technical support for subsequent fire area control and treatment.

[0127] The specific construction process of the large-scale coalfield fire area combustion evolution experimental device is as follows:

[0128] S1. When manufacturing the experimental box body 1, the pre-cut channel steel is initially positioned on the experimental site according to the design dimensions of length × width of 5 m (meters) × 3 m and welded into a rectangular base. Support columns are erected at the four corners and necessary intermediate positions of the base, and are welded to the cross beam or fixed with adjustable bolts to form the main load-bearing skeleton. The surface of the skeleton is subjected to anti-corrosion and rust-proof treatment, and adjustable bolts or stiffeners are installed at each connection node to facilitate possible fine-tuning or maintenance in subsequent experiments. A 12-mm-thick steel plate is enclosed outside and at the bottom area of the frame to form the main load-bearing frame 2 of the box body. The steel plate and the frame are combined by welding or bolt fastening to ensure tightness and durability. Ceramic fiber felt thermal insulation material 4 is filled in the interlayer between the external steel plate and the load-bearing frame 2 to reduce the impact of the high temperature generated by combustion on the experimental environment and operators.

[0129] S2. At the length × height position (5 m × 2 m), a 6-mm-thick transparent acrylic side plate 3 is selected and fixed on the channel steel frame with reference to the pre-designed hole positions. When installing the acrylic plate, buffer gaskets or elastic fasteners must be provided between the frame and the plate to avoid cracking or loosening of the plate caused by local stress. At the same time, according to the subsequent position of the combustion source and monitoring requirements, temperature sensing devices 10 and gas sampling ports 11 that need to be inserted are opened in the corresponding acrylic plate area.

[0130] S3. Assemble the fabricated movable roof and the hydraulic lifting device 6 on the top of the box body to form the movable roof activity platform 5, and set an openable observation port on the roof. Arrange the spray unit 7 and the humidity monitoring device 8 below the roof to simulate the humidity conditions in the coalfield fire area, monitor the humidity change, control the humidity environment, and cool down after the experiment is completed.

[0131] S4. Set the gas flow and pressure control unit 20 on the side of the experimental box body. Control the gas flow in the experimental cavity to conform to the outdoor environment, and apply air flow to the outcrop ignition point to simulate the ventilation situation after the formation of air leakage and oxygen supply caused by the formation of fissures.

[0132] S5. Lay a 0.3m-thick high-temperature-resistant rock filler at the bottom of the box body to form the bottom heat insulation layer 12, mainly simulating the bottom plate area 18. This heat insulation layer can effectively block the downward transfer of high temperature, avoid damaging the bottom structure or affecting the external environment. Above the heat insulation layer, bury the pressure sensors 13 according to the "matrix" distribution rule. Lead the signal wires of the sensors to the outside of the box body through the reserved wire grooves or special protection pipes and connect them to the central data acquisition system for monitoring the downward transfer of heat and the bottom stress change.

[0133] S6. For the coal seam area 15, according to the test objectives and the properties of the on-site coal samples, select a mixture of carbon powder + crushed coal samples + binder, which can not only ensure the combustion efficiency but also simulate the combustion heat characteristics of the real coal body in the coalfield fire area. If there is a need for inclined coal seams, install support guide plates 19 with an inclination angle of 20° - 45° in the corresponding area in advance for angle positioning when the coal seam is inclined, and can also play an auxiliary fixing or interlayer separation role during the layout of flat coal seams to improve the stability of the coal seam. If it is a flat coal seam, the horizontal layout method can be adopted. Fill the prepared coal seam materials in layers. If simulating an inclined coal seam, fill them section by section along the inclination direction; if it is a flat coal seam, they can be spread horizontally in layers. The thickness of the coal seam can be controlled according to the actual needs of the target area (0.3 - 1.0m). During the filling process, it is necessary to compact it slightly to ensure the uniformity and stability of the coal body structure.

[0134] S7. Insert the adjustable electric heating ignition device 9 at the position corresponding to the coal seam outcrop or the reserved hole position on the side plate (length × height). Fill the sandstone, mudstone or other lithology simulation materials in layers above the coal seam, with the thickness of each layer controlled between 5 and 10 cm (centimeters), and the material ratio (density, elastic modulus, thermal conductivity, etc.) is adjusted according to the actual geological conditions (as close as possible to the real environment). According to the research requirements of the multi-factor coupling of "fire - water - soil - air", install temperature sensing devices 10 in the coal seam, overlying strata and floor respectively, and install gas sampling ports 11 at the side plate. Install a pressure sensor 13 above the floor. Install a humidity monitoring device 8 at the top. Connect each sensor to the data acquisition and analysis system 14 through the reserved hole positions and cable ducts. Record the multi-field coupling data (temperature, gas, stress, humidity, etc.) in real time to provide a complete experimental basis for subsequent analysis.

[0135] S8. Set auxiliary operation platforms 21 on both sides of the experimental device, providing detachable stairs, safety guards and material boxes to facilitate personnel access and operation. Set up a safety assistance unit 22 around the experimental device, and place fire extinguishers, fire hoses, buckets and faucets to ensure the safety of experimental operators and the experiment. The gas flow and pressure control unit 20 is connected to the tail gas treatment device 23, which can be connected to the exhaust 24 hole, and then discharged after filtration or cooling.

[0136] In the embodiments of this aspect, based on the large-scale similarity model, aiming at the multi-factor dynamic coupling in the combustion process of coalfield fire areas, the mathematical formulas for the spatio-temporal distribution characteristics and combustion evolution control conditions of "fire - water - soil - air" are further deduced, and a prediction model for the combustion evolution of coalfield fire areas suitable for large-scale and outcrop conditions is constructed. By adding the multi-factor coupling simulation function and the self-heating combustion determination method, the evolution laws of ecological environment problems such as overlying rock movement, groundwater loss and evaporation, soil heating and impoverishment, vegetation degradation, and air pollution during the coal combustion process in the coalfield fire area are deeply studied, and the coupling interference feedback mechanism between "fire - water - soil - air" in the coalfield fire area is revealed, which can be used to guide the on-site fire prevention and extinguishment practice.

[0137] It should be understood that the "one embodiment" or "an embodiment" mentioned throughout the specification means that the specific features, structures or characteristics related to the embodiment are included in at least one embodiment of the present invention. Therefore, the appearances of "in one embodiment" or "in an embodiment" throughout the specification do not necessarily refer to the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner. It should be understood that in various embodiments of the present invention, the magnitudes of the serial numbers of the above processes do not mean the order of execution, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention. The serial numbers of the embodiments of the present invention above are only for description and do not represent the advantages and disadvantages of the embodiments.

[0138] It should be noted that in this text, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements not only includes those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising one..." does not exclude the presence of additional identical elements in the process, method, article or device comprising that element.

[0139] In several embodiments provided by the present invention, it should be understood that the disclosed methods can be implemented in other ways. The methods disclosed in several method embodiments provided by the present invention can be arbitrarily combined without conflict to obtain new method embodiments. The features disclosed in several method embodiments provided by the present invention can be arbitrarily combined without conflict to obtain new method embodiments.

[0140] As described above, the above are only the embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A large-scale coalfield fire zone combustion evolution experimental device, characterized in that: include: The main support module includes an experimental box (1), a load-bearing frame (2), a transparent acrylic side panel (3), a filling insulation material (4), a movable top plate movable platform (5), a hydraulic lifting device (6), and a bottom insulation layer (12); The geological environment simulation module includes a coal seam area (15), an overlying rock layer area (16), a bottom plate area (18), and a support guide plate (19), which are used to fill the coal seam and simulate surrounding rock materials according to the geological characteristics of the actual coalfield fire area; the coal seam is laid in an inclined or horizontal manner, and sandstone and mudstone are added in layers to form a three-dimensional structure similar to the actual geological environment; A multi-modal information detection module, comprising a temperature sensing device (10), a pressure sensor (13), a humidity monitoring device (8) and a gas sampling port (11), for monitoring the temperature field, pressure field, humidity, crack development and gas composition changes during the experiment at multiple points, multiple layers and multiple time periods, and transmitting the monitoring data to a data acquisition and analysis system in real time; The data acquisition and analysis system (14) is used to record multi-dimensional spatiotemporal distribution data in real time, and to construct the temperature field evolution equation, humidity field evolution equation, crack deformation equation, and gas evolution equation respectively, and to establish the four equations in parallel to form a coalfield fire zone combustion evolution control prediction model under multi-factor interference; at the same time, it proposes the combustion critical criterion and an operational control strategy; The environmental control module includes a spray unit (7), an ignition device (9), a gas flow and pressure control unit (20), an exhaust gas treatment device (23), and an exhaust hole (24), which is used to control the humidity of the fire area, provide cooling and fire extinguishing means, simulate the coal seam fire source, study the combustion and spread mechanism of the fire area, and simulate the air leakage oxygen supply environment after the formation of the crack, and can adjust the airflow according to the experimental requirements; The temperature field evolution equation is expressed as: ； in, T Represents the temperature field, which is used to represent the coalfield fire area in three-dimensional space ( x,y,z ) and time t Temperature distribution on the is the adaptive thermal diffusivity, which depends on the stress tensor of the rock formation σ Porosity ; is the Laplace operator; is the combustion gain function, which depends at least on the temperature field T , humidity field W , stress tensor σ , gas concentration G Four factors; For environmental heat dissipation, is the temperature field T The gradient vector of The humidity field evolution equation is expressed as: ； in, W is the humidity field, which characterizes the internal structure of coal body and fractures in three-dimensional space ( x,y,z ) and time t Moisture content or humidity distribution on the surface; is the water diffusion tensor, which is given by the stress tensor and damage variables coupling; is the gradient vector of the humidity field; is the evaporation loss term; is the seepage or external water supply term, which depends on the water phase pressure gradient and permeability C water , characterizes the process by which water from external sprinklers, rainfall, or aquifer injection enters the fire zone; The crack deformation equation is expressed as: ； in, σ Represents the stress tensor, describing the stress of a point in all directions ( x, y, z ) on the stress state; is the stress divergence, which represents the local equilibrium stress distribution in the rock and soil body; It represents the density of the medium simulated by the model, which is determined based on experimental data; g is the gravitational acceleration vector; D ∈[0,1] is the damage variable, C is the material elastic stiffness matrix, represents the comprehensive strain, Reflects the deformation of materials under the action of external or internal forces. Reflects the thermal expansion or contraction effects caused by high temperature or temperature gradient; represents the thermo-plastic model, which is calibrated by the stress-strain-temperature curves of large-scale experiments; Represents the crack growth rate coupled with temperature, water content, and gas pressure; The gas evolution equation is expressed as: ； in, is the porosity, which varies with the damage degree and stress field; Indicates gas concentration; represents the gas flow rate, described by the modified Darcy's law or the Forchheimer term; , They represent gas generation term and gas consumption term respectively, which are given by chemical kinetics or empirical formula; Indicates the correction term for air leakage or gas escape.

2. The experimental device according to claim 1, characterized in that: The load-bearing frame (2) is welded with steel sections, and the surface is treated with anti-corrosion and anti-rust. The bottom and sides of the frame are sealed with thick steel plates, and adjustable bolts or reinforcing ribs are left at the connection parts so that the device can be fine-tuned or repaired during the experiment or during the experiment interval. A transparent acrylic side panel (3) is installed on the outside of the length × height position to facilitate observation of the combustion process and rock formation changes inside the experiment. A channel steel is installed at the width × height position to form a fully enclosed experimental box. Safety auxiliary modules for providing on-site safety assurance for the experiment are also arranged on both sides and around the experimental device, including a safety auxiliary unit (22) and an auxiliary operation platform (21); the auxiliary operation platform (21) is used to assist personnel in entering the operation; the safety auxiliary unit (22) is used to ensure the safety of experimental operators and the experiment.

3. The experimental device according to claim 1, characterized in that: The experimental box (1) adopts a basic size of 5 meters in length, 3 meters in width and 2 meters in height. Inside the simulation space under this basic size, inclined coal seams or horizontal coal seams are flexibly set according to the geological characteristics of the actual fire area: When the target fire zone is an inclined coal seam, a support guide plate (19) with an inclination angle of 20° to 45° is set in the coal seam area for angle positioning; when the target fire zone is mainly a horizontal coal seam, a parallel layered method is used for filling.

4. The experimental device according to any one of claims 1 to 3, characterized in that: The position of the ignition device (9) is dynamically adjusted according to the position of the coal seam by the position of the reserved holes on the transparent acrylic side plate (3), so as to simulate the initial position of the coal seam fire source spreading; According to the subsequent combustion source location and monitoring requirements, a temperature sensor device (10) and a gas sampling port (11) are inserted into the reserved holes corresponding to the acrylic plate area to obtain temperature and gas information respectively.

5. The experimental device according to any one of claims 1 to 3, characterized in that: Assemble a movable top plate platform (5) and a hydraulic lifting device (6) on the top of the experimental box (1), and provide an openable observation port; A spray unit (7) and a humidity monitoring device (8) are arranged below the movable top plate platform (5) to simulate the humidity conditions in a coalfield fire zone, monitor humidity changes, control the humidity environment, and cool down after the experiment.

6. The experimental device according to any one of claims 1 to 3, characterized in that: A matrix of temperature sensing devices (10) and pressure sensors (13) is installed above the bottom insulation layer (12) of the experimental device to monitor the degree of heat conduction from the coal seam downward and stress changes; temperature sensing devices (10) are installed at multiple points and in layers in the coal seam area (15), the overlying rock layer area (16) and the bottom plate area (18) to achieve three-dimensional dynamic monitoring.

7. A combustion evolution experimental method for a large-scale coalfield fire zone, characterized in that: The experimental device as claimed in any one of claims 1 to 6 comprises: The sensor network deployed in the experimental device is used to obtain multi-dimensional spatiotemporal distribution data sets, including three-dimensional temperature distribution data, humidity information and water migration information, stress change and crack extension information, and natural characteristic gas information of coal; Based on the three-dimensional temperature distribution data, a temperature field evolution equation consisting of an adaptive thermal diffusion coefficient, a Laplace operator, a combustion gain function, and an environmental heat dissipation term is constructed to capture the dynamic changes in the combustion center position and quantify key indicators; Based on the moisture information and moisture migration information, a moisture field evolution equation is established to quantitatively describe the moisture content of the coal body and the water injection / evaporation process, and confirm the dual effect of moisture; Based on the stress change and crack extension information, a crack deformation equation is constructed to use the damage variable D and stress tensor σ Coupled description of deformation, crack propagation and collapse risk of coal seams and overlying rock formations; Based on the coal spontaneous combustion characteristic gas, a gas evolution equation is constructed to describe the coupling between external air leakage oxygen supply and internal combustion reaction, taking into account porosity, gas flow rate, gas generation / consumption, and air leakage or gas escape correction; The temperature field evolution equation, humidity field evolution equation, crack deformation equation and gas evolution equation are combined into a coalfield fire zone combustion evolution control prediction model, and the combustion critical criterion and operational control strategy are proposed.

8. The method according to claim 7, characterized in that The combustion criticality criteria include: The combustion critical judgment function is obtained based on the combination of temperature, moisture content, stress, gas concentration and damage variables with certain weights. When the combustion critical judgment value calculated at the current moment is greater than a specific threshold, it means that the fire area is about to enter the irreversible or high-risk stage of spontaneous combustion, and external intervention is required.

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