CN113504163A

CN113504163A - Experimental system and method for simulating particle deposition behavior in coal mine mining-induced fracture

Info

Publication number: CN113504163A
Application number: CN202110579823.4A
Authority: CN
Inventors: 刘应科; 戴宇航; 问小江; 王熙; 袁满; 王凤超
Original assignee: China University of Mining and Technology CUMT
Current assignee: China University of Mining and Technology CUMT
Priority date: 2021-05-26
Filing date: 2021-05-26
Publication date: 2021-10-15
Anticipated expiration: 2041-05-26
Also published as: CN113504163B

Abstract

The invention discloses an experimental system and method for simulating particle deposition behavior in a coal mine mining fracture. The method comprises the steps of simulating a coal mine underground negative pressure extraction working condition by using the air supply unit, simulating a coal mine underground mining fracture by using the fracture experiment unit, carrying out section scanning on a flat fracture experiment section by using a section scanner to generate an initial experiment fracture modeling model, pushing particulate matters into the flat fracture experiment section by using the air supply unit, carrying out section scanning after pressure difference data of the front end and the rear end of the flat fracture experiment section are stabilized in a set range, generating a secondary experiment fracture modeling model, comparing the secondary experiment fracture modeling model with the initial experiment fracture modeling model, determining specific coordinate positions and weight data of the particulate matters retained in the flat fracture experiment section, and providing theoretical basis and experimental data for optimizing the design of coal mine underground on-site mine gas extraction process parameters.

Description

Experimental system and method for simulating particle deposition behavior in coal mine mining-induced fracture

Technical Field

The invention relates to a gas-solid two-phase flow experiment system and method, in particular to an experiment system and method for simulating particle deposition behavior in a coal mine mining-induced fracture, and belongs to the technical field of coal mine gas efficient development.

Background

Mine gas is a harmful gas produced by physical and chemical actions during the lengthy formation and deterioration of coal. Coal bed gas can be released into a mining space in the coal mining process to cause the gas to exceed the limit, thereby bringing dangerous hidden danger to mine production and seriously restricting the safety production of coal mines. The establishment of a safe and efficient gas extraction technology is a fundamental measure for controlling coal mine gas disasters. At present, coal bed gas mining methods mainly comprise two methods: negative pressure extraction is carried out through ground drilling, and negative pressure extraction is carried out through underground drilling. Under the influence of mining, mining fracture networks formed by the intercommunication of the separation fractures and the vertical fractures are formed in the coal seam and the overlying rock layer, and the fracture networks provide sufficient channels for the flow of pressure relief gas in the coal seam and the goaf. Under the condition of negative pressure extraction, free gas flow in the coal seam or the goaf can enter a gas extraction borehole through the mining fracture network or be extracted to the ground for utilization.

However, in the process of mine gas extraction, a certain amount of coal and rock particles are inevitably carried in gas extraction airflow, the particles are inevitably settled in a mining fracture, particularly in areas with large local resistance such as fracture diameter reduction, the probability of settlement of the particles is higher, and the settled particles are gradually increased and accumulated along with the progress of the gas extraction work, so that the fracture overflow section is reduced, even the fracture is completely blocked, local embolism is formed, the permeability of a fracture field is reduced, and the difficulty of gas extraction is increased. Therefore, the gas flow is suddenly or gradually reduced in the mine gas extraction process, and the coal mine gas extraction efficiency is reduced. The method has important engineering significance for researching the migration and sedimentation rule of the particulate matters in the mining-induced fracture and further adopting corresponding measures to improve the gas extraction efficiency.

At present, few researches are conducted on the deposition behavior of particles in fractures in the mine gas extraction process. The method is used for researching the deposition behavior of the particles in the fracture in the mine gas extraction process, and not only needs to know the migration rule of the particles in the mining fracture under the negative pressure extraction environment, namely analyzing the characteristic quantity (negative pressure difference) of the negative pressure extraction and the action mechanism of the fracture form on the motion of the deposited particles in the fracture, but also needs to research the characteristics of the overlying strata with different lithologies or coal seams with different coal qualities forming the fracture, the problems of the particles with different dimensions and the like so as to determine the types and the forms of the fractures formed by the overlying strata with different lithologies or the coal seams with different coal qualities and the negative pressure extraction characteristic quantity corresponding to the particles with different dimensions, further avoid the blocking of the mining fracture by the particles to the maximum extent and effectively avoid the problem of the reduction of the permeability of the fracture field caused by the local embolism of the mining fracture. The invention discloses an experimental system for simulating solid-phase particles to block coal rock cracks, which mainly comprises a ventilation pipeline, a secondary hole sealing feeding device, a crack platform and the like, and aims to determine key process parameters of a secondary hole sealing technology although migration and blocking characteristics of particles in cracks in a secondary hole sealing process can be studied more intuitively. The secondary hole sealing technology is that on the basis of the first drilling and sealing, the compressed air is utilized to send the fine expansion powder into the coal seam drilling hole under a certain pressure, the fine expansion powder permeates into the hole (crack) gap area around the coal seam, the flowing resistance of gas in the crack is increased, the external air is blocked, the air leakage rate in the drilling hole is obviously reduced, and therefore the concentration of gas drainage in the first drilling and sealing hole is greatly improved. That is to say, the invention patent is essentially simulating and researching the plugging characteristic that a large amount of particles enter a fracture to form a large-area plug and prevent outside air from entering after a large amount of particles are fed into a coal seam drill hole outside the first drill hole and the first hole sealing by adopting compressed gas, but not researching the problem that the permeability of the fracture field is reduced and the gas extraction efficiency is reduced because a small amount of particles enter the fracture to form local plugs in the coal seam drill hole inside the first drill hole and the first hole sealing are avoided.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides an experimental system and method for simulating particle deposition behavior in a coal mine mining-induced fracture, which are used for researching the particle deposition behavior in the fracture on the premise of avoiding the blocking of the mining-induced fracture by the particles to the maximum extent and can provide theoretical basis and experimental data for optimizing the design of the process parameters of the underground on-site mine gas extraction.

In order to achieve the aim, the experiment system for simulating the particle deposition behavior in the mining fracture of the coal mine comprises an air supply unit, a feeding unit, a fracture experiment unit and a data acquisition unit;

the air supply unit comprises a variable frequency fan and an air supply pipeline, the output end of the variable frequency fan comprising a variable frequency controller I is connected with the input end of the air supply pipeline, and the air supply pipeline is provided with a flowmeter and a stop valve I;

the feeding unit comprises a storage bin, a belt conveyor and a particulate matter applicator, the bottom of the storage bin is in butt joint with the input end of the belt conveyor through a stop valve II, a driving motor of the belt conveyor comprises a variable frequency controller II, and the output end of the belt conveyor is in butt joint with the input end of the particulate matter applicator;

the fracture experiment unit sequentially comprises a particulate matter mixing input section, a flat fracture experiment section and a dust collection box from back to front; the particle mixing input section is of a Venturi tube structure and comprises an air inlet pipe, a mixing chamber, a throat and an expanding pipe, the rear end of the air inlet pipe is hermetically installed and connected with the output end of an air supply pipeline, the front end of the air inlet pipe is a reducing pipe which hermetically extends into the mixing chamber and is small in front and large in back, a feeding pipe which is hermetically communicated and connected with the output end of a particle applicator is arranged on the mixing chamber in a penetrating way, the feeding pipe is arranged corresponding to the outer wall of the reducing pipe, the outlet of the throat corresponding to the reducing pipe is arranged at the front end of the mixing chamber in a penetrating way, the inner diameter size of the throat is smaller than that of the outlet end of the reducing pipe, and the expanding pipe which is large in front and small in back is arranged at the front end of the throat in a butting way; the flat crack experimental section is of a box-type structure with a flat structure inner cavity, the height dimension of the flat structure inner cavity is far smaller than the width dimension of the flat structure inner cavity, and the rear end of the flat crack experimental section is fixedly installed and connected with the front end of the expanding tube in a sealing manner; the rear end of the dust collecting box communicated with the outside through the filter screen is hermetically and fixedly installed and connected with the front end of the flat crack experimental section;

the data acquisition unit include central controller, weighing sensor, section scanner, the differential pressure gauge, air feed control circuit, feed control circuit and data acquisition storage control circuit, two weighing sensor set up respectively in the bottom of feed bin and dust collecting box, section scanner sets up in the left side or right side or top side or the bottom side of flat crack experimental section, two sense terminals of differential pressure gauge are connected with the front and back both ends intercommunication of flat crack experimental section inner chamber respectively, central controller respectively with frequency conversion fan, frequency conversion controller I, driving motor, frequency conversion controller II, weighing sensor, section scanner and differential pressure gauge electricity are connected.

As an implementation mode of the invention, the flat fracture experimental section is an opening and closing positioning installation structure capable of being opened and closed for positioning installation, and a fracture is simulated by installing a 3D printing fracture model.

As another embodiment of the invention, a small section gap forming structure is arranged in the flat fracture experiment section along the left-right direction, and the structure simulation fracture is formed through the small section gap.

As a further improvement of the invention, the fracture experiment unit further comprises a front flat gradual change section and a rear flat gradual change section which are arranged at the front end and the rear end of the flat fracture experiment section; the rear end of the rear flat transition section is hermetically and fixedly installed and connected with the front end of the expanding tube, the front end of the rear flat transition section is hermetically and fixedly installed and connected with the rear end of the flat fracture experimental section, and the longitudinal section of the inner cavity of the rear flat transition section is of a smooth transition structure which is transited from a circular structure to a flat structure from back to front; the rear end of the front flat transition section is fixedly and fixedly installed and connected with the front end of the flat crack experimental section in a sealing mode, the front end of the front flat transition section is fixedly and fixedly installed and connected with the dust collection box in a sealing mode, and the longitudinal section of the inner cavity of the front flat transition section is of a smooth transition structure which is in a round structure and is transited from the rear to the front through a flat structure.

As a further improvement scheme of the invention, the stop valve I and the stop valve II are both electrically controlled stop valves electrically connected with the central controller.

As a further improvement of the invention, the flow meter is also provided with an electric control flow control valve which is electrically connected with the central controller.

As a further development of the invention, the silo and the particle applicator are both conical bottom structures which facilitate the sliding of the particles.

An experimental method for simulating particle deposition behaviors in a coal mine mining-induced fracture aims at simulating the fracture by installing a 3D printing fracture model, and comprises the following steps:

a. preparation of the experiment: scanning a coal sample or a rock sample and carrying out computer modeling to generate a fracture modeling model, then generating a 3D printing fracture model comprising a fracture top surface model and a fracture bottom surface model through 3D printing, opening a flat fracture experimental section, respectively and correspondingly installing the 3D printing fracture models of the fracture top surface model and the fracture bottom surface model on a top plane and a bottom plane of an inner cavity of a flat structure in a sealing and positioning mode, after the flat fracture experimental section is integrally installed in a sealing and positioning mode, respectively and hermetically connecting and installing a dust collection box and a particulate matter mixing input section at the front end and the rear end of the flat fracture experimental section, completing the integral assembly of a fracture experimental unit, recording the initial weight of an unloaded bin and the dust collection box by a central controller after connecting each pipeline and each circuit, and fitting the fracture form data fed back by a section scanner and the fracture modeling model generated by the computer to the same reference coordinate point, Generating an initial experimental fracture modeling model;

b. data acquisition and output: opening a stop valve I, after a central controller starts a variable frequency fan, adjusting and setting frequency parameters of the variable frequency fan to an experimental target working condition by controlling the variable frequency controller I, meanwhile, placing particles into a storage bin, recording the weight of the storage bin by the central controller, after the variable frequency fan stably runs through the feedback of a flow meter, starting a driving motor of a belt conveyor by the central controller, adjusting and setting the frequency parameters of the driving motor to the experimental target working condition by controlling a variable frequency controller II, opening a stop valve II after the belt conveyor stably runs, and then, processing and recording experimental data by the central controller according to the feedback of a differential pressure gauge; after the weighing sensor of the bin returns to the initial value and the data fed back by the pressure difference meter is stabilized within the set range, the central controller records the actual weight data fed back by the weighing sensor of the dust collection box, calculates the difference between the actual weight data and the initial weight data of the dust collection box, stores and outputs the weight data of the particles retained in the flat crack experimental section, controls the section scanner to perform section scanning on the flat crack experimental section by the central controller to generate a secondary experiment crack modeling model, compares the secondary experiment crack modeling model with the initial experiment crack modeling model by the central controller, positions the specific coordinate position of the particles retained in the flat crack experimental section, and stores and outputs the specific coordinate position.

An experimental method for simulating particle deposition behaviors in a coal mining fracture aims at forming a structural simulation fracture through a small gap of a section, and comprises the following steps:

a. preparation of the experiment: after connecting each pipeline and each circuit, the central controller records the initial weight of the empty bin and the dust collection box, and performs section scanning on the flat fracture experimental section through a section scanner to generate an initial experimental fracture modeling model;

b. data acquisition and output: opening a stop valve I, after a central controller starts a variable frequency fan, adjusting and setting frequency parameters of the variable frequency fan to an experimental target working condition by controlling the variable frequency controller I, meanwhile, placing particles into a storage bin, recording the weight of the storage bin by the central controller, after the variable frequency fan 1 is stably operated by feedback of a flowmeter, starting a driving motor of a belt conveyor by the central controller, adjusting and setting the frequency parameters of the driving motor to the experimental target working condition by controlling a variable frequency controller II, opening a stop valve II after the belt conveyor is stably operated, and then, processing and recording experimental data by the central controller according to the feedback of a differential pressure gauge; after the weighing sensor of the bin returns to the initial value and the data fed back by the pressure difference meter is stabilized within the set range, the central controller records the actual weight data fed back by the weighing sensor of the dust collection box, calculates the difference between the actual weight data and the initial weight data of the dust collection box, stores and outputs the weight data of the particles retained in the flat crack experimental section, controls the section scanner to perform section scanning on the flat crack experimental section by the central controller to generate a secondary experiment crack modeling model, compares the secondary experiment crack modeling model with the initial experiment crack modeling model by the central controller, positions the specific coordinate position of the particles retained in the flat crack experimental section, and stores and outputs the specific coordinate position.

Compared with the prior art, the experiment system for simulating the particle deposition behavior in the coal mine mining-induced fracture simulates the underground negative pressure extraction working condition of the coal mine by using the air supply unit and the underground mining-induced fracture by using the fracture experiment unit, firstly, the flat fracture experiment section is subjected to section scanning by the section scanner to generate an initial experiment fracture modeling model, then, the particulate matters fed by the feeding unit are pushed into the flat fracture experiment section by the air supply unit, after the pressure difference data of the front end and the rear end of the flat fracture experiment section are stabilized in a set range, the flat fracture experiment section is subjected to section scanning by the section scanner to generate a secondary experiment fracture modeling model, then, the secondary experiment fracture modeling model is compared with the initial experiment fracture modeling model to determine the specific coordinate position and the weight data of the particulate matters retained in the flat fracture experiment section, and not only can the simulation analysis of the negative pressure extraction characteristic quantity (negative pressure difference) and the weight data of the particulate matters retained in the flat fracture experiment section, The action mechanism of the fracture form on the movement of the deposited particles in the fracture can analyze the types and forms of the overlying strata with different lithology or coal beds with different coal qualities and the negative pressure extraction characteristic quantity corresponding to the particles with different dimensions by replacing the particles with different granularity specifications and weights, different air supply frequency parameters, different feed frequency parameters and different clearance quantity fracture models, researches the deposition behavior of the particles in the fracture on the premise of avoiding the particles from blocking the mining fracture to the maximum extent, and can provide theoretical basis and experimental data for optimizing the design of the process parameters of the on-site mine gas extraction under the coal mine.

Drawings

FIG. 1 is a schematic structural view of the present invention;

FIG. 2 is a schematic diagram of the particulate mixing input section of the present invention.

In the figure: 1. the device comprises a variable frequency fan, 2, variable frequency controllers I and 3, a flow meter, 4, stop valves I and 5, a storage bin, 6, stop valves II and 7, a belt conveyor, 8, variable frequency controllers II and 9, a driving motor, 10, a particulate matter applicator, 11, a particulate matter mixing input section, 11-1, an air inlet pipe, 11-2, a reducing pipe, 11-3, a feeding pipe, 11-4, a mixing chamber, 11-5, a throat, 11-6, an expanding pipe, 12-1, a rear flat gradual change section, 12-2, a front flat gradual change section, 13, a flat crack experiment section, 14, a small section gap forming structure, 15, a differential pressure meter, 16 and a dust collection box.

Detailed Description

The invention is further illustrated with reference to the accompanying drawings (the following description is made with reference to the direction of travel of the particulate matter in the experimental section of the flat fracture as the front).

As shown in figure 1, the experiment system for simulating the particle deposition behavior in the mining fracture of the coal mine comprises an air supply unit, a feeding unit, a fracture experiment unit and a data acquisition unit.

The air supply unit comprises a variable frequency fan 1 and an air supply pipeline, the output end of the variable frequency fan 1 comprising a variable frequency controller I2 is connected with the input end of the air supply pipeline, and a flowmeter 3 and a stop valve I4 are arranged on the air supply pipeline.

The feeding unit comprises a storage bin 5, a belt conveyor 7 and a particulate matter applicator 10, the bottom of the storage bin 5 is in butt joint with the input end of the belt conveyor 7 through a stop valve II 6, a driving motor 9 of the belt conveyor 7 comprises a variable frequency controller II 8, the output end of the belt conveyor 7 is in butt joint with the input end of the particulate matter applicator 10, and a sealing cover plate can be installed around the belt conveyor 7 and the particulate matter applicator 10 to prevent the particulate matter from deviating from the original migration track due to external influence.

The fracture experiment unit sequentially comprises a particulate matter mixing input section 11, a flat fracture experiment section 13 and a dust collection box 16 from back to front; as shown in figure 2, the particulate mixing input section 11 is a Venturi tube structure and comprises an air inlet pipe 11-1, a mixing chamber 11-4, a throat 11-5 and an expanding pipe 11-6, the rear end of the air inlet pipe 11-1 is hermetically installed and connected with the output end of an air supply pipeline, the front end of the air inlet pipe 11-1 is a reducing pipe 11-2 which is hermetically extended into the mixing chamber 11-4 and has a small front part and a large rear part, a feeding pipe 11-3 which is hermetically communicated and connected with the output end of a particulate applicator 10 penetrates through the mixing chamber 11-4, the feeding pipe 11-3 is arranged corresponding to the outer wall of the reducing pipe 11-2, the outlet of the throat 11-5 corresponding to the reducing pipe 11-2 is arranged at the front end of the mixing chamber 11-4 in a penetrating manner, and the inner diameter of the throat 11-5 is smaller than the inner diameter of the outlet end of the reducing pipe 11-2, the expanding pipe 11-6 with a big front and a small back is butted at the front end of the throat 11-5; the flat crack experimental section 13 is a box-type structure with a flat structure inner cavity, the height dimension of the flat structure inner cavity is far smaller than the width dimension of the flat structure inner cavity, cracks with uniform crack width can be directly simulated through the flat structure inner cavity, a section small gap forming structure 14 can be directly and simply arranged in the flat structure inner cavity of the flat crack experimental section 13 along the left and right directions, the section small gap forming structure 14 can form a gap surface or a gap line along the left and right directions, the section small gap forming structure 14 can be a one-way positioning bulge structure or a two-way positioning bulge structure which is arranged in a protruding way towards the inside of the flat structure inner cavity along the up and down direction, or a one-way telescopic bulge structure or a two-way telescopic bulge structure which is arranged in a telescopic way towards the inside of the flat structure inner cavity along the up and down direction, and the simulation of small gap surface cracks or small gap line cracks can be realized through the section small gap forming structure 14, in order to truly reflect the fracture form, the flat fracture experimental section 13 is an opening and closing positioning installation structure which can be opened, closed and positioned and installed, installation grooves which are arranged along the front and back directions can be arranged on the top plane and the bottom plane of an inner cavity of the flat structure, a fracture model comprising a fracture top surface model and a fracture bottom surface model can be generated through 3D printing after real fractures are scanned and computer modeling, the fracture top surface model and the fracture bottom surface model are respectively positioned and installed in the inner cavity of the flat structure in a sealing mode through fracture surface installation holes which are arranged on the installation grooves, flange plates are arranged at the front end and the back end of the flat fracture experimental section 13, O-shaped gasket installation grooves provided with O-shaped gaskets are arranged on the flange plates, and the back end of the flat fracture experimental section 13 and the front end of the expanding pipe 11-6 are fixedly installed and connected in a sealing mode through the flange plates and the O-shaped gaskets; the rear end of a dust collecting box 16 communicated with the outside through a filter screen is fixedly installed and connected with the front end of the flat crack experimental section 13 in a sealing way through a flange plate and an O-shaped gasket.

The data acquisition unit include central controller, the section scanner, weighing sensor, differential pressure gauge 15, air feed control circuit, feed control circuit and data acquisition storage control circuit, the section scanner sets up in the left side or right side or top side or the bottom side of flat crack experiment section 13, two weighing sensor set up respectively in the bottom of feed bin 5 and dust-collecting box 16, two sense terminals of differential pressure gauge 15 are connected with the front and back both ends intercommunication of flat crack experiment section 13 inner chamber respectively, central controller respectively with variable frequency fan 1, variable frequency controller I2, driving motor 9, variable frequency controller II 8, the section scanner, weighing sensor and differential pressure gauge 15 electricity are connected.

Aiming at a simple small-section gap forming structure 14, before the experiment is carried out by using the experiment system, the central controller records the initial weight of the unloaded bin 5 and the dust collecting box 16 after connecting each pipeline and each circuit, and carries out section scanning on the flat fracture experiment section 13 by using a section scanner to generate an initial experiment fracture modeling model, so that the experiment can be carried out; opening a stop valve I4, after a central controller starts a variable frequency fan 1, adjusting and setting the frequency parameter of the variable frequency fan 1 to an experimental target working condition by controlling a variable frequency controller I2, simultaneously putting particulate matters such as coal particles, rock particles or a coal-rock particle mixture with set granularity specification and weight into a storage bin 5, sequentially leading positive pressure air generated by the variable frequency fan 1 to enter a flat fracture experimental section 13 through an air inlet pipe 11-1, a reducing pipe 11-2, a mixing chamber 11-4, a throat 11-5 and an expanding pipe 11-6, passing through a gap between a fracture top surface model and a fracture bottom surface model, then discharging the positive pressure air through a filter screen of a dust collection box 16, recording the weight of the storage bin 5 by the central controller, starting a driving motor 9 of a belt conveyor 7 by the central controller after the variable frequency fan 1 is stably operated through feedback of a flowmeter 3, and adjusting and setting the frequency parameter of the driving motor 9 by controlling a variable frequency controller II 8, after the belt conveyor 7 runs stably, the stop valve II 6 is opened, the particulate matters are conveyed at a constant speed through the belt conveyor 7 and enter the mixing chamber 11-4 through the particulate matter applicator 10 and the feeding pipe 11-3, under the positive pressure action of positive pressure wind, the particulate matters enter the flat fracture experimental section 13 and form a gap of a structure 14 through a small gap of a section, and then the central controller processes and records experimental data according to the feedback of the differential pressure gauge 15; after the weighing sensor of the bin 5 feeds back the bin 5 to an initial value (namely, all the particles in the bin 5 enter the mixing chamber 11-4 through the particle applicator 10 and the feeding pipe 11-3), and the data fed back by the pressure difference meter 15 is stabilized within a set range, the central controller records the actual weight data fed back by the weighing sensor of the dust collection box 16, calculates the difference between the actual weight data and the initial weight data of the dust collection box 16, stores and outputs the weight data of the particles retained in the flat fracture experimental section 13, controls the section scanner to perform section scanning on the flat fracture experimental section 13 to generate a secondary experimental fracture modeling model, compares the secondary experimental fracture modeling model with the initial experimental fracture modeling model, positions specific coordinate positions of the particles retained in the flat fracture experimental section 13, and stores and outputs the specific coordinate positions, and finishing the deposition behavior experiment of the particulate matter with the set granularity specification and weight aiming at the small gap forming structure 14 of the section on the premise of the set frequency parameter of the variable frequency fan 1 and the set frequency parameter of the driving motor 9. The deposition behavior of the particles in the crack can be simulated and researched by replacing the particles with different particle size specifications and weights, different frequency parameters of the variable frequency fan 1, different frequency parameters of the driving motor 9 and different gaps between the sections to form the gap amount of the structure 14.

In order to simulate the fracture form truly, aiming at a 3D printing fracture model, before the experiment system is used for carrying out the experiment, a coal sample or a rock sample can be scanned and modeled by a computer to generate a fracture modeling model, then a 3D printing fracture model comprising a fracture top surface model and a fracture bottom surface model is generated by 3D printing, after a flat fracture experiment section 13 is opened, the 3D printing fracture models of the fracture top surface model and the fracture bottom surface model are respectively sealed, correspondingly positioned and installed on the top plane and the bottom plane of an inner cavity of a flat structure, after the flat fracture experiment section 13 is sealed, positioned and installed into a whole, the front end and the rear end of the flat fracture experiment section 13 are respectively sealed, connected with a dust collection box 16 and a particulate matter mixing input section 11, namely the whole assembly of a fracture experiment unit is completed, a central controller records the initial weight of a no-load bin 5 and the dust collection box 16 after each pipeline and each circuit are connected, fitting the same reference coordinate point of fracture form data fed back by the section scanner and a fracture modeling model generated by computer modeling to generate an initial experimental fracture modeling model, namely performing experiments; opening a stop valve I4, after a central controller starts a variable frequency fan 1, adjusting and setting the frequency parameter of the variable frequency fan 1 to an experimental target working condition by controlling a variable frequency controller I2, simultaneously putting particulate matters such as coal particles, rock particles or a coal-rock particle mixture with set granularity specification and weight into a storage bin 5, sequentially leading positive pressure air generated by the variable frequency fan 1 to enter a flat fracture experimental section 13 through an air inlet pipe 11-1, a reducing pipe 11-2, a mixing chamber 11-4, a throat 11-5 and an expanding pipe 11-6, passing through a gap between a fracture top surface model and a fracture bottom surface model, then discharging the positive pressure air through a filter screen of a dust collection box 16, recording the weight of the storage bin 5 by the central controller, starting a driving motor 9 of a belt conveyor 7 by the central controller after the variable frequency fan 1 is stably operated through feedback of a flowmeter 3, and adjusting and setting the frequency parameter of the driving motor 9 by controlling a variable frequency controller II 8, after the belt conveyor 7 runs stably, the stop valve II 6 is opened, the particulate matters are conveyed at a constant speed through the belt conveyor 7 and enter the mixing chamber 11-4 through the particulate matter applicator 10 and the feeding pipe 11-3, under the positive pressure action of positive pressure wind, the particulate matters enter a gap between a crack top surface model and a crack bottom surface model in the flat crack experimental section 13, and then the central controller processes and records experimental data according to the feedback of the differential pressure gauge 15; after the weighing sensor of the bin 5 feeds back the bin 5 to an initial value (namely, all the particles in the bin 5 enter the mixing chamber 11-4 through the particle applicator 10 and the feeding pipe 11-3), and the data fed back by the pressure difference meter 15 is stabilized within a set range, the central controller records the actual weight data fed back by the weighing sensor of the dust collection box 16, calculates the difference between the actual weight data and the initial weight data of the dust collection box 16, stores and outputs the weight data of the particles retained in the flat fracture experimental section 13, controls the section scanner to perform section scanning on the flat fracture experimental section 13 to generate a secondary experimental fracture modeling model, compares the secondary experimental fracture modeling model with the initial experimental fracture modeling model, positions specific coordinate positions of the particles retained in the flat fracture experimental section 13, and stores and outputs the specific coordinate positions, and finishing the deposition behavior experiment aiming at the 3D printing crack model on the premise of the set frequency parameter of the variable frequency fan 1 and the set frequency parameter of the driving motor 9. The deposition behavior of the particulate matters in the cracks can be simulated and researched by replacing the particulate matters with different grain sizes and weights, different frequency parameters of the variable-frequency fan 1, different frequency parameters of the driving motor 9 and different 3D printing crack models.

In the experimental process, the crack with the space direction azimuth angle can be simulated by positioning the space angle of the flat crack experimental section 13, and the influence of the self gravity and the crack direction azimuth angle of the particulate matter on the particulate matter deposition behavior can be researched.

In order to realize the uniformity of the positive pressure air flow passing through the flat fracture experimental section 13, as a further improvement scheme of the invention, the fracture experimental unit further comprises a front flat gradual change section 12-2 and a rear flat gradual change section 12-1 which are arranged at the front end and the rear end of the flat fracture experimental section 13; the rear end of the rear flat transition section 12-1 is hermetically and fixedly installed and connected with the front end of the expanding tube 11-6, the front end of the rear flat transition section 12-1 is hermetically and fixedly installed and connected with the rear end of the flat fracture experimental section 13 through a flange plate and an O-shaped gasket, and the longitudinal section of the inner cavity of the rear flat transition section 12-1 is of a smooth transition structure which is in a flat structure and is transited from a circular structure to the front from the rear; the rear end of the front flat transition section 12-2 is fixedly and hermetically connected with the front end of the flat crack experimental section 13 through a flange plate and an O-shaped gasket, the front end of the front flat transition section 12-2 is fixedly and hermetically connected with the dust collection box 16, and the longitudinal section of the inner cavity of the front flat transition section 12-2 is of a smooth transition structure which is in a round structure and transits from a flat structure to the front from the back. The two detection ends of the differential pressure gauge 15 can be respectively connected with the inner cavities of the front flat transition section 12-2 and the rear flat transition section 12-1 in a communication way.

In order to realize automatic control, as a further improvement scheme of the invention, the stop valve I4 and the stop valve II 6 are both electrically controlled stop valves electrically connected with the central controller.

In order to adjust the flow rate of the air flow conveniently, as a further improvement of the invention, the flow meter 3 is further provided with an electrically controlled flow control valve electrically connected with the central controller.

In order to facilitate the smooth entry of the granules into the mixing chamber 11-4, as a further development of the invention, the hopper 5 and the granule applicator 10 are both of a conical bottom structure to facilitate the sliding of the granules.

The experiment system for simulating the particle deposition behavior in the coal mine mining-induced fracture simulates the underground negative pressure extraction working condition of a coal mine by using the air supply unit and simulates the underground mining-induced fracture of the coal mine by using the fracture experiment unit, not only can simulate and analyze the negative pressure extraction characteristic quantity (negative pressure difference) and the action mechanism of fracture morphology on the motion of deposited particles in the fracture, but also can analyze the types and the morphologies of overlying strata with different lithology or coal seams with different coal quality and the negative pressure extraction characteristic quantities corresponding to particles with different dimensions by replacing the particles with different particle sizes and weights, different air supply frequency parameters, different material supply frequency parameters and different gap quantity fracture models, so as to research the deposition behavior of the particles in the fracture on the premise of avoiding the blocking of the mining-induced fracture by the particles to the maximum extent, theoretical basis and experimental data can be provided for optimizing the design of the process parameters of the on-site mine gas extraction in the underground coal mine.

Claims

1. An experiment system for simulating particle deposition behaviors in a mining-induced fracture of a coal mine is characterized by comprising an air supply unit, a feeding unit, a fracture experiment unit and a data acquisition unit;

the air supply unit comprises a variable frequency fan (1) and an air supply pipeline, the output end of the variable frequency fan (1) comprising a variable frequency controller I (2) is connected with the input end of the air supply pipeline, and the air supply pipeline is provided with a flowmeter (3) and a stop valve I (4);

the feeding unit comprises a storage bin (5), a belt conveyor (7) and a particulate matter applicator (10), the bottom of the storage bin (5) is in butt joint with the input end of the belt conveyor (7) through a stop valve II (6), a driving motor (9) of the belt conveyor (7) comprises a variable frequency controller II (8), and the output end of the belt conveyor (7) is in butt joint with the input end of the particulate matter applicator (10);

the fracture experiment unit sequentially comprises a particulate matter mixing input section (11), a flat fracture experiment section (13) and a dust collection box (16) from back to front; the particle mixing input section (11) is of a Venturi tube structure and comprises an air inlet pipe (11-1), a mixing chamber (11-4), a throat (11-5) and an expanding pipe (11-6), the rear end of the air inlet pipe (11-1) is hermetically installed and connected with the output end of an air supply pipeline, the front end of the air inlet pipe (11-1) is a reducing pipe (11-2) which is hermetically extended into the mixing chamber (11-4) and is small in front and large in back, a feeding pipe (11-3) which is hermetically communicated and connected with the output end of the particle applicator (10) is arranged on the mixing chamber (11-4) in a penetrating mode, the feeding pipe (11-3) is arranged corresponding to the outer wall of the reducing pipe (11-2), the outlet of the throat (11-5) corresponding to the reducing pipe (11-2) is arranged at the front end of the mixing chamber (11-4) in a penetrating mode, The inner diameter of the throat (11-5) is smaller than that of the outlet end of the reducing pipe (11-2), and the expanding pipe (11-6) with a larger front part and a smaller rear part is butted at the front end of the throat (11-5); the flat fracture experimental section (13) is of a box-shaped structure with a flat structure inner cavity, the height dimension of the flat structure inner cavity is far smaller than the width dimension of the flat structure inner cavity, and the rear end of the flat fracture experimental section (13) is fixedly installed and connected with the front end of the expanding tube (11-6) in a sealing manner; the rear end of a dust collecting box (16) communicated with the outside through a filter screen is fixedly installed and connected with the front end of the flat crack experimental section (13) in a sealing way;

the data acquisition unit include central controller, weighing sensor, the section scanner, differential pressure gauge (15), air feed control circuit, feed control circuit and data acquisition storage control circuit, two weighing sensor set up respectively in the bottom of feed bin (5) and dust-collecting box (16), the section scanner sets up the left side or right side or top side or bottom side at flat crack experiment section (13), two sense terminals of differential pressure gauge (15) are connected with the front and back both ends intercommunication of flat crack experiment section (13) inner chamber respectively, central controller respectively with variable frequency fan (1), frequency conversion controller I (2), driving motor (9), frequency conversion controller II (8), weighing sensor, section scanner and differential pressure gauge (15) electricity are connected.

2. The experimental system for simulating particle deposition behavior in a coal mine mining-induced fracture as claimed in claim 1, wherein the flat fracture experimental section (13) is an open-close positioning installation structure that can be opened and closed and positioned for installation, and the fracture is simulated by installing a 3D printing fracture model.

3. The experimental system for simulating particle deposition behavior in a coal mining-induced fracture as claimed in claim 1, wherein a small section gap forming structure (14) is arranged in the flat fracture experimental section (13) along the left-right direction, and the fracture is simulated by the small section gap forming structure (14).

4. An experimental system for simulating particle deposition behavior in a coal mine mining-induced fracture as defined in claim 1, 2 or 3, wherein the fracture experimental unit further comprises a front flat transition (12-2) and a rear flat transition (12-1) disposed at the front and rear ends of the flat fracture experimental section (13); the rear end of the rear flat transition section (12-1) is hermetically and fixedly installed and connected with the front end of the expanding tube (11-6), the front end of the rear flat transition section (12-1) is hermetically and fixedly installed and connected with the rear end of the flat fracture experimental section (13), and the longitudinal section of the inner cavity of the rear flat transition section (12-1) is of a smooth transition structure which is in a flat structure and is transited from a circular structure to the front from the rear; the rear end of the front flat transition section (12-2) is hermetically and fixedly installed and connected with the front end of the flat crack experimental section (13), the front end of the front flat transition section (12-2) is hermetically and fixedly installed and connected with the dust collection box (16), and the longitudinal section of the inner cavity of the front flat transition section (12-2) is of a smooth transition structure which is in a round structure and transits from a flat structure to the front from the back.

5. An experimental system for simulating particle deposition in a coal mine mining-induced fracture as claimed in claim 1, 2 or 3, wherein the stop valves I (4) and II (6) are electrically controlled stop valves electrically connected to the central controller.

6. An experimental system for simulating the sedimentation behavior of particles in a coal mine mining-induced fracture as claimed in claim 1, 2 or 3, wherein the flow meter (3) is further provided with an electrically controlled flow control valve electrically connected with the central controller.

7. An experimental system for simulating the settling behavior of particles in a coal mine mining-induced fracture as claimed in claim 1, 2 or 3, characterized in that the silo (5) and the particle applicator (10) are both conical bottom structures facilitating the sliding of particles.

8. An experimental method for simulating particle deposition behavior in a coal mine mining-induced fracture by using the experimental system as claimed in claim 2, wherein the method specifically comprises the following steps for simulating the fracture by installing a 3D printing fracture model:

a. preparation of the experiment: scanning a coal sample or a rock sample and carrying out computer modeling to generate a fracture modeling model, then generating a 3D printing fracture model comprising a fracture top surface model and a fracture bottom surface model through 3D printing, opening a flat fracture experimental section (13), respectively and correspondingly sealing and positioning the 3D printing fracture models of the fracture top surface model and the fracture bottom surface model on a top plane and a bottom plane of an inner cavity of a flat structure, sealing and positioning the flat fracture experimental section (13) into a whole, respectively and hermetically connecting and mounting a dust collection box (16) and a particulate matter mixing input section (11) at the front end and the rear end of the flat fracture experimental section (13), completing the integral assembly of a fracture experimental unit, recording the initial weight of the bin (5) and the dust collection box (16) by a central controller after connecting pipelines and circuits, and carrying out the fitting of the same reference coordinate point on fracture form data fed back by a section scanner and the fracture model generated through computer modeling, Generating an initial experimental fracture modeling model;

b. data acquisition and output: opening a stop valve I (4), after a central controller starts a variable frequency fan (1), adjusting and setting frequency parameters of the variable frequency fan (1) to an experimental target working condition by controlling a variable frequency controller I (2), simultaneously putting particles into a stock bin (5), recording the weight of the stock bin (5) by the central controller, after the variable frequency fan (1) stably operates through feedback of a flowmeter (3), starting a driving motor (9) of a belt conveyor (7) by the central controller, adjusting and setting frequency parameters of the driving motor (9) to the experimental target working condition by controlling a variable frequency controller II (8), opening a stop valve II (6) after the belt conveyor (7) stably operates, and then processing and recording experimental data by the central controller according to feedback of a differential pressure gauge (15); after the weighing sensor of the bin (5) returns to the initial value and the data fed back by the differential pressure gauge (15) is stabilized within a set range, the central controller records the actual weight data fed back by the weighing sensor of the dust collection box (16), calculates and stores the difference between the actual weight data and the initial weight data of the dust collection box (16) and outputs the weight data of the particles retained in the flat crack experimental section (13), controls the section scanner to perform section scanning on the flat crack experimental section (13) to generate a secondary experimental crack modeling model, compares the secondary experimental crack modeling model with the initial experimental crack modeling model, positions the specific coordinate position of the particles retained in the flat crack experimental section (13), and stores and outputs the specific coordinate position.

9. An experimental method for simulating particle deposition behavior in a coal mine mining-induced fracture using the experimental system of claim 3, characterized in that for simulating the fracture by a small gap-forming structure (14) of the fracture, the method comprises the following steps:

a. preparation of the experiment: after the pipelines and the circuits are connected, the central controller records the initial weight of the no-load storage bin (5) and the dust collection box (16), and performs section scanning on the flat fracture experimental section (13) through a section scanner to generate an initial experimental fracture modeling model;