Abstract: A multi-level cross-district surface well pattern deployment method is provided. Firstly, a horizontal well is drilled from a location on a land surface corresponding to a junction H1 of a district rise coal pillar of the first district C1 in a first level and an upper mine field boundary coal pillar. A multilateral well is drilled from a location on the land surface corresponding to a junction H3 of a level coal pillar between the first and second levels, and the district rise coal pillar of the first district C1 in the first level. Liquid nitrogen is injected for permeability improvement after a gas drainage quantity decreases to 20% of an initial quantity. Gas drainage is repeated multiple times until the drainage quantity of coal bed methane through a gas drainage pipe of the horizontal pipe is reached 3 m3/min.

Abstract: A multi-level cross-district surface well pattern deployment method is provided. Firstly, a first horizontal well is drilled from a location on a land surface corresponding to a junction H1 of a district rise coal pillar of the first district C1 in a first level and an upper mine field boundary coal pillar. A multilateral well is drilled from a location on the land surface corresponding to a junction H3 of a level coal pillar between the first and second levels, and the district rise coal pillar of the first district C1 in the first level. Liquid nitrogen is injected for permeability improvement after a gas drainage quantity decreases to 20% of an initial quantity. Gas drainage is repeated multiple times until the drainage quantity of coal bed methane through a gas drainage pipe of the horizontal pipe is reached 3 m3/min.

Abstract: A rock sanding device includes a base, a bottom sanding plate, an adjustable connecting rod, an elastic loader, a connector, a side sanding brush, a top sanding plate, an inner rod, a prong and a drill rod. The top of the drill rod is fixedly connected with the rotating shaft of the external water drilling rig and the external water drilling rig has a water inlet joint to introduce water into the drill rod. The inner rod and drill rod are connected and fixed coaxially, and the bottom of the drill rod is symmetrically welded with four prongs. The rock specimen is placed in the center of the side sanding brush. The top sanding plate and the bottom sanding plate are provided in the top side and bottom side of the rock specimen, respectively.

Abstract: A three-dimensional analog simulation test system for gas-liquid countercurrent in an abandoned mine goaf includes a three-dimensional analog simulation device configured to simulate an analog environment of gas-liquid countercurrent in an abandoned mine goaf, a gas supply system, an automatic water pressure control system and a hydraulic loading system. The three-dimensional analog simulation device includes a reaction frame and a three-dimensional analog simulation chamber. The reaction frame includes a beam, a base and a column for connecting the beam and the base. The three-dimensional analog simulation chamber is arranged inside the reaction frame. The test system can be used to simulate the gas-liquid countercurrent in an abandoned mine goaf so as to study the evolution of water accumulation and gas enrichment in long-term abandonment of closed mines and the migration evolution rules of gas-liquid two-phase in abandoned mines with high gas density.

Abstract: A supercritical CO2 reactor and a test system of creepage, diffusion and erosion of rock mass. The supercritical CO2 reactor includes a reactor body having a test chamber, a heating layer arranged in a side wall of the reactor body, a temperature sensor and a pressure sensor arranged in the test chamber, a sealing cover configured to seal an opening of the reactor body, a fixing component arranged on the sealing cover, a hydraulic loading component configured to apply an axial load on the specimen. The reactor body is provided with an air inlet/outlet pipe configured to communicate the test chamber with external environment. The air inlet/outlet pipe is provided with a air valve, and the fixing component includes vertical guide bars, an upper pad and a lower pad slideably arranged on the vertical guide bars. The hydraulic loading component includes a oil-loading tank and an axial loading rod.

Abstract: A three-dimensional analog simulation test system for gas-liquid countercurrent in an abandoned mine goaf includes a three-dimensional analog simulation device configured to simulate an analog environment of gas-liquid countercurrent in an abandoned mine goaf, a gas supply system, an automatic water pressure control system and a hydraulic loading system. The three-dimensional analog simulation device includes a reaction frame and a three-dimensional analog simulation chamber. The reaction frame includes a beam, a base and a column for connecting the beam and the base. The three-dimensional analog simulation chamber is arranged inside the reaction frame. The test system can be used to simulate the gas-liquid countercurrent in an abandoned mine goaf so as to study the evolution of water accumulation and gas enrichment in long-term abandonment of closed mines and the migration evolution rules of gas-liquid two-phase in abandoned mines with high gas density.

Abstract: A supercritical CO2 reactor and a test system of creepage, diffusion and erosion of rock mass. The supercritical CO2 reactor includes a reactor body having a test chamber, a heating layer arranged in a side wall of the reactor body, a temperature sensor and a pressure sensor arranged in the test chamber, a sealing cover configured to seal an opening of the reactor body, a fixing component arranged on the sealing cover, a hydraulic loading component configured to apply an axial load on the specimen. The reactor body is provided with an air inlet/outlet pipe configured to communicate the test chamber with external environment. The air inlet/outlet pipe is provided with a air valve, and the fixing component includes vertical guide bars, an upper pad and a lower pad slideably arranged on the vertical guide bars. The hydraulic loading component includes a oil-loading tank and an axial loading rod.

Abstract: A rock sanding device includes a base, a bottom sanding plate, an adjustable connecting rod, an elastic loader, a connector, a side sanding brush, a top sanding plate, an inner rod, a prong and a drill rod. The top of the drill rod is fixedly connected with the rotating shaft of the external water drilling rig and the external water drilling rig has a water inlet joint to introduce water into the drill rod. The inner rod and drill rod are connected and fixed coaxially, and the bottom of the drill rod is symmetrically welded with four prongs. The rock specimen is placed in the center of the side sanding brush. The top sanding plate and the bottom sanding plate are provided in the top side and bottom side of the rock specimen, respectively.

Abstract: An LED display screen case includes a module, a HUB plate, a case frame, a power supply and a receiving card. One side of the HUB plate is connected with the module by a plug A and an interface A in a plugging mode. The other side of the HUB plate is connected with the receiving card by a plug B and an interface B in the plugging mode. A through hole is formed at a position corresponding to the plug B on the case frame. The plug B passes through the through hole. The receiving card and the HUB plate are connected by the plug B and the interface B in the plugging mode and fixed to the two sides of the case frame. This kind of connection type reduces the space inside the case for accommodating devices, and also ensures the good radiating effect of the case.

Abstract: A locking connection device, an LED box and an LED display screen are provided. The device includes a locking module and an inserting module. The locking module includes a hook and a bump matching with each other. The inserting module includes a fixing pin and a fixing hole matching with each other. The fixing pin and hook are fixed on a first base, and the bump and the fixing hole are fixed on a second base. The locking connection device further includes a driving module that propels the hook and the fixing pin to move synchronously. When the driving module finishes a travel, the hook and the bump are securely connected, and the fixing pin and the fixing hole are securely connected. Since the locking module according to the present invention locks the movement of the first base and the second base along the axial direction of the fixing pin and meanwhile the inserting module locks a circumferential movement of the fixing pin, the first base and the second base are securely fixed.

Abstract: An LED display screen case includes a module, a HUB plate, a case frame, a power supply and a receiving card. One side of the HUB plate is connected with the module by a plug A and an interface A in a plugging mode. The other side of the HUB plate is connected with the receiving card by a plug B and an interface B in the plugging mode. A through hole is formed at a position corresponding to the plug B on the case frame. The plug B passes through the through hole. The receiving card and the HUB plate are connected by the plug B and the interface B in the plugging mode and fixed to the two sides of the case frame. This kind of connection type reduces the space inside the case for accommodating devices, and also ensures the good radiating effect of the case.

Abstract: A locking connection device, an LED box and an LED display screen are provided. The device includes a locking module and an inserting module. The locking module includes a hook and a bump matching with each other. The inserting module includes a fixing pin and a fixing hole matching with each other. The fixing pin and hook are fixed on a first base, and the bump and the fixing hole are fixed on a second base. The locking connection device further includes a driving module that propels the hook and the fixing pin to move synchronously. When the driving module finishes a travel, the hook and the bump are securely connected, and the fixing pin and the fixing hole are securely connected. Since the locking module according to the present invention locks the movement of the first base and the second base along the axial direction of the fixing pin and meanwhile the inserting module locks a circumferential movement of the fixing pin, the first base and the second base are securely fixed.