Coal-gas compound dynamic disasters in China: A review

Assessing the effectiveness of a high-temperature-programmed experimental system for simulating the spontaneous combustion properties of bituminous coal through thermokinetic analysis of four oxidation stages

Experimental investigation on the formation and transport mechanism of outburst coal-gas flow: Implications for the role of gas desorption in the development stage of outburst

Experimental study of pore structure and fractal characteristics of pulverized intact coal and tectonic coal by low temperature nitrogen adsorption

Mechanical behaviors and acoustic emission fractal characteristics of coal specimens with a pre-existing flaw of various inclinations under uniaxial compression

The invention discloses a low-resistance high-heat-capacity twist drill rod and a using method The drill rod comprises a steel pipe and a spiral steel belt The hollow interior of the steel pipe is blocked to form a water storage space An antifriction coating is arranged on the side, away from the steel pipe, of the spiral steel belt When the drill rod is in use, an end cap is opened at first, the water yield is injected according to a calculation result, and the end cap is screwed on; a drill bit is inserted into the drill rod through a female joint, an electric drill and a male joint are connected through a hexagonal plug, and dry drilling is performed in a coal layer; a new drill rod is connected in every time one drill rod is inserted till the preset depth is reached According to the drill rod, friction resistance between the drill rod and the coal layer can be lowered; meanwhile, a large amount of heat generated by friction in the drilling process can be absorbed, the dry drilling process is kept to be stably operated, a chip removal channel of the twist drill rod is made to be smooth, a drill hole with the maximum depth can be drilled in, and conditions are provided for the outburst prevention effect for detecting the section coal layer through a continuous flow method

Low-resistance high-heat-capacity twist drill rod and using method

Disclosed is a quick pressure relief gas discharge method for exposing an extra thick and soft projecting coal seam in a vertical shaft, comprising the following steps: designing drainage drill holes in several circles along a shaft excavation work surface contour; dividing the drainage drill holes into multiple nine-hole flushing and nine-hole injection units; performing drilling construction on each nine-hole flushing and nine-hole injection unit; performing a pressure test on the drilling holes; sequentially flushing coal of nine drill holes of the nine-hole flushing and nine-hole injection units; constructing a gas inspection hole in the area of the nine-hole flushing and nine-hole injection units completed flushing coal, and measuring the gas content; cementing the nine drill holes of the nine-hole flushing and nine-hole injection units completing measuring the gas content; and sequentially flushing coal and cementing all nine-hole flushing and nine-hole injection units. The method avoids problems such as shaft wall cracking caused by the change in the stress after punching, strengthens the coal, increases the discharge amount of a single hole under the premise of ensuring the safety, and achieves quick pressure relief gas discharge of an extra thick and soft projecting coal seam.

Quick pressure relief gas discharge method for exposing extra thick and soft projecting coal seam in vertical shaft

The invention discloses a repeatable hole digging gas extraction method for a down-hole high-stress soft coal seam. The method comprises steps as follows: rock drilling is constructed in a rock roadway drill site; a seamless steel pipe is pushed into a rock hole, the tail end of the seamless steel pipe is exposed out of the opening of the rock hole, and a flange cover plate provided with a high-pressure valve is mounted at the tail end of the seamless steel pipe; the seamless steel pipe is fixed; cement slurry is injected into the seamless steel pipe; after the cement slurry is solidified, extraction drilling is constructed in the seamless steel pipe; a pressure-tight test is performed on an extraction hole; the extraction drilling is constructed continuously until the hole penetrates through the coal seam to reach a rock stratum, and the high-pressure valve is connected with a drainage system for extraction; if the gas flow or the gas concentration is found to decrease obviously, the extraction hole is cleaned again until the extracted gas amount in the extraction range reaches the preset value. On the premise that hole sealing is guaranteed, the hole is dug repeatedly, the drainage concentration is increased, meanwhile, the ground stress of the area can be significantly reduced, and coal and gas outburst risks of the coal seam are reduced.

Repeatable hole digging gas extraction method for down-hole high-stress soft coal seam

To solve the problems of backward means of coal mine gas and coal dust explosion monitoring, late reporting, and low leakage rate, a sound recognition method of coal mine gas and coal dust explosion based on GoogLeNet was proposed. After installing mining pickups in key monitoring areas of coal mines to collect the sounds of the working equipment and the environment, the collected sound was analyzed by continuous wavelet to obtain its scale coefficient map. This was then imported into GoogLeNet to obtain the recognition model of coal mine gas and coal dust explosions. The test sound was obtained by continuous wavelet analysis to obtain the scale coefficient map, brought into the completed training recognition model to obtain the sound signal class, and verified by experiment. Firstly, the scale coefficient map extracted from the sound signal by continuous wavelet analysis showed that the similarity between the subjective and objective indicators of the wavelet coefficient maps of the gas explosion sound and coal dust explosion sound was higher, but the difference between these and the rest of the coal mine sounds was clearer, helping to effectively distinguish gas and coal dust explosion sounds from other sounds. Secondly, the experimental results of GoogLeNet parameters can be obtained. When the dropout parameter is 0.5 and the initial learning rate is 0.001, the recognition effect of the model established by GoogLeNet was optimal. According to the selected parameters, the training loss, testing loss, training recognition rate, and testing recognition rate of the model are all in line with expectations. Finally, the experimental recognition results show that the recognition rate of the proposed method is 97.38%, the recall rate is 86.1%, and the accuracy rate is 100% for the case of a 9:1 ratio of test data to training data, and the overall recognition effect of the proposed GoogLeNet is significantly better than that of vgg and Alexnet, which can effectively solve the problem of under-sampling of coal mine gas and coal dust explosion sounds and can meet the need for the intelligent recognition of coal mine gas and dust explosions.

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Xiaowei Li

Papers

Low-resistance high-heat-capacity twist drill rod and using method

Quick pressure relief gas discharge method for exposing extra thick and soft projecting coal seam in vertical shaft

Repeatable hole digging gas extraction method for down-hole high-stress soft coal seam

Sound Recognition Method of Coal Mine Gas and Coal Dust Explosion Based on GoogLeNet