In order to enhance the management level of coal mine safety production and promote the "safe, accurate and efficient" preventive treatments for gas in Guizhou of China, the occurrence and other prominent features of coal and gas are investigated. The characteristics and regularities of coal mine accidents in Guizhou during [2001][2002][2003][2004][2005][2006][2007][2008][2009][2010][2011][2012][2013][2014][2015] are summarized to analyze the commonness of gas accidents in general and determine the characteristics of gas preventive treatment. Geological data, gas basic parameters, and physical properties of coal of 386 mines and 761 sets of coal seams in Guizhou are also statistically analyzed. Based on step control theory of gas occurrence structure and the regionally tectonic regularity of coal-bearing stratum distribution, the deformations of coal measures in Guizhou mine area are mainly caused by great variation of stratigraphic occurrence, complicated geological structure, and high crustal stress. The regional occurrence of coal seam is obvious with the highest content of Tongzi-Zunyi-Liuzhi-Xingyi line, which gradually reduces to the both east and west sides. Influence factors and weights of gas occurrence are expounded from geological and coal factor by mathematical statistics, and the main influence factors of gas occurrence are the sedimentary environment, syncline structure, and metamorphic grade in proper sequence. Combined with the risk prediction of coal and gas outburst area, the prediction of gas pressure by gas content is not suitable under the special occurrence conditions. The initial velocity of gas emission, the solidity coefficient, and the damage type in more than 77%

In order to reduce the occurrence of coal and gas outburst accidents, and improve the capability to prevent gas hazards and realize the safe and efficient mining of coal enterprises. The distribution of the outburst coal mining area of Guizhou Province and the status of coal and gas outburst and the problems in the current outburst prevention methods were analyzed. The main issues were pointed out such as the lack of regional outburst prevention measures, unsatisfactory effect in drainage, poor management and implementation, as well as personnel that need more training. The prevention situation of coal and gas outburst in Guizhou Province was considered. In accordance with the above problems, from the perspective of strengthening geological exploration, testing coal seam parameters, studying outburst prevention technologies, deploying mining systems rationally, improving mine safety management systems, and strengthening protection facilities and other aspects, a targeted outburst prevention measure and proposals were put forward.

To study crack propagation around the fracture hole in the coal body induced by high-pressure CO2 gas produced by CO2 phase transition fracturing, the mechanism of permeability enhancement of fractured coal induced by liquid CO2 phase transition fracturing was studied from two aspects, the process of coal gas displacement by competitive adsorption and physical characteristics of fractured coal induced by phase transition. Crack propagation pattern in coal under different lateral coefficients was explored by using discrete-element numerical simulation software. Distribution characteristics of hoop stress of fractured coal were analyzed through theoretical calculation. The results show that: (1) Micro-cracks in damaged coal body generated during phase transition process are mainly crack_tension type, which are formed by the composite action of tension and compression. The crack propagation is the result of the continuous release of compressive stress from concentrated area to the surrounding units. Micro-cracks are radially distributed in a pattern of “flame”. (2) The main crack formed above the fracture hole grows in the direction of vertical minimum initial stress, and the main crack formed below the fracture hole develops in the direction of horizontal initial stress. As the lateral compression coefficient increases, the extension distance of the second crack will not change after reducing to a certain length. (3) As the distance from the fracture hole increases, the peak compression loaded at the monitoring point decays, and the loop stress in the cracked coal is distributed in a pattern of “peanut”. It provides practical methods and ideas for studying the macroscopic and microscopic development of cracks, as well as theoretical support for the on-site hole layout.

No abstract

No abstract