Fig 6 - available via license: CC BY-NC-ND
Content may be subject to copyright.
Source publication
The fractures in coal and rock mass are the main channels of gas seepage, and understanding the gas migration law during mining is the precondition of gas control. The long-term in-situ monitoring of the abutment pressure, fracture networks and gas-flow in front of a mining face was carried out and the 1-D connectivity ratio of boreholes were calcu...
Context in source publication
Context 1
... quantitatively evaluate the gas seepage characteristics under mining conditions, the gas flow monitoring in boreholes was carried out. It should be pointed out here that different monitoring times corresponded to different monitoring periods (distance to mining face) in each figure, and the same monitoring times were monitored in the same period in Figures 6 a to 6 The borehole monitoring results of gas flow showed that the natural gas emission from No. 15 coal seam fluctuated greatly and rose gradually in the initial stage, and gradually decreased with time in the medium term, but finally stabilized. In fact, the evolution process of gas flow could be understood as initial borehole penetration, gas gathering from primary fractures and mining associated fractures in coal and rock mass to borehole catheter, gas flow gradually rose. ...
Similar publications
Practices show that the triaxial stress change of mining-disturbed coal deeply affects its failure and permeability characteristics and easily cause the coal and rock dynamic disasters during deep underground mining process. The combined mechanic-damage-permeability experiments of gas-bearing coal were carried out under the mechanical paths of conv...
The efficient separation of coal and gangue in the mining process is of great significance for improving coal mining efficiency and reducing environmental pollution. Automatic detection of coal and gangue is the key and foundation for the separation of coal and gangue. In this paper, we proposed a hierarchical framework for coal and gangue detectio...
![Three basic types of cracks Anderson [3]. (a) Type I. (b) Type II. (c)...](publication/340278005/figure/fig1/AS:1084214703325239@1635508337651/Three-basic-types-of-cracks-Anderson-3-a-Type-I-b-Type-II-c-Type-III_Q320.jpg)
![Three basic types of cracks Anderson [3]. (a) Type I. (b) Type II. (c)...](publication/340278005/figure/fig2/AS:1084214703333441@1635508337675/Three-basic-types-of-cracks-Anderson-3-a-Type-I-b-Type-II-c-Type-III_Q320.jpg)
![Three basic types of cracks Anderson [3]. (a) Type I. (b) Type II. (c)...](publication/340278005/figure/fig3/AS:1084214703333443@1635508337723/Three-basic-types-of-cracks-Anderson-3-a-Type-I-b-Type-II-c-Type-III_Q320.jpg)
In China, coal-gas outburst is seriously affecting safety of the coal mine. To improve the safety status of underground coal mining, this work investigated the evolution process and occurrence mechanism of coal-gas outburst under the coupling action of stress and gas. Results show that increasing either gas pressure or in-situ stress can make coal...
Solid backfill coal mining (SBCM) is a green mining technology which can effectively alleviate the environmental problems induced by traditional coal mining techniques, such as surface subsidence, water resources loss, coal gangue occupation, and pollution. In this study, a multilayer Winkler foundation beam model for the overburden key strata is p...
Coal is the mainstay of China’s energy supply. With the gradual progress in China’s policy of phasing out backward coal production capacity, the intensive and deep mining of coal has gradually become the new norm. The current mining depth is increasing at a rate of 10~15 m/year. The high crust stress, high gas pressure, high ground temperature, and...
Citations
... Gao et al. [33] used a self-developed experimental device for measuring the kinetic effect of coal and gas protrusion to conduct protrusion experiments under different adsorption effects, and they investigated the role of adsorption in the dynamics of coal and gas protrusion. Liu et al. [34][35][36][37][38][39][40][41][42] selected a reasonable model to simulate a tunnel project through repeated comparisons and continuous summarization of the computational methods, and they analyzed the diffusion and accumulation of harmful gases in the tunnel. Wei et al. [43] constructed a thermo-hydraulic-mechanical coupled gas emission (THMGE) model and verified the gas emission results with three driving headings, and through calculations, they analyzed the effects of temperature, time, and gas pressure on gas emission. ...
Gas control and extraction are essential for energy use and sustainable development. In order to study the gas diffusion and transportation law of high-gas tunnels after excavation and blasting and the influence of ventilation on gas concentration, an engineering example is used as a research object. We put forward the “energy concentrating device + digital electronic detonator”, a new type of peripheral hole in the joint initiation of explosive technology, applied to a tunnel in the plateau, studied through field tests and the original “detonating cord + digital electronic detonator” joint detonation technology after a comparative analysis of the blasting effect. On this basis, the characteristics of gas diffusion and transportation near the palm face were studied by numerical simulation under the two working conditions of ventilated and unventilated, and the law of gas diffusion and transportation near the palm face was obtained. The research shows that: with the “energy concentrating device + digital electronic detonator”, a new perimeter hole joint detonation technology compared to the original “detonating cord + digital electronic detonator” joint detonation technology, the explosive unit consumption reduced by 0.2 kg/m3, half-hole retention rate increased by 5%, average charging time shortened from the original 1.3 h to 1.0 h, and stabilizing the cycle of footage at the same time greatly reduces the cost of consumables, improving the tunnel surface blasting effect; numerical simulation shows that under the condition of no ventilation, the gas accumulation near the arch top and arch waist at the tunnel face is severe, with the gas concentration close to 30%, the gas concentration is higher up to 7 m from the face after the gas state is stabilized, and the gradient of the gas concentration in the area beyond 7 m is small. The gas concentration in the area can be reduced to the safe range after ventilation in about 30 s, but gas accumulation easily occurs in the foot and arch waist on the opposite side of the wind pipe. The results of this study can provide a reference basis for similar gas tunnel blasting construction and ventilation optimization and promote the sustainable development of energy.
... Coal seam mining activities tend to destroy the stress balance states of overlying strata within the influence range of the production areas, resulting in the movement and destruction of the overlying strata. The creation of many fractures in the strata provide good migration channels for methane in goafs (Peng et al. 2019). Therefore, examining the fracturing processes of the overburden rock in mines and the distribution laws of the fracture evolution, are of major importance in determining the dominant channels of pressure relief methane in mining fracture fields. ...
The evolution and distribution laws of fracture fields directly affect the efficiency of mining methane extraction. In this study, a physical model test method and a DIC speckle analysis system were used to examine the distribution laws of the dominant mining fracture fields of pressure relief methane migration in working face advancement processes. The results revealed that during the advancement of working faces, the fracture angles on both sides of the goafs and the top separation fractures form ladder-type overburden fracture structures. A large number of penetrating cracks were generated in the caving zone, transition zone and vertical fracture zone in the ladder structure, which provided dominant channels for methane migration. The average extraction purity of 12 m³/min and the average concentration of methane extraction in surface wells were both above 90% in the fracture-filled area. Methane had an excellent migration channel and storage space. As the fracture begins to close, the methane extraction efficiency decreases until the methane extraction concentration was reduced to a minimum of 8.1% and the methane extraction purity was reduced to a minimum of 0.03 m³/min. The field data change results of methane extraction were consistent with the experimental theory. The research results can provide references for improving the efficiency of methane extraction and optimizing the layout of drilling wells and their horizons.
... The overlying rock of the working face will migrate and break after mining. The overlying strata will experience a significant number of fractures, providing pathways for gas storage and flow [4,5]. The gas reserve law in coal mines in China shows the feature of three high (high plasticity structure of coal seam, high gas adsorption ability of coal seam, and high gas content of coal seam) and three low (low gas pressure of coal seam, low gas saturation of coal seam, and low rate of gas permeability of coal seam), which causes the effect of pre-mining gas extraction to be ineffective. ...
... Moreover, the model equation of effective velocity and eddy modification gram mark was involved to adapt to the influences of the eddy on low Reynolds number, near-wall flow, and modified turbulence flow in the laminar flow: where ∧ v = (u + u t )/u; u t differs for different liquid states. Turbulence flow and eddy are determined according to Equation (4). ...
The key parameters of high-level boreholes in high drainage roadways affect the gas treatment effect of the working face directly. Therefore, the layout parameters of high-level boreholes in the lateral high drainage roadway (LHDR) are determined and optimized as necessary. Based on the LHDR layout on the 2-603 working face of the Liyazhuang coal mine, the key technological requirements on high-level borehole parameters were analyzed and the distribution characteristics of the gas volume fraction in the coal roof were studied. The gas migration law in the mined-out areas was obtained and the layout locations of high-level boreholes were determined finally. The research demonstrates that the high-level boreholes lag the 2-603 working face distance and the position of the final borehole (the position of the final borehole in this paper refers to the distance between the final borehole and the roof) influence the stability of boreholes and the gas extraction effect. The distribution of the gas volume fraction from the intake airway to the return airway can be divided into the stable stage, slow growth stage, and fast growth stage. Influenced by the flow field in the mined-out areas, the mean volume fraction of the borehole-extracted gas has no obvious relationship with the gas volume fraction at the upper corner. According to the final optimization, the high-level borehole is determined as having a 15 m lag behind the working face and the position of the final borehole is 44 m away from the coal seam roof. These have been applied successfully in engineering practice.
