scholarly journals Gas seepage characteristics of loaded coal under negative suction pressure

2020 ◽  
Author(s):  
Xiang-Chun Li ◽  
Jia-Xing Gao ◽  
Qi Zhang ◽  
Zhong-Bei Li ◽  
Lei Xie ◽  
...  
Keyword(s):  
Suction Pressure ◽  
Gas Seepage ◽  
Seepage Characteristics ◽  
Negative Suction

Experiment Study on the Relationship between the Height of Capping Layer and the Porosity of Broken Rocks

2012 ◽  
Vol 594-597 ◽  
pp. 2323-2330
Author(s):  
Cui Feng Du ◽  
Bin Li
Keyword(s):  
Simulation Experiment ◽  
Air Leakage ◽  
Experiment Study ◽  
Forchheimer Equation ◽  
Capping Layer ◽  
Numerical Fitting ◽  
Gas Seepage ◽  
Seepage Characteristics ◽  
The Relationship

The gas seepage characteristics of four kinds of broken rocks of different gradations and the relationship between the capping height and the porosity were studied by means of the simulation experiment and the theoretical analysis. The results show that the air flow in the capping layer composed of broken rocks is in the non-Darcy state which can be described as Forchheimer equation and Ergun equation. Moreover, on the basis of the experimental data, the relational expressions between the permeability, the non-Darcy β factor and the porosity were determined. Through the numerical fitting, the equation of the minimum capping height and the porosity was ultimately derived, which provided the basis and the reference for the determination of capping height and the air leakage control of mine.

scholarly journals Seepage and Damage Evolution Characteristics of Gas-Bearing Coal under Different Cyclic Loading–Unloading Stress Paths

Processes ◽  
2018 ◽  
Vol 6 (10) ◽  
pp. 190 ◽  
Author(s):  
Qingmiao Li ◽  
Yunpei Liang ◽  
Quanle Zou
Keyword(s):  
Cyclic Loading ◽  
Peak Stress ◽  
Cyclic Loading And Unloading ◽  
Evolution Characteristics ◽  
Three Phase ◽  
Boltzmann Function ◽  
Gas Seepage ◽  
Seepage Characteristics ◽  
Number Of Cycles ◽  
Gas Bearing

The mechanical properties and seepage characteristics of gas-bearing coal evolve with changes in the loading pattern, which could reveal the evolution of permeability in a protected coal seam and allow gas extraction engineering work to be designed by using the effect of mining multiple protective seams. Tests on gas seepage in raw coal under three paths (stepped-cyclic, stepped-increasing-cyclic, and crossed-cyclic loading and unloading) were carried out with a seepage tester under triaxial stress conditions. The permeability was subjected to the dual influence of stress and damage accumulation. After being subjected to stress unloading and loading, the permeability of coal samples gradually decreased and the permeability did not increase before the stress exceeded the yield stage of the coal samples. The mining-enhanced permeability of the coal samples in the loading stage showed a three-phase increase with the growth of stress and the number of cycles and exhibited an N-shaped increase under the stepped-cyclic loading while it linearly increased under the other two paths in the unloading stage. With the increase of peak stress and the accumulation of damage in coal samples, the sensitivity of the permeability of coal samples to stress gradually declined. The relationship between the damage variable and the number of cycles conformed to the Boltzmann function.

Experimental Study of Mechanical and Seepage Characteristics of Two Kinds of Coal Samples

2014 ◽  
Vol 1073-1076 ◽  
pp. 2098-2101
Author(s):  
Wen Pu Li
Keyword(s):  
Coal Sample ◽  
Axial Strain ◽  
Volumetric Strain ◽  
Quadratic Function ◽  
Coal Bed ◽  
Coal Bed Methane ◽  
Intensity Level ◽  
Methane Recovery ◽  
Gas Seepage ◽  
Seepage Characteristics

Mechanical and seepage characteristics of raw coal samples are the most important research contents of enhancing coal bed methane recovery, but the produce of raw coal sample is very difficult. Based on gas seepage instrument, mechanical and seepage characteristics were performed on normal briquette coal samples and coal samples containing gypsum. The results show that it can increase the cohesion and intensity level by adding gypsum in briquette coal. Porosity and permeability of coal containing gypsum is less than ordinary briquette coal sample. Permeability with axial strain curves of two kinds of coal samples can be fitted with a quadratic function well. In expansion stage, volumetric strain of ordinary coal sample is much smaller than the coal samples containing gypsum. The research has an important guiding significance on enhancing coal bed methane recovery and gateway supporting.

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