Experiment study on the law of effective stress of coal masses during methane drainage

摘要

The methane drainage can not only make coal seams deformation, but also effect its stress distribution. Based on lab experiment on methane drainage with a cubic coal sample of 500 mm × 500 mm × 500 mm, mutative law of coal of pore pressure (p) and effective stress (σ_(ef))_i were investigated during methane drainage with the coal sample of China Lu'an coal field No.3 coal seam. The experiment results indicate: during methane drainage, pore pressure (p) follows exponential attenuation law: p=aexp(-bt); effective stress (σ_(ef))_i of coal masses follows logarithm incremental law: (σ_(ef))_i=aln t+b, (i=x, y, z); effective stress coefficient(α) follows logarithm attenuation law: α=a-bln t; effective stress coefficient, volume stress (Θ_(ef)) and pore pressure (p) follow bilinear law.