Axial effect of gas seepage in bedding fractured coal under multistage loading and unloading and its application

Abstract

In order to obtain the law of gas seepage in the direction of parallel bedding and vertical bedding fracture in front of coal body under the influence of mining, the seepage experiments under loading and unloading paths were carried out by using gas permeability experimental device. The test results show that the loading process of coal sample goes through three stages of compaction, elastic deformation and plastic deformation, and the gas seepage rate in both directions decreases with the increase of stress. During the unloading process, the gas permeability in both directions is partially restored. The gas permeability in parallel bedding direction is always greater than that in vertical bedding direction under loading and unloading. In practice, boreholes withvertical bedding and parallel bedding direction are arranged in front of the mining face to investigate the gas drainage amount. The practice shows the gas permeability characteristics of coal samples obtained in the test can truly reflect the gas permeability law of the coal body in front of the working face. But the stress change process of the coal in front of the mining face is not completely equal to the loading and unloading process of the coal sample. After the coal body is fully depressurized, the permeability in all directions is greatly improved.

Keywords

• loading and unloading
• bedding fissures
• gas seepage
• mining influence
• gas drainage