Assessment of ground instability risk of lower seam longwall panels during crossing overlying remnant pillars.

One of the most challenging safety problems is ground instability during crossing overlying remnant pillars (CORP). Ground instability not only causes injury to miners or fatalities, but also leads to interruptions in the mining operations and breakdowns in equipment. In this paper, 12 major parameters influencing the ground instability were firstly determined based on extensive international experience associated with CORP.

The occurrence state of moisture in coal and its influence model on pore seepage.

Moisture is one of the most important factors that influences coal seepage and coal-bed methane (CBM) extraction. To obtain the water occurrence state and dynamic processes of water change in coal, a series of microscopic observation experiments of Wei Jiagou coal by using field-emission environmental scanning-electron microscopy (ESEM) was conducted under the condition of a fixed point. Afterwards, a mathematical model to explain the influence of water on porosity and permeability was proposed based on the ESEM observations.