Stress evolution of an irregular pillar protected roadway system remained along goal in fully mechanized top-coal caving mining field

The stress distribution and its evolution modes in surrounding rocks of a roadway were comprehensively studied with respect to different pillar widths, where the roadway had been protected by an irregular pillar remained along the goaf in mechanized top-coal caving mining and supported by bolt-mesh technique. The study manifested the uncoupled pattern of the peak stresses in vertical and horizontal directions, as well as the stress evolution trace varying with pillar width. The control variable was pointed out for the mechanical system, and the different stability areas were distinguished correspondent to its value. Through the general analysis and assessment on stability of the roadway system protected by the pillar with different widths, the reasonable pillar width was promoted for effective protection of the roadway in mechanized top-coal caving mining panel. A comprehensive control technique was proposed and employed in practice through reinforcing the irregular pillar as a main way and hanging the mesh and bolt rock mass as a auxiliary means to support the gateway remained along the goal.