Research progress and prospects of non-pillar mining technology with flexible formwork concrete support

The conventional practice of leaving coal pillars for roadway protection can readily induce dynamic disasters such as rockbursts,coal and gas outbursts,and goaf water inrush,which has long been a common challenge constraining safe and efficient coal mining. To address this challenge,based on the achievements of industry-university-research collaboration over the past two decades, systematic research on non-pillar mining technology and equipment systems has been conducted. Six generations of flexible formwork materials-preformed,self-forming,lightweight,high-strength,and three-dimensional textile-structured—have been successively and iteratively developed, and flexible formwork concrete support technology has been established. An innovative “six-in-one” integrated support equipment system has been constructed,covering anchor-avoidance protection in the end zone,mesh-laying roof protection in the transition zone,gangue-blocking and roof-cutting in the goaf, formwork-hanging support in the space to be poured,strengthened support in the retained roadway section,and temporary support in the advance section. Based on the above material and equipment systems,four types of flexible formwork non-pillar mining technologies have been further developed:gob-side entry retaining,gob-side retaining wall,gob-side entry driving,and gob-side pre-driving. This technology system can fundamentally avoid various mine dynamic disasters induced by leaving protective coal pillars,thereby enabling safe,efficient,and green mining of coal resources and providing important support for promoting the large-scale application of non-pillar mining technology in China.