Innovative backfilling longwall panel layout for better subsidence control effect—separating adjacent subcritical panels with pillars

Abstract

In recent years, field trials of non-pillar longwall mining using complete backfill have been implemented successively in the Chinese coal mining industry. The objective of this paper is to get a scientific understanding of surface subsidence control effect using such techniques. It begins with a brief overview on complete backfill methods primarily used in China, followed by an analysis of collected subsidence factors under mining with complete backfill. It is concluded that non-pillar longwall panel layout cannot protect surface structures against damages at a relatively large mining height, even though complete backfill is conducted. In such cases, separated longwall panel layout should be applied, i.e., panel width should be subcritical and stable coal pillars should be left between the adjacent panels. The proposed method takes the principles of subcritical extraction and partial extraction; in conjunction with gob backfilling, surface subsidence can be effectively mitigated, thus protecting surface buildings against mining-induced damage. A general design principle and method of separated panel layout have also been proposed.