Effect of lower seam old workings on longwall powered supports in upper seam

Abstract

Load bearing capacity of powered roof supports is a key issue in the design of longwall panels. The existence of multiple seams in a given project may involve over mining or undermining operations across different seams. The paper envisages variation in stress distribution and load on powered supports in the upper seam longwall panel due to the presence of already mined out bottom seam consisting goaf, pillars and openings through detailed field investigations in an underground coal mine followed by finite element modeling study. Studies revealed that for every 40 m of face retreat, the load from the roof gradually gets transferred from the panel to the goaf. Stress distribution over chock shields was considerably affected when the face in upper seam reached 15-25m zone above the openings in lower seam. The presence of barrier in the bottom seam increases load on the chock shields in longwall panel of upper seam. � 2007 Taylor & Francis Group, London.