Determination on start-up area for floor rockburst at retained entry and its stepwise control technology

WANG Shuwen; JU Wenjun; PAN Junfeng

doi:10.13225/j.cnki.jccs.2017.0474

Abstract：Entry floor usually suffers the greatest damage after floor rockburst.But the start-up area is not neces-sarily located within the floor.Based on the floor rockburst occurred at retained entry behind working face in a coal mine in Shanxi Province,the time and space sequences of rock burst associated with their corresponding relationship were analyzed,and then the possible start-up area was pointed out.Numerical simulation code FLAC was utilized to analyze the load evolution law for the retained entry,and the "relief channel" model within the floor was established.Based on field data,the key parameters for stepwise control technology for rockburst were determined,and on-site applications was carried out.The results showed that:" relief channel" mechanism occurred within retained entry floor among the range of failure depth after the lateral coal was mined-out.The vertical stress in pillar increased,while the horizontal stress in the retained entry floor released through "relief channel".And the decline extent was positively correlated with the channel width.The elastic core area within pillar was start-up area for floor rockburst,and its increasing vertical stress was the leading load source.Due to the low strength of the floor,it became the main area where vibration energy transformed to the crack surface energy and kinetic energy.In order to prevent start-up and mitigate the extent of damage of rockburst,the stepwise control technology was utilized,including the advanced pre-split within the hard roof,drilling within start-up area,setting drilling within cache corner to buffer shock,and non-asymmetric support at retained entry.After the application of technology above,the rock burst was successfully contained.