Mechanical Disturbances Accompanying Longwall Mining

Study based on large-scaled models

Abstract

Large-scaled model experiments have been conducted to study the strata behaviors accompanying longwall mining in a flat coal seam at a great depth, leading to the following results: With the face approaching, the abutment pressure appeared which was recognized by the increase of the in-situ stress, P-wave velocity and amplitude. With the face passing, the roof failure occurred which was characterized by the rapid decrease of P-wave velocity and amplitude. And then they were regained in the closed goaf. When the bonding strength between the seams was relatively large, roof caving hardly occurred in the goaf. It resulted in the maximum abutment stress of about five times the virgin stress. But, when the bonding strength was small, the bed seperation and the roof caving easily occurred with the face advancing, and the corresponding abutment stress was restricted twice the virgin stress.
In the field observations on stress changes and caving at Yotsuyama pit of Miike Colliery, the phenomena which are similar to those of the models were gained.