Model studies of subsidence and ground movement using laser holographic interferometry

Abstract

Laser holographic interferometry is a method of remotely monitoring surface movement even on the surface of granular material in three dimensions, without the surface disturbances associated with instrument emplacement. In this study models of longwall and room and pillar layouts were used to demonstrate the validity of the technique and, subsequently, to generate data as the parameters controlling displacement were varied. The effects of cavity size, depth and orientation and material elasticity, time and geologic structure on surface displacement were analyzed. Gelatin and sand were successfully used as model materials in the study which has demonstrated that laser holographic interferometry is a practical system with potential to examine complex structures such as multiple panel extraction in longwall, multiple seam extraction or extraction of seams associated with irregular geologic conditions which might otherwise be difficult to monitor.