DISCUSS ON SUPPORTING MEASUREMENT TIME TO THE SURROUNDING ROCK MASS OF UNDERGROUND EXCAVATION IN THE LOW GROUND STRESS REGION

This paper have summarized deformation and failure types of the surrounding rockmass in underground excavation, and the studied on the basis of a water conservancy nearby a municipality in Northwest China. It's put forward 3 failure types: they are gravity fall, tension collapse and extrusion press slide types. According to the relationship between displacement and time of the surround rockmass, then reasonable supporting measurement time for surrounding rock mass stability have been determined by authors. It's not only useful to practice engineering measurements which are suitable for surrounding rock mass stability, but also useful to study its theoretical and engineering significance.