Study on Compaction Deformation Characteristics of Collapsed Rock Mass of Goaf Under Different Water Content Conditions

In order to study the influence of water flling goaf on the surface deformation, and provide scientific basis for stability evaluation of goaf, collapsed rock were taken from No.5 Seam goaf in Yangzhuang Coal Mine, compaction tests were completed with natural and saturated loose rock mass under different loading grade s. These tests were finished to learn compaction deformation of loose rock mass under different conditions. Under every loading grade, axial stress measured by press ure sensor changed with increasing time, and axial compression deformation of loose rock mass could be also measured. Under every loading grade, axial stress monit ored by pressure sensor increased firstly then decreased, and stress concentration dissipated during compacting process of loose rock mass. With the increasing of loa d, the increment of compressive deformation decreased. Under the fixed load, the unsaturated loose rock mass which had no deformation any more would deform rapidI y and obviously affer water injection, which could lead to the secondary deformation of the surface of goaf.