| Supported by project of national science fund "the study of spatial structure of overlying strata due to mining and the dynamic relationship with stress field " and project of national science fund for international significant cooperation " the mechanism of disaster rupture of overlying strata in mines" , the paper studied the forming , evolution laws , relationship with abutment pressure distribution and controlling technology of "θ" letter type multilayer spatial structure of overlying strata by way of similar material simulation, theory analysis, field exploring and numerical simulation ."θ" letter type overlying multi-strata spatial structure theory of coal pillar surrounded by mined areas is put forward in this paper. The process of overlying multi-strata structure forming is dynamic and constitutes the transition of rock girder structure and arch structure. In the unsufficient mining stage, the whole spatial structure of mining field is made of the largest arch structure and smaller arch structure in twins under it. In the sufficient mining stage, the whole spatial structure of mining field is divided into two smaller spatial structures relatively."θ" letter type overlying multi-strata spatial structure comes into being from top to bottom.Evolution of "θ" letter type spatial structures and abutment stress distribution laws are: when the residual strick size of isolated coal pillar is L=2hcostδ ( h is the average distance between roof of the toppest overlying strata and the top of mining coal seam, 5 is displacement angle of strata). The first "θ" letter type spatial structure is formed on the top of mining field ; the abutment pressure of the structure begin to accumulate, then the abutment pressure of isolated coal pillars increases obviously.Bumping pressure or fast deformation of coal pillar may be the possible disaster when mining isolated coal under "θ" letter type multiplayer spatial...
|
PDF Full Text Request