The Stability Evaluation Of Rockfall Geological Hazard In The East Of Shanshuya Phosphorite Mine Areas, Hubei

As a main phosphate rock resources production province, Hubei has a long history of phosphate rock exploition, which also followed with frequently hazards. With the exploition of mine resources, mine geological disaters occur more and more. What’s more, the area of collapse of mine-out is also increasing. The geological hazards caused by the collapse of mine-out area always put threat on the local residents.This paper dealt with the analysis of dangerous rock body in the west ore block that of phosphorus mineral region in the Shanshuya, Yichang City, Hubei province. Firstly, we described the geological setting of the study area. Then, we analysed the characteristic and rule of the dangerous rock block. Finally, in order to understand the formation mechanism and predict the geological hazards, we applied visualized analysis of the formation and development process of the collapse of the dangerous rock. This will be benefit to the phosphate rock exploition and related research, and provide suggestions for prophylaxis and treatment.(1) Thick-layer dolomitite of Dengying Formation of sinian series is the main lithology in the slope of our study area. The study area is an area of high risk of dangerous rock blocks with complicate geological setting. The existence of several faults makes the requirement of collapse of dangerous rock.(2) We did field work in the dangerous rock area and summarized the structure characteristic, force analysis and distribution of the dang erous rock. We also analyzed the movement of dangerous rock after collapsing and found that it could happen suddenly and with uncertain motion trail.(3) We evaluated the implication of mine exploition on stabilize of the dangerous rock block by models. The modeling result shows that the roof of rock rack height is 189.13m which is caused by the underground mining. This is possible to effect the Dengying group layer and connect with the tectonic fracture, thus lead to the extension of surface rupture. With the affect of gravity and load, dangerous rock collapses and casuses geological hazards.(4) Based on the study of the characteristic of dangerous rock block, two collapse patterns of dangerous rock blocks was indentified:pull cracks-slump collapse, pull cracks-dump.(5) Using 3DEC numerical modeling program, we model the evolution process of slope destroy caused by the underground exploition of phosphate rock mine. With the formation of underground goaf, asymmetry subsidence occurred on the slope, surface damaging on the slope become clear. The deformation and breakage process can be divided into three stages:phosphorite mining stage, underground goaf collapse stage, collapse formation stage.(6) Combined with field work, modeling and numerical modeling, we found that the surface subsidence caused by the large goaf area caused by mine exploition could lead to the unstability of dangerous rock and this caused geological hazards.