Residual Subsidence Study Of Goaf Based On Key Stratum And Project Case Study

The coal mining presents the trend of increasing year by year in our country, but dueto the immature mining technology and management, coal mining causes many problems.There are two major categories: the first is the surface subsidence problem caused by coalbed mining; the second category is the stabilized old goaf’s residual subsidence problemcaused by new construction on its surface. Up to now, scholars at home and abroad havedone a lot of work on the first kind of problem, and have formed a variety of surfacesubsidence prediction methods in which the probability integral method is center. But forthe second problem, some theories and methods of calculation proposed by scholars isrelatively narrow, not yet formed a mature method, so the old goaf’s surface residualsubsidence problem caused by "activation" needs a further research.Based on above background, this paper summarizes the existing research results,combined with a new tailings project on a mined-out area, and focuses on studying thegoaf’s surface residual subsidence problem. First, analyze the mechanism of goaf’ssurface residual subsidence caused by new construction and establish the surface residualsubsidence prediction model which key stratum controls. Combine the theory of beam onelastic foundation and a new prediction formula of surface residual subsidence is derived;Then, combined with the specific circumstances of a new tailings on the mined-out areaproject, select the old mined-out area which under the new tailings and affected byrepeated mining as key research area. According to the field deformation observation test,collect and analyze the observation data; Last, apply the probability integration methodand surface residual subsidence prediction method which this paper put forward to the keyresearch area of the new tailings project. Then predict the surface subsidence caused bycoal bed mining and surface residual subsidence. Combine the two parts and comparedwith the field deformation observation data to verify the feasibility of this method.Through the research, get the following conclusions: when analyzing the residualsubsidence of mined-out area with a thick hard key stratum structure, the key stratumtheory in ground control can be introduced, then the residual settlement problem is converted to the deformation problem of a key stratum under overlying load, making theproblem simply. The biggest residual subsidence occurs at the center of the mined-outarea, and the maximum settlement is inversely proportional to the rock lithology underkey stratum, the thickness of key stratum and the completeness of key stratum and isproportional to the overlying load. This method is applied to a new tailings project on agoaf, the calculated values are in good agreement with the measured values, so thismethod is proved to be feasible.