Dynamic surface subsidence prediction model based on Bertalanffy time function

Conventional surface subsidence prediction is the final static surface movement and deformation prediction after finishing the working face mining. When involving a protective mining under buildings or structures,buildings or structures reinforcement and their rectifying governance,it needs to understand the law of surface dynamic movement and deformation under its geological and mining conditions. Firstly,this paper analyzes the advantages,disadvantages and applicability of the common time function,such as Knothe,Logistic,Weibull,segmented Knothe,power functionKnothe and hyperbolic curve common time function,and analyzes the characteristics of their curve forms,dynamic surface sinking,sinking speed and sinking acceleration in each period. Secondly,based on the measured data of surface moving deformation in Dongpo Coal mine and in view of the particularity of surface movement and deformation for extra thick seam using fully mechanized caving mining method,the Bertalanffy time function is introduced,based on that,the Bertalanffy three-parameters time function is improved. Also,the paper analyzes the influence law of each parameter in the improved Bertalanffy three-parameters time function. Internal relation of the physical meaning for each paramete and its geological and mining conditions are studied. Finally,the time function is used for No.1 mine of Pingshuo mining region whose mining method is extra thick seam fully mechanized caving mining method,and its dynamic subsidence goodness of fit under this condition is tested. Results show that the physical significance of the parameters based on the improved Bertalanffy three-parameters time function is intrinsically related to the geological and mining conditions. This model has strong plasticity,good prediction accuracy and application breadth,and can be applied to the prediction of dynamic surface deformation of coal mine. Based on the improved Bertalanffy three-parameters time function combined with the influence function method,this method can effectively solve the problem of dynamic surface subsidence prediction under the regional variable mining height conditions,such as the limited thickness extraction in extremely thick coal seam and the unstable thickness of the coal seam.