Aiming at the poor results of Knothe time function in predicting surface dynamic subsidence

Richards model is proposed. Based on analyzing the characteristics of the surface subsidence induced by coal mining

the elementary features of the perfect time function which could describe the full subsidence process are presented; and then

Richards growth model is introduced and established before the qualitative and quantitative relationships between parameters of model and geologic and mining conditions are given. Finally

model applicability is discussed; precise results could be attained while Richards model is applied to continuous and gradual subsidence area. A case study is given. The results show that: Richards model which satisfies the requirements of perfect time function could effectively simulate the whole process of surface subsidence and quickly calculate the parameters

including movement duration and subsidence

velocity and acceleration of a certain point in the surface movement basin at anytime; additionally; the flexibility of Richards model indicates it could be used in practice widely.