Based on the traditional Knothe time model hypothesis

a new hypothesis is proposed and an improved Knothe time model is constructed. The theoretical analysis shows that the improved Knothe time model conforms to the variation law of surface point subsidence and subsidence velocity. Based on the improved Knothe time model

a calculation expression of the maximum surface subsidence velocity is deduced

and a method to determine the model parameters is given. The monitored values of maximum surface subsidence velocity caused by mining in 20 mining areas are used to compared with the theoretically predicted values. It shows that the predicted value is in good agreement with the monitored value

and the relative standard deviation is only 2.1%

which verifies the accuracy and reliability of the present model. It is important to note that the maximum surface subsidence velocity is affected by mining height

mining speed

loose layer thickness

bedrock layer thickness and other parameters. The maximum surface subsidence velocity increases linearly with the increase of mining height and mining speed

decreases nonlinearly with the increase of loose layer thickness and bedrock layer thickness

and its sensitivity to the change of bedrock layer thickness is higher than to that of loose layer thickness.