Parameter calculation method for optimized segmented Knothe time function

To overcome the problem of parameters calculation for optimal segmented Knothe time function,two calcula- tion methods are presented. Firstly,based on the surface monitoring data of a mining area,or mining areas with similar geological and mining conditions,the back-calculation and comparison method of parameter determination is proposed. It gives a detailed parameter calculation process,which is intuitive,easy to operate,and versatile,and can also be used to obtain the parameters for other time functions. Secondly,based on the surface subsidence law when the goaf reaches its full mining size,and the corresponding probability integration parameters,a “direct calculation method” of parame- ter determination is proposed. The parameters of the method are clear in meaning,and the process of parameter calcu- lation is convenient and can be directly applied to program calculation. Through the dynamic prediction practice,it is shown that the maximum relative error of the dynamic prediction can be controlled within 9% using the method de- scribed in the paper. With the increase of mining time,the dynamic prediction accuracy will gradually increase and it will eventually be maintained at around 5% . According to the statistics,the relative prediction error of the maximum surface subsidence can be maintained at around 6% . Application practice proves the practicability and reliability of the method proposed in the paper.