Abstract: The similar material simulation test results show that the overlying joint rock mass subsidence caused by underground coal mining appears skewness characteristics. The geological and mathematical model considering the joint angle, trace length and the trace width is established and the probability distribution function of the overlying joint rock mass subsidence caused by the underground coal mining is deduced by using the random medium theory. At the same time, the probability distribution of surface subsidence caused by mass mining is assumed to be in accordance with the n-Bernoulli trial distribution. The n-Bernoulli trial distribution is equivalent to Poisson distribution when n is equal to or larger than ten. The overlying joint rock mass prediction equations considering the continuity of surface subsidence are proposed based on Gamma distribution (expanded version of Poisson distribution). The comparison between the results of surface subsidence computed by the model calculation and those measured by the similar material simulation experiment has shown that the presented model can predict a single set of joint rock mass subsidence caused by the underground coal mining with relatively good accuracy, which provides technical support for mining subsidence forecasting and strata movement monitoring.

Key words: coal mining, jointed rock mass, surface subsidence, skewness, Gamma distribution