Improvement of prediction method for heights of caving zone and fracturedzone induced by repeated mining of contiguous coal seams

In order to solve the inaccurate problems of calculation results of combined mining height (MZ) formula derived from‘ mining regulations under water, railway and buildings’, to contiguous seams group when the distance between the upper and lower coal seam is large, based on the mining-induced subsidence law and time effect, the authors put forward prediction method of height of “two zones”(caving zone and fractured zone) to two or more layers of contiguous coal seams. The results show that, according to the mining height (M), caving zone’s height (Hk) and interlayer’s distance(h), the contiguous coal seams group can be divided into close contiguous coal seams (M