In-situ stress measurements and analysis of action of geological structures of deep coal mines in Xuzhou

In order to ensure the safety of tunnel maintenance and mining operation of coal mines in Xuzhou, in-situ rock stresses are measured in 5 coal mines of Xuzhou mining area at a depth of over 800 m by means of the boring stress-relief method with hollow inclusion triaxial strain gauge. The stress measurement data indicate that the maximum horizontal principal stress at all measureing points are little greater than the vertical principal stress. The direction of the maximum principal stress is almost NW-SE nearly horizontal. The in-situ stress values have differences between the eastern and western areas because of geological structures. The stress in western and north-western areas shows the characteristics of hydrostatic-pressure, while the ratios of the maximum horizontal principal stresses to the vertical principal stress are 1.19～1.23 in the eastern minining areas. The variation of stress magnitude, and the stress and coeficient of horizontal pressure with buried depth is analyzed. The action of Xuzhou-Suxian nappe structure in NE direction induced by left traverse transition of Yan-Lu major dislocation is analyzed. The distribution laws of in-situ stress field obtained by the practical measurement show good agreement with the regional tectonic stress field. The results may provide reliable basic stress data for deep mining.