Distribution laws of in-situ stress in deep underground coal mines

With depth and intensity of coal mining increasing, effects of in-situ stress on deformation and failure of the surrounding rock are increasingly growing. Through data independently measured and collected within 600-1500m, this paper summaries distribution laws of in-situ stress in deep underground coal mines of our country, main existing types of in-situ stress and its directional characteristics. Maximum horizontal stress, minimum horizontal stress, vertical stress and lateral pressure ratio variation laws with depth are obtained by using regression analysis. Generally, in-situ stresses increase with depth. With increasing depth the rate of increase in horizontal stresses decreases. A considerable scatter in the in-situ stress test data may be due to distinct differences in both the strength and deformation moduli of strata located in varying geological environments and different coal districts. Two types of stress field distribution have been noted with sigma(Hvh) (sigma(Hmax)>sigma(v)>sigma(hmin)) and sigma(vHh)(sigma(v)>sigma(Hmax)>sigma(hmin)) found mainly in deep coal mines. The ratio of the maximum horizontal principal stresses to vertical stress is usually between 0.63 and 2.42 in the deep coal districts. (C) 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of China Academy of Safety Science and Technology, China University of Mining and Technology(Beijing), McGill University and University of Wollongong.