Characteristic of in-situ stress field in Huainan mining area

The hollow included technique was used to measure the in-situ stress of Huainan mining area.According the analysis of the measurement data,the characteristic of in-situ stress field is obtained.The result shows that:(1) two principal stresses are nearly horizontal and one is nearly vertical among three principal stresses on all sites.The magnitude of vertical stress is equal to the weight of overburden rock mass.The horizontal principal stress in-creased with the depth;(2) The ratio of major principal stress to minor principal stress did not increase with depth evidently,the difference between major principal stress and minor principal stress is large on 50% sites;(3) The orientation of major principal stress is NE,there is some deflection localy.According to the relation of three principal stresses,the type of Huainan mining area is dynamic stress field and quasi static stress field.In-situ stress field plays a important role in coal and gas outburst in Huainan mining area.It was suggested that in-situ stress field should be considered during the gas drainage design.