In Situ Stress Measurement And Distribution In Xuzhou Deep Mining Area

In situ stress is ultimate cause of failure of all underground or open-air geotechnical engineering. Deep mining has been beginning in Xuzhou area, and problems such as bad stability of roadway and rock burst due to high geo-stress are too serious to operate production. In order to develop distribution of in-situ stress in Xuzhou deep mining area, in-situ stress measurement was conducted to offer laws for seam mining and roadway supporting.Based on theory of geomechanics, tectonic background and pattern in mining area are analyzed. Character of prevailing tectonic stress field of large-scale mining area is analyzed through study of tectonic evolution. Over coring method by using hollow inclusion strain cells is applied for in-situ stress measurement. Several places in the eastern, western and northwest of mining area are chosen for behalf, and results are spread to whole mining area. Distribution of horizontal and vertical stress in Xuzhou deep mining area is achieved. During course of in situ stress measurement, some problems such as core discing, minification and caving of borehole due to horizontal stress are appeared, and their mechanism is studied.It is confirmed that Neocathaysian Tectonic System is predominant in Xuzhou mining area through geo-mechanics analysis, where is in contact with north of Jiangsu and south of Shandong Province. Prevailing tectonic stress field is controlled by XU-SU Nappe Structure, whose orientation is NW-SE with rotary trend to NWW-SEE, and stress strength of eastern is higher than that of western.Azimuth of the max principal stress measured is between 120°and 135°. Ratio of horizontal stress to vertical stress measured is between 1.48 and 1.56 in eastern mining area and is between 1.07 and 1.16 in western area. In situ stress measurement testifies geo-mechanics analysis.In situ stress measurement in Xuzhou mining area provides laws for deep coal mining, roadway layout and supporting. It also plays a great in prevention of geological hazards such as rock burst etc, which is very important for coal production safely.