Experimental study on geo-mechanics test of surrounding rock of underground roadway in coal mine

No. 4 coal seam from Yan’an Formation of the Jurassic in Jiangjiahe Coal Mine has a buried depth of more than 650 m, indicating that it has belonged to deep coal mining. Affected by deep buried depth, mining-induced pressure and tectonic stress, serious damage was observed in roadway and surrounding rocks with falling from large range of floor heave, rib spalling, and roof subsidence etc, causing serious disruption to normal mining operations. In order to solve the damage to roadway surrounding rock, investigations were carried out to obtain the geo-mechanical distribution law and mechanical parameters of the surrounding rock in the No.4 coal seam of Jiangjiahe Coal Mine.In-situ measurement of in-situ stress and strength of roadway surrounding rock were performed at two measuring points using methods such as in-situ measurement of in-situ stress and device and borehole penetration method. The studies have found that in Jiangjiahe Coal Mine the average value of the maximum horizontal principal stress is 16.00 MPa, the average value of the minimum horizontal principal stress is 8.56 MPa, the average value of the vertical stress is 15.31 MPa, and it has a stress field type of σH>σv>σh.The regional stress field is mainly a tectonic stress field, with dominating horizontal principal stress, and NEE as the direction of the maximum horizontal principal stress.The structure analysis for the roof, surrounding rock implied a coal layer with fairly significant deviation in depth and a relatively good wholeness of coal body.Besides the average strength of coal body is 16.84 MPa, a typical medium hard coal body,the area 20 meters above the roof of coal seam is mainly filled with mudstone, argillaceous sandstone and medium sandstone with even distribution of small coal inter-beds, wide range on lithology and a complex structure of rock layer. This study would provide an accurate technical base for the roadway layout and relating supporting methods in the second mining area of the mine.