Deformation and failure laws of roadway surrounding rock and support optimization during shallow-buried multi-seam mining

Gobs and coal pillars left in the upper coal seam exploitation bring a series of changes to the surrounding rock structures and stress environment of the roadway in the lower coal seams, which leads to difficulties in roadway maintenance. Firstly, the deformation and failure laws of roadway surrounding rock during shallow-buried multi-seam mining are studied using UDEC simulation. The results show that the vertical-stress concentration of the roadway under the coal pillar is stronger than that under the gobs and solid coal. The roadway displacement mainly undergoes three stages, i.e. severe deformation, slow deformation and deformation stabilization. Each of the three stages has the critical deformation value. The roadway displacement under the coal pillar also is larger than that under the gobs and solid coal. Then, allowing for its location, the roadway can be divided into three subareas, including below solid coal, below gobs and below coal pillars. The roadway below gobs consist of two kinds of subareas, i.e. the interlayer spacing is 3.2-4 m and the other is larger than 4 m. The support schemes corresponding to the four subareas are put forward. Finally, these proposed support schemes are used in the subareas of No. 20314 auxiliary haulage roadway. The field monitoring results show that the roadway displacement is small and bolt (cable) forces are stable, and the support effect is excellent. This study can provide a reference for roadway support in shallow-buried coal seams under similar geological conditions.