Stress evolution characteristics of the intensively mining-induced surrounding roadways within an extra-thick coal seam: A case study from the Tashan coal mine, China

The combined intensive mining effect of sequential-mining-process of two adjacent longwall top coal caving faces is prone to inducing disasters such as coal and gas outburst, roof caving and surface subsidence. However, it remains a big challenge to explore the mining-induced vertical stress evolution and its role played during such complex mining condition. A physical model with the geometric similarity ratio of 1: 100 was established to explore the mining-induced vertical stress characteristics, their influence on the surrounding rock failure mechanism and the high stress relief method. The results indicated that both coal ribs are the most intensive region of the surrounding roadway in the previous and next working faces. In addition, based on the experimental physical model and field monitoring results using borehole drilling stress device, the feasibility of high stress relief method using narrow pillar layout was technically proven. The research results can shed lights on optimization of coal pillar design, layout of roadways, the supporting schemes within extra-thick coal seam.