Formation mechanism of subsidence column in fold structure and roadway support technology

To guarantee the roadways of No.43211 and No.43212 of Changping Coal Mine pass through the collapsed pillars safely and quickly and the stability of the roadway surrounding rock in the broken zone in the following mining process, the formation mechanism of the subsidence column in the fold structure in the mine and numerical simulation of the original stress state are regarded as the theoretical basement. The authors proposed the reinforcement measures including the pre-anchor net, the shed passive joint support, reinforcing surrounding rock by medium-term grouting and later-stage strength of surrounding rock. The results show that the original rock stress changes after the formation of karst cave. Because of different layers of rock under tension and pressure anticline collapse column section shows the positive wedge geometry. While the syncline collapse column is adverse,local stress concentration occurs at the boundary of normal rock strata for a wedge-shaped subsidence column, and overallthe vertical stress in the column is low. The horizontal stress in the column is less than that in the normal rock strata. The combined support measures are used to act on the stress concentration zone in the initial stage in the field. In the middle stage, reasonable grouting lag time is 20 days. The deep and shallow mixed grouting mode is adopted. In the later stage, to prevent disturbance of external load and further consolidate the strength of surrounding rock, roof support is used to enhance the strength of column fracture zones. Monitoring results of the field stress showed that the surrounding rock is stable.