Research on Pier Column Gob- side Entry Retaining Technology

In order to solve the problem short mining distance, slow driving speed, conflict of exploitation and mining of working face in Jining No.2 Coal Mine, pier column pressure testing, mechanical model, theoretical calculations and field test methods were applied to put forward innovatively pier structure gob- side entry retaini ng. The results showed that the pier column could meet the strength requirements, the required for cutting the top pressure was 21.96 MPa. When the sand and stones weight ratio in steel pipe was 1. 0: 1. 6, the effect of pier column gob- side entry retainiuy was the best, the pier column not only could maintain a higher strength, but also had good scalability. The rock pressure observation showed that the maximum roof to floor convergence was 596 mm, the maximum rib to rib convergence was 29 9 mm, which could ensure the stability of gob- side entry retaining.