Research on Pillarless Mining by Gob-Side Caving under Soft Rock Roof Conditions: A Case Study

In China, soft rock roof makes up the majority of coal mine roof, yet it is easy to break due to low strength and poor integrity. As such, it is difficult for the traditional pillar-based roadway protection means and pillarless mining techniques to effectively control the roadway roof. In order to solve the problems with pillarless mining under soft rock roof conditions, using the 1510 working face of Xinyi Coal Mine as an example, a gob-side caving roadway forming (GSCRF) technique for broken immediate roof is developed. This paper discusses the adaptability and feasibility of this technology through theoretical modeling and on-site engineering testing. A roadway rock surrounding control scheme based on "cable + steel beams + yielding prop" is further designed, and field tests and monitoring are carried out. Field tests show that, during GSCRF of the 1510 working face, the maximum subsidence of the roof remains within 200 mm. The convergence of the two sides causes stabilization. The tension on the anchor cables is gradually becoming stable. The monitoring results show that the roadway has a good stress environment and the surrounding rock is effectively controlled. Compared with the traditional pillarless mining mode, this technology has the technical advantages of achieving complete elimination of coal pillars, reduced pressure on the roadway roof, and interference-free mining of the working face. The research outcome can provide useful reference for pillarless mining by GSCRF and a solution for pillarless mining under soft rock roof conditions.