Experimental study of axial stress distribution and transfer along the bolt rods in an underground coal mine

Abstract

Based on the data of experimental tests, underground pullout tests, and real-time monitoring of active anchor-bolt stress in the Dingji Coal Mine in the Huainan mining area, China, the axial stress distribution along the bolt rods in a coal mine roadway was obtained. The results show that the axial stress in bolts increases initially then decreases along the anchoring direction under a perfect anchoring state. As the pre-tension is increased, the stress variation displays nonlinear behavior. The external section of the anchoring bolt rod plays a primary role in restricting the deformation of the surrounding rock before failure occurs. The results also indicate that the bending moment in the bolt rod has a significant effect on the axial stress distribution and transfer, and the bearing and supporting effects of the bolt increase as the pre-tension increases to a certain extent. The axial stress and its transfer features in a working bolt along the embedded direction are nonuniformly distributed and fluctuate.