Abstract
Roadways in thick coal seams are widely distributed in China. However, due to the relatively developed cracks and brittleness of coal, the support failure of thick-coal-seam roadways frequently occurs. Therefore, the study of bolt failure characteristics and new anchoring technology is very important for the safety control of thick-coal-seam roadways. Based on field observations, the failure mechanism of selected roadway failures under distinct conditions at three representative coal mines in eastern and western China was analyzed. Recommendations are provided for roadway safety control. The results show that the strength and dimension of the anchoring structure in the coal roof of thick-coal-seam roadways are the decisive factors for the resistance of the roadway convergence and stress disturbance. The thick anchoring structure in the roof constructed by flexible long bolts can effectively solve the problem of support failure caused by insufficient support length of traditional rebar bolts under the condition of extra-thick coal roof and thick coal roof with weak interlayers. The concepts and techniques presented in the paper provide a reference for the design of roadway support under similar geological conditions and dynamic load.
Highlights
Proportion of accidents Proportion of deaths ground energy requirements and deformation capacity ranges
We selected three representative coal mines from the east and west of China for field observation of support failure, including the Jianxin coal mine and Wenjiapo coal mine in Shaanxi Province and Yaoqiao coal mine in Jiangsu Province. e failure modes of support under specific geological conditions are analyzed, and targeted support schemes and suggestions are provided
Restricted by roadway height and construction difficulty, the length of the conventional threaded steel anchor is 2–2.5 m. 3-meter bolts were used in the Jianxin coal mine owing to the roadway height; a threaded steel anchor rod cannot be used if the rod length exceeds 3.5 m to form a thicker anchoring structure
Summary
Compared with the original support, the stability of the surrounding rock is not well controlled (even if measures such as strengthening the strength, increasing the length, and increasing the pretension force have been applied to the bolt), and the risk of roof fall is still very serious. E small pretension force causes the bolts and cables to exert lower axial restraint force on the rock mass, and an effective pressure arch structure cannot form in the roof. When the artificial pressure arch does not provide an effective axial binding force to the roof rock, it cannot control the early rock deformation after roadway excavation, and results in the continuous expansion of small original cracks in the rock that eventually form large fractures and lead to rock separation. When loosening of the pretension force is detected, the bolt should be retorted and the anchor cable should be pretensioned to ensure an effective pretension force
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
