A New Model Test Method for Single-Fracture Oriented Roof-Cutting Technology

Single-fracture Oriented Roof-cutting Technology (SORT) is a key technology in the pillarless self-formed roadway mining method, which is a popular and widely used new coal mining method in China. In previous model tests, SORT was usually replaced by chain saw cutting or pre-installed isolation boards. This resulted in its process and effect being not realistically simulated. To solve this problem, the process and rock-breaking mechanism of SORT were analyzed in detail in this paper. Meanwhile, some factors affecting the performance of SORT were discussed by using the sensitivity analysis method. Based on this, a new SORT model test method was proposed and verified by a series of experiments. The results show that the most critical factors affecting the technical effect of SORT are blasting energy and energy concentration coefficient. In the model tests, explosive materials with fast reaction speed and good detonation effect should be preferred. On the other hand, compared with flexible energy guiding devices, rigid devices can play a better role in energy focusing and guidance, thus maximizing the simulation of the technical effect of SORT. Based on this idea, a series of tests were carried out with Ningtiaota coal mine as the engineering background. According to the test data, the optimal explosive material was determined to be low-cost black powder composed of potassium nitrate, sulfur and other components. Pre-fabricated slit steel pipe was determined as the optimal energy guiding device. In addition, the optimal values of other parameters were determined, including slit energy agent dosage and simulation device spacing. Finally, the method and device proposed in this paper were applied in the model test. The results show that the model test results are in good agreement with the field monitoring data. This proves that the SORT model test method, device, and test parameters proposed in this paper are feasible. This provides a new reference idea for further research on the pillarless self-formed roadway mining method, as well as other research involving SORT.