Detection of goaf accumulation morphology and optimization analysis of flow field based on follow-up casing percussion drilling perception

In view of the problems in goafs, such as strong spatial confinement, uneven medium distribution, and complex structural morphology, based on the practice at Shendong Shangwan Coal Mine, an innovative “measurement-simulation-verification” collaborative analysis framework is constructed. By considering the “O”-ring theoretical model and combining the follow-up casing percussion drilling technology with a local interpolation and stitching fusion algorithm, the precise capture of the internal fracture morphology distribution in the goaf is achieved, accurately depicting the airflow movement trajectories and evolution patterns. Based on the behavior perception technology of follow-up casing percussion drilling, characteristic parameters such as load and rotational speed fluctuations of the follow-up casing percussion drilling rig are monitored in real time. A multi-parameter dynamic distribution model for the goaf is established to invert the accumulation morphology and medium distribution characteristics of the goaf. It is found that roof suspension and loose large rock accumulations are prone to occur at the working face corner and the open-off cut. By comparing numerical simulations with field tests, the results show that the accuracy of both the porosity and the internal airflow field in the goaf is improved to varying degrees. The maximum increase in porosity accuracy is 14.3%, and the maximum increase in airflow velocity accuracy is 72.1%. Compared with traditional simulation technologies, this method provides a reliable theoretical basis and technical support for disaster prevention and control as well as efficient resource utilization in goafs.