Key parameters and mechanisms of ice cores autonomously breaking with air reverse-circulation drill systems

In recent years, a new ice-drilling method for continuous coring with air reverse circulation (CCARC) using a rapid air movement (RAM) ice drill system has been proposed that uses a dual-wall aluminum drill pipe. CCARC ice-drilling technology can effectively prevent compressed air circulation losses in snow-firn cover and continuously obtain ice cores using CCARC. When removing embedded ice cores without lifting the drill to the ice-sheet surface, the drilling operation remains uninterrupted; therefore, it can significantly improve the ice core production rate. However, a prerequisite for the realization of CCARC ice drilling is that the core splitter set on the internal surface of the drill bit inner tube can autonomously break ice cores of equal length. To further improve CCARC ice-drilling technology, key parameters such as the horizontal load and lateral displacement required to break ice cores with different diameters and lengths during drilling must be investigated because they are important for ice-coring drilling operations and drill design. In this study, the mechanism, and key parameters of the ice core breaking process under different conditions were theoretically calculated and experimentally measured. Subsequently, the influence of the ice core temperature, diameter, and splitting length on ice core breaking was quantified, and the feasibility of the ice core breaking mode was demonstrated.