Abstract
AbstractHot-water ice-coring drills are often used to recover ice core samples from desirable depths in conjunction with full-scale hot-water drilling systems. However, the recovered cores exhibit varying qualities. The coring performance of a hot-water ice-coring drill depends significantly on the structure of the coring drill head (nozzle angle, diameter and number). To discover the most significant factor affecting ice-coring performance, nine types of drill heads were designed and tested in this study according to the orthogonal test design. Results indicated that the nozzle angle is the most significant factor that affects the coring quality and the optimal angle is ~15°. The number of nozzles is the second most important factor; a large number assists in obtaining ice cores of high quality. The optimal nozzle configuration to recover good quality cores are the following: the nozzle diameter, number of nozzles and nozzle angle are 1 mm, 60 nozzles and 15°, respectively, with the maximum diameter and 2 mm, 60 nozzles and 15°, respectively, with the maximum length.
Highlights
Hot-water ice drill systems are actively used in polar science for the observation of ocean cavities under ice shelves; retrieval of sub-ice seabed samples; study of internal ice structures, video imaging and temperature logging; measurements of deformation within ice; determination of basal sliding velocity; clean access to subglacial lakes; and many other scientific objectives (Tsutaki and Sugiyama, 2009; Makinson and Anker, 2014; Rack and others, 2014)
A total of 27 testing runs were performed according to the orthogonal test design method (Supplementary material, Table S1)
The coring ratios are primarily between 0.593 and 0.885 except for head #8, which exhibits ratios exceeding 0.521; this indicates that most drill heads used in the tests can retrieve ice cores of relatively good quality
Summary
Hot-water ice drill systems are actively used in polar science for the observation of ocean cavities under ice shelves; retrieval of sub-ice seabed samples; study of internal ice structures, video imaging and temperature logging; measurements of deformation within ice; determination of basal sliding velocity; clean access to subglacial lakes; and many other scientific objectives (Tsutaki and Sugiyama, 2009; Makinson and Anker, 2014; Rack and others, 2014). Hot-water ice-coring drills can be used to recover ice core samples from desirable depths by drilling with annular nozzles. In the early 1990s, Caltech designed a hot-water ice-coring drill and used it in combination with a full-scale hot-water drilling system (Engelhardt and others, 2000). The most critical part of the hot-water ice coring drill is the annular drill head through which water jets to the bottom of the hole and forms the core. The effect of the drill head structure (diameter of water nozzles; their number and angle from the vertical axis of the drill) on the quality of ice cores (length and maximal diameter) and ROP remains unclear. We describe the results of the experimental investigations of a hot-water ice coring drill with nine drill heads according to the orthogonal test design method. The optimal design of the drill heads that yield the highest quality ice cores is determined
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