Borehole penetration and expansion devices for ice testing

Abstract

The paper presents two methods for in situ testing of strength and creep properties of ice, together with their theoretical interpretation and typical results. The two methods which are relatively new in this area of application, are the stress-controlled cone penetration test (CPT), and the sharp cone test (SCT). The CPT has been shown in the last few years to be an excellent tool for both ice quality profiling and ice creep and strength properties determination. The test can be used for penetrating vertically through an ice sheet, or laterally into an ice wall in a trench. The SCT is a special kind of borehole-expansion test. The method consists in pushing a smooth, low-angle, conical indentor into a predrilled conical portion of a borehole, which ends with a smaller diameter pilot hole. The creep properties of ice are then deduced from the relationship between the applied load, time, and cone penetration, which is directly related to the hole expansion. Key words: ice, creep, strength, in situ testing, cone penetration, borehole expansion, sharp cone.