A Practical Method to Establish the Apparent Fracture Toughness of Ice in the Field

There is a need to measure the apparent fracture toughness of ice in the field. Previously developed methods are laborious and consequently more practical methods would allow more data to be collected from a variety of settings, e.g. during short day trips and from onboard ships. To this end a compact and lightweight loading device was designed and constructed that could be used in the field. A digital control system was developed for the loading device that enables both load- and displacement-controlled tests. The device performs fracture tests with semi-circular bend specimens of 140 mm diameter, which can be easily cut from commonly collected ice cores. The design of the loading device is presented, and its compliance is compared to that of the specimens. The architecture of the digital control system is also presented, and the resolution of the measurement signals along with the different functions the system enables are explained. The system is then tested during a set of field experiments conducted at Van Mijenfjorden, Svalbard during March 2025. The accuracy of both the load- and displacement-control during these tests is discussed and the attained results are shown to be both comparable to and as repeatable as similar experiments conducted under laboratory conditions. Finally, the presented system is found to be a practical alternative to quickly measure the apparent fracture toughness of ice in the field.