Ice Tank Tests on Ridging of Non-Uniform Ice Sheets

摘要

A test program has been carried out to study ridging and rafting of model ice211u001esheets. During each test, a sheet of floating model ice was pushed against 211u001eanother similar ice sheet. Two types of ice sheets were used. Three different 211u001edeformation modes were observed: simple ridging (Type A), simple rafting (Type 211u001eC), and intermediate (Type B). It was discussed that all these deformation types 211u001ecan also be found in nature. The forces during the ridging and rafting processes 211u001ewere measured. The experiments suggested that there is a threshold force value 211u001ewhich must be reached before the rafting and subsequent ridging starts. During 211u001ethe initial rafting phase, the force increased linearly. The measurement data 211u001eshows further that the force continued to grow also after the initial linear 211u001etrend, albeit at a lower rate. A further characteristic of the measured force was 211u001ethat in some tests the force appeared to cease increasing and reach a plateau 211u001evalue. This levelling of the force was observed to be connected with either onset 211u001eof failure of the surrounding ice sheet against the ridge or onset of rafting at 211u001ea new site. The report includes also literature reviews on models for ridge 211u001eformations and for relations between ridging force and ridge geometry.