The Confined Compressive Strength of Polycrystalline Ice

Abstract Triaxial tests were carried out on randomly oriented, laboratory-made, polycrystalline ice, between strain-rates of 10–7 and 10–1 s–1 and with confining pressures from 0.1 to 85 MN m–2, at –11 ± 1°C. Below strain-rates of about 10–5 s–1 the confining pressure has little effect, but at higher strain-rates the confining pressure prevents cracking which allows the compressive strength to rise to a value greater than the unconfined compressive strength. At 1.4 ×10–2 s–1, the unconfined strength of 12 MN m–2 rises to 26 MN m–2 with a confining pressure of 25 MN m–2, before dropping slowly with greater confining pressures. Above 10–2 s–1 the unconfined strength decreases rapidly with increasing strain-rate, but the confined strength continues to increase. The dependence of strain rate on the maximum compressive stress is discussed.