Relaxation tests and young's modulus

A set of relaxation tests with cores sampled from three different depths in the floating landfast sea ice in the Van Mijen fjord on Svalbard, is discussed. Fifteen cores were tested twice in relaxation (one hour) and one core from each depth was tested 9 times in relaxation (also one hour of testing). Finally, the strength of all cores was tested with nominal strain-rate of 10-3s-1. One fast (nominal strain-rate of 10-3s-1) cyclic compression test is also presented, and the effective Young’s modulus in both tests is discussed. The residual stress increased with decreasing grain size, porosity and temperature and increased with increasing number of relaxation tests. The effective Young’s modulus measured from strength tests was not affected by the relaxation tests, but it increased during the fast cyclic test. The immediate (true) Young’s modulus increased with increasing number of relaxation cycles. The true Young’s modulus is governed by the number atomic bonds and increased when the samples were compacted in the relaxation tests. However, the effective Young’s modulus measured from strength tests is more governed by cracking and damage that developed during these tests. In the fast cyclic tests the sample both experienced compaction and damage and the competition between these two phenomena gave the firstly increasing and then decreasing Young’s modulus.