Collapse behavior of sand: Discussion

Abstract

The test data that are presented in paper are of most interest. The two constant deviator stress path tests may be compared with tests done by Lade et al. (1988) and Lade and Pradel (1990) for very loose sand under undrained conditions and by Chu (1991) and Chu et al. (1993) for medium loose to dense sand under non-undrained (or strain path controlled) conditions. It should be noted that testing procedures used in and test results obtained from these tests are verv similar. All above-mentioned tests were conducted uhder a constant deviator load and decreasing effective confining stress conditions. The prefailure instability observed in these tests appears to be same type. Although authors called instability observed in constant deviator stress path tests collapse behaviour, word drained does not carry same meaning as in a drained conventional compression test. This is because pore-water pressure of sample was controlled during tests, and thus volume change of sample is not totally free. As the volume of sample for constant deviator stress (q = 125 kPa) test was essentially unchanged and remained at 0.804 before sample collapse, this test was actually conducted under an undrained condition. Therefore, 'paper by S. Sasitharan, P.K. Robertson, D.C. Sego, and N.R. Morgenstern. 1993. Canadian Geotechnical Journal, 30: 569-577.