IDENTIFICATION AND CHARACTERIZATION OF COLLAPSIBLE GRAVELS

Collapsible coarse-grained deposits present a particular challenge in both identification and characterization. This is particularly the cas e with collapsible gravels, where sampling is a practical impossibilit y. Six case histories involving collapsible gravels arc presented that indicate the general characteristics of these materials and the metho ds that have been employed for evaluating their properties. Laboratory and field evidence suggests that the fine-grained matrix is responsib le for the collapse phenomenon and that as little as 5-20% fines may b e sufficient to produce collapsible behavior. In situ tests that have shown some promise include plate-load bearing tests and prebored press uremeter tests conducted first under dry natural conditions and then f ollowing wetting. Experience clearly shows that coarse-grained soils i n a geologically susceptible environment can collapse upon wetting eve n though they may have high densities and very high SPT blow counts.