Identification and Characterization of Collapsible Gravels

Abstract

Collapsible coarse‐grained deposits present a particular challenge in both identification and characterization. This is particularly the case with collapsible gravels, where sampling is a practical impossibility. Six case histories involving collapsible gravels are presented that indicate the general characteristics of these materials and the methods that have been employed for evaluating their properties. Laboratory and field evidence suggests that the fine‐grained matrix is responsible for the collapse phenomenon and that as little as 5–20% fines may be sufficient to produce collapsible behavior. In situ tests that have shown some promise include plate‐load bearing tests and prebored pressuremeter tests conducted first under dry natural conditions and then following wetting. Experience clearly shows that coarsegrained soils in a geologically susceptible environment can collapse upon wetting even though they may have high densities and very high SPT blow counts.