Wetting and Drying of Compacted Soils under Laterally Restrained Conditions

Compacted soils are components of geo-infrastructure applications that are unsaturated at the time of placement. Their responses to climate change, in the form of prolonged summers and wet winters, can be complex. This article examines the evolution through wet and dry cycles of horizontal stresses behind retaining structures backfilled with compacted soil during formation. Samples of kaolin clay and Belfast clay were tested. The horizontal stresses during the formation of these compacted samples were examined initially, and then the samples were subjected to wetting and drying cycles under horizontally restrained conditions. For design purposes, there are many proposals, including assuming the coefficient of earth pressure K0*≈Ka* compacted fills. However, the observations obtained on both clays have indicated clearly that the values of K0* can be below unity only at high overburden pressures. Further repeated wetting and drying of samples under constant overburden pressure resulted in a complex response. Belfast clay exhibited a gradual increase in K0* with wetting cycles, but kaolin exhibited a noticeable reduction in the value of K0* upon first wetting. However, subsequent wetting followed by drying showed a significant recovery of the K0* value.