On Collapse-Settlement Calculations for Heterogeneous Collapsible-Soil Subgrade

In a previous paper the authors have dealt with collapse-settlement calculations for embankments based on a homogenous collapsible soil subgrade. For this same subject the present paper represents modifications to the aforementioned collapse-settlement calculations to include in-situ cases of heterogeneous collapsible-soil subgrades. It is well known that collapsible soil deposits exhibit a high potential for collapse deformation under external loading. Evaluation of the collapse potential is, thus, required for settlement calculations relating to the base of embankments placed on a collapsible soil subgrade. The evaluation conducted leads to the conclusion that collapse potential is dependent upon the following parameters: (a) liquid limit, (b) plasticity limit, (c) in-situ dry density, (d) in-situ moisture content, and (e) applied pressure at wetting in the single-oedometer test. Knowledge of these parameters, together with that of the water-penetration depth into the subgrade stratum and the effect of partial saturation on a reduction of the full collapse potential, is shown to enable a calculation of the amount of collapse-settlement in a heterogeneous stratum.