Engineering properties of compacted loesses as construction materials

Loess often causes some problems when they are naturally deposited, or when they are used as fill materials in the construction of embankments. In the case of constructing the embankment on a thick, naturally deposited loess layer, the collapsibility, or consolidation will be a critical issue to be considered. In contrast, when a loess is used as a fill material, compactability, stiffness (resilient modulus), and pumping problem induced by repeated traffic loadings should be accounted for. In this study, in order to evaluate the mechanical characteristics of Indiana loess for constructing embankments, the following laboratory tests were conducted on four loesses having different clay contents (10%, 20%, 25%, and 30%): the standard compaction test, the collapse potential test, the CRS consolidation test, the direct shear test, the resilient modulus test, as well as the soil index test. Test results show that the collapsible potential can be significantly improved by well-compacting the loess when it is used as a fill material. Based on the results of collapsible tests on four loesses having different clay contents (10%, 20%, 25%, and 30%), it has been found that the higher the silt content, the higher the collapse potential at the given density corresponding to the naturally-deposited condition. This implies that the amount of silt in Indiana loess is the most influential factor in terms of collapsibility. The results of direct shear tests show that the effect of clay contents does not have much influence on the friction angle and cohesion of the compacted loess materials used in embankments. Unlike the shear behavior, the resilient behavior of compacted loess materials is considerably affected by the clay content such that the loess with the largest silt content shows the lowest resilient modulus due to the pumping-like phenomenon induced by the repeated loading.