GEOTECHNICAL EVALUATION OF LOESSIAL SOILS IN KANSAS

Much of western, central, and northeastern Kansas is covered with loess deposits from Bignell, Peoria, and Loveland formations along with Sangamon soils above Loveland unit. In this paper their significant geological and engineering properties are defined, and design guidelines are presented. Montmorillonite is the chief cementing agent in Kansas loess. The Sangamon soil and the Lovelenad loess contain more clay than the Bignell loess and the Peoria loess and have higher in situ density and less permeability. The in situ density of Bignell loess and Peoria loess is less than 85 pcf, and consolidation tests and field experience indicate that they are highly susceptible to hydroconsolidation. A key factor in the collapse potential of Kansas loessial soils appears to be the mineralogy of the soils, specifically the presence of montmorillonite as the chief cementing agent; montmorillonite has the ability to absorb more hydrogen cations than kaolinite and thus is able to adsorb more water. Total stress parameters must be used to design loess slopes approaching the vertical, and effective stress methods are particularly applicable in dealing with saturated loess and with seepage stress where flattened slopes are required. Saturated loess may liquefy due to the cyclic nature of earthquake loading. Stabilization and compaction of loess represent not only an antisubsidence but also an antiliquefaction measure. Proper consideration should be given to zoning of areas of collapsible loessial soils. (Author)