Creation of artificial loess soils

Abstract

Loess is a loose, open-structured metastable soil of aeolian origin, predominantly composed of 20–60 µm quartz particles bonded together by clay particles and, in some cases, carbonate compounds. When dry it can withstand high overburden stresses, whilst upon saturation it collapses creating potentially enormous engineering problems. The mechanisms controlling this metastable behaviour involve the disintegration of inter-particle clay and chemical bonding and variations in the pore water pressures (i.e. suctions) during saturation.

The paper describes methods of creation of artificial loess samples using an airfall approach to allow the variation of bonding constituents, arrangements and formation processes. The amount of powdered clay added to primary quartz particles (ground silica) was varied and three methods for activation of clay bonding were employed, i.e. water spray, capillary wetting and steaming. The reproducibility of the synthetic loess created was determined through oedometer testing of the resulting samples, the results of which are reported together with those for undisturbed samples of mid-European loess. Similarities and differences are discussed in the context of the likely bonding mechanisms. It is concluded that creation of reproducible synthetic loess samples, while controlling its constituents, makes possible the individual examination of the different parameters that control bonding in loess.