Laboratory experimental study of soil crusting: Relation between aggregate breakdown mechanisms and crust stucture

Abstract

Crusts formation on cores of air-dry and prewetted aggregates was studied, using a laboratory rainfall simulator. Samples were taken out during the experiment, in order to study changes in water content and aggregates size distribution inside the crust and under the crust. Pore space geometry of the crusts is described using light optical microscopy and mercury porosimetry. In the case of air-dry aggregates, aggregates become micro-cracked. Macropores at the surface are quickly closed and ponding occurs rapidly. With prewetted aggregates, microcracking does not occur, and only a very slow abrasion of the aggregates is observed. Porosity remains high and no ponding excess occurs. The discussion of these results shows that it is the way of the wetting and the initial water content which determine the breakdown mechanism, and therefore, the behaviour of the aggregates submitted to rainfall.