FACTORS INFLUENCING COMPACTION-INDUCED INCREASES IN SOIL STRENGTH

Cultivated soils, when subjected to compaction, often show a marked increase in strength, which may be unfavourable for root penetration and may increase the amount of tillage work required to produce acceptable seedbeds. Tensile strength was determined at two different levels of soil particle arrangement. The textural tensile strength may be defined as the intra-aggregate tensile strength and is measured on a small volume of soil, the organization of which mainly results from elementary particle packing. This textural tensile strength is shown to be highly correlated with clay content. The overall tensile strength of larger volumes of soil results from the textural tensile strength as well as from the structural tensile strength which is due to inter-aggregate bonds. Various factors leading to differences in the overall tensile strength of compacted samples are discussed, such as soil water content during compaction, degree of compactness and soil composition (mineral and organic). The effect of drying, subsequent to compaction at different water contents, is emphasized. © 1990.