The essential mechanics of capillary crumbling of structured agricultural soils

In soil loosening processes like seedbed preparation, significant soil crum bling is often desired. A better understanding of the mechanics of crumblin g is necessary to optimize crumbling operations, particularly in structured agricultural soils in which capillary bonds are dominant. To this end, a m odel of the mechanics of capillary crumbling in structured agricultural soi ls is developed. Four sets of experiments on cylindrical soil samples were carried out to investigate the validity of the model and soil crumbling cha racteristics as influenced by freezing, thawing and drying. After preparati on and sample pre-treatment, the samples were dried to different moisture c ontents and then tested to determine soil bonding strength. Soil water suct ion was also monitored at testing as were sample dimensions at different st ages of experimentation. The model was found to account satisfactorily for the mechanics of capillary crumbling in structured agricultural soils. Free zing had the effect of reducing the strength of inter-aggregate bonds whils t preserving the integrity of soil aggregates during crumbling. (C) 2000 El sevier Science B.V. All rights reserved.