HR: 0800h
AN: H31D-0449    [Abstracts]
TI: A new Approach for Interconnections Between Shrinkage Cracks and Soil Matrix
AU: * Chertkov, V Y
EM: agvictor@tx.technion.ac.il
AF: Agricultural Engineering Division, Faculty of Civil and Environmental Engineering, Technion, Technion City, Haifa, 32000 Israel
AB: The shrinkage geometry factor connects the changes of subsidence and the total crack volume at the shrinkage of a soil layer matrix. An available approach for estimating the factor does not account for the crack volume in samples, stretching a shrinking soil layer, and a possible change of the factor with water content. At the same time the concept of the shrinkage geometry factor is used for estimating the crack volume and water flow in shrink-swell soils. For these applications the accuracy of the value of the shrinkage geometry factor is very important. A recently suggested new approach for the factor estimation enables one to account for the water content dependence of the factor and the impact of crack presence in a sample. The present work develops this approach also accounting for the stretching of a shrinking soil layer. Corrected values of the shrinking geometry factor are described in terms of the shrinkage curves of: a layer that is composed of unconnected solid cubes from the available approach, a stretched layer with cracks, a sample with cracks, and the soil matrix without cracks. This correction leads to changes in the soil subsidence and total crack volume compared to those obtained from the available approach. The consideration is based on two physical conditions: the soil matrix volume without cracks is the same for the sample and the layer; and, the matrix deformations of an unlimited shrinking soil layer are longitudinal those of a thin quasi-elastic plate. Two available experimental examples are considered to illustrate the approach to be developed. The former relates to clay paste samples. The latter relates to an aggregate clay soil in situ and in samples. Results show that the shrinkage geometry factor from the available approach and that obtained after correction significantly differ. That is, the impacts of cracks in soil samples and of soil layer stretching at shrinkage should be taken into account when estimating the shrinkage geometry factor value. The results also show the appreciable change of the corrected shrinkage geometry factor with water content. They can be useful in discussing the possibility of transferring hydraulic properties and flow features of a swell-shrink soil that are observed on or calculated for soil samples, to the case of the soil in field conditions.
DE: 1866 Soil moisture
DE: 1875 Unsaturated zone
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting