Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
4744706 | Engineering Geology | 2007 | 17 Pages |
Abstract
Preconsolidation stress (Ïâ²p) is the maximum effective stress that a soil has suffered throughout its life. From a geotechnical point of view, preconsolidation stress has a great importance because it separates elastic and reversible deformations from inelastic and only partially irreversible deformations and marks the starting point of high compressibility. This study calculates the preconsolidation stress for 139 undisturbed soil samples from the Vega Baja and Media of the Segura river (SE Spain), using the uniaxial consolidation test and applying the method proposed by Casagrande while using a novel analytical procedure proposed by Gregory et al. [Gregory, A.S., Whalley, W.R., Watts, C.W., Bird, N.R.A., Hallet, P.D., Whitmore, A.P., 2006. Calculation of the compression index and precompression stress from soil compression test data. Soil and Till. Res., 89, 45-57] to avoid subjective interpretations of maximum curvature point. The results show overconsolidation ratio (OCR - the ratio of preconsolidation stress to current natural overburden stress) values for the 10-15Â m depth of soil varying from 2 to 14 and maximum preconsolidation stresses above 800Â kPa. The main causes of calculated preconsolidation identified are desiccation due to seasonal drying and wetting cycles that have induced additional stresses always lower than 42Â kPa for the more superficial samples. Water level decline due to the reduction of recharge suffered by the aquifer system during periods of drought and the uncontrolled withdrawal of water is considered to be the second cause of anomalous OCR values. This second cause induces low stresses to the more superficial layers (lower than 41Â kPa) that can reach values higher than 150Â kPa for the deeper layers for known water level decreases. In consequence, the soils of the Vega Baja and Media of the Segura river are highly overconsolidated for the first 5Â m, decreasing gradually with depth to 10-15Â m deep. For samples located deeper than 15Â m the soils seem to be underconsolidated, probably due to the existence of confined aquifers that cause deviations from a hydrostatic and linear pore pressure model. This fact has a huge practical significance which implies that deformations affecting superficial layers are lower than those expected for deeper layers for the same load.
Keywords
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Geotechnical Engineering and Engineering Geology
Authors
R. Tomás, C. Domenech, A. Mira, A. Cuenca, J. Delgado,