Preconsolidation stress in the Vega Baja and Media areas of the river Segura (SE Spain) : causes and relationship with piezometric level changes

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Title: Preconsolidation stress in the Vega Baja and Media areas of the river Segura (SE Spain) : causes and relationship with piezometric level changes
Authors: Tomás, Roberto | Doménech Morante, César | Mira, A. | Cuenca Payá, Artemio | Delgado, Jose
Research Group/s: Geología Aplicada e Hidrogeología | Ingeniería del Terreno y de las Estructuras
Center, Department or Service: Universidad de Alicante. Departamento de Ingeniería de la Construcción, Obras Públicas e Infraestructura Urbana | Universidad de Alicante. Departamento de Ciencias de la Tierra y del Medio Ambiente
Keywords: Preconsolidation stress | Piezometric level | Desiccation | Casagrande method
Knowledge Area: Geodinámica Externa | Ingeniería del Terreno
Issue Date: 22-May-2007
Publisher: Elsevier
Citation: TOMÁS JOVER, Roberto, et al. "Preconsolidation stress in the Vega Baja and Media areas of the river Segura (SE Spain) : causes and relationship with piezometric level changes". Engineering Geology. Vol. 91, Issues 2-4 (22 May 2007). ISSN 0013-7952, pp. 135-151
Abstract: Preconsolidation stress (σ′p) 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 10–15 m depth of soil varying from 2 to 14 and maximum preconsolidation stresses above 800 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 42 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 41 kPa) that can reach values higher than 150 kPa for the deeper layers for known water level decreases. In consequence, the soils of theVega Baja and Media of the Segura river are highly overconsolidated for the first 5 m, decreasing gradually with depth to 10–15 m deep. For samples located deeper than 15 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.
Sponsor: Financiado por el Ministerio de Ciencia y Tecnología y FEDER (Proyecto TEC- 2005–06863), por la Generalitat Valenciana (Proyecto GV06/179 y GRUPOS03/085) y por la Universidad de Alicante (Proyecto VIGROB-157).
ISSN: 0013-7952
DOI: 10.1016/j.enggeo.2007.01.006
Language: eng
Type: info:eu-repo/semantics/article
Peer Review: si
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Appears in Collections:INV - GAH - Artículos de Revistas
INV - INTERES - Artículos de Revistas

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