Self-weight consolidation of soft soils: an experimental and theoretical study

Abstract

Soil is laid down by sedimentation through water, passing through the phases of a fluid supported suspension, through a loose structure to a soft soil, the stiffness of which then gradually increases under additional load. Consolidation is caused by the self-weight of the soil and, while the sediment is soft, is accompanied by large strains. To predict magnitudes and rates of movement, the physical processes must be understood and used as the basis of a theoretical model. This Paper describes laboratory experiments on the development and consolidation of a soft soil in settling columns, with measurement of density (using an accurate, non-destructive X-ray technique), total stress, pore pressure and settlement. The results are compared with an earlier theoretical model. Modifications made to the model in the light of observed experimental features allow it to be used to predict the laboratory consolidation. Le sol est déposé par sédimentation à travers l'eau; il a d'abord la forme d'une suspension soutenue par un fluide, puis d'une structure sans cohésion et, enfin, d'un sol mou dont la rigidité s'accroit progressivement en fonction de la charge. La consolidation est entraînée par le poids intrinsèque du sol et, tant que le sédiment reste mou, ce processus de consolidation s'accompagne d'importantes déformations. Afin de pouvoir prédire l'ampleur et les taux de déplacement, il faut comprendre la nature des processus physiques qui ont lieu et en faire les base d'un modèle théorique. Le présent article décrit certaines expériences en laboratoire relatives à la formation et à la consolidation d'un sol mou dans des colonnes de sédimentation ainsi que les mesures de densité (à l'aide d'une technique faisant appel à des sondages précis par rayons X non destructifs), la contrainte globale, la pression interstitielle et la sédimentation. Les résultats sont comparés à ceux d'un modèle théorique précédent. Les modifications apportées au modèle en conséquence des phénomènes expérimentaux observés lui permettent de servir à prédire le processus de consolidation en laboratoire.

Applications of the phenomenological theory to several published experimental cases of sedimentation processes

“…5-8 in [30]). The decisive difference between these experiments is the initial concentration: in experiment 11, the initial suspension was so dilute that effective solid stress did not exist initially and that a distinctive hindered settling zone could form, while the initial concentration in experiment 15 was so high that the solid particles did already form a network, i.e.…”

“…1. Kynch batch flux density and effective solid stress functions f bk (φ) and σ e (φ) determined from data published by (a) Tiller et al [22]; (b) Bergström [27]; (c) Been and Sills [30]; (d) Dreher [34]; and (e) Damasceno et al [8].…”

“…The paper by Been and Sills [30] is one of the classical studies of the settling of flocculated suspensions and has been cited by many authors. Been and Sills performed experiments in settling columns using slurries of water mixed with real estuarine mud, producing various initial densities.…”

“…Been and Sills' experiment 7, for which the density measurements have also been plotted as a settling plot (see [30], Figs. 2 and 3) but for which the pressure measurements are available for one single time only (Fig.…”

The Use of C-/X-Band Time-Gapped SAR Data and Geotechnical Models for the Study of Shanghai’s Ocean-Reclaimed Lands through the SBAS-DInSAR Technique

“…These settlements may occur during and after foundation construction, and, when not correctly predicted, can cause delays and a considerable increase in costs of the whole reclamation project. Ground settlement of reclaimed coastal areas in Shanghai, which is caused by over-pumping groundwater and consolidation of dredger fills and alluvial deposits, have already been observed and reported in the literature [15][16][17][18][19][20]. In particular, field measurements indicate that ground settlement of the reclaimed foundations occurred during the construction of Lingang New City in Shanghai.…”