No abstract

No abstract

No abstract

A numerical model for consolidation of fissured clays, on the basis of the double-porosity concept, is presented. As applications of the model, two numerical examples are analysed: a one-dimensional soil column, and a strip loading on a two-dimensional medium of a fissured clay. It is shown that, in comparison to an equivalent single-porosity model, the settlement in a double-porosity medium is delayed due to the slow dissipation of excess fluid pressure in the clay matrix. In addition, three distinct time periods are identified in the consolidation of a fissured clay. The characteristic of each period are discussed and the parameters affecting these periods are highlighted. Moreover, it is shown that the Mandel–Cryer effect, which is often discussed in relation to consolidation of soils treated as single-porosity material, may not develop in fissured clays. Nous présentons un modéle numérique pour la consolidation des argiles fissurées sur la base du concept de double porosité. En applications du mod&acuate;le, nous analysons deux exemples numériques: une colonne de sol unidimensionnelle et une charge en bande sur un support bidimensionnel d'argile fissurée. Nous montrons que, en comparaison avec un modéle équivalent à une seule porosité, le tassement du support &grave double porosité est retardé en raison de la lenteur de la dissipation de la pression liquide excessive dans la matrice d'argile. De plus, nous identifions trois périodes de temps distinctes dans la consolidation d'une argile fissurée. Nous examinons les caractéristiques de chacune et nous soulignons les param&acaute;tres qui affectent ces périodes. En outre, nous montrons que l'effet Mandel–Cryer qui est souvent discuté dans un contexte de consolidation de sols traités en tant que matiéres &grave une seule porosit&acaute;, pent ne pas se développer dans les argiles fissurées.

Publication of the Environment Agency (EA) Guide to Risk Assessment for Reservoir Safety Management ( Bowles et al., 2013 ) has increased the interest and awareness in undertaking risk assessments on dams in the UK. The guide introduces a three-tier approach to risk assessments. Tier 1 is qualitative and tier 2 introduces some basic quantitative tools. Tier 3 introduces more detailed quantitative methods and methods of dealing with uncertainty. A key part of undertaking successful tier 3 internal erosion risk assessments is gathering and interpreting the correct geotechnical information. The International Committee on Large Dams bulletin ( Bridle, 2013 ) contains invaluable information taken from research around the world, which adds to our knowledge of the internal erosion processes via specialist test procedures and methods. On existing dams much of the information available is from historical site investigations using conventional investigation techniques and soil and rock testing. Many of the specialist tests used to evaluate the susceptibility of materials to internal erosion are not generally available in the UK and can be prohibitively expensive. This paper aims to make the most of commonly available standard classification test data to provide a means of obtaining information on the susceptibility of embankment materials to internal erosion. In many cases this may be sufficient to provide enough information for a reasonable tier 3 assessment to be made or identify areas where further information would be beneficial depending on the risk posed and potential consequences of dam failure.