Organic soils are susceptible to creep. When predicting settlement of organic deposits due to small load increments, the initial conditions, particularly the initial strain rate should be assessed carefully. Recent developments in predicting creep behaviour of clays are tested in an ongoing study on organic soil behaviour. A series of incremental loading tests on peat and organic clay shows that a framework of undisturbed isotachs cannot be used to predict strain rates in overconsolidated conditions. This complicates the applicability of conventional incremental loading test results for assessing field conditions. Additionally, the tests show the relevance of a large strain approach when dealing with soft organic soils. ... Read more

As the population in cities all over the world is increasing, the effects of climatic action on the resilience of communities is becoming more and more important. Cities situated in deltas are also under strong urbanization demands and these demands have to be met with due consideration of the challenges presented by climate change, land subsidence and sea-level rise. Within this context, the local geological conditions in the Netherlands present a particularly pressing challenge where water pressure under a clay cover may increase. The static equilibrium of the cover layer might be adversely affected, and uplift failure can be imminent. A recent research program into this failure path has been initiated. Besides the field tests and advanced numerical modelling approaches, the research program also made use of centrifuge tests to quantify the extent of uplift, cracking, and deformation phenomena. This contribution intends to exhibit the aspects of the centrifuge tests conducted as part of this study. The experimental setup design and design considerations will be explained as well as the instrumentation methodology and the reasoning behind the instrumentation choices. This contribution aims to improve the stability assessment of dikes under uplift conditions. ... Read more

The use of geogrids to anchor Sheet Pile Walls (SPW) is relatively new. A series of small-scale tests was performed to investigate the behaviour of geogrid-Anchored SPWs subjected to strip footing surcharge loading. Particle Image Velocimetry (PIV) techniques were used to measure soil displacement and analyse the global failure mechanism and dominant soil-geogrid interaction mechanisms. One of the tests was duplicated in a test box that was eight times as wide, showing that the influence of the small width of the test box was acceptably small. A 2D finite element model (PLAXIS) was used to simulate the tests and there was a reasonable match with the test results. The position of the strip footing load, and the length and number of the geogrid anchors, proved to be key factors in determining the bearing capacity. The results provide new insights into the stabilising effect and the effective length of the geogrid anchors, in other words the length along which geogrid-soil friction is mobilised. Contrary to the Dutch design guidelines for reinforced soil walls and conventionally anchored sheet pile walls, the results showed that the geogrid provides resistance in the active zone under the strip footing surcharge loading. ... Read more