Instability in Soft Sensitive Clays

Soft sensitive clays like quick clays are well known in Scandinavia and in some regions in Canada. The salt pore water of these marine clays has been leached out since last glaciations and left a brittle mineral structure. Slides in quick clays can be extremely disastrous, as in Verdal, Norway in 1893 or Rissa in 1978. The slides may be initiated by local overloading, river erosion or similar and can escalate in size in a retrogressive manner in which large volumes of clay finally may liquefy. Norwegian quick clay has a very low permeability and hence pore water pressure becomes a crucial parameter that can affect the stability of material. Failure in quick clay (with a post-peak strain softening behavior) is often associated with the development of shear bands, i.e. narrow zones of localized deformation, and the failure loads depend on the thickness of these shear bands. Plane strain compression tests were performed, at laboratory 3S, Grenoble France, to observe the formation and propagation of shear bands during undrained shearing. Biaxial plane strain tests were performed in quick clay having different sensitivity and local pore pressure variation throughout the test was monitored. Image analysis is done to detect shear band thickness and mode of failure. Further, usefulness of shear band analyses in landslide calculation using finite elements and consequence of such failure is also discussed numerically. A stability analysis of a quick clay slope is made to illustrate the progressive failure mechanism

Microstructural study of the deformation zones during cone penetration in silt at variable penetration rates

During conventional cone penetration testing in silt, the soil will normally be partially drained. If the penetration rate varies, time for drainage is altered and therefore the measured cone resistance and pore pressure will change. This paper studies the change in soil microstructure around the probe during cone penetration carried out at different penetration rates to investigate the failure mechanism and the processes controlling drainage in silt. Backscattered electron images of polished thin sections prepared from frozen samples at the end of penetration were used. Making use of advanced image processing techniques, the statistical distribution of particle orientations and the local porosity were investigated for the zones around the cone tip and the shaft. The spatial distribution of the measured microscale parameters in the region near the probe indicates that the soil deformation during CPTU in silt leads to the formation of both contractive and dilative zones. The macro response of the material, presented by the pore pressure and the cone penetration resistance measured during the test, results from the competition between these zones during penetration, which is shown to be dependent on the penetration rate

Microstructural study of the deformation zones around a penetrating coned tip in silty soil

The change in soil microstructure around the penetrating probe during a cone penetration test is investigated. Backscattered electron images of polished thin sections prepared from frozen samples at the end of penetration are used. The images have a spatial resolution of 0.4 µm/pixel that allow a clear identification of grains and pore spaces. The statistical distribution of the change of particles orientation is analyzed for the zones around the cone tip and the shaft. Quantitative analysis of the change in porosity near the penetrating object is investigated. An increase in porosity and a decrease in the anisotropy of particle orientations from the cone and further out confirm that the soil deformation during CPTU in silt is a combination of compaction and dilative behavior that might influence the pore pressure distribution during penetration

Instrumentation of Flexible Buried Culvert Subjected to Rockfall Loading

Natural hazards, like avalanches and rock falls, will always be a major concern for infrastructure, i.e. roads and railways, in mountain areas. Several measures are available to protect this infrastructure, but especially in areas with steep slopes, rockfall- or avalanche galleries are commonly used. These structures, which are made to withstand high impact forces, can be made of reinforced/pre-stressed concrete culverts covered with soil. A possibly cheaper and equally safe alternative could be to use a buried corrugated steel culvert. To investigate the use of buried corrugated steel culverts as rock fall protection structures an experimental study has been carried out. A 4.0 m span half arch corrugated steel culvert was buried in soil and instrumented during rockfall loading. Rock blocks with various weights have been dropped from different heights on a corrugated steel culvert covered with a cushion material. Tests were conducted with dense backfill in near zone and regular backfill in the cushion layer zone. Measurements were made during both construction phase and during rockfall phase. During construction phase measurements were made to monitor culvert shape and culvert strains. During impact loading from rock blocks decelerations and transmitted accelerations were monitored together with change of culvert shape and deformations. Deceleration of the rock blocks was also documented with a high speed camera. The goal of this study were to obtain knowledge which can be used in design codes in the future for flexible rockfall- and avalanche shelters

CPTU-detection of thin clay layers in sand: Results from calibration chamber tests

publishedVersio

Thin-layer detection from the cone resistance rate of change

publishedVersio

The uses of Kenyan aloes: an analysis of implications for names, distribution and conservation

Background The genus Aloe is renowned for its medicinal and cosmetic properties and long history of use. Sixty-three Aloe species occur in Kenya, of which around 50 % are endemic. Several species of aloes are threatened with extinction and knowledge about their use is of major importance for sound conservation strategies. The main aims of this study were to assess the biocultural value of Aloe in Kenya by documenting local uses of aloes and evaluating how the vernacular names reflect the relative importance in different ethnic groups. Methods Ethnobotanical and ethnotaxonomical data were collected using field observations and semi-structured interviews. Information was collected by interviewing 63 respondents from nine different ethnic groups, representing different ages, gender and occupations. Statistical analyses were performed using R version 3.1.2. Results A total of 19 species of Aloe were found in the study area, of which 16 were used. On the generic level Aloe was easily distinguished. At species level, the local and scientific delimitation were almost identical for frequently used taxa. Aloe secundiflora, with 57 unique use records was the most important species. The two most frequently mentioned Aloe treatments, were malaria and poultry diseases. In our study area neither age nor gender had a significant influence on the level of knowledge of Aloe use. Finally, no correlation was found between extent of use and people’s perception of decrease in local aloe populations. The aloes are highly appreciated and are therefore propagated and transported over large areas when people relocate. Conclusion Biocultural value is reflected in the ethnotaxonomy of Aloe in Kenya. Different ethnic groups recognise their most-valued Aloe at the genus level as “the aloe” and add explanatory names for the other species, such as the “spotted aloe” and the “one-legged aloe”. Widespread species of Aloe have the highest number of uses. There is no obvious correlation with high use and decrease in abundance of aloes locally, and we found no compelling evidence for local uses causing devastating damage to populations of the 19 species in use, whereas habitat loss and commercial harvesting appear to be of urgent concern for these important plants

Validity of a three-variable juvenile arthritis disease activity score in children with new-onset juvenile idiopathic arthritis

<p>Objectives To investigate the validity and feasibility of the Juvenile Arthritis Disease Activity Score (JADAS) in the routine clinical setting for all juvenile idiopathic arthritis (JIA) disease categories and explore whether exclusion of the erythrocyte sedimentation rate (ESR) from JADAS (the ‘JADAS3’) influences correlation with single markers of disease activity.</p> <p>Methods JADAS-71, JADAS-27 and JADAS-10 were determined at baseline for an inception cohort of children with JIA in the Childhood Arthritis Prospective Study. JADAS3-71, JADAS3-27 and JADAS3-10 were determined using an identical formula but with exclusion of ESR. Correlation of JADAS with JADAS3 and single measures of disease activity/severity were determined by category.</p> <p>Results Of 956 eligible children, sufficient data were available to calculate JADAS-71, JADAS-27 and JADAS-10 at baseline in 352 (37%) and JADAS3 in 551 (58%). The median (IQR) JADAS-71, JADAS-27 and JADAS-10 for all 352 children was 11 (5.9–18), 10.4 (5.7–17) and 11 (5.9–17.3), respectively. Median JADAS and JADAS3 varied significantly with the category (Kruskal–Wallis p=0.0001), with the highest values in children with polyarticular disease patterns. Correlation of JADAS and JADAS3 across all categories was excellent. Correlation of JADAS71 with single markers of disease activity/severity was good to moderate, with some variation across the categories. With the exception of ESR, correlation of JADAS3-71 was similar to correlation of JADAS-71 with the same indices.</p> <p>Conclusions This study is the first to apply JADAS to all categories of JIA in a routine clinical setting in the UK, adding further information about the feasibility and construct validity of JADAS. For the majority of categories, clinical applicability would be improved by exclusion of the ESR.</p&gt

HLA-B27 predicts a more extended disease with increasing age at onset in boys with juvenile idiopathic arthritis

Poster presentatiopn at 15th Paediatric Rheumatology European Society (PreS) Congress London, UK. 14–17 September 200