Effect of Smear Due to Vertical Drains on the Behaviour of Two Embankments Constructed on Soft Clays

This paper describes the methodology to include the effect of smear in the prediction of settlements beneath two embankments stabilized with vertical drains. The extent of smearing around the drains was studied using a detailed analytical formulation developed by the authors and used in conjunction with the finite clement code, CRISP. The smear zone propagation around vertical drains was studied in the laboratory using a large radial drainage consolidometer. The case histories selected in this study include (a) embankment stabilized with vertical sand drains at a Naval Dockyard, Thailand, and (b) embankment stabilized with vertical band drains in soft Muar clay, Malaysia. It may be concluded from this study that the inclusion of smearing improves the settlement predictions significantly. The numerical results indicate that the extent of smearing is mainly dependent upon the magnitude of horizontal permeability and the drain geometry

Plane-strain modeling of smear effects associated with vertical drains

The present study provides a methodology to include the smear effect of vertical drains in a two-dimensional (2D) plane-strain finite-element model, employing the modified Cam-clay theory. The analysis is conducted by converting the radius of the smear zone and its permeability (axisymmetric) into equivalent plane strain parameters. The introduction of smear effects improves the accuracy of the numerical model that is tested for a Malaysian soft clay, in this study

Predicted and observed behaviour of soft clay foundations stabilised with vertical drains

A novel plane strain approach is introduced to model the behaviour of embankment foundations on soft clay stabilised with vertical drains, where the classical axisymmetric solutions are converted to an equivalent plane strain model, incorporating the effects of smear and well resistance. This paper describes the behaviour of an embankment stabilised with vertical drains, where a specific case history is selected from Malaysia. The consolidation of soft clay is modelled on the basis of the modified Cam-clay. The settlement behaviour at various stages of embankment loading is analysed using the finite element technique, and the numerical results are compared with field measurements. The behaviour of drains with and without smear is also compared. Inclusion of smear effect in the mathematical model improves the prediction of settlements

Aquifers Selection Based on Geoelectric Method Data in the Framework of Drilling Wells

The selection of aquifers based on Geoelectric Method data in constructing drilling wells was discussed in the present study. The research was conducted at the International Hospital Project in Nyitdah Tabanan Bali. The research position was around 8,5736 LS 115,1215 LE. Before the study was conducted, a well drill (well 1) has been made. The results showed that there were two types of aquifers, namely unconfined aquifers and unconfined aquifers. Related to this study, well 1 took water in the unconfined aquifers of 4 m depth. If the water kept taken for a long period, the quality and quantity of the water would be worse since well 1 was unconfined aquifers that took surface water. This would adversely affect the hospital building being built. The land around the building would be hollow due to the water loss, and the building would become unstable. Another drill well (well 2), based on geoelectricity data, can be made on 5,25 m - 18,75 m. In-depth 23 m, it was suspected that unconfined aquifers would have been found in well 2. After being drilled, aquifers were found in 23 m depth. Drilling was kept doing to 55 m depth

A systematic map of studies testing the relationship between temperature and animal reproduction

Funding: This work was funded by the European Society for Evolution (which funds a Special Topic Network on Evolutionary Ecology of Thermal Fertility Limits to CF, AB, RRS and TARP), the Natural Environment Research Council (NE/P002692/1 to TARP, AB and RRS, NE/X011550/1 to LRD and TARP), the Biotechnology and \Biological Sciences Research Council (BB/W016753/1 to AB, TARP and RRS) and a Heisenberg fellowship from the German Research Foundation (FR 2973/11-1 to CF).1. Exposure to extreme temperatures can negatively affect animal reproduction, by disrupting the ability of individuals to produce any offspring (fertility), or the number of offspring produced by fertile individuals (fecundity). This has important ecological consequences, because reproduction is the ultimate measure of population fitness: a reduction in reproductive output lowers the population growth rate and increases the extinction risk. Despite this importance, there have been no large‐scale summaries of the evidence for effect of temperature on reproduction. 2. We provide a systematic map of studies testing the relationship between temperature and animal reproduction. We systematically searched for published studies that statistically test for a direct link between temperature and animal reproduction, in terms of fertility, fecundity or indirect measures of reproductive potential (gamete and gonad traits). 3. Overall, we collated a large and rich evidence base, with 1654 papers that met our inclusion criteria, encompassing 1191 species. 4. The map revealed several important research gaps. Insects made up almost half of the dataset, but reptiles and amphibians were uncommon, as were non‐arthropod invertebrates. Fecundity was the most common reproductive trait examined, and relatively few studies measured fertility. It was uncommon for experimental studies to test exposure of different life stages, exposure to short‐term heat or cold shock, exposure to temperature fluctuations, or to independently assess male and female effects. Studies were most often published in journals focusing on entomology and pest control, ecology and evolution, aquaculture and fisheries science, and marine biology. Finally, while individuals were sampled from every continent, there was a strong sampling bias towards mid‐latitudes in the Northern Hemisphere, such that the tropics and polar regions are less well sampled. 5. This map reveals a rich literature of studies testing the relationship between temperature and animal reproduction, but also uncovers substantial missing treatment of taxa, traits, and thermal regimes. This database will provide a valuable resource for future quantitative meta‐analyses, and direct future studies aiming to fill identified gaps.Publisher PDFPeer reviewe

Laboratory determination of smear zone due to vertical drain installation

This paper is mainly concerned with a laboratory study to investigate the effect of smear due to vertical drain installation. The extent of the smear zone around a vertical drain was studied utilizing a large-scale consolidometer apparatus. The test results reveal that a significant reduction in the horizontal permeability takes place toward a central drain, whereas the vertical permeabilty remains relatively unchanged. The radius of the smear zone was estimated to be a factor of four to five times the radius of the central drain (mandrel), and the measured ratio of horizontal to vertical permeability approached unity at the drain-soil interface. The laboratory measured settlements are subsequently compared with the predictions based on the theory of Hansbo and the finite element method. It is of relevance to note that the inclusion of the correct variation of permeability ratios of the smear zone in the plane strain finite element analysis improves the accuracy of settlement predictions

Numerical modeling of vertical drains with smear and well resistance installed in soft clay

This study describes the behavior of embankments stabilized with prefabricated vertical drains installed in soft clay foundations, based on several fully instrumented case histories selected from Thailand and Malaysia. A multidrain analysis is conducted based on an equivalent, plane strain model developed by the authors. The deformation of soft clay beneath an embankment (i.e., along and away from the centerline) is predicted and compared with the available field measurements. The effects of both smear and well resistance are incorporated in the analytical formulation, which is used in conjunction with the modified Cam-clay theory. It is demonstrated that the installation of vertical drains significantly increases the rate of settlement, improves the dissipation of pore-water pressure, and decreases the lateral deformation of the soft clay foundation. To obtain better predictions, especially of pore pressures and lateral displacements, the equivalent discharge capacity of the drains needs to be modeled appropriately. The inclusion of the effects of smear and well resistance in the analysis of vertical drains improves the accuracy of predictions significantly, in comparison with the field measurements.Key words: clay, consolidation, embankment, finite element method, settlement, smear zone, vertical drain