Bearing capacity charts of soft soil reinforced by deep mixing

A series of preliminary design charts were developed to predict the bearing capacity of fully and partially penetrated deep mixing (DM) of soft soil. The charts were produced by a new numerical analysis tool based on discontinuity layout optimisation (DLO) in which a previously proposed homogenisation method was used to define the improvement area. To measure the applicability of implementation of the homogenisation method in the DLO, a series of validation processes was performed against several previous studies under uniform soil strength. A new empirical solution was developed from the DLO method using the homogenisation method for the bearing capacity of soft ground under uniform soil strength, improved by the fully penetrated DM method. Results produced by the DLO approach were compared with existing analytical solutions and better agreement was found from the present model. The charts consider variation in improvement area ratio, column length and strength, and foundation width for the fully and partially penetrated DM cases. The simulations were related to real field cases in which the strength characteristics of soft soil increase with depth. An example is given to demonstrate use of the charts

The engineering properties of glacial tills

Glacial tills are a product of the glacial processes of erosion, transportation and deposition and could have been subjected to several glacial cycles and periglacial processes to the extent that they are complex, hazardous soils that are spatially variable in composition, structure, fabric and properties, making them very difficult to sample, test and classify. An overview of the formation of glacial tills and their properties shows that they are composite soils which should be classified according to their lithology, their mode of deposition to link the glacial processes with the facies characteristics and their engineering behaviour. This enables representative design properties to be assigned using frameworks developed for composite soils

Fluoride: A world ubiquitous compound, its chemistry, and ways of contamination

International audienceFluoride, an incompatible lithophile and the most electronegative element, forms a number of soluble, pH-dependent formation of complexes with polyvalent metal ions in water. The interaction between water and sedimentary carbonates ultimately causes fluoride concentration gradient as a sequel of hydrogeochemistry. The occurrence of fluoride in groundwater due to fluorapatite solubility and the other governing factors such as rock chemistry, residence time, well depth, preferential pathways for the upward movement of deep groundwater, hydrologic condition of the pathways, and geologic structure have also been discussed. In this chapter, in addition to the geochemistry of fluoride, the chemistry of fluoride in water and its association with the other physicochemical parametric factors such as total dissolved solids and dissolved ions such as sodium, calcium, magnesium, arsenic, boron, and hydrogen carbonate have been elaborated. As fluoride and arsenic ions participate together in their occurrence in soil and hence water, their co-contamination has been exemplified from the research reports. Fluoride solubility as a function of evaporation, evapotranspiration, temperature, and water softening has also been accounted. The leaching aspects of soil-based adsorption-desorption mechanism and its ultimate destiny on fluoride enrichment of groundwater have also been added in the chapter. © Springer International Publishing Switzerland 2016

Proposed mechanisms on fluoride sorption

International audienceMechanisms on fluoride sorption onto different chemically modified carbons derived from biomaterials have been discussed in this chapter. The workability of calcium, iron, and cerium active centers that spread on the carbon matrix toward fluoride sorption is quite incredible. The participation of calcium, cerium, and iron compounds through plausible mechanisms has been detailed in this chapter. © Springer International Publishing Switzerland 2016