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Aspects of probabalistic serviceability limit state design of dry deep mixing
An expanding population and increased need for infrastructure increasingly necessitate construction on surfaces with poor soil conditions. To facilitate the construction of buildings, roads and railroads in areas with poor soil conditions, these areas are often improved by means of foundation engineering. Constructions that are fairly limited in scope are often founded on shallow or deep foundations. However, these methods are relatively expensive and thus not applicable for large-scale constructions like roads and railroads. A cost-effective way to deal with poor soil conditions is to use ground improvement. This thesis deals with a ground improvement method called deep mixing (DD)using lime-cement columns. Lime-cement columns are manufactured by pushing a mechanical mixing tool to the desired depth, with the tool then rotated and retracted while a lime-cement binder is distributed into soil, forming lime-cement columns. Because of the complex mixing process and inherent soil variability, soil improved by DD shows high variability with respect to strength and deformation properties. Due to this high variability, it is difficult to predict the properties in advance; it is therefore important to verify the properties after installation. In Sweden, this is normally done using the column penetration test (KKK) method. Current design praxis considers evaluated mean values in the design, and the effect of variability and uncertainties is dealt with by using a sufficiently high total factor of safety. A more rational approach for dealing with the effect of variability and uncertainties on the reliability of a mechanical system is to include them as parameters in the design model. This can be done by using reliability-based design (RRR). A major incentive for using 𝑅𝑅𝑅 is that lower variability in design properties produces higher design values. This is important since it encourages contractors to improve their manufacturing methodologies because 𝑅𝑅𝑅 allows more homogenous columns to be assigned higher design values. ...
Aspects of probabalistic serviceability limit state design of dry deep mixing
An expanding population and increased need for infrastructure increasingly necessitate construction on surfaces with poor soil conditions. To facilitate the construction of buildings, roads and railroads in areas with poor soil conditions, these areas are often improved by means of foundation engineering. Constructions that are fairly limited in scope are often founded on shallow or deep foundations. However, these methods are relatively expensive and thus not applicable for large-scale constructions like roads and railroads. A cost-effective way to deal with poor soil conditions is to use ground improvement. This thesis deals with a ground improvement method called deep mixing (DD)using lime-cement columns. Lime-cement columns are manufactured by pushing a mechanical mixing tool to the desired depth, with the tool then rotated and retracted while a lime-cement binder is distributed into soil, forming lime-cement columns. Because of the complex mixing process and inherent soil variability, soil improved by DD shows high variability with respect to strength and deformation properties. Due to this high variability, it is difficult to predict the properties in advance; it is therefore important to verify the properties after installation. In Sweden, this is normally done using the column penetration test (KKK) method. Current design praxis considers evaluated mean values in the design, and the effect of variability and uncertainties is dealt with by using a sufficiently high total factor of safety. A more rational approach for dealing with the effect of variability and uncertainties on the reliability of a mechanical system is to include them as parameters in the design model. This can be done by using reliability-based design (RRR). A major incentive for using 𝑅𝑅𝑅 is that lower variability in design properties produces higher design values. This is important since it encourages contractors to improve their manufacturing methodologies because 𝑅𝑅𝑅 allows more homogenous columns to be assigned higher design values. ...
Aspects of probabalistic serviceability limit state design of dry deep mixing
Bergman, Niclas (author)
2015-01-01
1019
Theses
Electronic Resource
English
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