Performance of floating soil cement column on soft soil
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Date
2019
Authors
Journal Title
Journal ISSN
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Publisher
Universiti Teknologi Malaysia
Abstract
Deep Mixing (DM) method is a well-known in-situ soil stabilization technique that proved increase the bearing capacity and reduced settlement. The DM method can be formed in a group of columns as either installed in end-bearing or floating soil cement column. Nowadays, a study on the floating soil cement columns has gained interest, as it can reduce the construction cost and environmental impact during construction. However, there is limited study involving experiment to study the soil deformation corresponding to different values of improvement area ratio, ap column height, Hc and depth improvement ratio, ß. Thus, in this study, a series of small scale 1g physical test in 2 dimensional, 2D were conducted to investigate the effect of floating soil cement columns arrangement (area improvement ratio, ap and column height, Hc) on failure (Ultimate Limit State, ULS) and settlement (Serviceability Limit State, SLS) of foundation under design load, Wd. This study involved the used of area improvement ratio, ap of 20.7%, 31.1% and 41% with corresponding depth improvement ratio, ß of 0.25 and 0.5. Linear Vertical Displacement Transducer, LVDT, Load cell, Miniature Pressure Transducer, MSPT and Pore Pressure transducer, PPT were used to measure the vertical displacement, load, pressure of surrounding soil and column and the pore water pressure respectively. At the same time, the settlement and deformation under the design load was also captured through images of the exposed surface of the soil model during the load application. Then, the images were analyzed by using the Particle Image Velocimetry, PIV technique, GeoPIV: MATLAB software. It is observed from the study, that the bearing capacity of the soft soil has increased as the ratio of ap and ß increased. Meanwhile, with increasing ap and ß, the total settlement of soft soil reinforced by floating soil cement column reduced in comparison with the untreated soil. The settlement reduction effect can be seen from a non-linear relationship due to the differences in design load applied for test conditions. For the immediate settlement, Su it is significantly shows improvement by the increased ratio of ap and ß that contrast with consolidation settlement, Sc. In addition, the stress concentration ratio, ? was found to be in a range of 1 to 3. Furthermore, from the 3D numerical analysis by Plaxis that was performed using Mohr Coulomb, MC and Soft Soil, SS model, the results of the bearing capacity and settlement were alligned with the findings by physical modeling. A good interpretation of deformation and load transfer mechanism in floating soil cement column improved ground was also attained. Finally, a prediction of the settlement by using Skemptom and Bjerrum (1957) with an average weighted method for immediate settlement, Su was also found a good agreement with the physical and numerical analysis. While, the consolidation settlement, Sc was estimated by the use of mv parameter with an assumption of the load was distributed with 2V : 1H and transferred from the top. The method is found applicable for soft soil improved by floating soil cement column in over-consolidated condition.
Description
Thesis (PhD. (Civil Engineering))
Keywords
Soil stabilization—Research, Soil cement, Grouting (Soil stabilization)
Citation
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