Settlement behavior of embankment on geosynthetic-encased stone column installed soft ground – A numerical investigation

This paper presents the results of a numerical investigation of the performance of multifaced tunneling under a pile-supported building in water-bearing soft ground. Special attention was paid to the effect of tunneling and groundwater interaction on the tunneling performance. A fully coupled three-dimensional (3D) stress – pore pressure finite element model was adopted to realistically capture the mechanical and hydrological interaction between the tunneling and groundwater. The results indicate that the groundwater drawdown during tunneling yields a considerably larger settlement-affected zone than for cases with no groundwater drawdown, with a tendency for large portions of ground settlement and groundwater drawdown to be completed before the tunnel passes a monitoring section. Also revealed is that the presence of a building tends to reduce the ground settlements and cause subsurface settlements more or less uniformly with depth. It is shown that the lining deformation, and thus its stresses are not significantly affected by the presence of the building for the multifaced tunneling considered in this study. Axial loads in the piles supporting the building tend to either increase or decrease depending on the pile location relative to the tunnel axis. The patterns of changes in pile axial loads are different from the results of previous studies concerning a single pile.

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Behavior of Sand Compaction Columns Installed in Cohesionless Deposits

DFI Journal The Journal of the Deep Foundations Institute ◽

10.37308/dfijnl.20200820.221 ◽

2020 ◽

Vol 14 (2) ◽

Author(s):

N. Aarthi

Keyword(s):

Finite Element ◽

Numerical Model ◽

Internal Friction ◽

Critical Appraisal ◽

Diameter Ratio ◽

Composite Foundation ◽

Stone Column ◽

Fe Model ◽

Angle Of Internal Friction ◽

Settlement Behavior

A critical appraisal of the reviewed literature revealed that there are very limited studies avail-able on the strength characteristics focusing on the load-settlement behavior of sand compaction col-umns (SCCs) when installed in cohesionless deposits. The method, though contemporary to the reputed stone column technique, is not yet studied rigorously in the available past studies, more precisely on the load-bearing characteristics when compared to the latter. Therefore the present study focuses on studying the behavior of multiple column composite foundation supported by sand compaction columns installed in loose to medium dense sands on a lab-scale numerical model. The study is carried out using commercially available finite element (FE) code 3D PLAXIS. Spacing to diameter ratio (S/D) ranging from 1.5 to 3.5 and initial relative density (RD) from 30 to 60% was adopted to study the changes in the load-settlement behavior of the improved deposit. Extending the FE model to further parametric study, the effect of angle of internal friction of the column sand and diameter of the column on the bearing capacity and settlement characteristics were analysed with and without normalization. From the results obtained, it is found that, for the considered FE model, the improved deposit with 3D spacing between the SCCs behaves distinctly different from all other cases analyzed.

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