Abstract
This paper reviews the main modeling techniques for stone columns, both ordinary stone columns and geosynthetic-encased stone columns. The paper tries to encompass the more recent advances and recommendations in the topic. Regarding the geometrical model, the main options are the “unit cell”, longitudinal gravel trenches in plane strain conditions, cylindrical rings of gravel in axial symmetry conditions, equivalent homogeneous soil with improved properties and three-dimensional models, either a full three-dimensional model or just a three-dimensional row or slice of columns. Some guidelines for obtaining these simplified geometrical models are provided and the particular case of groups of columns under footings is also analyzed. For the latter case, there is a column critical length that is around twice the footing width for non-encased columns in a homogeneous soft soil. In the literature, the column critical length is sometimes given as a function of the column length, which leads to some disparities in its value. Here it is shown that the column critical length mainly depends on the footing dimensions. Some other features related with column modeling are also briefly presented, such as the influence of column installation. Finally, some guidance and recommendations are provided on parameter selection for the study of stone columns.
Highlights
Ground improvement using stone columns, known as granular piles or aggregate piers, is one of the most popular techniques to improve soft soils for the foundation of embankments or structures
The ground improvement technique started as an extension of traditional vibro-compaction to non-granular soils, whose low permeability and cohesion do not allow for a quick rearranging of soil particles in a denser configuration
This paper provides some guidelines for obtaining these simplified geometrical models
Summary
Ground improvement using stone columns, known as granular piles or aggregate piers, is one of the most popular techniques to improve soft soils for the foundation of embankments or structures. The idea of improving soft soils for foundation purposes using granular inclusions is relatively old It is documented [1] that in 1839 in Bayonne (France), the French colonel Burbach used for the first time sand piles as deep foundations instead of the classical wood piles that rapidly degrade with fluctuations of the ground water level. The increase in computer power and the availability of finite element codes makes numerical analyses very appealing in geotechnical design They usually lead to more detailed studies but require a clear conception of the modeling techniques. Ground improvement techniques, such as stone columns, are more and more popular due to the increasing occupation of natural soft soils and environmental concerns [9,10]. The results for an isolated column under concentrated load just on top of the column cannot be directly extrapolated for a large group of columns under distributed uniform load
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