Numerical Analysis of Stone Columns for the Reduction of the Risk of Soil Liquefaction
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Numerical Analysis of Stone Columns for the Reduction of the Risk of Soil Liquefaction Jamal Hleibieh1 · Ivo Herle2 Accepted: 2 April 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Although stone columns have been frequently used for the prevention of soil liquefaction in the last few years, their mechanical performance is still not fully understood. Both numerical calculations with conventional constitutive models and small-scale laboratory experiments do not explain the improving mechanisms satisfactorily. Under seismic effects, the interaction between the soil and the columns, especially between the pore water and the soil skeleton, makes the understanding of this method even more difficult. In this paper, an application of stone columns for the prevention of soil liquefaction is numerically investigated by means of 2D and 3D simulations. A hypoplastic model was used for the soil description. The drainage effect of the columns and their contribution to the stiffening of the ground were considered separately. Furthermore, the impact of the columns installation method was investigated by increasing soil density and stress ratio. Finally, the role of the intensity of the dynamic load was studied. Keywords Stone columns · Soil liquefaction · Earthquakes · Hypoplasticity
1 Introduction In order to prevent soil liquefaction, there are various ground improvement measures at disposal such as the soil cementation, soil compaction, or the use of drainage. Soil compaction using deep vibrator has a high effectiveness in cohesionless soils. However, this effectiveness decreases rapidly with an increase of the fine fraction. Jamal Hleibieh
[email protected] Ivo Herle [email protected] 1
Ed. Z¨ublin AG, Albstadtweg 3 70567, Stuttgart, Germany
2
Technische Universit¨at Dresden, George-B¨ahr-Str. 1a, 01069, Dresden Germany
Transportation Infrastructure Geotechnology
In this case, the soil improvement can be achieved using stone columns (Wehr and Trunk 2011). As an effective method for reducing the risk of liquefaction, the vibro replacement has been used frequently in the last years. The advantage of this method is the combination of a drainage effect, soil compaction, and a rigid support which prevent the liquefaction (Madhav and Krishna 2008). A high permeability of the stone columns decreases the build-up of the pore water pressure in the columns. This creates a pressure gradient between the columns and the surrounding soil. The pressure gradient induces water flow in the direction of columns, and thus results in a decrease of the pore water pressure in the soil (Brennan and Madabhushi 2002). Since the permeability of sand and gravel is greater in the horizontal direction than in the vertical one, the benefit of the stone columns is not only the shortening of the drainage path, but also the change in the direction of water flow to the more permeable direction (Madhav and Krishna 2008). Furthermore, the installation of stone columns causes a compaction of the surroun
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