Numerical Analysis of Stone Columns for Road Embankment Construction

Abstract

The highway, R2, between cities Trencin and Prievidza in Slovakia was constructed under adverse geological conditions. Some sections of the motorway were designed on embankments and require the use of soil improvement because of the unsuitable subsoil. Original subsoil was improved using vertical drains, stone columns, dynamic compaction, preloading and stone drainage ribs. This paper deals with the numerical analysis of selected profiles where the subsoil for road embankment can be improved using stone columns. The subsoil consisted of compressible soft soils with low permeability. Stone columns reduced the settlement of a road embankment and reduce the time required for consolidation. Stone columns with a diameter of 600 mm and length of 5 m were designed in a square mesh with an axial distance of 2 m. Numerical modelling was executed with Plaxis software using FEM. Stone columns are a displacement technique which significantly changes properties of the original subsoil. The geotechnical monitoring included results of road embankment settlement using horizontal inclinometers, as well as geodetical measurements. The analysis included the comparison of road embankment settlement determined using measurements with results of numerical models, which assumed different ways of stone column modelling. The results showed that numerical modelling leads to the acceptable determination of road embankment settlement. Advantages and disadvantages of different ways of stone columns modelling are discussed.