Field Measurements and Numerical Analysis of the Stress Distribution below Stone Column Supported Embankments and their Stability

Since decades vibro stone columns are used to improve the bearing capacity and the settlement behaviour of soft soils. The design is based on empirical or semi-analytical formulae, most of which using the unit cell approach. Such design procedures, e.g. the Priebe method, proved their reliability in many cases. Stone columns are also used to improve the ground below embankments constructed for infrastructural measures. In such cases the columns act predominantly in order to enhance the slope stability. To give a realistic picture of the actual situation the design of the stone column pattern needs to take into account the stress distribution between columns and soil. All approaches not considering the stress concentration in the columns gain results which are overconservative and thus lead to uneconomical solutions. In the paper the results of numerical analyses considering the spatial nature of the problem are presented. The results are compared with those of analytical approaches. In addition to the numerical analysis the results of long term monitoring of the stresses at a case history are presented. The knowledge of the stress distribution offers the possibility of a realistic approach for the calculation of the slope stability of embankments on improved ground.