Marián Drusa

The piled embankment represents one of the solutions for the realization of a soil body on a compressible subsoil where extended settlement or insufficient stability threatens the serviceability of related structures. Widely adopted analytical design procedures were analyzed: Marston’s formula and Hewlett and Randolph method contained in the British standard BS 8006-1, the German regulation EBGEO and the Dutch regulation CUR 226. Using these recommendations, the theoretical values of the individual parts of the load acting in the embankment and, subsequently, the values of the axial strain or tensile forces in the reinforcement were determined and compared with experimental data obtained from the tests in the large-scale physical model. For the presented case, without subsoil support, CUR 226 with the inverse load, which is recommended in the case of subsoil with low bearing capacity, shows better coincidence with the measured data. Overall, EBGEO and CUR 226 can be considered to be close to the real behavior of the piled embankment. Because of the frequent utilization of geosynthetic reinforcement and possible changes of subsoil parameters during the service life of the piled embankment, a rheological process of its elements should be investigated during the design process.

Analysis of pile bearing capacity is an important task in the investigation of soil-structure interaction. The paper is dedicated to the prediction methods for the pile bearing capacity calculation based on the cone penetration test (CPTu) results, namely UniCone method, Laboratoire Central des Ponts et Chaussées method (LCPC), and the method involved in the Eurocode 7—2. A set of CFA piles was tested to obtain reference bearing capacity. The ability of the prediction methods to determine the bearing capacity of the pile was investigated. In each evaluation criteria using statistical tools, the methods were ranked based on their performance. The results of the study indicate that the UniCone method is most applicable for the given conditions. The EC 7—2 method showed the largest variability of results, and we do not recommend its application without a deeper analysis. The applicability of any presented method cannot be considered final or universal. It is advisable to use more modern and updated methods which have been developed from a larger database of pile tests. The development of these methods should continue by expanding the database of tested piles together with the application of more advanced rock environment testing procedures.