Prestressed reinforced soil by geosynthetics – Concept and experimental investigations

This paper presents experimental investigations on an innovative construction method for reinforced soil structures by geosynthetics called prestressed reinforced soil. The concept of prestressed reinforced soil, (PRSi) developed to increase the bearing capacity of a reinforced soil structure and to improve its displacement behaviour is introduced. The concept of PRSi is validated by experimental studies. Large scale experimental tests conducted at the Institute of Soil Mechanics and Foundation Engineering at Graz University of Technology, Austria and their results are presented. Over 60 path-controlled static load displacement tests have been performed to investigate the load displacement behaviour of 10 different reinforced soil structures. The reinforced soil structures have been constructed under homogeneous laboratory conditions with respect to construction sequence, compaction, temperature and measurement equipment to assure high quality reproducible test results. The overall results show a considerable improvement of the macroscopic load displacement behaviour of the soil structure by utilizing the concept of prestressed reinforced soil. In addition 80 cyclic load displacement tests have been conducted in Weimar, Germany to validate the concept of PRSi under cyclic loading conditions. A soil element, theoretically taken out of a reinforced soil structure, is used to investigate its behaviour under vertical cyclic load and horizontal support conditions. The macroscopic research shows that displacements occurring under cyclic loading can be reduced tremendously by installing a geogrid with the concept of PRSi. Besides investigating the macroscopic load displacement behaviour of the reinforced soil structure a detailed mesoscopic analysis using the Particle Image Velocimetry (PIV) method has been performed. From the PIV analysis it was demonstrated that the vertical and horizontal displacements under cyclic loading and below the geogrid layer decreased rapidly.