Influence of capillarity on the mechanical behaviour of non-cohesive soils under dynamically loaded logistic areas

• Applicant: Professor Dr.-Ing. Jürgen Grabe
• Subject Area: Geotechnics, Hydraulic Engineering
• Term: from 2010 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 162924550

With regard to the results of the first project period, the sequel period consists of model tests and laboratory tests, intending to investigate the mechanical behaviour of non cohesive soils within their typical low suction range.For the investigation of the influence of capillarity on the results of static plate load tests, which are frequently used for densification control in road construction, plate load tests in a model scale are performed. Furthermore, laboratory tests with monotonic loading aim at the understanding of the stress-strain-behaviour and shear resistance of unsaturated sand. Afterwards further cyclic laboratory tests are performed in order to answer the question whether cyclic loading, for instance caused by crossing of heavy vehicles, has an impact on the change of matric suction in the pavement subsoil and whether this change is ofportance for an accumulation of settlements.The plate load tests in model scale will be done as planned for the first project period to the greatest possible extent and will be evaluated using the theory of similarity. For the laboratory tests on unsaturated sand specimens a new control and measurement concept for low matric suction ranges will be used owing to the hitherto existing results. The concept implies the occurrence of matric suction in the form of subatmospheric, negative pore water pressures as found in nature and will be applied in a comprehensive test programme, consisting of simple shear tests and triaxial tests with either constant suction or constant water content of the specimen. The loading will be applied monotonically and cyclically.Finally, a dynamic three-phase-model is supposed to be validated with the help of the test results of the laboratory tests performed on unsaturated sand specimens, in order to apply it to the recomputation of the model tests and chosen field tests.

• DFG Programme: Research Grants