Omnidirectional Simple Shear Device

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The increasing diversity and complexity of problems in the field of geotechnical engineering and the claim for an economical and sustainable use of geomaterials (soil and rock) and soil-like materials (e.g. mineral materials, RC-materials, industrial by-products, waste from industry and incineration plants) require a much deeper understanding of their mechanical behaviour, as observed experimentally. Despite of the scientific effort in the last decades, the development and validation of models to simulate the complex coupled hydro-mechanical response of multiphase geomaterials still belongs to the most challenging fields of research in geotechnical engineering.In order to achieve the goals of research proposals, an extension of the experimental capabilities of the Zentrum Geotechnik of the Technical University of Munich for the comprehensive examination of the coupled hydro-mechanical behaviour of soil and soil-like materials under cyclic, alternating and dynamic loadings is imperative. The focus of the required equipment lies primarily on the investigation of the behaviour during shear loadings at either controlled or monitored boundary conditions. The experiments to be carried out with the new equipment have to cover the large range of shear strain amplitudes, stress paths, pressures and drainage conditions, which are relevant for the different geotechnical problems under consideration. So far, the testing equipment available at the Technical University of Munich and at universities in Bavaria does not satisfy all these requirements. Therefore, the testing facility described in this application is of strategic importance for the future research in Bavaria.This grant application aims for the partial funding of an Omnidirectional Simple Shear Device (in short: ODSS-device) which is one component of the planned testing facility. In the ODSS-device, the cyclic, alternating and dynamic loadings is be applied by controlling either the shear strain or the shear stress in two kinematically independent directions of shear deformation. The device allows the investigation in the range of medium to large shear strain amplitude. Further components of the testing facility are a Resonant Column Device (in short: RC-device), a Cyclic Dynamic Triaxial Device (in short: DTX-device) and a new loading system as well as measurement equipment for testing large-scale models in an existing testing pit. In the RC-device, the stiffness and hysteretic damping in the range of small shear strain amplitude can be determined by bringing a cylindrical sample into resonance. The examinations using the DTX-device allow the analysis for a similar range of shear strain amplitudes as in the ODSS-device. Nonetheless, in the DTX-device stress and strain are applied and measured exclusively in the principal directions. The rotation of the principal directions in the sample is not possible using the DTX-device while it is one of the features of the ODSS-device.