Abstract
Abstract
Testing soils for earthquake and dynamic loads requires advanced equipment able to assess the effects of hydromechanical coupling on the soil response. The majority of laboratory element tests are either “slow tests”, which intend to approach drained conditions throughout the soil sample in order to obtain reliable pore water pressure measurements, or “fast undrained tests”, where flow is prevented by closing the drainage lines. However, many natural loads, including earthquakes, impose a wide range of high loading frequencies, typically triggering a partially drained response in the field. Although the rate effect plays an important role in soil behaviour, its investigation is hindered by the limitations of existing equipment. In addition, the ability to apply multidirectional loading to soil elements in the laboratory is important to fully understand the soil response under earthquakes. Currently, multidirectional simple shear devices are used to study the soil behaviour under earthquake loadings. Nevertheless, many shear devices suffer from stresses and strains non-uniformities, which could potentially mislead data interpretation and constitutive models development. This paper presents an innovative multidirectional shear device developed in the section of Geoengineering at TU Delft, which can apply higher loading frequencies compared to previous equipment and a wider variety of multidirectional cyclic loading patterns. The apparatus is equipped with advanced sensors, also developed at TU Delft, to capture the local response of specimens. The sensors are installed to reduce a priori assumptions on the soil response, better interpret the element experimental results and further investigate the rate effect of applied loading. Preliminary performance test results are provided to illustrate the complex load conditions which can be achieved.