Advanced dynamic soil testing - Introducing the new marum dynamic triaxial testing device

Abstract

Soil mechanical and submarine mass-movement initiation studies often use static and quasi-static approaches to determine the strength of soils against external mechanical stresses. However, many natural processes pose time variant stresses on soils, and hence exert key roles for submarine slope stability and submarine mass-movement initiation. Prominent examples are earthquake-, wind-, wave- and current-forces and alternating man-made loading on offshore constructions. Most soils show a weaker response to periodic loading - making dynamic and cyclic loading experiments mandatory for offshore natural hazard and risk assessment. Dynamic and cyclic triaxial testing are essential in liquefaction studies of granular soils and creep investigations of cohesive and granular sediments. So far, competing setups are used with mechanical spindles, pneumatic actuators or full hydraulic drives. The new MARUM dynamic triaxial testing device (DTTD) unit is addressing this increasing demand by enabling a wide range of test configurations. At its core it contains an ultra fast, hydraulically-driven ±20 kN cylinder and a 5 kHz real-time controller. This enables up to ±0.5 mm strokes at up to 50 Hz. Advantages to commercial systems are (1) the high flexibility in test setup, (2) the possibility to feed arbitrary signals derived from in situ measurements, and (3) full system access to all controls to expand and adjust the system abilities on the hard and software level. Applications so far include cyclic creep studies for offshore wind farms, liquefaction experiments on artificial sand-clay mixtures and studies on the behavior of submerged soils under dynamic stress conditions to evaluate slope stability and submarine landslide initiation. © Springer Science + Business Media B.V. 2010.