Combined loading apparatus for monotonic and cyclic planar loading of foundations

The paper introduces a new apparatus for centrifuge model testing of foundations subjected to monotonic and cyclic combined planar loading under constant vertical load. The new experimental setup was developed in-house, aiming to exploit the capabilities of the new beam centrifuge of the ETH Zurich (ETHZ) Geotechnical Centrifuge Centre. The developed assembly consists of a pair of stepper-motor actuators, applying lateral loading at different lever arms from the foundation reference point. The two actuators are connected to a rigid column by means of sliding-hinges. The latter facilitate transmission of the loads to the foundation system, while allowing for settlement or uplifting, depending on the studied system and the applied load path. The free vertical movement of the foundation under constant vertical load is a key feature of the proposed assembly. With appropriate regulation, the developed assembly is capable of applying any desired combination of lateral translation u and rotation θ (displacement-controlled mode), or lateral load H and overturning moment M (load-controlled mode). The target, constant, vertical load is achieved by adding a variable mass at the top of the rigid column. The paper introduces the key features of the experimental setup, along with its capabilities demonstrated through selected preliminary tests.