Numerical guidance to multi-direction cyclic testing of soft organic clay with the CYC-DoSS device for railway embankments

¹ Department of Geoscience and Engineering, Delft University of Technology, Delft, The Netherlands
² Dipartimento di Ingegneria Civile e Ambientale, Politecnico di Milano, Milano, Italy
³ Haskoning, Delft, The Netherlands

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

The subsoil beneath railway embankments experiences multi-directional cyclic loading across a wide frequency range, conditions that remain largely unexplored in the available literature. This paper presents coupled hydromechanical finite element analyses of two representative cross-sections of Dutch railway embankments to characterise the spatial distribution of cyclic stress increments in the underlying soft soil. The results show that the largest cyclic stress amplitudes occur below the embankment centreline, while stress increments normalised to the initial mean effective stress can become significant at the embankment toe and at the ditch. Principal stress rotations are also pronounced at these locations. In all cases, a greater embankment height reduces these effects. Replicating these conditions in the laboratory requires an apparatus capable of independent multi-axial control at high frequencies. Recent modifications to the CYC-DoSS multi-directional shearing device are presented, which enable accurate force measurement at frequencies up to at least 15 Hz. A pilot test on a natural organic clay specimen demonstrates the device capability to impose complex stress paths and multi-frequency cyclic loading. The results also show that pore pressure generation increases as multi-directional shearing is introduced.