Micromechanical numerical modelling of foundation punching in highly porous cemented geomaterials in a virtual centrifuge environment

Foundation design on collapsible soils, such as loess, volcanic soils, tuff or cemented soft calcareous rocks, is a challenging geotechnical problem. When subject to moderate loads, the settlement of the foundation is limited and more or less reversible. However, beyond a load threshold value, soil compressibility increases due to the progressive rupture of intergranular bonds. In some cases, when this threshold is achieved, the bond fracture is so brittle that causes the collapse of the foundation, i.e. a sudden settlement occurring at constant load. To address this problem numerically, the coupled DEM (discrete element method) - FDM (Finite Difference Method) modelling approach is useful because of its excellent ability to deal with non-linear problems with large deformations while also reducing the computational burden in boundary value problems (BVPs). In this work, a coupled model is used to create a virtual centrifuge environment by combining the fast-generation method and particle upscaling. The penetration of a shallow foundation into soft cemented granular materials under different gravity levels is simulated using the two most widely used contact models for cemented materials: the parallel-bonded model (PBM) and the soft-bonded model (SBM). The numerical results show that these contact laws are unsuitable to properly reproduce the collapse-like failure mechanism for highly porous structures efficiently. It is shown that such a feature can be reproduced if a contact law capable of capturing the softening behaviour at the microscale is used.