NUMERICAL AND PHYSICAL MODELING OF REVERSE FAULT PROPAGATION

Resumo

Regions subjected to greater geological activity can induce faults, through sedimentary
deposits, to the surface of the seabed, affecting structures sensitive to loss of support, especially direct
foundations, piles and pipelines. In the case of a pipeline design crossing an area with geological and
geotechnical threats, there are two options: (1) change the route, which can represent a significant
increase in costs; or (2) allowing the pipeline to cross through the fault with proper design and
understanding of the expected fault movement. Surface fault rupture case histories provide valuable
insights regarding the response of soils to underlying bedrock fault movements. The current studies for
understanding the phenomena of faults propagation are mostly concentrated in dry non-cohesive
granular soils. Therefore, the present work aims to investigate the mechanisms of reverse fault
propagation in loose sand through numerical analyses using the finite element method (FEM). The
elastoplastic Mohr-Coulomb constitutive model has been adopted. The numerical results obtained from
ABAQUS and Plaxis 2D were qualitative compared with those from the literature. This work is part of
a research project to carry out centrifuge and numerical modeling of fault propagation in offshore
seabed. The results obtained through ABAQUS were quite helpful in the design and planning of the
centrifuge tests. The analyses undertaken varied the vertical bedrock displacement (U) at the base up to
20% of the soil layer thickness in order to understand their effect on the fault propagation and ground
deformation using the geotechnical drum centrifuge at COPPE-UFRJ. Results were compared and
conclusions were drawn on the most suitable software to be used for the present studies.