  Unsaturated periporomechanics is a strong nonlocal poromechanics based on
peridynamic state and effective force concept. In the previous periporomechnics
the total Lagrangian formulation is adopted for the solid skeleton of porous
media. In this article as a new contribution we formulate and implement an
updated Lagrangian unsaturated periporomechanics framework for modeling extreme
large deformation in unsaturated soils under drained condition, e.g., soil
column collapse. In this new framework the so-called bond-associated
sub-horizon concept is utilized to enhance the stability and accuracy at
extreme large deformation of solid skeleton. The stabilized nonlocal velocity
gradient in the deformed configuration is used to update the effective force
state from a critical state based visco-plastic model for unsaturated soils.
The updated Lagrangian periporomechanics is implemented numerically through an
explicit Newmark scheme for high-performance computing. Numerical examples are
presented to demonstrate the efficacy of the updated Lagrangian
periporomechanics and its robustness in modeling unsaturated soil column
collapse under drained condition.

Geophysics;Fluid Dynamics