Cavitation:

*Cavitation, ...
<vapour pressure> [, <bulk modulus of gas>]

This keyword is used to limit the pore fluid pressure (with respect to the athmosperic pressure) to a minimum of the given value for <vapour pressure>. Numerically, this is realized by reducing the bulk modulus in case the rate of pore fluid pressure leads to a violation of the specified value. By default, a low value of 10 [F/A] is used. However, the user can specify this value specifing the <bulk modulus of gas> that occupies the fluid once cavitation occured.

Warning

This keyword is currently only available for the u-p-sat elements

To illustrate how to use the keyword, an undrained cyclic triaxial test with the AVISA model is performed. The input files are available here. One sinusoidal axial stress cycle is considered. A cavitational limit of -50 kPa is specified and the default value of the reduced bulk modulus is used. As is visible from the figure, the cavitational limit is fulfilled by the simulation for all but the first increment overshooting the limit value. This is because the limit is explicitly implemented and small time increments are required when approaching the limit.

Pore water pressure in a triaxial test using the AVISA model considering a cavitation limit of -50 kPa