The ground water flow equation can be combined with the materi equations. The solid will deform due to the ground water flow pressure gradient and ground water flow pressure will change due to solid volume changes. An example of a input file is given below
...
materi_velocity
materi_stress
groundflow_pressure
end_initia
...
type 0 -materi -groundflow
( solid material )
group_materi_elasti_young 0 ...
group_materi_memory -updated
( groundflow )
group_groundflow_compressibility 0 ...
...