Discrete Features for Tunnels

Hi all;
Can I turn off and turn on with different times (transient state) for the discrete features that I use to simulate the advancing of digging a tunnel?
How can I do it?

discrete features cannot be switched on and off during a run. you woud have to stop the run, add discrete features and start the run again.

Pete

Another option to simulate the propagating excavation is provided by element deactivation. Elements can be deactivated and reactivated during a simulation run. Of course, the deactivation of elements to simulate the digging of a tunnel requires a fully spatially discretized tunnel geometry in the FE-mesh.