Seepage for tunnels

Hi all;
Can you help me with my problem. I'm doing a simple vertical model  in 2D and I try to simulate the drilling of a tunnel in different zones of high and low conductivity that it cross, see the picture. I use the seepage-face to estimate the flow that infiltrate inside the tunnel with turn on and turn off elements, but I have many problems to do the following...

1. How can I do for the seepage conditions turn on and turn off in transient state with the desactivation of elements that simulate the excavation at the same time.. see the picture?
2. How can I do for quantify the flow in L[sup]3[/sup]/T that the drilling infiltrate with the seepage conditions or it exist other form?
3. The seepage conditions must be on the outline of the nodes of the polygon of the tunnel I turn .. see the picture?

http://www.subirimagenes.net/i/150514101726750351.jpg
Thank you!

You have to activate BC nodes as the tunnel advances, which can be set up using a "modulation function". To do add such a function, in the data panel, right-click (for example) "hydraulic-head bc", select "add parameter" and then select "modulation function". This will add an editable variable beneath hydraulic had bc that you can set up just like any other nodal variables.

Another approach would be to used transient material properties, simulating the advancing tunnel by increasing the K. You would still have a BC at the tunnel entrance to simulate discharge from it.

Pete

Thanks Pete!!
I appreciate your help and support with Feflow!