GWT for the trial trench excavation

Hi all, 

When we model the trial trenches in Plaxis (to find the utilities inside the ground, so can't provide embedded depths), how to draw the GWT to get the full water effect?

If I used the groundwater flow and the head pore water pressure provided as normal but there is a failure at the base due to tension as it doesn't have any embedded depth. 

I have provided like this way as shown

01. Draw the GWT and provided the head so that head is represented full water effect when applying groundwater flow analysis.

Thanks, 

Nitha.