Urgent: Regarding Seepage analysis

Hi all,

I performed flow only analysis in Plaxis 2D to get the water head loss due to MH excavation (axisymmetry model) and looked the hydraulic gradient it showed huge value (18m excavation and head loss is 1.5m). Please tell what is the reason and is any way to calculate the FOS for seepage analysis in plaxis 2D?

As i want the solution urgent, please help me ASAP.

Thanks.