Can Slide be used to calculate FS against uplift for a dam?

Not directly. Slide is a program to determine the FS against sliding (shear failure) not uplift.

However, you can use Slide to determine the pore pressure distribution along the base of the dam. You can also use Slide to determine the distribution of weight due to the dam. It is then up to you to compute the FS against uplift.

 

There is also a FS against piping/boiling that you can compute with Slide using the total hydraulic gradient from a groundwater analysis:

If you want to calculate the factor of safety against boiling/piping, then the factor of safety is equal to the ratio of the critical hydraulic gradient (defined as the buoyant unit weight divided by the unit weight of the water) to the exit hydraulic gradient at the toe (taken from the Slide seepage analysis). See the image below.  This approach is similar to the one discussed in "Soil mechanics in engineering practice" by Karl Terzaghi, Ralph Brazelton Peck, Gholamreza Mesri.

 

FS_piping.jpg