How to stop water seaping inbetween concrete slabs
Yes, most likely that is water pressure causing it. Ideally, you'd install a drain tile system with sump pump to pump the water elsewhere, essentially redirecting the water. That is a very labor intensive and expensive task to complete, due to the labor involved. It does work very well, though. 

I've seen people get away with sealing the joint well with something like Sikaflex. The issue there is you're simply impeding the pressure being relieved. It will either find another spot to relieve pressure (and hopefully not inside your office), or will push it's way through whatever sealant you use.