The Ox Road (not Chain Bridge) construction is a construction of a new set of bridges over a campus road to alleviate congestion around campus.
Source:
http://building.gmu.edu/campus-drive-construction-update-january-2013/
University Mall is undergoing a complete overhaul and they are tearing out the old brick wall in the back of the shopping center first.
Source:
http://www.ghrrc.com/Univ%20Mall%2011_29_11-website.pdf
In reply to justanother, there is a plan to change the intersection of Braddock and Ox into an overpass as well, here is the design for that. (unrelated to GMU, designed by FCDOT and VDOT)
Source:
http://www.fairfaxcounty.gov/fcdot/pdf/braddock_123_pres1.pdf