Posting this re during yesterday's televised practice...Hobbs and Machete were discussing that a
whole section of stands and seating had been demoed and removed because they were sinking! Reason was stated that "1/2 of world supply of styrofoam was used in building this Shanghai circuit..." on top of swampland. 
AUTOSPORT PRO Shanghai F1 track built on polystyrene
FIA-approved circuit designer Hermann Tilke has told Swiss newspaper Blick that the Shanghai International Circuit in China will be the first track in the world to be built on a polystyrene foundation, because the site is predominantly swampland.
So much polystyrene is involved that there is currently a shortage of the material in Asia.
"First we had to put 40-80m long posts into the marsh," Tilke explained. "Now we are putting polystyrene panels on the posts, up to 14m high in some places. Then we will add 2m of earth, and then the tarmac for the track surface." 
Link:
http://www.autosport.com/news/report.php/id/34061