mk wrote:
Generally if you have a PhD in one field, other PhD programs in the US will not admit you unless you have a very very good reason to want both. Getting a PhD in geotech will likely decrease or eliminate your chances of getting an applied math PhD later. If you think you can get the math education you want through the geotech program at TN, that's one thing, but definitely do not plan on going there and then applying for another PhD later.
Thank you very much for this notice. It is really very helpful for me now.