M.D.
Pi,
I don't know of anyone in the Dallas area. I used to work for a Geotechnical Engineering firm in San Antonio. I'm not sure if you are putting a claim in on your insurance, however, your insurance company would know of some good places. Now if you are putting a claim on your insurance company, make sure the insurance company doesn't try to be the engineer. I noticed a lot more insurance companies try to be the agent and engineer. They would rather pay the homeowner the money without getting anything tested.
Good Luck, sorry I'm not of more help,