Could have been a old peer and beam foundation. I worked under some of them in Arkansas that were built so close to the ground you would have to dig a tunnel to get where you were going.
I can tell you, it is no fun!
I highly doubt it was pier and beam in Flowermound, Tx. but the soil is that crappy expansive clay muck that causes problems with home foundations will too little or too much moisture content. This can also create plumbing leaks.