I seriously doubt there's anything left of them. It depends on how well preserved they were. If it's done badly, they're nothing but dust by now. Besides, it's not their bones that people want, it's the artifacts that get buried that will enlighten us more about the 3 Kingdoms era.
How do they know Xu Chu's and Zhang Liao's were nearby?
Only hints and guesses right now based on some text they found.