But because of hard to fix test ring in bedrock, so report of domestic deep worked-out area overlying rock subsidence observation by layers have not yet been heard so far.

• 研究采空区剩余沉降对上覆建(构)筑物造成的危害程度,分层沉降观测是比较直观的方法,但由于基岩内测试环固定困难,在大深度采空区上覆岩层中进行分层沉降观测国内未见报道。