Abstract: Taking Xishimen Iron Mine as engineering background,methods such as geophysical prospecting,monitoring and numerical simulation were used to study the surface subsidence regularity of goaf underlying river.The technical measure,compensation method,was proposed to treat the riverbed with differential settlement.The main research conclusions are drawn as follows.The research region can be divided into subsidence area,danger area and low-resistance abnormal area by controlled source audio-frequency magneto-telluric,and low-resistance abnormal area generally represents the goaf or ore body.Horizontal extruding tectonic stress results in the elliptic subsidence basin formed in surface,and its existence increases the ground movement scope of basin.Horizontal extruding tectonic stress reduces the maximal mining subsidence,but makes the accumulative subsidence behave as gusty increase mode.In the permanent treatment measure of "compensation method",the main anti-seepage reinforcement structure consists of rigid waterproofing layer,flexible waterproof layer and anti-scour layer,which can sink with riverbed subsidence and fully fill the surface differential settlement caused by ore body mining.

Key words: River,Goaf, Surface subsidence, Treatment measure