The rock mass of permanent shiplock high rock slope of the Three Gorges Project(TGP) has marked characteristics of unloading and relaxation. Kinds of methods such as geological investigation

sonic velocity test

monitor of deformation

in-situ test of elasticity modulus of rock mass

test of rock permeability

kinescope in hole

test of elasticity modulus of rock mass in hole

etc.

have been applied to studying the characteristics. The study shows that the rock mass of the slope can be divided into three zones

strong-unloading zone

middling-unloading zone and slight-unloading zone. The degeneration of properties of rock mass in strong-unloading zone and middling-unloading zone is notable，while degeneration of properties of slight-unloading rock mass is not obvious. The structure and properties of the rock in unloading zone do not alert obviously; but the unloading causes the growth of the joints’ length and width. The deformation of rock mass of the slope mainly depends on the deformation of joints and elastic deformation of rock block

which is affected by excavation. The reinforcement cables have obvious effect on confining deformation of joints.