Abstract：The reserved rock mass between two lines of TGP permanent ship lock is used as their division pier，which is obviously superior in economy to the scheme of removing the rock mass and constructing a concrete division pier at its location. The rock mechanics problems encountered in the course of excavating the lock chambers，such as cracking on the surface of reserved rock mass，the potential movable rock blocks on the top of vertical excavated wall，and the large faults，were all solved through engineering treatment measures developed by field dynamic design，and the reserved rock mass is strengthened.
