When the tunnel is excavated

the surrounding rock will be damaged and the damage zone will be formed around the profile where the acoustic velocity will weaken. Direct at the damage zone formed after diversion tunnel #3 of Jinping hydropower station

the distribution characteristic is discussed and the stress paths of characteristic points are monitored by simulation method. The stress states of characteristic points and locations of acoustic velocity weakened are confirmed. According to above work

the drill holes of detecting acoustic wave are arranged. The depth of damage zone is determined by single hole detection method. In order to realize the simulation of damage zone by the particle flow code(PFC)

the microscopic parameters are confirmed by triaxial compression test. The damage zone distribution is described by PFC. The local damage and damage extent are also analyzed by PFC. The simulated results are well consistent with the detections. The exact description of damage zone characteristics can be achieved by PFC. The research results can direct the detection of damage zone and support optimal design.