Abstract:Karst is fully developed in the surrounding rock of west anchor tunnel of Balinghe Bridge. The rock classification is considered as grades II to IV during the survey. In accordance with the actual karst excavation,advanced and initial supporting parameters should be adjusted for construction safety of the anchor tunnel. On the basis of karst geological forecast and general underground engineering rock mass classification,the physical and mathematical models of karst rock classification for the anchor tunnel are established,aiming at amending rock mass classification for different kinds of karst rocks. According to the tests of rock velocity,rock strength,as well as the extent of karst correction factor and other parameters,the karst rock classification for this anchor tunnel is determined as grade V. In fact,throughout the construction process,these measures are adopted as strong support of the anchor tunnel,such as advanced small pipe,advanced anchoring,steel frame,steel wire,shotcrete,etc.. And the bench cut method is also taken for the anchor tunnel excavation. In addition,the fractured rock and the surrounding cave are reinforced by grouting after the excavation of anchor tunnel. In other words,the parameters for initial support of the anchor-tunnel are taken by considering the rock mass as grade V. In practice,it indicates that the karst rock classification for this tunnel is reasonable,which can be taken as a reference for other similar projects.