Abstract:

The accurate surrounding rock classification and forecast are the important basis for properly selecting support parameters and deciding on the work  method in the process of road tunnel construction. In order to solve the problems of how to forecast the surrounding rock classification by the characteristics of Rayleigh wave velocity changes on the Raleigh wave frequency-disperse curve, the changes of surrounding rock were divided into three types, the same grade, the lower grade and the higher grade compared to the present surrounding rock condition. On the basis of the geological work principle, the Rayleigh wave velocity criterion for surrounding rock classification was given using the variety rate of the Rayleigh wave speed to depth as the surrounding rock classification. The regulations for using these criteria were also discussed. Then, the accuracy of the criterion was verified by the forecast results. An efficient in-situ test method for surrounding rock classification in tunnel construction was put forth.

Key words: surrounding rock classification; Rayleigh wave; velocity; criterion