A rock mass classification to estimate excavation rate, support and rock properties in a borehole survey

摘要

A method of evaluating engineering rock mass characteristics has been proposed for the purpose to help the adequate selection of the detailed investigation areas, which is an important decision making for the selection of the final disposal site of high level radioactive waste in Japan. The method requires classification of qu: uniaxial strength of rock core, RQD and Jc: joint condition. Relation between the 3 parameters and advance rate of excavation and support has been analyzed based on published records of tunnel excavation. Also Relation between the 3 parameter-rock mass description and rock mass properties of strength and Young's modulus has been analyzed based on published in situ rock shear tests and plate jack tests in Japan. Based on the findings, graphs of estimating the engineering rock mass characteristics of excavation rate, support, strength and Young's modulus have been made. The features of this method are that it uses the 3 dimensional information of qu, RQD and Jc without converting the information to one dimensional value as in RMR, and that the 3 parameters are able to be obtained in a borehole survey.