Abstract:

The implementary Code for Design of Road Tunnel (JTG D70－2004) can’t satisfy the requirement of design and construction sometimes due to no study of soil surrounding rock classification and sub-classification methods. After ascertaining the building foundation of surrounding rock sub-classification standard in road tunnel, it had been constituted through lots of test, numerical calculation and theoretical analysis. The researches show that self-stability span is synthetical reflection of surrounding rock stability, so sub-classification standard can be constituted based on it. Surrounding rock self-stability span can divide into long-term stability span, basic stability span, temporary stability span and instability span. Ⅲ class of Rocky surrounding rock in criterion can divide into two sub-classification according as surrounding rock stability, three for Ⅳ class and two for Ⅴ class. Though soil surrounding rock include clayey surrounding rock, sandy surrounding rock and debris surrounding rock, their stability can be unified. The uniform standard of rocky and soil surrounding rock sub-classification built by self-stability span has rationality and inheritance.

Key words: road tunnel, surrounding rock sub-classification, self-stability span