トンネル支保特性曲線の定量的評価に関する理論的考察

抄録

Active mobilization of bearing capacity of surrounding rock mass characterizes the NATM concept of supporting. However, no quantitative expression of this bearing capacity has been recognized yet. In the present paper, “a support load of surrounding rock mass”, “a support load of lining” and “the total support load of a tunnel” for a two-dimensional elastic circular tunnel were quantitatively evaluated by using a common index, support-stiffness, which is defined as the relative stiffness of each support to the original stiffness of the rock removed from the opening.
By advancing the above analysis, the procedure to construct theoretically the bearing characteristic curve of elastic rock mass in tunnelling was discussed rationally. By applying the principles of this procedure to general rock mass with non-linear stress-strain property, various bearing characteristic curves were obtained from elastic type to elasto-plastic type, Fenner-Pacher type, or catastrophic type, depending on the initial earth pressure level related to the strength of the rock mass.