Decision Plots for preliminary design of single-shield TBMs: Fid-Bau Portal

Decision Plots for preliminary design of single-shield TBMs

Repetto, L. / Fidelibus, C.

AbstractIn this note a procedure for a back-of-the-envelope estimation of the correct length of a single-shielded TBM is reported in the context of a TBM preliminary design phase. It is based on four Decision Plots (DPs) and some associated equations, whose input data are the isotropic in-situ stress, the rock mechanical parameters, the maximum tolerated over-excavation and the shield skin friction coefficient. The essential output is the friction force the machine must overcome (the required thrust force), that can be compared with the available thrust force. The derivation of the DPs is illustrated and their practical use shown. Although the procedure involves some simplifying approximations, its performance is confirmed through two application examples and a comparison with the results obtained using design monograms of other authors.

Highlights•A procedure for the assessment of the required thrust force of a TBM is proposed.•The procedure can be utilized at the early stage of design.•The input parameters are the in-situ stress and the Geological Strength Index.•Decision Plots (DPs) and associated equations of the procedure may be changed by user upon personal judgment and experience.•The constitutive law for the rock mass is elasto-plastic with modified Hoek-Brown failure criterion.