Laboratory tests to study the influence of rock stress confinement on the performances of TBM discs in tunnels

Abstract

To clarify some aspects of rock destruction with a disc acting on a high confined tunnel face, a series of tests were carried out to examine fracture mechanisms under an indenter that simulates the tunnel boring machine (TBM) tool action, in the presence of an adjacent groove, when a state of stress (lateral confinement) is imposed on a rock sample. These tests proved the importance of carefully establishing the optimal distance of grooves produced by discs acting on a confined surface, and the value (as a mere order of magnitude) of the increase of the thrust to produce the initiation of chip formation, as long as the confinement pressure becomes greater.

Keywords

tunnels / boring machines / rock mechanics / stress analysis

References

[1] R. Cordel, G. Comes, P. Duffaut, A. Valantin, M. Coder, and R. Perami, La géotechnique et le creusement mécanisé des tunnels, Institut Technique Du Batiment et des Travaux Publics, 1974.

[2] P.J. Tarkoy and M. Marconi, Difficult rock comminution and associated geological conditions, [in] Proceeding of the 6th Congress on Tunnelling, London, 1991, p.195.

[3] K. Gehring, Design criteria for TBM’s with respect to real rock response, [in] Proceeding of Tunnel Boring Machines: Trends in Design and Construction of Mechanised Tunnelling, Linz, 1995, p.43.

[4] S. Klein, M. Schmoll, and T. Avrey, TBM performance at four hard rock tunnels in California, [in] Proceedings of the Rapid Excavation Tunnel Conference, S. Francisco, 1995, p.61.

[5] N. Innaurato and P.P. Oreste, L’interazione roccia-utensile nelle macchine di scavo per roccia, [in] Atti dell’VIII Ciclo di Conferenze di Meccanica ed Ingegneria delle Rocce, Torino, 2000, p.111.

[6] N. Innaurato and P. Oreste, Theoretical approach for assessment of the mechanics of rock failure in the TBMs tools-rock interaction, [in] Proceedings of the AITES-ITA World Tunnel Congress, Milan, 2001, p.227.

[7] Barton N. TBM Tunnelling in Jointed and Faulted Rock, 2000 Rotterdam, Balkema, 177.

[8] Movinkel T., Johannesen O. Geological parameters for hard rock tunnel boring. Tunnels Tunnelling Int., 1986, 18(4): 45.

[9] Hartman H.L. Basic studies of percussion drilling. Min. Eng., 1959, 11, 68.

[10] W.C. Maurer, The state of rock mechanics knowledge in drilling, [in]_Proceedings of the 8th Symposium on Rock Mechanics, University of Minnesota, 1966, p.355.

[11] Nishimatsu Y. The mechanics of rock cutting. Int. J. Rock Mech. Min. Sci. Geomech. Abstr., 1972, 9, 261.

[12] Fourmaintraux, Machines foreuses pour tunnels et galeries, Techniques et bases théoriques de l’abattage mécanique des roches, Rapport de recherche N.20 L.C.P.C., 1972.

[13] Gaye F. Efficient excavation with particular reference to cutting head design of hard rock tunnelling machines. Tunnels Tunnelling, 1972, 4, 39.

[14] Itasca Consulting Group.. FLAC3D User’s Manual, 1996 Minnesota, ICG