Friction and end bearing tests on bedrock for high capacity socket design: Discussion

tinuous and indefinite increase of the displacements or the lining pressure. Some more detailed calculations and theoretical solutions show that the behavior is rather asymptotical, if the rock is stressed below its long term strength (Gill et al. 1970). For this reason, for rock, Zener's creep model is more appropriate than Maxwell's which contains a dash pot in polation should only serve as a means for finding out how the lining pressure will change with time before the rock around the tunnel attains the ultimate state, governed by the long-term strength. This approach may be quite appropriate in the situation described by the authors in which failure started even before the lining was installed. series. (b ) If the rock mass around the tunnel is GILL, D. E., COATES, D. F., and GELDART, L. P. 1970. Un modele mathhatique d'un souterrain cylindrique cirWessed the strength, culaire droit rev2tu et p e r ~ 6 dans un milieu visco6laswill occur locally after some creep. This obtique linCaire. Proc. 2nd Int. Congr. on Rock Mech., viously invalidates any design method based ~ e o g r a d , ~ugoslavia , vol. 2, pp. 625-632. only on extrapolation of creep displacements. HOYAUX, B. and LADANYI, B. 1970. Rock failure around a circular opening in a gravity field with tectonic forces. It is the opinion of the discusser that, when the ,,,: Rock mech. theory and practice, ed. W. H. Somerrock is highly stressed, in addition to the extraton, Am. Inst. Min. Metall. Pet. Eng., Inc., New York, polation method suggested by the authors, one N.Y, pp. 281-292. should also ,-heck what the lining pressure LADANYI, B. 1974. Use of the long term strength concept in the determination of ground pressure on tunnel linbecome if the long term strength the ings. Proc. 3rd Int. Congr. on Rock Mechanics, Denver, rock is attained and rock failure Occurs CO.. Nat. Acad. Sci.. Washington. D.C., vol. 2B, pp. . . (Ladanyi 1974). In other words, creep extra115@-1156.