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Support of weak rock with grouted bolts and shotcrete

1989; Elsevier BV; Volume: 26; Issue: 1 Linguagem: Inglês

10.1016/0148-9062(89)90530-5

1879-2073

Håkan Stille, Mats Holmberg, G Nord,

Geomechanics and Mining Engineering

This paper presents a closed form elastoplastic analytic solution of grouted bolts considering four different approaches to bolt performance. The equations consider bolt loads and displacements round a circular opening subjected to hydrostatic pressure. The solutions allow for the interaction of bolts and a shortcrete lining. The analytic results are compared with bolt load data and readings obtained from instrumented bolts and extensometers in the Kielder Experimental tunnel excavated in mudstone. Two different support systems are included in the study, one with grouted bolts and one with grouted bolts together with shotcrete. The bolt load distribution obtained from the analytic solutions show good consistency with the measured results for two of the four different theoretical solutions. The analytic solutions that correspond to the measured values take into account the existing low bond strength between rock mass and bolt and the effects of local deformations in the rock mass under the end plate. It is shown, that a good contact between the rock surface and the end plate have effects on the magnitude of the bolt load and that it is important to use grout of high quality to secure the transfer of load from rock mass to the bolt. The displacement values, obtained from extensometers installed together with the two different support systems, coincide with the deformations obtained from the corresponding analytic solution.