The interaction between fully bonded rock bolts and the ground is analyzed through the homogenized material approach. The action of each radial reinforcement is smeared throughout the bolted rock annulus around the tunnel which is then treated as a fibre-reinforced material with perfect bonding between fibres and rock matrix. In heavy squeezing rock masses the development of zones with rock and bolts in plastic conditions around the excavation is unavoidable. The analytical solution provided for the stress and strain in each zone around the excavation, characterized by elastic or plastic conditions of ground and/or rock-bolts can be utilized to calculate the convergence confinement curve of the bolted tunnel.

The influence of partial debonding can also be taken into account in a simplified way. An application of the method is shown making reference to the geotechnical conditions of a well-known case history. The proposed design method has the advantage of optimizing the main design parameters of the bolting system (bolt density and length, steel and grout quality) on the basis of detailed parametric studies. Moreover the influence of the construction process can be evaluated.

    The interaction …

AUTORI: Graziani A. RIG ANNO: 1999 NUMERO: 1 Numero di pagina: 64



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