Analytical approach for the design of active grouted rockbolts in tunnel stability based on convergence-confinement method

Assuming that grouted rockbolts increase internal pressure within a broken rock mass, a new procedure for computation of ground response curves for a tunnel reinforced with active grouted rockbolts is presented, while the effect of distance of bolted section to tunnel face has been also considered. This analytical solution for a circular underground excavation under hydrostatic stress field, and with consideration of a non-linear strength criterion for rock mass and on the basis of two material behavior models has been developed. In this work, the equation of the ground response curve for a tunnel which has been reinforced with passive grouted rockbolts is also derived. The proposed model allows one to take, the effect of the distance of the bolted section to the tunnel face, the effect of increasing rockbolts spacing, the influence of increasing pretension load in calculating of the ground response curve, and the effect of increasing the cross-section area of rockbolts, into account. The results show that decreasing rockbolts spacing increase the support system stiffness rather than preloading of them.

[1]  Yujing Jiang,et al.  An analytical model to predict axial load in grouted rock bolt for soft rock tunnelling , 2004 .

[2]  Pierpaolo Oreste,et al.  Distinct analysis of fully grouted bolts around a circular tunnel considering the congruence of displacements between the bar and the rock , 2008 .

[3]  E. T. Brown,et al.  Ground Response Curves for Rock Tunnels , 1983 .

[4]  E. T. Brown,et al.  Underground excavations in rock , 1980 .

[5]  Buddhima Indraratna,et al.  Analytical model for the design of grouted rock bolts , 1990 .

[6]  Håkan Stille,et al.  Support of weak rock with grouted bolts and shotcrete , 1989 .

[7]  A. Fahimifar,et al.  A theoretical approach for analysis of the interaction between grouted rockbolts and rock masses , 2005 .

[8]  M. Panet.  Le calcul des tunnels par la méthode convergence-confinement , 1995 .

[9]  Daniele Peila,et al.  RADIAL PASSIVE ROCKBOLTING IN TUNNELLING DESIGN WITH A NEW CONVERGENCE-CONFINEMENT MODEL , 1996 .

[10]  Buddhima Indraratna,et al.  Design for grouted rock bolts based on the convergence control method , 1990 .

[11]  Hongwei Huang,et al.  Reinforcement mechanics of passive bolts in conventional tunnelling , 2007 .

[12]  E. Hoek,et al.  Applicability of the geological strength index (GSI) classification for very weak and sheared rock masses. The case of the Athens Schist Formation , 1998 .

[13]  Fu-Shu Jeng,et al.  The holding mechanism of under-reamed rockbolts in soft rock , 1999 .

[14]  Bengt Stillborg,et al.  Analytical models for rock bolts , 1999 .

[15]  V Labiouse,et al.  Ground response curves for rock excavations supported by ungrouted tensioned rockbolts , 1996 .

[16]  Ing.D. Peila,et al.  Axisymmetric analysis of ground reinforcing in tunnelling design , 1995 .

[17]  Ming Lu,et al.  Cavern roof stability—mechanism of arching and stabilization by rockbolting , 2002 .