Stability of Nail Reinforced Boreholes
Rock nailing of the borehole is considered as a means to reinforce the rock and increase its borehole failure strength. The technique is modeled using Cox’s original shear-lag method. In the continuum sense, nail reinforcement is viewed as a body force that acts as a confinement. Borehole stability is analyzed using an analytical solution that couples the effects of the nails and the rock. Results for a reinforced with a given nail density and an un-reinforced borehole are presented. They show that the nail length and the nail-rock contact parameter play an important role in the stability. Rock dilation is also important since the action of the nails is mobilized from the difference in displacement between the rock and the nail. The results show the potential for a significant increase in borehole strength.
KeywordsRock nailing Rock reinforcement Borehole stability Free surface Contact force
The author wishes to thank Statoil for supporting this research and in particular JH Jøranson and JS Andrews for many discussions and their continuing support.
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