Slip zones around circular openings in a jointed Hoek-Brown medium

Abstract

Abstract The regions of joint influence around a circular opening located in a Mohr-Coulomb (MC) medium can be easily estimated by the procedure described in the published literature. Such computations, although based on simplifying assumptions, are thought to be sufficiently accurate for several important practical applications, particularly because the input parameters may have large associated uncertainties which may not justify a more elaborate and accurate computation. However, a jointed rockmass can be more appropriately described by the Hoek-Brown strength criterion (HBSC). This paper presents the theory and computation procedure to estimate the region of joint influence around circular openings located in a Hoek-Brown (HB) medium. In addition to the disturbance caused by the excavation in the existing joint system (inherent anisotropy), the theory presented herein accounts for the possibility of formation of new joints at a new orientation (induced anisotropy). An approximate procedure to compute support pressure, in order to prevent slip along discontinuities is presented. Several results are given to illustrate the special features of the HB criterion, in particular the ability to account for the brokenness of the medium.