Stresses induced by post-tensioned anchor in jointed rock mass

Abstract

A new analytical study on stresses around a post-tensioned anchor in rocks with two perpendicular joint sets is presented. The assumptions of orthotropic elastic rock with plane strain conditions are made in derivation of the formulations. A tri-linear bond-slip constitutive law is used for modeling the tendon-grout interface behavior and debonding of this interface. The bearing plate width is also considered in the analysis. The obtained solutions are in the integral forms and numerical techniques that have been used for evaluation. In the illustrative example given, the major principal stress is compressive in the anchor free zone and compressive stress concentrations of 815 kPa and 727 kPa (for the anchor load of 300 kN) are observed under the bearing plate and the bond length proximal end, respectively. However, large values of tensile stresses with the maximum of −434 kPa are formed at the bond length distal end. The results obtained using the proposed solution are compared very those of numerical method (FEM).

Keywords

post-tensioned anchor / jointed rock / stress distribution / analytical solution / tri-linear bond-slip model / bond length / bearing plate

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