Prediction of service life of pre-stressed anchorage bolt (cable) due to corrosion expansion

After it is corroded, the volume of anchorage bolt (cable) expands and corrosion expansion force is generated. With the increase of corrosion expansion force, peripheral grout appears to crack, which accelerates its corrosion, so the corrosion amount at this moment should be taken as the criterion to predict its service life. For analyzing the force of peripheral grout, the elastic theory of hole model under plane strain is adopted to calculate the limit corrosion expansion force at the time of grout cracking, and the deformation compatibility condition of contact surface between anchorage bolt (cable) and peripheral grout is used to calculate its corrosion amount corresponding to the limit corrosion expansion force. Meanwhile, the proportional parameter λ is adopted to consider geotechnical constraints on anchoring body, and two methods (with or without considering effect of internal cracks in grout) are used to calculate deformation of grout generated by corrosion expansion force. Then simple formulas for calculating the limit corrosion expansion force and the amount of its corresponding corrosion are attained after curve fitting in a certain range of parameters, and using two kinds of formulas for calculating corrosion rate of anchorage bolt (cable) under different applicable conditions, the service life of anchorage bolt (cable) can be predicted and analyzed. By comparing with examples, the feasibility of the proposed method is verified, and parameters affecting the service life of anchorage bolt (cable) are analyzed. It shows that: (1) The calculated amount of anchorage corrosion without considering effect of internal cracks in grout is more conservative. (2) The constraint of peripheral geotechnical body on grout has positive impact on the service life of anchorage bolt (cable). (3) The volume expansion rate n of rust has the minimum impact on the service life of anchorage bolt (cable), and the greater the Poisson’s ratio of grout (μ_c) and the thickness of protective layer (c), the longer the service life of anchorage bolt (cable).