Analysis Model for Relaxation Effect of Pulling Force of Prestressed Anchor Cables Used in Reinforcing Rock Mass

Based on the interaction mechanism between an anchor cable and rock mass, a series of models that one Hooke body of describing the anchor cable connects in series with one Kelvin-Hooke body of describing the rock mass was proposed to solve the relaxation problem of pulling force of prestressed anchor cables. In light of the model reflecting coupling relation between the anchor cable and rock mass, a formula corresponding to the relaxation effect of the pulling force was derived. It reveals quantitatively the influences of the spacing between the adjacent two anchor holes, elastic modulus of the anchor cable, rheological parameters of rock mass, and diameter of the anchor cable, and initial pulling force on the long-term pulling force. Analysis results of one laboratory and in-situ test example show that the predicted pulling force using the proposed model is identical with the observed one. The maximum error of final pulling force of the prestressed cables between the calculation and observation value is 7%. The proposed model is reasonable. Spacing between the adjacent two anchor holes, diameter of the anchor cable, and rheological parameters of the rock mass have obviously nonlinear influences on the relaxation effect of the cable.