Based on the role of prestressed anchor and the mechanical transmission mechanism of anchorage interface

an anchorage interface stress model is developed. Then an analytical method is proposed to calculate the anchorage stress by considering the shear slip of anchorage interface. On the basis of the prestress loss mechanism

various factors causing prestress loss are analyzed

and then a method for calculating prestress loss is developed under the influence of various factors. According to fundamental theory of the solution of stress distribution

a method is presented to estimate the initial tensile tonnage of the anchor cable. During the excavation of underground caverns

the stress increment is considered as safety margin of initial tension of the anchor cable

and the prestress loss can also be taken into account. From the above

a finite element calculation program is compiled

and a case study of an underground caverns shows that the proposed method is reasonable.