A method for calculating the anchor force of 3-D anchored slopes and its application

This paper proposes a method for determining the anchor force of a 3-D anchored slope based on the limit equilibrium analysis and the modification of the normal stress over the slip surface method. For a slip surface, the required anchor force can be calculated with the given factor of safety. Four limit equilibrium equations containing anchor forces are therefore established for 3-D slope. The nonlinear relationship between the factor of safety and the anchor force is turned into a linear relationship between the horizontal seismic coefficient and the anchor force by the force and moment equilibrium conditions. With a given factor of safety, the initial normal stress of the 3-D anchored slope is supposed and modified by a modifying function. An iterative procedure is proposed to determine the anchor force with a prescribed value of K_c and to ensure that the normal stresses are positive on the whole slip surface. The method applies to any slip surface, and its practical engineering application confirms its efficacy.