Tieback Walls in Sand: Numerical Simulation and Design Implications

Abstract

A three-dimensional nonlinear finite-element analysis is used to study the influence of various design decisions for tieback walls. The numerical model simulates the soldier piles and the tendon bonded length of the anchors with beam elements, the unbonded tendon with a spring element, the wood lagging with shell elements, and the soil with solid three-dimensional (3D) nonlinear elements. The soil model used is a modified hyperbolic model with unloading hysteresis. The complete sequence of construction is simulated including the excavation and the placement and stressing of the anchors. The numerical model is calibrated against an instrumented case history. Then a parametric study is conducted. The results give information on the influence of the following factors on the wall behavior: Location of the tendon unbonded zone, magnitude of the anchor forces, embedment of the soldier piles, and stiffnesses of the wood lagging and the piles. The implications in design are discussed.