Design of Tied‐Back Walls for Seismic Loading

Abstract

A finite element model is used to evaluate seismic behavior of static and seismic tiedback retaining wall designs. Two static designs are tested. The first design assumes active earth pressure resulting in a single‐anchor design. The second static design uses a rectangular apparent‐pressure diagram, resulting in a two‐anchor wall. These two designs are then modified using the Mononobe‐Okabe (M‐O) method to account for seismic loading. Results illustrate that static earth pressure design assumptions critically impact seismic response. The earth‐pressure magnitude and distribution assumed for static conditions are as important to seismic behavior as application of the M‐O seismic design. Not only does the two‐anchor static design suffer less displacement than the single‐anchor static design; it also exhibits less displacement than the single‐anchor seismic design. The two‐anchor seismic design suffers less displacement than the two‐anchor static design, only at accelerations greater than 0.2g. The effect of an increased depth of embedment beyond the M‐O calculated value provides no benefit in limiting displacements above the dredgeline. Use of a seismic preload results in significantly decreased displacements compared to the same design using a preload based on static conditions.