4.3
Tieback Walls
4.3.1 Introduction to Tieback Walls
Abutments for the proposed bridge planned at the gorge site shown in Figure 4.2.11 are a good place to consider use of tieback walls and rock bolts with shotcrete facing. In fact, any retaining structure over 15 feet in height is a candidate for tiebacks. A retaining wall that uses tiebacks may be called an anchored wall, although use of the term “anchor” has a nautical flavor that seems to be fading in favor of tiebacks when construction moves inland from the ocean fronts to Midwestern United States highways. Personally I use the terms “tieback ” and “tieback anchor ” interchangeably as you will see below.
Why do we use tieback anchors? The primary purpose of tiebacks is to provide additional lateral support to a retaining structure because it is too tall to be cantilevered. Retaining walls with tiebacks are, as you might expect, highly statically indeterminate structures. We have to make many assumptions about the nature of the retained soil and the wall structure to design tieback walls.
I like to think of this wall design process as one of self-fulfilling predictions, or as the old saying goes, “It is a self-fulfilling prophecy.” What do I mean? The idea is that you pick the magnitude and location of a retaining wall's tieback loading, and the tieback loading develops where you selected if the relative stiffnesses of the component wall parts are designed properly. Take a look at Figure 4.3.1; in this figure I propose that ...
