Engineering and Construction

Figure 11.19 shows a picture of a temporary retaining wall that consists of steel I-beams, wood lagging, and tieback anchors. The temporary retaining wall is being used to support the excavation during the construction of the foundation. This type of temporary retaining wall consists of steel I-beams that are either driven into place or installed in pre-drilled holes with the bottom portion cemented into place. During the excavation of the interior area, wood lagging is installed between the steel I-beams and the earth pressure exerted on the wood lagging is transferred to the steel I-beam flanges. In order to reduce bending moments in the steel I-beams and to reduce lateral deflections, tieback anchors are often installed as the excavation proceeds.

In some cases, the steel I-beams will be braced with struts and the earth pressure distributions would be similar to those as shown in Fig. 11.18. For cantilevered steel I-beam and wood lagging retaining walls, there will be sufficient movement of the top of the wall to develop the active earth pressure (i.e., Eq. 11.1).