Engineering and Construction

The use of steep or vertical slopes for a deep excavation is often necessitated by land area availability or economics.

Such slopes are commonly supported by a cantilever wall (only for shallow excavations), a braced wall, or a
tieback wall (fig 14-10).  In some cases, it may be economical to mix systems,  such as a free slope and a
tieback wall or a tieback wall and a braced wall.  Table 14-1 summarizes the wall types with their typical properties and advantages and disadvantages.  Table 14-2 lists factors for selecting wall support system sfor a deep excavation (>20 feet).  Table 14-3 gives design parameters, such as factors of safety, heave problems, and supplemental references.

Figure 14-10.  Types of support systems for excavation.

Table 14-1.  Types of Walls

Table 14-2.  Factors Involved in Choice of a Support System for a Deep Excavation