OVERVIEW

In order to understand the design of shoring systems, it is necessary to have a clear understanding of the types of failures which can occur to a shoring wall. These failures include

• Structural failure of some component of the shoring

• Geotechnical failure of some soil component in contact with the shoring

• Facial instability

• Basal instability

• Global instability

10.1 STRUCTURAL FAILURE

Structural failure of a shoring system occurs when some portion of the built system is not sufficiently strong to withstand the imposed loads. The overload could be the result of an inaccurate estimate of the imposed load, or may be caused by a geotechnical failure which then overloads a structural portion of the wall.

A failure in cantilever (see Figure 10.1) will occur when the cantilever portion of the structure (above the tieback, strut or raker level), is not sufficient to withstand the imposed loads and fails either in bending or in shear. This type of failure could also occur prior to the installation of the first row of tiebacks if the cantilever capacity of the piling is exceeded.

Figure 10.1: Structural failure-pile cantilever.

Failure in midspan of the wall piling between tieback or strut levels will occur if bending capacity is exceeded (see Figure 10.2).

Figure 10.2: Structural failure-pile midspan.

A structural failure could also occur if the connection between the wall and the tieback fails. A similar failure would occur if a strut or raker failed in buckling, or...