Civil Engineering Reference
In-Depth Information
8.3.3 Contiguous and secant bored pile walls
Contiguous bored pile walls
This type of wall is constructed from a single or double row of piles placed beside each other. Alternate
piles are cast first and the intermediate piles are then installed. The construction technique allows gaps
to be left between piles which can permit an inflow of water in granular conditions. The secant bored pile
wall offers a watertight alternative.
Secant bored pile walls
The construction technique is similar to that of the contiguous bored pile wall, except that the alternate
piles are drilled at a closer spacing. Then, while the concrete is still green, the intermediate holes are
drilled along a slightly offset line so that the holes cut into the first piles. These holes are then concreted
to create a watertight continuous wall.
8.4 Failure modes of retaining structures
Retaining structures are designed such that when constructed they will remain stable and support the
ground that they are retaining. To enable the design to proceed, an understanding of the potential failure
modes of the structure must be known. Common modes of failure, and how they are assessed using
Eurocode 7, have been illustrated in Fig.
5.8.
Additional examples of how different retaining structures
might fail when considering: (i) their overall stability, (ii) failure of their foundation and (iii) their failure by
Fig. 8.5
Examples of limit modes for overall stability of retaining structure (based on Fig
9.1,
EN 1997-1:2004).
Fig. 8.6
Examples of limit modes for foundation failures of gravity walls (based on Fig
9.2,
EN 1997-1:2004).
