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Figure 2-10: Scour effect on deep foundations (from O’Neill and Reese 1999). Scour ZoneSupport Zone2.1.2 Batter Piles for Lateral Load Applications Most the applications discussed herein are for vertical, or plumb, deep foundation elements. However, batter piles can also be used to resist lateral loads. Batter piles are installed at an angle (batter) that typically varies from 1H:12V to 1H:3V. Batter piles resist lateral loads primarily through the horizontal component of the axial load in the pile as determined
by the angle of the batter, whereas vertical piles resist lateral loads primarily through structural shear and bending resistance. Bending of batter piles can also contribute to resistance of applied lateral loads, particularly for cases with small batter angle. The axial resistance in batter piles can be either in compression or tension. Typical batter pile applications include two or more rows of driven piles for bridge foundations with batter piles in one or more rows of the group (see Figure 2-9). Micropiles can also be installed at a batter
for similar applications, as well as for slope stabilization in which one or more rows of micropiles maybe installed at different batter angles as shown in Figure 2-11. Micropiles in this type of configuration, often referred to as “A-frame,” resist the sliding forces of the slope
through axial compression, tension, and shear through the micropiles.
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Figure 2-11: Illustration of battered micropiles for slope stabilization (from Sabatini et al. 2005). Plumb, or vertical, piles are commonly used to resist vertical and lateral loads because they are easier and less
costly to construct however, batter piles typically provide the necessary resistance with less displacement and often with a smaller group of piles. In recent years, the use of batter piles has been discouraged in seismic areas or in projects where a ductile foundation response is necessary. It has been observed that batter piles exhibit relatively poor performance during earthquakes due to the lack of ductility in compression and tend to fail abruptly in shear (Ferritto et al. 1999).
As a stiffer foundation, batter piles can also lead to greater lateral load demand during a seismic event. When batter piles are used in seismically active areas, the increased stiffness of the foundation system must be accounted for in the design. Batter piles are also typically discouraged in areas where overlying soil is anticipated to settle significantly relative to the foundation.
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