Engineering and Construction

In the case of cantilevered sheet pile walls, the sheet piling is driven to an adequate depth to become fixed as a vertical cantilever in resisting the lateral active earth pressure. Cantilevered walls usually undergo large lateral deflections and are readily affected by scour and erosion in front to the wall. Because of these factors, penetration depths can be quite high, resulting in excess stresses and severe yield. According to the USS Steel Sheet Piling Design Manual (1984), cantilevered walls using steel sheet piling are restricted to a maximum height H of approximately 15 ft (4.6 m).

Design charts have been developed for the analysis of cantilevered sheet pile walls. For example, Fig. 11.16 is a design chart reproduced from the USS Steel Sheet Piling Design Manual (1984). The value of a is based on the location of the water level as indicated in Fig. 11.16. The chart is entered with the ratio of the passive earth pressure coefficient kp divided by the active earth pressure coefficient kA. By intersecting the depth ratio curves or moment ratio curves, the depth of the sheet pile wall (D) or maximum moment Mmax can be calculated. Note that the depth D from Fig. 11.16 corresponds to a factor of safety of 1.0. The USS Steel Sheet Piling Design Manual (1984) states that increasing the depth of embedment (D) by 20 to 40 percent will provide for a factor of safety of toe failure of approximately 1.5 to 2.0.