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Sheet pile and deflected shapes

Short answer

A sheet pile is a slender interlocking section driven to form a continuous retaining wall. Cantilever piles deflect toward the excavation, rotating about a point and moving the toe backward. An anchored bulkhead with shallow embedment (free earth) curves without contraflexure; with deeper fixed-earth embedment, the toe is fixed, producing a point of contraflexure and reverse curvature.

What is a sheet pile? Draw the clear deflected shapes for the following: (i) cantilever sheet pile, (ii) anchored bulkhead driven to shallow depth and (iii) anchored bulkhead driven to deeper depth.

A sheet pile is a slender, interlocking section of steel, timber or concrete driven into the ground to form a continuous wall that retains soil or water (for example in excavations, cofferdams and waterfronts).

Deflected shapes (schematic, retained soil on the left)

 (i) Cantilever           (ii) Anchored, shallow     (iii) Anchored, deeper
                              (free earth support)       (fixed earth support)

       |                     T o------->|              T o------->|
       |                                |                         |
       |                                |                         |
 ------+\----- dredge line     ---------+\----- dredge line  -----+\----- dredge line
       | \                              | \                       | \
       |  \                             |  \                      |  )   point of
       |   o  pivot point               |   \  tip rotates        | (    contraflexure
       |  /   toe moves back            |                          \ \
       | /    (into the soil)           |                           \| tip fixed
                                                                      (vertical)
  • (i) Cantilever: the wall deflects toward the excavation and rotates about a point near the lower part of the embedded length, so the toe moves backward (into the retained soil).
  • (ii) Anchored bulkhead, shallow depth (free earth support): the pile is held at the anchor and its tip rotates freely; there is a single curvature and no fixity at the bottom.
  • (iii) Anchored bulkhead, deeper depth (fixed earth support): the toe is fixed in the soil, so the deflected curve has a point of contraflexure, with reverse curvature near the bottom.

✓ Answer checked by Claude Sonnet 5.5

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