WES Theoretical Manual, Part VI: Slip Between Sheeting and Fill

This part examines slip between the sheeting and the fill, a failure Terzaghi raised in 1945. The fill would slide down relative to the sheeting if the friction between them was not enough to carry the loads.

The manual reviews the design rule in common use and finds it inadequate, because it ignores a basic mechanism: as the cell deflects, the direction of the force from the fill on the wall changes. It also points out that slip between fill and wall has not been established for a full-size cell, and that the only model studies in which it occurred were the TVA studies, whose validity has been questioned.

The part closes with a short summary of what is known and what is not, and recommends that a better analysis account for rotation of the piling. For designers, the message is that this check is less settled than the others, so judgment and conservatism are both needed.