Side Resistance In Piles and Drilled Shafts

TLDR

More than 20 years have passed since a Terzaghi Lecture focused on deep foundations, yet considerable research and experience have been gained in the intervening period. The paper aims to update earlier references by summarizing recent research on side resistance for driven piles in saturated clay, driven piles in siliceous sand under compression and uplift, and drilled shafts in clay and soft rock. It reviews recent studies on side resistance, focusing on the four mentioned contexts and highlighting key experimental and analytical findings. The review finds that while simple design relations exist for driven piles in saturated clay, significant gaps remain; compression and uplift loading yield differing side‑shear resistance; construction details such as stress relief, moisture migration, borehole roughness, and smear markedly affect performance; overall, deep foundation design remains complex and demands experienced engineers.

Abstract

More than 20 years have passed since a Terzaghi Lecture focused on the topic of deep foundations. However, considerable research has been performed, and experience gained, in this subject area in the intervening period. The objective of this paper is to update the earlier references on deep foundations by summarizing results of important recent research on a few aspects of the topic of side resistance, most notably (1) driven piles in saturated clay, (2) driven piles in siliceous sand loaded in compression and uplift, (3) drilled shafts in clay, and (4) drilled shafts in soft rock. It is concluded that, while simple design relations are available for topic (1), much is still to be learned. Under topic (2), the case is made that loading the pile in compression and uplift produces different values of unit side-shearing resistance. Regarding topics (3) and (4), the effects of details related to construction—such as stress relief, moisture migration from the concrete to the geomaterial, borehole roughness, and borehole smear—are shown to be significant. The final point made is that the design of deep foundations is a complex matter that should be addressed in a design context by engineers who are experienced in the observation of pile behavior, theoretical modeling, and the appropriate use of design methods.