SEDL / STP / STP670-EB / STP33741S

Interpretation of Load Tests on High-Capacity Driven Piles

Leonards, GA
Professor and graduate assistant, School of Civil Engineering, Purdue University, Lafayette, Ind.

Lovell, D
Professor and graduate assistant, School of Civil Engineering, Purdue University, Lafayette, Ind.

Pages: 28    Published: Jan 1979

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Abstract

Pipe piles and H-sections about 35 m (115 ft) long were driven through 24 m (80 ft) of alluvial materials to bearing in a stratum of glacial till about 15 m (50 ft) thick overlying bedrock. Load tests were conducted to establish the equipment and driving resistance needed to develop a capacity of 3560 kN (400 tons) solely in the underlying tills. Interpretation of these tests proved to be a challenge that led to the development of a new technique to analyze load transfer using only data obtained from conventional pile load tests. Among the conclusions reached were (1) ultimate shaft friction of steel piles driven into very stiff to hard tills did not exceed 120 kPa (1.25 tsf); (2) for piles as large as 460 mm (18 in.) in diameter, ultimate shaft friction is not necessarily mobilized before the pile capacity is reached; and (3) loading and unloading a pile can cause irreversible changes in the existing as well as on the ultimate shaft friction—methods of interpreting pile load tests to determine load transfer or residual stresses that rely on these changes being negligible, should be used with caution.