Geotechnical Data and Pile Design - Offshore Structures: Design, Construction and Maintenance - page 237

High-quality in-situ, laboratory, and model-prototype pile-load tests are essen-
tial in such characterizations. In developing soil-pile interaction characteriza-
tions, it is important that pile installation and pile-loading conditions be
integrated into the testing programs.
According to McClelland et al. (1971) , in-situ tests, such as vane shear, cone
penetrometer, pressure meter and other tests, can provide important insights into
in-place soil behavior and stress-strain properties.
Both low- and high-amplitude stress-strain properties can be developed.
Long-term static and creep loadings or short-term dynamic, impulsive and
cyclic loadings sometimes can be simulated with in-situ testing equipment.
Laboratory tests on representative soil samples permit a wide variety of stress-
strain conditions to be simulated and evaluated. Soil samples can be modified to
simulate pile-installation effects, such as remolding and reconsolidating, to esti-
mate in-situ stresses. The samples can be subjected to different boundary condi-
tions, such as tri-axial, simple shear and interface shear, and to different levels of
sustained and cyclic shear time histories to simulate in-place loading conditions.
Another important source of data to develop soil characterizations for cyclic
loading analyses are tests on model and prototype piles. Based on Bogard et al.
(1985) and Karlsrud and Haugen (1985) , model piles can be highly instrumented,
and repeated tests can be performed in soils and for a variety of loadings.
Geometric scale, time scale and other modeling effects should be carefully
considered in applying results from model tests to prototype behavior ana-
lyses. As discussed by Pelletier and Doyle (1982) and Arup et al. (1986) ,
the data from load tests on prototype piles are useful for calibrating analytical
models.
Such tests, even if not highly instrumented, can provide data to guide devel-
opment of analytical models. These tests can also provide data to verify results
of soil characterizations and analytical models.
Prototype pile-load testing, coupled with in-situ and laboratory soil testing
and realistic analytical models, can provide an essential framework for making
realistic evaluations of the responses of piles to cyclic axial loadings.
The foundation should be designed to carry static, cyclic and transient loads
without excessive deformations or vibrations in the platform. Special attention
should be given to the effects of cyclic and transient loading on the strength of
the supporting soils as well as on the structural response of piles.
It is very important to consider the possibility of movement of the sea floor
against the foundation members, and the forces caused by such movements, if
anticipated, should be considered in the design.
4.6 PILE FOUNDATIONS
Offshore structure platforms commonly use open driven piles. These piles are
usually driven into the seabed with impact hammers, which use steam, diesel
fuel or hydraulic power as the source of energy. Therefore, the pile wall