Offshore Foundation
Design
In the early days of the
industry it was important to develop reliable foundation designs for
offshore structures. McClelland Engineers, Inc. pioneered the
application of soil mechanics and foundation engineering (now called
geotechnical engineering) for the foundation design for both fixed and
mobile offshore platforms.
First it was necessary to
determine the composition of the seafloor. The first marine soil
mechanics boring was performed in August 1947 for the California Co. in
22 feet of water at a proposed platform site offshore Louisiana. It was
drilled by a conventional land rig placed on a small platform designed
and fabricated by McClelland Engineers. In the next six years about
twenty similar borings were done along the Texas/Louisiana coastline. In
1953, Robert Perkins developed the technique of drilling from an
anchored barge with a land rig cantilevered over the side.
In 1962, wireline
sampling in uncased boreholes was introduced and became a cost effective
procedure for conducting geotechnical investigations in deep water. In
1966, the remote vane was developed to make in situ
measurements of clay shear strength from floating vessels.
In addition to
determining the consistency of foundation materials, the technical
contributions to the design of offshore foundations by McClelland
Engineers were equally pioneering. In 1953, Bramlette McClelland and
John Focht made landmark analyses of lateral load tests on offshore
piles resulting in an ASME paper titled, "Soil Mechanics Applied to
Mobile Drilling Structures". In 1956, they introduced the concept of
limiting skin friction of stiff clays for driven piles, and they
proposed the technique, now known as the "p-y concept", for the analysis
of laterally loaded piles. API RP2A reflects their research on the
tensile capacity of driven and jetted piles in sand. During the 60s,
they developed comprehensive criteria for predicting capacity of driven
and grouted single piles or circular pile groups in sands and soft
marine clays. This program was paralleled by research on clay shear
strength as influenced by different sampling and testing methods.
Recognizing the
pioneering efforts of the following individuals and companies who
contributed to the development of this technology:
John A. Focht,
Jr., Bramlette McClelland, and Robert L. Perkins
McClelland Engineers, Inc. (Fugro-McClelland
Marine Geosciences, Inc.)
