Field experiments with laterally-loaded pile groups have been conducted in a very soft clay at Harvey, Louisiana.Six series of loadings were performed; both static and cyclic tests were done with five-and ten-pile circular groups of six-inch diameter pipe piles, and corresponding single-pile tests were performed for comparison. Deflections were enforced at two elevations by a special loading device to simulate pile-head restraints typical of offshore structures. The measurements taken to record the behavior of the piles throughout the history of loading included total load and deflection of the group, plus individual pile shears and bending moments. Center-tocenter spacing in the 5-pile groups was 3.4 pile diameters and 1.8 diameters in the 10-pile group.

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Because soil is a heterogeneous media, pile installation response does not always proceed according to plan. When driving performance variability occur, the capacity of the piling must be determined and the cause of these discrepancies analyzed. Procedures for evaluating available soil borings, geophysical information and pile driving records to determine pile capacity are detailed. BACKGROUND During installation of a four pile jacket in the East Cameron area of the Gulf of Mexico, difficulties were encountered in reaching the design penetration of 323 feet. Piles 1 and 4 reached refusal after the final section was added when driving with a Menck 3000 hammer. A Menck 7000 hammer was tried on pile 4 and also met refusal. The typical definition for refusal used by installation contractors for a Menck hammer is 150 blows per foot for five feet or 250 blows per foot for restarting a pile. This definition differs form the API RP 2A(Ref. 1) recommendation of 300 blows per foot for five consecutive feet or 800 blows for one foot of penetration. This lower blow count for refusal is favored to prevent damage to the hammer which can be caused by excessive pounding with the hammer. In this paper the former definition for refusal was used. Adding the final section and driving to refusal gained less than 10 feet of additional penetration and left a weld joint at a poor location for proper connection to the jacket. It was decided to drive piles 2 and 3 and to terminate pile driving after installation of the fourth section at a penetration of about 258 feet. This final penetration would leave the heavy wall pile section high in the profile, but in an acceptable location to provide the design lateral support because of proper underdrive design. The predicted pile capacity based on the nearby boring provided a capacity of about 5400 kips. This capacity of 5400 kips was sufficient for minimum design requirements but a determination of the as installed capacity consistent with normal design procedures was required to determine maximum allowable loading conditions. Final pile penetrations (measured from the seafloor) for piles 1,2,3 and 4 were 268.5, 259, 258.5 and 263.5 feet respectively. QUESTIONS TO BE ANSWERED The difficulties during installation on this project raised several questions on the design and installation of a jacket. The questions that were asked of Seafloor Engineers as geotechnical consultants and are addressed in this paper are as follows:What is the pile capacity of the piles in their as built condition?Based on a review of the boring log near the location, no driving problems were anticipated. Why did driving problems occur?

Various in situ and laboratory tests that have been used to study the behavior and engineering characteristics of granular carbonate sediments are described and evaluated. Based on success or failure of these different test procedures (in terms of foundation performance) in situ and laboratory tests are recommended to make future geotechnical investigations in these soils more cost effective while meetin8 the technical demands of designing foundations in a material that is not well understood. Such standardization schemes will lead to significant improvements in soil characterization procedures and ultimately pave the way for improved foundation design methods. It is hoped that this will lead to development of rational geotechnical investigation programs rather than the arbitrary selection of tests and test procedures which may not always be appropriate.