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.

This paper was presented at the 9th Annual O1C in Houston, Tex., May 2-5, 1977. The material is subjectto correction by the author. Permission to copy is restricted to an abstract of not more than 300 words. Abstract A method for computer-aided design and analysis of beam-columns under static axial and lateral loads is presented. Axial and lateral support reactions may be described as linear or nonlinear functions of beam-column displacement. The method utilizes discrete-element mechanical models of continuous members to facilitate numerical solutions of complex structural members. The axial and lateral solutions are coupled to include the effects of axial forces on the behavior of the member in bending.

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Freeport McMoRan Resource Partners are planning to construct a number of offshore platforms for the purpose of extracting sulphur from a large deposit discovered in Block 299 of the Main Pass Area of the Gulf of Mexico.Subsidence and lateral spreading of the nearsurface sediments are expected to accompany the removal of the sulphur. As the soil moves laterally, the foundation piles will generally conform closely with the displaced shape of the soil, particularly in deep layers of sand. At some locations, the differential movement of sand layers separated by weaker clay layers produces very severe bending deformations in the piles.The unique design problem for the Main Pass 299 platform foundations was not related to satis@ing conventional safety factors, but rather, was concerned with selecting cross-sections which, although strained lastically, will remain in [ equilibrium with t e imposed soil motions while retaining structural integrity.

Static load tests were performed on the pile two hours after driving and after four, sixteen, and twenty-nine months of consolidation and setup. The process of consolidation was essentially completed about twelve months after driving, so that the load tests encompass the complete life of a friction pile in highly plastic clays. Upon completion of the static load tests, the pile was subjected to a number of load variations that included cyclic loading in tension above and below a constant bias until failure was indicated by progressive pullout to large displacements. The pile was then subjected to alternate loading to failure in tension and compression to observe the maximum degree of cyclic degradation. Additional variations included studies of the effect of variations in the loading rate and large-displacement loading in compression to evaluate the end-bearing resistance, At the end of the field test program, load, pressure, and displacement data were recorded during pullout of the pile, Data were recorded for over fifty inches of axial displacement as the pile was removed, No significant losses in capacity were observed during pullout, indicating that temporary overload conditions on tension piles may not result in catastrophic failure particularly if redundancy is provided. Introduction At the time the study was initiated. little information was available regarding the setup behavior of long piles in normally consolidated highly plastic clays, The available load test data covering long periods of setup were limited to clays of low plasticity (Refs 1,2,3,4,5). Analytical methods that included consideration of reconsolidation and setup were limited to the empirical methods proposed by Soderberg (Ref 6) and the newly developed and untested finite-element solutions proposed by Carter, et at (Ref 7), Experimental data regarding the behavior of piles under cyclic axial loading in similar soils were limited to laboratory tests on model piles in a remolded soil (Refs 8, 9, 10). Computer programs had been developed to model the hysteretic nature of pile-soil interaction under cyclic loading. including the effects of cyclic degradation (Refs 11, 12), However. the programs had not been calibrated against actual load test data from prototype-size piles, The test program was therefore centered around a fully instrumented pile driven to a deep penetration in a soil deposit having a geologic history similar to Conoco's Green Canyon site in the deepwater Gulf of Mexico (Ref 13), In addition to measuring the load distribution along the pile the instrumentation was designed to obtain all the experimental data necessary to develop or verify evolving effective stress design procedures (Refs l4, 15), The load tests covered the full range of consolidation history and included static and cyclic loading in tension and two-way loading to failure in both tension and compression to provide a baseline for comparison of the effects of degradation during the cyclic tension tests. Load Test Programs While the load tests on the large-diameter instrumented pile provided invaluable information regarding the behavior of a long. elastic pile. the available variations in loading histories were very limited, Furthermore, the data were limited to only one pile of one diameter at one site.