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<p>This paper presents full-scale lateral load tests on single and grouped continuous flight auger (CFA) piles in sandy soil, focusing on load distribution, stiffness degradation, and group efficiency at serviceability levels. While ultimate responses of laterally loaded piles have been extensively investigated, field data on pile group mechanisms under small displacements remain scarce, limiting the calibration of design models. To address this gap, an experimental programme was carried out at a dedicated site in Northeast Brazil, comparing an isolated CFA pile (400&#xa0;mm diameter, 8.5&#xa0;m length) with two-pile and three-pile single-line groups at a centre-to-centre spacing of 2.5<i>D</i>. High-resolution instrumentation, including inclinometers and load cells, enabled detailed tracking of soil–pile–soil interaction mechanisms. The study yielded three main findings: (i) quantification of the coefficient of horizontal subgrade reaction (<i>n</i><sub>h</sub>) under service-level loading, with values of 221–317 MN/m<sup>3</sup> at displacements of 0.8–1.2&#xa0;mm, considerably higher than empirical estimates; (ii) documentation of progressive load redistribution within groups, where the front pile mobilised up to 70% of the total load under 60 kN, evidencing soil-arching effects; and (iii) identification of cyclic stiffness degradation, with a 15–20% reduction after four cycles. The experimental findings further indicate that, although classical soil resistance–displacement (<i>p–y</i>) formulations can reproduce the initial stiffness, they fail to capture its progressive reduction under cyclic loading, reflecting the limitations of conventional nonlinear constitutive frameworks that neglect strain-dependent stiffness degradation. These results provide field-based benchmarks to guide performance-oriented design of laterally loaded foundations in sandy soils, with direct implications for offshore wind turbines, bridge abutments, and waterfront structures where serviceability governs behaviour.</p>

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Full-Scale Study of Load Distribution and Group Efficiency in Laterally Loaded CFA Piles in Sand

  • 期刊论文

  • 发表日期：

    2025年11月7日

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  • D. A. Cavalcanti Jr.,
  • L. J. N. Guimarães,
  • A. D. Gusmão

摘要

This paper presents full-scale lateral load tests on single and grouped continuous flight auger (CFA) piles in sandy soil, focusing on load distribution, stiffness degradation, and group efficiency at serviceability levels. While ultimate responses of laterally loaded piles have been extensively investigated, field data on pile group mechanisms under small displacements remain scarce, limiting the calibration of design models. To address this gap, an experimental programme was carried out at a dedicated site in Northeast Brazil, comparing an isolated CFA pile (400 mm diameter, 8.5 m length) with two-pile and three-pile single-line groups at a centre-to-centre spacing of 2.5D. High-resolution instrumentation, including inclinometers and load cells, enabled detailed tracking of soil–pile–soil interaction mechanisms. The study yielded three main findings: (i) quantification of the coefficient of horizontal subgrade reaction (nh) under service-level loading, with values of 221–317 MN/m3 at displacements of 0.8–1.2 mm, considerably higher than empirical estimates; (ii) documentation of progressive load redistribution within groups, where the front pile mobilised up to 70% of the total load under 60 kN, evidencing soil-arching effects; and (iii) identification of cyclic stiffness degradation, with a 15–20% reduction after four cycles. The experimental findings further indicate that, although classical soil resistance–displacement (p–y) formulations can reproduce the initial stiffness, they fail to capture its progressive reduction under cyclic loading, reflecting the limitations of conventional nonlinear constitutive frameworks that neglect strain-dependent stiffness degradation. These results provide field-based benchmarks to guide performance-oriented design of laterally loaded foundations in sandy soils, with direct implications for offshore wind turbines, bridge abutments, and waterfront structures where serviceability governs behaviour.