Field and numerical study of the lateral response of rigid piles in sand

Abstract

Large diameter, short monopiles are the preferred foundation type for offshore wind turbines. These piles demonstrate a rigid response with significant rotation of the pile base under ultimate lateral load. As traditional empirical p-y curves used in lateral loaded pile analysis have been derived from tests on small diameter onshore piles, there is some doubt about their applicability to rigid monopiles, particularly in view of the significant difference in the response of the pile base compared with a typical onshore pile. To address this issue, this paper reports on a unique series of field tests using instrumented driven pipe piles, complimented by numerical analysis, which was performed to examine explicitly the contribution of the pile base to the response under lateral load. The field tests, which included tests on pipe piles that had the sand plug removed to below pile tip level prior to testing, confirmed that the influence of the base on the lateral response for the tested 273- and 457-mm-diameter piles was negligible. Numerical analyses that were calibrated using the field test data showed that the contribution of the base to the lateral capacity of a monopile with a diameter as large as 10 m is negligible. Results also indicated that p-y curves are not affected by the length to diameter ratio and can be used to predict the response of monopiles in sand.

An analytical method to evaluate the capacity of laterally loaded piles in unsaturated soils

“…It is worth noting that even a small amount of apparent cohesion may significantly increase the lateral pile capacity. With reference to the tests of Choi et al [14] and Wang et al [16], the apparent cohesion is relatively low (it ranges from 2.34 to 10.9), but its effect on the predicted lateral capacity of the pile is very evident in Fig. 3.…”

“…3. In the tests from Choi et al [14], the non-dimensional cohesive group 𝐶 is responsible for 40% to 72% of the pile capacity depending on the value of 𝐿/𝑑 while in the test from Wang et al [16] it accounts for 35% to 87% of the pile capacity.…”

“…The proposed method has been validated against field tests on free head short rigid piles embedded in three distinct unsaturated soils, i.e. a weathered granite [14], a sand with clay and silt [15] and a fine sand [16], . In all cases, the water table was deeper than the toe of the pile (𝑧 𝑤 > 𝐿) so that the unsaturated reacting depth coincides with the pile length (i.e.…”

“…The material and geometrical parameters of the testing campaigns are summarised in Table 2. Calibration details are reported in both the original publications [14][15][16] and in Lalicata et al [7].…”

Analyzing Laterally Loaded Piles in Multi-layered Cohesive Soils: a Hybrid Bnwf Approach With Validation and Parametric Study

“…In the prevailing soil structure interaction analysis, soil springs are commonly described by P-y curves (Wang et al [78], Wu et al [80]), representing the relations between the lateral soil resistance, P, and the pile deflection, y, at different embedded depths. During the past decades, several solutions have proposed for the soil structure interaction analysis of piles with the adoption of P-y curves, such as Matlock [52] and API [4] for the design of laterally loaded piles in soft clay, Reese et al [66] for the design of laterally loaded piles in stiff clay with free water, and Welch & Reese [79] for the design of laterally loaded piles in stiff clay without free water.…”