Numerical investigation of the monotonic drained lateral behaviour of large diameter rigid piles in medium dense uniform sand

Géotechnique ◽  
2021 ◽  
pp. 1-39
Author(s):  
Huan Wang ◽  
M. Fraser Bransby ◽  
Barry M. Lehane ◽  
Lizhong Wang ◽  
Yi Hong
Keyword(s):  
Numerical Investigation ◽  
Load Transfer ◽  
Large Diameter ◽  
Offshore Wind ◽  
Soil Pressure ◽  
Lateral Capacity ◽  
Pile Diameter ◽  
Centrifuge Tests ◽  
Lateral Response ◽  
Loading Eccentricity

This paper presents a numerical investigation of the monotonic lateral response of large diameter monopiles in drained sand with configurations typical of those employed to support offshore wind turbines. Results from new centrifuge tests using instrumented monopiles in uniform dry sand deposits are first presented and used to illustrate the suitability of an advanced hypoplastic constitutive model to represent the sand in finite element analyses of the experiments. These analyses are then extended to examine the influence of pile diameter and loading eccentricity on the lateral response of rigid monopiles. The results show no dependency of suitably normalized lateral load transfer curves on the pile diameter and loading eccentricity. It is also shown that, in a given uniform sand, the profile with depth of net soil pressure at ultimate lateral capacity is independent of the pile diameter because of the insensitivity of the depth to the rotation centre for a rigid pile. A normalization method is subsequently proposed which unifies the load-deflection responses of different diameter rigid piles at a given load eccentricity.

scholarly journals Influence of Pile Diameter and Aspect Ratio on the Lateral Response of Monopiles in Sand with Different Relative Densties

2021 ◽  
Vol 9 (6) ◽  
pp. 618
Author(s):  
Huan Wang ◽  
Lizhong Wang ◽  
Yi Hong ◽  
Amin Askarinejad ◽  
Ben He ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Large Diameter ◽  
Pressure Coefficient ◽  
Offshore Wind ◽  
Fe Model ◽  
Soil Pressure ◽  
Pile Diameter ◽  
Centrifuge Tests ◽  
Aspect Ratios ◽  
Wide Range

The large-diameter monopiles are the most preferred foundation used in offshore wind farms. However, the influence of pile diameter and aspect ratio on the lateral bearing behavior of monopiles in sand with different relative densities has not been systematically studied. This study presents a series of well-calibrated finite-element (FE) analyses using an advanced state dependent constitutive model. The FE model was first validated against the centrifuge tests on the large-diameter monopiles. Parametric studies were performed on rigid piles with different diameters (D = 4–10 m) and aspect ratios (L/D = 3–7.5) under a wide range of loading heights (e = 5–100 m) in sands with different relative densities (Dr = 40%, 65%, 80%). The API and PISA p-y models were systematically compared and evaluated against the FE simulation results. The numerical results revealed a rigid rotation failure mechanism of the rigid pile, which is independent of pile diameter and aspect ratio. The computed soil pressure coefficient (K = p/Dσ′v) of different diameter piles at same rotation is a function of z/L (z is depth) rather than z/D. The force–moment diagrams at different deflections were quantified in sands of different relative density. Based on the observed pile–soil interaction mechanism, a simple design model was proposed to calculate the combined capacity of rigid piles.

scholarly journals Centrifuge and Numerical Modeling of Monopiles for Offshore Wind Towers Installed in Clay

2015 ◽  
Author(s):  
Madhuri Murali ◽  
Francisco Grajales ◽  
Ryan D. Beemer ◽  
Giovanna Biscontin ◽  
Charles Aubeny
Keyword(s):  
Aspect Ratio ◽  
Oil And Gas ◽  
Numerical Models ◽  
Large Diameter ◽  
Oil And Gas Industry ◽  
Rensselaer Polytechnic Institute ◽  
Offshore Wind ◽  
Geotechnical Centrifuge ◽  
Low Aspect Ratio ◽  
Centrifuge Tests

Offshore wind power has gained momentum as a means to diversify the world’s energy infrastructure; however, little is still known of the global stiffness behavior of the large diameter low aspect ratio monopiles which have become the foundation of choice for offshore wind towers. Traditionally, offshore foundations have been associated with gravity structures for the oil and gas industry, which in general need to resist large vertical loads with limited lateral and moment loading. However, wind towers are purposely designed to be subjected to large lateral and moment loads from the wind and waves in order to maximize power generation. Geotechnical centrifuge tests were conducted and numerical models are being developed to examine the behavior of low aspect ratio piles in clayey soils. Monopiles with aspect ratio of two are being tested in the the 150g-ton centrifuge at Rensselaer Polytechnic Institute. Initial results include momenttheta and force-displacement for various loading conditions. Numerical studies consist of finite element (FE) simulations in order to predict capacities and permanent deformations. The comparisons are to be performed in terms of the total resistance that is exerted by the soil on the caisson. FE studies allow to model capacity for different displacement fields and also to compute interactions between different loading modes. This paper outlines our progress to date including both numerical and experimental results.

Experimental Investigation Into Pile Diameter Effects of Laterally Loaded Mono-Piles

2011 ◽  
Author(s):  
Etienne A. Alderlieste ◽  
Jelke Dijkstra ◽  
A. Frits van Tol
Keyword(s):  
Cyclic Load ◽  
Large Diameter ◽  
Load Control ◽  
Geotechnical Centrifuge ◽  
Lateral Capacity ◽  
Current Test ◽  
Pile Diameter ◽  
Validity Range ◽  
Load Tests ◽  
Laterally Loaded

This paper presents the results of model tests on laterally loaded mono-pile foundations in sand. The tests have been performed in a geotechnical centrifuge. The objective of the research is to quantify large diameter effects of these mono-piles on the lateral capacity and the stiffness response for cyclic lateral loading. These large diameters are out of the validity range of the commonly used design methods. For this reason prototype pile diameters up to 4.4 m with a length over diameter ratio of 5 have been investigated. The results show an increase in pile diameter from Ds = 2.2 m to Dl = 4.4 m leads to a significant increase in static lateral capacity and stiffness from cyclic load tests. All tests have been performed with constant L/D = 5, Id = 60% and a load eccentricity up to e = 4.8 m. However, the current test series needs to be extended to higher initial densities and the load control should be more strictly regulated before a clear diameter dependence, for pile diameters > 2.2 m, is proven.

Vertical Loading Test on the Bearing Capacity of Large-Diameter Filling-Piles in the Mudstone and Sandstone Foundation

2013 ◽  
Vol 639-640 ◽  
pp. 587-592 ◽  
Author(s):  
Hui Yang ◽  
Xue Liang Jiang ◽  
Jun Fu
Keyword(s):  
Bearing Capacity ◽  
Load Transfer ◽  
Large Diameter ◽  
Load Test ◽  
Sediment Thickness ◽  
Loading Test ◽  
Friction Resistance ◽  
Vertical Loading ◽  
Pile Diameter ◽  
Side Friction

Based on the vertical loading test results of large-diameter filling pile near an electric factory in the sandstone and mudstone foundation, the load transfer mechanism and vertical loading bearing behavior of the pile were discussed. The analysis shows that the pile mainly behaves as friction piles and the vertical bearing capacity is mainly supplied by side friction resistance. The pile side friction is related to the section displacement of pile, the pile load and the soil characteristic. The pile end resistence is related to pile end settlement, pile diameter, rock-socketed length,rock elasticity modulus of pile end, sediment thickness and pile construction technical. The pile end resistence linearly increases with the settlement of pile end. In tis paper, the dead-load test is recommended in determination the pile bearing capacity and the sediment thickness should be strictly controlled in order to meet the standard. In the intermediary weathered sand-mudstone, the pile end should inset two times of pile diameter for pile whose diameter is 800mm. The pile end should inset 2 meters for pile whose diameter is 1500mm.

scholarly journals Field Tests of Super-Long and Large-Diameter Drilled Shaft Pile Foundations

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Peisen Wang ◽  
Hongyan Ding ◽  
Jialin Zhou ◽  
Wenjun Hu ◽  
Xuechen Gu ◽  
...  
Keyword(s):  
Load Transfer ◽  
Large Diameter ◽  
Soil Layer ◽  
Field Tests ◽  
Load Test ◽  
Pile Foundations ◽  
Static Load Test ◽  
Mutual Compensation ◽  
Shaft Resistance ◽  
Pile Diameter

This study investigated the compressive behaviour of super-long pile foundations with large diameters. Three 52 m, 73 m, and 83 m long piles with a diameter of 1500 mm, 1500 mm, and 1800 mm were cast and tested, respectively. Given that large loading was required, an improved compressive static load test was introduced, and the load transfer mechanism, shaft resistance development, and distribution were analysed. This study found that the transferred load decreased along the pile during each applied load, but the gradients were different. For most layers, when increasing the load, the shaft resistance developed in the upper layers first, while the shaft resistance from the lower part did not always fully develop. Moreover, the “mutual compensation” phenomenon was discovered, which was when the shaft softening occurred from one soil layer, the shaft hardening of the other soil would occur simultaneously. Under consideration of the soil layer differences around these piles, it was recommended that shaft and base grouting should be applied on 52 m and 73 m piles, while only shaft grouting should be applied on the 83 m pile. For this longest pile design, whose toe resistance was discovered to be very small, increasing the pile length was not appropriate; thus, it was preferable to increase the pile diameter to increase the ultimate bearing capacity.

Effect of load eccentricity and stress level on monopile support for offshore wind turbines

2014 ◽  
Vol 51 (9) ◽  
pp. 966-974 ◽  
Author(s):  
Rasmus Tofte Klinkvort ◽  
Ole Hededal
Keyword(s):  
Wind Turbines ◽  
Large Diameter ◽  
Pressure Coefficient ◽  
Small Diameter ◽  
Earth Pressure ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Initial Stiffness ◽  
Offshore Wind Turbines ◽  
Centrifuge Tests

Currently monopiles are the most common foundation solution for offshore wind turbines. The design of monopiles relies on empirical data from tests performed on long, slender, small-diameter piles loaded predominantly in shear. In contrast, a monopile is a large-diameter, relatively short pile on which load is applied with a large eccentricity. With centrifuge tests as the basis, this paper investigates the behaviour of a rigid pile loaded with a high eccentricity. A test series was carried out to simulate idealized monotonic load cases for monopiles supporting an offshore wind turbine. Centrifuge tests were performed on model monopiles subjected to stress distributions equal to prototype monopiles with pile diameters ranging from 1–5 m and eccentricities ranging from 8.25–17.75 pile diameters. It was possible to identify a unified response of all of these tests by using dimensional analysis and Rankine’s passive earth pressure coefficient as a normalization parameter. The normalized ultimate soil resistance was unaffected by acceleration level and load eccentricity, indicating that the failure mechanism was the same for all tests. Based on the centrifuge tests, a reformulation of soil–pile interaction curves is presented. The normalized initial stiffness of the soil–pile resistance curves was seen to increase linearly with depth in the centrifuge tests. The reformulation differs from current guidelines in terms of the shape of the interaction curve and magnitude of ultimate resistance.

scholarly journals Influence of Vertical Loading on Behavior of Laterally Loaded Foundation Piles: A Review

2020 ◽  
Vol 8 (12) ◽  
pp. 1029
Author(s):  
Qiang Li ◽  
Luke J. Prendergast ◽  
Amin Askarinejad ◽  
Ken Gavin
Keyword(s):  
Large Diameter ◽  
Offshore Wind ◽  
Pile Foundations ◽  
Future Research ◽  
Gravitational Acceleration ◽  
Lateral Loads ◽  
Vertical Loading ◽  
Lateral Response ◽  
Current Design ◽  
Laterally Loaded

The majority of installed offshore wind turbines are supported on large-diameter, open-ended steel pile foundations, known as monopiles. These piles are subjected to vertical and lateral loads while in service. In current design practice, interaction of vertical and lateral loads are not considered, rather piles are designed to resist vertical and lateral loads independently. Whilst interaction effects are widely studied for shallow foundations, the limited research on this topic for pile foundations often produces conflicting results. This paper reviews the research of the influence of vertical loading on the lateral response of pile foundations under combined loads, from the perspective of analytical research, numerical research, and experimental research from tests performed on 1-g (gravitational acceleration) model, centrifuge, and full-scale piles. The potential reasons for the differences among the results of previous research are discussed. Some guidance for future research on the effect of vertical loads on the lateral response of piles is provided.

scholarly journals Load-Bearing Characteristics of Large-Diameter Rock-Socketed Piles Based on Ultimate Load Tests

2020 ◽  
Vol 2020 ◽  
pp. 1-12 ◽  
Author(s):  
Xueying Liu ◽  
Xiaoyu Bai ◽  
Mingyi Zhang ◽  
Yonghong Wang ◽  
Songkui Sang ◽  
...  
Keyword(s):  
Load Transfer ◽  
Large Diameter ◽  
Peak Load ◽  
Internal Force ◽  
Pile Diameter ◽  
Maximum Loading ◽  
Side Resistance ◽  
Load Tests ◽  
Resistance Performance ◽  
Ultimate Resistance

As part of a large converter project in Shandong Province, vertical static load tests and internal force tests were conducted on three large-diameter rock-socketed piles, their load transfer mechanism was clarified, and the ultimate side resistance and ultimate resistance performance characteristics of the rock-socketed sections were analyzed. The test results showed that the three test piles were damaged under maximum loading, the Q-s curve exhibited a steep drop, the pile compression was around 1.2 times the pile diameter, and the bearing capacity of a single pile did not meet the design requirements. The side and end resistances of the three test piles all reached their ultimate values, but the ultimate side resistance was lower than the lower limit of the recommended value in the current technical code for building pile foundations. The end resistance under maximum loading accounted for 38.4–53.8% of the peak load, which was relatively high. By comparing it with other studies, there was no significant correlation between the coefficient of rock ultimate side resistance of the rock-socketed segment and the pile diameter of the rock-socketed segment. However, the coefficient of ultimate resistance increased gradually with the pile diameter. However, the latter correlation was not significant when the pile diameter was less than 1000 mm.

Lateral Response of Large-Diameter Monopiles for Offshore Wind Turbines from Centrifuge Model Tests

2013 ◽  
Vol 37 (1) ◽  
pp. 20130081 ◽  
Author(s):  
Yun Wook Choo ◽  
Dongwook Kim ◽  
Jae-Hyun Park ◽  
Kiseok Kwak ◽  
Jae-Hyun Kim ◽  
...  
Keyword(s):  
Wind Turbines ◽  
Large Diameter ◽  
Model Tests ◽  
Offshore Wind ◽  
Offshore Wind Turbines ◽  
Centrifuge Model ◽  
Lateral Response ◽  
Centrifuge Model Tests

Static Analysis of New Type Composite Mono-Piles for Offshore Wind Farm

2013 ◽  
Author(s):  
Jian-hua Zhang ◽  
Dian-wei Gao ◽  
Xin-sheng Liu ◽  
Ke Sun
Keyword(s):  
Wind Energy ◽  
Wind Farm ◽  
Large Diameter ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Outer Diameter ◽  
Static Loads ◽  
Pile Diameter ◽  
Practical Engineering ◽  
New Type

The wind energy converters have extreme requirements to lateral deformation and rotation for support structures. Mono-pile, as a popular foundation structure for offshore wind energy towers, must be with sufficient large diameter and deep embedded length to limit the deformation and rotation within the tolerance under cyclic loads. Larger power offshore wind turbine (OWT), bigger pile diameter should be needed. However, large outer diameter pile will lead to difficult construction and high cost. In this study, a new conception of composite mono-pile is presented to decrease the outer diameter of pile. To investigate the structural behavior of composite mono-pile, the finite elements software ABAQUS is employed to analyze and compare with general mono-pile for 1.5 MW OWT under static loads. The numerical results demonstrate that stiffness of composite mono-pile can be improved effectively. Therefore, in same environment condition, composite mono-pipe diameter will be smaller than typical mono-pile, correspondingly, construction difficult and cost will be decreased. In addition, mechanical characteristics of composite mono-pile are analyzed and rational diameter and thickness selection of inserted pile are advised. The research results can provide the reference for practical engineering.

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