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.

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 In Situ Lateral Load Tests on Instrumented Bored Piles in Loessial Soils

2017 ◽  
Vol 13 (1) ◽  
pp. 1-11
Author(s):  
Sebastian Drăghici ◽  
Anatolie Marcu
Keyword(s):  
Large Diameter ◽  
In Situ Tests ◽  
Laterally Loaded Piles ◽  
Natural Moisture Content ◽  
Load Tests ◽  
Bored Piles ◽  
Strength And Stiffness ◽  
Laterally Loaded ◽  
Plaxis 3D

Abstract The aim of the paper is to provide some aspects regarding the behaviour of laterally loaded piles in loessial soils, by presenting and analysing the results of several in situ tests on large diameter bored piles in this type of soil. The major feature of loess is that it exhibits a massive decline of its strength and stiffness parameters when it comes into contact with water, leading to the collapse of its structure even under self-weight and creating difficult conditions for foundations. The load tests were performed both in natural moisture content loess and also in saturated loess. The results obtained by means of instrumentation are back-analysed using current analytical methods and also by finite element method using a numerical model in the geotechnical computation software Plaxis 3D.

scholarly journals Experimental and numerical investigation of the effect of vertical loading on the lateral behaviour of monopiles in sand

2021 ◽  
Author(s):  
Qiang Li ◽  
Kenneth Gavin ◽  
Amin Askarinejad ◽  
Luke J Prendergast
Keyword(s):  
Slenderness Ratio ◽  
Offshore Wind ◽  
Combined Loading ◽  
Initial Stiffness ◽  
Dense Sand ◽  
Geotechnical Centrifuge ◽  
Lateral Capacity ◽  
Vertical Loading ◽  
Load Tests ◽  
Observed Behaviour

The influence of combined loading on the response of monopiles used to support offshore wind turbines (OWTs) is investigated in this paper. In current practice, resistance of monopiles to vertical and lateral loading is considered separately. As OWT size has increased, the slenderness ratio (pile length, L, normalised by diameter, D) has decreased, and foundations are tending towards intermediate footings with geometries between those of piles and shallow foundations. Whilst load interaction effects are not significant for slender piles, they are critical for shallow footings. Previous research on pile load interaction has resulted in conflicting findings, potentially arising from variations in boundary conditions and pile slenderness. In this study, monotonic lateral load tests were conducted in a geotechnical centrifuge on vertically loaded monopiles in dense sand. Results indicate that for piles with L/D = 5, increasing vertical loading improved pile initial stiffness and lateral capacity. A similar trend was observed for piles with L/D = 3, when vertical loading was below ≈ 45% of the pile’s ultimate vertical capacity. For higher vertical loads considered, results tended towards the behaviour observed for shallow footings. Numerical analyses conducted show that changes in mean effective stress are potentially responsible for the observed behaviour.

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.

Cyclic Loading of Piles Using the P-Y Method

2019 ◽  
Vol 13 (2) ◽  
Author(s):  
Matt Bristow
Keyword(s):  
Cyclic Loading ◽  
Soil Depth ◽  
Large Diameter ◽  
Reference Conditions ◽  
Numerical Procedure ◽  
New Method ◽  
Shear Stresses ◽  
Applied Loading ◽  
Cyclic Degradation ◽  
Laterally Loaded

A new analytical method is presented to determine the effects of cyclic loading on laterally loaded piles. The method uses a new numerical procedure to quantify the effects of the cyclic loading at each soil depth and convert that to a set of cyclic p-y modifiers. The reduced foundation stiffness associated with the cyclic loading can be determined, including the residual static capacity and an estimate of the accumulated displacement. The new method introduces the concept of cyclic degradation damage, which is defined as sum of the cyclic degradation that is occurring at each soil depth. Cyclic degradation calculations are based on the shear stresses in the soil. Consequently, anything that causes the shear stresses to change (e.g. pile length, pile diameter, applied loading, etc.) will automatically be included in the calculation of cyclic p-y modifiers. The method has been validated by comparing the cyclic p-y curves produced using the new method with established cyclic p-y curves derived from fielding testing. The new method has also been used to investigate what happens to the cyclic p-y modifiers as one moves away from the reference conditions used to determine the established cyclic p-y curves in API RP2A (2000). The new method shows that every application (e.g. combination of cyclic loading, pile properties, and soil characteristics) has its own unique set of cyclic p-y curves, though most p-y curves fit within an upper and lower bound range. Examples are provided for large diameter monopiles.

Factors Affecting the Strength of Flexor Tendon Repair

1992 ◽  
Vol 17 (5) ◽  
pp. 550-552 ◽  
Author(s):  
D. BHATIA ◽  
K. E. TANNER ◽  
W. BONFIELD ◽  
N. D. CITRON
Keyword(s):  
Cyclic Load ◽  
Suture Material ◽  
Flexor Tendon ◽  
Tendon Repair ◽  
Flexor Tendon Repair ◽  
Factors Affecting ◽  
Full Strength ◽  
Load Tests

The effects of different thicknesses and configurations of core sutures were studied in human cadaveric flexor tendon repairs. Both straight and cyclic load tests were employed. To exploit the full strength of 4/0 suture material, the Kessler repair using four locked single knots would seem to be appropriate.

Response of Laterally Loaded Large-Diameter Bored Pile Groups

2001 ◽  
Vol 127 (8) ◽  
pp. 658-669 ◽  
Author(s):  
Charles W. W. Ng ◽  
Limin Zhang ◽  
Dora C. N. Nip
Keyword(s):  
Large Diameter ◽  
Pile Groups ◽  
Bored Pile ◽  
Laterally Loaded

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.

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