Performance of piles with enlarged bases subject to uplift forces

1990 ◽  
Vol 27 (5) ◽  
pp. 546-556 ◽  
Author(s):  
E. A. Dickin ◽  
C. F. Leung
Keyword(s):  
Empirical Equation ◽  
Slip Surface ◽  
Surface Model ◽  
Loose Sand ◽  
Uplift Capacity ◽  
Base Diameter ◽  
Dense Sand ◽  
Centrifuge Tests ◽  
Anchor Plates ◽  
Uplift Forces

The influence of embedment, base diameter, and backfill density on the uplift behaviour of piles with enlarged bases embedded in sand was investigated in a centrifuge. Comparitive tests on straight-shafted piles are also reported. For piles in dense sand, sensible agreement was found with earlier research on anchor plates and published field data. However, uplift capacities in loose sand were considerably lower than previously observed for anchor plates. A number of theories for anchors considerably overpredict the observed capacity for belled piers in both dense and loose sand, although in the case of dense sand, reasonable values are obtained using an empirical equation derived from centrifuge tests on anchor plates and a finite element based design approach. The normally conservative vertical slip-surface model is alone in providing reasonable agreement with the surprisingly low observations for piles in loose sand. Key words: piles, uplift capacity, centrifuge tests, sand.

Uplift Capacity of Suction Caissons in Sand for General Conditions Of Drainage

2021 ◽  
Author(s):  
Ragini Gogoi ◽  
Charles P. Aubeny ◽  
Phillip Watson ◽  
Fraser Bransby
Keyword(s):  
Constitutive Model ◽  
Load Capacity ◽  
System Capacity ◽  
Soil Conditions ◽  
Uplift Capacity ◽  
Soil Response ◽  
Dense Sand ◽  
Centrifuge Tests ◽  
Numerical Predictions ◽  
Suction Caissons

Abstract Suction caissons have emerged as a viable solution for the foundations of offshore wind turbines, which are gaining momentum worldwide as an alternate energy source. When used in a multi-bucket jacket system, the system capacity is often governed by the uplift capacity of the windward bucket foundation. Seabed conditions at offshore windfarm sites often comprise dense sand where the soil response may be drained, partially drained or undrained depending on the loading regime, the foundation dimensions and the soil conditions. Given the large difference in uplift capacity of caissons for these different drainage conditions, predicting the behavior of a suction caisson under a range of drainage conditions becomes a paramount concern. Consequently, this paper presents the findings of a coupled finite element investigation of the monotonic uplift response of the windward caisson of a multi-bucket jacket system in a typical dense silica sand for a range of drainage conditions. The study adopts a Hypoplastic soil constitutive model capable of simulating the stress-strain-strength behavior of dense sand. This choice is justified by conducting a comparative study with other soil models — namely the Mohr Coulomb and bounding surface sand models — to determine the most efficient soil failure model to capture the complex undrained behavior of dense sand. The numerical predictions made in this study are verified by recreating the test conditions adopted in centrifuge tests previously conducted at the University of Western Australia, and demonstrating that the capacity from numerical analysis is consistent with the test results. The Hypoplastic soil constitutive model also provides an efficient method to produce accurate load capacity transition curves from an undrained to a drained soil state.

The influence of foundation geometry on the uplift behaviour of piles with enlarged bases

1992 ◽  
Vol 29 (3) ◽  
pp. 498-505 ◽  
Author(s):  
E. A. Dickin ◽  
C. F. Leung
Keyword(s):  
Key Words ◽  
Design Method ◽  
Failure Mechanisms ◽  
Model Tests ◽  
Diameter Ratio ◽  
Uplift Capacity ◽  
Base Diameter ◽  
Centrifugal Model ◽  
Anchor Plates ◽  
Empirical Design

Centrifugal model tests investigating the influence of shaft to base diameter ratio and bell angle on the uplift capacity of piles with enlarged bases (or belled piers) in sand are reported. Increases in the angle of bell and in diameter ratio both result in a decrease in net uplift capacity and failure displacement. This appears to account for observed differences in uplift capacity between belled piers and anchor slabs. Studies of failure mechanisms around models of belled piers and anchor plates show distinctly different behaviour characteristics between foundation types. The comparatively low uplift capacities observed for belled piers are attributed to a lesser degree of soil mobilization. An empirical design method for belled piers is proposed in which appropriate factors which account for foundation geometry are applied to a simple continuous anchor formula. Key words : piles, sand, uplift capacity, centrifuge, design.

Bearing Capacity of Foundations with Inclusion of Dense Sand Layer over Loose Sand Strata

2017 ◽  
Vol 17 (10) ◽  
pp. 06017018 ◽  
Author(s):  
Vishwas N. Khatri ◽  
Jyant Kumar ◽  
Shamim Akhtar
Keyword(s):  
Bearing Capacity ◽  
Loose Sand ◽  
Sand Layer ◽  
Dense Sand

Plugging effect on uplift capacity of pipe-piles installed in loose sand

2013 ◽  
pp. 801-806 ◽  
Author(s):  
R Reis ◽  
F Saboya ◽  
D Neves ◽  
S Tibana ◽  
A Manhães ◽  
...  
Keyword(s):  
Loose Sand ◽  
Uplift Capacity

Uplift Capacity of Anchor Plates in Two-layered Cohesive-frictional Soils

2011 ◽  
Vol 11 (3) ◽  
pp. 589-591 ◽  
Author(s):  
Hamed Niroumand ◽  
Khairul Anuar Kassim ◽  
Ramli Nazir
Keyword(s):  
Uplift Capacity ◽  
Anchor Plates ◽  
Frictional Soils

scholarly journals A Centrifuge Modelling and Finite Element Analysis of Laterally Loaded Single Piles in Sand with Focus on P–Y Curves

2020 ◽  
Author(s):  
Hocine Haouari ◽  
Ali Bouafia
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Hyperbolic Function ◽  
Contact Method ◽  
Centrifuge Modelling ◽  
Element Analysis ◽  
Soil Response ◽  
Dense Sand ◽  
Centrifuge Tests ◽  
Abaqus Software

Centrifuge modelling and finite element analysis are powerful tools of research on the lateral pile/soil interaction. This paper aims at presenting the main results of experimental and numerical analysis of the pile response under monotonic lateral loading in sand. After description of the experimental devices, it focuses on the determination of the load-transfer P-Y curves for rigid and semi-rigid piles embedded in dry dense sand by using the experimental bending moment profiles obtained in centrifuge tests, as well as by a three-dimensional finite element models using ABAQUS Software. The elastic perfectly plastic Mohr-Coulomb constitutive model has been used to describe the soil response, and the surface-to-surface contact method of ABAQUS software has been used to take into account the nonlinear response at soil/pile interface. The analysis methodology has allowed to propose a hyperbolic function as a model to construct P-Y curves for rigid and semi-rigid piles embedded in dry dense sand, this model is governed by two main parameters, which are the initial subgrade reaction modulus, and the lateral soil resistance, the latter has been formulated in terms of Rankine’s passive earth pressure coefficient, the sand dry unit weight, and the pile diameter.

scholarly journals Effect of Slip Surface’s Continuity on Slope Dynamic Stability Based on Infinite Slope Model

Mathematics ◽  
2019 ◽  
Vol 7 (1) ◽  
pp. 58
Author(s):  
Chuanzheng Liu ◽  
Gang Wang ◽  
Wei Han
Keyword(s):  
Dynamic Stability ◽  
Stress Wave ◽  
Safety Factor ◽  
Slip Surface ◽  
Great Influence ◽  
Stress Wave Propagation ◽  
Surface Model ◽  
Infinite Slope ◽  
Research Results ◽  
The Stability

The slip surface is an important control structure surface existing in the landslide. It not only directly affects the stability of the slope through the strength, but also affects the stress field by affecting the propagation of the stress wave. Many research results have been made on the influence of non-continuous stress wave propagation in rock and soil mass and the dynamic response to seismic slopes. However, the effect of the continuity of the slip surface on the slope dynamic stability needs further researches. Therefore, in this paper, the effect of slip surface on the slope’s instantaneous safety factor is analyzed by the theoretical method with the infinite slope model. Firstly, three types of slip surface model were established, to realize the change of sliding surface continuity in the infinite slope. Then, based on wave field analysis, the instantaneous safety factor was used to analyze the effect of continuity of slip surface. The results show that with the decreasing of slip surface continuity, the safety factor does not simply increase or decrease, and is related to slope features, incident wave and continuity of slip surface. The safety factor does not decrease monotonically with the increasing of slope angle and thickness of slope body. Moreover, the reflection of slope surface has a great influence on the instantaneous safety factor of the slope. Research results in this paper can provide some references to evaluate the stability of seismic slope, and have an initial understanding of the influence of structural surface continuity on seismic slope engineering.

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