Design procedures for installation of suction caissons in sand
TL;DR: In this paper, the authors consider the calculations appropriate for the installation of caissons in sands and present methods for determining the resistance to penetration of open-ended cylindrical caisson foundations both with and without the application of suction inside the caisson.
Abstract: Suction-installed caisson foundations are being used or considered for a wide variety of offshore applications ranging from anchors for floating facilities to shallow foundations for offshore wind turbines. In the design of the caissons the installation procedure must be considered as well as the in-place performance. The scope of this paper is to consider the calculations appropriate for the installation of caissons in sands. Calculation methods are presented for determining the resistance to penetration of open-ended cylindrical caisson foundations both with and without the application of suction inside the caisson. Comparisons are made with case records. A companion paper addresses the calculation procedure for installation in clays as well as in other soils.
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TL;DR: In this article, the present state of knowledge concerning geotechnical and structural issues affecting foundation types under consideration for the support structures of offshore wind turbines, and recommendations for future research and development are provided.
Abstract: Offshore wind is a source of clean, renewable energy of great potential value to the power industry in the context of a low carbon society. Rapid development of offshore wind energy depends on a good understanding of technical issues related to offshore wind turbines, which is spurring ongoing research and development programmes. Foundations of offshore wind turbines present one of the main challenges in offshore wind turbine design. This paper reviews the present state of knowledge concerning geotechnical and structural issues affecting foundation types under consideration for the support structures of offshore wind turbines, and provides recommendations for future research and development.
214 citations
TL;DR: In this article, a program of testing on suction caisson foundations in an artificially prepared sand test bed near Luce Bay, in Scotland, is described, with the results relevant to the design of either monopod or quadruped foundations for offshore wind turbines.
Abstract: A programme of testing on suction caisson foundations in an artificially prepared sand test bed near Luce Bay, in Scotland, is described The tests are relevant to the design of either monopod or quadruped foundations for offshore wind turbines Records are presented for suction installation of the caissons, cyclic moment loading under both quasi-static and dynamic conditions to simulate the behaviour of a monopod foundation, and cyclic vertical loading and pullout of caissons to simulate one footing in a quadruped foundation Variations of stiffness with loading level of the foundation are observed, with high initial stiffness followed by hysteretic behaviour at moderate loads and degradation of response at high loads Some implications for the design of wind turbine foundations are briefly discussed
181 citations
Cites background or methods from "Design procedures for installation ..."
...Also shown in the figure are the computed profiles of suction, using the procedure described by Houlsby & Byrne (2005) V 9þ s D2i =4 ¼ ð h 0 9vodz K tan ð Þo Doð Þ þ ð h 0 9vidz K tan ð Þi Dið Þ þ 9viNq þ ª9tNª Dtð Þ (1) The subscripts i and o refer to internal and external properties respectively,…...
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...The reader is referred to Houlsby & Byrne (2005) for further details of this formulation....
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...The reader is referred to Houlsby & Byrne (2005) for further details of this formulation....
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...Also shown in the figure are the computed profiles of suction, using the procedure described by Houlsby & Byrne (2005) ...
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TL;DR: In this article, an expression to describe the combined capacity of bucket foundations was developed by calibrating the failure criteria for bucket foundations, and the experimental results were used to evaluate the behavior of the bucket foundations in accordance with the macromodel approach.
Abstract: A new concept with respect to offshore wind turbines, the bucket foundation, is known in the oil and gas industry, although the load conditions for wind turbines are significantly different. An extensive number of loading tests with small-scale bucket foundations subjected to combined loading were carried out in the geotechnical laboratory at Aalborg University in Aalborg, Denmark. Tests were performed on buckets of various sizes, embedment ratios, and load paths on saturated dense Aalborg University Sand No. 1. The experimental results were used to evaluate the behavior of the bucket foundations in accordance with the macromodel approach. An expression to describe the combined capacity of bucket foundations was developed by calibrating the failure criteria for bucket foundations.
162 citations
TL;DR: In this article, a review of foundations for offshore wind energy convertors considering the significant growth of offshore wind power since the early 2000s is presented, where the characteristics of various foundation types (i.e., gravity, pile, suction caisson, and float type) and current status of field application are discussed.
Abstract: This paper reviews foundations for offshore wind energy convertors considering the significant growth of offshore wind energy since the early 2000s. The characteristics of various foundation types (i.e., gravity, pile, suction caisson, and float type) and the current status of field application are discussed. Moreover, the mechanical characteristics of soil are described in the sense that these characteristics including modulus, strength, damping, and modulus degradation of soil play critical roles for the design of offshore foundations. By using these mechanical properties of soil, theoretical studies to consider structure-soil interaction are classified (into equivalent spring models, distributed spring models, and continuous element models) and explained. Field and laboratory experiments on the response of structure embedded in soil to static and dynamic loads are discussed. Based on the review of previous studies, directions for future research and study on offshore wind turbine are suggested.
155 citations
01 Jan 2005
TL;DR: In this paper, a review of the development of design methods for suction caissons for wind turbine in-service performance is presented, with some attention to installation, but the focus is on design for inservice performance, and the results of laboratory studies and field trials are reported.
Abstract: Suction caissons may be used in the future as the foundations for offshore wind turbines. We review recent research on the development of design methods for suction caissons for these applications. We give some attention to installation, but concentrate on design for in-service performance. Whilst much can be learned from previous offshore experience, the wind turbine problem poses a particularly challenging combin- ation of a relatively light structure, with large imposed horizontal forces and overturning moments. Monopod or tripod/tetrapod foundations result in very different loading regimes on the foundations, and we consider both cases. The results of laboratory studies and field trials are reported. We also outline briefly relevant numerical and theoretical work. Extensive references are given to sources of further information.
138 citations
Cites methods from "Design procedures for installation ..."
...The first method (Houlsby and Byrne, 2005a, b) involves use of adaptations of pile capacity analysis, in which the resistance to penetration is calculated as the sum of an end bearing term on the rim and friction on the inside and outside....
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References
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TL;DR: Previous work on the design of offshore foundations is reviewed, and some simple design calculations for sizing foundations and structures appropriate to the wind-turbine problem are presented, and deficiencies in the current design approaches are examined.
Abstract: An important engineering challenge of today, and a vital one for the future, is to develop and harvest alternative sources of energy. This is a firm priority in the UK, with the government setting ...
343 citations
01 Jan 1995
TL;DR: In this paper, the Europipe 16/11E and Sleipner T foundations are analyzed in terms of the performed field and model tests, as well as the theoretical models and practical analysis tools utilized for design.
Abstract: The successful installation of the Europipe 16/11E Riser jacket in July 1994 and the coming installation of Sleipner T jacket in spring 1996 proves that suction installed skirted plate foundations (buckets), may not only be a competitive alternative to piles, but also a complementary foundation solution both for noncohesive and cohesive soils. This paper presents the background for the design analyses of the Europipe 16/11E and Sleipner T foundations in terms of the performed field and model tests, as well as the theoretical models and practical analysis tools utilized for design.
113 citations
"Design procedures for installation ..." refers background in this paper
...are 15 m in diameter and the skirt depth is 5 m.(5,10) The wall thickness is taken to be 45 mm and again the internal stiffeners are neglected as there is insufficient information available on this detail....
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TL;DR: In this paper, the authors present calculation procedures for the installation of a caisson in clay, and a companion paper describes the calculation procedure for installation in sand soils, and comments are made about installation in a variety of soils other than homogeneous deposits of clay or sand.
Abstract: Suction-installed skirted foundations, often referred to as suction caissons, are increasingly being used for a variety of offshore applications. In designing a caisson a geotechnical engineer must consider the installation process as well as the in-place performance. The purpose of this paper is to present calculation procedures for the installation of a caisson in clay. For clay sites, the caisson will often be used as an anchor, with the ratio of the skirt length (L) to the diameter (D) as high as 5. Calculation methods are presented for determining the resistance to penetration of open-ended cylindrical caisson foundations with and without the application of suction inside the caisson. Comparisons between predictions and case records are made. A companion paper describes the calculation procedure for installation in sand soils. Finally, comments are made here about installation in a variety of soils other than homogeneous deposits of clay or sand.
101 citations
"Design procedures for installation ..." refers background in this paper
...Note that this limit is much smaller than for installation in clays.(8)...
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...In fact a slightly more stringent limit on suction-assisted penetration can be established on the same basis as the ‘reverse bearing capacity’ solution used for clays.(8) Again a plastic failure could occur with flow of soil into the caisson and without further penetration....
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TL;DR: In this paper, the authors performed experiments on model suction caisson foundations, where typical cyclic loading conditions are applied and found that the response depends on the vertical load level.
Abstract: Combined loading of foundations is a fundamental problem in civil engineering, particularly in the offshore industry where harsh environmental conditions occur. Large moment and horizontal loads may be applied to the foundation as well as vertical loads. Also, as the waves pass a structure, there can be rapid changes in the loads, so that transient effects need to be considered. When designing shallow foundations, such as suction caissons, there is uncertainty in the current understanding of how the foundation responds to these loads. This paper presents experiments, performed on model suction caisson foundations, where typical cyclic loading conditions are applied. The footing is embedded in oil-saturated sand so that dimensionless drainage times are comparable with the typical offshore conditions. Most of the testing was carried out with the vertical load held constant, to mimic the structural dead weight, while realistic ''pseudorandom'' moment and horizontal cyclic loads were applied. Experiments were carried out at different vertical loads, showing that the response depends on the vertical load level. Nondimensional relationships were established which accounted for this dependency. Surprisingly, the rate of loading had little impact on the load-displacement behavior for the experiments undertaken.
100 citations
01 May 1995
85 citations
"Design procedures for installation ..." refers methods in this paper
...Figure 8 shows the predictions as given by the spreadsheet program compared with the range of field measurements as obtained on site for the four caissons and reported by Tjelta.6....
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...Figure 8 shows the predictions as given by the spreadsheet program compared with the range of field measurements as obtained on site for the four caissons and reported by Tjelta.(6)....
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