ORCID Profile
0000-0002-0342-0698
Current Organisations
University of Adelaide
,
University of Western Australia
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Civil Engineering | Civil Geotechnical Engineering | Civil engineering | Geotechnical Engineering | Civil geotechnical engineering
Expanding Knowledge in Engineering | Wind Energy | Oil and gas | Oil and Gas Exploration | Wave Energy |
Publisher: American Society of Civil Engineers (ASCE)
Date: 05-2020
Publisher: Elsevier BV
Date: 12-2013
Publisher: American Society of Civil Engineers (ASCE)
Date: 07-2014
Publisher: Thomas Telford Ltd.
Date: 09-05-2023
Abstract: Suction bucket jackets are increasingly being used to support bottom-fixed offshore wind turbines. It is generally assumed that contact between the underside of the bucket lid and the seabed is mandatory to safeguard against additional settlement. Lid contact is usually ensured by underwater grout injection, albeit this has a significant impact on the duration and costs of installation. Although grouting is routine, there are limited available data regarding the benefits of ensuring contact between the lid and the soil. This paper presents data from centrifuge tests of completely and partially installed buckets in dense sand subjected to vertical cyclic loading to investigate the role of lid contact. Lid contact was shown to have a discernible effect on displacement accumulation when buckets were loaded beyond the drained skirt capacity in compression. Under these conditions, settlement of a completely installed bucket was limited by lid contact with the soil plug, while partially installed buckets experienced continuous settlement, as expected. The physical evidence indicates complex load transfer mechanisms that are influenced significantly by the drainage conditions. Hence, an understanding of the soil drainage characteristics at a particular site would provide value when evaluating the requirement for under-lid grouting.
Publisher: American Society of Civil Engineers (ASCE)
Date: 07-2017
Publisher: American Society of Civil Engineers (ASCE)
Date: 11-2018
Publisher: Elsevier BV
Date: 04-2015
Publisher: Elsevier BV
Date: 05-2021
Publisher: Elsevier BV
Date: 03-2015
Publisher: Elsevier BV
Date: 08-2019
DOI: 10.1016/J.AAP.2019.04.021
Abstract: The purpose of this study was to develop a serious injury risk prediction algorithm for pedestrians, using data from the South Australian Traffic Accident Reporting System. Two algorithms were developed to estimate serious injury risk, using a logistic regression analysis of 6,868 vehicle-pedestrian crashes extracted from TARS data. In this study, an optimal model based on the best combination of risk factors according to the Akaike information criterion (AIC) was developed. Additionally, a secondary GPS model using only crash site characteristics that can be derived from GPS coordinates from the crash scene was also developed. The optimal model is based on site and environmental conditions that could be derived from GPS data (posted speed limit, distance from crash site, natural lighting conditions, road geometry, road horizontal alignment and road vertical alignment) as well as pedestrian age/gender, driver age/gender and vehicle model year. The second model only included features that could be derived from GPS data. The optimal model was reasonable in accuracy and gave an under-triage rate of 10% when the injury threshold was set to 15%, with a corresponding over-triage rate of around 60%. The GPS model, despite not being as accurate as the optimal model may be adequate in the absence of all the risk factors required for the optimal model, requiring an injury threshold of 20% to give an under-triage rate of 10%, with the corresponding over-triage rate being around 70%. Both models can potentially be used for serious injury risk prediction (SIRP) for pedestrians involved in a collision with a vehicle.
Publisher: Canadian Science Publishing
Date: 08-2014
Abstract: Skirted mudmats are commonly used to support offshore infrastructure. However, these may not be able to provide sufficient capacity to notably withstand the lateral loads applied by jumpers and connectors. The concept of hybrid foundation system was therefore proposed to enhance the capacity in a targeted fashion, through addition of internal suction caisson compartments. This paper presents a numerical investigation into the undrained bearing capacity of a rectangular-shaped hybrid foundation with two caisson units. Uniaxial capacities under vertical, horizontal, and moment loading are reported, but the focus lies on the horizontal–moment planes due to the anticipated low vertical load on the foundation. Detailed discussion highlights the contribution of the internal caisson compartments to the significant increases in horizontal capacity compared to a simple rectangular skirted mat through changes in the failure mechanism. This results not only in changes in size, but also in shape, of the capacity envelope. The study was extended to more general horizontal–moment loading conditions, where the shape of the capacity envelope was found to remain approximately constant. This applies to the hybrid foundation and the rectangular skirted mat in the homogeneous soil considered here. An expression is proposed that provides a slightly conservative approximation of the capacity envelope under combined horizontal and moment loading from any direction.
Publisher: American Society of Mechanical Engineers
Date: 17-06-2018
Abstract: During the operational phase, the spudcan foundations of a mobile jack-up rig are subjected to combined vertical, horizontal and moment loading. Although previous research has indicated a substantial increase in vertical bearing capacity when a spudcan penetrates through a soft clay layer towards a sand layer, the response of spudcan foundations subjected to combined loadings in such stratification has yet to be understood. This study investigates the effect of the underlying stronger sand layer on the undrained VHM capacity of a spudcan foundation using three-dimensional small-strain finite element analysis. Results show the significant increase in vertical and moment capacity, whereas the horizontal capacity is minimally affected. The soil failure mechanisms are identified and changes in the size and shape of failure envelopes, accounting for the sand layer underneath, are quantified. An analytical expression is proposed to predict the combined capacity of a spudcan foundation in clay overlying sand.
Publisher: Thomas Telford Ltd.
Date: 11-2018
Abstract: Suction caissons have been used for numerous oil and gas installations and are increasingly considered as a foundation solution for offshore wind turbines (OWTs). There can be significant differences between the two offshore energy applications in the load paths and magnitudes, soil type and caisson aspect ratio (skirt length to diameter). This paper investigates the response of suction caissons in dense sand to a range of cyclic vertical loading histories relevant to a jacket-supported OWT, with an emphasis on cyclic tensile loading. The findings are based on a series of experiments performed in a centrifuge, such that soil stresses reflect those in the prototype. The caisson was installed using suction at enhanced gravity, followed by cyclic loading and then caisson extraction. The installation and extraction results are discussed in a companion paper. This paper focuses on the caisson load–displacement response under vertical cyclic loading. The centrifuge experimental results reinforce findings from previous work, add insights into the load transfer mechanisms and provide confidence in their applicability to the prototype, both qualitatively and quantitatively. The results highlight the complexity of the caisson response, particularly under tensile loading, with the influences of average load, cyclic load litude and drainage discussed in detail.
Publisher: CRC Press
Date: 14-05-2015
DOI: 10.1201/B18442-196
Publisher: Thomas Telford Ltd.
Date: 11-2018
Abstract: Suction caissons are a promising foundation concept for supporting offshore wind turbines. Compared to applications in the oil and gas industry, where most practical experience exists, significant differences arise in terms of load paths and magnitudes, soil type and caisson aspect ratio (skirt length to diameter). In a set of two companion papers, this contribution investigates the response of suction caissons in dense sand through a series of centrifuge experiments. The caisson was installed using suction, followed by sequences of cyclic loading and then extraction, all steps completed continuously in-flight. This first paper discusses installation, limiting capacities and drainage, whereas the second paper focuses on vertical cyclic loading into tension. The work demonstrates that suction caisson installation behaviour is well described by existing calculation methods. Tests performed at different installation rates demonstrate that careful assessment of the pumping rate is needed to ensure successful installation, with low pumping rates resulting in premature refusal. In the centrifuge tests, full skirt penetration was achieved without apparent loosening of the soil plug. The limiting capacity in tension, measured during the testing at both fast and slow uplift rates, was also well described by existing calculation methods.
Publisher: Elsevier BV
Date: 05-2014
Publisher: Elsevier BV
Date: 02-2022
Publisher: Thomas Telford Ltd.
Date: 12-2011
DOI: 10.1680/GEOT.8.P.152
Abstract: Retrieval of jack-up rigs at the end of their operations is common practice in the offshore industry, notably to move the rigs to another drilling location. In some cases the process is difficult, time consuming and costly, because the high extraction resistance on the jack-up's spudcan footings can exceed the capacity of the rig to pull. This is particularly the case in soft clay, where significant suction is developed at the spudcan invert. The main option available to operators to ease the spudcan extraction resistance is to use a jetting system at the spudcan invert to attempt to break the suction generated. However, there is a general consensus within the offshore industry that jetting systems, under their current configurations, have a limited efficiency. Centrifuge experiments have been performed at the University of Western Australia in order to understand the mechanisms taking place during jetting extraction, and to provide recommendations to optimise the jetting performance. A reduced-scale spudcan model simulating a 17·11 m diameter prototype spudcan with jets has been tested at 200 times the acceleration of Earth's gravity (known as 200g). It was extracted from penetrations of up to 1·5 diameters in normally consolidated clay at variable extraction rates and variable jetting flow rates. Measurements of the generated suction and the total extraction resistance after a preloading period have provided insight into the extraction mechanisms with jetting. The study has demonstrated that jetting can lead to significant reduction in extraction resistance, provided that the extraction rate is fast enough to ensure undrained extraction, and that a sufficiently high flow rate is applied with respect to the extraction rate.
Publisher: Thomas Telford Ltd.
Date: 2021
Abstract: Monopiles used as foundations for offshore wind turbines can be installed using different methods including jacking, vibratory driving and impact driving. Significant research efforts have been dedicated to the characterisation of monopile−soil interaction under lateral loading, mainly using p–y curves. There has also been extensive research in quantifying the effect of different installation methods on the axial response using numerical modelling and physical modelling techniques. Little attention has been paid to the effect of the installation method on the subsequent lateral response of a monopile under the in-service condition. In this paper, a purpose-designed apparatus is described that allows in-flight installation using different installation methods followed directly by lateral loading without stopping the centrifuge and thus retaining the installation-induced stress state. Test results from three lateral loading tests are discussed, with the piles either jacked at 1g and Ng or impact driven at Ng into a dry medium dense sand, allowing the effect of the installation method on the initial stiffness and ultimate capacity to be examined. The successfully conducted tests illustrate the capabilities of the new apparatus for centrifuge testing of laterally loaded driven piles.
Publisher: Elsevier BV
Date: 10-2014
Publisher: Informa UK Limited
Date: 10-02-2016
DOI: 10.1080/15389588.2015.1060556
Abstract: The aim of this study was to estimate the potential effectiveness of an in-vehicle automatic collision notification (ACN) system in reducing all road crash fatalities in South Australia (SA). For the years 2008 to 2009, traffic accident reporting system (TARS) data, emergency medical services (EMS) road crash dispatch data, and coroner's reports were matched and examined. This was done to initially determine the extent to which there were differences between the reported time of a fatal road crash in the mass crash data and the time EMS were notified and dispatched. In the subset of fatal crashes where there was a delay, injuries detailed by a forensic pathologist in in idual coroner's reports were examined to determine the likelihood of survival had there not been a delay in emergency medical assistance. In 25% (N = 53) of fatalities in SA in the period 2008 to 2009, there was a delay in the notification of the crash event, and hence dispatch of EMS, that exceeded 10 min. In the 2-year crash period, 5 people were likely to have survived through more prompt crash notification enabling quicker emergency medical assistance. Additionally, 3 people potentially would have survived if surgical intervention (or emergency medical assistance to sustain life until surgery) occurred more promptly. The minimum effectiveness rate of an ACN system in SA with full deployment is likely to be in the range of 2.4 to 3.8% of all road crash fatalities involving all vehicle types and all vulnerable road users (pedestrians, cyclists, and motorcyclists) from 2008 to 2009. Considering only passenger vehicle occupants, the benefit is likely to be 2.6 to 4.6%. These fatality reductions could only have been achieved through earlier notification of each crash and their location to enable a quicker medical response. This might be achievable through a fully deployed in-vehicle ACN system.
Publisher: Elsevier BV
Date: 12-2016
Publisher: American Society of Mechanical Engineers
Date: 03-08-2020
Abstract: Offshore wind is increasingly utilised as a renewable energy source. A growing number of bottom fixed wind turbines installed offshore are supported by suction caisson foundations. The suction-assisted installation remains a source of uncertainty towards the in-service performance due to the unknown post-installation soil plug state. Cone penetration tests within the suction caisson can help to improve the reliability. Therefore, cone penetration tests were employed in centrifuge tests to investigate the plug state in a previously installed suction caisson. However, the performance of a cone penetration test in a small-scale experiment is connected to uncertainties: A relatively large diameter device is required to conduct the cone penetration test — especially in a centrifuge test. Different finite element models are developed in order to visualise and investigate a cone penetration test inside a suction caisson. The numerical analysis results are validated through the back-calculation of centrifuge cone penetration tests. The results of the simulated cone penetration tests inside a suction caisson are evaluated and compared to the centrifuge experiments. This investigation reinforces the scope of the centrifuge experiments and emphasises a considerable effect of the pressure transferral through the caisson lid in the soil plug state. Hence, the results of this study reduce existing uncertainties regarding possible suction installation effects on the in-service performance of caisson foundations.
Publisher: Thomas Telford Ltd.
Date: 03-2013
Abstract: Foundations, especially those for offshore structures, are often subjected to combined vertical (V), horizontal (H) and moment (M) loading conditions. Experimental studies of foundation behaviour under complex combined loading are normally limited to laboratory testing at unit gravity. Only a few studies have been performed at enhanced gravities in a geotechnical centrifuge owing to difficulties in the design of actuators with independent control of movements in three degrees-of-freedom. In this paper, a combined VHM loading apparatus, with independent control of the in-plane vertical, horizontal and rotational movements is reported. Test results that measure the size and shape of the combined VHM yield surface of a spudcan footing of a mobile jack-up platform in soft clay illustrate the capabilities of the new apparatus.
Publisher: American Society of Mechanical Engineers
Date: 09-06-2013
Abstract: Extracting the spudcan footings of mobile jack-up rigs from the seabed at the end of their operations is challenging when the capacity of the rig to pull is low compared to the extraction resistance of the spudcans. This is particularly the case when the spudcans are deeply embedded in soft clay and subjected to long periods of operation that place load on the foundations and allow for consolidation to occur in the soil. A technical solution used by the offshore industry to overcome spudcan extraction resistance is to use a water jetting system that ejects pressurised water through nozzles on the spudcan face. The aim of using water jetting with nozzles located at the top of the spudcan is to reduce extraction resistance through fracturing and softening of the upper soil. However, the efficiencies of such systems are not known to offshore jack-up operators. Top jetting efficiency is therefore addressed in this paper, which reports a series of physical experiments on jetted spudcan extraction conducted in a geotechnical beam centrifuge. The efficiency of water jetting is reported for extraction from depths of up to three diameters in normally consolidated clay, for different jetting flow rates. The excess pore pressure and maximum breakout force measured reveal insights into the extraction process with top jetting. The maximum extraction resistance is shown to be unaffected by top jetting but relates to the suction developed at the spudcan base, which can be reduced by jetting at the spudcan base (Bienen et al. 2009 Gaudin et al. 2011). Top jetting can, however, reduce the extraction resistance post breakout as indicated by the experimental results of this study.
Publisher: Thomas Telford Ltd.
Date: 11-2014
Abstract: Spudcan foundations of mobile jack-up rigs are penetrated into the seabed under seawater ballast preload, which is shed prior to rig operations commencing. During pauses in the installation process and during operation, soil beneath the spudcan foundations stiffens and strengthens due to consolidation. On the application of further loading or during spudcan extraction, this causes increased resistance, which in extremis can result in punch-though type failure. This note reports results from a series of experiments with particle image velocimetry measurements that were performed in a drum centrifuge to facilitate observation of the effects of a load-hold period on the soil movements around a model spudcan during subsequent further loading. The results show that the dimensionless load-hold period dominates the enhancement in the penetration resistance, due to significantly more soil being mobilised following a long load-hold period. These observations might be useful to (a) predict the enhancement in bearing capacity factor due to a load-hold period during installation or operation and (b) predict the footing extraction resistance during jack-up re-deployment.
Publisher: Elsevier BV
Date: 04-2021
Publisher: Thomas Telford Ltd.
Date: 12-01-2023
Abstract: The ring penetrometer is a shallow rotational penetrometer that has been developed to characterise the mechanical behaviour of surficial marine sediments. The strain-rate dependency of soils is crucial to the design of a wide range of offshore geotechnical infrastructure founded in the upper layers of the seabed (e.g. pipelines, cables and shallow foundations). This paper explores the potential application of a ring penetrometer test to measure the strain-rate dependency of the interface friction generated in soft soils at low stresses. Large-deformation numerical models of the test are developed using an elastoplastic constitutive model and a viscoplastic variant with strain softening. Using parameters representative of kaolin clay and a calcareous silt from an offshore location, the numerical analyses demonstrate a clear and measurable influence of both the viscous and strain-softening behaviours on the device–soil interface friction. These simulations were used to design suitable experimental protocols for multi-rate ring penetrometer tests, the results of which yielded a strain-rate dependency of 9–16% and 22–26% per log cycle in the kaolin clay and calcareous silt, respectively, which compare favourably with measurements derived from T-bar twitch experiments. Finally, models are presented that can be applied in the interpretation of varying-rate ring penetrometer test data for application in practice.
Publisher: American Society of Civil Engineers (ASCE)
Date: 11-2020
Publisher: American Society of Civil Engineers (ASCE)
Date: 08-2021
Publisher: Thomas Telford Ltd.
Date: 11-2016
Abstract: Jack-up installation is typically discontinuous with seawater ballast being taken on and shed again periodically to elevate the hull out of the ocean as the spudcan footings penetrate the soil. Any pauses in the footing penetration provide the opportunity for consolidation to occur in sufficiently permeable cohesive soils. The undrained shear strength underneath the spudcan is increased during consolidation, which enhances the penetration resistance within a limited extent immediately after the consolidation. This phenomenon has been explored in a limited number of centrifuge tests, but cannot be reproduced using conventional finite-element methods. An effective stress large-deformation finite-element approach based on periodic mesh regeneration is employed to capture the entire process of ‘penetration–consolidation–penetration’, with the modified Cam-clay model being incorporated to represent the behaviour of normally consolidated kaolin clays. The numerical model established is verified by comparison with two series of centrifuge tests before exploring the influence of key parameters, including consolidation depth, consolidation duration, coefficient of consolidations, anisotropy of permeability and loads held during consolidation. The normalised consolidation duration is identified as the dominant factor that affects the post-consolidation peak in penetration resistance. A simple method is proposed to estimate the post-consolidation penetration resistance.
Publisher: Elsevier BV
Date: 07-2019
Publisher: Thomas Telford Ltd.
Date: 12-2014
Abstract: Suction caissons are currently considered as an alternative to monopile foundations for met masts and offshore wind turbines. This paper presents the results of a series of centrifuge tests conducted on cyclically loaded suction caissons in very dense dry sand. Two representative caisson foundations were modelled at a 1∶200 scale in a geotechnical centrifuge and were subjected to a number of different cyclic loading regimes, for up to 12 000 cycles, both of which add to previous data sets available in the literature. During each test, changes in stiffness, the accumulation of rotation and settlement of the system were measured. It was found that the rotational caisson stiffness increased logarithmically with the number of loading cycles, but to a much lower extent than previously reported for monopiles. Similarly the accumulation of rotation was also observed to increase with number of cycles and was well described using a power relationship. An aggregation of rotation was also observed during two-way tests and is believed to be caused by the initial loading cycles that create a differential stiffness within the local soil. Predictions were then made as to the behaviour of a prototype structure based upon the observed test results and established influence parameters.
Publisher: Thomas Telford Ltd.
Date: 06-2007
Publisher: Elsevier BV
Date: 05-2012
Publisher: Vilnius Gediminas Technical University
Date: 24-09-2016
Abstract: Open steel pipe piles are used for various applications in costal engineering and port structures and they are becoming increasingly more important for offshore structures. A plug formed during the installation of open steel pipe piles has an influence on the installation process of the steel pipe pile as well as on the final bearing behaviour and the pile resistance. Forming of the plug depends on different influences, e.g. the pile diameter, the soil conditions and the installation method. To obtain a better understanding of the formation of the plug and its consequences several experimental small-scale tests, experimental field tests and numerical simulations have been performed. But so far this phenomenon is not completely investigated yet. At the beginning of this paper a structured overview about the characterization of the plug as well as soil mechanical processes during the pile installation in non-cohesive soil are provided. Then, the results of a centrifuge study are shown. The focus of this paper is the numerical simulation of the installation process of impact and vibratory driven piles in non-cohesive soil to investigate the effect of plugging with regard to different installation methods. Centrifuge experimental results are utilized to validate the numerical model, which can provide detailed insights into the physical processes occurring in the soil but are difficult to measure in experiments. The numerical analyses hence illustrate zones of densification/loosening, which highlight the differences resulting from the installation methods.
Publisher: Elsevier BV
Date: 09-2016
Publisher: Elsevier BV
Date: 05-2011
Publisher: American Society of Civil Engineers (ASCE)
Date: 12-2013
Publisher: Thomas Telford Ltd.
Date: 08-2006
DOI: 10.1680/GEOT.2006.56.6.367
Abstract: Laboratory studies of the response of shallow foundations have previously considered only planar loading. This paper describes experimental work carried out using a loading device that applies general loading onto model shallow foundations. The loading, involving all six degrees of freedom [vertical (V), horizontal (H 2 , H 3 ), torsion (Q) and overturning moment (M 2 , M 3 )], has been applied to a 150 mm diameter circular flat rough foundation on a loose dry silica sand. Aspects of the loading rig design are briefly described, but the main focus is the presentation of the experimental results. These provide evidence for the generalisation of existing work-hardening plasticity models from planar loading to general loading conditions. This evidence is used to extend an existing numerical model to the six-degree-of-freedom case, and the simulation results are compared with the experimental results.
Publisher: Canadian Science Publishing
Date: 02-2009
DOI: 10.1139/T08-115
Abstract: Jack-up drilling rigs are usually founded on three shallow footings. Under wind, wave, and current loading offshore, the footings of these tall multi-footing systems transfer large moment loads in addition to self-weight, horizontal load, and even torsion to the underlying soil. To be able to deploy a jack-up safely at a particular offshore site, the unit’s capacity to withstand a 50 year return period storm is required to be checked in accordance with current guidelines (Site specific assessment of mobile jack-up units, The Society of Naval Architects & Marine Engineers). As the overall system behaviour is influenced significantly by the footing restraint, models that account for the complex nonlinear foundation–soil interaction behaviour are required to be integrated with the structural and loading models. Displacement-hardening plasticity theory has been suggested as an appropriate framework to formulate force-resultant models to predict shallow foundation behaviour. Recent research has extended such a model to account for six degree-of-freedom loading of circular footings on sand, allowing integrated structure–soil analysis in three dimensions. This paper discusses “class A” numerical predictions of experiments on a model jack-up in a geotechnical centrifuge, using the integrated modelling approach, and critically evaluates the predictive performance. The numerical simulations are shown to represent a significant improvement compared with the method outlined in the current guidelines.
Publisher: International Society of Offshore and Polar Engineers
Date: 06-2021
Publisher: Canadian Science Publishing
Date: 12-2009
DOI: 10.1139/T08-114
Abstract: Offshore jack-up drilling rigs are subjected to loading from wind, waves, and current in addition to their self-weight. This applies combined loading in all six degrees-of-freedom in space on the footings. Although the foundation–soil interaction is crucial to the overall response of a jack-up structure, current state-of-the-art models to predict jack-up footing behaviour, developed using data from single footing experiments, have not been validated for such multi-footing systems under general combined loading. This paper introduces the experimental development of a three-legged model jack-up and loading apparatus designed to investigate the rig’s response — in particular the footing load paths — under combined loading in three dimensions. Push-over experiments were performed in a geotechnical beam centrifuge on silica sand. Experimental results of two tests on dense sand are discussed, highlighting differences in response and mode of failure depending on the loading direction of the jack-up. The importance of three-dimensional modelling is also stressed by experimentally demonstrating that the symmetric load case is not necessarily conservative.
Publisher: Elsevier BV
Date: 09-2012
Publisher: SAGE Publications
Date: 02-2006
DOI: 10.1260/136943306776232873
Abstract: As mobile jack-up drilling rigs continue to move into deeper waters and harsher environments there is an increased need to understand their behaviour under storm loading conditions. To improve the assessment of jack-ups for a specific site it has become necessary to analyse these units in three dimensions with models that appropriately reflect the physical processes occurring. This motivated the development of SOS_3D, a computer program that takes a balanced approach to all three interrelated components of the structure, the foundations and the environmental loading in three dimensions. Geometrical structural nonlinearities are incorporated using a path-dependent formulation of beam-column theory to specify an incremental stiffness matrix. A six-degree of freedom strain-hardening plasticity model simulates the complex interaction between the soil and the spudcan foundations. Advanced formulations for environmental loads are also implemented. In this paper, the results of three-dimensional jack-up analyses (i) are compared with two-dimensional simulations (ii) highlight the importance of dynamic assessments and (iii) describe the influence of wave spatial dispersion and loading direction on the response.
Publisher: Elsevier BV
Date: 12-2018
Publisher: Elsevier BV
Date: 05-2021
Publisher: Society of Underwater Technology
Date: 2017
DOI: 10.3723/OSIG17.524
Publisher: American Society of Civil Engineers (ASCE)
Date: 03-2012
Publisher: Thomas Telford Ltd.
Date: 03-2015
Abstract: This paper reports a set of centrifuge tests to investigate the increase in bearing capacity of a skirted circular foundation that results from preloading with consolidation. Results are compared with coupled numerical analyses using the modified Cam Clay model. Fundamental mechanisms are revealed from the stress paths followed during preloading and consolidation at the element level, accounting for both the change in mean normal effective stress and in the hardening parameter. A formulation is developed to predict the gain in bearing capacity as a function of the level of preloading applied on the foundation and the degree of consolidation achieved. The formulation provides good agreement with the centrifuge results.
Publisher: CRC Press
Date: 18-12-2013
DOI: 10.1201/B16200-94
Publisher: Elsevier BV
Date: 07-2022
Publisher: Elsevier BV
Date: 04-2006
Publisher: Elsevier BV
Date: 08-2022
Publisher: Thomas Telford Ltd.
Date: 10-2021
Abstract: Most offshore wind turbines (OWTs) are supported by large-diameter monopiles, installed by impact driving. OWTs are dynamically sensitive structures, with a narrow design range for the eigenfrequency. Fatigue and serviceability limit states can be critical in design, so the foundation stiffness plays an important role. The pile installation process results in changes to the soil state, investigated here through large-deformation numerical analyses using the coupled Eulerian–Lagrangian approach with a hypoplastic constitutive relation to model the sand. The soil state is then mapped to a small-strain model to evaluate the effect of the installation process on the lateral response. Complementary physical modelling results from monopile installation and lateral load testing in a centrifuge provide confidence in the numerical model. Analyses for two different sands highlight commonalities and differences. Comparison with results featuring wished-in-place or jacked installation illustrates the effect of changes in the soil state on the lateral response. The results characterise the changes in soil state and allow quantification of their effects as impact driving tends to produce a stiffer lateral response, with the expected variations due to pile dimensions and sand relative density. Further research will provide insights into the role of pore fluid response during impact driving and investigate vibro-driven piles.
Publisher: Thomas Telford Ltd.
Date: 03-2017
Abstract: During offshore operations, the spudcan footings of mobile jack-ups are subjected to combined vertical, horizontal and moment (V, H, M) loading as a result of environmental wind, wave and currents acting on the platform. In seabeds of single-layer clay or sand it is now common to express spudcan capacity directly as a surface of allowable VHM loads. Although layered soil stratigraphies with sand overlying clay are encountered in the field, the effect of soil layering on the VHM surface is not well understood. Defining the VHM capacity of a spudcan when it has pushed a layer of sand into the underlying clay is the concern of this paper. Results from a series of centrifuge tests demonstrate that the general framework used in single layers is equally applicable in layered soils. Increases in vertical and moment capacity, compared with clay only soil, are similar in magnitude and arise from the sand plug being pushed into the clay layer by the penetrating spudcan. The most significant increase, however, was found in the horizontal capacity.
Publisher: Thomas Telford Ltd.
Date: 05-2020
Abstract: Suction buckets represent a viable solution as foundations for offshore wind turbines. Installation in sand is relatively straightforward, albeit with limited understanding of the resulting changes in soil state. This paper describes an experimental methodology that allows for visualisation and quantification of changes in soil state during suction bucket installation, validated in sand. Insights obtained from particle image velocimetry analyses, performed on images of a half-bucket installing against a Perspex window taken in a geotechnical centrifuge are discussed. Compared with the initial self-weight penetration, the deformation mechanism governing the suction-assisted phase shows a preference for the soil below the skirt tips to move inwards and upwards inside the bucket. The installation process is responsible for changes in relative density and permeability within the bucket. In these experiments, the majority of the soil plug heave can be attributed to the soil displaced inwards by the advancing skirts, with a minor contribution caused by dilation. The confidence in the experimental methodology provided through the results of suction bucket installation in sand discussed herein now enables suction bucket installation in more complex seabeds to be investigated.
Publisher: Elsevier BV
Date: 07-2009
Publisher: American Society of Mechanical Engineers
Date: 08-06-2014
Abstract: Offshore monopiles are usually designed using the p-y method for cyclic loading. While the method works for static loading, it was not developed for high numbers of cycles. Since the turbines are highly sensitive towards tilting, cyclic loading must be considered. The static results should therefore be combined with results from cyclic model tests with a high number of cycles to account for the accumulation of displacement or rotation during the lifetime of these structures. These model tests can underestimate the accumulation, however, as it has recently been shown that a change of loading direction can increase the accumulation considerably. These results have been verified using small scale modeling and centrifuge testing. The results from modeling the full problem of a laterally loaded pile are compared here with results from cyclic simple shear tests with a change of shearing direction during the cyclic loading. For these tests, a newly developed apparatus is used. This allows further insight into the question how a soil can “retain a memory” of its loading history.
Publisher: Canadian Science Publishing
Date: 06-2023
Abstract: Many offshore geotechnical problems—such as cyclic T-bar penetration and lateral buckling of pipelines—are affected by the tendency of fine-grained soils to strain-soften due to remoulding. Careful calibration of the constitutive model parameters that control strain softening is essential for accurate simulation of these processes. This is usually achieved by matching constitutive model response with standard element test data, which implicitly assumes that homogeneous stress/strain fields exist within the s le. However, popular element test protocols (e.g., triaxial, simple shear) cannot apply sufficient deformation—at least as measured at the boundaries—to achieve fully remoulded conditions. This work explores the potential to determine strain-softening parameters experimentally, directly from image-based full-field deformation measurements and external loading data. Artificial data generated from finite element simulations of biaxial compression and T-bar penetration tests, using a non-locally regularised strain-softening constitutive model based on Modified Cam Clay, are then used to demonstrate the potential of the proposed technique. The results demonstrate significant potential for the application of the technique to identify constitutive parameters from full-field measurements even when polluted with modest measurement noise.
Publisher: Elsevier BV
Date: 2018
Publisher: Canadian Science Publishing
Date: 10-2014
Abstract: Foundation piles supporting offshore structures experience cyclic lateral loading arising from waves and wind, which are not typically uni-directional over the lifetime of the structure. This paper presents results from centrifuge experiments in sand, representing a large diameter prototype tested at stress levels similar to the field subjected to cyclic lateral loading from varying directions. The results demonstrate increased deformation accumulation due to the changing loading direction, compared to the uni-directional case. Displacement accumulation is not limited to the main loading direction but includes transverse movement as well. Similar trends were observed in small-scale 1g modelling that allowed a larger number of load cycles to be applied. The centrifuge test results provide confidence of the applicability of the findings to the prototype. Current methods that neglect the effect of variation of the loading direction will provide predictions of displacement accumulation of piles that are un-conservative. Therefore, a simple approach is proposed here to estimate the augmentation of displacement accumulation due to variation in loading direction compared to the uni-directional case.
Publisher: Thomas Telford Ltd.
Date: 2020
Abstract: Static load tests (SLTs) are rarely performed on offshore piles, instead relying on dynamic load tests (DLTs). Evaluation techniques for DLTs were developed originally for solid piles, and caution is needed in applying the techniques directly to open-ended piles, particularly for the large-diameter monopiles used for offshore wind turbines. Centrifuge tests are reported here, investigating the influence of pile installation method and sand relative density for pairs of DLTs and SLTs. The piles were successfully driven to penetration of 3–4·6 diameters, which was much deeper than proved possible to jack the piles. Due to limited hammer energy, loads mobilised during the DLTs were less than 25% of the corresponding SLT values. The soil resistance mobilised at limited displacements was lowest for wished-in-place piles, and also for DLTs conducted on shallowly embedded jacked piles. For driven piles, the DLT and SLT results were relatively consistent, with surprisingly similar values for piles driven into loose and dense sand despite significant differences in cone resistance. Given the potential for low mobilisation of soil resistance in DLTs, care is needed when using DLTs for evaluating the static axial pile capacity of open-ended piles of low length-to-diameter ratio.
Publisher: Thomas Telford Ltd.
Date: 08-2018
Abstract: Suction caissons are being increasingly considered as an alternative foundation type to monopiles for offshore wind turbines. Single caisson foundations (or monopods) for offshore wind turbines are subjected to lateral cyclic loading from wind and waves acting on the structure. Recent studies have considered the response of suction caissons to such loading in sand, but have generally been limited to a few thousand cycles, whereas offshore wind turbines will generally experience millions of loading cycles over their lifetime. This paper presents the results from a programme of caisson tests in sand, clay and sand over clay seabed profiles, where each test involved about one million cycles of lateral load. The capacity and rotation response is shown to approach that measured in the sand seabed when the sand–clay interface is located at or beneath the caisson skirt tip. In contrast to previously published studies in sand, one-way cyclic loading is the most onerous loading symmetry for a layered seabed with a sand thickness equal to half the skirt length. However, the rotation for this seabed profile is essentially identical if the load is sustained or cyclic, provided that the cyclic loading remains one way. Lateral cyclic loading was seen to increase caisson capacity by up to 30% – with a bias towards clay-dominated seabed profiles – and stiffness by up to 50%. Such stiffness increases need to be considered when assessing the system dynamics for the offshore wind turbine, as demonstrated in the paper.
Publisher: CRC Press
Date: 11-07-2018
Publisher: ASMEDC
Date: 2009
Abstract: On location offshore, jack-up structures are subject to environmental loading from wind, waves and current in addition to self-weight. Over the operational period of the jack-up, the environmental loading on a given site may not be unidirectional along the jack-up’s ‘axis of symmetry’ but may act from different directions and/or be non-collinear (i.e. wind acting from a different direction than waves and current), resulting in complex load paths at the spudcan footings. This paper discusses load paths obtained from experiments on a scaled model jack-up for two different horizontal loading directions and illustrate the implications of spudcan load paths for the overall response of a jack-up to failure. Similar tests were performed at two different relative sand densities, allowing the influence of relative density on jack-up behavior to be investigated. Similitude to the prototype was achieved by conducting the experiments in a geotechnical centrifuge at 200g. The paper concludes with numerical predictions of the experimentally measured response, using a macro-element to model the soil-spudcan interaction coupled to a structural finite element program. The footing macro-element has been developed based on plasticity theory and single footing experiments, but its ability to predict the respective load paths of each of the spudcans in a multi-footing system is demonstrated here. The paper further provides the experimentally measured jack-up push-over capacity and numerical predictions in the context of recommendations of current guidelines. This highlights the requirement of nonlinear elasto-plastic modelling of the load-displacement behavior of the jack-up foundations in order to predict the overall response of the system.
Publisher: Thomas Telford Ltd.
Date: 03-2018
Abstract: This paper evaluates the effect of analysis parameter choices on the stability and efficiency of modelling cone penetration into sand. This very large deformation quasi-static boundary-value problem is modelled here using the arbitrary Lagrangian–Eulerian adaptive mesh technique available within Abaqus/Explicit. The sand response is captured using a hypoplastic constitutive model. It is demonstrated that many choices of analysis parameters lead to spurious results, some of which show clear instability, while other combinations show reasonable stability but over-estimation of the cone resistance. The accuracy of the numerical solution is shown through comparison against centrifuge experimental data for two different relative densities of the sand.
Publisher: CRC Press
Date: 18-12-2013
DOI: 10.1201/B16200-61
Publisher: OTC
Date: 30-04-2012
DOI: 10.4043/23002-MS
Abstract: Installation of offshore platforms in carbonate soils is challenging, asevidenced by numerous incidents and accidents. The installation process ofmobile jack-up drilling rigs is no exception. The prevalence of these soils insome oil and gas producing regions, such as offshore Australia, necessitatesthorough understanding of the foundation behaviour as well as predictionmethods capable of capturing the salient features. This contribution thereforedevelops a method to predict footing penetration in uncemented carbonate sand. The method directly correlates the cone penetrometer tip resistance with thefooting load-penetration, i.e. without the requirement of selection of afriction angle. The development is based on centrifuge model experiments aswell as large deformation finite element analyses incorporating an advancedconstitutive model for the soil. The direct use of in situ site investigationdata increases the confidence in load-penetration predictions for rig moves inthese challenging soil conditions, while at the same time reducing the timerequired to obtain a prediction. Jack-up rig installation in carbonate soils is challenging, with Erbrich (2005)recounting details of two ex le cases in the Bass Straight, Australia. Despite the complex soil behaviour, accurate prediction of the spudcaninstallation response is required. The prediction of load-penetration curves prior to a jack-up rig move istypically performed as a series of bearing capacity predictions at discretedepths. The use of the bearing capacity approach requires knowledge of theoperative friction angle. Unfortunately, the approach is rather sensitive, witha small uncertainty in the friction angle translating to a relatively largeuncertainty in the predicted bearing capacity. Further, based on experience ofoffshore jack-up installations, the SNAME (2008) guidelines recommend thefriction angle determined in the laboratory to be artificially reduced toaccount for " scale effects" (SNAME 2008). The above applies to silica sands, where the general shear failure mechanism isobserved and penetration typically remains shallow. Carbonate soils areacknowledged to pose further challenges, with predictions expected to be lessaccurate than in silica sand (SNAME 2008, ISO 2011). This is due tocharacteristics such as crushablibity of particles, high in-situ void ratios, and high compressibility compared to siliceous sand, resulting from differencesin mineral composition and particle shape. Despite high friction anglesmeasured in laboratory tests, the penetration resistance in uncementedcarbonate sand is typically low, resulting in relatively large footingpenetrations. SNAME (2008) therefore recommends a larger reduction of thefriction angle as compared to silica sand, to artificially account for thedifference in response. However, footing penetration in uncemented carbonate sand has been shown to begoverned by the punching shear mechanism (Finnie and Randolph 1994a, Yamamotoet al. 2009), rendering the bearing capacity approach inappropriate as it isbased on the general shear failure mechanism. This is reflected in ISO (2011), which proceed to recommend an alternative approach based on the concept of a‘bearing modulus’ (Randolph et al. 1993, Finnie and Randolph 1994a). Yamamotoet al. (2008, 2009) pursued the concept of a bearing modulus further for theprediction of the bearing response of shallow footings on uncemented carbonatesand.
Publisher: CRC Press
Date: 04-09-2014
DOI: 10.1201/B17435-152
Publisher: American Society of Civil Engineers (ASCE)
Date: 05-2021
Publisher: CRC Press
Date: 18-12-2013
DOI: 10.1201/B16200-66
Publisher: Thomas Telford Ltd.
Date: 06-2013
Abstract: Soil plugging in open-ended piles not only leads to an increase in compressive bearing capacity but also influences pile driving resistance. Numerous factors affect the tendency for soil plugging, for ex le pile geometry, penetration depth and installation method. In this study, the influence of the cross-sectional geometry of different open-ended piles (tubular, U- and sheet-piles) on the internal and external stress state at the pile toe is investigated. The underlying data were obtained from tests of pile installation (pile jacking) into dry silica sand conducted using a geotechnical beam centrifuge. During pile penetration the internal and external horizontal stresses at the pile toe were recorded to obtain the stress state inside the open-ended piles. The results are discussed with respect to the influence of the pile's geometrical properties (diameter of tubular piles, base width of U-piles and opening angle of sheet-piles) on the plugging tendency or the pile driving resistance. To conclude, a simple analytical approach based on equilibrium analyses is presented to predict the pile's bearing capacity.
Publisher: Thomas Telford Ltd.
Date: 06-2020
Abstract: Wind and wave action on offshore wind turbines causes irregular cyclic loading on the foundation that can lead to rotation accumulation of the structure. Such loading is generally considered in design using ‘counting methods’ that decompose the time history of irregular cyclic loads into a series of cyclic load parcels of uniform litude. These parcels are ordered in magnitude, with the rotation due to previous cyclic load parcels accounted for by including an equivalent number of cycles of the current cyclic load parcel. Hence, this superposition approach adopts Miner's rule, as the accumulated rotation is considered to be independent of the ordering of the cyclic load parcels. This paper examines the validity of this assumption for moment cyclic loading of suction caissons in sand, through a series of model tests involving both constant and varying litude cyclic loads, with each test involving at least one million cycles. In the varying litude cyclic tests, the accumulated rotation approximately doubled when the load ordering changed from ascending to descending. This is considered to be due to changes in grain contacts and beneficial densification effects from lower litude cyclic loads that are absent when the cyclic loads are arranged in descending order.
Publisher: Thomas Telford Ltd.
Date: 12-2020
Abstract: Foundations are commonly situated on layered soil deposits, where the elastic stiffnesses may differ from values calculated using solutions for single-layer elastic media. This paper reports elastic stiffness coefficients for a rigid circular footing subjected to vertical, horizontal and moment loads bearing on a clay layer above a stiffer sand layer. Three-dimensional finite-element analyses considered various shear modulus ratios of top to bottom soil layers, as well as the thickness of the top layer below the footing. The elastic stiffnesses are presented as dimensionless coefficients and are bounded by published solutions for circular footings on a single-layer elastic half-space. Analytical expressions that capture the numerical results well are also proposed. The results can be used in the assessment of the elastic response of circular foundations on clay overlying sand, with applications in soil–structure interaction analyses of offshore structures among others.
Publisher: American Society of Civil Engineers (ASCE)
Date: 11-2022
Publisher: Springer International Publishing
Date: 2021
Publisher: American Society of Civil Engineers (ASCE)
Date: 03-2012
Publisher: Thomas Telford Ltd.
Date: 10-2019
Abstract: This technical note considers experimental data on the long-term response of a suction caisson in sand and sand over clay to lateral cyclic loading. Installation of the caisson under suction in a geotechnical centrifuge provides insight into the contribution of this installation process, as well as the effects that soil drainage and consolidation in the clay layer have on the accumulated caisson rotation and change in stiffness. The tests focused on sand over clay, and considered variations in the cyclic load magnitude and symmetry. One-way cyclic loading in sand over clay is seen to result in higher rotation than two-way loading, which contrasts with findings from previous studies in sand. Excess pore pressure dissipation in the clay layer leads to strength increases that stabilise caisson rotation and increase stiffness. The rate of accumulation in caisson rotation is observed to be the same from centrifuge and single gravity tests, while the initial rotation differs with stress level, drainage regime, loading magnitude, soil profile and installation method. The centrifuge tests are considered collectively with equivalent single gravity tests to form a basis for predicting the long-term response of a monopod suction caisson.
Publisher: Wiley
Date: 29-09-2017
Publisher: Elsevier BV
Date: 10-2011
Publisher: American Society of Civil Engineers (ASCE)
Date: 05-2021
Publisher: American Society of Civil Engineers (ASCE)
Date: 09-2015
Publisher: Canadian Science Publishing
Date: 06-2014
Abstract: A plasticity model for predicting the load displacement behaviour of a typical spudcan foundation for offshore jack-up platforms under combined vertical, horizontal, and moment loading in soft clay is presented. Results from geotechnical centrifuge experiments of a spudcan embedded vertically to 0.7, 1.0, and 1.45 footing diameters are described. Augmented with finite element results, these centrifuge experiments are used to evaluate the plasticity model components. As a result of soil backflow on top of the spudcan, enhanced combined bearing capacity was measured and this is reflected in increased yield surface size. A tensile vertical load capacity is also incorporated. The excellent predictive capabilities of the model are demonstrated by retrospectively simulating a selection of centrifuge tests.
Publisher: OTC
Date: 30-04-2012
DOI: 10.4043/23049-MS
Abstract: With the development of the offshore oil and gas industry, mobile jack-updrilling platforms are increasingly required to operate in deeper waters andharsher environments. The improvement of the jack-up site-specific assessmentpractice is vital for safely meeting this demand. In soft clayey seabeds, thespudcan foundations of the jack-up platform penetrate deeply into the soil, andcomplete or partial backflow occurs. In recent years, a number of studies haveinvestigated the performance of spudcan foundations in soft clay to improve therelevant recommendations in the industry guideline published by SNAME. In thispaper, a brief review of recent research in this area is first provided. Then,a force-resultant model that is suitable for performing integratedsoil-structure analysis is proposed. An ex le of the application of thismodel is finally provided, and important comparisons with the SNAME model aredrawn. Although they were originally designed and built for shallow waters, mobilejack-up platforms are now more broadly used for offshore drilling activities. Due to the development of the offshore oil and gas industry, the demand forjack-ups to operate in deeper waters and harsher environments has increased, requiring improved site-specific assessment practices for both economical andsafety considerations. In many offshore areas, such as the Gulf of Mexico, theseabed consists of soft clayey soil, which often features an increasingundrained shear strength profile with a small intercept at the seabed surface. Jack-up installation in such soil conditions often results in significantfoundation embedment embedments up to several spudcan diameters are common. The SNAME T& PB 5-5A guidelines are often used by the industry to performsite-specific assessments for the suitability of jack-up platform (SNAME,2008). The recommendations in the SNAME guidelines, however, do not reflect themechanisms of a deeply embedded spudcan in soft clay, but they are derived fromthe observed behavior of shallowly embedded foundations. Conservatism in theSNAME guidelines exists and in practice this can result in an unfavorablesite-specific assessment for a jack-up platform. This paper will brieflyhighlight some recent studies on the behavior of spudcans in soft clay andcompare these to the SNAME guidelines. Then, a plasticity force-resultantfooting model appropriate for spudcans in soft clay is proposed. Ex lejack-up analyses with the proposed new model are provided, highlighting thedifferences in prediction with this new model.
Publisher: American Society of Mechanical Engineers
Date: 07-2012
Abstract: Prediction of the bearing behavior of vertical loaded shallow foundations is typically done using the classical bearing capacity approach. This approach is very sensitive to the friction angle assumed in the calculation. A conservative estimate of the bearing capacity is required for most applications, hence uncertainties in the friction angle may be absorbed by the safety factor applied. Spudcans are used to found mobile jack-up platforms in the oil and gas industry as well as in the offshore wind energy industry. Contrary to the classical approach, the bearing capacity of spudcans has to be predicted accurately. Spudcans are penetrated into the seabed and a continuous bearing failure proceeds until the target capacity is met. A Coupled Eulerian-Lagrangian (CEL) approach is used to simulate the penetration process of spudcans into silica sand. The sand is modeled using a hypoplastic constitutive model to capture the influence of the void ratio and stress state for ex le. A parametric study of foundation diameter and enclosed cone angle is presented. The numerical model is validated against results from centrifuge experiments of flat and conical circular footings penetrating into silica sand. A first empirical approach to estimate the bearing capacity depending on the diameter and enclosed cone angle is given for silica sand.
Publisher: Elsevier BV
Date: 06-2013
Publisher: Inderscience Publishers
Date: 2003
Publisher: Elsevier BV
Date: 11-2020
Publisher: ASME International
Date: 12-02-2016
DOI: 10.1115/1.4032157
Abstract: Self-elevating mobile jack-up units have been employed in offshore exploration and development in shallow waters at depths of up to approximately 150 m. Jack-ups are designed to move to a new site after operations are completed. The spudcan footings, which can be embedded up to three diameters deep in soft soil, must therefore be extracted by jacking down the hull into the water and then floating it beyond the neutral draft. This provides the maximum pull-out force to overcome the soil resistance to the jack-ups, but this force may not be sufficient. Problematic cases of this offshore are reported to take up to 10 weeks to extract, a costly exercise for the industry. A method sometimes used offshore is to cycle the spudcans vertically in an attempt to free them. This can be achieved by pushing and pulling the leg by leaving the hull afloat in the water and allowing the impact of small litude waves on the hull to generate cyclic loads on the spudcan. This paper reports a series of centrifuge tests investigating the ability to extract a spudcan under regular and irregular cyclic loading. Spudcan extraction tests were performed from a depth of three spudcan diameters in normally consolidated clay in a geotechnical beam centrifuge. The results demonstrate that successful extraction is dependent on the combination of mean pull-out load and the litude of the cycling. It is also shown that insufficient tensile static loads and prolonged small cyclic loads result in the dissipation of the negative excess pore pressure at the spudcan invert caused by the buoyancy of the hull in excess of neutral draft. It results in consolidation of soil and changes in the shear strength of the soil and consequently either extraction of the spudcan after a long period of time or unsuccessful leg extraction.
Publisher: Elsevier BV
Date: 06-2017
Publisher: Elsevier BV
Date: 11-2015
Publisher: American Society of Mechanical Engineers
Date: 25-06-2017
Abstract: In this paper the installation procedure of suction caissons is investigated by means of coupled seepage large deformation analysis performed with finite element methods. The modelling techniques employed to enable simulations of the penetration of a caisson into the soil under offshore conditions, i. e. several tens of meters below the water level. The numerical model includes a u-p-formulation, which is used to calculate the excess pore pressures and effective stresses from the total stresses. The Coupled-Eulerian-Lagrangian (CEL) approach available in conjunction with the Abaqus/Explicit solver is used. The calculation results are compared to centrifuge tests that were carried out recently at the Centre for Offshore Foundation Systems (COFS). This sheds light on the potential and the limitations of the presented numerical techniques. This paper concludes with a brief discussion of alternative numerical approaches that could be capable of the simulation of caisson installation.
Publisher: Thomas Telford Ltd.
Date: 04-2023
Abstract: A macro-element model for predicting the load–displacement behaviour of a spudcan foundation in clay overlying sand when subjected to combined vertical, horizontal and moment loading is introduced. Observations from detailed drum centrifuge tests that measured the effect of the underlying sand layer on the foundation behaviour are combined with finite-element results and theoretical developments to derive the components of the model. The yield surface defined by the centrifuge test results suggests that as the spudcan nears the underlying sand layer, the absolute horizontal capacity remains relatively constant, while the vertical and moment capacities increase at approximately the same normalised rate. The model is demonstrated to accurately predict foundation behaviour by retrospectively simulating the experimental results. This macro-element model has the advantage that it can be integrated into the structural analyses of jack-up platforms required for site-specific assessments.
Start Date: 07-2009
End Date: 12-2012
Amount: $175,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 01-2011
End Date: 01-2015
Amount: $330,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 03-2020
End Date: 12-2023
Amount: $300,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 11-2018
End Date: 03-2023
Amount: $395,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2023
End Date: 12-2025
Amount: $594,700.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2019
End Date: 06-2022
Amount: $335,000.00
Funder: Australian Research Council
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