Three-dimensional numerical analysis of centrifuge experiments on a model jack-up drilling rig on sand

2009 ◽  
Vol 46 (2) ◽  
pp. 208-224 ◽  
Author(s):  
B. Bienen ◽  
M. J. Cassidy
Keyword(s):  
Soil Analysis ◽  
Shallow Foundation ◽  
Integrated Modelling ◽  
Foundation Soil ◽  
Geotechnical Centrifuge ◽  
Drilling Rig ◽  
Numerical Predictions ◽  
Current Loading ◽  
Jack Up ◽  
Current Guidelines

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.

Push-Over Response of a Jack-Up on Sand of Different Relative Densities

2009 ◽  
Author(s):  
Britta Bienen ◽  
Mark J. Cassidy ◽  
Christophe Gaudin
Keyword(s):  
Wind Waves ◽  
Scaled Model ◽  
Environmental Loading ◽  
Complex Load ◽  
Geotechnical Centrifuge ◽  
Overall Response ◽  
Load Paths ◽  
Numerical Predictions ◽  
Macro Element ◽  
Jack Up

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.

Physical modelling of the push-over capacity of a jack-up structure on sand in a geotechnical centrifuge

2009 ◽  
Vol 46 (2) ◽  
pp. 190-207 ◽  
Author(s):  
B. Bienen ◽  
M. J. Cassidy ◽  
C. Gaudin
Keyword(s):  
Wind Waves ◽  
Physical Modelling ◽  
Three Dimensions ◽  
Combined Loading ◽  
Silica Sand ◽  
Foundation Soil ◽  
Experimental Development ◽  
Dense Sand ◽  
Geotechnical Centrifuge ◽  
Jack Up

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.

Evaluation on Features of Soft Foundation Engineering and Bearing Layer of Pile in Jiaxing City

2011 ◽  
Vol 90-93 ◽  
pp. 217-221
Author(s):  
Jin Long Zhou ◽  
Qiao Li ◽  
Wei Zhong Cai
Keyword(s):  
Soil Mass ◽  
Shallow Foundation ◽  
Silty Clay ◽  
Foundation Engineering ◽  
Foundation Soil ◽  
Cone Tip Resistance ◽  
Soft Foundation ◽  
Tip Resistance ◽  
Bearing Layer

Through the investigation into composition of major shallow foundation soil mass and the correlation of mechanical indicators in this study, the regression equation of mechanical indicators of the features of local foundation soil mass and the data of in situ testing was obtained. Based on massive quantities of exploration materials, this study analyzed engineering features, distribution status, and the feasibility of silty clay to be used as the bearing layer of the pile in Layer ④2 . The analytical results showed that the silty clay with the uniform depth of over 3.5m and the cone tip resistance in static sounding of over 400MPa could be used as bearing layer of the pile. This study could provide the reference for the accurate understanding of the engineering features of soil mass, and the design and evaluation of foundation in Jiaxing City.

Predicting the overall horizontal bearing capacity of jack-up rigs using deck–foundation–soil-coupled model

2020 ◽  
pp. 147509022092590
Author(s):  
Qilin Yin ◽  
Jinjin Zhai ◽  
Sheng Dong
Keyword(s):  
Bearing Capacity ◽  
Failure Mode ◽  
Double Layer ◽  
Soft Clay ◽  
Coupled Model ◽  
Single Layer ◽  
Horizontal Load ◽  
Foundation Soil ◽  
Failure Envelopes ◽  
Jack Up

The overall bearing capacity of a jack-up rig under horizontal load is conducted using finite element models that consider the deck–foundation–soil interaction. In these models, the simplified horizontal load acts on the deck and increases until the platform loses its stability. The effects of the self-weight of the platform W and load direction α on the ultimate horizontal bearing capacity Hult are investigated, and W- Hult failure envelopes under different α conditions are obtained. Two typical seabed types, including the double-layer seabed of sand overlying soft clay and the single-layer seabed of sand, are considered. The results show that a critical self-weight Wcritical exists in the double-layer seabed. Based on Wcritical, the failure of the platform presents two different modes. When W <  Wcritical, the windward leg is pulled up, and Hult increases with the increase in W. When W >  Wcritical, the failure mode is the leeward leg or legs puncturing the bearing sand layer, and Hult decreases with the increase in W. In the single-layer seabed, the failure mode is the windward leg being pulled up, and Hult increases with the increase in W throughout the whole range. The W- Hult envelopes in these two types of seabeds are basically the same when W <  Wcritical.

Influence of Spud-Can-Soil Interaction Modeling and Parameters on the Reliability Index of Neka Drilling Jack-Up Platform

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
M. R. Emami Azadi
Keyword(s):  
Reliability Index ◽  
Clayey Soil ◽  
Interaction Model ◽  
Soil Parameters ◽  
The Caspian Sea ◽  
Foundation Soil ◽  
Soil System ◽  
Dense Sand ◽  
Interaction Modeling ◽  
Jack Up

In the present study, the influence of spud-can-soil modeling and parameters on the reliability index of jack-up platform is investigated. Neka platform is studied as a case, which is a three-leg drilling jack-up type platform located in water depth of about 91 m in the Caspian Sea region. Various spud-can-soil interaction models such as pinned, fixed-base, hyperelastic, and nonlinear elastoplastic spud-can models are applied. The soil type is varied from loose to dense sand and also from soft NC clay to very stiff OC Clay. The effect of bias and coefficient of variation (COV) of the spud-can-soil interaction modeling and also the soil parameters such as the effective interface soil friction angle and also the undrained shear strength of clayey soil are studied. The results showed that inclusion of spud-can-soil interaction may have a considerable effect on the reliability of the jack-up platform. In particular, the bias and COV of soil have shown to have more significant effect on the reliability of jack-up platform in loose sand and soft clayey type soils. It is also found that bias in strength modeling of jack-up itself has less profound effect on the reliability index of the jack-up-foundation-soil system. Importance factors of spud-can-soil modeling are found to be quite considerable. The key aspect is that the inclusion of jack-up-spud-can-soil interaction is more crucial with respect to the reliability of jack-up platform than the choice of interaction model itself.

Numerical analysis of seismically induced liquefaction in earth embankment foundations. Part I. Benchmark model

2003 ◽  
Vol 40 (4) ◽  
pp. 753-765 ◽  
Author(s):  
Ogun Aydingun ◽  
Korhan Adalier
Keyword(s):  
Experimental Data ◽  
Numerical Analysis ◽  
Analysis Procedure ◽  
Finite Element Code ◽  
Remedial Measures ◽  
Foundation Soil ◽  
Benchmark Model ◽  
Numerical Predictions ◽  
Earth Embankment ◽  
Fully Coupled

A numerical analysis has been performed for a clayey embankment founded on a liquefiable foundation soil using an effective stress based, fully coupled, finite element code called DIANA-SWANDYNE II. The results were compared with data obtained from centrifuge experiments. In Part I, the numerical method and the analysis procedure are explained. The results obtained for a series of three consecutive, increasing amplitude shaking events are presented. An attempt has been made to calibrate a benchmark model to be used in the application of different remedial measures which are discussed in Part II. The numerical predictions compared well with the experimental data and provided further insights into the dynamic behavior of embankment–foundation systems.Key words: liquefaction, numerical modeling, coupled formulation, centrifuge, embankment, earthquakes.

Innovative Ice Protection for Shallow Water Drilling: Part I — Presentation of the Concept

2006 ◽  
Author(s):  
Arne Gu¨rtner ◽  
Ove Tobias Gudmestad ◽  
Alf To̸rum ◽  
Sveinung Lo̸set
Keyword(s):  
Shallow Water ◽  
Shallow Waters ◽  
Drilling Rig ◽  
Modular Concept ◽  
Drilling Operations ◽  
Drifting Ice ◽  
Ice Impacts ◽  
Jack Up ◽  
Near Future ◽  
Ice Period

Recent discoveries of hydrocarbons in the shallow waters of the Northern Caspian Sea arise the need for intensive drilling activities to be carried out in the near future in order to explore the potentials. Experience with mobile drilling units in the seasonally ice infested waters solely originates from the current drilling campaign of the Sunkar drilling barge at Kashagan and Kalamkas. However, with increased drilling activities upcoming, innovative drilling concepts are desirable due to the objective of maintaining drilling operations during the ice period with conventional non-ice-resistant drilling platforms. Hence, this paper suggests the employment of external Shoulder Ice Barriers (SIBs) to protect a conventional jack-up drilling rig from the hazards of drifting ice in shallow water. The SIB’s design is suggested to increase the ice rubble generation at the ice facing slope and thereby provide sufficient protection from drifting ice impacts. The modular concept of the SIB makes it possible to deploy each module in a floating mode to site, whereupon they are ballasted and connected to each other, forming a sheltered position for the jack-up. Subsequent to the termination of the drilling campaign the SIB modules may be retrieved by de-ballasting and tow out, without having significant impact on the environment. This paper presents, on a technical feasible level, the concept of ice protection in shallow water by means of SIBs.

scholarly journals INVESTIGATION OF SHALLOW FOUNDATION SOIL BEARING CAPACITY AND SETTLEMENT CHARACTERISTICS OF MINNA CITY CENTRE DEVELOPMENT SITE USING PLAXIS 2D SOFTWARE AND EMPIRICAL FORMULATIONS

2017 ◽  
Vol 36 (3) ◽  
pp. 663-670
Author(s):  
AB Salahudeen ◽  
JA Sadeeq
Keyword(s):  
Soil Properties ◽  
Bearing Capacity ◽  
Average Energy ◽  
Shallow Foundations ◽  
Shallow Foundation ◽  
Analytical Models ◽  
City Centre ◽  
Foundation Soil ◽  
Development Site ◽  
Allowable Bearing Pressure

This study investigated the soil bearing capacity and foundation settlement characteristics of Minna City Centre development site using standard penetration test (SPT) data obtained from10 SPT boreholes at 0.6, 2.1 and 3.6 m depths to correlate soil properties. Evaluation of foundation bearing capacity and settlement characteristics for geotechnical preliminary design of foundations was carried out using some conventional empirical/analytical models and numerical modelling. The aim was to investigate and determine the geotechnical parameters required for adequate design of Physical structures of the proposed Minna City Centre, at Minna the capital of Niger state. The SPT N-values were corrected to the standard average energy of 60% (N60) before the soil properties were evaluated. Using the corrected N-values, allowable bearing pressure and elastic settlement of shallow foundations were predicted at 50 kN/m2 applied foundation pressure. The numerical analysis results using Plaxis 2D, a finite element code, shows the analytical/empirical methods of estimating the allowable bearing pressure and settlements of shallow foundations that provided acceptable results. Results obtained show that an average bearing capacity value of 100 – 250 kN/m2 can be used for shallow foundations with embedment of 0.6 to 3.6 m on the site.  http://dx.doi.org/10.4314/njt.v36i3.1

scholarly journals Proximate underwater soundscape of a North Sea offshore petroleum exploration jack-up drilling rig in the Dogger Bank

2020 ◽  
Vol 148 (6) ◽  
pp. 3971-3979
Author(s):  
Victoria L. G. Todd ◽  
Laura D. Williamson ◽  
Jian Jiang ◽  
Sophie E Cox ◽  
Ian B. Todd ◽  
...  
Keyword(s):  
North Sea ◽  
Petroleum Exploration ◽  
Dogger Bank ◽  
Drilling Rig ◽  
Jack Up ◽  
Offshore Petroleum
Sign in / Sign up

Export Citation Format

Share Document