Spudcan Penetration in Loose Sand Over Uniform Clay

2009 ◽  
Author(s):  
Long Yu ◽  
Yuxia Hu ◽  
Jun Liu
Keyword(s):  
Finite Element ◽  
Clay Soil ◽  
Clay Soils ◽  
Loose Sand ◽  
Finite Element Analyses ◽  
Flow Mechanisms ◽  
Soil Flow ◽  
Jack Up ◽  
Penetration Depths ◽  
Sand Plug

Punch through failures of spudcan foundations of mobile jack-up rigs have been reported every year. The potential of punch through failure of spudcan foundations on loose sand over uniform clay soils was studied numerically in the present paper. Large deformation finite element analyses were carried out to simulate the load-penetration responses of a 14m diameter spudcan during continuous penetration into this sand over clay soil. The numerical results were compared with existing centrifuge data. The critical penetration depths were derived from the load-penetration responses. The soil flow mechanisms, the shape of sand plug and the distribution of plastic points were also reported.

Numerical Study of the Combined Loading Envelope of a Skirted Spudcan Foundation

2014 ◽  
Author(s):  
Ning Cheng ◽  
Mark J. Cassidy ◽  
Yinghui Tian
Keyword(s):  
Clay Soil ◽  
Numerical Study ◽  
Failure Mechanisms ◽  
Small Strain ◽  
Offshore Structures ◽  
Combined Loading ◽  
Finite Element Analyses ◽  
Failure Envelope ◽  
Foundation Type ◽  
Jack Up

Foundations for offshore structures, such as mobile jack-up units, are subjected to large horizontal (H) and moment (M) loads in addition to changing vertical (V) loads. The use of a combined vertical, horizontal and moment (V-H-M) loading envelope to define foundation capacities has become increasingly applied in recent years. However, there is no study on the skirted spudcan, a new alternative foundation type to the conventional spudcan footing for jack-ups. In this study, the combined V-H-M yield envelope of a skirted spudcan foundation in clay soil is investigated with small strain finite element analyses using 3D modeling. The footing’s uniaxial bearing capacities and failure mechanisms are described. The failure envelope for the combined V-H-M loadings is presented. A comparison of the bearing capacities between the spudcan and skirted spudcan of various dimensions is also presented.

Effect of a Strong Middle Layer on Spudcan Penetration

2014 ◽  
Author(s):  
Wen Gao ◽  
Tom Harrup ◽  
Yuxia Hu ◽  
David White
Keyword(s):  
Bearing Capacity ◽  
Layer Thickness ◽  
Soft Clay ◽  
Soil Layer ◽  
Strength Ratio ◽  
Top Soil ◽  
Flow Mechanisms ◽  
Soil Flow ◽  
Jack Up ◽  
Peak Resistance

The rapid penetration of one or more of the foundations of a mobile jack-up rig into the seabed is an ongoing major problem in the offshore industry, with the potential to cause major damage to the structure and endangering any personnel on board. A recent example is the jack-up drilling rig Perro Negro 6 incident happened near the mouth of the Congo river in July 2013 with one of the rig’s crew of 103 reported missing and six others injured. This uncontrollable displacement is due to a form of failure known as punch through failure and commonly occurs on stratified seabed profiles. It has been reported that unexpected punch-through accidents have resulted in both rig damage and lost drilling time at a rate of 1 incident per annum with consequential costs estimated at between US$1 and US$10 million [1]. This paper presents the bearing capacity profiles and associated soil flow mechanisms of a common spudcan foundation penetrating into a three layer soft-stiff-soft clay soil through the use of large deformation finite element (LDFE) analysis. The Remeshing and Interpolation with Small Strain (RITSS) [2, 3] technique was implemented in the software package AFENA [4] to conduct the LDFE analysis. Both soil layer thickness and soil layer strength ratios were varied to study their effect on the spudcan penetration responses. The LDFE results of spudcan penetration into the soft-stiff-soft clay soils were calibrated by existing centrifuge test data. A parametric study was then conducted to study the bearing capacity responses and soil flow mechanisms during spudcan large penetrations by varying the soil layer strength ratio and relative layer thickness to the diameter of spudcan. It was found that there were three types of bearing responses during continuous penetration of spudcan: (a) when the top soft layer is relatively thin, the spudcan bearing response was similar to that of two layer soils with stiff over soft clays; (b) when the top soil layer thickness is medium, a peak resistance is observed when spudcan penetrates into the middle stiff layer followed by reduction; (c) when the soil layer is thick, the peak resistance occurs when spudcan gets into the bottom soft soil layer. The critical thickness of top soil layer is a function of soil strength ratio and middle stiff soil layer thickness. The bearing response types were also corresponding to the soil cavity formations during spudcan initial penetration.

Large-deformation finite element analysis of pipe penetration and large-amplitude lateral displacement

2010 ◽  
Vol 47 (8) ◽  
pp. 842-856 ◽  
Author(s):  
Dong Wang ◽  
David J. White ◽  
Mark F. Randolph
Keyword(s):  
Finite Element ◽  
Large Deformation ◽  
Lateral Displacement ◽  
Soil Surface ◽  
Element Analysis ◽  
Rate Dependent ◽  
Soil Failure ◽  
Lateral Resistance ◽  
Flow Mechanisms ◽  
Soil Flow

Seabed pipelines must be designed to accommodate thermal expansion — which is commonly achieved through controlled lateral buckling — and to resist damage from submarine slides. In both cases, the pipe moves laterally by a significant distance and the overall pipeline response is strongly influenced by the lateral pipe–soil resistance. Here, the process of pipe penetration and lateral displacement is investigated using a large-deformation finite element method, with a softening rate–dependent soil model being incorporated. The calculated soil flow mechanisms, pipe resistances, and trajectories agree well with plasticity solutions and centrifuge test data. It was found that the lateral resistance is strongly influenced by soil heave during penetration and the berm formed ahead of the pipe during lateral displacement. For “light” pipes, the pipe rises to the soil surface and the soil failure mechanism involves sliding at the base of the berm. In contrast, “heavy” pipes dive downwards and a deep shearing zone is mobilized, expanding with continuing lateral movement. The different responses are reconciled by defining an “effective embedment” that includes the effect of the soil berm or wall ahead of the pipe. The relationship between normalized lateral resistance and effective embedment is well fitted using a power law.

Bearing Behaviour of Spudcan Foundation on Uniform Clay During Deep Penetration

2004 ◽  
Author(s):  
M. S. Hossain ◽  
Y. Hu ◽  
M. F. Randolph
Keyword(s):  
Bearing Capacity ◽  
Failure Mechanisms ◽  
Model Tests ◽  
Deep Penetration ◽  
Centrifuge Tests ◽  
Soil Failure ◽  
Flow Mechanisms ◽  
Soil Flow ◽  
Piv Analysis ◽  
Penetration Depths

In order to design a safe spudcan foundation, it is important to predict its bearing behaviour accurately based on the corresponding soil failure mechanisms. Thus, the performance of spudcan foundation, during deep penetration into uniform soil, is investigated physically and numerically. In physical testing, a series of centrifuge tests are carried out in a drum centrifuge. The half-spudcan model tests with subsequent Particle Image Velocimetry (PIV) analysis are conducted to reveal soil failure mechanisms during spudcan penetration. And the full spudcan model tests are conducted to investigate the bearing capacity of spudcan. In numerical simulation, FE analyses are performed considering smooth and rough soilspudcan interface. From the physical tests and numerical analyses, it is observed that the cavity is formed above the spudcan as it is penetrating into uniform clay. At certain penetration depths, the soil underneath the spudcan starts to flow back on top of the spudcan, which leads the spudcan to be embedded with further penetration. Soil flow mechanisms, at various penetration depths, play a key role in footing bearing response. And the ultimate undrained bearing capacity factor of Nc = 10.5 (smooth) and 12 (rough) are obtained at deep penetration.

scholarly journals Unidirectional consolidation of clay soils and flocculated suspensions

2021 ◽  
Author(s):  
Stephen Peppin
Keyword(s):  
Diffusion Equation ◽  
Mine Tailings ◽  
Clay Soil ◽  
Convective Diffusion ◽  
Clay Soils ◽  
Stress Profile ◽  
Soil Flow ◽  
Flocculated Suspension ◽  
Convective Diffusion Equation ◽  
Very High

A model of the unidirectional consolidation of a clay soil or flocculated suspension between a series of parallel drains is developed. A convective-diffusion equation for the pore pressure is derived, and an equal-strain approximation leads to an expression for the average effective stress profile between the drains. The solution depends on a Peclet number quantifying the ratio of the bulk soil flow rate to the rate of consolidation. By adjusting the number, height and spacing of the drains, very high rates of dewatering can be achieved. A potential application of the method to the rapid dewatering of mine tailings is described.

NUMERICAL MODELING OF STRESSES IN THE MASSIF OF A CLAY SOIL UNDER THE FOUNDATION

2019 ◽  
Vol 4 (1) ◽  
pp. 312-319
Author(s):  
D.V. Khristich ◽  
◽  
Y.V. Astapov ◽  
E.V. Artyukh ◽  
M.Y. Sokolova ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Numerical Modeling ◽  
Numerical Model ◽  
Nonlinear Model ◽  
Isotropic Material ◽  
Clay Soil ◽  
Clay Soils ◽  
Geometrically Nonlinear ◽  
The Finite Element Method

The results of the calculation of the base of the foundation, obtained using the previously proposed physically and geometrically nonlinear model of a hyperelastic isotropic material that can be applied to the description of strains of clay soils, are considered. A numerical model of the interaction of the foundation foot with the base is constructed using the finite element method. The obtained results allow to refine the known analytical calculations carried out within the framework of linear elasticity.

Design of flexure revolute joint based on compliance and stiffness ellipsoids

2021 ◽  
pp. 095441002110169
Author(s):  
Jing Zhang ◽  
Hong-wei Guo ◽  
Juan Wu ◽  
Zi-ming Kou ◽  
Anders Eriksson
Keyword(s):  
Finite Element ◽  
Single Point ◽  
Synthesis Method ◽  
Nonlinear Finite Element ◽  
Finite Element Analyses ◽  
Rotational Stiffness ◽  
Rotational Angle ◽  
Parameterized Model ◽  
Flexure Joints ◽  
Translational Stiffness

In view of the problems of low accuracy, small rotational angle, and large impact caused by flexure joints during the deployment process, an integrated flexure revolute (FR) joint for folding mechanisms was designed. The design was based on the method of compliance and stiffness ellipsoids, using a compliant dyad building block as its flexible unit. Using the single-point synthesis method, the parameterized model of the flexible unit was established to achieve a reasonable allocation of flexibility in different directions. Based on the single-parameter error analysis, two error models were established to evaluate the designed flexure joint. The rotational stiffness, the translational stiffness, and the maximum rotational angle of the joints were analyzed by nonlinear finite element analyses. The rotational angle of one joint can reach 25.5° in one direction. The rotational angle of the series FR joint can achieve 50° in one direction. Experiments on single and series flexure joints were carried out to verify the correctness of the design and analysis of the flexure joint.

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