Large Deformation FE Analyses of Cone Penetration in Single Layer Non-Homogeneous and Three-Layer Soft-Stiff-Soft Clays

2014 ◽  
Author(s):  
Hongliang Ma ◽  
Mi Zhou ◽  
Yuxia Hu ◽  
Muhammad Shazzad Hossain
Keyword(s):  
Bearing Capacity ◽  
Large Deformation ◽  
Single Layer ◽  
Offshore Structures ◽  
Capacity Factor ◽  
Cone Penetration ◽  
Soft Clays ◽  
Flow Mechanisms ◽  
Soil Flow ◽  
Bearing Capacity Factor

Continuous profiles from in-situ penetrometer tests are now identified as essential for site specific soil investigation as part of designing offshore structures in deep and ultradeep waters and in highly layered seabed conditions. This paper describes the results from large deformation FE (LDFE) analysis undertaken to provide insight into the behavior of cone penetrometer penetrating through single layer non-homogeneous clays and three-layer uniform soft-stiff-soft clays. For the smooth cone penetration in non-homogeneous clays, the soil strength non-homogeneity factor was shown to have insignificant effect on the cone bearing capacity factor. However, for the rough cone, the bearing capacity factor in non-homogeneous clay was about 10∼12% lower than that in uniform clay. Bearing capacity factors for smooth and rough cones were also similar for non-homogeneous clay. For cone penetration in stratified soft-stiff-soft clays, a minimum layer thickness of 20 diameters was required to mobilise the full resistance of the stiff layer. The corresponding soil flow mechanisms are also discussed linking directly to the profile of penetration resistance.

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.

Bearing capacity factor, N γ , for unsaturated soils by ZEL method

2010 ◽  
Vol 5 (3) ◽  
pp. 177-188 ◽  
Author(s):  
M. Jahanandish ◽  
G. Habibagahi ◽  
M. Veiskarami
Keyword(s):  
Bearing Capacity ◽  
Unsaturated Soils ◽  
Capacity Factor ◽  
Bearing Capacity Factor

scholarly journals Computation of Bearing Capacity Factor N-Prandtl's Mechanism

2003 ◽  
Vol 43 (3) ◽  
pp. 1-10 ◽  
Author(s):  
D.M. Dewaikar ◽  
B.G. Mohapatra
Keyword(s):  
Bearing Capacity ◽  
Capacity Factor ◽  
Bearing Capacity Factor

FEA-Based Stability Analysis of Mudmats: Coupled Soil-Structure-Flowline Interaction Model

2013 ◽  
Author(s):  
Basel Abdalla ◽  
F. Steven Wang ◽  
M. Kabir Hossain
Keyword(s):  
Bearing Capacity ◽  
Factor Of Safety ◽  
Interaction Model ◽  
Complex Loading ◽  
Capacity Factor ◽  
Classical Approach ◽  
Soil System ◽  
Sliding Mechanism ◽  
Assessment Approach ◽  
Bearing Capacity Factor

The traditional method of foundation stability assessment for subsea structures is to calculate the bearing capacity factor of safety using classical approach given in the API-RP-2A/2GEO. This classical approach can be overly conservative for foundations under complex loading conditions (e.g., multiple interacting loads). A typical example is pipeline end manifold or flowline sled, which can be subject to self-weight, structure-soil interaction, and multiple interface loads from flowline and jumpers under operational condition. A more rigorous 3D-FEA based assessment approach is developed in this paper to achieve more accurate bearing capacity estimates for a flowline sled supported by mudmat. This fully combined global model comprises the structure (with sliding mechanism), soil foundation, jumpers, and flowline as realistically as possible so as to capture the more accurate interactions among the different parts of whole sled-soil system. The use of such advanced numerical modeling has proven to improve the mudmat bearing capacity factor of safety.

Model Test Research of Surcharge Contribution to Ground Bearing Capacity

2013 ◽  
Vol 353-356 ◽  
pp. 815-818
Author(s):  
Le Yi Chen
Keyword(s):  
Bearing Capacity ◽  
Failure Mode ◽  
Model Test ◽  
Shear Failure ◽  
Theoretical Solution ◽  
Capacity Factor ◽  
Ground Failure ◽  
Capacity Model ◽  
Capacity Calculation ◽  
Bearing Capacity Factor

To investigate the influence of surcharge on bearing capacity, model tests were performed. In the tests, 5 kPa and 10 kPa surcharge was applied on silt respectively. The bearing capacity factor Nq is smaller than theoretical solution, and is only of 60.3% and 80.5% of theoretical solution. Model test show that the ground failure mode is not general shear failure mode in condition of ground under surcharge. In bearing capacity calculation, if bearing capacity factor theoretical solution which is from general shear failure mode is applied, the result will be overestimate.

Effect of stress level on the bearing capacity factor, N γ , by the ZEL method

2010 ◽  
Vol 14 (5) ◽  
pp. 709-723 ◽  
Author(s):  
M. Jahanandish ◽  
M. Veiskarami ◽  
A. Ghahramani
Keyword(s):  
Bearing Capacity ◽  
Stress Level ◽  
Capacity Factor ◽  
Bearing Capacity Factor
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