Probabilistic bearing capacity analysis of jack-up structures

1992 ◽  
Vol 29 (4) ◽  
pp. 580-588 ◽  
Author(s):  
Farrokh Nadim ◽  
Suzanne Lacasse
Keyword(s):  
Bearing Capacity ◽  
System Reliability ◽  
A Priori ◽  
Probabilistic Approach ◽  
Environmental Loads ◽  
Interaction Diagram ◽  
Soil Foundation ◽  
Analysis System ◽  
Layered Clay ◽  
Jack Up

A probabilistic approach to the analysis of the bearing capacity of jack-up spud can foundations is described. The procedure includes three steps: (i) a priori deterministic and probabilistic calculation of bearing capacity interaction diagram for the soil foundation under each leg of the jack up, (ii) updating of the interaction diagram from the measured vertical preloading values, and (iii) one-leg component and multileg system reliability analyses of the structure under environmental loads. The probabilistic formulation is based on the first- and second-order reliability approximations. An example calculation of a jack-up spud can structure on a layered clay profile is made to illustrate the procedure. Key words : jack up, bearing capacity, probabilistic analysis, system reliability.

scholarly journals Probabilistic assessment of pile capacity based on CPTu probing including random pile foundation depth

2018 ◽  
Vol 196 ◽  
pp. 01058 ◽  
Author(s):  
Marek Wyjadłowski ◽  
Irena Bagińska ◽  
Jakub Reiner
Keyword(s):  
Bearing Capacity ◽  
Objective Assessment ◽  
Probabilistic Approach ◽  
Measurement Data ◽  
Direct Methods ◽  
Side Surface ◽  
Design Stage ◽  
Direct Data ◽  
Design Calculations ◽  
The Impact

The modern recognition of subsoil with the use of CPTu static probes allows to obtain detailed information necessary for the designing. Registered basic two quantities, i.e. cone resistance qc and friction on the sleeve fs, often become direct data, which allow to estimate bearing capacity of the base and the side surface of the pile. Direct methods use similarity of the pile work and piezo-cone work during the examination. An important design stage is the appropriate development of measurement data prior to the commencement of the procedure of determining the pile bearing capacity. Algorithms generated on the basis of empirical experiments are often applied with the simultaneous use of test loads. The probabilistic approach is also significant, because it enables objective assessment of the reliability level of performed design calculations. This work contains an analysis of the impact on the estimated bearing capacity and reliability of a pile of variable random depth of the pile base. It also includes the determination of probabilities of obtaining the assumed safety index for the designed solution at random foundation depth.

Improved Calculation Method of Soil Bearing Capacity of Jack-Up Rig Based on Field Simulation Experiment

2018 ◽  
Author(s):  
Qishuai Yin ◽  
Jin Yang ◽  
Nanding Hu ◽  
Shanshan Shi ◽  
Yongqi Ma ◽  
...  
Keyword(s):  
Bearing Capacity ◽  
Calculation Method ◽  
Simulation Experiment ◽  
Field Simulation ◽  
Jack Up

Study on the Stability and Structural Optimization of Self-Elevating Platform Pile Foundation

2012 ◽  
Vol 203 ◽  
pp. 325-328
Author(s):  
Xin Jie Chu
Keyword(s):  
Stress Concentration ◽  
Structural Optimization ◽  
Bearing Capacity ◽  
Pile Foundation ◽  
Reference Value ◽  
The Self ◽  
Foundation Design ◽  
Operation Stability ◽  
Soil Foundation ◽  
The Stability

This paper analyzes the stability and structural optimization of self-elevating platform pile foundation, preliminarily discusses the method of analyzing the bearing capacity of the layer soil foundation, and establishes the numerical computation models for the whole platform, pile, pile shoe, etc. Besides, through these analyses, the pile structure is optimized, and the stress concentration in the joint between pile and pile shoe is reduced. Also, this study is of reference value for the analysis on the self-elevating platform pile foundation design and the platform operation stability.

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.

scholarly journals Vertical bearing capacity of a pile-liquefiable sandy soil foundation under horizontal seismic force

PLoS ONE ◽  
2020 ◽  
Vol 15 (3) ◽  
pp. e0229532 ◽  
Author(s):  
Huang Zhanfang ◽  
Bai Xiaohong ◽  
Yin Chao ◽  
Wang Yanping
Keyword(s):  
Bearing Capacity ◽  
Sandy Soil ◽  
Seismic Force ◽  
Vertical Bearing ◽  
Soil Foundation ◽  
Vertical Bearing Capacity

Effect of Spudcan Sliding on Structure and RPD of Jack-Up Platform

2020 ◽  
Author(s):  
Jie Gao ◽  
Menglan Duan
Keyword(s):  
Bearing Capacity ◽  
Phase Difference ◽  
Critical Distance ◽  
Offshore Platforms ◽  
Offshore Drilling ◽  
Symmetrical Structure ◽  
Sea Area ◽  
Jack Up ◽  
The Relationship ◽  
Sliding Distance

Abstract In the same sea area, with the increase of the number of operations, the situation of jack up offshore drilling platform carrying out secondary or multiple Jack-up leg embedment operations in the vicinity, or even in the same location will increase year by year. Therefore, the operation of jack up offshore drilling platform makes the sea area “step on the footprints” The problems become more and more frequent, and have a significant impact on the operation safety of offshore platforms. During the “footprint” process of jack-up drilling platform, the spudcan will slide transversely along the direction of Jack-up leg pits to varying degrees. If the sliding distance is too large, the leg or platform structure will be damaged. Based on the symmetrical structure of the three-leg jack-up offshore platform, the bow and the starboard spudcan are slided along x-axis at different angles, respectively. According to the critical bearing capacity of the platform legs, the critical distance of spudcans sliding is calculated. Finally, the relationship between the sliding distance of spudcan in different directions and RPD (Rack phase difference) is obtained by monitoring the RPD value of legs. It provides meaningful guidance for platform designers and operators.

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.

scholarly journals Analysis of Basic Failure Scenarios of a Truss Tower in a Probabilistic Approach

2019 ◽  
Vol 9 (13) ◽  
pp. 2662 ◽  
Author(s):  
Wojciech Mochocki ◽  
Urszula Radoń
Keyword(s):  
Standard Deviation ◽  
Reliability Analysis ◽  
System Reliability ◽  
Probabilistic Approach ◽  
Random Variable ◽  
Structure Reliability ◽  
System Reliability Analysis ◽  
Steel Truss ◽  
Buckling Coefficient ◽  
The Impact

This paper concerns the system reliability analysis of steel truss towers. Due to failures of towers, the assessment of their reliability seems to be a very important problem. In the analysis, two cases are examined: when the buckling coefficient is a deterministic value and when it is a random variable. The impact of failures of single elements on the structure reliability was investigated. Calculations of the standard deviation of the capacity and reliability indexes were made using author-developed programs in the Mathematica environment.

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