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.

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

The response of the time-term method to simulated crustal structures

1979 ◽  
Vol 69 (5) ◽  
pp. 1455-1473
Author(s):  
D. N. Whitcombe ◽  
P. K. H. Maguire
Keyword(s):  
Velocity Structure ◽  
Seismic Refraction ◽  
Critical Distance ◽  
Structural Variations ◽  
Data Set ◽  
Term Model ◽  
Time Term ◽  
Seismic Refraction Data ◽  
Relationship Of ◽  
The Relationship

abstract The time-term method of interpreting seismic refraction data is analyzed to examine inadequacies in the chosen time-term model by relating observational errors to the solution variance. The results obtained from data that has been simulated for various structures are investigated. This is done quantitatively for simple structures and semi-quantitatively for more complex cases. Velocity and topographic variations of the refractor are considered as signals having dominant wavelengths. It is found that the response of the time-term method to these structural variations depends on the relationship of the structural wavelength to the dimensions of the experiment and the critical distance. For all but the simplest structures, the standard error estimates that can be obtained from a time-term solution are likely to be completely inadequate as estimates of the true error. It is demonstrated that if the refractor is anything other than uniform, the effects of a complicated velocity structure may be absorbed into the time terms. Similarly it is argued that in situations in which the refractor is not horizontal, erroneous values for complex velocity coefficients (e.g., gradient, anisotropy, etc.) can be obtained if these coefficients are included in the chosen time-term model. Finally, it is indicated that reduced travel times can be used in a way that removes the “stirring pot” aspect of time-term analysis, and to determine if a data set is suitable for examination by the time-term method.

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 PENGEBORAN LEPAS PANTAI

2012 ◽  
Vol 16 (3) ◽  
pp. 113
Author(s):  
Budi Utomo
Keyword(s):  
Reinforced Concrete ◽  
Crude Oil ◽  
Oil Wells ◽  
Bridge Structure ◽  
Offshore Drilling ◽  
Drilling Equipment ◽  
Key Word ◽  
Jack Up ◽  
Structure Plate

Budi Utomo, in this paper explain that offshore drilling carried out to obtain crude oil through the oil wells. The means that must exist in the operation of offshore drilling is a bridge structure (plate form) as a place to put the drilling equipment. Known two kinds of platforms, that is platforms permanent (fixed) which stands on the feet of reinforced concrete, and the bridge is not fixed like swamp barges, drilling ship (floaters) and jack-up rig. Jack up rig is one of the offshore rigs that have the ability to elevation in accordance with a sea depth of drilling. Drilling equipment is a range of equipment that is prepared in such a way, so that such a drill rod, and all this equipment has a hole inside that allows for fluid or mud circulation.   Key word: Drilling equipment

scholarly journals Load Bearing Capacity Calculation of the System “Reinforced Concrete Beam – Deformable Base” under Torsion with Bending

2019 ◽  
Vol 97 ◽  
pp. 04059 ◽  
Author(s):  
Alexey Dem’yanov ◽  
Vladymir Kolchunov ◽  
Igor Iakovenko ◽  
Anastasiya Kozarez
Keyword(s):  
Reinforced Concrete ◽  
Bearing Capacity ◽  
Cross Sections ◽  
Concrete Beam ◽  
Equations Of State ◽  
Reinforced Concrete Beam ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Deformable Base ◽  
The Relationship

It is presented the formulation and solution of the load bearing capacity of statically indeterminable systems “reinforced concrete beam – deformable base” by spatial cross-sections under force and deformation effects. The solution of problem is currently practically absent in general form. It has been established the relationship between stresses and strains of compressed concrete and tensile reinforcement in the form of diagrams. The properties of the base model connections are described based on a variable rigidity coefficient. It is constructed a system of n equations in the form of the initial parameters method with using the modules of the force (strain) action vector. The equations of state are the dependences that establish the relationship between displacements which are acting on the beam with load. Constants of integration are determined by recurrent formulas. It makes possible to obtain the method of initial parameters in the expanded form and, consequently, the method of displacements for calculating statically indefinable systems. The values of the effort obtained could be used to determine the curvature and rigidity of the sections in this way. It is necessary not to set the vector modulusP, the deformation is set in any section (the module is considered as an unknown) during the problem is solving. This allows us to obtain an unambiguous solution even in the case when the dependence M–χ has a downward section, i.e one value of moment can correspond to two values of curvature.

Experimental Study on the Shear Capacity of Rabbet Cast-in-Place Prefabricated Beam

2020 ◽  
Vol 980 ◽  
pp. 266-274
Author(s):  
Jian Hua Xiao ◽  
Miao Liu ◽  
Jin Li Wang ◽  
Abdulhamid Yakubu Anvah
Keyword(s):  
Mechanical Properties ◽  
Bearing Capacity ◽  
Failure Mode ◽  
Concrete Beam ◽  
Joint Stiffness ◽  
Load Level ◽  
Shear Capacity ◽  
Oblique Section ◽  
Shear Bearing Capacity ◽  
The Relationship

In order to investigate the shear capacity of prefabricated beam, experiments about shear bearing were performed on one integral pouring contrast beam and two prefabrication and assembly beams. Inspecting the relationship between load and deflection under the load, the development regularity of strain between longitude reinforced and stirrup, the shear capacity of cracking load and ultimate bearing capacity, analyzing failure mode of oblique section and connection performance of old and new concrete in the groove, and compared with the mechanical properties of cast-in-place concrete beam. The experimental results indicate that: prefabrication and assembly beam and cast-in-place beams have similar shear bearing capacity and failure mode of oblique section, along with the load level continues to increase, the groove joint stiffness weakened, but has little effect on the overall deformation.

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.

Deterioration Identification of Structural Concrete Ground on Residual Bearing Capacities

2014 ◽  
Vol 501-504 ◽  
pp. 1963-1967
Author(s):  
Hua Shu Yang ◽  
Ying Ju Pu ◽  
Yu Lu Yang ◽  
Xin Long Peng ◽  
Yi Wang ◽  
...  
Keyword(s):  
Bearing Capacity ◽  
Accelerated Life Test ◽  
Life Test ◽  
Structural Concrete ◽  
Concrete Buildings ◽  
Accelerated Life ◽  
Key Points ◽  
Building Deterioration ◽  
The Relationship

Found on data of accelerated life test, the relationship between outward disease of structural concrete and holistic deterioration of building was analysed. The results indicated that: outward diseases of structural concrete, such as abrasion, scour erosion, and peeling, carbonization etc, are not hypostatic breakage for holistic building, so could not be regarded as the key points of deterioration identification at building. Deterioration appraisement should be focused on detections of engineering indices relating to structural inbeing quality and analyses of multifarious remainder relating to bearing capacity. Only in this way, deterioration degree of structural concrete and efficacious repair indices could be factually incarnated. Ground on testing multifarious bearing capacities, deterioration identification of concrete buildings was founded, and remedy principles corresponding to inbeing deterioration indices were put forward.

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