A Normalized Terzaghi Model and Time-Step FEA for Predicting the Adsorption of a Cylindrical Object in Subsea Salvage
Abstract
:1. Introduction
2. The Object and Salvage Process
3. Results of Off-Mud Process Modeling and FEA
3.1. Off-Mud Modelling
3.1.1. Failure Criterion
3.1.2. Mobility
3.1.3. Interface Model
3.1.4. Soil Parameters
3.1.5. Object Parameters
3.2. Finite Element Analysis
- The deformation of the cylindrical structures is not considered;
- The soil is saturated;
- The particles of the soil are incompressible.
Flow Chart of the Simulation
3.3. Initial Stress and Off-Mud Process
3.3.1. Initial Stress
3.3.2. Off-Mud Simulation
4. Comparison and Modification of the Terzaghi Model
4.1. Comparison with FEA Results
4.2. Normalized Terzaghi Model and Modification
5. Time-Step Analysis
5.1. Effects of Lifting Force and Burial Depth on Critical Displacement
5.2. Effects of Lifting Force and Burial Depth on Displacement
5.3. Effects of Lifting Force and Burial Depth on Velocity
5.4. Effects of Lifting Force and Burial Depth on Soil Displacement
6. Conclusions
- The normalized Terzaghi model can be used to predict the adsorption force in the salvage of cylindrical objects. The maximum relative error is less than 2.49% compared with finite element analysis;
- Time-step finite element analysis can be used to investigate the off-mud process with regard to the effects of the lifting force and burial depth;
- With increased lifting force and the same burial depth, the critical displacement is reduced slightly, soil separation on the bottom of the object occurs earlier, the velocity increases more quickly, soil displacement on the bottom stops increases earlier, and the off-mud process is completed earlier;
- With increased burial depth, the time required for soil separation is considerably increased, the velocity increases more slowly, the maximum soil displacement is increased, and the off-mud process takes longer.
Equation Symbols List
,, | The three components of the generalized stress vector. |
The material constants defined by the shear modulus and bulk modulus. | |
The material constants defined by the shear modulus and bulk modulus. | |
,, | The principal strains. |
The internal friction angle coefficient. | |
The angle of the internal friction. | |
The cohesive force. | |
The tensile strength. | |
The expansion angle coefficient. | |
The expansion angle. | |
The normal force vector at the time of . | |
The tangential force at the time of . | |
The absolute displacement of the interface node penetration into the target surface. | |
The relative shear displacement increment vector. | |
The additional normal stress. | |
The additional tangential stress. | |
The tangential stiffness of the interface unit. | |
The normal stiffness of the interface unit. | |
The area represented by the interface nodes. | |
The tangential force. | |
The interface cohesion. | |
The interface friction angle. | |
The water pressure. | |
The bulk modulus. | |
The shear modulus. | |
The minimum dimension over the connection area in the normal direction of the interface. | |
The tangential stiffness. | |
The normal stiffness. | |
Young’s modulus. | |
Poisson’s ratio. | |
A | The horizontal projection area of the structure. |
The shear strength of the soil. | |
The burial depth. | |
The width of the structure. | |
The length of the structure. | |
The contact area of the structure immersed in the soil. | |
The total surface area of the structure. | |
β | The nondimensional burial depth. |
γ | The nondimensional width. |
λ | The nondimensional burial surface. |
ψ | The modification coefficient. |
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
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Cohesion c (Pa) | Friction Angle
(°) | Tangential Stiffness
(Pa) | Normal Stiffness
(Pa) |
---|---|---|---|
Density (kg/m3) | Bulk Modulus (Pa) | Shear Modulus (Pa) | Cohesion (kPa) | Friction Angle (°) | Tensile Strength (Pa) |
---|---|---|---|---|---|
1290 |
Density (kg/m3) | Bulk Modulus (Pa) | Shear Modulus (Pa) | Diameter (m) | Length (Pa) |
---|---|---|---|---|
3002 |
Length (m) | Width (m) | Height (m) |
---|---|---|
14 | 12 | 6 |
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Nan, Y.; Yun, F.; Yao, S.; Liu, M.; Wang, L. A Normalized Terzaghi Model and Time-Step FEA for Predicting the Adsorption of a Cylindrical Object in Subsea Salvage. Machines 2023, 11, 245. https://doi.org/10.3390/machines11020245
Nan Y, Yun F, Yao S, Liu M, Wang L. A Normalized Terzaghi Model and Time-Step FEA for Predicting the Adsorption of a Cylindrical Object in Subsea Salvage. Machines. 2023; 11(2):245. https://doi.org/10.3390/machines11020245
Chicago/Turabian StyleNan, Yibo, Feihong Yun, Shaoming Yao, Ming Liu, and Liquan Wang. 2023. "A Normalized Terzaghi Model and Time-Step FEA for Predicting the Adsorption of a Cylindrical Object in Subsea Salvage" Machines 11, no. 2: 245. https://doi.org/10.3390/machines11020245