Finite element analysis method for spring friction pile driving model of single pile driving process

Abstract

This invention discloses a finite element analysis method for a spring friction pile driving model in a single pile driving process. First, a single pile driving finite element model of the pile driving process is established. Based on the actual pile driving process, the pile driving model is simplified to include: hammer core, replacement hammer, replacement ring, pile, and friction body, modeled according to component dimensions. Preprocessing: The 3D model is imported into ABAQUS software, and material properties are set for each component. For the analysis step setting, this model uses the Dynamic, Explicit analysis step, setting the pile driving time to 0.1 s and enabling the large deformation option. The contact type is set to face-to-face contact, the tangential friction coefficient is selected as 0.35, and the normal action is set to hard contact by default. Boundary conditions are set, with the initial boundary being the initial velocity input and the constraint boundary being fixed at the pile bottom. Mesh generation is also set. Solution: Simulation is performed in the ABAQUS solver. Post-processing: The mechanical response results of the pile driving system are analyzed, and the velocity, hammer force, and pile top displacement responses of the elements at the pile height strain detection points are verified and checked.

Description

Technical Field

[0001] This application relates to a finite element analysis method, specifically a finite element analysis method for a spring friction pile driving model in a single pile driving process, belonging to the field of transient impact research technology. Background Technology

[0002] Monopile foundations are the supporting components of offshore wind turbines (OWTs). Their fatigue life has a decisive impact on the service life of the OWT. Extensive research has been conducted on the structural dynamic response of monopile foundations after construction under external loads such as seawater corrosion, offshore wind loads, and pile-soil interaction. However, in the monopile-driven construction of large-capacity OWTs, the impact force and peak stress under impact conditions become significantly larger. Research in this area is limited.

[0003] Therefore, it is particularly important to establish a finite element model that conforms to engineering practice and can be quickly simulated for the single pile driving process. Summary of the Invention

[0004] The purpose of this invention is to provide a theoretical basis for the engineering application of marine pile driving systems, and to propose a finite element analysis method for a spring friction pile driving model in the single pile driving process.

[0005] This invention achieves the above objective through the following technical solution: a finite element analysis method for a spring friction pile driving model in a single pile driving process, comprising the following steps: Step 1: Preprocessing. First, establish a single-pile driven finite element model of the pile driving process. According to the actual pile driving process, simplify the pile driving model as: hammer core, replacement hammer, replacement ring, pile, friction body, and model according to the component dimensions.

[0006] Step 2: Preprocessing. Import the 3D model into ABAQUS software and set the material properties for each component. For the analysis step, this model uses the Dynamic, Explicit analysis step, sets the pile driving time to 0.1 s, and enables the large deformation option. Set the contact type to face-to-face contact, select a tangential friction coefficient of 0.35, and set the normal action to hard contact by default. Set the boundary conditions, with the initial boundary being the initial velocity input and the constraint boundary being fixed at the pile bottom. Set the mesh generation.

[0007] Step 3: Solve the problem and perform dynamic simulation in the ABAQUS solver.

[0008] Step 4: Post-processing. Analyze the mechanical response results of the pile driving system and verify the responses of the unit at the pile height strain detection point, including velocity, hammer force, and pile top displacement.

[0009] As a further aspect of the present invention: In step one, in order to simulate the calculation as closely as possible to the real situation, based on the pile-soil interaction theory, two friction bodies are added to both sides of the pile to simulate the pile-soil interaction and reflect the soil resistance on the inside and outside of the pile during the pile driving process; at the same time, a spring model is added to the pile end to adjust the penetration depth of the pile driving construction in different models, so as to realize a real pile driving process model.

[0010] As a further aspect of the present invention: In step two, the normal and tangential forces between the contact surfaces are defined. The normal force is assumed to be hard contact, meaning that the magnitude of the contact pressure that can be transmitted between the contact surfaces is unlimited. When the contact pressure becomes zero or negative, the contact surfaces separate. The commonly used friction model for the tangential force is Coulomb friction. The friction surfaces will not slide relative to each other before the shear stress reaches the critical shear stress. The friction coefficient is set to 0.35 in the dialog box.

[0011] As a further aspect of the present invention: in step three, the boundary conditions of the finite element model are set, and the energy input is still based on the principle of energy conservation, directly assigning an initial velocity to the hammer core in the initial time step of the finite element analysis.

[0012] The beneficial effects of this invention are: the simulation data of the spring friction model is more consistent with engineering data, and it has advantages such as high stability and fast calculation speed. The dynamic response of a single pile is accurately reflected. Various components in driven single piles can be studied. Numerical simulation is expected to provide reference data for the fatigue life analysis of driven single piles. Attached Figure Description

[0013] Figure 1 This is a flowchart illustrating the overall process framework of the finite element analysis method for a single-pile driving process spring friction pile driving model according to the present invention. Figure 2 This is a simplified three-dimensional model of each component of the pile-hammer system of the present invention; Figure 3 This is the boundary input diagram of the pile-hammer system of the present invention; Figure 4 This is a hammer impact force-time curve obtained by the present invention; Detailed Implementation

[0014] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to specific embodiments. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the present invention.

[0015] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings. According to one embodiment of the present invention, a finite element analysis method for a spring friction pile driving model in a single pile driving process is provided, and the flowchart of the method is as follows: Figure 1As shown, it includes the following steps: Step 1: Preprocessing. First, establish a single-pile driven finite element model of the pile driving process. According to the actual pile driving process, simplify the pile driving model as follows: hammer core, replacement hammer, replacement ring, pile, friction body. Model according to the component dimensions, where the pile diameter is 6.6 m, the pile length is 80 m, and the mass is 1124 t.

[0016] Step 2: Preprocessing. Import the 3D model into ABAQUS software and set the material properties for each component, as shown in Table 1. For the analysis step settings, this model uses the Dynamic, Explicit analysis step, sets the pile driving time to 0.1 s, and enables the large deformation option. Set the contact type to face-to-face contact, select a tangential friction coefficient of 0.35, and set the normal action to hard contact by default. Set the boundary conditions, with the initial boundary being the initial velocity input and the constraint boundary being fixed at the pile bottom. Based on the construction energy of 857 KJ from the high strain test report of the pile driving, and applying the law of conservation of energy... Set the grid division.

[0017] Table 1 Attribute Parameters density elastic modulus Poisson's ratio Yield strength quality Hammer Core 9480kg / m3 300GPa 0.3 1200MPa 218.95t Replacement items 7800kg / m3 206 GPa 0.3 835MPa 134.61t Replacement ring 7800kg / m3 206 GPa 0.3 835MPa 116.50t pile 7850kg / m3 206 GPa 0.3 355MPa 1124.0t Step 3: Solve the problem. Perform dynamic simulation in the ABAQUS solver and select a parallel processor to speed up the calculation.

[0018] Step 4: Post-processing. The mechanical response results of the pile driving system are analyzed, and the responses of the units at the pile height strain detection points, including velocity, hammer force, and pile top displacement, are verified and checked. Figure 4 The hammer impact force time curve is shown in Table 2. The finite element simulation results and high strain test results are compared. The errors are all within 15%, which verifies the rationality of the model.

[0019] Table 2 Comparison of Finite Element Simulation Results and High Strain Detection Results physical quantity Peak hammer force Maximum compressive stress in pile body Effective hammering energy Final hammer penetration Pile side friction High strain testing 235409kN 144.1 MPa 2530kJ 2.8mm 63453 kN Simulation data 204787 kN 159.6 MPa 2832kJ 3.1mm 59554 kN error 13.0% 7.7% 11.9% 10.7% 6.1%

Claims

1. A finite element analysis method for a spring friction pile driving model in a single pile driving process, characterized in that, include: Step 1: Preprocessing. First, establish a single-pile driven finite element model of the pile driving process. Based on the actual pile driving process, simplify the pile driving model to include: hammer core, replacement hammer, replacement ring, pile, and friction body, and model according to the component dimensions. Step 2: Preprocessing. Import the 3D pile-hammer system model into ABAQUS software, and set the material properties, analysis steps, contact types, boundary conditions, and mesh generation for each component. Step 3: Solve the problem and perform dynamic simulation in the ABAQUS solver; Step 4: Post-processing. Analyze the mechanical response results of the pile driving system and verify the responses of the unit at the pile height strain detection point, including velocity, hammer force, and pile top displacement.

2. The finite element analysis method for a spring friction pile driving model in a single pile driving process according to claim 1, characterized in that, In step one, in order to make the simulation calculation as close to the real situation as possible, based on the pile-soil interaction theory, two friction bodies are added to both sides of the pile to simulate the pile-soil interaction and reflect the soil resistance on the inside and outside of the pile during the pile driving process; at the same time, a spring model is added to the pile end to adjust the penetration depth of the pile driving construction in different models, so as to realize the real pile driving process model.

3. The finite element analysis method for a spring friction pile driving model in a single pile driving process according to claim 1, characterized in that, In step two, the normal and tangential forces between the contact surfaces are described. The normal force is set to hard contact by default, which means that the magnitude of the contact pressure that can be transmitted between the contact surfaces is unlimited. When the contact pressure becomes zero or negative, the contact surfaces separate. The commonly used friction model for the tangential force is Coulomb friction. The friction surfaces will not slide relative to each other before the shear stress reaches the critical shear stress. Set the friction coefficient to 0.35 in the dialog box.

4. The finite element analysis method for a spring friction pile driving model in a single pile driving process according to claim 1, characterized in that, In step two, the boundary conditions of the finite element model are set, and the energy input is still based on the principle of energy conservation, directly assigning an initial velocity to the hammer core in the initial time step of the finite element analysis.

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