Method, system and equipment for analyzing bearing characteristics of offshore fixed foundation pile-soil interface

Abstract

The embodiment of the invention provides an offshore fixed foundation pile-soil interface bearing characteristic analysis method, system and equipment. The method comprises the following steps: establishing a finite element model of an offshore fixed foundation; wherein the finite element model comprises a pile foundation geometric model, a soil constitutive model and a pile-soil interface cyclic load simplified constitutive model; obtaining load characteristic parameters; and the load characteristic parameters are input into the finite element model, and the limit load and the cyclic load of the offshore fixed foundation are obtained. According to the embodiment of the invention, the pile-soil interface cyclic load simplified constitutive model considering cyclic weakening is established by analyzing the mechanical properties of the pile-soil interface under the static / cyclic load, and is applied to the finite element model, so that the load characteristic analysis of the pile-soil interface of the offshore fixed foundation is carried out, and the pile-soil interface load characteristic analysis accuracy is improved. The pile-soil interface bearing capacity weakening phenomenon is well simulated, and guidance is provided for research and design of an offshore fixed foundation.

Description

Technical Field

[0001] The embodiments disclosed herein belong to the technical field of pile-soil interface bearing capacity analysis, specifically relating to a method, system, and equipment for analyzing the bearing capacity of the pile-soil interface of offshore fixed foundations. Background Technology

[0002] In marine engineering, the pile foundation structure at the bottom, in addition to bearing the working load from the superstructure, often also bears cyclic loads generated by wind, waves, and currents. These cyclic loads weaken the pile-soil interface. The pile-soil interface is the contact surface between the pile foundation and the surrounding soil. The contact surface problem has always been one of the research focuses in geotechnical engineering. How to comprehensively and accurately reflect the complex mechanical characteristics and volumetric deformation laws of the contact surface under cyclic loads is crucial to solving the problem of pile-soil interaction.

[0003] Currently, the constitutive models used to analyze the bearing characteristics of the pile-soil interface under cyclic loading are quite complex. There is an urgent need to propose a practical pile-soil interface constitutive model to provide a basis for the analysis of the bearing characteristics of the pile-soil interface under cyclic loading. Summary of the Invention

[0004] The embodiments disclosed herein aim to at least solve one of the technical problems existing in the prior art, and provide a method, system and equipment for analyzing the bearing characteristics of offshore fixed foundation pile-soil interface.

[0005] One aspect of this disclosure provides a method for analyzing the load characteristics of offshore fixed foundation piles-soil interfaces, the method comprising:

[0006] A finite element model of a fixed offshore foundation is established; wherein the finite element model includes a pile foundation geometric model, a soil constitutive model, and a simplified constitutive model of pile-soil interface cyclic load;

[0007] Obtain load characteristic parameters;

[0008] By inputting the load characteristic parameters into the finite element model, the ultimate load and cyclic load of the offshore fixed foundation are obtained.

[0009] Furthermore, the simplified constitutive model of the pile-soil interface cyclic load is expressed by the following equation:

[0010]

[0011] in, Let Δτ be the interfacial ultimate resistance during the Nth cycle, Δτ be the difference between the initial ultimate resistance and the residual value, and t be a model parameter. Re This represents the residual value of the interface ultimate resistance cycle.

[0012] Optionally, the pile foundation geometric model is established using axisymmetric model through ABAQUS finite element software.

[0013] Optionally, the soil constitutive model adopts the Mohr-Coulomb model.

[0014] Optionally, the bottom of the finite element model is provided with boundary conditions that restrict displacement and rotation in the horizontal and vertical directions, and the left and right boundaries of the finite element model are provided with boundary conditions that restrict displacement and rotation in the horizontal direction.

[0015] Optionally, the finite element model employs quadrilateral mesh generation and a neutral axis algorithm.

[0016] Optionally, the method uses four analysis steps to simulate the actual working conditions of the finite element model: the initial analysis step is used to apply boundary conditions and interactions; the second analysis step uses the geostress type to apply the self-weight stress of the pile and soil and the geostress; the third analysis step applies a load to the pile top; and the fourth analysis step changes the number of cycles to examine the load changes.

[0017] Another aspect of this disclosure provides a system for analyzing the load characteristics of offshore fixed foundation pile-soil interface, the system comprising:

[0018] The model module is used to establish a finite element model of a fixed offshore foundation; wherein, the finite element model includes a pile foundation geometric model, a soil constitutive model, and a simplified constitutive model of pile-soil interface cyclic load;

[0019] The parameter module is used to obtain load characteristic parameters;

[0020] The analysis module is used to input the load characteristic parameters into the finite element model to obtain the ultimate load and cyclic load of the offshore fixed foundation.

[0021] Furthermore, the simplified constitutive model of the pile-soil interface cyclic load is expressed by the following equation:

[0022]

[0023] in, Let Δτ be the interfacial ultimate resistance during the Nth cycle, Δτ be the difference between the initial ultimate resistance and the residual value, and t be a model parameter. Re This represents the residual value of the interface ultimate resistance cycle.

[0024] Another aspect of this disclosure provides an electronic device comprising:

[0025] At least one processor; and,

[0026] A memory communicatively connected to the at least one processor is used to store one or more programs that, when executed by the at least one processor, enable the at least one processor to implement the above-described method for analyzing the load characteristics of offshore fixed foundation pile-soil interface.

[0027] This disclosure discloses a method, system, and device for analyzing the bearing capacity characteristics of the pile-soil interface in offshore fixed foundations. By analyzing the mechanical properties of the pile-soil interface under static / cyclic loads, a simplified constitutive model of the pile-soil interface under cyclic loads considering cyclic weakening is established and applied to a finite element model to analyze the load characteristics of the pile-soil interface in offshore fixed foundations. This model effectively simulates the weakening phenomenon of the bearing capacity of the pile-soil interface and provides guidance for the research and design of offshore fixed foundations. Attached Figure Description

[0028] Figure 1 This is a flowchart illustrating a method for analyzing the load characteristics of a fixed marine foundation pile-soil interface according to an embodiment of this disclosure.

[0029] Figure 2 This is a schematic diagram of an ideal elastoplastic model of interfacial cyclic shear with hysteresis characteristics according to another embodiment of the present disclosure.

[0030] Figure 3 This is a schematic diagram of the load-displacement curve of another embodiment of the present disclosure;

[0031] Figure 4 This is a schematic diagram of the load-cycle curve of another embodiment of the present disclosure;

[0032] Figure 5 This is a structural schematic diagram of a marine fixed foundation pile-soil interface load characteristic analysis system according to another embodiment of this disclosure;

[0033] Figure 6 This is a schematic diagram of the structure of an electronic device according to another embodiment of the present disclosure. Detailed Implementation

[0034] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. Based on the embodiments of this disclosure, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this disclosure.

[0035] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this disclosure.

[0036] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0037] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various components, these components should not be limited by these terms. These terms are used to distinguish one component from another. Therefore, the first component discussed below may be referred to as the second component without departing from the teachings of this disclosure. As used in this disclosure, the term "and / or" includes all combinations of any and more of the associated listed items.

[0038] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of exemplary embodiments, and the modules or processes in the drawings are not necessarily necessary for implementing this disclosure, and therefore cannot be used to limit the scope of protection of this disclosure.

[0039] like Figure 1 As shown, one embodiment of this disclosure provides a method for analyzing the load characteristics of the offshore fixed foundation pile-soil interface, including:

[0040] Step S1: Establish a finite element model of the offshore fixed foundation.

[0041] Specifically, the finite element model includes a pile foundation geometric model, a soil constitutive model, and a simplified constitutive model of pile-soil interface cyclic load.

[0042] Among finite element method (FEM) software, ABAQUS is one of the most powerful FEM software programs, possessing two main solver modules: ABAQUS / Standard and ABAQUS / Explicit. ABAQUS boasts powerful simulation capabilities and computational functions, numerous element models and analysis methods, and can simulate constitutive models of linearly elastic and nonlinear materials, including metals, polymers, soils, concrete, and reinforced concrete. Consolidation settlement analysis, excavation problems, and penetration problems in geotechnical engineering can all be effectively handled in ABAQUS. It also provides users with 42 subroutines and 15 application programming interfaces (APIs) for independent development, allowing for the definition of new material properties, boundary conditions, and initial stress fields. This secondary development capability gives ABAQUS broad openness and high flexibility. To meet the diverse needs of users, ABAQUS provides several subroutines as a secondary development platform. Users can develop specialized subroutines based on their specific problems. Subroutines are diverse, including user-defined loads, user-defined field variables, user-defined materials and elements, and user-defined contact conditions.

[0043] (1) Pile Foundation Geometric Model: Considering the symmetry of the double-layer soil single-pile foundation, an axisymmetric model can be used to effectively reduce the amount of calculation and improve computational efficiency when establishing the pile foundation geometric model in the finite element software ABAQUS. In the model, the pile body adopts a linear elastic model with a length L = 20m, a diameter D = 2.0m, an elastic modulus E = 220GPa, a Poisson's ratio v = 0.3, and a unit weight γ = 75kN / m³. 3 The foundation modeling area has a horizontal width of 8m and a depth of 40m.

[0044] (2) Soil Constitutive Model: For any material, its constitutive relationship can be described by the material mechanics equation, which is usually expressed as a constitutive model, i.e., stress-strain. This relationship of soil is extremely complex, usually including several types such as elastoplastic, nonlinear, dilatancy, rheological, and anisotropic. In geotechnical engineering projects, the most commonly used constitutive models in ABAQUS analysis are mainly Mohr-Coulomb, elastic model, critical state plasticity, and modified Cambridge model. Based on the characteristics of the model constructed in this study, the soil is sand, and the widely used Mohr-Coulomb model was selected, with elastic modulus E = 30 MPa, Poisson's ratio ν = 0.35, and friction angle...

[0045] The above methods employ quadrilateral meshing for both pile foundations and soil, using the neutral axis algorithm. Curvature control is used to make the mesh denser near the pile center and sparser further away, thus saving computational resources for soil sections that are not the focus of the study and whose deformation is not significant, thereby improving computational efficiency.

[0046] (3) Cyclic weakening constitutive model of pile-soil interface:

[0047] Firstly, regarding the constitutive model of the pile-soil interface, in the finite element model, the contact between the pile and soil interface is simulated by setting special elements. The force transmission mechanism of the pile-soil interface is the key issue in the simulation. Currently, the main simulation methods for the pile-soil interface are the contact element method and the master-slave contact surface method, which is commonly used in large commercial software. The contact problem is a typical nonlinear problem and a special type of discontinuous constraint. The master-slave contact surface should follow two principles: first, the master contact surface should be a surface with a relatively coarse mesh; second, the element sizes should be similar, and the master contact surface should be a surface with high stiffness. Based on this, in the pile-soil dynamic analysis, the pile foundation surface of the pile-soil interface is used as the master contact surface, and the soil surface is used as the slave contact surface. Moreover, the nodes on the master contact surface can intrude into the slave contact surface. The master-slave contact surface can only transmit normal force when compressed. When separated, the contact constraint is canceled. This constraint is called hard contact. This contact pressure will change drastically, which can sometimes make the contact calculation difficult to converge. At this time, the medium boundary will be transformed into a normal boundary.

[0048] Due to the roughness of the contact surface, the tangential mechanical behavior of the contact surface is accompanied by normal mechanical behavior. When the contact surface is closed, it can transmit tangential force, i.e., frictional force τ, which is usually expressed by Coulomb's friction law: τ = μp; where μ is the coefficient of friction and p is the normal contact stress.

[0049] The frictional force between the contact surfaces is less than the critical frictional force τ. u When the contact surfaces move together, they are in an adhesive state; when the frictional force between the contact surfaces exceeds the critical frictional force τ... u When there is relative displacement between the contact surfaces, it is called the slip state.

[0050] To address the potential convergence of calculation results due to transitions between contact surface states, a bond-slip friction transition phase is allowed when the contact surface is in a bonded state. This transition phase involves small relative slip deformation. This idealized interface contact model is not entirely applicable to all working conditions. The following introduces an improved interface constitutive model: The study of the mechanical properties of the soil-structure contact surface mainly reflects the constitutive relationship of the contact interface. This primarily refers to the relationship between the normal and tangential components of the interaction forces or stresses on the contact interface and the tangential-normal component of the relative shear displacement on the contact surface. Current research mainly focuses on the relationship between shear stress τ and relative shear displacement Δs. The following are some methods reflecting the relationship between interface shear stress and relative displacement:

[0051] 1. Hyperbolic model

[0052] This disclosure uses a conventional strain-controlled direct shear apparatus to determine the shear stress and displacement relationship between the quartz sand and concrete interface, and proposes the following hyperbolic expression for shear stress and displacement:

[0053]

[0054] In the formula, Δs is the shear displacement; K and n are experimental constants; σ n Normal stress; P a R is atmospheric pressure; f The destruction ratio.

[0055] The main advantage of this hyperbolic model is that the nonlinear shear stress and displacement relationship on the contact surface can be well described by the above formula. This method is relatively easy to implement in the calculation of pile-soil contact interface.

[0056] 2. Elastic-plastic model

[0057] This disclosure, based on indoor test data and measurement data of retaining walls in engineering practice, proposes that the relationship between shear stress and displacement at the contact surface can be simplified to two straight lines, namely:

[0058]

[0059] (τ / σ)=(τ / σ)0+(w s -w s0 )

[0060] Furthermore, this disclosure proposes that the shear stress and shear displacement at the contact surface can be simplified into the following elastoplastic curve relationship, as shown in the following equation:

[0061] τ=k s w s τ <fσ n

[0062] w s ≥τ / k s τ>fσ n

[0063] In the formula, f is the interfacial friction coefficient; σ n For normal stress; k s ω is the shear modulus. s This represents the shear displacement.

[0064] 3. Thin-layer unit

[0065] Thin-layer contact surface elements employ special constitutive equations, but otherwise resemble ordinary finite element mesh elements, making them easily connectable to finite element meshes. A thin-layer element with thickness t and length B has an element stiffness matrix as follows:

[0066]

[0067] In the formula, [D ττ [D] is the shear component matrix. nn[D] is the normal component matrix. τn ] and [D nτ [D] is the coupling matrix between the normal and tangential directions. Without considering coupling, the normal component matrix [D] is... nn ] is represented as:

[0068] [D nn ]=λ3[D nn ] i +λ2[D nn ] τ +λ3[D nn ] n

[0069] 4. Finite element analysis of the contact surface model

[0070] The contact surface model is a four-node contact surface element without thickness, which can well reflect the tangential stress and deformation relationship of the contact surface and its nonlinear characteristics. In ABAQUS, this can be implemented by embedding the FRIC subroutine. The constitutive model of the contact surface is given by the following equation, where the tangential stiffness k... t The relation is:

[0071]

[0072] Stiffness k in both directions t1 and k t2 They are respectively:

[0073]

[0074] In the formula, K1, K2, n, and R f All are experimental parameters, p a Where δ is atmospheric pressure, γ is the contact surface friction angle, and γ is atmospheric pressure. w It is the density of water.

[0075] Secondly, regarding the constitutive model of the pile-soil interface under cyclic loading, the following aspects are included:

[0076] 1. Viscoelastic dynamic artificial boundary

[0077] The physical meaning of a viscoelastic dynamic artificial boundary is that a spring and a damping element are applied in the normal and tangential directions at the boundary nodes, respectively. The boundary conditions are simulated using viscous damping with energy absorption capacity and a spring with rigid restoring capacity. The viscoelastic artificial boundary is a stress boundary, and the stress can be expressed by the nodal displacements and velocities of the boundary nodes, generally written as:

[0078]

[0079] In the formula, σ li (t), u li (t), These represent stress, displacement, and velocity, respectively, K. li C li These represent the spring stiffness and damping coefficient in different directions.

[0080] When an S-wave propagates perpendicularly to the artificial boundary into an infinite domain, the shear stress at the boundary can be obtained:

[0081]

[0082]

[0083] When a P-wave propagates perpendicularly to an artificial boundary into an infinite domain, the normal stress at the boundary surface can be obtained:

[0084]

[0085] 2. Modify the RO model

[0086] The shear stress and displacement relationship between the soil-concrete interface under cyclic shear loading can be expressed by the modified Ramberg-Osgood model as follows:

[0087]

[0088] The relationship between the unloading and reloading curves is as follows:

[0089]

[0090] Among them, u y For reference relative displacement, u i K represents the relative displacement at the turning point. i Let R be the initial shear strength, α be the mechanical property parameters of the contact surface, and δ be the cycle index. Here, it is assumed that the ratio of the initial stiffness of the first cycle to the initial stiffness of the nth cycle is equal to the ratio of their secant stiffness.

[0091] 3. Contact Surface Boundary Model

[0092] An analytical model is established on a thin contact surface of thickness t at the pile-soil interface. Monotonic and cyclic loading of the contact surface is achieved using displacement control. Substituting the proposed contact surface boundary model and simplifying it, we get:

[0093]

[0094] The following describes the simplified constitutive model of the pile-soil interface under cyclic loading in this embodiment: In the CNS test, the interface normal stiffness K remains constant, and changes in soil volume will cause changes in normal stress. For the pile-soil interface, the boundary conditions in the CNS test are closer to the actual situation and can more realistically reflect the loading characteristics of the pile-soil interface. The change in shear stress is inseparable from the change in normal stress. Due to the shear contraction characteristics of the interface soil under cyclic loading, the normal stress will decrease proportionally with the normal displacement to maintain the constant interface stiffness. The reduction in normal stress will directly affect the shear stress, leading to a weakening of the shear stress at the maximum shear displacement. The above analysis reproduces the phenomenon of interface strength weakening under cyclic loading and also explains the reason for the weakening of side skin friction in the pile foundation under cyclic loading. Based on the interface shear weakening mechanism, the project establishes a simplified cyclic analysis model of the interface considering the weakening of strength and stiffness.

[0095] Interfacial ultimate resistance can generally be expressed as:

[0096]

[0097] In the formula, This represents the interfacial limit resistance during the Nth cycle. For the corresponding interface normal stress, δ peak The limit friction angle of the interface.

[0098] The change in ultimate drag caused by the change in normal stress is expressed as:

[0099]

[0100] In the formula, σ n0 For the initial normal stress, This represents the decrease in normal stress during the Nth cycle. When N=1, the interface has not undergone cycling. The actual normal stress during the process should be but Generally, it is similar to the initial value σ when unloaded. n0 The difference is not significant, therefore an approximate clamping is used in the model.

[0101] In the CNS interface experiment It can continuously increase with the increase of the number of iterations N, however However, the growth rate will continue to decrease until it reaches zero, after a certain number of cycles. It approaches a constant value.

[0102] It can be seen that, The variation of the number of iterations N can be approximately described by a power function.

[0103]

[0104] In the formula σ n,re Here, represents the cyclic residual value of the normal stress, N is the number of cycles, and t is a model parameter that controls the weakening rate of the normal stress. When N = 1, When N is infinite

[0105] Substituting equation ② into equation ① and rearranging, we get:

[0106]

[0107] Therefore, the cyclical weakening law of interfacial resistance can be expressed as:

[0108]

[0109] In the formula, τ represents the interfacial ultimate resistance during the Nth cycle, where Δτ is the difference between the initial ultimate resistance and the residual value; Re Let be the residual value of the interfacial ultimate resistance during the cycle. Where, interfacial ultimate resistance... It decreases exponentially with the number of iterations N.

[0110] This embodiment uses an ideal elastoplastic model that reflects the reciprocating shear hysteresis characteristics as the interface analysis model. Figure 2 The ideal elastoplastic model of interfacial cyclic shear with hysteretic characteristics is a pile-side load transfer model that reflects the hysteretic characteristics of loading and unloading. τ u The ultimate frictional resistance is the interfacial resistance, the magnitude of which is related to its direction. The ultimate negative frictional resistance is τ. u It is typically about 0.8 times the positive frictional resistance. However, in previous elastoplastic models, for the sake of simplicity in analysis, it is generally assumed that the two are equal.

[0111] w cr The shear stress τ is the ultimate relative displacement at the interface. When the relative displacement between the pile and the soil is less than the critical displacement, the shear stress τ has a linear relationship with the relative displacement. When the relative displacement is greater than the critical displacement, the shear stress τ remains constant and equal to the ultimate resistance τ at the interface. u .

[0112] k s The shear stiffness at the initial loading of the interface:

[0113] k s =τ u / w cr

[0114] The advantage of this definition is that it can reflect the increase of interface stiffness with ultimate strength. s This represents the interface shear stiffness during unloading. In general elastoplastic models, it is assumed that the unloading stiffness equals the loading stiffness, i.e., k. u =k sTherefore, when 0 < w ≤ w cr During unloading, the interface is completely elastic, and no residual displacement is generated. When the displacement exceeds the limit displacement, residual displacement is generated during unloading.

[0115] After the interface loads forward, the unloading stiffness k is used as a guide. u Unloading is performed, and once the shear stress decreases to zero, the interface begins to reverse to load stiffness k. s Loading continues until the interface reaches its reverse limit resistance τ. u The applicable range of loading and unloading stiffness is limited by the point of zero shear stress.

[0116] From the above definitions, it can be seen that assuming the interface loading path is as follows... Figure 2 As shown, the interfacial shear stress during the initial shearing process is:

[0117]

[0118] Interface shear stress during unloading:

[0119] τ=τ1-k u (w1-w)

[0120] In the formula, τ1 and w1 are the interface shear stress and relative displacement at the previous moment, respectively, and τ and w are the interface shear stress and relative displacement at the current moment, respectively.

[0121] Initial stiffness k during static loading s The experiment shows that the shear stress is not linear. After the shear stress decreases to zero, residual deformation occurs at the interface. If the relative displacement decreases further, the interface enters a reverse loading state, with the reverse loading starting from this point. During reverse shear, the interface shear stiffness is k. s =τ u / w cr However, the influence of residual deformation at the interface must be considered.

[0122]

[0123] In the formula, w cr The relative strain is the residual strain at the interface.

[0124] like Figure 2 As shown, during the loop, when |ww cr |≥w cr When the load is applied for the Nth cycle, the expression for the ultimate strength is as follows:

[0125]

[0126] In the above formula, the interfacial ultimate resistance decreases exponentially with the number of cycles. The residual stress ratio is defined as follows: Therefore a Re=σ n,re / σ n0 , 0≤a Re <1. a Re =1 indicates that the interface intensity has not changed.

[0127] Change Δτ to a Re express:

[0128]

[0129] The results were:

[0130]

[0131] Therefore, it can be seen that the shear stress in the same group of cyclic shear tests mainly occurs in the first shear. As the number of cyclic shears N increases, the interfacial shear stress continuously decreases. Fitting the experimental data with a nonlinear logarithmic formula reveals that the measured attenuation curve and the fitted logarithmic equation are in very high agreement. This demonstrates that this method can simulate the weakening phenomenon of interfacial strength under cyclic loading.

[0132] Step S2: Obtain load characteristic parameters.

[0133] Specifically, various parameters are obtained for the pile-soil interface load characteristic analysis simulation test using the finite element model of the offshore fixed foundation in this embodiment.

[0134] Step S3: Input the load characteristic parameters into the finite element model to obtain the ultimate load and cyclic load of the offshore fixed foundation.

[0135] Specifically, four analysis steps are used to simulate the actual working conditions using the finite element model:

[0136] The initial analysis step is used to apply boundary conditions and interactions. To avoid the influence of boundary conditions on the numerical simulation results, the influence range should be at least four times the pile diameter in the center-to-horizontal boundary width and at least twice the pile bottom distance from the pile base. To reflect actual working conditions, this paper sets horizontal and longitudinal boundary conditions restricting displacement and rotation at the bottom of the pile foundation finite element model, while horizontal boundary conditions restricting displacement and rotation are set at the left and right boundaries of the pile foundation finite element model, respectively.

[0137] The second analysis step uses the ground stress type to apply the self-weight stress of the pile and soil, as well as the ground stress. The third analysis step applies a load to the top of the pile. The fourth analysis step changes the number of cycles to examine the load changes.

[0138] like Figure 3The figure shows the load-displacement (PS) curves obtained from simulation analysis of steel pipe piles using the aforementioned finite element model in some embodiments. Methods for determining the ultimate bearing capacity are divided into the inflection point method and the displacement control method. For example... Figure 3 For PS curves showing a clear second inflection point that falls within displacement control, the bearing capacity is determined using the inflection point method, i.e., the pile top load corresponding to the second inflection point is directly read as the ultimate bearing capacity. However, for PS curves where the second inflection point is not clear, or where the displacement corresponding to the inflection point exceeds the displacement control value, the displacement control method should be used. Ultimately, the ultimate load of this pile foundation is determined to be 12200 kN.

[0139] The bearing capacity of a pile will change after different cycles, such as Figure 4 The load-cycle number curves of the piles after 0 to 50 cycles are shown. The graphs reveal that the pile bearing capacity decreases continuously with increasing cycle number, decreasing rapidly in the early stages and then more slowly, gradually leveling off. This is consistent with the experimental pattern observed in large-scale direct shear tests. Therefore, the interface bearing capacity weakening model proposed in this chapter can effectively simulate the weakening phenomenon of the pile foundation's interface bearing capacity.

[0140] This disclosure discloses a method for analyzing the load characteristics of the pile-soil interface in offshore fixed foundations. By analyzing the mechanical properties of the pile-soil interface under static / cyclic loads, a simplified constitutive model of the pile-soil interface under cyclic loads considering cyclic weakening is established and applied to a finite element model to analyze the load characteristics of the pile-soil interface in offshore fixed foundations. This method effectively simulates the weakening phenomenon of the bearing capacity of the pile-soil interface and provides guidance for the research and design of offshore fixed foundations.

[0141] like Figure 5 As shown, another embodiment of this disclosure provides a system for analyzing the load characteristics of offshore fixed foundation piles-soil interfaces, the system comprising:

[0142] Model module 510 is used to establish a finite element model of a fixed offshore foundation; wherein, the finite element model includes a pile foundation geometric model, a soil constitutive model, and a simplified constitutive model of pile-soil interface cyclic load;

[0143] Parameter module 520 is used to obtain load characteristic parameters;

[0144] Analysis module 530 is used to input the load characteristic parameters into the finite element model to obtain the ultimate load and cyclic load of the offshore fixed foundation.

[0145] For example, the simplified constitutive model of the pile-soil interface cyclic load is expressed by the following equation:

[0146]

[0147] in, Let Δτ be the interfacial ultimate resistance during the Nth cycle, Δτ be the difference between the initial ultimate resistance and the residual value, and t be a model parameter. Re This represents the residual value of the interface ultimate resistance cycle.

[0148] Specifically, the offshore fixed foundation pile-soil interface load characteristic analysis system of this disclosure is used to implement the offshore fixed foundation pile-soil interface load characteristic analysis method described in the above embodiments. The specific implementation process has been described in detail in the previous embodiment, and will not be repeated here.

[0149] This disclosure discloses a system for analyzing the load characteristics of the pile-soil interface of a fixed offshore foundation. By analyzing the mechanical properties of the pile-soil interface under static / cyclic loads, a simplified constitutive model of the pile-soil interface under cyclic loads considering cyclic weakening is established and applied to a finite element model to analyze the load characteristics of the pile-soil interface of a fixed offshore foundation. This system effectively simulates the weakening phenomenon of the bearing capacity of the pile-soil interface and provides guidance for the research and design of fixed offshore foundations.

[0150] like Figure 6 As shown, another embodiment of this disclosure provides an electronic device, including:

[0151] At least one processor 601; and a memory 602 communicatively connected to the at least one processor 601 for storing one or more programs that, when executed by the at least one processor 601, enable the at least one processor 601 to implement the above-described method for analyzing the load characteristics of offshore fixed foundation pile-soil interface.

[0152] The memory 602 and processor 601 are connected via a bus, which may include any number of interconnecting buses and bridges. The bus connects various circuits of one or more processors 601 and memory 602 together. The bus can also connect various other circuits, such as peripheral devices, voltage regulators, and power management circuits, which are well known in the art and therefore will not be described further herein. A bus interface provides an interface between the bus and the transceiver. The transceiver can be a single element or multiple elements, such as multiple receivers and transmitters, providing a unit for communicating with various other devices over a transmission medium. Data processed by processor 601 is transmitted over a wireless medium via an antenna, which further receives data and transmits it to processor 601.

[0153] Processor 601 is responsible for managing the bus and general processing, and can also provide various functions, including timing, peripheral interfaces, voltage regulation, power management, and other control functions. Memory 602 can be used to store data used by processor 601 during operation.

[0154] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A method for analyzing the load characteristics of the pile-soil interface in offshore fixed foundations, characterized in that, The method includes: A finite element model of a fixed offshore foundation is established; wherein the finite element model includes a pile foundation geometric model, a soil constitutive model, and a simplified constitutive model of pile-soil interface cyclic load; Obtain load characteristic parameters; By inputting the load characteristic parameters into the finite element model, the ultimate load and cyclic load of the offshore fixed foundation are obtained.

2. The method according to claim 1, characterized in that, The simplified constitutive model of the pile-soil interface cyclic load is expressed by the following equation: in, Let Δτ be the interfacial ultimate resistance during the Nth cycle, Δτ be the difference between the initial ultimate resistance and the residual value, and t be a model parameter. Re This represents the residual value of the interface ultimate resistance cycle.

3. The method according to claim 1 or 2, characterized in that, The geometric model of the pile foundation was established using the ABAQUS finite element software with an axisymmetric model.

4. The method according to claim 1 or 2, characterized in that, The soil constitutive model adopts the Mohr-Coulomb model.

5. The method according to claim 1 or 2, characterized in that, The bottom of the finite element model is provided with horizontal and vertical boundary conditions that restrict displacement and rotation, and the left and right boundaries of the finite element model are provided with horizontal boundary conditions that restrict displacement and rotation.

6. The method according to claim 1 or 2, characterized in that, The finite element model uses quadrilateral mesh generation and a neutral axis algorithm.

7. The method according to claim 1 or 2, characterized in that, The method uses four analysis steps to simulate the actual working conditions of the finite element model: the initial analysis step is used to apply boundary conditions and interactions; the second analysis step uses the geostress type to apply the self-weight stress of the pile and soil and the geostress; the third analysis step applies a load to the top of the pile; and the fourth analysis step changes the number of cycles to examine the load changes.

8. A system for analyzing the load characteristics of a fixed marine foundation pile-soil interface, characterized in that, The system includes: The model module is used to establish a finite element model of a fixed offshore foundation; wherein, the finite element model includes a pile foundation geometric model, a soil constitutive model, and a simplified constitutive model of pile-soil interface cyclic load; The parameter module is used to obtain load characteristic parameters; The analysis module is used to input the load characteristic parameters into the finite element model to obtain the ultimate load and cyclic load of the offshore fixed foundation.

9. The system according to claim 8, characterized in that, The simplified constitutive model of the pile-soil interface cyclic load is expressed by the following equation: in, Let Δτ be the interfacial ultimate resistance during the Nth cycle, Δτ be the difference between the initial ultimate resistance and the residual value, and t be a model parameter. Re This represents the residual value of the interface ultimate resistance cycle.

10. An electronic device, characterized in that, include: At least one processor; as well as, A memory communicatively connected to the at least one processor is used to store one or more programs that, when executed by the at least one processor, enable the at least one processor to implement the method for analyzing the load characteristics of the marine fixed foundation pile-soil interface as described in any one of claims 1 to 7.

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