A distributed pile-soil interaction damping calculation method, equipment, and medium for offshore single pile foundation

Abstract

The present invention relates to a method, device, and medium for calculating distributed pile-soil interaction damping for an offshore single pile foundation. The calculation method comprises: S1, obtaining a soil unit damping ratio-cyclic shear strain curve for a target site soil layer; S2, calculating the pile-soil interaction damping of the single pile foundation at the p-y spring level; S3, calculating the deformation of the single pile body along the depth direction under a target cyclic load amplitude; S4, obtaining the p-y spring reaction force based on the pile body displacement response and determining the corresponding damping ratio based on the horizontal displacement of each p-y spring, and calculating the secant stiffness of the corresponding p-y spring at the displacement amplitude; and S5, calculating the damping coefficient at the p-y spring level. Compared with the prior art, the present invention can take into account the actual soil layer distribution and the damping-strain characteristics of each soil layer, resulting in more accurate calculation results; the method is simple and easy to operate; and it can provide input for integrated wind turbine time-domain analysis software to explore the load-reducing effect of pile-soil interaction damping on the dynamic response of the wind turbine structure.

Description

Technical Field

[0001] The present invention relates to the technical field of offshore wind power and oil and gas monopile foundations, and in particular to a distributed pile-soil interaction damping calculation method, equipment, and medium for an offshore monopile foundation. Background Art

[0002] The load response of large-diameter single piles depends on the pile-soil interaction stiffness and damping. The stiffness significantly impacts the overall frequency of offshore wind turbines and is crucial for accurately predicting fatigue damage to wind turbine structures. In many cases, it will dominate the design of wind turbine foundation dimensions and even influence the type of offshore wind turbine foundation. Pile-soil interaction damping has a positive effect on reducing wind turbine loads and fatigue damage to single pile foundations, particularly during shutdown conditions and when wind and waves are in opposite directions. However, compared to pile-soil stiffness, research on pile-soil interaction damping for offshore wind turbines is still lacking, and a consensus has yet to be reached within the industry.

[0003] In existing offshore wind turbine foundation design practices, pile-soil interaction damping is typically assessed using simplified methods or empirical estimates. While these methods can meet design requirements to a certain extent, they often overlook the impact of soil properties, load characteristics, and marine environmental factors on pile-soil interaction damping. With the continuous expansion of offshore wind farms and the increase in the capacity of individual wind turbines, the requirements for wind turbine foundation design accuracy and reliability are becoming increasingly stringent. Therefore, developing a method that can accurately calculate pile-soil interaction damping is of great practical significance for optimizing wind turbine foundation design, improving structural safety, and reducing project costs. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a method, equipment and medium for calculating the distributed pile-soil interaction damping of an offshore single pile foundation. The present invention takes into account the actual soil layer distribution and the damping-strain characteristics of each soil layer, and the calculation results are more accurate; the method is simple, easy to operate, and has high application value.

[0005] During the design process, the applicant determined that under normal operating conditions, foundation damping is the second-largest contributor to overall wind turbine damping, second only to aerodynamic damping. Under shutdown conditions, aerodynamic damping is negligible, leaving foundation damping as the most significant contributor. Due to the lack of detailed methodologies in current design guidelines, foundation damping is often overlooked in offshore wind turbine designs. Typically, offshore wind turbines experience wind and wave loads with a frequency below 1 Hz, so radiation damping is negligible, and only foundation viscous damping needs to be considered.

[0006] During the course of conception, the applicant further believed that the connotation of the viscous damping of the pile-soil interaction is the energy loss dissipated by the soil under cyclic shear within the mobilization range of the pile foundation. At the microscopic level, the energy dissipation of each soil unit is related to the damping characteristics of the material itself and the amplitude of the cyclic shear strain it undergoes. Based on this, the inventors conducted a large number of finite element parametric analyses in the early stage and found that at the py spring level, the damping characteristics of the pile-soil interaction can be very easily obtained from the damping characteristics of the soil at the unit level. By adopting this model, the damping of the pile-soil interaction at the py level can be quickly evaluated based on the damping characteristics of the geotechnical materials measured at the actual project site without the need for three-dimensional finite element analysis and post-processing of the results. The damping ratio model captures the characteristics of the nonlinear response of the pile-soil damping ratio and takes into account the influence of the foundation soil characteristics on the pile-soil damping ratio.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] A first aspect of the present invention provides a method for calculating distributed pile-soil interaction damping of an offshore single pile foundation, comprising the following steps:

[0009] S1. Obtain the soil unit damping ratio-cyclic shear strain curve of the soil layer at the target site;

[0010] S2. Calculating the pile-soil interaction damping of the single pile foundation at the py spring level based on the soil unit damping ratio-cyclic shear strain curve;

[0011] S3, calculating the deformation of the single pile along the depth direction under the target cyclic load amplitude to obtain the pile displacement response;

[0012] S4. Based on the pile displacement response obtained in S3, the reaction force of each py spring is determined using the py calculation method for sand and clay. Combined with the horizontal displacement of each py spring, the damping ratio of each spring is determined, and the secant stiffness of each py spring at the corresponding displacement amplitude is calculated.

[0013] S5. Combining the soil unit damping ratio-cyclic shear strain curve and the py spring secant stiffness in S4, as well as the actual wave load dominant frequency, calculate the damping coefficient c at the py spring level to complete the distributed pile-soil interaction damping calculation of the offshore single pile foundation.

[0014] Furthermore, in S1, the soil element damping ratio-cyclic shear strain curve of the target site soil layer is obtained from data obtained in one of the following ways:

[0015] 1) Data obtained by the test method, i.e., data obtained by combining resonant column and cyclic simple shear or cyclic triaxial testing;

[0016] 2) Data obtained by empirical methods, including data calculated using the damping ratio model of Derendeli (2001).

[0017] Furthermore, in S1, the Derendeli (2001) damping ratio model is as follows:

[0018]

[0019]

[0020]

[0021]

[0022] d Masing =c1×d Masing,a＝1.0 +c2×d Masing,a＝1.0 2 +c3×d Masing,a＝1.0 3

[0023]

[0024] c1=-1.1143×a 2 +1.8618×a+0.2523

[0025] c2=0.0805×a 2 -0.0710×a-0.0095

[0026] c3=-0.0005×a 2 +0.0002×a+0.0003

[0027] Where: γ is the cyclic shear strain, γ r is the reference shear strain (%), d min is the minimum strain damping ratio of the material (%), and a is the curve shape parameter Equal to, b is the scaling factor, d Adiusted is the damping ratio of the adjusted material (%), σ′0 is the average effective confining pressure (atm), PI is the plasticity index (%), OCR is the overconsolidation ratio, frq is the loading frequency, N is the number of cycles, is the calculation parameter, G / G max is the normalized shear modulus.

[0028] Furthermore, in S3, finite element software is used to model and calculate the deformation of the single pile along the depth direction under the target cyclic load amplitude based on the single pile parameters and site conditions.

[0029] Furthermore, in S4, for the method of obtaining py of the clay layer, the method in S1 and S2 is adopted to calculate the single pile-soil interaction model from the soil stress-strain curve.

[0030] Furthermore, in S4, for the py acquisition method of the sand layer, the current API sand py spring is adopted.

[0031] Furthermore, in S4, the secant stiffness of the corresponding py spring at the displacement amplitude is calculated as follows:

[0032]

[0033] in:

[0034] kp-y: py spring secant stiffness;

[0035] p:py spring reaction force;

[0036] u x : Typical displacement amplitude.

[0037] Furthermore, in S4, the damping coefficient c is calculated as follows:

[0038]

[0039] Where k is the stiffness of the system, which is related to the elastic properties of the structure; d is the damping ratio, a dimensionless value used to describe the intensity of the system damping; and ω is the dominant frequency of the actual wave load.

[0040] A second aspect of the present invention provides an electronic device, comprising a memory and a processor, wherein the processor is configured to execute a program in the memory, thereby implementing the above-mentioned distributed pile-soil interaction damping calculation method for an offshore single pile foundation.

[0041] A third aspect of the present invention provides a storage medium containing computer-executable instructions, which, when executed by a computer processor, is used to perform the above-mentioned distributed pile-soil interaction damping calculation method for an offshore single pile foundation.

[0042] Compared with the prior art, the present invention has the following technical advantages:

[0043] 1. The distributed pile-soil interaction damping calculation method for offshore single pile foundations described in the present invention is simple, easy to operate, and has high application value;

[0044] 2. The distributed pile-soil interaction damping calculation method for offshore single pile foundations described in the present invention directly calculates the relationship between the pile-soil interaction damping and pile deformation at the py level of the single pile foundation using the damping ratio-cyclic shear strain relationship at the soil unit level. This method can take into account the actual soil layer distribution and the damping-strain characteristics of each soil layer, resulting in more accurate calculation results.

[0045] 3. The calculation method for distributed pile-soil interaction damping of offshore single pile foundations described in the present invention can be used as input for wind turbine integrated time-domain analysis software (such as Bladed and OpenFAST) to study the impact of single pile foundation pile-soil interaction damping on the dynamic response of wind turbine structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 Schematic diagram of the core principle of distributed pile-soil interaction damping calculation for offshore single pile foundation in the present invention;

[0047] Figure 2 is the cyclic shear strain-damping ratio relationship curve of the clay of the present invention;

[0048] Figure 3 is the cyclic shear strain-damping ratio relationship curve of the sand of the present invention;

[0049] Figure 4 The mapping relationship between the damping ratio of soil element and cyclic shear strain and the pile-soil interaction damping and single pile deformation is shown in the present invention.

[0050] Figure 5 The present invention is a clay site py spring layer single pile foundation pile-soil interaction damping;

[0051] Figure 6 The present invention is a sandy soil site py spring layer single pile foundation pile-soil interaction damping;

[0052] Figure 7 is the displacement response amplitude of the pile body of the present invention;

[0053] Figure 8 is the normalized stress-strain curve of the clay layer of the present invention;

[0054] Figure 9 is the spring reaction force and secant stiffness in the depth direction of the pile body of the present invention;

[0055] Figure 10 It is the damping coefficient of the spring layer along the pile body py of the present invention. DETAILED DESCRIPTION

[0056] Overall, the present application relates to a method for calculating distributed pile-soil interaction damping of an offshore single pile foundation, which belongs to the technical field of offshore wind power and oil and gas single pile foundations. The method includes the following steps: S1, obtaining the soil unit damping ratio-cyclic shear strain curve of the soil layer of the target site; S2, calculating the pile-soil interaction damping of the single pile foundation at the py spring level; S3, calculating the pile body deformation of the single pile along the depth direction under the target cyclic load amplitude; S4, obtaining the py spring reaction force according to the pile body displacement response in S2 and determining the corresponding damping ratio according to the horizontal displacement of each py spring, and calculating the secant stiffness of the corresponding py spring at the displacement amplitude; S5, calculating the damping coefficient at the py spring level; it has the advantages of being able to take into account the actual soil layer distribution and the damping-strain characteristics of each soil layer, and the calculation results are more accurate; the method is simple, easy to operate, and has high application value; it can provide input for the wind turbine integrated time domain analysis software to explore the load-reducing effect of the pile-soil interaction damping on the dynamic response of the wind turbine structure, and provide support for the optimization design of the offshore single pile foundation.

[0057] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. In the description of this application, it should be understood that the terms "left side", "right side", "upper part", "lower part" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. "First", "second" and the like do not indicate the importance of the components, and therefore cannot be understood as limiting the present invention. The specific dimensions used in this embodiment are only for illustrating the technical solution and do not limit the scope of protection of the present invention.

[0058] Any features such as component models, material names, connection structures, control methods, algorithms, etc. that are not clearly stated in this technical solution shall be deemed as common technical features disclosed in the prior art.

[0059] Example 1

[0060] like Figure 1 As shown, a distributed pile-soil interaction damping calculation method for an offshore single pile foundation in the present invention can be calculated using Python or Excel software. The method includes the following steps:

[0061] S1. Obtain the damping ratio-cyclic shear strain curve of the soil element of the target site. There are two options for this step: 1) Indoor test method, using a resonant column (under a strain level of ≤0.01%) and cyclic simple shear or cyclic triaxial (under a strain level of ≥0.1%) for combined testing; 2) Empirical method. If there is a lack of experimental data on the damping ratio-cyclic shear strain curve of the soil element, an empirical method can be used, such as the Derendeli (2001) damping ratio model calculation.

[0062] The Derendeli (2001) damping ratio model is as follows:

[0063]

[0064]

[0065]

[0066]

[0067] d Masing =c1×d Masing,a＝1.0 +c2×d Masing,a＝1.0 2 +c3×d Masing,a＝1.0 3

[0068]

[0069] c1=-1.1143×a 2 +1.8618×a+0.2523

[0070] c2=0.0805×a 2 -0.0710×a-0.0095

[0071] c3=-0.0005×a 2 +0.0002×a+0.0003

[0072] Where: γ is the cyclic shear strain, γ r is the reference shear strain (%), d min is the minimum strain damping ratio of the material (%), and a is the curve shape parameter Equal to, b is the scaling factor, d Adiusted is the damping ratio of the adjusted material (%), σ′0 is the average effective confining pressure (atm), PI is the plasticity index (%), OCR is the overconsolidation ratio, frq is the loading frequency, N is the number of cycles, is the calculation parameter, G / G max is the normalized shear modulus.

[0073] There are two different sets of calculation parameters for sand and clay.

[0074] Mixed sand and soil:

[0075]

[0076] Clay:

[0077]

[0078] like Figure 2 and Figure 3 As shown in Figure 3, the cyclic shear strain-damping ratio relationship curves of clay and sand in a target site were obtained through the combined indoor resonant column test and dynamic simple shear test.

[0079] S2. Calculate the pile-soil interaction damping of the single pile foundation at the py spring level. Directly deduce the pile-soil interaction damping of the single pile foundation at the py spring level from the soil unit damping ratio-cyclic shear strain, as follows: Figure 4 As shown, the mapping coefficient is 3.6; Figure 5 and Figure 6 Pile-soil interaction damping for single pile foundations at the py spring level on clay and sand sites;

[0080] S3. Calculate the pile deformation along the depth direction under the target cyclic load amplitude. This step can be obtained by modeling and calculating the pile body using finite element software such as marine engineering software SACS and Abaqus based on the single pile and site conditions.

[0081] As shown in Table 1, the main geotechnical parameters of the target site, the pile diameter of the single pile foundation is 10m, the wall thickness is 0.1m, and the penetration depth is 45m. According to the above stratum and single pile parameters, the modeling calculation is performed to obtain the pile displacement response amplitude, as shown in Figure 7 It should be noted that the pile displacement response amplitude is calculated using Abaqus software in this embodiment, so the software used in this step to calculate the pile displacement response is not limited by the present invention.

[0082] Table 1

[0083]

[0084] S4. Based on the pile displacement response in S2, calculate the Py spring reaction force using the Py calculation method for sand and clay. Determine the corresponding damping ratio based on the horizontal displacement of each Py spring. Calculate the secant stiffness of the corresponding Py spring at that displacement amplitude using the following formula.

[0085]

[0086] kp-y: py spring secant stiffness;

[0087] p:py spring reaction force;

[0088] u x : Typical displacement amplitude.

[0089] The clay layer in this embodiment adopts the single pile-soil interaction model proposed by the inventor to calculate the single pile from the soil stress-strain curve, such as Figure 8 As shown, the normalized stress-strain curve of the clay layer is input, and the current API sand py spring is used for the sand layer.

[0090] The spring reaction force and secant stiffness along the depth direction of the pile body are calculated, as follows: Figure 9 It should be noted that the py spring in this embodiment only embodies a method for calculating the pile-soil py spring curve from the soil stress-strain relationship. However, any py spring model can be replaced for this step. The present invention does not limit the use of any pile-soil py spring model, but the use of the py spring to calculate the secant stiffness in this step is protected.

[0091] S5. Calculate the damping coefficient c at the py spring level using formula 11, combining the pile-soil interaction damping at the py spring level in S2 and the py spring secant stiffness in S3, with a frequency based on the actual dominant frequency of the wave load (0.1 Hz is recommended).

[0092] The damping coefficient c is calculated as:

[0093]

[0094] Where k is the stiffness of the system, which is related to the elastic properties of the structure; d is the damping ratio, a dimensionless value used to describe the intensity of the system damping; and ω is the dominant frequency of the actual wave load.

[0095] Combining the pile-soil interaction damping and the py spring secant stiffness, in this embodiment, the frequency conversion is taken as 0.13 according to the period of 7.5s of the wave excitation load in the target sea area, and the damping coefficient of the py spring layer along the pile body is calculated as follows: Figure 10 shown.

[0096] In summary, this application proposes an innovative method for calculating the damping coefficient of pile-soil interaction of a single pile, in which the theory adopted has been rigorously verified.

[0097] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art and, unless defined as such herein, will not be interpreted in an idealized or overly formal sense.

[0098] This embodiment also proposes a distributed pile-soil interaction damping calculation device for an offshore single pile foundation, which includes a processor and a memory. The processor and the memory are coupled, and the memory stores program instructions. When the program instructions stored in the memory are executed by the processor, the above-mentioned task management method is implemented. The processor can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components; the memory may include random access memory (RAM) and may also include non-volatile memory (Non-Volatile Memory), such as at least one disk storage. The memory can be an internal memory of the random access memory (RAM) type. The processor and memory can be integrated into one or more independent circuits or hardware, such as an application-specific integrated circuit (ASIC). It should be noted that the computer program in the aforementioned memory can be implemented in the form of a software functional unit and, when sold or used as an independent product, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the portion that contributes to the prior art, or the portion of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, electronic device, or network device, etc.) to execute all or part of the steps of the methods of various embodiments of the present invention.

[0099] This embodiment also provides a computer-readable storage medium, wherein the storage medium stores computer instructions, and the computer instructions are used to cause a computer to execute the above-mentioned distributed pile-soil interaction damping calculation method for an offshore single pile foundation. The storage medium can be an electronic medium, a magnetic medium, an optical medium, an electromagnetic medium, an infrared medium, or a semiconductor system or a propagation medium. The storage medium can also include a semiconductor or solid-state memory, a magnetic tape, a removable computer disk, a random access memory (RAM), a read-only memory (ROM), a hard disk, and an optical disk. The optical disk can include a compact disk - read-only memory (CD-ROM), a compact disk - read / write (CD-RW), and a DVD.

[0100] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for calculating the distributed pile-soil interaction damping of an offshore single pile foundation, characterized in that: The following steps are involved: S1. Obtain the soil unit damping ratio-cyclic shear strain curve of the soil layer at the target site; S2. Based on the soil element damping ratio-cyclic shear strain curve, calculate py Pile-soil interaction damping of single pile foundation at spring level; S3, calculating the deformation of the single pile along the depth direction under the target cyclic load amplitude to obtain the pile displacement response; S4. Based on the pile displacement response obtained in S3, the sand and clay py The calculation method determines each py The reaction force of the spring, combined with each py The horizontal displacement of the spring, determine the damping ratio of each spring, and then calculate the py Secant stiffness of the spring at the corresponding displacement amplitude; S5, combining the soil element damping ratio-cyclic shear strain curve and S4 py The spring secant stiffness, as well as the actual wave load dominant frequency, is calculated py The damping coefficient c at the spring level is used to calculate the distributed pile-soil interaction damping of the offshore single pile foundation; In S1, the damping ratio-cyclic shear strain curve of the soil element of the target site soil layer is obtained from data obtained in one of the following ways: 1) Data obtained by the test method, i.e., data obtained by combining resonant column and cyclic simple shear or cyclic triaxial testing; 2) Data obtained by empirical methods, including data calculated using the damping ratio model of Derendeli (2001); In S1, the damping ratio model of the Derendeli 2001 version is as follows: in: γ is the cyclic shear strain , γ r is the reference shear strain, d min is the minimum strain damping ratio of the material, a is the curve shape parameter, b is the scaling factor, d Adiusted is the damping ratio of the adjusted material, σ′ 0 is the average effective confining pressure, PI is the plasticity index, OCR is the overconsolidation ratio, frq is the loading frequency, N is the number of cycles, φ i is the calculation parameter, G / G max is the normalized shear modulus.

2. The method for calculating the distributed pile-soil interaction damping of an offshore single pile foundation according to claim 1 is characterized in that: In S3, finite element software is used to model and calculate the deformation of the single pile along the depth direction under the target cyclic load amplitude based on the single pile parameters and site conditions.

3. The distributed pile-soil interaction damping calculation method for an offshore single pile foundation according to claim 1 is characterized in that: In S4, for the clay layer py The acquisition method is to calculate the single pile-soil interaction model from the soil stress-strain curve by adopting a method based on the soil unit damping ratio-cyclic shear strain curve.

4. The method for calculating the distributed pile-soil interaction damping of an offshore single pile foundation according to claim 1, characterized in that: In S4, for the sand layer py Acquisition method: using current API sand py spring.

5. The method for calculating the distributed pile-soil interaction damping of an offshore single pile foundation according to claim 1, characterized in that: In S4, calculate the corresponding py The secant stiffness of the spring at this displacement amplitude is expressed as: in: k p-y : py Spring secant stiffness; p : py Spring reaction force; u x : Typical displacement amplitude.

6. The method for calculating the distributed pile-soil interaction damping of an offshore single pile foundation according to claim 1, characterized in that: In S4, the damping coefficient c The calculation method is: in, k is the stiffness of the system, which is related to the elastic properties of the structure; d is the damping ratio, a dimensionless value used to describe the intensity of the system damping. ω is the dominant frequency of the actual wave load.

7. An electronic device comprising a memory and a processor, characterized in that: The processor is used to execute the program in the memory, so as to implement the distributed pile-soil interaction damping calculation method for offshore single pile foundation according to any one of claims 1 to 6.

8. A storage medium containing computer-executable instructions, characterized in that: When the computer-executable instruction storage medium is executed by a computer processor, it is used to perform the distributed pile-soil interaction damping calculation method for offshore single pile foundation according to any one of claims 1 to 6.

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