A calculation method for the horizontal cumulative displacement of large-diameter single piles in offshore wind power

Abstract

The present invention relates to the field of marine geotechnical engineering technology, and in particular to a method for calculating the horizontal cumulative displacement of a large-diameter single pile of offshore wind power, including: obtaining the position of the single pile and the type of soil, constructing a dynamic p-y curve and embedding it into a finite element software, inputting the physical and mechanical parameters of the target large-diameter single pile, simulating under different cyclic loads, analyzing the horizontal dynamic response of the single pile and constructing it as a data set; obtaining the peak displacement and model parameters at the end of monotonic loading based on the data set, constructing a single pile horizontal cumulative displacement prediction model, inputting the dimensionless load parameters of the target large-diameter single pile into the single pile horizontal cumulative displacement prediction model, and outputting the horizontal cumulative displacement of the target large-diameter single pile and the changing trend of the horizontal cumulative displacement with the number of cycles. The present invention realizes the accurate calculation of the horizontal cumulative displacement of a large-diameter single pile by constructing a dynamic p-y curve considering cyclic softening and a single pile horizontal cumulative displacement prediction model under different cyclic loads.

Description

Technical Field

[0001] The invention relates to the technical field of marine geotechnical engineering, and in particular to a method for calculating the horizontal cumulative displacement of a large-diameter single pile of offshore wind power. Background Art

[0002] As the supporting system of offshore wind turbines, offshore wind turbine foundations are crucial in the construction of offshore wind power. Monopile foundations are easy to make, efficient to install, and have excellent bearing performance. Large-diameter monopiles are the preferred foundation type for building offshore wind farms, and are suitable for offshore wind farms within a seawater depth of 50m. The accumulated horizontal displacement of large-diameter monopiles under long-term wind and wave loads is related to the operational safety of wind turbines and is a key issue of wind turbine operation and maintenance.

[0003] There are two main methods for evaluating the horizontal response of pile foundations: 1) using three-dimensional numerical analysis methods to evaluate. This type of model uses a constitutive model to simulate the cyclic softening behavior of the soil, and then analyzes its impact on the cumulative horizontal displacement of the pile foundation, but the modeling process of this type of model is relatively complicated; 2) The Winkler foundation beam method is usually used in pile foundation design, but most of the existing py curves are nonlinear and are generally used to determine the horizontal bearing capacity of a single pile, but it is difficult to describe the cumulative horizontal displacement characteristics of a single pile under constant amplitude cyclic loads. Therefore, a method for calculating the cumulative horizontal displacement of a large-diameter single pile in offshore wind power is urgently needed. Summary of the invention

[0004] The purpose of the present invention is to provide a method for calculating the horizontal cumulative displacement of a large-diameter single pile of offshore wind power, construct a dynamic py curve considering cyclic softening, and combine the Winkler foundation beam single pile dynamic response calculation data set to construct a single pile horizontal cumulative displacement prediction model under different cyclic loads to achieve accurate calculation.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A method for calculating the horizontal cumulative displacement of a large-diameter single pile of offshore wind power generation includes:

[0007] Obtain the position of the single pile and the soil type, and construct the dynamic py curve;

[0008] The dynamic py curve is embedded into the finite element software, the physical and mechanical parameters of the target large-diameter single pile are input, simulation is performed under different cyclic loads, the horizontal dynamic response of the single pile is analyzed and constructed as a data set;

[0009] Based on the data set, the peak displacement and model parameters at the end of monotonic loading are obtained, a single pile horizontal cumulative displacement prediction model is constructed, the dimensionless load parameters of the target large-diameter single pile are input into the single pile horizontal cumulative displacement prediction model, and the horizontal cumulative displacement of the target large-diameter single pile and the changing trend of the horizontal cumulative displacement with the number of cycles are output.

[0010] Optionally, the dynamic py curve includes a skeleton py curve and a hysteresis py curve.

[0011] Optionally, constructing the skeleton py curve includes:

[0012] The curve parameters are determined according to the soil type and physical and mechanical parameters, and the curve parameters are corrected to construct the skeleton py curve.

[0013] Optionally, the curve parameters include the initial horizontal foundation reaction modulus coefficient , soil ultimate resistance , Peak displacement coefficient , residual soil resistance ratio , where the initial horizontal foundation reaction modulus coefficient is According to the initial horizontal foundation reaction modulus Determine that the peak displacement coefficient According to the strain corresponding to half the peak strength of the soil Determine that the residual soil resistance ratio According to the preset code recommended value, the soil ultimate resistance Calculation is performed based on different soil types.

[0014] Optionally, modifying the curve parameters includes:

[0015] ;

[0016] ;

[0017] ;

[0018] ;

[0019] in, is the corrected soil ultimate resistance, and is the intermediate variable in the process of correcting the ultimate resistance of soil. is the residual soil resistance, is the horizontal displacement, is the diameter of the pile, for The corresponding horizontal displacement.

[0020] Optionally, the skeleton py curve is:

[0021] ;

[0022] in, is the initial horizontal base reaction modulus The reciprocal of is the modified soil ultimate resistance The reciprocal of .

[0023] Optionally, the hysteresis py curve is constructed using the Pyke criterion.

[0024] Optionally, the model parameters are:

[0025] ;

[0026] ;

[0027] in, and are model parameters, and is the dimensionless load parameter, and is dependent on Two functions of and is dependent on Two functions of .

[0028] Optionally, the dimensionless load parameter and for:

[0029] ;

[0030] ;

[0031] in, is the ultimate horizontal bearing capacity of a single pile, and are the maximum load and minimum load of equal-amplitude cyclic loading, respectively.

[0032] Optionally, the single pile horizontal cumulative displacement prediction model is:

[0033] ;

[0034] in, is the horizontal cumulative peak displacement during the Nth cycle loading, corresponding to the When loading a cycle , Corresponds to the peak displacement at the end of monotonic loading.

[0035] The beneficial effects of the present invention are:

[0036] The method proposed in the present invention, by constructing a dynamic py curve suitable for horizontal cyclic softening and a large-diameter single pile horizontal cumulative displacement prediction model, can predict the horizontal cumulative displacement of a large-diameter single pile and its changing trend with the number of cycles, providing a theoretical basis for the design of large-diameter single piles and long-term risk assessment. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 This is a flow chart of a method for calculating the horizontal cumulative displacement of a large-diameter single pile of offshore wind power according to an embodiment of the present invention;

[0039] Figure 2 A schematic diagram of a power py curve considering cycle softening according to an embodiment of the present invention;

[0040] Figure 3 A schematic diagram of applied cyclic load and corresponding horizontal cumulative displacement according to an embodiment of the present invention;

[0041] Figure 4 Schematic diagram of a finite element model for predicting the horizontal dynamic response of a single pile according to an embodiment of the present invention, wherein (a) is a single-spring model, (b) is a double-spring model, and (c) is a four-spring model. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] This embodiment provides a method for calculating the horizontal cumulative displacement of a large-diameter single pile of an offshore wind power plant, including:

[0045] Obtain the position of the single pile and the soil type, and construct the dynamic py curve;

[0046] The dynamic py curve is embedded into the finite element software, the physical and mechanical parameters of the target large-diameter single pile are input, simulation is performed under different cyclic loads, the horizontal dynamic response of the single pile is analyzed and constructed as a data set;

[0047] Based on the data set, the peak displacement and model parameters at the end of monotonic loading are obtained, a single pile horizontal cumulative displacement prediction model is constructed, the dimensionless load parameters of the target large-diameter single pile are input into the single pile horizontal cumulative displacement prediction model, and the horizontal cumulative displacement of the target large-diameter single pile and the changing trend of the horizontal cumulative displacement with the number of cycles are output.

[0048] Specifically, this embodiment constructs a dynamic py curve suitable for horizontal cyclic softening and a large-diameter single pile horizontal cumulative displacement prediction model, which can predict the horizontal cumulative displacement of a large-diameter single pile and its changing trend with the number of cycles, providing a theoretical basis for the design of large-diameter single piles and long-term risk assessment.

[0049] Furthermore, the dynamic py curve includes a skeleton py curve and a hysteresis py curve.

[0050] Wherein, constructing the skeleton py curve includes:

[0051] The curve parameters are determined according to the soil type and physical and mechanical parameters, and the curve parameters are corrected to construct the skeleton py curve.

[0052] The curve parameters include the initial horizontal foundation reaction modulus coefficient , soil ultimate resistance , Peak displacement coefficient , residual soil resistance ratio , where the initial horizontal foundation reaction modulus coefficient is According to the initial horizontal foundation reaction modulus Determine that the peak displacement coefficient According to the strain corresponding to half the peak strength of the soil Determine that the residual soil resistance ratio According to the preset code recommended value, the soil ultimate resistance Calculation is performed based on different soil types.

[0053] Correcting the curve parameters includes:

[0054] ;

[0055] ;

[0056] ;

[0057] ;

[0058] in, is the corrected soil ultimate resistance, and is the intermediate variable in the process of correcting the ultimate resistance of soil. is the residual soil resistance, is the horizontal displacement, is the diameter of the pile, for The corresponding horizontal displacement.

[0059] Furthermore, the skeleton py curve is:

[0060] ;

[0061] in, is the initial horizontal base reaction modulus The reciprocal of is the modified soil ultimate resistance The reciprocal of .

[0062] Furthermore, the hysteresis py curve is constructed using the Pyke criterion.

[0063] Furthermore, the model parameters are:

[0064] ;

[0065] ;

[0066] in, and are model parameters, and is the dimensionless load parameter, and is dependent on Two functions of and is dependent on Two functions of .

[0067] The dimensionless load parameters and for:

[0068] ;

[0069] ;

[0070] in, is the ultimate horizontal bearing capacity of a single pile, and are the maximum load and minimum load of equal-amplitude cyclic loading, respectively.

[0071] Furthermore, the single pile horizontal cumulative displacement prediction model is:

[0072] ;

[0073] in, is the horizontal cumulative peak displacement during the Nth cycle loading, corresponding to the When loading a cycle , Corresponds to the peak displacement at the end of monotonic loading.

[0074] Combine the following Figure 1 A method for calculating the horizontal cumulative displacement of a large-diameter single pile of offshore wind power proposed in this embodiment is described in detail, and specifically includes the following steps:

[0075] S1. Dynamic py curve construction: The dynamic py curve is designed to consist of a skeleton py curve and a hysteresis py curve.

[0076] S2. Determine the skeleton py curve and its parameters considering cyclic softening: According to the soil type and physical and mechanical parameters, determine the four curve parameters of the skeleton py curve, including the initial horizontal foundation reaction modulus coefficient , soil ultimate resistance , Peak displacement coefficient , residual soil resistance ratio .

[0077] S3. Establish a method to describe the effect of cyclic softening on soil resistance: using the horizontal cumulative displacement Make corrections, consider It decreases as the horizontal cumulative displacement increases.

[0078] S4. Construct hysteresis py curve: Based on the Pyke criterion, the hysteresis py curve is constructed, so that the dynamic py curve can adapt to irregular cyclic loading without increasing parameters; more optimally, the parameters can be set to control the size of the hysteresis loop.

[0079] S5. Finite element analysis: secondary development is carried out in the finite element software, the dynamic py curve is embedded into the Winkler foundation beam model, the physical and mechanical parameters of the target large-diameter single pile are input, the single pile is simulated using beam elements, and the finite element method is used to solve the horizontal dynamic response of the single pile;

[0080] S6. Construct a prediction model: Determine the amplitude of the cyclic load under the action of wind and waves through the specifications, and load it at a certain height. Consider the coupling effect of horizontal force and bending moment, calculate the horizontal dynamic response of a single pile, form a data set through finite element calculation analysis, and construct a single pile horizontal cumulative displacement prediction model.

[0081] S7. Predict the horizontal cumulative displacement of large-diameter single pile and its changing trend with the number of cycles through the prediction model.

[0082] Furthermore, the design skeleton py curve expression in step S1 is:

[0083] ;

[0084] in, is the initial horizontal base reaction modulus ( ), is the modified soil ultimate resistance ( ), is the horizontal displacement. In this embodiment, and is defined as:

[0085] ;

[0086] ;

[0087] Assuming the initial horizontal foundation reaction modulus , is a model constant, calculated as: , is the diameter of the pile.

[0088] Furthermore, the method for determining the curve parameters in step S2 includes: for sand and clay, using different methods to calculate ;

[0089] (1) Clay:

[0090] ;

[0091] ;

[0092] in, is the undrained shear strength, For depth, is an empirical parameter, the value for soft clay is 0.5, and the value for hard clay is 0.25. is the limit depth, is the effective weight of soil, is the diameter of the pile.

[0093] (2) Sandy soil:

[0094] ;

[0095] ;

[0096] in, represents the passive earth pressure coefficient, is the internal friction angle of soil.

[0097] According to the initial horizontal foundation reaction modulus Sure ; According to the strain corresponding to half the peak strength of the soil Sure ; Determined according to the recommended values ​​of existing specifications .

[0098] Further, in step S3, the soil type is determined After that, the horizontal cumulative displacement Corrections are made to reflect the softening behavior of soil resistance under horizontal cyclic loading.

[0099] like Remains unchanged and equal to , the formula can be simplified to a hyperbolic model, taking into account the softening of soil response, is specified to decrease with increasing pile deflection according to the formula:

[0100] ;

[0101] in, and Determined by satisfying two conditions: 1) The skeleton py curve passes through the point ( , ), for Corresponding horizontal displacement; 2) p in y= The first derivative with respect to y is zero.

[0102] and The expression is:

[0103] ;

[0104] ;

[0105] ;

[0106] in, is the residual soil resistance, .

[0107] Furthermore, in step S4, the Pyke criterion is used to adjust the dynamic py curve to adapt to the pile-soil interaction simulation under irregular cyclic loading conditions.

[0108] Furthermore, the proposed dynamic py curve is verified in step S5, mainly by simulating the pile using beam elements through the finite element method to solve the horizontal response of a single pile. In the finite element analysis, the py curve is to divide the pile into a series of elastic beam elements connected to the horizontal soil spring, and the length of each beam element is kept at 1 meter or less to ensure the accuracy of the calculation.

[0109] The beam elements used in the finite element program are able to simulate the response of large-diameter single piles under horizontal loads, and the length of each beam element is kept to 1 meter or less to ensure the accuracy of the calculation.

[0110] Furthermore, in step S6, the method of separating variables is first used to construct and and , A function of the two dimensionless load parameters , Describes the amplitude of the cyclic load:

[0111] ;

[0112] ;

[0113] in, is the ultimate horizontal bearing capacity of a single pile, which can be determined by a monotonic loading test. and are the maximum load and minimum load of equal-amplitude cyclic loading, respectively.

[0114] Model parameters and It can be written as the product of two independent variables:

[0115] ;

[0116] ;

[0117] in, and is dependent on Two functions of and is dependent on Two functions of . , , and It is obtained by linear fitting or nonlinear fitting of the data set calculated by finite element calculation.

[0118] Secondly, a single pile horizontal cumulative displacement prediction model is established, and the power function is used to fit the normalized cumulative peak lateral displacement and the number of cyclic loading. The relationship between:

[0119] ;

[0120] in, is the horizontal cumulative peak displacement during the Nth cycle loading, corresponding to the When loading a cycle , Corresponds to the peak displacement at the end of monotonic loading.

[0121] The single pile horizontal cumulative displacement prediction model is further used to predict the horizontal cumulative displacement of a large-diameter single pile and its changing trend with the number of cycles, providing a method for the design of offshore wind power foundations.

[0122] This embodiment first determines the four curve parameters of the dynamic py curve according to the specific location of the single pile and the soil type; then establishes a cyclic softening method and a dynamic py curve suitable for clay and sand, such as Figure 2 As shown; secondary development is carried out in the finite element software, the dynamic py curve is embedded in the finite element program, the Timoshenko beam unit is used to simulate the single pile, the physical and mechanical parameters of the large-diameter single pile are input, and the finite element method is used to solve the horizontal dynamic response; finally, the DNV specification is used to determine the cyclic load amplitude and loading times under the action of wind and waves, and the load is loaded at a certain height. Considering the coupling effect of horizontal force and bending moment, the dynamic response is calculated, and a single pile horizontal cumulative displacement prediction model is constructed through a large number of data sets. The dimensionless load parameters are input into the single pile horizontal cumulative displacement prediction model, and the horizontal cumulative displacement of the large-diameter single pile and the changing trend of the horizontal cumulative displacement with the number of cycles are output.

[0123] Specifically, the dynamic response analysis of a single pile based on the Winkler foundation beam theory determines the four curve parameters of the dynamic py curve according to the specific location of the single pile, such as the geological exploration data of the offshore wind farm, and the soil type, such as clay or sand. The dynamic py curve is embedded in the finite element calculation model. The models that can be considered include the single spring model, which only considers the horizontal soil resistance, such as Figure 4 As shown in (a); double spring model, considering the horizontal soil resistance and pile bottom shear force, as shown in Figure 4 As shown in (b); and the four-spring model, considering the horizontal soil resistance, pile bottom shear force, pile bottom bending moment, and vertical pile body shear stress), as shown in Figure 4 As shown in (c) in the figure, in the finite element calculation, the horizontal cyclic load is applied at a certain height and the horizontal cumulative displacement of the pile is calculated. Figure 3The applied cyclic load and the corresponding horizontal cumulative displacement are represented. Based on the data sets under different cyclic loads, a single pile horizontal cumulative displacement prediction model is constructed. The dimensionless load parameters of the large-diameter single pile are input into the single pile horizontal cumulative displacement prediction model, and the horizontal cumulative displacement and the changing trend of the horizontal cumulative displacement with the number of cycles are output.

[0124] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for calculating the horizontal cumulative displacement of a large-diameter single pile of offshore wind power, characterized in that: include: Obtain the position of the single pile and the soil type, and construct the dynamic py curve; The dynamic py curve is embedded into the finite element software, the physical and mechanical parameters of the target large-diameter single pile are input, simulation is performed under different cyclic loads, the horizontal dynamic response of the single pile is analyzed and constructed as a data set; Based on the data set, the peak displacement and model parameters at the end of monotonic loading are obtained, a single pile horizontal cumulative displacement prediction model is constructed, the dimensionless load parameters of the target large-diameter single pile are input into the single pile horizontal cumulative displacement prediction model, and the horizontal cumulative displacement of the target large-diameter single pile and the variation trend of the horizontal cumulative displacement with the number of cycles are output; Wherein, the dynamic py curve includes a skeleton py curve and a hysteresis py curve; Constructing the skeleton py curve includes: Determine the curve parameters according to the soil type and physical and mechanical parameters, and modify the curve parameters to construct the skeleton py curve; The curve parameters include the initial horizontal foundation reaction modulus coefficient , soil ultimate resistance , Peak displacement coefficient , residual soil resistance ratio , where the initial horizontal foundation reaction modulus coefficient is According to the initial horizontal foundation reaction modulus Determine that the peak displacement coefficient According to the strain corresponding to half the peak strength of the soil Determine that the residual soil resistance ratio According to the preset code recommended value, the soil ultimate resistance Calculate and determine according to different soil types; Correcting the curve parameters includes: ； ； ； ； in, is the corrected soil ultimate resistance, and is the intermediate variable in the process of correcting the ultimate resistance of soil. is the residual soil resistance, is the horizontal displacement, is the diameter of the pile, for The corresponding horizontal displacement; The skeleton py curve is: ； in, is the initial horizontal foundation reaction modulus The reciprocal of is the modified soil ultimate resistance The reciprocal of .

2. The method for calculating the horizontal cumulative displacement of a large-diameter single pile for offshore wind power according to claim 1 is characterized in that: The Pyke criterion is used to construct the hysteresis py curve.

3. The method for calculating the horizontal cumulative displacement of a large-diameter single pile of offshore wind power according to claim 1 is characterized in that: The model parameters are: ； ； in, and are model parameters, and is the dimensionless load parameter, and is dependent on Two functions of and is dependent on Two functions of .

4. The method for calculating the horizontal cumulative displacement of a large-diameter single pile of offshore wind power according to claim 3 is characterized in that: The dimensionless load parameters and for: ； ； in, is the ultimate horizontal bearing capacity of a single pile, and are the maximum load and minimum load of equal-amplitude cyclic loading, respectively.

5. The method for calculating the horizontal cumulative displacement of a large-diameter single pile of offshore wind power according to claim 4 is characterized in that: The single pile horizontal cumulative displacement prediction model is: ； in, is the horizontal cumulative peak displacement during the Nth cycle loading, corresponding to the When loading a cycle , Corresponds to the peak displacement at the end of monotonic loading.

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