CN-122021100-A - Offshore wind power pile foundation pile soil effect design method under multi-scale coupling effect

CN122021100ACN 122021100 ACN122021100 ACN 122021100ACN-122021100-A

Abstract

The invention provides a method for designing the pile foundation soil effect of an offshore wind power pile under a multi-scale coupling effect, which relates to the technical field of offshore wind power engineering and comprises the steps of obtaining engineering geology, hydrology and fan design parameters of a target sea area, and determining a preliminary design scheme of a pile foundation; identifying each soil layer, extracting macroscopic mechanical parameters, determining a microscopic soil body structural factor reflecting the microstructure characteristics of the soil body, establishing a multi-scale analysis frame dividing a near pile area and a far field area, constructing a constitutive relation considering structural damage in the near pile area, calculating a pile periphery soil body impedance attenuation coefficient considering time-varying effects such as wave flow circulation and microbial corrosion based on the frame, coupling the coefficient into a multi-scale model, establishing a modified three-dimensional finite element model, carrying out nonlinear static-dynamic coupling analysis on the model, obtaining pile foundation response, evaluating performance and carrying out iterative optimization. The invention realizes the quantitative coupling of soil body structural and environmental long-term effect, and improves the precision of pile foundation design and the reliability of long-term performance prediction.

Inventors

LI BAOJIAN
YANG ZHONGXUAN
Fu Sai
PAN KUN
LI TAO

Assignees

杭州市拱墅区工大未来技术研究院
杭州世宗未来科技研究有限公司

Dates

Publication Date: 20260512
Application Date: 20251211

Claims (10)

1. The method for designing the pile foundation soil effect of the offshore wind turbine under the multi-scale coupling effect is characterized by comprising the following steps of: s1, acquiring engineering geological survey data, marine hydrologic data and fan structure design parameters of a target sea area, and determining the preliminary geometric dimension and material properties of a pile foundation; S2, identifying each soil layer penetrated by the pile foundation based on the engineering geological survey data, and extracting macroscopic physical mechanical parameters of each soil layer; S3, establishing a multi-scale analysis framework of pile-soil interaction, namely dividing a pile-soil system into a near pile area microscopic scale analysis domain and a far field area macroscopic continuous medium analysis domain, constructing constitutive relation considering soil structural damage evolution according to the microscopic soil structural factors and soil macroscopic mechanical parameters in the near pile area microscopic scale analysis domain, and adopting a macroscopic soil constitutive model in the far field area macroscopic continuous medium analysis domain; S4, calculating the impedance attenuation coefficient of the soil body around the pile under the coupling effect of the cyclic load and the marine environment based on the multi-scale analysis frame established in the step S3, wherein the calculation comprehensively considers the stress field redistribution, the weakening of the soil body rigidity and the material characteristic time-varying effect caused by the microbial activity of the soil body around the pile caused by waves and ocean currents; s5, coupling the pile periphery soil body impedance attenuation coefficient obtained by calculation in the step S4 into constitutive relation of a near pile area microscopic scale analysis domain constructed in the step S3 and boundary conditions of a far field region macroscopic continuous medium analysis domain, and establishing a corrected pile-soil body system three-dimensional finite element numerical model; S6, applying a design wave flow load, a fan operation load and an extreme working condition load to the corrected three-dimensional finite element numerical model, and carrying out nonlinear static-dynamic coupling analysis on the pile foundation under the complex load to obtain the displacement, internal force distribution and pile end bearing characteristics of the pile body; and S7, based on the analysis result of the step S6, evaluating the bearing capacity safety margin, the deformation control index and the long-term service performance of the pile foundation, if the evaluation result does not meet the design requirement, returning to the step S1, adjusting the geometric dimension or the material property of the pile foundation, and iteratively executing the steps S2 to S7 until all the design indexes meet the requirement, and outputting a final pile foundation design scheme.
2. The method for designing the pile foundation pile soil effect of the offshore wind turbine under the multi-scale coupling effect according to claim 1, wherein in the step S4, the calculation of the pile foundation soil body impedance attenuation coefficient is realized by the following steps: s401, determining additional cyclic shear stress amplitude caused by waves and ocean current loads at specific depths around the pile in the current calculation time step Average static shear stress ; S402, acquiring the initial non-drainage shear strength of the soil body at the depth Super-junction ratio OCR, mesoscopic soil structure factor defined in step S2 ; S403, calculating the impedance attenuation coefficient of the soil body around the pile at the current time step at the depth according to the following formula ; Wherein z is the depth of a calculated point, t is the current service time, and N is the equivalent cyclic load frequency corresponding to the current time step; Is the reference number of cycles; The material constants related to the soil body type and state are calibrated through an indoor circulating triaxial test; Is a reference mesoscopic soil body structural factor; Is the reference time; As a factor of the influence of the microbial activity, based on time-varying parameters determined by in-situ monitoring or in-house microbiological tests.
3. The method for designing the pile foundation soil effect of the offshore wind turbine under the multi-scale coupling effect according to claim 1, wherein in the step S2, the determination of the mesoscopic soil body structural factor is realized by the following steps: S201, sampling undisturbed soil of a target soil layer to obtain a representative soil sample; s202, acquiring a pore distribution curve or microstructure image of a soil sample through mercury intrusion test or scanning electron microscope image analysis; s203, quantifying indexes for representing soil body structure, including but not limited to structural yield stress Yield stress with remolded soil Ratio of (2) And a pore distribution uniformity coefficient ; S204, comprehensively calculating the mesoscopic soil body structural factors through the following formula : Wherein, the Is the ratio of the structural yield stress to the remolded soil yield stress; The non-uniform coefficient of pore distribution is obtained by mercury intrusion test; The initial pore ratio of the soil sample; Respectively the maximum and minimum pore ratios of the soil sample; Is determined by regression analysis of test data of soil samples with different structures for fitting coefficients and meets the requirement of 。
4. The method for designing the pile foundation soil action of the offshore wind turbine under the multi-scale coupling effect according to claim 1, wherein in the step S3, the boundary of the near-pile area microscopic scale analysis domain is determined by taking the outer surface of the pile body as a starting point and expanding the pile body to an annular soil area within a range of 3 times of the pile diameter outwards, and the far-field region macroscopic continuous medium analysis domain is a soil area outside the boundary of the near-pile area microscopic scale analysis domain.
5. The method for designing the pile foundation soil action of the offshore wind turbine under the multi-scale coupling effect according to claim 1, wherein in the step S3, the constitutive relation constructed in the near pile area microscopic scale analysis domain is an elastoplastic constitutive model considering the structural anisotropic damage of the soil, and the microscopic soil structural factors are introduced into the yield surface function As an internal state variable to describe the gradual loss of soil structure during loading.
6. The method for designing the pile foundation soil effect of the offshore wind turbine according to claim 1, wherein in the step S5, the specific mode of coupling is to attenuate the impedance coefficient of the soil body around the pile As a reduction coefficient, directly multiplying the initial elastic modulus and the strength parameter of the soil body unit in the microscopic scale analysis domain of the near pile area, and simultaneously The spatial distribution of the far field region macroscopic continuous medium analysis domain is used as the correction basis of the stress boundary condition of the near pile boundary.
7. The method for designing the foundation pile soil effect of the offshore wind turbine under the multi-scale coupling effect according to claim 1, wherein in the step S6, the nonlinear static-dynamic coupling analysis adopts an implicit-explicit alternating solving strategy, namely, firstly, static balance analysis is carried out, dead weight, superstructure constant load and average ocean current load are applied, and then, on the basis of static balance results, an explicit time integration method is adopted, and then, dynamic time course analysis is carried out by gradually applying wave dynamic load and time-varying fan running load.
8. The method for designing the pile foundation soil effect of the offshore wind turbine under the multi-scale coupling effect according to claim 7, wherein when the dynamic time-course analysis is carried out, after the explicit calculation of a preset time length is completed, an implicit iterative solution is carried out to correct numerical drift possibly caused by large deformation or strong nonlinearity, so that the long-term stability of the calculation is ensured.
9. The method for designing the pile foundation pile soil effect under the multi-scale coupling effect according to claim 1, wherein in the step S7, the long-term service performance evaluation comprises the steps of calculating the pile circumference soil body impedance attenuation coefficient based on the step S4 Predicting the changes of pile foundation horizontal displacement, rotation angle and natural frequency in the designed life cycle, and checking whether the pile foundation horizontal displacement, rotation angle and natural frequency are always within the allowable limit values.
10. The method for designing the foundation pile soil action of the offshore wind turbine under the multi-scale coupling effect according to claim 1, wherein in the step S1, when the marine hydrologic data are acquired, the maximum local scouring depth and scouring pit morphology possibly occurring in the service life of the design are analyzed and calculated, particularly for pile foundation positions, and the scouring topography is used as the initial geometric boundary condition of the seabed surface when the three-dimensional finite element numerical model is established in the step S5.

Description

Offshore wind power pile foundation pile soil effect design method under multi-scale coupling effect Technical Field The invention relates to the technical field of offshore wind power engineering, in particular to a method for designing the pile foundation soil effect of an offshore wind power pile under a multi-scale coupling effect. Background The long-term safety and economy of the basic structure of the offshore wind power serving as an important development direction of clean energy are key to the success and failure of engineering. Pile foundations, in particular to large-diameter single piles, become the most widely used offshore wind power foundation form at present due to the advantages of convenience in construction, high bearing capacity and the like. However, the pile foundation of offshore wind power is under the coupling effect of complex marine environment and severe load condition for a long time, the pile-soil interaction mechanism is extremely complex, and the traditional design method faces a series of significant challenges and limitations. The traditional design method generally regards soil as a macroscopically homogeneous continuous medium, and adopts mechanical parameters obtained based on remolded soil or completely disturbed soil samples for design. This approach completely ignores the ubiquitous structural nature of naturally deposited soil. The arrangement, cementing and organization characteristics of the particles formed by the natural soil body in the sedimentary and geological history endow the natural soil body with initial strength and rigidity which are far higher than those of remolded soil. The traditional method ignores the 'primary strength' caused by microscopic and microscopic structures, so that in design calculation, the deformation of a soil body in initial loading is overestimated, so that the design is too conservative and uneconomical, or more serious, the rapid damage and loss process of the soil body structure under cyclic load is not foreseen, and the long-term rigidity and bearing capacity of a pile foundation are overestimated. How to quantify and introduce the soil body structural key attribute becomes a primary difficult problem for improving the design precision. The problem of long-term performance degradation due to coupling effects of marine environment and load is severely underestimated. The traditional design mostly adopts static force analysis to assist in simple fatigue check, and cannot fully couple the interaction of environmental loads such as waves, ocean currents and the like and pile foundation dynamic response. Under millions or hundreds of millions of wave current cyclic loads, the rigidity and the strength of the pile soil body can be obviously weakened in a cumulative way. In addition, special factors in the marine environment, such as local scouring of the pile periphery to change the constraint condition of the soil body and biochemical corrosion and the like effect of microbial activity on the soil body around the pile, lack of system consideration and quantization models in the existing design framework. This results in an inability to accurately predict displacement development, load bearing capacity decay, and natural frequency drift of pile foundations over the full life cycle based on initial state designs, and a significant risk of loss of control in long-term service performance predictions for fans, which are extremely deformation and vibration sensitive structures. In the existing design flow, load analysis, soil response calculation and pile foundation design optimization are often relatively isolated links. The primary load calculation and the safety checking calculation are generally carried out based on the initially assumed pile foundation size, and if the pile foundation size is not qualified, the pile foundation size is adjusted empirically and then checked again. The process breaks the dynamic coupling and iterative feedback relation between the load-soil response-pile foundation size. For example, the change of pile foundation size can directly influence the dynamic characteristics of the pile foundation, so that the magnitude of wave load is changed, and the pile circumferential stress field is also changed, so that the soil degradation process is influenced. The inability of conventional static, isolated iterations to capture such dynamic interactions makes the design optimization process inefficient, and the end result may be just a safety threshold met, rather than a truly optimal economic safety balance scheme under multi-factor coupling. Disclosure of Invention The invention provides a method for designing the pile foundation soil effect of an offshore wind power pile under a multi-scale coupling effect, aiming at solving the technical problems of insufficient design precision and uncontrolled prediction of long-term performance caused by neglecting soil body structural property, uncoupled multi-factor long-