Near-field bridge pile foundation p-y curve correction method based on dynamic response test and numerical simulation

Abstract

The invention belongs to the technical field of bridge pile foundation earthquake resistance, and particularly discloses a near-field bridge pile foundation p-y curve correction method based on a dynamic response test and numerical simulation, and the method comprises the following steps: carrying out statistical analysis on near-field vibration characteristics; carrying out a soil dynamic response test under the earthquake action; establishing a numerical model considering the influence of near-site vibration; obtaining a p-y curve based on a numerical analysis result; and establishing a corrected p-y curve considering the influence of the near-field vibration characteristics. The near-field bridge pile foundation p-y curve capable of accurately reflecting the near-field vibration effect is obtained by systematically researching the near-field vibration characteristics, and the problems of pile-soil interaction simulation deviation, unreasonable design method and the like caused by inaccurate p-y curve in the bridge pile foundation aseismic design under near-field vibration are solved; and the anti-seismic performance of the bridge pile foundation under the near-field earthquake is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge pile foundation seismic resistance, and in particular to a near-field bridge pile foundation PY curve correction method based on dynamic response tests and numerical simulations. Background Art

[0002] Earthquakes are powerful and unpredictable natural disasters, causing massive property losses, casualties, and devastating ecological impacts. With the continuous expansion of human engineering construction needs, a large number of engineering structures will inevitably be built near active fault zones, subject to the constant threat of potential earthquakes. Pile foundations have been widely used in bridge engineering due to their excellent bearing capacity, stability, uniform settlement, ease of construction, low material consumption, and adaptability to various hydrogeological conditions and load characteristics. However, under earthquake action, bridge pile foundations and the surrounding rock and soil will be severely disturbed, significantly affecting the stability and bearing capacity of the pile foundations. Therefore, the impact of ground motion must be fully considered in the design. Compared with far-field ground motion, near-fault ground motion is influenced by factors such as the focal mechanism, fault rupture process, and site conditions. It exhibits characteristics such as pulse effects caused by directional and slip effects, hanging wall effects of fault rupture, and significant vertical ground motion, which have a more significant impact on bridge pile foundations.

[0003] The near-field vibration velocity pulse effect causes bridge pile foundations to withstand enormous impact forces in a short period of time, triggering large, instantaneous displacements of the pile body. These large displacements exceed the applicable range of the conventional P-Y curve and damage the pile structure. The hanging plate effect subjects the pile foundation to greater vertical loads and displacements, leading to damage and failure. The significant vertical force forces bridge pile foundations to withstand not only horizontal seismic forces but also huge vertical axial force fluctuations. Excessive vertical axial forces can easily cause compression buckling or tensile cracking of the pile body, severely weakening the pile foundation's bearing capacity. In bridge seismic design, the impact of near-field vibration characteristics on pile foundations must be fully considered to improve the seismic performance of bridge structures.

[0004] The Py curve method is the most commonly used in the seismic design of existing bridge pile foundations. It reflects the relationship between the horizontal resistance of the soil surrounding the pile and the horizontal displacement of the pile foundation when the pile foundation is horizontally loaded. The Py curve can be used to calculate the lateral deformation and internal forces of the pile foundation under earthquake action, thus providing a basis for the seismic design of bridges. However, existing Py curves are generally based on experimental data and empirical formulas of far-field vibrations and do not fully consider the complexity of near-field vibrations. As a result, bridge pile foundations designed according to traditional Py curves are prone to excessive deformation or even failure in near-field earthquakes, seriously threatening the safe use of bridges.

[0005] Therefore, it is urgent to develop a method that can fully consider the near-field site vibration characteristics and accurately obtain the near-field bridge pile foundation py curve. Summary of the Invention

[0006] In order to solve the problems existing in the prior art, the present invention provides a near-field bridge pile foundation py curve correction method based on dynamic response tests and numerical simulations. By systematically studying the near-field field vibration characteristics, the near-field bridge pile foundation py curve that can accurately reflect the near-field field vibration effect is obtained. The problems of pile-soil interaction simulation deviation and unreasonable design method caused by inaccurate py curve in the seismic design of bridge pile foundation under near-field field vibration are solved, the seismic performance of bridge pile foundation under near-field earthquake is improved, and the problems mentioned in the above background technology are solved.

[0007] To achieve the above object, the present invention provides the following technical solution: a near-field bridge pile foundation py curve correction method based on dynamic response test and numerical simulation, comprising the following steps: S1. Statistical analysis of near-field vibration characteristics; S2. Soil dynamic response test under earthquake: Conduct triaxial tests on soil sample units and pile foundation shaking table model tests to analyze the dynamic response of soil under different near-site vibrations; S3. Establish a numerical model considering the influence of near-field vibration; S4. Obtaining a py curve based on the numerical analysis results; S5. Establish a modified py curve that takes into account the influence of near-field vibration characteristics.

[0008] Preferably, in step S1, the following is specifically included: S11. Filtering near-field earthquake data from multiple earthquake databases, including seismic wave records, focal mechanisms, source parameters, and site condition information; S12. Use the M&P equivalent pulse model to identify pulse ground motions, clarify the relationship between pulse duration, peak velocity, focal distance, fault type, and the energy distribution of pulse components under different site conditions; S13. Extract the vertical acceleration component from the seismic wave, calculate its amplitude range and frequency, analyze the magnitude and phase relationship between the vertical acceleration and the horizontal acceleration, and evaluate its impact on the vertical load of the pile foundation; conduct comprehensive statistics on the above analysis results and establish a near-field vibration characteristics database.

[0009] Preferably, in step S2, the following is specifically included: S21. Conduct dynamic triaxial tests on soil sample units. The dynamic triaxial tests use undisturbed soil on site and undergo bidirectional excitation loading. The input load is the measured near-site vibration, taking into account different velocity pulse sizes and vertical accelerations. During the test, the dynamic shear modulus, damping ratio, pore water pressure, and axial strain parameters of the soil sample are monitored in real time to analyze the strength degradation, stiffness attenuation, and liquefaction characteristics of the soil under near-field earthquake action. S22. Conduct a shaking table model test on a pile foundation. The model pile shall be scaled according to the shaking table dimensions and the pile design drawings to determine the pile diameter, pile length, elastic modulus, and flexural stiffness. The model soil shall be kept as consistent as possible with the on-site bored soil layer. Strain gauges and displacement meters shall be arranged along the pile body, and pore pressure sensors and soil pressure gauges shall be arranged in the soil around the pile. Based on the screening of near-field pulse seismic motion, the coupling relationship between vertical acceleration and horizontal motion shall be considered at the same time. The coordinated loading of three-dimensional seismic motion shall be achieved through nonlinear superposition. The data of pile displacement, pile strain, soil pressure, and pore pressure shall be collected to analyze the pile-soil dynamic response law.

[0010] Preferably, in step S3, a pile-soil interaction numerical model is constructed using finite difference software; in the model, a nonlinear constitutive relationship that takes into account soil stiffness attenuation is adopted to accurately simulate the mechanical behavior of the soil under complex stress states, and soil layer information is determined by combining field in-situ tests and indoor tests; According to the actual pile foundation design drawings and material properties, the geometric dimensions, elastic modulus, Poisson's ratio, and bending stiffness parameters of the pile foundation are determined, and the linear elastic constitutive relationship is selected; The boundary conditions of the model are set to a sufficiently large range to reduce the influence of boundary reflection on the calculation results; the initial conditions include the initial stress state of the soil and the installation conditions of the pile foundation; The input load is consistent with the model test, and the numerical simulation results are compared with the test results to perform parameter verification and optimization.

[0011] Preferably, in step S4, in the numerical simulation results, nodes at different depths of the pile body are selected to extract their lateral displacement y and corresponding soil resistance p data under earthquake action; by drawing the relationship curve between lateral displacement and soil resistance, py curves at different positions are obtained; and by changing the input conditions, including different velocity pulses, pulse periods and vertical acceleration sizes, a py curve database under different working conditions is formed.

[0012] Preferably, in step S5, based on the py curve: (1) A dual-parameter correction is introduced to fully consider the influence of near-field vibration. The corrected py curve is as follows: (2) Where, is the initial foundation modulus; is the horizontal ultimate soil resistance; In order to consider the reduction factor of the initial foundation modulus due to the characteristics of the near-site vibration, It is the reduction factor of the horizontal ultimate soil resistance considering the near-site vibration characteristics.

[0013] Preferably, Calculate according to soil type: For clay, The calculation formula is as follows: (3) Where, is the undrained shear strength; D is the pile diameter; is the effective density of the soil; z is the depth below the ground surface; J is a dimensionless empirical constant determined by field tests, with a value ranging from 0.25 to 0.5; is the turning point depth of ultimate soil resistance; For sandy soil, The calculation formula is as follows: (4) Where, All represent functions of the friction angle within the soil; For weathered rocks, The calculation formula is as follows: (5) Where, is the compressive strength of the rock; is the strength reduction factor; By performing multivariate parameter regression analysis, the functional relationship between the correction coefficient and the seismic parameters is established: (6) (7) Where h is the depth of the calculation point (m); L is the pile length (m); PGV P is the pulse peak velocity (m / s); T p is the pulse period (s); is the vertical acceleration (m / s²).

[0014] Substituting equations (6) and (7) into equation (2), we can obtain the corrected py curve.

[0015] The present invention has the following beneficial effects: Through systematic statistical analysis of near-site vibration characteristics, in-depth experimental research on soil dynamic response, precise numerical model development, and scientific P-Y curve correction, the present method can obtain a near-field bridge pile foundation P-Y curve that accurately reflects the near-site vibration characteristics. Based on this corrected P-Y curve, seismic design of bridge pile foundations can more accurately simulate pile-soil interaction under near-site vibration, greatly improving the accuracy and reliability of bridge pile foundation seismic design. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1Schematic diagram of the process of the near-field bridge pile foundation py curve correction method based on dynamic response test and numerical simulation; Figure 2 Schematic diagram of the py curve. DETAILED DESCRIPTION

[0017] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0018] The present invention provides a technical solution: a near-field bridge pile foundation py curve correction method based on dynamic response test and numerical simulation, such as Figure 1 As shown, the following steps are included: S1. Statistical analysis of near-field vibration characteristics; specifically including the following: S11. Filter near-field earthquake data from multiple global earthquake databases, including seismic wave records, focal mechanisms, source parameters, site conditions, and other information; S12. Use the M&P equivalent pulse model to identify pulse ground motions, clarify the relationship between pulse duration, peak velocity, focal distance, fault type, and the energy distribution of pulse components under different site conditions; S13. Extract the vertical acceleration component from the seismic wave, calculate its amplitude range and frequency, analyze the magnitude and phase relationship between the vertical acceleration and the horizontal acceleration, and evaluate its impact on the vertical load of the pile foundation; conduct comprehensive statistics on the above analysis results and establish a near-field vibration characteristics database.

[0019] S2. Soil dynamic response test under earthquake: Conduct triaxial tests on soil sample units and pile foundation shaking table model tests to analyze the dynamic response of soil under different near-field vibrations. The specific tests include the following: S21. Conduct dynamic triaxial tests on soil sample units. The dynamic triaxial tests use undisturbed soil on site and undergo bidirectional excitation loading. The input load is the measured near-site vibration, taking into account different velocity pulse sizes and vertical accelerations. During the test, the dynamic shear modulus, damping ratio, pore water pressure, and axial strain parameters of the soil sample are monitored in real time to analyze the strength degradation, stiffness attenuation, and liquefaction characteristics of the soil under near-field earthquake action. S22. Conduct a shaking table model test on a pile foundation. The model pile shall be scaled according to the shaking table dimensions and the pile design drawings to determine the pile diameter, pile length, elastic modulus, and flexural stiffness. The model soil shall be kept as consistent as possible with the on-site bored soil layer. Strain gauges and displacement meters shall be arranged along the pile body, and pore pressure sensors and soil pressure gauges shall be arranged in the soil around the pile. Based on the screening of near-field pulse seismic motion, the coupling relationship between vertical acceleration and horizontal motion shall be considered at the same time. The coordinated loading of three-dimensional seismic motion shall be achieved through nonlinear superposition. The data of pile displacement, pile strain, soil pressure, and pore pressure shall be collected to analyze the pile-soil dynamic response law.

[0020] S3. Establish a numerical model that considers the influence of near-field vibrations; use finite difference software to construct a numerical model of pile-soil interaction; in the model, adopt a nonlinear constitutive relationship that considers the attenuation of soil stiffness to accurately simulate the mechanical behavior of soil under complex stress states, and the soil layer information is determined by combining on-site in-situ tests and indoor tests; according to the design drawings and material properties of the actual pile foundation, determine the geometric dimensions, elastic modulus, Poisson's ratio, and bending stiffness parameters of the pile foundation, and select a linear elastic constitutive relationship; the boundary conditions of the model are set to a sufficiently large range to reduce the influence of boundary reflections on the calculation results; the initial conditions include the initial stress state of the soil and the installation conditions of the pile foundation; the input load is consistent with the model test, and the numerical simulation results are compared with the test results to perform parameter verification and optimization to verify the accuracy of the model.

[0021] S4. Obtain the py curve based on the numerical analysis results. In the numerical simulation results, select nodes at different depths of the pile body and extract their lateral displacement y and corresponding soil resistance p data under earthquake action. By plotting the relationship curve between lateral displacement and soil resistance, the py curves at different positions are obtained, such as Figure 2 As shown; by changing the input conditions, including different speed pulses, pulse periods and vertical acceleration sizes, a py curve database under different working conditions is formed.

[0022] S5. Establish a modified py curve that takes into account the influence of near-field vibration characteristics.

[0023] Based on py curve (py curve of hyperbolic model): (1) A dual-parameter correction is introduced to fully consider the influence of near-field vibration characteristics. The corrected py curve is as follows: (2) Where, is the initial foundation modulus (kN / m 2 ); is the horizontal ultimate soil resistance (kN / m); In order to consider the reduction factor of the initial foundation modulus due to the characteristics of the near-site vibration, It is the reduction factor of the horizontal ultimate soil resistance considering the near-site vibration characteristics.

[0024] Furthermore, according to the API specification, the parameters can be obtained and ,in Calculate according to soil type: For clay, The calculation formula is as follows: (3) Where, is the undrained shear strength (kPa); D is the pile diameter (m); is the effective density of soil (kN / m 3 ); z is the depth below the ground surface (m); J is a dimensionless empirical constant determined by field tests, with a value ranging from 0.25 to 0.5; is the turning point depth of ultimate soil resistance (m); For sandy soil, The calculation formula is as follows: (4) Where, All represent functions of the friction angle within the soil; For weathered rocks, The calculation formula is as follows: (5) Where, is the compressive strength of rock (kPa); is the strength reduction factor; The correction coefficient is obtained by fitting the py curve drawn according to the numerical simulation and , the calculation results under different working conditions are summarized in Table 1: Through multivariate parameter regression analysis, the functional relationship between the correction coefficient and the seismic parameters is established: (6) (7) Where h is the depth of the calculation point (m); L is the pile length (m); PGV P is the pulse peak velocity (m / s); T p is the pulse period (s); is the vertical acceleration (m / s²). Substituting equations (6) and (7) into equation (2), we can obtain the corrected py curve.

[0025] Through systematic statistical analysis of near-site vibration characteristics, in-depth experimental research on soil dynamic response, precise numerical model development, and scientific Py curve correction, this method can obtain a near-field Py curve for bridge pile foundations that accurately reflects the near-site vibration characteristics. Using this corrected Py curve for seismic design of bridge pile foundations can more accurately simulate pile-soil interaction under near-site vibration, significantly improving the accuracy and reliability of bridge pile foundation seismic design.

[0026] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0027] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The singular forms "a", "an", "the" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0028] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0029] The word "if," as used herein, may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to the determination" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)," depending on the context.

[0030] The references to "first" and "second" in the embodiments merely distinguish similar objects and do not represent a specific ordering of the objects. It is understood that the specific order or precedence of "first" and "second" can be interchanged where appropriate. It should be understood that the objects distinguished by "first" and "second" can be interchanged where appropriate, so that the embodiments described herein can be implemented in an order other than that illustrated or described herein.

[0031] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A near-field bridge pile foundation py curve correction method based on dynamic response test and numerical simulation, characterized in that: The steps include: S1. Statistical analysis of near-field vibration characteristics; S2. Soil dynamic response test under earthquake: Conduct triaxial tests on soil sample units and pile foundation shaking table model tests to analyze the dynamic response of soil under different near-site vibrations; S3. Establish a numerical model considering the influence of near-field vibration; S4. Obtaining a py curve based on the numerical analysis results; S5. Establish a modified py curve that takes into account the influence of near-field vibration characteristics.

2. The near-field bridge pile foundation py curve correction method based on dynamic response test and numerical simulation according to claim 1 is characterized by: In step S1, the specific steps include: S11. Filtering near-field earthquake data from multiple earthquake databases, including seismic wave records, focal mechanisms, source parameters, and site condition information; S12. Use the M&P equivalent pulse model to identify pulse ground motions, clarify the relationship between pulse duration, peak velocity, focal distance, fault type, and the energy distribution of pulse components under different site conditions; S13. Extract the vertical acceleration component from the seismic wave, calculate its amplitude range and frequency, analyze the magnitude and phase relationship between the vertical acceleration and the horizontal acceleration, and evaluate its impact on the vertical load of the pile foundation; conduct comprehensive statistics on the above analysis results and establish a near-field vibration characteristics database.

3. The near-field bridge pile foundation py curve correction method based on dynamic response test and numerical simulation according to claim 1 is characterized by: In step S2, the specific steps include: S21. Conduct dynamic triaxial tests on soil sample units. The dynamic triaxial tests use undisturbed soil on site and undergo bidirectional excitation loading. The input load is the measured near-site vibration, taking into account different velocity pulse sizes and vertical accelerations. During the test, the dynamic shear modulus, damping ratio, pore water pressure, and axial strain parameters of the soil sample are monitored in real time to analyze the strength degradation, stiffness attenuation, and liquefaction characteristics of the soil under near-field earthquake action. S22. Conduct a shaking table model test on the pile foundation. The model pile is scaled according to the shaking table dimensions and the pile design drawings to determine the pile diameter, pile length, elastic modulus, and flexural stiffness. The model soil should be as consistent as possible with the on-site drilled soil conditions; strain gauges and displacement meters should be arranged along the pile body, and pore pressure sensors and earth pressure gauges should be arranged in the soil around the pile; Based on the screening of near-field pulse seismic motion, the coupling relationship between vertical acceleration and horizontal motion is considered at the same time, and the coordinated loading of three-axis seismic motion is achieved through nonlinear superposition. The pile displacement, pile strain, soil pressure and pore pressure data are collected to analyze the pile-soil dynamic response law.

4. The near-field bridge pile foundation py curve correction method based on dynamic response test and numerical simulation according to claim 1 is characterized by: In step S3, a numerical model of pile-soil interaction is constructed using finite difference software. In the model, a nonlinear constitutive relationship that takes into account soil stiffness attenuation is adopted to accurately simulate the mechanical behavior of the soil under complex stress states. The soil layer information is determined by combining in-situ and indoor tests. According to the actual pile foundation design drawings and material properties, the geometric dimensions, elastic modulus, Poisson's ratio, and bending stiffness parameters of the pile foundation are determined, and the linear elastic constitutive relationship is selected; The boundary conditions of the model are set to a sufficiently large range to reduce the influence of boundary reflection on the calculation results; the initial conditions include the initial stress state of the soil and the installation conditions of the pile foundation; The input load is consistent with the model test, and the numerical simulation results are compared with the test results to perform parameter verification and optimization.

5. The near-field bridge pile foundation py curve correction method based on dynamic response test and numerical simulation according to claim 1 is characterized by: In step S4, in the numerical simulation results, nodes at different depths of the pile body are selected to extract their lateral displacement y and corresponding soil resistance p data under earthquake action; by plotting the relationship curve between lateral displacement and soil resistance, py curves at different positions are obtained; and by changing the input conditions, including different velocity pulses, pulse periods, and vertical acceleration sizes, a py curve database under different working conditions is formed.

6. The near-field bridge pile foundation py curve correction method based on dynamic response test and numerical simulation according to claim 1 is characterized by: In step S5, based on the py curve: （1） A dual-parameter correction is introduced to fully consider the influence of near-field vibration. The corrected py curve is as follows: （2） Where, is the initial foundation modulus; is the horizontal ultimate soil resistance; In order to consider the reduction factor of the initial foundation modulus due to the characteristics of the near-site vibration, It is the reduction factor of the horizontal ultimate soil resistance considering the near-site vibration characteristics.

7. The near-field bridge pile foundation py curve correction method based on dynamic response test and numerical simulation according to claim 6 is characterized by: Calculate according to soil type: For clay, The calculation formula is as follows: （3） Where, is the undrained shear strength; D is the pile diameter; is the effective density of the soil; z is the depth below the ground surface; J is a dimensionless empirical constant determined by field tests, with a value ranging from 0.25 to 0.5; is the turning point depth of ultimate soil resistance; For sandy soil, The calculation formula is as follows: （4） Where, All represent functions of the internal friction angle of soil; For weathered rocks, The calculation formula is as follows: （5） Where, is the compressive strength of the rock; is the strength reduction factor; By performing multivariate parameter regression analysis, the functional relationship between the correction coefficient and the seismic parameters is established: （6） （7） Where h is the depth of the calculation point; L is the pile length; PGV P is the pulse peak velocity; T p is the pulse period; is the vertical acceleration; Substituting equations (6) and (7) into equation (2), we can obtain the corrected py curve.

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