Method for evaluating horizontal bearing characteristics of screw steel piles based on modified p-y curve

Abstract

The application discloses a kind of based on the horizontal bearing characteristic evaluation method of correction p-y curve spiral steel pile, comprising: obtaining in-situ static sounding test data and pile body design parameter, and establish the initial p-y curve of eliminating the experience dependence of soil body;Determine the influence area of spiral plate horizontal load, and introduce amplification factor in the influence area to the initial p-y curve in the pile around soil resistance is corrected;Based on the elastic foundation beam theory, establish finite difference equation group and iteratively solve the horizontal displacement of pile body;Further determine the angle of pile body, bending moment, shear force and the distribution of pile around soil resistance, draw the horizontal load-displacement curve of spiral steel pile, compared with design load to obtain horizontal bearing characteristic evaluation conclusion.The application uses in-situ static sounding test data to replace traditional experience parameter, and is combined based on the geometric parameter of pile body, realizes the objective, standardization evaluation of spiral steel pile horizontal bearing characteristic.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical engineering and pile foundation design technology, specifically relating to a method for correcting the Py curve and predicting and evaluating the horizontal bearing characteristics of helical steel piles. Background Technology

[0002] Spiral steel piles are becoming increasingly popular due to their rapid installation, immediate load-bearing capacity upon installation, and other advantages compared to traditional piles. The mainstream form of spiral steel pile consists of one or more spiral plates welded at regular intervals onto a circular steel pipe. These spiral plates allow the pile to be rapidly driven into the soil with slight disturbance through rotational pressing.

[0003] In practical engineering applications, spiral steel piles are subjected to both axial loads and the coupling effect of horizontal loads. Accurately assessing the lateral deflection and bending moment of spiral steel piles under horizontal loads is crucial for optimizing the structural dimensions of the pile and ensuring the safety of the superstructure.

[0004] Currently, the mainstream method for predicting the horizontal bearing capacity of pile foundations is the Py curve method. However, existing traditional Py curves have the following main drawbacks: First, traditional models rely heavily on empirical values ​​of soil parameters (such as the internal friction angle or undrained shear strength). These parameters are often affected by uncertain factors such as soil microstructure and stress history, resulting in a high degree of subjectivity and significant calculation errors. Second, existing Py curves are mainly designed for conventional straight-axis cylindrical piles with uniform cross-sections, failing to truly consider the additional stress mechanism of the "spiral plates" on helical steel piles. When a helical steel pile is subjected to a horizontal load, the helical blades will exhibit a rotational tendency and mobilize additional lateral soil resistance, forming a reaction moment to enhance bending resistance. If traditional formulas are directly used to calculate helical steel piles, the predicted bending moment and displacement of the pile will be too large, leading to overly conservative designs and material waste.

[0005] Therefore, there is an urgent need for an evaluation method for the horizontal bearing characteristics of spiral steel piles that can eliminate the empirical dependence on soil parameters and accurately account for the additional effect of the horizontal resistance of the spiral plate. Summary of the Invention

[0006] The purpose of this invention is to provide a method and system for evaluating the horizontal bearing characteristics of helical steel piles based on static cone penetration test modified Py curves, which solves the problem that the traditional Py curve method in the prior art relies on empirical parameters and cannot accurately evaluate the additional resistance of the helical plate, and realizes accurate evaluation of the horizontal bearing characteristics of helical steel piles.

[0007] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: A method for evaluating the horizontal bearing capacity characteristics of helical steel piles based on modified py curves includes the following steps: S1: Obtain in-situ static cone penetration test data and design parameters of the spiral steel pile at the target site. The design parameters include the diameter of the central pile shaft, the diameter of the spiral plate, the installation depth of the spiral plate, and the embedment depth of the pile body. S2: Based on the in-situ static cone penetration test data, establish an in-situ static cone penetration initial py curve that eliminates the dependence on empirical soil parameters; S3: Based on the design parameters of the spiral steel pile, determine the influence area of ​​the spiral plate under horizontal load, and introduce an amplification factor within the influence area to correct the soil resistance around the pile in the initial py curve of the in-situ static penetration test, thereby obtaining a corrected py curve suitable for the spiral steel pile; wherein, the amplification factor is the product of the ratio obtained by dividing the difference between the diameter of the spiral plate and the diameter of the central pile axis by the diameter of the central pile axis and the pile coefficient; S4: Based on the theory of elastic foundation beams, a single pile is discretized into a preset number of calculation units along the burial depth direction (the number of units depends on the calculation accuracy), and combined with the modified py curve, a set of finite difference equations for solving the horizontal displacement of the pile body when the helical steel pile is under horizontal load is established and solved iteratively. S5: Based on the horizontal displacement of the pile, solve the rotation angle, bending moment, shear force and soil resistance distribution around the pile through the central difference equation; S6: Based on the obtained pile bending moment, shear force and soil resistance distribution around the pile, calculate the pile top displacement corresponding to different pile top horizontal loads for the horizontal load of the spiral steel pile, and generate the horizontal load-displacement curve of the spiral steel pile; wherein, the horizontal ultimate bearing capacity is taken as the smaller value between the load corresponding to the yield bending moment of the pile material or the load corresponding to the ultimate resistance of the soil. S7: Based on the horizontal load-displacement curve, extract the load corresponding to the moment when the horizontal displacement at the top of the pile reaches the allowable value of the specification or when the pile body first yields as the characteristic value of the horizontal bearing capacity, and compare it with the design load to output the evaluation conclusion of the horizontal bearing characteristics of the spiral steel pile.

[0008] In step S3, the area affected by the spiral plate under horizontal load is: a region with a span of 1.75 times the diameter of the spiral plate along the depth direction of the pile body, centered on the installation position of the spiral plate.

[0009] Preferably, in step S2, for clay, the effective conic coefficient N in the initial py curve of the in-situ static cone penetration test is... e The value is a specific value obtained in advance through site marking.

[0010] Preferably, in step S4, the establishment of the finite difference equation set includes: based on the differential equilibrium equation of the elastic foundation beam, discretizing the pile body into several nodes using the central difference scheme, constructing a stiffness matrix according to the boundary conditions of the pile top and pile bottom, and obtaining the horizontal displacement of the pile body at each node through iterative solution.

[0011] The present invention also provides an electronic device, comprising: One or more processors; A memory for storing one or more programs; when the one or more programs are executed by the one or more processors, the one or more processors implement the evaluation method.

[0012] The present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the evaluation method described above.

[0013] The present invention also provides a computer program product, including a computer program or computer instructions that, when executed by a processor, implement the evaluation method described above.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention introduces in-situ static cone penetration test (CPT) parameters (cone tip resistance q). c (etc.) directly replace traditional empirical parameters such as internal friction angle, and use continuous CPT profile data to avoid hypothetical simplification of soil layers and improve the benchmark prediction accuracy of py curve.

[0015] 2. This invention addresses the unique geometric structure of helical steel piles by introducing a linearly amplified correction factor within the influence area of ​​the helical plate to correct the soil resistance around the pile. This reflects the additional effect of the helical plate mobilizing extra soil resistance to resist deformation during horizontal displacement, and proposes a py curve suitable for predicting the horizontal bearing characteristics of helical steel piles.

[0016] 3. The evaluation method of this invention can realize the calculation solution of the entire solution process through a programming language, which improves the calculation efficiency and accuracy, and can be quickly applied to the design calculation of helical steel piles under horizontal loads. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the evaluation method for the horizontal bearing capacity characteristics of helical steel piles based on the modified py curve.

[0018] Figure 2 This is a schematic diagram of the distribution of soil resistance around the spiral steel pile and the area affected by the correction in an embodiment of the present invention.

[0019] Figure 3 This is a comparison between the horizontal load-bearing characteristic evaluation results and the measured values ​​of the present invention.

[0020] Figure 4 This is a comparison chart of the predicted pile bending moment and the measured pile bending moment using the method of this invention and the API specification py curve prediction method. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and technical features described in this application can be combined with each other. It should also be pointed out that, unless otherwise indicated, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0022] Example 1 like Figure 1 As shown, this invention provides a method for evaluating the horizontal bearing capacity characteristics of helical steel piles based on a modified py curve, comprising the following steps: S1: Obtain in-situ static cone penetration test data and design parameters of the helical steel piles at the target site. The design parameters include the central pile diameter D. p Diameter D of the spiral plate h Spiral plate installation depth L h and pile embedment depth L e The steel pipe wall thickness t; the in-situ static cone penetration test data were obtained through on-site in-situ surveys; S2: Based on the in-situ static cone penetration test data, establish an in-situ static cone penetration initial py curve that eliminates the dependence on empirical soil parameters; S3: Based on the design parameters of the spiral steel pile, determine the influence area of ​​the spiral plate under horizontal load, and introduce an amplification factor within the influence area to correct the soil resistance around the pile in the initial py curve of the in-situ static penetration test, thereby obtaining a corrected py curve suitable for the spiral steel pile; wherein, the amplification factor is the product of the ratio obtained by dividing the difference between the diameter of the spiral plate and the diameter of the central pile axis by the diameter of the central pile axis and the pile coefficient; S4: Based on the theory of elastic foundation beams, a single pile is discretized into a preset number of calculation units along the burial depth direction. Combined with the modified py curve, a set of finite difference equations for solving the horizontal displacement of the pile body when the helical steel pile is under horizontal load is established and solved iteratively. S5: Based on the horizontal displacement of the pile, the rotation angle, bending moment, shear force and soil resistance distribution around the pile are solved by central difference. S6: Based on the obtained pile bending moment, shear force and soil resistance distribution around the pile, calculate the pile top displacement corresponding to different pile top horizontal loads for the horizontal load of the spiral steel pile, and generate the horizontal load-displacement curve of the spiral steel pile; wherein, the horizontal ultimate bearing capacity is taken as the smaller value between the load corresponding to the yield bending moment of the pile material or the load corresponding to the ultimate resistance of the soil. S7: Based on the horizontal load-displacement curve, extract the load corresponding to the moment when the horizontal displacement at the top of the pile reaches the allowable value of the specification or when the pile body first yields as the characteristic value of the horizontal bearing capacity, and compare it with the design load to output the evaluation conclusion of the horizontal bearing characteristics of the spiral steel pile. The evaluation conclusion includes whether the bearing capacity meets the design requirements, the safety reserve factor, and the deformation control level.

[0023] The process of establishing the initial py curve of in-situ static cone penetration test to eliminate dependence on empirical soil parameters in step S2 is as follows: For sandy soil layers, a hyperbola is used to reflect the nonlinear response of the pile and soil, and in-situ static cone penetration test (CPT) data is used for replacement. The expression is as follows: (1); (2); (3); In the formula, p is the soil resistance around the pile; y is the horizontal displacement of the pile; m is the stiffness degradation coefficient; B is the ultimate soil resistance coefficient; k ini p represents the initial stiffness of the foundation. u The ultimate soil resistance around the pile; ρ T q represents the density of the overlying soil layer. c For the CPT cone tip resistance; σ v΄ denoted as , where is the effective stress of the overlying soil layer; and D is the diameter of the helical steel pile. Specifically, the ultimate soil resistance coefficient B, based on existing literature research, is less affected by the pile's length-to-diameter ratio, and when the soil layer is less than 5m, the ultimate soil resistance is usually not corrected. In this case, the value of the ultimate soil resistance coefficient B in step S2 of this embodiment is 1. For the initial py curve established based on the in-situ static cone penetration test data in clay, the mathematical expression is: (4); In the formula, N e For clay, the effective conic section N in the initial py curve of the in-situ static cone penetration test is the effective conic section coefficient. e The value is a specific value obtained in advance through site marking; q e Effective cone tip resistance; N c ε is the ultimate bearing capacity coefficient of the soil around the pile; CPT For ε 50 Correction value, ε 50 N represents the ultimate strain corresponding to 50% failure stress in a triaxial test. c and ε CPT The mathematical expression is: (5); (6); (7); (8); In the formula is the effective unit weight of the soil; z is the depth below the ground surface; s u The undrained shear strength of the soil; z r is the critical depth; u0 is the static pore pressure.

[0024] like Figure 2 As shown, when the pile top is subjected to a horizontal load, the central pile axis of the helical steel pile needs to resist overall bending deformation. During the horizontal loading process, the helical plate rotates, causing its left and right sides to interact with the soil, generating opposing and equal resistance forces, exhibiting symmetry. This couple acts on the central pile axis, thus forming an additional bending moment, improving the pile's bending stiffness and horizontal bearing capacity. Within the helical plate area, it is not only subject to the initial pile perimeter soil resistance P of the central pile axis... normal The impact is also affected by the soil resistance of the spiral plate. Therefore, in step S3 of this embodiment, a correction factor is used in the influence area of ​​the spiral plate to adjust the soil resistance around the pile in the initial py curve to account for the contribution of the spiral plate to the horizontal load of the pile.

[0025] In this embodiment, the influence area of ​​the spiral plate is defined as follows: centered on the installation position of the spiral plate, with a span along the pile depth direction of 1.75 times the diameter of the spiral plate (1.75D). h (area).

[0026] Within this region of influence, a linearly amplified correction factor P is introduced. mult Its mathematical expression is: (9); (10); In the formula D h D is the diameter of the spiral plate; p Ω is the diameter of the central pile axis; L is the pile coefficient; e D represents the depth of the pile embedment. p The diameter of the central pile axis.

[0027] In step S4 of this embodiment, based on the elastic foundation beam theory, the single pile is divided into several segments (each segment has a length of h). The differential equilibrium equation for any segment of the pile is then: (11); In the formula, EI is the bending stiffness of the pile; Q is the axial load; and W is the load distributed along the pile. From formula (11), the following formula can be derived: The corner of the pile body : (12); Bending moment of the pile : (13); Shear force of the pile body : (14); Pile perimeter soil resistance p: (15); Equation (11) can be solved based on the finite difference rule. When using the finite difference method, two main conditions need to be met: the finite difference form of the general differential equation and the boundary conditions. This method requires deriving the central difference approximation of the lateral deflection curve. The slope of the elastic curve is approximately the secant line passing through two adjacent points of the curve. The finite difference form of the general differential equation in equation (11) is shown in equation (16).

[0028] (16); in, , , , , These represent the horizontal displacements of the pile body at nodes i-2, i-1, i, i+1, and i+2, respectively. for coefficient, for coefficient, for coefficient, for coefficient, for coefficient, Let be the horizontal load at node i, where i represents the number of nodes corresponding to the discrete pile end. The definitions of each coefficient are as follows: (17); (18); (19); (20); (twenty one); (twenty two); In the formula: R i-1 R is the bending stiffness of the pile at node i-1; i R is the bending stiffness of the pile at node i; i+1 The bending stiffness of the pile at node i+1; h is the length of the segmented pile; Epyi Let Q be the soil spring secant modulus at node i corresponding to each modified py curve, and let W be the value of the py curve. If the pile top is only subjected to horizontal load, then Q and W are set to 0.

[0029] Since a unique solution can be obtained by performing finite difference finite difference on the fourth-order differential equilibrium equation, four boundary conditions must be provided. The following boundary conditions are established at the pile bottom and pile top respectively: (twenty three); (twenty four); (25); (26); In the formula, y n y represents the horizontal displacement at node n at the bottom of the pile; n-2 y n-1 y represents the horizontal displacements at the actual nodes n-2 and n-1 above the pile bottom, respectively; n+1 y n+2 These represent the horizontal displacements at virtual nodes n+1 and n+2 below the pile bottom, respectively; R n V represents the bending stiffness of the pile at node n at the bottom of the pile; n y0 is the shear force at the pile bottom node n; y0 is the horizontal displacement at the pile top node. -2 y -1 y1 and y2 are the horizontal displacements of the two virtual nodes above the pile top, respectively; R0 is the bending stiffness of the pile at the pile top node; M0 is the bending moment at the pile top node; and P0 is the shear force at the pile top node.

[0030] The system of equations consisting of the finite difference form of the differential equations and the boundary conditions can be written in matrix form: (27); In the formula Here is the stiffness matrix; This represents the horizontal displacement matrix vector of the pile. This represents the horizontal load matrix vector. The stiffness matrix [A] contains the finite difference form of the differential equations and the governing equations of the boundary conditions. The pile's horizontal displacement matrix vector (y) can be obtained through the inverse of the stiffness matrix [A]. -1 get.

[0031] Furthermore, the mathematical expressions for the pile rotation angle, bending moment, shear force, and the center of gravity of the soil resistance around the pile after finite difference processing in this example are as follows: (28); (29); (30); (31); In the formula θ i Let M be the rotation angle at any node i on the pile body; i Let i be the bending moment at any node i of the pile. V represents the soil resistance around the pile at any node i on the pile shaft; i Let i be the shear force at any node i in the pile.

[0032] In particular, to improve the prediction accuracy of single piles, the ultimate soil resistance p around the pile is... u The stiffness degradation coefficient m is controlled by the stiffness degradation coefficient. In step S2 of this embodiment, the stiffness degradation coefficient m is determined by the length-to-diameter ratio L / D of the helical steel pile (greater than 3) and the average cone tip resistance. The decision was made jointly. Based on the indoor model test data from the literature (Liu Zhentao et al. Py model of horizontally loaded single pile in sand based on CPT [J]. Marine Structures, 2025, 101: 103767.), the surface was obtained by fitting using the rational Taylor model: (32); In the formula, L is the length of the spiral steel pile, and m0 is the fitted surface in... Compared with the length-to-diameter ratio of spiral steel piles The stiffness degradation coefficient obtained when both are 0 (m0=1.186); a 01 b 01 b 02 In the molecules respectively , , The surface fitting coefficients, a1, a2, b1, b2, and c1 are respectively the coefficients in the denominator. , , , , The surface fitting coefficients, where a 01 =-0.358, b 01 =0.085, b 02 =0.061, a1=-0.791, a2=-0.086, b1=1.113, b2=0.143, c1=-0.233.

[0033] To facilitate understanding and application by technical personnel in this industry, the following examples demonstrate the discretization and node division of the helical steel pile, the determination of soil parameters and CPT test parameters of the soil layer where the helical steel pile is located, the determination of structural parameters and the magnitude of the horizontal load on the pile top, the construction of the difference equation at any node on the helical steel pile, and the establishment and solution of the stiffness matrix corresponding to the finite difference linear equation system of the entire helical steel pile. Finally, the predicted pile bending moment of the helical steel pile under horizontal load predicted by the method of this invention and the predicted pile bending moment of the API specification py curve prediction method (API specification is existing technology and will not be described in detail) are compared and verified with the in-situ measured pile bending moment.

[0034] Unless otherwise specified, the units of measurement for all process parameters or calculation parameters involved in the following calculation methods shall be in standard units.

[0035] 1. Parameters of spiral steel pile structure: A certain onshore solar power generation project uses helical steel piles as pile foundations, and its basic parameters are as follows: The length of the spiral steel pile is L: L = 2.7m; Spiral steel pile embedment depth L e :L e =2.5m; The diameter D of the center steel pile of the spiral steel pile p :D p =0.0891m; Spiral plate embedment depth L h and diameter D h Spiral plate No. 1: L h1 =0.5m, D h1= 0.4m; Spiral plate No. 2: L h2 =1.4m, D h2= 0.2m; Spiral plate No. 3: L h3 =2.3m, D h3= 0.2m; The wall thickness t of the central pile axis of the spiral steel pile: t = 0.0032 m; The elastic modulus E of the spiral steel pile: E = 210 GPa; The bending stiffness EI of the spiral steel pile is: EI = 167520 N·m 2 .

[0036] 2. Soil parameters of the soil layer: The strata where the spiral steel piles are located consist of two layers. The first 1.5m of the soil profile consists of sandy silt to silty sand, which can be approximated as a sand layer. This is followed by a clay layer, extending to a depth of 2.5m. The groundwater level is 0.70m below the surface. Other soil layer information is as follows: The internal friction angle of the first sand layer is φ = 33˚; the effective unit weight is γ΄ = 8.4 kN / m. 3 ; The undrained shear strength S of the first clay layer u =28kN / m 2 Effective specific gravity γ΄ = 7.7 kN / m 3 The ultimate strain ε corresponding to 50% failure stress in the triaxial test. 50 =0.02; empirical coefficient J=0.5.

[0037] 3. CPT test parameters and the range of horizontal loads applied to the pile top: Cone tip resistance q c : Shallow (0~1.5m): Starting from the surface (depth 0m), the cone tip drag rises rapidly, reaching the first local peak (approximately 2~3MPa) at around 0.5m, followed by a slight fluctuation and decline. A second, higher peak (close to 4MPa) appears near a depth of about 1m, after which the cone tip drag decreases again, maintaining an overall high level of 2~4MPa.

[0038] In the middle section (1.5~3.5m): the cone tip resistance decreases rapidly and continuously with increasing depth, gradually decreasing from about 2MPa to close to 0MPa, with no obvious local peaks, only accompanied by slight fluctuations.

[0039] Deep (3.5~4m): The cone tip resistance remains at an extremely low level, fluctuating only slightly between 0~1MPa, close to the base resistance state.

[0040] Horizontal load P t scope: In this embodiment, the horizontal load P applied to the top of the pile is... t It is divided into five levels: 1.36kN, 2.72kN, 4.10kN, 5.46kN and 6.82kN.

[0041] 4. Correction of Py curves Based on the soil layer parameters of the spiral steel pile, establish the corresponding py curves at different depths of different soil layers. For sandy soil layers, use formulas (1) to (3), and for clay layers, use formulas (4) to (8).

[0042] Based on the structural parameters of the spiral steel pile, the size of the affected area is determined, and the amplification factor P corresponding to different spiral plates is calculated using formulas (9) to (10). mult .

[0043] Based on the already obtained amplification factor P multThe soil resistance p around the pile in the initial py curve of the influence area corresponding to different spiral plates is amplified and corrected to take into account the additional effect provided by the spiral plates under lateral loading.

[0044] 5. Solving for the internal forces and deformations of spiral steel piles Based on the structural characteristics of the spiral steel pile and the soil stratification, the pile body is divided into 50 segments, with a segment length h of 0.05m. The soil spring secant modulus E corresponding to the py curve at each segment node is extracted. pyi Substituting it into formula (16) yields the general differential equations in finite difference form for each node. Combined with the supplementary boundary condition equations (formulas (23) to (26)), a total of 55 equations are obtained, which can be used to construct the stiffness matrix [A]. The horizontal displacement y of the pile at each of the 55 nodes can then be solved using the matrix. i .

[0045] The specific solution process is as follows: (1) Set the initial displacement to 0, and substitute it into the corrected py curve to obtain E. pyi Substitute this into the stiffness matrix [A], assuming a horizontal load P is applied at the pile top. t Increasing the value from 0 to 6.82 kN in increments of 0.01 kN yields a system of equations with constant coefficients. ; (2) Solve the system of equations with constant coefficients The horizontal displacement y of each node of the pile is obtained. i ; (3) Take the y obtained in step (2) i Substituting this into the corresponding corrected py curve yields a new set of E values. pyi ΄, and E pyi Substituting ΄ into [A], we obtain the new stiffness matrix [A]΄; (4) Repeat steps (2) to (3), and use the horizontal displacement of the pile body calculated in the previous iteration as the initial displacement for the next iteration, until the difference between the horizontal displacements of the pile body obtained in the previous and next iterations is less than the allowable error ε, i.e., y new -y old <ε, y new Let y be the horizontal displacement of the pile body obtained in this iteration. old This represents the horizontal displacement of the pile body obtained in the previous iteration. In this embodiment, ε = 10. -6 m, considering the accuracy requirements met, terminate the current horizontal load P. t The corresponding iteration.

[0046] (5) Repeat steps (2) to (4) until all P tThe iterations within the range converge. The horizontal displacement matrix vector (y) of the pile body is output, yielding the horizontal displacement y of the pile body at each node. i .

[0047] 6. Based on the obtained pile bending moment, shear force, and soil resistance distribution, calculate the pile top displacement corresponding to different pile top horizontal loads for the helical steel pile. Plot the horizontal displacement-load curves of the helical steel pile under different pile top horizontal loads (1.36kN, 2.72kN, 4.10kN, 5.46kN, 6.82kN), and determine the horizontal ultimate bearing capacity of the helical steel pile. This horizontal ultimate bearing capacity is taken as the smaller value between the load corresponding to the yield moment of the pile material and the load corresponding to the ultimate resistance of the soil. The horizontal displacement-load curves can clearly show the trend of pile top displacement under each load level, providing a quantitative basis for subsequent bearing capacity assessment.

[0048] 7. Comparative verification of pile bending moment Based on the horizontal load-displacement curve, the load corresponding to the moment when the horizontal displacement at the top of the pile reaches the allowable value or when the pile body first yields is extracted as the characteristic value of the horizontal bearing capacity. This value is then compared with the design load to output the evaluation conclusion of the horizontal bearing characteristics of the spiral steel pile. Figure 3 The comparison between the load obtained by the evaluation method of the present invention and the measured value shows that the deviation between the evaluation method of the present invention and the measured value is very small.

[0049] To further compare the accuracy of the method of the present invention, this embodiment selects the pile bending moment as a representative index of the lateral bearing characteristics, and compares and verifies it with the predicted pile bending moment and the measured pile bending moment obtained by the API specification py curve prediction method. The linear fitting results of the method of the present invention and the linear fitting results of the API specification py curve prediction method are then obtained.

[0050] Based on the calculated horizontal displacement y of the pile body i According to formula (29), the load P at each node under different horizontal loads can be obtained. t The pile bending moment obtained by the method of this invention is compared with the predicted pile bending moment M obtained by the API specification py curve prediction method. pre Same as the measured pile bending moment M mea The comparison effect is as follows Figure 4 As shown, Figure 4 Chinese R 2 The determining factor is used. In this embodiment, the predicted pile bending moment M obtained by the API specification py curve prediction method is... pre For the measured bending moment M of the pile body mea The predicted pile bending moment M obtained by the method of this invention is 1.96 times that of the original method. pre Only the measured bending moment M of the pile body meaThe result is 1.09 times that of the previous method. This demonstrates that the method of the present invention can more accurately predict the horizontal bearing characteristics of helical steel piles, which is of guiding significance for the practical application of helical steel piles. It solves the problem that the traditional Py curve method in the prior art relies on empirical parameters and cannot accurately evaluate the additional resistance of the helical plate, thereby ensuring the safety and applicability of the design of helical steel pile foundation structures.

[0051] Example 2 This embodiment also provides an electronic device, including: One or more processors; A memory for storing one or more programs; when the one or more programs are executed by the one or more processors, the one or more processors implement the evaluation method described in Embodiment 1.

[0052] Example 3 The present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the evaluation method described in Embodiment 1.

[0053] Example 4 The present invention also provides a computer program product, including a computer program or computer instructions, which, when executed by a processor, implement the evaluation method described in Embodiment 1.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for evaluating the horizontal bearing capacity characteristics of helical steel piles based on a modified py curve, characterized in that, Includes the following steps: S1: Obtain in-situ static cone penetration test data and design parameters of the spiral steel pile at the target site. The design parameters include the diameter of the central pile shaft, the diameter of the spiral plate, the installation depth of the spiral plate, and the embedment depth of the pile body. S2: Based on the in-situ static cone penetration test data, establish an initial py curve for in-situ static cone penetration that eliminates the dependence on empirical soil parameters; for sandy soil layers, the expression for the initial py curve for in-situ static cone penetration is as follows: (1)； (2)； (3)； In the formula, p is the soil resistance around the pile; y is the horizontal displacement of the pile; m is the stiffness degradation coefficient; B is the ultimate soil resistance coefficient; k ini p represents the initial stiffness of the foundation. u This refers to the ultimate soil resistance around the pile. ρ T q represents the density of the overlying soil layer. c For the CPT cone tip resistance; σ v΄ D represents the effective stress of the overlying soil layer; D is the diameter of the helical steel pile. For clay, the mathematical expression for the initial py curve of in-situ static cone penetration testing is: ； In the formula, N e For the effective conic coefficient, q e Effective cone tip resistance; N c ε is the ultimate bearing capacity coefficient of the soil around the pile; CPT For ε 50 Correction value, ε 50 This represents the ultimate strain corresponding to 50% failure stress in a triaxial test. S3: Based on the design parameters of the spiral steel pile, determine the influence area of ​​the spiral plate under horizontal load, and introduce an amplification factor within the influence area to correct the soil resistance around the pile in the initial py curve of the in-situ static penetration test, thereby obtaining a corrected py curve suitable for the spiral steel pile; wherein, the amplification factor is the product of the ratio obtained by dividing the difference between the diameter of the spiral plate and the diameter of the central pile axis by the diameter of the central pile axis and the pile coefficient; the influence area is the area with a span of 1.75 times the diameter of the spiral plate along the depth direction of the pile body, centered on the installation position of the spiral plate; S4: Based on the theory of elastic foundation beam, a single pile is discretized into a preset number of calculation units along the burial depth direction. Combined with the modified py curve, a set of finite difference equations is established to solve the horizontal displacement of the pile body when the helical steel pile is under horizontal load. The equations are then iteratively solved to obtain the horizontal displacement distributed along the pile body corresponding to the pile top under different horizontal load levels. Thus, the horizontal load-displacement curve of the pile top is obtained. S5: Based on the horizontal displacement of the pile, solve the rotation angle, bending moment, shear force and soil resistance distribution around the pile through the central difference equation; S6: Based on the obtained pile bending moment, shear force and soil resistance distribution around the pile, determine the horizontal ultimate bearing capacity of the spiral steel pile. The horizontal ultimate bearing capacity is taken as the smaller value between the load corresponding to the yield moment of the pile material and the load corresponding to the ultimate resistance of the soil. S7: Based on the horizontal load-displacement curve, extract the load corresponding to the moment when the horizontal displacement at the top of the pile reaches the allowable value of the specification or when the pile body first yields as the characteristic value of the horizontal bearing capacity, and compare it with the design load to output the evaluation conclusion of the horizontal bearing characteristics of the spiral steel pile.

2. The evaluation method according to claim 1, characterized in that, In step S3, the amplification factor P mult The mathematical expression is: ； In the formula, D h D is the diameter of the spiral plate; p Ω represents the diameter of the central pile axis; Ω is the pile coefficient. L e This refers to the depth of the pile embedment.

3. The evaluation method according to claim 1, characterized in that, In step S2, for sandy soil, the stiffness degradation coefficient m in the initial py curve of the in-situ static cone penetration test is determined by the following rational Taylor fitting formula: ； In the formula, L is the length of the spiral steel pile, and D is the diameter of the spiral steel pile. Let m0 be the average cone tip resistance, and m0 be the fitted surface at... Compared with the length-to-diameter ratio of spiral steel piles Stiffness degradation coefficients obtained when both are 0; a 01 b 01 b 02 In the molecules respectively , , The surface fitting coefficients, a1, a2, b1, b2, and c1 are respectively the coefficients in the denominator. , , , , The surface fitting coefficients.

4. The evaluation method according to claim 1, characterized in that, In step S2, for clay, the effective conic coefficient N in the initial py curve of the in-situ static cone penetration test is... e The value is a specific value obtained in advance through site marking.

5. The evaluation method according to claim 1, characterized in that, In step S4, the establishment of the finite difference equation set includes: based on the differential equilibrium equation of the elastic foundation beam, the pile body is discretized into several nodes using the central difference scheme, and a stiffness matrix is ​​constructed according to the boundary conditions of the pile top and the pile bottom. The horizontal displacement of the pile body at each node is obtained by iterative solution.

6. The evaluation method according to claim 4, characterized in that, In step S5, the rotation angle, bending moment, shear force, and soil resistance distribution around the pile are calculated from the horizontal displacement using the following central difference equation: ； ； ； ； In the formula θ i M is the rotation angle at pile node i; i p is the bending moment at node i of the pile body; i V represents the soil resistance around the pile at pile node i; i The shear force at node i of the pile body; , , , denoted as , i, and i+1 respectively, represent the horizontal displacements of the pile body at nodes i-1, i, and i+1; h represents the segmented pile length.

7. An electronic device, characterized in that, include: One or more processors; Memory, used to store one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the evaluation method as described in any one of claims 1 to 6.

8. A computer-readable storage medium, characterized in that, It stores a computer program that, when executed by a processor, implements the evaluation method as described in any one of claims 1 to 6.

9. A computer program product, comprising a computer program or computer instructions, characterized in that, When the computer program or computer instructions are executed by the processor, they implement the evaluation method as described in any one of claims 1 to 6.

Images