Efficient analysis method for failure mode and ultimate bearing capacity of pile anchor under inclined load
By establishing a mechanical model of pile anchors under inclined loads, and combining the minimum resistance criterion and derivative extreme value analysis, the problem of insufficient prediction of failure modes and ultimate bearing capacity of pile anchors in seabeds with both cohesive and non-cohesive soils is solved. This achieves efficient and accurate analysis of failure modes and ultimate bearing capacity, as well as prediction of the optimal mooring point location.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-25
- Publication Date
- 2026-03-27
AI Technical Summary
Existing research lacks effective theoretical methods for predicting the failure mode and ultimate bearing capacity of pile anchors under arbitrary inclined loads, especially in seabeds with both cohesive and non-cohesive soils, and cannot accurately predict the optimal mooring point location.
Based on the characteristics of the optimal mooring point and the theory of limit equilibrium analysis, combined with the minimum resistance criterion and derivative extreme value analysis method, a mechanical model of the failure mode and ultimate bearing capacity of pile anchor under inclined load is established. The failure mode and ultimate bearing capacity are determined by the minimum resistance criterion and derivative extreme value analysis, thereby predicting the location of the optimal mooring point.
It enables rapid and economical analysis of pile-anchor failure modes and ultimate bearing capacities under arbitrary inclined loads, and is applicable to clay, sand, and seabeds with both cohesive and non-cohesive soils. It can also accurately predict the optimal mooring point location, thus improving computational efficiency and applicability.
Smart Images
Figure CN121744696A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of offshore engineering anchoring technology, in particular to a high-efficiency analysis method for failure mode and ultimate bearing capacity of pile anchors under inclined load. BACKGROUND
[0002] In offshore engineering anchoring structures, pile anchors are widely used for various mooring purposes, such as catenary mooring systems under horizontal load, tension leg platforms under vertical load, and tension mooring systems under inclined load. The bearing efficiency and reliability of pile anchors are closely related to their failure mode and ultimate bearing capacity. However, existing research has deficiencies in reliably predicting the failure mode and ultimate bearing capacity under arbitrary inclined load, especially in seabeds with both cohesive and non-cohesive soil.
[0003] There are three methods to study the failure mode and ultimate bearing capacity of pile anchors: theoretical analysis, numerical simulation, and experiment. Among them, experiment and numerical simulation are relatively complex. For example, numerical simulation requires complex plastic or large deformation analysis, and it is time-consuming to calculate a large number of working conditions. In contrast, theoretical analysis has obvious advantages in economy and efficiency.
[0004] Currently, there are two main types of theoretical models for analyzing the ultimate bearing capacity of pile anchors under inclined load: one is semi-empirical models, such as those proposed by Das, Seeley, and Raghu (1976), Chattopadhyay and Pise (1986), Shin et al. (1993), Jamnejad and Hesar (1995), Rao et al. (2006), Achmus and Thieken (2010), and Bhardwaj and Singh (2015). These models rely heavily on experimental data, and some expressions and coefficients need to be determined by experiments. The other type is models based on vertical and horizontal bearing capacity of pile anchors, such as the method proposed by Poulos and Davis (1980), but this type of model cannot directly evaluate the ultimate bearing capacity of pile anchors under arbitrary inclined load. Andersen and Jostad (1999) established a failure model for the ultimate bearing capacity of suction anchors in cohesive soil under inclined load using the limit equilibrium method, but the failure mode and some parameters need to be determined by experiments. Other studies, such as Watson, Randolph, and Bransby (2000), Jones, Bang, and Cho (2007), and Bang et al. (2011), use "yield envelope" or "failure envelope" to analyze the inclined ultimate bearing capacity of suction anchors in cohesive or non-cohesive seabed, but these methods require "fitting analysis" and rely on experimental data to determine the related coefficients and envelope shapes.
[0005] An important characteristic of pile anchors is that when an external force is applied to the optimal mooring point, the pile anchor only translates at failure and the corresponding ultimate capacity is maximum, which has been verified by experimental observations or numerical simulations, such as Keaveny et al. (1994), Tjelta (2001), Aubeny, Han and Murff (2003), Clukey, Aubeny and Murff (2003), Randolph et al. (2005) and Kim et al. (2009). However, in the existing research, there is no theoretical work that can predict the optimal mooring point position of the pile anchor in the seabed with both cohesive and non-cohesive soil.
[0006] In summary, the existing research technology shows that the theoretical method for predicting the failure mode and ultimate capacity of the pile anchor under any inclined load needs to be combined with experimental data, and is only applicable to the seabed with single cohesive or non-cohesive soil, which limits its applicability. In addition, the theoretical analysis for predicting the optimal mooring point position of the pile anchor is insufficient, especially in the seabed with both cohesive and non-cohesive soil.
[0007] Therefore, it has important theoretical value and engineering significance to develop a theoretical method that is applicable to both clay and sand seabed and seabed with both cohesive and non-cohesive soil, and can efficiently predict the failure mode, ultimate capacity and optimal mooring point position of the pile anchor under any inclined load. SUMMARY
[0008] The purpose of the present application is to provide an efficient analysis method for the failure mode and ultimate capacity of a pile anchor under an inclined load, and to solve the problems in the above background technology.
[0009] To achieve the above purpose, the present application provides an efficient analysis method for the failure mode and ultimate capacity of a pile anchor under an inclined load, comprising the following steps: Step S1, obtaining the initial position, geometric parameters and soil parameters in the environment of the pile anchor in the seabed; Step S2, based on the optimal mooring point characteristics and the limit equilibrium analysis theory, establishing a mechanical model for predicting the failure mode and ultimate capacity of the pile anchor under any inclined load; Step S3, based on the minimum resistance criterion and the derivative extremum analysis method, establishing an analysis model for predicting the failure mode and ultimate capacity of the pile anchor under any inclined load; Step S4, based on the mechanical model and the analysis model of the pile anchor, predicting the failure mode and ultimate capacity of the pile anchor under any inclined load; Step S5, based on the predicted failure mode, ultimate capacity and moment balance method, predicting the optimal mooring point position of the pile anchor in the seabed.
[0010] Preferably, the parameters in step S1 include: diameter of the anchor, height of the anchor, embedded depth of the anchor in the soil, buoyant unit weight of the soil, depth of the soil, cohesion of the soil, viscosity coefficient, interface friction angle, internal friction angle.
[0011] Preferably, the mechanical model in step S2 is expressed by the following formula: ; ; wherein, is the end resistance acting on the pile-anchor in the failure direction, is the end resistance coefficient, is the average cohesion of the soil at the middle position of the embedded depth of the pile-anchor, is the diameter of the anchor, is the embedded depth of the anchor in the soil, is the failure direction angle, and , is the shear force acting on the surface of the pile-anchor in the failure direction, is the viscosity coefficient, is the vertical resistance of the soil acting on the bottom end of the pile-anchor, is the introduced inclination coefficient to represent the in the arbitrary failure mode , is the cohesion of the soil at the bottom end of the pile-anchor, and , is the reverse end resistance coefficient, is the effective stress at the bottom end of the pile-anchor, is the bottom area of the pile-anchor, and , is the horizontal shear force of the soil acting on the bottom end of the pile-anchor, is the bottom area of the soil inside the pile-anchor, is the area of the annular region at the bottom of the anchor cylinder, is the buoyant unit weight of the soil, is the maximum bearing stress coefficient, is the static earth pressure coefficient, is the interface friction angle, is the internal friction angle.
[0012] Preferably, step S3 includes: based on the minimum resistance criterion, in all motion states of the pile-anchor, the actual motion state is the state in which the soil resistance is most easily overcome by the external load, and the state in which the minimum external load is required to overcome the soil resistance is the true motion state of the pile-anchor.
[0013] Preferably, the true failure direction of the pile-anchor can be determined according to the following formula: ; by the mooring force The first derivative of is determined to determine the real failure direction of the pile anchor.
[0014] Preferably, based on the derivative extremum analysis method, the minimum value of the mooring force can only be obtained at three special points, including: Boundary points, including and ; Points satisfying ; Points that do not exist.
[0015] Preferably, the step S4 comprises: Based on the established pile anchor mechanical model and analysis model, the values at the three types of special points are calculated, that is, the minimum value of , that is, the ultimate bearing capacity of the pile anchor, and the corresponding movement direction of is the real failure mode of the anchor.
[0016] Preferably, the calculation formula of the optimal mooring point position of the pile anchor in the seabed in the step S5 is as follows: ; In the formula, represents the distance between the point and the seabed surface.
[0017] Preferably, the distance between the point and the seabed surface is calculated by the following formula: ; The above formula is obtained by the moment balance relationship between the combined soil resistance of the point and its component forces.
[0018] Therefore, the present application adopts the above-mentioned efficient analysis method of the failure mode and the ultimate bearing capacity of the pile anchor under inclined load, and has the following beneficial effects: (1) The present method can quickly and conveniently analyze and predict the failure mode and the ultimate bearing capacity of the pile anchor under any inclined load. At present, the theoretical analysis of the pile anchor under any inclined load is still very limited. Based on the reasonable analysis of the movement state of the pile anchor in the seabed soil and its deep mechanism in the steps S2 and S3, the influence of the mooring angle is considered and a theoretical model is established. Compared with experimental methods and numerical simulation, the present method has obvious advantages in economy and calculation efficiency when facing a large number of cases.
[0019] (2) This method is applicable to both clay and sandy seabeds, as well as seabeds with both cohesive and non-cohesive soils. Step S2 considers soil cohesion, which represents the cohesive and non-cohesive properties of the seabed soil, when establishing the mechanical model. and internal friction angle The soil resistance expression in step S2 is applicable to seabeds with both cohesive and non-cohesive soils because of the influence of soil composition. However, existing theoretical analyses focus on clay or sand, making this method more universal and reasonable.
[0020] (3) This method proposes a prediction method for the optimal mooring point location of pile anchors under arbitrary inclined loads. The prediction method for the optimal mooring point location in step S5 is based on the failure mode, ultimate bearing capacity, and moment balance method determined in step S4. Therefore, it is applicable to the determination of the optimal mooring point location under arbitrary inclined loads and is a theoretical method. Currently, there is no theoretical work that can calculate the optimal mooring point location of pile anchors under arbitrary inclined loads. Therefore, this method is innovative and has high computational efficiency.
[0021] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description
[0022] Figure 1 The geometric characteristics and mechanical model of the pile anchor are shown in the embodiment of the efficient analysis method for the failure mode and ultimate bearing capacity of the pile anchor under inclined load of the present invention. Figure 2 The diagram shows the stress distribution in the horizontal direction of the pile anchor, which is the result of the efficient analysis method for the failure mode and ultimate bearing capacity of the pile anchor under inclined load according to the present invention. Figure 3 This invention provides a mechanical model of the optimal mooring point location for the efficient analysis method of pile anchor failure mode and ultimate bearing capacity under inclined load. Figure 4 This is a flowchart of the efficient analysis method for the failure mode and ultimate bearing capacity of pile anchors under inclined loads according to the present invention. Figure 5 The following is a prediction result of Example 1 of the efficient analysis method for pile anchor failure mode and ultimate bearing capacity under inclined load of the present invention, wherein (a) is the ultimate bearing capacity result diagram and (b) is the failure direction angle result diagram. Figure 6 This is the prediction result of Example 2 of the efficient analysis method for failure mode and ultimate bearing capacity of pile anchors under inclined loads according to the present invention. Detailed Implementation
[0023] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.
[0024] Unless otherwise defined, technical terms or scientific terms used in the present application shall have the meanings that can be commonly understood by a person with ordinary skill in the art to which the present application belongs. The terms "first", "second", and similar terms in the present application do not denote any order, quantity, or importance, but are used to distinguish different components. The terms "comprising" or "including" or similar terms mean that the elements or objects before the term encompass the elements or objects listed after the term and their equivalents, without excluding other elements or objects. The terms "connected" or "connected" or similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms "up", "down", "left", "right", and the like are only used to represent relative positional relationships, which can change accordingly when the absolute positions of the described objects change.
[0025] Embodiments Please refer to Figures 1-6 The present application provides an efficient analysis method for the failure mode and ultimate bearing capacity of a pile anchor under an inclined load, comprising the following steps: Step S1, obtaining the initial position, geometric parameters of the loaded pile anchor in the seabed, and soil parameters in the environment. The parameters include: the diameter of the anchor , the height of the anchor , the embedded depth of the anchor in the soil , the buoyant weight of the soil , the depth of the soil , the cohesion of the soil , the viscosity coefficient , the interface friction angle , the internal friction angle .
[0026] Step S2, based on the optimal mooring point characteristics and the limit equilibrium analysis theory, a mechanical model is established to predict the failure mode and ultimate bearing capacity of the pile anchor under any inclined load.
[0027] The geometric characteristics and mechanical model of the pile anchor are shown in Figure 1 . Among them, is the mooring force at the mooring point, the components perpendicular and parallel to the failure direction are represented by and respectively; is the shear force acting on the surface of the pile anchor in the failure direction; is the end resistance acting on the pile anchor in the failure direction; is the total buoyant weight of the pile anchor and the soil inside the pile anchor; and are the horizontal shear force and vertical resistance of the soil acting on the bottom end of the pile anchor, respectively; is the mooring angle, that is, the angle between the mooring force at the mooring point and the horizontal plane; To disrupt the direction angle ( ), which is the angle between the mooring point and the horizontal plane.
[0028] When an external load is applied at the optimal mooring point of the pile anchor, the pile anchor only undergoes translational behavior under the failure state, and at this point, the ultimate bearing capacity of the pile anchor reaches its maximum. Translational behavior refers to the movement of the pile anchor along the failure direction. This is based on the force balance relationship along the failure direction: (1) In the formula, This represents the mooring force at the mooring point in the translational direction. This is the resultant force of the soil resistance and the anchor weight acting on the pile anchor in the translation direction.
[0029] The ultimate mooring tension or ultimate bearing capacity of the pile anchor at the mooring point is calculated using the following formula: (2) In the formula, the meaning of each parameter is expressed. For end resistance... and shear force This is related to the distribution of bearing stress acting on the surface of the pile anchor. This method assumes the distribution of bearing stress in the horizontal direction at a certain depth of the pile anchor, such as... Figure 2 As shown, where, The bearing stress is perpendicular to the outer surface of the anchor; This is the angle between the load-bearing stress and the horizontal axis. Based on previous research, The following formula is used for calculation: (3) In the formula, For when and The bearing stress at that time; For when and The bearing stress at that time; This is the coefficient of earth pressure at rest; This refers to the end drag coefficient. For soil cohesion ( ,in The soil cohesion at the seabed surface; (This refers to the soil cohesion gradient). The maximum bearing stress coefficient ( ,in (This refers to the passive earth pressure coefficient).
[0030] For bearing stress Integral, end resistance is obtained. expression: (4) In the formula, This represents the average soil cohesion at the midpoint of the pile anchor depth. .
[0031] According to the Mohr-Coulomb equation, the shear stress acting on the pile anchor surface... Calculate using the following formula: (5) In the formula, .
[0032] For shear stress Integrate to obtain the shear force. expression: (6) Based on the standard bearing capacity theory, the vertical resistance acting on the anchor bottom end Calculate using the following formula: (7) In the formula, The introduced tilt coefficient is used to represent arbitrary failure modes. ; The soil cohesion at the bottom of the pile anchor and ; This is the drag coefficient at the reverse end; This represents the net reverse end resistance stress. The effective stress at the bottom end of the pile anchor; This represents the base area of the pile anchor.
[0033] When the pile anchor is subjected to a horizontal load ( ), horizontal shear force acting on the bottom end of the pile anchor Calculate using the following formula: (8) In the formula, This refers to the bottom area of the soil inside the pile anchor. This represents the area of the annular region at the bottom of the anchor tube. The horizontal shear force acting at the anchor bottom. Its value changes with the loading conditions, which is addressed by introducing a tilt coefficient. , It can be represented as: (9) The above soil resistance expression is applicable to seabeds with both cohesive and non-cohesive soils. Therefore, the expression of relevant forces in clay or sandy seabeds can also be obtained, namely Equation (10) and Equation (11).
[0034] (10) (11) In the formula, To compensate for the end resistance acting on the pile anchor in the direction of failure, The end drag coefficient, This represents the average soil cohesion at the midpoint of the pile anchor embedment depth. The diameter of the anchor. The embedment depth of the anchor in the soil. To disrupt the direction angle, and , The shear force acting on the pile anchor surface in the direction of failure, The viscosity coefficient, The vertical resistance of the soil acting at the bottom of the pile anchor. The introduced tilt coefficient is used to represent arbitrary failure modes. , The soil cohesion at the bottom of the pile anchor and , This is the reverse end drag coefficient. The effective stress at the bottom of the pile anchor. Let be the base area of the pile anchor, and , The horizontal shear force acting on the soil at the bottom of the pile anchor. This represents the bottom area of the soil inside the pile anchor. The area of the annular region at the bottom of the anchor tube. For the buoyant density of soil, The maximum bearing stress coefficient, The coefficient of earth pressure at rest. The angle of friction at the interface. It is the internal friction angle.
[0035] The mechanical model established above can fully depict the mechanical properties of pile anchors in seabed soil.
[0036] Step S3: Based on the minimum resistance criterion and derivative extreme value analysis method, establish an analytical model to predict the failure mode and ultimate bearing capacity of pile anchors under arbitrary inclined loads.
[0037] Based on the minimum resistance criterion, among all possible motion states of the pile anchor, the actual motion state that occurs must be the state in which the soil resistance is most easily overcome by the external load, that is, the state in which the minimum external load is required to overcome the soil resistance is the true motion state of the pile anchor. The true failure direction of the pile anchor can be calculated according to formula (2), through the mooring force. right The first derivative is used to determine the true failure direction of the pile anchor. Based on the derivative extremum analysis method, the mooring force... The minimum value can only be obtained at three special points (extreme points), including: Boundary points, including and ; satisfy points; points of nonexistence.
[0038] Step S4, based on the pile-anchor mechanical model and the analysis model, the failure mode and the ultimate bearing capacity of the pile-anchor under any inclined load are predicted. Based on the established pile-anchor mechanical model and the analysis model, the values of the three special points are calculated, and the minimum value of the three special points is obtained, i.e. the ultimate bearing capacity of the pile-anchor, and the corresponding movement direction of the three special points is the real failure mode of the anchor.
[0039] Step S5, based on the predicted failure mode, the ultimate bearing capacity and the moment balance method, the optimal mooring point position of the pile-anchor in the seabed is predicted.
[0040] The mechanical model of the optimal mooring point position of the pile-anchor is shown in Figure 3 . The vertical dashed line is the symmetry axis of the pile-anchor; is the optimal mooring point; is located on the symmetry axis of the pile-anchor and at the same time is located at the centroid depth of the soil strength profile; is the intersection point of the external load and the symmetry axis of the anchor; is the distance between the optimal mooring point and the seabed surface; is the distance between the point and the seabed surface; is the distance between the point and the seabed surface; is the soil strength at the bottom end of the pile-anchor; is the soil strength at the seabed surface. By setting the moment of the force at the point to zero, the optimal mooring point position of the pile-anchor can be obtained, i.e. where only and need to be considered.
[0041] where and have a specific geometric relationship, i.e. . Combined with the geometric relationship and , the calculation formula of the optimal mooring point position of the pile-anchor can be obtained: (12) where represents the distance between the point and the seabed surface.
[0042] Distance between the point and seabed surface The following formula is used for calculation: (13) The above formula is obtained by moment balance between the total soil resistance of the point and its components. Based on the predicted failure mode and ultimate capacity of the pile-anchor in step S4, the optimal mooring point position of the pile-anchor in seabed can be further predicted by formula (12). As shown in
[0043] , the complete analysis process of the method of the present application is as follows: Figure 4 (1) Obtain the initial position, geometric parameters of the loaded pile-anchor in seabed and soil parameters in the environment; (2) Apply the theoretical model of the pile-anchor to express the calculation formula of in detail; (3) Analyze the first derivative of to obtain three special points; (4) Calculate the values at the three special points to obtain the minimum value of and the corresponding failure direction angle ; (5) Predict the optimal mooring point position of the pile-anchor in seabed.
[0044] Example 1 A series of model experiments are conducted to examine the behavior of suction anchors in clay under different load conditions to test the prediction effect of the method. In the experiment, the diameter of the anchor is 0.10 m, the embedded depth of the anchor in the soil is 0.81 m, the viscosity coefficient is 0.78, the end resistance coefficient is 9.46, the reverse end resistance coefficient is 15, the soil cohesion is 7.5 kN / m , and the soil buoyant weight 3 is 7.5 kN / m Figure 5 . The experiment includes six different mooring angles, i.e. 0°, 10°, 20°, 30°, 45° and 90°. According to the analysis process, the relevant parameters are substituted into formula (10) to predict the failure mode and ultimate capacity of the anchor, which shows the prediction results of the method of the present application. Since EI-Sherbiny did not investigate the optimal mooring point position of the suction anchor, step 5 is not analyzed and processed.
[0045] Figure 5 As shown, the method of this invention reasonably evaluates the ultimate bearing capacity and failure direction angle of the anchor. The average absolute relative errors of the predicted and experimental results for the ultimate bearing capacity and failure direction angle of the anchor are 8.7% and 13.9%, respectively. Figure 5 As shown in (a), the mooring force and mooring cape There is a monotonic relationship between them. Figure 5 (b) indicates the critical angle It is approximately 40°.
[0046] Example 2 The predictive effectiveness of this method was verified through a series of centrifuge model experiments conducted to investigate the bearing characteristics of suction anchors in sand under different load conditions. The prototype anchor had a height of 6m, a diameter of 3m, and a thickness of 0.1m. The interfacial friction angle was [not specified]. The internal friction angle is 23.1°. The angle is 33°, and the coefficient of earth pressure at rest is 33°. The buoyant unit weight of the soil is 0.65. The value is 10.1 kN / m³. Five different mooring angles were investigated in the experiment: 0°, 22.5°, 45°, 67.5°, and 90°. By substituting the relevant parameters into formula (11) according to the analysis procedure, the failure mode and ultimate bearing capacity of the anchor can be predicted. Figure 6 The prediction results of the method of the present invention are shown in the figure. Since Kim et al. did not investigate the optimal mooring point of the suction anchor, the analysis and processing of step 5 are not performed.
[0047] like Figure 6 As shown, four out of the five measurement data points agree well with the predictions of this invention. The average absolute relative error between the analysis predictions and experimental results is 7.6%. (Tethering force) and mooring cape There is also a monotonic relationship between them.
[0048] The comparison between the results of the method of the present invention and the results of two specific embodiments shows that the predictions and experimental results of the present invention are in good agreement for both clay and sand, and the comparison results verify the effectiveness of the present invention.
[0049] Therefore, the present invention employs the above-mentioned efficient analysis method for the failure mode and ultimate bearing capacity of pile anchors under inclined loads, which can quickly and conveniently analyze and predict the failure mode and ultimate bearing capacity of pile anchors under arbitrary inclined loads.
[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.
Claims
1. An efficient analysis method for the failure mode and ultimate bearing capacity of pile anchors under inclined loads, characterized in that, Includes the following steps: Step S1: Obtain the initial position, geometric parameters, and soil parameters of the loaded pile anchor in the seabed. Step S2: Based on the optimal mooring point characteristics and limit equilibrium analysis theory, establish a mechanical model to predict the failure mode and ultimate bearing capacity of the pile anchor under arbitrary inclined load. Step S3: Based on the minimum resistance criterion and derivative extreme value analysis method, establish an analytical model to predict the failure mode and ultimate bearing capacity of pile anchors under arbitrary inclined loads; Step S4: Based on the pile-anchor mechanical model and analysis model, predict the failure mode and ultimate bearing capacity of the pile anchor under arbitrary inclined load; Step S5: Based on the predicted failure mode, ultimate bearing capacity and moment balance method, predict the optimal mooring point location of the pile anchor in the seabed.
2. The efficient analysis method for failure modes and ultimate bearing capacity of pile anchors under inclined loads according to claim 1, characterized in that, The parameters in step S1 include: anchor diameter, anchor height, anchor embedment depth in the soil, soil buoyancy density, soil depth, soil cohesion, viscosity coefficient, interfacial friction angle, and internal friction angle.
3. The efficient analysis method for failure modes and ultimate bearing capacity of pile anchors under inclined loads according to claim 2, characterized in that, The mechanical model in step S2 is expressed by the following formula: ； ； In the formula, To compensate for the end resistance acting on the pile anchor in the direction of failure, The end drag coefficient, This represents the average soil cohesion at the midpoint of the pile anchor embedment depth. The diameter of the anchor. The embedment depth of the anchor in the soil. To disrupt the direction angle, and , The shear force acting on the pile anchor surface in the direction of failure, The viscosity coefficient, The vertical resistance of the soil acting at the bottom of the pile anchor. The introduced tilt coefficient is used to represent arbitrary failure modes. , The soil cohesion at the bottom of the pile anchor and , This is the reverse end drag coefficient. The effective stress at the bottom of the pile anchor. Let be the base area of the pile anchor, and , The horizontal shear force acting on the soil at the bottom of the pile anchor. This represents the bottom area of the soil inside the pile anchor. The area of the annular region at the bottom of the anchor tube. For the buoyant density of soil, The maximum bearing stress coefficient, The coefficient of earth pressure at rest. The angle of friction at the interface. It is the internal friction angle.
4. The efficient analysis method for failure mode and ultimate bearing capacity of pile anchors under inclined load as described in claim 3, characterized in that, Step S3 includes: based on the minimum resistance criterion, among all the movement states of the pile anchor, the actual movement state is the state in which the soil resistance is most easily overcome by the external load, and the state in which the minimum external load is required to overcome the soil resistance is the true movement state of the pile anchor.
5. The efficient analysis method for the failure mode and ultimate bearing capacity of pile anchors under inclined loads according to claim 4, characterized in that, The actual failure direction of the pile anchor can be determined according to the following formula: ； Through mooring force right The first derivative is used to determine the true failure direction of the pile anchor.
6. The efficient analysis method for failure mode and ultimate bearing capacity of pile anchors under inclined load as described in claim 5, characterized in that, Based on the derivative extremum analysis method, mooring force The minimum value can only be obtained at three special points, including: Boundary points, including and ; satisfy point; Points that do not exist.
7. The efficient analysis method for failure mode and ultimate bearing capacity of pile anchors under inclined load as described in claim 6, characterized in that, Step S4 includes: Based on the established pile-anchor mechanical model and analysis model, calculations were performed and compared at three special points. Value, get minimum value , is the ultimate bearing capacity of the pile anchor, and Corresponding direction of motion This represents the actual failure mode of the anchor.
8. The efficient analysis method for failure mode and ultimate bearing capacity of pile anchors under inclined load as described in claim 7, characterized in that, The formula for calculating the optimal mooring point location of the pile anchor in the seabed in step S5 is as follows: ； In the formula, express The distance between a point and the seabed surface.
9. The efficient analysis method for failure mode and ultimate bearing capacity of pile anchors under inclined load as described in claim 8, characterized in that, Distance between point and seabed surface Calculate using the following formula: ； The above formula is based on... The moment balance relationship between the soil resistance at a point and its component forces is obtained.