Calculation method for complex bearing capacity of gravity penetration anchor in clay seabed

Abstract

The invention discloses a method for calculating the complex bearing capacity of a gravity penetration anchor in a clay seabed, and relates to the technical field of anchoring of ocean floating structures. The method comprises the steps that relevant parameters of clay and the anchor are obtained; a fitting formula of the burial depth ratio to the anchor rod end resistance bearing capacity coefficient in the uniform weightlessness clay is obtained; a fitting formula of the undrained shear strength gradient to the anchor rod end resistance bearing capacity strength heterogeneous factors in the clay is obtained; a fitting formula of the anchor direction angle to the end resistance bearing capacity coefficient of the inclined anchor rod in the clay is obtained; obtaining a fitting formula of a loading angle coefficient; a fitting formula of the bearing area to the bearing capacity bearing area coefficient of the anchor end resistance in clay is obtained; obtaining an explicit expression of an end resistance bearing capacity coefficient under the influence of multiple factors; obtaining an end resistance bearing capacity coefficient; and the bearing capacity of the gravity penetration anchor is obtained. According to the calculation method for the complex bearing capacity of the gravity penetration anchor in the clay seabed, scientificity, accuracy and engineering practicability of anchor foundation design and analysis are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of anchoring technology of offshore floating structures, and particularly to a calculation method of complex bearing capacity of gravity penetration anchors in clay seabed. BACKGROUND

[0002] With the increasing demand for resources and energy, the development of the ocean is constantly moving from the near shore to the deep sea. At the same time, various types of floating structures are also becoming increasingly widespread. However, these floating structures often need to face extremely harsh marine environments, and how to ensure their safety and reliability in complex and variable marine environments faces great challenges.

[0003] In actual engineering, mooring systems are used to ensure the safe operation of floating structures due to their economy and effectiveness. Deep water anchoring structures, such as piles, suction anchors, drag anchors and gravity penetration anchors, as important components of deep water mooring systems, play a key role in ensuring the safety and stability of the mooring system. Early studies on the uplift capacity of gravity penetration anchors mainly include 1g or centrifugal laboratory experiments, field tests, and small strain or large deformation numerical models. However, these early studies only involve cases with limited influencing parameters, so the effects of influencing parameters can be evaluated under specific conditions, but the results cannot be universally extended to quantitative analysis. SUMMARY

[0004] The purpose of the present application is to provide a calculation method of complex bearing capacity of gravity penetration anchors in clay seabed, which solves the problems raised in the background.

[0005] To achieve the above purpose, the present application provides a calculation method of complex bearing capacity of gravity penetration anchors in clay seabed, comprising the following steps: Step S1, a large deformation finite element model of the gravity penetration anchor is established, and the relevant parameters of the clay and the anchor are obtained; Step S2, a fitting formula of the buried depth ratio on the end resistance bearing capacity coefficient of the anchor rod in uniform weightlessness clay is obtained; Step S3, a fitting formula of the undrained shear strength gradient on the end resistance bearing capacity strength heterogeneity factor of the anchor rod in clay is obtained; Step S4, a fitting formula of the anchor direction angle on the end resistance bearing capacity coefficient of the inclined anchor rod in clay is obtained; Step S5, a fitting formula of the loading angle coefficient is obtained; Step S6, a fitting formula of the bearing area on the end resistance bearing capacity bearing area coefficient of the anchor in clay is obtained; Step S7, an explicit expression of the end resistance bearing capacity coefficient under the influence of multiple factors is obtained; Step S8, the relevant parameters of the clay and the anchor are brought into the explicit expression of the end resistance bearing capacity coefficient, and then the end resistance bearing capacity coefficient is obtained; Step S9, according to the formula derivation, the bearing capacity of gravity penetration anchor is obtained.

[0006] Preferably, the influencing factors in step S1 include: buried depth ratio , undrained shear strength gradient of clay , direction angle of anchor , loading angle of anchor , angle between anchor shank and nearest wing plate , wing plate area of anchor , weight of anchor under water , horizontal loading angle at mooring point , adhesion coefficient .

[0007] Preferably, the step S2 includes: Step S21, a fitting formula of buried depth ratio to end resistance bearing capacity coefficient of horizontal anchor rod in uniform weight loss clay is obtained by numerical calculation, as shown in the following formula: ; Step S22, a fitting formula of buried depth ratio to end resistance bearing capacity coefficient of vertical anchor rod in uniform weight loss clay is obtained by numerical calculation, as shown in the following formula: ; In the formula, represents buried depth ratio, represents unit weight of effective soil, represents undrained shear strength gradient of clay, represents direction angle of anchor.

[0008] Preferably, the step S3 includes: Step S31, a fitting formula of undrained shear strength gradient to strength heterogeneity factor of end resistance bearing capacity of horizontal anchor rod in clay is obtained by numerical calculation, as shown in the following formula: ; Step S32, a fitting formula of undrained shear strength gradient to strength heterogeneity factor of end resistance bearing capacity of vertical anchor rod in clay is obtained by numerical calculation, as shown in the following formula: ; In the formula, is strength heterogeneity coefficient of anchor, represents buried depth ratio, represents unit weight of effective soil, represents undrained shear strength gradient of clay, represents direction angle of anchor.

[0009] Preferably, the step S4 obtains a fitting formula of the anchorage direction angle to the end resistance bearing capacity coefficient of the inclined anchor end in clay through numerical calculation, as shown in the following formula: ; In the formula, represents the buried depth ratio, represents the undrained shear strength gradient of clay, represents the anchorage direction angle.

[0010] Preferably, the step S5 obtains a fitting formula of the loading angle coefficient through numerical calculation, as shown in the following formula: ; In the formula, represents the loading angle coefficient, represents the buried depth ratio, represents the undrained shear strength gradient of clay, represents the anchorage direction angle, represents the loading angle, represents the wing plate included angle.

[0011] Preferably, the step S6 obtains a fitting formula of the bearing area to the bearing area coefficient of the end resistance bearing capacity of the anchor end in clay through numerical calculation, as shown in the following formula: ; In the formula, represents the bearing area coefficient, represents the buried depth ratio, represents the undrained shear strength gradient of clay, represents the anchorage direction angle, represents the loading angle, represents the wing plate included angle.

[0012] Preferably, the step S7 obtains an explicit expression of the end resistance bearing capacity coefficient, as shown in the following formula: ; In the formula, represents the loading angle coefficient, represents the bearing area coefficient, represents the buried depth ratio, represents the undrained shear strength gradient of clay, represents the anchorage direction angle.

[0013] Preferably, the step S8 obtains the end resistance bearing capacity coefficient as shown in the following formula: ; In the formula, represents the buried depth ratio, represents the undrained shear strength gradient of clay, denotes the direction angle of the anchor, denotes the loading angle, denotes the wing plate angle.

[0014] Preferably, the bearing capacity of the gravity penetration anchor in step S9 is obtained by the following formula: ; ; ; ; wherein, is the uplift resistance of the anchor in the loading direction; is the end resistance bearing capacity of the anchor in the loading direction; is the shear force of the anchor in the loading direction; is the weight of the anchor under water; is the horizontal loading angle at the mooring point; is the effective bearing area of the anchor; is the effective shear area of the anchor; is the adhesion coefficient, denotes the undrained shear strength of the clay.

[0015] Therefore, the present application adopts the above-mentioned calculation method of the complex bearing capacity of the gravity penetration anchor in the clay seabed, and has the following beneficial effects: (1) The anchor direction angle, loading angle, bearing area and other factors are generally considered qualitatively in the prior art, and there is a lack of a universal and simple quantitative tool. The present application establishes a complete and quantitative calculation method of the complex bearing capacity of the gravity penetration anchor, which significantly improves the scientificity, accuracy and engineering practicability of the anchor foundation design and analysis.

[0016] (2) The explicit expression of the end resistance bearing capacity coefficient under the influence of multiple factors proposed by the present application can be applied to the gravity penetration anchor under a wide range of loading conditions, and can effectively estimate the bearing capacity coefficient of the torpedo anchor, DEPLA anchor and fish-shaped anchor under specific conditions.

[0017] (3) The present application gives an explicit expression of the end resistance bearing capacity under the influence of multiple factors, and through the sensitivity analysis of these parameters, the influence of the five parameters on the end bearing capacity and uplift resistance of the anchor can be quantified by the expression. This helps to analyze the possible working performance of the anchor under complex conditions, which is of great significance to the engineering application and safety control of the mooring system.

[0018] The technical solutions of the present application will be further described in detail below with reference to the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 Flow chart of the embodiment of the method for calculating the complex bearing capacity of the gravity driven pile anchor in the clay seabed of the present application; Figure 2 Schematic diagram of the complex bearing capacity of the OMNI-Max anchor in the clay seabed of the method for calculating the complex bearing capacity of the gravity driven pile anchor in the clay seabed of the present application; Figure 3 Schematic diagram of the bearing area of the OMNI-Max anchor in the clay seabed of the method for calculating the complex bearing capacity of the gravity driven pile anchor in the clay seabed of the present application; Figure 4 Structural schematic diagram of the DEPLA anchor of the method for calculating the complex bearing capacity of the gravity driven pile anchor in the clay seabed of the present application. DETAILED DESCRIPTION

[0020] The technical solutions of the present application are further described below by means of the accompanying drawings and embodiments.

[0021] Unless otherwise defined, the technical terms or scientific terms used in the present application shall be understood as the usual meanings understood by those skilled in the art to which the present application belongs. The terms "first", "second", and similar terms used in the present application do not represent any order, number, or importance, but are only used to distinguish different components. The terms "include" or "contain" and similar terms mean that the elements or objects appearing before the terms cover the elements or objects listed after the terms and their equivalents, without excluding other elements or objects. The terms "connect" or "connected" and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms "upper", "lower", "left", "right", and the like are only used to represent relative positional relationships, and when the absolute positions of the described objects change, the relative positional relationships may also change accordingly.

[0022] EMBODIMENT Please refer to Figures 1-4 The present application provides a method for calculating the complex bearing capacity of a gravity driven pile anchor in a clay seabed, comprising the following steps: Step S1, a large deformation finite element model of the gravity driven pile anchor (OMNI-Max anchor) is established, and relevant parameters of the clay and the anchor are obtained. The influencing factors include: the undrained shear strength gradient of the clay the directional angle of the anchor the loading angle of the anchor the angle between the anchor shank and the nearest wing plate the wing plate area of the anchor the weight of the anchor under water the horizontal loading angle at the mooring point the adhesion coefficient .

[0023] Step S2, obtaining the fitting formula of the buried depth ratio on the end resistance bearing capacity coefficient of the anchor in the uniform weight loss clay. Including: Step S21, obtaining the fitting formula of the buried depth ratio on the end resistance bearing capacity coefficient of the horizontal anchor in the uniform weight loss clay through numerical calculation, as shown in the following formula: = (1) Step S22, obtaining the fitting formula of the buried depth ratio on the end resistance bearing capacity coefficient of the vertical anchor in the uniform weight loss clay through numerical calculation, as shown in the following formula: (2) In the formula, indicates the buried depth ratio, indicates the unit weight of the effective soil, indicates the undrained shear strength gradient of the clay, indicates the direction angle of the anchor.

[0024] Step S3, obtaining the fitting formula of the undrained shear strength gradient on the strength heterogeneity factor of the anchor end resistance bearing capacity in the clay. Including: Step S31, obtaining the fitting formula of the undrained shear strength gradient on the strength heterogeneity factor of the horizontal anchor end resistance bearing capacity in the clay through numerical calculation, as shown in the following formula: (3) Step S32, obtaining the fitting formula of the undrained shear strength gradient on the strength heterogeneity factor of the vertical anchor end resistance bearing capacity in the clay through numerical calculation, as shown in the following formula: (4) In the formula, is the strength heterogeneity coefficient of the anchor, is the coefficient, the value of which depends on the horizontal or vertical buried condition, the undrained shear strength of the clay, indicates the buried depth ratio, indicates the unit weight of the effective soil, indicates the undrained shear strength gradient of the clay, indicates the direction angle of the anchor.

[0025] Step S4, obtaining the fitting formula of the anchor direction angle on the end resistance bearing capacity coefficient of the inclined anchor in the clay through numerical calculation, as shown in the following formula: (5) In the formula, Indicates the burial depth ratio. This represents the gradient of undrained shear strength of clay. Indicates the anchor's direction angle.

[0026] Step S5: Obtain the fitting formula for the loading angle coefficient through numerical calculation, as shown in the following formula: ; Further calculations are as follows: when hour: (6) when hour: (7) In the formula, Indicates the loading angle coefficient. Indicates the burial depth ratio. This represents the gradient of undrained shear strength of clay. Indicates the anchor's direction angle. Indicates the loading angle. Indicates the included angle of the airfoil.

[0027] Step S6: Obtain the fitting formula for the bearing area coefficient of the anchor end bearing capacity in clay through numerical calculation, as shown in the following formula: ; Further calculations are as follows: when hour: (8) when hour: (9) In the formula, Indicates the bearing area coefficient. Indicates the burial depth ratio. This represents the gradient of undrained shear strength of clay. Indicates the anchor's direction angle. Indicates the loading angle. Indicates the included angle of the airfoil.

[0028] Step S7: Obtain the explicit expression for the bearing capacity coefficient of the lower end bearing capacity influenced by multiple factors through calculation, as shown in the following formula: ; In the formula, Indicates the loading angle coefficient. Indicates the bearing area coefficient. Indicates the burial depth ratio. This represents the gradient of undrained shear strength of clay. Indicates the anchor's direction angle.

[0029] Step S8: Substitute the relevant parameters of clay and anchor into the explicit expression of the end bearing capacity coefficient to obtain the end bearing capacity coefficient, as shown in the following formula: ; In the formula, Indicates the burial depth ratio. This represents the gradient of undrained shear strength of clay. Indicates the anchor's direction angle. Indicates the loading angle. Indicates the included angle of the airfoil.

[0030] Step S9: Based on the formula derivation, the bearing capacity of the gravity-penetrated anchor is obtained. The bearing capacity is obtained through the following formula: (10) (11) (12) (13) In the formula, The anchor's pull-out resistance in the loading direction; The end resistance bearing capacity of the anchor in the loading direction; The shear force of the anchor in the loading direction; The weight of the anchor underwater; The horizontal loading angle at the mooring point; The effective bearing area of ​​the anchor; The effective shear area of ​​the anchor; The adhesion coefficient, This represents the undrained shear strength of clay.

[0031] like Figure 1 The diagram shown is a flowchart of the present invention. Figure 2 , Figure 3 These diagrams illustrate the complex bearing capacity and bearing area of ​​the OMNI-Max anchor proposed in this invention in clayey seabeds. In practical applications, the anchor may be embedded in the seabed with different soil properties, directions, and depths, and the direction of the load applied to the anchor may also vary, resulting in different bearing areas and therefore different pull-out capabilities. The designed 360° omnidirectional load arm may produce different bearing areas at specific load angles, varying between maximum and minimum values. If the load angle changes, the problem becomes even more complex, resulting in various bearing areas. Under such complex conditions, accurately assessing the pull-out capability of the anchor is not an easy task. The anchor's embedment depth, direction, bearing area, applied loading angle, and soil strength are all important factors affecting the pull-out capability of the OMNI-Max anchor.

[0032] Table 1 shows the different coefficients of the fitting formula. Different coefficients are selected according to the formula under different conditions.

[0033] Table 1. Coefficients of Fitting Formula

[0034] Example 1 The method is illustrated using the pull-out of an OMNI-Max anchor in clay as an example. There is a linear clay layer on the seabed with a gradient of undrained shear strength. OMNI-Max anchor burial depth ratio Anchor direction angle for Loading angle for Angle between the anchor shank and the nearest wingplate for The area of ​​the anchor's wing plate The weight of the anchor underwater is 11.45 m2. The horizontal loading angle at the mooring point is 341kN. for Effective shear area It is 5.04m2. The adhesion coefficient is 0.4.

[0035] The implementation steps are as follows: (1) Determine the relevant parameters of clay and anchor.

[0036] (2) Substituting the burial depth ratio data into the fitting formula (1) yields: ; (3) Substituting the burial depth ratio data into the fitting formula (2) yields: ; (4) Substituting the undrained shear strength gradient data into the fitting formula (3) yields: ; (5) Substituting the undrained shear strength gradient data into the fitting formula (4) yields: ; (6) Substituting the anchor direction data into the fitting formula (5) yields: ; (7) Substituting the loading angle data into the fitting formula (6) yields: ; (8) Substituting the angle data between the anchor shank and the nearest wingplate into the fitting formula (8) yields: ; (9) The explicit expression for the bearing capacity coefficient of the lower end bearing capacity under multiple factors is obtained through calculation: ; (10) Substituting the relevant parameters of the anchor and soil into the explicit expression of the end bearing capacity coefficient under multiple factors, the end bearing capacity coefficient is obtained as follows: ； (11) Based on the formula derivation, the bearing capacity of gravity-penetrated anchor is obtained. .

[0037] ; ; ; Obtained through numerical calculation It is 7.59. =3846.48kN, and the relative error of the result predicted by this method is 1.6% compared with that. This indicates that the formula has high accuracy in predicting the complex bearing capacity of gravity-penetrated anchors in clay seabeds, and can obtain results more quickly and conveniently than direct numerical calculation.

[0038] Example 2 The shape of the DEPLA anchor in the case is as follows: Figure 4 The method is illustrated using the example of an anchor being pulled out of clay. There is a linear clay layer on the seabed with a gradient of undrained shear strength. DEPLA anchor burial depth ratio Anchor direction angle Loading angle Angle between the anchor shank and the nearest wingplate .

[0039] The implementation steps are the same as above, and will not be repeated here.

[0040] The explicit expression for the bearing capacity coefficient of the lower end bearing capacity under multiple factors is obtained. The value is 12.54, obtained through numerical calculation. The value is 13.12, and the relative error of the prediction result of this invention is 4.6% compared with that. This indicates that the formula has high accuracy when extended to calculate the complex bearing capacity of DEPLA anchors in clay seabeds.

[0041] Therefore, the present invention employs the above-mentioned method for calculating the complex bearing capacity of gravity-penetrated anchors in clay seabeds, which significantly improves the scientific rigor, accuracy, and engineering practicality of anchor foundation design and analysis.

[0042] 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. A method for calculating the complex bearing capacity of gravity-penetrated anchors in clayey seabeds, characterized in that, Includes the following steps: Step S1: Establish a large deformation finite element model of the gravity-penetrated anchor and obtain the relevant parameters of the clay and the anchor; Step S2: Obtain the fitting formula for the bearing capacity coefficient of the anchor end in uniformly weightless clay with a burial depth ratio; Step S3: Obtain the fitting formula for the heterogeneous factor of the undrained shear strength gradient on the bearing capacity of the anchor end in clay. Step S4: Obtain the fitting formula for the bearing capacity coefficient of the inclined anchor rod end in clay with respect to the anchor direction angle; Step S5: Obtain the fitting formula for the loading angle coefficient; Step S6: Obtain the fitting formula for the bearing area coefficient of the anchor end bearing capacity in clay; Step S7: Obtain the explicit expression for the bearing capacity coefficient of the lower end under the influence of multiple factors; Step S8: Substitute the relevant parameters of clay and anchor into the explicit expression of the end bearing capacity coefficient to obtain the end bearing capacity coefficient. Step S9: Based on the formula derivation, the bearing capacity of the gravity-penetrated anchor is obtained.

2. The method for calculating the complex bearing capacity of a gravity penetration anchor in a clayey seabed according to claim 1, characterized in that, The influencing factors in step S1 include: burial depth ratio. Undrained shear strength gradient of clay Anchor direction angle Anchor loading angle Angle between the anchor shank and the nearest wingplate , Anchor wing plate area The weight of the anchor underwater Horizontal loading angle at the mooring point Adhesion coefficient .

3. The method for calculating the complex bearing capacity of a gravity penetration anchor in a clayey seabed according to claim 2, characterized in that, Step S2 includes: Step S21: Obtain the fitting formula for the bearing capacity coefficient of the horizontal anchor end in uniformly weightless clay by numerical calculation, as shown in the following formula: ； Step S22: Obtain the fitting formula for the bearing capacity coefficient of the vertical anchor rod end in uniformly weightless clay with a burial depth ratio through numerical calculation, as shown in the following formula: ； In the formula, Indicates the burial depth ratio. Indicates the effective unit weight of soil. This represents the gradient of undrained shear strength of clay. Indicates the anchor's direction angle.

4. The method for calculating the complex bearing capacity of a gravity penetration anchor in a clayey seabed according to claim 3, characterized in that, Step S3 includes: Step S31: The fitting formula for the heterogeneity factor of the end bearing capacity of horizontal anchors in clay is obtained through numerical calculation, as shown in the following formula: ； Step S32: The fitting formula for the heterogeneity factor of the undrained shear strength gradient on the end bearing capacity of vertical anchors in clay is obtained through numerical calculation, as shown in the following formula: ； In the formula, The strength heterogeneity coefficient of the anchor. Indicates the burial depth ratio. Indicates the effective unit weight of soil. This represents the gradient of undrained shear strength of clay. Indicates the anchor's direction angle.

5. The method for calculating the complex bearing capacity of a gravity penetration anchor in a clayey seabed according to claim 4, characterized in that, Step S4 obtains the fitting formula for the bearing capacity coefficient of the inclined anchor rod end in clay through numerical calculation, as shown in the following formula: ； In the formula, Indicates the burial depth ratio. This represents the gradient of undrained shear strength of clay. Indicates the anchor's direction angle.

6. The method for calculating the complex bearing capacity of a gravity penetration anchor in a clayey seabed according to claim 5, characterized in that, Step S5 obtains the fitting formula for the loading angle coefficient through numerical calculation, as shown in the following formula: ； In the formula, Indicates the loading angle coefficient. Indicates the burial depth ratio. This represents the gradient of undrained shear strength of clay. Indicates the anchor's direction angle. Indicates the loading angle. Indicates the included angle of the airfoil.

7. The method for calculating the complex bearing capacity of a gravity penetration anchor in a clayey seabed according to claim 6, characterized in that, In step S6, the fitting formula for the bearing area coefficient of the anchor end bearing capacity in clay is obtained through numerical calculation, as shown in the following formula: ； In the formula, Indicates the bearing area coefficient. Indicates the burial depth ratio. This represents the gradient of undrained shear strength of clay. Indicates the anchor's direction angle. Indicates the loading angle. Indicates the included angle of the airfoil.

8. The method for calculating the complex bearing capacity of a gravity penetration anchor in a clayey seabed according to claim 7, characterized in that, The explicit expression for the end resistance bearing capacity coefficient in step S7 is shown in the following formula: ； In the formula, Indicates the loading angle coefficient. Indicates the bearing area coefficient. Indicates the burial depth ratio. This represents the gradient of undrained shear strength of clay. Indicates the anchor's direction angle.

9. The method for calculating the complex bearing capacity of a gravity penetration anchor in a clayey seabed according to claim 8, characterized in that, The end resistance bearing capacity coefficient in step S8 is shown in the following formula: ； In the formula, Indicates the burial depth ratio. This represents the gradient of undrained shear strength of clay. Indicates the anchor's direction angle. Indicates the loading angle. Indicates the included angle of the airfoil.

10. The method for calculating the complex bearing capacity of a gravity penetration anchor in a clayey seabed according to claim 9, characterized in that, The bearing capacity of the gravity-penetrated anchor in step S9 is obtained by the following formula: ； ； ； ； In the formula, The anchor's pull-out resistance in the loading direction; The end resistance bearing capacity of the anchor in the loading direction; The shear force of the anchor in the loading direction; The weight of the anchor underwater; The horizontal loading angle at the mooring point; The effective bearing area of ​​the anchor; The effective shear area of ​​the anchor; The adhesion coefficient, This represents the undrained shear strength of clay.

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