Method for calculating circumferential stress of wrapping rib material of wrapping type gravel pile under action of axial force

Abstract

The invention discloses a method for calculating the circumferential stress of a wrapped rib material of a wrapped gravel pile under the action of axial force, which comprises the following steps: step 100, taking the wrapped gravel pile as an elastic pile body, taking a pile bottom foundation as an elastic foundation, taking a pile top as an origin of coordinates, taking the downward direction along the longitudinal axis of the pile body as a coordinate z axis, and calculating the circumferential stress of the wrapped rib material of the wrapped gravel pile; calculating the axial pressure stress of the pile body according to the static balance condition, the physical equation, the geometric equation, the pile top boundary condition, the general characteristics of the axial deformation of the pile body and the displacement coordination of the pile bottom end of the pile body at the coordinate z; and step 200, according to the Hooke law, the deformation coordination of the pile body and the pile body wrapping rib material, the elastic mechanics theory and the coefficient correction considering the inelasticity of the actual pile body and the stratum, calculating to obtain the circumferential tensile stress and the circumferential tensile force of the pile body wrapping rib material. The method is simple in concept, practical and easy to operate.

Description

Technical Field

[0001] The present invention relates to the technical field of force calculation of the wrapping reinforcement of the wrapped gravel pile. Specifically, it relates to a method for calculating the circumferential force of the wrapping reinforcement of the wrapped gravel pile under the action of axial force. Background Art

[0002] The wrapped gravel pile composite foundation is a technical improvement of the traditional ordinary gravel pile composite foundation and can be used for the treatment of soft foundations in projects such as railways, highways, and building construction. It has outstanding economy and is beneficial to the drainage consolidation of the foundation. The action of the upper load on the wrapped gravel pile causes it to mainly bear the axial pressure load at the pile top. Under the action of this load and the constraint of the surrounding strata of the pile, the pile body produces radial deformation, causing circumferential tension in the pile body wrapping reinforcement. Therefore, reasonably determining the circumferential force of the pile body wrapping reinforcement of the wrapped gravel pile under the action of axial pressure load is of great significance for comprehensively understanding the mechanical behavior of the wrapped gravel pile and then carrying out reasonable relevant engineering designs.

[0003] Under the action of axial pressure load, the mechanical behaviors such as the pile body axial force and the circumferential force of the pile body wrapping reinforcement of the wrapped gravel pile in the soil show a relatively complex non-linear variation pattern along the depth. In the past, numerical simulation methods such as finite element and finite difference were often used. However, for numerical simulation methods, first, a numerical model needs to be established, and the rationality of the numerical model depends on elements such as model parameters, grid accuracy, material constitutive models, and boundary conditions. Not only is the modeling process complex and cumbersome, but there are also subjective human operation interferences, and it is difficult to have "inheritance" (different people need to start from the modeling operation). It can be used as a reference means for the study of complex problems, but it is not conducive to the rapid analysis and operation of actual engineering technicians. In particular, for the analysis of the circumferential force of the pile body wrapping reinforcement of the wrapped gravel pile, due to the very small thickness of the pile body wrapping reinforcement (usually only a few millimeters), the numerical modeling operation process is particularly complex. Therefore, at present, there is still a lack of a simplified theoretical calculation method with a simple concept and easy practical operation for the circumferential force analysis of the pile body wrapping reinforcement of the wrapped gravel pile under the action of axial pressure load, making the relevant engineering designs lack sufficient and reasonable basis in specific application analysis or the calculation and analysis operation process is cumbersome. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for calculating the circumferential force of the wrapping reinforcement of the wrapped gravel pile under the action of axial force with a simple concept and easy practical operation.

[0005] To achieve the above object, the present invention provides a method for calculating the circumferential force of the wrapping reinforcement of the wrapped gravel pile under the action of axial force, and the technical solution is as follows:

[0006] The method for calculating the circumferential force of the wrapping reinforcement of the wrapped gravel pile under the action of axial force includes the steps:

[0007] Step 100: Consider the wrapped gravel pile as an elastic pile body and the pile bottom foundation as an elastic foundation. Take the pile top as the coordinate origin, and the downward direction along the longitudinal axis of the pile body as the coordinate z-axis. Based on the static equilibrium conditions, physical equations, geometric equations, pile top boundary conditions, general characteristics of the axial deformation of the pile body, and displacement coordination at the pile bottom, calculate the axial compressive stress of the pile body.

[0008] Step 200: According to Hooke's law, the deformation coordination between the pile body and the wrapped reinforcement of the pile body, the theory of elasticity, and by using a coefficient correction considering the inelasticity of the actual pile body and the side formation, calculate the circumferential tensile stress of the wrapped reinforcement of the pile body and the circumferential tensile force per unit height of the wrapped reinforcement of the pile body.

[0009] Preferably, step 100 specifically includes the following steps:

[0010] Step 110: Consider the wrapped gravel pile as an elastic pile body. Based on the static equilibrium conditions, physical equations, geometric equations, pile top boundary conditions, and general characteristics of the axial deformation of the pile body at the coordinate z, obtain the calculation expression of the axial force N(z) of the pile body at the cross-section of the pile body at a depth z from the pile top.

[0011] Step 120: Consider the pile bottom foundation as an elastic foundation. Based on the displacement coordination at the pile bottom, calculate the undetermined coefficient in the calculation expression of the pile body axial force N(z).

[0012] Step 130: According to the mutual relationship between the pile body axial force N(z) and the axial compressive stress σ z of the pile body, that is, obtain the calculation expression of the axial compressive stress σ z of the pile body.

[0013] Preferably, step 200 specifically includes the following steps:

[0014] Step 210: According to Hooke's law and the deformation coordination between the pile body and the wrapped reinforcement of the pile body, obtain the relational expression between the axial compressive stress σ z of the pile body and the circumferential tensile stress σ c of the wrapped reinforcement of the pile body.

[0015] Step 220: According to the theory of elasticity and by using a coefficient correction considering the inelasticity of the actual pile body and the formation, obtain the corrected calculation expression of the circumferential tensile stress σ c of the wrapped reinforcement of the pile body, and further obtain the calculation expression of the circumferential tensile force T c of the wrapped reinforcement of the pile body.

[0016] The prominent advantages of the calculation method for the circumferential force of the wrapping reinforcement of the wrapped gravel pile under axial force of the present invention are as follows: The concept of the present invention is clear, and comprehensive factors are considered. The deformation coordination and interaction between the pile body and the wrapping reinforcement of the pile body, as well as the characteristics of the wrapping reinforcement of the pile body, the pile body, the formation on the side of the pile body, and the foundation at the bottom of the pile, are fully considered. The circumferential force of the wrapping reinforcement of the wrapped gravel pile under the axial pressure load (referred to as axial force for short) is presented in a simple calculation expression. The relevant parameters in the expression are easy to determine, the algorithm is simple, and it is convenient for quick operation. By using the calculation method of the present invention, it is possible to simply estimate and determine the circumferential force of the wrapping reinforcement of the wrapped gravel pile under the axial pressure load in the foundation soil without the need for time-consuming, laborious, and costly tests or numerical simulation calculations, which is convenient for quickly conducting engineering design analysis and has important technical method significance and engineering application value.

[0017] The following further describes the present invention in conjunction with the drawings and specific embodiments. Some of the additional aspects and advantages of the present invention will be given in the following description, some will become obvious from the following description, or will be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings constituting a part of the present invention are used to assist in understanding the present invention. The content provided in the drawings and the related descriptions in the present invention can be used to explain the present invention, but do not constitute an improper limitation to the present invention. In the drawings:

[0019] Figure 1 It is a schematic structural diagram of a wrapped gravel pile located in a soft soil foundation under axial force in an embodiment of the present invention.

[0020] Figure 2 It is a calculation result diagram of the axial force of the pile body in an embodiment of the present invention.

[0021] Figure 3 It is a calculation result diagram of the axial compressive stress of the pile body in an embodiment of the present invention.

[0022] Figure 4 It is a calculation result diagram of the circumferential tensile stress of the wrapping reinforcement of the pile body in an embodiment of the present invention.

[0023] Figure 5 It is a calculation result diagram of the circumferential tension of the wrapping reinforcement of the pile body per unit height in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The following clearly and completely describes the present invention in conjunction with the drawings. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. Before describing the present invention in conjunction with the drawings, it should be particularly noted that:

[0025] In the present invention, the technical solutions and technical features provided in each part including the following description can be combined with each other without conflict.

[0026] In addition, the embodiments of the present invention involved in the following description are generally only a part of the embodiments of the present invention, rather than all embodiments. Therefore, all other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0027] Regarding the terms and units in the present invention. The terms "comprising", "having" and any variations thereof in the specification, claims and relevant parts of the present invention are intended to cover non-exclusive inclusion.

[0028] The specific implementation manner of the calculation method for the circumferential force of the wrapping reinforcement of the wrapped gravel pile under the axial force of the present invention includes the steps:

[0029] Step 100, regarding the wrapped gravel pile as an elastic pile body and the pile bottom foundation as an elastic foundation, taking the pile top as the coordinate origin and the downward direction along the longitudinal axis of the pile body as the coordinate z-axis, and calculating the axial compressive stress of the pile body from the static equilibrium conditions, physical equations, geometric equations, pile top boundary conditions, general characteristics of the axial deformation of the pile body, and displacement coordination at the pile bottom end of the pile body microelement at coordinate z; specifically, step 100 includes the following steps:

[0030] Step 110, regarding the wrapped gravel pile as an elastic pile body, and obtaining the calculation expression of the axial force N(z) of the pile body at the cross-section of the pile body at a depth z from the pile top from the static equilibrium conditions, physical equations, geometric equations, pile top boundary conditions, and general characteristics of the axial deformation of the pile body at coordinate z;

[0031] Step 120, regarding the pile bottom foundation as an elastic foundation, and calculating the undetermined coefficients in the calculation expression of the axial force N(z) of the pile body from the displacement coordination at the pile bottom end;

[0032] Step 130, according to the mutual relationship between the axial force N(z) of the pile body and the axial compressive stress σ z of the pile body, that is, obtaining the calculation expression of the axial compressive stress σ z of the pile body.

[0033] Step 200, calculating the circumferential tensile stress of the pile body wrapping reinforcement and the circumferential tensile force of the pile body wrapping reinforcement per unit height according to Hooke's law, the deformation coordination between the pile body and the pile body wrapping reinforcement, the theory of elasticity, and by using a coefficient correction considering the non-elasticity of the actual pile body and the pile side formation; specifically, step 200 includes the following steps:

[0034] Step 210: According to Hooke's law and the deformation coordination between the pile body and the wrapped reinforcement of the pile shaft, the axial compressive stress σ of the pile shaft is obtained. z And the relationship expression between the circumferential tensile stress σ c of the wrapped reinforcement of the pile shaft.

[0035] Step 220: According to the theory of elasticity and by using a coefficient correction that takes into account the inelasticity of the actual pile body and the formation, the corrected calculation expression of the circumferential tensile stress σ c of the wrapped reinforcement of the pile shaft is obtained, and then the calculation expression of the circumferential tensile force T c of the wrapped reinforcement of the pile shaft is obtained.

[0036] The following is a specific description of each step.

[0037] Step 110: When the wrapped gravel pile is under the action of normal pressure load, the wrapped gravel pile is regarded as an elastic pile body. Taking the pile top as the coordinate origin and the downward direction along the longitudinal axis of the pile body as the coordinate z-axis, from the static equilibrium conditions, physical equations and geometric equations of the pile shaft microelement at the coordinate z, we can obtain:

[0038]

[0039] In the formula, N(z) is the axial force of the pile body at the pile shaft cross-section at a depth z from the pile top, τ(z) is the corresponding lateral friction resistance of the pile shaft at this place, ω(z) is the corresponding axial displacement of the pile body at this place, ε z is the corresponding axial strain of the pile shaft at this place; π is the pi; r0 is the radius of the pile body; γ p is the unit weight of the pile body; E p is the elastic modulus of the pile body.

[0040] According to the pile top boundary conditions, we can obtain:

[0041]

[0042] In the formula, N′ is the first derivative of N(z) with respect to the coordinate z; N t is the axial pressure load at the pile top.

[0043] From the general characteristics of the axial deformation of the pile body (RANDOLPH M F, WROTH C P. An analysis of the vertical deformation of pile groups. Géotechnique, 1979, 29(4): 423 - 439.), the axial displacement ω(z) of any cross-section of the pile body can be approximately simplified and expressed as:

[0044]

[0045] In the formula, A, B, and n are positive undetermined coefficients reflecting the displacement distribution characteristics of the pile body, where n is a dimensionless number; l is the length of the pile body; exp represents the exponential function with the natural constant e as the base.

[0046] Therefore, at the pile bottom where z = l, the axial displacement ω(l) of the pile bottom can be obtained as:

[0047]

[0048] Thus, substituting Equation (3) into Equation (1), the calculation expression for the pile shaft force N(z) can be obtained as:

[0049]

[0050] Among them, by simultaneously solving Equations (1) to (4), the expressions for the two undetermined coefficients A and B can also be determined as:

[0051]

[0052] Step 120: Regarding the pile bottom foundation as an elastic foundation, according to the classical Winkler foundation model, the calculation expression for the settlement of the pile bottom foundation can be obtained as:

[0053]

[0054] In the formula, ω b is the settlement of the pile bottom foundation; A0 is the calculated cross-sectional area at the pile bottom, A0 = πR0 2 , R0 is the equivalent radius of the calculated cross-section at the pile bottom; C0 is the vertical elastic resistance coefficient of the pile bottom foundation. According to the railway code (Code for Design of Subgrade and Foundation of Railway Bridges and Culverts (TB 10093 - 2017)), the maximum value of 10m0 and m0l can be taken, where m0 is the proportionality coefficient of the vertical elastic resistance coefficient of the pile bottom foundation; N b is the axial force at the pile bottom;

[0055] Substituting z = l into Equation (4) gives the calculation expression for the axial force N b at the pile bottom as:

[0056]

[0057] The calculation expression for R0 is:

[0058]

[0059] In the formula, min represents taking the minimum value; for end-bearing piles or column piles, then take R0 = r0; S is the pile spacing; is the weighted average of the internal friction angles of the soil on the side of the pile foundation;

[0060] The calculation expression is:

[0061]

[0062] In the formula, m is the number of soil layers of the foundation soil on the pile side; i is the serial number starting from 1 from top to bottom of the formation on the pile side, h i is the thickness of the i-th layer of the formation; is the internal friction angle of the i-th layer of the formation.

[0063] From the displacement coordination at the pile bottom, that is: the foundation settlement ω b at the pile bottom is equal to the axial displacement ω(l) at the pile bottom end, which is equal to Equation (6) according to Equation (3a), and the control equation for the undetermined coefficient n can be obtained as:

[0064]

[0065] Then, by substituting Equations (5) and (7) into Equation (10), the undetermined coefficient n can be solved, and then substituting it into Equation (5), the undetermined coefficients A and B can be determined, and thus the pile axial force N(z) can be determined according to Equation (4).

[0066] Step 130: According to the mutual relationship between the pile axial force N(z) and the axial compressive stress σ z of the pile body, the calculation expression of the axial compressive stress σ z of the pile body is obtained as:

[0067]

[0068] Step 210: Assume that the pile body is an elastic body. According to Hooke's law, there is:

[0069]

[0070] In the formula, ε zs is the axial compressive strain of the pile body; μ p is the Poisson's ratio of the pile body; p is the radial compressive stress on the periphery of the pile body at the depth z from the pile top; ε rs is the radial strain of the pile body.

[0071] For the wrapped reinforcement of the pile body under the action of the circumferential tensile stress σ c , its circumferential strain ε c can be expressed as:

[0072]

[0073] In the formula, σ c is the circumferential tensile stress of the wrapped reinforcement of the pile body; E c is the elastic modulus of the wrapped reinforcement of the pile body; ε c is the circumferential strain of the wrapped reinforcement of the pile body; r0 is the radius of the pile body; Δr is the radial displacement of the pile body.

[0074] According to the deformation coordination between the pile body and the wrapped reinforcement of the pile shaft, we have:

[0075]

[0076] Therefore, by combining equations (12) to (14), we can obtain:

[0077]

[0078] Step 220: For the wrapped reinforcement of the pile shaft, according to the theory of elasticity, we can obtain:

[0079]

[0080] In the formula, Δp is the difference in radial stress between the inner and outer sides of the wrapped reinforcement of the pile shaft; D is the diameter of the pile body, D = 2r0; t is the thickness of the wrapped reinforcement of the pile shaft.

[0081] Since the thickness of the wrapped reinforcement of the pile shaft is much smaller than the radius of the pile body and it is a flexible material, according to the force balance condition, Δp can be expressed as:

[0082] Δp = p - k0(γz + σ0) (17)

[0083] In the formula, k0 is the lateral pressure coefficient of the foundation soil on the pile side, and generally the coefficient of earth pressure at rest can be taken; γ is the unit weight of the foundation soil on the pile side; σ0 is the vertical compressive stress at the ground surface of the pile top.

[0084] According to the deformation coordination between the pile body and the wrapped reinforcement of the pile shaft, and by combining equations (15) to (17), we can obtain:

[0085]

[0086] Considering the inelasticity of the actual pile body and the formation, a coefficient correction is introduced to equation (16), that is:

[0087]

[0088] In the formula, λ is the comprehensive correction coefficient. Based on the results of physical model tests and numerical simulations, generally 4 - 5 can be taken.

[0089] Therefore, substituting equation (11) into equation (18), and then substituting equation (18) into equation (19), the circumferential tensile stress σ of the wrapped reinforcement of the pile shaft after correction can be obtained c .

[0090] Furthermore, from equation (19), the circumferential tension T c of the wrapped reinforcement of the pile shaft per unit height can be obtained, and its calculation expression is:

[0091] Tc = λ·Δp·r0 (20)

[0092] The beneficial effects of the present invention will be described below through application examples.

[0093] Figure 1 It is a schematic structural diagram of a wrapped gravel pile located in a soft soil foundation under axial force. As Figure 1 shown, the soil body of the pile side foundation is soft cohesive soil, and the soil body of the pile bottom foundation is fine silt. According to the engineering geological investigation and basic design data, the relevant calculation parameters are determined as shown in Table 1.

[0094] Table 1

[0095]

[0096] According to the relevant parameters, substituting Eqs. (5) and (7) into Eq. (10), the coefficient n = 2.004 is obtained by solving, and then substituting it into Eq. (5), the coefficients A = 0.0575 m and B = 0.069547 / m can be calculated. Thus, according to Eq. (4), the calculation result of the pile shaft force N(z) can be determined as shown in Figure 2 , and then the axial compressive stress σ z of the pile body is calculated from Eq. (11), and the results are shown in Table 2 and Figure 3 .

[0097] Furthermore, according to Eqs. (19) and (20), the circumferential tensile stress σ c of the pile body wrapping reinforcement and the circumferential tensile force T c per unit height of the pile body wrapping reinforcement can be calculated respectively. The calculation results are shown in Table 2 and Figure 4 、 Figure 5 .

[0098] Table 2

[0099] z (m) <![CDATA[σ z (kPa)]]> <![CDATA[σ c (kPa)]]> <![CDATA[T c (kN / m)]]> 0 240 1609.9 8.05 0.9 256.26 1719.1 8.6 1.2 260.55 1745.5 8.73 2.1 270.26 1796.5 8.98 3 275.59 1808.6 9.04 3.9 276.99 1785.7 8.93 4.8 274.91 1731.8 8.66 5.1 273.52 1707.6 8.54 6 267.46 1618.4 8.09 6.9 258.91 1507.0 7.53 7.2 255.58 1465.5 7.33 8.1 244.32 1330.0 6.65 9 231.45 1180.3 5.90 9.9 217.33 1019.3 5.10 10.2 212.39 963.6 4.82 11.1 197.08 792.1 3.96 12 181.20 615.5 3.08 12.9 165.03 436.3 2.18 13.8 148.77 256.4 1.28 14.1 143.37 196.6 0.98 15 127.33 18.5 0.09

[0100] The comparison between the calculation result of the circumferential tensile stress σ c of the pile body wrapping reinforcement obtained by the ABAQUS numerical simulation method and the calculation result of the method of the present invention is shown in Table 3.

[0101] Table 3

[0102]

[0103] It can be seen that the circumferential tensile stress results of the method of the present invention and the numerical simulation method are relatively consistent, and the maximum value of the absolute value of the relative deviation between the two is 11.5%.

[0104] In summary, it can be known that the deviation between the calculation results of the method of the present invention and the traditional method is within 15%, which is acceptable in practical engineering and is reasonable.

[0105] The above describes the relevant content of the present invention. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. Based on the above content of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

Claims

1. A method for calculating the circumferential force of the wrapped reinforcement of a wrapped stone pile under axial force, characterized in that: Includes steps: Step 100, the wrapped gravel pile is regarded as an elastic pile body, the pile bottom foundation is regarded as an elastic foundation, the pile top is taken as the coordinate origin, and the vertical axis of the pile body is taken downward as the coordinate z axis, and the axial compressive stress of the pile body is calculated based on the static equilibrium condition of the pile body microelement at the coordinate z, the physical equation, the geometric equation, the pile top boundary condition, the general characteristics of the axial deformation of the pile body, and the coordination of the displacement of the pile bottom end; Step 200, according to Hooke's law, the deformation coordination of the pile body and the pile body wrapping reinforcement, the elastic mechanics theory and the coefficient correction considering the inelasticity of the actual pile body and the pile side strata, the circumferential tensile stress of the pile body wrapping reinforcement and the circumferential tension of the pile body wrapping reinforcement per unit height are calculated.

2. The method for calculating the circumferential force of the wrapped reinforcement of the wrapped gravel pile under the action of axial force as claimed in claim 1, characterized in that: Step 100 specifically includes the following steps: Step 110, regarding the wrapped gravel pile as an elastic pile body, the calculation expression of the pile body axial force N(z) at the cross section of the pile body at a depth z from the pile top is obtained based on the static equilibrium condition of the pile body microelement at the coordinate z, the physical equation, the geometric equation, the pile top boundary condition, and the general characteristics of the pile body axial deformation; Step 120, regarding the pile bottom foundation as an elastic foundation, and calculating the undetermined coefficients in the calculation expression of the pile body axial force N(z) based on the compatibility of the displacement of the pile bottom end; Step 130, according to the pile body axial force N(z) and the pile body axial compressive stress σ z The relationship between the axial compressive stress σ of the pile body is obtained. z The computational expression of .

3. The method for calculating the circumferential force of the wrapped reinforcement of the wrapped gravel pile under the axial force as claimed in claim 2, characterized in that: In step 110, According to the static equilibrium condition, physical equation and geometric equation of the pile body microelement at coordinate z, we can get: According to the boundary conditions at the pile top, we can get: According to the general characteristics of the axial deformation of the pile, it can be obtained that: Thus, at the pile bottom z=l, the axial displacement ω(l) of the pile bottom is obtained as: The axial force N(z) of the pile body and the axial force N(z) at the bottom of the pile are obtained by simultaneous solution. b The calculation expressions are: Where N(z) is the axial force of the pile at the cross section of the pile body at a depth z from the pile top, τ(z) is the corresponding side friction of the pile body at that location, ω(z) is the corresponding axial displacement of the pile body at that location, and ε z is the corresponding axial strain of the pile body; π is the circumference of the circle; r0 is the radius of the pile body; γ p E is the weight of the pile; p is the elastic modulus of the pile; N t is the axial pressure load on the pile top; N′ is the first-order derivative of N(z) with respect to the coordinate z; A, B, n are positive unknown coefficients reflecting the displacement distribution characteristics of the pile body, where n is a dimensionless number; l is the length of the pile body; exp represents an exponential function with the natural constant e as the base; N b is the axial force at the bottom of the pile.

4. The method for calculating the circumferential force of the wrapped reinforcement of the wrapped gravel pile under the axial force as claimed in claim 3, characterized in that: In step 120, Considering the pile bottom foundation as an elastic foundation, the pile bottom foundation settlement ω is obtained according to the Winkler foundation model. b The calculation expression of ; Then, according to the coordination of the displacement of the pile bottom, the settlement of the foundation at the pile bottom ω b It is equal to the axial displacement ω(l) of the bottom end of the pile. According to the equality of their calculation expressions, the unknown coefficients A, B, and n in the calculation expression of the pile axial force N(z) are solved.

5. The method for calculating the circumferential force of the wrapped reinforcement of the wrapped gravel pile under the action of axial force as claimed in claim 1, characterized in that: Step 200 specifically includes the following steps: Step 210, according to Hooke's law and the deformation coordination of the pile body and the reinforcement wrapped around the pile body, the axial compressive stress σ of the pile body is obtained. z The hoop tensile stress of the pile body wrapped reinforcement σ c The relational expression of Step 220, according to the elastic mechanics theory and by using the coefficient correction considering the inelasticity of the actual pile body and the stratum, the hoop tensile stress σ of the pile body wrapped reinforcement is obtained. c The modified calculation expression of , and then the hoop tension T of the reinforcement wrapped around the pile body per unit height is obtained. c The computational expression of .

6. The method for calculating the circumferential force of the wrapped reinforcement of the wrapped gravel pile under the action of axial force as claimed in claim 5, characterized in that: In step 210, According to Hooke's law, we can get: For the hoop tensile stress σ c The hoop strain ε of the pile wrapped reinforcement under the action c It can be expressed as: According to the deformation coordination of the pile body and the reinforcement wrapped around the pile body, it can be obtained: The axial compressive stress σ of the pile body is obtained by simultaneous solution: z The hoop tensile stress of the pile body wrapped reinforcement σ c The relational expression is: In the formula, ε zs is the axial compressive strain of the pile; ε rs is the radial strain of the pile; E p is the elastic modulus of the pile; σ z is the vertical compressive stress at the pile top at a depth z from the pile top; μ p is the Poisson's ratio of the pile; p is the radial compressive stress around the pile at a depth z from the pile top; σ c E is the hoop tensile stress of the reinforcement wrapped around the pile body; c is the elastic modulus of the reinforcement wrapped around the pile body; ε c is the hoop strain of the reinforcement wrapped around the pile body; Δ r is the radial displacement of the pile; r0 is the radius of the pile.

7. The method for calculating the circumferential force of the wrapped reinforcement of the wrapped gravel pile under the action of axial force as claimed in claim 6, characterized in that: In step 220, Hoop tensile stress of pile body wrapped reinforcement σ c The corrected calculation expression is: Hoop tension T of the reinforcement wrapped around the pile body per unit height c The calculation expression is: T c =λ·Δp·r0; Where λ is the comprehensive correction coefficient based on the results of physical model test and numerical simulation; Δp is the difference in radial stress between the inner and outer sides of the pile body; r0 is the radius of the pile; t is the thickness of the pile body; T c It is the hoop tension of the reinforcement wrapped around the pile body per unit height.

8. The method for calculating the circumferential force of the wrapped reinforcement of the wrapped gravel pile under the action of axial force as claimed in claim 7, characterized in that: The calculation expression of the difference in radial stress Δp between the inner and outer sides of the pile body wrapped reinforcement is: Where k0 is the lateral pressure coefficient of the foundation soil on the pile side; γ is the weight of the foundation soil on the pile side; σ0 is the vertical compressive stress at the ground level on the top of the pile.

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