Safety assessment method for existing high-pile wharf pile foundation

Abstract

The invention discloses a safety assessment method for an existing high-pile wharf pile foundation, which comprises the following steps of: S1, symmetrically mounting two stress sensors on each of the upper cross section and the lower cross section of the top of the pile foundation to obtain stress values of the pile foundation on the upper cross section and the lower cross section; the bending moment and the axial force of the pile foundation on the upper cross section and the lower cross section are obtained through the stress values of the pile foundation on the upper cross section and the lower cross section and the geometric parameters of the pile foundation; s2, the shearing force of the pile body is obtained according to the bending moments of the pile foundation on the upper cross section and the lower cross section; s4, obtaining the bending moment of the pile foundation at the mud surface according to the shearing force of the pile body; S5, modeling by adopting an m value method or a P-Y curve method to obtain the bending moment and the axial force of the pile foundation at any depth below the mud surface, and then obtaining the stress value of the pile foundation at any depth below the mud surface; and S6, the safety state of the pile body structure is evaluated according to the stress value of the pile body at any depth below the mud surface and the material yield strength of the pile foundation. Data support can be provided for safe operation of the wharf.

Description

Technical Field

[0001] The invention relates to a safety assessment method for an existing high-pile wharf pile foundation. Background Art

[0002] High-pile piers, after years of operation, are subject to significant aging due to factors such as wind, waves, and loads, reducing their ability to withstand risks. As their service life increases, structural safety issues are becoming increasingly prominent, with many existing high-pile piers experiencing degradation in material performance and reduced functionality. Therefore, the inspection and evaluation of existing piers has become increasingly important, and is receiving significant attention from relevant pier organizations.

[0003] By testing the stress state of existing wharf pile foundations through inspection methods, we can comprehensively assess the overall safety status of the wharf. In terms of wharf safety, existing wharves require long-term, continuous, and stable monitoring to support safe operations. Periodic wharf inspections focus on current repairs and subsequent maintenance, and cannot provide assistance for emergencies. Therefore, long-term monitoring research on in-service wharves is essential. This not only supports ongoing maintenance, but also improves the wharf's risk resistance through assessment and early warning, providing data support for safe operations. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a safety assessment method for the pile foundation of an existing high-pile wharf. It can realize the structural safety assessment and early warning of the existing pile foundation of an in-service coastal wharf during the operation stage, and provide data support for the safe operation of the wharf.

[0005] The object of the present invention is achieved as follows: A safety assessment method for an existing high-pile wharf pile foundation comprises the following steps:

[0006] S1, two stress sensors are symmetrically installed on an upper cross section and a lower cross section of the top of the pile foundation, and the stress value of the pile foundation at the upper cross section measured by the two stress sensors on the upper cross section is σ A , σ B , and the stress value of the pile foundation at the lower cross section measured by the two stress sensors on the lower cross section is σ C , σ D The stress value measured by each stress sensor is the sum of the stress value generated by the bending moment and the stress value generated by the axial force, which can be expressed by the following formulas (1) and (2):

[0007]

[0008] In the above formulas (1) and (2), σ N is the stress generated by the axial force; σ Mis the stress caused by the bending moment; M1 is the bending moment of the pile foundation at the upper cross section; F1 is the axial force of the pile foundation at the upper cross section; y is the distance from a point on the upper cross section of the pile foundation to the neutral axis; A is the area of the pile foundation at the upper cross section; I is the moment of inertia of the pile foundation at the upper cross section, d is the diameter of the pile foundation at the upper cross section;

[0009] The bending moment M1 of the pile foundation at the upper cross section and the axial force F1 of the pile foundation at the upper cross section are obtained by the above formulas (1) and (2);

[0010] Similarly, the stress values σ measured by the two stress sensors on the lower cross section C , σ D , the bending moment M2 of the pile foundation at the lower cross section and the axial force F2 of the pile foundation at the lower cross section are obtained;

[0011] S2, based on the bending moment M1 of the pile foundation at the upper cross section and the bending moment M2 of the pile foundation at the lower cross section, the shear force V of the pile body is calculated by the following formula (3):

[0012]

[0013] In the above formula (3), ΔL 1-2 is the distance from the upper cross section of the pile foundation to the lower cross section of the pile foundation;

[0014] S3, the axial force N of the pile foundation at the mud surface is obtained by the following formula (4):

[0015] N=G+F (4)

[0016] In the above formula (4), G is the deadweight of the pile foundation above the mud surface; F is the axial force exerted on the pile foundation above the mud surface;

[0017] S4, based on the shear force V of the pile body and ignoring the influence of wave and water flow on the shear force of the pile body, the bending moment M of the pile foundation at the mud surface is obtained by the following formula (5): 泥面 :

[0018] M 泥面 =M2+V*ΔL 2-泥面 (5)

[0019] In the above formula (5), ΔL 2-泥面 is the distance from the lower cross section of the pile foundation to the mud surface;

[0020] S5, based on the bending moment M of the pile foundation at the mud surface 泥面 The m-value method or PY curve method is used to establish a numerical model of pile-soil interaction and the shear force V of the pile body to obtain the bending moment M of the pile foundation at any depth below the mud surface. n and the axial force F acting on the pile foundation at any depth below the mud surface n, and then the stress value σ of the pile foundation at any depth below the mud surface is obtained by the following formula (6): n :

[0021]

[0022] S6, based on the stress value of the pile at any depth below the mud surface σ n and the material yield strength σ of the pile foundation y Assess the safety status of the pile structure.

[0023] The safety assessment method for the pile foundation of an existing high-pile wharf of the present invention is characterized by: the process from real-time measurement of the stress value at the pile top to the stress estimation of the pile foundation below the mud surface is continuous and efficient. On the one hand, it can provide support for the subsequent maintenance of the wharf; on the other hand, it can improve the risk resistance of the wharf through evaluation and early warning, and provide data support for the safe operation of the wharf. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural diagram when performing step S1 of the safety assessment method of the existing high-piled wharf pile foundation of the present invention. DETAILED DESCRIPTION

[0025] The present invention will be further described below with reference to the accompanying drawings.

[0026] The safety assessment method of an existing high-piled wharf pile foundation of the present invention comprises the following steps:

[0027] S1, two stress sensors are symmetrically installed on an upper cross section and a lower cross section of the top of the pile foundation, and the stress value of the pile foundation at the upper cross section measured by the two stress sensors on the upper cross section is σ A , σ B , and the stress value of the pile foundation at the lower cross section measured by the two stress sensors on the lower cross section is σ C , σ D The stress value measured by each stress sensor is the sum of the stress value generated by the bending moment and the stress value generated by the axial force, which can be expressed by the following formulas (1) and (2):

[0028]

[0029] In the above formulas (1) and (2), σ N is the stress generated by the axial force; σ M is the stress caused by the bending moment; M1 is the bending moment of the pile foundation at the upper cross section; F1 is the axial force of the pile foundation at the upper cross section; y is the distance from a point on the upper cross section of the pile foundation to the neutral axis; A is the area of the pile foundation at the upper cross section; I is the moment of inertia of the pile foundation at the upper cross section, d is the diameter of the pile foundation at the upper cross section;

[0030] The bending moment M1 of the pile foundation at the upper cross section and the axial force F1 of the pile foundation at the upper cross section are obtained by the above formulas (1) and (2);

[0031] Similarly, the stress values σ measured by the two stress sensors on the lower cross section C , σ D Obtain the bending moment M2 of the pile foundation at the lower cross section and the axial force F2 of the pile foundation at the lower cross section;

[0032] S2, based on the bending moment M1 of the pile foundation at the upper cross section and the bending moment M2 of the pile foundation at the lower cross section, the shear force V of the pile body is calculated by the following formula (3):

[0033]

[0034] In the above formula (3), ΔL 1-2 is the distance from the upper cross section of the pile foundation to the lower cross section of the pile foundation;

[0035] S3, the axial force N of the pile foundation at the mud surface is obtained by the following formula (4):

[0036] N=G+F (4)

[0037] In the above formula (4), G is the deadweight of the pile foundation above the mud surface; F is the axial force exerted on the pile foundation above the mud surface;

[0038] S4, based on the shear force V of the pile body and ignoring the influence of wave and water flow on the shear force of the pile body, the bending moment M of the pile foundation at the mud surface is obtained by the following formula (5): 泥面 :

[0039] M 泥面 =M2+V*ΔL 2-泥面 (5)

[0040] In the above formula (5), ΔL 2-泥面 is the distance from the lower cross section of the pile foundation to the mud surface;

[0041] S5, based on the bending moment M of the pile foundation at the mud surface 泥面 The m-value method or PY curve method is used to establish a numerical model of pile-soil interaction and the shear force V of the pile body to obtain the bending moment M of the pile foundation at any depth below the mud surface. n and the axial force F acting on the pile foundation at any depth below the mud surface n , and then the stress value σ of the pile foundation at any depth below the mud surface is obtained by the following formula (6): n :

[0042]

[0043] S6, based on the stress value of the pile at any depth below the mud surface σn and the material yield strength σ of the pile foundation y Assess the safety status of the pile structure.

[0044] The present invention is described below with reference to a specific embodiment.

[0045] The parameters of a pile foundation in a high-pile wharf in actual operation along the coast are as follows:

[0046] Pile type: circular concrete pile (concrete grade is C40), pile diameter d = 1.2m; pile length above the mud surface L = 5m; pile material yield strength σ y =26.8MPa.

[0047] The safety assessment method of an existing high-piled wharf pile foundation of the present invention comprises the following steps:

[0048] S1, two fiber Bragg grating stress sensors are symmetrically installed at two cross sections on the top of the pile body of the pier foundation, marked as upper cross section 1 and lower cross section 2 (see Figure 1 ); the distance ΔL from the upper cross section 1 to the lower cross section 2 1-2 = 2m; the stress value collected in real time by the two stress sensors on the upper cross section 1 is σ 11 =12Mpa,σ 12 =-8MPa; the stress value collected in real time by the two stress sensors in the lower cross section 2 is σ 21 =10MPa,σ 22 =-6MPa, and transmit the monitoring data to the cloud monitoring platform;

[0049] Cross-sectional area of the pile foundation

[0050] Moment of inertia of pile foundation

[0051] Section modulus of pile foundation Get the distance y from a certain point on the upper cross section of the pile foundation to the neutral axis;

[0052] The stress value σ measured by the two stress sensors on the upper cross section 1 11 , σ 12 , and combined with the cross-sectional geometric parameters of the pile foundation, the bending moment M1=1.7 and the axial force F1 of the upper cross section 1 are calculated by the following formulas (1) and (2):

[0053]

[0054] Combining equations (1) and (2):

[0055]

[0056] The bending moment of the upper cross section 1 is M1 = 1.7;

[0057] Similarly, the stress values σ measured by the two stress sensors at the lower cross section 2 are 21 , σ 22 , and combined with the cross-sectional geometric parameters of the pile foundation, calculate the bending moment M2=1.36 and axial force F2 of the lower cross section 2;

[0058] S2, using the difference between the bending moment of the upper cross section 1 and the bending moment of the lower cross section 2 and the distance from the upper cross section 1 to the lower cross section 2 of the pile foundation, calculate the shear force V of the pile body:

[0059]

[0060] S3, based on the deadweight G of the pile foundation above the mud surface and the axial force F exerted on the pile foundation above the mud surface, the axial force N of the pile foundation at the mud surface is obtained by the following formula (4):

[0061] N=G+F (4)

[0062] Deadweight of pile foundation above mud surface: G = ALρg = 0.1386MN

[0063] Axial force of pile foundation at mud surface: N = F + G = 2.3986 MN

[0064] S4, based on the shear force V of the pile body and ignoring the influence of wave and water flow on the shear force of the pile body, the bending moment Mmudsurface of the pile foundation at the mud surface is obtained by the following formula (5):

[0065] M 泥面 =M2+V*ΔL 2-泥面 (5)

[0066] S5, based on the bending moment M of the pile foundation at the mud surface 泥面 The PY curve method is used to establish a numerical model of pile-soil interaction. In the model, the spring stiffness is applied to the pile body, and a bending moment M is applied to the pile body at the mud surface. 泥面 , axial forces N and F 水平力 , the bending moment M of the pile foundation at any depth below the mud surface is obtained n The axial force F of the pile foundation at any depth below the mud surface n , and then calculate the composite stress value σ of the pile foundation at any depth below the mud surface by the following formula (6): n :

[0067]

[0068] The composite stress value σ of the pile foundation at any depth below the mud surface calculated according to formula (6) is n , generate the stress distribution cloud diagram of the pile foundation below the mud surface;

[0069] If the depth of the pile foundation below the mud surface is 3m, the PY curve method is used to establish the stress distribution model of the pile foundation below the mud surface. The PY curve method is a composite foundation reaction method that considers the nonlinear effect of the soil. It is based on the relationship curve between the horizontal reaction force of the soil at a certain depth below the mud surface and the deflection of the pile at that point under the action of horizontal load;

[0070] The bending moment distribution of the pile foundation below the mud surface is: M(z)=M 泥面 ·e -kz

[0071] In the above formula, z is the depth of the pile foundation below the mud surface (unit: m); k is the foundation reaction coefficient, which reflects the lateral restraint capacity of the soil on the pile (unit: MN / m°). The larger the k value, the harder the soil. In this embodiment, k is 50MN / m°; e -kz is an exponential decay function, which represents the trend of the bending moment decreasing gradually with increasing depth;

[0072] Calculate the bending moment of the pile foundation at a depth of 3m below the mud surface: M3 = 0.85·e -50×0.003 ≈0.731MNm

[0073] The axial force on the pile foundation at a depth of 3m below the mud surface is F3 = N = 2.3986MN (assuming the axial force remains constant along the depth)

[0074] The composite stress value of the pile foundation at a depth of 3m below the mud surface is:

[0075]

[0076] S6, based on the stress value of the pile at any depth below the mud surface σ n and the material yield strength σ of the pile foundation y , and evaluate the safety status of the pile structure.

[0077] Pile stress is the stress generated within the pile when subjected to external loads. If this stress exceeds the ultimate strength of the pile material, it can lead to yielding, fracture, or deformation, compromising the structural integrity of the pile. The integrity of the pile structure is crucial for its bearing capacity. If this stress causes defects such as cracks, fractures, or deformation, it reduces the effective length and cross-sectional area of the pile, further reducing its bearing capacity. The magnitude and distribution of pile stress directly impacts the structural integrity of the pile, and thus the safety and stability of the entire pile foundation.

[0078] Compare the calculated composite stress value of the pile foundation at a depth of 3m below the mud surface with the allowable stress threshold of the pile foundation material;

[0079] The allowable stress threshold of the pile foundation material is: 0.8σy =0.8×26.8=21.44MPa

[0080] The composite stress value of the pile foundation at a depth of 3m below the mud surface is σ3 = 6.43MPa < 21.44MPa, which does not exceed the allowable stress threshold of the pile foundation material, so the pile foundation is safe.

[0081] If the composite stress value of the pile foundation at a certain depth below the mud surface exceeds the allowable stress threshold of the pile foundation material, the system automatically triggers an early warning signal, indicating that the pile foundation needs to be reinforced or load-limited.

[0082] The safety assessment method for pile foundations of existing high-pile docks of the present invention is continuous and efficient, from the real-time measurement of the load on the cross-section of the pile foundation (stress value at the pile top) to the stress estimation of the pile foundation below the mud surface. The long-term monitoring data can also be used to analyze the deterioration trend of the pile foundation and optimize the maintenance cycle of the dock, providing theoretical support for the safe operation of the dock.

[0083] The above embodiments are only used to illustrate the present invention, rather than to limit the present invention. Those skilled in the art may make various changes or modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions should also fall within the scope of the present invention and should be defined by the claims.

Claims

1. A safety assessment method for existing high-pile wharf pile foundations, characterized in that: The safety assessment method comprises the following steps: S1, two stress sensors are symmetrically installed on an upper cross section and a lower cross section of the top of the pile foundation, and the stress value of the pile foundation at the upper cross section measured by the two stress sensors on the upper cross section is σ A , σ B , and the stress value of the pile foundation at the lower cross section measured by the two stress sensors on the lower cross section is σ C , σ D The stress value measured by each stress sensor is the sum of the stress value generated by the bending moment and the stress value generated by the axial force, which can be expressed by the following formulas (1) and (2): In the above formulas (1) and (2), σ N is the stress generated by the axial force; σ M is the stress caused by the bending moment; M1 is the bending moment of the pile foundation at the upper cross section; F1 is the axial force of the pile foundation at the upper cross section; y is the distance from a point on the upper cross section of the pile foundation to the neutral axis; A is the area of the pile foundation at the upper cross section; I is the moment of inertia of the pile foundation at the upper cross section, d is the diameter of the pile foundation at the upper cross section; The bending moment M1 of the pile foundation at the upper cross section and the axial force F1 of the pile foundation at the upper cross section are obtained by the above formulas (1) and (2); Similarly, the stress values σ measured by the two stress sensors on the lower cross section C , σ D , the bending moment M2 of the pile foundation at the lower cross section and the axial force F2 of the pile foundation at the lower cross section are obtained; S2, based on the bending moment M1 of the pile foundation at the upper cross section and the bending moment M2 of the pile foundation at the lower cross section, the shear force V of the pile body is calculated by the following formula (3): In the above formula (3), ΔL 1-2 is the distance from the upper cross section of the pile foundation to the lower cross section of the pile foundation; S3, the axial force N of the pile foundation at the mud surface is obtained by the following formula (4): N=G+F (4) In the above formula (4), G is the deadweight of the pile foundation above the mud surface; F is the axial force exerted on the pile foundation above the mud surface; S4, based on the shear force V of the pile body and ignoring the influence of wave and water flow on the shear force of the pile body, the bending moment M of the pile foundation at the mud surface is obtained by the following formula (5): 泥面 : M 泥面 =M2+V*ΔL 2-泥面 (5) In the above formula (5), ΔL 2-泥面 is the distance from the lower cross section of the pile foundation to the mud surface; S5, based on the bending moment M of the pile foundation at the mud surface 泥面 The m-value method or PY curve method is used to establish a numerical model of pile-soil interaction and the shear force V of the pile body to obtain the bending moment M of the pile foundation at any depth below the mud surface. n and the axial force F acting on the pile foundation at any depth below the mud surface n , and then the stress value σ of the pile foundation at any depth below the mud surface is obtained by the following formula (6): n : S6, based on the stress value of the pile at any depth below the mud surface σ n and the material yield strength σ of the pile foundation y Assess the safety status of the pile structure.

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