Method and device for processing pile foundation axial strain monitoring data based on distributed optical fiber

Abstract

The present invention discloses a method and device for processing pile foundation axial strain monitoring data based on distributed optical fiber. The method includes dividing the pile foundation into several calculation units, establishing the relationship between the pile top load and the strain of each calculation unit based on the average axial force of each calculation unit, combining the bilinear model of the pile-soil interface, solving the relationship under different magnitudes of pile top loads, obtaining the strain distribution of the pile body, and using the method closest to the inner envelope method to determine the true strain distribution of the pile body from the data information obtained by optical fiber monitoring. The present invention solves the problem of large fluctuations in optical fiber measurement data and obtains the true strain and axial force of the pile body.

Description

Technical Field

[0001] The present invention relates to the technical field of pile foundation monitoring, and particularly to a method and device for processing pile foundation axial strain monitoring data based on distributed optical fiber. Background Art

[0002] At present, distributed optical fiber sensing technology is widely used in monitoring the temperature, vibration, stress, etc. of concrete structures. According to different optical signals, it is divided into three types: Rayleigh scattering, Raman scattering, and Brillouin scattering. In the entire distributed optical fiber sensing system, the optical fiber is a continuously distributed sensing point, and information at any position along the optical fiber can be measured through the transmission of electrical signals. At the same time, the optical fiber has the advantages of good durability, no zero drift, non-electric operation, large transmission bandwidth, etc. Therefore, applying the distributed optical fiber sensing system to the whole life cycle monitoring of concrete structures can obtain real-time information such as structural temperature changes, vibration amplitudes, crack derivation and positioning.

[0003] However, in current pile foundation projects, generally materials such as iron wire, rubber bands, and epoxy resin are used to simply tie the optical fiber sensor to the longitudinal stressed steel bars of the pile body, and then it is fixed in shape by pouring concrete. Although its installation operation is simple and the cost is low, it will directly affect the monitoring results, which are specifically manifested in the following aspects: (1) In actual projects, when the optical fiber is installed on the surface or inside the steel bars of the pile foundation, it cannot be completely straightened, and due to the bending of the optical fiber, the measurement data of the optical fiber sensor is fluctuating; (2) In actual projects, during the pile forming process such as pouring and vibrating, the optical fiber is collided or squeezed by soil particles, cement slurry, etc., resulting in small lateral deformations, and the initial strain values of the optical fiber sensors on the same axis are fluctuating, which will also affect subsequent monitoring calculations. In the existing technologies, from the methods and designs of the monitoring system (such as CN 216049709 U, CN 107560712 A, CN209603207 U, CN 103215974 B), to the installation methods of the optical fiber (such as CN 211013221 U, CN 110332902A), and then to the application in different types of pile foundations (such as anti-slide piles CN 110110332902 A, prestressed pipe piles CN 210089629U), in summary, the technical defects existing in the existing pile foundation strain data monitoring methods are:

[0004] 1. When the optical fiber is installed on the surface or inside the steel bars of the pile foundation, it cannot be completely straightened, and due to the bending of the optical fiber, the measurement data of the optical fiber sensor is fluctuating;

[0005] 2. Due to the lateral deformation of the optical fiber on the same axis caused by the collision or extrusion of the optical fiber by particles or cement slurry during the pile forming process such as pouring and vibrating, the initial strain value has large fluctuations, affecting subsequent monitoring results;

[0006] 3. In the full - life - cycle monitoring, the vertical load and settlement at the top of the pile foundation cannot be accurately calculated or measured, which brings difficulties to the analysis and further affects the availability of monitoring data.

[0007] 4. There is often a certain bending moment at the top of the building pile foundation, which causes great interference to the measurement of the axial strain of the pile foundation.

[0008] It can be seen that although the development of the distributed optical fiber monitoring technology applied to the pile foundation project has been relatively mature, the method for processing the pile foundation strain monitoring data based on the distributed optical fiber sensing technology is still lacking. There is an urgent need to propose a method for processing the distributed optical fiber monitoring strain data. Summary of the Invention

[0009] In view of the above problems, the present invention provides a method and device for processing pile foundation axial strain monitoring data based on distributed optical fiber, which solves the problem of large fluctuations in optical fiber measurement data and obtains the true strain and axial force of the pile body.

[0010] In the first aspect of the present invention, a method for processing pile foundation axial strain monitoring data based on distributed optical fiber is provided. The method includes the following steps:

[0011] S1. Divide the pile foundation into several calculation units, and determine the axial - force - strain relationship of each calculation unit based on the average axial force of the forces in each calculation unit.

[0012] S2. Determine the axial force on the lower surface of each calculation unit according to the force balance.

[0013] S3. Conduct a pile - soil interface shear test, fit an interface bilinear model according to the test results, and determine the initial slope and ultimate frictional resistance.

[0014] S4. Obtain the pile - side soil frictional resistance of each calculation unit according to the initial slope, ultimate frictional resistance, and vertical displacements of the upper and lower surfaces.

[0015] S5. Obtain the pile - side frictional resistance of each calculation unit according to the initial slope, ultimate frictional resistance, vertical displacements of the upper and lower surfaces, and the pile - body perimeter.

[0016] S6. Combine the axial - force - strain relationship, the axial force on the lower surface, and the pile - side frictional resistance of each calculation unit to obtain the relationship between the strain of each calculation unit, the upper load, and the initial displacement of the pile - foundation top.

[0017] S7. Combine the axial - force - strain relationship, the axial force on the lower surface of the pile foundation, and the pile - side frictional resistance to obtain the initial displacement of the pile - foundation top.

[0018] S8. Combine the relationship between the strain of the calculation unit, the upper load, and the initial displacement of the pile - foundation top and the initial displacement of the pile - foundation top to obtain the relationship between the vertical load of the pile head and the axial strain of each calculation unit.

[0019] S9. Obtain the axial strain of different calculation units of the pile foundation when the vertical load at the pile head takes different values according to the relationship between the vertical load at the pile head and the strain of each calculation unit.

[0020] S10. Calculate the Euclidean distance between the axial strain of different calculation units of the pile foundation when the vertical load at the pile head takes different values and the strain measured by the distributed optical fiber monitoring. Take the axial strain when the Euclidean distance is the smallest and the axial strain of the pile foundation calculation unit is less than or equal to the strain measured by the distributed optical fiber monitoring as the inner envelope strain of the monitoring strain curve. The pile head load corresponding to the inner envelope strain is the pile head load obtained by measurement.

[0021] Further, in S1, determine the axial force-strain relationship of each calculation unit based on the average axial force of each calculation unit. The specific expression is:

[0022]

[0023] where the pile body is divided into M calculation units with a length of Δl each. The average axial force of the i-th unit, the strain of the i-th calculation unit when the pile head is under the vertical load N1 is ε i , the axial force on the upper surface of the i-th calculation unit is N i , the axial force on the lower surface of the i-th calculation unit is N i+1 , E is the compressive modulus of the pile body, A b is the cross-sectional area of the pile body.

[0024] Further, in S2, determine the axial force on the lower surface of each calculation unit according to the force balance. The specific expression is: N i+1 = N i - ΔN i = N1 - (ΔN1 + ΔN2 + ΔN3 + … + ΔN i )

[0025] where N i+1 represents the axial force on the lower surface of the i-th calculation unit, N i represents the axial force on the upper surface of the i-th calculation unit, ΔN i represents the side friction of the pile of the i-th calculation unit, ΔN i = τ i uΔl, τ i represents the side soil friction of the pile of the i-th calculation unit, u is the perimeter of the pile body, Δl represents the length of the calculation unit, and Nl represents the vertical load at the pile head.

[0026] Further, in S4, obtain the side soil friction τ i of each calculation unit according to the initial slope, ultimate friction resistance, and vertical displacements of the upper and lower surfaces. The specific expression is:

[0027]

[0028]

[0029] s i =s1-(ε1+ε2+…+ε i-1 )Δl

[0030] s i+1 =s1-(ε1+ε2+…+ε i )Δl

[0031] Among them, k i Represents the slope of soil friction resistance of the i-th calculation unit. When k i =k ini , k ini represents the initial slope, when When k i =k sec , k sec represents the slope of the secant line, k sec =τ u / s, τ u represents the ultimate friction resistance, s1 represents the initial displacement of the pile top, s i represents the vertical displacement of the upper surface of the i-th calculation unit, s i+1 represents the vertical displacement of the lower surface of the i-th calculation unit, ε i It represents the strain of the i-th calculation unit when the pile head is subjected to vertical load N1, s cr Represents the critical displacement of the pile-soil interface.

[0032] Furthermore, in S5, the pile side friction resistance ΔN of each calculation unit is obtained according to the initial slope, the ultimate friction resistance, the vertical displacement of the upper and lower surfaces, and the circumference of the pile body. i , the specific expression is:

[0033]

[0034] Among them, B=u(Δl) 2 .

[0035] Furthermore, the relationship between the strain of each calculation unit in S6 and the upper load and the initial displacement of the pile top is expressed as follows:

[0036]

[0037] Furthermore, in S7, the initial displacement of the pile top is obtained by combining the axial force-strain relationship of each calculation unit, the axial force on the lower surface of the pile foundation, and the pile side friction resistance. The specific expression is:

[0038]

[0039] Among them, k b represents the stiffness of the soil layer at the pile bottom, and M represents the number of calculation units..

[0040] Furthermore, in S8, the relationship between the strain of the combined calculation unit, the upper load, and the initial displacement at the top of the pile foundation is used to obtain the relationship between the vertical load at the pile head and the axial strain of each calculation unit. The specific expression is:

[0041]

[0042]

[0043] B = u(Δl) 2

[0044]

[0045] Furthermore, the Euclidean distance formula in S10 is: where 1 ≤ j ≤ p, p represents the total number of times the vertical load N1 is taken, M represents the number of calculation units, represents the axial strain of the i-th calculation unit of the pile foundation when the vertical load N1 takes different values, represents the strain of the i-th calculation unit monitored by the distributed optical fiber.

[0046] In the second aspect of the present invention, a device for processing axial strain monitoring data of a pile foundation based on distributed optical fiber includes:

[0047] An axial force-strain relationship acquisition module, which is used to divide the pile foundation into several calculation units and determine the axial force-strain relationship of each calculation unit based on the average axial force of the forces on each calculation unit;

[0048] A lower surface axial force acquisition module, which is used to determine the lower surface axial force of each calculation unit according to the force balance;

[0049] An initial slope and ultimate skin friction acquisition module, which is used to conduct a pile-soil interface shear test, fit an interface bilinear model according to the test results, and determine the initial slope and ultimate skin friction;

[0050] A pile-side soil skin friction acquisition module, which is used to obtain the pile-side soil skin friction of each calculation unit according to the initial slope, ultimate skin friction, and vertical displacements of the upper and lower surfaces;

[0051] A pile-side skin friction acquisition module, which is used to obtain the pile-side skin friction of each calculation unit according to the initial slope, ultimate skin friction, vertical displacements of the upper and lower surfaces, and the pile body circumference;

[0052] The strain variable relationship acquisition module is used to obtain the relationship between the strain variables of each calculation unit and the upper load and the initial displacement of the pile top by combining the axial force-strain relationship of each calculation unit, the axial force on the lower surface of the pile foundation, and the skin friction of the pile side;

[0053] The initial displacement acquisition module of the pile top is used to obtain the initial displacement of the pile top by combining the axial force-strain relationship of each calculation unit, the axial force on the lower surface of the pile foundation, and the skin friction of the pile side;

[0054] The vertical load-strain variable relationship acquisition module is used to calculate the relationship between the vertical load of the pile head and the axial strain of each calculation unit by combining the relationship between the strain variables of the calculation unit and the upper load and the initial displacement of the pile top and the initial displacement of the pile top;

[0055] The axial strain variable acquisition module is used to obtain the axial strain variables of different calculation units of the pile foundation when the vertical load of the pile head takes different values according to the relationship between the vertical load of the pile head and the strain variables of each calculation unit;

[0056] The pile head load acquisition module is used to calculate the Euclidean distance between the axial strain variables of different calculation units of the pile foundation and the distributed optical fiber monitoring strain variables when the vertical load of the pile head takes different values, and take the axial strain when the Euclidean distance is the smallest and the axial strain of the pile foundation calculation unit is less than or equal to the distributed optical fiber monitoring strain variable as the inner envelope strain of the monitoring strain curve, and the pile head load corresponding to the inner envelope strain is the measured pile head load.

[0057] A method and device for processing axial strain monitoring data of a pile foundation based on distributed optical fiber provided by the present invention divides the pile foundation into several calculation units, establishes the relationship between the pile top load and the strain of each calculation unit based on the force balance relationship of each calculation unit, combines the bilinear model of the pile-soil interface, solves the relationship under different pile top loads of different sizes, obtains the strain distribution of the pile body, and adopts the closest inner envelope method to determine the true strain distribution of the pile body from the data information obtained by optical fiber monitoring, so as to solve the problem of large fluctuations in optical fiber measurement data and obtain the true strain and axial force of the pile body. The method of the present invention divides the pile foundation into several calculation units, combines the deformation amounts of several calculation units and the data information obtained by optical fiber monitoring, calculates the displacement of the pile top and the deformation amount of the pile body, and eliminates the problem of large fluctuations in the initial strain values of the optical fiber on the same axis; the method of the present invention also fills the gap in the data processing method of the existing distributed optical fiber monitoring technology. Description of the Drawings

[0058] Figure 1 is a schematic flowchart of the method for processing axial strain monitoring data of a pile foundation based on distributed optical fiber in Embodiment 1 of the present invention;

[0059] Figure 2 is a schematic diagram of the division of optical fiber calculation units in Embodiment 1 of the present invention;

[0060] Figure 3 It is a schematic diagram of the bilinear model in the first embodiment of the present invention;

[0061] Figure 4 It is a strain curve graph fitted under different vertical loads of pile heads in the first embodiment of the present invention;

[0062] Figure 5 It is the fitted inner envelope strain curve graph in the first embodiment of the present invention;

[0063] Figure 6 It is a schematic structural diagram of a pile foundation axial strain monitoring data processing device based on distributed optical fiber in the second embodiment of the present invention. Detailed implementation manners

[0064] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. Additionally, it should be noted that for the sake of description, only the parts related to the present invention rather than all the structures are shown in the drawings.

[0065] Before discussing the exemplary embodiments in more detail, it should be mentioned that some exemplary embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts describe the steps as sequential processes, many of the steps can be implemented in parallel, concurrently, or simultaneously. In addition, the order of the steps can be rearranged. The process can be terminated when its operations are completed, but it can also have additional steps not included in the drawings. The process can correspond to a method, function, procedure, subroutine, subprogram, etc.

[0066] The embodiments of the present invention provide the following embodiments for a method and device for processing pile foundation axial strain monitoring data based on distributed optical fiber:

[0067] Based on the first embodiment of the present invention

[0068] This embodiment is used to illustrate the method for processing pile foundation axial strain monitoring data based on distributed optical fiber. The process is as Figure 1 shown and includes the following steps:

[0069] Step 1: Divide the pile foundation into several calculation units, and determine the axial force-strain relationship of each calculation unit based on the average axial force of the forces of each calculation unit;

[0070] In a preferred implementation manner, as Figure 2 shown, divide the pile body into M calculation units with a length of Δl each. Let the strain of the i-th calculation unit be ε i when the pile head is under the vertical load N1, and the vertical displacement of the upper surface of the i-th calculation unit be s i, the axial force on the upper surface is N i , the vertical displacement of the lower surface of the i-th calculation unit is s i+1 , the axial force on the lower surface is N i+1 It should be noted that the upper load N1, vertical load N1, upper surface axial force N1 of the first calculation unit, and top external load N1 are the same concept;

[0071] Then the axial force-strain relationship of the i-th calculation unit is as follows:

[0072]

[0073] in, The average axial force of the i-th unit, the strain of the i-th calculation unit when the pile head is subjected to the vertical load N1 is ε i , the axial force on the upper surface of the i-th calculation unit is N i , the axial force on the lower surface of the i-th calculation unit is N i+1 , E is the compressive modulus of the pile body, A b is the cross-sectional area of the pile body.

[0074] Step 2: Determine the lower surface axial force of each calculation unit based on the balance of forces;

[0075] In a preferred embodiment, according to the balance of forces, the axial force N of the lower surface of the i-th calculation unit is i+1 The calculation method is:

[0076] N i+1 =N i -ΔN i =N1-(ΔN1+ΔN2+ΔN3+…+ΔN i ) (2)

[0077] Among them, N i+1 Represents the axial force on the lower surface of the i-th calculation unit, N i represents the axial force on the upper surface of the i-th calculation unit, ΔN i represents the pile side friction of the i-th calculation unit, ΔN i =τ i uΔl,τ i represents the soil friction resistance on the pile side of the i-th calculation unit, u is the circumference of the pile body, Δl represents the length of the calculation unit, and N1 represents the vertical load on the pile head.

[0078] Step 3: Conduct a pile-soil interface shear test, fit a bilinear model of the interface based on the test results, and determine the initial slope and ultimate friction resistance;

[0079] In the preferred embodiment, a pile-soil interface shear test is carried out, and the interface shear strength at different pile-soil relative displacements is measured respectively. According to the test results, a bilinear model of the interface is fitted, and the bilinear model is as shown in Figure 3 , and its initial slope k and ultimate frictional resistance τ u are determined.

[0080] Step Four: Obtain the pile-side soil frictional resistance of each calculation unit according to the initial slope, ultimate frictional resistance, and vertical displacements of the upper and lower surfaces;

[0081] In the preferred embodiment, the pile-side soil frictional resistance of the i-th calculation unit is calculated, and the specific expression is:

[0082]

[0083]

[0084] s i = s1 - (ε1 + ε2 + … + ε i-1 )Δl (5)

[0085] s i+1 = s1 - (ε1 + ε2 + … + ε i )Δl (6)

[0086] where k i represents the slope of the soil frictional resistance of the i-th calculation unit. When , take k i = k ini , k ini represents the initial slope. When , take k i = k sec , k sec represents the secant slope, k sec = τ u / s, τ u represents the ultimate frictional resistance, s1 represents the initial displacement at the top of the pile foundation, s i represents the vertical displacement of the upper surface of the i-th calculation unit, s i+1 represents the vertical displacement of the lower surface of the i-th calculation unit, ε i represents the strain of the i-th calculation unit when the pile head is under the vertical load N1, s cr represents the critical displacement of the pile-soil interface.

[0087] Step Five: Obtain the pile-side frictional resistance of each calculation unit according to the initial slope, ultimate frictional resistance, vertical displacements of the upper and lower surfaces, and the pile perimeter;

[0088] In the preferred embodiment, the pile-side frictional resistance ΔN i of the i-th calculation unit is:

[0089]

[0090] where B = u(Δl) 2 .

[0091] Step Six: Obtain the relationship between the strain of each calculation unit, the upper load, and the initial displacement of the pile top by combining the axial force-strain relationship of each calculation unit, the axial force on the lower surface of the pile foundation, and the skin friction of the pile side;

[0092] In the preferred embodiment, by combining Equations (1), (2), and (7), obtain the relationship between the elastic stiffness, strain of the calculation unit, the upper load N1, and the initial displacement s1 of the pile top:

[0093]

[0094] Step Seven: Obtain the initial displacement of the pile top by combining the axial force-strain relationship of each calculation unit, the axial force on the lower surface of the pile foundation, and the skin friction of the pile side;

[0095] In the preferred embodiment, calculate the pressure N at the bottom of the pile M+1 : N M+1 = A b k b s M+1 , where k b represents the stiffness of the soil layer at the pile bottom, A b represents the cross-sectional area of the pile, and s M+1 represents the displacement at the pile bottom

[0096] By combining Equations (1), (2), and (7), obtain the initial displacement of the pile top:

[0097]

[0098] where k b represents the stiffness of the soil layer at the pile bottom,

[0099] Step Eight: Obtain the relationship between the vertical load at the pile head and the axial strain of each calculation unit by combining the relationship between the strain of the calculation unit, the upper load, and the initial displacement of the pile top and the initial displacement of the pile top;

[0100] In the preferred embodiment, by combining Equation (8) and (9), and after rearrangement, obtain the relationship between N1 and the strain ε i of each unit:

[0101]

[0102]

[0103] B = u(Δl) 2

[0104]

[0105] Step Nine: Obtain the axial strain of different calculation units of the pile foundation when the vertical load of the pile head takes different values according to the relationship between the vertical load of the pile head and the strain of each calculation unit.

[0106] In the preferred embodiment, when calculating different values of N1 according to Equation (10), such as (p represents the total number of values of N1) the axial strain of different calculation units of the pile foundation (1 ≤ i ≤ M, 1 ≤ j ≤ p), such as Figure 4 As shown, it is the strain curve graph fitted under different vertical loads of the pile head.

[0107] Step Ten: Calculate the Euclidean distance between the axial strain of different calculation units of the pile foundation and the strain measured by the distributed optical fiber monitoring when the vertical load of the pile head takes different values. Take the axial strain when the Euclidean distance is the smallest and the axial strain of the pile foundation calculation unit is less than or equal to the strain measured by the distributed optical fiber monitoring as the inner envelope strain of the monitoring strain curve, and the pile head load corresponding to the inner envelope strain is the pile head load obtained by measurement.

[0108] In the preferred embodiment, when calculating different values of N1, such as Calculate the Euclidean distance between the axial strain and the strain measured by the distributed optical fiber monitoring represents the strain measured by the distributed optical fiber monitoring, which is obtained by burying the distributed optical fiber into the pile body and measuring when a load is applied to the pile top. Take d j as the smallest and satisfy when the strain is the inner envelope strain of the monitoring strain curve. Among them, the fitted inner envelope strain curve graph is as Figure 5 shown, and the pile head load corresponding to it is the pile head load obtained by measurement.

[0109] Based on Embodiment 2 of the present invention

[0110] A device 600 for processing monitoring data of axial strain of a pile foundation based on distributed optical fiber provided in Embodiment 2 of the present invention can execute the method for processing monitoring data of axial strain of a pile foundation based on distributed optical fiber provided in Embodiment 1 of the present invention, and has corresponding functional modules and beneficial effects for executing the method. This device can be implemented in the form of software and / or hardware (integrated circuit), and is generally integrated in a server or a terminal device. Figure 6 It is a schematic structural diagram of the device 600 for processing monitoring data of axial strain of a pile foundation based on distributed optical fiber in Embodiment 2 of the present invention. Refer to Figure 6 , the device 600 for processing monitoring data of axial strain of a pile foundation based on distributed optical fiber in the embodiment of the present invention may specifically include: 1]

[0111] The axial force-strain relationship acquisition module 601 is used to divide the pile foundation into several calculation units and determine the axial force-strain relationship of each calculation unit based on the average axial force of the forces of each calculation unit;

[0112] The lower surface axial force acquisition module 602 is used to determine the lower surface axial force of each calculation unit according to the force balance;

[0113] The initial slope and ultimate skin friction acquisition module 603 is used to conduct a pile-soil interface shear test, fit an interface bilinear model according to the test results, and determine the initial slope and ultimate skin friction;

[0114] The pile side soil skin friction acquisition module 604 is used to obtain the pile side soil skin friction of each calculation unit according to the initial slope, ultimate skin friction, and vertical displacements of the upper and lower surfaces;

[0115] The pile side skin friction acquisition module 605 is used to obtain the pile side skin friction of each calculation unit according to the initial slope, ultimate skin friction, vertical displacements of the upper and lower surfaces, and the pile body circumference;

[0116] The strain relationship acquisition module 606 is used to combine the axial force-strain relationship of each calculation unit, the axial force of the lower surface of the pile foundation, and the pile side skin friction to obtain the relationship between the strain of each calculation unit and the upper load and the initial displacement of the top of the pile foundation;

[0117] The initial displacement acquisition module 607 of the top of the pile foundation is used to combine the axial force-strain relationship of each calculation unit, the axial force of the lower surface of the pile foundation, and the pile side skin friction to obtain the initial displacement of the top of the pile foundation;

[0118] The vertical load-strain relationship acquisition module 608 is used to jointly calculate the relationship between the strain of the unit and the upper load and the initial displacement of the top of the pile foundation and the initial displacement of the top of the pile foundation to obtain the relationship between the vertical load of the pile head and the axial strain of each calculation unit;

[0119] The axial strain acquisition module 609 is used to obtain the axial strain of different calculation units of the pile foundation when the vertical load of the pile head takes different values according to the relationship between the vertical load of the pile head and the strain of each calculation unit;

[0120] The pile head load acquisition module 610 is used to calculate the Euclidean distance between the axial strain of different calculation units of the pile foundation and the strain measured by the distributed optical fiber when the vertical load of the pile head takes different values, and take the axial strain when the Euclidean distance is the smallest and the axial strain of the pile foundation calculation unit is less than or equal to the strain measured by the distributed optical fiber as the internal envelope strain of the monitoring strain curve, and the pile head load corresponding to the internal envelope strain is the pile head load obtained by measurement.

[0121] In addition to the upper module, a data processing device 600 for monitoring the axial strain of a pile foundation based on distributed optical fiber may also include other components. However, since these components are not relevant to the content of the embodiments of the present disclosure, their illustrations and descriptions are omitted here.

[0122] For the specific working process of a data processing device 600 for monitoring the axial strain of a pile foundation based on distributed optical fiber, refer to the description of Embodiment 1 of the above-mentioned method for processing data for monitoring the axial strain of a pile foundation based on distributed optical fiber, and details are not repeated here.

[0123] The technical solution of the embodiments of the present invention divides the pile foundation into several calculation units, establishes the relationship between the pile top load and the strain of each calculation unit based on the force balance relationship of each calculation unit, combines the bilinear model of the pile-soil interface, solves the relationship under different pile top loads, obtains the strain distribution of the pile body, and adopts the method closest to the inner envelope method to determine the true strain distribution of the pile body from the data information obtained by optical fiber monitoring, thereby solving the problem of large fluctuations in optical fiber measurement data and obtaining the true strain and axial force of the pile body. The method of the present invention divides the pile foundation into several calculation units, combines the deformation amounts of several calculation units with the data information obtained by optical fiber monitoring, calculates the displacement of the pile top and the deformation amount of the pile body, and eliminates the problem of large fluctuations in the initial strain values of the optical fibers on the same axis; the method of the present invention also fills the gap in the data processing method of the existing distributed optical fiber monitoring technology.

[0124] Note that the above is only the preferred embodiment of the present invention and the applied technical principle. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described here, and various obvious changes, re-adjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments only. Without departing from the concept of the present invention, more other equivalent embodiments can be included, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A method for processing pile foundation axial strain monitoring data based on distributed optical fiber, characterized in that: The method comprises the following steps: S1. Divide the pile foundation into several calculation units, and determine the axial force-strain relationship of each calculation unit based on the average axial force of each calculation unit; S2. Determine the axial force on the lower surface of each calculation unit based on the balance of forces; S3. Conduct a pile-soil interface shear test, fit a bilinear model of the interface based on the test results, and determine the initial slope and ultimate friction resistance; S4. Obtaining the pile side soil friction of each calculation unit according to the initial slope, the ultimate friction resistance, and the vertical displacement of the upper and lower surfaces; S5. Obtaining the pile side friction of each calculation unit according to the initial slope, the ultimate friction, the vertical displacement of the upper and lower surfaces, and the circumference of the pile body; S6. Combining the axial force-strain relationship of each calculation unit, the axial force on the lower surface of the pile foundation, and the pile side friction, obtain the relationship between the strain of each calculation unit and the upper load and the initial displacement of the pile foundation top; S7, combining the axial force-strain relationship of each calculation unit, the axial force on the lower surface of the pile foundation, and the pile side friction resistance to obtain the initial displacement of the pile foundation top; S8. Combine the relationship between the strain of the calculation unit and the upper load, the initial displacement of the pile foundation top, and the relationship between the vertical load of the pile head and the axial strain of each calculation unit obtained from the initial displacement of the pile foundation top; S9. Obtaining the axial strain of different calculation units of the pile foundation when the vertical load of the pile head takes different values according to the relationship between the vertical load of the pile head and the strain of each calculation unit; S10. Calculate the Euclidean distance between the axial strain of different calculation units of the pile foundation and the distributed optical fiber monitoring strain when the vertical load on the pile head is different. The axial strain when the Euclidean distance is the smallest and the axial strain of the pile foundation calculation unit is less than or equal to the distributed optical fiber monitoring strain is taken as the inner envelope strain of the monitoring strain curve. The pile head load corresponding to the inner envelope strain is the measured pile head load. In S1, the axial force-strain relationship of each calculation unit is determined based on the average axial force of each calculation unit force. The specific expression is: The pile body is divided into M calculation units with the same length of Δl. The average axial force of the i-th unit, the strain of the i-th calculation unit when the pile head is subjected to the vertical load N1 is ε i , the axial force on the upper surface of the i-th calculation unit is N i , the axial force on the lower surface of the i-th calculation unit is N i+1 , E is the compressive modulus of the pile body, A b is the cross-sectional area of the pile; In S2, the axial force on the lower surface of each calculation unit is determined based on the balance of forces. The specific expression is: N i+1 =N i -ΔN i =N1-(ΔN1+ΔN2+ΔN3+…+ΔN i ) Among them, N i+1 Represents the axial force on the lower surface of the i-th calculation unit, N i represents the axial force on the upper surface of the i-th calculation unit, ΔN i represents the pile side friction of the i-th calculation unit, ΔN i =τ i uΔl,τ i represents the soil friction resistance on the pile side of the i-th calculation unit, u is the circumference of the pile body, Δl represents the length of the calculation unit, and N1 represents the vertical load on the pile head; In S4, the pile side soil friction resistance τ of each calculation unit is obtained according to the initial slope, ultimate friction resistance and vertical displacement of the upper and lower surfaces. i , the specific expression is: s i =s1-(ε1+ε2+…+ε i-1 )Δl s i+1 =s1-(ε1+ε2+…+ε i )Δl Among them, k i Represents the slope of soil friction resistance of the i-th calculation unit. When k i =k ini , k ini represents the initial slope, when When k i =k sec , k sec represents the slope of the secant line, k sec =τ u / s1,τ u represents the ultimate friction resistance, s1 represents the initial displacement of the pile top, s i represents the vertical displacement of the upper surface of the i-th calculation unit, s i+1 represents the vertical displacement of the lower surface of the i-th calculation unit, ε i It represents the strain of the i-th calculation unit when the pile head is subjected to vertical load N1, s cr represents the critical displacement of the pile-soil interface; In S5, the pile side friction resistance ΔN of each calculation unit is obtained according to the initial slope, the ultimate friction resistance, the vertical displacement of the upper and lower surfaces, and the circumference of the pile body. i , the specific expression is: Where, B = u(Δl) 2 ; The relationship between the strain of each calculation unit in S6 and the upper load and the initial displacement of the pile top is expressed as follows: In S7, the initial displacement of the pile top is obtained by combining the axial force-strain relationship of each calculation unit, the axial force on the lower surface of the pile foundation, and the pile side friction resistance. The specific expression is: Among them, k b represents the stiffness of the soil layer at the bottom of the pile, M represents the number of computing units.

2. The method for processing pile foundation axial strain monitoring data based on distributed optical fiber according to claim 1, characterized in that: The relationship between the strain of the combined calculation unit in S8 and the upper load and the initial displacement of the pile top is used to obtain the relationship between the vertical load of the pile head and the axial strain of each calculation unit. The specific expression is: B=u(Δl) 2 3. The method for processing pile foundation axial strain monitoring data based on distributed optical fiber according to claim 1, characterized in that: The Euclidean distance formula in S10 is: Where 1≤j≤p, p represents the total number of times the vertical load N1 takes value, and M represents the number of calculation units. It represents the axial strain of the i-th calculation unit of the pile foundation when the vertical load N1 takes different values. represents the strain of the i-th computing unit of distributed optical fiber monitoring.

4. A distributed optical fiber-based pile foundation axial strain monitoring data processing device, characterized in that: The device is used to implement the method according to any one of claims 1 to 3, comprising: An axial force-strain relationship acquisition module is used to divide the pile foundation into a number of calculation units and determine the axial force-strain relationship of each calculation unit based on the average axial force of each calculation unit; A lower surface axial force acquisition module is used to determine the lower surface axial force of each calculation unit according to the balance of forces; The module for obtaining the initial slope and ultimate friction resistance is used to conduct a pile-soil interface shear test, fit the interface bilinear model based on the test results, and determine the initial slope and ultimate friction resistance; The pile side soil friction resistance acquisition module is used to obtain the pile side soil friction resistance of each calculation unit based on the initial slope, the ultimate friction resistance and the vertical displacement of the upper and lower surfaces; The pile side friction resistance acquisition module is used to obtain the pile side friction resistance of each calculation unit based on the initial slope, the ultimate friction resistance, the vertical displacement of the upper and lower surfaces, and the circumference of the pile body; The strain relationship acquisition module is used to combine the axial force-strain relationship of each calculation unit, the axial force on the lower surface of the pile foundation, and the pile side friction to obtain the relationship between the strain of each calculation unit and the upper load and the initial displacement of the pile foundation top; The module for obtaining the initial displacement of the pile foundation top is used to obtain the initial displacement of the pile foundation top by combining the axial force-strain relationship of each calculation unit, the axial force on the lower surface of the pile foundation, and the pile side friction resistance; The module for obtaining the relationship between vertical load and strain is used to obtain the relationship between the vertical load of the pile head and the axial strain of each calculation unit by combining the relationship between the strain of the calculation unit and the upper load and the initial displacement of the pile foundation top; The axial strain acquisition module is used to obtain the axial strain of different calculation units of the pile foundation when the vertical load of the pile head takes different values according to the relationship between the vertical load of the pile head and the strain of each calculation unit; The pile head load acquisition module is used to calculate the Euclidean distance between the axial strain of different calculation units of the pile foundation and the distributed optical fiber monitoring strain when the pile head vertical load takes different values. The axial strain when the Euclidean distance is the smallest and the axial strain of the pile foundation calculation unit is less than or equal to the distributed optical fiber monitoring strain is taken as the inner envelope strain of the monitoring strain curve. The pile head load corresponding to the inner envelope strain is the measured pile head load.

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