Distributed temperature measurement optical cable and integrity accurate evaluation method applied to cast-in-place pile

Abstract

The invention discloses a distributed temperature measurement optical cable and an integrity accurate evaluation method applied to a cast-in-place pile. The method comprises the steps that temperature measurement optical cables are arranged along a cast-in-place pile reinforcement cage; the temperature measuring optical cable is used for finely measuring the temperature of the cast-in-place pile at different depths before and after casting; correcting the measured temperature to obtain temperature data at different depths of the cast-in-place pile; the temperature data at the corresponding depth are inversed to be equivalent to the concrete covering thickness, and the equivalent radius of the cast-in-place pile at the current depth is obtained by combining the radius of the reinforcement cage; drawing a cross section corresponding to the cast-in-place pile at the current depth from the equivalent radius by adopting a spline interpolation method; the 3D shape of the cast-in-place pile is constructed through the cross sections at different depths, and visualization is achieved; through fine temperature measurement, the spatial resolution of temperature measurement is effectively improved, defect missing detection and severity evaluation errors of the cast-in-place pile are reduced or even avoided, visualization and transparency of the cast-in-place pile are achieved, overall operation is simple and convenient, visual and accurate, and the application prospect is wide.

Description

Technical Field

[0001] This invention relates to the field of pile foundation engineering testing technology, and in particular to a distributed temperature-measuring optical cable and a method for accurately evaluating the integrity of cast-in-place piles. Background Technology

[0002] Cast-in-place piles are the most widely used type of pile, extensively applied in the foundations of high-rise buildings, bridges, offshore wind farms, and other superstructures. During the grouting process, unstable ground can easily cause borehole collapse, with soil entering the pile and creating defects of various types and sizes. These defects reduce the bearing capacity of the cast-in-place pile, posing potential risks to the construction and operation of the superstructure. Therefore, the integrity testing of cast-in-place piles is crucial for project safety.

[0003] Thermal integrity profiling is a novel method applied to the integrity testing of cast-in-place piles. It detects defects based on temperature distribution during the initial stage of pile construction and attributes the difference between measured and theoretical values ​​to grouting defects.

[0004] However, existing point thermocouples or array thermometers can only provide temperature data for specific points, making them prone to missed detections. Existing distributed temperature sensing technologies based on Raman time-domain reflectometry have a spatial resolution of only meters, which can lead to missed defects and evaluation errors. Furthermore, existing methods for evaluating the integrity of cast-in-place piles based on thermal integrity profiling are not intuitive or accurate enough, and are complex to operate. Summary of the Invention

[0005] To address the aforementioned issues, this application provides a structurally sound distributed temperature-measuring optical cable and a method for accurately evaluating the integrity of cast-in-place piles. This effectively improves the spatial resolution of temperature measurement, reduces or even eliminates missed detections of defects and errors in severity assessment of cast-in-place piles, and achieves visual transparency of the piles. The overall operation is simple, convenient, intuitive, and accurate, with broad application prospects.

[0006] The technical solution adopted in this invention is as follows: A distributed temperature measurement optical cable includes a fiber core, a coating layer wrapped around the outside of the fiber core, a plurality of strain isolation components arranged circumferentially around the outside of the coating layer, and a sheath wrapped around the outside of the strain isolation components; adjacent strain isolation components are fitted together and abutted, and a hollow region is formed by the multiple strain isolation components on the inside, and the fiber core is freely housed in the hollow region.

[0007] As a further improvement to the above technical solution: The strain isolation component is made of glass fiber. Each strain isolation component is cylindrical in shape. The outer circumference of adjacent strain isolation components is pressed against each other along the length direction, and together with the sheath, they form a structurally stable hollow area.

[0008] A method for accurately evaluating the integrity of cast-in-place piles using distributed temperature-measuring optical cables includes: Temperature data at different depths during the pouring of cast-in-place piles were obtained using a temperature-measuring optical cable. The temperature data at the corresponding depth is inverted and converted into the equivalent concrete cover thickness. Combined with the radius of the reinforcing cage, the equivalent radius of the cast-in-place pile at the current depth is obtained. The cross-section of the cast-in-place pile at the current depth is plotted using spline interpolation based on the equivalent radius. The 3D shape of the cast-in-place pile is constructed from cross-sections at different depths, enabling visualization.

[0009] As a further improvement to the above technical solution: The temperature measuring optical cable is deployed vertically in one direction from bottom to top along the steel cage of the cast-in-place pile, and the bottom end of the temperature measuring optical cable is sealed; three or more temperature measuring optical cables are deployed at intervals along the circumference of the cross-section of the cast-in-place pile, and the temperature measuring optical cables are deployed independently and temperature data is measured separately; the deployment of three or more temperature measuring optical cables corresponds to obtaining three or more equivalent radii at the same depth of the cross-section of the cast-in-place pile.

[0010] The number of temperature-measuring optical cables is set to... , Not less than 3, get the corresponding One equivalent radius; The equivalent radius is arranged in order of the temperature measuring optical cable in 2 Arranged sequentially within, and within 0~ The inner repeating arrangement forms a sequence. For even numbers greater than 2; plotted using spline interpolation method from the sequence. Continuous curve within; extraction An effective radius in ~ The continuous curves between these points serve as the contour of the corresponding depth cross-section, where... , .

[0011] The initial internal temperature of the cast-in-place pile before pouring is obtained; during pouring, the temperature-measuring optical cable combined with optical frequency domain reflection technology is used to measure the peak temperature of the cast-in-place pile at different depths during the hydration process, and combined with the initial temperature, the peak hydration temperature at different depths is obtained.

[0012] Considering that the depth direction of cast-in-place piles often crosses different strata, and the thermal properties of different strata are different, resulting in different temperature diffusion rates, a thermal diffusion coefficient is introduced to correct the hydration peak temperature at different depths. The corrected value is used as the temperature data at different depths during the casting process of cast-in-place piles.

[0013] The temperature-measuring optical cable, combined with optical frequency domain reflection technology, performs millimeter-level spatial resolution measurements along the depth direction of the cast-in-place pile.

[0014] The equivalent radius of the cast-in-place pile is compared with the design radius. If the equivalent radius is not less than the design radius, it is determined to be a normal area. If the equivalent radius is less than the design radius, it is determined to be a defective area. The effective bearing area at the current depth of the cast-in-place pile is obtained through the equivalent radius of the cast-in-place pile, and the severity is assessed.

[0015] The equivalent radius of the cast-in-place pile is obtained using the following formula: in, The equivalent radius of the cast-in-place pile; The radius of the reinforcing cage; The thickness of the concrete cover; Temperature data at the corresponding depth of the cast-in-place pile; and It is a constant, depending on the thermal properties of the soil. The value ranges from 1.45 to 1.57. The value ranges from 30.87 to 36.08.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention employs distributed temperature-measuring optical cables deployed within the reinforcing cage of cast-in-place piles. Through precise temperature measurement, it effectively improves the spatial resolution of temperature measurement, reducing or even eliminating missed detections of defects in cast-in-place piles and errors in severity assessment. Furthermore, it achieves visual transparency of the cast-in-place piles. The overall operation is simple, convenient, intuitive, and accurate, with broad application prospects. The present invention also includes the following advantages: The temperature-measuring optical cable uses high-strength encapsulation materials and GFRP, which gives it high shear and bending resistance and makes it less prone to displacement. This effectively isolates the deformation caused by the hydration heat process of the cast-in-place pile from the influence of temperature measurement, enabling accurate measurement of the temperature of the cast-in-place pile.

[0017] By combining a temperature-measuring optical cable with optical frequency domain reflectance (OFDR) technology, high spatial resolution temperature measurement can be used to detect defects smaller than 5cm, and the influence of the temperature in the normal location around the defect can be avoided, thus more accurately assessing the severity of the defect. Attached Figure Description

[0018] Figure 1 This is a flowchart of the method for accurately evaluating the integrity of the present invention.

[0019] Figure 2 This is a schematic diagram of the structure of the temperature-measuring optical cable of the present invention.

[0020] Figure 3 This is a schematic diagram showing the deployment of the temperature-measuring optical cable of the present invention on a cast-in-place pile.

[0021] Figure 4 This is a schematic diagram illustrating the use of spline interpolation to obtain continuous curves in this invention.

[0022] Figure 5 This is a schematic diagram illustrating the inversion of the cross-section of a cast-in-place pile from the equivalent radius according to the present invention.

[0023] Figure 6 This is a schematic diagram for verifying the model pile of the present invention.

[0024] Figure 7 This is a schematic diagram illustrating the 3D shape visualization of the cast-in-place pile of the present invention.

[0025] The components are: 1. Temperature-measuring optical cable; 101. Fiber core; 102. Coating layer; 103. Strain isolation component; 104. Sheath; 2. Cast-in-place piles; 301. Circumferential reinforcement; 302. Longitudinal reinforcement; 401. Equivalent radius one; 402. Equivalent radius two; 403. Equivalent radius three; 5. Spline interpolation curve. Detailed Implementation

[0026] The specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0027] like Figure 2 As shown, this embodiment proposes a distributed temperature measurement optical cable, including a fiber core 101, a coating layer 102 wrapped around the outside of the fiber core 101, a plurality of strain isolation members 103 arranged circumferentially around the outside of the coating layer 102, and a sheath 104 wrapped around the outside of the strain isolation members 103; adjacent strain isolation members 103 are fitted together and abut against each other, and a hollow region is formed by the plurality of strain isolation members 103 on the inside, and the fiber core 101 is freely accommodated in the hollow region. In this embodiment, the fiber core 101 housed in the hollow region is always in a relaxed state, thereby effectively ensuring accurate temperature measurement.

[0028] The strain isolation member 103 is made of glass fiber reinforced polymer (GFRP). The shape of a single strain isolation member 103 is cylindrical. The outer circumferential surfaces of adjacent strain isolation members 103 are closely attached to each other along the length direction and tightly fixed. Combined with the sheath 104, it forms a structurally stable hollow area. This allows the strain isolation member 103 to bear the compressive force generated during the hydration process of the cast-in-place pile, without affecting the fiber core 101.

[0029] The temperature measuring optical cable 1 in this embodiment uses high-strength encapsulation material and GFRP, which gives it high shear and bending resistance and makes it less prone to displacement. This effectively isolates the influence of deformation generated during the hydration heat process of the cast-in-place pile on temperature measurement, thus enabling accurate measurement of the temperature of the cast-in-place pile.

[0030] In this embodiment, the temperature-measuring optical cable 1, combined with optical frequency domain reflectance (OFDR) technology, can detect defects smaller than 5cm through high spatial resolution temperature measurement, and can avoid the influence of the temperature at the normal location around the defect, thus more accurately assessing the severity of the defect.

[0031] This embodiment also proposes a method for accurately evaluating the integrity of distributed temperature-measuring optical cables applied to cast-in-place piles, such as... Figure 1 As shown, it includes: Step 1: Deploy the temperature measuring optical cable 1 along the steel reinforcement cage of the cast-in-place pile 2; Step 2: Use temperature measuring optical cable 1 to perform precise temperature measurements of the cast-in-place pile 2 at different depths before and after pouring; Step 3: Correct the measured temperature to obtain temperature data at different depths of the cast-in-place pile 2; Step 4: Based on the temperature data, perform the equivalent radius inversion of the cast-in-place pile 2; Step 5: Visualize the 3D shape of the cast-in-place pile.

[0032] In the first step, such as Figure 3 As shown, the temperature measuring optical cable 1 is deployed vertically in one direction from bottom to top along the steel cage of the cast-in-place pile 2. The bottom end of the temperature measuring optical cable 2 is sealed to prevent concrete slurry from entering the temperature measuring optical cable 1 and affecting the accurate measurement.

[0033] In actual operation, the steel cage is usually composed of multiple circumferential steel bars 301 and multiple longitudinal steel bars 302. In this embodiment, the temperature measuring optical cable 1 can be deployed along the longitudinal steel bars 302 of the steel cage.

[0034] In this embodiment, three or more temperature-measuring optical cables 1 are deployed circumferentially along the cross-section of the cast-in-place pile 2. The temperature-measuring optical cables 1 are deployed independently and their temperature data is measured separately, thereby measuring the temperature data at different circumferential positions of the cast-in-place pile 2. The deployment of three or more temperature-measuring optical cables 1 corresponds to obtaining three or more equivalent radii at the same depth cross-section of the cast-in-place pile 2, which helps to improve the accuracy of the 3D shape visualization of the cast-in-place pile.

[0035] In practice, increasing the number of upward temperature measuring optical cables around the 2nd circumference of the cast-in-place pile helps to more accurately invert the cross-sectional profile of the 2nd circumference of the cast-in-place pile, making the 3D shape of the 2nd circumference more accurate and more in line with reality.

[0036] By combining the second and third steps, temperature data at different depths during the pouring of the cast-in-place pile 2 are obtained using temperature-measuring optical cable 1.

[0037] In the second step, the initial internal temperature of the cast-in-place pile is obtained before pouring. During pouring, the temperature measurement fiber optic cable combined with optical frequency domain reflectance (OFDR) technology is used to measure the peak temperature of the cast-in-place pile at different depths during the hydration process. Combined with the initial temperature, the peak hydration temperature at different depths is obtained.

[0038] In this embodiment, the peak hydration temperature is used as the source of temperature data to more accurately invert the 3D shape of the cast-in-place pile.

[0039] In this embodiment, since OFDR technology measures the temperature change value of the cast-in-place pile, it is necessary to obtain the temperature of the borehole of the cast-in-place pile before pouring as the initial temperature, and combine it with the measured peak temperature of the change to obtain the hydration peak temperature.

[0040] In this embodiment, the initial temperature can be obtained by detecting at different depths as needed. In actual operation, since the initial temperature difference at different depths is not significant, the same detection temperature can also be used as the initial temperature to facilitate actual operation.

[0041] Starting from the pouring of the cast-in-place pile concrete, continuous measurements are taken to obtain the peak temperature changes during the concrete hydration process. At the peak temperature, the difference between the pouring defects and the normal area is most obvious. Therefore, the peak temperature during the concrete hydration process is obtained to calculate the amount of temperature change.

[0042] The temperature-measuring optical cable, combined with optical frequency domain reflection technology, performs millimeter-level spatial resolution measurements along the depth direction of the cast-in-place pile, thereby providing rich and detailed temperature data along the depth direction of the cast-in-place pile.

[0043] In the third step, considering that the depth direction of the cast-in-place pile often traverses different strata, and that the different thermal properties of these strata lead to different temperature diffusion rates, a thermal diffusivity coefficient is introduced. The peak hydration temperature at different depths was corrected, and the corrected value was used as the temperature data at different depths during the casting of the cast-in-place pile, so as to eliminate the influence of changes in stratum properties on the temperature rise measured by the temperature measuring optical cable.

[0044] thermal diffusivity Calculated using the following formula: Where k is the thermal conductivity of the formation; c is the specific heat capacity of the formation; and ρ is the density of the formation.

[0045] In this embodiment, the thermal diffusivity is used. Corrections are made to the hydration peak temperature at different depths to eliminate the influence of formation properties on temperature measurements, thereby ensuring the reliability and accuracy of defect detection and evaluation.

[0046] In this embodiment, the obtained peak hydration temperature and thermal diffusivity can be compared. The ratio is used to obtain the correction value.

[0047] In the fourth step, the temperature data at the corresponding depth is converted into the equivalent concrete cover thickness, and combined with the radius of the reinforcing cage, the equivalent radius of the cast-in-place pile at the current depth is obtained.

[0048] The equivalent radius of a cast-in-place pile is obtained using the following formula: in, The equivalent radius of the cast-in-place pile; The radius of the reinforcing cage; The thickness of the concrete cover; Temperature data at the corresponding depth of the cast-in-place pile; and It is a constant, depending on the thermal properties of the soil. The value ranges from 1.45 to 1.57. The value ranges from 30.87 to 36.08.

[0049] In the fifth step, the cross-section of the cast-in-place pile at the current depth is drawn using spline interpolation based on the equivalent radius.

[0050] In this embodiment, the cross-section of the cast-in-place pile is drawn using spline interpolation. Spline interpolation provides better continuity than linear interpolation, making the cross-sectional profile closer to reality.

[0051] The number of temperature-measuring optical cables is set to... , Not less than 3, get the corresponding One equivalent radius; The equivalent radius is arranged in order of the temperature measuring optical cable in 2 Arranged sequentially within, and within 0~ The inner repeating arrangement forms a sequence. For even numbers greater than 2; plotted using spline interpolation method from the sequence. Continuous curve within; extraction An effective radius in ~ The continuous curves between these points serve as the contour of the corresponding depth cross-section, where... , .

[0052] The 3D shape of the cast-in-place pile is constructed from cross-sections at different depths, enabling visualization.

[0053] In this embodiment, since there are only a finite number of ( ) on a single cross-section Using the equivalent radius value corresponding to the number of temperature-measuring optical cables (e.g., three) might lead to discontinuous interpolation; therefore, by... The equivalent radii are arranged in sequence to form a series, which forms a continuous curve. Then, the outline of the cross section is cut from the middle of the continuous curve, thereby effectively improving and ensuring the accuracy of the cross section outline.

[0054] In one embodiment, three temperature-measuring optical cables are spaced apart around the circumference of the cast-in-place pile, thereby enabling the acquisition of the equivalent radius at three different locations on a cross-section at a certain depth of the pile, i.e., three equivalent radii, such as... Figure 4 The equivalent radii are 401, 402, and 403. Using the known radii, i.e., equivalent radius 1 (401), equivalent radius 2 (402), and equivalent radius 3 (403), in... Figure 4 The numbers are arranged repeatedly within the range of 0 to 6π to form a sequence. A continuous curve is plotted using spline interpolation, with a full circle (2π) as the interval. The continuous curves with effective radii between 2π and 4π are extracted as the final contours of the corresponding cross-sections, such as... Figure 5 As shown. Similarly, all cross-sections are drawn along the length of the cast-in-place pile. A cross-section can be drawn for each measuring point, thus drawing the 3D shape of the cast-in-place pile.

[0055] It should be noted that, since the temperature-measuring optical cable combined with OFDR technology provides dense vertical depth data, the 3D outline of the cast-in-place pile can be drawn without interpolation in the vertical depth direction, which greatly improves the accuracy of the 3D shape inversion of the cast-in-place pile.

[0056] exist Figure 1 In the illustrated embodiment, the equivalent radius of the cast-in-place pile is compared with the design radius (i.e., the actual radius r). If the equivalent radius is not less than the design radius, it is determined to be a normal area; if the equivalent radius is less than the design radius, it is determined to be a defective area. The effective bearing area at the current depth of the cast-in-place pile is obtained through the equivalent radius of the cast-in-place pile, and the severity is assessed.

[0057] In this embodiment, the design bearing area of ​​the cast-in-place pile can be obtained from the design radius. In actual grouting, the bearing area will be reduced due to the occurrence of defects. The concrete area after removing the defects is called the effective bearing area. The ratio of the effective bearing area to the design bearing area is used to assess the severity of the cast-in-place pile.

[0058] In this embodiment, the concrete area after removing defects, which is the effective bearing area, can be estimated based on actual needs, either from the cross-section obtained after spline interpolation or from the equivalent radius corresponding to the current cross-section obtained through inversion.

[0059] In this embodiment, to verify the accuracy and necessity of combining the temperature-measuring optical cable with OFDR testing, the following method is used: Figure 6 The indoor cast-in-place model piles shown were used for testing. Two model piles, P1 and P2, were constructed using PVC pipes, with lengths of 5 m and 6 m respectively, and a diameter of 0.15 m. Five defects of different sizes (D1~D5) were set inside the model piles P1 and P2. Sandbags were used as pile defects and were cast into specific locations within the pile body. Detailed information on the defects is shown in Table 1.

[0060] Table 1. Detailed information on the defects Considering the possibility of fiber optic cable deformation due to the expansion of reinforcing steel in the project, in this experiment, the reinforcing steel was cast into the model pile along the pile length, and the fiber optic cable was tied to the reinforcing steel.

[0061] In this experiment, the results of measurements using Raman Optical Time Domain Reflectometry (ROTDR) and Optical Frequency Domain Reflectometry (OFDR) were compared. The limiting spatial resolution of ROTDR was 1 m, while that of OFDR was set to 5 cm. The results showed that the temperature-measuring optical cable combined with OFDR could identify defects shorter than 5 cm, while ROTDR could only identify defects longer than 33 cm.

[0062] In another embodiment, taking a cast-in-place pile as an example, the above-mentioned distributed temperature-measuring optical cable is applied to the accurate evaluation method of the integrity of the cast-in-place pile. The cast-in-place pile is set to be 41 m long and 1 m in diameter. The diameter of the reinforcing cage in the cast-in-place pile is 0.8 m, and the concrete cover layer outside the reinforcing cage is designed to be 0.2 m. Three optical cables 1 are deployed in an orderly manner in the pile. OFDR technology is used, with a spatial resolution set to 5 cm. Data is collected every half hour for 20 consecutive hours to measure the change in peak temperature at different depths of the cast-in-place pile during the hydration process, thereby obtaining the hydration peak temperature at different depths; then, the equivalent radius inversion is performed on the hydration peak temperature at each depth, and the 3D shape of the cast-in-place pile is drawn, such as... Figure 7 As shown.

[0063] This invention effectively improves the spatial resolution of temperature measurement, which not only reduces or even avoids missed detection of defects in cast-in-place piles and errors in severity assessment, but also makes the cast-in-place piles visible and transparent. The overall operation is simple, convenient, intuitive and accurate, and has broad application prospects.

[0064] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0065] The above description is an explanation of the present invention and not a limitation thereof. The scope of the present invention is defined by the claims. Within the scope of protection of the present invention, any form of modification may be made.

Claims

1. A distributed temperature-measuring optical cable, characterized in that: It includes a fiber core, a coating layer wrapped around the outside of the fiber core, and multiple strain isolation components arranged circumferentially around the outside of the coating layer. The strain isolation components are wrapped with a sheath. Adjacent strain isolation components are fitted together and abutted against each other. Multiple strain isolation components together form a hollow area on the inside, and the fiber core is freely contained in the hollow area.

2. The distributed temperature measurement optical cable as described in claim 1, characterized in that: The strain isolation component is made of glass fiber. Each strain isolation component is cylindrical in shape. The outer circumference of adjacent strain isolation components is pressed against each other along the length direction, and together with the sheath, they form a structurally stable hollow area.

3. A method for accurately evaluating the integrity of a distributed temperature-measuring optical cable applied to cast-in-place piles, characterized in that: include: Temperature data at different depths during the pouring of cast-in-place piles were obtained using a temperature-measuring optical cable. The temperature data at the corresponding depth is inverted and converted into the equivalent concrete cover thickness. Combined with the radius of the reinforcing cage, the equivalent radius of the cast-in-place pile at the current depth is obtained. The cross-section of the cast-in-place pile at the current depth is plotted using spline interpolation based on the equivalent radius. The 3D shape of the cast-in-place pile is constructed from cross-sections at different depths, enabling visualization.

4. The method for accurate integrity evaluation of distributed temperature-measuring optical cables applied to cast-in-place piles as described in claim 3, characterized in that: The temperature measuring optical cable is deployed vertically in one direction from bottom to top along the steel cage of the cast-in-place pile, and the bottom end of the temperature measuring optical cable is sealed; three or more temperature measuring optical cables are deployed at intervals along the circumference of the cross-section of the cast-in-place pile, and the temperature measuring optical cables are deployed independently and temperature data is measured separately; the deployment of three or more temperature measuring optical cables corresponds to obtaining three or more equivalent radii at the same depth of the cross-section of the cast-in-place pile.

5. The method for accurate integrity evaluation of distributed temperature-measuring optical cables applied to cast-in-place piles as described in claim 4, characterized in that: The number of temperature-measuring optical cables is set to... , Not less than 3, get the corresponding One equivalent radius; The equivalent radius is arranged in order of the temperature measuring optical cable in 2 Arranged sequentially within, and within 0~ The inner repeating arrangement forms a sequence. For even numbers greater than 2; plotted using spline interpolation method from the sequence. Continuous curve within; extraction An effective radius in ~ The continuous curves between these points serve as the contour of the corresponding depth cross-section, where... , .

6. The method for accurately evaluating the integrity of a distributed temperature-measuring optical cable applied to cast-in-place piles as described in claim 3, characterized in that: The initial internal temperature of the cast-in-place pile before pouring is obtained; during pouring, the temperature-measuring optical cable combined with optical frequency domain reflection technology is used to measure the peak temperature of the cast-in-place pile at different depths during the hydration process, and combined with the initial temperature, the peak hydration temperature at different depths is obtained.

7. The method for accurate integrity evaluation of distributed temperature-measuring optical cables applied to cast-in-place piles as described in claim 6, characterized in that: Considering that the depth direction of cast-in-place piles often crosses different strata, and the thermal properties of different strata are different, resulting in different temperature diffusion rates, a thermal diffusion coefficient is introduced to correct the hydration peak temperature at different depths. The corrected value is used as the temperature data at different depths during the casting process of cast-in-place piles.

8. The method for accurate integrity evaluation of distributed temperature-measuring optical cables applied to cast-in-place piles as described in claim 6, characterized in that: The temperature-measuring optical cable, combined with optical frequency domain reflection technology, performs millimeter-level spatial resolution measurements along the depth direction of the cast-in-place pile.

9. The method for accurate integrity evaluation of distributed temperature-measuring optical cables applied to cast-in-place piles as described in claim 3, characterized in that: The equivalent radius of the cast-in-place pile is compared with the design radius. If the equivalent radius is not less than the design radius, it is determined to be a normal area. If the equivalent radius is less than the design radius, it is determined to be a defective area. The effective bearing area at the current depth of the cast-in-place pile is obtained through the equivalent radius of the cast-in-place pile, and the severity is assessed.

10. The method for accurate integrity evaluation of distributed temperature-measuring optical cables applied to cast-in-place piles as described in claim 3, characterized in that: The equivalent radius of the cast-in-place pile is obtained using the following formula: in, The equivalent radius of the cast-in-place pile; The radius of the reinforcing cage; The thickness of the concrete cover; Temperature data at the corresponding depth of the cast-in-place pile; and It is a constant, depending on the thermal properties of the soil. The value ranges from 1.45 to 1.

57. The value ranges from 30.87 to 36.08.

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