A precast pipe pile length and integrity detection system and method

Abstract

The present invention discloses a precast pipe pile length and integrity detection system and method. The system includes: an excitation tool, excitation points, signal pickup devices, and a detection host. A plurality of excitation points and signal pickup devices are provided. The plurality of excitation points and the plurality of signal pickup devices are arranged on the top of the precast pipe pile and are located at the intersection of the pipe pile diameter direction and the middle ring line of the pipe wall thickness. The plurality of excitation points and the plurality of signal pickup devices are symmetrically arranged along the pipe pile diameter respectively; the signal pickup devices are connected to the detection host through signal cables, and the excitation tool is used to apply an excitation signal to the excitation points. The present invention fully combines the structural characteristics of the pipe pile, reduces the influence of the pipe pile connection part on the test signal, realizes the effective extraction of the pipe pile body defect and the bottom reflection signal, breaks through the technical bottleneck that the low-strain detection technology is not suitable for detecting the hollow thin-wall structure, and realizes the detection of the pile length and integrity of the prestressed pipe pile body.

Description

Technical Field

[0001] The present invention relates to the technical field of precast pipe pile detection, and particularly to a detection system and method for the length and integrity of precast pipe piles. Background Art

[0002] At present, according to the specification "Technical Specification for Detection of Foundation Piles in Highway Engineering" (JTG / T 3512-2020), for the detection of the pile body integrity of pipe piles, the low-strain method can be used. In actual engineering applications, the pile top excitation signal is affected by the inner wall of the pipe pile, the welding quality at the pipe pile joints, and the outer wall restraint, resulting in signal interference, making it difficult to identify the soundness of the pile body and the position of the pile bottom. Therefore, the detection accuracy is difficult to guarantee. In addition, when precast pipe piles are constructed, they are generally composed of 1 to 4 precast piles welded or spliced together. During low-strain method detection, the signal is affected by the gaps at the welds or joints. Most of the signal energy after excitation at the pile top is reflected at the gap part, and only a small part propagates downward. After reflections at multiple interfaces, the sensor installed at the pile top cannot collect effective pile bottom reflection signals, and thus the pile length and the defects of the pile body cannot be analyzed and determined.

[0003] Through the actual on-site application of the low-strain method, the detection effect on prestressed pipe piles is not ideal, mainly reflected in: 1) The prestressed pipe pile has a hollow structure, and the oscillation signal generated by pile top excitation affects the pickup of the pile bottom / pile body echo signal; 2) The reflection signal at the impedance difference interface between the connecting parts of each precast segment pile interferes with the pile bottom / pile body reflection signal. Therefore, it is difficult to accurately detect the quality of precast pipe piles using the low-strain method.

[0004] For pile length detection, researchers in the industry have conducted a large number of studies, and there are also a small number of reports on actual applications. The main detection methods include the acoustic transmission method, the magnetic measurement method, the cross-hole transmission method, etc. The test principle of the acoustic transmission method is the same as that of the ultrasonic method for detecting the integrity of bored cast-in-place piles. It is necessary to drill holes inside and outside the pipe pile. As shown in Figure 1a and Figure 1b , the maximum hole depth needs to be greater than the estimated length of the pipe pile by 3 - 5m, and a sonic logging tube is placed. During detection, when ultrasonic waves pass through the pile bottom mud layer medium, the acoustic properties of the prestressed pipe pile body and the surrounding rock and soil are very different. The acoustic parameter characteristic values of the sound waves will change, such as an increase in acoustic time and a decrease in wave velocity due to attenuation, and there will also be obvious changes in the wave train diagram. The acoustic transmission method determines the position of the pile bottom based on the position of the change in acoustic parameters and the wave train diagram, providing reliable theoretical support for determining the pile length. Magnetic measurement method: Without the influence of other ferromagnetic objects on the pipe pile, the length of the pipe pile is estimated by measuring the change position of the earth's magnetic field at the bottom of the pipe pile. Cross-hole transmission method: The cross-hole transmission method is to use a hand hammer (or force bar) to strike vertically on the pile top surface to generate stress waves, which propagate downward along the pile body. As shown in Figure 2As shown in the figure, when encountering the surrounding soil layer for transmission, sensors are placed in the holes drilled in advance beside the pile to receive the transmitted wave signals, thereby reading the wave arrival times at different depths and drawing the time-depth relationship diagram. When the sensor is below the pile bottom, the sound velocity will change, and an inflection point will be shown on the time-depth diagram. The length of the pile is inferred from the position where the slope of the straight line in the diagram changes.

[0005] For the above existing methods for detecting the length of pipe piles, it is necessary to drill holes near the pipe piles in advance and place probes in the holes. Under the condition that the conditions are available, the detection accuracy is relatively high, but the detection preparation work is time-consuming. However, for soft soil foundations, after drilling, the hole formation is difficult, and pipe piles are mainly applied to soft soil foundations. Therefore, the above methods are rarely used in actual engineering detection. Due to the many drawbacks of the existing methods for detecting the length and integrity of pipe piles, combined with the large demand for pipe pile detection in the industry, it is of great significance to strengthen the research on the detection system and method for the length and integrity of precast pipe piles. Summary of the Invention

[0006] The object of the present invention is to provide a detection system and method for the length and integrity of precast pipe piles, which fully combines the structural characteristics of pipe piles, reduces the signal influence at the joint part of pipe piles, realizes the effective extraction of the signal of the pile body defect and the bottom reflection of the pipe pile, breaks through the technical bottleneck that the low-strain detection technology is not suitable for detecting the hollow thin-wall structure, and realizes the detection of the length and integrity of the pile body of prestressed pipe piles.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] A detection system for the length and integrity of precast pipe piles includes an excitation tool, excitation points, signal pickup devices, and a detection host. A plurality of excitation points and signal pickup devices are provided. The plurality of excitation points and the plurality of signal pickup devices are arranged on the top of the precast pipe pile and are located at the intersection of the pipe diameter direction and the midline of the pipe wall thickness. The plurality of excitation points and the plurality of signal pickup devices are symmetrically arranged along the pipe diameter respectively; the signal pickup devices are connected to the detection host through signal cables, and the excitation tool is used to apply an excitation signal to the excitation points.

[0009] Further, the signal pickup device is a damping sensor.

[0010] Further, the signal pickup device is coupled to the top of the precast pipe pile, and the coupling agent used includes but is not limited to butter, toothpaste, or vaseline.

[0011] Further, the excitation tool is an excitation hammer, and the detection host is a machine with calculation and analysis functions.

[0012] Further, there are 2 excitation points and 2 signal pickup devices. The 2 signal pickup devices are located at two points where the diameter of the pipe pile intersects with the midline of the pipe pile wall thickness. The 2 excitation points are located at two points where the diameter of the pipe pile perpendicular to the line connecting the two signal pickup devices intersects with the midline of the pipe pile wall thickness.

[0013] The present invention also provides a method for detecting the length and integrity of a precast pipe pile, which is applied to the above-mentioned precast pipe pile length and integrity detection system, and includes the following steps:

[0014] S1, apply an appropriate amount of coupling agent to the top of the precast pipe pile after grinding treatment;

[0015] S2, couple and install two signal pickup devices on the top of the precast pipe pile, located at two points where the diameter of the pipe pile intersects with the midline of the pipe pile wall thickness, and two excitation points are formed at the intersection of the diameter of the pipe pile perpendicular to the line connecting the two signal pickup devices and the midline of the pipe pile wall thickness;

[0016] S3, the excitation tool applies an excitation signal to the excitation point, and the two signal pickup devices collect the reflection signal and transmit it to the detection host through the signal cable;

[0017] S4, the detection host performs band-pass filtering, integration processing, and signal region enhancement processing on the reflection signal; when the reflection signal is in the same phase as the starting signal and the reflection amplitude is twice the amplitude of the previous waveform, it is determined as the pile bottom reflection signal, and the waveform recognition method is used to determine the pile length and the position of the defect reflection;

[0018] S5, statistically process the analysis results and save the results.

[0019] Further, in the step S4, the waveform recognition method is used to determine the pile length and the position of the defect reflection, which specifically includes:

[0020] The pile length is obtained by the following formula:

[0021] L = V×(T / 2)

[0022] where V is the propagation speed of the elastic wave signal in the pipe pile, and T is the pile bottom reflection time;

[0023] The position of the defect reflection is obtained by the following formula:

[0024] L1 = V×(T2 - T1) / 2

[0025] where L1 represents the distance from the defect position to the top of the pile; T1 represents the starting moment of excitation, and T2 represents the defect reflection time including the starting moment.

[0026] Further, the step S4 also includes:

[0027] After the pile bottom reflection signal is determined, analyze the phase situation between the pile top and pile bottom reflection signals. When the peak amplitude of the reflection signal is more than 1.5 times that of the previous waveform but lower than the amplitude of the pile bottom reflection signal compared with the previous waveform, and the phase is the same as the starting phase of the pile top, then the reflection point is the defective position of the pile body.

[0028] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects: The precast pipe pile length and integrity detection system and method provided by the present invention. The system uses a special excitation hammer to excite at the excitation point on the midline of the pipe pile wall thickness at the same distance from two damping sensors. The elastic wave signal generated by the excitation is transmitted along the axial direction of the pipe pile to the bottom of the pipe pile and reflected. The damping sensor senses the reflection signal propagating from the pile bottom direction and converts it into a charge signal. The charge signal is transmitted to the detection host by the signal cable. The detection host identifies and converts it into a signal that can be recognized and recorded, and displays and analyzes it on the detection host. After processing the test signal, when the reflection signal has the same phase as the starting signal and the reflection amplitude is significantly enhanced, it is determined as the pile bottom reflection signal. Then, the reflection position and pile length are determined according to this reflection point. After the pile bottom reflection signal is determined, analyze the phase situation between the pile top and pile bottom reflection signals. When the signal phase is significantly enhanced compared with the previous waveform but lower than the amplitude of the pile bottom reflection signal, and the phase is the same as the first wave signal phase of the pile top, then this position is the defect of the pile body. The present invention gives the detection system and the method steps of the detection, realizing the rapid, simple and accurate detection of the length and integrity of the precast pipe pile. Description of the Drawings

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0030] Figure 1a It is a top view of detecting the length of a pipe pile by the acoustic wave transmission method in the prior art;

[0031] Figure 1b It is a side view of detecting the length of a pipe pile by the acoustic wave transmission method in the prior art;

[0032] Figure 2 It is a schematic principle diagram of detecting the length of a pipe pile by the cross-hole transmission method in the prior art;

[0033] Figure 3 It is a structural schematic diagram of the precast pipe pile length and integrity detection system in the embodiment of the present invention;

[0034] Figure 4 It is a flowchart of the precast pipe pile length and integrity detection method in the embodiment of the present invention;

[0035] Figure 5 Schematic diagram of signal propagation along a precast pipe pile according to an embodiment of the present invention;

[0036] Figure 6 Schematic diagram of the detected waveform analysis interface according to an embodiment of the present invention;

[0037] Reference numerals: 1, precast pipe pile; 2, first excitation point; 3, second excitation point; 4, signal pickup device; 5, signal cable; 6, detection host. Detailed implementation manners

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0039] The object of the present invention is to provide a detection system and method for the length and integrity of a precast pipe pile, which fully combines the structural characteristics of the pipe pile, reduces the signal influence at the joint part of the pipe pile, realizes the effective extraction of the signal of the pile body defect and the bottom reflection of the pipe pile, breaks through the technical bottleneck that the low-strain detection technology is not suitable for detecting the hollow thin-wall structure, and realizes the detection of the length and integrity of the pile body of the prestressed pipe pile.

[0040] To make the above objects, features and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation manners.

[0041] As Figure 3 shown, the detection system for the length and integrity of a precast pipe pile provided by the present invention includes an excitation tool, excitation points, a signal pickup device 4 and a detection host 6. A plurality of the excitation points and the signal pickup device 4 are provided. The plurality of excitation points and the plurality of signal pickup devices 4 are arranged on the top of the precast pipe pile 1 and are located at the intersection of the pipe diameter direction and the middle ring line of the pipe wall thickness. The plurality of excitation points and the plurality of signal pickup devices 4 are symmetrically arranged in pairs along the pipe diameter; the signal pickup device 4 is electrically connected to the detection host 6 through a signal cable 5, and the excitation tool is used to apply an excitation signal to the excitation points.

[0042] The signal pickup device 4 is a damping sensor. The signal pickup device 4 is coupled to the top of the precast pipe pile 1, and the coupling agent used includes but is not limited to butter, toothpaste or vaseline.

[0043] The excitation tool is an excitation hammer, and the detection host 6 is a machine with calculation and analysis functions, which is used to realize signal acquisition, display, storage and analysis.

[0044] There are 2 excitation points and 2 signal pickup devices 4. The 2 signal pickup devices 4 are located at two points where the diameter of the pipe pile intersects the mid-circle line of the pipe pile wall thickness. The 2 excitation points are located at two points where the diameter of the pipe pile perpendicular to the line connecting the two signal pickup devices intersects the mid-circle line of the pipe pile wall thickness. The 2 excitation points are the first excitation point 2 and the second excitation point 3 respectively. The distance between the two signal pickup devices 4 is the diameter of the center circle of the precast pipe pile wall thickness.

[0045] As Figure 4 shown, the present invention also provides a method for detecting the length and integrity of a precast pipe pile, which is applied to the above-mentioned precast pipe pile length and integrity detection system, and includes the following steps:

[0046] S1, apply an appropriate amount of coupling agent to the top of the precast pipe pile after grinding treatment;

[0047] S2, couple and install two signal pickup devices on the top of the precast pipe pile, located at two points where the diameter of the pipe pile intersects the mid-circle line of the pipe pile wall thickness, and two excitation points are formed where the diameter of the pipe pile perpendicular to the line connecting the two signal pickup devices intersects the mid-circle line of the pipe pile wall thickness;

[0048] S3, the excitation tool applies an excitation signal to the excitation point, and the two signal pickup devices collect the reflected signal and transmit it to the detection host through the signal cable;

[0049] S4, the detection host performs band-pass filtering, integration processing, and signal region enhancement processing on the reflected signal; when the reflected signal has the same phase as the starting signal and the reflected amplitude is 2 times the amplitude of the previous waveform, it is determined as the pile bottom reflection signal, and the waveform recognition method is used to determine the pile length and the defect reflection position;

[0050] S5, statistically process the analysis results and save the results.

[0051] Among them, in the step S4, the waveform recognition method is used to determine the pile length and the defect reflection position, which specifically includes:

[0052] The pile length is obtained by the following formula:

[0053] L = V×(T / 2)

[0054] Among them, V is the propagation speed of the elastic wave signal in the pipe pile, and T is the pile bottom reflection time; for a precast pipe pile with a concrete strength grade of C80, the elastic wave (P wave) speed is 4100 m / s.

[0055] The defect reflection position is obtained by the following formula:

[0056] L1 = V×(T2 - T1) / 2

[0057] Among them, L1 represents the distance from the defect position to the top of the pile; T1 represents the starting moment of excitation, and T2 represents the defect reflection time including the starting moment of excitation.

[0058] Such as Figure 5 , the step S4 further includes:

[0059] After the pile bottom reflection signal is determined ( Figure 5 at the moment T3 in ), analyze the phase situation between the pile top and pile bottom reflection signals. When the signal phase is compared with the previous waveform, and the peak amplitude of the reflection signal is more than 1.5 times that of the previous waveform but lower than the amplitude of the pile bottom reflection signal, and the phase is in phase with the pile top, then the reflection point is the defect position of the pile body.

[0060] Before detection, it is necessary to expose the top of the pipe pile and arrange two excitation points and two signal pickup devices on the center line of the pipe wall thickness. The excitation points and signal pickup devices are both symmetrically arranged. Then, perform grinding treatment, combine and couple the signal pickup device 4 at the corresponding position of the precast pipe pile 1. The excited elastic wave propagates along the axial direction of the pipe pile, reflects at the pile bottom, and analyze the characteristics of its reflected wave to calculate the pile length and the integrity of the pile body.

[0061] This detection technology and equipment adopt the reflection characteristics of elastic waves, and the processing method is: waveform recognition method.

[0062] Due to the existence of a metal plate at the top of the precast pipe pile, the residual vibration signal after excitation is strong. At the same time, when the welding quality between precast pipe piles is poor and the reflected wave is not easy to identify, methods such as increasing the mass of the excitation hammer, signal filtering, and signal amplification can be used to improve the quality of the pile bottom reflection signal, eliminate the influence of most of the inherent oscillation signals and the reflected signals of the welds between piles, and directly identify the reflected wave.

[0063] According to the investigation of relevant research and products at home and abroad, there are not many studies that can effectively detect the length and integrity of precast pipe piles. However, for the detection technology of the length of the hollow columns of steel guardrails, many institutions have conducted a lot of research and formed detection specifications. Through the present invention, the influence of the gap between precast pipe pile segments on the signal can be effectively reduced, the quality of the pile bottom reflection signal is significantly improved, and the accuracy of the detection of the pile length and the integrity of the pile body is also correspondingly improved; compared with the existing methods for burying pipelines (such as acoustic transmission method, magnetic measurement method, crosshole transmission method, etc.), the detection efficiency and detection cost have been significantly improved.

[0064] Use the present invention to conduct quality inspection on the precast pipe piles of a certain highway. According to relevant data, the concrete strength grade of the precast pile body is C80, the pile diameter is 400mm, the wall thickness is 60mm, the designed length of the pipe pile is 30m, and the length connection is 10m / section. During construction, the connection between piles is welded. For the detection and analysis of typical waveforms, please refer to Figure 6。Through on-site testing, there are defects in the middle of the pipe pile, and the reflection signal at the pile bottom is relatively clear. It is analyzed that the total length of the pipe pile is 29.3 m. Compared with the designed pile length, the test deviation is -2.33%, and the test effect is good.

[0065] In summary, for the precast pipe pile length and integrity detection system and method provided by the present invention, the system uses a special excitation hammer to excite at the excitation point on the center line of the pipe wall thickness at the same distance from two damping sensors. The elastic wave signal generated by the excitation is transmitted along the axial direction of the pipe pile to the bottom of the pipe pile and reflected. The damping sensor senses the reflected signal propagating from the direction of the pile bottom and converts it into a charge signal. The charge signal is transmitted to the detection host by the signal cable. The detection host identifies and converts it into a signal that can be recognized and recorded, and is displayed and analyzed on the detection host; after processing the test signal, when the reflection signal has the same phase as the starting signal and the reflection amplitude is significantly enhanced, it is determined as the pile bottom reflection signal. Then, the reflection position and pile length are determined according to this reflection point. After the pile bottom reflection signal is determined, analyze the phase situation between the pile top and pile bottom reflection signals. When the signal phase is significantly enhanced compared with the previous waveform but lower than the amplitude of the pile bottom reflection signal, and the phase is in phase with the pile top, this position is the defect of the pile body; the present invention gives the detection system and the method steps of the detection, realizing the rapid, simple and accurate detection of the length and integrity of the precast pipe pile.

[0066] In this article, specific examples are used to elaborate on the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A method for detecting the length and integrity of precast pipe piles, which is applied to a detection system for the length and integrity of precast pipe piles, is characterized in that, The detection system includes: an excitation tool, excitation points, signal pickup devices, and a detection host. A number of excitation points and signal pickup devices are provided. The number of excitation points and signal pickup devices are arranged on the top of the precast pipe pile and are located at the intersection of the pipe diameter direction and the mid-line of the pipe wall thickness. The number of excitation points and signal pickup devices are symmetrically arranged along the pipe diameter respectively; the signal pickup devices are connected to the detection host through signal cables, and the excitation tool is used to apply an elastic wave excitation signal to the excitation points; The signal pickup device is a damping sensor; The detection method includes the following steps: S1, Apply an appropriate amount of coupling agent to the top of the precast pipe pile after grinding treatment; S2, Couple and install two signal pickup devices on the top of the precast pipe pile and are located at two points where the pipe diameter intersects the mid-line of the pipe wall thickness. Two excitation points are formed at the intersection of the pipe diameter perpendicular to the line connecting the two signal pickup devices and the mid-line of the pipe wall thickness. The distance between the two signal pickup devices is the diameter of the center circle of the pipe wall thickness; S3, The excitation tool applies an elastic wave excitation signal to the excitation points, and the two signal pickup devices collect the reflected signals and transmit them to the detection host through signal cables; S4, The detection host performs band-pass filtering, integration processing, and signal region enhancement processing on the reflected signals; when the reflected signal has the same phase as the starting signal and the reflected amplitude is greater than 1.5 times the amplitude of the previous waveform, it is determined as the pile bottom reflected signal, and the waveform recognition method is used to determine the pile length and the position of the defect reflection; The step S4 further includes: After the pile bottom reflected signal is determined, analyze the phase situation between the pile top and pile bottom reflected signals. When the signal phase is compared with the previous waveform, the peak amplitude of the reflected signal is more than 1.5 times that of the previous waveform but lower than the amplitude of the pile bottom reflected signal, and the phase is the same as the starting phase of the first wave, then the reflection point is the defect position of the pile body; In the step S4, the waveform recognition method is used to determine the pile length and the position of the defect reflection, specifically including: The pile length is obtained by the following formula: L = V×(T / 2) where, V is the propagation speed of the elastic wave in the precast pipe pile, and T is the pile bottom reflection time; The position of the defect reflection is obtained by the following formula: L1 = V×(T2 - T1) / 2 where, L1 represents the distance from the defect position to the pile top; T1 represents the starting moment of excitation, and T2 represents the defect reflection time including the starting moment; S5, Statistically process the analysis results and save the results.

2. The method for detecting the pile length and integrity of precast pipe piles according to claim 1, wherein, The signal pickup device is coupled to the top of the precast pipe pile and is coupled by a coupling agent. The coupling materials include but are not limited to butter, toothpaste, or vaseline.

3. The method for detecting the length and integrity of precast pipe piles according to claim 1, characterized in that, The excitation tool is an excitation hammer, and the detection host is a machine with calculation and analysis functions.

4. The method for detecting the length and integrity of precast pipe piles according to claim 1, characterized in that, Two excitation points and two signal pickup devices are provided. The two signal pickup devices are located at two points where the pipe diameter intersects the mid-line of the pipe wall thickness. The two excitation points are located at two points where the pipe diameter perpendicular to the line connecting the two signal pickup devices intersects the mid-line of the pipe wall thickness.

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