Tubular pile integrity detection method based on low-strain transmission waves

Abstract

The invention discloses a low-strain transmission wave-based tubular pile integrity detection method, which comprises the following steps of: calculating and determining a pile-soil rigidity ratio, and determining a transmission wave attenuation factor of a to-be-detected tubular pile; constructing an excitation hammering parameter prediction model, and determining excitation hammering parameters of the detected pipe pile; the amplitude of incident waves on the upper portion of the welding seam and the amplitude of transmission waves passing through the welding seam are obtained; calculating the ratio of the amplitude of incident waves at the upper part of the welding seam to the amplitude of transmission waves passing through the welding seam, and identifying the welding quality of the pipe pile splicing part; the maximum value of the total energy transmissivity is calculated, and the welding quality of the pipe pile splicing part is recognized; a tubular pile welding defect type identification model is constructed, and tubular pile welding defect types are identified; and determining management measures of the pile splicing part of the tubular pile according to the welding quality judgment result of the pile splicing part of the tubular pile. By combining a low-strain transmission wave detection technology and an intelligent data processing method, the limitation of a traditional low-strain method under the condition of a long pile or a non-uniform pile body is effectively solved, and the precision and reliability of tubular pile detection are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of engineering detection, and particularly to a method for detecting the integrity of pipe piles based on low-strain transmitted waves. Background Art

[0002] With the continuous development of engineering construction, pipe piles, as important components in foundation engineering, are widely used in various large-scale projects such as urban construction, bridges, and dams. Especially in complex geological environments, the integrity and bearing capacity of pipe piles directly affect the safety and stability of the project. In order to ensure the construction quality of pipe piles and quickly and accurately detect the integrity of pipe piles, it has become an important task in engineering construction. Among the existing pile body detection technologies, the low-strain method has become a common detection method in the market due to its simple operation, low cost, and applicability to large-scale detection. This method vibrates the pile top through a vibrator and measures the stress wave signal transmitted from the pile body to the pile top, thereby inferring the defects and non-uniformities of the pile body and evaluating the structural integrity of the pile. The low-strain method is mainly applicable to short piles or piles with relatively uniform pile bodies, and can quickly conduct a preliminary assessment of the construction quality of the pile, and is widely used in the general survey of engineering quality. However, the low-strain method has certain limitations in practical applications. Especially when the pile body is long or the cross-section of the pile body is non-uniform, the size effect of the pile body and the too small pile-soil stiffness ratio will cause multiple reflections of the stress wave during propagation, the waveform becomes complex, and the energy dissipates rapidly or reflects in advance. For such piles, it is difficult for the traditional low-strain method to accurately obtain a complete stress wave signal, resulting in the inability to judge the reflected wave at the pile bottom, and thus unable to evaluate the integrity of the entire pile. Especially in the case of long piles or soft soil geological conditions, the wave impedance difference of the pile body is large, and the measurement results of the traditional method are often affected, resulting in inaccurate detection results and unable to fully reflect the health status of the pile body. Therefore, although the low-strain method is widely used, the accuracy and comprehensiveness of its detection results are still restricted by geological conditions, pile body morphology, and construction quality. Against this background, a more accurate technical method that can overcome the limitations of the traditional low-strain method is needed to improve the ability to evaluate the integrity of long piles and complex pile bodies. Summary of the Invention

[0003] In view of the above problems existing in the prior art, the present invention provides a method for detecting the integrity of pipe piles based on low-strain transmitted waves, which mainly includes: Calculating and determining the pile-soil stiffness ratio according to the cross-sectional area and length of the pipe pile to be inspected, and determining the transmitted wave attenuation factor of the pipe pile to be detected; Constructing an excitation hammering parameter prediction model based on the weld position of the pipe pile and the transmitted wave attenuation factor data, and determining the excitation hammering parameters with excellent received effect of the transmitted wave signal of the pipe pile to be inspected; Based on the weld position of the inspected pipe pile, vertically arrange the hydrophones at preset positions equidistant above and below the weld, and obtain the amplitude of the incident wave above the weld and the amplitude of the transmitted wave passing through the weld; Identify the welding quality of the pipe pile joint by calculating the ratio of the amplitude of the incident wave above the weld to the amplitude of the transmitted wave passing through the weld; If the wave impedances of the pipe pile above the weld and the pipe pile below the weld are different, then determine the maximum value of the total energy transmittance based on the amplitude of the incident wave above the weld and the amplitude of the transmitted wave passing through the weld, and identify the welding quality of the pipe pile joint in combination with the measured energy transmittance; Extract the spectral characteristics of the velocity signal from the complete time-domain velocity signal with general welding quality at the pipe pile joint, construct an identification model for the type of pipe pile welding defect, and identify the type of pipe pile welding defect; Determine the management measures for the pipe pile joint according to the judgment result of the welding quality of the pipe pile joint.

[0004] Further, the calculation and determination of the pile-soil stiffness ratio according to the cross-sectional area and length of the inspected pipe pile, and the determination of the transmitted wave attenuation factor of the pipe pile to be detected include: Obtain the cross-sectional area and length of the inspected pipe pile through the pipe pile body integrity test project document, and use the pipe pile stiffness formula to determine the pipe pile stiffness , where is the elastic modulus of the pile material, A is the cross-sectional area of the pipe pile, and L is the length of the pipe pile; obtain the elastic modulus of the soil around the pile according to the geological exploration data, and use the soil stiffness formula to determine the soil stiffness , where is the elastic modulus of the soil, is the stress area of the soil layer around the pile, equal to the contact area of the soil around the pile, is the effective length of the soil, equal to the depth of the pile body or the depth of the pile body in contact with the soil layer; determine the pile-soil stiffness ratio according to the pipe pile stiffness and the soil stiffness ; according to the pile-soil stiffness ratio, use the transmitted wave attenuation factor formula to determine the transmitted wave attenuation factor of the pipe pile to be detected , and store the transmitted wave attenuation factor of the pipe pile in the pipe pile monitoring database, where is a constant related to the soil type and wave propagation characteristics, obtained through experiments or numerical simulations, and n is the interaction coefficient, a constant used to describe the interaction strength between the pile and the soil, obtained through experiments or numerical simulations.

[0005] Further, based on the weld position of the pipe pile and the data of the transmitted wave attenuation factor, a prediction model for the impact hammering parameters is constructed to determine the impact hammering parameters with excellent received effect of the transmitted wave signal of the pipe pile to be inspected, including: Through the pipe pile monitoring database, obtain the historical weld position of the pipe pile and the data of the transmitted wave attenuation factor, mark the impact hammering parameters with excellent received effect of the transmitted wave signal of the pipe pile, use the recurrent neural network for model training, and construct a prediction model for the impact hammering parameters. The impact hammering parameters include the hammering force, the number of hammering times, and the material of the hammer head; according to the length of the pipe pile to be inspected, determine the weld position of the pipe pile to be inspected, obtain the transmitted wave attenuation factor, and use the prediction model for the impact hammering parameters to determine the impact hammering parameters with excellent received effect of the transmitted wave signal of the pipe pile to be inspected.

[0006] Further, based on the weld position of the pipe pile to be inspected, vertically arrange the hydrophones at preset positions with equal spacing above and below the weld, and obtain the amplitude of the incident wave above the weld and the amplitude of the transmitted wave passing through the weld, including: Fill the cavity of the pipe pile to be inspected with water, adjust the lowering depth of the hydrophone according to the weld position of the pipe pile to be inspected, and vertically arrange the hydrophones at preset positions with equal spacing above and below the weld; based on the impact hammering parameters with excellent received effect of the transmitted wave signal, hammer the center of the pile top of the pipe pile to be inspected, and apply a transient excitation force downward along the axis of the pile; obtain the complete time-domain velocity signal through the hydrophone above the weld, and calculate the average value of the peak amplitudes of the first waves of the velocity signals of each hydrophone as the amplitude of the incident wave above the weld; obtain the complete time-domain velocity signal through the hydrophone below the weld, and calculate the average value of the peak amplitudes of the first waves of the velocity signals of each hydrophone as the amplitude of the transmitted wave passing through the weld.

[0007] Further, by calculating the ratio of the amplitude of the incident wave above the weld and the amplitude of the transmitted wave passing through the weld, identify the welding quality of the pipe pile joint part, including: Through the pipe pile body integrity test project document, obtain the cross-sectional area and material density of the pipe pile to be inspected, and use the pile body wave impedance calculation formula , determine the wave impedance Z of the pile body of the pipe pile to be inspected, where is the material density of the pipe pile, c is the stress wave propagation velocity, and A is the cross-sectional area of the pipe pile; according to the amplitude of the incident wave above the weld and the amplitude of the transmitted wave passing through the weld, based on the formula , calculate the ratio of the two amplitudes , where is the amplitude of the incident wave above the weld, is the amplitude of the transmitted wave passing through the weld, is the amplitude of the incident velocity of the pipe pile above the weld, is the amplitude of the transmitted velocity transmitted from the weld interface to the pipe pile below the weld. The wave impedances of the pipe pile above the weld and the pipe pile below the weld are the same, both being , is the wave impedance at the weld interface; if , it indicates that the welding quality of the pipe pile joint is extremely high. If , it indicates that the welding quality of the pipe pile joint is extremely poor. The remaining values indicate that the welding quality of the pipe pile joint is average.

[0008] Furthermore, if the wave impedances of the upper pipe pile and the lower pipe pile of the weld are different, then based on the amplitude of the incident wave on the upper part of the weld and the amplitude of the transmitted wave passing through the weld, the maximum value of the total energy transmittance is determined, and the welding quality of the pipe pile joint is identified by combining the measured energy transmittance, including: If the wave impedances of the upper pipe pile and the lower pipe pile of the weld are different, then based on the amplitude of the incident wave on the upper part of the weld and the amplitude of the transmitted wave passing through the weld, according to the formula , calculate the ratio of the two amplitudes , where is the amplitude of the transmitted wave transmitted to the lower part of the pipe pile from the weld interface, is the wave impedance of the upper pipe pile of the weld, is the wave impedance of the welding material, is the wave impedance of the lower pipe pile of the weld; according to the three-layer medium model, obtain the total energy transmittance , take the derivative of and set the derivative to zero to determine the maximum value of the total energy transmittance ; according to the amplitude of the incident wave on the upper part of the weld and the amplitude of the transmitted wave passing through the weld, use the formula to calculate the measured energy transmittance ; if and the difference is 0, it indicates that the welding quality of the pipe pile joint is extremely high. If and the difference is less than the preset difference threshold, it indicates that the welding quality of the pipe pile joint is average. If and the difference is greater than the preset difference threshold, it indicates that the welding quality of the pipe pile joint is extremely poor.

[0009] Furthermore, from the complete time-domain velocity signal with average welding quality at the pipe pile joint, extract the spectral characteristics of the velocity signal, and construct a pipe pile welding defect type identification model to identify the pipe pile welding defect type, including: Through the hydrophone above the weld, a complete time-domain velocity signal with general welding quality at the pipe pile joint is obtained. The time-domain signal of the velocity signal is converted into frequency-domain data using the short-time Fourier transform algorithm, the spectral characteristics of the velocity signal are extracted and saved in the pipe pile monitoring database. The spectral characteristics include frequency, frequency peak, and amplitude. Through the pipe pile monitoring database, the historical spectral characteristics of the pipe pile are obtained, and the types of welding defects of the pipe pile are marked. A cyclic neural network is used for model training to construct an identification model for the types of welding defects of the pipe pile. The types of welding defects of the pipe pile include weld cracks, uneven welds, pores, or slag inclusions. According to the spectral characteristics of the pipe pile obtained in real time, the identification model for the types of welding defects of the pipe pile is used to identify the types of welding defects of the pipe pile.

[0010] Further, determining the management measures for the pipe pile joint according to the judgment result of the welding quality of the pipe pile joint includes: According to the judgment result of the welding quality of the pipe pile joint and in combination with the pipe pile joint, determine the management measures for the pipe pile joint; if the welding quality of the pipe pile joint is extremely high, regularly monitor the welding quality of the pipe pile joint at a preset time interval; if the welding quality of the pipe pile joint is general, perform local repair in the weld area according to the type of welding defect of the pipe pile, including repairing, grinding, or cleaning the local area by welding; if the welding quality of the pipe pile joint is extremely poor, take pipe pile repair measures to repair the pipe pile, and perform welding quality inspection on the pipe pile joint again after the pipe pile is repaired until the quality of the joint meets the standard requirements. The pipe pile repair measures include rewelding, reinforcement, or replacement of the damaged part.

[0011] The technical solution provided by the embodiment of the present invention may include the following beneficial effects: The present invention provides a method for detecting the integrity of pipe piles based on low-strain transmitted waves. By calculating the pile-soil stiffness ratio of the pipe pile and determining the transmitted wave attenuation factor, the present invention can more accurately evaluate the structural characteristics of the pile body. Based on the transmitted wave attenuation factor and the weld position, the present invention constructs a prediction model for the exciting hammering parameters, optimizes the selection of the exciting parameters, thereby maximizing the reception effect of the transmitted wave signal and ensuring the high quality of the detection data. During the detection process, through the vertical arrangement of the hydrophones and the accurate measurement of the amplitudes of the incident wave and the transmitted wave above and below the weld, the welding quality of the joint part of the pipe pile can be accurately evaluated. In the welding quality assessment, the present invention particularly considers the wave impedance difference between the pipe piles above and below the weld. By analyzing the amplitude of the incident wave above the weld and the amplitude of the transmitted wave passing through the weld, the maximum value of the total energy transmittance can be determined, and this maximum value is compared with the measured energy transmittance to accurately identify the welding quality of the joint part of the pipe pile. This method ensures the efficient identification of welding defects, especially in the case of inconsistent wave impedance, and improves the accuracy of the welding quality assessment. In addition, by using the spectrum feature extraction and welding defect type identification model, the present invention can automatically identify the types of welding defects of the pipe pile, greatly improving the automation level of defect detection and reducing the manual error. The present invention has significant advantages in improving the detection accuracy of pipe piles, enhancing the management efficiency and reducing the engineering risks, and can provide more accurate quality assurance for the project to ensure the long-term safe operation of the infrastructure. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a flowchart of a method for detecting the integrity of pipe piles based on low-strain transmitted waves according to the present invention; Figure 2 is a schematic diagram of a method for detecting the integrity of pipe piles based on low-strain transmitted waves according to the present invention; Figure 3 is another schematic diagram of a method for detecting the integrity of pipe piles based on low-strain transmitted waves according to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0013] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0014] As Figures 1 - 3 shown, a method for detecting the integrity of pipe piles based on low-strain transmitted waves in this embodiment may specifically include: Step S101: Calculate and determine the pile-soil stiffness ratio according to the cross-sectional area and length of the pipe pile to be inspected, and determine the transmitted wave attenuation factor of the pipe pile to be detected.

[0015] Obtain the cross-sectional area and length of the pipe pile to be inspected through the pipe pile body integrity test project file, and use the pipe pile stiffness formula to determine the pipe pile stiffness , where is the elastic modulus of the pile material, A is the cross-sectional area of the pipe pile, and L is the length of the pipe pile. According to the geological exploration data, the elastic modulus of the soil around the pile is obtained, and the soil stiffness formula is used to determine the soil stiffness , where is the elastic modulus of the soil, is the stress area of the soil layer around the pile, which is equal to the contact area of the soil around the pile, is the effective length of the soil, which is equal to the depth of the pile body or the depth of the pile body in contact with the soil layer. According to the pipe pile stiffness and soil stiffness, the pile-soil stiffness ratio is determined. According to the pile-soil stiffness ratio, the transmission wave attenuation factor formula is used to determine the transmission wave attenuation factor of the pipe pile to be detected, and the transmission wave attenuation factor of the pipe pile is stored in the pipe pile monitoring database, where is a constant related to the soil type and wave propagation characteristics, obtained through experiments or numerical simulations, and n is the interaction coefficient, a constant used to describe the interaction strength between the pile and the soil, obtained through experiments or numerical simulations.

[0016] Exemplarily, there is a pipe pile with a cross-sectional area of 0.3 m 2 , a length of 20 m, and the elastic modulus of the pile material. Through the pipe pile stiffness formula , the pipe pile stiffness is determined, where is the elastic modulus of the pile material, A is the cross-sectional area of the pipe pile, and L is the length of the pipe pile. According to the geological exploration data, the elastic modulus of the soil around the pile is obtained. If the elastic modulus of the soil, the contact area of the soil around the pile is 0.4 m 2 , and the effective length is 15 m. Through the soil stiffness formula , the soil stiffness is calculated as , where is the elastic modulus of the soil, is the stress area of the soil layer around the pile, approximately equal to the contact area of the soil around the pile, is the effective length of the soil, equal to the depth of the pile body or the depth of the pile body in contact with the soil layer. According to the pipe pile stiffness and soil stiffness, the pile-soil stiffness ratio is calculated. According to the pile-soil stiffness ratio, the transmission wave attenuation factor formula is used to determine the transmission wave attenuation factor of the pipe pile to be detected, where is a constant related to soil type and wave propagation characteristics, obtained through experiments or numerical simulations. n is the interaction coefficient, a constant used to describe the interaction strength between the pile and the soil, obtained through experiments or numerical simulations. If , , then the calculated transmission wave attenuation factor , and store the transmission wave attenuation factor of the pipe pile into the pipe pile monitoring database.

[0017] Step S102: According to the weld position of the pipe pile and the transmission wave attenuation factor data, construct an excitation hammering parameter prediction model to determine the excitation hammering parameters with excellent reception effect of the transmission wave signal of the pipe pile to be inspected.

[0018] Through the pipe pile monitoring database, obtain the historical weld position and transmission wave attenuation factor data of the pipe pile, mark the excitation hammering parameters with excellent reception effect of the transmission wave signal of the pipe pile, use a recurrent neural network for model training, and construct an excitation hammering parameter prediction model. The excitation hammering parameters include hammering force, hammering times, and hammer head material. According to the pile length of the pipe pile to be inspected, determine the weld position of the pipe pile to be inspected, and obtain the transmission wave attenuation factor. Use the excitation hammering parameter prediction model to determine the excitation hammering parameters with excellent reception effect of the transmission wave signal of the pipe pile to be inspected.

[0019] Exemplarily, through data analysis, it can be known that the reception effect of the transmission wave signal of the pipe pile is closely related to the excitation hammering parameters. The excitation hammering parameters include hammering force, hammering times, and hammer head material. The pipe pile monitoring database contains the weld position and transmission wave attenuation factor data of multiple pipe piles. Through the pipe pile monitoring database, obtain different excitation hammering parameters and the corresponding reception effects of the transmission wave signals. For example, the pile length of a certain pipe pile is 30m, the welds are located at the 10m and 20m positions of the pile body, and the transmission wave attenuation factor is 0.5m -1 . Correlate the reception effects of the transmission wave signals in the historical data with the excitation hammering parameters, and mark the combination of excitation hammering parameters with excellent reception effects. For example, on this pipe pile, when the excitation hammering force is set to 1000N, the hammering times are 50 times, and the hammer head material is steel, the signal reception effect is excellent. Input these data into the recurrent neural network for training to construct an excitation hammering parameter prediction model. Through multiple trainings, the model has learned to predict new excitation hammering parameters based on the weld position, transmission wave attenuation factor of the pipe pile, and the historical data of the excitation hammering parameters. In practical applications, if another pipe pile with a length of 25m is to be inspected, and the weld positions of this pipe pile are at the 8m and 18m positions. Through measurement, the transmission wave attenuation factor of this pipe pile is obtained as 0.4m -1，Using the trained excitation hammering parameter prediction model, input the weld position and transmission wave attenuation factor of the pipe pile. The excitation hammering parameter prediction model predicts the most suitable excitation hammering parameters based on historical data as the hammering force of 900 N, the number of hammering times of 40 times, and the hammer head material being steel.

[0020] Step S103: Based on the weld position of the pipe pile under inspection, vertically arrange the hydrophones at preset positions equidistant above and below the weld, and obtain the incident wave amplitude above the weld and the transmission wave amplitude passing through the weld.

[0021] Fill the cavity of the pipe pile under inspection with water. According to the weld position of the pipe pile under inspection, adjust the lowering depth of the hydrophone, and vertically arrange the hydrophones at preset positions equidistant above and below the weld. Based on the excitation hammering parameters with excellent transmission wave signal reception effect, hammer the center of the pile top of the pipe pile under inspection, and apply a transient excitation force downward along the pile body axis. Obtain the complete time-domain velocity signal through the hydrophone above the weld, and calculate the average value of the peak amplitudes of the first waves of the velocity signals of each hydrophone as the incident wave amplitude above the weld. Obtain the complete time-domain velocity signal through the hydrophone below the weld, and calculate the average value of the peak amplitudes of the first waves of the velocity signals of each hydrophone as the transmission wave amplitude passing through the weld.

[0022] Exemplarily, it is now necessary to inspect a 25-m long pipe pile, which has 1 weld located at the 10-m position of the pile body. For the transmission wave detection, first fill the cavity of the pipe pile with water to ensure the best wave propagation effect. According to the weld position, adjust the lowering depth of the hydrophone, and vertically arrange the hydrophones at preset positions above and below the weld. To ensure signal quality, evenly place the hydrophones at the positions of 8 m, 9 m, 11 m, and 12 m, that is, set the hydrophones equidistantly above and below each weld. According to the best excitation hammering parameters obtained in previous experiments, select a hammering force of 1200 N, a number of hammering times of 60 times, and the hammer head material being steel. Apply a transient excitation force downward along the pile body axis at the center position of the pile top according to these parameters to excite the pipe pile to generate a transmission wave. After the excitation force acts, the transmission wave propagates through the pile body and reflects and transmits at the weld. In the signal acquisition stage, obtain the complete time-domain velocity signal through the hydrophone above the weld. If the peak amplitudes of the first waves of the signals collected by the hydrophones at 8 m and 9 m above the weld are both 0.5 cm / s. Then the amplitude of the incident wave above the weld is the average value of these two peak amplitudes, that is, the incident wave amplitude above the weld = 0.5 cm / s. Obtain the complete time-domain velocity signal through the hydrophone below the weld. If the peak amplitudes of the first waves of the signals collected by the hydrophones at 11 m and 12 m are 0.4 cm / s and 0.4 cm / s respectively, calculate the average value of the peak amplitudes of the first waves of the velocity signals of the hydrophones below the weld to obtain the transmission wave amplitude passing through the weld = 0.4 cm / s.

[0023] Step S104, identify the welding quality of the pipe pile joint part by calculating the ratio of the amplitude of the incident wave at the upper part of the weld seam to the amplitude of the transmitted wave passing through the weld seam.

[0024] Obtain the cross-sectional area and material density of the inspected pipe pile from the pipe pile integrity test project document, and use the pile body wave impedance calculation formula to determine the wave impedance Z of the inspected pipe pile, where is the material density of the pipe pile, c is the stress wave propagation velocity, and A is the cross-sectional area of the pipe pile. Based on the amplitude of the incident wave at the upper part of the weld seam and the amplitude of the transmitted wave passing through the weld seam, according to the formula , calculate the ratio of the two amplitudes , where is the amplitude of the incident wave at the upper part of the weld seam, is the amplitude of the transmitted wave passing through the weld seam, is the amplitude of the incident velocity of the pipe pile at the upper part of the weld seam, is the amplitude of the transmitted velocity transmitted from the weld interface to the pipe pile at the lower part of the weld seam. The wave impedances of the pipe pile at the upper part of the weld seam and the pipe pile at the lower part of the weld seam are the same, both being , is the wave impedance at the weld interface. If , it indicates that the welding quality of the pipe pile joint part is extremely high. If , it indicates that the welding quality of the pipe pile joint part is extremely poor. The remaining values indicate that the welding quality of the pipe pile joint part is average.

[0025] Exemplarily, from the pipe pile integrity test project document, the inspected pipe pile is a 30m long concrete pipe pile. The upper pipe pile L1 is 15m long, and the lower pipe pile L2 is 15m long. The cross-sectional area A = 0.1473m 2 , the material density ρ = 2.6t / m 3 , the stress wave propagation velocity c = 4200m / s, and the wave impedance of the pile body Z = ρcA = 1608kN·s / m. Based on the amplitude of the incident wave at the upper part of the weld seam and the amplitude of the transmitted wave passing through the weld seam, according to the formula , calculate the ratio of the two amplitudes . Therefore, after the first transmission, the amplitude of the transmitted velocity from the pipe pile at the upper part of the weld seam to the weld interface is , and after the second transmission, the amplitude of the transmitted velocity from the weld interface to the pipe pile at the lower part of the weld seam . At this time, , where the wave impedances of the pipe pile at the upper part of the weld seam and the pipe pile at the lower part of the weld seam are the same, both being , is the wave impedance at the weld interface, then the integrity coefficient of the stress wave transmitted from the pipe pile L1 into the welding material is , and the integrity coefficient of the stress wave transmitted from the welding material to the pipe pile L2 is When the welding quality of the pipe pile joint is extremely high, the weld can be regarded as a complete steel material, and the upper and lower pipe piles are completely connected. At this time , , when the welding quality of the pipe pile joint is extremely poor, the weld can be regarded as muddy, and the upper and lower pipe piles are completely disconnected. At this time , , and the remaining values indicate that the joint condition is between complete connection and complete disconnection, and the welding quality of the pipe pile joint is average.

[0026] Step S105: If the wave impedances of the upper and lower pipe piles of the weld are different, then based on the amplitude of the incident wave on the upper part of the weld and the amplitude of the transmitted wave passing through the weld, determine the maximum value of the total energy transmittance, and identify the welding quality of the pipe pile joint in combination with the measured energy transmittance.

[0027] If the wave impedances of the upper and lower pipe piles of the weld are different, then based on the amplitude of the incident wave on the upper part of the weld and the amplitude of the transmitted wave passing through the weld, based on the formula , calculate the ratio of the two amplitudes , where is the amplitude of the transmitted wave transmitted to the lower part of the pipe pile from the weld interface, is the wave impedance of the upper pipe pile of the weld, is the wave impedance of the welding material, is the wave impedance of the lower pipe pile of the weld. According to the three-layer medium model, obtain the total energy transmittance , take the derivative of and set the derivative to zero to determine the maximum value of the total energy transmittance . According to the amplitude of the incident wave on the upper part of the weld and the amplitude of the transmitted wave passing through the weld, use the formula to calculate the measured energy transmittance . If and have a difference of 0, it indicates that the welding quality of the pipe pile joint is extremely high. If and have a difference less than the preset difference threshold, it indicates that the welding quality of the pipe pile joint is average. If and have a difference greater than the preset difference threshold, it indicates that the welding quality of the pipe pile joint is extremely poor.

[0028] Exemplarily, if the wave impedances of the upper and lower pipe piles of the weld are different, where the length of the upper pipe pile L3 is 15 m, the cross-sectional area is 0.1473 m 2 , the material density is 2.6 t / m 3 , and the stress wave velocity is 4200 m / s. The length of the lower pipe pile L4 is 15 m, and the cross-sectional area is 0.1100 m 2, the material density is 2.6 t / m 3 , and the stress wave velocity is 4200 m / s. Calculate the wave impedance according to the material parameters. The wave impedance of the upper pipe pile is 1601.58 kN·s / m, and the wave impedance of the lower pipe pile is 1200.72 kN·s / m. Based on the formula , calculate the ratio of the two amplitudes . The incident wave When transmitting from the upper pipe pile to the weld, there is a transmitted velocity amplitude from the upper pipe pile of the weld to the weld interface . When transmitting from the weld to the lower pipe pile, there is a transmitted wave amplitude from the weld interface to the lower part of the pipe pile , so the total transmission ratio is , where is the wave impedance of the upper pipe pile of the weld is the wave impedance of the welding material is the wave impedance of the lower pipe pile of the weld, and the impedance ratio , . According to the three-layer medium model, the total energy transmittance . To maximize , it is necessary to take the derivative of and set the derivative to zero to obtain that when , the total energy transmittance is the largest, and determine the maximum value of the total energy transmittance . If the measured upper weld velocity amplitude by the hydrophone is , and the measured lower weld velocity amplitude is , use the formula to calculate the measured energy transmittance . is 0.31 is 0.96 The difference between is 0.65, which is greater than the preset difference threshold of 0.1, indicating that the welding quality of the pipe pile joint is extremely poor. If the difference between and measured for another pipe pile is 0.05, which is less than the preset difference threshold of 0.1, it indicates that the welding quality of the pipe pile joint is average. If the difference between and measured for another pipe pile is 0, it indicates that the welding quality of the pipe pile joint is extremely high.

[0029] Step S106, extract the spectral characteristics of the velocity signal from the complete time-domain velocity signal of the pipe pile joint with average welding quality, construct a pipe pile welding defect type recognition model, and identify the pipe pile welding defect type.

[0030] Through the hydrophone above the weld, a complete time-domain velocity signal of average welding quality at the joint of the pipe pile is obtained. The short-time Fourier transform algorithm is used to convert the time-domain signal of the velocity signal into frequency-domain data, extract the spectral characteristics of the velocity signal, and save them to the pipe pile monitoring database. The spectral characteristics include frequency, frequency peak, and amplitude. Through the pipe pile monitoring database, the historical spectral characteristics of the pipe pile are obtained, and the types of welding defects of the pipe pile are marked. A recurrent neural network is used for model training to construct a pipe pile welding defect type recognition model. The types of welding defects of the pipe pile include, but are not limited to, weld cracks, uneven welds, pores, or slag inclusions. According to the spectral characteristics of the pipe pile obtained in real time, the pipe pile welding defect type recognition model is used to identify the types of welding defects of the pipe pile.

[0031] Exemplarily, the welding quality of the joint of a pipe pile is detected. The weld quality of this pipe pile is average. After detection, the hydrophone is placed above the weld, and a complete time-domain velocity signal is successfully obtained. These signals reflect the wave propagation characteristics of the welding part. The short-time Fourier transform algorithm is used to convert these time-domain signals into frequency-domain data, and the spectral characteristics are extracted. The main characteristics extracted from the spectrum include a frequency of 500 Hz, a frequency peak of 520 Hz, and an amplitude of 0.8 m / s. These spectral characteristics are saved to the monitoring database of the pipe pile. The database stores the spectral characteristics of previous pipe piles, and the types of welding defects of each pipe pile are also marked in the database. The types of welding defects of the pipe pile include weld cracks, uneven welds, pores, or slag inclusions, etc. Through the pipe pile monitoring database, the historical spectral characteristics of the pipe pile are obtained, and the types of welding defects of the pipe pile are marked. A recurrent neural network is used to train the types of welding defects of the pipe pile to construct a pipe pile welding defect type recognition model. After training, the pipe pile welding defect type recognition model can automatically identify the types of welding defects of the pipe pile according to the spectral characteristics obtained in real time. For example, when we conduct real-time detection on the welding part of the pipe pile on-site, new spectral characteristics are obtained again through the hydrophone. The frequency of the real-time signal is 505 Hz, the frequency peak is 515 Hz, and the amplitude is 0.75 m / s. These data are input into the pipe pile welding defect type recognition model, and it is identified that the type of welding defect of this pipe pile is uneven weld.

[0032] Step S107, determine the management measures for the joint of the pipe pile according to the judgment result of the welding quality of the joint of the pipe pile.

[0033] Based on the judgment result of the welding quality of the pipe pile splicing part, combined with the pipe pile splicing part, determine the management measures for the pipe pile splicing part. If the welding quality of the pipe pile splicing part is extremely high, regularly monitor the welding quality of the pipe pile splicing part according to the preset time interval. If the welding quality of the pipe pile splicing part is average, perform local repair in the weld area according to the type of welding defect of the pipe pile, including but not limited to repairing the local area by welding, grinding or cleaning. If the welding quality of the pipe pile splicing part is extremely poor, take pipe pile repair measures to repair the pipe pile, and conduct welding quality inspection on the pipe pile splicing part again after the pipe pile repair until the quality of the splicing part meets the standard requirements. The pipe pile repair measures include re-welding, reinforcement or replacement of damaged parts.

[0034] Exemplarily, conduct a welding quality assessment on the splicing part of a pipe pile. The length of the pipe pile is 30 meters, and the welding positions are at the 10th meter and the 20th meter of the pile body. According to the previous inspection results, the welding quality is rated as average, and slight non-uniformity is found in the welding area through spectral analysis. In this case, the management measures for the splicing part of the pipe pile will be adjusted according to the specific type of welding defect. Given that the welding quality is rated as average and the phenomenon of welding non-uniformity is found through spectral feature analysis, manifested as slight fluctuations in the frequency peak and amplitude. For this situation, perform local repair in the weld area. The repair work includes repairing the weld area by welding, especially at the welding positions of the 10th meter and the 20th meter, to ensure the uniformity and integrity of the weld. In addition, the local area needs to be ground to smooth the welding surface and clean the pores and impurities that may be generated during the welding process, thereby improving the welding quality. If the welding quality of the splicing part of the pipe pile is rated as extremely high, conduct regular monitoring according to the preset time interval, which may mean checking the splicing part of the pipe pile once a month or every half month to monitor whether any new cracks or welding non-uniformity occur. In the case of extremely poor welding quality, more severe repair measures need to be taken for the pipe pile. If a certain inspection shows that the welding quality is very poor, resulting in the strength of the splicing part being far lower than the standard requirements, we will conduct large-scale repair on the pipe pile. This may include completely re-welding the splicing part, or re-welding, reinforcing or replacing the damaged parts in the damaged area. After the repair, conduct detailed welding quality inspection again to ensure that the splicing part of the repaired pipe pile meets the standard and can be used normally.

[0035] The above description is only a preferred embodiment of the present application and an explanation of the applied technical principles. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by the specific combination of the above technical features, and should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the concept of the present application. For example, the technical solutions formed by mutually replacing the above features with the (but not limited to) technical features with similar functions disclosed in the present application.

Claims

1. A method for detecting the integrity of pipe piles based on low-strain transmission waves, characterized in that, The method includes: Calculating and determining the pile - soil stiffness ratio according to the cross - sectional area and length of the pile to be inspected, and determining the transmission wave attenuation factor of the pile to be detected; Constructing a prediction model for the exciting hammering parameters based on the weld position of the pile and the transmission wave attenuation factor data, and determining the exciting hammering parameters with excellent receiving effect of the transmission wave signal of the pile to be inspected; Based on the weld position of the pile to be inspected, arranging hydrophones vertically at preset positions with equal spacing above and below the weld, and obtaining the incident wave amplitude above the weld and the transmission wave amplitude passing through the weld; Identifying the welding quality of the pile splicing part by calculating the ratio of the incident wave amplitude above the weld and the transmission wave amplitude passing through the weld; If the wave impedances of the pile above the weld and the pile below the weld are different, then determining the maximum value of the total energy transmittance according to the incident wave amplitude above the weld and the transmission wave amplitude passing through the weld, and identifying the welding quality of the pile splicing part by combining the measured energy transmittance; Extracting the spectral characteristics of the velocity signal from the complete time - domain velocity signal with general welding quality at the pile splicing part of the pile, constructing a recognition model for the type of pile welding defect, and identifying the type of pile welding defect; Determining the management measures for the pile splicing part according to the judgment result of the welding quality of the pile splicing part.

2. The method according to claim 1, wherein The calculating and determining the pile - soil stiffness ratio according to the cross - sectional area and length of the pile to be inspected, and determining the transmission wave attenuation factor of the pile to be detected includes: Obtain the cross-sectional area and length of the inspected pipe pile through the project documents of the pipe pile integrity test, and use the pipe pile stiffness formula to determine the pipe pile stiffness , where is the elastic modulus of the pile material, A is the cross-sectional area of the pipe pile, and L is the length of the pipe pile; obtain the elastic modulus of the soil around the pile according to the geological exploration data, and use the soil stiffness formula to determine the soil stiffness , where is the elastic modulus of the soil is the stress area of the soil layer around the pile, equal to the contact area of the soil around the pile is the effective length of the soil, equal to the depth of the pile or the depth of the pile in contact with the soil layer; determine the pile-soil stiffness ratio according to the pipe pile stiffness and the soil stiffness ; according to the pile-soil stiffness ratio, use the transmission wave attenuation factor formula to determine the transmission wave attenuation factor of the pipe pile to be detected, and store the transmission wave attenuation factor of the pipe pile in the pipe pile monitoring database, where is a constant related to the soil type and wave propagation characteristics, obtained through experiments or numerical simulations, and n is the interaction coefficient, a constant used to describe the interaction strength between the pile and the soil, obtained through experiments or numerical simulations 3. The method according to claim 1, wherein, The constructing a prediction model for the exciting hammering parameters based on the weld position of the pile and the transmission wave attenuation factor data, and determining the exciting hammering parameters with excellent receiving effect of the transmission wave signal of the pile to be inspected includes: Obtaining historical pile weld position and transmission wave attenuation factor data through the pile monitoring database, marking the exciting hammering parameters with excellent receiving effect of the pile transmission wave signal, using a recurrent neural network for model training to construct a prediction model for the exciting hammering parameters. The exciting hammering parameters include hammering force, number of hammering times, and hammer head material; determining the weld position of the pile to be inspected according to the pile length of the pile to be inspected, obtaining the transmission wave attenuation factor, and using the prediction model for the exciting hammering parameters to determine the exciting hammering parameters with excellent receiving effect of the transmission wave signal of the pile to be inspected.

4. The method according to claim 1, wherein The arranging hydrophones vertically at preset positions with equal spacing above and below the weld based on the weld position of the pile to be inspected, and obtaining the incident wave amplitude above the weld and the transmission wave amplitude passing through the weld includes: Filling the cavity of the pile to be inspected with water, adjusting the lowering depth of the hydrophone according to the weld position of the pile to be inspected, and arranging the hydrophones vertically at preset positions with equal spacing above and below the weld; based on the exciting hammering parameters with excellent receiving effect of the transmission wave signal, hammering the center of the pile top of the pile to be inspected to apply a transient exciting force downward along the pile axis; obtaining the complete time - domain velocity signal through the hydrophone above the weld, and calculating the average value of the peak amplitudes of the first waves of the velocity signals of each hydrophone as the incident wave amplitude above the weld; obtaining the complete time - domain velocity signal through the hydrophone below the weld, and calculating the average value of the peak amplitudes of the first waves of the velocity signals of each hydrophone as the transmission wave amplitude passing through the weld.

5. The method according to claim 1, wherein, The identifying the welding quality of the pile splicing part by calculating the ratio of the incident wave amplitude above the weld and the transmission wave amplitude passing through the weld includes: Obtain the cross-sectional area and material density of the inspected pipe pile through the pipe pile integrity test project documents, and use the pile body wave impedance calculation formula to determine the pile body wave impedance Z of the inspected pipe pile, where is the material density of the pipe pile, c is the stress wave propagation velocity, and A is the cross-sectional area of the pipe pile; based on the amplitude of the incident wave above the weld and the amplitude of the transmitted wave passing through the weld, according to the formula , calculate the ratio of the two amplitudes , where is the amplitude of the incident wave above the weld, is the amplitude of the transmitted wave passing through the weld, is the amplitude of the incident velocity of the pipe pile above the weld, is the amplitude of the transmitted velocity transmitted from the weld interface to the pipe pile below the weld. The wave impedances of the pipe pile above the weld and the pipe pile below the weld are the same, both being , is the wave impedance at the weld interface; if , it indicates that the welding quality of the pipe pile joint is extremely high. If , it indicates that the welding quality of the pipe pile joint is extremely poor. The remaining values indicate that the welding quality of the pipe pile joint is average.

6. The method according to claim 1, wherein, If the wave impedances of the upper and lower pipe piles at the weld are different, the maximum value of the total energy transmittance is determined based on the amplitude of the incident wave at the upper part of the weld and the amplitude of the transmitted wave passing through the weld, and the welding quality of the pipe pile joint is identified by combining the measured energy transmittance, including: If the wave impedances of the pile above the weld and the pile below the weld are different, then based on the amplitude of the incident wave above the weld and the amplitude of the transmitted wave passing through the weld, according to the formula , calculate the ratio of the two amplitudes , where is the amplitude of the transmitted wave transmitted to the lower part of the pile from the weld interface, is the wave impedance of the pile above the weld, is the wave impedance of the welding material, is the wave impedance of the pile below the weld; according to the three-layer medium model, obtain the total energy transmittance , take the derivative of and set the derivative to zero to determine the maximum value of the total energy transmittance ; based on the amplitude of the incident wave above the weld and the amplitude of the transmitted wave passing through the weld, use the formula to calculate the measured energy transmittance ; if and have a difference of 0, it means that the welding quality of the pile splicing part is extremely high. If and have a difference less than the preset difference threshold, it means that the welding quality of the pile splicing part is average. If and have a difference greater than the preset difference threshold, it means that the welding quality of the pile splicing part is extremely poor.

7. The method according to claim 1, wherein The spectral characteristics of the velocity signal are extracted from the complete time-domain velocity signal with general welding quality at the pipe pile joint, and a recognition model for the types of pipe pile welding defects is constructed to identify the types of pipe pile welding defects, including: The complete time-domain velocity signal with general welding quality at the pipe pile joint is obtained through the hydrophone at the upper part of the weld. The time-domain signal of the velocity signal is converted into frequency-domain data using the short-time Fourier transform algorithm, the spectral characteristics of the velocity signal are extracted and saved in the pipe pile monitoring database. The spectral characteristics include frequency, frequency peak, and amplitude. The historical spectral characteristics of the pipe pile are obtained from the pipe pile monitoring database, and the types of pipe pile welding defects are marked. The cyclic neural network is used for model training to construct a recognition model for the types of pipe pile welding defects. The types of pipe pile welding defects include weld cracks, uneven welds, pores, or slag inclusions. The types of pipe pile welding defects are identified using the recognition model for the types of pipe pile welding defects based on the real-time obtained spectral characteristics of the pipe pile.

8. The method according to claim 1, wherein, The management measures for the pipe pile joint are determined according to the judgment result of the welding quality of the pipe pile joint, including: The management measures for the pipe pile joint are determined by combining the judgment result of the welding quality of the pipe pile joint with the pipe pile joint. If the welding quality of the pipe pile joint is extremely high, the welding quality of the pipe pile joint is regularly monitored at preset time intervals. If the welding quality of the pipe pile joint is general, local repair is carried out in the weld area according to the type of pipe pile welding defect, including repairing, grinding, or cleaning the local area by welding. If the welding quality of the pipe pile joint is extremely poor, pipe pile repair measures are taken for pipe pile repair, and the welding quality of the pipe pile joint is detected again after the pipe pile repair until the quality of the joint meets the standard requirements. The pipe pile repair measures include re-welding, reinforcement, or replacement of the damaged part.

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