A system and method for pile foundation quality detection

Abstract

The application discloses a system and method for pile foundation quality detection, and relates to the technical field of pile foundation quality detection, and solves the problems of difficulty in determining the optimal excitation energy range, deviation of damage quantization criteria, and low reliability of detection results, wherein the application randomly distributes excitation pulses with different energies to different excitation areas, ensures that each energy is excited only once in one area and the same area is not continuously used, combines with environment monitoring and correction during resetting, effectively eliminates the cumulative effect of previous excitation and environmental interference, obtains pure damage increment data, identifies the inflection point of the damage increment-energy curve, takes the inflection point energy as the critical excitation energy of the depth, takes the minimum value and the maximum value of all depths to form an adaptive detection energy window, and fundamentally solves the technical problems of difficulty in determining the excitation energy range and contradiction between detection results of the same pile under different energies.

Description

Technical Field

[0001] This invention relates to the field of pile foundation quality testing technology, specifically to a system and method for pile foundation quality testing. Background Technology

[0002] As a crucial foundation type in building engineering, the quality of pile foundations directly affects the safety of the superstructure. Currently, commonly used pile foundation testing methods in engineering include the low-strain reflected wave method and the acoustic transmission method. The low-strain reflected wave method applies a transient impact force to the pile top, generating a stress wave that propagates downwards along the pile. When it encounters an interface with varying pile impedance, a reflected wave is generated. By analyzing the arrival time and amplitude characteristics of the reflected wave, the location and extent of pile defects can be determined. This method has the advantages of lightweight equipment, fast testing speed, and low cost, and has been widely used in engineering.

[0003] However, real concrete exhibits nonlinear characteristics such as microcracks and segregation zones. Defects do not open under low-energy excitation, but only produce identifiable reflections under high-energy excitation. This lack of a method for selecting the optimal excitation energy threshold for different pile diameters and lengths leads to inconsistencies in test results for the same pile under different energies, making it impossible to determine the cause. Existing methods rely on a shallow, intact section as a near-zero damage benchmark, using a universal coefficient to calculate the damage degree. However, the shallow section may contain unknown minor damage, causing benchmark deviation. Furthermore, the discreteness of concrete makes the universal coefficient inconsistent with reality. This benchmark uncertainty is transmitted to the damage increment calculation, causing the energy inflection point identification to deviate. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a system and method for pile foundation quality testing, which solves the problems of difficulty in determining the optimal excitation energy range and deviations in damage quantification benchmarks, leading to low reliability of test results.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for pile foundation quality testing, comprising the following steps: Multiple rings of sensors are deployed along the depth direction of the pile. The middle part of the pile is regarded as the reference section. The tail wave travel time offset τ and the temperature T at each moment of the reference section are obtained to form a linear relationship between temperature and travel time offset, which serves as the environmental drift correction benchmark. The pile top is divided into multiple excitation zones. According to the preset incremental energy sequence, excitation pulses of different energies are applied to different excitation zones in sequence. The tail wave signal is collected before and after each excitation. The high-frequency energy attenuation rate is obtained and converted into damage degree. The influence of environmental drift is deducted according to the environmental drift correction benchmark, and the pure damage increment generated at each depth by each excitation is calculated. For each depth, a damage increment-energy curve is constructed with excitation energy as the x-axis and the corresponding pure damage increment as the y-axis. Identify the inflection point in each curve where the damage increment changes from a slow linear growth to a rapid nonlinear growth with energy, and take the energy corresponding to the inflection point as the critical excitation energy for that depth. The minimum value of the critical excitation energy at all depths is taken as the upper limit of safe detection, and the maximum value is taken as the minimum excitation energy to cover all pile defects, thereby determining the detection energy window applicable to this pile foundation.

[0006] As a further aspect of the present invention, the environmental drift correction benchmark is established in the following manner: A reference section is selected in the middle of the pile body, and fiber optic sensors and temperature sensors corresponding to the excitation area are installed along this section. Acquire tailwave signals and temperature data during stable periods where temperature fluctuations do not exceed a preset threshold within a continuous time period; Using the initial tailwave waveform as a reference template, the tailwave travel time offset τ at each time point relative to the initial time point is calculated through sliding cross-correlation. The data points are combined with the temperature T at the corresponding time. The temperature-time sensitivity coefficient b is calculated by linear regression, and then the linear relationship τ=b×(T-T0) is obtained, where T0 is the reference temperature when τ=0, which is used as the environmental drift correction benchmark.

[0007] As a further aspect of the present invention: before the excitation according to the preset incremental energy sequence, a preliminary damage detection step is also included: Excite any excitation region with weak pulse energy, and collect the high-frequency energy attenuation rate a(z,θ) at various depths and directions; A healthy benchmark zone is determined in the shallow part of the pile body, and the arithmetic mean of the high-frequency energy attenuation rate in three directions of this zone is calculated as the preliminary benchmark attenuation rate a0. Based on the preliminary baseline attenuation rate a0 and the concrete calibration coefficient k, the preliminary damage degree D0(z) = (a(z) - a0) / k at each depth is calculated, where a(z) is the average value of a(z,θ) in three directions, and directional defects are identified based on the difference in attenuation rate in each direction.

[0008] As a further aspect of the present invention: the step of applying excitation pulses of different energies sequentially to different excitation regions according to a preset increasing energy sequence includes: Using the initial energy Ea and the final energy Eb, generate an N-level increasing energy sequence {E1, E2, ..., EN} with a step size ΔE; The energy sequence is randomly assigned to regions A, B, and C. During the assignment, it is ensured that each energy value is excited only once in one region, and there is at least a gap of M energy levels between two adjacent excitations in the same region, and excitation commands are not received continuously, where M is N divided by 3 and rounded up. Excitation operations are performed on each group of energy and region in a randomly assigned order.

[0009] As a further aspect of the present invention: the wake signal is acquired before and after each excitation, the high-frequency energy attenuation rate is obtained and converted into damage degree, and the environmental drift effect is subtracted according to the environmental drift correction benchmark to calculate the pure damage increment generated at each depth for each excitation, including: Before excitation, the wake signal is collected by the sensor in the corresponding area to obtain the high-frequency energy attenuation rate at each depth and convert it into the original damage degree Dbr before excitation. At the same time, the wake travel time offset and temperature of the reference section are recorded, and the environmental equivalent damage change ΔDb before excitation is calculated using the environmental drift correction benchmark. The energy Ei is set to excite the center of the corresponding region; After excitation and reset, record the wake travel time offset and temperature of the reference section again, and calculate the equivalent environmental damage change ΔDa after excitation. After excitation, the wake signal is collected again to obtain the original damage level Dar after excitation; By correcting for environmental drift, we obtain the true damage degree before excitation Db=Dbr-ΔDb and the true damage degree after excitation Da=Dar-ΔDa, and then obtain the pure damage increment ΔD=Da-Db. If the difference in environmental equivalent damage or the rate of temperature change exceeds a preset threshold, the data is deemed invalid and a retest is required.

[0010] As a further aspect of the present invention: after constructing the damage increment-energy curve, a zero-damage baseline decay calibration step is also included. For each depth, take three consecutive energy points forward from the maximum energy as a group, calculate the average growth rate of damage increment for each group, and when the growth rate of a group is less than or equal to the preset proportion of the average growth rate of the initial segment, the interval where the group is located is determined to be a saturation zone, and the average value of the damage increment in the interval is taken as the saturation damage increment ΔDs for that depth. Using the measured high-frequency energy attenuation rate αpost corresponding to each energy point in the saturation zone, combined with the saturation damage increment ΔDs and the initial damage degree D0, the zero-damage benchmark attenuation rate αcal=αpost- k×(D0+ΔDs) at each depth and in each direction at each saturation energy point is inferred, where k is the linear proportionality coefficient between the high-frequency attenuation and the damage degree of concrete. Outlier values ​​were removed from the sample set consisting of all αcal values ​​by interquartile range, and the median of the remaining samples was taken as the final calibrated zero-damage baseline decay rate aF.

[0011] As a further aspect of the present invention: based on the calibrated zero-damage reference attenuation rate aF, the damage degree Dc(z)=(a(z)-aF) / k at each depth and in each direction, and the damage increment ΔDc(z,Ei)= (αpost(z,θ,Ei)-aF) / k - Dc(z) under each excitation energy are recalculated, and the damage increment-energy curve for each depth is redrawn.

[0012] As a further aspect of the present invention: the inflection point at which the damage increment in each curve changes from a slow linear increase to a rapid nonlinear increase with energy includes: The energy points are arranged in ascending order, and the average slope of the damage increment within each window is calculated using a sliding window. The average slope of the first few windows is taken as the reference slope s0 of the linear segment. Starting from the fourth window, the slope of the current window is compared with s0. When the slope of the current window is greater than or equal to the preset multiple s0 and the subsequent two consecutive windows also meet the condition, the energy corresponding to the starting point of the current window is determined to be the critical excitation energy at that depth.

[0013] As a further aspect of the present invention: for the depth where the directional defect exists, damage increment-energy curves are constructed for each direction and the critical excitation energy of each direction is identified. The minimum value of the critical energy of all depths and all directions is taken as the upper limit of safe detection, and the maximum value is taken as the minimum excitation energy covering the entire pile defect, thereby determining the detection energy window.

[0014] Systems for pile foundation quality testing include: The sensor module outputs data monitored by each sensor; The environmental correction module is used to acquire the wake travel time offset and temperature data of the reference section, and establish a linear relationship between temperature and travel time offset as a benchmark for environmental drift correction. The vibration control module is used to divide the pile top into multiple vibration zones and control the vibrator to apply vibration pulses of different energies to different vibration zones in sequence according to a preset incremental energy sequence. The signal acquisition and processing module is used to acquire the wake signal before and after each excitation, obtain the high-frequency energy attenuation rate and convert it into damage degree, and calculate the pure damage increment generated at each depth for each excitation by deducting the environmental drift effect according to the environmental drift correction benchmark. The data analysis module is used to construct a damage increment-energy curve for each depth, with the excitation energy as the x-axis and the corresponding pure damage increment as the y-axis, and to identify the inflection point of each curve, and take the energy corresponding to the inflection point as the critical excitation energy for that depth. The detection window determination module is used to take the minimum value of the critical excitation energy of all depths as the upper limit of safe detection, and take the maximum value as the minimum excitation energy to cover all pile defects, thereby determining the detection energy window applicable to the pile foundation.

[0015] This invention provides a system and method for pile foundation quality testing. Compared with the prior art, it has the following advantages: (1) This invention randomly assigns excitation pulses of different energies to different excitation regions, ensuring that each energy is used only once in one region and is not used continuously in the same region. Combined with environmental monitoring and correction during the reset period, it effectively eliminates the cumulative effect of previous excitation and environmental interference, obtains pure damage increment data, identifies the inflection point of the damage increment-energy curve, takes the inflection point energy as the critical excitation energy at that depth, and takes the minimum and maximum values ​​of all depths to form an adaptive detection energy window. This fundamentally solves the technical problem that the range of excitation energy is difficult to determine and the test results of the same pile under different energies cannot be determined. (2) This invention establishes an environmental drift correction benchmark by referencing a section, which can monitor and deduct the tail wave travel time offset caused by factors such as temperature in real time, eliminate the influence of environmental interference on detection accuracy, and use the high-energy section damage increment saturation characteristics to back-calculate the zero damage benchmark attenuation rate, thereby realizing the self-calibration of the damage benchmark, eliminating the influence of shallow benchmark deviation and concrete material discreteness on damage quantification, and significantly improving the accuracy of damage degree calculation. (3) This invention obtains the preliminary damage distribution by self-referenced wake wave scanning, identifies directional defects and calculates the damage degree in each direction, and presents the spatial distribution characteristics of pile damage in the final health map, providing a precise positioning basis for subsequent reinforcement treatment. At the same time, the damage degree at each depth is recalculated based on the calibrated benchmark, and the difference before and after calibration is added as an uncertainty band, so that the test results have traceability and reliability evaluation indicators, and comprehensively improve the application value of the test results. Attached Figure Description

[0016] Figure 1 This is a diagram illustrating the method steps of the present invention; Figure 2 This is a system flowchart of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1 Please see Figure 1 This application provides a method for pile foundation quality testing, comprising the following steps: Multiple rings of sensors are deployed along the depth direction of the pile. The middle part of the pile is regarded as the reference section. The tail wave travel time offset τ and the temperature T at each moment of the reference section are obtained to form a linear relationship between temperature and travel time offset, which serves as the environmental drift correction benchmark. The pile top is divided into multiple excitation zones. According to the preset incremental energy sequence, excitation pulses of different energies are applied to different excitation zones in sequence. The tail wave signal is collected before and after each excitation. The high-frequency energy attenuation rate is obtained and converted into damage degree. The influence of environmental drift is deducted according to the environmental drift correction benchmark, and the pure damage increment generated at each depth by each excitation is calculated. For each depth, a damage increment-energy curve is constructed with excitation energy as the x-axis and the corresponding pure damage increment as the y-axis. Identify the inflection point in each curve where the damage increment changes from a slow linear growth to a rapid nonlinear growth with energy, and take the energy corresponding to the inflection point as the critical excitation energy for that depth. The minimum value of the critical excitation energy at all depths is taken as the upper limit of safe detection, and the maximum value is taken as the minimum excitation energy to cover all pile defects, thereby determining the detection energy window applicable to this pile foundation.

[0019] Example 2 Furthermore, based on Example 1, a method for pile foundation quality testing is described in more detail, specifically including the following steps: Step 1: Obtain the effective length L of the pile body to be inspected, and determine the inspection positions along the depth direction according to the preset inspection interval d (e.g., d=1 meter). Where m is the total number of cross sections, and Not exceeding the pile length; At each depth location, three fiber optic sensors are evenly distributed along the outer perimeter of the pile. The pile top plane is divided into three independent excitation regions with the geometric center of the pile top as the origin. These regions are labeled as region A, region B and region C, respectively. Each excitation region corresponds to a fiber optic sensor at a depth position Di. At the location of stress concentration zone Z=L / 2 in the middle of the pile, a complete section of length Lr is cut out as a reference section, and three independent fiber optic sensors and temperature sensors corresponding to the three regions are set along the reference section. Acquire the wake signal and temperature data continuously collected by the fiber optic sensor during the stable period when the temperature fluctuation does not exceed the preset threshold △T within the continuous time period of the reference section; The acquired wake signals are sorted according to time series, the wake signal waveform at each moment is extracted, the waveform at the initial moment is used as a reference template, the waveform at the current moment is slid along the time axis, the correlation coefficients of the two at different time offsets are calculated, and the cross-correlation function curve is obtained. Extract the peak position of the cross-correlation function curve. The time offset corresponding to the peak is the tail wave travel time offset τ at that moment relative to the initial moment. Repeat the above calculation for each moment in the stable period to obtain a series of tail wave travel time offsets τ at each moment. The wake travel offset τ at each moment is combined with the temperature T collected by the temperature sensor at that moment to form a (T,τ) data point set. The temperature-travel sensitivity coefficient b is then calculated using the formula: ; in For the i-th temperature data, For the i-th travel time offset data, This is the average of all temperature data. The average value of all travel offset data is given by N, where N is the total number of data points. Based on the temperature-time sensitivity coefficient b, a linear relationship τ=b×(T-T0) is established between temperature and time travel offset, where T0 is the temperature value corresponding to τ=0, i.e., the reference temperature. This relationship is used as the environmental drift correction benchmark, and is used in subsequent detection to calculate the tail wave time travel offset caused by environmental factors based on the measured temperature, and then deduct the influence of environmental drift from the measured data.

[0020] Step Two: The electromagnetic vibrator is placed at the center of any excitation area on the top of the pile, and a weak pulse with energy E0 is used to synchronously acquire the tail wave signal with a sampling frequency of fs and a duration of Tw after excitation. For each depth z and azimuth θ of the wake signal, the high-frequency energy attenuation a(z,θ) is obtained by analyzing the attenuation law of the signal value in the high-frequency band [f1,f2] of the analyzer over time. Within the shallow depth range [z1, z2] of the pile body, calculate the average value μ of all measuring points a (z, θ), and select continuous segments where a in all three directions is less than μ and the relative difference between them does not exceed the threshold θth. Take the longest segment as the healthy reference zone, and take the arithmetic mean of a in the three directions of the segment as the preliminary reference attenuation rate a0. For each depth, take the average value a(z) of the three orientations 'a', and substitute it into the formula: D0(z)=(a(z)-a0) / k, where k is the concrete calibration ratio coefficient, to obtain the degree of non-damage D0(z). At the same time, calculate the difference Δa(z) between the maximum and minimum values ​​of 'a' in the three orientations. If Δa(z) exceeds the percentage dth of the minimum value of 'a', then determine that there is a directional defect at that depth, and calculate the degree of damage D0(z,θ) in each orientation respectively. The average damage degree at each depth z and the damage degree in each direction are integrated to form a preliminary three-dimensional damage map, which serves as the initial state data for subsequent graded excitation.

[0021] Step 3: Based on the preliminary loss distribution results and combined with the mechanical parameters of the pile concrete, the weak pulse energy E0 is used as the starting energy Ea, and the preset termination energy Eb is used as the maximum excitation energy. An N-level incremental energy sequence {E1,E2,...,EN} is generated according to the step size ΔE, where E1=Ea, EN=Eb, and adjacent energies satisfy Ei+1=Ei+ΔE. Randomly assign N energy values ​​to regions A, B, and C, ensuring the following during assignment: Each energy value is excited only once in one excitation region; There must be at least M energy levels between two adjacent excitations in the same excitation region, where M = ceil(N / 3), which is the value of N divided by 3 and rounded up. Excitation commands are not received continuously within the same excitation region; A random permutation generator generates a region allocation sequence of length N, with elements taken from {A,B,C} and no consecutive identical letters. This sequence is then matched sequentially with the energy sequence {E1,E2,...,EN} to form an excitation combination of (Ei,Ri), where Ri is the excitation region corresponding to the i-th energy level. Then, perform the following operations on each group (Ei, Ri) in sequence according to the excitation combination: S1: Before excitation, a wake wave scan is performed using sensors in the Ri region. The high-frequency energy attenuation rate at each depth under the current state is obtained using the signal processing method in step two. Substituting the initial reference attenuation rate a0 and the proportional coefficient k, the original damage degree Dbr(z, Ri) before excitation at each depth is calculated, and the wake wave travel time offset energy of the reference section is extracted. The theoretical offset τcal=b×(Tb-T0) is calculated by calling the linear relationship between temperature and travel time offset in step one, and the equivalent damage change of the environment before excitation ΔDb=(τb-τcal) / γ is calculated by using the preset conversion factor γ. S2: Adjust the exciter to energy Ei, apply a single pulse at the excitation point in the center of the Ri region, and keep the excitation point position and exciter contact conditions constant during the excitation process. The waiting time after excitation is the reset time of treset. During this time, the reference section is monitored at frequency Fm. After the reset is completed, the wake travel time offset τa and temperature Ta are read. The theoretical offset tacal=b×(Ta-T0) and the environmental equivalent damage change △Da=(τa-tacal) / γ are calculated. S4: Immediately after reset, perform another wake wave scan on the Ri region, calculate the original damage degree Dar(z,Ri) after excitation, and record the measured high-frequency attenuation rate αpost(z,θ,Ei). S5: Correction for environmental drift: True damage before excitation Db=Dbr-△Db, True damage after excitation Da=Dar-△Da; S6: Calculate the pure damage increment ΔD(z,Ri,Ei)=Da-Db; S7: If |△Da-△Db| exceeds the threshold or the temperature change rate vtemp exceeds the threshold vth, then the data for this level is invalid and subsequent random retests will be conducted. After all excitations are completed, a clean damage increment dataset {(Ei,△D(z))} sorted by energy is generated for each depth z.

[0022] Step Four: For each depth z, a scatter plot is drawn with excitation energy E as the x-axis and pure damage increment ΔD as the y-axis. The plot is then smoothed using cubic spline interpolation to obtain the preliminary ΔDE curve. Starting from the maximum energy EN, take three consecutive energy points in the forward region as a group, and calculate the average growth rate r of ΔD for each group = (ΔDi + 2 - ΔDi) / (Ei + 2 - Ei). At the same time, calculate the average growth rate r0 of the first three energy points at the starting end. If r ≤ H × r0 (H is a preset proportional threshold) for a certain group, then the interval where the group is located is the saturation region. Take the average value of all ΔD in the interval as the saturation damage increment ΔDs(z) at that depth. For each energy point Es in the saturation zone, the corresponding measured high-frequency attenuation rate αpost(z, θ, Es) is extracted, and the total saturation damage degree at that depth is calculated as Dt(z) = D0(z) + ΔDs(z). The zero-damage benchmark attenuation rate αcal(z, θ, Es) = αpost(z, θ, Es) - k × Dt(z) is back-calculated, where k is the linear proportionality coefficient between the high-frequency attenuation of concrete and the damage degree. The αcal values ​​back-calculated from all depths, orientations, and saturation energy points of the entire pile are used to form a sample set. Calculate the first quartile Q1, the third quartile Q3, and the interquartile range IQR = Q3 - Q1 of the sample. Remove values ​​exceeding [Q1 - 3IQR, Q3 + 3IQR]. The median of the remaining samples is the final calibrated zero-damage baseline attenuation rate aF.

[0023] Step 5: Replace a0 with aF and recalculate the damage degree after calibration at each depth of the entire pile: Dc(z)=(a(z)-aF) / k. For depths with directional defects, recalculate the damage degree Dc(z,θ) in each direction using the new benchmark. For each excitation energy Ei, the damage degree after excitation is recalculated using aF: Dcafter(z,Ei)=(αpost(z,θ,Ei)-aF) / k, and then the damage increment after calibration △Dc(z,Ei)=Dcafter-Dc(z) is obtained. With energy E as the abscissa and ΔDc as the ordinate, the calibrated ΔDE curve for each depth z is plotted again. For the calibrated ΔDE curve at each depth z, the energy points are arranged in ascending order. The sliding window width is w=3. Starting from the smallest energy point, the window is slid sequentially. The average slope of ΔD in each window is calculated as sj=[ΔDc(Ej+2)-ΔDc(Ej)] / (Ej+2-Ej). The average slope of the first 3 windows is taken as the reference slope s0 of the linear segment. Starting from the fourth window, sj and s0 are compared sequentially. When sj≥P×s0 (P is a preset multiple) and the following two consecutive windows also satisfy this condition, the starting point Ej of the current window is determined to be the inflection point of the curve. This energy is the street excitation energy Ec(z) at this depth. For the depth of the directional defect, the above process is repeated for the curves in each direction to obtain the street energy Ec(z,θ) in each direction. The critical energy Ec of all depths and directions of the entire pile is extracted. The minimum value is taken as the upper limit of safe detection Esf, and the maximum value is taken as the minimum excitation energy Emn covering the defects of the entire pile, forming the detection energy window [Emn, Esf].

[0024] Example 3 Please see Figure 2 This embodiment provides a system for pile foundation quality testing, used to perform the method described in any one of claims 1-9, comprising: The sensor module outputs data monitored by each sensor; The environmental correction module is used to acquire the wake travel time offset and temperature data of the reference section, and establish a linear relationship between temperature and travel time offset as a benchmark for environmental drift correction. The vibration control module is used to divide the pile top into multiple vibration zones and control the vibrator to apply vibration pulses of different energies to different vibration zones in sequence according to a preset incremental energy sequence. The signal acquisition and processing module is used to acquire the wake signal before and after each excitation, obtain the high-frequency energy attenuation rate and convert it into damage degree, and calculate the pure damage increment generated at each depth for each excitation by deducting the environmental drift effect according to the environmental drift correction benchmark. The data analysis module is used to construct a damage increment-energy curve for each depth, with the excitation energy as the x-axis and the corresponding pure damage increment as the y-axis, and to identify the inflection point of each curve, and take the energy corresponding to the inflection point as the critical excitation energy for that depth. The detection window determination module is used to take the minimum value of the critical excitation energy of all depths as the upper limit of safe detection, and take the maximum value as the minimum excitation energy to cover all pile defects, thereby determining the detection energy window applicable to the pile foundation.

[0025] Some of the data in the above formulas are numerical calculations with dimensions removed, and the contents not described in detail in this specification are all prior art known to those skilled in the art.

[0026] The above embodiments are only used to illustrate the technical methods of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical methods of the present invention without departing from the spirit and scope of the technical methods of the present invention.

Claims

1. A method for detecting the quality of pile foundations, characterized in that, Includes the following steps: Multiple rings of sensors are deployed along the depth direction of the pile. The middle part of the pile is regarded as the reference section. The tail wave travel time offset τ and the temperature T at each moment of the reference section are obtained to form a linear relationship between temperature and travel time offset, which serves as the environmental drift correction benchmark. The pile top is divided into multiple excitation zones. According to the preset incremental energy sequence, excitation pulses of different energies are applied to different excitation zones in sequence. The tail wave signal is collected before and after each excitation. The high-frequency energy attenuation rate is obtained and converted into damage degree. The influence of environmental drift is deducted according to the environmental drift correction benchmark, and the pure damage increment generated at each depth by each excitation is calculated. For each depth, a damage increment-energy curve is constructed with excitation energy as the x-axis and the corresponding pure damage increment as the y-axis. Identify the inflection point in each curve where the damage increment changes from a slow linear growth to a rapid nonlinear growth with energy, and take the energy corresponding to the inflection point as the critical excitation energy for that depth. The minimum value of the critical excitation energy at all depths is taken as the upper limit of safe detection, and the maximum value is taken as the minimum excitation energy to cover all pile defects, thereby determining the detection energy window applicable to this pile foundation.

2. The method for pile foundation quality testing according to claim 1, characterized in that, The environmental drift correction benchmark is established in the following manner: A reference section is selected in the middle of the pile body, and fiber optic sensors and temperature sensors corresponding to the excitation area are installed along this section. Acquire tailwave signals and temperature data during stable periods where temperature fluctuations do not exceed a preset threshold within a continuous time period; Using the initial tailwave waveform as a reference template, the tailwave travel time offset τ at each time point relative to the initial time point is calculated through sliding cross-correlation. The data points are combined with the temperature T at the corresponding time. The temperature-time sensitivity coefficient b is calculated by linear regression, and then the linear relationship τ=b×(T-T0) is obtained, where T0 is the reference temperature when τ=0, which is used as the environmental drift correction benchmark.

3. The method for pile foundation quality testing according to claim 1, characterized in that, Before the excitation according to the preset incremental energy sequence, a preliminary damage detection step is also included: The high-frequency energy attenuation rate a(z,θ) at various depths and directions is collected by exciting the vibration in any excitation region with weak pulse energy. A healthy benchmark zone is determined in the shallow part of the pile body, and the arithmetic mean of the high-frequency energy attenuation rate in three directions of this zone is calculated as the preliminary benchmark attenuation rate a0. Based on the preliminary baseline attenuation rate a0 and the concrete calibration coefficient k, the preliminary damage degree D0(z) = (a(z) - a0) / k at each depth is calculated, where a(z) is the average value of a(z,θ) in three directions, and directional defects are identified based on the difference in attenuation rate in each direction.

4. The method for pile foundation quality testing according to claim 1, characterized in that, The step of sequentially applying excitation pulses of different energies to different excitation regions according to a preset increasing energy sequence includes: Using the initial energy Ea and the final energy Eb, generate an N-level increasing energy sequence {E1, E2, ..., EN} with a step size ΔE; The energy sequence is randomly assigned to regions A, B, and C. During the assignment, it is ensured that each energy value is excited only once in one region, and there is at least a gap of M energy levels between two adjacent excitations in the same region, and excitation commands are not received continuously, where M is N divided by 3 and rounded up. Excitation operations are performed on each group of energy and region in a randomly assigned order.

5. The method for pile foundation quality testing according to claim 1, characterized in that, The wake wave signal is collected before and after each excitation to obtain the high-frequency energy attenuation rate and convert it into damage degree. The environmental drift effect is subtracted according to the environmental drift correction benchmark to calculate the pure damage increment generated at each depth for each excitation, including: Before excitation, the wake signal is collected by the sensor in the corresponding area to obtain the high-frequency energy attenuation rate at each depth and convert it into the original damage degree Dbr before excitation. At the same time, the wake travel time offset and temperature of the reference section are recorded, and the environmental equivalent damage change ΔDb before excitation is calculated using the environmental drift correction benchmark. The energy Ei is set to excite the center of the corresponding region; After excitation and reset, record the wake travel time offset and temperature of the reference section again, and calculate the equivalent environmental damage change ΔDa after excitation. After excitation, the wake signal is collected again to obtain the original damage level Dar after excitation; By correcting for environmental drift, we obtain the true damage degree before excitation Db=Dbr-ΔDb and the true damage degree after excitation Da=Dar-ΔDa, and then obtain the pure damage increment ΔD=Da-Db. If the difference in environmental equivalent damage or the rate of temperature change exceeds a preset threshold, the data is deemed invalid and a retest is required.

6. The method for pile foundation quality testing according to claim 1, characterized in that, Following the construction of the damage increment-energy curve, a zero-damage baseline attenuation calibration step is also included: For each depth, take three consecutive energy points forward from the maximum energy as a group, calculate the average growth rate of damage increment for each group, and when the growth rate of a group is less than or equal to the preset proportion of the average growth rate of the initial segment, the interval where the group is located is determined to be a saturation zone, and the average value of the damage increment in the interval is taken as the saturation damage increment ΔDs for that depth. Using the measured high-frequency energy attenuation rate αpost corresponding to each energy point in the saturation zone, combined with the saturation damage increment ΔDs and the initial damage degree D0, the zero-damage benchmark attenuation rate αcal=αpost - k×(D0+ΔDs) at each saturation energy point at each depth and in each direction is inversely calculated, where k is the linear proportionality coefficient between the high-frequency attenuation and the damage degree of concrete. Outlier values ​​were removed from the sample set consisting of all αcal values ​​by interquartile range, and the median of the remaining samples was taken as the final calibrated zero-damage baseline decay rate aF.

7. A method for pile foundation quality testing according to claim 6, characterized in that, Based on the calibrated zero-damage baseline attenuation rate aF, the damage degree Dc(z)=(a(z)-aF) / k at each depth and in each direction is recalculated, as well as the damage increment ΔDc(z,Ei)= (αpost(z,θ,Ei)-aF) / k - Dc(z) at each excitation energy, and the damage increment-energy curve for each depth is redrawn.

8. The method for pile foundation quality testing according to claim 1, characterized in that, The inflection point at which the damage increment in each curve changes from a slow linear increase to a rapid nonlinear increase with energy includes: The energy points are arranged in ascending order, and the average slope of the damage increment within each window is calculated using a sliding window. The average slope of the first few windows is taken as the reference slope s0 of the linear segment. Starting from the fourth window, the slope of the current window is compared with s0. When the slope of the current window is greater than or equal to the preset multiple s0 and the subsequent two consecutive windows also meet the condition, the energy corresponding to the starting point of the current window is determined to be the critical excitation energy at that depth.

9. A method for pile foundation quality testing according to claim 3, characterized in that, For each direction of the directional defect, a damage increment-energy curve is constructed and the critical excitation energy of each direction is identified. The minimum critical energy of all depths and directions is taken as the upper limit of safe detection, and the maximum value is taken as the minimum excitation energy covering the entire pile defect, thereby determining the detection energy window.

10. A system for pile foundation quality testing, used to perform the method described in any one of claims 1-9, characterized in that, include: The sensor module outputs data monitored by each sensor; The environmental correction module is used to acquire the wake travel time offset and temperature data of the reference section, and establish a linear relationship between temperature and travel time offset as a benchmark for environmental drift correction. The vibration control module is used to divide the pile top into multiple vibration zones and control the vibrator to apply vibration pulses of different energies to different vibration zones in sequence according to a preset incremental energy sequence. The signal acquisition and processing module is used to acquire the wake signal before and after each excitation, obtain the high-frequency energy attenuation rate and convert it into damage degree, and calculate the pure damage increment generated at each depth for each excitation by deducting the environmental drift effect according to the environmental drift correction benchmark. The data analysis module is used to construct a damage increment-energy curve for each depth, with the excitation energy as the x-axis and the corresponding pure damage increment as the y-axis, and to identify the inflection point of each curve, and take the energy corresponding to the inflection point as the critical excitation energy for that depth. The detection window determination module is used to take the minimum value of the critical excitation energy of all depths as the upper limit of safe detection, and take the maximum value as the minimum excitation energy to cover all pile defects, thereby determining the detection energy window applicable to the pile foundation.

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