A pile bottom karst detection method, system and electronic device

Abstract

The application discloses a pile bottom karst detection method and system and electronic equipment, and the method comprises the following steps: arranging measuring points at the pile bottom, lowering an array transducer to the pile bottom, and moving to each measuring point in sequence, when the array transducer reaches each measuring point, controlling the array transducer to collect full matrix data corresponding to the measuring point, and measuring the position of the transducer probe and recording the position of the array when collecting data; according to the position of the probe and the position of the array when collecting data, the coordinates of each array element in the array are calculated; imaging point division is performed in the imaging area, the imaging amplitudes of all transmitting / receiving pairs of signals at the imaging points are accumulated and summed, the imaging amplitudes of all imaging points are calculated, and a three-dimensional imaging model is obtained. The application calculates the coordinates of the array and the array elements of each measuring point by the measuring method, adopts the multi-point array data joint imaging mode, solves the problem of low transverse resolution of single-point phased array focusing imaging, and realizes three-dimensional high-precision imaging of the pile bottom karst.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of geotechnical engineering investigation, and particularly relates to a pile bottom karst high-precision detection method and system and an electronic device. BACKGROUND

[0002] Pile foundation can adapt to various engineering geological conditions, various engineering requirements, has the characteristics of high bearing capacity and strong load transmission capacity, and can effectively reduce the uneven settlement of buildings (structures), and to a certain extent, can reduce the adverse effects of karst on the foundation. Therefore, pile foundation is widely used in track engineering construction in karst areas. The size of the karst development varies greatly, the shape is changing, and the cross section is extremely irregular, which brings great difficulties to the design and construction of pile foundation in karst areas.

[0003] The main target of pile bottom karst detection is the karst hidden in the bedrock, which is extremely complex in size and spatial development range. When using drilling to investigate the pile bottom karst, the karst beside the hole is very easy to be missed. In terms of planar distribution, it is difficult to explore the spatial range by point instead of surface, and it is possible to cause adverse conditions such as half rock-embedded pile foundation in the actual construction process. The selection of exploration method is multiple holes for one pile, which is very high in cost and construction period, and even so, it is difficult to clearly grasp the specific development of karst at the whole pile position. In serious cases, it may cause instability and damage of the bridge, and the unexposed will exist in the form of hidden danger and gradually exposed during the operation period.

[0004] Pile bottom karst detection is a survey technology for detecting the distribution characteristics of karst within a certain range of pile bottom bearing stratum by direct (drilling method) or indirect method (geophysical method).

[0005] The main investigation methods in the construction stage are geological radar method and acoustic reflection method. The geological radar method arranges annular or cross section at the bottom of the pile to collect geological radar data, but the radar signal is disturbed by the side wall due to the limitation of the detection area of the site, and the detection depth is limited, and it is only suitable for artificial hole digging pile detection. The acoustic reflection method (see patent No. CN104101896A, "Pile bottom karst sonar detection device and method") arranges transducers at the bottom of the pile to excite and receive ultrasonic waves by mud coupling for detecting the development of pile bottom karst. The device has limited data collection, and the offset distance is fixed, which cannot collect high-density reflection wave data of multiple angles and multiple offset distances. The identification of pile bottom karst mainly relies on the identification of reflection waveform change and waveform time-frequency feature analysis, and cannot determine the height or range of karst cave, and the detection is easily disturbed by hole wall wave reflection.

[0006] Existing methods for detecting karst at the pile bottom cannot meet the needs of engineering investigation. The main problems are: high requirements for the pile bottom environment; limited data collection, resulting in low-quality imaging; and the ability to perform qualitative analysis of the detection results without being able to determine the specific development of karst at the pile bottom.

[0007] A search of existing technologies revealed that patent CN112904348A, entitled "A Three-Dimensional Detection Method, Device, Equipment, and Storage Medium," uses multiple transducers arranged in a one-dimensional linear array to perform three-dimensional detection of the pile bottom through a single-transmitter-multiple-receiver acquisition method combined with rotational acquisition. Patent CN112817039A, also entitled "A Three-Dimensional Detection Method, Device, Equipment, and Storage Medium," uses multiple transducers arranged in a two-dimensional sensor array and employs different combinations of points, lines, and surfaces for three-dimensional detection. The technologies described in these patents primarily target transducer arrays composed of multiple transducers. This method requires extremely high consistency among each transducer unit and results in limited data acquisition, hindering high-quality imaging.

[0008] The patent CN112630764A, entitled "Method, Device and System, Electronic Equipment and Storage Medium for Karst Detection at the Bottom of Pile," uses a transducer array with transmit delay control to perform beam phase control on each sensor for three-dimensional detection of the pile bottom. This patent only performs phase scanning in two directions, which cannot cover the entire pile bottom detection range. Furthermore, using a phased array requires a large number of transducer units, and each channel needs individual control, resulting in complex and costly circuit design.

[0009] When using phased array transducers to detect karst at the bottom of piles, the number of transducer array elements is limited by cost and weight, and the size of the transducer cannot be increased indefinitely. This results in the detection range not being able to fully cover the bottom of the pile, and the radiation angle of smaller transducers is larger, which leads to low lateral resolution of the detection results.

[0010] As mentioned above, existing methods for detecting karst at the bottom of piles mainly have the following limitations:

[0011] (1) Conventional detection methods have high requirements for the pile bottom environment; the detection results can only be qualitatively analyzed and cannot determine the specific situation of karst development at the pile bottom; the collected data is limited and cannot produce high-quality imaging.

[0012] (2) Detection methods based on ultrasonic array or phased array imaging only collect data at one point, which is limited by the large radiation angle of the transducer array and has low lateral resolution. Summary of the Invention

[0013] The purpose of this invention is to overcome at least one defect in the prior art and to provide a high-precision detection method, system and electronic equipment for pile bottom karst.

[0014] The technical solution of this invention is implemented as follows: This invention discloses a method for detecting karst at the bottom of a pile, comprising the following steps:

[0015] S1) After the pile foundation is drilled, measuring points are arranged at the bottom of the pile. The array transducer is lowered to the bottom of the pile and moved to each set measuring point in sequence. When the array transducer reaches a measuring point, the transmitting unit of the array transducer is controlled to transmit a detection signal, the receiving unit receives the detection signal, collects the full matrix data corresponding to the measuring point, and obtains the position and orientation of the transducer probe when the array data is collected.

[0016] S2) Calculate the coordinates of each element in the array based on the position and orientation of the transducer probe during array data acquisition;

[0017] S3) Focused imaging calculation, including:

[0018] Divide the imaging area into imaging points;

[0019] The propagation time of the detection signal from the transmitting unit to the imaging point and from the imaging point to the receiving unit is calculated based on the coordinates of each element in the array.

[0020] The imaging amplitude of all imaging points is calculated based on the amplitude of the detection signal arriving at the receiving unit and the propagation time, thus obtaining a three-dimensional imaging model of the karst at the pile bottom.

[0021] Further, in step S1), the array transducer is lowered to the bottom of the pile, specifically including: setting up a support rod at the pile opening, fixing pulleys on the support rod, suspending the array transducer to the bottom of the pile by a traction rope, and after the transducer reaches each measuring point at the bottom of the pile, pulling the transducer by the traction rope to finely adjust it to be horizontal and coupled with the bedrock at the bottom of the pile.

[0022] In step S1), the array transducer is moved to each set measuring point by moving the support rod.

[0023] Furthermore, the position of the transducer probe during array data acquisition is obtained by: determining the probe position by measuring the position of the pile opening pulley or by placing a distance sensor on the transducer and measuring the distance from the probe to the surrounding pile walls to determine the position of the probe center.

[0024] Furthermore, the probe position is determined by measuring the position of the pulley at the pile opening. Specifically, this includes: calculating the relative coordinates C(x,y) between the pulley on the support rod and the center O of the pile opening to determine the position of the transducer, or using GNSS to measure the coordinates of the pulley at the pile opening to determine the position of the transducer.

[0025] After the support rod is placed stably, measure the distance l from the line connecting the pulley position C and the center O of the pile hole to the steel casing D at the pile opening. Simultaneously measure the azimuth angle α of the line connecting the pulley C and the center O of the pile hole. Calculate the position of the transducer relative to the pile center using the relative position measurement parameters of the pulley at the pile opening. The calculation formula in a Cartesian coordinate system with true north as the Y-axis is:

[0026]

[0027]

[0028] In the formula: R is the radius of the pile opening casing, x is the abscissa of the pile opening pulley relative to the center of the pile, y is the ordinate of the pile opening pulley relative to the center of the pile, and the pulley position is the center position of the transducer probe.

[0029] Further, step S2) calculates the coordinates of each element within the array based on the probe position and orientation during array data acquisition, specifically including:

[0030] Calculating the coordinates of the array elements within the transducer array includes: taking the center of the transducer array as the relative coordinate origin, calculating the relative coordinates (x', y') of each element based on the element spacing dx, and rotating the coordinates according to the azimuth angle β when the array acquired data.

[0031] rx=x′*cos(β)-y′*sin(β)

[0032] ry=x′*sin(β)+y′*cos(β)

[0033] Where rx is the x-coordinate of the array element after rotation relative to the x-coordinate; ry is the y-coordinate of the array element after rotation relative to the y-coordinate.

[0034] Calculate the coordinates of each array element relative to the center of the pile foundation:

[0035] zx = rx + x

[0036] zy = ry + y

[0037] Where zx is the abscissa of the array element relative to the center of the pile foundation, zy is the ordinate of the array element relative to the center of the pile foundation, x is the abscissa of the pile pulley relative to the center of the pile, and y is the ordinate of the pile pulley relative to the center of the pile.

[0038] Furthermore, the control array transducer acquires full matrix data, specifically including: controlling the array transducer to acquire full matrix data at the bottom of the pile using point, line, or surface scanning methods, wherein,

[0039] When collecting full matrix data in a point scan manner, each element of the array transducer is used as a transmitting unit, and each element of the array transducer is used as a receiving unit of each transmitting unit. Each element of the array transducer transmits detection signals in sequence as a transmitting unit, and all elements receive signals synchronously until the full matrix scan dataset is collected.

[0040] When acquiring full matrix data in line scan mode, each row or column of array transducer is used as a transmitting unit, and each array element of array transducer is used as a receiving unit of each transmitting unit. Each row or column of array transducer as a transmitting unit transmits detection signals in sequence, and all array elements receive signals synchronously until the full line array scan data is acquired.

[0041] When acquiring full matrix data using a surface scanning method, the entire array element of the array transducer is used as the transmitting unit, and each element of the array transducer is used as the receiving unit of the transmitting unit. The entire array of the array transducer transmits signals as the transmitting unit, and all elements receive signals synchronously until the surface scan data is acquired.

[0042] Furthermore, the propagation time of the detection signal from the transmitting unit to the imaging point and from the imaging point to the receiving unit is calculated based on the coordinates of each array element within the array. Specifically, this includes: when the transmitting unit is a single array element, obtaining the propagation distance ds of the detection signal from the transmitting unit to the imaging point and the propagation distance dg from the imaging point to the corresponding receiving unit; and obtaining the propagation time ts of the detection signal from the transmitting unit to the imaging point and the propagation time tg from the imaging point to the corresponding receiving unit based on the propagation speed and the propagation distance.

[0043] When the transmitting element is a linear array or a planar array, the method for calculating the minimum time Ts from the linear / planar array to the imaging point can obtain an accurate wave field propagation time in isotropic homogeneous media. For more complex media, it can also be obtained by solving the equation, the three-dimensional equation being: Where t represents the first arrival time of the sound wave, and x, y, and z are the directions of the rectangular coordinate system. By setting the initial coordinates of the excitation array elements, the partial differential equation of time with respect to space can be solved to obtain the three-dimensional wave arrival and travel time of the line / surface excitation form. Then, the time ts of the sound wave signal emitted by the line / surface array as the transmitting unit to the imaging point can be obtained, and the propagation distance dg of the detection signal from the imaging point to the corresponding receiving unit can be obtained. Based on the propagation speed and the propagation distance, the propagation time tg of the detection signal from the imaging point to the corresponding receiving unit can be obtained.

[0044] Furthermore, the imaging amplitude Ip of a single imaging point P is:

[0045]

[0046] In the formula t s,p,g To detect the propagation time of the signal from the transmitting unit to the imaging point and from the imaging point to the receiving unit, W m,i,j D represents the full matrix data acquired by the transducer at the m-th measurement point. sD is the calibration coefficient for the transducer pointing to the transmitting unit. g B is the calibration coefficient for the transducer pointing to the receiving unit. s B is the diffusion calibration coefficient for the transducer pointing towards the transmitting unit. g The diffusion calibration coefficient for the transducer pointing towards the receiving unit;

[0047] in,

[0048]

[0049] In the formula, D is the transducer directivity calibration coefficient, B is the diffusion calibration coefficient, a is the side length of the transducer array element, θ is the angle from the imaging point to the transmitting or receiving unit, λ is the ultrasonic wavelength, and d is the distance from the imaging point to the transmitting or receiving unit.

[0050] The imaging values ​​of all transmit / receive pairs at imaging point P are summed, and the imaging values ​​of all imaging points P are calculated to obtain the three-dimensional imaging model.

[0051] Furthermore, step S3 is followed by step S4, which includes instantaneous energy calculation, including calculating the instantaneous amplitude value by using Hilbert transform on the superimposed amplitude value sequence of imaging points at the same horizontal position and different depths in the imaging area. This amplitude value is positively correlated with the reflection coefficient of the bedrock at the pile bottom. The relative change of this amplitude value can be used to semi-quantitatively analyze the three-dimensional development of karst, fissures and fractures at the pile bottom.

[0052] Furthermore, the transducer is moved to multiple set measuring points by moving the support rod.

[0053] Furthermore, full matrix data is collected at each measuring point using the same parameters.

[0054] This invention also discloses a pile bottom karst detection system, comprising:

[0055] An array-type transducer is used to acquire full matrix data;

[0056] A transducer delivery device is used to deliver array transducers into the pile and adjust the transducers to different measuring point positions.

[0057] The controller is used to acquire the full matrix data collected by the array transducer, as well as the probe position and orientation during the data acquisition of the array transducer, calculate the coordinates of each array element in the array, and perform focused imaging calculations to obtain a three-dimensional imaging model.

[0058] The present invention also discloses an electronic device, comprising: a processor and a memory for storing a computer program capable of running on the processor; wherein,

[0059] When the processor runs the computer program, it performs the steps of the pile bottom karst detection method as described above.

[0060] The present invention has at least the following beneficial effects: The method of the present invention is based on phased array transducer focusing imaging to detect the karst development at the pile bottom, utilizing pile bottom mud coupling, thus having low requirements for the pile bottom construction environment. The detection method is simple; the position of each array element relative to the pile center can be calculated using a simple measurement method, supporting irregular measurement point arrangements. Compared with conventional single-point imaging methods, the use of multi-point acquired area array data for joint imaging greatly improves the lateral resolution and signal-to-noise ratio. Attached Figure Description

[0061] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0062] Figure 1 This is a flowchart of a pile bottom karst detection method provided in an embodiment of the present invention;

[0063] Figure 2 This is a schematic diagram of the arrangement of multiple measuring points at the bottom of a pile according to one embodiment of the present invention;

[0064] Figure 3 This is a schematic diagram of the arrangement of multiple measuring points at the bottom of the pile provided in another embodiment of the present invention;

[0065] Figure 4 This is a schematic diagram of the relative position measurement of the pile opening pulley provided in an embodiment of the present invention;

[0066] Figure 5 The diagram shows a three-dimensional high-precision focusing imaging of a phased array transducer, where (a) is a schematic diagram of the focusing imaging result of multi-plane array data and (b) is a schematic diagram of the focusing imaging result of single-plane array data. Detailed Implementation

[0067] 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.

[0068] In the description of this invention, unless otherwise stated, "a plurality of" or "several" means two or more.

[0069] Example 1

[0070] See Figure 1 This invention discloses a method for detecting karst at the bottom of a pile, comprising the following steps:

[0071] S1) After the pile foundation is drilled, measuring points are arranged at the bottom of the pile. The array transducer is lowered to the bottom of the pile and moved sequentially to each set measuring point. Each time the array transducer reaches a measuring point, the array elements on the array transducer are controlled to transmit and receive detection signals, collect full matrix data, and simultaneously record the position X of that measuring point. m And the orientation β of the array transducer at the bottom of the pile m ,β m For the transducer azimuth angle of the m-th measuring point, measure and record the probe position and azimuth when acquiring transducer array data, until the full matrix data corresponding to all measuring points are acquired;

[0072] S2) Calculate the coordinates of each array element in the array based on the probe position and orientation during array data acquisition;

[0073] S3) Focused imaging calculation, including: dividing the imaging area into imaging points, summing the imaging amplitudes of all transmit / receive pairs at the imaging points, calculating the imaging amplitudes of all imaging points, and obtaining a three-dimensional imaging model.

[0074] Furthermore, the array transducer contains m rows and n columns of array elements, each element using an independent excitation and reception circuit module. The element spacing is dx. An array element is the smallest unit of the array transducer, used for both transmitting and receiving signals. Multiple array elements form a transducer array. The transducer array, along with the housing and circuitry, forms a single unit, which is the probe. The detected signal is an ultrasonic signal.

[0075] Furthermore, when the transducer is placed at the bottom of the pile, a support rod is erected at the pile opening, and a pulley is fixed on the support rod. The array transducer is lowered to the bottom of the pile by a traction rope. After the transducer reaches each measuring point at the bottom of the pile, the transducer can be pulled by the traction rope to finely adjust it to be horizontal and well coupled with the bedrock at the bottom of the pile.

[0076] Furthermore, in step S1), the array transducer is moved to the set measurement points by moving the support rod.

[0077] Furthermore, full matrix data is collected at each measuring point using the same parameters.

[0078] Furthermore, the probe position in step S1) can be determined by measuring the position of the pulley at the pile opening. Since the transducer has a large mass, it naturally hangs to the bottom of the pile under gravity via a single steel wire rope. Therefore, the transducer's position can be determined by calculating the relative coordinates C(x, y) of the pulley on the support rod. The position of the pulley at the pile opening can be measured using high-precision GNSS to determine its absolute coordinates. It can also be determined by measuring its relative coordinates to the center O of the pile opening. The measurement method is as follows: after the support rod is placed stably, refer to... Figure 4 Measure the distance l from the line connecting the pulley position C point and the center O of the pile hole to the steel casing D at the pile opening, and simultaneously measure the azimuth angle α of the line connecting the pulley C and the center O of the pile hole.

[0079] The probe position can also be measured by placing a distance sensor on the transducer and determining the center position of the probe by measuring the distance from the probe to the surrounding pile walls.

[0080] The position of the transducer relative to the center of the pile is calculated using the relative position measurement parameters of the pile head pulley. The calculation formula is as follows in a Cartesian coordinate system with true north as the Y-axis:

[0081]

[0082]

[0083] In the formula: R is the radius of the pile opening casing, x is the abscissa of the pile opening pulley relative to the center of the pile, and y is the ordinate of the pile opening pulley relative to the center of the pile.

[0084] Calculating the coordinates of the array elements within the transducer array includes: taking the center of the transducer array as the relative coordinate origin, calculating the relative coordinates (x′, y′) of each element based on the element spacing dx, and rotating the coordinates according to the azimuth angle β when the array acquired data.

[0085] rx=x′*cos(β)-y′*sin(β)

[0086] ry=x′*sin(β)+y′*cos(β)

[0087] The above formula is used to calculate the phase position of each array element based on the probe azimuth β rotation, where rx is the abscissa of the array element after rotation relative to the abscissa; ry is the ordinate of the array element after rotation relative to the ordinate.

[0088] Calculate the coordinates of each array element relative to the center of the pile foundation:

[0089] zx = rx + x

[0090] zy = ry + y

[0091] The above formula is used to calculate the relative coordinates of each array element within the probe. This formula is based on the translation of the probe's center point coordinates. Where zx is the abscissa of the array element relative to the pile foundation center, zy is the ordinate of the array element relative to the pile foundation center, x is the abscissa of the pile pulley relative to the pile center, and y is the ordinate of the pile pulley relative to the pile center.

[0092] The absolute coordinates of the pulley at the pile opening are measured using GNSS. These coordinates can then be converted to relative coordinates with respect to the pile center (0), yielding the transducer's position relative to the pile center. The phase position is the relative coordinate C(x, y) of each measuring point relative to the origin (0) of the pile hole. The absolute coordinates are obtained from high-precision GPS or RTK measurements of the geodetic coordinates. The primary purpose of measuring the pulley coordinates is to calculate the distances ds and dg from the transmitting element S to the imaging point P and from the imaging point P to the receiving element G; both relative and absolute coordinates can be used.

[0093] This patent assumes the pulley position is the center of the transducer. This is because the transducer hangs naturally via a single steel wire rope, and its default horizontal position is the same.

[0094] Furthermore, during single-array data acquisition, the array elements on the control array transducer transmit and receive detection signals to acquire full matrix data. Specifically, this includes controlling the transducer array acquisition circuit to acquire full matrix data at the bottom of the pile using point, line, or surface scanning methods.

[0095] The full matrix data is acquired by point scanning, specifically including: each element of the array transducer transmits a detection signal in sequence, and all elements receive the signal synchronously until the full matrix scan dataset is acquired.

[0096] The full matrix data is acquired by line scanning, specifically including: each row or column of array elements of the array transducer transmits detection signals in sequence, and all array elements receive signals synchronously until the full linear array scan data is acquired.

[0097] The entire matrix data is acquired using a surface scanning method, which specifically includes: the array transducer transmitting signals across the entire array surface, and all array elements receiving signals synchronously until the surface scan data is acquired.

[0098] The control array transducer collects full matrix data, specifically including: first, exciting the first array element to emit ultrasonic waves, and all array elements simultaneously receiving the signal, where the data received by the j-th array element is denoted as W(1,j). Then, the other array elements are excited sequentially to emit ultrasonic waves to obtain full matrix data, where the data obtained by all array elements receiving the signal when the i-th array element emits ultrasonic waves is denoted as W(i,j).

[0099] One embodiment involves using a two-dimensional phased array transducer with m rows and n columns (N elements) to acquire full matrix data. First, the first element is excited to emit ultrasonic waves, and all 64 elements simultaneously receive the signals. The data received by the j-th element is denoted as W(1,j). Then, the i-th element is excited sequentially to emit ultrasonic waves, and the data is obtained from the signals received by all elements, ultimately yielding the full matrix data W(i,j), (1≤i≤64, 1≤j≤64).

[0100] By moving the support rod to control the transducer to different positions (different positions being multiple regular or irregular measuring points at the bottom of the pile foundation), the above deployment and data acquisition steps are repeated to achieve multi-point array data acquisition. See also Figure 2 and Figure 3 This is a schematic diagram of the arrangement of multiple measuring points at the bottom of the pile.

[0101] One embodiment involves uniformly arranging measuring points at the bottom of the pile, with each measuring point collecting full matrix data W according to the same ground parameters. m,i,j Where m is the m-th measurement point collected, and the position X of each measurement point also needs to be recorded. m And the orientation β of the transducer at the bottom of the pile m (1≤m≤M, where M is the number of measurement points). Simultaneously measure the position (x,y) of the transducer probe and record the azimuth β when acquiring data for each array.

[0102] In the point-based data acquisition and processing, one embodiment of step S3) is as follows: Step S3) specifically includes: dividing the imaging area into imaging points P at equal intervals; in the point-based data acquisition dataset, W(m,i,j) represents the area array data of the m-th measurement point; the i-th array element S transmits the signal, and the j-th array element G receives the signal; calculating the distances ds and dg from the transmitting array element S to the imaging point P and from the imaging point P to the receiving array element G, respectively, with corresponding propagation times ts = ds / v and tg = dg / v. Then, the imaging amplitude Ip of the imaging point P is:

[0103]

[0104] In the formula t s,p,g Let ts + tg be the propagation speed of ultrasound in bedrock, and W be the velocity of the ultrasound wave. m,i,j D represents the full matrix data acquired by the transducer at the m-th measurement point. s D is the calibration coefficient for the transducer pointing to the transmitting array element. g B is the calibration coefficient for the transducer pointing to the receiving array element. s B is the diffusion calibration coefficient for the transducer pointing towards the transmitting array element. g The diffusion calibration coefficient for the transducer pointing towards the receiving array element;

[0105] in,

[0106]

[0107] In the formula, D is the transducer directivity calibration coefficient, B is the diffusion calibration coefficient, a is the side length of the transducer element, θ is the angle from the imaging point to the transmitting or receiving element, λ is the ultrasonic wavelength, and d is the distance from the imaging point to the transmitting or receiving element.

[0108] When using linear or area array scanning, the calculation method for ts is as follows: The above method for calculating the minimum time ts from the linear / area array S to the imaging point P can obtain accurate wave field propagation time in isotropic homogeneous media. For more complex media, it can also be obtained by solving the equation. The three-dimensional equation is: Where t represents the first arrival time of the sound wave, and x, y, and z are the directions of the rectangular coordinate system, respectively. By setting the partial differential equation of time with respect to space for each excitation source, the three-dimensional wave arrival and travel time in the surface excitation form is obtained, and thus the time ts of the sound wave signal emitted by the area array sensor to the imaging point is obtained. The calculation method of tg when using linear or area array scanning is the same as the calculation method of tg when processing point-based acquisition data.

[0109] Repeat the above process to sum the imaging values ​​of all transmit / receive pairs at imaging point P. The summation of the imaging values ​​at all imaging points P yields the three-dimensional imaging model of the observation system.

[0110] Furthermore, step S3 is followed by step S4, which includes instantaneous energy calculation, including calculating the instantaneous amplitude value by using Hilbert transform on the superimposed amplitude value sequence of imaging points at the same horizontal position and different depths in the imaging area. This amplitude value is positively correlated with the reflection coefficient of the bedrock at the pile bottom. The relative change of this value can be used to semi-quantitatively analyze the three-dimensional development of karst, fissures and fractures at the pile bottom.

[0111] The method was tested on a model pile. A phased array transducer was used to collect multi-point area array data along the X-axis, with a point spacing of 20 cm. The combined imaging result using the multi-area array data is shown in Figure (a). The imaging result using area array data collected at a single measuring point at the pile center is shown in Figure (b). Figure 5 The image shows the cavity in the model corresponding to the high energy amplitude, and the resolution of the multi-array joint imaging result in the X direction is much higher than that of the single-point imaging result.

[0112] Example 2

[0113] This invention also discloses a pile bottom karst detection system for implementing the pile bottom karst detection method described in Embodiment 1, comprising:

[0114] An array-type transducer is used to acquire full matrix data;

[0115] A transducer delivery device is used to deliver array transducers into the pile and adjust the transducers to different measuring point positions.

[0116] The controller is used to acquire the full matrix data collected by the array transducer, as well as the probe position and orientation during the data acquisition of the array transducer, calculate the coordinates of each array element in the array, and perform focused imaging calculations to obtain a three-dimensional imaging model of the karst at the bottom of the pile.

[0117] The transducer deployment device includes a pulley and a traction rope for pulling the transducer. The pulley is fixed on a support rod, which is erected at the pile opening. The traction rope is mounted on the pulley, with one end connected to the transducer and the other end connected to a winding device.

[0118] Example 3

[0119] This invention also discloses an electronic device, comprising: a processor and a memory for storing a computer program capable of running on the processor; wherein,

[0120] When the processor runs the computer program, it executes the steps of the pile bottom karst detection method as described in Embodiment 1.

[0121] This invention discloses a method for detecting karst at the pile bottom after borehole drilling and before pile construction in large-diameter pile foundations. It utilizes high-frequency ultrasonic phased array focusing imaging to detect karst at the pile bottom, leveraging pile bottom mud coupling, thus minimizing requirements on the pile bottom construction environment. By calculating the coordinates of each measuring point array and its elements using a simple measurement method, and employing multi-point array data joint imaging, the method solves the problem of low lateral resolution in single-point phased array focusing imaging, achieving high-precision three-dimensional imaging of karst at the pile bottom.

[0122] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for detecting karst at the bottom of a pile, characterized in that, Includes the following steps: S1) After the pile foundation is drilled, measuring points are arranged at the bottom of the pile. The array transducer is lowered to the bottom of the pile and moved to each set measuring point in sequence. When the array transducer reaches a measuring point, the transmitting unit of the array transducer is controlled to transmit a detection signal, the receiving unit receives the detection signal, collects the full matrix data corresponding to the measuring point, and obtains the position and orientation of the transducer probe when the array data is collected. S2) Calculate the coordinates of each element in the array based on the position and orientation of the transducer probe during array data acquisition; S3) Focused imaging calculation, including: Divide the imaging area into imaging points; The propagation time of the detection signal from the transmitting unit to the imaging point and from the imaging point to the receiving unit is calculated based on the coordinates of each element in the array. The imaging amplitude of all imaging points is calculated based on the amplitude of the detection signal arriving at the receiving unit and the propagation time, thus obtaining a three-dimensional imaging model of the karst at the pile bottom. The propagation time of the detection signal from the transmitting unit to the imaging point and from the imaging point to the receiving unit is calculated based on the coordinates of each element in the array. Specifically, this includes: when the transmitting unit is a single element, obtaining the propagation distance ds of the detection signal from the transmitting unit to the imaging point and the propagation distance dg from the imaging point to the corresponding receiving unit; obtaining the propagation time ts of the detection signal from the transmitting unit to the imaging point based on the propagation speed of the detection signal from the transmitting unit to the imaging point and the propagation distance ds; and obtaining the propagation time tg of the detection signal from the imaging point to the corresponding receiving unit based on the propagation speed of the detection signal from the imaging point to the corresponding receiving unit and the propagation distance dg. When the transmitting element is a linear array or a planar array, the method for calculating the minimum time Ts from the linear / planar array to the imaging point yields an accurate wave field propagation time in isotropic homogeneous media. For more complex media, it is obtained by deriving the equation, the three-dimensional equation being: Where t represents the first arrival time of the sound wave, and x, y, and z are the directions of the rectangular coordinate system. By setting the initial coordinates of the excitation array elements, the partial differential equation of time with respect to space can be solved to obtain the three-dimensional wave arrival time of the line / surface excitation form. Then, the time ts of the sound wave signal emitted by the line / surface array as the transmitting unit to the imaging point can be obtained, and the propagation distance dg of the detection signal from the imaging point to the corresponding receiving unit can be obtained. Based on the propagation speed of the detection signal from the imaging point to the corresponding receiving unit and the propagation distance dg, the propagation time tg of the detection signal from the imaging point to the corresponding receiving unit can be obtained. The imaging amplitude Ip of a single imaging point P is: ； In the formula t s,p,g To detect the propagation time of the signal from the transmitting unit to the imaging point and from the imaging point to the receiving unit, W m,i,j D represents the full matrix data acquired by the transducer at the m-th measurement point. s D is the calibration coefficient for the transducer pointing to the transmitting unit. g B is the calibration coefficient for the transducer pointing to the receiving unit. s B is the diffusion calibration coefficient for the transducer pointing towards the transmitting unit. g The diffusion calibration coefficient for the transducer pointing towards the receiving unit; in, ； In the formula, D is the transducer directivity calibration coefficient, B is the diffusion calibration coefficient, a is the side length of the transducer element, and θ is the angle from the imaging point to the transmitting or receiving element. d is the ultrasonic wavelength, and d is the distance from the imaging point to the transmitting or receiving unit; The imaging values ​​of all transmit / receive pairs at imaging point P are summed, and the imaging values ​​of all imaging points P are calculated to obtain the three-dimensional imaging model.

2. The method for detecting karst at the bottom of a pile as described in claim 1, characterized in that: In step S1), the array transducer is lowered to the bottom of the pile. Specifically, this includes: setting up a support rod at the pile opening, fixing pulleys on the support rod, and suspending the array transducer to the bottom of the pile by a traction rope. After the transducer reaches each measuring point at the bottom of the pile, the transducer is pulled by the traction rope to finely adjust it to be horizontal and coupled with the bedrock at the bottom of the pile. In step S1), the array transducer is moved to each set measuring point by moving the support rod.

3. The method for detecting karst at the bottom of a pile as described in claim 2, characterized in that: The position of the transducer probe during array data acquisition is determined by measuring the position of the pulley at the pile opening or by placing a distance sensor on the transducer and measuring the distance from the probe to the surrounding pile walls.

4. The method for detecting karst at the bottom of a pile as described in claim 3, characterized in that: The probe position is determined by measuring the position of the pulley at the pile opening. Specifically, this includes calculating the relative coordinates C(x,y) between the pulley on the support rod and the center O of the pile opening to determine the position of the transducer, or using GNSS to measure the coordinates of the pulley at the pile opening to determine the position of the transducer. After the support rod is placed and stabilized, measure the distance from point C (the position of the pulley) to point O (the center of the pile hole), extending to the steel casing D at the pile opening. Simultaneously measure the azimuth angle of the line connecting pulley C and the center O of the pile hole. The position of the transducer relative to the center of the pile is calculated using the relative position measurement parameters of the pile pulley. The calculation formula is as follows in a Cartesian coordinate system with true north as the Y-axis: ； ； In the formula: R is the radius of the pile opening casing, x is the abscissa of the pile opening pulley relative to the center of the pile, y is the ordinate of the pile opening pulley relative to the center of the pile, and the pulley position is the center position of the transducer probe.

5. The method for detecting karst at the bottom of a pile as described in claim 4, characterized in that: Step S2) Calculate the coordinates of each element within the array based on the probe position and azimuth during array data acquisition. This includes: Calculating the coordinates of the array elements within the transducer array includes: taking the center of the transducer array as the relative coordinate origin, and calculating the coordinates based on the element spacing. Calculate the relative coordinates of each array element. Based on the azimuth angle when the array data is acquired Perform coordinate rotation: ； ； Where rx is the x-coordinate of the array element after rotation relative to the x-coordinate; ry is the y-coordinate of the array element after rotation relative to the y-coordinate. Calculate the coordinates of each array element relative to the center of the pile foundation: ； ； Where zx is the abscissa of the array element relative to the center of the pile foundation, zy is the ordinate of the array element relative to the center of the pile foundation, x is the abscissa of the pile pulley relative to the center of the pile, and y is the ordinate of the pile pulley relative to the center of the pile.

6. The method for detecting karst at the bottom of a pile as described in claim 1, characterized in that: The control array transducer acquires full matrix data, specifically including: controlling the array transducer to acquire full matrix data at the bottom of the pile using point, line, or surface scanning methods, wherein, When collecting full matrix data in a point scan manner, each element of the array transducer is used as a transmitting unit, and each element of the array transducer is used as a receiving unit of each transmitting unit. Each element of the array transducer transmits detection signals in sequence as a transmitting unit, and all elements receive signals synchronously until the full matrix scan dataset is collected. When acquiring full matrix data in line scan mode, each row or column of array transducer is used as a transmitting unit, and each array element of array transducer is used as a receiving unit of each transmitting unit. Each row or column of array transducer as a transmitting unit transmits detection signals in sequence, and all array elements receive signals synchronously until the full line array scan data is acquired. When acquiring full matrix data using a surface scanning method, the entire array element of the array transducer is used as the transmitting unit, and each element of the array transducer is used as the receiving unit of the transmitting unit. The entire array of the array transducer transmits signals as the transmitting unit, and all elements receive signals synchronously until the surface scan data is acquired.

7. The method for detecting karst at the bottom of a pile as described in claim 1, characterized in that: Step S3 is followed by step S4, which includes instantaneous energy calculation, including: calculating the instantaneous amplitude value by superimposing the amplitude value sequence of imaging points at different depths at the same horizontal position in the imaging area through Hilbert transformation. This amplitude value is positively correlated with the reflection coefficient of the bedrock at the pile bottom. The relative change of this amplitude value can be used to semi-quantitatively analyze the three-dimensional development of karst, fissures and fractures at the pile bottom.

8. A pile bottom karst detection system, characterized in that, include: An array-type transducer is used to acquire full matrix data; A transducer delivery device is used to deliver array transducers into the pile and adjust the transducers to different measuring point positions. The controller is used to acquire the full matrix data collected by the array transducer and the probe position and orientation during the data acquisition of the array transducer, calculate the coordinates of each array element in the array, and perform focusing imaging calculations to obtain a three-dimensional imaging model. Focused imaging calculations include: Divide the imaging area into imaging points; The propagation time of the detection signal from the transmitting unit to the imaging point and from the imaging point to the receiving unit is calculated based on the coordinates of each element in the array. The imaging amplitude of all imaging points is calculated based on the amplitude of the detection signal arriving at the receiving unit and the propagation time, thus obtaining a three-dimensional imaging model of the karst at the pile bottom. The propagation time of the detection signal from the transmitting unit to the imaging point and from the imaging point to the receiving unit is calculated based on the coordinates of each element in the array. Specifically, this includes: when the transmitting unit is a single element, obtaining the propagation distance ds of the detection signal from the transmitting unit to the imaging point and the propagation distance dg from the imaging point to the corresponding receiving unit; obtaining the propagation time ts of the detection signal from the transmitting unit to the imaging point based on the propagation speed of the detection signal from the transmitting unit to the imaging point and the propagation distance ds; and obtaining the propagation time tg of the detection signal from the imaging point to the corresponding receiving unit based on the propagation speed of the detection signal from the imaging point to the corresponding receiving unit and the propagation distance dg. When the transmitting element is a linear array or a planar array, the method for calculating the minimum time Ts from the linear / planar array to the imaging point yields an accurate wave field propagation time in isotropic homogeneous media. For more complex media, it is obtained by deriving the equation, the three-dimensional equation being: Where t represents the first arrival time of the sound wave, and x, y, and z are the directions of the rectangular coordinate system. By setting the initial coordinates of the excitation array elements, the partial differential equation of time with respect to space can be solved to obtain the three-dimensional wave arrival time of the line / surface excitation form. Then, the time ts of the sound wave signal emitted by the line / surface array as the transmitting unit to the imaging point can be obtained, and the propagation distance dg of the detection signal from the imaging point to the corresponding receiving unit can be obtained. Based on the propagation speed of the detection signal from the imaging point to the corresponding receiving unit and the propagation distance dg, the propagation time tg of the detection signal from the imaging point to the corresponding receiving unit can be obtained. The imaging amplitude Ip of a single imaging point P is: ； In the formula t s,p,g To detect the propagation time of the signal from the transmitting unit to the imaging point and from the imaging point to the receiving unit, W m,i,j D represents the full matrix data acquired by the transducer at the m-th measurement point. s D is the calibration coefficient for the transducer pointing to the transmitting unit. g B is the calibration coefficient for the transducer pointing to the receiving unit. s B is the diffusion calibration coefficient for the transducer pointing towards the transmitting unit. g The diffusion calibration coefficient for the transducer pointing towards the receiving unit; in, ； In the formula, D is the transducer directivity calibration coefficient, B is the diffusion calibration coefficient, a is the side length of the transducer element, and θ is the angle from the imaging point to the transmitting or receiving element. d is the ultrasonic wavelength, and d is the distance from the imaging point to the transmitting or receiving unit; The imaging values ​​of all transmit / receive pairs at imaging point P are summed, and the imaging values ​​of all imaging points P are calculated to obtain the three-dimensional imaging model.

9. An electronic device, characterized in that, include: A processor and memory for storing computer programs that can run on the processor; wherein, When the processor runs the computer program, it performs the steps of the pile bottom karst detection method according to any one of claims 1 to 7.

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