System and method for detecting compactness of metal joint of underground diaphragm wall based on acoustic transmission method

Abstract

The invention provides a system and a method for detecting the compactness of a metal joint of an underground diaphragm wall based on a sound wave transmission method. The system for detecting the compactness of the metal joint of the underground diaphragm wall based on the acoustic transmission method comprises a plurality of groups of sounding pipes arranged in the underground diaphragm wall in a penetrating mode, each group of sounding pipes comprises a first sounding pipe and a second sounding pipe which are located on the two sides of the metal joint correspondingly, and the first sounding pipes and the second sounding pipes are symmetrically arranged relative to the metal joint; the connecting line of the centers of the first sounding pipe and the second sounding pipe is perpendicular to the metal connector. According to the system for detecting the compactness of the metal joint of the underground diaphragm wall based on the acoustic transmission method, the problem that the compactness of the metal joint of the large underground diaphragm wall cannot be simply, conveniently and quickly detected by an existing traditional method is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of density detection, and in particular to a system and method for detecting the density of metal joints of underground continuous walls based on an acoustic wave transmission method. Background Art

[0002] Underground continuous walls are widely used in the retaining structures of large deep foundation pit projects or directly as the foundation of buildings due to their good bearing capacity and anti-seepage performance. Actual projects show that the construction quality control of underground continuous wall joints is difficult to guarantee, and the construction density problem of each underground continuous wall joint is often difficult to be well solved. Sand and mud defects are prone to occur at the joints, which can easily cause water and sand leakage at the joints during foundation pit excavation, which is a fatal risk point in foundation pit construction. Metal joints are a commonly used form of underground continuous wall joints. How to detect the density of underground continuous wall metal joints through convenient and effective means is of great engineering significance to ensure construction safety and the stability of later building structures.

[0003] At present, as an important method of non-destructive testing, the acoustic wave transmission method is widely used in the integrity detection of various types of cast-in-place piles due to its advantages such as convenient detection, no damage to the structure, and low cost. This method can effectively detect the defect type, location, and degree of defect in bored cast-in-place pile concrete, and is an effective means of evaluating the integrity of pile foundations. However, there is no relevant application of the acoustic wave transmission method for the density detection of metal joints of large underground continuous walls. The traditional detection method has the problems of cumbersomeness, damage to the structure, and high cost. Therefore, it is very necessary to propose a new density detection method and system for metal joints of large underground continuous walls. Summary of the invention

[0004] The main purpose of the present invention is to provide a system and method for detecting the density of underground continuous wall metal joints based on the acoustic wave transmission method, aiming to complete the detection process more conveniently and greatly improve the efficiency in the field of density detection of large underground continuous wall metal joints.

[0005] To achieve the above-mentioned purpose, the present invention provides a system for detecting the density of metal joints of underground continuous walls based on the sound wave transmission method, including multiple groups of acoustic detection tubes penetrating the underground continuous wall, each group of acoustic detection tubes including a first acoustic detection tube and a second acoustic detection tube respectively located on both sides of the metal joint, the first acoustic detection tube and the second acoustic detection tube are symmetrically arranged relative to the metal joint, and the line connecting the centers of the first acoustic detection tube and the second acoustic detection tube is perpendicular to the metal joint.

[0006] Preferably, the interval between two adjacent sonic detection tubes located on the same side of the metal joint is 150 mm-200 mm.

[0007] Preferably, the distance between the first acoustic detection tube and the second acoustic detection tube in each group of acoustic detection tubes is 1m-1.5m.

[0008] The present invention proposes a method for detecting the density of metal joints of underground continuous walls based on the above-mentioned system based on the acoustic wave transmission method, comprising the following steps:

[0009] Take two symmetrical acoustic testing tubes on both sides of the metal joint as a group of acoustic testing tubes to measure a test section, complete the test of each group of acoustic testing tubes in turn, complete all section tests and record the relevant parameters and data of the section test;

[0010] According to the sound velocity in the acoustic wave parameter value obtained by the test, the critical value of sound velocity anomaly is determined by the bilateral elimination method based on the probability method. When the sound velocity value of a measuring line is lower than the critical value of sound velocity anomaly, the measuring line is determined to be an abnormal measuring line.

[0011] Determine the location of the defect according to the location of the abnormal measurement line and calculate the defect size in the abnormal measurement line according to the relationship between the abnormal value of the acoustic wave parameter and the defect size;

[0012] The density of the metal joints of the underground continuous wall is determined based on the location and size of the defects in each group of test sections with defects.

[0013] Preferably, the steps of measuring a test section by using two symmetrical acoustic detection tubes on both sides of the metal joint as a group of acoustic detection tubes, completing the test of each group of acoustic detection tubes in sequence, completing all section tests and recording relevant parameters specifically include:

[0014] Connect the power supply, check all instruments and equipment, and set various instrument parameters;

[0015] Open the covers of each acoustic detection pipe opening and fill the pipe with clean water;

[0016] Using water as a coupling agent, the transmitting transducer in the acoustic detection tube on one side of the metal joint transmits the acoustic wave signal, and the receiving transducer in the acoustic detection tube on the other side of the metal joint receives the acoustic wave signal;

[0017] The transmitting and receiving transducers measure the sound time, sound speed and amplitude point by point from the bottom upward synchronously;

[0018] Observe the waveform for distortion and perform encrypted measurements when suspicious waveforms appear;

[0019] Collect, record and store all relevant parameters and data of cross-section testing;

[0020] Repeat the above steps to complete all test section tests.

[0021] Preferably, the cross-sectional test related parameters and data include: the distance L between the outer walls of each group of acoustic detection tubes, the distances L1 and L3 between the outer walls of the left and right acoustic detection tubes and the metal joint, and the thickness L2 of the metal joint; the wave velocity V of the ultrasonic wave in the metal joint; G ; The wave velocity V of ultrasonic wave in underground continuous wall H ; Test the acoustic wave parameters of the section: acoustic time t, acoustic velocity v, and amplitude A.

[0022] Preferably, the steps of determining the critical value of abnormal sound velocity by using the bilateral elimination method based on the probability method are as follows:

[0023] Calculate the average sound velocity v of each test section m With standard deviation s x ;

[0024] Arrange the test sound velocity values ​​in descending order. The minimum sound velocity v that may occur under normal circumstances 01 =v m -λs x and the maximum value v 02 =v m +λs x , and the minimum value in the sound speed arrangement is 01 Compare, when the minimum value is less than v 01 The data is removed when

[0025] Combine the maximum value in the arrangement with v 02 Compare, when the maximum value is greater than v 02 The data is removed when

[0026] Each time a piece of data is removed, a new arrangement of the remaining data is formed and the average value v is recalculated. m With standard deviation s x and v 01 With v 02 ;

[0027] Repeat the above process until all data meet the requirements of v 01 With v 02 At this time, v 01 It is the critical value of sound speed anomaly.

[0028] Preferably, the step of determining the position of the defect according to the position of the abnormal measurement line and calculating the defect size in the abnormal measurement line according to the relationship between the abnormal value of the acoustic wave parameter and the defect size specifically includes:

[0029] Assuming the defect in concrete is a sphere with a radius of r, the relationship between the abnormal sound velocity and the defect radius is as follows:

[0030]

[0031] Wherein, L is the distance between the outer walls of the acoustic detection pipes, L1, L3, and L2 are the distance between the outer walls of the acoustic detection pipes on both sides and the metal joints and the thickness of the metal joints, and L = L1 + L2 + L3, r is the radius of the spherical defect of the metal joint of the underground continuous wall, V G The speed of sound waves in metal joints, V H The speed of sound waves in concrete, V C The speed of sound waves in air;

[0032] Known v R and L1, L2, L3, L, V G 、V H , Substitute into the above formula to obtain the defect radius r.

[0033] Preferably, when there are multiple groups of test sections with abnormal measurement lines, it is assumed that the abnormal measurement lines of each group of sections are located at the same depth, and the size of each group of defects is calculated to be r1, r2, ..., r n , if 2.(r1+r2+…+r n )>0.8·H, H is the thickness of the underground continuous wall at the metal joint. At this time, it is considered that the defects have been connected, that is, a through defect is formed along the metal joint of the underground continuous wall.

[0034] Preferably, when α is the oblique incident angle of the sound wave, α satisfies When the defect radius r is measured, the oblique measurement method is used to supplement the measurement.

[0035] The relationship between the abnormal sound velocity value and the defect radius is expressed by the following formula:

[0036]

[0037] Where: L' is the distance between the outer walls of the two acoustic detection pipes measured obliquely, L is the distance between the outer walls of the acoustic detection pipes measured horizontally, L1, L3, L2 are the distance between the outer walls of the acoustic detection pipes on both sides and the metal joints and the thickness of the metal joints, and L = L1 + L2 + L3, r is the radius of the spherical defect of the metal joint of the underground continuous wall, V G The speed of sound waves in metal joints, V H The speed of sound waves in concrete, V C The speed of sound waves in air;

[0038] Known v R and L1, L2, L3, L, L', V G 、V H , Substitute into the above formula to obtain the defect radius r.

[0039] The method for detecting the density of underground continuous wall metal joints based on the sound wave transmission method proposed in the present invention uses the sound wave transmission method commonly used in the field of pile foundation integrity detection to detect the density of underground continuous wall metal joints, which can solve the problems of cumbersomeness, damage to the structure, high cost, etc. of conventional methods, and can complete the detection process more conveniently, greatly improving the efficiency in the field of density detection of large underground continuous wall metal joints. The detection method proposed in the present invention can effectively detect the density of large underground continuous wall metal joints. At the same time, compared with the existing regulations that only provide an estimation formula for the calculation of the size of concrete defect voids, and do not mention the calculation formula for the defect size at the large underground continuous wall metal joints, the defect size calculation formula applicable to the large underground continuous wall metal joints proposed in the present invention can well fill the gap in this field, can better solve practical engineering problems, and has a high application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a structural schematic diagram of a metal joint of an underground continuous wall in the prior art;

[0041] Figure 2 It is a schematic diagram of the arrangement of measuring points of a system for detecting the density of metal joints of underground continuous walls based on the acoustic wave transmission method of the present invention;

[0042] Figure 3 It is a schematic diagram of the measuring line when the method for detecting the density of metal joints of underground continuous walls based on the acoustic wave transmission method of the present invention is carried out in a single group of test sections;

[0043] Figure 4 The method for detecting the density of metal joints of underground continuous walls based on the acoustic wave transmission method of the present invention is a schematic diagram of possible propagation paths of acoustic waves at defects when any test section is tested flatly, where path ① is the transmission path and path ② is the diffraction path;

[0044] Figure 5 This is a schematic diagram of possible propagation paths of sound waves at defects when an oblique measurement is performed on any test section in the method for detecting the density of metal joints of underground continuous walls based on the sound wave transmission method of the present invention, where path ③ is a transmission path and path ④ is a diffraction path;

[0045] Figure 6 The present invention is a method for detecting the density of metal joints of underground continuous walls based on the acoustic wave transmission method, and a schematic diagram of judging the density of metal joints of underground continuous walls when there are multiple defects at the same depth along the metal joints of underground continuous walls.

[0046] In the figure, 1-metal joint, 2-underground continuous wall, 3-sonic detection pipe, 31-outer wall of the sonic detection pipe.

[0047] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0048] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0049] The invention provides a method for detecting the density of metal joints of underground continuous walls based on the sound wave transmission method.

[0050] Reference Figures 2 to 6 The system for detecting the density of metal joints of underground continuous walls based on the sound wave transmission method includes multiple groups of acoustic detection tubes penetrating the underground continuous wall, each group of acoustic detection tubes includes a first acoustic detection tube and a second acoustic detection tube respectively located on both sides of the metal joint, the first acoustic detection tube and the second acoustic detection tube are symmetrically arranged relative to the metal joint, and the connecting line of the centers of the first acoustic detection tube and the second acoustic detection tube is perpendicular to the metal joint.

[0051] In the present invention, the acoustic detection tube is arranged as follows Figure 2 As shown, the single-side acoustic detection tube ( Figure 2 A, B, C, D, E, F, G, H and A', B', C', D', E', F', G', H') are arranged along the direction of the metal joints of the underground continuous wall, and the intervals between the acoustic detection pipes are as follows: Figure 2 The value of b is 150-200mm; the lower end of each acoustic detection pipe is set flush with the bottom end of the metal joint, the mouth of the acoustic detection pipe is 300mm higher than the top, and the height of the mouths of all acoustic detection pipes is consistent; the double-sided acoustic detection pipes are tested as a group of sections with the acoustic detection pipes on both sides of the metal joint (such as Figure 2 A A', B B', C C', D D', E E', F F', G G', and H H' are one group of test sections respectively). The distance between the first and second acoustic detection tubes of each group of acoustic detection tubes is 1m-1.5m.

[0052] The metal joints of the underground continuous wall can be constructed by I-beams, cross steel plates, and lock pipes. In this embodiment, the metal joints are constructed by I-beams.

[0053] The method for detecting the density of metal joints of underground continuous walls based on the acoustic wave transmission method comprises the following steps:

[0054] Step S10, using two symmetrical acoustic detection tubes on both sides of the metal joint as a group of acoustic detection tubes to measure a test section, completing the test of each group of acoustic detection tubes in turn, completing all section tests and recording relevant parameters and data of the section tests;

[0055] Step S20, determining a critical value of abnormal sound velocity using a bilateral elimination method based on a probability method according to the sound velocity in the sound wave parameter value obtained by the test, and when a sound velocity value of a measuring line is lower than the critical value of abnormal sound velocity, the measuring line is determined to be an abnormal measuring line;

[0056] Step S30, determining the location of the defect according to the location of the abnormal measurement line and calculating the defect size in the abnormal measurement line according to the relationship between the abnormal value of the acoustic wave parameter and the defect size;

[0057] Step S40, judging the density of the metal joints of the underground continuous wall based on the location and size of the defects in each group of test sections with defects.

[0058] Specifically, step S10 includes:

[0059] Step S101, connect the power supply, check all instruments and equipment, and set various instrument parameters;

[0060] Step S102, opening the covers of each acoustic detection pipe opening and filling the pipe with clean water;

[0061] Step S103, using water as a coupling agent, the transmitting transducer in the acoustic detection tube on one side of the metal joint transmits an acoustic wave signal, and the receiving transducer in the acoustic detection tube on the other side of the metal joint receives the acoustic wave signal;

[0062] Step S104, the transmitting and receiving transducers synchronously measure the sound time, sound speed and amplitude point by point from the bottom upward;

[0063] Step S105, observe whether the waveform is distorted, and perform encrypted measurement when a suspicious waveform appears;

[0064] Step S106, collecting, recording and storing all cross-section test related parameters and data;

[0065] Step S107, repeat the above steps to complete the test of all test sections.

[0066] Specifically, in step S10, the parameters and data related to the cross-sectional test include: the distance L between the outer walls of each group of acoustic detection tubes, the distances L1 and L3 between the outer walls of the acoustic detection tubes on the left and right sides and the metal joint, and the thickness L2 of the metal joint; the wave velocity V of the ultrasonic wave in the metal joint; G ; Ultrasonic wave velocity V in underground continuous wall H ; Test the acoustic wave parameters of the section: acoustic time t, acoustic velocity v, and amplitude A.

[0067] In step S20, the steps of determining the critical value of abnormal sound velocity by using the bilateral elimination method based on the probability method are as follows:

[0068] Calculate the average sound velocity v of each test section m With standard deviation s x ;

[0069] Arrange the test sound velocity values ​​in descending order. The minimum sound velocity v that may occur under normal circumstances 01 =v m -λs xand the maximum value v 02 =v m +λs x , and the minimum value in the sound speed arrangement is 01 Compare, when the minimum value is less than v 01 The data is removed when

[0070] Combine the maximum value in the arrangement with v 02 Compare, when the maximum value is greater than v 02 The data is removed when

[0071] Each time a piece of data is removed, a new arrangement of the remaining data is formed and the average value v is recalculated. m With standard deviation s x and v 01 With v 02 ;

[0072] Repeat the above process until all data meet the requirements of v 01 With v 02 At this time, v 01 It is the critical value of sound speed anomaly.

[0073] In step S30, determining the position of the defect according to the position of the abnormal measurement line and calculating the defect size in the abnormal measurement line according to the relationship between the abnormal value of the acoustic wave parameter and the defect size specifically includes:

[0074] The defects in concrete are assumed to be spheres with a radius of r, which are close to the metal joints and exist symmetrically (the actual defects may be irregular shapes, and the sphere is the smallest sphere whose measuring line passes through the center of the sphere and is tangent to the actual defect size). The relationship between the abnormal sound velocity value and the defect radius is as follows:

[0075]

[0076] Wherein, L is the distance between the outer walls of the acoustic detection pipes, L1, L3, and L2 are the distance between the outer walls of the acoustic detection pipes on both sides and the metal joints and the thickness of the metal joints, and L = L1 + L2 + L3, r is the radius of the spherical defect of the metal joint of the underground continuous wall, V G The speed of sound waves in metal joints, V H The speed of sound waves in concrete, V C The speed of sound waves in air;

[0077] Known v R and L1, L2, L3, L, V G 、V H , Substitute into the above formula to obtain the defect radius r.

[0078] When the sound wave propagation path is intact and without defects:

[0079]

[0080] When the sound wave propagation path is transmission, that is, Figure 4 When using path ①:

[0081]

[0082] When the sound wave propagation path is diffraction, it is Figure 4 For the middle path ②:

[0083]

[0084] Since the propagation speed of ultrasound in metal is greater than that in concrete and much greater than that in air, v T <v R It can be seen that the propagation mode of ultrasonic wave at the defective position of the metal joint of the underground continuous wall is diffraction, that is, the propagation speed is v R Therefore, when there is a defect, substitute v R The defect radius r is obtained from the calculation formula.

[0085] In addition, when α is the incident angle of the oblique sound wave, When the defect radius r is measured, the oblique measurement method is used to supplement the measurement. It is also assumed that the defect is a sphere with a radius of r and is only located on one side of the metal joint (the actual defect may be an irregular shape, and the sphere is the smallest sphere whose measuring line passes through the center of the sphere and is tangent to the actual defect size).

[0086] The relationship between the abnormal sound velocity value and the defect radius is expressed by the following formula:

[0087]

[0088] Where: L' is the distance between the outer walls of the two acoustic detection pipes measured obliquely, L is the distance between the outer walls of the acoustic detection pipes measured horizontally, L1, L3, L2 are the distance between the outer walls of the acoustic detection pipes on both sides and the metal joints and the thickness of the metal joints, and L = L1 + L2 + L3, r is the radius of the spherical defect of the metal joint of the underground continuous wall, V G The speed of sound waves in metal joints, V H The speed of sound waves in concrete, V C The speed of sound waves in air;

[0089] Known v R and L1, L2, L3, L, L', V G 、V H , Substitute into the above formula to obtain the defect radius r.

[0090] In the oblique measurement method, the possible paths of sound wave propagation at the defect are as follows: Figure 5 Shown

[0091] When the sound wave propagation path is intact and without defects:

[0092] When the sound wave propagation path is transmission, it is Figure 5 Path ③:

[0093]

[0094] The sound wave propagation path is diffraction, which is Figure 5 For the middle ④ path:

[0095]

[0096] Since the propagation speed of ultrasound in metal is greater than that in concrete and much greater than that in air, v T <v R It can be seen that the propagation mode of ultrasonic waves at the defective position of the metal joint of the underground continuous wall is diffraction, that is, the propagation speed is v R . Because v R In the formula, L1, L2, L3, L, L', V G 、V H Both can be obtained through measurement, therefore, the defect size r can be calculated based on the sound velocity value of the abnormal measuring line.

[0097] In step S40, when there are multiple groups of test sections with abnormal measurement lines, it is assumed that the abnormal measurement lines of each group of sections are located at the same depth, and the size of each group of defects is calculated to be r1, r2, ..., r n , if 2.(r1+r2+…+r n )>0.8·H, H is the thickness of the underground continuous wall at the metal joint. At this time, it is considered that the defects have been connected, that is, a through defect has been formed along the metal joint of the underground continuous wall, indicating that there is a serious problem in the density of the metal joint of the underground continuous wall.

[0098] The method for detecting the density of underground continuous wall metal joints based on the acoustic wave transmission method proposed in this embodiment uses the acoustic wave transmission method commonly used in the field of pile foundation integrity detection to detect the density of underground continuous wall metal joints, which can solve the problems of cumbersomeness, damage to the structure, and high cost of conventional methods, and can complete the detection process more conveniently, greatly improving the efficiency in the field of density detection of large underground continuous wall metal joints. The detection method proposed in the present invention can effectively detect the density of large underground continuous wall metal joints. At the same time, compared with the existing regulations that only provide an estimation formula for the calculation of the size of concrete defect voids, and do not mention the calculation formula for the defect size at the large underground continuous wall metal joints, the defect size calculation formula applicable to the large underground continuous wall metal joints proposed in the present invention can well fill the gap in this field, can better solve practical engineering problems, and has a high application value.

[0099] The invention also proposes a system for detecting the density of metal joints of underground continuous walls based on the sound wave transmission method.

[0100] In this preferred embodiment, a system for detecting the density of metal joints of underground continuous walls based on the sound wave transmission method includes multiple groups of acoustic detection tubes penetrating the underground continuous wall, each group of acoustic detection tubes includes a first acoustic detection tube and a second acoustic detection tube respectively located on both sides of the metal joint, the first acoustic detection tube and the second acoustic detection tube are symmetrically arranged relative to the metal joint, and the line connecting the centers of the first acoustic detection tube and the second acoustic detection tube is perpendicular to the metal joint.

[0101] Specifically, the distance between two adjacent acoustic detection tubes on the same side of the metal joint is 150mm-200mm. The distance between the first acoustic detection tube and the second acoustic detection tube of each group of acoustic detection tubes is 1m-1.5m.

[0102] The system for detecting the density of metal joints of underground continuous walls based on the sound wave transmission method proposed by the present invention has a simple structure and is easy to implement.

[0103] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A system for detecting the density of metal joints of underground continuous walls based on the acoustic wave transmission method, characterized in that: It includes multiple groups of acoustic detection tubes penetrating into an underground continuous wall, each group of acoustic detection tubes includes a first acoustic detection tube and a second acoustic detection tube respectively located on both sides of a metal joint, the first acoustic detection tube and the second acoustic detection tube are symmetrically arranged relative to the metal joint, and a connecting line of the centers of the first acoustic detection tube and the second acoustic detection tube is perpendicular to the metal joint.

2. The system for detecting the density of metal joints of underground continuous walls based on the acoustic wave transmission method according to claim 1, characterized in that: The interval between two adjacent acoustic detection pipes on the same side of the metal joint is 150mm-200mm.

3. The system for detecting the density of underground continuous wall metal joints based on the acoustic wave transmission method according to claim 1, characterized in that: The distance between the first acoustic detection tube and the second acoustic detection tube of each group of acoustic detection tubes is 1m-1.5m.

4. A method for detecting the density of metal joints of underground continuous walls based on the system of any one of claims 1 to 3 using the acoustic wave transmission method, characterized in that: The following steps are involved: Take two symmetrical acoustic testing tubes on both sides of the metal joint as a group of acoustic testing tubes to measure a test section, complete the test of each group of acoustic testing tubes in turn, complete all section tests and record the relevant parameters and data of the section test; According to the sound velocity in the acoustic wave parameter value obtained by the test, the critical value of sound velocity anomaly is determined by the bilateral elimination method based on the probability method. When the sound velocity value of a measuring line is lower than the critical value of sound velocity anomaly, the measuring line is determined to be an abnormal measuring line. Determine the location of the defect according to the location of the abnormal measurement line and calculate the defect size in the abnormal measurement line according to the relationship between the abnormal value of the acoustic wave parameter and the defect size; The density of the metal joints of the underground continuous wall is determined based on the location and size of the defects in each group of test sections with defects.

5. The method for detecting the density of metal joints of underground continuous walls based on the acoustic wave transmission method according to claim 4, characterized in that: The steps of measuring a test section by using two symmetrical acoustic detection tubes on both sides of the metal joint as a group of acoustic detection tubes, completing the test of each group of acoustic detection tubes in turn, completing all section tests and recording relevant parameters specifically include: Connect the power supply, check all instruments and equipment, and set various instrument parameters; Open the covers of each acoustic detection pipe opening and fill the pipe with clean water; Using water as a coupling agent, the transmitting transducer in the acoustic detection tube on one side of the metal joint transmits the acoustic wave signal, and the receiving transducer in the acoustic detection tube on the other side of the metal joint receives the acoustic wave signal; The transmitting and receiving transducers measure the sound time, sound speed and amplitude point by point from the bottom upward synchronously; Observe the waveform for distortion and perform encrypted measurements when suspicious waveforms appear; Collect, record and store all relevant parameters and data of cross-section testing; Repeat the above steps to complete all test section tests.

6. The method for detecting the density of underground continuous wall metal joints based on the acoustic wave transmission method according to claim 4, characterized in that: The cross-sectional test related parameters and data include: the distance L between the outer walls of each group of acoustic detection tubes, the distances L1 and L3 between the outer walls of the left and right acoustic detection tubes and the metal joint, and the thickness L2 of the metal joint; the wave velocity V of the ultrasonic wave in the metal joint; G ; Ultrasonic wave velocity V in underground continuous wall H ; Test the acoustic wave parameters of the section: acoustic time t, acoustic velocity v, and amplitude A.

7. The method for detecting the density of underground continuous wall metal joints based on the acoustic wave transmission method according to claim 4, characterized in that: The steps for determining the critical value of sound velocity anomaly by the bilateral elimination method based on the probability method are as follows: Calculate the average sound velocity v of each test section m With standard deviation s x ; Arrange the test sound velocity values ​​in descending order. The minimum sound velocity v that may occur under normal circumstances 01 =v m -λs x and the maximum value v 02 =v m +λs x , and the minimum value in the sound speed arrangement is 01 Compare, when the minimum value is less than v 01 The data is removed when Combine the maximum value in the arrangement with v 02 Compare, when the maximum value is greater than v 02 The data is removed when Each time a piece of data is removed, a new arrangement of the remaining data is formed and the average value v is recalculated. m With standard deviation s x and v 01 With v 02 ; Repeat the above process until all data meet the requirements of v 01 With v 02 At this time, v 01 It is the critical value of sound speed anomaly.

8. The method for detecting the density of metal joints of underground continuous walls based on the acoustic wave transmission method according to claim 4, characterized in that: The steps of determining the position of the defect according to the position of the abnormal measurement line and calculating the defect size in the abnormal measurement line according to the relationship between the abnormal value of the acoustic wave parameter and the defect size specifically include: Assuming the defect in concrete is a sphere with a radius of r, the relationship between the abnormal sound velocity and the defect radius is as follows: Wherein, L is the distance between the outer walls of the acoustic detection pipes, L1, L3, and L2 are the distance between the outer walls of the acoustic detection pipes on both sides and the metal joints and the thickness of the metal joints, and L = L1 + L2 + L3, r is the radius of the spherical defect of the metal joint of the underground continuous wall, V G The speed of sound waves in metal joints, V H The speed of sound waves in concrete, V C The speed of sound waves in air; Known v R and L1, L2, L3, L, V G 、V H , Substitute into the above formula to obtain the defect radius r.

9. The method for detecting the density of metal joints of underground continuous walls based on the acoustic wave transmission method according to claim 8, characterized in that: When there are multiple groups of test sections with abnormal measurement lines, assuming that the abnormal measurement lines of each group of sections are located at the same depth, the size of each group of defects is calculated and determined as r1, r2, …, r n , if 2.(r1+r2+…+r n )>0.8·H, H is the thickness of the underground continuous wall at the metal joint. At this time, it is considered that the defects have been connected, that is, a through defect is formed along the metal joint of the underground continuous wall.

10. The method for detecting the density of metal joints of underground continuous walls based on the acoustic wave transmission method according to claim 8, characterized in that: When α is the incident angle of the oblique sound wave, When the defect radius r is measured, the oblique measurement method is used to supplement the measurement. The relationship between the abnormal sound velocity value and the defect radius is expressed by the following formula: Where: L' is the distance between the outer walls of the two acoustic detection pipes measured obliquely, L is the distance between the outer walls of the acoustic detection pipes measured horizontally, L1, L3, L2 are the distance between the outer walls of the acoustic detection pipes on both sides and the metal joints and the thickness of the metal joints, and L = L1 + L2 + L3, r is the radius of the spherical defect of the metal joint of the underground continuous wall, V G The speed of sound waves in metal joints, V H The speed of sound waves in concrete, V C The speed of sound waves in air; Known v R and L1, L2, L3, L, L', V G 、V H , Substitute into the above formula to obtain the defect radius r.

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