Method and apparatus for determining the path of a concrete diagonal crack tip

Abstract

The present application relates to a kind of method and device for judging the trend of concrete oblique crack tip, fill metal powder in the crack to be measured;Determine the beginning and end point of crack trend according to the opening trend of crack surface to be measured, draw the center line of the connecting line of beginning and end point as the first measuring line, respectively from the two end points of the first measuring line along the first measuring line to crack opening position detection using electromagnetic wave radar detector, record the position and depth of the first fluctuation point on radar development map;With the first measuring line as reference line, rotate to make several new measuring lines, obtain the position and depth of the first fluctuation point of each new measuring line;Fluctuation point is sorted according to measuring line sequence, draw the connecting line diagram, i.e. the trend curve of oblique crack tip.The present application is based on the essential characteristics such as the height and form of oblique crack tip position, combined with the measurement mode from far to near, multi-angle, multiple measuring points and the reflection law of radar wave by metal powder, the position and depth of multiple points of concrete oblique crack tip are measured, and then the trend of crack tip is effectively judged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete crack detection, and particularly relates to a method and device for judging the trend of a concrete oblique crack tip. BACKGROUND

[0002] Cracks are the most common disease of concrete structures. When concrete structures are subjected to loads, temperature changes or shrinkage changes, irregular oblique cracks are often formed. By investigating the development trend of the cracks, the influence of the cracks on the safety and durability of the structure can be judged. Current mature detection methods and technical processes can accurately detect the development trend of the crack surface opening, but the development of the cracks into the concrete cannot be investigated, mainly because the crack depth detection technology is not mature and not perfect. In fact, investigating the development trend of the crack inside, especially the tip, is more important. For important components, the trend and position of the crack tip directly determine the bearing capacity of the component. At present, crack depth detection is still a technical problem, and the detection method and technical process for the crack tip trend are still blank.

[0003] Chinese patent CN107561097A uses a grouting device to press a detection agent containing iron powder into the cracks of a concrete structure, and then uses an X-ray machine to irradiate the concrete cracks, thereby displaying the morphological characteristics of the cracks on a computer to measure the depth and trend of the cracks. The detection agent in this method contains a liquid, which makes it impossible for the iron powder to fill the cracks completely during the grouting period, so the distribution of the iron powder in the cracks cannot be guaranteed, thereby affecting the true reflection of the crack tip by the X-ray machine. Chinese patent CN114636759A discloses a method for determining the maximum depth of cracks in a concrete structure based on acoustic emission. This method uses broken lead as an acoustic emission source, and the acoustic emission signal is easily disturbed by various noises during propagation, thereby affecting the accuracy of the acoustic emission signal attenuation relationship with the propagation distance obtained, and affecting the crack depth detection accuracy. Since the crack tip size is very small and its own electrical property is weak, it has almost no reflection to electromagnetic waves, and an external tracer is needed. Current technology uses grouting to fill powder tracers into concrete cracks, but existing technology cannot grout metal powder to the crack tip, the reasons including: first, the inner wall of the crack cavity is tortuous and the surface is rough, which easily causes the powder to be blocked at a shallow position; second, as the crack depth increases, the crack cavity volume becomes smaller and smaller, and the powder is difficult to further approach the crack tip. Therefore, the existing technology cannot accurately detect the crack depth, and cannot effectively investigate the trend of the oblique crack tip of the concrete structure. SUMMARY

[0004] In order to overcome the defects of the prior art, the present application provides a method and device for judging the trend of the tip of a concrete oblique crack, which is simple to operate, easy to realize, effectively ascertains the trend of the tip of the oblique crack, has strong practicality and is suitable for engineering site application under different environments.

[0005] In order to achieve the above object, the present application adopts the following technical scheme:

[0006] A method for judging the trend of the tip of a concrete oblique crack, comprising:

[0007] filling metal powder in the crack to be measured;

[0008] determining the start and end points of the crack trend according to the opening trend of the surface of the crack to be measured, drawing a perpendicular line of the start and end point connecting line as a first measuring line, detecting from the two end points of the first measuring line to the crack opening position along the first measuring line by using an electromagnetic wave radar detector, recording the depth of the first fluctuation point on the radar development map and the vertical distance of the radar detector corresponding to the fluctuation point from the start and end point connecting line, and judging the side where the crack tip is located according to the point position;

[0009] taking the first measuring line as a reference line, rotating the reference line with the intersection of the reference line and the start and end point connecting line as the center within the range of the crack opening trend and the reference line, drawing a plurality of new measuring lines, the adjacent measuring lines have equal angles, marking the end points of the new measuring lines on the side where the crack tip is located, controlling the radar detector to detect from the marked end points to the crack opening position along the measuring lines in sequence, observing the radar development map and recording the depth of the first fluctuation point on the map and the vertical distance of the corresponding radar detector from the start and end point connecting line;

[0010] sorting the fluctuation points according to the measuring line sequence, taking the vertical distance of the radar detector corresponding to the fluctuation point from the start and end point connecting line as the abscissa and the depth as the ordinate to draw a fluctuation point connecting line diagram, i.e. the trend curve of the tip of the oblique crack.

[0011] In the present application, the first fluctuation point is the initial point on the radar development map where the radar signal changes strongly and uniformly.

[0012] As a preferred embodiment, the way of filling metal powder in the crack to be measured is:

[0013] a. inserting a spraying needle into the crack to be measured, and injecting metal powder into the crack to be measured through the spraying needle;

[0014] b. when the powder overflows on the surface of the crack, stopping the powder injection and pulling out the spraying needle, placing a vibration exciter on both sides of the crack to perform vibration excitation, and after the metal powder on the surface of the crack is stable and does not sink any more, stopping the vibration excitation;

[0015] c. repeating a-b until the metal powder on the surface of the crack does not sink any more, and removing the metal powder on the surface of the concrete crack.

[0016] As a preferred embodiment, in a, the metal powder is injected into the crack to be detected through the injection needle by using the air pressure pump as the power device.

[0017] As a preferred embodiment, the exciter is an ultrasonic exciter.

[0018] As a preferred embodiment, from the start of injection of the metal powder to the first overflow of the metal powder on the surface of the crack, the powder / gas flow ratio is ≤1 / 6, and the powder / gas flow ratio is increased after the first overflow of the metal powder on the surface of the crack.

[0019] As a preferred embodiment, the working range of the exciter is a rectangular area with the length of the crack opening trend as the width and three times the length of the crack opening trend as the length, and the long side of the rectangular area is along the direction of the crack opening trend.

[0020] As a preferred embodiment, the exciter is at least 2-5 cm away from the nearest crack opening during operation to prevent the metal powder in the crack from being shaken out, and excitation is performed every 2-5 cm within the working range.

[0021] As a preferred embodiment, the exciter is first excited near one side of the crack opening trend during operation.

[0022] As a preferred embodiment, the particle size of the metal powder is 100-5000 mesh, and the particle size is less than 1 / 5 of the width of the crack to be detected; the needle port of the injection needle is wedge-shaped, the inner diameter of the needle port is greater than 5 times the particle size of the metal powder, and the outer diameter of the needle port allows at least half of the needle port to be inserted into the crack to be detected.

[0023] As a preferred embodiment, the position of the end point is such that the radar detector placed at the end point cannot detect the reflected radar waves of the metal powder.

[0024] Another object of the present application is to provide a device for the above-mentioned method, which comprises an electromagnetic wave radar detector, an exciter and a metal powder injection device.

[0025] The metal powder injection device comprises a powder storage device, a power device, a conduit, an injection pipe and an injection needle connected in sequence.

[0026] The power device sucks the metal powder from the powder storage device and delivers it to the injection needle through the conduit and the injection pipe, and the injection needle is inserted into the crack to be detected to inject the metal powder into the crack to be detected through the injection needle.

[0027] As a preferred embodiment, the powder storage device, the conduit and the injection pipe are made of transparent materials, and the conduit is made of transparent silica gel tube.

[0028] As a preferred embodiment, the working surface of the exciter is smooth and round.

[0029] The principle of judging the trend of the crack tip in the present application: the radar detector emits high-frequency electromagnetic waves to the concrete, and the electromagnetic waves will be reflected when encountering a target body with electrical difference in the propagation process. In the present application, the metal powder is filled into the position close to or at the crack tip by the way of mutual combination and alternation of air pressure pump perfusion and exciter vibration. The metal powder has strong total reflection effect on the electromagnetic waves. The shape of the crack tip is essentially a spatial curve with uneven height, and for the inclined crack, the crack tip has a certain horizontal distance from the crack opening position. After the crack is filled with metal powder, a metal curve with uneven height appears at the crack tip position, and a metal curved surface appears from the crack surface opening position to the tip. By moving the radar detector from the far crack opening end to the crack opening position, the radar detector will preferentially sense the position of the crack tip, and a fluctuation area will appear on the radar display diagram, and the vertex of the first fluctuation point is the tip position of the measurement point. Further, by moving the radar detector from different angles of the far crack opening end to the crack opening position, the radar detector senses and identifies the positions and depths of the crack tips of different measurement points, and the trend of the crack tip is inferred from the positions and depths.

[0030] In the present application, the metal powder reaches the position of the inclined crack tip by the way of mutual combination and alternation of air pressure pump perfusion and exciter vibration at multiple points. Based on the essential characteristics of the height and shape of the inclined crack tip position, combined with the measurement method from far to near, multiple angles, and multiple measurement points, and the reflection law of the metal powder on the radar wave, the positions and depths of the inclined crack tip of the concrete can be measured, and the trend of the crack tip can be effectively judged by combining the positions and depths. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 It is a device for judging the trend of the inclined crack tip of the concrete.

[0032] Figure 2 It is a schematic diagram of the nozzle device.

[0033] Figure 3 It is the concrete structure and crack to be inspected in the embodiment.

[0034] Figure 4 It is a curve diagram of the trend of the inclined crack tip of the concrete to be measured in the embodiment.

[0035] In the figure: 1-radar detector; 2-power device; 3-powder storage device; 4-flow control valve; 5-conduit; 6-nozzle; 7-injection pipe; 8-injection needle; 9-concrete structure to be inspected; 10-crack; 11-exciter. EMBODIMENT

[0036] The technical solutions of the application are further described below through specific examples.

[0037] A method for judging the trend of a concrete oblique crack tip, comprising the following steps:

[0038] The engineering task is that a crack appears on the top surface of a concrete structure, and the trend of the crack tip is required to be detected.

[0039] 1. Preparation work, the steps are as follows:

[0040] (1) Determine that the surface opening trend of the crack 10 to be measured is a straight line, determine the starting point and the ending point of the surface crack 10, measure the length of the crack 10 as 30 cm, the width of the crack 10 is uniform and is 1 mm, and the working surface diameter of the excitation vibrator 11 is 6 cm.

[0041] (2) Open the cover of the powder storage device 3, pour the homogeneous iron powder with a fineness of 1000 mesh into the powder storage device 3, and after tightening the cover, connect the powder storage device 3 to the air pressure pump 2, and sequentially assemble the flow control valve 4, the conduit 5 and the nozzle 6, the nozzle 6 is composed of the jet pipe 7 and the jet needle 8, the flow control valve 4 is used for adjusting the volume ratio of the metal powder and the gas entering the jet pipe, and is used for adjusting the kinetic energy of the powder spraying.

[0042] 2. Powder spraying work, the steps are as follows:

[0043] (1) Insert the jet needle 8 into the crack 10 to be measured, start the air pressure pump 2, the air pressure pump 2 makes the iron powder in the powder storage device 3 enter the crack 10 to be measured through the flow control valve 4, the conduit 5, the jet pipe 7 and the jet needle 8, when the iron powder overflows from the surface of the crack 10, stop powder spraying and pull out the jet needle.

[0044] (2) Define the working range of the excitation vibrator 11. The specific operation is as follows: draw two parallel lines parallel to the opening trend of the crack 10, the lengths of the two parallel lines are both 30 cm, and the distances from the opening trend of the crack 10 are both 3 cm, and respectively define a rectangle on the two sides of the opening of the crack 10 with the two parallel lines as the wide sides, and the long side length of the rectangle is 90 cm.

[0045] (3) First, excite the excitation area on the left side of the crack 10 opening, excite once every 3 cm from top to bottom and from right to left, and the duration of each time is 5 seconds; after the excitation on the left side of the crack 10 opening is completed, excite the right side of the crack 10 opening, excite once every 3 cm from top to bottom and from left to right, and the duration of each time is 5 seconds.

[0046] (4) After the vibration process in (3) is completed, it is found that the metal powder at the crack 10 opening subsides, and step (1) is repeated again. After step (1) is completed, the vibration process in (3) is performed again. After this process is repeated four times, it is found that the metal powder at the crack 10 opening no longer subsides.

[0047] 3. Radar detection work, the steps are as follows:

[0048] (1) Connect the starting point and the ending point as a reference line, and take the vertical distance from the radar detector to the reference line as the horizontal distance from the fluctuation point to the crack. Draw a perpendicular line to the reference line, denoted as L1, and mark the two endpoints of the perpendicular line as a1 and a2. Endpoint a1 is on the left side of the crack 10 opening, and endpoint a2 is on the right side of the crack 10 opening, both endpoints are 60 cm away from the center of the crack 10 trend. Control the radar detector to detect from endpoint a1 along L1 to the crack 10 opening position, and observe that there is no fluctuation reflection on the radar development map. Then control the radar detector to detect from endpoint a2 along L1 to the crack 10 opening position, and when the vertical distance from the radar detector to the reference line is 25 cm, the first fluctuation point appears on the radar development map, and the depth of the fluctuation point is 15 cm. It is judged that the crack tip is on the left side of the crack 10 opening.

[0049] (2) Take L1 as the reference line, and draw a new measuring line every 9° around the center of the crack 10 trend on the left side of the crack 10 opening, with the perpendicular line L1 as the reference line. Mark the outer endpoints of the 10 new measuring lines, and the 10 outer endpoints are all 60 cm away from the crack 10 opening. Control the radar detector 11 to detect from the outer endpoint of each new measuring line to the crack 10 opening position along the measuring line in turn, observe the radar development map and record the position and depth of the first fluctuation point on the map, and find that there are radar fluctuation points on 8 new measuring lines. The radar detection task is completed. Finally, 9 fluctuation points are obtained, from the left to the right of the perpendicular line L1, and the vertical distance from the radar detector to the reference line for each fluctuation point is 30 cm, 28 cm, 26 cm, 26 cm, 25 cm, 27 cm, 23 cm, 18 cm, and 17 cm, respectively. The depth of each fluctuation point is 23 cm, 20 cm, 20 cm, 18 cm, 15 cm, 15 cm, 14 cm, 14 cm, and 12 cm, respectively.

[0050] According to the above detection results, it is judged that the crack tip is on the left side of the crack 10 opening, the crack tip is an irregular curve, and the upper endpoint of the curve is far away from the crack 10 opening, the lower endpoint is close to the crack 10 opening, and the curve gradually becomes shallow from the upper endpoint to the lower endpoint.

[0051] In this embodiment: the center frequency of the radar detector 1 is 2.6 GHz; the exciter 11 is selected as an ultrasonic exciter, and the working frequency is 35 kHz; the working pressure of the gas pressure pump is 1.0 MPa; the powder storage device 3 is a transparent plastic bucket, and the maximum capacity is 4 L; the flow control valve 4 has a flow of 2 L / min, wherein before the first overflow of metal powder on the crack surface, the gas flow is 1.8 L / min, the iron powder flow is 0.2 L / min, the gas flow is increased to increase the powder spraying kinetic energy, and the iron powder accumulation is avoided; after the first excitation is completed, the gas flow is adjusted to 1.5 L / min, and the iron powder flow is 0.5 L / min; the conduit 5 is a transparent soft silica gel tube; the spray pipe 3 is a transparent plastic tube, and the maximum capacity is 0.2 L; the spray needle 8 has an outer diameter of 0.2 mm and an inner diameter of 0.15 mm.

[0052] The above has carried on the detailed description to one embodiment of the present application, but the content described is only the preferred embodiment of the present application, and cannot be considered as being used to limit the implementation scope of the present application. Any equivalent changes and improvements made according to the scope of the present application should still belong to the patent coverage scope of the present application.

Claims

1. A method for determining the trend of the tip of a diagonal crack in concrete, characterized in that, include: Metal powder is injected into the crack to be tested using a jet needle combined with multi-point excitation by a vibrator, filling the crack to the crack tip with metal powder; the method of filling the crack to the crack tip with metal powder is as follows: a. Insert the injection needle into the crack to be tested, and inject the metal powder into the crack through the injection needle; b. When powder overflows from the crack surface, stop the powder injection and pull out the injection needle. Place vibrators on both sides of the crack to vibrate. Stop vibrating after the metal powder on the crack surface has stabilized and stopped settling. c. Repeat steps a and b until the surface metal powder no longer settles after vibration, then remove the metal powder from the concrete crack surface; The starting and ending points of the crack direction are determined based on the opening direction of the crack surface to be tested. The perpendicular bisector of the line connecting the starting and ending points is drawn as the first measuring line. An electromagnetic wave radar detector is used to detect the crack opening position from the two endpoints of the first measuring line along the first measuring line. The depth of the first fluctuation point on the radar image and the perpendicular distance between the radar detector corresponding to the fluctuation point and the line connecting the starting and ending points are recorded. The side where the crack tip is located is determined based on the point position. Using the first survey line as the baseline, within the direction of the crack opening and the range of the baseline, rotate the baseline around the intersection of the baseline and the line connecting the start and end points to draw several new survey lines, with adjacent survey lines having equal included angles; mark the endpoints of each new survey line on the side where the crack tip is located; control the radar detector to detect from the marked endpoints along each survey line toward the crack opening position, observe the radar development map and record the depth of the first fluctuation point on the map and the corresponding perpendicular distance between the radar detector and the line connecting the start and end points. The fluctuation points are sorted according to the survey line order. The vertical distance between the radar detector corresponding to the fluctuation point and the line connecting the beginning and end points is used as the horizontal axis and the depth is used as the vertical axis to draw the fluctuation point connection diagram, that is, the trend curve of the tip of the oblique crack.

2. The method according to claim 1, characterized in that, In step a, a pneumatic pump is used as the power device to inject metal powder into the crack to be tested through a jet needle; the exciter is an ultrasonic exciter.

3. The method according to claim 1, characterized in that, From the start of metal powder injection until the first metal powder overflows from the crack surface, the powder-to-gas flow ratio should be ≤1 / 6. After the first metal powder overflows from the crack surface, the powder-to-gas flow ratio should be increased.

4. The method according to claim 1, characterized in that, The working range of the vibrator is a rectangular area with the width of the crack opening direction as the width side and three times the width of the crack opening direction as the length side; the length side of the rectangular area is along the crack opening direction.

5. The method according to claim 1, characterized in that, When the vibrator is working, it is at least 2-5 cm away from the nearest point of the crack opening, and it vibrates every 2-5 cm within the working range.

6. The method according to claim 1, characterized in that, When the vibrator is working, it first excites the area close to the crack opening to one side.

7. The method according to claim 1, characterized in that, The metal powder has a particle size of 100-5000 mesh, and the particle size is less than 1 / 5 of the opening width of the crack to be tested; the nozzle of the injection needle is wedge-shaped, the inner diameter of the nozzle is greater than 5 times the particle size of the metal powder, and the outer diameter of the nozzle allows at least half of the nozzle to be inserted into the crack to be tested.

8. The method according to claim 1, characterized in that, The position of the endpoint is such that the radar detector is placed at the endpoint so that it cannot detect the reflected radar waves of the metal powder.

9. The apparatus used in the method according to any one of claims 1 to 8, characterized in that, It includes an electromagnetic wave radar detector (1), a vibrator (11), and a metal powder spraying device; The metal powder injection device includes a powder storage device (3), a power device (2), a conduit (5), an injection pipe (7), and an injection needle (8) connected in sequence. The power unit (2) draws metal powder from the powder storage device (3) and delivers it to the injection needle (8) through the conduit (5) and the injection pipe (7). The injection needle (8) is inserted into the crack to be tested and injects the metal powder into the crack through the injection needle.

Images