CN115248014A - Monitoring pipe-sleeve assembly for detecting cracks of underwater concrete structure - Google Patents
Monitoring pipe-sleeve assembly for detecting cracks of underwater concrete structure Download PDFInfo
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- CN115248014A CN115248014A CN202210827188.1A CN202210827188A CN115248014A CN 115248014 A CN115248014 A CN 115248014A CN 202210827188 A CN202210827188 A CN 202210827188A CN 115248014 A CN115248014 A CN 115248014A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B13/00—Measuring arrangements characterised by the use of fluids
- G01B13/02—Measuring arrangements characterised by the use of fluids for measuring length, width or thickness
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
- G01N25/20—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity
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Abstract
The invention relates to a monitoring pipe-sleeve assembly for detecting cracks of an underwater concrete structure, which is arranged in a shallow layer of the concrete structure; the monitoring tube-sleeve assembly comprises a sensing heating integrated circuit (7), a sensing heating unit (6), a monitoring tube (1), a sleeve (2), a sealant (3), a vacuum tube (4) and a vacuum valve (5). The invention has the advantages that (1) the monitoring pipe has a protection effect on a monitoring line, the survival rate of the measuring points is ensured, the sensing and heating unit can freely drag and change the positions of the measuring points in the monitoring pipe to implement mobile distributed measurement, and can be taken out of the monitoring pipe for replacement, so that the long-term monitoring requirement is met; (2) The monitoring pipe can replace a steel bar and is stressed with the tested structure in a coordinated manner; (3) The crack monitoring sensitivity is improved, and the crack width quantitative identification is realized.
Description
Technical Field
The invention belongs to the technical field of crack detection devices, and particularly relates to the technical field of a crack detection device for an underwater concrete structure.
Background
Referring to fig. 1, the invention relates to a monitoring scheme for an underwater concrete crack in the prior art, the system is composed of a heating and temperature measuring integrated system, a monitoring pipe 1 and a sleeve 2, wherein: the heating and temperature measuring integrated system has two functions of heating and temperature monitoring and consists of a heating and temperature measuring integrated circuit 3, a demodulator 4 and a stabilized voltage power supply 5. Wherein: the monitoring tube has certain flexibility, and the sleeve is made of porous water-absorbing material.
The monitoring principle is as follows: after the concrete is cracked, when the cracked part is contacted with water, water can permeate into the sleeve 2 along the crack surface due to the capillary action of the porous material, so that the water content of the sleeve 2 is changed, the density, specific heat and heat conduction coefficient of the sleeve 2 are all related to the water content of the sleeve, the larger the water content is, the larger the three thermodynamic parameters are, and the higher the cooling speed of the heat source in the monitoring pipe 1 is, therefore, the cooling speed index can be determined according to a cooling time course curve after the temperature of a measuring point in the monitoring pipe 1 is raised, and the cracked part is identified.
The prior art has the following disadvantages:
1) The embedded monitoring pipe 1 and the embedded sleeve 2 in the figure 1 need to occupy a certain space, and are difficult to implement when the steel bars distributed by concrete are dense;
2) Before and after cracking, the difference of the heat source cooling curves is small, and the sensitivity of crack identification is low;
3) Only the crack position can be identified and the crack width cannot be determined.
Disclosure of Invention
The present invention is directed to solving the above-mentioned problems and providing a monitor tube-sleeve assembly for crack detection of an underwater concrete structure.
The invention is realized by adopting the following technical scheme.
The invention relates to a monitoring pipe-sleeve assembly for detecting cracks of an underwater concrete structure, which is arranged in a shallow layer of the concrete structure; the monitoring tube-sleeve assembly comprises a sensing heating integrated circuit 7, a sensing heating unit 6, a monitoring tube 1, a sleeve 2, a sealant 3, a vacuum tube 4 and a vacuum valve 5;
the sensing heating units 6 are arranged in a plurality; the sensing heating unit 6 is connected with the sensing heating integrated circuit 7 in series;
the monitoring pipe 1 is integrally sleeved on the outer side of the connecting section of the plurality of sensing heating units 6 and the sensing heating integrated circuit 7;
the sleeve 2 is sleeved on the outer side of the monitoring pipe 1 corresponding to the single sensing heating unit 6;
the method comprises the following steps that a gap between two ends of a casing pipe 2 is filled with a sealant 3, and the sealant 3 sets a space between a monitoring pipe 1 and the casing pipe 2 as a sealed space 8;
a vacuum tube 4 is fixedly arranged between the monitoring tube 1 and the sleeve 2;
the vacuum valve 4 is provided with a vacuum valve 5.
The monitoring tube-sleeve assembly further comprises a vacuum pump; the vacuum pump is connected with the vacuum pipe 4 through a vacuum valve 5; the sealed space 8 is set as a vacuum space.
The monitor tube-sleeve assembly further comprises an anchoring steel plate 9; the anchoring steel plate 9 is arranged between two adjacent single sensing heating units 6 and is fixedly connected with the monitoring pipe 1.
The sensing heating integrated circuit 7 is integrated with a heating element and a temperature measuring element.
The monitoring pipe 1 is made of a rigid material; the sleeve 2 is made of a brittle material.
The monitoring tube 1 is made of stainless steel or copper; the sleeve 2 is made of ceramic.
The dimension specification of the monitoring tube 1 is 20mm of outer diameter, 2mm of wall thickness and 600mm of length.
The size specification of the sleeve 2 is 35mm of outer diameter, 5mm of wall thickness and 200mm of length.
The crack detection method of the monitoring pipe-sleeve assembly is used, and the detection method comprises the steps of electrifying the heating element to implement multipoint distributed heating, then cooling, and identifying cracks by monitoring the heat source cooling rule;
the heat transfer law is expressed by the following formula:
where ρ is density; c is the specific heat; t is the temperature; v is the velocity vector of heat transfer, equal to v x v y v z } T (ii) a { L } is the vector operator; [ D ]]Is a heat conducting matrix; q T Is per unit volumeThe heat generation rate;
before cracking, the cavity of the monitoring pipe-sleeve assembly is in vacuum, and after cracking, external water is sucked into the cavity due to the suction effect of the cavity, so that the medium around the sensing heating unit corresponding to the cracking part is changed;
since the heat transfer efficiency of heat transfer is related to the heat transfer coefficient of the medium, the amount of heat transferred from the high-temperature object to the low-temperature object per unit time is expressed as:
q(t)＝γ·ζ(t).A (2)
in the formula: t is time; q (t) is the amount of heat conducted per unit time; gamma is a heat transfer coefficient; ζ (t) is the temperature gradient at time t; a is the heat transfer area;
because the heat conductivity coefficient of water is much larger than that of vacuum, after each heat source is heated, the temperature reduction speed of the heat source corresponding to the cracked part is obviously higher than that of the uncracked part, and the position of the crack can be determined according to the phenomenon.
In the method for calculating the crack width by using the crack detection method, the crack width and the crack judgment index have a linear relation in the range of the crack width:
ξ＝-0.0789w-0.3003(R 2 ＝0.9914) (4)
crack determination index ([ xi ]), crack width (w).
The invention has the advantages that 1) the monitoring pipe has a protection effect on a monitoring line, the survival rate of the measuring points is ensured, the sensing and heating unit can freely drag and change the positions of the measuring points in the monitoring pipe to implement mobile distributed measurement, and can be taken out of the monitoring pipe for replacement, so that the long-term monitoring requirement is met;
2) The monitoring pipe can replace a steel bar and is stressed with the tested structure in a coordinated manner;
3) The crack monitoring sensitivity is improved, and the crack width quantitative identification is realized.
The invention is further explained below with reference to the drawings and the detailed description.
Drawings
Fig. 1 is a diagram of a concrete structure crack monitoring scheme in the prior art.
FIG. 2 is a schematic view of a monitoring pipe-sleeve assembly for crack detection of an underwater concrete structure according to the present invention.
FIG. 3 is a schematic diagram of a vacuum tube structure with a vacuum valve embedded at the sealing position of a monitoring tube and a sleeve.
FIG. 4 is a comparison of the present invention before and after cracking of the casing.
FIG. 5 shows ln (λ - λ) of the sensor during the cooling phase of the present invention θ ) Time course graph.
FIG. 6 is a graph showing the relationship between the crack width (w) and the discrimination index according to the present invention.
The components and reference numbers in the figures are denoted as: the device comprises a monitoring pipe (1), a sleeve (2), a sealant (3), a vacuum pipe (4), a vacuum valve (5), a sensing heating unit (6), a sensing heating integrated circuit (7), a sealed space (8), an anchoring steel plate (9), a concrete structure (10), a crack (11) and a water space (12).
Detailed Description
The invention discloses a monitoring pipe-sleeve assembly for detecting cracks of an underwater concrete structure, which is shown in figure 2. The monitoring pipe is made of stainless steel pipes and other rigid materials with high strength, the sleeve pipe is made of brittle materials, the sleeve pipe is wrapped outside the monitoring pipe in a segmented mode, a certain gap exists between the monitoring pipe and the sleeve pipe, and gaps at two ends of the sleeve pipe are sealed by sealing glue. A vacuum tube with a vacuum valve is pre-embedded at the sealing position of the monitoring tube and the sleeve, as shown in fig. 3. And vacuumizing the gap between the monitoring pipe and the sleeve by using a vacuum pump. The anchor steel plates are welded on the monitoring pipe in a segmented mode, so that the monitoring pipe and concrete generate enough occlusion force, the monitoring pipe and a tested structure are ensured to be stressed cooperatively, the monitoring pipe can replace reinforcing steel bars inside the concrete, and the space requirement for embedding the monitoring pipe is reduced. The monitoring pipe-sleeve assembly is embedded in the concrete like a crack sensing nerve, and meanwhile, the monitoring pipe is also used as a crack detection channel, so that the sensing and heating integrated circuit can be conveniently and freely dragged in the monitoring pipe, and when the sensing and heating integrated circuit is damaged, the sensing and heating integrated circuit can be dragged out of the monitoring pipe for maintenance or replacement. The sensing heating integration line is integrated with heating element and temperature element, and to heating element circular telegram implementation multiple spot decentralized heating, then the cooling, through monitoring heat source cooling law discernment crack.
The monitoring principle is as follows:
the heat transfer mode is three: thermal conduction, thermal convection, and thermal radiation. For most heat transfer problems, the proportion of thermal radiation is negligible. At this time, the heat transfer law can be expressed by the following formula:
where ρ is density; c is the specific heat; t is the temperature; v is the velocity vector of heat transfer, equal to v x v y v z } T (ii) a { L } is the vector operator; [ D ]]Is a heat conducting matrix; q T Is the heat generation rate per unit volume.
Before cracking, the cavity of the monitoring tube-sleeve assembly is in vacuum, and after cracking, external water is sucked into the cavity due to the suction effect of the cavity, so that the medium around the sensing heating unit corresponding to the cracking part is changed. Since the heat transfer coefficient of the heat transfer efficiency medium for heat transfer is related, according to the heat transfer theory, the amount of heat transferred from the high temperature object to the low temperature object per unit time can be expressed as:
q(t)＝γ·ζ(t).A (2)
in the formula: t is time; q (t) is the amount of heat conducted per unit time; gamma is a heat transfer coefficient; ζ (t) is the temperature gradient at time t; a is the heat transfer area.
Because the heat conductivity coefficient of water is much larger than that of vacuum, after each heat source is heated, the temperature reduction speed of the heat source corresponding to the cracked part is obviously higher than that of the uncracked part, and the position of the crack can be determined according to the phenomenon.
After cracking, the water in the cavity of the monitoring pipe-sleeve assembly flows due to pressure difference and temperature gradient, and the crack is used as a channel to exchange heat with the external water, so that a convection heat transfer effect is generated. The convection heat transfer is a heat transfer mode for taking away heat through fluid flow, the heat transfer efficiency of the convection heat transfer is related to the convection heat transfer coefficient, and according to the newton's law of cooling, the heat flow generated by the fluid flowing on the solid surface can be expressed as:
{q} T {n}＝h f (T s -T B ) (3)
in the formula: { q } heat flow vector; { n } is the normal vector of the radiating surface; h is f A convective heat transfer coefficient; t is s Solid surface temperature; t is B The temperature of the fluid.
As can be seen from equation (3): the efficiency of convective heat transfer is proportional to the convective heat transfer coefficient. The convective heat transfer coefficient is related to the fluid flow rate, which in turn is related to the fracture width in the cavity. The wider the crack, the more obvious the convective heat transfer, and the faster the cooling, therefore, the cooling speed of the heat source can also reflect the width of the crack.
In order to verify the effectiveness of the monitoring pipe-sleeve assembly for detecting the crack of the underwater concrete structure, 1 concrete test piece is manufactured, and the size specification of the test piece is 150mm 550mm. 1 monitoring tube-sleeve assembly is embedded in the test piece. Wherein the monitoring pipe is a stainless steel pipe with the outer diameter of 20mm, the wall thickness of 2mm and the length of 600 mm; the sleeve pipe adopts a ceramic pipe with the outer diameter of 35mm, the wall thickness of 5mm and the length of 200mm. The bottom end of the monitoring tube is plugged by hot melt adhesive, the tube is filled with water, and then a sensing heating element consisting of a fiber grating temperature sensor with the diameter of 4mm and the length of 60mm, a ceramic heating tube with the outer diameter of 12mm, the inner diameter of 8mm and the length of 12mm, a copper tube with the outer diameter of 15mm, the wall thickness of 1mm and the length of 12mm is inserted into the tube from the top end of the monitoring tube.
Carrying out heating-cooling test on the sensing heating unit, wherein: the heating adopts a stabilized voltage power supply, and the temperature measurement adopts a fiber grating demodulator.
According to ln (lambda-lambda) of the sensor during the cooling phase θ ) The time course curve (as shown in fig. 5) is used to calculate the crack discrimination index (#), and then the relationship between the crack width (w) and the discrimination index is established, as shown in fig. 6, the fitting formula is shown in formula (4). As can be seen from fig. 5: before and after cracking, cooling stage ln (lambda-lambda) θ ) The time course curves are clearly distinguished, and the absolute value of the initial slope basically increases with the increase of the crack width, but the increasing trend is not obvious, and the absolute value of the later slope increases with the increase of the crack width. As can be seen from fig. 6 and equation (4): crack width in the range of test crack widthHas good linear relation with the crack judging index.
ξ＝-0.0789w-0.3003(R 2 ＝0.9914) (4)
The foregoing is only a part of the specific embodiments of the present invention and specific details or common general knowledge in the schemes have not been described herein in more detail. It should be noted that the above-mentioned embodiments do not limit the present invention in any way, and it is obvious for those skilled in the art that all the technical solutions obtained by using the equivalent substitution or the equivalent change fall within the protection scope of the present invention. The scope of the claims of the present application shall be defined by the claims, and the description of the embodiments and the like in the specification shall be used to explain the contents of the claims.
Claims (10)
1. A monitoring pipe-sleeve assembly for detecting cracks of an underwater concrete structure is characterized by comprising a sensing heating integrated circuit (7), a sensing heating unit (6), a monitoring pipe (1), a sleeve (2), sealant (3), a vacuum pipe (4) and a vacuum valve (5);
the sensing heating units (6) are arranged in a plurality; the sensing heating unit (6) is connected with the sensing heating integrated circuit (7) in series;
the monitoring pipe (1) is integrally sleeved on the outer side of the connection section of the sensing heating units (6) and the sensing heating integrated circuit (7);
a sleeve (2) is sleeved on the outer side of the monitoring pipe (1) corresponding to the single sensing heating unit (6);
a sealant (3) is filled in a gap at two ends of the casing pipe (2), and the sealant (3) sets a space between the monitoring pipe (1) and the casing pipe (2) as a sealed space (8);
a vacuum tube (4) is fixedly arranged between the monitoring tube (1) and the sleeve (2);
the vacuum tube (4) is provided with a vacuum valve (5).
2. The monitor tube and sleeve assembly for crack detection of an underwater concrete structure according to claim 1, wherein the monitor tube and sleeve assembly further comprises a vacuum pump; the vacuum pump is connected with the vacuum pipe (4) through a vacuum valve (5); the sealed space (8) is set as a vacuum space.
3. A monitor tube-sleeve assembly for crack detection of underwater concrete structures according to claim 1, characterized in that said monitor tube-sleeve assembly further comprises an anchoring steel plate (9); the anchoring steel plate (9) is arranged between two adjacent single sensing heating units (6) and is fixedly connected with the monitoring pipe (1).
4. The monitor tube-sleeve assembly for detecting the crack of the underwater concrete structure as claimed in claim 1, wherein the sensor heating integrated circuit (7) is integrated with a heating element and a temperature measuring element.
5. A monitor tube-sleeve assembly for crack detection of underwater concrete structures according to claim 1, characterized in that the material of the monitor tube (1) is a rigid material; the sleeve (2) is made of a brittle material.
6. A monitor tube-sleeve assembly for crack detection of underwater concrete structures according to claim 1, characterized in that the material of the monitor tube (1) is stainless steel or copper; the sleeve (2) is made of ceramic.
7. A monitor tube-sleeve assembly for crack detection of underwater concrete structures according to claim 1, characterized in that the monitor tube (1) has the dimensions of 20mm outer diameter, 2mm wall thickness and 600mm length.
8. The monitor tube-sleeve assembly for crack detection of underwater concrete structure as claimed in claim 1, wherein the size specification of the sleeve (2) is 35mm in outer diameter, 5mm in wall thickness and 200mm in length.
9. The crack detection method of the monitor tube-sleeve assembly according to claim 1, wherein the detection method comprises the steps of electrifying the heating element to perform multipoint distributed heating, then cooling, and identifying the crack by monitoring the cooling rule of the heat source;
the heat transfer law is expressed by the following formula:
where ρ is density; c is the specific heat; t is the temperature; v is the velocity vector of heat transfer, equal to v x v y v z } T (ii) a { L } is the vector operator; [ D ]]Is a heat conducting matrix; q T Is the heat generation rate per unit volume;
before cracking, the cavity of the monitoring tube-sleeve assembly is in vacuum, and after cracking, external water is sucked into the cavity due to the suction effect of the cavity, so that the medium around the sensing heating unit corresponding to the cracking part is changed;
since the heat transfer efficiency of heat transfer is related to the heat transfer coefficient of the medium, the amount of heat transferred from the high-temperature object to the low-temperature object per unit time is expressed as:
q(t)＝γ·ζ(t).A (2)
in the formula: t is time; q (t) is the amount of heat conducted per unit time; gamma is a heat transfer coefficient; ζ (t) is the temperature gradient at time t; a is the heat transfer area;
because the heat conductivity coefficient of water is much larger than that of vacuum, after each heat source is heated, the temperature reduction speed of the heat source corresponding to the cracked part is obviously higher than that of the uncracked part, and the position of the crack can be determined according to the phenomenon.
10. The method for calculating the crack width by using the crack detection method according to claim 9, wherein the crack width has a linear relationship with a crack discrimination index within the range of the crack width:
ξ＝-0.0789w-0.3003(R 2 ＝0.9914) (4)
crack determination index ([ xi ]), crack width (w).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210827188.1A CN115248014A (en) | 2022-07-13 | 2022-07-13 | Monitoring pipe-sleeve assembly for detecting cracks of underwater concrete structure |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202210827188.1A CN115248014A (en) | 2022-07-13 | 2022-07-13 | Monitoring pipe-sleeve assembly for detecting cracks of underwater concrete structure |
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| CN115248014A true CN115248014A (en) | 2022-10-28 |
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| CN202210827188.1A Pending CN115248014A (en) | 2022-07-13 | 2022-07-13 | Monitoring pipe-sleeve assembly for detecting cracks of underwater concrete structure |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112198193A (en) * | 2020-10-30 | 2021-01-08 | 四川大学 | Concrete structure crack monitoring device and monitoring method thereof |
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2022
- 2022-07-13 CN CN202210827188.1A patent/CN115248014A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112198193A (en) * | 2020-10-30 | 2021-01-08 | 四川大学 | Concrete structure crack monitoring device and monitoring method thereof |
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