CN1032607C - Method for detecting concrete porosity under steel plate by use of neutron technique - Google Patents
Method for detecting concrete porosity under steel plate by use of neutron technique Download PDFInfo
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- CN1032607C CN1032607C CN 92112969 CN92112969A CN1032607C CN 1032607 C CN1032607 C CN 1032607C CN 92112969 CN92112969 CN 92112969 CN 92112969 A CN92112969 A CN 92112969A CN 1032607 C CN1032607 C CN 1032607C
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Abstract
The present invention relates to a method for detecting a depositing concrete hollow hole under a steel plate by use of the neutron technique. According to the method, a neutron probe is calibrated in a room, a working curve of the relation between the height from steel plates of different thicknesses to the surface of concrete and the thermal neutron count rate is obtained, the surface of the steel plate of concrete to be detected is provided with networks, each cross point is detected, the thermal neutron count rate of each detection point is obtained, and a range in which the thermal neutron count rate is obviously low is a hollow hole plane surface range. According to the thickness of the steel plate of the concrete to be detected, a corresponding working curve is selected. According to the thermal neutron count rate of each detection point in the hollow hole plane surface range, through the working curve, the corresponding hollow hole depth can be detected.
Description
The invention belongs to the technical field of using the neutron technology analysis of material, particularly a kind of method that detects deposit concrete cavity under the steel plate with neutron technology.
Large water conservancy hydroelectric engineering often has some steel plates to make the concrete structures such as water culvert pipe, tunnel excessively of back boxing, as the tubular seat and the draft tube of hydropower generator group.These concrete structures that have the steel back boxing are when carrying out pouring concrete construction; because there is closeer reinforcing bar the existence of steel back boxing and inside; casting and constructing is very inconvenient; it is quite difficult to vibrate; concrete is difficult to enrich; therefore regular meeting exists space or cavity between concrete and the back lining of steel plate, thereby influences construction quality and security of operation.Need to detect empty size and scope in light of this situation and necessary repairing and reinforcing is carried out in the hole grouting of drilling.At present can only adopt the mallet method of hitting to judge by rule of thumb on the engineering, but that chopping is not only judged is unreliable, accuracy rate is very low, but also therefore mistake be beaten many useless holes destruction steel plate structures and original intensity.If adopt x-ray method, because of being covered with steel plate on the concrete in above-mentioned engineering usually, and can only detect, and the penetration power of X-ray is lower, so can't adopt at single face.If adopt the big gamma-radiation of energy to detect, then certainly will bring the difficulty in the protection.Equally, if adopt ultrasound examination, because measured object often is multiple medium, thereby lower to its ability to see things in their true light, and also difficult reaching detected the degree of depth that requires.Empty localization method in a kind of concrete structure and the prefabricated components is disclosed in the former Deutsches Reichs-Patent 3823220, it is tentatively to judge the hole of drilling behind the cavity position by chopping, inject the radioactivity flow media by boring again, determine cavity position through measurement detector.Because by chopping, to punch unavoidably by mistake, certainly will cause to a certain degree damage to member, particularly inject radiomaterial and bring pollution will for detection means itself and environment.And it also can only measure in xoncrete structure and the prefabricated components position in cavity, and the horizontal level in cavity in the concrete block can only be determined in the position in cavity in the concrete under the energy measurement steel plate not, the degree of depth that can not the quantitative measurment cavity.
It is a kind of harmless fully that purpose of the present invention will provide, the method for deposit concrete space and cavity blemish under the steel plate particularly under the detection steel plate that can carry out describing in the space to cavity in the concrete block fast of environmentally safe.
The present invention utilizes neutron irradiation to survey deposit concrete space and cavity blemish under the steel plate.Neutron source can be launched fast neutron radiation, and the neutron that most of neutron source produced all is that energy is the fast neutron of several million-electron-volts.The atomic nucleus generation elastic collision of this fast neutron and medium reduces energy gradually with other effect, finally becomes slow neutron and thermal neutron.So-called thermal neutron is meant the neutron that is in thermal equilibrium state with surrounding medium atom (or molecule), and its energy is 1 * 10
-2About the electron-volt, when medium temperature was 20 ℃, the average energy of thermal neutron was 0.025 electron-volt, and this thermal neutron can be surveyed by thermal neutron detector.When neutron and matter interaction gradually the process of off-energy be called moderation of neutrons or deceleration.Medium is relevant with medium nuclear quality size to fast neutron slowing down decelerating effect, promptly reduces along with atomic weight and the increase of slowing down decelerating effect.The atomic weight minimum of hydrogen atom, so hydrogen atom is the strongest neutron moderator.The moderating power of hydrogen atom comprises big 2～3 orders of magnitude of iron than general soil element as oxygen, silicon, aluminium, calcium, magnesium, thus medium to the slowing down decelerating effect of fast neutron mainly be by in the medium hydrogeneous what determined.Concrete is by gravel aggregate, and coarse sand and cement add that certain water gaging mix forms.The major part of these water and cement generation hydration become water of constitution, and a small amount of remaining water exists with free state, and water base of these two kinds of forms is evenly distributed among the concrete.Because concrete is a kind of hydrous material, and contains hydrogen atom in the hydrone, so concrete is a kind of good fast neutron moderator.Given this, fast neutron radiation is afraid of that " gently " be not afraid of " weight ", and it is easy to run through heavy substance such as steel plate and concrete material interaction below it, and institute's hydrogen atoms that wherein main is in the concrete is had an effect and is decelerated slowing down formation thermal neutron.For concrete with definite water cut, formed thermal neutron concentration instant heating neutron count rate is relevant with unit volume inner concrete total amount, all have a cavity, in its unit volume of void defects position contain the concrete position more closely knit and obviously reduce than filling, so this position thermal neutron counting rate is with corresponding reduction.The cavity is bigger, and corresponding thermal neutron counting rate is just lower.This shows, adopt fast neutron source and thermal neutron detector to determine the position thermal neutron counting rate size of surveying, then can determine empty size and the empty planimetric position and the plane distribution thereof of deposit concrete under the steel plate.
Concrete detection method of the present invention and step are: neutron detector is carried out indoor standardization before measurement 1.: the concrete plate module of preparation standard, and as water cut 240kg/m
3Distinguish the steel plate that cladding thickness does not wait thereon, as 1.0cm, 2.0cm, 3.0cm, 4.0cm thick steel plate, and steel plate maked somebody a mere figurehead on concrete slab measure, to determine when steel plate and the change of concrete surface spacing, the relation curve of the built on stilts height of thermal neutron counting rate that probe is measured and steel plate, thus different-thickness steel plate corresponding work curve (being the empty degree of depth and thermal neutron counting rate relation curve) obtained, as 4 working curves of above-mentioned thickness steel plate, with these curve plottings on square paper with usefulness for future reference (as shown in Figure 1, table 1～table 4 is a measurement data); 2. differentiate because of the neutron detection device is minimum in the plane and be of a size of 5cm, maximum measurement radius is 30cm, area according to measuring accuracy requirement and testing material, stamp the grid of 5cm * 5cm to 30cm * 30cm at the concrete surface of steel plate of testing, and the grid intersection point made corresponding coordinate and sequence notation, then probe is placed on the pointwise of grid intersection point and measures, determine the thermal neutron digit rate of each measuring point; 3. according to the distribution of each measuring point thermal neutron counting rate on the plane, determine obviously scope on the low side of thermal neutron counting rate; It promptly is empty plane distributing scope; 4. promptly mainly being that steel plate thickness is selected the corresponding work curve according to the concrete structures condition that has the steel back boxing, is the indoor standardization curve that 2.0cm just selects corresponding 2.0cm steel plate as steel plate thickness; 5. according to the thermal neutron counting rate of each measuring point in the empty scope, search the corresponding empty degree of depth by working curve; 6. each opposite position work cavity and empty sounding mark are handled so that carry out engineering on the testing surface.
Fig. 1 is 240kg/m for the present invention at the concrete total moisture content
3The time different-thickness steel plate under the empty degree of depth and thermal neutron counting rate correlation curve, i.e. working curve.N-thermal neutron counting rate (pulse/minute) wherein, the empty degree of depth under D-steel plate, 1-10mm steel plate, 2-20mm steel plate, 3-30mm steel plate, 4-40mm steel plate.
The empty degree of depth and the thermal neutron counting rate correlation curve cavity degree of depth (mm) 0 50 100 150 200 250 thermal neutron counting rates under the table 1.10mm steel plate (pulse/minute) 1,470 1,070 910 780 740 720
The empty degree of depth and the thermal neutron counting rate correlation curve cavity degree of depth (mm) 0 50 100 150 200 250 thermal neutron counting rates under the table 2.20mm steel plate (pulse/minute) 1,350 1,010 850 760 730 710
The empty degree of depth and the thermal neutron counting rate correlation curve cavity degree of depth (mm) 0 50 100 150 200 250 thermal neutron counting rates under the table 3.30mm steel plate (pulse/minute) 1,140 960 810 740 720 700
The empty degree of depth and the thermal neutron counting rate correlation curve cavity degree of depth (mm) 0 50 100 150 200 250 thermal neutron counting rates under the table 4.40mm steel plate (pulse/minute) 1,020 900 790 730 710 690
Carrying out at the scene actual measurement can adopt respectively following two kinds of methods to carry out the cavity deeply The hole is determined: at first select corresponding worker according to institute's measuring tool body concrete works light plate thickness Make curve, determine corresponding at the thermal neutron counting rate that records at each measuring point according to probe The empty degree of depth of point. When engineering is had relatively high expectations to the cavity measurement, or on-site concrete contains The water yield and standard value (240kg/m3) in the time of may larger difference being arranged, can be after measurement, Choose the obvious measuring point on the low side of thermal neutron counting rate namely at some measuring point drillings that the cavity is being arranged Measure its actual grade, if the degree of depth words devious that check in working curve, again logarithm According to necessarily revising.
The present invention compared with prior art has following advantage:
1. can not only survey cavity position in general concrete structure and the prefabricated components, and And can solve the orientation problem in (the thick 40mm of reaching) cast concrete cavity under the steel plate;
2. the plane positioning in cavity can not only be solved and the empty degree of depth can be determined;
3. without rig, nondestructive measurement can not destroy concrete and steel construction fully; Do not need chopping fully, therefore can avoid judging by accident the disconnected damage that causes to material;
4. utilize the neutron source emission fast neutron radiation in the neutron detector to measure, do not need to inject in addition the radioactive isotope flow media, therefore without any radioactive contamination and environmental impact problem;
5. simple to operate, to measure fast, the probe that is adopted among the present invention is light to be taken, can be placed on any surperficial optional position measures, the maximum measurement range of every measuring point is 0.3m * 0.3m on the plane, and the every measuring point of Measuring Time only needs 1 minute, and the depth capacity of institute's energy exploration cavity is 25cm.
Provide embodiments of the invention below:
Embodiment 1: it is the concrete slab of 60cm * 120cm that thick 15cm, a planar dimension are made in cast, and certain position has been made cavity blemish artificially within it, and has covered the steel plate of a bed thickness 20mm on this concrete slab.Adopt the present invention to measure at surface of steel plate.Earlier testing face is carried out coordinate setting, draw the network of 10cm * 19cm again, measuring point is arranged on the network intersection point measures.Can most clearly determine cavity blemish position and scope by thermal neutron counting rate data measured on the measuring point.Measurement result shows, entopic thermal neutron meter rate is all about in the of 1200, and the thermal neutron counting rate on average has only about in the of 1000 in the cavity blemish scope, the center, cavity only has 930, the planar dimension of determining the cavity thus is approximately 25 * 30cm, by the pairing working curve of 20mm thickness steel plate, can determine that its depth capacity is 15cm.Be consistent fully with actual conditions with measured result of the present invention.
Embodiment 2: it is the concrete slab of 150cm * 150cm that thick 30cm, a planar dimension are made in cast, and to have made a diameter be 30cm at heart position therein, and the degree of depth is 20cm cavity (cylindric).At this concrete slab surface coverage 42mm thickness steel plate, adopt the present invention to measure, select the network of 10cm * 10cm size for use.Measurement result shows, normal position thermal neutron counting rate is about in the of 950, and the thermal neutron counting rate on average has only about 760 in the cavity blemish scope, and its profile is the circle that diameter is 30cm, and getting its degree of depth according to the pairing working curve of 42mm steel plate should be about 20cm.
3: one of embodiment have steel plate to make the circular concrete pipe of liner, and its internal diameter is 8m, and the concrete pipe wall thickness is more than the 1m, and the inner lining steel thickness of slab is 16mm.Because casting quality is bad, has cavity blemish between steel plate and concrete, adopt the present invention to measure, select the network of 30cm * 30cm for use, the about 200m of overall measurement area
2Measurement result shows, entopic thermal neutron counting rate is generally all in the 1350-1450 scope, and has the cavity blemish position obviously on the low side promptly below 1000, and the big darker position thermal neutron counting rate in cavity is minimum to 700-800.Depicted empty distribution on the plane according to above data, and determined the empty degree of depth according to working curve.By drill hole sampling on 17 point positions relatively, test findings is consistent fully with actual conditions.
Claims (1)
1. method that detects concrete porosity under steel plate with neutron technology, it is characterized in that earlier neutron probe being demarcated: the concrete plate module of preparation standard, distinguish the different steel plate of cladding thickness thereon, and steel plate maked somebody a mere figurehead measuring on the concrete slab when determining when steel plate and the change of concrete surface spacing, the relation curve of the built on stilts height of thermal neutron counting rate that probe is measured and steel plate is the empty degree of depth and thermal neutron counting rate relation curve thereby obtain different-thickness steel plate corresponding work curve; The concrete surface of steel plate of testing is stamped the network of 5 * 5cm～30 * 30cm, and make corresponding coordinate, neutron probe at every intersection measurement, is obtained the thermal neutron counting rate of every measuring point with the network intersection point; According to the distribution of each measuring point thermal neutron counting rate on the plane, determine obviously scope on the low side of thermal neutron counting rate, be empty plane distributing scope; According to the thickness of the covering steel plate of survey concrete component, select the working curve of respective thickness steel plate; According to the thermal neutron counting rate of each measuring point in the empty plane distributing scope, obtain the corresponding empty degree of depth by working curve.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 92112969 CN1032607C (en) | 1992-11-17 | 1992-11-17 | Method for detecting concrete porosity under steel plate by use of neutron technique |
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| CN 92112969 CN1032607C (en) | 1992-11-17 | 1992-11-17 | Method for detecting concrete porosity under steel plate by use of neutron technique |
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| CN1073013A CN1073013A (en) | 1993-06-09 |
| CN1032607C true CN1032607C (en) | 1996-08-21 |
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| CN 92112969 Expired - Fee Related CN1032607C (en) | 1992-11-17 | 1992-11-17 | Method for detecting concrete porosity under steel plate by use of neutron technique |
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| US9528952B1 (en) * | 2016-05-17 | 2016-12-27 | Westinghouse Electric Company Llc | Pulsed neutron generated prompt gamma emission measurement system for surface defect detection and analysis |
| CN107991328B (en) * | 2017-12-27 | 2024-04-19 | 同方威视技术股份有限公司 | Method, device and system for measuring void information |
| CN108548833B (en) * | 2018-03-27 | 2020-07-07 | 深圳市中核共创科技有限公司 | Concrete void detection method and device and terminal equipment |
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| CN109342469B (en) * | 2018-11-13 | 2021-04-09 | 深圳市中核共创科技有限公司 | Method and device for detecting concrete void depth and terminal equipment |
| CN109444176A (en) * | 2018-11-29 | 2019-03-08 | 水利部交通运输部国家能源局南京水利科学研究院 | Concrete void depth detection method under a kind of steel shell |
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| CN110286137B (en) * | 2019-07-24 | 2022-04-08 | 水利部交通运输部国家能源局南京水利科学研究院 | Steel shell concrete interface equivalent void neutron method detection device |
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