JPH1010064A - Method of inspecting mortar sprayed slope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To safely, quickly and precisely detect the abnormal part of a slope by composing the infrared thermal image of a spraying slope with the visual digital image of the slope into one image after quantitatively grasping the surface temperature behavior of the slope. SOLUTION: An object surface is first two-dimensionally scanned by use of an infrared sensor to take the thermal image of the surface temperature distribution of the object, and a non-steady heat transfer analyzing system using finite element method is then constructed to quantitatively grasp the surface temperature behavior of a spraying slope. The visual digital steel picture of the spraying slope is also taken by use of a high performance digital steel, camera. Each of the resulting images is corrected in distortion by geometric correction, and composed into one image by the patchwork of a computer. The abnormal part of the thermal image is displayed with emphasis by photographing the same slope twice in the daytime and the night, and imaging the temperature difference between the two images. Thereafter, the infrared thermal image and the visual digital picture are composed into one image by the computer. Thus, the position, form and area of the abnormal part of the spraying surface can be precisely judged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting a mortar spraying slope, which is generated on a mortar spraying slope which is constructed as a protection work for a surrounding ground cut-off portion when constructing a road, a railway or a tunnel. The present invention relates to a technique for safely and quickly detecting an abnormal portion such as a back cavity, a crack or water leakage.

[0002]

2. Description of the Related Art Conventionally, inspections of civil engineering structures have been carried out mainly by investigators recording cracks and water leaks or confirming soundness by hammering, but this is due to human work. Leaks and variations in the judgment results involving the investigator's subjectivity were unavoidable, and the inspection work itself was very dangerous.

In particular, when constructing roads, railways or tunnels, mortar spraying slopes, which are constructed as protection works for cutting through the surrounding ground, require the development of inspection methods that are excellent in safety, speed and reliability. Was urgently needed. As a nondestructive inspection method that can detect abnormal parts on the mortar spraying slope safely and at high speed, a method that measures the surface temperature of mortar using an infrared imaging device and distinguishes abnormal parts and healthy parts from the temperature distribution has attracted attention. For example, Japanese Patent Publication No. 63-6
It is also disclosed in Japanese Patent Publication No. 16035 and already partially used. However, it is difficult to fit a slope having a large area in one thermal image, and therefore, in many cases, shooting involves dividing the slope into a plurality of thermal images as shown in FIG. Done in the form. In FIG. 16, 1
10 of 110 to 110 partially wrapped around one slope 1
An example in which the image is divided and photographed is shown.

In such a case, if it is an ordinary still photograph, the position of each image on the slope is read from the shape of the slope, the breeding state of the plant, or the surrounding situation such as a road sign, and the image generated on the slope is obtained. Although the position and area of the abnormal part can be known accurately, the thermal image displayed by the infrared imaging device shows the surface temperature distribution of the slope and the objects existing around it, and the remarkable distance between them If there is no significant surface temperature difference, it is extremely difficult to accurately know the position and area on the slope even if an abnormal part is detected.

[0005]

SUMMARY OF THE INVENTION The present invention basically relates to a technique for inspecting a mortar spraying slope using an infrared imaging device. The prior art has the following problems. (A) The position and shape of the abnormal part on the slope cannot be accurately known from only the infrared video image, and it was empirically determined based on the thermal image, and the quantitative basis was poor. (B) Imaging must be performed with the camera at a fixed point.
Depending on traffic conditions, measurement was difficult and sometimes dangerous. (C) Since the distortion of the image cannot be corrected, the position and area of the abnormal part have to be estimated by eye measurement. (D) It was not possible to determine abnormal portions such as cracks, water leakage, dirt, and plant development other than the back cavity of the mortar. (E) The judgment result was manually transcribed on the drawing.

The present invention has been constructed as an optimal system for inspecting a mortar spraying slope, and solves the above-mentioned conventional problems, and can quantitatively and accurately determine the position and shape of an abnormal portion on the slope. The purpose is to detect abnormalities such as back cavities, cracks, and water leaks generated on the mortar spraying slope more safely, promptly and more accurately than conventional methods.

According to the present invention, an operation can be performed at an arbitrary position while traveling with a camera loaded on a moving vehicle, all operations can be performed in the traveling vehicle, and nighttime photographing can be easily performed. This makes it possible to easily detect a defect such as a target surface or a curved surface having a large area.

[0008]

SUMMARY OF THE INVENTION The present invention provides an infrared thermal image of a mortar sprayed slope, performs a transient thermal heat conduction analysis using a finite element method, and quantitatively grasps the surface temperature behavior of the slope. On the other hand, the slope is visible digitally imaged, and the obtained digital still photograph is synthesized with the infrared thermal image, and the highlight is performed by performing a shading enhancement process, and an abnormal portion of the mortar spraying slope is detected. This is a method for checking the mortar spraying slope.

In this case, the infrared thermal image and the visible digital image are captured from an arbitrary position, and geometrically corrected and combined. For example, an image capturing device and an image processing device are mounted on a running vehicle to prevent traffic obstruction. It is preferable that the measurement be performed safely, quickly and accurately without any occurrence of the above.
In addition, it is preferable that the infrared thermal images are captured during the daytime and at nighttime, synthesized, and subjected to shading enhancement processing.

[0010] Further, the abnormal portion can be detected for a mortar back cavity, a crack, water leakage, and plant vegetation.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a flowchart of the present invention. First, weather conditions are determined, avoid rainy weather, and if cloudy, only visible digital photography may be performed. If the weather is fine, perform visible digital photography, infrared measurement, and computer analysis. Visible digital photography may be replaced with that taken on a cloudy day. Computer image processing of these data,
Determine the soundness of the mortar spraying slope. The determination of the soundness of the mortar spraying slope described above includes (A) infrared measurement technology, (B) surface temperature analysis technology, (C) visible digital still photography, (D) image processing geometric correction and synthesis technology. Judgment is made from the results of a survey using two basic technologies.
Hereinafter, each technique will be described in detail. (A) Infrared measurement (A-1) Measurement method of surface temperature distribution All objects emit electromagnetic waves according to their temperature due to the movement of atoms or molecules on the object surface if the temperature is above absolute zero. I have. The radiation intensity (Wλ) per unit area and wavelength of an object having an emissivity of ε is given by equation (1) and is called Planck's equation.

[0012]

(Equation 1)

Here, Wλ: unit wavelength, radiation amount per area (W / cm ² · μ)
m) ε: emissivity (%) h: Planck's constant = 6.6261 × 10 ⁻³⁴ (W / s
² ) c: light velocity = 2.9997 × 10 ¹⁰ (cm / s) λ: wavelength (μm) k: Boltzmann constant = 1.3807 × 10 ⁻²³ (W · s)
/ K) T: Absolute temperature (K) The emissivity indicates the ratio of the radiant intensity of an object to the radiant intensity of a black body, and the emissivity of an object existing in the natural world is 0 to 1 in all cases.
Take a value between. According to Kirchhoff's law, the infrared emissivity and infrared absorptance of an object are equal, and the relationship of equation (2) holds between the infrared emissivity α and the infrared reflectance β.

Β = 1−α (2) This means that an object having a higher infrared emissivity absorbs infrared rays better, and an object having a lower infrared emissivity reflects infrared rays better. Therefore, the detection wavelength band is a (μ
m) to b (μm), the amount of radiation incident on the infrared sensor is
The result is as shown in Expression (3).

[0015]

(Equation 2)

An apparatus for measuring the surface temperature of an object using the above principle is a radiation thermometer, and if the emissivity of the object in the detection wavelength band of the infrared sensor is known, the object emits light using the infrared sensor. By measuring the infrared intensity, the surface temperature of the object can be known. (A-2) Detection Method of Backward Cavity The infrared imaging device used in the present invention is a radiation thermometer that scans the surface of an object two-dimensionally using an infrared sensor and images the surface temperature distribution of the object. It is a kind of one that detects a cavity formed on the back side of the mortar spraying slope by the following principle.

The mortar cast on the cut slope of the ground cannot be expected to have any structural strength per se, and its safety is ensured only when it is in close contact with the ground. Therefore, detecting the cavity generated on the back of the mortar greatly contributes to advance prediction of the occurrence of collapse.
FIG. 2 is a model showing the heat balance of the slope 1 due to a change in the external climate. As shown in FIG. 2, the surface temperature of the slope 1 is changed by the inflow and outflow of heat such as solar radiation by solar radiation 2 and convective heat transfer 4 from molecules in the air, radiant heat transfer 3 and heat transfer 5 from the ground. I do. Therefore, as shown in FIG. 3A, if there is a cavity 12 between the mortar 10 and the ground 11 on the back, the cavity 12 serves as a heat insulating layer, and is shown in FIG. 3B. Mortar 10 like ground 11
In the diurnal variation of the surface temperature of the slope 1 caused by the insolation and the temperature change in the rocky portion that is in close contact with the surface, the portion between the back surface where the cavity 12 exists and the good rocky portion Causes a surface temperature difference. Usually, this type of surface temperature difference is
During the daytime when the surface temperature of the cavity 1 rises, the cavity 1 shown in FIG.
The abnormal part having the number 2 appears on the high temperature side with respect to the healthy part as shown in FIG.
A temperature distribution curve 13 shown in FIG. 3A and a temperature curve 14 shown in FIG. Conversely, during the night when the surface temperature of the mortar 10 decreases, the abnormal part appears on the low temperature side with respect to the healthy part. In any case, since the surface temperature difference generated in the abnormal part appears on the thermal screen photographed by the infrared imaging device, it is possible to detect the presence of the cavity generated on the back of the mortar 10.

In the present invention, based on these principles, a traveling vehicle equipped with a measuring device is driven to perform all operations related to photographing, thereby enabling safer and quicker inspection work. (B) Quantitative analysis of surface temperature The surface temperature difference between the part where the cavity exists on the back of the mortar and the good rocking part depends on the meteorological conditions at the time of measurement, such as solar radiation, temperature, and temperature of the ground. , To varying degrees,
With only the surface temperature information on the thermal image, it is difficult to distinguish the surface temperature difference caused by the existence of the back cavity from the surface temperature difference caused by dirt or water leakage on the mortar surface. Thus, in the present invention, by using a computer analysis technique to simulate a surface temperature difference generated in an abnormal part, the inventors succeeded in quantitatively grasping a surface temperature difference caused by the existence of a back cavity. In the present invention, as follows:
A transient heat conduction analysis system using the finite element method is constructed, and the surface temperature behavior of the mortar sprayed slope is quantitatively grasped.

The basic differential equation for the transient heat conduction problem for isotropic materials such as mortar is given by equation (4).

[0020]

(Equation 3)

Here, T = T (x, y, z, t) is a temperature and is a function of space (x, y, z) and time t. ρ is the density, C is the specific heat, κ is the thermal conductivity, and Q is the amount of heat supplied per unit volume per unit time, that is, the heat generation rate. The following boundary conditions are imposed on the unsteady heat conduction related to the heat balance of the outer wall. B) When the temperature is specified on the boundary S1 On the temperature specified boundary:

[0022]

(Equation 4)

Here,

[0024]

(Equation 5)

B) When the heat flow velocity flows in (out) on the boundary S2 On the heat flux boundary: q = q ₀ (4.2) where q ₀ : heat flux c) heat on the boundary S3 When there is transfer On the heat transfer boundary: q = α _c (T−T _c ) (4.3) where α _{c is the} heat transfer coefficient, and T _{c is the} external temperature. And the temperature distribution in each element is expressed as follows.

T (x, y, z, t) = [N (x, y, z)] {φ (t)} (5) Here, [N] links the nodal temperature and the in-element temperature. This is an interpolation function matrix, and {φ (t)} is a node temperature vector of the element at time t. By formulating the above equation, the following finite element equation is obtained. [C] {φ} + [K] {φ} = {F} (6) where [C]: heat capacity matrix [K]: heat conduction matrix {φ}: node temperature vector {F}: heat flow Flux vector [C] = {[c] [K] = {[k] {F} = {f} [c]: Element heat capacity matrix [k]: Element heat conduction matrix {f}: Element heat flux When the vector equation (6) is discretized with respect to time using the Crank-Nicholson difference equation, the following equation is obtained.

[0027]

(Equation 6)

Here, Δt is a time increment, and if {φ (t)} on the right side is known, the unsteady heat conduction problem is solved by repeatedly calculating the above equation (7) in the time direction. be able to. This analysis system simulates the surface temperature behavior of a mortar spraying slope by giving weather conditions such as air temperature and solar radiation at the time of measurement as external force conditions based on the above calculation principle.

FIG. 4 shows a comparison result between the analysis value of the surface temperature of the mortar spraying slope by the present analysis system and the actually measured temperature value measured on the actual slope. The measured values are indicated by x, and the analysis values are indicated by Δ. From FIG. 4, it is clear that the analysis system can accurately simulate the surface of the mortar spraying slope. (C) Visible digital still photography As described above, in the present invention, (A) the infrared measurement technology and (B) the quantitative analysis technology of the surface temperature accurately detect the back cavity of the mortar spraying method. be able to. However, in determining the soundness of the mortar spraying slope, it is necessary to check the occurrence of cracks, which are important data, their positions and quantities, using another method. In the present invention, cracks on the mortar surface can be easily monitored by taking a visible digital still photograph of the mortar sprayed slope surface using a digital still photographing technique.

In recent years, computer processing power has been dramatically improved, and it has become possible to digitize color information on a still photograph having a huge data amount and handle it on a computer. The digital still camera used in the present invention is 1670
It is possible to record color information of up to 10,000 colors.
An ultra-high resolution of 300,000 was used. Therefore, a visible digital still picture with high definition equivalent to or higher than that of a normal still picture can be obtained. Further, it complies with the JPEG system which is an international standard that defines a compression system for transmitting and storing color still images. For this reason, computer processing is extremely fast, even though the photograph information has a huge data amount.
In the present invention, by using such a high-performance digital still camera, it is possible to accurately record information, such as cracks, vegetation, dirt, and water leakage, which can be useful data for determining the soundness of a slope. is there. (D) Image processing (geometric correction and synthesis) In the above-mentioned (A) infrared measurement technology and (C) visible digital still photography technology, information on a mortar spraying slope is recorded as fragmentary information for each shooting cut. Is done.
However, on the surface of the slope, there is no target to be used as a mark at the time of position identification, and it is difficult to associate the positional relationship of each shooting cut on the slope.
This is a source of confusion when determining shape and size. Therefore, in the present invention, as shown in the flowchart of FIG. 5, image processing such as geometric correction, synthesis, and abnormal portion enhancement processing is performed on each captured image, and a determination diagram is automatically created. As a result, the position, shape,
Area and the like can be accurately and quickly measured. Less than,
The details of each process will be described. (D-1) Geometric Correction When photographing a mortar spraying slope from the ground, it is difficult to photograph all the surveyed parts from directly in front, and therefore, the photographed image has distortion according to the photographing angle. Occurs. According to the present invention, it is possible to perform geometric correction on an image in which distortion has occurred, and restore the image to the same shape as that projected from the front.

FIG. 6 is a photograph taken obliquely. The image has a distortion corresponding to the imaging angle, and this is corrected to a distortion-free shape as shown in FIG. This correction can be performed using a computer according to a geometric correction algorithm. (D-2) Compositing Each of the photographed cuts whose distortion has been corrected by the geometric correction is subjected to patchwork on a computer and composited into one image. For example, FIG. 8 shows a cut of the left half before synthesis, and FIG.
8 and 9 are combined to obtain FIG. 10 which is an image after the combination, assuming that the right half of the cut before the combination is cut. Here, since the entire mortar spraying slope can be finished as one image, the position, shape, area, and the like of the abnormal portion that has occurred on the slope 1 can be accurately known. In this manner, the entire slope as described above and shown in FIG. 17 can be combined into one image, and the position, shape, and size of an abnormal portion or the like of the slope can be grasped. (D-3) Abnormal part emphasis processing (D-3-1) Abnormal part emphasis processing in thermal image The abnormal part in the thermal image is obtained by photographing the same slope twice in the daytime and the nighttime, Is highlighted by imaging the difference between the temperature values. 11 to 13 show an embodiment of the abnormal portion emphasizing process according to this method. FIGS. 11 and 12 are thermal images measured at daytime and nighttime, respectively, where the back cavity 21 appears at a higher temperature in the former and the back cavity 22 appears at a lower temperature in the latter. However, the surface temperature difference from the healthy part is not sufficient, and the existence of the back cavity 22 is not clear. On the other hand, FIG.
13 is a difference image obtained by imaging a difference in temperature value between the two images of FIG. 12. In FIG. 11, the information of the back cavity 23 is shown in FIG.
12 is much more emphasized than the two images in FIG. 12, and the effectiveness of the difference processing is clear. However, in the conventional method that does not perform image processing, in order to create a difference image of the temperature value between the two images, it is necessary to measure both at exactly the same position and at the same angle of view. However, this is a practical obstacle in performing the difference between images. However, in the present invention, geometric correction processing is performed in advance,
Since the shapes of the two images to be subjected to the inter-image difference can be made identical, the two images to be subjected to the inter-image difference processing do not necessarily need to be photographed from the same position at the same angle of view. We succeeded in greatly improving the practicality of the part emphasis processing.

(D-3-2) Synthesis with Visible Digital Still Photograph In the above-mentioned infrared measurement technology and visible digital still photographing technology, information on the mortar spraying slope is recorded as fragmentary information for each photographing cut. Is done. Visible digital still photographs record the shape of the slope, the breeding status of plants, road signs, and other objects that exist around the mortar surface and the slope, so it is not possible to interpret the position of each image on the slope. It is easy (see FIG. 14). However, what is displayed on the thermal image by the infrared imaging apparatus is the surface temperature distribution (color pattern) of the slope and the object existing around the slope as shown in FIG. In the case where there is no surface temperature difference, it is extremely difficult to accurately know the position and area on the slope surface even if the abnormal portion 24 is detected as shown in FIG.

Therefore, the present invention combines a thermal image measured using an infrared imaging device and a visible digital still photograph taken using a digital still camera using a computer image processing technique, as shown in FIG. In addition, the information from the two was combined into a single image, making it possible to accurately know the position, shape, and area of the abnormal part that occurred on the mortar spray slope. As a result, the position of the abnormal part,
The problem of infrared measurement that it is difficult to grasp the shape and area has been overcome. In addition, information on cracks, vegetation, dirt, water leakage, etc. recorded by a visible digital still camera is added to the occurrence state of the back cavity detected from the thermal image, so that the soundness of the slope can be more comprehensively performed. It has become possible.

According to the present invention, the position of the abnormal part,
Measurement accuracy of shape and area can be improved. Also, visible digital still photos include cracks, vegetation, dirt,
Information that can be useful in determining the soundness of the slope, such as water leakage, is recorded.By combining these with information on the back cavity detected by the infrared imaging device, the reliability of the soundness determination of the slope can be improved. It has become possible to improve dramatically.

[0035]

As described above, the present invention relates to (A)
Infrared measurement technology, (B) Surface temperature analysis technology based on unsteady heat transfer analysis using the finite element method, (C) Synthesis of visible digital still photography and thermal image, (D) Geometric correction, synthesis, abnormal part enhancement, etc. Using the image processing technology, it was constructed as the best method for inspecting the mortar spraying slope, and the back cavities, cracks,
An abnormal part such as water leakage can be detected safely, quickly and accurately as compared with the conventional method. Therefore, the present invention is enormous in that it contributes to society as a method of predicting the occurrence of a rock drop or the like in advance and preventing a disaster before it occurs.

[Brief description of the drawings]

FIG. 1 is a flowchart showing the entire process of the present invention.

FIG. 2 is a model showing a heat balance of a slope.

FIG. 3 is a partial cross-sectional view showing adhesion between mortar and ground.

FIG. 4 is a graph showing a comparison between an analytical value and a measured value of the surface temperature of a mortar spraying slope.

FIG. 5 is a flowchart of image processing.

FIG. 6 is a schematic view of a distorted image.

FIG. 7 is a schematic diagram of an image after geometric correction.

FIG. 8 is a schematic diagram of an image before composition.

FIG. 9 is a schematic diagram of an image before composition.

FIG. 10 is a schematic diagram of an image after composition.

FIG. 11 is a schematic diagram of a daytime thermal image.

FIG. 12 is a schematic diagram of a thermal image at night.

FIG. 13 is a schematic diagram of an image after an enhancement process.

FIG. 14 is a schematic diagram of a digital still image.

FIG. 15 is a schematic diagram of a thermal image.

FIG. 16 is a schematic diagram of an image after composition.

FIG. 17 is an explanatory diagram of divided shooting of a slope.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Slope 2 Solar radiation 3 Radiant heat transfer 4 Convective heat transfer 5 Heat transfer 10 Mortar 11 Ground 12 Cavity 21 Back cavity (of thermal image measured at daytime) 22 Back cavity (of thermal image measured at night) 23 Back cavity 101-110 (divisional image) (of difference image)

Claims (4)

[Claims] 1. An infrared thermal image of a mortar sprayed slope is taken, and an unsteady thermal heat conduction analysis is performed by using a finite element method to quantitatively grasp a surface temperature behavior of the slope. Inspection of a mortar spraying slope characterized by digitally imaging and synthesizing the obtained digital still picture with the infrared thermal image, performing a shading emphasis process and highlighting, and detecting an abnormal portion of the mortar spraying slope. Method. 2. The method for inspecting a mortar spraying slope according to claim 1, wherein the infrared thermal image and the visible digital image are captured from an arbitrary position, and geometrically corrected and combined. 3. A method for inspecting a mortar spraying slope, characterized in that the infrared thermal image is taken during the day and at night, synthesized, shade-enhanced and embossed. 4. The abnormal part includes a mortar back cavity, a crack,
Inspection method of mortar spraying slope characterized by water leakage and plant vegetation.