DE10150437A1

DE10150437A1 - Non-destructive evaluation of the inner surface of a tunnel using an optical technique, such as laser speckle interferometry, that allows the surface to be quickly and reliably evaluated from inside the tunnel

Info

Publication number: DE10150437A1
Application number: DE2001150437
Authority: DE
Inventors: Andreas Ettemeyer
Original assignee: ETTEMEYER AG
Current assignee: ETTEMEYER AG
Priority date: 2001-10-12
Filing date: 2001-10-12
Publication date: 2003-04-17

Abstract

Method for testing tunnel walls for cracks and cavities in the wall surface uses an optical, contactless measurement method for detection of deformation of the wall inner wall. Possible measurement methods include speckle interferometry, such as laser or electronic speckle interferometry, electronic speckle pattern interferometry, DSPI, shearography or holography. An Independent claim is made for a device for detection of the 3-D form and shape of the inner surface of a tunnel wall comprises a speckle interferometer with a laser light source, and a camera detection device.

Description

I. Field of application

The invention relates to the testing of tunnel structures.

II. Technical background

Tunnels can be due to defects in the construction phase, but especially due to the Natural aging has defects as in the inner surface of the tunnel wall ending cracks, self-contained in the tunnel wall Cavities without connection to the inner surface. Such cracks or voids If not discovered, parts of the tunnel wall can become detached.

Previously it was known to knock tunnel walls manually and acoustically Testing the tone to test. Furthermore, there are already optical measuring methods known to check the surface deformation of objects Load of the object can be used. However, this has only been the case so far finally large objects have been applied, for example overall could be placed in a vacuum or overpressure chamber or at which at least the back facing away from the observation side Introducing charges was accessible.

The problem with tunnels, however, is that away from the inner surface the tunnel wall has a quasi-infinitely thick wall, namely the z. B. mountain, and thereby a load introduction is not expedient from the outside of this wall.

III. Presentation of the invention a) Technical task

It is therefore the object according to the invention, a method and a To create a device for testing tunnel walls, which simple and is inexpensive to use, especially without damaging the tunnel wall works and can only be used from inside the tunnel.

b) solving the problem

This object is solved by the features of claims 1 and 26. Advantageous embodiments result from the subclaims. As a result of that the inside of the tunnel wall can be visually loaded Measuring methods such as speckle interferometry to determine under load deformations of the inner surface occurring in the tunnel wall are used, what information about cracks in or behind the inner surface or Give voids.

Classic methods such as holography or Schearography can be used, but in particular the known speckle interferometry used, especially with a laser as Illumination source. ESPI and DSPI are particularly suitable for this.

As is known, in speckle interferometry, non-contact and areal displacements of surface points are determined in that a large number of points on the surface, usually a grid with a maximum point spacing of 0.1 mm, with regard to their displacement between an initial state and a measuring state, usually in a state under power. The addition or subtraction of the raster images or their data fields produced in this way results in typical stripe images in the case of optical display, and permit both computer-aided and qualitative optical-manual evaluation. Both 2D and 3D speckle interferometers are known, with which the deformation in only two coordinate axes (usually the two spatial directions of the observed surface) or in three coordinate axes (additionally the perpendicular to the observed surface) can be determined. The loading of the inner surface of the tunnel wall necessary for the measurement can take place in different ways:
For example, sections of the tunnel can be closed in a pressure-tight manner and the inside of the tunnel can be placed under an overpressure or underpressure. This is possible, for example, by sealing off the entire tunnel cross-section at two points spaced apart from one another in the longitudinal direction of the tunnel or by placing a pressure-tight bell on the current test area of the tunnel wall, and opening up the areas of the tunnel sealed in this way with overpressure or underpressure.

However, the mechanical introduction of a load into the is preferable Inner surface of the tunnel wall, in particular the short-term introduction by impact or vibration excitation of this inner surface, preferably only at one point or in a narrow area.

The inclusion of the inner wall must then of course be timed Time of the debit or at the correct time interval after the Load take place at the time when the maximum deformation of the Detect inner surface in the measuring range. For this purpose, it also makes sense several recordings in quick succession, for example by means of a pulsed Laser, for a defined period of time, in particular immediately after the Introduce the shock or vibration load.

The impact or vibration can either be contactless, preferably via strong electromechanical vibrations (ultrasound or low frequency vibration in the range from 1 to 30 Hz, preferably from 1 to 10 Hz) or by mechanical contact with an abutment mass hits the wall surface once or several times, in particular a so-called shaker for introducing mechanical Vibrations caused by physical contact that are placed on the inner surface can.

In this case, it is mainly due to an oscillatory end coupling of the Shakers from the measuring device, especially the recording camera, in the Usually a CCD sensor to watch out for.

While contactless insertion usually over a large area at least takes place in the entire current observation area, the contacting mechanical insertion usually only in a small area, so quasipunktuell. The introduction is preferably in or just outside of the observation area to take place due to short distances To keep the attenuation as low as possible and thus the Keep the size of the load to be kept low.

In exceptional cases it can be useful, in contrast to the Mechanical loading when checking the tunnel walls and the tunnel ceiling nevertheless carry out in the tunnel floor, and then correspondingly strong shape. This is useful if the tunnel floor can withstand high loads is executed and a good connection between the vibration Floor and the side walls and the ceiling of the tunnel is given.

For the presence of cracks or voids at all As a rule, it is sufficient to determine whether deformations, preferably perpendicular to the inner surface, occur under load greater than one are predetermined threshold.

In addition, however, there are also quantitative statements about such cracks and Cavities possible.

The size of the deformation perpendicular to the inner surface (always related to one defined, in particular equally high load) provides information about the size of the Crack or cavity measured perpendicular to the inner surface.

The size of the deformation in the direction of the surface - if it is determined - can provide information about the extent of the crack or cavity in Direction of the extension of the inner surface.

The time delay of the occurrence of the greatest deformation or the Post-vibration behavior of this deformation compared to the time of occurrence the load can provide information about the depth, ie the distance of the Crack or cavity from the inner surface and / or the material properties of the material between the inner surface and the crack or cavity.

For the reasons mentioned, it can make sense, despite the necessary increased effort for the measuring device and the evaluation of the measurement signals also determine the deformations in the direction of the inner surface.

Preferably, the measuring device containing the measuring unit is not applied to the Placed on the inner surface to provide a vibration coupling from the Ensure suggestion.

Placing on the inner surface, for example immediately outside the respective current observation area, which can be approximately one m ² , is particularly useful if the load is also applied, for example in the center, of the observation area.

An embodiment according to the invention is exemplified below described. Show it:

c) working examples

Embodiments of the invention are hereinafter with reference to the figures described in more detail by way of example. Show it:
FIG. 1a schematic diagram of the electronic speckle pattern interferometry (ESPI), with the object to be measured in the initial state
FIG. 1b shows a representation according to Fig. 1a with the measurement object in the loaded state,
Fig. 1c a geometrical situation
Fig. 2 is a system of equations,
Fig. 3 is a schematic representation of the ESPI means of dual illumination,
Fig. 4 is a schematic representation of a three-dimensional ESPI measuring device,
Fig. 5 schematic representation of the device in the tunnel.
First, 1 to determine the relative displacement of points on the surface of the measurement object 1 between the initial state or starting state of a part, and the measuring state, ie a state in which the measurement object 1 acted upon by a force or is displaced with reference to the FIGS. To 4 was, on the other hand, explained how it is according to the ESPI state of the art.
As a rule, the measurement state is a loaded state of the measurement object 1 , in that the surface of the measurement object 1 as a whole, e.g. B. due to compressive stress, the measuring unit 2 , or also away from it (z. B. due to tensile stress parallel to the observed surface of the object). Partial displacements of the surface of the measurement object are also possible, for example by B. small bulges occur in the measurement state on the object surface, as can be seen in Fig. 1b. In contrast, FIG. 1 a shows the situation in the initial state of the measurement object 1 . Except for the bulge shown in FIG. 1b, the relative position between the measurement object and the measurement unit is the same.
The basic principle of electronic speckle pattern interferometry, hereinafter referred to as ESPI for short, will first be described with reference to FIGS. 1a and 1b:
In this case, an observation area 6 on the surface of the measurement object 1 is irradiated with light of the same wavelength, in particular a laser 3 , in the illumination direction 8 , directly or via at least one deflection mirror 30 . The light rays reflected by the object surface are recorded in a different viewing direction 9 by a camera 4 , usually a high-resolution, flat CCD sensor. For each individual object point of the surface in the observation area 6 of the measurement object 1 , a light wave, the object wave 28 , strikes the camera 4 , which, when it strikes the camera, has a specific phase position, corresponding to the total path length traveled from the laser 3 to the camera 4 and the wavelength used. However, the total path length of the object wave is not absolutely known.
A reference wave 27 , which also originates from the laser 3 and thus has the same wavelength, still strikes the camera 4 , but when it strikes the camera 4 in a different phase position from the object wave 28 , it may strike due to a different path. The reference wave 27 was not reflected by the measurement object and is branched off in particular from the illumination beam for the object by means of a semi-transparent first mirror 21 , which is inclined to the illumination direction 8 and is located between the laser 3 and the measurement object 1 , and is branched off via a second semitransparent mirror 22 , which is located transversely to the direction of observation 9 on this direction of observation 9 , also directed to the camera 4 .
For the central rays of the conical or cylindrical bundle of illuminating rays and reflected rays, this is shown in the figures for a specific object point 7 , which is imaged as an imaging point 17 on the light-sensitive surface of the camera 4 .
The same happens for every other point on the surface of the observation area 6 of the surface of the measurement object 1 , each point of the observation area 6 corresponding to a point on the light-sensitive surface of the camera 4 .
In the following, all procedures are only described with reference to the central object point 7 and the central imaging point 17 , but the same also applies to all other points of the observation area 6 and the light-sensitive surface 16 of the camera 4 , since neither the illumination nor the observation only by means of a single light beam or light source, but in each case by means of a bundle, so that areal observation of the measurement object is given.
A reference wave 27 and an object wave 28 thus impinge on the imaging point 17 of the camera, which generally differ in their phase position when they strike the imaging point 17 by a phase difference 4 ′, and can only have the phase difference 0 by chance.
For example, the object wave 28 from the laser 3 to the camera 4 has traveled a path length of x + 0.1 times the wavelength λ used, while the reference wave 27 has traveled a path of y + 0.3 times the wavelength λ used. The phase difference Φ is therefore 0.2. x and y, the integer multiples of the wavelength, are not known and are not recorded either.
This phase difference Φ is different for each of the imaging points on the photosensitive surface 16 of the camera 4 , and accordingly each imaging point is more or less bright. For the entire photosensitive surface 16 , this results in an irregular patch image with light and dark areas.
If one carries out the same process as was just described for a test object 1 in the initial state, for the measured state of the test object 1 according to FIG. 1b, then the object point 7 has a different position from the initial state due to the surface of the test object being raised in this area of the measuring unit 2 somewhat approximated so that the object wave 28 'now strikes the imaging point 17 in a different phase position, corresponding to the changed shorter travel of the object wave. The reference wave 27 ', on the other hand, is identical to the reference wave 27 of the measurement in the initial state, since the path of the reference wave has not changed.
Thus, between the reference wave 27 'and the object wave 28 ' in the imaging point 17, there is the measurement phase difference Φ + Δ, which consequently also differs in brightness from the imaging point 17 of the photosensitive surface 16 in comparison with the normal phase difference Φ obtained in the initial state.
In the measurement state, there is thus a qualitatively approximately the same for the entire photosensitive surface 16 , in detail, for. B. in the arrangement of the spots, however, irregular spots.
The difference value Δ, that is to say the difference between the normal phase difference Φ and the measurement phase difference Φ + Δ between the measurement in the initial state and the measurement in the measured state in a specific imaging point 17 thus corresponds - with small displacements of the object point 7 between the initial state and the measured state - the changed path length of the object wave between the initial state and the measuring state.
Based on the angular relationships in the triangle - as shown in FIG. 1c - the displacement e of the object point 7 between the initial state ( 7 ) and the measuring state ( 7 ') in the measuring direction 10 can be determined.
The triangle formed by the laser 3 , the camera 4 and the object point 7 or 7 ′ can be divided into two triangles by the bisector of the object point 7 , which represents the measuring direction 10 , the angle α, at which the measuring direction 10 strikes the connecting line between laser 3 and camera 4 , is known by the geometry of the arrangement of laser and camera to each other, and roughly also the angles β and γ, which represent the orientation of the laser and camera.
The length of the triangle side a is also known, namely half the direct distance between laser 3 and camera 4 . Since it is also known that the difference between the triangle sides c and c 'corresponds to half the difference value Δ / 2, the angular relationships in the triangle can be used to calculate the displacement component e of the object point 7 in the measuring direction 10 to the object point 7 ' in the measuring state.
It is always assumed that the displacement e is less than half the Difference value, Δ / 2. If the displacement e is larger, the additional integer multiples of λ or λ / 2 from the comparison with neighboring Find points.
In practice, this is done not only for an imaging point 17 on the camera, but for the entire photosensitive surface 16 of the camera, by subtracting the spot images from the initial state and from the measurement state by the light value from the for each point of the photosensitive surface 16 Measurement state is subtracted from the light value from the initial state. This then results in a stripe image for the photosensitive surface 16 as a whole.
The fact that the difference between two irregular spot images in the subtraction from one another results in a regular, strip-shaped image is due to the fact that object points 7 , 7 a, 7 b, which are closely adjacent to one another, shift similarly between the initial state and the measured state, provided that the measured state in the Surface of the object no crack or hard paragraph is generated.
Since the light difference values in each individual point can be ascertained the difference value Δ for each individual point of the light-sensitive surface 16 by means of the CCD sensor, in particular a digitally working CCD sensor, it is possible to evaluate the strip image by means of electronics and an associated one Software to perform the calculation according to FIG. 1c, namely the displacement of each individual object point in the measurement direction 10 , for each point of the observation area on the surface of the measurement object 1 .
From the above description it is thus clear that ESPI is based on the Impact of two light waves arriving at the same point on the camera, the phase difference between the two waves in the initial state and in Measurement state is different, and from the difference value of the two Phase differences the displacement of the corresponding object point is determined.
The two required light waves do not necessarily have to be the object wave 28 reflected by the object and the reference wave 27 . As FIG. 3 shows, two object waves 28 a, 28 b can also be used for this, which are obtained by simultaneously illuminating the observation area 6 of the object 1 from two different illumination directions 8 a, 8 b.
The different directions of illumination can be achieved from one and the same laser 3 by means of a beam splitter 5 . The laser 3 is directed approximately towards the observation area 6 and passes through a first semi-transparent mirror 21 in the beam splitter 5 , which deflects a first object wave 28 a laterally, while the remaining wave as the second object wave 28 b laterally in the direction of the laser 3 , is deflected in the opposite direction to the first object wave 28 a.
Each of the two object waves 28 a, 28 b is directed in the further course via a completely opaque mirror 22 or 23 to the same observation area 6 . From there, the object waves 28 a, 28 b are thrown back to a camera 4 , for example on the bisector between the illumination directions 8 a, 8 b, and recorded there, which is located approximately between the laser 3 and the observation area 6 .
An additional reference wave, which means that it does not directly touch the object from the laser is directed to the camera is no longer used.
However, the essential difference between the procedure according to FIG. 3 and FIG. 1 is that this dual illumination means that displacements of the object point 7 in the direction of observation 9 , i.e. towards the camera 4 , cannot be determined, since when the object point 7 is displaced on the Observation direction - provided that this is the bisector of the illumination directions 8 a and 8 b - would also lead to the same phase shift in the case of both object waves 28 a, 28 b and consequently to a difference value Δ = 0.
With the procedure according to FIG. 3, however, displacements of the object point 7 transversely to the direction of observation 9 between the initial state and the measured state can be determined, since this changes the phase position of the two object waves 28 a, 28 b differently, and thus leads to a difference value Δ, which over the Angular relationships in a triangle allow the offset perpendicular to the direction of observation 9 , in the plane spanned by the two directions of illumination 8 a, 8 b, to be determined.
The measurement direction 10 b of the dual illumination method according to FIG. 3 is thus transverse, in particular perpendicular, to the observation direction 9 and in the plane which is defined by the two illumination directions 8 a, 8 b. The direction of observation 9 is again in particular the bisector of the angle between the two directions of illumination 8 a and 8 b.
Fig. 4 shows a device which combines the devices and methods of FIGS. 1 and 3:
On the one hand, a shift in a measuring direction 10 b transverse to the observation direction 9 b, usually the bisector between the two lighting directions 8 a and 8 b, and therefore generally in the direction of the object surface, is determined by two illuminations which occur from different directions.
On the other hand, the displacement of the same object point 7 is determined in a measuring direction 10 a, which is at an angle to the measuring direction 10 b, and the bisector between one of the lighting directions, for. B. 8 a, and the observation direction 9 a = 9 b.
The reference wave 27 required for this is - in addition to the beam splitter 5 - branched off from the course of the light beams between the laser 3 and the beam splitter 5, preferably in front of the beam splitter 5, by means of a semi-transparent mirror 21 , and again directly and without using further mirrors 22 a, 22 b Object contact directed to the camera 4 .
If, in addition, the dual lighting is present twice, not only in the form of the lighting directions 8 a and 8 b, which are in the plane of the drawing in FIG. 4, but by further lighting devices 8 c and 8 d, not shown, which are preferably in the right There are angles to this, but the resulting bisector, the observation direction 9 is identical to the observation direction 9 , which is shown in Fig. 4, results in addition to the measurement direction 10 b shown in Fig. 4, a further measurement direction 10 c, which also is perpendicular to the direction of observation and thus preferably in the plane of the object surface, but at an angle, in particular at right angles, to the measuring direction 10 b.
The displacement of the object point 7 of the initial state into the object point 7 'of the measuring state in three mutually different measuring directions 10 a, 10 b, 10 c is thus known, it being irrelevant whether the displacements in the three different measuring directions 10 a, 10 b, 10 c is determined by one and the same measuring device or by separate measuring devices or even measuring methods.
An equation system according to FIG. 2 can be created from this, the components e _1x , e _1y , e _{1Z being} the displacement components of the object point 7 in the first measurement direction 10 a, and N1 the amount of this displacement in the measurement direction 10 a, indicated in the process wavelength λ1 used.
If measurements are carried out in more than three different measuring directions, the system of equations is theoretically over-determined. In practice, however, serve the 4th and each further direction of reduction of the influence of Incorrect measurements, signal noise etc. and the improvement of the measurement result.
The same applies to the second and third lines of the system of equations for the other measuring directions 10 b and 10 c.
It is usually used to investigate the relocation in the three Measuring directions used wavelength to be the same, so that λ1 = λ2 = λ3 to set is.
According to the known rules for solving a system of equations from three equations with three unknowns, the factors dx, dy, dz can be determined which are the components in the three mutually perpendicular spatial directions x, y and z about which an object point 7 is based shifted from the initial state to an object point 7 'in the measuring state, ie in the loaded state of the measuring object. The relative displacement of the object point in spatial coordinates is thus known.
The same result can also be achieved by comparing the three stripe images, which result for the three measuring directions 10 a, 10 b, 10 c as a difference image of the speckle patterns, if the camera surface remains the same in its orientation with respect to the object is like B. in the arrangement according to FIG. 4, with which the 3D ESPI is operated:
One and the same object point always occupies the same position on the camera surface in the three stripe images, for example horizontally by the distance L1 from the left edge and vertically by the distance L2 from the upper edge. If you put z. B. firmly that in the measuring direction 10 a this imaging point 17 is arranged between the second and third strips, 10% from the second strip, on the other hand in the strip image of the measuring direction 10 b between the same two strips, but 80% from the second strip and with respect to the measuring direction 10 c exactly in the middle between the second and third strips, so the three-dimensional displacement of the imaging point can be determined taking into account the spatial assignment of the three measuring directions 10 a, 10 b, 10 c, even if the object point should be between different stripes in the two stripe images.
It should also be borne in mind that all of the above considerations were based on the fact that the displacement of an object point between the initial state and the measuring state in the measuring direction, that is to say the vector e in FIG. 1c, should be less than approximately half the wavelength of the light used. If this were not ensured, it could be that the path length of the light between the initial state and the measured state would have differed not only by the measured difference value Δ, but also by integer multiples of the wavelength λ.
If the vector e is greater than λ / 2, the displacement can still be determined if the entire displacement vector for at least one object point in the measurement window is known from the initial state to the measuring state by this point then serves as a comparison point for neighboring points, and this again for theirs Neighboring points etc.
If this requirement is not met, z. B. several measuring steps be carried out one after the other, e.g. B. only one for the first measurement state Partial loading of the object can be carried out. The second measurement step is that the first measurement state, ie the measurement state of the first measurement step, at the same time is the initial state for the second measuring step, in which in turn a further partial load is applied until the desired final load is reached.
The resulting part for each individual surface point Shifts are added at the end.
Another problem is that - just for the determination of the strain and tension in the surface of a hollow body - the partial, disproportionate strains in a certain surface area, which usually are due to material defects and you want to investigate precisely for this reason are superimposed by the total elongation of the hollow body due to the Pressurization.
As shown in FIG. 6, however, the entire surface of the object 1 - due to the expansion when the interior of the hollow object 1 is pressurized - moves relatively strongly outwards, that is to say towards the measuring unit 2 .
In contrast, the additional displacement of the bulge 15 from the course of the rest of the surface of the object 1 is relatively small.
The measuring unit 2 is therefore preferably placed with its feet 31 , 32 , 33 directly on the surface of the measurement object 1 , and remains there even during the transition of the object from the initial state to the measurement state.
Since - with respect to the observation area 6 - the shape of the surface of the object 1 does not change, but is only shifted together with the measuring unit 3 relative to the center of the measuring object 1 , the measuring unit 1 de facto only creates the result between the initial state and the measuring state the bulge 15 detected.
Fig. 5 shows a cross section through a conventional tunnel with a tunnel surrounding tunnel wall 100th The resulting inner surface 104 is usually divided into a tunnel floor 108 and the rest of the inner surface, which is usually to be subjected to the test described.
The arch-shaped remaining inner surface 104 is generally not scanned in one cross section, but rather distributed over different segments as the respective observation area 6 . Since such an observation area can cover the area of 1 m ² , for example, the same procedure must be followed in the longitudinal direction of the tunnel.
The measuring unit 2 , consisting of one or more lighting units and the CCD sensor used as a camera, is mounted on a carriage 111 , which in turn can be moved in the transverse direction in the transverse direction of the tunnel on a measuring carriage 107 . The measuring carriage 107 either sits firmly on the floor 108 at a certain position or, as shown on the right-hand side of the measuring carriage 107, can be moved in the longitudinal direction, but is fixedly adjustable.
The measuring unit 2 is both height-adjustable and pivotable with respect to the cross slide 111 about at least one swivel axis running in the longitudinal direction of the tunnel, in order to be able to align the measuring unit 2 to the respectively desired observation area.
A shaker 105 is shown as an example at a point in the border area between two different observation areas 6 , with the aid of which a shock-like load or vibration can be introduced into the wall 100 by being placed on the inner surface 104 . The shaker 105 is preferably decoupled in terms of vibration technology from the measuring carriage 107 and the measuring unit 2 built thereon. The electronics necessary for the evaluation is not shown in FIG. 5 and is preferably either also on the measuring carriage 107 or outside the tunnel, preferably coupled to the measuring unit 2 via a wireless data connection.
In order to ensure that the measuring unit 2 is located at the desired distance from the inner wall 104 and the correct observation area 6 is also set, a plurality of rod-shaped distance sensors 109 , which are always together, can preferably be arranged on the component carrying the measuring unit or the measuring unit 2 itself are displaced and pivoted with the measuring unit 2 and represent the edge region of the beam path of the measuring unit and thus also strike the edge of the observation region 6 with their free ends when they are brought into contact with the inner surface 104 with their free ends. In addition, these free ends of the distance sensors 109 can generally carry three or four distance sensors per measuring unit 2 , a marking device 110 , in order to visibly mark the observation areas 6 of the inner wall 4 that have already been checked.
Of course, several measuring units 2 can also be accommodated on a measuring carriage 107 , which preferably can process the entire cross-section of the tunnel with one another in one operation. REFERENCE SIGN LIST 1 target
2 measuring unit
3 lasers
4 camera
5 beam splitters
6 observation area
7 object point
8 direction of illumination
9 direction of observation
10 a, 10 b direction of measurement
11 1. Optics
12 2. Optics
13 3. Optics
14 4. Optics
15 bulge
16 photosensitive surface
17 figure point
21 1st mirror
22 2nd mirror
23 3rd mirror
24 4. Mirror
25 5. Mirror
26 6. Mirror
27 reference wave
28 1st object wave
29 2nd object wave
30 deflecting mirror
31 feet
32 feet
33 feet
34 distance
100 tunnel wall
101 crack
102 cavity
103 deformation
104 inner surface
105 shaker
107 measuring car
108 tunnel floor
109 distance sensors
110 marking device
111 sledges
Φ normal phase difference
Φ + Δ measurement phase difference
Δ difference value
e relocation
s shearing route

Claims

1. A method for checking a tunnel wall ( 100 ) for cracks ( 101 ) or cavities ( 102 ) in or under the inner surface ( 104 ) of the tunnel wall ( 100 ), characterized in that the occurrence of deformations by means of an optical, in particular non-contact, measuring method ( 103 ) of the inner surface ( 104 ) of the tunnel wall ( 100 ) under load of the tunnel wall ( 100 ) from the inside of the tunnel.

2. The method according to claim 1, characterized in that Speckle interferometry, in particular laser Speckle Interferometry, ESPI = Electronic Speckle Pattern Interferometry, DSPI, Shearography or holography is used.

3. The method according to any one of the preceding claims, characterized in that the load due to pressure change, in particular overpressure, in particular of more than 1 bar overpressure, is applied inside the tunnel.

4. The method according to any one of the preceding claims, characterized in that the load in the form of a, especially punctual, shock or Vibrations are introduced into the wall.

5. The method according to claim 4, characterized in that the introduction of vibrations without contact, in particular by means of ultrasound or low-frequency vibration, in particular from 1-30 Hertz, takes place.

6. The method according to claim 4, characterized in that the vibration is introduced by means of contact of the inner surface ( 104 ) to an abutment mass (shaker 105 ).

7. The method according to any one of the preceding claims, characterized in that the selective impact or vibration introduction in the current observation area ( 6 ) or just outside the edge of the current observation area ( 6 ).

8. The method according to any one of the preceding claims, characterized in that the shock or vibration is introduced in the tunnel floor ( 108 ).

9. The method according to any one of the preceding claims, characterized in that the size of the deformation ( 103 ), in particular perpendicular to the direction of the inner surface ( 104 ), takes place only with regard to the exceeding of a minimum deformation (Dmax).

10. The method according to any one of the preceding claims, characterized in that the size of the deformation ( 103 ) in the perpendicular to the inner surface ( 104 ) for determining the size of the crack ( 101 ) or cavity ( 102 ) in the direction radially from the inner surface ( 104 ) is used away.

11. The method according to any one of the preceding claims, characterized in that the determined size of the deformation ( 103 ) in the direction of the inner surface ( 104 ) for distinguishing between cracks ( 101 ) and self-contained cavities ( 102 ) is used.

12. The method according to any one of the preceding claims, characterized in that the time delay and / or the post-vibration behavior of the deformation ( 103 ) with respect to the shock or vibration excitation to determine the distance of the crack ( 101 ) or cavity ( 102 ) from the Inner surface ( 104 ) is used.

13. The method according to any one of the preceding claims, characterized in that the deformation ( 103 ) of the inner surface ( 104 ) is also determined in the direction of the inner surface ( 104 ), in particular for determining hairline cracks in the inner surface.

14. The method according to any one of the preceding claims, characterized in that the measuring unit ( 2 ) is not placed on the inner surface ( 104 ) of the wall ( 100 ), but is spaced apart therefrom.

15. The method according to any one of the preceding claims, characterized in that the measurement of the entire inner surface ( 104 ) or the desired areas of the inner surface is carried out sequentially in sections, in particular by means of coarse markings visible to the naked eye to distinguish the individual sections.

16. The method according to any one of the preceding claims, characterized in that a common electronic control for controlling the load source on the one hand and the measuring unit ( 2 ) on the other hand is used.

17. The method according to any one of the preceding claims, characterized in that a pulsed laser is used as laser speckle interferometry, the two or several recordings in quick succession, especially with one Interval of less than 1/10 of a second.

18. The method according to any one of the preceding claims, wherein the displacement of the inner surface ( 104 ) of the tunnel wall ( 100 ) is a partial deformation of the inner surface ( 104 ) of the tunnel wall, which is associated with an expansion or shrinkage of the tunnel wall ( 100 ) overall, thereby characterized in that the measuring unit ( 2 ) is held in a position relative to the inner surface ( 104 ) of the tunnel wall ( 100 ) which is identical for the initial state and the measuring state, in particular by placing the measuring unit ( 2 ) directly on the inner surface ( 104 ) of the tunnel wall ( 100 ) ,

19. The method according to any one of the preceding claims, characterized in that the absolute position of at least one object point ( 7 , 7 a) of the inner surface ( 104 ) of the tunnel wall ( 100 ) is determined in at least one of its states, initial state or measurement state, and from this the absolute position of the entire surface of the tunnel wall ( 100 ) in the observation area is calculated both for the initial state and for the measuring state.

20. The method according to claim 19, characterized in that the absolute position of an object point ( 7 ) of the inner surface ( 104 ) of the tunnel wall ( 100 ) is determined by determining the absolute position of the measuring unit ( 2 ) in space and the relative position of the object point ( 7 ) to the measuring unit ( 2 ) is determined.

21. The method according to any one of the preceding claims, characterized in that the determination of the shape of the inner surface ( 104 ) of the tunnel wall ( 100 ) by means of speckle interferometry by changing the path length of at least one of the object waves ( 28 , 29 ) is carried out.

22. The method according to any one of the preceding claims, characterized in that the change in the path length by moving one or more lighting units, in particular the laser ( 3 ), takes place.

23. The method according to any one of the preceding claims, characterized in that the change in the path length by shifting one or more deflecting mirrors arranged in the beam path of the object waves ( 28 , 29 ) before hitting the tunnel wall ( 100 ), preferably transversely to the direction of observation ( 9 ) or measuring direction ( 10 ).

24. The method according to claims 23, characterized in that in the dual illumination method, the deflecting mirrors ( 22 , 23 ) are displaced transversely to the observation direction ( 9 ) by the same amount to the right or to the left with respect to the observation direction or by the same amount an axis which is perpendicular to the measurement plane spanned by the direction of observation and the direction of illumination is pivoted.

25. The method according to any one of the preceding claims, characterized in that the change in the path length by changing the wavelength of the used laser light takes place.

26. Measuring device for three-dimensional determination of the shape and displacement of at least part of the inner surface ( 104 ) of a tunnel wall ( 100 ), in particular for carrying out the method according to one of the preceding claims, wherein the measuring device
using a speckle interferometer
at least one laser ( 3 ),
at least three different lighting directions ( 8 a, 8 b, 8 c),
a camera ( 4 ) with a light-sensitive surface ( 16 )
comprises, characterized in that
two illumination directions ( 8 a, 8 b) can be shifted by the same amounts and to the same side with respect to the observation direction ( 9 ) of the camera ( 4 ), and
the measuring unit ( 2 ) comprises a computing unit for evaluating the recordings of the camera and a display element for displaying the evaluation results.

27. Measuring device according to claim 26, characterized in that in addition to the two symmetrical to the observation direction ( 9 ) arranged observation directions ( 8 a, 8 b) existing illumination direction ( 8 c) in a perpendicular to the through the illumination directions ( 8 a, 8 b ) spanned level.

28. Measuring device according to one of claims 26 to 27, characterized in that the displacement of the lighting directions ( 8 a, 8 b) by a common or several separate, jointly controllable, stepper motors or piezo-driven translators.

29. Measuring device according to one of claims 26 to 28, characterized in that the laser ( 3 ) is variable in its wavelength.

30. Measuring device according to one of claims 26 to 29, characterized in that the measuring unit ( 2 ) at least one foot ( 31 , 32 , 33 ) for placement on the inner surface ( 104 ) of the tunnel wall ( 100 ) in a defined position with respect to the inner surface ( 104 ).

31. Measuring device according to one of claims 26 to 30, characterized in that the measuring unit ( 2 ) has three feet ( 31 , 32 , 33 ) not lying on a line, preferably arranged in the form of an isosceles triangle.

32. Measuring device according to one of claims 26 to 31, characterized in that the measuring unit ( 2 ) is arranged at a defined point in space and a measuring device for determining the distance and the direction of at least one object point ( 7 ) of the inner surface ( 104 ) of Tunnel wall ( 100 ) ( 1 ) relative to the measuring unit ( 2 ).

33. Measuring device according to one of the preceding device claims, characterized in that the measuring device comprises a measuring carriage ( 107 ) on which the measuring unit ( 2 ) is adjustable with respect to the relative position and relative direction to the measuring carriage ( 107 ) and the measuring carriage ( 107 ) in particular on the Tunnel floor ( 108 ) rests.

34. Measuring device according to one of the preceding device claims, characterized in that the measuring carriage ( 107 ) can be moved, in particular can be moved in the longitudinal direction of the tunnel.

35. Measuring device according to one of the preceding device claims, characterized in that the measuring unit ( 2 ) has distance sensors ( 109 ) for the correct spacing and positioning relative to the inner surface ( 104 ), in particular at its front end contacting the inner surface ( 102 ) comprise a marking device ( 110 ).