JP5835862B2 - Diagnostic method for concrete pipes - Google Patents

Description

The present invention relates to a non-destructive diagnostic method for diagnosing a deterioration state of a concrete pipe by impact vibration. More specifically, the present invention relates to a method of diagnosing a deterioration state of a cover coat portion by applying an impact from the inside of the concrete pipe having a cover coat portion and elastic wave vibration thereof.

Numerous pipes are buried underground as supply pipes for agricultural water and industrial water, etc., and many pipes that have passed for more than 40 years have passed since laying. Damage accidents are frequent throughout the country. Prestressed concrete pipes (PC pipes), especially in pipelines with high internal water pressure, are becoming thinner (decrease in member thickness) due to the special chemical erosion due to the influence of the embedded environment. There are many pipes, and there is a concern about pipe damage accidents. For the long-term maintenance of the pipeline, there is a strong demand for preventive diagnosis technology to prevent these tube damage accidents in advance. On the other hand, the buried PC pipe has an extension of several thousand km, and it is difficult to diagnose all the pipes due to budget constraints, special diagnosis timing, and lack of diagnostic equipment.

For example, Japanese Patent No. 4662890 “Functional Diagnosis Method for Concrete Structures” is known as a preventive maintenance diagnosis technique related to an embedded PC pipe. This method is a degradation diagnosis method for PC pipes using ultrasonic waves and electromagnetic induction. The thickness of the PC pipe cover coat is measured by the ultrasonic reflection method, and the soundness evaluation of PC steel wires is performed using the electromagnetic induction method. This is a deterioration diagnosis method that combines the diagnosis methods according to the above.

This diagnostic method based on the ultrasonic reflection method is effective as a method for diagnosing individual pipes that have been screened in advance as a dangerous section or a dangerous place. However, measurement is performed at nine representative places for each pipe. As a rule, there are many measurement points and it is not suitable for the diagnosis of a large number of tubes.

As a general method for efficiently diagnosing a large number of tubes in a short time, a diagnostic method using elastic waves is suitable. Since this method has a simple mechanism, it does not require complicated analysis and has an advantage that it is not easily affected by the external environment. The electromagnetic wave radar exploration method is also used as an overview method, but it is easily affected by the external environment such as electric and magnetic fields, and has a complicated component structure unique to PC pipes (such as a method for removing false images due to the influence of reinforcing and curing muscles). There are many problems in the analysis, such as inhomogeneity of the moisture content (setting of the relative dielectric constant of the member) due to the embedded pipe and lack of simplicity.

Conventionally, several methods are known as diagnostic methods for reinforced concrete pipes using impact elastic waves. For example, Japanese Patent Application Laid-Open No. 2008-261871 (Japanese Patent Application No. 2008-142922) “Reinforced Concrete Pipe Inspection Method and Reinforced Concrete Pipe Inspection Equipment” applies a shock from the inside of a reinforced concrete pipe and uses the impact elastic wave. This is a method for inspecting the deterioration state, using a receiver having an elastic wave receiver having a cone shape or a needle shape, separating the elastic wave incident position and the receiving position by 1/4 or more, and positioning the television camera for positioning. This is a method that focuses on the efficiency of inspection work by forming an inspection device on which a striking mechanism and a receiving mechanism are mounted.

In Japanese Patent No. 4162967 “Reinforced Concrete Pipe Inspection Method”, the deterioration state of the reinforced concrete pipe is inspected with shock elastic waves from inside the pipe, and the area ratio of the high frequency component to the low frequency component of the resonant frequency spectrum of the propagating wave A method has been proposed in which a change in the maximum amplitude value of a propagating wave, a change in the decay time of the propagating wave, and the like are used as determination criteria.

In addition, as a method for diagnosing deterioration of concrete structures using shock elastic waves, Japanese Patent Application Laid-Open No. 2001-289829 (Japanese Patent Application No. 2000-137836) “Non-destructive measurement technology of concrete deterioration caused by shock elastic waves” The impact elastic wave is oscillated on the surface of the structure using an impact device, and this is received by multiple pickups, and the mechanical properties or degree of deterioration of the concrete is measured by comparative analysis based on the propagation characteristics of the surface wave. Proposed methods to measure the degradation in the concrete depth direction by changing the wavelength of the elastic wave by using the filter to reduce the measurement error of the measuring machine, change the oscillation mechanism, or change the wavelength of the elastic wave using a filter. Yes.

Furthermore, Japanese Patent Application Laid-Open No. 2004-163227 (Japanese Patent Application No. 2002-328754) “Concrete Neutralization Depth Measurement Method” compares the initial elastic wave velocity with the secular change in elastic wave velocity. A method has been proposed in which the rate is obtained and the neutralization depth is calculated from the relational expression with the neutralization depth.

Japanese Patent No. 4626890 Japanese Patent Application Laid-Open No. 2008-261871 Japanese Patent No. 4162967 JP 2001-289829 A JP 2004-163227 A

Conventional diagnostic methods using shock elastic waves for PC pipes, etc. cannot fully grasp the deterioration state of the cover coat part, and some methods have complicated analysis methods, and the deterioration state of concrete pipes can be easily There is a problem that cannot be detected.

The present invention solves the above-mentioned problem in the conventional diagnosis method. For a concrete pipe having a cover coat portion, the deterioration state of the cover coat portion is easily diagnosed by hitting from the inside of the pipe and its elastic wave vibration. Provide a method.

According to the present invention, a diagnostic method for a concrete pipe having the following configuration is provided.
[1] For a concrete pipe having a cover coat portion on the surface, an elastic wave is applied to the inner end of one pipe, the elastic wave vibration is received at the inner end of the other pipe, and the elastic wave is received via the sound part of the concrete pipe. In the method of diagnosing the deterioration state of the surface portion of the concrete pipe by comparing the propagation velocity Vps of the elastic wave and the propagation speed Vpd of the elastic wave received via the deterioration portion of the concrete pipe ,
The range that is 90 degrees left and right from the top of the concrete pipe and that excludes the range of 10 degrees on the left and right sides of the pipe top or the bottom of the pipe is the healthy part, and the top and the pipe side that are removed from the healthy part are the deteriorated parts. ,
The ratio F / [F = [(Vpd / Vps) -1] of the propagation velocity Vps of the elastic wave received via the healthy portion and the propagation velocity Vpd of the elastic wave received via the deteriorated portion. × 100%],
In each stage where F is F ≦ −20%, −20% to −2%, −2% to + 6%, + 6% ≦ F,
When F ≦ −20%, sand is sludged, when F is −20% to −2%, when porous, when F is −2% to + 6%, when thinned, and when + 6% ≦ F, PC steel wire A method for diagnosing a concrete pipe, characterized by diagnosing an exposed state of the concrete.
[2] When the rate of change F is in the range of -2% to + 6%,
(A1) -2% ≦ F ≦ 0% if healthy,
(A2) In the case of 0% ≦ F ≦ + 2%, the remaining thickness of the cover coat portion is ½ or more of the design member thickness, and the thinning start state,
(A3) When + 2% <F <+ 6%, the remaining thickness of the cover coat part is less than 1/2 of the design member thickness, and the thinning progressing state;
The method for diagnosing a concrete pipe according to the above [1] .
[3] When the rate of change F is in the range of -20% to -2%,
When (B1) -10% ≦ F <-2%, the porous state,
(B2) In the case of -20% <F <-10%, the progress of porosification and sand mudification,
The method for diagnosing a concrete pipe according to the above [1] .
[4] Place the receiving geophone (S1) at the inner end of the pipe, and install a large number of receiving geophones (d1 to d8) on the inner circumferential surface of the pipe end so as to go around the pipe body. The vicinity of the geophone (S1) is hit, the elastic waves are received by the plurality of receiving geophones (d1 to d8), and the propagation velocity Vpd (1) of the elastic wave received through the plurality of paths including the degraded portion The method for diagnosing a concrete pipe according to any one of [1] to [3] above , wherein the degradation scale is grasped by comparing Vpd (8) .
[5] Based on the propagation speeds Vpd (1) to Vpd (n) of elastic waves received from a plurality of paths including the deteriorated part, the deterioration is caused by the distribution of the propagation speeds of the plurality of paths or the difference of the speed difference from the healthy part. The method for diagnosing a concrete pipe according to any one of the above [1] to [3], wherein the scale of the section is detected .
[6] Any of [1] to [5] above, wherein the concrete pipe is a reinforced concrete pipe, a prestressed concrete pipe (PC pipe), a resin concrete pipe (RC pipe), an RC segment, an asbestos pipe (ACP), or a box culvert. Method for diagnosing concrete pipes described in 1.

[Specific description]
Hereinafter, a concrete pipe diagnosis method according to the present invention will be described in detail.
Diagnostic methods of the invention, the concrete pipe having a cover coat section on the surface, hurt one tube end, it receives the acoustic wave oscillation at the other tube end, via a healthy section of the concrete pipe In the method of diagnosing the deterioration state of the surface portion of the concrete pipe by comparing the propagation velocity Vps of the received elastic wave and the propagation velocity Vpd of the elastic wave received via the deterioration portion of the concrete pipe, The range from the left and right 90 degrees and the range excluding the range of 10 degrees on both the left and right sides of the pipe top or the bottom of the pipe is a healthy part, the top and the pipe side removed from the healthy part is a deteriorated part, and the healthy part is The ratio of the propagation velocity Vps of the elastic wave received via the path to the propagation velocity Vpd of the elastic wave received via the degraded portion is an increase / decrease rate F [F = [(Vpd / Vps) -1] × 100%] And F is F ≦ −20%, −20 % To -2%, -2% to + 6%, and + 6% ≦ F at each stage of F ≦ −20%, a state of sand mudification, and F from −20% to −2% of a porous state, A diagnosis method for a concrete pipe characterized by diagnosing a thinned state when F is from −2% to + 6% and an exposed state of PC steel wire when + 6% ≦ F.

As a cause of deterioration of a PC pipe or the like having a cover coat portion, a chemical erosion action on the cover coat portion due to an embedded environment is considered to be a major factor. In particular, erosion is observed in high-concentration sites such as erodible free carbonic acid in surface groundwater and sulfate ions, nitrate ions, and chloride ions due to soil infiltration by fertilization.

The deterioration mechanism of PC pipes, etc. is affected by the chemical erosion caused by the environment (water quality, soil, etc.) in which such PC pipes are embedded, and the cover coat part is eroded to reduce the thickness (a phenomenon in which the member thickness decreases). As a result, the PC steel wire is exposed, rusted or broken, and finally cracks in the pipe are induced.

Therefore, it is effective to measure the remaining thickness of the cover coat portion from the inside of the pipe in order to diagnose the deterioration state of the PC pipe or the like. When the member thickness of the cover coat portion is reduced, the PC steel wire and the core concrete are exposed, so that originally the engineering characteristics of the composite member composed of the cover coat and the core concrete are changed to the engineering characteristics of the core concrete only. For this reason, the elastic wave velocity of a pipe made only of core concrete (higher density and higher strength material than the cover coat) is higher than that of a healthy pipe having a predetermined cover coat thickness. It has the property of becoming faster than the elastic wave velocity. The present invention uses this phenomenon to distinguish and evaluate a healthy part and a deteriorated part.

In the diagnosis method of the present invention, a concrete pipe having a cover coat portion of a PC pipe is first hit from one of the inner ends of the pipe, and the elastic wave vibration is received at the other end of the pipe, and is received via the sound portion. The propagation velocity Vps of the generated elastic wave is compared with the propagation velocity Vpd of the elastic wave received via the deteriorated portion. In the following description, the elastic wave vibration is also simply referred to as an elastic wave.

Specifically, for example, for calibration, one line is set between the pipe top and the left and right pipe sides for the measurement line passing through the healthy part. Conventionally, the deteriorated portions where many deteriorated portions are found are the tube top and the left and right tube sides. Therefore, a calibration line is basically set by regarding the range of 90 degrees left and right from the top of the tube (excluding the top of the tube) as a healthy part (see FIG. 2).
In addition, what is necessary is just to exclude the range of 10 degree | times on both the right and left sides of a pipe top from a healthy part.

If it is expected that there is a degraded part in the range of 90 degrees left and right from the top of the tube, use a line (measurement line) that passes through the bottom of the tube for calibration, or measure the thickness of several parts by the ultrasonic reflection method, etc. It is recommended to check the healthy part line by the method.

A tube inner end is lightly hit with a hammer, and an elastic wave generated by the hit is received at the opposite tube inner end. FIG. 1 shows an image of shock elastic wave measurement. The measurement image of Fig. 1 shows that a transmitting geophone is installed on the inner peripheral surface of the pipe near the top of the pipe top where the deteriorated part exists, and a receiving geophone is installed on the pipe top near the receiving port on the opposite side. This is an example in which an installation is made, the vicinity of the transmitting geophone is hit, and the elastic vibration is received by the receiving geophone. The calibration line that passes through the sound part has a line (measurement line) at the bottom of the tube, a transmission geophone is installed at the bottom of the tube near the outlet, and a receiving vibration is received at the bottom of the tube near the outlet. A vessel is installed. A calibration line may be set on the tube side portion.

If the line passing through the healthy part and the line passing through the deteriorated part are parallel, the comparison is easy. Therefore, when there is a deteriorated part at the top of the tube as shown in FIG. Is set as the measurement line of the deteriorated part by setting the pipe top part, and the transmitting and receiving geophones are installed on the pipe bottom part or pipe side part so as to be parallel to this measurement line and pass through the sound part. A calibration line to be formed may be formed. The measurement image in FIG. 1 is an example in which lines are set in this way.

In measurement, the distance between the striking position (transmitting geophone) and the receiving position (receiving geophone) is measured. The hammer used may be a commercially available inspection hammer, but since the tubular body has a curved surface structure, a spherical hammer in which the point of hitting is point contact is preferable.

Based on the equation of V = R / T from the measured propagation time (T) and the set propagation distance (R), the initial velocity is read from the received waveform data, and the propagation speed (Vps) through the healthy part and deterioration Calculate the propagation velocity (Vpd) via the part.

In the diagnosis method of the present invention, the ratio of the propagation velocity (Vpd) passing through the deteriorated portion to the propagation velocity (Vps) of the healthy portion as a reference is defined as the rate of change (F) in the propagation velocity (the following equation [ 1)), the deterioration state is diagnosed according to the degree of the increase / decrease.
Rate of increase / decrease in propagation velocity (F) = [(Vpd / Vps) −1] × 100% [1]

In general, in concrete pipes with a cover coat part, the propagation speed of shock waves is the fastest in the core concrete part, and the propagation speed (Vps) that passed through the healthy part is the combined speed of the cover coat part and the core concrete part, which deteriorates. The propagation speed (Vpd) that has passed through the section is increased or decreased according to the deterioration state of the cover coat section.

There are two types of PC tube deterioration states: thin cover coat and material deterioration. In particular, deterioration due to thinning is noticeably observed in the roll compaction tube. On the other hand, for centrifugally formed tubes, the cover coat part is generally thicker than the roll compaction tube, and so on. The degree of thinning is small. When a concrete pipe other than a PC pipe is subjected to chemical erosion from the external environment, it has a two-layer structure of a deteriorated part layer and a healthy part layer on the inner surface, and the deteriorated part layer is deteriorated either by thinning or material deterioration. Since it becomes an event, it can be regarded as a pattern similar to a PC tube deterioration event.

The propagation speed of shock elastic waves is the fastest in the core concrete part, so if the deterioration state is thin, the influence of the core concrete part will increase due to the progress of thinning of the cover coat part, and the propagation speed will increase. (Change rate F becomes positive). On the other hand, when the deterioration state is material deterioration, the propagation speed is reduced due to the deteriorated portion, so that the propagation speed is reduced as compared with the healthy portion (the rate of change is negative). FIG. 4 shows changes in propagation speed according to the deterioration state of the cover coat portion. Further, FIG. 5 shows the change in propagation speed due to the progress of thinning of the cover coat portion.

Furthermore, when the deterioration state of the cover coat portion is thin, the propagation speed changes depending on the ratio of the deterioration zone (the area of the thin portion and the remaining thickness of the cover coat portion). FIG. 6 and FIG. 7 show the relationship between the area of the thinned portion and the propagation speed.

As shown in FIG. 6, when the deteriorated part spreads along the side line direction in a pipe having a total length of 4 m, the propagation speed of the core concrete part is 5.4 km / sec to 5.7 km / sec. When the speed is 5.1 km / sec, the thinned portion proceeds at the propagation speed of the core concrete, and the proportion of the deteriorated portion on the survey line (thinning ratio G: from the relationship between the speed difference between the healthy portion and the deteriorated portion). When the area ratio of the deteriorated portion: the following formula [2]) is calculated, the result shown in FIG. 4 is obtained.
Thinning ratio (G) = [length of longitudinal direction of deteriorated part (long axis length) / measurement distance] × 100% [2]

As shown in FIG. 7, the thinning rate (G) and the speed difference (ΔV) are in a monotonically increasing straight line relationship.
G = A (ΔV) + B
(G: thinning rate%, ΔV: speed difference from healthy part (m / sec), A, B: constant)

As shown in FIG. 7, when the speed difference [(Vpd) − (Vps)] between the propagation speed (Vps) of the healthy part and the propagation speed (Vpd) of the deteriorated part is 100 m / sec, the total length is about 20 It can be seen that the portion of about 25% to 25% is thinned, and if this speed difference is about 150 m / sec, the portion of about 25% to 40% is thinned.

As described above, if the propagation speed of the core concrete is obtained in advance by an ultrasonic method (double search method) or the like, it is possible to grasp the thinning rate from the speed difference between the deteriorated portion and the healthy portion. Further, the deterioration state can be diagnosed by the rate of increase / decrease F of the propagation speed.

Specifically, when an investigation is performed on a PC pipe or the like that is actually constructed, for example, when the rate of increase / decrease F in the propagation speed is + 6% ≦ F or F ≦ −20%, the cover coat portion is in a deteriorated state. Can be diagnosed.

Further, in the range where the increase / decrease rate F is from −2% to + 6% or more, the cover coat portion can be diagnosed as follows.
(A1) -2% ≦ F ≦ 0%, sound condition.
(A2) In the case of 0% ≦ F ≦ + 2%, the remaining thickness of the cover coat portion is 1/2 or more of the design member thickness, and the thinning is started.
In the case of (A3) + 2% <F <+ 6%, the remaining thickness of the cover coat part is less than 1/2 of the design member thickness, and the thinning progresses.
In the case of (A4) + 6% ≦ F, there is almost no cover coat portion, so the PC steel wire is exposed and deteriorated.

Furthermore, in the range where the increase / decrease rate F is in the range of −20% to −2% or less, the cover coat portion can be diagnosed as follows.
(B1) In the case of −10% ≦ F <−2%, it is a porous state.
(B2) In the case of -20% <F <-10%, the progress of porous and sand mudification.
(B3) When F ≦ −20%, sandy state.

Furthermore, in the diagnosis method of the present invention, the elastic waves passing through the degraded portion are received by a plurality of geophones having different set positions, and the propagation speeds Vpd (1) to Vpd of the elastic waves received from the plurality of paths including the degraded portion. Based on (n), the scale of the degraded portion can be detected.

Specifically, as shown in FIG. 9, a transmitting geophone is installed at the inner end of the pipe near the tube outlet, while a large number of receiving receivers are provided on the inner peripheral surface of the pipe end so as to go around the pipe. Install a geophone (d1-dn), hit the vicinity of the geophone for transmission, receive the elastic wave by multiple geophones for reception, and propagate the elastic wave received through multiple paths including the degraded part By comparing the speeds Vpd (1) to Vpd (n), the scale of the deteriorated portion can be grasped.

When comparing the survey line A passing near the center of the deteriorated part and the survey line B passing the edge of the deteriorated part, the length of the survey line B passing through the deteriorated part is shorter than the length of the survey line A passing through the deteriorated part, The propagation speed of the survey line B is less affected by the deteriorated portion. The scale of the deteriorated portion can be diagnosed based on the change in the propagation speed.

The diagnostic method of the present invention is a diagnostic method using shock elastic waves that receives the elastic wave vibration caused by striking the pipe inner end at the other pipe inner end and diagnoses the deterioration state of the surface portion of the concrete pipe. This method has the advantage that it is difficult to be affected by the external environment because it can be diagnosed with

The diagnostic method of the present invention can be widely applied to various concrete pipes such as reinforced concrete pipes, prestressed concrete pipes (PC pipes), resin concrete pipes (RC pipes), RC segments, asbestos pipes (ACP), and box culverts. The diagnostic method of the present invention is the most suitable method for detecting a deteriorated pipe as an in-pipe outline inspection method in a dangerous section of a trunk line screened in advance by a buried environment survey or the like.

According to the diagnostic method of the present invention, it becomes possible to extract a PC tube or the like having a deteriorated portion by an inspection from the inside of the tube. If a deteriorated pipe can be identified from the PC pipe main canal that is several thousand kilometers long, efficient and systematic maintenance management, such as planning preventive maintenance measures and formulating priority orders for countermeasures, becomes possible.

With buried pipes, it is difficult to detect from the ground unless the deteriorated state is at the final stage, so detection of deteriorated pipes is delayed, and it is easy to perform post-conservation measures after an accident occurs. In future maintenance and management, technology for predicting possible risks is required from the viewpoint of risk management, and it is necessary to accurately grasp the current state of facilities. Furthermore, the maintenance cost is under strict budget constraints, and the inspection of the entire length of the pipe line is very expensive and difficult to implement, and the screening method for the dangerous section and the dangerous place is extremely important.

In response to these requirements, the diagnostic method of the present invention has the advantage that a deteriorated tube can be extracted by a general method for comparing the propagation velocity of shock elastic waves, and can be combined with detailed inspection as necessary. Thus, the cost can be reduced and diagnosis according to the deteriorated state is possible, so that it is possible to take measures according to the deteriorated state.

The longitudinal cross-sectional conceptual diagram which shows the measuring method of the impact elastic wave in a PC pipe | tube. The cross-sectional conceptual diagram which shows the setting range of a survey line about PC pipe | tube. The block conceptual diagram which shows the connection state of the geophone which measures a shock elastic wave. The conceptual diagram which shows the change of the propagation speed according to the deterioration state of a cover coat. The graph which shows the change of the propagation speed in the thinning process. The conceptual diagram which shows the breadth of the degradation part of a longitudinal direction. The graph which shows the relationship between a thinning rate and a propagation speed difference. The flowchart of the deterioration diagnosis using the diagnostic method which concerns on this invention. The conceptual diagram of a multipoint vibration receiving measurement method. The conceptual diagram which measures the scale of the degradation part in a multipoint vibration receiving measurement method. Diagnostic flow diagram by multi-point vibration measurement method. The graph which shows the example of a determination division by the speed difference of the increase / decrease rate of propagation speed, and the healthy part. The flowchart which shows the determination procedure of repair and reinforcement measures. The partial external appearance photograph which shows the example which the core concrete exposed by thinning of the cover coat part. The partial external appearance photograph which shows the example which PC steel wire rusted and fractured by thinning of the cover coat. The partial external appearance photograph which shows the example which a part of cover coat part became sand mud.

Hereinafter, the present invention will be described based on embodiments.
As shown in FIG. 1, with respect to the PC pipe 10 having the cover coat portion 12 on the surface of the core concrete 11 and having the deteriorated portion 13 of the cover coat portion near the top of the pipe, one inner end (near the insertion port) Is installed on the opposite pipe inner end (near the receiving port), and a receiving receiver 22 is installed at the opposite end of the pipe, and the vicinity of the receiver 21 is struck with a hammer and passes through the deteriorated portion. Wave vibration is received by the geophone 22.

Further, as a calibration line, a transmitting geophone 31 is installed in the vicinity of the opening at the bottom of the tube, a receiving geophone 32 is installed in the vicinity of the opposite receiving port, and the vicinity of the geophone 21 with a hammer. The vibration receiving device 32 receives the elastic wave vibration that hits and passes through the healthy portion.

As shown in FIG. 3, an oscilloscope 23 and an amplifier 24 are provided between the transmitting geophone 21 and the receiving geophone 22, and the received waveform is displayed on the oscilloscope 23. These geophones 21, 22, 31, and 32 are mounted on the wall surface inside the pipe (core concrete part). Since the inner surface of the tube is a curved surface, it is preferable to attach these geophones by pressing the putty to the set position. Commercially available products (product of NF) can be used for these geophones. For example, the product symbol AE-901S (frequency: 140 kHz) can be used as the transmitting geophone, and the product symbol AE-901S-WB (frequency: 100 kHz to 1 MHz) can be used as the receiving geophone.

An example of a diagnosis flow based on the configuration example of FIG. 1 is shown in FIG. This diagnosis example is a diagnosis flow when the cover coat portion is eroded and thinned with the progress of carbonation. When the propagation speed of the core concrete part was 5.0 km / sec and the set thickness of the cover coat part was 20 mm to 25 mm, the deteriorated part was evaluated in four stages. What is necessary is just to measure the member thickness of a cover-coat part by the ultrasonic reflection method etc. The results are shown in Table 1.

In the above diagnosis result, when the diagnosis category is “degraded”, the propagation speed (Vpd) through the deteriorated portion is 5.3 km / sec or more, and therefore the propagation speed (Vps) through the healthy portion is 5.0 km / sec. The rate of increase / decrease in propagation velocity (sec) with respect to sec is 6% or more. In this case, when the remaining thickness of the cover coat portion is measured by the ultrasonic reflection method, it is almost 0 mm. At such a stage, it is considered that the PC steel wire is exposed due to floating / peeling of the deteriorated part, so the propagation speed (Vpd) passing through the deteriorated part is close to the propagation speed of the core concrete part. Become. There is a high possibility that the PC steel wire is rusted or locally broken at this deteriorated portion.

Further, in this case, when the distance is 260 cm, the longitudinal length of the deteriorated portion is about 25 cm × the width is 10 cm or more, the thinning rate (G) is G = [the longitudinal length of the deteriorated portion (0.25 m). / Survey distance (2.6m)] × 100% = about 10%.

As a countermeasure for the deterioration stage, the deteriorated part is deleted by excavation, and when the PC steel wire is cut or partially repaired, emergency measures are taken by applying reinforced concrete winding or stainless steel sheet winding, etc. Efforts such as implementing permanent countermeasures (replacement of pipes, etc.) in accordance with the countermeasure scenarios discussed in the above are necessary.

The stage where the diagnosis category is “Needs attention” is a state between “healthy” and “deteriorated”, and the propagation speed (Vpd) passing through the deteriorated part is approximately (Vpd) = 5.1 to 5.3 km / sec. Range. When the propagation speed (Vpd) is close to 5.3 km / sec, care must be taken because the thinning is progressing. On the other hand, if the propagation velocity (Vpd) is close to the 5.1 km / sec side, it can be estimated that it is on the healthy side.

For example, when the propagation speed (Vpd) through the deteriorated part is 5.29 km / sec and the propagation speed (Vps) through the healthy part is 5.11 km / sec, the rate of change (F) in the propagation speed is F = [(5.29 / 5.11) −1] × 100% = 3.52%, which is a “careful” stage in which the cover coat portion has become thinner. When the remaining thickness of the cover coat portion is measured by the ultrasonic reflection method, it is about 10 mm, and rusting of the PC steel wire has started.

The above diagnosis example is based on the composite propagation speed of the centrifugally formed pipe and the propagation speed of the core concrete, and the roll rolling formed pipe is about 1 km / sec lower than this standard. When diagnosing a pressure-formed tube, it may be corrected by about 1 km / sec.

Table 2 shows the results of diagnosis for the case of material deterioration of the cover coat portion. In this case, since the propagation speed (VPS) passing through the deteriorated portion decreases due to the porous portion or sand mud of the deteriorated portion, the rate of change (F) in the propagation velocity becomes negative, and the deterioration state depends on the magnitude. Can be diagnosed.

Next, examples of the multipoint vibration receiving method are shown in FIGS. The multipoint vibration receiving method is a method of installing a plurality of vibration receivers for one hitting point. According to this multipoint vibration receiving method, the scale of the deteriorated portion can be grasped. The scale of the deteriorated part is a range in the tube axis direction (longitudinal direction) of the deteriorated part.

As shown in FIG. 9, a transmitting geophone (S1) is installed at the inner end of the pipe near the opening of the pipe body, and on the other hand, a large number of receiving geophones are installed on the inner peripheral surface of the pipe end so as to go around the pipe body. (D1 to d8) are installed, the vicinity of the transmitting geophone S1 is hit, the elastic waves are received by a plurality of receiving geophones (d1 to d8), and are received via a plurality of paths including a deteriorated portion. The degradation scale is grasped by comparing the propagation speeds Vpd (1) to Vpd (8) of the elastic waves.

As shown in FIG. 10, when the line B passing near the center of the deteriorated part and the lines A and C passing through the edge of the deteriorated part have distances L0, L1, and L2 that each line passes through the deteriorated part. The passing distances L0 and L2 of the survey lines B and C are shorter than the passing distance L1 of the survey line B. Therefore, the propagation speed of the survey lines A and C is less affected by the deteriorated portion than the survey line B. Therefore, the scale of the deteriorated part can be grasped from the distribution of the propagation speed for each of these survey lines or the distribution of the speed difference from the healthy part.

The multi-point vibration measurement method can be applied as a detailed investigation method if a large number of receiving geophones are installed. If a large number of geophones are installed, a function as an elastic wave tomography is obtained, and if a plurality of impact points are provided, a detailed elastic wave tomography can be obtained. FIG. 10 shows an example in which three receiving geophones are installed for one striking point.

FIG. 11 shows a diagnosis flow by the multipoint vibration measurement method. As a basic diagnosis (primary diagnosis), for example, when deterioration is expected at the top of the tube, first, a geophone is installed as shown in FIG. ) Is + 6% ≦ F or F ≦ −20%, it can be determined that it has a deteriorated portion, so a secondary diagnosis is performed.

In the secondary diagnosis, for example, the striking point is moved to a position where the distance (measurement distance) between the geophones is halved, and the striking point is hit again to check whether it is a healthy part or a deteriorated part. If it is determined that there is a degraded part, geophones are installed at multiple points. Next, as the third diagnosis, one-stroke multipoint vibration (hit at one place and receive waves at multiple points) is performed to grasp the scale of the deteriorated portion. If necessary, a grid-like survey line including a degradation range is provided, and the member thickness is measured by a combined diagnosis using an ultrasonic reflection method or the like. By these diagnoses, it is possible to grasp the detailed deterioration state such as the position and scale of the deteriorated part and the degree of thinning.

According to the diagnosis method of the present invention, the deterioration state is diagnosed from the rate of increase / decrease in propagation speed (F) and the speed difference (ΔV) between the propagation speed (Vpd) of the deteriorated part and the propagation speed (Vps) of the healthy part. Can do. An example of this diagnosis is shown in FIG. This is an example of determination classification when the propagation speed of the healthy part is 5.1 km / sec.

In this diagnosis example, the area where the rate of increase / decrease in propagation velocity (F) is F <3% and the speed difference <100 m is determined as “healthy pipe”, and the area where F <3% and the speed difference <150 m is determined as “caution pipe”. doing. 3% ≦ F may be determined as “degraded pipe”. Here, the basic propagation speed of the healthy part (synthetic sound speed including a cover coat with a pipe diameter of 1350 mm) is a representative speed value of the centrifugal force molded tube collected by the present inventors. In addition, what is necessary is just to adjust a determination classification according to the grade of the fall, when a speed fall arises by material deterioration.

If the diagnostic method of the present invention is used, measures such as repair and reinforcement can be easily performed on the PC pipe and the like, and the measures can be made more efficient. In the maintenance management of PC tubes and the like, decision making for quick response based on the diagnosis result is important, and it is beneficial to be able to provide a judgment material as a support system for the manager.

FIG. 13 shows a determination flow of repair / reinforcement measures based on the index values of the propagation velocity increase / decrease rate (F) and the thinning rate (G) calculated by the diagnostic method of the present invention. The measures shown in the figure are mainly “partial repair measures”, “completely thinning measures”, and “thinning progress measures”.

When the rate of increase / decrease in propagation speed (F) is −2% ≦ F ≦ 0%, it is possible to diagnose a healthy state, so no countermeasure is required. Next, when the increase / decrease rate (F) is 0% ≦ F ≦ + 2%, the cover coat portion is in a thinning start state, and the progress is observed. When the increase / decrease rate (F) is + 2% <F, the cover coat portion is in a state of thinning, so it is necessary to grasp the degradation site and its scale. Here, the information on the thinning rate (G) is effective. Using the degree of speed difference from the healthy part as a guide, the thinning rate (G) is calculated from the relationship between the two and the degree of deterioration is grasped.

When considering countermeasures, the scale of the countermeasures (identification of the degradation area) and the details of the degradation (local, overall, etc.) must be known. For that purpose, the secondary diagnosis and the tertiary diagnosis by the combined diagnosis such as the member thickness measurement by the multipoint receiving method and the ultrasonic reflection method described above are effective in examining the details.

Specifically, for example, when the thinning rate (G) is 30% or less, it can be determined that the partial deterioration has occurred. Therefore, the deterioration section is identified and the partial repair countermeasure work is examined. Basically, the damaged part of the pipe body is checked by excavation, and partial repair measures such as cross-section repair work, plastering method, and surface protection work are taken. When the deterioration such as the thinning rate (G) is 10% or less, measures such as injecting a repair material from the inside of the pipe to the damaged portion through a hole or the like are taken as necessary.

When the rate of increase / decrease in propagation speed (F) is 6% or more, it is judged that the entire tubular body has deteriorated and the PC steel wire is almost exposed, and there is a concern about rusting and fracture of the PC steel wire. Since there is a high possibility of tube damage, it is necessary to take immediate measures. Basically, it is necessary to take measures such as remodeling and renewal by replacing the pipe.

In addition, when the rate of increase / decrease in propagation speed (F) is + 2% <F <+ 6% (when close to the propagation speed of the core concrete part, propagation speed (Vps) = 5.1 to 5.3 km / sec), It is judged that it is in the process of thinning. Accordingly, the remaining thickness of the cover coat portion (sound cover thickness excluding the carbonated portion) is confirmed by an ultrasonic reflection method or the like, and when the remaining thickness is approximately 10 mm or less, preventive maintenance treatment is performed as a deteriorated pipe.

In addition, when the remaining thickness of the cover coat portion is approximately 10 mm or less, there is a high possibility that the PC steel wire is rusted, and the PC steel wire may be broken depending on the state. It is desirable to check the soundness of the line. Diagnosis by electromagnetic induction can be used to confirm the soundness of the PC steel wire. However, the diagnosis of PC steel wire by the electromagnetic induction method cannot be performed accurately due to the influence of the barbs that are wound all around in the case of centrifugally formed pipes. Limited to tubes. If this diagnosis reveals that a plurality of PC steel wires have been cut, it is extremely likely to cause a pipe damage accident, so measures such as replacement of new pipes and pipe rehabilitation are required. .

By performing diagnosis according to the flow shown in FIG. 13, appropriate measures based on the diagnosis results can be examined in advance, and effective information can be obtained in the formulation of repair / reinforcement procedures and budget preparations. it can.

[Example 1]
The deterioration state of the embedded PC pipe (tube diameter φ1350 mm, cover coat design member thickness 20 to 25 mm) was diagnosed by the diagnostic method of the present invention. Further, the remaining thickness of the cover coat was measured by drilling the deteriorated portion, and the deteriorated state was visually observed. The results are shown in Table 3.
It was confirmed that the deterioration state by the diagnostic method of the present invention was in good agreement with the actually measured cover coat residual thickness and the deterioration state of visual observation. In addition, in the material deterioration part in which the increase / decrease rate is minus (−), although there is a remaining thickness of the cover coat part, it is fragile and is an event different from the thinning process.

In addition, the photograph of the excavated PC pipe was shown in FIGS. FIG. 14 is an example in which the core concrete is exposed by thinning the cover coat part, and FIG. 15 is an example in which the PC steel wire is rusted and broken by thinning the cover coat (both No. 7 in Table 3). . Moreover, FIG. 16 is an example in which a part of the cover coat part is sand mud (No. 3 in Table 3). In this example, the member thickness of the cover coat portion is about 20 mm, but this is an example of material deterioration in which scars estimated to be locally caused by running water remain.

10-PC pipe, 11-core concrete, 12-cover coat part, 13-deterioration part, 21-transmission receiver, 22-reception receiver, 23-oscilloscope, 24-amplifier, 31-transmission receiver, 32-receiver geophone

Claims (6)

For a concrete pipe having a cover coat portion on the surface, the velocity of the elastic wave propagating through the sound part of the concrete pipe is struck at one pipe inner end and the elastic wave vibration is received at the other pipe inner end. In the method of diagnosing the deterioration state of the surface portion of the concrete pipe by comparing Vps and the propagation velocity Vpd of the elastic wave received via the deterioration portion of the concrete pipe ,
The range that is 90 degrees left and right from the top of the concrete pipe and that excludes the range of 10 degrees on the left and right sides of the pipe top or the bottom of the pipe is the healthy part, and the top and the pipe side that are removed from the healthy part are the deteriorated parts. ,
The ratio F / [F = [(Vpd / Vps) -1] of the propagation velocity Vps of the elastic wave received via the healthy portion and the propagation velocity Vpd of the elastic wave received via the deteriorated portion. × 100%],
In each stage where F is F ≦ −20%, −20% to −2%, −2% to + 6%, + 6% ≦ F,
When F ≦ −20%, sand is sludged, when F is −20% to −2%, when porous, when F is −2% to + 6%, when thinned, and when + 6% ≦ F, PC steel wire A method for diagnosing a concrete pipe, characterized by diagnosing an exposed state of the concrete. When the rate of change F is in the range of -2% to + 6%,
(A1) -2% ≦ F ≦ 0% if healthy,
(A2) In the case of 0% ≦ F ≦ + 2%, the remaining thickness of the cover coat portion is ½ or more of the design member thickness, and the thinning start state,
(A3) When + 2% <F <+ 6%, the remaining thickness of the cover coat part is less than 1/2 of the design member thickness, and the thinning progressing state;
The method for diagnosing a concrete pipe according to claim 1 , wherein: When the change rate F is in the range of -20% to -2%,
When (B1) -10% ≦ F <-2%, the porous state,
(B2) In the case of -20% <F <-10%, the progress of porosification and sand mudification,
The method for diagnosing a concrete pipe according to claim 1 , wherein: A transmitting geophone (S1) is installed at the inner end of the pipe, while a large number of receiving geophones (d1 to d8) are installed on the inner peripheral surface of the pipe end so as to go around the pipe body. The vicinity of S1) is hit, the elastic waves are received by the plurality of receiving geophones (d1 to d8), and the propagation speeds Vpd (1) to Vpd of the elastic waves received through the plurality of paths including the degraded portion The method for diagnosing a concrete pipe according to any one of claims 1 to 3, wherein the deterioration scale is grasped by comparing (8) . Based on the propagation speeds Vpd (1) to Vpd (n) of elastic waves received from a plurality of paths including the deteriorated part, the scale of the deteriorated part depends on the distribution of the propagation speeds of the plurality of paths or the difference in speed from the healthy part. The method for diagnosing a concrete pipe according to any one of claims 1 to 3, wherein the method is used. The concrete pipe according to any one of claims 1 to 5, wherein the concrete pipe is a reinforced concrete pipe, a prestressed concrete pipe (PC pipe), a resin concrete pipe (RC pipe), an RC segment, an asbestos pipe (ACP), or a box culvert. Diagnosis method.