JP2014098598A - Monitoring method under object surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a monitoring method under a road surface or the like that uses an electromagnetic wave radar.SOLUTION: A monitoring method under an object surface performs a data obtaining step of obtaining reflection wave data 50 in each reflection wave detection position 40, by making electromagnetic waves incident into a depth direction from the upper side of an object surface R to the under side of the object surface R, with an electromagnetic wave radar, with predetermined spacing in a direction along the object surface R at least all over the predetermined unit object area in the object surface R such as a road surface and by detecting their reflection waves in the upper side of the object surface R. The monitoring method performs the data obtaining step two or more times with the predetermined spacing for the same unit object area, and monitors changes under the object surface R in the unit object area on the basis of the comparison of new data with old data of the reflection data 50 itself or processed data obtained by processing the reflection data 50, in the same reflection wave detection position 40.

Description

  The present invention relates to a monitoring method under a target surface.

  Under the surface of roads, runways, aprons in harbors, traffic surfaces of other people and vehicles, and storage areas, cracks and cavities occur in the pavement and ground as time passes. As they grow (grow), these explorations are required to maintain the surface. For example, since the depression of the target surface is caused by a cavity generated below the target surface, it is necessary to search for the presence of an underground cavity in order to prevent the depression. As such a search method under the target surface, as shown in Patent Documents 1 to 4, a non-destructive investigation method in which an electromagnetic wave radar is mounted on a vehicle and travels on a road is efficient. When a cavity is found, as a repair work, it is common to drill an injection hole from the target surface to the cavity and fill the cavity with the solidified material from the injection hole. Also, pavement internal damage (cracks that exist only inside and are not exposed on the surface, delamination, stagnant water, cracks that are exposed on the surface but extend to the inside, potholes, If patching, local replacement, etc.) are found, repair work is performed according to the degree of damage.

  However, the conventional method has a problem that only the state below the target surface at the time of exploration is known, and the change below the target surface cannot be grasped. For this reason, it is impossible to distinguish between cavities that grow or rise rapidly and cavities that are slow, and it may be difficult to evaluate the necessity of repair or to formulate a repair plan. For example, if a cavity below the target surface is found, it can be judged that the deeper one is generally less likely to sink at that time, but if it is deeper, the sinking will occur The risk is higher. Therefore, it is desired to monitor the cavity below the target surface, but such a monitoring method has not been proposed at present.

JP-A-5-87945 JP-A-8-62339 JP 2004-301610 A JP 2012-184624 A

  Then, the main subject of this invention is providing the monitoring method under the object surface which uses electromagnetic wave radar.

The present invention that has solved the above problems is as follows.
<Invention of Claim 1>
Using electromagnetic wave radar, electromagnetic waves are incident in the depth direction from the upper side of the target surface to the lower side of the target surface with a predetermined interval in the direction along the target surface over at least the predetermined unit target area on the target surface and reflected. A data acquisition step of acquiring reflected wave data at each reflected wave detection position by detecting waves on the upper side of the target surface,
For the same unit target area, perform multiple times with a predetermined period,
Based on the new and old comparison of the reflected wave data itself or the processed data obtained by processing the reflected wave data at the same reflected wave detection position, the change below the target surface in the unit target area is monitored.
A monitoring method under the target surface characterized by the above.

(Function and effect)
In this way, for the same unit target area, it is performed several times with a predetermined period, and the reflected wave data at the same reflected wave detection position is compared between old and new, thereby monitoring the change below the target surface in the unit target area. become able to. As a result, for example, the generation of the cavity 85, as well as the cavity that grows and rises quickly, and the cavity that is slow can be distinguished, and it becomes easy to evaluate the necessity of repair and to formulate a repair plan.

<Invention of Claim 2>
Based on the reflected wave data acquired in each data acquisition step, the cavity at each reflected wave detection position is explored, and when the cavity is detected, the size of the cavity top surface and the depth of the cavity top surface are obtained,
Monitor the generation, growth and rise of cavities based on new and old comparisons of the dimensions and depth of the cavity top surface at the same reflected wave detection position.
The subsurface monitoring method according to claim 1.

(Function and effect)
For example, if a cavity is found deep below the target surface, it can be determined that the risk of depression is low at that time, but if it rises or grows quickly, the risk of depression is high and the need for repair is high. . Therefore, it is preferable to monitor the generation, growth, and rise of cavities as described above because the risk of depression can be evaluated.

<Invention of Claim 3>
Based on the reflected wave data acquired in each data acquisition step, the buried object at each reflected wave detection position is searched, or the position of the buried object is known,
When a buried object is detected or there is a known buried object, the generation of cavities will occur based on the comparison of the reflected wave data itself or the processed data obtained by processing the reflected wave data around the detection position of the buried object. Monitoring growth and rise,
The monitoring method under a target surface according to claim 2.

(Function and effect)
When there is an embedded object under the target surface, there is a high possibility that a cavity will be generated around it, and the growth rate and the rising rate of the generated cavity are relatively fast. Therefore, the cavity monitoring can be performed more efficiently by monitoring the cavity having such factors.

<Invention of Claim 4>
The monitoring method under the target surface according to any one of claims 1 to 3, wherein the monitoring is performed for a target surface whose traffic volume is a predetermined value or more.

(Function and effect)
As the traffic volume on the target surface increases, there is a higher possibility that cavities and the like are generated due to more load and vibration being applied, and the growth rate and rising speed of the generated cavities and the like are faster. Moreover, the greater the amount of traffic on the target surface, the greater the degree of influence when the depression occurs (the probability of an accident occurring increases, the degree of traffic congestion increases, etc.). Therefore, cavity monitoring can be performed more efficiently by monitoring below the target surface having such factors.

<Invention of Claim 5>
The monitoring method under the target surface according to claim 1, wherein the target surface is a road surface and the monitoring is performed in a lane.

(Function and effect)
If the target surface is a roadway, the more the vehicle travels in the roadway (for example, the vehicle travels more in the lane than in the shoulder, the vehicle travels more in the intersection even in the lane) It is highly possible that cavities and the like are generated when more load and vibration are applied, and the growth rate and the rising rate of the generated cavities and the like are high. In addition, the greater the position of the vehicle traveling on the roadway, the greater the degree of influence when the depression occurs (the probability of an accident occurring increases, the degree of traffic congestion increases, etc.). Therefore, cavity monitoring can be performed more efficiently by monitoring a position having such a factor.

<Invention of Claim 6>
While traveling the exploration vehicle, electromagnetic waves are incident in the depth direction from the vehicle below the target surface at predetermined intervals in the vehicle width direction and the traveling direction, and the reflected waves are detected, so that both the vehicle width direction and the traveling direction are detected. The monitoring method under a target surface given in any 1 paragraph of Claims 1-5 which acquires reflected wave data of each position at intervals of 10 cm or less.

(Function and effect)
By obtaining the reflected wave data finely in this way, the shape and dimensions of the cavity and the buried object can be obtained with high accuracy, and more accurate monitoring can be performed. Nevertheless, reflected wave data can be acquired simply by traveling on the target surface with an exploration vehicle, and secondary surveys are unnecessary, so there are advantages such as no traffic regulation, intersections can be handled, emergency cases can be handled, etc. It is very easy to acquire monitoring data several times.

  As described above, according to the present invention, it is possible to monitor below the target surface using an electromagnetic wave radar.

It is the schematic of an electromagnetic wave radar. It is a block diagram of a radar system. It is a top view which shows the sensor array example of a radar system. It is a top view which shows the sensor array example of a radar system. It is the schematic of an exploration vehicle. It is the schematic which shows the processing process of a radar system. It is the schematic which shows the acquisition outline | summary of reflected wave data. It is explanatory drawing which shows the multi-value conversion principle of reflected wave data. It is a figure of a running direction longitudinal section image, a horizontal section image, and a vehicle width direction longitudinal section image. It is explanatory drawing which shows the detection principle of a cavity candidate location. It is a running direction longitudinal cross-section image which shows the example of a cavity candidate location. It is explanatory drawing of the dimension and depth of a cavity top surface. It is a figure which shows the danger evaluation criteria of a depression. It is explanatory drawing which shows a cavity growth factor. It is explanatory drawing which shows a cavity growth factor. It is explanatory drawing which shows a cavity growth factor. It is explanatory drawing which shows a cavity growth factor. It is a horizontal cross-sectional image in the case of having a cavity growth factor (branch pipe). It is a depression risk map.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
<Target surface>
The target surface R of the present invention is not particularly limited as long as it is a surface in a place where there is a risk of depression, for example, a road, a runway, an apron in a port, a road surface such as a traffic surface of other people and vehicles, and a storeroom The surface of any place such as a place can be targeted. It does not matter whether the target surface R is a paved surface (regardless of the type of pavement, such as asphalt pavement or concrete pavement) or a non-paved surface.

<Measurement>
The present invention uses an electromagnetic wave radar to search below the target surface R. As electromagnetic wave radar, various electromagnetic wave radar systems (for example, SIR3000) manufactured by GSSI (USA), RC radar (for example, Handy Search NJJ-95B) manufactured by Japan Radio Co., Ltd. Known devices such as equipment (for example, Light Esper) and Komatsu Engineering's radar probe (for example, iron seeker) can be used without any particular limitation, but a radar system in which a large number of transmission / reception sensors are arranged in parallel is highly efficient and highly accurate. Therefore, it is preferable. Hereinafter, specific examples will be described.

  FIG. 1 is a schematic diagram of an electromagnetic wave radar. Symbol a is a sensor a in which an electromagnetic wave transmission / reception antenna and a transmission / reception circuit are integrated in a case, symbol c is an array antenna in which n sensors a are connected in parallel, and symbol b is an array antenna c. A control unit is shown in which functions are switched by switching for each sensor a to perform transmission / reception and signal processing individually. The array antenna c and the control unit b constitute a radar system k.

  As the sensor a used in the radar system, one using impulse transmission by a step waveform and having a center band with a frequency of 0.5 to 3 GHz is preferable, and the search is performed with a frequency of 1 GHz or more. And since the wavelength is short, the resolution in the depth direction is improved. The resolution in the depth direction is not particularly limited, but is preferably less than 5 cm. On the other hand, as the frequency of the electromagnetic wave increases, the attenuation in the object becomes severe. However, if the search is performed at 2 GHz or less, a sufficient search can be performed to a certain depth (40 cm or more).

  According to the knowledge of the present inventor, the depth at which cavities are likely to occur is up to about 60 cm in sand ground, and the depth at which the risk of depression should be considered is up to about 60 cm. Therefore, in the case of cavity exploration, by limiting the frequency of electromagnetic waves to be used to a frequency suitable for this depth range, that is, the center band is limited to a frequency of 1 to 2 GHz, not only the detection accuracy of the cavity and the like is improved, but also unnecessary. The exploration efficiency and the evaluation efficiency are improved because the exploration at a certain depth is not performed.

  From each sensor a controlled by the control unit b, electromagnetic waves are oscillated substantially vertically from the target surface R toward the inside. And the reflected wave from under the object surface R is received by each sensor a. The reflected wave received by each sensor a is output to the data processing device as data converted from an analog signal to a digital signal via the control unit b.

  More specifically, the radar system k can be configured as shown in FIG. That is, the sensor a in the radar system k is configured by the transmission unit Tx and the reception unit Rx, and power supply to the n sensors a is supplied by, for example, the power supply battery 31 provided in the control unit b. Is fed to each circuit in the control unit b.

  The transmission command to the transmission unit of the n sensors a is sequentially transmitted by the switch switching control circuit 34 sequentially switching the first changeover switch 34a, and the timing of this switching is the timing source oscillation circuit. This is performed by a clock pulse of several tens of MHz generated at 33b. For example, the switching is sequentially performed every period of the timing clock pulse, and after a few μs, the n sensors a of the array antenna are made a round.

  The electromagnetic wave transmitted by the transmission unit Tx of each sensor a repeats reflection and transmission with respect to the measurement object, and receives the internal state as a reflection signal by the reception unit Rx of the sensor a. The received reflected signal is sampled according to the synchronizing signal from the synchronizing signal generation circuit 33, converted into low frequency received signals 1 to n, and output from each sensor. The received signals output from the sensors are processed in the switch switching circuit 34 by the A / D conversion circuit 35 and the buffer 36, and are sequentially output to the data processing device by switching the second selector switch 34b. .

  FIG. 3A shows the single array state shown in FIG. 1 when the radar system k is shown in FIG. 1. When the distance between the sensors a in the vehicle width direction (sub-scanning direction) is d, the resolution of this single array state is d. It becomes. On the other hand, as shown in FIG. 3B, the array antenna c2 can obtain m times the resolution by arranging the array antenna c1 of the single array of n columns in a staggered pattern of m rows. This determines the horizontal resolution. The array antenna c2 arranged in m rows has a resolution of d / m with respect to the resolution d of the array antenna c1 in the single array. Moreover, as shown in FIG. 4, it is good also as the array antenna c3 which arranged the sensor a in m row xn column. In this configuration, the search can be performed in a range of m rows × n columns at a time without moving the array antenna c3.

  During the exploration, the operator may perform the measurement while sequentially moving the antenna. However, as shown in FIG. 5, the object is moved while traveling on the object plane R with the exploration vehicle 10 such as an automobile equipped with the radar system k. It is desirable to perform a search at a predetermined interval in the traveling direction over the entire investigation target area on the surface R. In addition to the radar system k, the exploration vehicle 10 shown in FIG. 5 includes an optical distance meter (or a rotary distance meter) 11, a camera 12 for imaging the state of the target surface R, and a GPS device 13. These output signals are input to the data processing device 14. A general-purpose computer can be used as the data recording device 14. In the illustrated example, a device such as the data processing device 14 is pulled, and thus a control device 15 for controlling the device such as the data processing device 14 is mounted on the vehicle.

  If the arrangement direction of the sensors a in the radar system k is the sub-scanning direction, and the direction perpendicular to the sub-scanning direction and the electromagnetic wave transmission direction is the main scanning direction, the main scanning direction of the radar system k is the traveling direction of the exploration vehicle 10. Thus, the travel distance associated with travel is input from the distance meter 11 to the data processing device 14.

  FIG. 6 shows a process for processing information obtained by moving the radar system k in the main scanning direction. The radar system k is supported on the object surface R to be inspected and moved along the main scanning direction. At that time, the control unit b drives, for example, n sensors a (1, 2,... N) in order, and the reflected wave data at each position in the sub-scanning direction is output momentarily in the main scanning direction. . That is, as shown in FIG. 7, the reflected wave data (intensity (amplitude) and depth (time)) 42 has a predetermined reflected wave detection interval (position interval in the traveling direction) in the main scanning direction and in the sub-scanning direction. It is acquired at each detection position 41 determined by a predetermined reflected wave detection interval (sensor array interval). Although these detection intervals can be determined as appropriate, they are desirably 10 cm or less (of course, 0 is not included and the interval is wider than 0), and can be, for example, about 1 to 5 cm. The reflected wave detection interval in the main scanning direction (position interval in the traveling direction) and the reflected wave detection interval in the sub-scanning direction (sensor array interval) can be different. For example, the former is set to about 1 to 5 cm, and the latter is It can be wider than that, for example, about 6 to 10 cm.

  The acquired reflected wave data 50 at each detection position 40 is recorded in a storage device (not shown) built in or connected to the data processing device 14 in association with the position information of each detection position 40. At this time, the raw data of the position information of each detection position 40 is the movement distance in the main scanning direction and the sensor array interval in the sub-scanning direction, but is converted into three-dimensional coordinates as necessary and recorded together with the raw data. The reflected wave data 50 is waveform data, but can be recorded together with other data as necessary.

<Detection of cavity>
If the reflected wave data 50 is acquired over the entire investigation target region on the target surface R by the above-described measurement, a cavity or the like can be detected by analyzing the acquired data 50 next. The method for detecting the cavity is not particularly limited, and the method described in Patent Document 3 can also be adopted. For example, an image below the target surface R is created as described below, and the cavity is detected based on this image. Can do.

  That is, based on the acquired data 50, a traveling direction longitudinal cross-sectional image (see FIG. 9) in which the reflected wave intensity (amplitude) at each depth at each reflected wave detection position 40 is expressed in shades. Create depth.). For example, as shown in FIG. 8, the reflected wave intensity at each depth at each reflected wave detection position 40 is multivalued. Multi-value conversion can be performed by an appropriate method. For example, the upper limit value 70 on the positive side and the lower limit value 71 on the negative side are respectively set with the reflected wave intensity 0 as the median value, and the intensity lower limit value 70 to the intensity upper limit value 71 are set. The range of the reflected wave intensity value is equally divided into multiple stages (if it is 3 or more, it is suitable for creating a visualized image to be described later if it is about 256 or 65536), and at each reflected wave detection position 40 The number of steps corresponding to the reflected wave intensity at each depth can be set as the multi-level reflected wave intensity at that position. The “depth” can be obtained from the propagation speed of electromagnetic waves and the time from transmission of electromagnetic waves to reception of reflected waves. Then, as shown in FIG. 9, the horizontal axis is the travel direction distance, the vertical axis is the depth, and the unit pixel having the gradation of the multilevel reflected wave intensity at each travel direction position and each depth is two-dimensionally represented. By arranging them, a traveling direction longitudinal section image 80 can be created. In addition, the crosshair of each image in FIG. 9 shows the corresponding position between images. The travel direction longitudinal cross-sectional image 80 is created for all the reflected wave detection positions 40 in the vehicle width direction, and any one (for example, the center in the vehicle width direction) or a plurality (for example, three of the both ends in the vehicle width direction and the center portion). Only) may be created. The traveling direction longitudinal cross-sectional image 80 may be created in real time while the vehicle is traveling for obtaining the reflected wave data 50, or may be created collectively after the reflected wave data 50 is obtained. Further, according to the knowledge of the present invention, since the cavities are shallower than 60 cm and cavities at deep positions are unlikely to cause depression, the traveling direction longitudinal cross-sectional image 80 is limited to a predetermined depth (1.5 m or less). Creation is also a preferred form.

  Since it is difficult to determine the cavity only with the longitudinal cross-sectional image 80 in the traveling direction, for example, as shown in FIG. 9, the horizontal cross-sectional image 90 expressing the reflected wave intensity at an arbitrary depth in shades, or the vehicle width at an arbitrary traveling direction position It is desirable to create a directional longitudinal cross-sectional image 100 and comprehensively determine from these images 80, 90, 100. The horizontal cross-sectional image 90 and the vehicle width direction vertical cross-sectional image 100 can be created, for example, by the same method as the traveling direction vertical cross-sectional image 80 described above. That is, the horizontal cross-sectional image 90 multi-values the reflected wave intensity at each depth at each reflected wave detection position 40, the horizontal axis is the travel direction distance, the vertical axis is the vehicle width direction distance, and each position at the target depth. It can be created by two-dimensionally arranging unit pixels having the gradation of the multilevel reflected wave intensity. In addition, the vehicle width direction longitudinal cross-sectional image 100 multi-values the reflected wave intensity at each depth at each reflected wave detection position 40, the horizontal axis is the vehicle width direction distance, the vertical axis is the depth, and the target traveling direction position is It can be created by two-dimensionally arranging unit pixels having gradations of multilevel reflected wave intensity at each position. When creating these images 90 and 100, if there are a plurality of cavities with different positions, the images 90 and 100 can be created for each cavity. Of course, the images 90 and 100 can be created at any position different from the cavity.

  When searching for a cavity, it is desirable to first use the longitudinal section images 80 and 100. For example, in the longitudinal cross-sectional images 80 and 100, a portion where the reflected wave is positive and stronger than the surroundings (hereinafter also referred to as a strong signal portion), that is, a portion where a black layer portion overlaps below a white layer portion in the illustrated example. 81 is likely to be a cavity. Therefore, this strong signal portion 81 can be detected as a cavity. FIG. 10 is a comparison diagram showing an example of the relationship between the layer structure under the normal asphalt pavement surface, the reflected wave polarity, and the traveling direction longitudinal section image 80. In this example, in a place where there is no cavity, as shown in FIG. 10A, the relative dielectric constant εr increases as it goes to the lower layer, and the reflected wave between the target surface R and the layer has negative polarity (black to white in the image). On the other hand, in a place where there is a cavity, as shown in FIG. 10B, the relative permittivity εr of the cavity portion is the smallest, and the electromagnetic wave is reflected positively on the top surface of the cavity (white in the image). To black), the shape of the top of the cavity appears.

  When searching for a cavity, the shape of the strong signal portion 81 is also a reference in addition to the reflection polarity and the reflected wave intensity. For example, the wedge-shaped (or dome-shaped) strong signal portion 81 shown in FIG. 11A is the most common one generated in the hollow portion. This shape is due to the fact that the independent cavity often has a dome shape. On the other hand, the intermittent strong signal part 81 shown in FIG. 11 (b) is often generated in the upper part of the multi-tubular pipe or in the cavity when the concrete plate is removed, and the strong signal part shown in FIG. 11 (c). 81 is generated in a cavity caused by consolidation settlement on the side of the structure. Moreover, the strong signal site | part 81 shown in FIG.11 (d) generate | occur | produces in the space | gap in the change points (replacement location etc.) of a pavement structure. Therefore, the coincidence between the shape of the strong signal portion 81 and these shapes is evaluated, and when they coincide, it can be detected as a cavity.

  When the strong signal portion 81 is found based on the longitudinal cross-sectional image in this way, the coincidence between the shape of the strong signal portion 81 and the shape of the embedded object such as a tube is next determined based on the horizontal cross-sectional image 90 in the strong signal portion 81. It is also preferred to evaluate and detect as a cavity only if they do not match. As a result, it is possible to discriminate buried objects and cavities that are difficult to distinguish only by the reflection polarity. In particular, when such a horizontal cross-sectional image 90 is created, if the reflected wave detection is performed at a fine interval of 10 cm or less, the shape of the embedded object such as a tube appears clearly, so that the difference between the cavity and the embedded object can be easily distinguished. Further, if there is an embedded object under the target surface R, there is a high possibility that a cavity is generated around the object. Therefore, as shown in FIG. 18, the strong signal part 81 that is in contact with or overlaps the strong signal part 82 of the embedded object 122. If detected, the possibility of the cavity 85 can be determined to be extremely high.

  The above-described detection processing of the cavities and embedded objects can be performed visually by an operator, but the acquired data may be directly processed by a computer (the data processing device 14 described above or another one may be used). In this case, it is not necessary to generate an image.

<Evaluation of the risk of depression>
When a cavity is detected, the risk of depression at each reflected wave detection position 40 can be evaluated as follows. That is, as shown in FIG. 12, the top surface dimension W and the top surface depth P of the cavity 85 are obtained. The dimension W and depth P of the top surface of the cavity 85 are measured by the operator by measuring the printed matter of the images 80, 90, 100 with a ruler, or inputting (specifying) the dimension measurement positions of the images 80, 90, 100 to the computer. It can be obtained by calculating with a computer or analyzing the images 80, 90, and 100 with a computer. As shown in FIG. 13, it is assumed that the higher the dimension W of the top surface of the cavity and the deeper the depth P of the top surface of the cavity 85, the higher the risk of the sinking. Assess sex. In this way, not only the cavity 85 but also the risk of depression caused by the cavity 85 is evaluated, so that the cavity 85 with a high risk of depression is repaired first, and the cavity with a very low risk of depression is found. It is possible to easily carry out an appropriate repair plan such that 85 is not repaired or delayed.

  Since the depression occurs due to the collapse of the layer above the cavity 85, as described above, the depression is more likely to occur as the dimension W of the cavity top surface is larger. Therefore, the dimension W of the top surface of the cavity 85 can be determined as appropriate, such as the area of the top surface, the major axis, the minor axis, etc. However, if the cavity 85 extends long with a narrow width, there is a risk of collapse. There is little nature. Therefore, as the dimension W of the cavity top surface, as shown in FIG. 12B, it is preferable to use a short side W when the shape of the cavity 85 top surface is approximated to an ellipse. The method for calculating the short side by the ellipse approximation is not particularly limited, and a known method can be used as appropriate. For example, the above-described horizontal cross-sectional image is created, and the image is obtained assuming that the portion having a predetermined reflection intensity or more is the cavity 85. The short side can be calculated by detecting the coordinates of the edge by analysis and approximating the edge with an ellipse by the least square method or the like.

  The depth P of the top surface of the cavity 85 can also be determined as appropriate. The reference position is not the target surface R but an arbitrary position such as the lower surface of the asphalt mixture layer, or the depth measurement site on the top surface of the cavity 85 is Although it can be the peripheral edge of the top surface, it is desirable that the reference position is the target surface R because it can be accurately obtained from the reflected wave data 50, and the cavity 85 is highly correlated with the depression. The depth measurement site on the top surface is preferably the top of the top surface of the cavity 85. That is, as shown in FIG. 12, the depth P of the top surface of the cavity 85 is most preferably the depth from the target surface R to the top of the top surface of the cavity 85.

  In this evaluation method, as long as both the dimension of the top surface of the cavity 85 and the depth P of the top surface of the cavity 85 are used as indices, the weighting can be determined as appropriate. For example, as shown in FIG. By taking the dimension W of the top surface on the horizontal axis and the depth P of the top surface of the cavity 85 on the vertical axis, a straight line having a predetermined inclination passing through the origin (the dimension W of the cavity top surface is 0 and the depth P of the cavity 85 top surface is 0). The area is divided into a plurality of depression risk areas, and the depression risk caused by the cavity 85 is ranked according to which area the detection cavity 85 belongs to depending on the top surface size and the top surface depth (in the illustrated example, the risk is high). It is possible to make an evaluation by assigning a rank in the order of A, B, and C) and a score.

  In addition, if the detected top surface dimension of the cavity 85 is small but at a shallow position, there is a high risk of depression, and the top surface dimension of the cavity 85 may not be detected accurately. The evaluation criteria shown in Fig. 13 (b) and Fig. 13 (c) are modified as shown in Fig. 13 (c), and those with a depth of less than a predetermined depth can be given a higher rank and score for the risk of depression, regardless of the top surface dimensions. This is a preferable evaluation method. In addition, although this predetermined depth is about 20 cm in the example of illustration, it is not limited to this, For example, you may set to about 10-30 cm.

  By the way, the growth and rise of the cavity 85 are extremely important in evaluating the risk of depression. That is, the cavity 85 existing under the target surface R has different growth and rise speeds from occurrence to depression depending on the surrounding environment and the like. Therefore, in evaluating the danger of depression, such growth factors are considered, When there is a growth factor, it is preferable to evaluate the risk of depression by raising the rank or adding points, assuming that the risk of depression is higher. For example, in the cavity 85 of the type shown in FIG. 14 (a), breakage or a gap 111 occurs in the revetment retaining wall 110 or an abutment, and seawater or the like enters the ground 100. Due to the increase in water, etc., water repeatedly flows into and out of the ground, and gradually erodes and forms, and grows and rises. Reference numeral 100 indicates an asphalt mixture layer, reference numeral 101 indicates a roadbed layer, and reference numeral 102 indicates a ground layer including a roadbed. In addition, the cavity 85 of the type shown in FIG. 14B is displaced or damaged in the underground buried pipes 121 and 122 due to an earthquake or ground subsidence (particularly, the connection between the main pipe 121 and the branch pipe 122 of the sewer) Sediment flows from the damaged part into the pipes 121 and 122 from a damaged part such as during a heavy rain, and a cavity 85 is generated and grows and rises. These can be classified as cavities 85 due to earth and sand suction, and grow and rise rapidly. Therefore, when there are these growth factors, it is evaluated that the risk is higher than that based on the evaluation result based on the top surface size and the depth of the cavity 85 (for example, the above-mentioned risk B is the following). Or A + by adding a “+” indicating a growth factor to the above-mentioned risk A.

  On the other hand, the cavity 85 of the type shown in FIG. 15A is formed by loosening due to insufficient rolling pressure during construction of the structure 130, or the groundwater flows by the structure 130. As a result, the water channel 131 is generated, and the fine grains of the ground are formed by flowing out into the water channel due to rainwater intrusion and groundwater fluctuation, and grows and rises. In addition, the cavity 85 of the type shown in FIG. 15B is loosened due to insufficient rolling pressure during laying, particularly in the vicinity of the multi-tube 140 such as telephone, electricity, CAB, or in a congested portion of a buried object. It is formed by consolidation and sinking over time, and grows and rises. A cavity 85 of the type shown in FIG. 16 (a) is formed by the consolidation and subsidence over time when chestnut or concrete glass is mixed in the backfill 150 and there are many voids around it.・ It will rise. A cavity 85 of the type shown in FIG. 16 (b) is formed by a local loosening caused by excavation of a tube 160 such as a shield tube or a propulsion tube being concentrated in one direction without being dispersed.・ It will rise. A cavity 85 of the type shown in FIG. 17 (a) is formed by the consolidation and subsidence over time when there is local loosening around the object 170 (temporary earth retaining, manhole, dead tube, etc.).・ It will rise. Cavity 85 of the type shown in FIG. 17 (b) is formed by uneven subsidence as shown by the arrow of a solid subgrade such as a concrete plate or slag, which grows and rises. It is. These can be classified as cavities 85 due to the consolidation of sediment, and the growth stops when they are compacted to some extent, but the danger increases compared to the case where there is no growth factor. Therefore, when there are these growth factors, it is evaluated that the risk is higher than that based on the evaluation result based on the top surface size and the depth of the cavity 85 (for example, the above-mentioned risk B is the following). Or A + by adding a “+” indicating a growth factor to the above-mentioned risk A.

  Furthermore, the degree of risk can be evaluated differently depending on the types of these growth factors. For example, when the growth factor is “suction of sediment”, the growth rate is faster than in the case of “sediment sedimentation”, and the growth does not stop, so the risk is evaluated higher than the sediment settlement of sediment. Can do. When the growth factor is “consolidation of sediment”, the growth will stop once it has been compacted to some extent, so the risk assessment may not be high (the basic evaluation result remains as it is).

  These growth factors include buried objects 121, 122, and 130 other than buried objects whose positions are known (including buried objects whose positions can be grasped on the ground such as buried objects extending from the ground to the ground). , 140, 150, 160, and 170 cannot be grasped in advance. Therefore, not only the exploration of the cavity 85 but also the buried objects 121, 122, 130, 140, 150, 160, and 170, which are growth factors, are explored by creating and using the above-described traveling direction longitudinal sectional image 80 and horizontal sectional image. However, as shown in FIG. 18, when the cavity 85 is detected and an embedded object such as the branch pipe 122 is detected around the cavity 85, it is preferable that the evaluation of the risk of depression is higher because there is a growth factor. It is a form. Similarly, for a buried object whose position is known, when the cavity 85 is detected and there is a known buried object therearound, it is possible to make the evaluation of the risk of depression higher because there is a growth factor.

  In particular, as will be described later, when monitoring changes under the target surface R based on a comparison between new and old reflected wave data 50 at the same reflected wave detection position 40, the growth and rise of the cavity 85 are monitored, and the growth rate and It is also a preferable form to obtain a higher evaluation of the risk of depression when the speed is determined and the speed is equal to or higher than a predetermined value.

  Further, for example, when the traffic volume on the target surface R is large, such as traffic on a roadway or a sidewalk, more load or vibration is applied. When the target surface R is a roadway, the position where the vehicle travels more frequently in the roadway (for example, The vehicle travels more in the lane than in the road shoulder, and the vehicle travels more in the intersection even in the lane). Therefore, in these cases, there is a high possibility that the cavities 85 are generated, and the growth speed and the rising speed of the generated cavities 85 are high. In addition, in these cases, the degree of influence at the time of the occurrence of depression (the probability of occurrence of an accident increases, the degree of traffic congestion increases, etc.) increases. Therefore, it is also proposed to perform more accurate evaluation by evaluating the risk of depression by adding these factors or adding an impact evaluation.

  That is, when the traffic volume of the target surface R is taken into account, the traffic volume of the target surface R is evaluated or known, and when the cavity 85 is detected, the traffic volume of the target surface R that detected the cavity 85 is determined. The greater the number, the higher the risk of depression due to the cavity 85, and the risk of depression is evaluated (for example, the above-mentioned risk B is assigned to the next rank A, or the risk A is the growth factor. A + can be added to indicate A +). Instead of this, an influence degree evaluation that the influence degree at the time of depression due to the cavity 85 is larger as the traffic volume of the target surface R that detects the cavity 85 is larger can be added to the risk evaluation of the depression. For example, in the case of a roadway, the degree of congestion of the road where the cavity 85 is detected is obtained from the national road / street traffic situation survey (road traffic census) general traffic survey summary table, and the congestion degree and influence degree correspondence shown in Table 1 below are obtained. Based on the table, it is also possible to evaluate the degree of influence (congestion degree due to traffic regulation) when a depression occurs by ranking.

  In addition, when the position where the cavity 85 is generated in the roadway is taken into account, when the cavity 85 is detected, the more the vehicle is traveling, the higher the danger of the depression, A sex evaluation can be performed (for example, the above-mentioned risk level B is set to the next rank A, or “+” indicating a growth factor is added to the above-mentioned risk level A and set to A +). Instead, for example, as shown in Table 2, an influence degree evaluation that the influence degree at the time of depression is larger as the detection position of the cavity 85 on the roadway is a position where the vehicle travels more is added to the risk evaluation of depression. You can also.

  On the other hand, even if the size and depth of the top surface of the cavity 85 are the same, the risk of depression will decrease as the supporting force of the layer located above the top surface of the cavity 85 is stronger. Therefore, in consideration of this, the stronger the supporting force of the layer located above the top surface of the cavity 85, the lower the risk, based on the evaluation result based on the top surface size and depth of the cavity 85. (For example, the above-mentioned risk A is assigned to the next rank B, or the above-mentioned risk A is attached with “-” indicating a risk reduction factor to A-). For example, in the case of the asphalt pavement surface shown in FIG. 14 and the like, it is possible to evaluate the equivalent value conversion coefficient as the supporting force, and the thickness of each layer in this case may adopt a known value, An operator measures the reflected wave data 50 and the traveling direction longitudinal cross-sectional image 80, or directly processes the reflected wave data 50 by a computer (the data processing device 14 described above or another one) or a longitudinal section. It can be obtained by image analysis of the image.

<Monitoring>
Characteristically, the same target surface R is repeatedly surveyed under the target surface R by an electromagnetic wave radar after a predetermined period of time, such as one year or six months, and the reflected wave data 50 itself at the same reflected wave detection position 40 is detected. Alternatively, the target surface in the unit target region based on the new and old comparison of the processing data obtained by processing the reflected wave data 50 (for example, the above-described traveling direction longitudinal section image 80, vehicle width direction longitudinal section image 100, horizontal section image 90). Monitor changes under R, for example, the generation, growth and rise of cavities 85. As a result, for example, the generation of the cavity 85, of course, it is possible to distinguish between the cavity 85 or the like that grows and rises quickly and the cavity 85 or the like that is slow, and it is easy to evaluate the necessity of repair and formulate a repair plan. Become. That is, when the cavity 85 is found deep under the target surface R, it can be determined that the risk of depression is low at that time, but if the rise or growth is fast, the risk of depression is high and the need for repair is high. It becomes. Therefore, if the generation, growth, and rise of the cavity 85 are monitored as described above, the risk of depression can be evaluated.

  As described above, if there are the buried objects 121, 122, 130, 140, 150, 160, and 170 under the target surface R, there is a high possibility that the cavities 85 are generated around them, and the growth rate of the generated cavities 85, The rising speed is relatively fast. Therefore, when a buried object is detected based on the reflected wave data 50, if cavity generation, growth, and rise are monitored based on a comparison between the reflected wave data 50 around the detection position of the buried object, the cavity monitoring is more efficient. Can be done.

  In addition, as described above, for example, when the traffic volume on the target surface R is large, such as traffic on a roadway or a sidewalk, more loads and vibrations are applied. When the target surface R is a roadway, the position where the vehicle travels frequently in the roadway As a result (for example, the vehicle travels more in the lane than in the road shoulder, the vehicle travels more in the intersection even in the lane), more load and vibration are applied. Therefore, in these cases, there is a high possibility that the cavities 85 are generated, and the growth speed and the rising speed of the generated cavities 85 are high. In addition, in these cases, the degree of influence at the time of the occurrence of depression (the probability of occurrence of an accident increases, the degree of traffic congestion increases, etc.) increases. Therefore, cavity monitoring can be performed more efficiently by monitoring the target surface R having a traffic volume of a predetermined value or more, or by monitoring the inside of the lane (including an intersection) when the target surface R is a road surface. it can. For example, in the case of a roadway, the target surface R whose traffic volume is greater than or equal to a predetermined value is a road whose traffic volume and congestion level are greater than or equal to a predetermined value in the national road / street traffic situation survey (road traffic census) general traffic survey summary table. be able to.

  The comparison between the old and new data can be performed visually by the operator by creating the above-described traveling direction longitudinal section image 80 and horizontal section image, but can also be performed by directly processing the acquired data by a computer. In that case, it is not necessary to generate an image. Also, when comparing, the difference between the old and new reflected wave intensity at the same position was taken, and the part where the difference intensity was a predetermined value or more, or the part where it continued in the running direction or the vehicle width direction was changed. You may detect as a position. For this reason, the traveling direction longitudinal section image 80, the horizontal section image 90, and the vehicle width direction longitudinal section image 100 based on the difference intensity can be created.

<Mapping>
In order to make a cavity investigation plan and repair plan, it is desirable to grasp the overall picture of the danger of depression at the level of the region. Therefore, based on the evaluation result of the risk of depression described above, as shown in FIG. 19, the road display unit 201 on the map 200 (which may be an aerial photograph or a combination of a map and an aerial photograph or other photographs) It is also preferable to create a depression risk map displaying the danger of depression at that position at the survey position. The display form is not particularly limited. For example, the danger display mark 202 or the like can be attached to the position of the depression danger display. Further, as shown in the figure, the color of the road display section 201 is made different between the surveyed section and the unsurveyed section, or the color, pattern, shape, and size of the danger display mark 202 are changed according to the degree of risk. It is also preferable to make them different. Furthermore, it is also preferable to classify colors and patterns according to the degree of risk and unexamined / investigated for each region as shown in the figure. The display form is a display form that considers only the number of cavities found, but a display form that considers only the degree of danger, a display form that considers both the number of cavities and the degree of danger, a display form that takes into account other factors, etc. Appropriate changes are possible. The area can be set as appropriate, such as dividing into squares as shown in the figure, dividing into an appropriate shape such as a triangle or a hexagon, or setting based on an address. Furthermore, it is also one preferable form that the depression risk map is integrated with other maps such as a disaster prevention map, a flooded map, and an earthquake ease map.

  INDUSTRIAL APPLICABILITY The present invention can be used to monitor changes under the surface of every place such as roads, runways, aprons in harbors, road surfaces such as traffic surfaces of other people and vehicles, storage areas, etc. It can be used regardless of whether it is an asphalt pavement, a concrete pavement, etc., or a non-paved surface.

  P: Depth of the top surface, R: Target surface, W: Dimensions of the top surface of the cavity, a ... Sensor, k ... Electromagnetic radar system, 10 ... Exploration vehicle, 11 ... Optical distance meter, 12 ... Camera, 13 ... GPS device , 14 ... Data processing device, 15 ... Control device, 40 ... Reflected wave detection position, 50 ... Reflected wave data, 80 ... Longitudinal section image in traveling direction, 81 ... Strong signal region, 85 ... Cavity, 90 ... Horizontal sectional image, 100 ... Vertical cross-sectional image in the vehicle width direction.

Claims (6)

Using electromagnetic wave radar, electromagnetic waves are incident in the depth direction from the upper side of the target surface to the lower side of the target surface with a predetermined interval in the direction along the target surface over at least the predetermined unit target area on the target surface and reflected. A data acquisition step of acquiring reflected wave data at each reflected wave detection position by detecting waves on the upper side of the target surface,
For the same unit target area, perform multiple times with a predetermined period,
Based on the new and old comparison of the reflected wave data itself or the processed data obtained by processing the reflected wave data at the same reflected wave detection position, the change below the target surface in the unit target area is monitored.
A monitoring method under the target surface characterized by the above. Based on the reflected wave data acquired in each data acquisition step, the cavity at each reflected wave detection position is explored, and when the cavity is detected, the size of the cavity top surface and the depth of the cavity top surface are obtained,
Monitor the generation, growth and rise of cavities based on new and old comparisons of the dimensions and depth of the cavity top surface at the same reflected wave detection position.
The subsurface monitoring method according to claim 1. Based on the reflected wave data acquired in each data acquisition step, the buried object at each reflected wave detection position is searched, or the position of the buried object is known,
When a buried object is detected or there is a known buried object, the generation of cavities will occur based on the comparison of the reflected wave data itself or the processed data obtained by processing the reflected wave data around the detection position of the buried object. Monitoring growth and rise,
The monitoring method under a target surface according to claim 2.   The monitoring method under the target surface according to any one of claims 1 to 3, wherein the monitoring is performed for a target surface whose traffic volume is a predetermined value or more.   The monitoring method under the target surface according to claim 1, wherein the target surface is a road surface and the monitoring is performed in a lane.   While traveling the exploration vehicle, electromagnetic waves are incident in the depth direction from the vehicle below the target surface at predetermined intervals in the vehicle width direction and the traveling direction, and the reflected waves are detected, so that both the vehicle width direction and the traveling direction are detected. The monitoring method under a target surface given in any 1 paragraph of Claims 1-5 which acquires reflected wave data of each position at intervals of 10 cm or less.