Pipe material and ground measurement system

Abstract

A pipe material (10) is embedded underground and comprises one or more scintillators (11) disposed inside a pipe wall 13. Additionally, a ground measurement system (1) includes: the pipe material (1); a photodetector (12) that detects light outputted from each scintillator (11) among said one or more scintillators (11); and an information processing device 20 including a control unit (22) that estimates, on the basis of a detection signal from the photodetector (12) and disposition information of the scintillators (11), information related to the ground density around the pipe material (10).

Description

Pipe and Ground Measurement System

[0001] The present disclosure relates to a pipe and a ground measurement system.

[0002] Ground density is an important factor related to the safety of building structures and civil engineering structures installed on the ground, as well as the efficiency and safety of construction work. From the perspective of ensuring the safety of structures, if appropriate ground density is not ensured, there is a risk of settlement and inclination of the structures. Also, in the design of construction work, it is necessary to determine the structure of the foundation based on the ground density data of the original ground.

[0003] Currently, as general methods for measuring ground density, there are a method of collecting core samples and measuring them in a laboratory, and a method of hitting the ground surface using a test piece. However, when these methods are implemented for a wide range of ground, there are problems with workability and cost. For this problem, non-contact measurement methods such as X-ray CT (Computed Tomography) and geotomography using elastic waves or electromagnetic waves (for example, see Non-Patent Document 1) are effective.

[0004] On the other hand, a ground density measurement method using cosmic ray mu particles, which is a type of secondary cosmic ray generated by the collision of the atmosphere and cosmic rays, is known (for example, see Non-Patent Document 2). Mu particles can easily reach the ground surface and have the characteristic of attenuating when passing through the ground. The attenuation pattern varies depending on the density in the ground. The method using mu particles can measure the ground density only by installing a mu particle measuring device underground.

[0005] Mori Mitsuhiro, Nagatsuka Isamu, "Geotomography", Journal of the Japanese Society of Agricultural Engineering, Vol. 68, No. 1 (2000.1), p83 - 84 Suzuki Keiichi, "Possibility of Civil Engineering Geophysical Exploration Using Mu Particles", Geophysical Exploration, Vol. 65, No. 4 (2012), pp251 - 259

[0006] However, the method described in Non-Patent Document 1 requires the installation of transceivers in the ground being investigated. Furthermore, the use of X-rays poses a risk of exposure to the surrounding area. Also, the method described in Non-Patent Document 2 requires an underground space to install a muon detector. However, securing an underground space for these devices can be difficult. Moreover, placing measuring devices inside underground pipes or other structures each time a measurement is taken is time-consuming and costly.

[0007] Therefore, the purpose of this disclosure, which focuses on these points, is to improve the technology for measuring ground density.

[0008] According to one embodiment, the pipe material is buried underground and comprises one or more scintillators arranged inside the pipe wall.

[0009] A ground measurement system according to one embodiment comprises a pipe material buried underground, which includes one or more scintillators arranged inside the pipe wall; a photodetector that detects light emitted from each of the one or more scintillators; and an information processing device including a control unit that estimates information regarding the ground density around the pipe material based on the detection signal from the photodetector and the arrangement information of each of the scintillators.

[0010] According to this disclosure, since the pipe material used for underground piping has one or more scintillators placed inside the pipe wall, there is no need to install a separate measuring device inside the pipe for measuring ground density using muons. As a result, ground measurement becomes possible wherever the pipe material of this disclosure is used, and the effort and cost of installing measuring devices are reduced. This improves the technology for measuring ground density.

[0011] This is a block diagram showing the schematic configuration of the ground measurement system according to the first embodiment. This is a cross-sectional view of the pipe material in Figure 1. This is a side view of the pipe material in Figure 1. This diagram illustrates an example of the arrangement of the ground measurement system in Figure 1 placed underground. This diagram illustrates the schematic configuration of the ground measurement system according to the second embodiment, which is a flowchart of the processing performed by the control unit of the information processing device. This is a cross-sectional view of the pipe material according to the third embodiment. This is a side view of the pipe material in Figure 3. This diagram illustrates a method for determining the direction from which muons are coming. This is a side view of the pipe material according to another example that incorporates a photodetector. This is a cross-sectional view showing an example of an underground buried pipeline including the pipe material according to the fourth embodiment.

[0012] Embodiments of this disclosure will be described below with reference to the drawings. The figures used in the following description are schematic. Dimensions and proportions shown in the drawings do not necessarily correspond to those of reality.

[0013] [First Embodiment] A ground measurement system 1 according to one embodiment of the present disclosure is a system that measures ground density by detecting cosmic ray muons generated when primary cosmic rays collide with the Earth's atmosphere using a muon detection unit including a scintillator 11 placed in underground piping. Hereinafter, cosmic ray muons will be simply referred to as muons. As shown in Figure 1, the ground measurement system 1 includes one or more pipe materials 10 and an information processing device 20. In one embodiment, the ground measurement system 1 may further include a position detector 30.

[0014] (Structure of the pipe material) The pipe material 10 is a substantially cylindrical member that is buried underground and constitutes an underground buried pipeline. The underground buried pipeline can accommodate communication cables, power cables, etc. The pipe material 10 includes a scintillator 11. The pipe material 10 may further include a photodetector 12. The scintillator 11 and the photodetector 12 constitute a muon detection unit that detects muons. The photodetector 12 does not need to be built into the pipe material 10. For example, the photodetector 12 may be attachable to the scintillator 11 of the pipe material 10.

[0015] As shown in Figures 2 and 3, the pipe material 10 includes a cylindrical pipe wall 13 surrounding the cavity 14. One or more scintillators 11 are arranged inside the pipe wall 13. In the example shown in Figures 2 and 3, four scintillators 11 extending in the longitudinal direction of the pipe wall 13 are arranged at positions 90 degrees apart in the circumferential direction of the cylindrical pipe wall 13. The arrangement of the scintillators 11 inside the pipe wall 13 is not limited to this. The number of scintillators 11 can be any number.

[0016] The scintillator 11 is made of a material that emits light when muons pass through it. The scintillator 11 can be an inorganic or organic scintillator. Inorganic scintillators include those using sodium iodide (NaI) crystals or cesium iodide (CsI) crystals with a small amount of thallium (Tl) added. Organic scintillators include plastic scintillators. Plastic scintillators are made by mixing an organic light-emitting material into a plastic such as polystyrene. Plastic scintillators are characterized by being easy to process and having a fast response speed. In this embodiment, the scintillator 11 is a plastic scintillator.

[0017] The photodetector 12 is connected to the scintillator 11 at the end 15 of the tube material 10 and converts the light generated in the scintillator 11 into an electrical signal. The photodetector 12 can use a photomultiplier tube that converts light into electrons using the photoelectric effect and multiplies the converted electrons. Light generated inside the scintillator 11 by the passage of muons undergoes repeated total internal reflection inside the scintillator 11 and propagates to the end of the scintillator 11, and is incident on the photodetector 12. The scintillator 11 and the photodetector 12 do not need to be directly connected. The scintillator 11 and the photodetector 12 may be connected via a light guide such as an optical fiber that is transparent to the light generated in the scintillator 11.

[0018] The pipe material 10 can be made of plastic or steel. If the pipe material 10 is made of plastic, the pipe wall 13 and the plastic scintillator 11 can be made of materials having equivalent mechanical properties. Table 1 is a table comparing the physical properties of polyvinyl chloride, as an example of the material for the pipe material 10, and polystyrene, which is the material for the plastic scintillator 11.

[0019]

[0020] As shown in Table 1, the similarity in mechanical properties between the material of the pipe 10 and the material of the scintillator 11 ensures the structural strength of underground pipelines using plastic pipes 10. Therefore, even if the scintillator 11 is installed inside the pipe wall 13 of the pipe 10, the mechanical properties of the pipe 10 can be maintained.

[0021] The wall 13 of a commonly used plastic pipe 10 with an inner diameter of approximately 100 mm has a thickness of approximately 6 mm. Therefore, if the scintillator 11 is thinner than this, it can be embedded in a pipe 10 of the same thickness as the existing pipe. Also, if the thickness of the scintillator 11 is greater than 6 mm, the thickness of the wall 13 of the pipe 10 can be increased.

[0022] When the pipe material 10 is made of steel, the pipe wall 13 of a commonly used underground buried pipe material 10 with an inner diameter of approximately 100 mm has a thickness of approximately 7 mm. If the plastic scintillator 11 has a thickness smaller than this, it can be placed without changing the dimensions of the steel pipe material 10. Furthermore, in electromagnetic wave exploration methods used in geophysical exploration, if there is a steel pipe material 10, the electromagnetic waves are reflected from its surface and cannot be transmitted. On the other hand, in measurements using the pipe material 10 of this disclosure, highly penetrating muons are used. Therefore, even if the pipe material 10 is made of steel, the muons can at least partially penetrate the pipe wall 13, and can be used to measure the presence or absence of buried objects in the surrounding area.

[0023] (Example of Ground Measurement System Arrangement) Figure 4 shows the arrangement configuration of a ground measurement system 1 that measures muon particles by burying a pipe 10 in the ground. As shown in Figure 4, the pipe 10 is buried in the ground 40. The distance from the pipe 10 to the ground surface 41 is called the ground height D. The ground height D can be several tens of centimeters to several hundred meters. The pipe 10 is arranged connecting two manholes 42 or underground spaces. A manhole 42 is a space that a person can enter, provided for the management and maintenance of underground equipment such as the pipe 10 installed underground. A manhole iron cover 43 is provided on top of the manhole 42. A position detector 30 may be placed inside the manhole iron cover 43. The ground height D of the pipe 10 may be measured in advance when the pipe 10 is placed in the ground 40. Alternatively, the ground measurement system 1 may include a sensor inside the manhole 42 to measure the ground height D of the pipe 10.

[0024] The photodetector 12 may be positioned on the manhole 42 side of the scintillator 11. The photodetector 12 may be positioned not only at one end of the scintillator 11, but also at both ends. The photodetector 12 outputs a detection signal, which is an electrical signal obtained as a result of detecting muons, to the information processing device 20. A multiplexer 50 that multiplexes the outputs from multiple scintillators 11, and / or an amplifier that amplifies the signal may be positioned between the photodetector 12 and the information processing device 20.

[0025] (Configuration of the Information Processing Device) The information processing device 20 is a PC (Personal Computer), a workstation, and other general-purpose or dedicated computer. As shown in Figure 1, the information processing device 20 includes a signal transmission / reception unit 21, a control unit 22, an input / output unit 23, and a storage unit 24. In Figure 1, the information processing device 20 is shown as a single device, but the information processing device 20 is not limited to a single device. Multiple devices may share the functions of the information processing device 20. For example, the information processing device 20 may include a part located inside the manhole 42 and a part located above ground. When the functions of the information processing device 20 are distributed among multiple devices, each device may be able to communicate by any means of communication.

[0026] The signal transmission / reception unit 21 includes a communication module that supports wired and / or wireless communication. The signal transmission / reception unit 21 may include a detection signal acquisition unit 21a and a position information acquisition unit 21b. The detection signal acquisition unit 21a sequentially receives detection signals from photodetectors 12 connected to each scintillator 11 arranged inside each pipe material 10. The position information acquisition unit 21b acquires absolute position information, including the elevation of the manhole 42 where the information processing device 20 is located, from the position detector 30.

[0027] The control unit 22 includes one or more processors. In one embodiment, the "processor" is a general-purpose processor or a dedicated processor specialized for a specific process, but is not limited to these. The processor may be, for example, a CPU (Central Processing Unit), a DSP (Digital Signal Processor), or an ASIC (Application Specific Integrated Circuit). The control unit 22 may manage the overall operation of the ground measurement system 1. The control unit 22 may execute processing according to a program stored in the storage unit 24.

[0028] The control unit 22 may include the counting unit 22a and the analysis unit 22b. Each component of the control unit 22 may be a hardware module or a software module. The processing performed by each component can be executed by the control unit 22. In the following, the processing performed by each component may be described as being performed by the control unit 22.

[0029] The counting unit 22a acquires a muon detection signal from the photodetector 12 via the detection signal acquisition unit 21a. The counting unit 22a is configured to record the time at which the detection signal was acquired and to count the number of muon detections. The counting unit 22a may store the time at which the muon detection signal was acquired and the number of detections in the storage unit 24.

[0030] The analysis unit 22b estimates information regarding the ground density around the pipe material 10 based on the number of muons detected per unit time by the counting unit 22a, and the arrangement information of the scintillators 11, including the position, orientation, and size of each scintillator 11. The analysis unit 22b can estimate the ground density ρ above the scintillators 11. The method for estimating the ground density ρ is described below.

[0031] Muons, generated by cosmic rays approximately 10 km above the Earth's surface, travel through the atmosphere at near the speed of light and reach the Earth's surface 41. The number of muons raining down on the Earth's surface 41 per unit time, unit area, and unit solid angle is approximately constant. When muons enter the Earth's surface 51, they decay into electrons and neutrinos through interactions with surrounding atoms, reducing their number. The rate of decrease in muons depends on the density of the material they pass through and the distance they travel. Therefore, the rate of decrease per unit length in the direction of muon transmission is related to the density of the material along the muon's transmission path.

[0032] A flow of multiple muons is called a muon flux. In this embodiment, the unit area (cm²) of the muon flux incident from the vertical direction, i.e., from a direction of 90° to the ground surface 41, is ２ The number of muons per unit time (s) and unit solid angle (sr) is defined as the muon flux I.

[0033] The analysis unit 22b estimates the muon flux I for the scintillator 11 based on the number of muons measured per unit time and the arrangement information of the scintillator 11. In this case, all muons incident on the scintillator 11 are counted by the counting unit 22a, regardless of the direction in which they are incident on the scintillator 11. The analysis unit 22b estimates the muon flux I incident from the vertical direction based on the number of muons per unit time counted by the counting unit 22a and the average angular distribution of muons incident on the ground surface 41.

[0034] The muon flux I is the initial value I ００ It can be expressed by the following formula (1), which is obtained by multiplying by an attenuation rate corresponding to the surface density h of the ground 40, represented by exp(-Λ(h)).

[0035]

[0036] Here, according to Non-Patent Document 2, I ００ It is known that the density is 0.00723 ( / cm² / s / sr). The damping weighting function Λ(h) is determined based on various known conditions. According to this formula (1), the surface density h can be calculated from the estimated value of the muon particle flux I estimated by measurement. Furthermore, the control unit 22 can determine the ground density ρ of the ground 40 using the ground height D with the following formula (2): ρ = h / D (2)

[0037] Instead of estimating the ground density ρ, the analysis unit 22b may periodically monitor the number of muons counted by the counting unit 22a and measure the relative change in ground density over time. When the number of measured muons increases, the analysis unit 22b can estimate that the decay rate of the muons is decreasing, and therefore there is a possibility that the ground density is decreasing above the pipe material 10.

[0038] The analysis unit 22b can output the surface density h and ground density ρ obtained as a result of the analysis, as well as other information related to ground density, to the input / output unit 23 and store it in the storage unit 24.

[0039] The input / output unit 23 may include an input device for the user of the ground measurement system 1 to input instructions and information, and a display for the ground measurement system 1 to display measurement results. The input device may include a keyboard and mouse, etc. The display may be, for example, a liquid crystal display (LCD), an organic electro-luminescence (OLED) display, or an inorganic EL display. The input / output unit 23 may include a touch panel that detects input by contacting the surface of the display.

[0040] The storage unit 24 may be configured to include any one or more of, for example, a semiconductor memory, a magnetic memory, and an optical memory. The semiconductor memory may include a volatile memory and a non-volatile memory. The magnetic memory may include, for example, a hard disk. The optical memory may include, for example, a CD (Compact Disc), a DVD (Digital Versatile Disc), and a BD (Blu-ray (registered trademark) Disc), etc. The storage unit 24 may function as, for example, a main memory device, an auxiliary storage device, or a cache memory. The storage unit 24 may store information acquired by the information processing device 20, information processed by the information processing device 20, and information for operating the information processing device 20. The storage unit 24 may store a program for operating the control unit 22.

[0041] (Position detector) The position detector 30 is disposed within the manhole iron lid 43 and detects the accurate absolute position information of the ground surface 41 portion of the manhole 42 including the elevation. By specifying the accurate position of the manhole 42, the accurate position of the pipe material 10 connecting the manholes 42 can be specified. Further, by detecting the elevation of the ground surface 41 at the position of the manhole 42, considering the attenuation of mu particles by the atmosphere, the initial value I of the mu particle flux in the formula (1) ００ can be corrected. The position detector 30 may include, for example, a GNSS receiver corresponding to a Global Navigation Satellite System (GNSS). The position detector 30 can obtain information on the latitude, longitude, and elevation of the manhole 42 using signals from the GNSS receiver. GNSS includes, for example, GPS (Global Positioning System), GLONASS, Galileo, BeiDou, etc.

[0042] (Ground measurement method) With the above configuration, the information processing device 20 of the ground measurement system 1 can measure the ground density ρ above the scintillator 11. Based on the flowchart of FIG. 5, the procedure of the ground density measurement method executed by the control unit 22 of the information processing device 20 will be described. The process shown in FIG. 5 may be executed by the control unit 22 according to a program stored in the storage unit 24. The program can be stored in a non-temporary computer-readable medium.

[0043] First, the control unit 22 acquires, via the signal transceiver 21, the detection signal detected by the non-photodetector 12 when the mu particles pass through the scintillator 11 (step S1). The control unit 22 sequentially stores the time when the detection signal is acquired in the storage unit 24 and counts the number of detection signals acquired. The control unit 22 may store in the storage unit 24 the number of detection signals per unit time.

[0044] The control unit 22 may execute the processes after step S2 in real time in parallel with the acquisition of the detection signal. Alternatively, the control unit 22 may execute the processes after step S2 based on the information stored in the storage unit 24 after acquiring the detection signals for a certain period.

[0045] The control unit 22 estimates the mu particle flux I in the vertical direction with respect to the ground surface 41 based on the detection signal of the mu particles per unit time (step S2).

[0046] The control unit 22 substitutes the value of the mu particle flux I estimated in Equation (1) and calculates the surface density h of the ground (step S3). In Equation (1), the initial value I of the mu particle flux ００ may be corrected in consideration of the elevation of the ground surface 41 detected by the position detector 30.

[0047] The control unit 22 substitutes the value of the surface density h calculated in step S3 into Equation (2) and calculates the ground density ρ (step S4)

[0048] The control unit 22 stores the ground density ρ calculated in step S4 in the storage unit 24 and displays it on the display of the input / output unit 23 (step S5).

[0049] As described above, the ground measurement system 1 of this embodiment can estimate the ground density ρ above the scintillator 11 by counting the muon particles incident from the top of the scintillator 11 of each pipe material 10. In many cases, pipelines are buried underground beneath existing roads, so by using the pipe material 10 of this embodiment as the pipe material for the underground buried pipeline and performing measurements with the ground measurement system 1, it becomes possible to perform area-wide measurement of the ground density ρ.

[0050] Furthermore, in the ground measurement system 1, since the pipe material 10 has a configuration in which the scintillator 11 is included inside the pipe wall 13, it is not necessary to place a detection device equipped with a scintillator inside the pipe material 10 each time to measure muon particles. Therefore, the method of measuring ground density using the ground measurement system 1 can significantly reduce the effort and cost of measurement. Moreover, by incorporating the scintillator 11 into the pipe wall 13, the scintillator 11 can be made larger in the longitudinal direction of the pipe material 10. This allows for a larger number of muon particles to be detected, thus enabling more accurate measurements.

[0051] Furthermore, since the pipe 10 of the ground measurement system 1 has a scintillator 11 built into it, it is easy to repeatedly and periodically detect muon particles under the same conditions. Therefore, the ground measurement system 1 can be used to monitor the change in the number of detected muon particles over time and to estimate the change in ground density ρ above the pipe 10. In this case, it is not necessarily required to calculate a specific value for ground density ρ.

[0052] [Second Embodiment] Figure 6 shows the configuration of a ground measurement system 1A, which is an improvement over the ground measurement system 1 of Figure 4. In the ground measurement system 1A, the pipe material 10 is placed between two manholes 42A and 42B. A scintillator 11 is placed between both ends of the pipe material 10. In Figure 6, only one scintillator 11 is shown, but there may be multiple scintillators 11. Photodetectors 12A and 12B are placed at both ends of the scintillator 11 located in manholes 42A and 42B, respectively. In addition, relay devices 51A and 51B are placed in manholes 42A and 42B, respectively, to transmit the signals output from the photodetectors 12A and 12B to a single information processing device 20. The information processing device 20 may be placed in any location.

[0053] The control unit 22 of the information processing device 20 can measure the time difference between the time of light detection at photodetector 12A and the time of light detection at photodetector 12B. This time difference corresponds to the optical path difference from the position where the muon particle 5 passed through the scintillator 11 to photodetector 12A and to photodetector 12B. Therefore, based on this time difference, the control unit 22 can identify the position where the muon particle passed through the scintillator 11, which is the position in the longitudinal direction of the pipe material 10.

[0054] In the ground measurement system 1 shown in Figure 4, muon particles are detected using scintillators 11 arranged from end to end along the longitudinal direction of the pipe material 10 as the unit, so there was no resolution in the longitudinal direction, which is along the pipe material 10. In contrast, the ground measurement system 1A shown in Figure 6 can identify the position through which the muon particles 5 have passed in the longitudinal direction of the scintillator 11, making it possible to estimate the muon particle flux I according to the longitudinal position of the scintillator 11. Therefore, the ground measurement system 1A makes it possible to measure the change in ground density ρ along the longitudinal direction of the pipe material 10.

[0055] [Third Embodiment] A third embodiment will be described in which the pipe material 10 of the first embodiment is replaced with another pipe material 10A. Figures 7 and 8 show the configuration of the pipe material 10A. Other components are configured in the same way as in the first embodiment. In the cross-sectional view of Figure 7, the pipe material 10A has eight scintillators 11 arranged at 45-degree intervals in the circumferential direction. Also, in the side view of Figure 8, the pipe material 10A has one or more scintillators 11 divided into multiple sections in the longitudinal direction of the pipe material 10A and arranged apart from each other. In the example of Figure 8, one or more scintillators 11 are divided into three groups in the longitudinal direction of the pipe material 10A. Each scintillator 11 is connected directly or via a light guide to a photodetector 12 located at the end 15 of the pipe material 10. The same number of photodetectors 12 as the number of scintillators 11 are located at the end 15 of the pipe material 10. The number of scintillators 11 in the circumferential direction and the number of divisions in the longitudinal direction shown in Figures 7 and 8 are merely illustrative. The number of divisions in the circumferential direction and the number of divisions in the longitudinal direction of the scintillator 11 can be arbitrarily selected.

[0056] In the pipe material 10A, each scintillator 11 is paired with another scintillator 11 of the same group, separated by a cavity 14. Figure 9 shows the same pipe material 10A as in Figures 7 and 8, embedded in the ground 40. As shown in Figure 9, scintillators 11a, 11b, 11c, and 11d are paired with scintillators 11e, 11f, 11g, and 11h, respectively. Since muons 5 move at high speed, muons 5 passing through the paired scintillators 11a and 11e are detected substantially simultaneously by the respective photodetectors 12 connected to scintillators 11a and 11e. Therefore, when muons 5 are detected substantially simultaneously by scintillators 11a and 11e, it can be seen that the muons 5 were incident from the direction connecting scintillators 11a and 11e. In the example shown in Figure 9, only muons incident from directions within the range of a solid angle Ω centered in the vertical direction are measured substantially simultaneously by scintillators 11a and 11e. Furthermore, for example, muons incident at an oblique angle to the horizontal plane can be detected by using scintillators 11b and 11f, and scintillators 11d and 11h.

[0057] The detection signals of muons detected by the photodetector 12 are input to the information processing device 20 and processed by the counting unit 22a via the detection signal acquisition unit 21a. The counting unit 22a can pass information on the number of muons for each direction of incidence to the analysis unit 22b by counting the detection signals of muons detected substantially simultaneously by the pair of scintillators 11. The analysis unit 22b can then estimate the ground surface density h and ground density ρ for each direction of incidence of the muons.

[0058] In this way, by pairing two scintillators 11, it is possible to distinguish, count, and analyze the number of muons incident from different directions. Furthermore, since it is possible to measure the surface density h and ground density ρ in directions other than those perpendicular to the ground surface 41 when viewed from the pipe 10A, the measurement range of ground density ρ can be extended by using the pipe 10A.

[0059] Furthermore, the pipe material 10A includes multiple scintillators 11 divided into multiple rows in the longitudinal direction of the pipe material 10A. This makes it possible to distinguish and detect muons in different ranges along the direction of the pipe material 10A. In other words, by using the pipe material 10A shown in Figures 7 to 9, the resolution of the ground density measurement in the longitudinal direction of the pipe material 10A can be increased without having to place photodetectors 12 at both ends of the scintillators 11 as in Figure 6 and measure minute time differences in detection times.

[0060] Furthermore, the counting unit 22a may count detection signals simultaneously acquired from photodetectors 12 connected to two scintillators 11 belonging to the same group divided along the longitudinal direction of the pipe material 10A, as well as from two scintillators 11 belonging to different groups. This allows the counting unit 22a to detect not only muons 5a incident at an angle nearly perpendicular to the longitudinal direction of the pipe material 10A in Figure 8, but also muons 5b arriving at an oblique angle to the longitudinal direction of the pipe material 10A, distinguishing between their incident directions.

[0061] Note that the tube material 10A in Figure 8 includes multiple scintillators 11 but does not include a photodetector 12 inside. However, in other configuration examples shown in Figure 10, the tube material 10B may be configured to include a photodetector 12 inside the tube wall 13. In this case, a photodetector 12 is placed at the end of each scintillator 11. Furthermore, signal lines are provided inside the tube wall 13 of the tube material 10B to output detection signals from each photodetector 12 to electrodes at the end 15 of the tube material 10B. The electrodes at the end 15 of the tube material 10B are connected to the information processing device 20 via a multiplexer 50 or the like.

[0062] [Fourth Embodiment] In the above embodiments, the pipe material of the underground buried conduit was configured to have a scintillator inside the pipe wall. In this embodiment, the underground buried conduit 60 includes an inner pipe 61, and the scintillator 63 is provided in the inner pipe 61. The other configurations are the same as in the first embodiment. Figure 11 is a cross-sectional view of an underground buried conduit 60 on which multiple cables 62 are installed. The cables 62 are, for example, communication cables. Although only one cable 62 is shown in Figure 11, multiple cables 62 may be arranged in the underground buried conduit 60.

[0063] The underground buried conduit 60 is provided with the pipe material of this disclosure having a scintillator 63 as an inner pipe 61 that has a protective function for the cable 62. The inner pipe 61 has the function of securing space for the installation of the cables 62 and preventing the cables 62 from coming into contact with each other when multiple cables 62 are installed in the underground buried conduit 60.

[0064] The inner pipe 61 is made of a plastic such as polyethylene, and a cable protection function can be provided by using a plastic scintillator 63 with equivalent mechanical properties. In this way, similar to the pipe material 10 described using Figures 1 to 4, muon particles can be detected using the scintillator 63 provided on the inner pipe 61, and the ground density ρ above the underground buried pipeline 60 can be measured.

[0065] Although the embodiments described above are representative examples, it will be apparent to those skilled in the art that many modifications and substitutions are possible within the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited by the embodiments and examples described above, and various modifications and / or changes are possible without departing from the scope of the claims. For example, it is possible to combine multiple component blocks described in the embodiments and examples into one, or to divide one component block.

[0066] The following additional information is disclosed regarding the embodiments described above.

[0067] (Note 1) A pipe material to be buried underground, comprising one or more scintillators arranged inside the pipe wall. (Note 2) The pipe material according to claim 1, wherein the one or more scintillators include a plurality of sets of scintillators arranged opposite each other with a cavity in between the pipe material. (Note 3) The pipe material according to claim 1 or 2, wherein the one or more scintillators include a plurality of scintillators arranged spaced apart from each other in the longitudinal direction of the pipe material. (Note 4) A ground measurement system comprising: a pipe material to be buried underground, comprising one or more scintillators arranged inside the pipe wall; a photodetector for detecting light output from each of the one or more scintillators; and an information processing device including a control unit that estimates information regarding the ground density around the pipe material by analyzing the frequency of muons passing through the pipe material based on the detection signal of the light output from each of the scintillators by the photodetector and the arrangement information of each of the scintillators.

[0068] 1, 1A Ground measurement system 10, 10A Piping (pipe material) 11 Scintillator 12, 12A, 12B Photodetector 13 Pipe wall 14 Cavity 15 End 20 Information processing device 21 Signal transmission / reception unit 21a Detection signal acquisition unit 21b Position information acquisition unit 22 Control unit 22a Counting unit 22b Analysis unit 23 Input / output unit 24 Storage unit 30 Position detector 40 Ground 41 Ground surface 42, 42A, 42B Manhole 43 Manhole iron cover 50 Multiplexing device 51A, 51B Relay device 60 Underground buried pipeline 61 Inner pipe 62 Cable 63 Scintillator D Ground height

Claims

1. A pipe material buried underground, comprising one or more scintillators arranged inside the pipe wall.

2. The pipe material according to claim 1, wherein the one or more scintillators include a plurality of sets of scintillators arranged opposite each other with a hollow portion of the pipe material in between.

3. The pipe material according to claim 1 or 2, wherein the one or more scintillators include a plurality of scintillators that are spaced apart from each other in the longitudinal direction of the pipe material.

4. A ground measurement system comprising: a pipe material buried underground, having one or more scintillators arranged inside the pipe wall; a photodetector for detecting light emitted from each of the one or more scintillators; and an information processing device including a control unit for estimating information regarding the ground density around the pipe material based on the detection signal from the photodetector and the arrangement information of each of the scintillators.

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