JP2023062772A - Sediment characteristics measuring device - Google Patents

Abstract

To provide sediment property measuring device capable of accurately and safely measuring in real time the property of sediment filled in a chamber.SOLUTION: A sediment characteristics measuring device for measuring the sediment characteristics filled in a chamber 2 formed between a cutter head and a partition wall 8 in a shield machine comprises an opening closing lid 30 having a radiation transmitting surface 31 closing an opening formed in the partition wall 8, and a density measuring device 40 that measures the wet density ρt of sediment filled in the chamber 2 using gamma rays. The radiation transmitting surface 31 is formed with a projecting portion 33 of a cylindrical body projecting into the chamber. The density measuring device 40 comprises a gamma ray source 411 mounted on the inside of the radiation transmitting surface 31, and a gamma ray detector 421 arranged in the projecting portion 33 for detecting the radiation dose of gamma rays emitted from the gamma ray source 411.SELECTED DRAWING: Figure 3

Description

The present invention relates to a sediment characteristic measuring device for measuring the sediment characteristics filled in the chamber of a shield machine.

In the earth pressure shield construction method, the chamber (the space between the face and the bulkhead) is filled with earth and sand excavated by the cutter on the front of the shield, and by maintaining the pressurized state of the filled earth and sand, excavation is carried out while stabilizing the face. , is a construction method in which soil is discharged by a screw conveyor that is installed through the bulkhead.

In the earth pressure shield construction method, the main purpose is to give fluidity and water stoppage to the earth and sand filled in the chamber. ) is injected from the front of the cutter or the partition wall. In order for the injected additive material to impart fluidity and water stoppage to the soil in the chamber, it must be surely mixed with the excavated soil. In particular, when air bubbles are used as an additive, it is assumed that the injected air bubbles may leak out to the surrounding ground when the ground has high water permeability. When air bubbles leak out, not only is it impossible to ensure the fluidity of the sediment in the chamber, but the leaked air bubbles may float up to the bottom of the impermeable layer, creating cavities in the ground.

In the management of the amount of air bubbles added (understanding the amount of air bubbles leaking from the ground), the amount of air bubbles injected into the earth and sand (Input) can be managed and grasped. Output) is unknown. As a method for grasping the air bubble mixture amount of the actual excavated earth and sand, there is also an idea to measure the air bubble mixture amount of the earth and sand discharged from the screw conveyor. In this case, since the bubbles injected into the pressurized chamber are released to the atmospheric pressure, the expansion of the bubbles causes a change in volume and dissipation into the atmosphere due to breakage of the bubbles. It is not possible to measure the correct amount of air bubbles mixed.

In the earth pressure shield construction method, it is important to manage the amount of excavated/discharged soil. In the unlikely event that more earth and sand than planned is excavated/discharged, loosening and cavities will occur inside the ground, increasing the risk of subsidence of the ground surface.

In order to manage the amount of excavated/discharged soil, the “planned excavated soil volume” is calculated from the excavation cross-sectional area and excavation length, and the product of the soil density obtained from the soil survey results and the planned excavated soil volume. Calculate the “planned weight of excavated soil” from the above. After that, the weight and volume of the earth and sand discharged from the screw conveyor are measured and compared with the planned values to verify the adequacy of the amount of excavated/discharged earth and sand. However, if the density of the actual excavated ground differs from the representative value obtained from the results of the ground investigation due to the effects of excavating alternate layers, etc., correct weight evaluation cannot be performed. In addition, since the sediment in the ground under pressure and the sediment released to the atmospheric pressure have different densities, it is difficult to accurately evaluate the volume. In addition, when bubbles are used as the additive, volume evaluation becomes more difficult due to the expansion action of the bubbles under atmospheric pressure.

In order to improve the accuracy of the amount of air bubble addition and excavated/discharged soil management, it is necessary to accurately grasp the air bubble mixture amount and density of the soil in the chamber under the same pressurized conditions as in the ground. be. Therefore, a technique has been proposed in which a pipe for sampling the soil in the chamber is provided in the partition wall and the density of the soil under pressure is measured (see, for example, Patent Document 1).

JP 2016-69822 JP-A-3-233095

However, with the method of Patent Document 1, continuous data collection is difficult, so the sediment density cannot be grasped in real time. In addition, in the case of a layer of gravel with low fluidity, it is assumed that it will be difficult for sediment to flow into the cylinder. becomes difficult.

Further, in the slurry shield construction method, a technique for measuring the density of earth and sand in a chamber using a scattering-type gamma-ray densitometer has been proposed (see, for example, Patent Document 2). However, the scattering type gamma ray density meter has lower measurement accuracy than the transmission type. Furthermore, in Patent Document 2, since the radiation source protrudes into the chamber, it is feared that the radiation source may interfere with the kneading rod provided on the cutter head, causing an accident in which the radiation source is lost in the chamber.

The present invention has been made in view of such circumstances, and solves the above-mentioned problems, and is an earth and sand characteristic measuring device capable of accurately and safely measuring the characteristics of earth and sand filled in a chamber in real time. is to provide

A soil characteristic measuring device according to the present invention is a soil characteristics measuring device for measuring characteristics of soil filled in a chamber formed between a cutter head and a partition in a shield tunneling machine. and a density measuring device for measuring the wet density of soil filled in the chamber using gamma rays. A protruding part of a cylindrical body protruding inward is formed, and the density measuring device measures a gamma ray source mounted on the inner side of the radiation transmitting surface and a radiation dose of the gamma ray emitted from the gamma ray source. and a gamma ray detector arranged in the protrusion for detecting.
Furthermore, in the sediment property measuring device of the present invention, the radiation transmitting surface may be thinner than the partition wall.
Furthermore, in the sediment property measuring device of the present invention, the gamma ray source and the gamma ray detection unit may be arranged at a predetermined interval across the center of the radiation transmitting surface in a plan view of the radiation transmitting surface. .
Further, in the sediment property measuring device of the present invention, the projecting angle of the projecting portion is such that the gamma ray detecting portion disposed inside is inclined in a direction facing the gamma ray source in the direction perpendicular to the radiation transmitting surface. Also good.
Furthermore, in the sediment property measuring device of the present invention, even if a scattering type moisture measuring device for measuring the water content of the sediment filled in the chamber using a neutron beam is attached to the inside of the radiation transmitting surface good.
Furthermore, in the soil property measuring device of the present invention, the moisture measuring device may be mounted between the gamma ray source and the gamma ray detector in a plan view of the radiation transmitting surface.

According to the present invention, the gamma ray source disposed inside the machine and the gamma ray detector in the protruding portion face each other with the earth and sand in the chamber interposed therebetween, thereby forming a transmission type density measuring device. , the characteristics of the earth and sand filled in the chamber can be accurately and safely measured in real time.

1 is a configuration diagram showing the configuration of a shield machine equipped with an embodiment of a soil characteristic measuring device according to the present invention; FIG. FIG. 2 is a plan view showing the configuration of the soil characteristic measuring device shown in FIG. 1; FIG. 3 is a cross-sectional view taken along the line XX shown in FIG. 2; 1. It is a figure which shows the experimental example of the earth-and-sand characteristic measuring apparatus shown in FIG. It is a figure which shows the example of a measurement of the experimental apparatus shown in FIG. It is a figure which shows the modification of the earth-and-sand characteristic measuring apparatus shown in FIG.

Next, modes for carrying out the present invention (hereinafter simply referred to as "embodiments") will be specifically described with reference to the drawings.

A soil characteristic measuring device 20 of the present embodiment is a device for measuring the characteristics of excavated soil filled in the chamber 2 of the shield machine 1 shown in FIG. The shield machine 1 is an earth pressure type shield machine, and includes a cylindrical skin plate 3 and a cutter head 4 rotatably attached to the tip of the skin plate 3 in the traveling direction. A rotating ring 5 is rotatably supported on the front portion of the skin plate 3 via a bearing portion such as a bearing. The rotating ring 5 is connected to the cutter head 4 via a connecting beam 6 . A plurality of cutter turning motors 7 for rotating the rotating ring 5 are mounted on the skin plate 3 . Accordingly, when the cutter turning motor 7 is rotationally driven, the cutter head 4 is rotated via the connecting beam 6 .

The skin plate 3 is provided with a steel plate partition 8 located behind the cutter head 4 , and the chamber 2 is formed between the cutter head 4 and the partition 8 . The chamber 2 is a space filled with the earth and sand excavated by the cutter head 4, and the partition wall 8 separates the chamber 2 filled with the excavated earth and sand from the machine interior 9 where the operator enters.

The shield excavator 1 also includes an excavating additive injection pipe 10 that penetrates the partition wall 8 and supplies an additive (clay, bentonite, air bubbles, water-soluble polymer, etc.) to the front surface of the cutter head 4 and the chamber 2. there is For the purpose of imparting fluidity and water stoppage to the earth and sand filled in the chamber 2, the additive is used in accordance with the ground conditions.

The earth and sand excavated by the cutter head 4 fills the chamber 2 as mud, is agitated by the kneading rod 11 provided with the cutter head 4, and then conveyed rearward by the screw conveyor 12.

2 and 3, the sediment characteristic measuring device 20 includes a steel plate opening closing lid 30 that closes the opening 13 formed in the partition wall 8, a transmission type density measuring device 40, and a scattering type moisture measuring device. A density measuring device 40 and a moisture measuring device 50 are attached to the opening closing lid 30 to form a unit.

The partition wall 8 forming the chamber 2 generally has a steel plate thickness of about 40 to 60 mm, and measurement using a general radiation (gamma ray or neutron ray) source is difficult. Therefore, in this embodiment, the sediment characteristic measuring device 20 is installed in the circular opening 13 (about 500 mm in diameter) formed after reinforcing the partition wall 8 .

The opening blocking lid 30 includes a radiation transmitting surface 31 having substantially the same shape (disk shape) as the opening 13 formed in the partition wall 8, a forehead portion 32 extending from the periphery of the radiation transmitting surface 31, and a radiation transmitting surface 31. and a protrusion 33 protruding into the chamber 2 .

The radiation transmitting surface 31 functions as an opening closing portion that closes the opening 13 formed in the partition wall 8 . The radiation transmitting surface 31 closes the opening 13 formed in the partition wall 8 by fastening the forehead portion 32 to the peripheral edge portion of the opening 13 formed in the partition wall 8 via packing with a bolt or the like. Fixed.

The steel plate thickness of the radiation transmitting surface 31 is thinner than the steel plate thickness of the partition wall 8 (for example, about 25 mm). That is, since the radiation transmitting surface 31 only needs to have the strength to block the small-area opening 13 formed in the partition wall 8, the steel plate thickness of the radiation transmitting surface 31 is made thinner than the steel plate thickness of the partition wall 8. be able to.

The protruding part 33 is a cylindrical body that protrudes in the vertical direction of the radiation transmitting surface 31, has a closed end that protrudes into the chamber 2, and is open to the inside of the machine. The projecting portion 33 is formed at a position shifted from the center of the radiation transmitting surface 31 . Further, the projecting portion 33 is sized and positioned so as not to come into contact with the kneading rod 11 provided with the cutter head 4 .

The density measuring device 40 includes a gamma ray source unit 41 that emits gamma rays to the chamber 2 through the radiation transmitting surface 31, and a gamma ray measuring unit 42 that obtains the wet density ρ _t of the soil from the radiation dose of the received gamma rays. there is

The gamma ray source unit 41 includes a gamma ray source 411 that emits gamma rays, and a cover 412 that shields the gamma rays emitted from the gamma ray source 411 from being emitted toward the cabin 9 side. The radiation transmitting surface 31 is mounted so that the gamma ray emitting surface is in contact with the inside 9 side of the radiation transmitting surface 31 . That is, the gamma ray source 411 is arranged on the aircraft interior 9 side, and gamma rays emitted from the gamma ray source 411 are radiated into the chamber 2 through the radiation transmitting surface 31 . Since the radiation transmitting surface 31 is made thin, a gamma ray source 411 with low intensity can be used.

The gamma ray measurement unit 42 includes a gamma ray detection unit 421 that detects the radiation dose of gamma rays, and a density calculation unit 422 that calculates the wet density ρ _t of sand and sand based on the detection value of the gamma ray detection unit 421. The gamma ray detection unit 421 is configured as a rod-shaped body having a The gamma ray measuring unit 42 is composed of a sodium iodide (NaI) scintillation detector, a germanium (Ge) semiconductor detector, or the like, and is installed inside the machine so that the gamma ray detecting unit 421 is positioned in the protrusion 33 that protrudes into the chamber 2 . It is inserted into the hollow portion of the projecting portion 33 from the 9 side and attached to the opening closing lid 30 .

As a result, the gamma ray detector 421 faces the gamma ray source 411 with the earth and sand in the chamber 2 interposed therebetween, and the transmission type density measuring device 40 is configured. Accordingly, since the density measuring device 40 functions as a transmission type, it can measure the wet density ρ _t with higher accuracy than a scattering type.

The relative positions of the gamma ray source 411 and the gamma ray detector 421 are arranged at an angle of 90 degrees, unlike the measurement method of a general gamma ray density meter. This was confirmed by the experiments described below.

Referring to FIG. 4, a sample 61 to be measured is placed in a steel plate soil tank 60, and the gamma ray source unit 41 and the gamma ray measurement unit 42 are positioned at a relative angle of 90° using the side wall corner of the steel plate soil tank 60. The experiment was conducted by arranging it in the position. The steel plate thickness of the steel plate earth tank 60 is 25 mm at the location where the gamma ray source unit 41 is arranged and 22 mm at the location where the gamma ray measurement unit 42 is arranged. Also, the gamma ray source 411 of the gamma ray source unit 41 and the gamma ray detection unit 421 of the gamma ray measurement unit 42 were arranged at 200 mm from the side wall corner.

Water (substantial wet density: 1.000 g/cm ³ ), sandy soil (substantial wet density: 1.588 g/cm ³ ), and cohesive soil (substantial wet density: 1.755 g/cm ³ ) were prepared as the sample 61 to be measured. , the radiation count rate was measured by the gamma ray detection unit 421, and the radiation count rate ratio (radiation count rate/standard count rate) was obtained.

FIG. 5(a) shows the measurement results. The radiation count rate is a value excluding the background. Also, the standard counting rate is a value considering the measurement date (half-life) from the reference value of the gamma ray source 411 .

As a result, as shown in FIG. 5(b), a very high correlation (decision coefficient R ² =0.9792) can be confirmed between the radiation count rate ratio and the real wet density. Even when the gamma ray source 411 and the gamma ray detection unit 421 of the gamma ray measurement unit 42 are arranged at a relative angle of 90°, it is found that the wet density of the measurement target sample 61 can be calculated from the measurement result of the radiation count rate. rice field.

The gamma ray source 411 and the gamma ray detector 421 are arranged at a predetermined interval with the center of the radiation transmitting surface 31 interposed therebetween in the plan view of the opening closing lid 30 shown in FIG. That is, the mounting position of the gamma ray measuring unit 42 (gamma ray source 411) and the forming position of the protruding portion 33 (gamma ray detecting unit 421) are arranged with the center of the radiation transmitting surface 31 interposed therebetween. As a result, the area of the radiation transmitting surface 31 (the area of the opening 13 formed in the partition wall 8) can be reduced, which contributes to making the radiation transmitting surface 31 thinner.

The water content measuring device 50 includes a neutron beam source 51 that transmits neutron beams to the chamber 2 via the radiation transmitting surface 31, and the water content _ρm of the sediment from the radiation dose of the neutron beams received via the radiation transmitting surface 31. A desired neutron beam measuring unit 52 is provided. The water content _ρm indicates the mass of water contained in a unit volume of earth and sand. The moisture measurement device 50 has an integral structure in which a neutron beam source 51 and a neutron beam measurement unit 52 are enclosed in a cover 53 that shields radiation of neutron beams to the machine interior 9 side. In the moisture measuring device 50, the neutron radiation surface from which the neutron beam from the neutron beam source 51 is emitted and the neutron receiving surface from which the neutron beam measurement unit 52 receives the neutron beam are located on the inside 9 side of the radiation transmitting surface 31. is mounted so as to abut on the

The moisture measuring device 50 is mounted between the gamma ray source 411 and the gamma ray detector 421 in the plan view of the opening closing lid 30 shown in FIG. It is placed at a position to measure the water content ρ _m of the soil. In other words, the density measuring device 40 and the moisture measuring device 50 measure the same area of soil.

By using the wet density ρ _t measured by the density measuring device 40 and the water content ρ _m measured by the moisture measuring device 50, the air mixing rate Va/V of the air volume Va in the soil volume V can be calculated. That is, if the soil particle density that can be assumed to be approximately 2.6 to 2.7 g/cm ³ is _ρs , the air mixing rate Va/V can be calculated by the following equation.
Va/V=1- _ρm- ( _ρt - _ρm )/ _ρs

Since the density measuring device 40 and the moisture measuring device 50 measure the same region of soil, the air mixing ratio Va/V calculated using the wet density ρ _t and the water content ρ _m is also accurate. value.

In the present embodiment, the projecting portion 33 is configured to project in the vertical direction of the radiation transmitting surface 31, but the gamma ray detecting portion 421 arranged in the projecting portion 33 is interposed by the earth and sand in the chamber 2. The projection angle of the projecting portion 33 is not particularly limited as long as it faces the gamma ray source 411 in this state. For example, as shown in FIG. 6, the projection angle of the projecting portion 33 may be inclined in the direction in which the gamma ray detecting portion 421 disposed inside faces the gamma ray source 411 and the radiation transmitting surface 31 in the vertical direction. In this case, since the radiation amount of gamma rays reaching the gamma ray detector 421 increases, a gamma ray source 411 with a lower intensity can be used.

Generally, when installing an RI measuring instrument that uses a radioactive isotope (RI) such as the density measuring device 40 or the moisture measuring device 50 at the construction site, the thickness of the intervening steel plate and the radiation source and the relative position of the detector is different. Therefore, it is necessary to actually measure the relationship between the radiation count amount of the detector and the physical quantity (density and water content) of the earth and sand before using the measuring instrument, and then create a calibration curve.

In contrast, in this embodiment, the density measuring device 40 and the moisture measuring device 50 are attached to the opening closing lid 30 to form a unit. Therefore, the thickness of the intervening steel plate (radiation transmitting surface 31) and the relative position between the radiation source (gamma ray source 411, neutron beam source 51) and the detection unit (gamma ray detection unit 421, neutron beam measurement unit 52) are determined in advance. be. Therefore, after preparing a calibration curve in advance, the earth/sand characteristics measuring device 20 can be attached to the shield machine 1, and the attachment work can be greatly simplified.

In addition, by unitizing the earth and sand characteristic measuring device 20, even if the size and structure of the shield machine 1 are different, the earth and sand characteristic measuring device can be easily installed by installing a predetermined opening 13 in the partition wall 8. 20 can be attached, improving versatility.

As described above, the present embodiment is a soil characteristic measuring device 20 for measuring the characteristics of soil filled in the chamber 2 formed between the cutter head 4 and the partition wall 8 in the shield machine 1. , an opening closing lid 30 having a radiation transmitting surface 31 for closing the opening 13 formed in the partition wall 8, and a density measuring device 40 for measuring the wet density ρ _t of the soil filled in the chamber 2 using gamma rays. , and the radiation transmitting surface 31 is formed with a cylindrical projecting portion 33 projecting into the chamber, and the density measuring device 40 is equipped with a gamma ray source 411 mounted on the inside of the radiation transmitting surface 31. , and a gamma ray detector 421 arranged in the protrusion 33 for detecting the radiation dose of gamma rays emitted from the gamma ray source 411 .
With this configuration, the gamma ray detection unit 421 is opposed to the gamma ray source 411 arranged on the inside 9 side with the sand in the chamber 2 interposed therebetween, and the transmission type density measurement device 40 is configured. The characteristics of the earth and sand filled in the chamber 2 can be accurately and safely measured in real time. In addition, since the opening blocking lid 30 and the density measuring device 40 are unitized, the sediment property measuring device 20 can be attached to the shield machine 1 after preparing a calibration curve in advance, which greatly reduces the installation work. is simplified to

Furthermore, in this embodiment, the radiation transmitting surface 31 is made thinner than the partition wall 8 .
This configuration allows the use of a low intensity gamma ray source 411 .

Furthermore, in the present embodiment, the gamma ray source 411 and the gamma ray detector 421 are arranged at a predetermined interval across the center of the radiation transmitting surface 31 when the radiation transmitting surface 31 is viewed from above.
With this configuration, the area of the radiation transmitting surface 31 (the area of the opening 13 formed in the partition wall 8) can be reduced, and the thickness of the radiation transmitting surface 31 can be reduced.

Furthermore, in this embodiment, the projection angle of the projecting portion 33 is such that the gamma ray detecting portion 421 disposed inside faces the gamma ray source 411 in the vertical direction of the radiation transmitting surface 31 .
With this configuration, the radiation amount of gamma rays reaching the gamma ray detection unit 421 is increased, so a gamma ray source 411 with a lower intensity can be used.

Furthermore, in the present embodiment, a scattering-type moisture measuring device 50 that measures the moisture content _ρm of the soil filled in the chamber 2 using neutron beams is mounted inside the radiation transmitting surface 31 .
With this configuration, the wet density ρ _t and the water content ρ _m of the earth and sand filled in the chamber 2 can be measured, so the air mixing ratio Va/V can be calculated using the wet density ρ _t and the water content ρ _m . Also when using air bubbles as an additive, the amount of air bubbles mixed can be evaluated in real time.

Furthermore, in the present embodiment, the moisture measuring device 50 is mounted between the gamma ray source 411 and the gamma ray detector 421 in plan view of the radiation transmitting surface 31 .
With this configuration, the density measuring device 40 and the moisture measuring device 50 measure the sediment in the same area, so the wet density ρ _t and the water content ρ _m are used to calculate an accurate air mixing ratio Va/V. can do.

The present invention has been described above based on the embodiments. It should be understood by those skilled in the art that this embodiment is an example, and that various modifications can be made to the combination of each component, etc., and that such modifications are also within the scope of the present invention.

1 Shield Machine 2 Chamber 3 Skin Plate 4 Cutter Head 5 Rotating Ring 6 Connection Beam 7 Cutter Rotation Motor 8 Partition Wall 9 Machine Inside 10 Excavation Additive Injection Pipe 11 Mixing Rod 12 Screw Conveyor 13 Opening 20 Earth and Sand Characteristic Measuring Device 30 Opening Blocking Lid 31 Radiation transparent surface 32 Forehead 33 Projection 40 Density measuring device 41 Gamma ray source 42 Gamma ray measuring unit 50 Moisture measuring device 51 Neutron ray source 52 Neutron ray measuring unit 53 Cover 411 Gamma ray source 412 Cover 421 Gamma ray detector 422 Density calculator

A soil characteristic measuring device according to the present invention is a soil characteristics measuring device for measuring characteristics of soil filled in a chamber formed between a cutter head and a partition in a shield tunneling machine. and a density measuring device for measuring the wet density of soil filled in the chamber using gamma rays. A protruding part of a cylindrical body protruding inward is formed, and the density measuring device measures a gamma ray source mounted on the inner side of the radiation transmitting surface and a radiation dose of the gamma ray emitted from the gamma ray source. a gamma ray detection unit disposed within the protrusion for detecting, wherein the projection angle of the protrusion is such that the gamma ray detection unit disposed inside faces the gamma ray source in a direction perpendicular to the radiation transmitting surface. It is characterized by being tilted in a direction .
Further, the earth and sand characteristic measuring apparatus of the present invention is an earth and sand characteristic measuring apparatus for measuring the characteristics of earth and sand filled in a chamber formed between a cutter head and a partition in a shield machine, wherein and a density measuring device for measuring the wet density of the soil filled in the chamber using gamma rays, wherein the radiation transmitting surface has , a projecting portion of a cylindrical body projecting into the chamber is formed, and the density measuring device includes a gamma ray source mounted on the inner side of the radiation transmitting surface, and the gamma ray radiation emitted from the gamma ray source. a gamma ray detector arranged in the projecting portion for detecting the amount of water, and a scattering type moisture measuring device for measuring the moisture content of the soil filled in the chamber using a neutron beam on the radiation transmitting surface. It is characterized by being installed inside the aircraft.
Furthermore, in the soil property measuring device of the present invention, the moisture measuring device may be mounted between the gamma ray source and the gamma ray detector in a plan view of the radiation transmitting surface.
Furthermore, in the soil property measuring device of the present invention, the radiation transmitting surface may be thinner than the partition wall.
Furthermore, in the sediment property measuring apparatus of the present invention, the gamma ray source and the gamma ray detection unit may be arranged at a predetermined interval across the center of the radiation transmitting surface in a plan view of the radiation transmitting surface. .

Claims (6)

A soil characteristics measuring device for measuring characteristics of soil filled in a chamber formed between a cutter head and a bulkhead in a shield machine,
an opening closing lid having a radiation transmitting surface that closes the opening formed in the partition;
a density measuring device that measures the wet density of the soil filled in the chamber using gamma rays,
The radiation transmitting surface is formed with a projecting portion of a cylindrical body projecting into the chamber,
The density measuring device includes a gamma ray source mounted on the inner side of the radiation transmitting surface, and a gamma ray detector arranged in the protruding portion for detecting the radiation dose of the gamma rays emitted from the gamma ray source. A sediment characteristic measuring device, comprising: 2. The sediment property measuring apparatus according to claim 1, wherein said radiation transmitting surface is thinner than said partition wall. 3. The gamma ray source and the gamma ray detector according to claim 1, wherein the gamma ray source and the gamma ray detector are arranged at a predetermined interval across the center of the radiation transmissive surface in plan view of the radiation transmissive surface. Sediment characteristics measuring device. 4. The projection angle of the projecting portion is such that the gamma ray detecting portion arranged inside is inclined in a direction facing the gamma ray source in a direction perpendicular to the radiation transmitting surface. The earth and sand characteristic measuring device according to any one of the above. 5. The apparatus according to any one of claims 1 to 4, wherein a scattering type moisture measuring device for measuring the moisture content of the earth and sand filled in the chamber using a neutron beam is mounted on the inside of the radiation transmitting surface. The earth and sand characteristic measuring device according to . 6. The sediment property measuring device according to claim 5, wherein said moisture measuring device is mounted between said gamma ray source and said gamma ray detector in plan view of said radiation transmitting surface.

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