JP4704607B2 - Centrifugal loading device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a centrifugal loading device for performing various strength experiments by applying a required centrifugal acceleration to a test material such as ground or rock body, and in particular, a function capable of investigating a crack propagation mechanism due to freezing pressure of a rock body. The present invention relates to a centrifugal loading device provided with
[0002]
[Problems to be solved by the invention]
Regarding large-scale rock collapse accidents that occur in snowy and cold regions such as Hokkaido, it is considered that one of the common causes of these accidents is the progress of cracks due to the weight of the rock mass, groundwater pressure, freezing pressure, etc.
[0003]
That is, the steep cliff slopes located on the coast of the Sea of Japan, such as Hokkaido, have many slopes composed of water-cooled crushed rocks made by lava being rapidly cooled in water. Water-cooled crushed rocks are said to be homogeneous but brittle and have few cracks. If cracks develop on such steep hill slopes for some reason, there is a possibility that a relatively large collapse will occur due to the connection of few cracks on the back of the slope. For this reason, it is important to investigate the mechanism of crack propagation from the viewpoint of rock dynamics.
[0004]
Conventionally, however, there has not been an experimental device capable of simulating the progress of a crack in such a rock mass, and therefore, the mechanism of the crack propagation has hardly been investigated.
[0005]
The present invention has been made in view of such circumstances, and is suitable for carrying out a simulation experiment on the elucidation of the mechanism of crack propagation, one of the causes of large-scale rock collapse in a snowy cold region, on an indoor scale. The purpose is to provide equipment.
[0006]
[Means for Solving the Problems]
An apparatus of the present invention that achieves the above object includes a vertical rotating shaft, a rotating body that rotates horizontally around the rotating shaft, and a sample container supported by the rotating body. In the centrifugal loading device for applying a predetermined centrifugal acceleration to the stored test material, a refrigeration system is provided in the sample container, the test material in the container can be frozen in a state of applying the centrifugal acceleration, and the rotating body is It is formed in a disk shape that rotates horizontally around the rotation axis, and the sample container for storing the test material is installed inside the disk-shaped rotating body and supported by the horizontal beam that constitutes the rotating body. The gist is a centrifugal loading device installed horizontally through a slide base movable in the horizontal direction .
[0007]
Here, the centrifugal loading device is a device that can impart centrifugal acceleration to the test object. The weight of a substance in the gravitational acceleration field on the earth as is known is obtained by multiplying the mass by the gravitational acceleration. This is obvious when seen in the SI unit system, and the weight of a substance with a mass of 1 kg is 9.81 kgm / sec ² = 9.81 N multiplied by the gravitational acceleration G = 9.81 m / sec ² . If this is mounted on a centrifugal loading device and given, for example, a centrifugal acceleration of 100 times of gravitational acceleration, the weight becomes 981 N of 100 times in the centrifugal acceleration field.
[0008]
The present invention utilizes the above principle of a centrifugal loading device, and freely increases the weight of a solid test material such as a rock body, generates tensile stress or shear stress due to the weight of the solid test material. It is intended to investigate the effects of these factors on crack growth and rock fracture, making it possible to conduct experiments in which freezing pressure acts.
[0009]
In the centrifugal loading device of the present invention, the refrigeration system is provided in the sample container in order to allow an experiment in which the test material stored in the sample container is frozen and the freezing pressure is applied in a state where the weight of the test material is increased. .
[0010]
The reason why the rotating body is formed in a disk shape is that air resistance during rotation is small, centrifugal acceleration is stabilized, and power consumption of the rotary drive device is saved.
[0011]
The sample container for storing the test material adopts an installation method in which the sample container is fixed horizontally on the horizontal beam constituting the rotating body via a slide base, instead of being suspended from the rotating body. This is because the test materials handled by this device are limited to large solid objects such as rock bodies for the purpose of destruction, and it is easier to install the test material in the device than in the normal suspension system. is there. Further, by installing the sample container inside a disk-shaped rotating body, it is possible to alleviate the impact when the test material such as a rock body is broken and to prevent scattering to the surroundings. In addition, the slide base on which the sample container is installed is supported by a beam that constitutes a rotating body and is movable in the horizontal direction along the beam, so that the load of the entire sample container on which centrifugal acceleration has acted is reduced. It is securely supported by four beams through the plate.
[0012]
Furthermore, the refrigeration system provided in the sample container circulates the antifreeze liquid cooled to a predetermined temperature by a refrigerator installed outside the rotating system between the refrigerator and the heat exchanger installed in the sample container inside the rotating system. It is preferable that the test material is frozen by feeding the heat-exchanged cold air into the sample container with a fan.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
1 and 2 show an example in which a centrifugal loading device according to the present invention is installed in a cylindrical underground pit P, where 1 is a vertical rotating shaft and 9 is a disk-type attached to the rotating shaft 1. A rotating body 15 is a sample container installed inside the rotating body 9.
[0014]
That is, the rotary shaft 1 is rotatably mounted on the bearing 2 incorporated in the upper deck D1 of the underground pit P and the bearing 3 incorporated in the inner deck D2 at the lower portion of the shaft. It is installed vertically in the center of the pit P. The lower end portion of the rotating shaft 1 is connected to a driving device 4 installed on the lower deck D3 of the underground pit P via a speed reducer 5. A slip ring 6 for exchanging information between the rotation side (inside the apparatus) and the outside of the apparatus is attached to the lower end portion of the rotating shaft 1.
[0015]
The rotary shaft 1 includes four long beams 7 ₁ , 7 ₂ , 7 ₃ , 7 ₄ combined in a prismatic shape, and a rotating body 9 formed by attaching back plates 8, 8 to both end faces thereof, The rotating shaft 1 is fixed horizontally. In the illustrated example, as shown in FIG. 3, the rotating body 9 is coated with steel plates 11 a and 11 a that are curved in a semicircular shape, and both upper and lower surfaces are covered with circular steel plates 11 b and 11 b. Thus, it is formed into a disk shape with low air resistance.
[0016]
Openings 12a and 12b are respectively provided on the upper surface 11b of the rotating body 9 having a disk shape at symmetrical positions with the rotating shaft 1 in between. One opening 12a is for inserting a counterweight 14 to be attached to a weight attaching device 13 formed inside the rotating body 9, and the other opening 12b is a sample container 15 in the rotating body 9 and the sample container 15 therein. This is for inserting a test material 16 such as a rock body. Although not shown, the semicircular curved steel plates 11a and 11a covering the side surface of the rotating body 9 are provided with cutout windows for video shooting at positions where the test material 16 can be seen.
[0017]
As shown in FIGS. 4 and 5, the sample container 15 is supported by lower beams 7 ₃ and 7 ₄ constituting the rotating body 9 and can be disassembled into a plurality of plates assembled on a slide base 17 that is movable in the horizontal direction. It is a box-shaped airtight container, in which a tensile load frame 18 and a test material 16 such as a rock that is horizontally fixed with a number of bolts 19 and a heat exchanger 20 installed on the back surface of the tensile load frame 18. Is to be stored.
[0018]
The test material 16 is formed in a block shape, and a plate 22 provided with a large number of tap holes 21 screwed to the bolts 19 is bonded to one end surface thereof. In the sample container 15, a level-adjustable roller 23 and a thrust bolt 24 that support the test material 16 fixed to the tensile load frame 18 from below are provided.
[0019]
The heat exchanger 20 installed on the back surface of the tensile load frame 18 in the sample container 15 is brought to a predetermined temperature (about minus 30 °) by a refrigerator (not shown) installed outside the apparatus in a pipe line 25 inside the heat exchanger 20. The cooled antifreeze (brine) is circulated and introduced through the rotary joint 26 at the top of the rotating shaft 1 and the heat-exchanged cold air is fed into the sample container 15 sealed by the fan 27 as indicated by an arrow. The test material 16 fixed to the tensile load frame 18 is frozen.
[0020]
In order to simulate the progress of a crack due to freezing pressure of a rock body using the centrifugal loading device having the above-described configuration, the rock body 16 as a test material is formed in a block shape of a required size and cut into the surface thereof. Insert. Further, a plate 22 having a tap hole 21 is bonded to one end face of the rock body 16. The rock body 16 is placed on the roller 23 and the thrust bolt 24 in the sample container 15 placed on the slide base 17 inside the rotary body 9 through one opening 12b on the upper surface of the disk-type rotary body 9 and pulled. The load frame 18 is fixed with bolts 19. When the fixing is completed, the thrust bolt 24 is retracted and the support of the rock body 16 by the bolt 24 is released.
[0021]
Next, the heat exchanger 20 is installed on the slide base 17, and a pipe line for circulating and introducing the antifreeze liquid cooled by the refrigerator outside the apparatus is connected to the internal pipe line 25 via the rotary joint 26. Next, after subjecting the fixed rock body 16 to a sewage treatment, the disassembled sample container 15 is assembled on the slide base 17 to thereby fix the rock body 16 fixed to the tensile load frame 18 and the heat exchanger. 20 is sealed inside the sample container 15.
[0022]
Then, the heat exchanger 20 is operated, and the cold air that has been heat-exchanged by circulating the cooled antifreeze liquid into the internal conduit 25 is fed into the sample container 15 by the fan 27. When the surface temperature of the rock body 16, which is the test material in the sample container 15, drops to a required freezing temperature, the driving device 4 of the rotating shaft 1 is driven to rotate the disk-shaped rotating body 9 horizontally. As a result, a tensile load due to centrifugal acceleration is applied to the rock body 16 fixed to the tensile load frame 18 in the rotating body 9. Therefore, when the rotational speed of the rotating body 9 is increased, the tensile load applied to the rock body 16 also increases for a while, the incision further progresses, and eventually the rock body 16 is destroyed.
[0023]
The progress of the cracks in the frozen rock body 16 simulated in this way can be observed entirely by video shooting. It is also possible to analyze the information from various sensors attached to the rock body 16 etc. and investigate the mechanism of crack propagation from the viewpoint of rock dynamics.
[0024]
【The invention's effect】
As described above, the centrifugal loading device of the present invention can freeze the test material by the refrigeration system provided in the sample container for storing the test material. Therefore, it is possible to experimentally observe the mechanism of crack propagation due to the freezing pressure of rock mass, which was not possible in the past. In addition to such a freezing pressure load test, the present invention can be applied to a hydraulic load test, a vibration test by hydraulic pressure supply, and the like.
[0025]
In addition, the sample container is not suspended from the rotating body as in the past, but is installed horizontally on the horizontal beam that constitutes the rotating body via the slide base. The material is easy to install and has excellent impact resistance when the test material is crushed. Since the rotating beam is a disk type with low air resistance, stable centrifugal acceleration can be obtained, and the power consumption of the rotating shaft driving device can be greatly reduced.
[Brief description of the drawings]
FIG. 1 is a longitudinal side view of a centrifugal loading device of the present invention.
2 is a plan view of FIG. 1. FIG.
3 is a view taken along the line AA in FIG.
FIG. 4 is a longitudinal side view for explaining a sample container according to the present invention.
FIG. 5 is a plan view of FIG. 4;
[Explanation of symbols]
1 Rotating shaft 7 ₁ , 7 ₂ , 7 ₃ , 7 ₄ Beam 9 Rotating body 15 Sample container 16 Test material (rock body)
17 Slide base 18 Tensile load frame 20 Heat exchanger

Claims (2)

A vertical rotating shaft, a rotating body that rotates horizontally around the rotating shaft, and a sample container supported by the rotating body are provided, and a predetermined centrifugal acceleration is imparted to the test material stored in the sample container by the rotation of the rotating body. In the centrifugal loading device, the sample container is provided with a refrigeration system so that the test material in the container can be frozen with centrifugal acceleration applied, and the rotating body is formed in a disk shape that rotates horizontally around the rotation axis. The sample container for storing the test material is installed inside a disk-shaped rotator, supported by a horizontal beam constituting the rotator, and horizontally through a slide base movable in the horizontal direction. Centrifugal loading device characterized by being installed in a stand.   The refrigeration system provided in the sample container circulates the antifreeze liquid cooled to a predetermined temperature by a refrigerator installed outside the rotating system between the refrigerator and the heat exchanger installed in the sample container inside the rotating system, The centrifugal loading device according to claim 1, wherein the test material is frozen by feeding the exchanged cold air into the sample container with a fan.

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