JP7348157B2 - Friction coefficient measuring device and friction coefficient measuring method - Google Patents

Description

The present invention relates to a friction coefficient measuring device and a friction coefficient measuring method.

With the propulsion method, it is necessary to understand the frictional force that acts between the propulsion box and the ground, and then perform construction with an appropriate propulsion force. Regarding the frictional force that acts between the propulsion box and the ground, guidelines are presented in various guidelines based on knowledge and data accumulated from past research and construction results (for example, see Non-Patent Document 1). ).
Furthermore, Patent Document 1 discloses that the specimen is rotated by being pulled in the tangential direction of the specimen while the specimen is placed on the earth and sand spread out in a cylindrical tray. A friction coefficient measuring method is disclosed in which the friction coefficient is measured by the rotational torque of a specimen.
In the propulsion method at great depths, it is expected that in addition to the weight of the propulsion box, large groundwater pressure and earth pressure will act from a direction that intersects the direction of movement of the propulsion box. In addition, in the curved propulsion method, a pressing force acts on the propulsion box in the radial direction of the curve.
As described above, the guidelines of Non-Patent Document 1 may not be directly applicable to the frictional force that acts between the propulsion box and the ground in the deep propulsion method or the curved propulsion method.
Furthermore, the method for measuring the coefficient of friction in Patent Document 1 measures the coefficient of friction that acts on the earth and sand using the weight and rotational force of the specimen, but a large pressing force (pressing force, earth pressure, water pressure, etc.) acts on the method. It is not possible to evaluate the friction coefficient under these conditions.

“Guidelines and Explanations of Sewerage Promotion Methods - 2010 Edition” Japan Sewage Works Association, October 2010

Jitszenhei 01-015944 publication

The present invention proposes a friction coefficient measuring device and a friction coefficient measuring method that make it possible to evaluate the friction coefficient during propulsion under conditions where excessive pressure is expected to be applied from a direction intersecting the propulsion direction. That is the issue.

A friction coefficient measuring device of the present invention for solving the above problems includes a rotary table that rotates around a vertical axis, a container that is fixed to the rotary table and stores a soil sample, and a container that is fixed to the rotary table and stores the soil sample, and A loading body placed on the soil sample, a pressing means that applies a pressing force in a vertical direction to the loading body, a torque measuring stay extending circumferentially from the loading body, and a tip end of the torque measuring stay are in contact with each other. It is equipped with a load cell installed at a position where the
Further, the friction coefficient measuring method of the present invention using the friction coefficient measuring device includes a measuring step of measuring the torque when rotating the rotary table, and a calculating step of calculating the friction coefficient using the torque. It is equipped with In the measurement step, the soil sample is packed into the container and the load is placed on the top surface of the soil sample, and the rotary table is rotated and the pressing means is used to apply the load to the load in the vertical direction. The work of applying a pressing force and the work of measuring torque using the load cell are performed. Further, in the calculation step, a friction coefficient is calculated based on the torque, the pressing force, and the shape of the container.

According to such a friction coefficient measuring device and friction coefficient measuring method, a pressing force in the vertical direction is applied when rotating the container and measuring the frictional resistance generated between the soil sample in the container and the loading object. Therefore, it is possible to quantitatively evaluate the friction coefficient that occurs between the soil sample (ground) and the loading body (propulsion box) under high pressure conditions.
In addition, if a gap is formed between the outer circumferential surface of the aforementioned cargo and the inner circumferential surface of the container, under conditions where the slipping material (the material filled around the propulsion box) flows out from the gap, Friction coefficient can be evaluated. Therefore, it becomes possible to quantitatively evaluate the friction reduction effect of the lubricant in the propulsion method under conditions where the lubricant diffuses.
Furthermore, if a potentiometer for measuring the rotation angle of the rotary table is attached to the rotary table, it is possible to measure the rotation angle and number of revolutions of the container (i.e., the sliding distance of the container), so that the propulsion distance can be measured. This can be used to evaluate how the frictional force changes depending on the

According to the friction coefficient measuring device and friction coefficient measuring method of the present invention, it is possible to estimate the friction coefficient during propulsion under conditions where excessive pressure is expected to be applied from a direction intersecting the propulsion direction. .

1 is a plan view showing a friction coefficient measuring device according to an embodiment of the present invention. 2 is a sectional view taken along line AA in FIG. 1. FIG. 2 is a sectional view taken along line BB in FIG. 1. FIG. 2 is a sectional view taken along the line CC in FIG. 1. FIG. It is a flowchart of the friction coefficient measuring method of this embodiment.

In this embodiment, when constructing a curved tunnel using the propulsion method, the coefficient of friction that acts on the propulsion box is estimated by laboratory tests. The friction coefficient measuring device 1 is used to estimate the friction coefficient. FIG. 1 shows a plan view of the friction coefficient measuring device 1, and FIG. 2 shows a cross-sectional view (AA sectional view) of the friction coefficient measuring device 1.
As shown in FIG. 1, the friction coefficient measuring device 1 includes a base 11, a device main body 12, and a power source 13.
The base 11 is made of a steel plate, and constitutes the basic part of the friction coefficient measuring device 1, as shown in FIG. The device main body 12 and the power source (electric motor) 13 are fixed to the upper surface of the same base 11. A case (not shown) that covers at least a portion (for example, a lower part) of the device main body 12 and the power source 13 may be fixed to the base 11. Although the dimensions of the steel plate constituting the base 11 are not limited, it should be thick enough to prevent movement, deformation, or damage due to vibrations when the friction coefficient measuring device 1 is driven. and weight.
As shown in FIGS. 1 and 2, the device main body 12 includes a rotary table 2, a container 3, a loading body 4, a pressing means 5, a torque measuring stay 6, a load cell 7, and a potentiometer 8.

The rotary table 2 rotates around a vertical axis. As shown in FIG. 2, the rotary table 2 includes a shaft portion 21, a base portion 22 fixed to the base 11, a rotating portion 23 placed on the base portion 22, and a table portion 24 placed on the rotating portion 23. We are prepared.
The shaft portion 21 is a cylindrical member disposed at the center of the rotary table 2 . The shaft portion 21 is disposed perpendicular to the base 11. The lower end of the shaft portion 21 is connected to the base portion 22, and the upper end of the shaft portion 21 is fixed to the table portion 24. A rotating part 23 is fixed to an intermediate part of the shaft part 21.

A recess 25 is formed in the center of the base 22 . The lower end of the shaft portion 21 is inserted into the recess 25 . A first bearing 26 and a second bearing 27 are arranged in the recess 25 . The first bearing 26 is interposed between the lower end of the shaft portion 21 and the bottom surface of the recess 25 , and the second bearing 27 is interposed between the inner wall surface of the recess 25 and the side surface of the shaft portion 21 . There is. That is, the shaft portion 21 is rotatably supported by the base portion 22 (recessed portion 25) via the first bearing 26 and the second bearing 27.
The rotating portion 23 is mounted on the base portion 22 via a third bearing 28 . That is, the base portion 22 rotatably supports the rotating portion 23 via the third bearing 28.

The rotating part 23 is externally mounted on the shaft part 21 between the base part 22 and the table part 24. That is, the rotating part 23 rotates around the shaft part 21. A gear 23a is formed on the outer surface of the rotating portion 23. The gear 23a consists of a disk concentric with the shaft portion 21. A power transmission means 14 (for example, a chain, a belt, etc.) extending from the power source 13 is wound around teeth formed on the outer peripheral edge of the gear 23a. The rotating section 23 rotates around the vertical axis (shaft section 21) by power transmitted from the power source 13 via the power transmitting means 14. At this time, the shaft portion 21 also rotates together with the rotating portion 23.
The table section 24 is a member that supports the container 3, and rotates around the vertical axis as the shaft section 21 (rotating section 23) rotates. A through hole 24a is formed in the center of the table portion 24. The upper end of the shaft portion 21 is inserted into the through hole 24a, and the upper end of the shaft portion 21 is fixed to the table 24 via a jig 24b. Further, in this embodiment, a fourth bearing 29 is provided between the table section 24 and the rotating section 23 as a buffer material when an overload is applied. Since the fourth bearing 29 absorbs the pressing force due to the overload, it prevents the rotating portion 23 from being pressed against the base portion 22 and thereby preventing rotation.

The container 3 stores the soil sample S. The container 3 is fixed to the upper surface of the rotary table 2 (table part 24). The container 3 of this embodiment includes a cylindrical container body 31 and a bottom plate 32 that covers the bottom surface of the container body 31.
The container body 31 is fixed to the upper surface of the bottom plate 32.
The bottom plate 32 is fixed to the upper surface of the rotary table 2 (table portion 24) via a jig (bolts 33). In this embodiment, a recess 24c having the same shape as the bottom plate 32 is formed on the upper surface of the table portion 24. The bottom plate 32 is fixed with bolts 33 while being accommodated (fitted) in the recess 24c. That is, the bottom plate 32 (container 3) rotates as the rotary table 2 rotates.

The loading body 4 is provided on the upper surface of the soil sample S housed in the container 3. The loading body 4 includes a plate part 41 in contact with the soil sample S, a load transmitting part 42 attached to the upper surface of the plate part 41, and a load receiving part 43 placed on the load transmitting part 42. The loading body 4 is placed on the soil sample S.
The outer diameter of the plate portion 41 is smaller than the inner diameter of the container 3 (container body 31), and a gap is formed between the outer circumferential surface of the plate portion 41 and the inner circumferential surface of the container body 31.
The load transmission section 42 is a cylindrical member and is fixed to the upper surface of the plate section 41. A through hole through which a bolt 44 can be inserted passes vertically through the load transmitting portion 42 . In this embodiment, the load transmitting section 42 is fixed to the plate section 41 by screwing the lower end of a bolt 44 that passes through the load transmitting section 42 into the plate section 41 .
The load receiving section 43 transmits the pressing force applied by the pressing means 5 to the plate section 41 via the load transmitting section 42 . The pressing means 5 applies a vertical pressing force to the loading body 4. The load receiving part 43 is mounted on the load transmitting part 42 via the fifth bearing 45 and is rotatable with respect to the load transmitting part 42 . That is, even if the plate part 41 and the load transmitting part 42 rotate due to the frictional force with the soil sample S in the container 3, the load receiving part 43 does not rotate and continues to apply the load in the vertical direction. A spherical recess 46 is formed on the upper surface of the load receiving portion 43, and transmits the pressing force applied from above by the pressing means 5 in the vertical direction.

The torque measurement stay 6 extends from the loading body 4 in the circumferential direction and is connected to the load cell 7. FIG. 3 shows the torque measurement stay 6 and the load cell 7. As shown in FIGS. 1 and 3, the torque measurement stay 6 includes a connecting portion 61 and a transmitting portion 62.
The connecting portion 61 is a member attached to the load transmitting portion 42 of the loading body 4. The configuration of the connecting portion 61 is not limited as long as it can be fixed to the load transmitting portion 42, but the connecting portion 61 of this embodiment is a load transmitting member formed by combining a pair of divided members 63, 63. It is an annular member having an inner diameter equivalent to the outer diameter of the portion 42. The connecting portion 61 is fixed to the load transmitting portion 42 by combining a pair of divided members 63, 63 with the load transmitting portion 42 sandwiched therebetween.
The transmission section 62 is a rod-shaped member having one end fixed to the connecting section 61 and the other end connected to the load cell 7.

As shown in FIGS. 1 and 3, the load cell 7 is provided at a position where the tip of the torque measurement stay 6 (the other end of the transmission section 62) comes into contact. The load cell 7 of this embodiment is arranged at the upper end of the support column 71. The load cell 7 measures the pressing force received from the torque measuring stay 6 when a rotational force is applied to the load body 4 due to the frictional force with the soil sample S in the container 3.
The support column 71 supports the load cell 7 at a predetermined position. The lower end of the support column 71 is fixed to the base 11. Although the pillar 71 of this embodiment is made of a steel material such as an L-shaped steel, the material of which the pillar 71 is made is not limited, and may be made of, for example, a steel pipe.

Potentiometer 8 measures the rotation angle of rotary table 2 . FIG. 4 shows the potentiometer 8. The potentiometer 8 is attached to the table portion 24 of the rotary table 2, as shown in FIGS. 1 and 4. Potentiometer 8 is attached to support column 81 via connecting member 82 . The support column 81 is a member erected on the base 11, and has a lower end fixed to the base 11. The support column 81 is made of a member (for example, a steel pipe, steel material, etc.) that has a height (length) and strength that can support the potentiometer 8 at a predetermined height position. The connecting member 82 is a member for connecting the potentiometer 8 to the support column 81. The connecting member 82 of this embodiment is detachable from the support column 81 (can be moved up and down), and supports the potentiometer 8 so that its height position can be adjusted.

Next, a friction coefficient measuring method using the friction coefficient measuring device 1 will be explained. FIG. 5 is a flowchart of a friction coefficient measuring method. As shown in FIG. 5, the friction coefficient measuring method of this embodiment includes a measuring step S1 and a calculating step S2.
The measurement step S1 is a step of measuring the torque when the rotary table 2 is rotated. In the measurement step S1, a preparation work S11, a rotation work S12, and a measurement work S13 are performed.
In the preparatory work S11, the soil sample S is packed into the container 3, and the container 3 is fixed to the rotary table 2. Next, the loading body 4 is placed on the top surface of the soil sample S. In this embodiment, as the soil sample S, a material collected at the site is used. Furthermore, a slipping material filled around the propulsion box is interposed on the contact surface between the soil sample S and the loading body 4.
In the rotation work S12, the power source 13 is started to rotate the rotary table 2, and the pressing means 5 is used to apply vertical pressure to the soil sample S via the loading body 4. That is, the pressing means 5 applies a pressing force corresponding to the pressure applied from a direction perpendicular to the propulsion direction in the propulsion method.
In the measurement work S13, torque is measured by the load cell 7. By rotating the rotary table 2, a frictional force is generated at the contact surface between the loading body 4 and the soil sample S, and rotational force is transmitted to the loading body 4. The load cell 7 measures the rotational force of the load body 4 transmitted via the torque measurement stay 6. That is, the torque that correlates to the frictional force generated between the propulsion box and the ground in the propulsion method is measured.
At this time, the number of revolutions of the rotary table 2 is measured by the potentiometer 8. The number of revolutions of the rotary table 2 correlates with the propelling distance of the propulsion box, so by measuring the change in torque with respect to the number of revolutions of the rotary table 2, it is possible to evaluate the change in frictional force with respect to the propelling distance. .

In the calculation step S2, the friction coefficient and the friction force are calculated using the torque measured in the measurement step S13. The friction coefficient and the frictional force are calculated using Equations 1 to 3 based on the torque, the pressing force (overload), and the shape of the container 3. Note that since the fifth bearing 45 is interposed between the load transmitting section 42 and the load receiving section 43, the frictional force acting between the load transmitting section 42 and the load receiving section 43 is ignored.

According to the friction coefficient measuring device 1 and the friction coefficient measuring method of the present embodiment, when rotating the container 3 and measuring the frictional resistance generated between the soil sample S in the container 3 and the loading body 4, it is possible to Due to the pressing force acting on the soil sample S (ground) and the loading body 4 (propulsion box) under high pressure conditions, such as propulsion methods with curved sections or propulsion methods at great depths, etc. The friction coefficient can be quantitatively evaluated. As a result, it can be used to estimate the pushing force required to determine the performance and number of hydraulic jacks to be used in construction plans and calculations of construction costs in propulsion construction methods.
Further, since a gap is formed between the outer circumferential surface of the loading body 4 and the inner circumferential surface of the container 3, the coefficient of friction can be evaluated under the condition that the lubricant flows out from the gap. Therefore, it becomes possible to quantitatively evaluate the friction reduction effect of the lubricant in the propulsion method under conditions where the lubricant spreads.
In addition, since the rotation angle and number of revolutions (i.e., the sliding distance of the container 3) of the container 2 (container 3) can be measured by the potentiometer 8, it is possible to evaluate how the frictional force changes depending on the propulsion distance. It can be used for That is, by converting the number of revolutions of the rotary table 2 into a propulsion distance, it is possible to estimate the relationship between the propulsion distance and frictional resistance in the propulsion method. Therefore, it can be used to determine the performance of jacks required for constructing long-distance propulsion tunnels.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and each of the above-mentioned components can be modified as appropriate without departing from the spirit of the present invention.
The configuration of the power source 13 is not limited. Furthermore, the stress transmitting means is not limited to chains, belts, etc., and may be gears, for example.
In the embodiment, the rotating part 23 and the table part 24 of the rotary table 2 are configured as separate members, and the fourth bearing 29 is interposed between the rotating part 23 and the table part 24. However, the fourth bearing 29 may be provided as necessary. Moreover, the rotating part 23 and the table 24 may be formed integrally.
In the embodiment described above, a case has been described in which the container 3 includes a cylindrical container main body 31 and a bottom plate 32, but the container 3 may be a cylindrical member with a bottom.
The gap between the container 3 and the loading body 4 may be formed as necessary. If there is no risk of slipping material flowing out of the ground, there is no need to form gaps. Further, the size of the gap between the container 3 and the loading body 4 may be determined as appropriate.
The potentiometer 8 may be installed as necessary. The means for measuring the rotational speed of the rotary table 2 may be determined as appropriate.

1 Friction coefficient measuring device 11 Base 12 Device body 13 Power source 2 Rotary table 3 Container 4 Loading body 5 Pressing means 6 Torque measurement stay 7 Load cell 8 Potentiometer S Soil sample S1 Measurement process S2 Calculation process

Claims (4)

A rotary table that rotates around a vertical axis,
a container fixed to the rotary table and containing a soil sample;
a loading body placed on the soil sample with controlled rotation;
a pressing means that applies a pressing force in a vertical direction to the load;
a torque measuring stay extending circumferentially from the aforementioned load;
A friction coefficient measuring device comprising: a load cell provided at a position where the tip of the torque measuring stay contacts. 2. The friction coefficient measuring device according to claim 1, wherein a gap is formed between an outer circumferential surface of the cargo and an inner circumferential surface of the container. 3. The friction coefficient measuring device according to claim 1, wherein a potentiometer for measuring the rotation angle of the rotary table is attached to the rotary table. A friction coefficient measuring method using the friction coefficient measuring device according to any one of claims 1 to 3,
a measuring step of measuring torque when rotating the rotary table;
a calculation step of calculating a friction coefficient using the torque,
In the measurement step,
Loading the soil sample into the container and placing the load on top of the soil sample;
Rotating the rotary table and applying a vertical pressing force to the load using the pressing means;
Measuring torque with the load cell,
A friction coefficient measuring method, wherein in the calculation step, a friction coefficient is calculated based on the torque, the pressing force, and the shape of the container.

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