JP2021173552A - Soil mechanics tester - Google Patents

Abstract

To provide a soil mechanics tester which is small and can apply a restraining pressure to a sample.SOLUTION: A soil mechanics tester 1 which stores a sample used for a soil mechanics test includes: a tubular body portion 10; a first lid portion 20 which covers one end of the body portion 10; a second lid portion 30 which covers the other end of the body portion 10; and an inner lid 40 which can slide an inner surface along the axial direction of the body portion 10. A space partitioned by the first lid portion 20, the inner lid 40, and the body portion 10 is a fluid filling chamber 55, a space partitioned by the second lid portion 30, the inner lid 40, and the body portion 10 is a sample filling chamber 56. The inner lid 40 is moved by pressure of the fluid filled in the fluid filling chamber 55 so that the sample filled in the sample filling chamber 56 is in a pressed state.SELECTED DRAWING: Figure 2

Description

The present invention relates to a soil mechanics tester used for a vane shear test.

In the mud pressure shield method, mud material is added to the face portion, excavated soil and mud material are mixed and kneaded in the chamber, and discharged by a screw conveyor. The mud material provides the excavated soil with face stability, fluidity for mud drainage and water stoppage. Since mud becomes industrial waste, it is necessary to satisfy these functions with a small injection amount in order to reduce the environmental load.

Currently, a bubble stabilizer is being developed in which a chemical that generates bubbles and water are added and kneaded according to the excavated soil, and vane shear tests and the like are conducted to quantitatively measure the flow characteristics of the mud. There is. Since the excavated soil in the chamber is pressurized, it is preferable to perform the vane shear test with the sample pressurized.

As an apparatus for performing a vane shear test in a state where a sample is pressurized, for example, there is one shown in Non-Patent Document 1. The pressurized vane shear test shown in Non-Patent Document 1 is a method in which a container containing a sample is housed in a closed airtight container and the vane shear test is performed under a predetermined restraining pressure. be. By using this vane shear test apparatus, since the sample is put in a container, the test can be performed even on a sample that does not stand on its own.

Yuta Kurihashi, Hirokazu Akagi, Yoshimasa Kondo, Shuzo Innan, Keiichi Mori, Atsuo Tsuchiya: Flow characteristics of excavation stabilizer for soil cement wall construction using air bubbles, Proceedings of the 64th Annual Scientific Lecture Meeting of the Japan Society of Civil Engineers, p. .715-716

Since the vane shear test apparatus requires a container for sealing that is larger than the container in which the sample is placed, there is a problem that the apparatus becomes large. In addition, since the pressure is applied directly to the sample by air pressure, it is not possible to measure the volume change of soil, which is characteristic of being largely dependent on the restraining pressure, and it also contributes to the increase in the contact force between soil particles. Only the pore water pressure increases.

From this point of view, it is an object of the present invention to provide a soil mechanics tester which is small in size and can apply a restraining pressure to a sample.

The present invention for solving such a problem is a soil mechanics tester for storing a sample used for a soil mechanics test. Such a soil mechanics tester includes a tubular body portion, a first lid portion covering one end of the body portion, a second lid portion covering the other end of the body portion, and an axial direction of the body portion. It has an inner lid that can slide on the inner surface. In the present invention, the space partitioned by the first lid portion, the inner lid, and the body portion serves as a fluid filling chamber, and the space partitioned by the second lid portion, the inner lid, and the body portion is a sample. It becomes a filling chamber, and by moving the inner lid by the pressure of the fluid filled in the fluid filling chamber, the sample filled in the sample filling chamber is put into a pressed state.

According to the soil mechanics tester according to the present invention, since the sample is pressed and pressed by the inner lid provided in the body, the pressurization mechanism is simplified and the restraining pressure can be applied by the container itself. Therefore, it is smaller than the conventional device and easy to operate. Further, since the inner lid directly presses the sample, it is possible to reproduce the same pressurized state as the excavated soil in the chamber of the shield machine, for example.

In the soil mechanics tester of the present invention, it is preferable that the inner lid is provided with a seal packing that abuts on the inner peripheral surface of the body portion. According to such a configuration, the fluid filled in the fluid filling chamber is less likely to leak into the sample filling chamber, so that the pressure control of the sample can be performed accurately.

Further, in the soil mechanics tester of the present invention, it is preferable that the inner lid further includes a pair of plate materials for sandwiching the seal packing. According to such a configuration, the inner lid is less likely to be deformed, so that the pressure control of the sample can be performed more accurately.

Further, in the soil mechanics tester of the present invention, it is preferable that an insertion hole is formed in the central portion of the second lid portion so that the inserted bladed shaft is rotatably contacted. According to such a configuration, a shearing force can be smoothly applied to the sample.

According to the soil mechanics tester according to the present invention, it is possible to reduce the size of the container and to apply a restraining pressure to the sample, which is an excellent effect.

It is a perspective view which showed the soil mechanics tester which concerns on embodiment of this invention. It is sectional drawing which showed the soil mechanics tester which concerns on embodiment of this invention. It is an exploded perspective view which showed the soil mechanics tester which concerns on embodiment of this invention. It is a graph which showed the relationship between torque and rotation angle. It is a graph which showed the relationship between torque and rotation angle. It is a graph which showed the relationship between pressure and maximum torque. It is a graph which showed the relationship between torque and rotation angle.

The soil mechanics tester according to the embodiment of the present invention will be described with reference to the attached drawings. The soil mechanics tester of the present embodiment is used for a vane shear test, and can contain, for example, muddy soil excavated soil discharged from the chamber of a shield excavator as a sample and pressurize it.

FIG. 1 is a perspective view showing a soil mechanics tester 1 according to the present embodiment. As shown in FIG. 1, the soil mechanics tester 1 has a tubular body portion 10, a first lid portion 20 that covers one end of the body portion 10, and a second lid portion 30 that covers the other end of the body portion 10. And an inner lid 40 that can slide the inner surface of the body portion 10 along the axial direction of the body portion 10.

FIG. 2 is a cross-sectional view of the soil mechanics tester 1, and FIG. 3 is an exploded perspective view of the soil mechanics tester 1. As shown in FIGS. 2 and 3, the body portion 10 has a cylindrical shape with the upper and lower sides open. A collar portion 11 for fixing the first lid portion 20 is provided at the lower end portion of the body portion 10. The collar portion 11 has a circular band shape. A plurality of bolt insertion holes 12, 12, ... Are formed in the flange portion 11 at predetermined intervals in the circumferential direction. A collar portion 13 for fixing the second lid portion 30 is provided at the upper end portion of the body portion 10. The collar portion 13 has the same circular band shape as the collar portion 11. A plurality of bolt insertion holes 12, 12, ... Are formed in the flange portion 13 at predetermined intervals in the circumferential direction. A through hole 14 is formed in the lower part of the body portion 10. The through holes 14 are formed at two places. The two through holes 14, 14 are arranged at positions facing each other.

The first lid portion 20 is a lower lid that covers the opening at the lower end of the body portion 10. The first lid portion 20 has a disk shape. A plurality of bolt insertion holes 21 are formed on the peripheral edge of the first lid portion 20. The bolt insertion hole 21 is formed at a position corresponding to the bolt insertion hole 12 of the flange portion 11. The first lid portion 20 is fixed to the body portion 10 by inserting the bolt B into the bolt insertion holes 21 and 12 and screwing the nut N. A ring-shaped groove 22 is formed on the upper surface of the first lid 20. The groove 22 is open upward. The groove portion 22 is located closer to the center than the bolt insertion hole 21 and outside the hole on the inner peripheral edge of the flange portion 11. The groove 22 is equipped with an O-ring 23 for ensuring airtightness between the inside and the outside of the container. The first lid portion 20 may be integrally formed with the body portion 10. In this case, since the airtightness between the body portion 10 and the first lid portion 20 can be ensured, the O-ring 23 can be omitted.

The second lid portion 30 is an upper lid that covers the opening at the upper end of the body portion 10. The second lid portion 30 has a disk shape. A plurality of bolt insertion holes 31 are formed on the peripheral edge of the second lid portion 30. The bolt insertion hole 31 is formed at a position corresponding to the bolt insertion hole 12 of the flange portion 13. By inserting the bolt B into the bolt insertion holes 31 and 12 and screwing the nut N, the second lid portion 30 is fixed to the body portion 10. A ring-shaped groove 32 is formed on the lower surface of the second lid 30. The groove 32 opens downward. The groove portion 32 is located closer to the center than the bolt insertion hole 31 and outside the hole on the inner peripheral edge of the flange portion 13. The groove portion 32 is equipped with an O-ring 33 for ensuring airtightness between the inside and the outside of the container. The O-ring 33 prevents internal pressure leakage and sample outflow.

An insertion hole 34 is formed in the central portion of the second lid portion 30. A rotating shaft 50 serving as a vane shaft is inserted into the insertion hole 34. The insertion hole 34 is provided with a bearing portion 35 that rotatably supports the rotating shaft 50 above the insertion hole 34. An insertion hole 39 is formed in the bearing portion 35. The inserted rotating shaft 50 rotatably contacts the insertion hole 39. A ring-shaped groove 36 along the circumferential direction is formed on the inner peripheral surface of the insertion hole 39. The groove 36 opens toward the axis. The groove 36 is equipped with an O-ring 37 for ensuring airtightness between the inside and the outside of the container. The O-ring 37 is in contact with the rotating shaft 50 while maintaining airtightness.

The lower end of the rotating shaft 50 is inserted inside the soil mechanics tester 1. A vane 51 for applying a shearing force to the sample housed in the soil mechanics tester 1 is attached to the lower end of the rotating shaft 50, and the rotating shaft 50 is combined with the vane 51 to form a bladed shaft. Become. The vane 51 is formed by combining four vane blades 52, 52, ... In a cross shape in a plan view. The upper end portion of the rotating shaft 50 projects above the bearing portion 35. A motor 53 (see FIG. 1) for rotating the rotating shaft 50 is provided at the upper end of the rotating shaft 50. The motor 53 is attached to a fixed system (not shown) to rotate the rotating shaft 50.

A pressure gauge (earth pressure gauge) 38 is provided on the lower surface of the second lid portion 30. The pressure gauge 38 measures the pressure acting on the sample housed inside the body portion 10 (earth pressure in this embodiment).

The inner lid 40 is housed inside the body portion 10. The inner lid 40 has a disk shape. The inner lid 40 is in peripheral contact with the inner surface of the body portion 10, and divides the internal space of the body portion 10 in an airtight state. The space partitioned by the body 10, the first lid 20, and the inner lid 40 becomes the fluid filling chamber 55, and the space partitioned by the body 10, the second lid 30, and the inner lid 40 is the sample filling chamber. It becomes 56. The inner lid 40 is slidable on the inner surface (inner peripheral surface) of the body portion 10 along the axial direction of the body portion 10. The inner lid 40 moves toward the upper second lid portion 30 due to the pressure of the fluid filled in the fluid filling chamber 55, and presses the sample filled in the sample filling chamber 56. That is, the inner lid 40 serves as a pressure piston that increases the pressure in the sample filling chamber 56. The inner lid 40 is arranged above the through holes 14, 14 of the body portion 10.

The inner lid 40 includes a seal packing 41 and a pair of upper and lower plate materials (upper plate 42 and lower plate 43). The seal packing 41 is made of rubber and comes into contact with the entire inner peripheral surface of the body portion 10. A skirt portion 44 that inclines downward toward the outside is formed on the outer peripheral edge portion of the seal packing 41. The upper surface (outer peripheral surface) of the skirt portion 44 abuts on the inner peripheral surface of the body portion 10. A circular opening 45 is formed in the central portion of the seal packing 41. A flat bolt B2 for fixing the upper plate 42 and the lower plate 43 is inserted through the opening 45. The upper plate 42 is made of a metal disk and is in contact with the upper surface of the seal packing 41. The outer diameter of the upper plate 42 is slightly smaller than the inner diameter of the body portion 10. An insertion hole 46 for the flat bolt B2 is formed in the central portion of the upper plate 42. The insertion hole 46 has a tapered shape. When the flat bolt B2 is attached, the surface of the head of the flat bolt B2 is flush with the surface of the upper plate 42. The lower plate 43 is made of a metal disk and is in contact with the lower surface of the seal packing 41. The outer diameter of the lower plate 43 is smaller than the outer diameter of the upper plate 42, and the lower plate 43 can be installed inside the inner peripheral portion of the skirt portion 44 of the seal packing 41. The outer diameter of the lower plate 43 is larger than the inner diameter of the opening 45 of the seal packing 41.

The through holes 14 and 14 at the lower part of the body portion 10 serve to inject or discharge the fluid into the fluid filling chamber 55. When the fluid to be filled is an incompressible liquid (for example, water), the liquid is injected through one through hole 14, and the internal air is evacuated from the other through hole 14 when the liquid is injected. When the fluid to be filled is a gas, one through hole 14 is closed and the gas is injected through the other through hole 14. The number of through holes 14 is not limited to two, and may be a large number of three or more. If the fluid to be filled is a gas, it may be singular.

Next, an example of the procedure of the vane shear test using the soil mechanics tester 1 having the above configuration will be described. When water is used as the fluid, first, the fluid filling chamber 55 between the first lid portion 20 and the inner lid 40 in the body portion 10 is filled with water. At this time, the air in the fluid filling chamber 55 is discharged to the outside through the other through hole 14. After that, the sample filling chamber 56 above the inner lid 40 is filled with the sample, and the second lid portion 30 is installed on the body portion 10 with the rotating shaft 50 provided with the vane 51 attached to the second lid portion 30. .. Then, the rotating shaft 50 is penetrated so that the vane 51 has a predetermined depth.

After that, water is additionally supplied to the fluid filling chamber 55 to increase the water pressure in the fluid filling chamber 55. As a result, the inner lid 40 is pressed toward the sample filling chamber 56, and pressure is applied to the sample. The pressure of the sample is directly measured by the pressure gauge 38 installed in the second lid portion 30. At this time, in the present embodiment, since water is supplied into the fluid filling chamber 55 to pressurize the sample, there is almost no time lag between the supply of water and the pressure rise of the sample, and the pressure control becomes easy and accurate. .. When the sample reaches a predetermined pressure, the rotation shaft 50 is rotated to perform a vane shear test. The sample filling chamber 56 is filled with a sample in a state where a spacer (not shown) is interposed between the first lid portion 20 and the inner lid 40 (a state in which the inner lid 40 is supported from below). After installing the second lid portion 30 on which the rotating shaft 50 is mounted on the body portion 10, water or gas may be supplied into the fluid filling chamber 55 to pressurize the sample.

According to the soil mechanics tester 1 of the present embodiment, the inner lid 40 is slidably provided in the body portion 10, and the inside of the body portion 10 is divided into a fluid filling chamber 55 and a sample filling chamber 56 by the inner lid 40. ing. That is, since the inner lid 40 acts as a pressurizing piston to press and pressurize the sample, the pressurizing mechanism is simplified. Further, since the restraining pressure can be applied by the container itself, the pressure can be increased from all directions, and the size of the device is smaller than that of the conventional device, which makes the operation easier. Further, since the inner lid directly presses the sample, it is possible to reproduce the same pressurized state as the excavated soil in the chamber of the shield machine. Further, when an incompressible fluid (for example, water) is supplied to the fluid filling chamber 55, the amount of movement of the inner lid 40 can be grasped from the amount of fluid supplied, so that the state change of the soil (the amount of change in the volume of the sample, etc.) can be grasped. ) Can be measured accurately.

In addition, since the sample is housed in the body 10, the soil mechanics test can be performed even on a sample that cannot stand on its own.

Further, in the soil mechanics tester 1 of the present embodiment, since the inner lid 40 is provided with a seal packing 41 that abuts on the inner peripheral surface of the body portion 10, the fluid filled in the fluid filling chamber 55 is a sample filling chamber. It is hard to leak to 56. In particular, since the skirt portion 44 of the seal packing 41 is pressed against the inner peripheral surface of the body portion 10 by the pressure of the fluid, the airtightness between the fluid filling chamber 55 and the sample filling chamber 56 is improved. Further, since the seal packing 41 is sandwiched between the upper plate 42 and the lower plate 43, the inner lid 40 is not easily deformed. Therefore, since the pressure of the fluid can be uniformly transmitted to the sample on the surface, the pressure control of the sample can be performed more accurately.

As described above, according to the soil mechanics tester 1 according to the present invention, the container can be miniaturized and the sample can be pressurized in a state close to the actual excavated soil.

Next, a test conducted to examine suitable conditions for use of the soil mechanics tester 1 will be described.
First, the torque was measured without the sample and the inner lid 40. The torque was measured with air pressure from the through hole 14 of the body portion 10 and the pressure gauge 38 showed 0 kPa, 100 kPa, 200 kPa, 500 kPa. FIG. 4 shows the relationship between the torque and the rotation angle at a rotation speed of 0.002 rad / s. As shown in FIG. 4, when the rotation angle is 35 ° or less, the torque is about 0.03 [Nm] or less in all cases. On the other hand, above the rotation angle of 35 °, the torque tended to increase. Specifically, the torque generation status differs between 0 kPa-1 (L1a in FIG. 4) and 0 kPa-2 (L1b) whose reproducibility has been confirmed, and the maximum value is about doubled. There is no significant difference between the torque increasing tendency and the maximum value between 200 kPa (L1d) and 500 kPa (L1e). Therefore, it is considered that the influence of the torque due to the friction of the O-ring 37 is more influenced by the installation accuracy such as the contact state between the rotating shaft (vane shaft) 50 and the O-ring 37 than the pressure as the rotation angle increases.

Next, a vane shear test was conducted using the excavated soil collected in the mud pressure shield construction as a sample. The size of the vane is 20 mm in diameter and 40 mm in height, and the rotation speed is 0.002 rad / s, 0.05 rad / s, 0.1 rad / s and the pressure is set to 0.002 rad / s, 0.05 rad / s, 0.1 rad / s in order to consider the influence of the rotation speed. Four levels (0 kPa, 100 kPa, 200 kPa, 500 kPa) were set. Since the excavated soil contained gravel, this time it was used by sieving it with a 2 mm sieve. The size of the sieve was selected based on the fact that the maximum particle size is 1/5 or less of the radius of the vane 51. In addition to the above pressure conditions, in order to grasp the influence of the state of the sample on the torque, water addition was adjusted with reference to an appropriate range (105 mm to 135 mm) of the table flow value, which is a conventional judgment index. It was confirmed that the adjusted table flow values were 106 mm, 114 mm, and 136 mm, and in the following results and discussion, they are referred to as TF106, TF114, and TF136, respectively.

FIG. 5 shows the relationship between the torque and the rotation angle of the test performed at a rotation speed of 0.002 rad / s with respect to the TF106. As shown in FIG. 5, there are cases where the torque peaks up to a rotation angle of 35 ° (0 kPa (L2a in FIG. 5), 500 kPa (L2d)) and cases where the torque slowly increases even after 35 ° (100 kPa). The tendency is divided into (L2b) and 200 kPa (L2c)). From the above, it is considered that the frictional effect of the O-ring 37 is large after 35 °. Therefore, the maximum value in the range up to 35 ° is extracted as the maximum torque and arranged in a series of results.

FIG. 6 shows the relationship between the maximum torque at a rotation speed of 0.002 rad / s and the value of the pressure gauge. As shown in FIG. 6, in TF106 (L3a in FIG. 6), the maximum torque increases as the pressure increases. The maximum torque ratio of 500 kPa to 0 kPa was 1.42 for TF106, 1.22 for TF114 (L3b), and 1.10 for TF136 (L3c). Therefore, it is considered that the smaller the table flow value, the more easily it is affected by the pressure.

FIG. 7 shows the relationship between the maximum torque at rotation speeds of 0.1 rad / s and 0.05 rad / s and the maximum torque at 0.002 rad / s. As shown in FIG. 7, it was found that the results of 0.1 rad / s and 0.05 rad / s in TF106, TF114, and TF136 were all randomly plotted near the 45 ° line (TF106 is shown in the graph). TF114 is distributed in the middle part, and TF136 is distributed in the lower left part). This means that the influence of the rotation speed on the maximum torque is small regardless of the table flow value and the pressure. Previous findings have reported that there is no effect of rotational speed on a completely kneaded sample, and in this test, the conditions were faster, but the same tendency was observed. rice field.

That is, in the soil mechanics tester 1 according to the present embodiment, the influence of the pressure due to the friction of the O-ring 37 has a slight range up to a rotation angle of 35 °, and the maximum torque is extracted from this range and used for examination. Was judged to be appropriate. On top of that, it was confirmed that the smaller the table flow value, the more remarkable the tendency of the maximum torque to increase with the increase in pressure, and the smaller the influence of the rotation speed on the maximum torque regardless of the table flow value and pressure. .. From the results obtained this time, it was found that the soil mechanics tester 1 can also be applied to the evaluation of the plastic fluidity of the excavated soil in the chamber in the large-depth, large-section shield construction.

Although the embodiment for carrying out the present invention has been described above, the present invention is not intended to be limited to the above-described embodiment, and the design can be appropriately changed without departing from the spirit of the present invention. For example, in the above embodiment, the soil mechanics tester 1 is used for the vane shear test, but is not limited thereto. If the shape of the upper lid is changed as appropriate, it can be applied to other mechanical tests such as a cone penetration test.

Further, in the above embodiment, the fluid filling chamber 55 is filled with water to pressurize the sample, but the present invention is not limited to this. It may be a liquid other than water or a gas such as air. However, it is preferable to use a fluid having a small time lag between the supply of the fluid and the increase in the pressure of the sample.

1 Soil mechanics tester 10 Body part 20 First lid part 30 Second lid part 39 Through hole 40 Inner lid 41 Seal packing 42 Top plate (plate material)
43 Lower plate (plate material)
50 rotating shaft (shaft with blades)
51 vane 55 fluid filling chamber 56 sample filling chamber

Claims (4)

In a soil mechanics tester that stores samples used for soil mechanics tests
A tubular body portion, a first lid portion covering one end of the body portion, a second lid portion covering the other end of the body portion, and an inner surface slidable along the axial direction of the body portion. Equipped with an inner lid,
The space partitioned by the first lid portion, the inner lid, and the body portion serves as a fluid filling chamber, and the space partitioned by the second lid portion, the inner lid, and the body portion serves as a sample filling chamber.
A soil mechanics tester characterized in that the sample filled in the sample filling chamber is put into a pressed state by moving the inner lid by the pressure of the fluid filled in the fluid filling chamber. The soil mechanics tester according to claim 1, wherein the inner lid is provided with a seal packing that abuts on the inner peripheral surface of the body portion. The soil mechanics tester according to claim 2, wherein the inner lid further includes a pair of plate members for sandwiching the seal packing. The soil mechanics according to any one of claims 1 to 3, wherein an insertion hole is formed in the central portion of the second lid portion so that the inserted bladed shaft is rotatably contacted. Tester.

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