JP2024138564A - Permeability evaluation device and method - Google Patents

Abstract

To evaluate water permeability of a shear zone of a sample in an arbitrary shear state.SOLUTION: A water permeation evaluation device comprises a first holding member 3 that holds an upper surface side of a sample 2 and a second holding member 4 that holds a lower surface side of the sample 2, relatively moves the first holding member 3 and the second holding member 4 with shear means 6 to deform the sample 2, generates a displacement in the sample 2 to form a shear zone 5, causes water to flow in the shear zone 5 in a direction along the surfaces with water flow means 7, detects the state of water flow with water flow detection means 8, and evaluates a water permeation state of a portion of the shear zone 5 in the sample 2 in the direction along the surfaces with evaluation means 9.SELECTED DRAWING: Figure 1

Description

The present invention relates to a permeability evaluation device and a permeability evaluation method that evaluates permeability by deforming a material.

For example, when disposing of radioactive waste underground, it is considered to use a material with extremely low permeability as a buffer material such as covering soil in order to prevent the migration of nuclides due to groundwater flow. Examples of materials with extremely low permeability that are being considered include those with swelling properties (bentonite, or a mixture of bentonite and sand).

When evaluating materials that make up buried facilities, such as buffer materials, it is necessary to understand the state of groundwater flow. In order to understand the state of groundwater flow, it is important to understand the permeability of materials such as buffer materials. For this reason, technology has been proposed that can appropriately detect the movement of very small amounts of water even in materials with extremely low permeability (for example, Patent Document 1).

On the other hand, it is important to understand the strength of the materials used in the disposal of radioactive waste, such as cover soil, and shear strength is investigated to understand the strength of the materials that make up the ground, such as buffer materials. Understanding the shear strength makes it possible to evaluate the mechanical behavior of buffer materials, such as cover soil, in response to changes in the surrounding environment.

The state of groundwater flow in materials such as buffer materials requires long-term evaluation taking into account shear stress, and the current situation requires an understanding of the situation regarding the occurrence of water paths when localized deformation (shear deformation) occurs in the material.

JP 2015-125078 A

The present invention has been made in consideration of the above situation, and aims to provide a permeability evaluation device and a permeability evaluation method that can evaluate the permeability of the shear band of a material in any shear state (process).

In order to achieve the above object, the water permeability evaluation device of the present invention according to claim 1 comprises:
A first holding member that holds one surface of the sample;
a second holding member that holds the other surface side of the sample and restrains the sample between itself and the first holding member;
a shearing means for relatively moving the first holding member and the second holding member to deform the sample and form a shear band in the sample;
water passing means for passing a desired amount of water through the restrained sample from at least directions along the one surface and the other surface before shear bands are formed in the sample, and for passing water through the shear bands formed in the sample in a direction along the surface after shear bands are formed in the sample;
and an evaluation means for detecting the state of water flow by the water flow means and evaluating the water permeability of the shear band.

The method for evaluating permeability according to claim 2 of the present invention for achieving the above object is characterized in that a sample is restrained from both sides of a central axis, a desired water flow is made through the restrained sample from a direction intersecting the central axis, and after the desired water flow is made, the sample is displaced and sheared so that a shear band is formed in the direction along the desired water flow, and water is passed in the direction along the shear band to evaluate the permeability of the area including the sheared surface.

The permeability evaluation method of the present invention according to claim 3 is characterized in that in the permeability evaluation method according to claim 2, the direction intersecting the one central axis is a direction perpendicular to the one central axis.

The method for evaluating permeability of the present invention according to claim 4 is characterized in that in the method for evaluating permeability according to claim 2 or 3, the displacement for shearing the sample is in the direction of rotation.

In other words, the present invention is characterized in that the permeability evaluation device comprises a first holding member that holds one side of the sample, a second holding member that holds the other side of the sample, a shearing means that moves the first holding member and the second holding member relatively to deform the sample and form a shear band in the sample, a water passing means that passes water through the shear band formed in the sample in a direction along the surface, and an evaluation means that detects the state of water passing by the water passing means and evaluates the permeability of the shear band.

In this way, the shear means applies deformation to the sample, causing a displacement within the sample and forming a shear band in the sample, the water passing means passes water through the shear band in a direction along the surface of the shear band, and the evaluation means evaluates the permeability (permeability rate) of the shear band. This makes it possible to pass water through the shear band and evaluate the permeability of the shear band of the sample in any shear state (process).

Incidentally, a non-patent document (Yohei Katayama, Hiroaki Kyo, Takashi Tsuchida, Hiroki Murakami, Study on the horizontal permeability coefficient of geomaterials after shear deformation using a hollow torsion testing machine, Proceedings of the Japan Society of Civil Engineers B3 (Marine Development) Vol. 71, No. 2, I_1143-I_1148, 2015.) discloses a technique in which a clay sample is consolidated and subjected to shear deformation, and then water is passed through the entire outer cylindrical surface of the hollow sample into the hollow portion to evaluate the permeability.

However, although the technology shown in the non-patent document is a technology for evaluating the state of water flow after shear deformation has been applied, water is passed through the entire outer cylindrical surface of the sample after shearing caused by torsional displacement. Therefore, while the technology shown in the non-patent document can infer the water permeability of the entire sample where shearing has occurred, water is not passed through the shear bands.

Therefore, it is obviously impossible to obtain the feature of the present invention according to claim 1, namely, the ability to evaluate the permeability of the shear band of a material in any shear state (process), from the technology shown in the non-patent literature.

The permeability evaluation device preferably includes a recess formed on the opposing surfaces of the first and second holding members for holding the sample, a pressurizing means for bringing the peripheral areas of the opposing surfaces of the first and second holding members, excluding the recess, into surface contact when the sample is held, and a separating means for separating the first and second holding members to form gaps in the peripheral areas before the sample is displaced by deforming the sample, and the water passing means is a means for passing water through the gaps formed in the peripheral areas to pass water through the shear bands of the sample.

By using the above-mentioned configuration, the pressure means is used to bring the opposing surfaces of the first and second holding members into contact with each other, excluding the recesses, and then the separating means is used to separate the first and second holding members to provide a gap, displacing the sample and allowing water to pass through the gap, thereby allowing water to pass through the shear band of the sample. Therefore, by passing water through a specified gap, water can pass through the vicinity of the shear surface, and the permeability of the shear band can be appropriately evaluated.

It is also preferable to provide a restraint maintaining means for maintaining the restrained state of the sample when the first holding member and the second holding member are separated.

By using the above-mentioned configuration, water can be passed through the vicinity of the shear band while the restraint maintenance means maintains the restrained state of the sample, and water can be passed accurately through the shear band without changing the state of the sample after shearing.

The shearing means is preferably a means for relatively rotating the first holding member and the second holding member around an axis that intersects with the holding surface of the sample to deform the sample.

By using the above-mentioned configuration, shearing is performed by displacement in the rotational direction, so there is no restriction on the amount of displacement. Therefore, shearing can be performed in any displacement state, and it is possible to evaluate the permeability in a sheared state where the material has been deformed to the state of residual strength after the peak strength, as well as to evaluate the change in permeability as the shearing progresses.

In addition, the first holding member holds the upper side of the sample, and the second holding member holds the lower side of the sample, and the first holding member and the second holding member each have an annular recess in the opposing portion, and the recess of the first holding member and the recess of the second holding member define a storage space for storing a cylindrical sample, and when the sample is stored in the storage space, a pressure means presses the first holding member against the second holding member in the axial direction of the cylindrical sample and brings the portions other than the recess into surface contact when the sample is stored in the storage space, and a pressure means presses the first holding member against the second holding member in the axial direction of the cylindrical sample and brings the portions other than the recess into surface contact when the sample is stored in the storage space. It is preferable to have a separation means for separating the first and second holding members at the portions other than the recessed portion from a state in which the outer portions are in surface contact with each other while restraining the sample to form a desired gap, a shearing means for rotating the second holding member to an arbitrary angle around the axis of the annular cylindrical sample to deform the sample, a water passing means for passing water through the gap between the outside and inside of the recessed portion to pass water through the shear band of the sample, and an evaluation means for detecting the state of water passing by the water passing means and evaluating the permeability of the shear band.

With the above-mentioned configuration, a circular cylindrical sample is placed in the storage space, and the first holding member is pressed against the second holding member in the axial direction of the circular cylindrical sample by the pressurizing means to bring the portions other than the recess into surface contact. With the sample restrained, the first holding member and the second holding member are separated from each other by the separating means at the portions other than the recess, forming a desired gap between the first holding member and the second holding member. The second holding member is rotated to an arbitrary angle around the axial center of the circular cylindrical sample by the shearing means to deform the sample. The water passing means passes water through the gap between the outside and inside of the recess, passing water through the shear band of the sample, and the evaluation means detects the state of water passing to evaluate the permeability of the shear band.

This reduces the constraints on the displacement of the sample by shearing through deformation in the rotational direction, and by passing water through a specified gap, water can be passed near the shear surface while maintaining the sample's restrained state. Therefore, the sample can be deformed and sheared to the state of residual strength after the peak strength, and by passing water through the shear band without changing the state of the sample after shearing, the condition of the water flowing through the shear band (water flow condition) can be accurately grasped. This makes it possible to evaluate the permeability of the shear band of a material in any shear state (process). In other words, it is possible to evaluate the permeability in a shear state displaced to the state of residual strength after the peak strength, and to evaluate the change in permeability as shearing progresses.

It is preferable that the apparatus further includes an up-down water passage means for passing water vertically across the shear bands of the sample by passing water from the annular recess of the second holding member toward the annular recess of the first holding member, or from the annular recess of the first holding member toward the annular recess of the second holding member, and that the evaluation means has a function of detecting the state of water passage by the up-down water passage means and evaluating the permeability across the shear bands.

The above-mentioned configuration makes it possible to evaluate the water permeability of the sample in both the vertical and vertical directions.

It is also preferable to provide a saturation means for saturating the sample (with water) by supplying water to the sample before the water is passed through the water passing means.

By using the above-mentioned configuration, it is possible to supply water to the sample before passing it through, saturating the sample (discharging air), and accurately evaluate the state of water passing through the sample without being affected by air bubbles, etc.

It is also preferable to shear the sample to deform it and pass water through it in a direction along the shear band, thereby evaluating the permeability of the area including the shear surface.

This makes it possible to evaluate the permeability of the shear bands of a material in any shear state (process). In other words, it is possible to evaluate the permeability of the shear bands that are generated by the displacement resulting from the application of shear force.

Another feature is that the deformation of the sample is in the rotational direction.

As a result, deformation is caused by shearing in the rotational direction, so there are no restrictions on the amount of displacement. This means that shearing can be performed in any deformation state, and by applying shear force to the sample to deform it to the state of residual strength after the peak strength, permeability can be evaluated, and changes in permeability as the shearing progresses can be evaluated.

The permeability evaluation device and permeability evaluation method of the present invention make it possible to evaluate the permeability of the shear band of a material in any shear state (process).

FIG. 1 is a conceptual diagram of a water permeability evaluation device according to the present invention. FIG. 1 is a conceptual diagram of a permeability evaluation device according to an embodiment of the present invention. 1 is an overall configuration diagram of a permeability evaluation device according to an embodiment of the present invention. 1 is an overall configuration diagram of a permeability evaluation device according to an embodiment of the present invention. FIG. 2 is an exploded perspective view of a main part of a water permeability evaluation device according to an embodiment of the present invention. 11 is an external view illustrating a configuration of a second holding portion. FIG. 4A and 4B are external views illustrating a configuration of a first holding member. 13 is a flowchart of a process for evaluating a water flow state. FIG. 2 is an explanatory diagram of the operation of the permeability evaluation device according to one embodiment of the present invention. FIG. 2 is an explanatory diagram of the operation of the permeability evaluation device according to one embodiment of the present invention. FIG. 4 is a cross-sectional view illustrating a water flow state. 1 is a graph showing the relationship between shear displacement and shear stress.

Figure 1 shows a conceptual diagram of the device to explain the permeability evaluation device of the present invention. Figure 1(a) shows the state before the sample is deformed (before displacement occurs in the sample), and Figure 1(b) shows the state after the sample is deformed (after displacement occurs in the sample).

As shown in the figure, the permeability evaluation device 1 of the present invention is equipped with a first holding member 3 that holds the upper side (one side) of a sample (low permeability material: for example, a material containing bentonite) 2, and a second holding member 4 that holds the lower side (the other side) of the sample 2. In other words, the first holding member 3 and the second holding member 4 are configured to restrain the sample from both sides in the direction of one central axis.

Then, a shearing means 6 is provided that moves the first holding member 3 and the second holding member 4 relative to each other to deform the sample 2 and apply a displacement to the sample 2, thereby forming a shear band 5 in the sample 2.

Furthermore, a water passage means 7 is provided for passing water (desired water passage/water passage) in a direction along the surface of the shear band 5 of the sample 2 (in a direction intersecting one central axis). The state of water passage by the water passage means 7 is detected by a water passage detection means 8. The state of water passage detected by the water passage detection means 8 is input to an evaluation means 9, which evaluates the permeability (percentage of permeability based on the permeability coefficient, etc.) in the direction along the surface of the shear band 5 of the sample 2.

This makes it possible to evaluate the permeability by passing water through the shear band 5 (by passing water under pressure), and by arbitrarily setting the state of displacement caused by the shear means 6, it becomes possible to evaluate the permeability of the shear band 5 of the sample 2 in any shear state (process: any shear process).

Figure 2 shows a conceptual diagram of the device to explain a permeability evaluation device according to one embodiment of the present invention.

As shown in the figure, the permeability evaluation device 11 is equipped with a first holding member 13 that holds the upper side (one side) of a circular sample (low permeability material: for example, a material containing bentonite) 12, and a second holding member 14 that holds the lower side (the other side) of the sample 12. Recesses 13a and 14a for holding the circular sample 12 are formed on the opposing surfaces of the first holding member 13 and the second holding member 14, respectively. A storage space is formed by the recesses 13a and 14a.

A pressure means 15 is provided to lower the first holding member 13 (downward) toward the second holding member 14. By lowering the first holding member 13 with the pressure means, the peripheral areas (surfaces 13b, 14b) of the opposing surfaces of the first holding member 13 and the second holding member 14, excluding the recesses 13a, 14a, are brought into surface contact.

A rotation drive means 16 is provided as a shear means for separating the first and second holding members 13 and 14 from a state in which the peripheral portions (surfaces 13b, 14b) of the first and second holding members 13 and 14 are in surface contact, and rotating the second holding member 14 to an arbitrary angle around the axis (central axis extending vertically in the figure) of the annular cylindrical sample 12 to cause a displacement in the sample 12. By rotating the second holding member 14 to an arbitrary angle using the rotation drive means 16, a displacement occurs in the sample 12, the sample 12 is sheared, and a shear band 17 parallel to the peripheral portions (surfaces 13b, 14b) of the first and second holding members 13 and 14 is formed in the sample 12.

Before the second holding member 14 is rotated to an arbitrary angle by the rotation drive means 16 to deform the sample 12 and displace it, a lifting means 18 is provided as a separation means for lifting a part of the first holding member 13 and separating the peripheral portions (surfaces 13b, 14b) of the first holding member 13 and the second holding member 14 while the sample 12 is restrained (restraint means described later). By lifting a part of the first holding member 13 by the lifting means 18, a predetermined gap S is formed between the peripheral portions (surfaces 13b, 14b) of the first holding member 13 and the second holding member 14.

A water passing means 19 is provided to pass water pressurized at a predetermined pressure through the gap in the peripheral area (surfaces 13b, 14b) between the first holding member 13 and the second holding member 14. In addition, a saturation means is provided to saturate the sample 12 with water by supplying water to the sample 12 before passing water through the water passing means 19.

That is, the second holding member 14 is provided with a water supply means 24 for supplying water for saturation, and the second holding member 14 is formed with a downstream flow path 25 connected to the water supply means 24 and communicating with the lower surface of the sample 12. The first holding member 13 is formed with an upstream flow path 26 communicating with the upper surface of the sample 12, and the upstream flow path 26 is connected to a discharge path 27. A valve 28 is provided on the discharge path 27.

Before water is passed through the water passing means 19, the valve 28 is opened to supply water from the water supply means 24. Water is supplied to the sample 12 from the downstream flow path 25, and the water is sent to the upstream flow path 26 together with the air that has accumulated in the sample 12. The sent water is discharged from the discharge path 27 together with air bubbles, and the air is discharged from the sample 12 and the sample 12 is saturated with water.

When the sample 12 is saturated, pressurized water is passed through the gap between the peripheral areas (surfaces 13b, 14b) of the first holding member 13 and the second holding member 14 by the water passing means 19, so that water pressurized at a predetermined pressure is passed through the shear band 17 of the sample 12.

A detection means 20 is provided for detecting the state of water flow (e.g., water flow rate) by the water flow means 19, and the state of water flow detected by the detection means 20 is input to the evaluation means 21. The evaluation means 21 evaluates the permeability of the shear band 17 (e.g., the rate of permeability based on the permeability coefficient) from the state of water flow along the shear band 17.

In the permeability evaluation device 11 described above, a cylindrical sample 12 is placed in the storage space formed by the recesses 13a and 14a of the first and second holding members 13 and 14, and the first holding member 13 is pressed against the second holding member 14 in the axial direction of the sample 12 by the pressure means 15, so that the peripheral areas (surfaces 13b, 14b) excluding the recesses 13a and 14a are in surface contact.

Before displacing the sample 12, the sample 12 is restrained (restraint means described below) and the first holding member 13 and the second holding member 14 are separated from each other by the lifting means 18 at the peripheral areas (surfaces 13b, 14b) excluding the recesses 13a, 14a, forming a gap S parallel to the shear band 17 at the peripheral areas (surfaces 13b, 14b) excluding the recesses 13a, 14a. The gap S can be formed to any desired dimension.

The second holding member 14 is rotated to an arbitrary angle by the rotation drive means 16 to deform the sample 12. By deforming the sample 12, a displacement occurs in the sample 12, and a shear band 17 is formed in the sample 12.

The sample 12 is saturated with water, and the water passing means 19 passes pressurized water at a predetermined pressure through the gap between the outside and inside of the recesses 13a and 14a of the first and second holding members 13 and 14. By passing water using the water passing means 19, the pressurized water is passed along the direction along the surface of the shear band 17 of the sample 12, and the state of water passing (water passing amount, etc.) is detected by the detection means 20.

The detection information from the detection means 20 is input to the evaluation means 21, and the permeability of the shear band 17 (e.g., the permeability coefficient) is evaluated by the evaluation means 21 based on the state of water flow along the shear band 17.

This allows shearing to be performed by deformation in the rotational direction, i.e., by generating a displacement in the rotational direction in the sample 12, the constraints on the amount of displacement are reduced, and pressurized water can be passed through a specified gap S, and water can be passed in the direction along the surface of the shear band 17 near the shear band 17 of the saturated sample 12, thereby allowing water to be passed near the shear band 17 while maintaining the restrained state of the sample 12.

Therefore, the sample 12 can be deformed and sheared to the state of residual strength after the peak strength, and by passing water through the shear band without changing the state of the sample 12 after shearing, the state of the water flowing through the shear band 17 (water flow state) can be accurately grasped. This makes it possible to evaluate the permeability of the shear band of the sample 12 in any shear state (process). In other words, it is possible to evaluate the permeability in a shear state that has caused displacement to the state of residual strength after the peak strength, and to evaluate the change in permeability as the shear progresses.

In other words, by deforming the sample 12 by shearing in the rotational direction, there is no restriction on the amount of shear (amount of displacement), and it is possible to evaluate the permeability in a state (shear state) in which the sample 12 is deformed to the residual strength state after the peak strength, and to evaluate the change in permeability as the shearing progresses.

The configuration of the permeability evaluation device 11 will be specifically explained with reference to Figures 3 to 7.

Figure 3 shows a schematic cross-sectional view of the entire permeability evaluation device 11, Figure 4 shows the first holding member 13 of the permeability evaluation device 11 rising, Figure 5 shows an exploded perspective view of the main components of the permeability evaluation device 11, Figure 6 shows the external view of the second holding member 14, and Figure 7 shows the external view of the first holding member 13.

As shown mainly in Figures 3 to 6, a rotation drive means 16 is provided on the lower frame 31 of the permeability evaluation device 11, and a drive base 32 is fixed to the drive part of the rotation drive means 16 (shear means). A base 33 constituting the second holding member 14 is attached to the drive base 32 to form a holding base 34.

A circular annular lower retaining portion 35 is formed on the upper surface of the base 33. The retaining base 34 is provided with a lower tube portion 36 arranged on the outside of the base 33, and a lower column portion 37 arranged on the inside of the base 33. The upper surfaces of the lower tube portion 36 and lower column portion 37 are higher than the height of the upper surface of the lower retaining portion 35, and the lower tube portion 36 and lower column portion 37 are formed at the same height. The upper surface of the lower retaining portion 35 forms the lower bottom surface of the circular annular recess 14a.

A horizontal water passage 38 (water passage means 19) is formed in the base 33, and pressurized water adjusted to a predetermined pressure is supplied to the horizontal water passage 38. A vertical water passage 39 is formed in the lower column section 37, the lower end of which is connected to the horizontal water passage 38 and the upper end of which opens to the upper surface of the lower column section 37. The pressurized water sent to the horizontal water passage 38 is sent from the vertical water passage 39 to the upper surface of the lower column section 37.

As shown mainly in Figures 3 to 5 and 7, a screw shaft 41 extending in the vertical direction is provided on the frame 31, and the screw shaft 41 is rotated in conjunction with the screw shaft 41. A nut member 42 is screwed onto the screw shaft 41, and a load frame 43 is attached to the nut member 42 (pressure hand). A lifting base 45 is provided below the load frame 43 via a load cell 44.

As shown in FIG. 4, the lift base 45 is provided with a pressing member 46 (first holding member 13). The pressing member 46 is composed of a notched cylindrical portion 47, which is formed by cutting out the central portion of a cylindrical body with a predetermined width in the radial direction, and a pressing ring 48 (first holding member 13) provided at the lower end of the notched cylindrical portion 47.

As shown in FIG. 5, an upper retaining portion 49 (first retaining member 13) is provided in the notched space 47a of the notched cylindrical portion 47 of the pressing member 46. The upper retaining portion 49 is composed of a plate-shaped upper frame material 51 arranged in the notched space 47a and a cylindrical upper column portion 52 provided on the underside of the upper frame material 51. Both ends of the upper frame material 51 are formed with flange portions 53 arranged outside the notched space 47a (radially outside the notched cylindrical portion 47).

The upper holding portion 49 is provided so as to be freely raised and lowered inside the notched space 47a relative to the notched tube portion 47. Meanwhile, an upper tube portion 54 is disposed on the upper surface of the lower tube portion 36, and a flange 55 that faces the flange portion 53 and can be fastened to the flange portion 53 is formed on the upper tube portion 54.

As shown in FIG. 4, the outer periphery of the lower cylinder 36 and the upper cylinder 54 is connected by a ring flange 58, which is connected to a drainage channel 59. A circumferential groove 58a is formed on the inside of the ring flange 58, which is connected to the drainage channel 59. In other words, water that is passed radially through the sample 12 is guided from the circumferential groove 58a to the drainage channel 59 and discharged.

As shown in FIG. 5, when the upper retaining portion 49 is pressed downward, the lower surface of the upper tube portion 54 comes into contact with the upper surface of the lower tube portion 36 (their metal surfaces come into contact), and the lower surface of the upper column portion 52 comes into contact with the upper surface of the lower column portion 37 (their metal surfaces come into contact).

As shown in FIG. 3, the rotation of the screw shaft 41 lowers the load frame 43 via the nut member 42, and the upper holding part 49, which is composed of the load cell 44, the lifting base 45, the pressing member 46, and the pressing ring 48, is pressed downward.

When the upper holding part 49 is pressed downward, the height position of the lower surface of the upper column part 52 is positioned lower than the height position of the pressure ring 48. This forms a circular recess 13a between the upper surface of the lower holding part 35 and the lower surface of the pressure ring 48. A storage space for storing the circular cylindrical sample 12 is defined by the recess 13a and the aforementioned circular recess 14a. The sample 12 is stored in the storage space with porous members 40 (members for passing water evenly over the surface of the sample 12) interposed above and below.

With gaps formed between the lower cylinder 36 and the upper cylinder 54, and on the contact surface between the lower column 37 and the upper column 52, pressurized water is passed through the horizontal water passage 38 and the vertical water passage 39, and the pressurized water is drained through the gaps (through the sample 12) to the drainage passage 59 of the ring flange 58. In other words, with the annular cylindrical sample 12 contained in the containment space, pressurized water is passed from the radial inside to the radial outside of the sample 12 (water passage means 19).

Meanwhile, a flow path 61 for venting air is formed through the upper column portion 52, the upper frame material 51, and the flange portion 53, and the flow path 61 is connected to the vertical water passage 39 and can be opened by a valve 62 (see FIG. 9 described later). In addition, although not shown, an upper and lower water passage means is provided from the second holding member 14 to the first holding member 13 (or vice versa) to pass a predetermined amount of pressurized water above and below the storage space (above and below the sample 12: crossing the shear band described later).

A position detection means 65 is provided to detect the lifting position of the lifting base 45 (first holding member 13). That is, a sensor rod 66 is provided on the frame 31, and a detection arm 67 is provided on the lifting base 45 to detect the position relative to the sensor rod 66. Based on the detection results of the load cell 44 and the position detection means 65, it is evaluated whether the lifting position of the first holding member 13 is being performed under the desired pressure.

A screw jack 71 is provided on the top of the frame 31, and a lifting plate 72 is provided that is raised and lowered by operating the screw jack 71. The lifting plate 72 can be raised and lowered independently of the load frame 43. The upper end of a connecting bar 73 is attached to the lifting plate 72, and the lower end of the connecting bar 73 is attached to the flange portion 53 of the upper holding portion 49. In the figure, 74 is a load detector.

With the upper holding part 49 pressed downward, the flange part 53 and the flange 55 of the upper cylinder part 54 are connected, and the lifting plate 72, which moves up and down by operating the screw jack 71, can be raised. As a result, with the pressure ring 48 of the pressing member 46 pressing the sample 12 against the lower holding part 35 (with the sample 12 restrained: restraining means), the upper holding part 49 (upper column part 52) and the upper cylinder part 54 can be raised to form a predetermined gap at the contact surface with the lower cylinder part 36 and the lower column part 37 (separation means).

A gap detection means (dial gauge) 75 is provided facing downward from the top of the frame 31, and the tip of the detection portion 76 of the dial gauge 75 is in contact with the upper surface of the lift plate 72. In other words, the dial gauge 75 detects the lift position of the lift plate 72 (upper holding portion 49, upper column portion 52, upper tube portion 54) relative to the frame 31, i.e., the gap between the contact surfaces of the upper column portion 52 and the lower column portion 37, and the upper tube portion 54 and the lower tube portion 36.

The sample 12 is accommodated in the accommodation space defined by the recess 13a of the first holding member 13 and the recess 14a of the second holding member 14, with the porous member 40 interposed therebetween. The first holding member 13 is pressed against the second holding member 14 in the axial direction of the annular cylindrical sample 12 by a pressure means, so that the areas other than the recesses 13a and 14a are in surface contact.

With the sample 12 restrained by the pressure ring 48 of the lift base 45, the lift plate 72 is raised, separating the first holding member 13 and the second holding member 14 in areas other than the recesses 13a and 14a, forming gaps at the contact surfaces between the upper column portion 52 and the lower column portion 37, and the upper tube portion 54 and the lower tube portion 36. The second holding member 14 is rotated by the rotation drive means 16 to an arbitrary angle around the axis of the annular cylindrical sample 12, deforming the sample 12. This causes the sample 12 to deform and shear, forming a shear band 17 on a horizontal surface.

After the sample 12 is saturated with water, pressurized water is supplied to the horizontal water channel 38 and the vertical water channel 39 (water passage means), and water is passed through the gaps from the inside to the outside of the recess 13a of the first holding member 13 and the recess 14a of the second holding member 14. This allows water to pass directly through the shear band 17 of the sample 12, and water is passed along the shear band 17. The state of the water drained from the drainage channel 59 (water flow rate, etc.) is detected by the detection means 20, and the information from the detection means 20 is sent to the evaluation means 21, and the permeability of the shear band 17 is evaluated.

Therefore, the shearing means applies deformation to the sample 12, the water passing means passes water in a direction along the surface of the shear band 17 of the sample 12, and the evaluation means 21 evaluates the permeability (permeability rate) of the pressurized water that has passed through the shear band 17. Therefore, the permeability can be evaluated by passing water through the shear band 17, making it possible to evaluate the permeability of the shear band 17 of the sample 12 in any shear state (process).

The operation of the water permeability evaluation device described above will be explained in more detail with reference to Figures 8 to 12.

Figure 8 is a flowchart showing the process of evaluating the water flow condition, Figure 9(a) is a side view of the state in which the sample 12 is set, Figure 9(b) is a side view of the state in which the width of the gap (upper and lower gaps) at the contact surfaces between the upper column section 52 and the lower column section 37 and the upper tube section 54 and the lower tube section 36 is set to zero, Figure 10(a) is a side view of the state in which the width between the upper and lower corners has been adjusted to a specified width, Figure 10(b) is a side view of the state in which pressurized water is flowing horizontally, Figure 11 is a plan view explaining the state of the flow of pressurized water, and Figure 12 is a graph showing the relationship between shear displacement and shear stress.

As shown in FIG. 8, in step S1, the sample 12 is placed and the device is prepared. That is, as shown in FIG. 9(a), the upper cylinder portion 54 is placed relative to the lower cylinder portion 36, and the lower surface of the upper cylinder portion 54 and the upper surface of the lower cylinder portion 36 are brought into surface contact (with zero gap) and the peripheries are connected to each other by the ring flange 58.

With the upper cylinder 54 fixed, the sample 12 is placed in the annular recess 13a (accommodation space) formed by the lower holding portion 35 and the lower cylinder 36. In this state, the loading frame 43 (see FIG. 3) is lowered, the pressing member 46 and the upper holding portion 49 are lowered, and the lower surface of the upper column portion 52 and the lower surface of the lower column portion 37 are brought into surface contact. This restrains the sample 12 in the accommodation space.

As shown in FIG. 9(b), the flange portion 53 of the upper holding portion 49 and the flange 55 of the upper cylinder portion 54 are fastened together with bolts to form a single unit. If necessary, the loading frame 43 (see FIG. 3) is lowered to consolidate the sample 12 in the storage space. The valve 62 of the flow path 61 is opened, and water is supplied to the horizontal water path 38, the vertical water path 39, and the flow path 61 by the water supplying means 19, and the air is removed from the horizontal water path 38, the vertical water path 39, and the flow path 61, and the flow paths are saturated with water and the valve 62 is closed.

As shown in FIG. 8, the gap is adjusted in step S2. That is, as shown in FIG. 10(a), the upper holding part 49 (upper column part 52) and the upper cylinder part 54 are raised while the pressing member 46 presses the sample 12 against the lower holding part 35 (restraining the sample 12). This forms a predetermined gap at the contact surface between the lower cylinder part 36 and the lower column part 37, as shown in FIG. 10(b).

As shown in Figure 8, in step S3, water is passed through the horizontal water passage 38 and the vertical water passage 39 (desired water passage) to supply water to the sample 12 (valve 30 shown in Figure 10 is opened). That is, with the sample restrained from both sides in the direction of one central axis by the first holding member 3 (see Figure 1) and the second holding member 4 (see Figure 1), water is passed through (desired water passage) in a direction intersecting one central axis (the direction in which water is discharged from the valve 30 shown in Figure 10).

At the same time (or separately from the water flowing through the horizontal water passage 38 and the vertical water passage 39), as shown in FIG. 10(a), the valve 28 is opened to supply water from the water supply means 24, water is supplied to the sample 12 through the downstream flow passage 25, and water is sent to the upstream flow passage 26 together with the air that has accumulated in the sample 12. As a result, water is sent from the bottom to the top of the sample 12, water is discharged from the discharge passage 27 together with air bubbles, air is discharged from the sample 12, and the sample 12 is saturated with water (saturation means).

As for the saturation means, if air can be discharged only by passing water through the horizontal water passage 38 and the vertical water passage 39, it is possible to omit the water supply means 24, the downstream flow path 25, the upstream flow path 26, the discharge path 27, and the valve 28. It is also possible to adopt a configuration in which water is passed through the horizontal water passage 38 and the vertical water passage 39, and the water that has passed through the sample 12 is drawn by negative pressure.

Returning to FIG. 8, in step S4, the driving base 32 is rotated and rotated around the axis of the annular cylindrical sample 12 to any desired angle (between an angle greater than 0 degrees and any angle greater than 360 degrees). For example, it is rotated to an angle that results in the residual strength state after the peak strength. In step S5, the driving base 32 is stopped. As a result, a (horizontal) shear band 17 that intersects with the axis is formed in the sample 12.

In step S6, water is passed through the horizontal water passage 38 and the vertical water passage 39 (pressurized water is supplied). That is, the valve 30 shown in FIG. 10 is opened, and pressurized water is supplied to the horizontal water passage 38 and the vertical water passage 39. As a result, as shown in FIG. 11(a), water is passed from the center of the sample 12 to the outside (from the inside to the outside gap of the recess 13a of the first holding member 13 and the recess 14a of the second holding member 14), and is drained from the drainage channel 59. Note that the direction of water passage can also be from the outside to the center of the sample 12 (from the outside to the inside gap of the recess 13a of the first holding member 13 and the recess 14a of the second holding member 14) as shown in FIG. 11(b) (water can also be passed from the drainage channel 59 side).

As shown in FIG. 10(b), pressurized water is passed along the surface of the shear band 17 of the sample 12, and the state of water flow (water flow rate, etc.) is detected by the detection means 20. The detection information of the detection means 20 is input to the evaluation means 21, and the permeability of the shear band 17 (e.g., the permeability coefficient) is evaluated by the evaluation means 21 from the state of water flow along the shear band 17.

Therefore, water can be passed directly through the shear band 17 of the sample 12, and water can be passed along the shear band 17. The state of the water passing through the drainage channel 59 (water flow rate, etc.) is detected by the detection means 20.

For example, when evaluating the permeability at residual strength, in step S7 it is determined whether the sample 12 is in a state of residual strength after the peak strength, and if it is determined that it is in a state of residual strength, the process ends and the information from the detection means 20 is sent to the evaluation means 21 for evaluation. If it is determined in step S7 that it is not in a state of residual strength, the process moves to step S4 and the rotation of the drive base 32 continues (for example, until it is in a state of residual strength).

As shown in Figure 12, the shear stress with respect to shear displacement changes from the state before shear (1), to the state before peak strength appears (2), to the state after peak strength appears (3), to the state of residual strength (4). In step S7, it is determined whether or not the state of residual strength (4) has been reached. Therefore, the permeability of the shear band 17 in the state of residual strength can be evaluated.

It is also possible to evaluate the permeability of the shear band 17 in any state, such as before the peak strength is reached (2) or after the peak strength is reached (3).

As described above, the displacement in the rotation direction causes shearing of the sample 12, reducing the constraint on the amount of displacement, and by passing pressurized water through a specified gap, water can be passed along the surface of the shear band 17 near the shear band 17, allowing water to be passed near the shear band 17 while maintaining the restrained state of the sample 12.

Therefore, the sample 12 can be deformed and sheared to a state of residual strength after the peak strength, causing a displacement in the sample 12, and water can be passed through the sheared surface of the shear band 17 without changing the state of the sample 12 after shearing, allowing the water permeability to be accurately evaluated by passing water through the shear band 17, making it possible to evaluate the permeability of the shear band 17 of the sample 12 in any shear state (process). In other words, the permeability of the shear band 17 caused by the displacement resulting from the application of a shear force to the sample 12 can be evaluated.

In other words, it is possible to evaluate the permeability in the shear state (process) in which the sample 12 is deformed to the residual strength state after the peak strength, and to evaluate the change in permeability as the shear progresses.

The permeability evaluation device 11 described above makes it possible to evaluate the permeability of the shear band 17 of the sample 12 in any shear state (process).

The present invention can be used in the industrial field of permeability evaluation devices and permeability evaluation methods.

LIST OF SYMBOLS 1, 11 Permeability evaluation device 2, 12 Sample 3, 13 First holding member 4, 14 Second holding member 5, 17 Shear band 6 Shear means 7 Water flow means 8 Water flow detection means 9 Evaluation means 15 Pressurizing means 16 Rotation driving means 18 Lifting means 19 Water flow means 20 Detection means 21 Evaluation means 24 Water supply means 25 Downstream flow path 26 Upstream flow path 27 Discharge path 28, 30, 62 Valve 31 Frame 32 Drive base 33 Base 34 Holding base 35 Lower holding portion 36 Lower cylinder portion 37 Lower column portion 38 Horizontal water passage 39 Longitudinal water passage 40 Porous member 41 Screw shaft 42 Nut member 43 Loading frame 44 Load cell 45 Lifting base 46 Pressing member 47 Notched cylinder portion 48 Pressing ring 49 Upper holding portion 51 Upper frame member 52 Upper column portion 53 Flange portion 54 Upper cylinder portion 55 Flange 58 Ring flange 59 Drainage channel 61 Flow path 65 Position detection means 66 Sensor rod 67 Detection arm 71 Screw jack 72 Lifting plate 73 Connecting bar 74 Load detector 75 Gap detection means (dial gauge)
76 Detection unit

Claims (4)

A first holding member that holds one surface of the sample;
a second holding member that holds the other surface side of the sample and restrains the sample between itself and the first holding member;
a shearing means for relatively moving the first holding member and the second holding member to deform the sample and form a shear band in the sample;
water passing means for passing a desired amount of water through the restrained sample from at least directions along the one surface and the other surface before shear bands are formed in the sample, and for passing water through the shear bands formed in the sample in a direction along the surface after shear bands are formed in the sample;
and an evaluation means for detecting a state of water flow by the water flow means and evaluating a water permeability state of the shear band. The sample is restrained from both sides of a central axis,
The desired amount of water is passed through the restrained sample from a direction intersecting one central axis.
After the desired water flow, the sample is displaced and sheared in a direction along the desired water flow so that a shear band is formed;
A method for evaluating permeability, comprising: passing water through a shear zone in a direction parallel to the shear zone to evaluate the permeability of a portion including a shear plane. The method for evaluating water permeability according to claim 2,
The method for evaluating permeability, wherein the direction intersecting the one central axis is a direction perpendicular to the one central axis. The method for evaluating water permeability according to claim 2 or 3,
The method for evaluating permeability, wherein the displacement for shearing the sample is in a rotational direction.

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