Shear soil tank

Abstract

To provide a shear soil tank for enabling transformation of simulated ground and transformation of an underground structure to be observed from a front side.SOLUTION: A shear soil tank 1 is used when a vibration table experiment is performed by forming simulated ground M in a frame where multiple shear frames are laminated. The shear soil tank includes: an outer shell part 2 having a bottom part 21 and side wall parts 22, 22A; a transparent board 3 placed in a rectangular opening part formed in the side wall part 22A; a plurality of shear frames 4 arranged to face a nearly U-shaped open side in a plane view with respect to the transparent board; slide support parts 6 for performing a support to allow a movement of the shear frames in an excitation direction K to be permitted with respect to the side wall parts; and a film part 5 for covering an inner peripheral side of the shear frames laminated on the bottom part.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a shear soil tank used when conducting a shaking table experiment by forming a simulated ground within a frame in which multiple shear frames are stacked. [Background technology]

[0002] In shaking table experiments of underground structures and foundation structures, shear soil tanks are used to reproduce deformation of the ground (see Patent Documents 1-3, etc.). A typical shear soil tank uses a square-shaped steel shear frame, which is stacked vertically with ball bearings between them to form the periphery of the simulated ground.

[0003] In a typical shear soil tank, a square-shaped shear frame with a thickness of about 0.5-2m (when the model scale is 1 / 50) is stacked. In order to reproduce the shear behavior of a thin soft layer or liquefied layer of about 1m, it is necessary to further divide the layer into smaller parts, so it is desirable to make the thickness of the shear frame as thin as possible. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2001-296202 A [Patent Document 2] JP 2018-31628 A [Patent Document 3] Patent Publication No. 2022-12607 Summary of the Invention [Problem to be solved by the invention]

[0005] By the way, when using a square-shaped shear frame, the entire circumference of the simulated ground is surrounded by the shear frame, so it is not possible to observe the deformation of the ground or the deformation of underground structures from the front. Visual observation of the shear deformation of the ground in a shaking table experiment can contribute to elucidating the phenomena related to the earthquake response of the ground and to the development of earthquake-resistant designs of pile foundations and underground structures.

[0006] Therefore, an object of the present invention is to provide a shear soil tank that makes it possible to observe deformation of a simulated ground and deformation of an underground structure from the front. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the shear soil tank of the present invention is a shear soil tank used when conducting a shaking table experiment by forming a simulated ground within a frame in which multiple shear frames are stacked, and is characterized by comprising an outer shell portion having a bottom and side wall portions, a transparent plate to be placed in a rectangular opening formed in one of the side wall portions, multiple shear frames arranged with their open sides, which are approximately C-shaped in a plan view, facing the transparent plate, a sliding support portion that supports the shear frames relative to the side wall portions so as to allow movement of the shear frames in the width direction of the transparent plate, and a membrane portion that covers the inner side of the shear frames stacked on the bottom portion.

[0008] Here, the outer shell portion has a lid portion covering the upper surface, and an upper retaining material can be interposed between the lower surface of the lid portion and the upper surface of the shear frame, which is the top layer, so as to allow movement of the shear frame in the width direction.

[0009] The shear frame may be configured such that a plurality of rectangular holes are drilled in the width direction as a longitudinal direction, and ball bearings or rollers having a diameter larger than the thickness of the shear frame are disposed in the holes. Furthermore, it is preferable that two types of shear frames are prepared, in which the holes are drilled so that the positions of the holes do not overlap in a projection direction in a plan view, and the two types of shear frames are stacked alternately. Effect of the Invention

[0010] In the shear soil tank of the present invention configured in this manner, a transparent plate is placed in a rectangular opening formed in one of the side wall portions of the outer shell, and a shear frame which is roughly U-shaped in plan view is positioned facing the transparent plate with its open side.

[0011] This makes it possible to observe the deformation of the simulated ground and the underground structure from the front through the transparent plate. If the shear deformation of the simulated ground on the surface in contact with the transparent plate can be observed with the naked eye, it will be possible to carry out research that will greatly contribute to elucidating phenomena related to the earthquake response of the ground and to the development of earthquake-resistant designs for pile foundations and underground structures. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is an explanatory diagram showing the configuration of the shear soil tank of the present embodiment in a plan view. [Diagram 2] FIG. 2 is an explanatory diagram showing the configuration of the shear soil tank of the present embodiment from a front view. [Diagram 3] FIG. 13 is a plan view illustrating shear frames arranged in odd-numbered stages. [Figure 4] FIG. 13 is a plan view illustrating shear frames arranged in even-numbered tiers. [Diagram 5] FIG. 2 is an explanatory diagram showing an enlarged view of the periphery of a hole in a shear frame in which a ball bearing is arranged. [Figure 6] 6 is an explanatory diagram showing the positional relationship between a shear frame and ball bearings as viewed in the direction of the arrow AA in FIG. 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 and 2 are explanatory diagrams showing the configuration of a shear soil tank 1 of this embodiment in plan view and front view.

[0014] The shear soil tank 1 of this embodiment is used to reproduce deformation of the ground in a shaking table experiment of the ground, an underground structure, or a foundation structure. In the shaking table experiment, by observing the shear deformation of the ground and reproducing the shear deformation of a thin soft layer or a liquefied layer of about 1 m, it becomes possible to contribute to elucidating the phenomenon related to the earthquake response of the ground and to the development of earthquake-resistant design of pile foundations, underground structures, etc.

[0015] As shown in Figures 1 and 2, the shear soil tank 1 of this embodiment includes an outer shell 2 formed in a rectangular parallelepiped shape, a transparent plate 3 arranged on the side of the outer shell 2, a plurality of shear frames 4 stacked in the inner space of the outer shell 2, a sliding support portion 6 that supports the stacked shear frames 4 from the sides, a membrane portion 5 that covers the inner sides of the shear frames 4 stacked on the bottom portion 21, and a lid portion 23 that covers the upper surface of the outer shell 2.

[0016] The simulated ground M, whose behavior is to be reproduced in the shaking table experiment, is formed within the framework of multiple shear frames 4 stacked in the space inside the outer shell 2. In other words, when the shear soil tank 1 is vibrated in the vibration direction K in the shaking table experiment, an external force acts on the simulated ground M from the inner periphery of the shear frames 4.

[0017] The outer shell 2 is mainly composed of a bottom 21 having a rectangular shape in a plan view, side walls 22, 22A erected on the four sides of the bottom 21, and a lid 23 closing the top of the box-shaped side walls 22, 22A. Here, the bottom 21 and the side walls 22, 22A are depicted as being integral in the figures, but Figures 1 and 2 are schematic diagrams and are not limited to this, and the configuration may be such that the lower end surfaces of the side walls 22, 22A are placed on the upper surface of the plate-shaped bottom 21 and assembled into a box shape.

[0018] Among the four side surfaces of the outer shell 2, the side wall 22 forming three surfaces that are U-shaped in plan view may be uniform wall surfaces without openings, and is not particularly limited. In contrast, the side wall 22A, which is one of the four side surfaces, has a rectangular opening formed in the center.

[0019] The opening of the side wall 22A is formed to a size that exposes one entire side of the rectangular parallelepiped simulated ground M formed inside the outer shell 2. A transparent plate 3 is placed in the opening. In Fig. 2, the positional relationship between the transparent plate 3 and the simulated ground M is shown by a two-dot chain line. The side of the simulated ground M that faces the transparent plate 3 is referred to as the front here.

[0020] As shown in Fig. 2, the rectangular area that forms the front of the simulated ground M is contained within the area of ​​a transparent plate 3 that serves as an observation window. A transparent material such as an acrylic plate or a glass plate is used for the transparent plate 3. This makes it possible to visually observe the state of the front of the simulated ground M at any time from outside the outer shell 2 through the transparent plate 3.

[0021] The front of the rectangular parallelepiped simulated ground M faces the transparent plate 3 and is in close contact with it, while the remaining three sides face the inner peripheral surface of the shear frame 4. As shown in Fig. 1, the shear frame 4 is formed in a roughly U-shape when viewed from above, and the three inner sides of the shear frame 4 and the transparent plate 3 surround the outer periphery of the simulated ground M, which is rectangular when viewed from above.

[0022] The shear frame 4, which is roughly U-shaped in plan view, is disposed with its open side facing the transparent plate 3. The shear frame 4 is manufactured by processing a metal plate such as a steel plate or an aluminum plate. The shear frame 4 is formed in a U-shape in plan view by a rectangular main body 4a and rectangular arm portions 4b that are perpendicular to the main body 4a at both ends. For example, the shear frame 4 can be manufactured by cutting out a U-shape in plan view from a single steel plate so that the main body 4a and the arm portions 4b at both ends are formed.

[0023] As shown in Fig. 1, the shear frame 4 is perforated with a plurality of rectangular holes 41 whose longitudinal direction is the width direction of the transparent plate 3. Here, the width direction of the transparent plate 3 and the vibration direction K (the left-right direction in Figs. 1 and 2) of the shaking table experiment are the same direction. In other words, the simulated ground M vibrates in the vibration direction K along the transparent plate 3.

[0024] In order not to impede the vibration in the excitation direction K, a plurality of sliding support parts 6 are arranged around the stacked shear frame 4. In short, the sliding support parts 6 support the shear frame 4 relative to the side wall part 22A on which the transparent plate 3 is arranged and the opposing side wall part 22 so as to allow movement of the transparent plate 3 in the width direction (excitation direction K).

[0025] 1, the sliding support parts 6 are disposed at the four corners of the shear frame 4 and near the center of the main body part 4a facing the transparent plate 3. The sliding support parts 6 are constituted by vertical rollers 61 having, for example, a cylindrical or cylindrical shape.

[0026] For example, rectangular parallelepiped cutouts are provided on the side wall portions 22A on both sides of the transparent plate 3 and on the surface of the side wall portion 22 opposite the side wall portion 22A that faces the shear frame 4, and multiple vertical rollers 61 are housed in the cutouts.

[0027] The vertical rollers 61 are formed to have the same height as the side walls 22A, 22 and are at least longer than the height of the stacked shear frames 4. Therefore, the movement of the shear frame 4 in the direction perpendicular to the vibration direction K is restricted by the sliding support parts 6.

[0028] On the other hand, the movement of the shear frame 4 in the vibration direction K is smoothly performed by, for example, rotating the vertical rollers 61 in contact with the shear frame 4. The shear frame 4 can be moved until it hits the side wall portion 22 perpendicular to the vibration direction K unless a separate stopper or the like is provided.

[0029] Since groundwater usually exists around the simulated ground M, water is injected between the arm 4b of the shear frame 4 and the side wall 22 perpendicular to the vibration direction K. Figure 2 shows a water surface W simulating groundwater. The simulated ground M can also be made to imitate a thin liquefied layer M1 or soft layer of about 1 m. Figure 2 shows the shear frames 4 stacked in about 250 layers.

[0030] The sides of the simulated ground M other than the front side facing the transparent plate 3 are covered with a membrane part 5. That is, the inner periphery side of the stacked shear frames 4 is covered with the membrane part 5. For the membrane part 5, a membrane sheet such as a rubber sheet can be used.

[0031] By interposing the membrane part 5 between the shear frame 4 and the simulated ground M, it is possible to prevent particles such as sand and soil that make up the simulated ground M from invading the shear frame 4. The membrane part 5 can be arranged, for example, on each of the three side surfaces of the inner periphery of the shear frame 4.

[0032] Since the membrane portion 5 is not required to have water-stopping properties, the water injected on the outer periphery of the shear frame 4 can move freely toward the simulated ground M. For example, water can move freely on the underside of the simulated ground M. Water can also move freely through the gaps between the membrane portions 5, 5 and the gap between the transparent plate 3 and the membrane portion 5.

[0033] As shown in Fig. 2, the shear frame 4 is stacked on the bottom part 21 and moves in the excitation direction K with the simulated ground M accommodated on the inner periphery side. To ensure smooth movement in the excitation direction K, an upper retaining member is interposed between the lower surface of the lid part 23 and the upper surface of the shear frame 4, which is the top layer, to allow the shear frame 4 to move in the excitation direction K.

[0034] The upper holding member is composed of, for example, a columnar or cylindrical horizontal roller 24. By interposing the horizontal roller 24 between the cover 23 and the top shear frame 4, the shear frame 4 can stably move in the vibration direction K without floating up.

[0035] The horizontal rollers 24 have a length similar to that of the arm portions 4b of the shear frame 4, and the horizontal rollers 24 in contact with the shear frame 4 rotate to smoothly move in the vibration direction K. Ball bearings 42 are also provided between the upper and lower stacked shear frames 4, 4 to ensure smooth movement between them.

[0036] 3 and 4 are examples of the shear frame 4, where Fig. 3 is a plan view of the shear frame 4A arranged in the odd-numbered stage, and Fig. 4 is a plan view of the shear frame 4B arranged in the even-numbered stage. The two types of shear frames 4A and 4B have the same configuration except for the position of the hole 41, so the common parts will be described using the symbols of the shear frame 4.

[0037] A plurality of rectangular holes 41 are drilled in the shear frames 4A and 4B, with the longitudinal direction being the vibration direction K, and ball bearings 42 are housed in the holes 41. The dimensions shown in Figures 3 and 4 are examples.

[0038] For example, in the shear frames 4A and 4B having a width of about 750 mm, a plurality of holes 41 are drilled at intervals of about 25 to 50 mm. The size of the simulated ground M formed within the shear frames 4A and 4B in a plan view is a rectangle with a short side of 200 mm and a long side of 500 mm.

[0039] The two types of shear frames 4A, 4B are used by stacking them alternately in the vertical direction, and the positions of the holes 41 of the shear frames 4A, 4B are set so as not to overlap in the projection direction in a plan view. Fig. 5 is an explanatory diagram showing an enlarged view of the periphery of the hole 41 of the shear frame 4B in which the ball bearing 42 is arranged.

[0040] As shown in this figure, the upper surface of the shear frame 4A, which is placed below, where no hole 41 is drilled, is located below the hole 41 drilled in the shear frame 4B, so the ball bearings 42 housed in the hole 41 will not fall out. The ball bearings 42 can roll between the lower and upper surfaces of the upper and lower shear frames 4A.

[0041] The short side of the rectangular hole 41 is set to be approximately equal to the diameter of the ball bearing 42, and the length of the long side can be set arbitrarily according to the number of ball bearings 42 to be accommodated. Fig. 5 shows a state in which ten ball bearings 42 are lined up in the hole 41 in the vibration direction K.

[0042] Fig. 6 is an explanatory diagram showing the positional relationship between the shear frames 4A, 4B and the ball bearings 42 as seen in the direction of the arrows AA in Fig. 5. Here, the thickness of the shear frames 4A, 4B can be set arbitrarily.

[0043] For example, when the shear frame 4 (4A, 4B) is manufactured using a steel plate of about 1.5 mm, if the model scale is set to 1 / 50 and steel balls of 2 mm diameter are used for the ball bearings 42, a layer thickness of about 10 cm in actual size can be reproduced.

[0044] If it is possible to control the behavior of the surrounding area of ​​the simulated ground M with a layer thickness of about 10-20 cm in actual terms, then even a thin liquefaction layer M1 of about 1 m can be divided into 5 to 10 parts, making it possible to reproduce its shear behavior with high accuracy.

[0045] Next, the operation of the shear soil tank 1 of this embodiment will be described. In the shear soil tank 1 of this embodiment configured as described above, a transparent plate 3 is placed in a rectangular opening formed in the side wall portion 22A of the outer shell portion 2, and a shear frame 4, which is approximately U-shaped in plan view, is placed toward the transparent plate 3 with its open side facing it.

[0046] Therefore, the deformation of the simulated ground M and the deformation of underground structures can be observed from the front (front side) through the transparent plate 3. If the shear deformation of the simulated ground M in front of the transparent plate 3 can be visually observed, it will be possible to carry out research that will greatly contribute to elucidating phenomena related to the earthquake response of the ground and to the development of earthquake-resistant designs of pile foundations, underground structures, and the like.

[0047] In particular, by using a shear frame 4 with a thickness of approximately 1.5 mm to 2.0 mm, it becomes possible to reproduce a sudden increase in local ground displacement in a thin soft layer of approximately 1 m in actual size and in the liquefaction layer M1, which has not been possible to reproduce experimentally until now.

[0048] Furthermore, if two types of shear frames 4A, 4B, each having holes 41 in which ball bearings 42 are arranged, are alternately stacked so that they do not overlap in the projection direction when viewed in a plane, the shear soil tank 1 can be constructed with a minimum number of types of parts.

[0049] Furthermore, if the topmost shear frame 4 is held down by the horizontal rollers 24 serving as upper holding members without restricting its movement in the vibration direction K, the stacked shear frames 4 can be stably vibrated inside the outer shell portion 2.

[0050] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes that do not deviate from the gist of the present invention are included in the present invention.

[0051] For example, in the above embodiment, a case has been described in which a layer thickness of about 10 cm is reproduced in actuality by combining a shear frame 4 having a thickness of 1.5 mm with a ball bearing 42 having a diameter of 2 mm, but the present invention is not limited to this. For example, a thickness that corresponds to a layer thickness of about 20 cm in actuality can be about 4 mm (assuming a 1 / 50 model scale. The thickness of the shear frame is about 3.5 mm). There is no upper limit that can be applied to the thickness of the shear frame, so even if it is thicker than 3.5 mm, it can be used in the shear soil tank of the present invention.

[0052] In the above embodiment, the outer shell 2 is formed in a rectangular parallelepiped shape, and the structure in which water simulating groundwater can be poured is described, but the present invention is not limited to this. For example, if the shear soil tank is used only when there is no groundwater, the configuration may be such that only the side wall 22A on which the transparent plate 3 is arranged and the side wall 22 facing it are parallel to each other, and the side wall 22 on the gable side perpendicular to them is omitted.

[0053] Furthermore, in the above embodiment, a configuration in which a plurality of ball bearings 42 are housed in the holes 41 of the shear frames 4, 4A, and 4B has been described, but the present invention is not limited to this. For example, cylindrical rollers may be placed in the holes of the shear frames instead of the ball bearings 42. In this case, for example, flat rollers in which a plurality of rollers are incorporated in a cage may be used. [Explanation of symbols]

[0054] 1: Shear soil tank 2: Outer shell 21: Bottom 22: Side wall 22A: Side wall part 23: Lid 24: Horizontal roller (upper support material) 3: Transparent plate 4, 4A, 4B: Shear frame 41: Hole 42: Ball bearings 5: Membrane part 6: Sliding support part K: Vibration direction (width direction) M: Simulated ground

Claims

1. A shear soil tank used when conducting a shaking table experiment by forming a simulated ground in a frame in which multiple shear frames are stacked, a shell having a bottom and a sidewall; a transparent plate disposed in a rectangular opening formed in one of the side walls; A plurality of shear frames arranged with an open side of a generally U-shape in a plan view facing the transparent plate; a sliding support portion that supports the shear frame relative to the side wall portion so as to allow the movement of the shear frame in the width direction of the transparent plate; A shear soil tank characterized by comprising a membrane portion covering the inner side of the shear frame stacked on top of the bottom.

2. The outer shell portion has a lid portion covering an upper surface, The shear soil tank according to claim 1, characterized in that an upper support material is interposed between the lower surface of the lid portion and the upper surface of the shear frame, which is the uppermost layer, so as to allow movement of the shear frame in the width direction.

3. The shear frame is perforated with a plurality of rectangular holes whose longitudinal direction is the width direction, 3. The shear soil tank according to claim 1 or 2, characterized in that a ball bearing or roller having a diameter larger than the thickness of the shear frame is disposed in the hole.

4. The shear soil tank described in claim 3, characterized in that two types of shear frames are prepared, each of which is perforated so that the positions of the holes do not overlap in the projection direction when viewed in a plane, and the two types of shear frames are stacked alternately.

5. 3. The shear soil tank according to claim 1 or 2, characterized in that the thickness of the shear frame is 10cm to 20cm in actual size.

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