Displacement measuring device, and displacement measuring method

Abstract

To provide a displacement measuring device and a displacement measuring method that can directly measure displacement including a ground subsidence amount at a foundation bottom level.SOLUTION: A first measurement unit A includes a reference anchor 16 fixed to a back side of a first borehole 14, a first rod 20, and first displacement meters 18A to 18D fixed to a hole wall of the first borehole 14 around an extended end side of the first rod 20 and measuring an axial displacement of the first rod 20. A second measurement unit B includes a fixing portion 32 fixed to an entrance side of a second borehole 28, a second rod 34 extending from the fixing portion 32 towards a back side of the second borehole 28, and a second displacement meter 30 fixed to a hole wall of the second borehole 28 around an extended end side of the second rod 34 and measuring an axial displacement of the second rod 34. The first displacement meter 18A and the second displacement meter 30 are provided at positions equidistant from a predetermined reference plane.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a displacement measuring device and a displacement measuring method suitable for measuring the amount of ground subsidence and the like. [Background technology]

[0002] In recent years, the number of super-high-rise buildings exceeding 200 meters in height has been increasing in Japan, with some buildings exceeding 300 meters in height. Such buildings are heavy, and the supporting ground that supports the building can settle by several tens of millimeters to nearly 10 cm during construction, which has a significant impact on construction accuracy. Therefore, it is important to understand the amount of settlement of buildings during construction in order to ensure the quality of construction.

[0003] One method for measuring the amount of subsidence is to measure ground displacement using a layer-by-layer settlement meter (see, for example, Patent Document 1). Figure 7 shows a schematic diagram of a conventional layer-by-layer settlement meter. The layer-by-layer settlement meter 1 comprises a reference anchor unit (hereinafter sometimes referred to as the "anchor") 2, a subsidence detection element unit (hereinafter referred to as the "subsidence sensor") 3, a conduit 4 connecting them in series, and cables 5 for transmitting measurement data. It directly measures vertical displacement of the ground G by burying it in the ground through a pre-bored hole 6. The anchor 2 is installed at a sufficient depth (typically about 1 to 2 times the building width from the base level BL of the building foundation 7), and this is considered a fixed point. The subsidence sensor 3 measures the relative displacement with the conduit 4 using a built-in differential transformer displacement meter, thereby measuring the inter-story displacement between the anchor 2 or the subsidence sensor 3 below. The inter-story displacements are then accumulated from below to determine the absolute displacement of the ground G.

[0004] It is common to install subsidence sensors 3 at multiple depths, such as at the boundary between layers of rock, in addition to the depth directly below the foundation 7, to determine which layer of rock has the greatest effect on subsidence. The electrical conduits 4 between the subsidence sensors 3 and between the subsidence sensors 3 and the anchors 2 are protected by friction cut hoses 8, and the space between the friction cut hoses 8 and the hole wall is sealed off by filling with grout 9.

[0005] In addition to measuring the amount of ground subsidence when a building is constructed, layer-by-layer settlement meters generally also measure the amount of rebound (ground uplift) during the ground excavation stage before the building is constructed. Also, since the installation of a layer-by-layer settlement meter takes approximately 10 days, including pre-boring, performing it after the ground excavation is complete would have a significant impact on the building construction process. For these two reasons, layer-by-layer settlement meters are generally buried underground before excavation begins. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-114079 Summary of the Invention [Problem to be solved by the invention]

[0007] Incidentally, it is desirable to install the shallowest subsidence sensor 3 at a depth as close as possible to the foundation bottom level BL in order to accurately measure the subsidence behavior of the building. However, in order to prevent the subsidence sensor 3 from being damaged by heavy machinery during the excavation process of the ground G, the shallowest subsidence sensor 3 is generally installed at a position about 1.5 to 2 m deep from the foundation bottom level BL.

[0008] Figure 8 shows an example of measurement results using a layer-by-layer settlement meter. The vertical axis represents depth and the horizontal axis represents settlement. The graph shows the depth distribution of the subsidence of the supporting ground during the construction of a certain building. The depth of the base level (BL) of the building's foundation is TP-10m, but for the reasons mentioned above, the shallowest subsidence sensor 3 was installed at TP-12m. This graph shows that the amount of subsidence of the ground G increases the closer to the base level (BL), with the shallowest sensor 3 measuring approximately 40mm of settlement. It is believed that the subsidence at the base level (BL) of the foundation is even greater, but because it is not possible to install the subsidence sensor 3 directly at the base level (BL), it is not possible to directly measure the amount of subsidence at the base level (BL). Therefore, there was a need for technology that could directly measure the amount of subsidence at the base level (BL).

[0009] The present invention has been made in view of the above, and aims to provide a displacement measuring device and a displacement measuring method that can directly measure displacement including the amount of ground subsidence at the base level of the foundation. [Means for solving the problem]

[0010] In order to solve the above-mentioned problems and achieve the object, the displacement measuring device of the present invention is a device for measuring displacement of the ground, and comprises a first measurement unit provided in a first borehole formed in the ground, and a second measurement unit provided in a second borehole formed in the ground parallel to and spaced a predetermined distance from the first borehole, and the first measurement unit comprises a reference anchor fixed to the back side of the first borehole, a first rod extending from the reference anchor towards the entrance side of the first borehole, and a first borehole around the extending end side of the first rod. The second measurement unit includes a first displacement meter fixed to the borehole wall and measuring the axial displacement of the first rod, and the second measurement unit includes an anchoring portion fixed to the entrance side of the second borehole, a second rod extending from the anchoring portion toward the back side of the second borehole, and a second displacement meter fixed to the borehole wall around the extended end side of the second rod and measuring the axial displacement of the second rod, wherein the first displacement meter and the second displacement meter are located at positions equidistant from a predetermined reference plane, and the second displacement meter is installed in the ground with its top side and bottom side reversed compared to the first displacement meter.

[0011] Another displacement measuring device according to the present invention is characterized in that, in the above-mentioned invention, the first borehole and the second borehole are formed vertically in the ground, and the first measuring unit is a layer-by-layer settlement meter that measures the amount of subsidence of each layer in the ground by including a first rod extending from the first displacement meter toward the entrance side of the first borehole and a plurality of first displacement meter(s) spaced apart vertically, and the first displacement meter at the shallowest position and the second displacement meter of the second measuring unit are arranged at the same height.

[0012] Further, another displacement measuring device according to the present invention is characterized in that, in the above-mentioned invention, the anchoring portion is buried in a structure provided on the ground.

[0013] Furthermore, another displacement measuring device according to the present invention is characterized in that, in the above-mentioned invention, the anchoring portion includes a fixing plate fixed to the upper end of the second rod by a fixing bolt, and an anchoring bolt attached to the fixing plate, and is buried in a structure provided on the ground.

[0014] Further, a displacement measurement method according to the present invention is a method for measuring displacement of the ground, comprising the steps of: before excavating the ground, forming a first borehole in the ground and providing a first measurement unit in the first borehole; and after excavating the ground, forming a second borehole in the ground parallel to and spaced a predetermined distance from the first borehole and providing a second measurement unit in the second borehole, wherein the first measurement unit comprises a reference anchor fixed to the back side of the first borehole, a first rod extending from the reference anchor towards the entrance side of the first borehole, and a first rod. and a first displacement meter fixed to the wall of the first borehole around the extension end side of the first rod and measuring the axial displacement of the first rod, and the second measurement unit includes an anchoring part fixed to the entrance side of the second borehole, a second rod extending from the anchoring part towards the back side of the second borehole, and a second displacement meter fixed to the wall of the second borehole around the extension end side of the second rod and measuring the axial displacement of the second rod, wherein the first displacement meter and the second displacement meter are located at positions equidistant from a predetermined reference plane, and the second displacement meter is installed in the ground with the top side and the bottom side reversed relative to the first displacement meter.

[0015] Another displacement measurement method according to the present invention is characterized in that, in the above-mentioned invention, the first borehole and the second borehole are formed vertically in the ground, the first measurement unit includes a first rod extending from the first displacement meter toward the entrance side of the first borehole and a plurality of first displacement meter(s) spaced apart vertically, thereby forming a layer-by-layer settlement meter that measures the amount of subsidence of each layer in the ground, and the first displacement meter at the shallowest position and the second displacement meter of the second measurement unit are arranged at the same height.

[0016] Further, another displacement measuring method according to the present invention is characterized in that, in the above-mentioned invention, the anchoring portion is buried in a structure provided on the ground.

[0017] Furthermore, another displacement measurement method according to the present invention is characterized in that, in the above-mentioned invention, the anchoring portion includes a fixing plate fixed to the upper end of the second rod by a fixing bolt, and an anchoring bolt attached to the fixing plate, and is buried in a structure provided on the ground. [Effects of the Invention]

[0018] According to the displacement measuring device of the present invention, there is provided a device for measuring displacement of the ground, comprising a first measurement unit provided in a first borehole formed in the ground, and a second measurement unit provided in a second borehole formed in the ground parallel to and spaced apart from the first borehole at a predetermined distance, the first measurement unit comprising a reference anchor fixed to the inner side of the first borehole, a first rod extending from the reference anchor towards the entrance of the first borehole, and a first displacement measuring device fixed to the wall of the first borehole around the extending end of the first rod, for measuring displacement in the axial direction of the first rod. The second measurement unit includes a reference anchor and a displacement meter. The second measurement unit includes an anchorage fixed to the entrance side of the second borehole, a second rod extending from the anchorage toward the back of the second borehole, and a second displacement meter fixed to the wall of the second borehole around the extended end of the second rod and measuring the axial displacement of the second rod. The first and second displacement meter are located equidistant from a predetermined reference plane, and the second displacement meter is installed in the ground with its top side and bottom side reversed relative to the first displacement meter. This allows the first measurement unit to directly measure ground displacement between the reference anchor and the first displacement meter. Furthermore, the second measurement unit can directly measure ground displacement between the anchorage and the second displacement meter. This allows direct measurement of ground displacement from the reference anchor to the anchorage. If the anchorage is located at the bottom level of the foundation on the entrance side of the second borehole, it is possible to directly measure displacement, including the amount of ground subsidence at the bottom level of the foundation.

[0019] In addition, according to another displacement measuring device of the present invention, the first borehole and the second borehole are formed vertically in the ground, and the first measuring unit includes a first rod extending from the first displacement meter toward the entrance side of the first borehole and a plurality of first displacement meter(s) spaced vertically apart, thereby forming a layer-by-layer subsidence meter that measures the amount of subsidence of each layer in the ground, and since the first displacement meter at the shallowest position and the second displacement meter of the second measuring unit are arranged at the same height, it has the effect of being able to directly measure displacement including the amount of ground subsidence at the bottom level of the foundation.

[0020] In addition, according to another displacement measuring device of the present invention, the anchoring portion is buried in a structure provided on the ground, thereby achieving the effect of allowing the anchoring portion to be fixed easily and reliably.

[0021] In addition, according to another displacement measuring device of the present invention, the anchoring portion includes a fixing plate fixed to the upper end of the second rod by a fixing bolt and a fixing bolt attached to the fixing plate, and is buried in a structure provided on the ground, thereby achieving the effect of simplifying the anchoring portion.

[0022] Further, according to a displacement measurement method of the present invention, there is provided a method for measuring displacement of the ground, the method comprising the steps of: before excavating the ground, forming a first borehole in the ground and providing a first measurement unit in the first borehole; and after excavating the ground, forming a second borehole in the ground parallel to and spaced a predetermined distance from the first borehole and providing a second measurement unit in the second borehole, the first measurement unit comprising a reference anchor fixed to the back side of the first borehole, a first rod extending from the reference anchor towards the entrance side of the first borehole, and a hole in the first borehole around the extended end side of the first rod. The second measurement unit includes a first displacement meter fixed to the wall of the second borehole and measuring the axial displacement of the first rod. The second measurement unit includes an anchorage fixed to the entrance side of the second borehole, a second rod extending from the anchorage toward the back of the second borehole, and a second displacement meter fixed to the wall of the second borehole around the extended end of the second rod and measuring the axial displacement of the second rod. The first and second displacement meter are located equidistant from a predetermined reference plane, and the second displacement meter is installed in the ground with its top side and bottom side reversed relative to the first displacement meter. This allows the first measurement unit to directly measure ground displacement between the reference anchor and the first displacement meter. Furthermore, the second measurement unit can directly measure ground displacement between the anchorage and the second displacement meter. This allows direct measurement of ground displacement from the reference anchor to the anchorage. If the anchorage is located at the bottom level of the foundation on the entrance side of the second borehole, it is possible to directly measure displacement, including ground subsidence at the bottom level of the foundation.

[0023] In addition, according to another displacement measurement method of the present invention, the first borehole and the second borehole are formed vertically in the ground, and the first measurement unit includes a first rod extending from the first displacement meter toward the entrance side of the first borehole and a plurality of first displacement meter(s) spaced vertically apart, thereby forming a layer-by-layer settlement meter that measures the amount of subsidence of each layer in the ground, and since the first displacement meter at the shallowest position and the second displacement meter of the second measurement unit are arranged at the same height, it has the effect of being able to directly measure displacement including the amount of ground subsidence at the bottom level of the foundation.

[0024] In addition, according to another displacement measurement method of the present invention, the anchoring portion is buried in a structure provided on the ground, thereby achieving the effect of allowing the anchoring portion to be fixed easily and reliably.

[0025] In addition, according to another displacement measurement method of the present invention, the anchoring portion includes a fixing plate fixed to the upper end of the second rod by a fixing bolt and a fixing bolt attached to the fixing plate, and is buried in a structure provided on the ground, thereby achieving the effect of simplifying the anchoring portion. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a schematic vertical cross-sectional view showing an embodiment of a displacement measuring device and a displacement measuring method according to the present invention. [Figure 2] FIG. 2 is a schematic plan view showing an embodiment of the displacement measuring device according to the present invention. [Figure 3] FIG. 3 is a schematic vertical cross-sectional view showing an example of the fixing unit of the present embodiment. [Figure 4] FIG. 4 is a vertical cross-sectional view of a specific example of the third embodiment of the present invention. [Figure 5] FIG. 5 is a partial plan view of FIG. [Figure 6] FIG. 6 is a partially enlarged view of FIG. [Figure 7] FIG. 7 is a schematic diagram showing an example of a conventional layer-by-layer settlement meter. [Figure 8] FIG. 8 is a diagram showing an example of the measurement results obtained by a conventional layer-by-layer settlement meter. DETAILED DESCRIPTION OF THE INVENTION

[0027] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of a displacement measuring device and a displacement measuring method according to the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to these preferred embodiments.

[0028] As shown in Fig. 1, a displacement measuring device 10 according to an embodiment of the present invention is a device for measuring the amount of subsidence (displacement) of ground G on which a foundation 12 of a building is constructed, and is composed of two layer-specific settlement meters A and B installed adjacent to each other in the ground G. The foundation 12 is a structure constructed in the ground G by excavating the surface layer of the ground G.

[0029] The layer-specific settlement meter A is a first measurement unit installed in a first borehole 14 formed vertically in the ground G. A layer-specific settlement meter A can be a layer-specific settlement meter installed by a conventional method. Specifically, the layer-specific settlement meter A includes a reference anchor 16 fixed to the lower end (rear end) of the first borehole 14 at a depth of approximately 1 to 2 times the building width from the foundation bottom level BL, a shallowest subsidence sensor 18A installed at a depth of approximately 1.5 to 2 m from the foundation bottom level BL, multiple subsidence sensors 18B to 18D installed at multiple depths between the two, an electric conduit 20, and cables (not shown) that transmit measurement data from the subsidence sensors 18A to 18D to a recording device on the ground. The reference anchor 16 is considered a fixed point. The layer-specific settlement meter A is buried in the first borehole 14 formed underground before excavation of the ground G begins.

[0030] The electrical conduit 20 is a first rod fixed to the upper end of the reference anchor 16 and the upper ends of the subsidence sensors 18B-18D, and extends upward (toward the entrance of the first borehole 14) from each of them. The electrical conduit 20 may be a steel electrical conduit or the like. The electrical conduit 20 is installed inside the friction-cutting hose 22 to protect it from the surroundings. The friction-cutting hose 22 is a flexible, stretchable tube that vertically connects the reference anchor 16 and the lowest subsidence sensor 18D, each of the subsidence sensors 18B-18D, and the highest subsidence sensor 18B and the foundation bottom level BL. The space between the friction-cutting hose 22 and the borehole wall 14A is sealed by grout 24. For ease of explanation, the friction-cutting hose 22 is shown in dashed lines in the example of Figure 1.

[0031] The subsidence sensors 18A-18D are first displacement meters that measure the axial displacement of each electrical conduit 20, and in this embodiment are configured as differential transformer displacement meters. The subsidence sensors 18A-18D have a cylindrical housing, into which the extended ends of the electrical conduits 20 are inserted from below so as to be freely movable in the vertical direction. The extended ends of the electrical conduits 20 are configured with iron cores, and the relative positional difference between the iron core and the subsidence sensors 18A-18D can be measured. A Bourdon tube-type anchor 26 is provided on the outer periphery of the subsidence sensors 18A-18D. The subsidence sensors 18A-18D are fixed to the hole wall 14A of the first borehole 14 via the anchor 26. The anchor 26 can be expanded in diameter by applying hydraulic pressure from a pump or the like (not shown) to engage with the hole wall 14A, and can be contracted in diameter by reducing the hydraulic pressure to release the engagement.

[0032] The layer-by-layer settlement meter B is a second measurement unit installed in a second borehole 28 formed vertically in the ground G. The layer-by-layer settlement meter B comprises one subsidence sensor 30 installed at a depth of approximately 1.5 to 2 m from the foundation bottom level BL, an anchoring part 32 installed as a fixed point at the entrance side of the second borehole 28, an electric conduit 34 connecting them, and cables (not shown) for transmitting measurement data from the subsidence sensor 30 to a recording device on the ground. The anchoring part 32 is buried and fixed in the foundation 12 or level concrete (not shown). This allows the anchoring part 32 to be fixed simply and reliably. The layer-by-layer settlement meter B is buried in the second borehole 28 formed in the ground when excavation of the ground G is completed.

[0033] The electrical conduit 34 is a second rod fixed to the lower end of the anchorage 32, and extends downward from the anchorage 32 (toward the back of the second borehole 28). A steel electrical conduit or the like can be used for the electrical conduit 34. The electrical conduit 34 is installed inside the friction-cutting hose 36 and is protected from the surroundings. The friction-cutting hose 36 is a flexible and stretchable tube that vertically connects the foundation bottom level BL and the subsidence sensor 30. The space between the friction-cutting hose 36 and the borehole wall 28A is sealed by the filled grout 38. Note that in the example of Figure 1, the friction-cutting hose 36 is shown by a dashed line for ease of explanation.

[0034] The subsidence sensor 30 is a second displacement meter that measures the axial displacement of the electrical conduit 34, and is configured as a differential transformer displacement meter, similar to the subsidence sensor 18A of the layer-by-layer subsidence meter A. The subsidence sensor 30 is installed at the same depth (same height) as the subsidence sensor 18A of the topmost layer (shallowest depth) of the layer-by-layer subsidence meter A, but with its top and bottom (top and bottom sides) reversed. In this way, the subsidence sensors 30 (second displacement meter) and 18A (first displacement meter) are installed at equal distances (same depths) from the foundation bottom level BL (predetermined reference plane). Similar to the subsidence sensor 18A, the subsidence sensor 30 has a cylindrical housing, and the extending end of the electrical conduit 34 is inserted into the housing from above so as to be movable up and down. The extending end of the electrical conduit 34 is configured as an iron core, and the difference in relative position between this iron core and the subsidence sensor 30 can be measured. A Bourdon tube type anchor 40 similar to that of the subsidence sensor 18A is provided on the outer periphery of the subsidence sensor 30. The subsidence sensor 30 is fixed to the hole wall 28A of the second borehole 28 via the anchor 40.

[0035] The layer-by-layer settlement meter B directly measures the relative displacement occurring between the base level BL of the foundation or the level concrete (not shown) and the subsidence sensor 30 by fixing the upper end of the electrical conduit 34 to an anchoring portion 32 in the foundation 12 or level concrete (not shown). In this way, the layer-by-layer settlement meter B installed in a separate hole can measure the amount of ground subsidence between 1.5 and 2 m from the base level BL, which could not be measured using the conventional method of installing only the layer-by-layer settlement meter A. The second borehole 28 for installing the layer-by-layer settlement meter B is about 2 m long, so the time required for installation, including pre-boring, is about half a day to two days, and the impact on the building construction process and the cost of installation are relatively small compared to conventional methods.

[0036] According to this embodiment, the layer-by-layer settlement meter A can directly measure the amount of ground subsidence between the reference anchor 16 and the subsidence sensor 18A. Furthermore, the layer-by-layer settlement meter B can directly measure the amount of ground subsidence between the foundation bottom level BL and the subsidence sensor 30. This makes it possible to directly measure the amount of ground subsidence from the reference anchor 16 to the foundation bottom level BL. Therefore, it is possible to directly measure the amount of ground subsidence including the amount of ground subsidence at the foundation bottom level BL.

[0037] In this way, in this embodiment, by installing the layer-by-layer settlement meter B in a separate hole, it becomes possible to measure the maximum settlement at the foundation bottom level BL, which could not be measured by conventional methods, and the accuracy of settlement measurement required for construction management is improved, which leads to an improvement in the construction quality of the building.

[0038] In the above embodiment, it is desirable that the layer-specific settlement meters A and B are installed close to each other in plan view, with a separation distance of 2 m or more in consideration of construction accuracy, and that they be installed within the same span of the building. Figure 2 shows an example of the plan view of the layer-specific settlement meters A and B. As shown in this figure, in consideration of the subsidence characteristics of the ground G supporting the building foundation 12, the layer-specific settlement meter B may be installed offset from the layer-specific settlement meter A in the direction along the building outline line S. For example, when measuring at a building corner P1, the layer-specific settlement meter A is installed at the building corner P1, and the layer-specific settlement meter B is installed to the right and rear of the layer-specific settlement meter A along the building outline line S. Furthermore, when measuring at the front building end P2, the layer-specific settlement meter A is installed at the building end P2, and the layer-specific settlement meter B is installed on the left and right of the layer-specific settlement meter A along the building outline line S. Furthermore, when measuring at the left end P3 of the building, layer-by-layer settlement meter A is placed at the end P3 of the building, and layer-by-layer settlement meter B is placed in front and behind layer-by-layer settlement meter A along the building outline S. When measuring at the center P4 of the building, layer-by-layer settlement meter A is placed at the center P4 of the building, and layer-by-layer settlement meter B is placed in front, behind, left and right of layer-by-layer settlement meter A. If the building has a complex shape or the building weight is uneven, it is preferable to confirm the subsidence characteristics by conducting a separate numerical analysis before deciding the installation location of layer-by-layer settlement meter B.

[0039] Moreover, various configurations can be adopted for the structure of the anchoring part 32 of the layer-by-layer settlement meter B. Fig. 3 shows an example of the anchoring part 32.

[0040] As shown in FIG. 3(1), the anchoring portion 32A of the first embodiment is formed by fastening a reinforcing bar 42 to the head of the electrical conduit 34 and anchoring it in the foundation 12. The reinforcing bar 42 may be, for example, a deformed reinforcing bar SD295A, D22, which has the same diameter as the electrical conduit 34. The electrical conduit 34 and the reinforcing bar 42 may be fastened together using, for example, a U-bolt. The reinforcing bar is preferably fixed in a straight line in the foundation 12, with an anchoring length of 15d, where d is the diameter of the reinforcing bar.

[0041] As shown in FIG. 3(2), the anchoring portion 32B of the second embodiment is formed by fastening a reinforcing bar 44 to the head of the electric conduit 34, and then bending the reinforcing bar 44 to anchor it in the level concrete 12A below the foundation 12. This embodiment can be used, for example, when the foundation 12 of a building is thin and the anchoring portion 32B cannot be anchored in the foundation 12. The specifications for fastening the reinforcing bar 44 are the same as those of the first embodiment. The anchoring length is preferably 15d.

[0042] As shown in Figure 3 (3), the anchoring portion 32C of Example 3 is formed by attaching an anchoring steel plate 46 to the head of the electrical conduit 34 and anchoring it in the level concrete 12A. The material of the plate 46 may be, for example, SS400, and its dimensions may be approximately 10 to 20 cm in width, 10 to 20 cm in length, and 5 to 10 mm in thickness. Screws may be welded to the plate 46 so as to fit into the screw holes in the head of the electrical conduit 34, and then screwed into the electrical conduit 34 to secure it.

[0043] Next, a specific example of the third embodiment will be described. As shown in Figures 4 to 6, the fixing portion 32C of the specific example of this Example 3 is composed of three elements: a conduit fixing plate 50 (fixing plate) that is fixed to the head (upper end) of the conduit 34, an upper end fixing bolt 52 (fixing bolt) for fixing the conduit fixing plate 50 to the head of the conduit 34, and a fixing bolt 54 that is attached to the conduit fixing plate 50.

[0044] The conduit fixing plate 50 is a square steel plate measuring 300 mm in length, 300 mm in width, and 10 mm in thickness. Near the center of the conduit fixing plate 50, four screw holes 56 for attaching the top-end fixing bolts 52 are drilled in a grid pattern around the center of the plate in a plan view. In addition, four screw holes 58 for attaching the anchoring bolts 54 are drilled near the corners of the conduit fixing plate 50. The screw holes 58 are positioned inward, a distance L both vertically and horizontally from the side edges of the conduit fixing plate 50. L is assumed to be approximately 50 mm.

[0045] The conduit fixing plate 50 is placed directly on the flooring surface (foundation bottom level BL). When laying a crushed stone layer 60 (for example, about 60 mm thick) on the flooring surface as shown in Figure 4, the crushed stone layer 60 should not be laid around the conduit fixing plate 50.

[0046] The upper end fixing bolt 52 is an M6 bolt. The upper end fixing bolt 52 is passed through the threaded hole 56 from above the conduit fixing plate 50 and attached to the threaded hole 64 on the upper surface of a thick-walled cylindrical fixing part 62 that is fixed around the head of the conduit 34. The friction-cut hose 36 is arranged on the outside of the fixing part 62 and fastened and fixed with a hose fastener 36A. The space between the friction-cut hose 36 and the hole wall 28A is waterproofed by the filled grout 38. By connecting the upper end fixing bolt 52 to the head of the conduit 34, the vicinity of the center of the conduit fixing plate 50 can be attached to the conduit 34.

[0047] The anchoring bolt 54 is an M16 hex bolt (neck length: 80 mm). The anchoring bolt 54 is inserted into the screw hole 58 from above the electric conduit fixing plate 50, and the lower end 54A of the anchoring bolt 54 is threaded into the screw hole 58. The shank 54B and head 54C of the anchoring bolt 54, excluding the lower end 54A, are placed inside the level concrete 12A that is laid below the foundation 12 of the building. The thickness D of the level concrete 12A is assumed to be approximately 110 mm.

[0048] The electric conduit fixing plate 50 and the fixing bolts 54 are fixed inside the level concrete 12A. When the building sinks, the electric conduit fixing plate 50 is pushed down, and when the building rebounds (floats), the electric conduit fixing plate 50 is lifted up via the fixing bolts 54, causing the head of the layer-by-layer settlement meter B and the foundation 12 of the building to move as a unit, thereby measuring the vertical displacement of the foundation 12.

[0049] According to the specific example of Example 3, by combining the electric conduit fixing plate 50 and the fixing bolts 54, it is possible to reliably measure the displacement amount in both cases of the building settling and rebounding (rising). This makes it possible to measure the maximum amount of settlement at the foundation bottom level BL, which could not be measured using conventional methods, and improves the accuracy of measuring the amount of settlement required for construction management. This leads to an improvement in the construction quality of the building.

[0050] As explained above, the displacement measuring device according to the present invention is a device for measuring displacement of the ground, and comprises a first measurement unit provided in a first borehole formed in the ground, and a second measurement unit provided in a second borehole formed in the ground parallel to and spaced a predetermined distance from the first borehole, the first measurement unit comprising a reference anchor fixed to the back side of the first borehole, a first rod extending from the reference anchor towards the entrance side of the first borehole, and a first measurement unit fixed to the hole wall of the first borehole around the extending end side of the first rod, and for measuring displacement in the axial direction of the first rod. The second measurement unit includes a first displacement meter that measures the displacement of the reference anchor and the first displacement meter. The second measurement unit includes an anchorage fixed to the entrance side of the second borehole, a second rod extending from the anchorage toward the back of the second borehole, and a second displacement meter fixed to the wall of the second borehole around the extended end of the second rod and measuring the axial displacement of the second rod. The first and second displacement meter are installed equidistant from a predetermined reference plane, and the second displacement meter is installed in the ground with its top side and bottom side reversed to the first displacement meter. Therefore, the first measurement unit can directly measure the displacement of the ground between the reference anchor and the first displacement meter. Furthermore, the second measurement unit can directly measure the displacement of the ground between the anchorage and the second displacement meter. This allows direct measurement of the displacement of the ground from the reference anchor to the anchorage. If the anchorage is installed at the bottom level of the foundation on the entrance side of the second borehole, displacement including the amount of ground subsidence at the bottom level of the foundation can be directly measured.

[0051] In addition, according to another displacement measuring device of the present invention, the first borehole and the second borehole are formed vertically in the ground, and the first measuring unit includes a first rod extending from the first displacement meter toward the entrance side of the first borehole and a plurality of first displacement meter(s) spaced vertically apart, thereby forming a layer-by-layer settlement meter that measures the amount of subsidence of each layer in the ground, and since the first displacement meter at the shallowest position and the second displacement meter of the second measuring unit are arranged at the same height, it is possible to directly measure displacement including the amount of ground subsidence at the bottom level of the foundation.

[0052] Furthermore, according to another displacement measuring device of the present invention, the anchoring portion is buried in a structure provided on the ground, so that the anchoring portion can be fixed easily and reliably.

[0053] In addition, according to another displacement measuring device of the present invention, the anchoring portion includes a fixing plate fixed to the upper end of the second rod by a fixing bolt and a fixing bolt attached to the fixing plate, and is buried in a structure provided on the ground, so that the anchoring portion can be simplified.

[0054] Further, according to a displacement measurement method of the present invention, there is provided a method for measuring displacement of the ground, the method comprising the steps of: before excavating the ground, forming a first borehole in the ground and providing a first measurement unit in the first borehole; and after excavating the ground, forming a second borehole in the ground parallel to and spaced a predetermined distance from the first borehole and providing a second measurement unit in the second borehole, the first measurement unit comprising a reference anchor fixed to the back side of the first borehole, a first rod extending from the reference anchor towards the entrance side of the first borehole, and a hole in the first borehole around the extended end side of the first rod. The second measurement unit includes a first displacement meter fixed to the wall of the second borehole and measuring the axial displacement of the first rod. The second measurement unit includes an anchorage fixed to the entrance side of the second borehole, a second rod extending from the anchorage toward the back of the second borehole, and a second displacement meter fixed to the wall of the second borehole around the extended end of the second rod and measuring the axial displacement of the second rod. The first and second displacement meter are installed equidistant from a predetermined reference plane, and the second displacement meter is installed in the ground with its top side and bottom side reversed relative to the first displacement meter. This allows the first measurement unit to directly measure ground displacement between the reference anchor and the first displacement meter. The second measurement unit can also directly measure ground displacement between the anchorage and the second displacement meter. This allows direct measurement of ground displacement from the reference anchor to the anchorage. If the anchorage is installed at the bottom level of the foundation on the entrance side of the second borehole, displacement including ground subsidence at the bottom level of the foundation can be directly measured.

[0055] In addition, according to another displacement measurement method of the present invention, the first borehole and the second borehole are formed vertically in the ground, and the first measurement unit includes a first rod extending from the first displacement meter toward the entrance side of the first borehole and a plurality of first displacement meter(s) spaced vertically apart, thereby forming a layer-by-layer settlement meter that measures the amount of subsidence of each layer in the ground, and since the first displacement meter at the shallowest position and the second displacement meter of the second measurement unit are arranged at the same height, it is possible to directly measure displacement including the amount of ground subsidence at the bottom level of the foundation.

[0056] Furthermore, according to another displacement measuring method of the present invention, the anchoring portion is buried in a structure provided on the ground, so that the anchoring portion can be fixed simply and reliably.

[0057] In addition, according to another displacement measurement method of the present invention, the anchoring portion includes a fixing plate fixed to the upper end of the second rod by a fixing bolt and a fixing bolt attached to the fixing plate, and is buried in a structure provided on the ground, so that the anchoring portion can be simplified.

[0058] The Sustainable Development Goals (SDGs) are 17 international goals that were adopted at the United Nations Summit in September 2015. The displacement measurement device and displacement measurement method according to this embodiment can contribute to achieving one of the 17 SDGs, for example, goal 12: Responsible Consumption and Production. [Industrial Applicability]

[0059] As described above, the displacement measuring device and displacement measuring method according to the present invention are useful for measuring the amount of ground subsidence, and are particularly suitable for directly measuring displacement including the amount of ground subsidence at the base level of the foundation. [Explanation of symbols]

[0060] 10. Displacement measuring device 12 Foundation (Structure) 14 First Borehole 16 Reference Anchor 18A~18D Subsidence sensor 20 Electrical conduit (first rod) 22,36 Friction cut hose 24,38 Grout 26,40 Anchor 28 Second Borehole 30 Subsidence sensor (second displacement meter) 32 Fixing section 34 Electrical conduit (second rod) 50 Conduit fixing plate (fixing plate) 52 Upper end fixing bolt (fixing bolt) 54 Fixing bolt 56, 58, 64 screw holes 60 Crushed Stone Layer 62 Fixed part A Layer-specific settlement meter (first measurement unit) B Layer-specific settlement meter (second measurement unit) G Ground BL: Base level

Claims

1. A device for measuring ground displacement, A first measurement unit is provided in a first borehole formed in the ground, and a second measurement unit is provided in a second borehole formed in the ground parallel to the first borehole at a predetermined interval, The first measurement unit includes a reference anchor fixed to the back side of the first borehole, a first rod extending from the reference anchor toward the entrance side of the first borehole, and a first displacement meter fixed to the hole wall of the first borehole around the extending end side of the first rod and measuring the axial displacement of the first rod; The second measurement unit includes a fixing portion fixed to the entrance side of the second borehole, a second rod extending from the fixing portion toward the back side of the second borehole, and a second displacement meter fixed to the hole wall of the second borehole around the extending end side of the second rod and measuring the axial displacement of the second rod; A displacement measuring device characterized in that the first displacement meter and the second displacement meter are installed at positions equidistant from a predetermined reference plane, and the second displacement meter is installed in the ground with its top side and bottom side reversed relative to the first displacement meter.

2. The first borehole and the second borehole are formed vertically in the ground, the first measurement unit is a layer-by-layer settlement meter that measures the amount of subsidence of each layer in the ground by including a first rod extending from the first displacement meter toward the entrance side of the first borehole and a plurality of first displacement meter(s) spaced apart in the vertical direction, 2. The displacement measuring device according to claim 1, wherein the first displacement meter at the shallowest position and the second displacement meter of the second measuring unit are provided at the same height.

3. 3. The displacement measuring device according to claim 2, wherein the anchoring portion is embedded in a structure provided on the ground.

4. The displacement measuring device described in claim 3, characterized in that the anchoring portion includes a fixing plate fixed to the upper end of the second rod by a fixing bolt and an anchoring bolt attached to the fixing plate, and is buried in a structure provided on the ground.

5. A method for measuring ground displacement, comprising the steps of: before excavating the ground, forming a first borehole in the ground and providing a first measurement unit in the first borehole; and after excavating the ground, forming a second borehole in the ground parallel to and spaced a predetermined distance from the first borehole and providing a second measurement unit in the second borehole; The first measurement unit includes a reference anchor fixed to the back side of the first borehole, a first rod extending from the reference anchor toward the entrance side of the first borehole, and a first displacement meter fixed to the hole wall of the first borehole around the extending end side of the first rod and measuring the axial displacement of the first rod; The second measurement unit includes a fixing portion fixed to the entrance side of the second borehole, a second rod extending from the fixing portion toward the back side of the second borehole, and a second displacement meter fixed to the hole wall of the second borehole around the extending end side of the second rod and measuring the axial displacement of the second rod; A displacement measurement method characterized in that the first displacement meter and the second displacement meter are installed at positions equidistant from a predetermined reference plane, and the second displacement meter is installed in the ground with its top side and bottom side reversed relative to the first displacement meter.

6. The first borehole and the second borehole are formed vertically in the ground, the first measurement unit is a layer-by-layer settlement meter that measures the amount of subsidence of each layer in the ground by including a first rod extending from the first displacement meter toward the entrance side of the first borehole and a plurality of first displacement meter(s) spaced apart in the vertical direction, 6. The displacement measuring method according to claim 5, wherein the first displacement meter at the shallowest position and the second displacement meter of the second measuring unit are provided at the same height.

7. 7. The displacement measuring method according to claim 6, wherein the anchoring portion is embedded in a structure provided on the ground.

8. The displacement measurement method described in claim 7, characterized in that the anchoring portion includes a fixing plate fixed to the upper end of the second rod by a fixing bolt and a fixing bolt attached to the fixing plate, and is buried in a structure provided on the ground.

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