Stress measuring device and its operating tools

Abstract

To provide a stress measurement device that can accurately measure stress.SOLUTION: A stress measurement device includes: a first housing that has a slender shape; at least one first sensor that is disposed on a side of a first end part in a longitudinal direction of the first housing, and includes a first strain gauge; at least one second sensor that is disposed on a side of a second end part opposite the first end part of the first housing, and includes a second strain gauge; and a second housing that is coupled to the first housing. The first sensor has: an elastic plate that extends in a direction parallel with the longitudinal direction of the first housing, and has the first strain gauge attached; a contact pin which is coupled to the elastic plate; and a sensor support member which extends in the same direction as the elastic plate, and to which the elastic plate is attached. The sensor support member has a rear end coupled to the first housing by a rotatable joint, and a tip end provided to be displaceable in a cross-section center direction of the first housing.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] An embodiment of the present invention relates to the structure of a stress measuring device using a stress release method and the structure of an operating tool for handling the stress measuring device. [Background technology]

[0002] Numerical analysis techniques are used when designing mountain tunnels. When performing numerical analysis, the initial stress state of the ground has a significant impact on the analysis results. Therefore, it is important to accurately grasp the initial stress state of the ground. The overcoring method is known as one method for measuring stress in the ground. In the overcoring method, a stress measurement device is inserted into a measurement hole (also called a "borehole") formed in the ground, and the initial stress state is evaluated by measuring the deformation of the measurement hole caused by drilling the outer periphery of the measurement hole.

[0003] A known example of an apparatus for measuring the deformation of a measurement hole is a stress measuring device that includes a long main body, a measurement ring member that protrudes from the main body, support ring members that are provided at the front and rear of the main body so as to sandwich the measurement ring member from the front and rear, a first intra-hole support member that is provided at the tip end of the main body, a second intra-hole support member that is provided at the base end of the main body, and a measuring unit that is provided between each intra-hole support member of the main body (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-066843 Summary of the Invention [Problem to be solved by the invention]

[0005] The stress measurement device disclosed in Patent Document 1 has a structure in which the measurement ring member for measuring the diameter displacement of the measurement hole protrudes significantly outward. However, if the measurement ring member protrudes significantly, the measurement ring member slides on the inner wall surface when the stress measurement device is inserted into the measurement hole, which causes a problem in that strain in the hole length direction is applied to the strain gauge even before measurement.

[0006] In view of the above problems, an object of one embodiment of the present invention is to provide a stress measuring device that can accurately measure stress. [Means for solving the problem]

[0007] A stress measuring device according to one embodiment of the present invention includes a first housing having an elongated shape, at least one first sensor including a first strain gauge and disposed on a first end side of the first housing in the longitudinal direction, at least one second sensor including a second strain gauge and disposed on a second end side of the first housing opposite the first end, and a second housing connected to the first housing. The first sensor includes an elastic plate extending in a direction parallel to the longitudinal direction of the first housing and having the first strain gauge attached thereto, contact pins connected to the elastic plate, and a sensor support member extending in the same direction as the elastic plate and to which the elastic plate is attached. The rear end of the sensor support member is connected to the first housing by a rotatable joint, and the front end is provided so as to be displaceable toward the center of the cross section of the first housing.

[0008] In one embodiment of the present invention, a gap may be provided between the tip portion of the sensor support member and the first housing, and an elastic body may be provided in the gap to apply a reaction force to displacement of the tip toward the center of the cross section.A stopper may be detachably provided on the first end side of the first housing to limit the range of outward displacement of the tip of the sensor support member.The tip of the sensor support member may have a tapered portion.

[0009] In one embodiment of the present invention, the sensor support member of the first sensor preferably has a slit extending in the longitudinal direction between its front and rear ends, and the contact pin is preferably provided so as to be displaceable in one axial direction along the slit. Preferably, the elastic plate of the first sensor has a curved portion, and the first strain gauge is provided in the curved portion.

[0010] In one embodiment of the present invention, the first sensor may be configured to measure displacement of the measurement hole in the diameter direction, and the second sensor may be configured to measure displacement of the measurement hole in the length direction. Preferably, the at least one first sensor comprises a plurality of first sensors, and the plurality of first sensors are arranged to surround the periphery of the first housing.

[0011] An operating tool for holding and handling a stress measuring device according to one embodiment of the present invention includes a cap having an opening that fits onto the tip of the sensor support member of a plurality of first sensors arranged in a first housing, and a gripping device that grips a gripping rod provided on the first housing of the stress measuring device, with the cap and gripping device arranged side by side so that the gripping rod is inserted through the opening and reaches the gripping device.

[0012] In one embodiment of the present invention, the portion of the cap that fits onto the tip of the sensor support member may have a tapered shape. The cap may have a handle that extends to the gripping tool. The operating tool may have a housing that surrounds the gripping tool, and the cap and the housing may be integrated. [Effects of the Invention]

[0013] According to one embodiment of the stress measuring device of the present invention, a sensor that measures the distortion in the hole length direction of the measurement hole is connected to the main body with a hinge, and the contact pin that contacts the inner wall surface is configured to sink during insertion, thereby preventing distortion when the main body is inserted into the measurement hole and improving measurement accuracy. [Brief explanation of the drawings]

[0014] [Figure 1] 1 shows the configuration of a stress measuring device according to one embodiment of the present invention. [Figure 2] 1A and 1B show the structure of a first sensor part of a stress measuring device according to an embodiment of the present invention, in which (A) is a cross-sectional structure thereof, (B) is a plan view of the first sensor, (C) is a cross-sectional structure corresponding to the section A1-A2, and (D) is a cross-sectional structure corresponding to the section B1-B2. [Figure 3] 2 shows the structure of a first sensor unit of a stress measuring device according to one embodiment of the present invention. [Figure 4] 1A and 1B show the structure of a second sensor unit of a stress measuring device according to an embodiment of the present invention, in which (A) shows the cross-sectional structure thereof, and (B) shows the cross-sectional structure corresponding to the section C1-C2. [Figure 5] 1 shows the structure of an operating tool for handling a stress measuring device according to one embodiment of the present invention, where (A) shows its side structure, (B) shows its front structure, (C) shows the side structure of the cap, (D) shows the side structure of the housing, and (E) shows the side structure of the gripping device. [Figure 6] 1A to 1C are diagrams illustrating the steps for inserting a stress measurement device according to an embodiment of the present invention into a measurement hole, in which (A) shows the state before insertion, (B) shows the state during insertion, and (C) shows the state after insertion. [Figure 7] 1 shows a state in which a stress measuring device according to an embodiment of the present invention is inserted into a measurement hole. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention can be implemented in many different forms, and should not be construed as being limited to the description of the embodiments exemplified below. For clarity of explanation, the drawings may show the length, width, height, thickness, shape, etc. of each part schematically compared to the actual form, but these are merely examples and do not limit the interpretation of the present invention. Furthermore, in this specification and each drawing, elements similar to those previously described with reference to the previous drawings may be designated by the same reference numerals (or reference numerals with A, B, a, b, etc. suffixed thereto), and detailed description thereof may be omitted as appropriate. Furthermore, the letters "first" and "second" attached to each element are convenient labels used to distinguish each element and have no further meaning unless otherwise specified.

[0016] FIG. 1 shows the configuration of a stress measurement device 100 according to one embodiment of the present invention. The stress measurement device 100 according to this embodiment can be used to evaluate initial stress using the overcoring method and can measure the displacement in the diameter and length directions of the measurement hole formed by boring due to stress release. The stress measurement device 100 includes a first sensor unit 1001 that measures the displacement in the length direction of the measurement hole and a second sensor unit 1002 that measures the displacement in the diameter direction of the measurement hole. The stress measurement device 100 has a cylindrical external shape, and the diameter and length directions of the measurement hole approximately coincide with the axial diameter and length directions of the stress measurement device 100, respectively. Therefore, the displacement in the diameter direction of the stress measurement device 100 corresponds to the displacement in the diameter direction of the measurement hole, and the displacement in the axial length direction of the stress measurement device 100 corresponds to the displacement in the length direction of the measurement hole. The stress measurement device 100 also includes a data logger 124 that collects data measured by the first sensor unit 1001 and the second sensor unit 1002.

[0017] As shown in FIG. 1, the stress measurement device 100 is composed of a first housing 102 and a second housing 104. The first housing 102 and the second housing 104 are elongated so that they can be inserted into the measurement hole, and are arranged in series in the longitudinal direction. The first housing 102 and the second housing 104 preferably have a cylindrical shape to stabilize their position within the measurement hole. The first housing 102 and the second housing 104 are separate housings and connected by a universal joint 122. The first housing 102 is provided with a first sensor unit 1001 and a second sensor unit 1002, and the second housing 104 houses a data logger 124, a battery 126, etc. The first sensor unit 1001 is provided with a first sensor 106, and the second sensor unit 1002 is provided with a second sensor 108.

[0018] The stress measurement device 100 is inserted into the measurement hole in the X1 direction shown in FIG. 1 and removed in the X2 direction. That is, the stress measurement device 100 is inserted into the measurement hole with the second housing 104 first, followed by the first housing 102. The first housing 102 includes a rod 1023, a first support member 1021 provided on the first end R1 side of the first housing 102, and a second support member 1022 provided on the second end L1 side. The rod 1023 is formed, for example, of a cylindrical or rod-shaped member extending linearly in the material axis direction. In addition, a gripping rod 105 protruding outward along the axial length direction of the stress measurement device 100 is provided on the first end R1 side of the first housing 102.

[0019] A first sensor 106 is attached to the first support member 1021, and a second sensor 108 is attached to the second support member 1022. The first sensor 106 has a structure in which a first strain gauge 110 is attached to a first elastic plate 114 and a contact pin 118 is connected to it. The second sensor 108 has a structure in which a second strain gauge 112 and a contact roller 120 are attached to a second elastic plate 116. The contact pin 118 and the contact roller 120 are arranged to protrude outside the first housing 102, and are structured to come into contact with the inner wall when the stress measuring device 100 is placed inside the measurement hole.

[0020] The second housing 104 houses a data logger 124, a battery 126, and the like. The data logger 124 is connected to the first strain gauge 110 and the second strain gauge 112 by wiring (not shown). The data logger 124 may also be connected to the first strain gauge 110 and the second strain gauge 112 wirelessly. The data logger 124 is supplied with power from the battery 126, so that it can collect data without the need for wired or wireless remote control. In other words, the stress measuring device 100 can operate independently and independently within the measurement hole.

[0021] Contact pins 130 are provided on the second housing 104. The contact pins 130 may include a first contact pin 1301 provided on the first end R2 side of the second housing 104 (the side connected to the first housing 102) and a second contact pin 1302 provided on the second end L2 opposite the first end R2. The first contact pins 1301 and the second contact pins 1302 are preferably provided at multiple locations along the outer periphery of the second housing 104. The first contact pins 1301 and the second contact pins 1302 are provided so as to protrude from the second housing 104. The first contact pins 1301 and the second contact pins 1302 are elastic, and the height at which they protrude from the second housing 104 can be adjusted as needed.

[0022] The first housing 102 has contact pins 118 and contact rollers 120 protruding outward, preventing the body of the first housing 102 from coming into direct contact with the inner wall surface of the measurement hole. The second housing 104 is provided with elastic contact pins 130 (first contact pin 1301, second contact pin 1302), which similarly prevents the body from coming into direct contact with the inner wall surface of the measurement hole. When the second housing 104 is installed in the measurement hole, the contact pins 130 (first contact pin 1301, second contact pin 1302) can be brought into contact with the inner wall surface at two points, allowing the stress measuring device 100 to be securely fixed. The first housing 102 and the second housing 104 are connected by a universal joint 122, and the first housing 102 is provided with a contact pin 118 and a contact roller 120, while the second housing 104 is provided with elastic contact pins 130 (first contact pin 1301, second contact pin 1302), so that each housing does not slide directly on the inner wall surface of the measurement hole.Since the first housing 102 and the second housing 104 are connected by the universal joint 122, any wobble that occurs in the hole diameter direction when the stress measuring device 100 is inserted into the measurement hole is absorbed, and the straightness of the stress measuring device 100 can be improved.

[0023] 1, the first housing 102 may have a different shape as long as it allows the first sensor unit 1001 and the second sensor unit 1102 to be arranged along the insertion direction X1 of the stress measurement device 100. For example, a member corresponding to the rod 1023 may have a shape that also serves as the functions of the first support member 1021 and the second support member 1022.

[0024] FIG. 2(A) shows a side view of the first sensor unit 1001. The first sensor unit 1001 is provided with a first sensor 106. FIG. 2(A) shows a part of the rod 1023 constituting the first housing 102, the first support member 1021, and the structure of the first sensor 106. FIG. 2(B) shows a plan view of the first sensor 106. FIG. 2(C) shows a cross-sectional structure corresponding to the A1-A2 section shown in FIG. 2(A), and FIG. 2(D) shows a cross-sectional structure corresponding to the B1-B2 structure.

[0025] 2(A), a first support member 1021 is attached to a rod 1023. The first support member 1021 has an outer diameter larger than that of the rod 1023, and a first sensor 106 is attached to the first support member 1021. The first sensor 106 includes a first strain gauge 110, a first elastic plate 114, and a contact pin 118. The first elastic plate 114 is a plate-like member extending in a direction parallel to the axial length of the rod 1023. The first elastic plate 114 has a curved portion 1141 between one end and the other end in the axial length direction.

[0026] The first sensor 106 is not directly attached to the first support member 1021, but is attached to the first support member 1021 via a sensor support member 132. One end of the first elastic plate 114 is fixed to the sensor support member 132, and a curved portion 1141 protrudes from the sensor support member 132. The other end of the first elastic plate 114 is attached to a fixture 1324. The fixture 1324 is a member slidably attached to the sensor support member 132, and functions as a spacer that ensures that the heights of one end and the other end of the first elastic plate 114 are horizontal. A contact pin 118 is attached to the fixture 1324. That is, the contact pin 118 is attached to the first elastic plate 114 via the fixture 1324. The fixing member 1324 has a function of connecting the contact pin 118 to the first elastic plate 114 and transmitting the displacement of the contact pin 118 to the first elastic plate 114 .

[0027] As shown in FIG. 2(B), a slit 1321 is formed in the sensor support member 132. A contact pin 118 is inserted into the slit 1321, and a fixing device 1324 is attached from below. At the location where the contact pin 118 is inserted into the slit 1321, the sensor support member 132 and the fixing device 1324 are sandwiched between fasteners (bolts) from above and below. The movement of the contact pin 118 is restricted by the slit 1321 and the fasteners (bolts). The contact pin 118 can be displaced in the longitudinal direction of the slit 1321, but cannot be displaced in the width direction of the slit 1321 or in the thickness direction of the sensor support member 132.

[0028] When the stress measurement device 100 is inserted into the measurement hole, the contact pin 118 comes into contact with the inner wall surface of the measurement hole. The tip of the contact pin 118 preferably has a tapered shape. When the first sensor 106 has the contact pin 118 with such a shape, it becomes possible to accurately measure the displacement of the measurement hole in the hole length direction.

[0029] The first sensor 106 has a rectangular shape in a plan view, and is disposed so that its longitudinal direction is parallel to the axial direction of the rod 1023. The contact pin 118 is provided so as to be displaceable in the direction parallel to the axial direction, so that the first sensor 106 can measure the displacement of the measurement hole in the hole length direction.

[0030] The first sensor 106 measures the displacement of the measurement hole in the hole length direction by the first elastic plate 114 being deformed in the axial direction as a result of the contact pin 118 being displaced in the axial direction, which in turn changes the resistance value of the first strain gauge 110. The data logger 124 electrically detects the change in electrical resistance of the first strain gauge 110 and records the change in strain over time.

[0031] The sensor support member 132 is attached to the first support member 1021 via a joint 134 (a hinge or a universal joint). The tip of the sensor support member 132 (the end opposite to the side where the joint 134 is attached) is arranged so that the inner surface thereof is spaced apart from the first support member 1021, and a stopper 138 having a protruding upper portion like a canopy is inserted through the tip. The stopper 138 stands in a direction parallel to the axial direction of the first support member 1021. An elastic body 136 is provided to be interposed in the gap between the sensor support member 132 and the first support member 1021. The elastic body 136 is, for example, a spring. The sensor support member 132 is restricted by the stopper 138 so that the tip does not open too far outward from the first housing 102, and is displaced inward so that the tip sinks toward the center of the first housing 102, with the joint 134 as a fulcrum, while receiving the reaction force of the elastic body 136.

[0032] The tip portion of the sensor support member 132 has a tapered portion 1322 formed into a tapered shape. As will be described later, an operating tool is used when inserting the stress measuring device 100 into the measurement hole. A cap is provided at the tip of the operating tool, which is fitted onto the tip of the sensor support member 132. When the cap is fitted onto the sensor support member 132, the tip sinks toward the center of the first housing 102, allowing the height of the contact pin 118 to be lowered, and the stress measuring device 100 can be inserted into the measurement hole without causing strain on the first strain gauge 110.

[0033] As shown in FIG. 2(C), a plurality of first sensors 106 are attached to surround the periphery of the first support member 1021. There is no limitation on the number of first sensors 106, and for example, as shown in FIG. 2(C), four first sensors 106 may be provided around the first support member 1021 at 90-degree angular intervals. FIG. 2(D) shows the cross-sectional shape of the tip of the sensor support member 132. At the tip, a stopper 138 is inserted into the sensor support member 132, and the movable range of the tip of the sensor support member 132 is restricted to the space between the stopper 138 and the floor surface formed by the first support member 1021. The sensor support member 132 is prevented from easily swinging due to vibration by the holding down of the stopper 138 and the repulsive force of the elastic body 136.

[0034] 3, when stopper 138 is removed, sensor support member 132 can be opened widely outward, using joint 134 as a fulcrum. Because first strain gauge 110 and first elastic plate 114 are provided on the underside of sensor support member 132, opening sensor support member 132 outward makes maintenance of these components easier.

[0035] First sensor 106 is provided so that contact pin 118 can contact the inner wall surface of the measurement hole. In first sensor unit 1001, a plurality of first sensors 106 are provided along the outer periphery of first housing 102, so that deformation of the measurement hole in the hole length direction can be accurately measured.

[0036] Fig. 4(A) shows a side view of the second sensor unit 1002, and Fig. 4(B) shows a cross-sectional structure corresponding to the C1-C2 line shown in Fig. 4(A). Fig. 4(A) shows the configuration of the first housing 102, including the rod 1023, the second support member 1022, and a portion of the first support member 1021. A universal joint 122 is attached to the second end L1 (one end of the rod 1023) of the first housing 102. The universal joint 122 is connected to the second housing 104.

[0037] As shown in FIG. 4A, a gap G1 is provided between the second end L1 of the first housing 102 and the adjacent end (first end R2 side) of the second housing 104. The first housing 102 and the second housing 104 are connected by a universal joint 122, allowing for bending at this connection. However, the range of bending is restricted by arranging the first housing 102 and the second housing 104 in close proximity to each other with the gap G1. The range of the gap G1 can be set appropriately, but is set to a distance of 0.5 mm to 2 mm, for example, 1 mm. As described above, by arranging the first housing 102 and the second housing 104 with the gap G1, it is possible to absorb vibrations that occur in the diameter direction of the measurement hole when the stress measurement device 100 is inserted into and removed from the measurement hole.

[0038] The second support member 1022 is provided on the second end L1 side of the first housing 102 (in other words, on the second end L1 side of the rod 1023). The second support member 1022 is attached to the rod 1023. Furthermore, the first support member 1021 is provided on the first end R1 side of the first housing 102. As shown in FIG. 4(A), the first housing 102 may have a structure in which the first support member 1021, the second support member 1022, and the rod 1023 are formed as individual parts and assembled together. Furthermore, although not shown, the first housing 102 may have a structure in which portions corresponding to the first support member 1021, the second support member 1022, and the rod 1023 are integrally molded.

[0039] The second elastic plate 116 is attached to the second support member 1022. The second elastic plate 116 is attached to the outer periphery of the second support member 1022. There is no limitation on the method of attaching the second elastic plate 116, and it may be fastened with a fastener such as a screw, for example. The second elastic plate 116 is formed of a plate-like member extending in a direction parallel to the axial length direction of the rod 1023. The second elastic plate 116 is attached such that one end is fixed to the second support member 1022 and the other end is spaced apart from the first housing 102. In other words, the second elastic plate 116 is attached to the second support member 1022 in a cantilevered state, with one end being a fixed end and the other end being a free end. The cantilevered second elastic plate 116 has a free end that is displaceable in the axial radial direction of the rod 1023.

[0040] A second strain gauge 112 is attached to the second support member 1022. The second strain gauge 112 is attached between the fixed end and the free end of the second elastic plate 116. The second strain gauge 112 is attached to at least one surface of the second elastic plate 116, and preferably to both surfaces. The second strain gauge 112 deforms and changes its resistance value as the free end of the second elastic plate 116 is displaced in the axial radial direction. The data logger 124 has the function of electrically detecting changes in the electrical resistance of the second strain gauge 112 and recording changes in strain over time.

[0041] A contact roller 120 is attached to the other end (free end) of the second elastic plate 116. The contact roller 120 is attached so that the rolling direction of the roller is parallel to the axial direction of the stress measurement device 100. As shown in FIGS. 4(A) and 4(B), the contact roller 120 attached to the second elastic plate 116 is provided so as to protrude from the second support member 1022. Because the contact roller 120 protrudes from the second support member 1022, the contact roller 120 comes into contact with the inner wall surface of the measurement hole when the stress measurement device 100 is inserted into the measurement hole. Even if the contact roller 120 comes into contact with the inner wall surface of the measurement hole, the second elastic plate 116 does not deform in the axial direction because almost no friction is generated by the rotation of the roller in response to displacement in the axial direction. On the other hand, the contact roller 120 is pressed against the inner wall surface of the measurement hole by the elastic force of the second elastic plate 116, and can therefore deform the second elastic plate 116 in accordance with the deformation of the measurement hole in the diameter direction.

[0042] As shown in FIG. 4(B), a plurality of second sensors 108, each comprising a second elastic plate 116 to which a second strain gauge 112 and a contact roller 120 are attached, are attached to surround the periphery of the second support member 1022. There is no limit to the number of second sensors 108; for example, as shown in FIG. 4(B), eight second sensors 108 may be provided around the rod 1023 at 45-degree angular intervals. The contact rollers 120 attached facing each direction are all arranged so as to contact the inner wall surface of the measurement hole. By providing the second sensors 108 facing each direction in this manner, the displacement of the measurement hole in the diameter direction can be accurately measured.

[0043] The first sensor 106 and the second sensor 108 have different shapes but use the same material. For example, a leaf spring is used for the first elastic plate 114 and the second elastic plate 116. The leaf spring may be made of a metal such as carbon steel, stainless steel, nickel steel, or a titanium alloy, or may be made of a non-metallic material such as rubber, plastic, or ceramic. Note that it is preferable to use a plate-shaped member for the second elastic plate 116 in order to attach a strain gauge, but if a wire-shaped strain gauge (wire strain gauge) is used, an elastic wire material such as piano wire may be used.

[0044] The first strain gauge 110 and the second strain gauge 112 are, for example, metal strain gauges in which metal resistors are formed in a zigzag layout on a thin insulator.

[0045] As described with reference to Figures 1, 2, and 4, the contact pin 118 of the first sensor 106 is arranged closer to the first end R1 of the first housing 102. The contact roller 120 of the second sensor 108 is arranged closer to the first end R1 of the first housing 102 than the fixed end of the second elastic plate 116. Such an arrangement of the contact pin 118 and the contact roller 120 allows the stress measuring device 100 to be smoothly inserted into the measurement hole. Furthermore, when the stress measuring device 100 is inserted into the measurement hole, it is possible to prevent stress (strain) in the axial direction from being applied to the first sensor 106 and the second sensor 108, allowing the initial stress of the natural ground to be measured accurately.

[0046] 5(A) and 5(B) show an example of the structure of an operating tool 200 used when inserting the stress measuring device 100 into a measurement hole. Fig. 5(A) shows the side structure of the operating tool 200, and Fig. 5(B) shows its front structure.

[0047] The operating tool 200 includes a first cap 202, a second cap 203, a gripping device 204, and a housing 206. The gripping device 204 is stored in the housing 206, and the first cap 202 and the second cap 203 are attached to the housing 206 so as to sandwich the gripping device 204. Of the two caps attached to the housing 206, the first cap 202 is attached to the side of the stress measurement device 100, and the second cap 203 is attached to the opposite side. The operating tool 200 is used to grip and operate the gripping rod 105 attached to the side of the first end R1 of the first housing 102 when inserting the stress measurement device 100 into the measurement hole.

[0048] As shown in FIG. 5(C), the first cap 202 has a first opening 2021. The first cap 202 has a first opening 2021 whose diameter decreases from the outside toward the housing 206 (inside). That is, the inner surface of the first opening 2021 has a first tapered surface 2022 that fits with the tapered portion 1322 provided at the tip of the sensor support member 132. When the stress measurement device 100 is inserted into the measurement hole, the gripping rod 105 is inserted into the first cap 202, and the tapered portion 1322 of the sensor support member 132 fits into the inner surface of the first opening 2021. The first opening 2021, which has the first tapered surface 2022 of the first cap 202, fits into the tapered portion 1322 at the tip of the sensor support member 132, allowing the operating tool 200 to be connected to the stress measurement device 100. The second cap 203 has a second opening 2031. The second opening 2031 has a second tapered surface 2032 whose hole diameter decreases from the housing 206 side (inside) to the outside. When the stress measurement device 100 is inserted into the measurement hole, the gripping rod 105 is inserted into the second cap 203. At this time, the second opening 2031 has the second tapered surface 2032, so that the gripping rod 105 can be guided to the center of the second opening 2031. In other words, the operating tool 200 can grasp the axial center of the gripping rod 105. As shown in FIG. 5(D), the housing 206 has, for example, a cylindrical shape and has a structure in which the first cap 202 is attached from one side and the second cap 203 is attached from the other side.

[0049] As shown in FIG. 5(E), the gripping device 204 has a main body 2041 having a hollow structure and a gripping portion 2042 provided in the hollow portion of the main body 2041. The gripping portion 2042 is formed of an elastic material and is configured, for example, by controlling air pressure to control the expansion of the gripping portion 2042, thereby changing the cross-sectional area of ​​the hollow portion. The gripping portion 2042 is formed of, for example, a rubber material. The gripping device 204 is fixed inside the housing 206. The gripping device 204 can grip and release the gripping rod 105 attached to the stress measuring device 100 by controlling the state of the gripping portion 2042. The operating tool 200 has a structure in which the first cap 202 and the second cap 203 are arranged on either side of the gripping device 204, so that the gripping rod 105 can be grasped on the central axis of the stress measuring device 100 while holding down the tip of the first sensor 106 (i.e., the tip of the sensor support member 132).

[0050] The configuration of the operating tool 200 shown in FIGS. 5(A) to 5(E) is an example, and the operating tool 200 is not limited to the illustrated structure.

[0051] 6(A) to 6(C) show the change in state of the first sensor unit 1001 when the stress measurement device 100 is inserted into the measurement hole 300. FIG. 6(A) shows the state before the operation tool 200 is attached to the tip of the sensor support member 132. As shown in FIG. 6(A), before the operation tool 200 is attached, the first sensor 106 is placed horizontally on the first housing 102. On the operation tool 200 side, the gripping portion 2042 of the gripping device 204 is in an open state, and when the stress measurement device 100 is inserted into the measurement hole 300, the operation tool 200 is inserted into the gripping rod 105.

[0052] 6(B) shows the stage in which the operating tool 200 is attached to the sensor support member 132 of the first housing 102 and the stress measuring device 100 is inserted into the measurement hole 300. As described with reference to FIGS. 2(A) to 2(D), the first housing 102 is provided with a plurality of first sensors 106 along the outer periphery of the first support member 1021, and the tip of the sensor support member 132 is arranged so as to protrude from the first end R1. The first cap 202 of the operating tool 200 has a first opening 2021 having a first tapered surface 2022, and the operating tool 200 is attached so that this first tapered surface 2022 and the tapered portion 1322 at the tip of the sensor support member 132 fit together.

[0053] By attaching the first cap 202 so that it fits into the tapered portion 1322 at the tip of the sensor support member 132, the tip of the sensor support member 132 sinks, and the contact pin 118 does not come into contact with the inner wall surface of the measurement hole 300. This allows the stress measuring device 100 to be inserted into the measurement hole 300 without the contact pin 118 sliding on the inner wall surface. As a result, it is possible to prevent distortion of the first strain gauge 110 in the hole length direction of the measurement hole 300 (depth direction of the measurement hole 300).

[0054] After the operating tool 200 is attached to the first housing 102 in this manner, the gripping device 204 grips the gripping rod 105. For example, an air supply tube (not shown) is connected to the main body 2041 of the gripping device 204, and air can be sent to the gripping portion 2042 via the tube. The air pressure is increased to inflate the gripping portion 2042, thereby gripping the gripping rod 105. The operating tool 200 is connected to an insertion rod (not shown), and the stress measuring device 100 is inserted by pushing the insertion rod into the measurement hole 300. The operating tool 200 is attached to the first housing 102 with the first cap 202 fitted onto the tip of the sensor support member 132 and the gripping device 204 gripping the gripping rod 105. Therefore, the stress measuring device 100 can be inserted into the measurement hole 300 in a stable state without coming off.

[0055] FIG. 6(C) shows the stage where the stress measurement device 100 is placed at the measurement position of the measurement hole 300. Once the stress measurement device 100 is placed at the measurement position of the measurement hole 300, the operation tool 200 is removed. The operation tool 200 can release the gripping rod 105 by opening the gripping portion 2042 of the gripping device 204. For example, the gripping rod 105 can be released by releasing the air from the gripping portion 2042 (or reducing the air pressure). The operation tool 200 can be removed from the first housing 102 by pulling out the insertion rod. By separating the operation tool 200 from the stress measurement device 100, the tip of the sensor support member 132 is lifted by the action of the elastic body 136, allowing the contact pin 118 to contact the inner wall of the measurement hole 300.

[0056] It is preferable to provide an uneven portion or roughen the surface of one or both of the first tapered surface 2022 of the first cap 202 of the operating tool 200 and the tapered portion 1322 at the tip of the sensor support member 132. As a result, friction occurs between the first tapered surface 2022 and the tip of the sensor support member 132, which makes it possible to prevent the stress measurement device 100 from coming off the operating tool 200 when the stress measurement device 100 is inserted into the measurement hole 300.

[0057] 7 shows a state in which the stress measurement device 100 is inserted into the measurement hole 300 and the first cap 202 is removed. With the first cap 202 removed, the contact pin 118 of the first sensor unit 1001 comes into contact with the inner wall surface of the measurement hole 300. When the stress measurement device 100 is placed in the measurement position and the first cap 202 is removed, the contact pin 118 of the first sensor 106 is pushed up by the reaction force of the elastic body 136 and comes into contact with the inner wall of the measurement hole 300. Specifically, the tip of the sensor support member 132 is displaced so as to open outward with the position of the joint 134 as the center of rotation, and the contact pin 118 comes into contact with the inner wall surface of the measurement hole 300. As explained with reference to Figures 2(A) and 2(B), the contact pin 118 is attached to the sensor support member 132 and is capable of displacement only in the direction of the slit 1321, so that the first sensor 106 can measure displacement in the hole length direction without being affected by displacement in the hole diameter direction of the measurement hole 300.

[0058] 6(A) to 6(C), the stress measurement device 100 is inserted into the measurement hole 300 with the second housing 104 at the front, followed by the first housing 102. The second housing 104 has a built-in data logger 124 and battery 126 and has a stable center of gravity, so even if the first housing 102 is inserted into the measurement hole 300 while being pushed using the operating tool 200, the stress measurement device 100 can be inserted without shaking.

[0059] In the first sensor 106, as described above, the position of the contact pin 118 can be lowered by the first cap 202, so that the contact pin 118 does not rub against the inner wall surface when the stress measuring device 100 is inserted into the measurement hole 300, thereby preventing distortion of the first strain gauge 110 in the hole length direction of the measurement hole 300.

[0060] On the second sensor 108 side, the contact roller 120 is pushed inward, displacing from its initial position to its measurement position. Because the second elastic plate 116 is elastic, it bends as the contact roller 120 displaces. At this time, a gap is preferably left between the contact roller 120 and the rod 1023 to allow the contact roller 120 to displace further inward. Since the contact roller 120 contacts the inner wall surface of the measurement hole 300, the rotation of the contact roller 120 can dissipate any displacement in the hole length direction when the stress measurement device 100 is inserted into the measurement hole 300 and when the device is positioned at the measurement position. This prevents the displacement in the hole length direction from acting on the second elastic plate 116. This configuration allows the second sensor 108 to measure the displacement of the measurement hole 300 in the hole length direction without being affected by distortion in the hole length direction that occurs during insertion. Furthermore, the second sensor 108 can accurately measure positive and negative displacements in the diameter direction of the measurement hole 300 without being affected by displacements occurring in the hole length direction.

[0061] A plurality of contact pins 118 of first sensor 106 and a plurality of contact rollers 120 of second sensor 108 are arranged around the periphery of first housing 102 and abut against the inner wall surface of measurement hole 300 with elastic force, thereby positioning first housing 102 at the center of measurement hole 300 (centered). A plurality of elastic contact pins 130 (first contact pin 1301, second contact pin 1302) are arranged around the periphery of second housing 104. These contact pins 130 abut against the inner wall surface of measurement hole 300 with elastic force, thereby positioning second housing 104 at the center of measurement hole 300 (centered). In this way, first housing 102 and second housing 104 are positioned at the center of measurement hole 300 without being biased in one direction, so that stress measuring device 100 can be inserted stably and smoothly into measurement hole 300. Furthermore, when inserting and removing the stress measurement device 100 into and from the measurement hole 300, the central axis of the measurement hole 300 and the central axis of the stress measurement device 100 can be aligned, thereby improving measurement accuracy.

[0062] The stress measuring device 100 of this embodiment can measure the initial stress of the natural ground using the overcoring method. The stress measuring device of this embodiment can measure the initial stress of the natural ground using the hole diameter change method. The stress measuring device 100 is inserted into a measurement hole 300 drilled into the natural ground, and then the outer periphery of the measurement hole is drilled to release the stress, and the stress measuring device 100 measures the displacement of the measurement hole 300. After measurement, the stress measuring device 100 is removed from the measurement hole 300, and the measured data is read out from the data logger 124, and the initial stress of the natural ground is calculated.

[0063] Although not shown in FIG. 7 , in the overcoring method, stress measurement device 100 is inserted into measurement hole 300, and then the outer periphery of measurement hole 300 is bored. Stress measurement device 100 detects deformation of measurement hole 300 in the hole length direction associated with boring using first sensor 106, and detects deformation in the hole diameter direction using second sensor 108. As described above, first sensor 106 can measure deformation of measurement hole 300 in the hole length direction because first elastic plate 114 has a curved portion and contact pin 118 is pressed against the inner wall surface by the action of elastic body 136. Second sensor 108 receives deformation of measurement hole 300 in the hole length direction because contact roller 120 is in contact with the inner wall surface, and can accurately measure deformation in the hole diameter direction. A plurality of first sensors 106 and second sensors 108 are provided along the outer periphery of the first housing 102, so that displacement in any direction of the diameter direction and length direction of the measurement hole 300 can be measured.

[0064] Data logger 124 has the function of recording the displacement of measurement hole 300 measured by first strain gauge 110 and second strain gauge 112 in chronological order at predetermined intervals. The displacement of measurement hole 300 recorded in data logger 124 is read out by a computer or the like after stress measuring device 100 is removed from measurement hole 300, and the stress of the natural ground is calculated from the displacement of measurement hole 300. Because second housing 104 has a built-in battery 126, there is no need to supply power via a wire to drive data logger 124, and data logger 124 can collect data autonomously within measurement hole 300.

[0065] Although not shown, the second housing 104 may be equipped with a camera and lighting, and may be configured to allow the operator to insert and remove the stress measuring device 100 into and from the measurement hole while watching the image captured by the camera. This allows the operator to smoothly perform the insertion and removal operations while checking the position and state of the stress measuring device 100 without relying solely on visual inspection.

[0066] As described above, according to the stress measuring device 100 of one embodiment of the present invention, the position of the tip of the contact pin 118 of the first sensor 106, which detects displacement in the hole length direction of the measurement hole 300, is configured to be depressed by the operating tool 200 during insertion, thereby preventing the influence of distortion in the hole length direction of the first sensor 106 that occurs during insertion. Furthermore, the second sensor 108 is provided with a contact roller 120 that contacts the inner wall surface of the measurement hole, thereby deflecting displacement in the hole length direction that occurs during insertion into the insertion hole and during measurement (overcoring), thereby enabling accurate measurement of displacement in the hole diameter direction. The stress measuring device 100 having this configuration allows accurate evaluation of the initial stress of the natural ground using the overcoring method.

[0067] Although this embodiment has been described based on the case of measuring the initial stress of the ground, the stress measuring device 100 can also be applied to measuring stress in existing tunnels, the back ground of underground cavities, and existing concrete structures. [Explanation of symbols]

[0068] 100: stress measuring device, 1001: first sensor unit, 1002: second sensor unit, 102: first housing, 1021: first support member, 1022: second support member, 1023: rod, 104: second housing, 105: gripping rod, 106: first sensor, 108: second sensor, 110: first strain gauge, 112: second strain gauge, 114: first elastic plate, 1141: bending portion, 116: second elastic plate, 118: contact pin, 120: contact roller, 122: universal joint, 124: data logger, 126: battery, 1 30: contact pin, 1301: first contact pin, 1302: second contact pin, 132: sensor support member, 1321: slit, 1322: tapered portion, 1324: fixing device, 134: joint, 136: elastic body, 138: stopper, 200: operation tool, 202: first cap, 2021: first opening, 2022: first tapered surface, second cap 203, 2031: second opening, 2032: second tapered surface, 204: gripping device, 2041: main body, 2042: gripping portion, 206: housing, 300: measurement hole

Claims

1. a first housing having an elongated shape; At least one first sensor including a first strain gauge and disposed on a side of a first end of the first housing in the longitudinal direction; at least one second sensor disposed on a second end of the first housing opposite the first end and including a second strain gauge; a second housing coupled to the first housing, The first sensor is an elastic plate extending in a direction parallel to the longitudinal direction of the first housing and having the first strain gauge attached thereto; a contact pin connected to the elastic plate; a sensor support member extending in the same direction as the elastic plate and to which the elastic plate is attached; The sensor support member has a rear end connected to the first housing by a rotatable joint, and a front end that is movable toward the center of a cross section of the first housing. A stress measuring device characterized by:

2. 2. The stress measuring device according to claim 1, wherein a gap is formed between the tip portion of the sensor support member and the first housing, and an elastic body is provided in the gap to apply a reaction force to displacement of the tip toward the center of the cross section.

3. 3. The stress measuring device according to claim 2, wherein a stopper for restricting the range of outward displacement of the tip of said sensor support member is detachably provided on the first end side of said first housing.

4. 4. The stress measuring device according to claim 1, wherein the sensor support member has a tapered portion at a tip end thereof.

5. 5. The stress measuring device according to claim 1, wherein the sensor support member has a slit extending in a longitudinal direction between the front end and the rear end, and the contact pin is provided so as to be displaceable in one axial direction along the slit.

6. 6. The stress measuring device according to claim 1, wherein the elastic plate has a curved portion, and the first strain gauge is provided at the curved portion.

7. 7. The stress measuring device according to claim 1, wherein the first sensor measures displacement of the measurement hole in a hole length direction, and the second sensor measures displacement of the measurement hole in a hole diameter direction.

8. 8. The stress measuring device according to claim 1, wherein the at least one first sensor comprises a plurality of first sensors, the plurality of first sensors being arranged around the periphery of the first housing and having a gripping rod extending outward from the first end of the first housing.

9. An operating tool for gripping and handling the stress measuring device according to claim 8, a cap that fits onto a tip of the sensor support member of the plurality of first sensors disposed in the first housing and has an opening; a gripping tool for gripping the gripping rod, The cap and the gripping tool are arranged side by side so that the gripping bar can be inserted through the opening and reach the gripping tool. An operating tool for a stress measuring device.

10. 10. The operating tool for a stress measuring device according to claim 9, wherein the cap has a tapered surface at a portion that fits onto the tip of the sensor support member.

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