Hybrid reaction anchor and assembly kit thereof

Abstract

To provide an anchor which does not cause any trouble to subsequent underground construction work etc. even if it is left underground.SOLUTION: A hybrid reaction anchor comprises a connection sleeve 15 which is hollow inside and open at both ends, a PC steel stranded wire 2 with a crimping sleeve 13 fixed to an end thereof and a ring-shaped joint screw member 14 passing therethrough inside the crimping sleeve 13, and a carbon fiber reinforced plastic cable 3 with a socket 11 fixed to an end thereof. Female threads are formed on an inner peripheral surface of at least both end portions of the connection sleeve 15, and male threads are formed on an outer peripheral surface of the joint screw member 14 and the outer peripheral surface of the tip of the socket 11. The joint screw member 14 and the socket 11 are screwed to respective both end portions of the connection sleeve 15.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a hybrid reaction anchor and a kit used for assembling the hybrid reaction anchor. [Background technology]

[0002] In underground construction, such as sewer construction, a starting shaft and an arrival shaft are installed at two locations separated by a distance of several tens of meters to several kilometers to allow people to enter and exit and to transport excavators and materials. A horizontal tunnel (main tunnel) is excavated from the starting shaft to the arrival shaft using an excavating machine such as a shield machine. Sewer pipes are laid in the main tunnel to complete the sewer pipeline from the starting shaft to the arrival shaft.

[0003] One of the construction methods for departure and arrival shafts is to bury concrete pipes or steel pipes with cylindrical or oval shapes.

[0004] Anchors made of PC steel strand wire are buried deep underground around the shaft in advance, and the reaction force acting on these anchors is sometimes used to press concrete pipes or steel pipes into the ground (reaction anchors) (see Patent Document 1). The lower end of the reaction anchor is firmly fixed to the ground deep underground, and the upper end of the anchor that is exposed to the ground is pulled (tensioned) using a jack. The reaction force (compression force) generated in the anchor presses the concrete pipe or steel pipe into the ground.

[0005] The above-mentioned PC steel strand anchors are sometimes left in the ground even after underground construction work is completed. However, when digging a horizontal tunnel for new underground construction, if an excavator hits a PC steel strand reaction anchor left in the ground during previous underground construction work, the left PC steel strand anchor may become entangled with the excavator and become inoperable.

[0006] PC steel strand anchors are sometimes removed by pulling them out after construction is complete, rather than being left in the ground. However, if the PC steel strand gets twisted while the anchor is being pulled out, it may become impossible to pull it out. In this case, removing the anchor requires a considerable amount of effort. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-227198 DISCLOSURE OF THE INVENTION

[0008] The object of this invention is to provide a reaction anchor that can be left underground without interfering with subsequent underground construction work, etc.

[0009] The hybrid reaction anchor of this invention comprises a connecting sleeve which is hollow inside and open at both ends, a PC steel stranded wire with a crimping sleeve fixed to its end and a ring-shaped joint screw member passed through it inside the crimping sleeve, and a fiber-reinforced plastic cable with a socket fixed to its end, wherein a female thread is formed on the inner surface of at least both end portions of the connecting sleeve, and a male thread is formed on the outer surface of the joint screw member and on the outer surface of the tip of the socket, and the joint screw member and the socket are screwed to each end of the connecting sleeve.

[0010] According to this invention, the PC steel strand and the fiber-reinforced plastic cable can be connected via the connection sleeve. The PC steel strand and the fiber-reinforced plastic cable are screwed to both ends of the connection sleeve via the joint screw member and the socket, respectively, so there is little chance that the connection will come loose even if a strong tensile force is applied.

[0011] The hybrid reaction anchor of this invention comprises a PC steel strand and a fiber-reinforced plastic cable. The PC steel strand has high strength against longitudinal tension and is also resistant to localized shear forces and surface scratches. A jack is generally used to introduce tension into the hybrid reaction anchor. The PC steel strand that makes up the hybrid reaction anchor is wedged into the anchor head, and the hybrid reaction anchor is tensioned when the anchor head is lifted by the jack.

[0012] On the other hand, fiber-reinforced plastic cables exhibit the same strength as PC steel strands against longitudinal tension, but are vulnerable to localized shear forces and surface scratches. Conversely, if a fiber-reinforced plastic cable is subjected to localized shear forces or surface scratches, the fiber-reinforced plastic cable will not maintain its shape. If a hybrid reaction anchor according to this invention is left in the ground during prior underground construction work, and an excavator hits the fiber-reinforced plastic cable during subsequent underground construction work, the excavator will not become entangled in the fiber-reinforced plastic cable, but will instead be destroyed. In this way, by positioning the fiber-reinforced plastic cable in an area where excavation is expected to occur at a later date, the hybrid reaction anchor according to this invention can be left in the ground without interfering with subsequent underground construction work, even if it is left in the ground. A reaction anchor suitable for leaving in place is provided.

[0013] In one embodiment, the socket is hollow and open at both ends, the socket is filled with an expansion agent, and the end of the fiber-reinforced plastic cable inserted into the socket is embedded in the expansion agent. The expansion pressure of the expansion agent filled in the socket allows the socket to be firmly fixed to the end of the fiber-reinforced plastic cable.

[0014] This invention also provides a hybrid reaction anchor assembly kit (parts set) comprising: a connecting sleeve having a hollow interior and open at both ends; a PC steel stranded wire with a crimping sleeve fixed to its end and a ring-shaped joint screw member passing through it inside the crimping sleeve; and a fiber-reinforced plastic cable with a socket fixed to its end, wherein female threads are formed on the inner circumferential surface of at least both end portions of the connecting sleeve, and male threads are formed on the outer circumferential surface of the joint screw member and the outer circumferential surface of the tip of the socket. At a construction site or the like, the above-mentioned hybrid reaction anchor is assembled by screwing the joint screw member and the socket to both end portions of the connecting sleeve, respectively. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 10 is a cross-sectional view showing the construction of a vertical shaft. [Figure 2] FIG. [Figure 3] FIG. 2 is a cross-sectional view of the connecting member in an assembled state. [Example]

[0016] Figure 1 shows a schematic diagram of the shaft construction.

[0017] A shaft is a tunnel that is dug vertically. Generally, a shaft is constructed by burying a hollow concrete pipe or steel pipe (hereinafter referred to as pipe 21) in the ground. The pipe 21 is pressed into the ground by pressing downward on the upper end of the pipe 21 that is above ground. The soil inside the pipe 21 is excavated and removed. The length (total height) of the pipe 21 buried in the ground can be adjusted as desired by constructing a new upper end on the upper end of the existing pipe 21. In this case, the shaft is constructed by repeating the work of constructing the upper end, pressing in, and excavating.

[0018] A hybrid reaction anchor is used to press the upper end of the pipe 21 downward into the ground.

[0019] The hybrid reaction anchor is composed of a connection member 1, a PC steel strand 2, and a carbon fiber reinforced plastic (CFRP) cable 3 (hereinafter referred to as the CFRP cable 3). The hybrid reaction anchor is buried in the ground through a long, narrow hole that is drilled in the ground beforehand.

[0020] The PC steel strand 2 is made by twisting together multiple PC steel wires with a circular cross section. For example, a PC steel strand 2 with a diameter of 12.7 mm and seven strands with a 1x7 structure (a structure in which six PC steel wires are twisted around one PC steel wire at the center) can be used. The structure and diameter of the PC steel strand 2 can be designed as desired.

[0021] The CFRP cable 3 is constructed by further twisting together multiple strands (CFRP strands) with a circular cross section made from a composite material of carbon fiber and epoxy resin. Each CFRP strand is formed into a circular cross section by many continuous carbon fibers and epoxy resin impregnated into the carbon fibers. For example, a CFRP cable 3 with a diameter of 12.5 mm and a 1x7 structure (a structure in which six CFRP strands are twisted around one CFRP strand at the center) can be used. The structure and diameter of the CFRP cable 3 can also be designed as desired.

[0022] A PC steel strand 2 is connected to one end of the connecting member 1, and a CFRP cable 3 is connected to the other end, with the PC steel strand 2 and CFRP cable 3 extending in a straight line via the connecting member 1. The tip (head) of the PC steel strand 2, whose end is connected to one end of the connecting member 1, is exposed above ground. The connecting member 1 and the CFRP cable 3, whose end is connected to the other end of the connecting member 1, are entirely buried underground. Grout (not shown) is injected into the ground around the tip of the CFRP cable 3, and the grout firmly integrates it with the surrounding ground.

[0023] A bearing girder 22 is placed on the upper end of the pipe 21. A bearing plate (not shown) may be provided between the bearing girder 22 and the upper end surface of the pipe 21. The bearing girder 22 has holes (not shown) through which the PC steel strand wires 2 pass, and the tip portions of the PC steel strand wires 2 pass through the holes in the bearing girder 22 and reach above the bearing girder 22.

[0024] A jack 23 is installed on the upper surface of the bearing girder 22, and the tip of the PC steel strand 2 that reaches above the bearing girder 22 is pulled by the jack 23. An anchor head (not shown) is fixed to the tip of the PC steel strand 2 by, for example, wedging, and the anchor head is lifted by the jack 23.

[0025] When the hybrid reaction anchor (the tip of the PC steel strand 2) is pulled by the jack 23, a reaction force (compression force) is generated in the hybrid reaction anchor. This reaction force is used to press the pipe 21 into the ground. Generally, 2 to 10 hybrid reaction anchors are buried at equal intervals around the pipe 21, and the same number of jacks 23 as the number of hybrid reaction anchors are used. The multiple jacks 23 are controlled by a control device (not shown), which controls the posture of the pipe 21.

[0026] It is also possible to simultaneously pull multiple closely spaced hybrid reaction anchors with one jack 23. In this case, the prestressing steel strands 2 of multiple, for example, five, hybrid reaction anchors are fixed to one anchor head, and the five hybrid reaction anchors (five prestressing steel strands 2) are simultaneously pulled by the jack 23. The number of hybrid reaction anchors is adjusted according to the force required to press-fit the pipe 21.

[0027] 2 is an exploded perspective view of the connection member 1 (hybrid reaction anchor), and FIG.

[0028] The connection member 1 includes a CFRP terminal socket 11 , a crimp sleeve 13 , a joint screw member 14 and a connection sleeve 15 .

[0029] The connection sleeve 15 is a hollow cylinder made of a hard metal such as iron. An internal thread is formed on the inner circumferential surface of each end of the connection sleeve 15 (only one internal thread 15A is visible in Figure 2).

[0030] The CFRP terminal socket 11 is used to protect the end portion of the CFRP cable 3 from external damage and to connect the CFRP cable 3 to the connecting member 1, and is made of metal and has a hollow, elongated cylindrical shape. The diameter of the hollow of the CFRP terminal socket 11 is larger than the diameter of the CFRP cable 3. The end portion of the CFRP cable 3 is housed (inserted) in the internal space of the CFRP terminal socket 11, preferably with the centers aligned.

[0031] The internal space of the CFRP terminal socket 11 is filled with an expansion agent 12, and the CFRP cable 3 is embedded in the expansion agent 12 within the CFRP terminal socket 11. The expansion agent 12 undergoes moderate expansion and solidifies under appropriate temperature control. The expansion pressure generated when the expansion agent 12 expands tightly binds the end portion of the CFRP cable 3 within the CFRP terminal socket 11. The expansion agent 12 can be, for example, so-called cement milk, which is primarily composed of calcium oxide and expands when it reacts with water.

[0032] A male thread 11A is formed on the outer peripheral surface of the tip portion of the CFRP terminal socket 11 (the end portion where the CFRP cable 3 does not protrude), and one end of a connection sleeve 15, which has a female thread 15A formed on its inner peripheral surface, is screwed onto this, thereby connecting the CFRP cable 3 to one end of the connection sleeve 15. The terminal socket 11 is fixed to the CFRP cable 3 via an expansion agent 12, and the terminal socket 11 is screwed onto the connection sleeve 15, so the CFRP cable 3 will not slip out of the connection sleeve 15.

[0033] A metal ring-shaped joint screw member 14 is passed through the PC steel strand 2. The inner diameter of the joint screw member 14 is slightly larger than the diameter of the PC steel strand 2, and the joint screw member 14 is movable along the PC steel strand 2.

[0034] A cylindrical metal crimping sleeve 13 is crimped onto the end portion of the PC steel strand 2. The crimping sleeve 13 is firmly crimped (tightly adhered) from its periphery, thereby firmly fixing it to the PC steel strand 2. The above-mentioned joint screw member 14 is located inside the crimping sleeve 13 (on the side closer to the end than the crimping sleeve 13).

[0035] A male thread 14A is formed on the outer peripheral surface of the joint screw member 14, and the other end of a connection sleeve 15, which has a female thread formed on its inner peripheral surface, is screwed onto this to connect the PC steel strand 2 to the other end of the connection sleeve 15. Even if a strong tensile force is applied to the PC steel strand 2, the crimping sleeve 13, which is crimped onto the end portion of the PC steel strand 2, will abut against the joint screw member 14, which is screwed onto the connection sleeve 15, so the PC steel strand 2 will not come loose from the connection sleeve 15.

[0036] The hybrid reaction anchor may be provided with multiple connecting members 1. For example, by using two connecting members 1, it is possible to manufacture a hybrid reaction anchor in which a CFRP cable 3 is placed in the center and PC steel strands 2 are placed on both ends of the CFRP cable 3 via connecting members 1.

[0037] The CFRP cable 3 has a high tensile strength in its longitudinal direction equivalent to that of the PC steel strand 2, but is vulnerable to local shear forces and surface scratches. Suppose a hybrid reaction anchor is left underground during prior underground construction work. If an excavator or similar machine collides with the CFRP cable 3 of the hybrid reaction anchor during later construction work, the CFRP cable 3 will not become entangled with the machine, but rather the CFRP cable 3 will be destroyed. In other words, by positioning the CFRP cable 3 in an area where excavation or the like is expected to take place at a later date, the hybrid reaction anchor will not cause any interference with subsequent underground construction work, even if it is left underground.

[0038] In the above-mentioned embodiment, an example was explained in which a CFRP cable 3 made of carbon fiber and epoxy resin was used, but instead of carbon fiber, glass fiber, aramid fiber, basalt fiber, or other synthetic fiber may be used. Also, as for the resin impregnated into the synthetic fiber, instead of epoxy resin, polyamide resin, phenol resin, or other resin may be used.

[0039] In addition, in the above-mentioned embodiment, an example was described in which a PC steel strand 2 made by twisting together multiple PC steel wires was used, but it is also possible to use an unbonded PC steel strand in which high-performance grease with excellent corrosion resistance is applied to the outer surface of the PC steel strand 2 and then covered with polyethylene. [Explanation of symbols]

[0040] 1. Connecting member 2 PC steel strand 3 CFRP cable 11 CFRP terminal socket 11A, 14A male thread 12 Leavening Agent 13 Crimp sleeve 14 Joint screw member 15 Connecting sleeve 15A female thread

Claims

1. a connecting sleeve having a hollow interior and open at both ends; A PC steel strand having a crimping sleeve fixed to the end and a ring-shaped joint screw member passed through inside the crimping sleeve; a fiber-reinforced plastic cable having a socket fixed to its end, A female thread is formed on the inner circumferential surface of at least both end portions of the connection sleeve, Male threads are formed on the outer peripheral surface of the joint screw member and the outer peripheral surface of the tip of the socket, The joint screw member and the socket are screwed onto both ends of the connecting sleeve, respectively. Hybrid reaction anchor.

2. The socket is hollow inside and open at both ends, the socket is filled with an expansion agent, and the end of the fiber-reinforced plastic cable inserted into the socket is embedded in the expansion agent.

10. The hybrid reaction anchor of claim 1.

3. a connecting sleeve having a hollow interior and open at both ends; A PC steel strand having a crimping sleeve fixed to the end and a ring-shaped joint screw member passed through inside the crimping sleeve; a fiber-reinforced plastic cable having a socket fixed to its end, A female thread is formed on the inner circumferential surface of at least both end portions of the connection sleeve, Male threads are formed on the outer peripheral surface of the joint screw member and the outer peripheral surface of the tip of the socket. Assembly kit for hybrid reaction anchors.

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