Reinforcement anchors, methods for reinforcing retaining walls

Abstract

To provide a reinforcing anchor that can reduce influence of groundwater pressure and buoyancy and can be stably fixed into an anchor fixing hole formed in an earth retaining wall, and a reinforcing method for an earth retaining wall using the same.SOLUTION: A reinforcing anchor 1 comprises a plurality of resin fiber wires 2 inside a sheath 3, and a first end structure 4 at one end 2A and a second end structure 5 at the other end 2B of the resin fiber wires 2. The first end structure 4 includes: a first resin covering the outer periphery of the resin fiber wire 2 and filled between the strands of the resin fiber wire 2; an unbonded tube covering the resin fiber wire 2 via the first resin; and a first heat shrinkable member binding the unbonded tube. The second end structure 5 includes: a second resin covering the resin fiber wire 2 and filled between the strands of the resin fiber wire 2; a second heat shrinkable member binding the resin fiber wire 2 via the second resin; and a hardened portion made of filling material arranged on the outside of the second heat shrinkable member.SELECTED DRAWING: Figure 1

Description

Technical Field

[0005] , ,

[0001] The present invention relates to a reinforcing anchor and a method for reinforcing a retaining wall using the reinforcing anchor.

Background Art

[0002] Conventionally, for tunnel construction of subways, subways, utility tunnels, sewer pipes, etc. (hereinafter also referred to as "subways, etc."), the shield method using a shield tunneling machine has been widely adopted. Generally, the shield method first forms a vertical shaft (launch shaft), which is a vertical hole, by the open cut method, transports a shield tunneling machine underground from this launch shaft, excavates the excavation side surface of the launch shaft with the shield tunneling machine, advances horizontally, and excavates a tunnel to the end point, which is the target point. In general, in the shield method, at the end point, which is the target point of the tunnel, a vertical hole (arrival shaft) similar to the launch shaft is formed, and the shield tunneling machine is made to reach the arrival shaft.

[0003] By the way, on the side surface of the launch shaft and arrival shaft (hereinafter also collectively referred to as "shaft") formed by the open cut method, in order to prevent the collapse of the side surface due to earth pressure and water pressure (hereinafter referred to as "earth pressure, etc.") and the outflow of groundwater from the side surface, a retaining wall, which is a temporary wall using reinforced concrete, corrugated sheet piles, or H-shaped steel, etc., is constructed.

[0004] Thus, in the shaft of the shield method, in order to hold the space against earth pressure, etc., a core material is installed in the inner peripheral part of the shaft, and a retaining wall is provided. Further, in the retaining wall thus formed, usually, an opening must be formed when the shield tunneling machine starts and arrives (so-called mirror cutting). Conventionally, for such mirror cutting work of the retaining wall, means using heavy machinery or manpower have been taken. Further, since the retaining wall is provided to resist earth pressure, etc., providing an opening, etc. may reduce the resistance force. ​​Therefore, in recent years, a shield tunneling method has been implemented in which components made of fiber-reinforced plastics (FRP) or the like are incorporated into the retaining wall of the shaft, and the FRP portion (cuttable area) is directly cut with a shield tunneling machine (SEW method: Shield Earth Retaining Wall System).

[0006] However, with conventional SEW construction methods, it was difficult to use retaining walls with cuttable areas in environments where soil pressure exceeding a certain level occurred. Therefore, in order to enable the adoption of the SEW method even in such environments, there is a method (hereinafter referred to as the "anchor reinforcement method") in which cuttable reinforcing anchors are installed in the cuttable area, and the strength of the cuttable area is indirectly reinforced by these reinforcing anchors. The anchor reinforcement method involves reinforcing the cuttable area using a reinforcing anchor equipped with a tendon grip and resin fiber wire.

[0007] In the anchor reinforcement method, reinforcing anchors are driven into the cuttable area during the excavation process inside the shaft surrounded by core materials. When driving the reinforcing anchors, the soil cement portion between the core materials is excavated to form anchor fixing holes. Next, the reinforcing anchor is inserted into the anchor fixing hole, and then the reinforcing anchor is fixed with the anchor head (bolt and nut structure) and pressure plate (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Patent No. 6163380 [Overview of the project] [Problems that the invention aims to solve]

[0009] In the process of forming the anchor fixing holes described above, if a low-permeability, poor-permeability layer (pressure layer) exists above the location where the anchor fixing holes for driving in reinforcing anchors are made, pressure from groundwater is applied to the anchor fixing holes. Therefore, in the process of inserting reinforcing anchors into the anchor fixing holes, the pressure and buoyancy from the groundwater push back the lightweight resin reinforcing anchors, resulting in the problem that the reinforcing anchors cannot be inserted to their full length into the drilled section.

[0010] Furthermore, in the reinforcing anchor described in Patent Document 1, up to six resin fiber wires are bundled together to form a free length (a region that does not adhere to the grout used to form the anchorage length during anchor installation), and one end of the resin fiber wires is covered with a free length sheath. When adopting a structure in which each resin fiber wire is covered with a sheath to mitigate the effects of groundwater pressure and buoyancy as described above, it is necessary to reduce the gap between the resin fiber wire and the sheath so that the grout used to form the anchorage length does not penetrate into the free length portion (so that the resin fiber wire and grout in the free length portion do not adhere during construction). However, there was a problem in that the other end of the resin fiber wire could not be covered with a free length sheath while up to six resin fiber wires were bundled together.

[0011] The present invention has been made in view of the above circumstances, and aims to provide a reinforcing anchor that can reduce the effects of pressure and buoyancy caused by groundwater and be stably fixed to an anchor fixing hole formed in a retaining wall, and a method for reinforcing a retaining wall using the reinforcing anchor. [Means for solving the problem]

[0012] The present invention has the following aspects. [1] A reinforcing anchor comprising multiple resin fiber wires bundled together with their longitudinal directions in the same direction, provided inside a sheath, The resin fiber wire comprises a first end structure formed at one end in the longitudinal direction of the resin fiber wire, and a second end structure formed at the other end in the longitudinal direction of the resin fiber wire. The first end structure comprises an unbonded tube that covers the resin fiber wire from the outside, and a first heat-shrinkable member that restrains the unbonded tube from the outside. The second end structure is a reinforcing anchor comprising: a second resin covering the outer circumference of the resin fiber wire and filling the spaces between the strands of the resin fiber wire; a second heat-shrinkable member that binds the resin fiber wire from the outside via the second resin; and a hardened portion made of a filling material disposed outside the second heat-shrinkable member. [2] The filling material is an expansive mortar, The reinforcing anchor according to [1], wherein the expansion pressure of the hardened portion is 40 MPa or more and 60 MPa or less. [3] The second end structure side is provided with a tension member into which the second end structure is inserted, The reinforcing anchor according to [1], wherein the longitudinal length of the second end structure inserted into the tension member is 10 mm or more and 20 mm or less. [4] The reinforcing anchor according to [1], wherein the first resin and the second resin are ethylene-vinyl acetate copolymer resins. [5] The reinforcing anchor according to [1], wherein the content of the first resin is 1 g or more and 10 g or less per 60 mm length of the resin fiber wire. [6] The reinforcing anchor according to [1], wherein the content of the second resin is 1 g or more and 10 g or less per 60 mm length of the resin fiber wire. [7] The reinforcing anchor according to [1], further comprising a first anchoring material injection pipe extending in the longitudinal direction of the resin fiber wire inside the sheath. [8] The reinforcing anchor according to [1], further comprising a second anchoring material injection pipe extending in the longitudinal direction of the resin fiber wire on the outside of the sheath. A method for reinforcing an earth retaining wall having a cuttable area using reinforcing anchors as described in [9], [7], or [8], A method for reinforcing an earth retaining wall, comprising forming multiple anchor fixing holes that span the cuttable area and the surrounding ground, and inserting the reinforcing anchors into the anchor fixing holes while injecting anchoring material into the anchoring material injection pipe.

Advantages of the Invention

[0013] According to the present invention, it is possible to provide a reinforcing anchor that can reduce the influence of pressure and buoyancy caused by groundwater and stably fix it to an anchor fixing hole formed in a retaining wall, and a method for reinforcing a retaining wall using the reinforcing anchor.

Brief Description of the Drawings

[0014] [Figure 1] It is a cross-sectional view showing a longitudinal cross-section of a reinforcing anchor according to an embodiment of the present invention. [Figure 2] It shows a reinforcing anchor according to an embodiment of the present invention and is a view showing an end face of a cross-section along line A-A in FIG. 1. [Figure 3] It shows a reinforcing anchor according to an embodiment of the present invention and is a view showing an end face of a cross-section along line B-B in FIG. 1. [Figure 4] It shows a reinforcing anchor according to an embodiment of the present invention and is a view showing an end face of a cross-section along line C-C in FIG. 1. [Figure 5] It is a cross-sectional view showing a method for reinforcing a retaining wall according to an embodiment of the present invention. [Figure 6] It is a front view showing a method for reinforcing a retaining wall according to an embodiment of the present invention. [Figure 7] It is a cross-sectional view showing a method for reinforcing a retaining wall according to an embodiment of the present invention. [Figure 8] It is a cross-sectional view showing a method for reinforcing a retaining wall according to an embodiment of the present invention. [Figure 9] It is a cross-sectional view showing a method for reinforcing a retaining wall according to an embodiment of the present invention.

Modes for Carrying Out the Invention

[0015] Hereinafter, embodiments of the reinforcing anchor of the present invention and a method for reinforcing a retaining wall using the reinforcing anchor will be shown and described. However, the present invention is not limited to the following embodiments.

[0016] [Reinforcement anchors] Figure 1 is a cross-sectional view showing a longitudinal section of a reinforcing anchor according to one embodiment of the present invention. Figure 2 shows a reinforcing anchor according to one embodiment of the present invention, and is a view of the end face of the section along line AA in Figure 1. Figure 3 shows a reinforcing anchor according to one embodiment of the present invention, and is a view of the end face of the section along line BB in Figure 1. Figure 4 shows a reinforcing anchor according to one embodiment of the present invention, and is a view of the end face of the section along line CC in Figure 1. Please note that the drawings used in the following explanation may be enlarged for clarity, highlighting key features, and therefore the dimensional ratios of each component may differ from those of the actual components.

[0017] As shown in Figure 1, the reinforcing anchor 1 of this embodiment has multiple resin fiber wires 2 bundled together with their longitudinal directions in the same direction inside a sheath 3. Furthermore, the reinforcing anchor 1 of this embodiment includes a first end structure 4 formed at one end (tip) 2A in the longitudinal direction of the resin fiber wire 2, and a second end structure 5 formed at the other end (rear end) 2B in the longitudinal direction of the resin fiber wire 2. The first end structure 4 is the part at one end of the reinforcing anchor 1 where the resin fiber wire 2 is covered by a first resin (not shown). The second end structure 5 is the part at the other end of the reinforcing anchor 1 where the resin fiber wire 2 is covered by a second resin (not shown).

[0018] As shown in Figure 2, the first end structure 4 has, in order from the resin fiber wire 2 side outwards, a first resin, an unbonded tube 18, and a first heat-shrinkable member 8. The first resin covers the outer circumference of the multiple resin fiber wires 2 (referring to one of up to six) and fills the spaces between the strands of the resin fiber wires 2, filling the gaps between the strands. The unbonded tube 18 covers the resin fiber wire 2 (one wire) consisting of multiple strands from the outside via the first resin. The first heat-shrinkable member 8 restrains the unbonded tube 18 from the outside. Six resin fiber wires 2 configured in this way are bundled together and enclosed in the sheath 3.

[0019] As shown in Figure 3, the second end structure 5 has, in order from the resin fiber wire 2 side outwards, an unbonded tube 18, a second heat shrink member 10, and a curing section 11. The second resin covers the outer circumference of the multiple resin fiber wires 2 and fills the spaces between the strands of the resin fiber wires 2, filling the gaps between the strands. The second heat shrink member 10 binds the multiple resin fiber wires 2 from the outside via the second resin. The curing section 11 consists of a filling material placed outside the second heat shrink member 10. In addition, a temperature-controlled pipe 21 for curing the filling material that forms the curing section 11 is located in the center of the second end structure 5.

[0020] The reinforcing anchor 1 has a tip cap 13 at its tip, that is, at the end of the first end structure 4, which covers one end of the resin fiber wire 2 in the longitudinal direction. The reinforcing anchor 1 has a tip grout waterproofing section 14 at the rear end of the tip cap 13, extending from the tip cap 13 to the other end of the resin fiber wire 2 in the longitudinal direction. The tip grout waterproofing section 14 consists of grout that covers the outer circumference of the multiple resin fiber wires 2 and fills the spaces between the multiple resin fiber wires 2.

[0021] The reinforcing anchor 1 has a tension member (tendon grip) 15 at its rear end, i.e., the end of the second end structure 5, into which the second end structure 5 is inserted. The tension member 15 has an internal space into which a portion of the second end structure 5 can be inserted. This internal space is a space that communicates with the inside and outside of the tension member 15.

[0022] As shown in Figure 1, the resin fiber wire 2 has a free length portion 16 extending in the longitudinal direction and a fixed length portion 17. The free length portion 16 is provided on the second end structure 5 side and is the part that transmits the tensile force acting on the tension member 15 to the anchored length portion 17 when the earth retaining wall is reinforced by the reinforcing anchor 1. In addition, as shown in Figures 3 and 4, the outer circumference of the resin fiber wire 2 in the free length portion 16 is covered with an unbonded tube 18. The anchored section 17 is the part that becomes integrated with the ground via the anchoring material when the retaining wall is reinforced by the reinforcing anchor 1. In other words, the anchored section 17 is the part whose movement is restricted by the anchoring material when the retaining wall is reinforced by the reinforcing anchor 1.

[0023] The reinforcing anchor 1 preferably includes a first anchoring material injection pipe 19 inside the sheath 3, extending in the longitudinal direction of the resin fiber wire 2, as shown in Figure 1. The first anchoring material injection pipe 19 extends along the longitudinal direction of the resin fiber wire 2 from the tension member 15 side to the vicinity of the tip grout watertight section 14. Grout can be injected into the inside of the sheath 3 from the tension member 15 side via the first anchoring material injection pipe 19.

[0024] The reinforcing anchor 1 preferably includes a second anchoring material injection pipe 20 extending in the longitudinal direction of the resin fiber wire 2 on the outside of the sheath 3, as shown in Figure 1. The second anchoring material injection pipe 20 extends along the longitudinal direction of the resin fiber wire 2 from the tension member 15 side to the vicinity of the first end structure 4. Grout can be injected from the tension member 15 side to the outside of the sheath 3 through the second anchoring material injection pipe 20.

[0025] The resin fiber wire 2 is a rope-like material that is flexible and easy to cut. The material of the resin fiber wire 2 is not particularly limited as long as it is a fiber-reinforced resin, but from the viewpoint of high tensile strength and light weight, a thermosetting resin reinforced with carbon fiber is preferred. The core wire constituting each resin fiber wire 2 may also contain glass fibers. The resin fiber wire 2 is designed so that the direction of the fibers is almost aligned with the axial direction (the longitudinal direction of the reinforcing anchor 1). In other words, the resin fiber wire 2 is a component with high strength against tensile forces acting in the longitudinal direction of the reinforcing anchor 1. Furthermore, because the reinforcing fibers of the reinforcing anchor 1 are carbon fibers, it is easily destroyed by cutting with a shield drilling machine, making it a component that is easy to cut.

[0026] Sheath 3 is not particularly limited, but examples include a corrugated sheath with a wavy surface. The material of sheath 3 is not particularly limited, but polypropylene, nylon, etc. are preferred from the viewpoint of excellent flexibility and weather resistance.

[0027] The longitudinal length of the resin fiber wire 2 of the first end structure 4 is preferably 100 mm to 500 mm, more preferably 100 mm to 300 mm, and even more preferably 100 mm to 200 mm. If the length of the first end structure 4 is greater than or equal to the lower limit, a sufficiently long watertight section can be formed, ensuring watertightness at the end of the unbonded tube covering portion of the resin fiber wire 2. If the length of the first end structure 4 is less than or equal to the upper limit, the material cost used for watertightness and the processing time for the tip grout watertight section 14 can be reduced.

[0028] The longitudinal length of the resin fiber wire 2 of the second end structure 5 is preferably 10 mm to 50 mm, more preferably 10 mm to 30 mm, and even more preferably 10 mm to 20 mm. If the length of the second end structure 5 is greater than or equal to the lower limit, the length of the anchoring portion 17 with the resin fiber wire 2 by the expanding mortar can be maintained while simultaneously ensuring watertightness at the end of the unbonded tube covering portion. If the length of the second end structure 5 is less than or equal to the upper limit, the material costs used for watertightness and the processing time of the tip grout watertight portion 14 can be reduced.

[0029] The first and second resins are not particularly limited as long as they can cover the outer circumference of a plurality of resin fiber wires 2, fill the spaces between the strands of the resin fiber wires 2, and fill the gaps between the strands of the resin fiber wires 2. However, from the viewpoint of excellent water resistance, ethylene-vinyl acetate copolymer resin (EVA) is preferred.

[0030] The content of the first resin is preferably 1g to 20g per 60mm length of resin fiber wire 2, more preferably 1g to 15g, and even more preferably 1g to 10g. If the content of the first resin is above the lower limit, sufficient first resin can be filled between the strands of the resin fiber wire 2, thereby improving watertightness. If the content of the first resin is below the upper limit, the material costs used for watertightness and the processing time for the tip grout watertight section 14 can be reduced.

[0031] The content of the second resin is preferably 1g to 20g per 60mm length of resin fiber wire 2, more preferably 1g to 15g, and even more preferably 1g to 10g. If the content of the second resin is above the lower limit, sufficient second resin can be filled between the strands of the resin fiber wire 2, thereby improving watertightness. If the content of the second resin is below the upper limit, the material costs used for watertightness and the processing time for the tip grout watertight section 14 can be reduced.

[0032] The material of the unbonded tube 18 is not particularly limited, but examples include polyethylene.

[0033] The unbonded tube 18 covers the entire first resin that surrounds the resin fiber wire 2.

[0034] The first heat-shrinkable member 8 is a member that shrinks when heat is applied. The material of the first heat-shrinkable member 8 is not particularly limited, but examples include SUMITUBE F2 (electron beam crosslinked flexible flame-retardant polyolefin resin) manufactured by Sumitomo Electric Industries, Ltd.

[0035] The length over which the resin fiber wire 2 is covered by the first heat-shrinkable member 8 is preferably 20 mm to 200 mm, more preferably 20 mm to 150 mm, and even more preferably 20 mm to 100 mm. If the length over which the resin fiber wire 2 is covered by the first heat-shrinkable member 8 is greater than or equal to the lower limit, watertightness during grout injection can be ensured. If the length over which the resin fiber wire 2 is covered by the first heat-shrinkable member 8 is less than or equal to the upper limit, the material costs used for watertightness and the processing time for the tip grout watertight section 14 can be reduced.

[0036] The first heat-shrinkable member 8 should cover at least a portion of the unbonded tube 18 and overlap with the unbonded tube 18. The overlapping length between the first heat-shrinkable member 8 and the unbonded tube 18 is preferably 20 mm to 200 mm, more preferably 20 mm to 150 mm, and even more preferably 20 mm to 100 mm. If the overlapping length between the first heat-shrinkable member 8 and the unbonded tube 18 is greater than or equal to the lower limit, the area (adhesion length) of the integrated portion of the first heat-shrinkable member 8 and the unbonded tube 18 can be secured, and watertightness during grout injection can be ensured. If the overlapping length between the first heat-shrinkable member 8 and the unbonded tube 18 is less than or equal to the upper limit, the material cost used for watertightness and the processing time of the tip grout watertight section 14 can be reduced.

[0037] The second heat-shrinkable member 10 is the same member as the first heat-shrinkable member 8.

[0038] The second heat-shrinkable member 10 covers the entire second resin that covers the resin fiber wire 2. The length over which the resin fiber wire 2 is covered by the second heat-shrinkable member 10 is preferably 20 mm to 200 mm, more preferably 20 mm to 150 mm, and even more preferably 20 mm to 100 mm. If the length over which the resin fiber wire 2 is covered by the second heat-shrinkable member 10 is greater than or equal to the lower limit, watertightness during grout injection can be ensured. If the length over which the resin fiber wire 2 is covered by the second heat-shrinkable member 10 is less than or equal to the upper limit, the material costs used for watertightness and the processing time for the tip grout watertight section 14 can be reduced.

[0039] As the filling material for forming the hardened portion 11, an expansive mortar is preferred. Specific examples of expansive mortar include mortar that exhibits an expansion pressure of 40 MPa to 60 MPa when the curing temperature is maintained between 10 degrees Celsius and 60 degrees Celsius.

[0040] The expansion pressure of the cured portion 11 is preferably 40 MPa to 60 MPa, and more preferably 40 MPa to 50 MPa. If the expansion pressure of the cured portion 11 is above the lower limit, an improvement in the integrated strength between the resin fiber wire 2 and the tensile member 15 can be expected. If the expansion pressure of the cured portion 11 is below the upper limit, the effect of dimensional changes on the tensile member 15 can be reduced.

[0041] The expansion pressure of the hardened portion 11 can be measured by preparing a dummy material with the same cross-sectional structure and using a general-purpose pressure sensor.

[0042] As shown in Figure 1, the tip cap 13 has a tapered shape, becoming smaller in diameter towards the tip. The material of the tip cap 13 is not particularly limited, but examples include high-density polyethylene and polyvinyl chloride resin. High-density polyethylene is preferred from the viewpoint of excellent water resistance (water-sealing properties).

[0043] The grout (anchoring material) that forms the tip grout watertight section 14 is used during tunnel excavation in injection methods, shield tunneling methods, etc., to anchor rock bolts and to fill gaps between the ground and the tunnel lining. As grout, cement (mortar) based materials, glass-based materials, synthetic resins, etc., can be used.

[0044] The longitudinal length of the resin fiber wire 2 of the tip grout watertight section 14 is preferably 50 mm or more and 500 mm or less, more preferably 50 mm or more and 300 mm or less, and even more preferably 50 mm or more and 200 mm or less. If the longitudinal length of the resin fiber wire 2 of the tip grout watertight section 14 is greater than or equal to the lower limit, watertightness on one end side of the reinforcing anchor 1 can be ensured when grout is injected during construction. If the longitudinal length of the resin fiber wire 2 of the tip grout watertight section 14 is less than or equal to the upper limit, the material cost used for watertightness and the processing time of the tip grout watertight section 14 can be reduced.

[0045] The tensile member 15 is a resin molded product made of fiber-reinforced plastic (FRP). The tension member 15 is designed so that the orientation of its fibers is almost aligned in the axial and circumferential directions. In other words, the tension member 15 is a member with high rigidity against bending moments of forces acting in a direction intersecting the longitudinal direction of the reinforcing anchor 1. Furthermore, since the tension member 15 is made of FRP, it is easily destroyed by cutting with a shield drilling machine, and is also a member with easy cutting properties. In other words, the tension member 15 is a member with high rigidity against bending moments of forces and easy cutting properties.

[0046] The longitudinal length of the second end structure 5 inserted into the tension member 15 is preferably 10 mm or more and 50 mm or less, and more preferably 10 mm or more and 30 mm or less. If the length of the second end structure 5 inserted into the tension member 15 is greater than or equal to the lower limit, watertightness on the other end of the reinforcing anchor 1 can be ensured when grout is injected during construction. If the length of the second end structure 5 inserted into the tension member 15 is less than or equal to the upper limit, the adhesion length between the resin fiber wire 2 and the expanding mortar inside the tension member 15 can be ensured.

[0047] The material of the first anchoring material injection pipe 19 and the second anchoring material injection pipe 20 is not particularly limited, but examples include polyethylene and polyvinyl chloride resin. Polyethylene is preferred from the viewpoint of excellent resistance to grout.

[0048] The reinforcing anchor 1 of this embodiment is an anchor that can also be used to reinforce slopes, and as will be described later, it is suitably used to reinforce the cut portion (cuttable area) of the earth retaining wall used in the SEW method (Shield Earth Retaining Wall System), which is a temporary wall cutting method. Furthermore, the reinforcing anchor 1 of this embodiment has the function of reinforcing and stabilizing the earth retaining wall of the shaft formed when excavating a shield tunnel, and also being easily cut together with the earth retaining wall by the shield excavator during excavation.

[0049] According to the reinforcing anchor 1 of this embodiment, since it has the first end structure 4 and the second end structure 5 described above, it can reduce the effects of pressure and buoyancy from groundwater and be stably fixed to the anchor fixing hole formed in the retaining wall. Therefore, the work efficiency of shield tunnel excavation can be improved.

[0050] [Methods for reinforcing retaining walls] A method for reinforcing an earth retaining wall according to one embodiment of the present invention will be described with reference to Figures 5 to 9.

[0051] The method for reinforcing a retaining wall according to this embodiment is a method for reinforcing a retaining wall having a cuttable area using the reinforcing anchors of this embodiment, wherein a plurality of anchor fixing holes are formed spanning the cuttable area and the surrounding ground, and the reinforcing anchors are inserted into the anchor fixing holes while injecting a fixing material into the fixing material injection pipe.

[0052] The method for reinforcing the retaining wall in this embodiment, as shown in Figure 5, is a method of reinforcing and stabilizing the retaining wall 31 (structure) of the shaft 30 formed when excavating a shield tunnel with a shield excavator S, using the reinforcing anchor 1 of the above-described embodiment.

[0053] As shown in Figure 5, a retaining wall 31, which is the side wall of a rectangular shaft 30 in plan view, is constructed using a known soil-cement construction method. At this time, a cuttable area 41 that can be directly cut by the shield excavator S is formed in the retaining wall 31b in the direction of departure of the shield excavator S. That is, in the construction of the retaining wall 31b, as shown in Figure 6, multiple long resin bodies 43 are placed in the part where the cuttable area 41 is located, and metal members 45 are placed in the other parts (non-cutting areas).

[0054] More specifically, the retaining wall 31b is formed by arranging multiple metal members 45 in parallel in a position extended vertically (height direction), with a portion of them replaced by a cuttable area 41. That is, non-cuttable areas are arranged above, below, to the left and right of the cuttable area 41, and in particular, in the vertical direction, the long resin body 43 and the metal members 45 are connected by joints and fastening elements such as bolts and nuts (not shown). Then, a soil cement hardened body 46 is filled between the long resin body 43 and the metal members 45 arranged in this manner. In other words, the retaining wall 31b is formed by combining the long resin body 43, the metal members 45 and the soil cement hardened body 46. Note that the retaining wall 31 without a cuttable area 41 is formed only of multiple metal members 45 and the soil cement hardened body 46.

[0055] After the retaining wall 31 is completed in this manner, the area enclosed by the retaining wall 31 is excavated (shaft excavation) using a designated excavator. Furthermore, in order to counteract the earth pressure and water pressure (hereinafter referred to as "earth pressure, etc.") acting on the retaining wall 31, known bracing (not shown) is provided at regular intervals in the shaft 30.

[0056] Once shaft excavation is carried out and the excavation progresses to the middle of the height of the cuttable area 41, the process switches to the ground anchor method, and multiple anchor fixing holes 37 (see Figure 7) are formed that span the cuttable area 41 and the surrounding ground, based on conditions such as the earth pressure acting from around the cuttable area 41 (first step). More specifically, the anchor fixing holes 37 are formed to have a downward slope of a predetermined angle (for example, 5 to 45 degrees) from the cuttable area 41 towards the ground.

[0057] Furthermore, most of the reinforcing anchor 1 is inserted into each anchor fixing hole 37. More specifically, the anchoring length portion 17 of the reinforcing anchor 1 (tip cap 13, tip grout watertight portion 14, and first end structure 4) is inserted so that it is located inside the anchor fixing hole 37. That is, as shown in Figure 7, the reinforcing anchor 1 is positioned such that a portion of the free length portion 16 and the tension member 15 are exposed from the anchor fixing hole 37 towards the shaft 30.

[0058] Then, after inserting the reinforcing anchor 1 into the anchor fixing hole 37, grout 22 is injected into the inside of the sheath 3 from the first anchoring material injection pipe 19, and the grout 22 is allowed to harden through curing. The grout 22 is injected until it fills the entire inside of the sheath 3 surrounding the first end structure 4 (Figures 7 to 8). In this case, any known grouting material can be used as grout 22. For example, cement milk can be used as grout 22. At this time, the sheath 3 expands as the grout 22 is filled, and the resulting expansion pressure compresses the inner surface of the anchor fixing hole 37. The grout 22 then hardens while maintaining this state. As a result, the reinforcing anchor 1 adheres tightly to the anchor fixing hole 37, preventing it from falling out of the anchor fixing hole 37. Furthermore, the anchored portion 17 of the resin fiber wire 2 inside the sheath 3 is exposed to the grout 22 and is therefore anchored to the sheath 3.

[0059] Alternatively, after inserting the reinforcing anchor 1 into the anchor fixing hole 37, grout 22 may be injected from the second anchoring material injection pipe 20 to the outside of the sheath 3 and allowed to cure to harden. The grout 22 is injected until it completely fills the gap between the sheath 3 and the anchor fixing hole 37 around the first end structure 4. Once the grout 22 hardens, the anchor fixing hole 37 and the reinforcing anchor 1 will be tightly fitted together through the grout 22, preventing the reinforcing anchor 1 from falling out of the anchor fixing hole 37.

[0060] The injection of grout 22 through the first anchoring material injection pipe 19 and the injection of grout 22 through the second anchoring material injection pipe 20 may be performed either individually or both.

[0061] Grout 22 is injected into the sheath 3, and after the grout 22 hardens and is fixed in the anchor fixing hole 37 while the sheath 3 is expanded, the pressure plate 26 is inserted into the reinforcing anchor 1. Specifically, the pressure plate 26 is positioned so that it is exposed on the side of the shaft 30. The pressure plate 26 is a component molded using GFFU.

[0062] Next, the bearing plate 27 is placed on the pressure receiving plate 26, and in that state, as shown in Figure 9, the nut 28 is screwed onto the threaded portion of the tension member 15 from the upper side of the bearing plate 27, thereby tightening the bearing plate 27 toward the pressure receiving plate 26.

[0063] Subsequently, a jack-up device (not shown) is installed on the bearing plate 27. Then, the jack-up device applies a pulling force to the free length portion 16 of the resin fiber wire 2, and the nut 28 is further tightened to maintain the tension. At this time, the resin fiber wire 2 is held in a taut state, following the tension member 15.

[0064] Then, the jack-up device (not shown) is removed from the bearing plate 27, and shaft excavation is carried out again. That is, provided that the reinforcement of the cuttable area 41 by the reinforcing anchor 1 is completed and the anchor-reinforced area 51 is completed, shaft excavation and bracing are carried out until the cuttable area 41 is completely exposed. Once the construction of the cuttable area 41 is completed, it becomes possible to directly cut using the shield drilling machine S.

[0065] As described above, according to the earth retaining wall reinforcement method of this embodiment, since the first end structure 4 of the reinforcing anchor 1 is waterproofed, when inserting and fixing the reinforcing anchor 1 into the anchor fixing hole 37, it is possible to suppress the reinforcing anchor 1 from falling out of the anchor fixing hole 37 due to pressure from groundwater, etc. Therefore, the efficiency of tunnel excavation work can be improved. [Explanation of symbols]

[0066] 1. Reinforcement anchor 2. Resin fiber wire 3 Sheath 4. First end structure 5. Second end structure 7. Covered pipe 8. First heat-shrinkable member 10. Second heat-shrinkable member 11 Hardened part 13 Tip cap 14. Grout sealing section at the tip 15. Tensile members 16 Free length section 17. Long-term maintenance 18 Unbonded Tubes 19. First anchoring material injection pipe 20 Second anchoring material injection pipe 21 Temperature control piping

Claims

1. A reinforcing anchor comprising multiple resin fiber wires bundled together with their longitudinal directions in the same direction, with these wires inside a sheath, The resin fiber wire comprises a first end structure formed at one end located in one longitudinal direction of the resin fiber wire, and a second end structure formed at the other end located in the other longitudinal direction of the resin fiber wire. The first end structure is a portion at one end where the resin fiber wire is covered with the first resin, The second end structure is the portion at the other end where the resin fiber wire is covered with the second resin. The first end structure comprises a first resin covering the outer circumference of the resin fiber wire and filling the spaces between the strands of the resin fiber wire, an unbonded tube covering the resin fiber wire from the outside via the first resin, and a first heat-shrinkable member binding the unbonded tube from the outside. The second end structure is a reinforcing anchor comprising: a second resin covering the outer circumference of the resin fiber wire and filling the spaces between the strands of the resin fiber wire; a second heat-shrinkable member that binds the resin fiber wire from the outside via the second resin; and a hardened portion made of a filling material disposed outside the second heat-shrinkable member.

2. The aforementioned filling material is an expandable mortar, The reinforcing anchor according to claim 1, wherein the expansion pressure of the hardened portion is 40 MPa or more and 60 MPa or less.

3. The second end structure side is provided with a tension member into which the second end structure is inserted, The reinforcing anchor according to claim 1, wherein the longitudinal length of the second end structure inserted into the tension member is 10 mm or more and 20 mm or less.

4. The reinforcing anchor according to claim 1, wherein the first resin and the second resin are ethylene-vinyl acetate copolymer resins.

5. The reinforcing anchor according to claim 1, wherein the content of the first resin is 1 g or more and 10 g or less per 60 mm length of the resin fiber wire.

6. The reinforcing anchor according to claim 1, wherein the content of the second resin is 1 g or more and 10 g or less per 60 mm length of the resin fiber wire.

7. The reinforcing anchor according to claim 1, further comprising a first anchoring material injection pipe extending in the longitudinal direction of the resin fiber wire inside the sheath.

8. The reinforcing anchor according to claim 1, further comprising a second anchoring material injection pipe extending in the longitudinal direction of the resin fiber wire on the outside of the sheath.

9. A method for reinforcing an earth retaining wall having a cuttable area using a reinforcing anchor according to claim 7 or 8, Multiple anchor fixing holes are formed that span the cuttable area and the surrounding ground, A method for reinforcing a retaining wall, comprising injecting a fixing material into the fixing material injection pipe while inserting the reinforcing anchor into the anchor fixing hole.

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