JP2024051558A - Reinforcing anchor, and reinforcing method for earth retaining wall - Google Patents

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

The present invention relates to a reinforcing anchor and a method for reinforcing an earth retaining wall using the reinforcing anchor.

2. Description of the Related Art Conventionally, the shield method using a shield tunneling machine has been widely adopted for tunnel construction such as subways, underpasses, utility tunnels, sewerage systems, etc. (hereinafter, also referred to as "subways, etc.").
Generally, the shield tunneling method involves first forming a vertical shaft (starting shaft) using an open cut method, then bringing a shield tunneling machine underground from this starting shaft, using the shield tunneling machine to excavate the side of the starting shaft, then starting out laterally, and excavating a tunnel to the destination, or end point.
Typically, in shield tunneling, a vertical hole (arrival shaft) similar to the departure shaft is formed at the end point, which is the destination of the tunnel, and the shield tunneling machine is driven to reach this arrival shaft.

Meanwhile, on the sides of departure shafts and arrival shafts (hereinafter collectively referred to as "shafts") formed by the open cut method, temporary retaining walls made of reinforced concrete, grooved sheet piles, H-shaped steel, etc. are constructed to prevent the sides from collapsing due to earth pressure or water pressure (hereinafter referred to as "earth pressure, etc.") and to prevent groundwater from leaking from the sides.

In this way, in the shafts used in shield tunneling, a core material is placed on the inner circumference of the shaft to maintain space against earth pressure and other factors, and a retaining wall is constructed. Furthermore, in the retaining walls thus constructed, openings must usually be made when the shield excavator departs and arrives (so-called "recess cutting"). Conventionally, the recess cutting work for such retaining walls has been carried out using heavy machinery or manual labor. Furthermore, because the retaining walls are constructed to resist earth pressure and other factors, creating openings can reduce the resisting force.

In recent years, therefore, a shield construction method has been implemented in which components made of fiber-reinforced resin moldings (FRP: Fiber Reinforced Plastics) are incorporated into the earth retaining walls of the shaft, and the FRP parts (cuttable areas) are directly cut with a shield excavator (SEW method: Shield Earth Retaining Wall System).

However, in conventional SEW construction methods, it was difficult to use retaining walls with cuttable areas in environments where a certain level of earth pressure or the like was generated.
Therefore, in order to make it possible to adopt the SEW method even in such an environment, there is a method in which cuttable reinforcing anchors are provided in the cuttable area, and the strength of the cuttable area is indirectly reinforced by these reinforcing anchors (hereinafter referred to as the "anchor reinforcement method").
The anchor reinforcement method is a method of reinforcing the cuttable area using a reinforcing anchor equipped with a tendon grip and a resin fiber wire.

In the anchor reinforcement method, reinforcing anchors are cast in the cuttable area during the process of excavating the inside of the shaft surrounded by the core material. When casting the reinforcing anchors, the soil cement portion between the core materials is excavated to form an anchor fixing hole (hole). Next, the reinforcing anchor is inserted into the anchor fixing hole, and then the reinforcing anchor is fixed in place using the anchor head (bolt and nut structure) and pressure plate (see, for example, Patent Document 1).

Japanese Patent No. 6163380

In the process of forming the above anchor fixing holes, if a low-permeability layer (pressurized layer) exists above the position where the anchor fixing holes for driving the reinforcing anchors are provided, pressure from groundwater is applied to the anchor fixing holes. Therefore, in the process of inserting the reinforcing anchors into the anchor fixing holes, the lightweight resin reinforcing anchors are pushed back by the pressure and buoyancy of the groundwater, creating an issue in that the reinforcing anchors cannot be inserted to their full length into the drilled hole.

In addition, in the reinforcing anchor described in Patent Document 1, in order to form a free length (a region that does not adhere to the grout for forming the anchor length when the anchor is installed), one end of the resin fiber wire is covered with a free length sheath in a state where up to six resin fiber wires are bundled together. In order to reduce the effects of pressure and buoyancy due to groundwater as described above, when a structure is adopted in which the resin fiber wires are covered one by one with a sheath, it is necessary to reduce the gap between the resin fiber wire and the sheath so that the grout for forming the anchor length does not penetrate into the free length part (so that the resin fiber wire and grout in the free length part do not adhere to each other during construction). However, at the other end of the resin fiber wire, there was a problem that the resin fiber wire cannot be covered with a free length sheath in a state where up to six resin fiber wires are bundled together.

The present invention was made in consideration of the above circumstances, and aims to provide a reinforcing anchor that can reduce the effects of groundwater pressure and buoyancy and can be stably fixed into an anchor fixing hole formed in an earth retaining wall, and a method of reinforcing an earth retaining wall using a reinforcing anchor.

The present invention has the following aspects.
[1] A reinforcing anchor having a plurality of resin fiber wires bundled together with their longitudinal ends in the same direction inside a sheath,
a first end structure formed at one end in a 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 includes an unbonded tube that covers the resin fiber wire from the outside, and a first heat shrink member that binds the unbonded tube from the outside,
The second end structure includes a second resin covering an outer periphery of the resin fiber wire and filled between the strands of the resin fiber wire, a second heat-shrinkable member binding the resin fiber wire from the outside via the second resin, and a hardened portion made of a filling material and arranged on the outside of the second heat-shrinkable member.
[2] The filling material is an expansive 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] A tension member for inserting the second end structure is provided on the second end structure side,
The reinforcement anchor according to claim 1, wherein the longitudinal length of the second end structure inserted into the tension member is greater than or equal to 10 mm and less than or equal to 20 mm.
[4] The reinforcing anchor described in [1], wherein the first resin and the second resin are ethylene-vinyl acetate copolymer resins.
[5] The reinforcing anchor described in [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 described in [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 described in [1], further comprising a first fixing material injection pipe inside the sheath and extending in the longitudinal direction of the resin fiber wire.
[8] The reinforcing anchor described in [1], further comprising a second fixing agent injection pipe on the outside of the sheath and extending in the longitudinal direction of the resin fiber wire.
[9] A method for reinforcing a retaining wall having a cuttable area using the reinforcing anchor according to [7] or [8],
A method for reinforcing a retaining wall, comprising forming a plurality of anchor fixing holes spanning the cuttable area and the surrounding ground, and inserting the reinforcing anchors into the anchor fixing holes while injecting an anchor into the anchor injection pipe.

The present invention provides a reinforcing anchor that can reduce the effects of groundwater pressure and buoyancy and can be stably fixed into an anchor fixing hole formed in an earth retaining wall, and a method for reinforcing an earth retaining wall using the reinforcing anchor.

1 is a cross-sectional view showing a longitudinal section of a reinforcing anchor according to one embodiment of the present invention; 2 is a diagram showing a cross-sectional end view of a reinforcement anchor according to an embodiment of the present invention taken along line AA in FIG. 1. FIG. 2 is a diagram showing a cross-sectional end face of a reinforcing anchor according to an embodiment of the present invention taken along line BB in FIG. 1. FIG. 2 is a diagram showing a cross-sectional end face of a reinforcing anchor according to an embodiment of the present invention taken along line CC in FIG. 1 is a cross-sectional view showing a method for reinforcing an earth retaining wall according to one embodiment of the present invention. 1 is a front view showing a method for reinforcing an earth retaining wall according to one embodiment of the present invention; 1 is a cross-sectional view showing a method for reinforcing an earth retaining wall according to one embodiment of the present invention. 1 is a cross-sectional view showing a method for reinforcing an earth retaining wall according to one embodiment of the present invention. 1 is a cross-sectional view showing a method for reinforcing an earth retaining wall according to one embodiment of the present invention.

The reinforcing anchor of the present invention and the method of reinforcing an earth retaining wall using the reinforcing anchor are described below with reference to the embodiments. However, the present invention is not limited to the following embodiments.

[Reinforcement anchor]
Fig. 1 is a cross-sectional view showing a longitudinal section of a reinforcement anchor according to one embodiment of the present invention. Fig. 2 is a view showing an end face of a cross section of a reinforcement anchor according to one embodiment of the present invention taken along line A-A in Fig. 1. Fig. 3 is a view showing an end face of a cross section of a reinforcement anchor according to one embodiment of the present invention taken along line B-B in Fig. 1. Fig. 4 is a view showing an end face of a cross section of a reinforcement anchor according to one embodiment of the present invention taken along line CC in Fig. 1.
In addition, the drawings used in the following description may show characteristic parts in an enlarged scale for convenience in order to make the features easier to understand, and the dimensional ratios of each component may differ from the actual ones.

As shown in FIG. 1, the reinforcing anchor 1 of this embodiment includes a plurality of resin fiber wires 2 bundled together with their longitudinal ends in the same direction inside a sheath 3. The reinforcing anchor 1 of this embodiment also includes a first end structure 4 formed at one end (tip end) 2A of the resin fiber wire 2 in the longitudinal direction, and a second end structure 5 formed at the other end (rear end) 2B of the resin fiber wire 2 in the longitudinal direction. The first end structure 4 is a portion at one end of the reinforcing anchor 1 where the resin fiber wire 2 is covered with a first resin (not shown). The second end structure 5 is a portion at the other end of the reinforcing anchor 1 where the resin fiber wire 2 is covered with a second resin (not shown).

As shown in FIG. 2, the first end structure 4 has, in order from the resin fiber wire 2 side toward the outside, 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 (referring to one of a maximum of six) 2 and fills the gaps between the wires of the resin fiber wire 2. The unbonded tube 18 covers the resin fiber wire 2 (one wire) consisting of multiple wires from the outside via the first resin. The first heat shrinkable member 8 binds the unbonded tube 18 from the outside. Six resin fiber wires 2 configured in this way are bundled and enclosed in the sheath 3.

As shown in FIG. 3, the second end structure 5 has, in order from the resin fiber wire 2 side toward the outside, an unbond tube 18, a second heat shrinkable member 10, and a hardened portion 11. The second resin covers the outer periphery of the multiple resin fiber wires 2 and is filled between the wires of the resin fiber wires 2, filling the gaps between the wires of the resin fiber wires 2. The second heat shrinkable member 10 binds the multiple resin fiber wires 2 from the outside via the second resin. The hardened portion 11 is made of a filling material arranged on the outside of the second heat shrinkable member 10. In addition, a temperature control pipe 21 for curing the filling material that forms the hardened portion 11 is arranged in the center of the second end structure 5.

The reinforcing anchor 1 has a tip cap 13 at the tip portion, i.e., 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 water stop part 14 on the rear end side of the tip cap 13, which extends from the tip cap 13 to the other end side in the longitudinal direction of the resin fiber wire 2. The tip grout water stop part 14 covers the outer periphery of the plurality of resin fiber wires 2 and is made of grout filled between the plurality of resin fiber wires 2.

The reinforcing anchor 1 has a tension member (tendon grip) 15 at the 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 is connected to the inside and outside of the tension member 15.

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

As shown in FIG. 1, the reinforcing anchor 1 preferably includes a first fixing material injection pipe 19 inside the sheath 3, which extends in the longitudinal direction of the resin fiber wire 2. The first fixing 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 portion 14. Grout can be injected into the inside of the sheath 3 from the tension member 15 side via the first fixing material injection pipe 19.

As shown in FIG. 1, the reinforcing anchor 1 preferably includes a second fixing material injection pipe 20 extending in the longitudinal direction of the resin fiber wire 2 on the outside of the sheath 3. The second fixing 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 via the second fixing material injection pipe 20.

The resin fiber wire 2 is a rope-like body that is flexible and easy to cut.
The material of the resin fiber wires 2 is not particularly limited as long as it is a fiber-reinforced resin, but from the viewpoints of high tensile strength and light weight, a thermosetting resin reinforced with carbon fiber is preferable. Note that the core wire constituting each resin fiber wire 2 may have glass fiber.
The resin fiber wire 2 is designed so that the fiber direction is aligned approximately in the axial direction (the longitudinal direction of the reinforcing anchor 1). That is, the resin fiber wire 2 is a member with high strength against tensile forces acting in the longitudinal direction of the reinforcing anchor 1. In addition, since the reinforcing fibers of the reinforcing anchor 1 are carbon fibers, the reinforcing anchor 1 is easily destroyed by cutting with a shield excavator, and is also a member that is easily cuttable.

The sheath 3 is not particularly limited, but may be, for example, a corrugated sheath having a corrugated surface.
The material of the sheath 3 is not particularly limited, but polypropylene, nylon, etc. are preferable from the viewpoint of excellent flexibility and weather resistance.

The length of the resin fiber wire 2 in the first end structure 4 in the longitudinal direction is preferably 100 mm or more and 500 mm or less, more preferably 100 mm or more and 300 mm or less, and even more preferably 100 mm or more and 200 mm or less. When the length of the first end structure 4 is equal to or more than the lower limit, a water-stopping section of sufficient length can be formed, and the water-stopping properties of the end of the unbonded tube covering part of the resin fiber wire 2 can be ensured. When the length of the first end structure 4 is equal to or less than the upper limit, the material cost used for water-stopping and the labor required for processing the tip grout water-stopping part 14 can be reduced.

The length of the resin fiber wire 2 of the second end structure 5 in the longitudinal direction is preferably 10 mm or more and 50 mm or less, more preferably 10 mm or more and 30 mm or less, and even more preferably 10 mm or more and 20 mm or less. When the length of the second end structure 5 is equal to or more than the lower limit, the length of the fixing length portion 17 with the resin fiber wire 2 by the expanding mortar is not impaired, and at the same time, the watertightness of the end of the unbonded tube covering portion can be ensured. When the length of the second end structure 5 is equal to or less than the upper limit, the material cost used for watertightness and the labor required for processing the tip grout watertight portion 14 can be reduced.

The first resin and the second resin are not particularly limited as long as they cover the outer circumference of the multiple resin fiber wires 2, fill the spaces between the strands of the resin fiber wires 2, and can 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 (Ethylene-Vinyl Acetate: EVA) is preferred.

The content of the first resin is preferably 1 g to 20 g per 60 mm length of one resin fiber wire 2, more preferably 1 g to 15 g, and even more preferably 1 g to 10 g. When the content of the first resin is equal to or greater than the lower limit, a sufficient amount of the first resin can be filled between the strands of the resin fiber wire 2, improving the water stopping ability. When the content of the first resin is equal to or less than the upper limit, the material cost used for water stopping and the man-hours required for processing the tip grout water stopping portion 14 can be reduced.

The content of the second resin is preferably 1 g to 20 g per 60 mm length of one resin fiber wire 2, more preferably 1 g to 15 g, and even more preferably 1 g to 10 g. When the content of the second resin is equal to or greater than the lower limit, a sufficient amount of the second resin can be filled between the strands of the resin fiber wire 2, improving the water stopping ability. When the content of the second resin is equal to or less than the upper limit, the material cost used for water stopping and the man-hours required for processing the tip grout water stopping portion 14 can be reduced.

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

The unbonded tube 18 covers the entire first resin that covers the resin fiber wire 2.

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 cross-linked soft flame-retardant polyolefin resin) manufactured by Sumitomo Electric Industries, Ltd.

The length of the resin fiber wire 2 covered by the first heat shrink member 8 is preferably 20 mm or more and 200 mm or less, more preferably 20 mm or more and 150 mm or less, and even more preferably 20 mm or more and 100 mm or less. If the length of the resin fiber wire 2 covered by the first heat shrink member 8 is equal to or more than the lower limit, watertightness during grout injection can be ensured. If the length of the resin fiber wire 2 covered by the first heat shrink member 8 is equal to or less than the upper limit, the material cost used for watertightness and the man-hours required for processing the tip grout watertight portion 14 can be reduced.

The first heat shrink member 8 may cover at least a portion of the unbonded tube 18 and overlap the unbonded tube 18. The overlap length of the first heat shrink 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 overlap length of the first heat shrink member 8 and the unbonded tube 18 is equal to or greater than the lower limit, the area (attachment length) of the integrated portion of the first heat shrink member 8 and the unbonded tube 18 can be secured, and water stoppage during grout injection can be secured. If the overlap length of the first heat shrink member 8 and the unbonded tube 18 is equal to or less than the upper limit, the material cost used for water stoppage and the man-hours required for processing the tip grout water stoppage portion 14 can be reduced.

The second heat shrink member 10 is the same material as the first heat shrink member 8.

The second heat-shrinkable member 10 covers the entire second resin that covers the resin fiber wires 2 .
The length of the resin fiber wire 2 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. When the length of the resin fiber wire 2 covered by the second heat shrinkable member 10 is equal to or greater than the lower limit, watertightness during grout injection can be ensured. When the length of the resin fiber wire 2 covered by the second heat shrinkable member 10 is equal to or less than the upper limit, the cost of materials used for watertightness and the number of steps required for processing the tip grout watertight portion 14 can be reduced.

Expansive mortar is preferable as the filling material that forms the hardened portion 11. A specific example of expansive mortar is mortar that exhibits an expansion pressure of 40 MPa to 60 MPa when the temperature during curing is maintained at 10 degrees Celsius or more and 60 degrees Celsius or less.

The expansion pressure of the hardened portion 11 is preferably 40 MPa or more and 60 MPa or less, and more preferably 40 MPa or more and 50 MPa or less. If the expansion pressure of the hardened portion 11 is equal to or more than the lower limit, the integrated strength of the resin fiber wire 2 and the tensile member 15 can be improved. If the expansion pressure of the hardened portion 11 is equal to or less than the upper limit, the effect of dimensional change of the tensile member 15 can be reduced.

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.

As shown in FIG. 1, the tip cap 13 is tapered so that its diameter decreases toward the tip side.
The material of the tip cap 13 is not particularly limited, but examples thereof include high-density polyethylene, polyvinyl chloride resin, etc. From the viewpoint of excellent water resistance (water stopping ability), high-density polyethylene is preferable.

The grout (fixing material) that forms the tip grout watertight section 14 is used to fix rock bolts and fill gaps between the ground and the lining in injection methods, shield methods, etc., during tunnel excavation. Cement (mortar)-based materials, glass-based materials, synthetic resins, etc. can be used as grout.

The longitudinal length of the resin fiber wire 2 of the tip grout water stop portion 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 water stop portion 14 is equal to or more than the lower limit, water stoppage of 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 water stop portion 14 is equal to or less than the upper limit, the cost of materials used for water stoppage and the labor required for processing the tip grout water stop portion 14 can be reduced.

The tension member 15 is a resin molded product made of fiber reinforced plastic (FRP).
The tension member 15 is designed so that the orientation of the fibers is substantially aligned in the axial and circumferential directions. That is, the tension member 15 is a member having high rigidity against the bending moment of a force acting in a direction intersecting the longitudinal direction of the reinforcing anchor 1. In addition, since the tension member 15 is made of FRP, it is easily destroyed by cutting with a shield excavator, and is also a member that has ease of cutting. That is, the tension member 15 is a member having high rigidity against the bending moment of a force and has ease of cutting.

The longitudinal length of the second end structure 5 inserted into the tensile 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 tensile member 15 is equal to or more than the lower limit, the watertightness of the other end side 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 tensile member 15 is equal to or less than the upper limit, the adhesion length of the resin fiber wire 2 and the expanding mortar within the tensile member 15 can be ensured.

The material of the first fixing material injection pipe 19 and the second fixing 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.

The reinforcing anchor 1 of this embodiment is an anchor that is also used to reinforce the slope, and as described below, is suitable for use in reinforcing 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. The reinforcing anchor 1 of this embodiment also has the function of reinforcing and stabilizing the earth retaining wall of the shaft formed when excavating a shield tunnel, and can be easily cut together with the earth retaining wall by the shield excavator during excavation.

The reinforcing anchor 1 of this embodiment has the above-mentioned first end structure 4 and the above-mentioned second end structure 5, so that it can reduce the effects of pressure and buoyancy due to groundwater and can be stably fixed in the anchor fixing hole formed in the retaining wall. Therefore, it is possible to improve the work efficiency of excavating a shield tunnel.

[Method of reinforcing earth retaining walls]
A method for reinforcing an earth retaining wall according to one embodiment of the present invention will be described with reference to FIGS.

The method for reinforcing an earth retaining wall of this embodiment is a method for reinforcing an earth retaining wall having a cuttable area using the reinforcing anchor of this embodiment, in which multiple anchor fixing holes are formed across the cuttable area and the surrounding ground, and the reinforcing anchor is inserted into the anchor fixing holes while injecting an anchor into the anchor injection pipe.

The method for reinforcing the retaining wall in this embodiment is a method for reinforcing and stabilizing the retaining wall 31 (structural body) of the shaft 30 formed when excavating a shield tunnel by a shield excavator S, using the reinforcing anchor 1 in the above-described embodiment, as shown in FIG. 5.

As shown in FIG. 5, a known soil cement method is used to construct a retaining wall 31, which is the side wall of a vertical shaft 30 that has a rectangular shape in plan view. 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 starting direction of the shield excavator S. That is, in constructing the retaining wall 31b, as shown in FIG. 6, multiple long resin bodies 43 are placed in the area where the cuttable area 41 is located, and metal members 45 are placed in the other areas (non-cutting areas).

More specifically, the retaining wall 31b is formed by arranging multiple metal members 45 in parallel in a vertical (height) extended position, with a portion of the metal members 45 being replaced by the cuttable area 41. That is, non-cutting areas are arranged above, below, left and right of the cuttable area 41, and particularly at the top and bottom of the height direction, the long resin body 43 and the metal member 45 are connected by fastening elements such as joints and bolts and nuts (not shown). Then, the soil cement hardened body 46 is filled between the long resin body 43 and the metal member 45 arranged in this way. That is, the retaining wall 31b is formed by combining the long resin body 43, the metal member 45 and the soil cement hardened body 46. Note that the retaining wall 31, which does not have the cuttable area 41, is formed only by multiple metal members 45 and the soil cement hardened body 46.

After the retaining wall 31 is completed in this manner, the portion surrounded by the retaining wall 31 is excavated (shaft excavation) using a designated excavator.
In addition, in the shaft 30, well-known struts (not shown) are provided at certain depth intervals to resist earth pressure and water pressure (hereinafter referred to as "earth pressure, etc.") acting on the retaining wall 31.

When the shaft is excavated and reaches the middle of the cutting area 41 in the height direction, the method transitions to the ground anchor method, and multiple anchor fixing holes 37 (see Figure 7) are formed across the cutting area 41 and the surrounding ground based on conditions such as the earth pressure acting from around the cutting area 41 (first step). More specifically, the anchor fixing holes 37 are formed so as to have a downward slope of a specified angle (e.g., 5 degrees to 45 degrees) from the cutting area 41 toward the ground.

Moreover, most of the reinforcing anchor 1 is inserted into each anchor fixing hole 37. More specifically, the reinforcing anchor 1 is inserted so that its fixed length portion 17 (tip cap 13, tip grout waterstop portion 14, and first end structure 4) is positioned within the anchor fixing hole 37. That is, the reinforcing anchor 1 is positioned so that a part of the free length portion 16 and the tension member 15 are exposed from the anchor fixing hole 37 to the shaft 30 side, as shown in FIG. 7.

Then, after the reinforcing anchor 1 is inserted into the anchor fixing hole 37, grout 22 is injected into the inside of the sheath 3 from the first fixing material injection pipe 19, and the grout 22 is cured and hardened. The grout 22 is injected until the entire inside of the sheath 3 around the first end structure 4 is filled with the grout 22 (FIGS. 7 to 8).
At this time, a known grout material can be used as the grout 22. As the grout 22, for example, cement milk can be used.
At this time, the sheath 3 expands as the grout 22 is filled, and the expansion pressure presses the inner surface of the anchor fixing hole 37. Then, this state is maintained as the grout 22 hardens. Therefore, the reinforcing anchor 1 adheres closely to the anchor fixing hole 37, and the reinforcing anchor 1 does not fall out of the anchor fixing hole 37.
In addition, the fixing length portion 17 of the resin fiber wire 2 in the sheath 3 is exposed to the grout 22 and is therefore fixed to the sheath 3 .

After the reinforcing anchor 1 is inserted into the anchor fixing hole 37, grout 22 may be injected from the second fixing material injection pipe 20 onto the outside of the sheath 3 and cured to harden the grout 22. The grout 22 is injected until it fills all of the gaps between the sheath 3 and the anchor fixing hole 37 around the first end structure 4. When the grout 22 hardens, the anchor fixing hole 37 and the reinforcing anchor 1 are tightly attached via the grout 22, and the reinforcing anchor 1 will not fall out of the anchor fixing hole 37.

Either the injection of grout 22 through the first fixing material injection pipe 19 or the injection of grout 22 through the second fixing material injection pipe 20 may be performed, or both may be performed.

The 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 in an expanded state, the pressure plate 26 is inserted into the reinforcing anchor 1. Specifically, the pressure plate 26 is disposed in a position exposed on the shaft 30 side.
The pressure plate 26 is a member molded from GFFU.

Next, the support plate 27 is placed on the pressure plate 26, and in this state, as shown in FIG. 9, the nut 28 is screwed onto the threaded portion of the tension member 15 from the upper side of the support plate 27, and the support plate 27 is tightened to the pressure plate 26 side.

Thereafter, a jack-up device (not shown) is installed on the support plate 27. Then, the jack-up device applies a force in the pulling direction 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 tensile state by following the tension member 15 .

Then, the jack-up device (not shown) is removed from above the bearing plate 27, and the shaft is excavated again. That is, on the condition that the reinforcement of the cuttable area 41 by the reinforcing anchor 1 is completed and the anchor reinforcement area 51 is completed, the shaft is excavated and the struts are installed until the cuttable area 41 is completely exposed.
In this way, once construction of the cuttable area 41 is completed, it becomes possible to perform cutting directly using the shield excavator S.

As described above, according to the method for reinforcing an earth retaining wall of this embodiment, the first end structure 4 of the reinforcing anchor 1 is watertight, so when the reinforcing anchor 1 is inserted and fixed in the anchor fixing hole 37, it is possible to prevent the reinforcing anchor 1 from falling out of the anchor fixing hole 37 due to pressure from groundwater, etc. This can improve the efficiency of the tunnel excavation work.

REFERENCE SIGNS LIST 1 Reinforcing anchor 2 Resin fiber wire 3 Sheath 4 First end structure 5 Second end structure 7 Covering pipe 8 First heat shrinkable member 10 Second heat shrinkable member 11 Hardened portion 13 Tip cap 14 Tip grout water stop portion 15 Tensile member 16 Free length portion 17 Anchored length portion 18 Unbonded tube 19 First anchoring material injection pipe 20 Second anchoring material injection pipe 21 Temperature control piping

Claims (9)

A reinforcing anchor including a plurality of resin fiber wires bundled together with their longitudinal ends in the same direction inside a sheath,
a first end structure formed at one end in a 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 includes a first resin that covers an outer periphery of the resin fiber wire and fills spaces between the wires of the resin fiber wire, an unbonded tube that covers the resin fiber wire from the outside via the first resin, and a first heat shrinkable member that binds the unbonded tube from the outside,
The second end structure includes a second resin covering an outer periphery of the resin fiber wire and filled between the strands of the resin fiber wire, a second heat-shrinkable member binding the resin fiber wire from the outside via the second resin, and a hardened portion made of a filling material and arranged on the outside of the second heat-shrinkable member. The filling material is an expansive 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. a tension member for inserting the second end structure on the second end structure side;
2. The reinforcement anchor of claim 1, wherein the longitudinal length of the second end structure inserted into the tension member is greater than or equal to 10 mm and less than or equal to 20 mm. The reinforcing anchor according to claim 1, wherein the first resin and the second resin are ethylene-vinyl acetate copolymer resins. 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. 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. The reinforcing anchor according to claim 1, further comprising a first fixing agent injection pipe extending in the longitudinal direction of the resin fiber wire inside the sheath. The reinforcing anchor according to claim 1, further comprising a second fixing agent 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 the reinforcing anchor according to claim 7 or 8,
A plurality of anchor fixing holes are formed across the cuttable area and the surrounding ground,
A method for reinforcing an earth retaining wall, comprising inserting the reinforcing anchor into the anchor fixing hole while injecting an anchor into the anchor injection pipe.

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