JP3412809B2 - FRP lock bolt - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an FRP lock bolt used for fixing and reinforcing a natural ground in tunnel construction or the like, and more particularly to an FRP lock bolt having a screw formed on the outer circumference.

[0002]

2. Description of the Related Art In the NATO method (NATM method), which is common in tunnel construction in mountains, etc., after excavating the natural ground (when necessary, after cementing the wall with cement), a large number of pieces are vertically inserted into the bedrock. The rock bolts are driven in and fixed with a predetermined fixing material such as cement or resin to strengthen the ground near the tunnel wall and support the ground inside the rock to prevent collapse around the inner wall. I am doing it (support work). The lock bolt is vertically driven into the side wall of the construction tunnel and fixed, and then left in the ground as it is for reinforcement of the ground for a long time, and it is driven into the face mirror and silot etc. at the tip of the construction tunnel and fixed. However, it is for temporary support work that will be cut off along with the tunnel excavation with only temporary reinforcement.

In the former case of supporting work, it is desirable that the structural member has as high strength as possible, and a steel lock bolt is used. After the driving, the plate is tightened to the ground by using a plate such as a plate and a washer and a nut so that the fixing is firmly performed for a long period of time. In the latter case of temporary support work, FRP lock bolts (bolts obtained by hardening a bundle of reinforcing fibers such as glass fibers with a thermosetting resin) are often used so that they can be cut later. Initially, many FRP lock bolts were used without screws. This is because it is difficult to obtain sufficient tensile strength as compared with the strength of the main body even if the threaded portion is formed. In other words, the FRP lock bolt, like a steel lock bolt, has the required effect because the tensile strength at the screw part is weak even if it is tightened to the ground using the seat plate and nut after the screw is formed and placed. I can't.
However, in the case of the above temporary support work, the FRP lock bolt is often removed within a short period of time, so tightening with a nut is not necessary and it is simply placed in the ground.
Even if it does not have a screw part, no problem occurs.

By the way, when the temporary period becomes long, the FRP
Even with a lock bolt, it is necessary to tighten it to the ground by using a seat plate and a nut after mounting and firmly fix it. Also, F
RP lock bolts are light and strong, have no corrosion, are electrically insulating, and have the characteristic that they can be easily cut, and it would be convenient if they could be used in place of steel lock bolts. Therefore, it has been desired to improve its tensile strength.

Therefore, a FRP lock bolt has been developed which has a rope screw shape over its entire length, which is obtained by narrowing down the surface in a spiral shape with a thread-like member (Patent No. 262913).
No. 0). FIG. 7 is a partially cutaway view of the FRP lock bolt 1, in which (1) a long fibrous fiber assembly 2 made of glass fiber and / or aramid fiber is heat-curable with unsaturated polyester, vinyl ester, epoxy resin or the like. Impregnated with resin,
(2) A filamentous fiber material 3 made of vinylon, tetoron kepler, nylon, glass yarn, glass roving, etc. is spirally wound and tightened, thereby forming an uneven shape in the axial direction of the outer peripheral surface. (3) After that, It is heat-cured and processed into a so-called rope screw shape (pitch is coarser than the male screw portion formed on the steel lock bolt).

According to this FRP lock bolt, a tensile strength equivalent to about 50% of the strength of the main body can be obtained by using a nut, but the screw strength per unit length (tensile strength of thread) is It's still small. For this reason, when the nut combined with the seat plate is fitted into the FRP lock bolt after driving to fix it, the tensile load applied to the screw thread at the fitting portion of the lock bolt and the nut is reduced to reduce the tensile strength of the screw thread. It needs to be able to withstand even low materials. Therefore, as shown in FIG. 8, the fitting length L of the lock bolt 1 and the nut 5 is considerably long, and the nut 5 is made long to secure a sufficient length in the female screw portion. However, such a structure requires a fitting length L several times as large as that of the steel lock bolt,
The end portion of the lock bolt 1 including the seat plate 4 and the nut 5 largely projects into the tunnel space. As a result, when it interferes with other work in the middle of tunnel construction or when laying sheets 7 such as a waterproof sheet and an isolation sheet in the next process, the sheets 7 are blocked by the protruding lock bolt heads. As a result, unevenness may occur, the desired sheet performance may not be exhibited, and further, problems may occur such as damage to the sheet during subsequent placement of secondary lining concrete.

In order to solve the above-mentioned problem, there has been proposed an FRP lock bolt in which a nut having a special shape is used to shorten the protruding length of the lock bolt (JP-A-9-13).
898). FIG. 9 is a perspective view of such an FRP lock bolt. A male screw portion (rope screw) 1a is formed on the outer periphery of the FRP lock bolt 1, and a specially shaped nut 5 having a female screw portion of a predetermined length is screwed onto the lock bolt 1. Is possible. The nut 5 includes a shaft portion 5a that can be loosely inserted into the round hole 4a of the seat plate 4, and a head portion 5b that is fixed to the proximal side of the shaft portion and that is larger than the seat plate hole 4a. A female screw portion 5c having a predetermined length is formed so as to be continuous up to.

As shown in FIG. 10, the lock bolt 1 is fixed to the ground by fitting the nut 5 in combination with the seat plate 4 into the lock bolt 1 driven into the ground 6. That is, the borehole 8 is bored in the natural ground 6, and then the lock bolt 1 is driven. After that, the nut 5 is put in the hole 4a of the seat plate 4.
With the shaft portion 5a of FIG. 1 loosely inserted, the female screw portion of the nut 5 is fitted into the male screw portion of the head of the lock bolt 1. As the fitting progresses, the shaft portion 5a of the nut 5 enters into the bore hole 8, the seat plate 4 is pressed against the ground by the head portion 5b of the nut 5, and the lock bolt 1 is firmly fixed to the ground. Most of the nut 5 goes into the bore hole, and only the thickness of the nut head 5 and the seat plate 4 is exposed to the outside. Therefore, the protruding length L ′ of the lock bolt can be shortened, which hinders other work. In addition, since unevenness becomes small when sheets such as a waterproof sheet and an isolation sheet are laid in the next step, desired sheet performance can be exhibited.

[0009]

[Problems to be Solved by the Invention] However, the FRP of FIG.
With the lock bolt, the fitting length L cannot be reduced, the nut 5 is integrally fixed when the fixing material is used, and the tightening force cannot be adjusted after fixing. Further, all of the above-mentioned conventional FRP lock bolts have problems in construction management.

When the rock bolt is actually installed, it is necessary to confirm whether or not the rock bolt is sufficiently fixed to the ground (construction management), and the test methods thereof include a pull-out test and a torque test. The pull-out test is a test for confirming the fixing force by applying a pull-out force to the lock bolt using a hydraulic jack, and FIG. 11 is a drawing for explaining the pull-out test of the steel lock bolt (metal full screw bolt). The steel lock bolt 1 ′ is fixed to the ground 6 by the fixing material 9. In order to perform a pull-out test of the steel lock bolt 1 ', a pull-out test device (square washer 10, ram chair 11, angle adjustment pedestal 12, center hole type hydraulic jack 13,
A reaction plate 14, etc.) is attached in a testable manner. Also, the tension bolt (extension rod) 15 formed with a female screw that fits with the male screw of the lock bolt 1 ′ is inserted into the reaction force plate 14 → the hydraulic jack 13 → the ram chair 11 so that the lock bolt can be inserted. Screw it into one end of 1 '. After that, the tension bar nut 16 is fitted to the M thread portion formed on the outer circumference of the other end of the tension bar 15 and tightened to the reaction force plate 14. In this state, when oil is sent from the hydraulic pump (not shown) to the hydraulic jack 13, the hydraulic jack 13 tries to move the reaction plate 14 to the right by the piston (not shown) by hydraulic pressure. Therefore, when the hydraulic force is further applied to increase the moving force (withdrawal force), the reaction force plate 14 moves and the lock bolt 1'is withdrawn. Therefore, the fixing force can be measured by measuring the pull-out force at that time with the hydraulic gauge of the hydraulic pump. In the pull-out test, if the lock bolt 1'is not pulled out even if a predetermined pulling force is applied, it is determined that the fixing is normal.

In the conventional FRP lock bolt formed with a rope screw, it is not necessary to fit a nut if it is only temporarily installed. Therefore, the length of the bolt end projecting from the ground into the tunnel space can be shortened. However, in the pull-out test, the length of the bolt main body (the portion protruding from the ground) is short, and therefore the length required for fitting with the tension bar 15 cannot be obtained. Therefore, as shown in FIG. 12, the FR of the length L required to sufficiently fit the tension bar 15 is obtained.
The P-lock bolt is taken out from the construction surface and cut after the test is completed, but this takes extra time.

In the pull-out test of the FRP lock bolts shown in FIGS. 9 and 10, the bolt body 1 has a short protrusion (screw portion protruding from the ground), so that the tension bar 15 is fitted. I can't get the length I need. For this reason,
It is necessary to take out the bolt main body 1 of a length necessary for sufficiently fitting with the tension bar 15 from the construction surface and cut it after the test is completed, which requires extra labor. Further, the torque test is a test for tightening a nut with a torque trench and applying a torque corresponding to a confirmation load to confirm the fixing force. However, the FRP lock bolt 1 is weak against a twisting force. Therefore, in the case of the FRP lock bolt having the rope screw formed over the entire length, when the nut 5 is tightened in the torque test, as shown in FIG. 13, the boundary between the portion fixed by the fixing material 9 and the portion not fixed (nut end portion). There is a problem that the twisting force acts at the boundary A) and the lock bolt 1 is threaded before the required axial force is generated.

From the above, the object of the present invention is to reduce the height of the nut and to shorten the protruding length from the working surface, and
An object of the present invention is to provide an FRP lock bolt having a screw fastening portion having a fastening ability equivalent to that of a metallic lock bolt.
Another object of the present invention is to provide an FRP lock bolt that can carry out construction management tests such as pull-out tests and torque tests without problems.

[0014]

According to the present invention, there is provided a first screw portion, which can be screwed with a screw formed on the outer circumference of the FRP lock bolt main body, on the inner circumference of the cylinder, and the nut and the screw are screwed on the outer circumference. The metal pipe-shaped member formed with the matching second screw portion is fitted into one end of the FRP lock bolt main body, and the FR
The screw fastening part of the P lock bolt is formed. According to the FRP lock bolt having such a screw fastening portion, a thread portion equivalent to the thread portion of the metallic lock bolt can be formed, so that the nut height can be reduced and the length of protrusion from the construction surface of the pipe-shaped member can be reduced. The pull-out test can be performed with the same length as the protruding length of the metal lock bolt, and the thread does not break even in the torque test. Further, by providing the pipe-shaped member with the rotation preventing groove, when the nut is tightened, the pipe-shaped member is surely movable only in the axial direction, so that the twisting in the FRP bolt main body portion is more reliably prevented. It can be avoided.

[0015]

1 is an exploded view of an FRP lock bolt according to the present invention. Reference numeral 51 denotes a main body of the FRP lock bolt, which is a bundle of reinforcing fibers such as glass fibers fixed with a thermosetting resin, and has a rope screw shape (male screw) 5 over the entire length.
1a. The screw pitch is, for example, 14 mm, and the total length of the lock bolt body is 3000 mm. Reference numeral 52 denotes a metallic pipe-shaped member having a female screw 52a formed on the outer periphery of the lock bolt main body 51 and capable of being screwed on the inner periphery of the cylinder, and a part of the outer periphery (for example, full length). Male screw (M36) 52b is formed in about half of the area). The overall length of the pipe-shaped member 52 is, for example, 120 mm, and in the figure, it is shown that it is screwed into one end of the lock bolt main body 51 to form a screw portion of the lock bolt. Further, although the drawing shows the case where the male screw 52b is formed in a part of the outer peripheral portion, it may be formed over the entire length of the outer peripheral portion.

Reference numeral 53 is a square washer having a round hole 53a larger than the outer diameter of the pipe member 52.
The square washer 53 is inserted into the pipe-shaped member 52 when the lock bolt main body 51 is fixed to the ground and is tightened by a nut described later. The size of the square washer 53 is 100 mm x 100 mm, and the diameter of the round hole is 38φ. Reference numeral 54 denotes a nut, which is a male screw (M36) 52 formed on the outer peripheral portion of the pipe-shaped member 52 which is the screw portion of the lock bolt.
The square washer 53, which is screwed into b and is inserted into the pipe-shaped member 52, is pressed against the ground and is tightened to firmly fix the lock bolt main body 51 to the ground. The nut has a thickness of 29 mm, for example.

FIG. 2 is an explanatory view of a method of constructing the lock bolt. A borehole 63 having a predetermined depth is drilled from the inner wall 62 of the tunnel excavated in the natural ground 61 to the inside of the bedrock.
The fixing material 64 is injected into the inside 3 using an injection hose or the like. After that, the tip of the lock bolt main body 51 is struck at the tip and the pipe-shaped member 52 is screwed into the other end (FIG. 2).
(A)). In this case, one end of the pipe-shaped member 52 is driven to a position where it projects slightly longer than the total thickness of the square washer 53 and the nut 54. Then, with the round hole of the square washer 53 inserted in the pipe-shaped member 52, a nut 54 is screwed from the tip end side of the pipe-shaped member 52 and fitted.
The bolt body 51 is fixed to the ground by pressing the square washer 53 against the inner wall of the ground and tightening it (see FIG. 2).
(B)). When the fixing material 64 hardens in such a state, the lock bolt main body 51 and the hole wall periphery of the bore hole 63 are integrally fixed, and the rock bolt tip end portion is supported by the hard internal rock that has been driven, so that the mine wall periphery Is prevented from falling.

FIG. 3 is a table showing the results of a tensile test of the FRP lock bolt of the present invention, and FIG. 4 is a test device. The test, as shown in Fig. 4, has an outer diameter of about 25 mm and a tensile strength of about 43 tf
A pipe-shaped member 52 having an outer diameter of 39 mm (peripheral screw M39) is fitted to both ends of the FRP bolt 51 of No. 1, and a metal nut (thickness of about 32 mm) is fitted to the peripheral screw 52b of the pipe-shaped member.
54 was loaded. In the test apparatus, 71 is a hydraulic pump, 72 is a hydraulic gauge, 73 and 74 are square washers, and 75 is a hydraulic jack.

When oil is sent from the hydraulic pump 71 to the hydraulic jack 75, the hydraulic jack tries to move the square washer 74 to the right via the piston 76 by the hydraulic pressure. When the square washer 74 starts moving by further applying hydraulic pressure, the value of the oil gauge at the time of starting the movement becomes the tensile strength of the screw fastening portion of the lock bolt 51.

As is clear from the test results of FIG. 3, according to the lock bolt of the present invention, even if the fitting length of the pipe-shaped member 52 and the lock bolt main body 51 is short (120 mm to 140 mm),
A screw portion that generates a sufficient tensile force can be formed on the bolt body 51. With this, the FRP lock bolt can be effectively fixed to the ground by fitting the seat plate and the nut into the threaded portion and pressing them against the ground. Further, even if a pulling force required for confirmation of fixing is applied, the screw portion does not break, and the pulling-out test can be correctly performed. The above is the case where the adhesive is not used together for fitting the bolt main body 51 and the pipe-shaped member 52, but if used together, the maximum load is further increased by 10%.
It can be increased to some extent. In this case, since the bolt main body 51 and the pipe-shaped member 52 are coupled with each other by screws, the adhesive can be applied thinly on the surface of the bolt in advance and the two can be integrated by screwing them together, and no special curing is required and immediately used. I can. Therefore, the screw portion can be formed in the lock bolt main body 51 extremely easily and in a short time. Also, of the construction management tests, for the pull-out test using a hydraulic jack, the pull-out test similar to the case of a normal metal lock bolt is possible by making the screw part protruding from the construction surface metal. . That is, it is not necessary to lengthen the bolt margin as in the conventional FRP bolt.

FIG. 5 is an explanatory view of the pull-out test of the lock bolt of the present invention. The lock bolt main body 51 is fixed to the ground 61 by a fixing material 64. In order to perform the pull-out test of this lock bolt, a pull-out test device (square washer 10, ram chair 11, angle adjustment pedestal 12, center hole type hydraulic jack 13, reaction plate 14, etc.) is attached so that it can be tested. Then, the tension bar 15 having the adapter 17 attached to the tip thereof is inserted into the reaction force plate 14, the hydraulic jack 13, and the ram chair 11, and the adapter 1
7 is screwed and coupled to a male screw formed on the outer peripheral portion of the pipe-shaped member 52. After that, the tension bar nut 16 is fitted to the M thread portion formed on the outer circumference of the other end of the tension bar 15 and tightened to the reaction force plate 14. In this state, when oil is sent from the hydraulic pump to the hydraulic jack 13, the hydraulic jack 13 generates a force to move the reaction plate 14 to the right by a piston (not shown). If the lock bolt 51 is not pulled out even if the moving force (pulling force) is increased by further applying hydraulic pressure and the pulling force equal to or more than the set force is applied, it is determined that the fixing is normal.

It is preferable to take the following means in order to accurately measure the fixing force of the FRP lock bolt body with respect to the ground level. That is, the portion of the pipe-shaped member 52 (FIG. 2) that is inserted into the bore hole 63 and is in direct contact with the fixing material 64 is (1) so as not to adhere to the fixing material.
Alternatively, finish so that it is sufficiently small for the load that needs to be confirmed, or (2) apply oil, or (3) attach a taper that narrows toward the inner side of the bore hole.

Furthermore, it is possible to prevent thread breakage in the torque addition test of the construction management tests. That is, the tightening force of the nut 54 causes an axial force to the lock bolt main body 51 via the pipe-shaped member 52, so that the lock bolt main body does not directly twist, thereby preventing the thread breakage, and confirmation is required. The test can be performed by applying torque up to various axial forces. It is effective to provide the pipe-shaped member 52 with a groove for preventing rotation in order to prevent the FRP lock bolt main body 51 from being further twisted when the nut 54 is tightened. Fig. 6 shows 9 in the axial direction of the outer peripheral portion.
It is the side view and front view of the pipe-shaped member 52 which formed four rotation prevention grooves 52c at intervals of ⁰ . According to this grooved pipe-shaped member, the fixing material enters the groove 52c and hinders the rotation of the pipe-shaped member. Therefore, when the nut 54 is fitted into the threaded portion 52b and tightened, the rotation of the pipe-shaped member 52 is blocked and the nut 54 is movable only in the axial direction, so that the FRP bolt main body portion 51 is more reliably prevented from twisting. Occurrence can be avoided.

The rotation preventing groove 52 of the pipe-shaped member 52
c functions only to suppress the rotation of the member 52, and makes it difficult to adhere to the fixing material as in the pull-out test, or is sufficiently small with respect to the pull-out force corresponding to the axial force that needs to be confirmed. It is necessary to allow the force to break the attachment against movement in the axial direction of the bolt. For this purpose, the following measures should be taken. That is, (1) the portion of the pipe-shaped member 52 that is inserted into the bore hole and is in direct contact with the fixing material is smoothly finished, including the groove 52c, or
(2) Apply oil, or (3) taper so that it becomes finer toward the inner side of the bore hole. Although the present invention has been described above with reference to the embodiments, the present invention can be variously modified according to the gist of the present invention described in the claims, and the present invention does not exclude these.

[0025]

As described above, according to the present invention, the first threaded portion which can be screwed with the screw formed on the outer circumference of the FRP lock bolt main body is provided on the inner circumference of the cylinder, and the nut is screwed on the outer circumference. the metal pipe-shaped member having a second threaded portion is formed to, F
The RP lock bolt body is fitted into one end to form a screw fastening portion of the FRP lock bolt.
It is possible to form a threaded portion on the P lock bolt that is equivalent to the threaded portion of the metal lock bolt, and as a result, the nut height can be reduced, and moreover, the protruding length of the metal lock bolt from the working surface of the pipe-shaped member can be reduced. The pull-out test can be performed at the same length as the length, and the thread does not break even in the torque test.

Further, according to the present invention, the tightening force of the nut causes an axial force to the bolt main body through the metal pipe-shaped member, so that the bolt main body is not directly twisted, and confirmation can be made. The test can be performed by applying torque to the required axial force. Further, according to the present invention, since the rotation preventing groove is provided in the pipe-shaped member, the fixing material enters the groove and hardens. Therefore, when the nut is fitted into the screw portion of the pipe-shaped member and tightened, Since the rotation of the member is blocked and the member is movable only in the axial direction, it is possible to more reliably avoid the occurrence of twist in the FRP bolt main body portion.

[Brief description of drawings]

FIG. 1 is an exploded view of an FRP lock bolt of the present invention.

FIG. 2 is an explanatory view of a method of applying the FRP lock bolt of the present invention.

FIG. 3 is a test result showing the ratio of the length of the pipe-shaped member to the maximum load and the strength of the bolt main body.

FIG. 4 is a configuration diagram of a test apparatus.

FIG. 5 is a drawing for explaining the pull-out test of the lock bolt of the present invention.

FIG. 6 is an external view of a grooved pipe-shaped member.

FIG. 7 is a partial cutaway view of an FRP lock bolt.

FIG. 8 is a diagram illustrating a problem of a conventional FRP lock bolt.

FIG. 9 is a perspective view of a conventional FRP lock bolt provided with a specially shaped nut.

FIG. 10 is an explanatory diagram of how to use the FRP lock bolt.

FIG. 11 is an explanatory diagram of a pull-out test of a steel lock bolt.

FIG. 12 is a drawing explaining a conventional FRP lock bolt pull-out test.

FIG. 13 is a diagram illustrating a problem during a torque test.

[Explanation of symbols]

51 ... FRP lock bolt body 52..Metallic pipe-shaped member 52a ... Female screw 52b ... Male screw 53 ... Square washer 54 ... Nuts

   ─────────────────────────────────────────────────── ─── Continued front page       (56) References JP-A-9-13898 (JP, A)                 Actual public Sho 57-55437 (JP, Y2)

Claims (2)

(57) [Claims] 1. A comprising FRP rock bolt body thread is formed on the outer circumference, a first thread portion the available screw screwed formed on the outer periphery of the FRP rock bolt body cylindrical inner peripheral portion, and the outer periphery A metal pipe-shaped member having a second screw portion that is screwed with a nut is formed in the portion, and the pipe-shaped member is fitted into one end of the FRP lock bolt body to form a screw fastening portion of the FRP lock bolt. FRP lock bolt characterized by the following. 2. The FRP lock bolt according to claim 1, wherein the pipe-shaped member is provided with a rotation preventing groove.