JP2009097260A - Self-boring lock bolt - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a self-boring lock bolt with excellent durability at low cost by using a welded steel pipe formed of a plated steel plate as a lock bolt body. <P>SOLUTION: This self-boring lock bolt comprises: the hollow lock bolt body 1 having an injection hole 4 for grout, high-pressure air, and high-pressure water formed through the center part and a male screw 2 formed over the outer peripheral entire length; and a drilling bit 3 attached to the end of the bolt body and having an ejection hole 5 communicating with the injection hole 4. The hollow lock bolt body 1 is formed of a welded steel pipe by using, as a raw material, a coated steel plate on which a Zn plated layer, an Al-plated layer, a Zn-Al alloy plated layer, or a Zn-Al-Mg alloy plated layer is formed. The welded steel pipe is desirably one in which a plate correction layer is formed at or near a weld part on the outer surface of the pipe. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a self-drilling lock bolt that is driven into a mountain, a slope of a road, a tunnel surface or the like to prevent rock collapse.

Conventionally, it is well known that a hollow rock bolt is used for self-drilling and supporting a natural ground. In this method, first, a hollow lock bolt with a drilling bit attached to the tip is rotated and inserted while drilling a hole in a natural ground or the like, and if necessary, a lock bolt is added with a coupling nut and drilled to a predetermined depth. . After completion of the drilling operation, the grout is pressure-injected between the lock bolt and the inner wall surface of the hole through the hollow portion of the lock bolt while remaining in the hole, and the grout is solidified to fix the lock bolt. Is.
Some of the applicants are also introduced in, for example, Patent Documents 1 and 2.
Japanese Patent Publication No. 5-60040 No. 7-8638

Pipes that make up the conventional self-drilling lock bolt body, including those introduced in Patent Documents 1 and 2, are usually made by rolling a small-diameter wall-thick seamless steel pipe, and then subjecting it to immersion plating. That have been subjected to rolling processing on a welded steel pipe and then subjected to immersion plating are used. When a self-drilling lock bolt is screwed into a strong ground, a large torsional moment is applied. Therefore, it is preferable to use a thick seamless steel pipe with uniform characteristics as the lock bolt body. .
However, the use of seamless steel pipes is expensive. Therefore, the use of thick welded steel pipes is assumed, but there are problems associated with the use of welded steel pipes.

Since the self-drilling lock bolt body may be left for a long time at the work site, that is, in the field, the pipe of the lock bolt body is generated. Appearance deteriorates when red rust occurs. Moreover, in welded steel pipes, the welded part and the heat-affected zone in the vicinity thereof are originally more fragile than the base material part. Resistance decreases.
In order to prevent galling, when plated steel is applied after rolling the seamless steel pipe or welded steel pipe, it is inevitable that the plating metal adheres excessively to the rolling groove. Plating metal becomes “tama” and adheres to the surface of valleys and ridges of rolling grooves, and drill bits that are rock cutters, couplings that connect rock bolt bodies, or driving equipment There arises a problem that the sleeve as the connecting member cannot be normally attached. For this reason, a process for removing excess plating metal is required, resulting in an increase in cost.
From such a background, it is not practical to use a welded steel pipe for a self-drilling lock bolt body.

  The present invention has been devised to solve such problems, and provides a self-drilling lock bolt with excellent durability at a low cost by using a welded steel pipe made of a plated steel plate as the lock bolt body. The purpose is to do.

In order to achieve the object, the self-drilling lock bolt of the present invention is provided with a hollow lock bolt body in which a grout, high-pressure air, high-pressure water injection hole is provided in the center and a male screw is formed over the entire length of the outer periphery, A self-drilling lock bolt having a drilling bit attached to its tip and having a spout opening communicating with the injection hole, wherein the hollow lock bolt body is formed of a welded steel pipe made of a plated steel plate. It is characterized by being.
As the welded steel pipe, a welded part on the outer surface of the pipe and a plating repair layer provided in the vicinity of the welded part are preferable.
The material-plated steel sheet is preferably provided with a Zn plating layer, an Al plating layer, a Zn—Al alloy plating layer, or a Zn—Al—Mg alloy plating layer.
And as a plating repair layer, the thermal spray repair layer of an Al-Zn alloy or an Al-Mg alloy is preferable.

The self-drilling lock bolt provided by the present invention has a hollow lock bolt as a main body formed of a welded steel pipe made of a plated steel plate. For this reason, it is excellent in corrosion resistance and can maintain its appearance over a long period of time without generating red rust even when left outdoors. In addition, since cracking is suppressed, in particular, when a plating repair layer is provided in the welded part and in the vicinity of the welded part, substantial thinning does not occur, and the torsional resistance as designed. Can be demonstrated. In addition, since a thread is formed on the outer surface of the welded steel pipe made of plated steel, a highly accurate rolled part is formed, and a threaded bit such as a drill bit or sleeve is screwed together. Can be done without problems.
Therefore, according to the present invention, a self-drilling lock bolt having characteristics comparable to those of a seamless steel pipe can be provided at low cost.

The inventors of the present invention have studied the problems in changing the hollow lock bolt, which is the main body of the self-drilling lock bolt, from an expensive seamless steel pipe to a welded steel pipe.
As described above, when the self-drilling lock bolt body is left in the field, which is a work site, for a long period of time, the pipe of the lock bolt body is generated. When red rust is generated, not only the appearance is deteriorated, but also the torsional resistance as a steel pipe is lowered. If a large torsional moment is applied during drilling, the welded portion of the steel pipe may be broken or buckled, and further drilling may not be performed.
In addition, after rolling the seamless steel pipe or welded steel pipe, it is also possible to prevent dripping by applying immersion plating, but as described above, the plated metal may be excessively adhered to the rolling groove. Inevitable, screwing of a drill bit, sleeve or the like cannot be performed normally.

Therefore, in the present invention, a rolled steel welded steel pipe made of a pre-plated steel plate is used for the self-drilling lock bolt body.
A threaded portion is formed by rolling a welded steel pipe having a plating layer to form a rolled groove with excellent accuracy. In addition, since it is not subjected to soaking plating after rolling, the plated metal layer remains even after the rolling grooves are formed. Corrosion resistance is maintained over a long period of time by the action of the plated metal layer.
As the material-plated steel sheet, one provided with a Zn plating layer, an Al plating layer, a Zn—Al alloy plating layer or a Zn—Al—Mg alloy plating layer is used.

  In particular, if a Zn-Al-Mg alloy with excellent plating adhesion is used as the plating metal applied to the material steel plate, the plating metal layer will not be peeled off during rolling, and the plating metal layer may be cracked. Even if defects occur, corrosion resistance can be maintained over a long period of time due to the sacrificial anticorrosive action of the plated metal itself. This Zn-Al-Mg based plating alloy includes Al: 4.0-10.0 mass%, Mg: 1.0-4.0 mass%, the balance being Zn, and a trace amount of Ti Those containing Si and B, or further containing Si are preferred.

Even when a welded steel pipe made of a plated steel sheet is used, the welded part and the plating layer in the vicinity thereof are lost during welding, and the corrosion resistance may be reduced.
Therefore, it is preferable to construct the lock bolt body with a welded steel pipe provided with a repair layer in which a welded steel pipe made of a plated steel plate is covered with a plated metal in the welded portion and a portion where the plated layer in the vicinity of the welded portion disappears.
For example, a weld-plated steel pipe is manufactured from a plated steel sheet provided with a Zn plating layer, an Al plating layer, a Zn-Al alloy plating layer or a Zn-Al-Mg alloy plating layer, and the outer bead is cut. It is preferable to use a welded steel pipe coated with a metal layer on the welded part from which the plating layer has been removed by cutting and the surface near the welded part.

  Although it does not specifically limit as a coating metal layer, The thing of thermal spray coating of the Al-Zn type alloy and the Al-Mg type alloy is preferable. Although the thermal spray repair layer can be formed by single spraying of an Al—Zn alloy or an Al—Mg alloy, it is preferable to form a thick spray repair layer by two-phase spraying. In the double spraying, it is preferable to spray Al—Zn alloy or Al—Mg alloy after spraying Al.

For example, in a welded steel pipe made of a Zn-based plated steel sheet, improvement in corrosion resistance when a coating layer is formed by Al spraying → Al-Zn alloy spraying is considered as follows.
That is, when an open pipe of a plated steel sheet on which a plating layer is formed is welded, a thin oxide film is generated on the surface of the plating layer heated by welding heat. In the welded portion from which the plating layer has been removed by bead cutting, a thin oxide film is formed on the surface of the exposed base steel.
The first layer of Al sprayed on the weld is a metal having an oxygen affinity greater than that of iron. Al sprayed in the molten state reacts with the exposed underlying steel and the oxide film on the surface of the plating layer, and combines with oxygen in the oxide film by a strong reducing action to form Al oxide.

Whether the Al oxide is replaced with the exposed base steel and the oxide film on the surface of the plating layer or dispersed in the sprayed molten Al, the sprayed Al is strongly Combined with the base steel.
Vapor defects such as vacancies and shrinkage cavities are inevitably generated in the sprayed coating, but Zn in the second sprayed layer exhibits a sacrificial anticorrosive action against iron in such inevitable void defects in the Al layer. To suppress the corrosion of the base steel. And Al in a 2nd layer exhibits the suppression effect of white rust generation | occurrence | production which is one end of the sacrificial anticorrosion action of Zn in a 2nd layer. As a result, the corrosion resistance of the weld-plated steel pipe can be further improved by the two-part thermal spraying of Al → Al—Zn alloy.

From the above, it can be understood that the corrosion resistance and durability of the self-drilling lock bolt can be remarkably improved by using a welded steel pipe with significantly improved corrosion resistance for the lock bolt body. In addition, it is manufactured using a pre-plated steel sheet, and after rolling the material steel sheet, it is manufactured in a form in which it is rolled, so that the thread part has high forming accuracy and can be screwed in a bit or sleeve without any problems. Perforated lock bolts can be provided.
Then, it is possible to use a weld-plated steel pipe instead of a seamless steel pipe, and to provide a self-drilling lock bolt that is significantly reduced in cost.

Below, the specific example of the self-drilling lock bolt which used the weld plating steel pipe as a raw material is demonstrated.
A steel plate having a predetermined plating layer is used as a raw material, and a welded plated steel pipe provided with a plating repair layer in the vicinity of the welded portion and the welded portion is subjected to rolling, and a male screw is formed over the entire length of the outer periphery thereof. For example, as shown in FIG. 1, a weld-plated steel pipe having a male thread 2 formed on the surface thereof is used as a hollow lock bolt body 1, and a drill bit 3 for excavation is attached to the tip thereof. There is no restriction on the drill bit itself. A boring chip (cutter) integrated type as described in Patent Document 1 or Japanese Utility Model Publication No. 5-45680 may be used, or a cutter head and a cutter as described in Patent Document 2 may be used. May be attached. In any case, it is necessary to provide a spout 5 for discharging grout, high-pressure air, and high-pressure water fed from the inlet 4 via the hollow lock bolt body 1. Although there is no limitation on the mounting mode of the drill bit, as shown in FIG. 1, a male screw is formed on the outer periphery of the hollow lock bolt body 1 by forming a female screw in the opening provided at the rear end of the drill bit. It is preferable to be screwed in. In FIG. 1, 6 is a boring tip, and 7 is a connecting hole for communicating the inlet 4 and the outlet 5.

  The rock bolts that are actually driven into the ground are usually those with an outer diameter of 28.5 to 31.0 mm and a length of 1.0 to 6.0 m. If the length is longer, two or three lock bolts are added. As the second and third lock bolts, those after rolling before attaching the drill bit to the tip are used. It may be a hollow rod body provided with male threads for coupling nuts to be described later at both ends. It is preferable that this hollow rod is also made of a weld-plated steel pipe in which the welded portion and the vicinity of the welded portion are repaired. A hollow coupling nut (8 in FIG. 2 described later) having a female screw on the inner wall is used for the second or third addition.

Next, an example of a method for supporting a natural ground using the self-piercing lock bolt of the present invention will be described with reference to FIG.
A drill bit is attached to the tip of the hollow rock bolt main body 1 to drill a hole in the rock, and a drilling operation is performed while the next hollow rock bolt main body 1 is connected using a coupling nut 8 as necessary. At this time, if necessary, high-pressure water or high-pressure air is injected from the injection hole 4 of the hollow lock bolt 1 and discharged from the discharge port 5 to cool the drill bit 3 or rock powder or earth and sand generated by drilling. Clean the inside of the hole dug out. Then, after digging a hole to a predetermined depth, grout is injected from the injection hole 4 of the hollow lock bolt 1 at that position. The grout reaches the outer periphery of the hollow lock bolt main body 1 from the injection hole 4 through the spout 5 of the drill bit 3 and fills the hole along the outer peripheral surface of the hollow lock bolt main body 1 to the position of the restraining plate 9. After injecting the grout, the holding plate 9 is applied to the end of the hollow lock bolt 1 and stopped with the nut 10.
In this series of operations, the required number of rock bolts are driven into the rock and the support work is completed.

Plates having a plate thickness of 5.5 mm and hot-plated Zn-6% Al-3% Mg alloy in an amount of 190 g / m ² were butted together and subjected to high frequency welding to obtain a welded steel pipe having an outer diameter of 31.8 mm. The weld bead on the outer surface of the obtained welded steel pipe was cut, and a thermal spray repair layer was formed by performing two-part thermal spraying in the order of Al → Al—Zn alloy in a portion where the welded portion and the plating layer in the vicinity of the welded portion disappeared.
Using a weld-plated steel pipe with a thermal spray repair layer as a raw material, a hollow steel pipe having a male thread with a height of 1.8 mm and a pitch of 12.8 mm on the surface was produced by rolling. Although fine cracks existed in the plating layer and the thermal spray repair layer, no occurrence of cracking or peeling was observed.
This surface male threaded hollow steel pipe was used as a main body, and an existing drilling bit was screwed and connected to the tip thereof to obtain a self-drilling lock bolt.

Sectional drawing explaining the shape of a general self-drilling lock bolt Sectional drawing explaining the embedding aspect of a self-drilling lock bolt

Explanation of symbols

1: Hollow lock bolt body 2: Male screw 3: Drilling bit 4: Injection port
5: Discharge port 6: Boring tip 7: Connection hole 8: Coupling nut
9: Holding plate 10: Nut

Claims (4)

  A hollow lock bolt body that has a grout, high-pressure air, or high-pressure water injection hole penetrating in the center and has an external thread formed over the entire length of the outer periphery, and a spout that is attached to the tip and communicates with the injection hole. A self-drilling lock bolt comprising a perforated drill bit, wherein the hollow lock bolt main body is formed of a welded steel pipe made of a plated steel plate.   The self-drilling lock bolt according to claim 1, wherein the welded steel pipe is provided with a plating repair layer in the welded portion on the outer surface of the tube and in the vicinity of the welded portion.   The self-drilling rock bolt according to claim 1 or 2, wherein the plated steel sheet is provided with a Zn plating layer, an Al plating layer, a Zn-Al alloy plating layer, or a Zn-Al-Mg alloy plating layer.   The self-drilling lock bolt according to claim 2 or 3, wherein the plating repair layer is an Al-Zn alloy or an Al-Mg alloy thermal spray repair layer.

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