WO2003091542A1

WO2003091542A1 - Rock bolt

Info

Publication number: WO2003091542A1
Application number: PCT/KR2002/001272
Authority: WO
Inventors: Jae-Sool Na
Original assignee: Jae-Sool Na
Priority date: 2002-04-24
Filing date: 2002-07-05
Publication date: 2003-11-06
Also published as: KR100479955B1; KR20030084084A; AU2002315933A1

Abstract

Disclosed is a rock bolt anchored to a rock mass by boring a hole in the rock mass and inserting a nail into the hole. The rock bolt comprises a body member locked to a front end of the nail and defined, in a lengthwise direction thereof, with an operating space; a pair of cutting blades capable of being rotatingly moved from an inoperative position in which they are received in the body member to an operative position in which they project out of an outer surface of the body member; and an operating element having one end which is disposed in the operating space and the other end which forwardly extends through a front end of the body member, in a manner such that, when the operating element is retracted into the operating space, it urges the cutting blades to be rotatingly moved to the operative position.

Description

ROCK BOLT

Technical Field

The present invention relates to a rock bolt which serves as a rock support upon digging a tunnel or building an underground structure, and more particularly, the present invention relates to a rock bolt which is configured to be firmly anchored to a rock mass and quickly installed to thereby shorten a duration of construction work.

Background Art

Generally, a rock bolt is used as a kind of rock support upon digging a tunnel or building an underground structure and is also called a roof bolt. The rock bolt is fixed in a manner such that a hole having a diameter of about 36-40 mm and a depth of no less than 2 m is bored in a rock mass inside a tunnel and then the rock bolt is inserted into the bored hole. The rock bolt can be installed in accordance with two ways. First, when a rock formation existing above a direct contact roof is sufficiently solid, the roof is hung on the rock formation by rock bolts. Second, when there exist several rock layers which are likely to be delaminated, a roof load is supported by a girder or a crossbeam. Methods for anchoring a rock bolt to a rock mass are divided into a distal end bonding type and a full surface bonding type. In these two types of anchoring methods, a bonding action between the rock bolt and the rock mass is accomplished by filling a bored hole with a mechanical wedge, resin, mortar, etc. The rock bolt can be varied in its diameter and length depending upon a condition of the rock mass.

When performing civil engineering and construction works, particularly, a tunneling work, an opening is initially defined in the face of a mountain including rock masses. Then, by inserting into the opening and setting off explosives such as dynamite to break rock masses, the opening is gradually widened. In this way, after a basic tunnel having a predetermined height and width is formed, in order to prevent the basic tunnel from caving in, rock bolts are anchored to a roof of the basic tunnel, a mesh-shaped net is put on the rock bolts, and finally, concrete is applied to form a reinforcing membrane. Upon performing the reinforcing membrane forming work, after holes are bored in the rock mass using a drill, cement mortar is first filled and then the rock bolts are inserted into the bored holes, or the rock bolts are first inserted and then cement mortar is filled into the bored holes. When the cement mortar is completely set, the rock bolts are firmly anchored to the rock mass. The rock bolts are anchored to be spaced apart one from another by a predetermined distance, so that they can sustain a load of concrete transferred to the mesh-shaped net, while being securely maintained with respect to the rock mass. However, in the conventional art, the rock bolts are installed in a manner such that mortar flow prevention caps are respectively fitted into the bored holes, cement mortar is filled in the bored holes, and then, after a period of 3 or 4 days is elapsed to allow the cement mortar to be completely set, pressure bearing plates are rigidly locked to the rock bolts. Therefore, problems are caused in that a duration of construction work is lengthy, and a number of rock bolts must be used to provide sufficient rock mass supporting force.

Disclosure of the Invention

Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and a primary object of the present invention is to provide a rock bolt which can be firmly anchored to a rock mass in such a way as to maximize supporting force.

Another object of the present invention is to provide a rock bolt which can be fixedly positioned with respect to a rock mass irrespective of whether cement mortar is set, so as to shorten a duration of construction work. Still another object of the present invention is to provide a rock bolt which can be installed in a simple manner to improve a working efficiency.

Yet still another object of the present invention is to provide a rock bolt which can be precisely arranged along an axis of a bored hole.

According to the present invention, there is provided a rock bolt anchored to a rock mass by boring a hole in the rock mass and inserting a nail into the bored hole, the rock bolt comprising: a body member locked to a front end of the nail and defined, in a lengthwise direction thereof, with an operating space; a pair of cutting blades capable of being rotatingly moved from an inoperative position in which they are received in the body member to an operative position in which they project out of an outer surface of the body member; and an operating element having one end which is disposed in the operating space and the other end which forwardly extends through a front end of the body member, in a manner such that, when the operating element is retracted into the operating space, it urges the cutting blades to be rotatingly moved to the operative position. Brief Description of the Drawings

The above objects, and other features and advantages of the present invention will become more apparent after a reading of the following detailed description when taken in conjunction with the drawings, in which: FIG. 1 is a perspective view illustrating a rock bolt in accordance with an embodiment of the present invention;

FIG. 2 is a perspective view independently illustrating a body member and an operating element which constitute the rock bolt according to the present invention; FIG. 3 is a cross-sectional view of FIG. 2; and

FIGs. 4a through 4c are cross-sectional views explaining an installing procedure of the rock bolt according to the present invention, wherein FIG. 4a illustrates a state in which the rock bolt is inserted into a bored hole defined in a rock mass, FIG. 4b illustrates a state in which the rock bolt is fixedly positioned with respect to the rock mass after cutting out a portion of the rock mass by being rotated, and FIG. 4c illustrates a state in which cement mortar is filled in the bored hole having fixedly positioned therein the rock bolt.

Best Mode for Carrying Out the Invention

Reference will now be made in greater detail to a preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings.

Wherever possible, the same reference numerals will be used throughout the drawings and the description to refer to the same or like parts.

Referring to FIGs. 1 through 4, a rock bolt 100 in accordance with an embodiment of the present invention is adapted for being anchored to a rock mass 1 by boring a hole 10 in the rock mass 1 and inserting a nail 110 into the bored hole

10. The rock bolt 100 includes a body member 120, a pair of cutting blades 130, and an operating element 140. The body member 120 is locked to a front end of the nail 110 and is defined, in a lengthwise direction thereof, with an operating space 121. The pair of cutting blades 130 can be rotatingly moved from an inoperative position in which they are received in the body member 120 to an operative position in which they project out of an outer surface of the body member 120. The operating element 140 has one end which is disposed in the operating space 121 and the other end which forwardly extends through a front end of the body member 120, in a manner such that, when the operating element 140 is retracted into the operating space 121 defined in the body member 120, it urges the cutting blades 130 to be rotatingly moved to the operative position.

It is preferred that the nail 110 is formed, on a circumferential outer surface thereof, with an external thread 111 and, at a rear end thereof, with a coupling projection 112 to be fitted into a drill, and the like, to thereby allow the nail 1 10 to be rotated while being pressed.

The body member 120 which is defined in the lengthwise direction thereof with the operating space 121, is formed, at the front end thereof, with an inward flange 122 which delimits a front end of the operating space 121. Also, the body member 120 is formed, at a rear portion thereof, with an internal thread 123 which is to be threadedly coupled with the external thread 111 of the nail 110.

The body member 120 is defined, on the outer surface thereof, with a pair of rectangular receiving grooves 124 which are opposed to each other and communicated with the operating space 121 and in which the pair of cutting blades

130 are respectively received. A pair of pin holes 125 are defined through both side walls of each receiving groove 124.

Here, it can be envisaged that one receiving groove 124 is defined in the body member 120, or three or more receiving grooves 124 are defined in the body member 120 to be spaced apart one from another by the same angle along a circumferential direction.

Each cutting blade 130 is received in the receiving groove 124 which is defined in the body member 120, and a fixing pin 132 is fitted into the pair of pin holes 125 in a manner such that it passes through a shaft hole 133 defined in the cutting blade 130 to rotatably support the cutting blade 130.

At this time, when each cutting blade 130 is received in the receiving groove 124, the fixing pin 132 passes through a front portion of the cutting blade

130 in a manner such that a rear end of the cutting blade 130 can be rotated forward through a predetermined angle. Further, it is preferred that a front end of each cutting blade 130 is formed with a cam portion 134 which radially inwardly projects past an inner surface of the body member 120 when each cutting blade 130 is received in the receiving groove

124, in such a way as to allow the cutting blade 130 to be rotated through the predetermined angle of no greater than 90 degrees. It is preferred that the shaft hole 133 is eccentrically defined in the cutting blade 130 in such a way as to ensure smooth rotation of the cutting blade 130.

The operating element 140 has a projecting rod part 141 and a head part

142. The projecting rod part 141 is disposed in the operating space 121 of the body member 120 to be reciprocated forward and rearward. A distal end of the projecting rod part 141 projects through the front end of the operating space 121.

The head part 142 is operationally associated with cam portions 134 of the cutting blades 130 in a manner such that, when the operating element 140 is moved rearward, the head part 142 pushes the cam portions 134 so as to rotate the cutting blades 130. It is preferred that an outer surface of the head part 142 is formed as a tapered portion 143 for ensuring smooth rotation of the cutting blades 130.

The head part 142 has a shoulder 144 which can be engaged with the inward flange 122 of the body member 120 to prevent release of the operating element 140 from the body member 120. Hereafter, an installing procedure of the rock bolt 100 according to the present invention, constructed as mentioned above, will be described in detail.

First, the hole 10 is bored in the rock mass 1. Then, the rock bolt 100 with the body member 120 locked to the front end of the nail 110 is inserted into the bored hole 10, and the coupling projection 112 which is formed at the rear end of the nail 1 10 is coupled to the drill.

In this state, by actuating the drill, the rock bolt 100 is rotated and at the same time pressed into the bored hole 10.

At this time, as the projecting rod part 141 of the operating element 140, which projects out of the front end of the body member 120, is brought into contact with a bottom of the bored hole 10, the operating element 140 is retracted into the operating space 121. Thereby, as the head part 142 pushes rearward the cam portions 134 of the cutting blades 130, the cutting blades 130 are rotatingly moved while being integrally rotated with the operating member 120. By this fact, the nail

110 is precisely arranged along an axis of the bored hole 10, and the cutting blades 130 cut out a portion of the rock mass 1 around the bored hole 10 to define a reverse-rotation preventing surface 11, whereby the rock bolt 100 is fixedly positioned with respect to the rock mass 1.

Due to the fact that the cutting blades 130 define the reverse-rotation preventing surface 11, the cutting blades 130 are prevented from being reversely rotated, and the rock bolt 100 is securely maintained with respect to the rock mass 1. In this state, unless the rock mass 1 caves in or is collapsed, release of the rock bolt 100 from the bored hole 10 is prevented, and, in this way, the rock bolt 100 can be fixedly positioned with respect to the rock mass 1.

Accordingly, due to the fact that the rock bolt 100 is securely positioned with respect to the rock mass 1, it is possible to fit a mortar flow prevention cap around the rear end of the nail 110 to close the bored hole 10, fill cement mortar 12 into the bored hole 10 through a mortar pouring gate 161, and then immediately fit and lock a pressure bearing plate 150 around the nail 110 using a nut 151. Therefore, it is possible to shorten a duration of construction work to the minimum.

Industrial Applicability

As apparent from the above description, according to the present invention, the rock bolt anchored to a rock mass by boring a hole in the rock mass and inserting a nail into the bored hole, comprises a body member locked to a front end of the nail and defined, in a lengthwise direction thereof, with an operating space; a pair of cutting blades capable of being rotatingly moved from an inoperative position in which they are received in the body member to an operative position in which they project out of an outer surface of the body member; and an operating element having one end which is disposed in the operating space and the other end which forwardly extends through a front end of the body member, in a manner such that, when the operating element is retracted into the operating space, it urges the cutting blades to be rotatingly moved to the operative position. Therefore, advantages are provided in that the rock bolt can be firmly anchored to the rock mass in such a way as to maximize supporting force. Also, the rock bolt can be fixedly positioned with respect to the rock mass irrespective of whether cement mortar is set, so as to shorten a duration of construction work. Further, the rock bolt can be installed in a simple manner to improve a working efficiency. Moreover, the rock bolt can be precisely arranged along an axis of the bored hole.

Claims

1. A rock bolt comprising: a nail inserted into a hole bored in a rock mass; a body member locked to a front end of the nail and defined, in a lengthwise direction thereof, with an operating space; a pair of cutting blades capable of being rotatingly moved from an inoperative position in which they are received in the body member to an operative position in which they project out of an outer surface of the body member; and an operating element having one end which is disposed in the operating space and the other end which forwardly extends through a front end of the body member, in a manner such that, when the operating element is retracted into the operating space, it urges the cutting blades to be rotatingly moved to the operative position.

2. The rock bolt as set forth in claim 1, wherein the nail is formed, on a circumferential outer surface thereof, with an external thread and, at a rear end thereof, with a coupling projection to be fitted into a drill and the like, in a manner such that the nail can be rotated while being pressed.

3. The rock bolt as set forth in claim 1 , wherein the front end of the body member is formed with an inward flange which delimits a front end of the operating space, and the body member is formed with an internal thread which is to be threadedly coupled with the external thread of the nail.

4. The rock bolt as set forth in claim 1, wherein the body member is defined, on the outer surface thereof, with a pair of rectangular receiving grooves which are opposed to each other and communicated with the operating space and in which the pair of cutting blades are respectively received; and a pair of pin holes are defined through both side walls of each receiving groove.

5. The rock bolt as set forth in claim 1, wherein each cutting blade is received in the receiving groove defined in the body member, and a fixing pin is fitted into the pair of pin holes in a manner such that it passes through a shaft hole defined in the cutting blade to rotatingly support the cutting blade.

6. The rock bolt as set forth in claim 1, wherein, when each cutting blade is received in the receiving groove, the fixing pin passes through a front end of the cutting blade in a manner such that a rear end of the cutting blade can be rotated forward through a predetermined angle.

7. The rock bolt as set forth in claim 1, wherein the front end of each cutting blade is formed with a cam portion which radially inwardly projects past an inner surface of the body member when each cutting blade is received in the receiving groove, in such a way as to allow the cutting blade to be rotated through the predetermined angle of no greater than 90 degrees.

8. The rock bolt as set forth in claim 1, wherein the shaft hole is eccentrically defined in the cutting blade in such a way as to ensure smooth rotation of the cutting blade.

9. The rock bolt as set forth in claim 1, wherein the operating element has a projecting rod part which is disposed in the operating space of the body member to be reciprocated forward and rearward and a distal end of which projects through the front end of the operating space, and a head part which is operationally associated with cam portions of the cutting blades in a manner such that, when the operating element is moved rearward, the head part pushes the cam portions so as to rotate the cutting blades.

10. The rock bolt as set forth in claim 9, wherein an outer surface of the head part is formed as a tapered portion for smoothly pushing the cam portions.

11. The rock bolt as set forth in claim 9, wherein the head part has a shoulder which can be engaged with the inward flange of the body member to prevent the operating element from being freed from the body member.