GB2099885A

GB2099885A - Rock cleaving

Info

Publication number: GB2099885A
Application number: GB8214252A
Authority: GB
Original assignee: Tampella Oy AB
Current assignee: Tampella Oy AB
Priority date: 1981-06-04
Filing date: 1982-05-17
Publication date: 1982-12-15
Also published as: NO821852L; JPS6145033B2; SE455956B; IT1151450B; FI64438C; AU556541B2; FI64438B; ES8403564A1; IT8221685A0; CA1187474A; AU8431482A; DE3219618A1; FR2507245A1; DE3219618C2; ES520669A0; GB2099885B; FR2507245B1; SE8203368L; JPS5841189A

Abstract

A rock cleaving and excavating method according to which a hole (8) is bored in the rock (7) and a cleaving rod (1) is inserted in said hole which rod is provided with a pressure element (6) of elastic material. By compressing said pressure element axially in the hole said pressure element is caused to expand radially and to apply on the wall of the hole a pressing force which exceeds the breaking strength of the rock and cleaves the rock. The elastic pressure element is uniformly pressed also against an uneven wall of a bore hole and produces a controlled cleaving. The cleaving tool comprises a cleaving rod (1) connected to a power means (2) and provided with an elastic pressure element (6) located axially between two axially displaceable supports (4, 5). The supports are displaced by means of the power means so that the supports compress the pressure element axially and force tile pressure element to expand radially in a corresponding manner. <IMAGE>

Description

SPECIFICATION Method and tool for cleaving of rock The present invention relates to a method of cleaving of rock according to which method a hole is bored in the rock, a radially expansible cleaving rod is inserted in the hole and said cleaving rod is expanded by power means, for applying a pressing force exceeding the breaking strength of the rock on the wall of the hole.

In this connection, the word "rock" mainly refers to the rock material itself or any other similar material, and the method according to the invention is intended to cover not only cleaving of separate stones and rock blocks but also rock excavation.

In order to avoid the disadvantages associated with cleaving and excavation carried out by blasting, a number of methods and tools have been developed which are based on breaking of the rock by mechanical means actuated by a pressure fluid.

From German patent publication 1,294,305 a cleaving appratus is previously known which operates by means of compressed air and in which the cleaving rod to be inserted in the hole bored in the rock comprises a flexible hose which at one end is connected to a compressed-air accumulator and at the other end is provided with a valve which by means of a safety pin is tensioned in closed position. As the pressure increases in the flexible hose, the hose expands radially outwards so that it is pressed against the wall of the bore hole and at the same time seals the hole and applies a prepressure on the rock.When the pressure has reached a sufficiently high level, the safety cotter of the valve is broken at which moment air jets are ejected from radially directed holes in the valve into the bore hole, whereby the pressure impulse produced by said air jets together with said prepressure breaks the rock.

However, such a cleaving method suffers of the disadvantage that sudden pressure impulse generated causes a cleavage comparable to an explosion whereby rock pieces are easily thrown into the surroundings and the cleavage does not always take place in a sufficiently controlled manner.

From Swedish patent publication 401,706 a hydraulically operated mechanical wedge is previously known in which the cleaving rod comprises two wedge-shaped jaws and a wedge displaceable between said jaws. A hydraulic cylinder pushes the wedge in between the jaws whereby the pressure caused by the jaws breaks the rock.

Such a cleaving method suffers from the disadvantage that if the wall of the bore hole is uneven, concentrated force peaks are produced between the rigid jaws and the wall of the hole which break the rock in an uncontrolled manner.

The object of the present invention is to provide a method which eliminates the above-mentioned disadvantages and permits a precise control of cleaving. This object is achieved by means of the method according to the invention which is characterized In that the cleaving rod is expanded radially by axially compressing a pressure element of elastic material in the hole.

According to the invention a cleaving method is provided wherein an uniformly distributed pressure action is produced in the bore hole in spite of unevenness therein because the pressure element of elastic material is able to conform to the unevennesses in the wall of the bore hole. The pressure action can be increased steadily until the rock is broken because the pressure action is produced as a result of the radial expansion of the elastic pressure element when said element is more and more compressed axially in the hole.

Therefore, no sudden oversized outburst of force takes place which might result in rock pieces being thrown into the surroundings and in uncontrolled cleaving.

The invention also relates to a tool for carrying out the method described above, and this tool is characterized by what is defined in claim 2.

The tool according to the invention is simple in construction and is easy to make automatically operated.

The invention will now be described in more detail with reference to the accompanying drawing, in which Figure 1 and 2 illustrate one preferred embodiment of a cleaving tool according to the invention in partial axial section when installed in a bore hole before and after cleaving, respectively.

Figure 3 illustrates several cleaving tools connected to the same pressure source.

The cleaving tool shown in Figures 1 and 2 mainly comprises a cleaving rod 1 and a hydraulic cylinder 2 fastened thereto. Instead of a hydraulic cylinder, any other commonly known power means may be used.

The cleaving rod 1 comprises a cylindrical bar 3 provided at one end with a head-4 wider than the rod and a tube 5 through which the bar 3 extends slideably with a small clearance, and a sleeve-like pressure element 6 located between the head 4 and the tube 5 and through which the bar 3 extends. The head 4 forms an annular support surface 4a which abuts against one end surface of the pressure element, and the tube 5 forms a support surface 5a which abuts against the other end surface of said element. The head 4, the tube 5 and the element 6 form in their inoperative position a cylindrical surface of a somewhat smaller diameter than the diameter of a hole 8 bored in the rock 7 to be broken.

The hydraulic cylinder 2 includes a housing 9 which is rigidly fastened, for example, to the tube 5 and a piston 10 which is rigidly fastened to the bar 3. A cylinder space 11 is connected by a pipe 12 through a conventional actuating valve 1 3 to a source of hydraulic fluid 14.

The pressure element 6 is made of such an elastic material that said element is deformable but remains substantially incompressible in volume when compressed by external forces.

Suitable materials are, for example, various rubber qualities and polyurethane.

The cleaving tool is operated in the following manner: The tool rod 1 is inserted in the hole bored in the rock to be cleaved so that the pressure element 6 is located entirely within the hole. Hereafter, hydraulic pressure is applied to the cylinder space 11 whereby the piston is displaced upwards with respect to the housing and pushes the bar 3 in a corresponding manner with respect to the tube 5.

This results in a radial compression of the pressure element between the support surfaces 4a and Sa, whereby said element in a corresponding manner expands radially outwards while being sealingly pressed against the wall of the bore hole with its entire mantle surface. As the hydraulic cylinder pulls the bar upwards, the pressure applied by the radially expanding pressure element on the rock increases. When the pressure exceeds the breaking strength of the rock, the rock is cleaved.

Hereupon the pressure is released from the cylinder space, whereby the bar is displaced back to its initial position by the pushing action of the elastic pressure element so that the cleaving rod is ready to be inserted in the next bore hole.

It will be noted that the cleaving tool is very simple in construction and operation and that, owing to the elastic pressure element, the pressing force exerted by the cleaving tool on the rock will be uniformly distributed over the entire wall surface of the bore hole in spite of any unevennesses. The force used for cleaving the rock is not greater than required by the breaking strength of the rock wherefore no breaking similar to an explosion occurs and the cleaving can be controlled precisely.

According to Figure 3, a plurality of cleaving rods can, when using pressure fluid, be connected to the same pressure source, for example, for loosening a block of a certain shape. A flow control valve 1 5 may, in addition, be installed for each tool 1, 2. Without a flow control valve, the tools will, when the rock is broken, expand somewhat more at the location where the breaking starts while at the same time causing a momentary pressure reduction in the other tools.

Consequently, the cleaving takes place smoothly.

When using flow control valves, the pressure reduction has no effect on the other tools but their pressing force remains unchanged and cleaving takes place with more strength.

The drawing and the description related thereto are only intended to illustrate the idea of the invention. In its details, the method according to the invention and the tool for carrying out said method may vary within the scope of the claims.

Claims

1. A method of cleaving of rock according to which method a hole (8) is bored in the rock (7), a radially expansible cleaving rod (1) is inserted in the hole and said cleaving rod is expanded by power means for applying a pressing force exceeding the breaking strength of the rock on the wall of the hole, characterized in that the cleaving rod (1) is expanded radially by axially compressing pressure element (6) of elastic material in the liole.

2. A method according to claim 1, characterized in that a plurality of cleaving rods (1 ) are connected to a common power source (14), and that the cleaving rods are simultaneously expanded.

3. A tool for cleaving of rock comprising a cleaving rod (1) provided with two supports (4, 5) axially displaceable with respect to each other and a power means (2) fastened to the cleaving rod for displacing said supports, characterized in that a pressure element (6) of elastic material is provided between said supports so that the displacement of said supports with respect to each other compresses said pressure element axially and expands it radially.

4. A tool according to claim 3, characterized in that the pressure element (6) is sleeve-shaped and surrounds a rod-shaped support (3) which extends through a tubular support (5) fastened to a housing (9)of said power means and is connected to an actuating element (10) of said power means, both said supports (3, 5) being provided with annular support surfaces (4a, 5a) abutting from opposite sides against corresponding end surfaces of the sleeve-shaped pressure element.

5. A tool according to claim 3 or 4, characterized in that the pressure element (6) is made of a deformable material which is substantially incompressible in volume.

6. A tool according to claim 3 or 4, in which the power means (2) is pressure fluid operated, characterized in that the power means (2) is provided with a flow control valve (15) for maintaining the compression force acting on the pressure element (6).