US3698196A

US3698196A - Method for reinforcing loose rock and coal

Info

Publication number: US3698196A
Application number: US119822A
Authority: US
Inventors: Alfons Jankowski; Otto-Ernst Glaesmann; Gerhard Haake
Original assignee: Bergwerksverband GmbH
Current assignee: Bergwerksverband GmbH
Priority date: 1970-03-04
Filing date: 1971-03-03
Publication date: 1972-10-17
Anticipated expiration: 1989-10-17
Also published as: FR2084181A6; GB1286782A

Abstract

A plastic foil container having two separate compartments filled with the components of a foaming mixture, is inserted into a bore drilled into loose and caving rock or coal, and broken by a pointed rod inserted into the bore so that after sealing said bore with a plug a foam mixture fills, expanding due to swelling pressure, the bore and surrounds loose and caving rock or coal and reinforces the rock after hardening, particularly when the rod is left in the bore.

Description

United States Patent J ankowski et al.

[54] METHOD FOR REINFORCING LOOSE ROCKAND COAL [72] Inventors: Alfons Jankowski, Essen-Heisingen;

Otto-Ernst Glaesmann, Castrop- Rauxel; Gerhard Haake, Essen- Kray, all of Germany [73] Assignee: Bergwerksverband GmbH, Essen,

Germany [22] Filed: March 3,1971

21 Appl. No.: 119,822

[30] Foreign Application Priority Data March'4, 1970 Germany ..P 20 10 140.0

[52] US. Cl. ..61/45 B, 52/741, 61/63 [51] Int. Cl. ..E21d 20/02 [58] Field of Search ..61/45 B, 63, 36, 35; 52/698,

[56] References Cited UNITED STATES PATENTS 3,430,449 3/1969 Novotny et al ..61/45 B 51 Oct. 17, 1972 Primary Examiner-Dennis L. Taylor Attorney-Michae1 S. Striker [5 7 ABSTRACT A plastic foil container having two separate compartments filled with the components of a foaming mixture, is inserted into a bore drilled into loose and caving rock or coal, and broken by a pointed rod inserted into the bore so that after sealing said bore with a plug a foam mixture fills, expanding due to swelling pressure, the bore and surrounds loose and caving rock or coal and reinforces the rock after hardening, particularly when the rod is left in the bore.

12 Claims, 4 Drawing Figures METHOD FOR REINFORCING LOOSE ROCK AND COAL BACKGROUND OF THE INVENTION The method of the prior art has been successful in coal mining when coal is deposited in steep seams. Also in very large gently sloping seams, the method has been successful for preventing weak coal faces from loosen ing. For these purposes, the foam-forming resin mixture is filled, before foaming, and only due to the action of the force of gravity, into downward slanting bores in which the mixture, after closing of the bores, expands due to swelling pressure, and enters cracks and crevices, filling and sealing the same. Before the bores are closed, reinforcing rods, preferably made of inexpensive wood, are inserted into the bore and reinforce the loose rock. At the same time, the amount of the resin mixture required for filling the bore is reduced, since part of the volume of the bore is taken up by the rod, which remains in the same after hardening of the resin mixture.

However, it is not possible to use this method to fill bores which are horizontal or upward slanted, since the foam mixture would run out of the bore before filling process has been done. It has been proposed to pump the components of the foam mixture separately into the bore in the rock, and to mix the components directly before, or in the bore. It has also been proposed to insert a foam-forming resin mixture in mixed condition by means of a pressure pump into the bore, but this method has not been found successful, since an apparatus for injecting the mixture is expensive, and furthermore because the sealing and closing of the bores is difficult and also expensive.

If expandable probes are used for the pressure injection, a great part of the injected resin mixture flows out of the bore when the pressure probe is exchanged for a plug closing the bore. The use of expandable pressure probes which remain in the bore, sealing the same, is also too expensive.

SUMMARY OF THE INVENTION It is one object of the invention to overcome the disadvantages of prior art methods for reinforcing loose rock by filling bores in the rock by a resin mixture, and to provide a new method permitting the filling of upward slanted bores in the rock.

Another object of the invention is to prevent the mixing of the components of the foam-forming mixture before all components are in the bore.

Another object of the invention is to plug the entrance opening of the bore by a quickly hardening resin mixture, before the foam in the bore has hardened.

With these objects in view, a method of the invention comprises drilling at least one bore into loose rock; inserting into the bore at least one breakable container having at least two separate compartments filled with two components which form a resinous hardenable foam, when mixed; and breaking the container in the bore to establish communication between the compartments.

As a result, the components mix in the bore to form a foaming mixture filling, expanding due to swelling pressure, the closed bore and the surrounding loose and caving rock and coal then hardening in the bore so that the rock is reinforced.

Preferably, the breaking of the container is carried out by inserting a pointed rod into the bore after insertion of the container, and it is advantageous to use the rod for mixing the components, and to then leave the rod in the bore for reinforcing the hardened foam mixture which fills the volume of the bore not taken up by the rod.

Due to the fact that the components of the foamforming mixture are inserted into the bore separated by the walls of the container, which preferably consists of plastic foil material, bores which slant upward or which are horizontal, can be filled by the: reinforcing hardenable mixture.

It is a particular advantage of the invention that the rod, which is usually inserted into "the bore for reinforcing the rock, can also be used for breaking the container in the bore. Very little equipment is required for carrying out the method of the invention, and the method can be practiced by unskilled workers.

For the foam-forming synthetic resin mixture used in the method of the invention, polyurethanes with added water have been found advantageous. The properties of the hardened foam, and the reaction and hardening times, can be easily varied by suitably selecting the ratios of the components forming the mixture.

In the preferred embodiment of the invention, the container includes an outer tubular wall and an inner tubular wall in the outer tubular wall and having the same length. Clips close the ends of both tubular walls at the ends of the container. One of the compartments is formed in the inner wall which is filled by one component, and the other compartment is formed within the outer tubular wall and around the inner tubular wall, and filled with the other component.

The tubular walls are made of synthetic plastic foil, which may consist of polyethylene, polypropylene, polyester, or polyamide. Double-wall tubular containers of this type can be easily mass-produced, and are very inexpensive. Although they are reliably holding the components of the mixture during transport, they can be easily destroyed in the bore in the rock by a pointed wooden rod.

The following examples are illustrative, and not limiting for the invention.

EXAMPLE I which is foamed by a propellant, as set forth in the following example.

EXAMPLE 2 A first component in the outer annular compartment within the outer tubular wall of the container, consists of 100 weight units of a polyester forming a dough with 200 weight units of rock powder. The second component within the inner tubular wall of the container, has 3 weight units of a 50 percent benzoylperoxide paste. A third component in a third tubular foil compartment contains 8.6 weight units of a propellant.

The proportions of the components in the above examples are not critical, and can be varied.

When the bore is upward slanted, it is advantageous to thicken and thixotropicly adjust the mixture by addition of suitable powdery additives, such as rock powder, soot, aerosil, talcum, kaolin, or asbestos flakes, so that the flowing out of the mixture during the mixing and foam formation is reduced. Such a mixture is set forth in the following example, but the ratios are not critical and may be varied.

EXAMPLE 3 The first component in the outer annular compartment of the container consists of 100 weight units of a polyalcohol, 17.5 weight units of castor oil, and 2.1 weight units of water. Asbestos flakes and aerosil are added to the components until the same is thixotropic. The second component in the inner compartment consists of a diisocyanate.

It is possible to close the entrance opening of the bore after insertion of the rod, by wooden plugs or other mechanically or hydraulically expansible closures. However, in accordance with the present invention, this is obtained by using a special container which is inserted after the first container, and placed at the entrance opening of the bore. The second container has two compartments filled with the components of a rapidly hardening resin-forming or foam-forming mixture. When the second container is broken together with the first container, resin or foam forms at the entrance opening of the bore and hardens quickly before the foam in the inner part of the bore has filled the bore and fully formed and has hardened. In this manner, the foam developing from the components inserted with the first container, is prevented to flow out of the entrance opening of a upward slanting bore, since a hard plug is formed at the entrance of the bore. In this manner, in accordance with the invention, the step of closing the bore need not be separately carried out by a plug.

The following example concerns a foam-forming, rapidly hardening resin mixture which is used for plugging the entrance of the bore.

EXAMPLE 4 The plugging container is also made of two tubular walls forming an outer and an inner compartment. The first component is placed in one of the compartments, and consists of 28 weight units of a cold, hardening, unsaturated polyester resin, and of 70 weight units of rock powder and aerosil. The second component in the other compartment consists of a peroxide.

The reinforcing rods preferably consist of wood having a profiled cross section, which may be square, rectangular, or otherwise non-circular. The leading end of the rod is sharpened or pointed to cut and break the plastic foil container easily. When the rod is quickly rotated, a mixing efi'ect is obtained which has been found entirely sufficient, if the rotation is fast enough. Drilling machines may be used for rotating the rod, particularly rotary-drilling machines of conventional construction, which are provided with a chuck for clamping the rod.

It is advantageous to cover the sharpened end of the rod with a metal or plastic fitting which reliably assures the breaking of the plastic foil container walls.

Particularly if thickened resin mixtures are used, it is particularly advantageous to attach an agitating tool consisting of metal or synthetic plastic material to the leading end of the rod so that the mixing effect of the rotated rod is improved.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic side view illustrating a container with two compartments, in accordance with the invention;

FIG. 2 is a perspective view illustrating a first embodiment of the rod;

FIG. 3 is a fragmentary perspective view illustrating a second embodiment of the rod used in the method of the invention; and

FIG. 4 is a perspective view illustrating a third embodiment of the rod provided with an agitating tool.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1, a container 1 is made of synthetic plastic foil material, and includes an outer tubular wall 2, an inner tubular wall 3, and clips 6, closing the ends of the tubular walls 2 and 3, so that an outer annular compartment 4 is formed between walls 2 and 3, and an inner compartment is formed within the inner wall 3. Container 1 is elongated and slender, and can be longitudinally inserted into a drilled bore.

A first embodiment of the rod 7 is shown in FIG. 2. Rod 7 has a square cross-section schematically indicated at 8, and has a slanted end face forming a cutting edge 9. In the embodiment of FIG. 3, the rod 7 has a leading end covered by a fitting 10 having a pyramid-shaped pointed end portion 1 l.

Fitting 10,11 may consist of metal or a hard plastic synthetic material. It is evident that insertion of one of the rods 7, shown in FIGS. 2 and 3, into a bore in which container 1 is located, will cut up and break the plastic foil walls of the container 1 which will cause the components of the resin mixture to mix and foam, and then harden in the bore.

The embodiment of the rod 7 shown in FIG. 4 is provided with a fitting 10' to which an agitating tool consisting of two

blades

12 and 13 is secured so that rotation of rod 7' causes thorough mixing and agitation of the components flowing out of the broken container when rod 7 is rotated.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of methods for reinforcing loose rock differing from the types described above.

While the invention has been illustrated and described as embodied in a method for reinforcing loose rock by inserting into a hole drilled in the rock, a breakable container having two compartments for the components of a foam-forming mixture, and then breaking the container, it is' not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can be applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention, and therefore such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

We claim:

1. A method for reinforcing loose rock, comprising drilling into the rock at least one bore having a closed bottom portion and an entrance opening on the rock surface; inserting a breakable container into said closed bottom portion spaced from said entrance opening, said container having at least two separate compartments filled with two components, respectively, which form a resinous hardenable expanding foaming mixture, when mixed; breaking said container in said bottom portion to establish communication between said compartments so that said components mix in said bottom portion of said bore; and closing said entrance opening before said mixture fully expands and hardens so that said mixture is confined and enclosed within a closed space in said bore while expanding, said mixture expanding and filling said closed space to said closed entrance port and entering under pressure between loose rock portions surrounding said bore whereupon said mixture hardens so that the rock around said bore is reinforced.

2. The method of claim 1 wherein said breaking of said container is carried out by inserting a rod into said bore after insertion of said container into said bottom portion, said rod having a length corresponding to the depth of said bore so as to leave said entrance opening free for closing so that after closing of said entrance bore, said rod remains in said bore for reducing the free volume of said bore.

3. The method of claim 1 wherein the step of closing said entrance opening includes the steps of inserting an other container into said entrance opening after inserting of said container into said bottom portion of said bore, said other container having at least two compartments filled with substances, respectively, which form, when mixed, an other mixture which hardens quicker than said foaming mixture, and breaking said other container when breaking said container in said bottom portion of said bore so that said other mixture is formed which quickly hardens in said entrance opening to close said entrance opening before said foaming mixt hfll add'thlsdb.

T l 'i e b me tfi o i c laiir i 2 v vlie e in said rod consists of wood and has a non-circular cross section; and wherein the leading end of said rod is shaped for cutting said container.

5. The method of claim 4 wherein said leading end of said rod has a sharp metal or plastic fitting.

6. The method of claim 2 wherein said rod has an agitating means attached to the leading end thereof, and including the step of turning said rod with said agitating means in said bore for mixing said components.

7. The method of claim 2 wherein said container includes an outer tubular wall, an inner tubular wall in said outer tubular wall having the same length, and clips closing the ends of said tubular walls at the ends of said container; and wherein one of said compartments in formed in said inner tubular wall, and the other compartment is formed within said outer tubular wall and around said inner tubular wall.

8. The method of claim 7 wherein said inner and outer tubular walls consist of synthetic plastic foils adapted to be pierced and broken by said inserted rod.

9. The method of claim 1 wherein said mixture includes polyurethanes and water.

10. The method of claim 1 wherein said mixture includes a polyester and a propellant.

11. The method of claim 1 wherein said mixture includes in addition to said components, a thickening powder for thixotropicly adjusting said mixture.

12. The method of claim 11 where said thickening powder is a mineral powder selected from the group consisting of rock-powder, aerosil, talcum, kaolin and asbestos flakes.

Claims

3. The method of claim 1 wherein the step of closing said entrance opening includes the steps of inserting an other container into said entrance opening after inserting of said container into said bottom portion of said bore, said other container having at least two compartments filled with substances, respectively, which form, when mixed, an other mixture which hardens quicker than said foaming mixture, and breaking said other container when breaking said container in said bottom portion of said bore so that said other mixture is formed which quickly hardens in said entrance opening to close said entrance opening before said foaming mixture has fully expanded in the closed bore.

4. The method of claim 2 wherein said rod consists of wood and has a non-circular cross section; and wherein the leading end of said rod is shaped for cutting said container.

7. The method of claim 2 wherein said container includes an outer tubular wall, an inner tubular wall in said outer tubular wall having the same length, and clips closing the ends of said tubular walls at the ends of said container; and wherein one of said compartments is formed in said inner tubular wall, and the other compartment is formed within said outer tubular wall and around said inner tubular wall.

9. The method of claim 1 wherein said mixture includes polyurethanes and water.

12. The method of claim 11 wherein said thickening powder is a mineral powder selected from the group consisting of rock-powder, aerosil, talcum, kaolin and asbestos flakes.