AU2021277596A1

AU2021277596A1 - Method, System and Media for Stabilising a Rock Mass

Info

Publication number: AU2021277596A1
Application number: AU2021277596A
Authority: AU
Inventors: Ethan Cornford
Original assignee: Vacrest Pty Ltd
Current assignee: Vacrest Pty Ltd
Priority date: 2020-11-30
Filing date: 2021-11-29
Publication date: 2022-06-16

Abstract

A method of stabilising a rock mass including injecting into a hole at pressure a stabilising media including a polymer-modified gypsum composition formed by an admixture of a Part A and a Part B. A system and an injectable media are also disclosed.

Description

Method, System and Media for Stabilising a Rock Mass

Related Applications

[001] This application claims priority from Australian provisional patent application no. 2020904424 filed on 30 November 2020, the contents of which are incorporated by reference.

Technical Field

[002] The invention relates to a method, a system and media for stabilising a rock mass. In particular, the invention relates to a method, a system and media for stabilising a rock mass in which media is injected into the rock mass.

Background

[003] Rock masses such as coal, shale, mudstone and sandstone may be stabilised by a variety of techniques. One method of stabilising a rock mass includes drilling hole and then injecting a media into that hole. The media may be, for example, a slurry, or a resin such as polyurea silicates and polyurethanes, that are forced under pressure into the hole to fill the voids and cracks in the broken rock mass to form a solid block or strataband which functions to increase the strength of the rock mass.

[004] A problem with such media such as those including polyurea silicates and/or polyurethanes relates to the toxicity, for example, high levels of formaldehydes and carcinogens that may be produced which may require stringent safety controls and pose health checks for operators.

[005] Another problem relates to the exothermic reaction caused by the polyurea silicates and/or polyurethanes. This exothermic reaction has been known to cause the surrounding coal rock mass to reach a temperature which given the right conditions can lead to thermal runaway and dangerous conditions in an underground mine. As a result of this, limits to the quantity in which the product may be delivered are implemented which can affect the performance of the stabilised rock mass. Some events have shown that the quantity limits imposed are not always effective on stopping the surrounding rock mass from reaching temperatures where thermal runaway can occur.

[006] The invention disclosed herein seeks to overcome one or more of the above identified problems, or at least provide a useful alternative.

Summary

[007] In accordance with a first broad aspect there is provided, a method of stabilising a rock mass. The method may include injecting into a hole at pressure a stabilising media including a polymer-modified gypsum composition formed by an admixture, that may include a Part A and a Part B.

[008] In accordance with a second broad aspect there is provided, a method of stabilising rock mass using injectable media, the method including the steps of: providing a hole into the rock mass; inserting a rod into the hole and fitting a packer thereto to inhibit egress of injectable media; pumping, a Part A and a Part B into the rod so as to be mixed to form the injectable media, the pumping being at a pressure such that the injectable media moves into at least one of voids, spaces and cracks of the rock mass.

[009] In an aspect, the step of pumping includes pumping to a predetermined pressure.

[0010] In another aspect, the predetermined pressure is a maximum pressure of the pump.

[0011] In yet another aspect, the packer is an inflatable packer including a static mixer.

[0012] In yet another aspect, the media is a polymer-modified gypsum composition formed by an admixture of Part A and Part B.

[0013] In another aspect, the Part A and Part B may be brought to the application site as aqueous solutions, or the Part A may be brought to the application site as a pre-mixed polymer solution and mixed with the gypsum directly before pumping into the rock mass.

[0014] In yet another aspect, Part A includes gypsum, an alkaline polymer resin, and a hydration inhibitor comprising at least one of acrylic acid, methacrylic acid, and itaconic acid; and Part B includes: an acidic polymer resin, a filler, and an activator; wherein both components A and B are dispersed in water to create an aqueous dispersion.

[0015] In yet another aspect, Part A includes gypsum, an alkaline polymer resin, and a hydration inhibitor comprising at least one of acrylic acid, methacrylic acid, and itaconic acid; and Part B includes an acidic polymer resin, and an activator; wherein both Parts A and B are dispersed in water to create an aqueous dispersion.

[0016] In yet another aspect, the volume ratio of Part A to Part B is in the range of about 1:1 to 5:1.

[0017] In yet another aspect, the volume ratio of Part A to Part B is about 2:1.

[0018] In accordance with a third broad aspect there is provided, a system for stabilising rock mass using injectable media, the system including: a rod adapted to be insertable into hole within the rock mass; a packer adapted to seal the rod to the hole to inhibit egress of injectable media; a pump in fluid communication with the rod via Part A and Part B conduits; and a Part A and a Part B adapted to be pumped by the pump via respective Part A and Part B conduits into the rod so as to be mixed to form the injectable media, the pump being at a pressure such that the injectable media moves into at least one of voids, spaces and cracks of the rock mass.

[0019] In an aspect, the media is a polymer-modified gypsum composition formed by an admixture of Part A and Part B.

[0020] In another aspect, Part A includes gypsum, an alkaline polymer resin, and a hydration inhibitor comprising at least one of acrylic acid, methacrylic acid, and itaconic acid; and Part B includes: an acidic polymer resin, a filler, and an activator; wherein both components A and B are dispersed in water to create an aqueous dispersion.

[0021] In yet another aspect, Part A includes gypsum, an alkaline polymer resin, and a hydration inhibitor comprising at least one of acrylic acid, methacrylic acid, and itaconic acid; and Part B includes an acidic polymer resin, and an activator; wherein both Parts A and B are dispersed in water to create an aqueous dispersion.

[0022] In yet another aspect, the volume ratio of Part A to Part B is in the range of about 1:1 to 5:1.

[0023] In yet another aspect, the volume ratio of Part A to Part B is about 2:1.

[0024] In accordance with a fourth broad aspect there is provided, a media to inject into a rock mass to stabilise the rock mass, the media including: a Part A including gypsum, an alkaline polymer resin, and a hydration inhibitor comprising at least one of acrylic acid, methacrylic acid, and itaconic acid; and a Part B including: an acidic polymer resin, a filler, and an activator; wherein both components A and B are dispersed in water to create an aqueous dispersion.

[0025] In accordance with a sixth broad aspect there is provided, a media to inject into a rock mass to stabilise the rock mass, the media including: a Part A including a gypsum, an alkaline polymer resin, and a hydration inhibitor comprising at least one of acrylic acid, methacrylic acid, and itaconic acid; and a Part B including an acidic polymer resin, and an activator; wherein both Parts A and B are dispersed in water to create an aqueous dispersion.

Brief Description of the Figures

[0026] The invention is described, by way of non-limiting example only, by reference to the accompanying figures, in which;

[0027] Figures 1 to 6 illustrate a sequence of steps to stabilise a rock mass using injectable media.

Detailed Description

[0028] Referring to Figures 1 to 6, there is shown a system 5 for stabilising a rock mass 9 using an injectable media or composition 11. The system 5 includes a hollow rod 10 for inserting into a hole 12 of the rock mass 9, a packer 14 that in use forms an inflatable seal between the rod 10 and the hole 12 to inhibit egress of injected media, a pump 16, a Part A composition and a Part B composition (located in containers or the like, not shown, in communication with the pump 16), and associated Part A and Part B conduits 18, 20 to communicate the Part A and Part B between the pump 16 to be mixed to form the injectable media 11 within the rod 10. A mixer 22 may be provided that in this example may be a static mixer formed within the packer 14 to assist to mix the Part A and Part B composition.

[0029] The rod 10 may be hollow steel rod with a length in the range of, but not limited to, 1 to 5 metres and may be include a plurality of connectable rods that form a string of rods. The diameter of the rods may be in the range of about 20 to 50 mm. The pump 16 may be any suitable pump capable to pumping a two-part viscous material quantity in the range of 100 litres to 1000 litres to a predetermined pressure that may be a predetermined value or the maximum pressure of the pump. The pressure may be in the range of about 100 BAR to 500 BAR, 200 BAR to 400 BAR, and may in some examples be about 300 BAR depending on the selection of the pump 16, as further detailed below.

[0030] The pump 16 may be a high-pressure pump capable of providing a pressure of about 300 BAR. A suitable pump is model XP-hf available from GracoTM. Of course, other suitable pumps may be utilised. The packer 14 may be an inflatable packer that inflates in response to the follow of media 11 into the rod 14. An example of the suitable packer that includes a static mixer is model HT-40 or X-Grid available from StamixcoTM. Of course, other suitable seals may be utilised. The composition of Part A and Part B is further outlined below after a description of the method.

[0031] Turing now to a method for stabilising a rock mass 9 using the injectable media 11, the method may include drilling one or more holes 12 into the rock mass 9. The rod 10 and pressure packer 14 including the mixer 22 are inserted into the drill hole 22 proximate the opening 15 of the hole 12.

[0032] The Part A and Part B component product conduits 18, 20 are connected to the rod 10 and mixed in the packer 14 to form the media 11. The pump 16 is activated to pump Part A and Part B into the packer 14 to inflate the packer 14, seal the hole 12 and also anchor the rod 10. The packer 14 may include a plug (not shown) that is adapted to release at a release pressure to allow the media to flow into rod 10 and therefrom into the rock mass. The media 11 may flow from an inserted end 17 of the rod 19 proximate an end 19 of the hole 12 and into any crack, void or the like of the surrounding rock mass 9.

[0033] When a predetermined pressure is reached such as, but not limited to, 300 BAR, at the pump 16, this indicates all cracks, void or the like have been filled within the hole 12 to a certain penetration distance within the rock mass 9. The distance consolidated is determined by products viscosity, available pump pressure and rock mass crack network. When the hole 12 is filled the conduits 18, 20 are disconnected and then connected to the rod in the next hole etc.

[0034] Now, turning to the composition of the injectable media or composition 9 in more detail, an example of a suitable composition is disclosed in Australian patent no. 2003244600 "Polymer modified gypsum composition" in the name of Rohm and Haas Company T M, and the contents of which are incorporated by reference.

[0035] The disclosed composition provides two components (Part A and Part B) that are admixed to provide a polymer-modified gypsum composition. The admixture exhibits a useful balance of setting time and stability. The composition is disclosed as being suitable for coating surfaces of subterranean mines such as walls and ceilings. However, the use as a two-part injectable media or composition is not contemplated or considered for this type of material, and the subject invention has advantageously discovered a new use for such a substance as an injectable media for internally stabilising a rock mass.

[0036] The examples herein contemplate a variety of these polymer modified gypsum compositions to inject into a rock mass to stabilise the rock mass. One example of the media includes a Part A including gypsum, an alkaline polymer resin, and a hydration inhibitor comprising at least one of acrylic acid, methacrylic acid, and itaconic acid, and, a Part B including: an acidic polymer resin, a filler, and an activator, in which wherein both components A and B are dispersed in water to create an aqueous dispersion.

[0037] Another example of the media to inject into a rock mass to stabilise the rock mass, includes a Part A including a gypsum, an alkaline polymer resin, and a hydration inhibitor comprising at least one of acrylic acid, methacrylic acid, and itaconic acid; and a Part B including an acidic polymer resin, and an activator; wherein both Parts A and B are dispersed in water to create an aqueous dispersion. Other examples may able be suitable. Examples of the media may have an increased viscosity and may be in the range of 0 and 10,000 CPS.

[0038] A more specific example formulation of Part A and Part B (Component A and Component B) composition as disclosed in "Example 1" of Australian patent no. 2003244600 includes:

Component A

Ingredient parts by weight

Alkaline first polymer(PRIMALTM AC-339) 27.68 Antifoam (Wacker S-882) 0.29 Surfactant (TRITONTM X-405) (1:1 in water) 1.03 Alkaline agent (AMP-90) 0.10 Hydration inhibitor (OROTAN TM 963 0.40 Coalescent (Butyl CARBITOLTM) (2:1 in water) 1.18 Gypsum (Crystacal; alpha hemi-hydrate) 69.23 Pigment (Ml Black Pigment; GK 5493) 0.03 Rheology modifier (ACRYSOLTM RM-1020) (1:1 in water) 0.06

Component B

Ingredient parts by weight Second (acidic)polymer (PRIMALTm HA-16) 31.90 Defoamer (Wacker S-882) 0.24 Surfactant (TRITONTm X-405) (1:1 in water) 0.99 Water 1.39 Activator (Al2SO4.18 H20 (1:1 in water) 1.19 Filler (ATH Nyala M20-G 64.09 Rheology modifier (ACRYSOLTM SCT-275) (1:1 in water) 0.20

[0039] Such an example, and other examples disclosed herein, may be mixed at a volume ratio of 1:1 to 5:1 for the present application, and it has been found that a volume ratio of about 2:1 (Part A to PartB) is most preferable. Relatively increasing Part B reduces the set time, but also reduces the strength, hence the preference for a volume ratio of about 2:1 which has been found in the present application to provide a relatively fast set time whilst maintaining strength which is important in this application. Other suitable ratios may, of course, be selected.

[0040] Advantageously, there has been described a method, a system and media for stabilising a rock mass in which media is injecting to the rock mass. In particular, a media including polymer modified gypsum composition has been identified and found suitable for injecting under pressure into a rock mass via a rod to stabilise the rock mass. The use of the media has been found to provide the advantages of having microfine particle size to be able to flow into very small crack, limited or no dust and minimal quantities of toxic vapours.

[0041] Further advantageously, the present media may have only a limited exothermic reaction, being an admixture, and as such may not need to be limited in quantity like may products that have a significant exothermic reaction. In industry, this value may be around 350 Litres per hole. The present media does not have this constraint due to its low exothermic properties so product quantity per hole may be increased and may only be limited by available pump pressure. This allows the rock mass to be stabilised or "glued" to a greater extent. The present media may also have a controlled set time and can be adjusted to ensure the product does not set whilst cracks in a consolidation are still being filled.

[0042] Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0043] The reference in this specification to any known matter or any prior publication is not, and should not be taken to be, an acknowledgment or admission or suggestion that the known matter or prior art publication forms part of the common general knowledge in the field to which this specification relates.

[0044] While specific examples of the invention have been described, it will be understood that the invention extends to alternative combinations of the features disclosed or evident from the disclosure provided herein.

[0045] Many and various modifications will be apparent to those skilled in the art without departing from the scope of the invention disclosed or evident from the disclosure provided herein.

Claims

The claims defining the Invention are as follows:

1. A method of stabilising a rock mass including injecting into a hole at pressure a stabilising media including a polymer-modified gypsum composition formed by an admixture of a Part A and a Part B.

2. A method of stabilising rock mass using injectable media, the method including the steps of: a. Providing a hole into the rock mass; b. Inserting a rod into the hole and fitting a packer thereto to inhibit egress of injectable media; c. Pumping, a Part A and a Part B into the rod so as to be mixed to form the injectable media, the pumping being at a pressure such that the injectable media moves into at least one of voids, spaces and cracks of the rock mass.

3. The method according to clam 2, wherein the step of pumping includes pumping to a predetermined pressure.

4. The method according to clam 3, wherein the predetermined pressure is a maximum pressure of the pump.

5. The method according to clam 3, wherein the predetermined pressure is in the range of 100 to 500 BAR, more preferably in the range 200 to 400 BAR, and most preferably about 300 BAR.

6. The method according to clam 2, wherein the packer is an inflatable packer including a static mixer.

7. The method according to claim 2, wherein the media is a polymer-modified gypsum composition formed by an admixture of Part A and Part B.

8. The method according to claim 1 or claim 2, wherein:

Part A includes gypsum, an alkaline polymer resin, and a hydration inhibitor comprising at least one of acrylic acid, methacrylic acid, and itaconic acid; and Part B includes: an acidic polymer resin, a filler, and an activator; wherein both components A and B are dispersed in water to create an aqueous dispersion.

9. The method according to claim 1 or claim 2, wherein: Part A includes gypsum, an alkaline polymer resin, and a hydration inhibitor comprising at least one of acrylic acid, methacrylic acid, and itaconic acid; and Part B includes an acidic polymer resin, and an activator; wherein both Parts A and B are dispersed in water to create an aqueous dispersion.

10. The method according to claim 1 or claim 2, wherein: the volume ratio of Part A to Part B is in the range of about 1:1 to 5:1.

11. The method according to claim 1 or claim 2, wherein: the volume ratio of Part A to Part B is about 2:1.

12. A system to stabilise a rock mass using injectable media, the system including: A rod adapted to be insertable into hole within the rock mass; A packer adapted to seal the rod to the hole to inhibit egress of injectable media; A pump in fluid communication with the rod via Part A and Part B conduits; and a Part A and a Part B adapted to be pumped by the pump via respective Part A and Part B conduits into the rod so as to be mixed to form the injectable media, the pump being at a pressure such that the injectable media moves into at least one of voids, spaces and cracks of the rock mass.

13. The method according to claim 12, wherein the media is a polymer-modified gypsum composition formed by an admixture of Part A and Part B.

14. The system according to claim 12, wherein: Part A includes gypsum, an alkaline polymer resin, and a hydration inhibitor comprising at least one of acrylic acid, methacrylic acid, and itaconic acid; and

Part B includes: an acidic polymer resin, a filler, and an activator; wherein both components A and B are dispersed in water to create an aqueous dispersion.

15. The system according to claim 12, wherein: Part A includes gypsum, an alkaline polymer resin, and a hydration inhibitor comprising at least one of acrylic acid, methacrylic acid, and itaconic acid; and Part B includes an acidic polymer resin, and an activator; wherein both Parts A and B are dispersed in water to create an aqueous dispersion.

16. The system according to claim 12, wherein: the volume ratio of Part A to Part B is in the range of about 1:1 to 5:1.

17. The system according to claim 12, wherein: the volume ratio of Part A to Part B is about 2:1.

18. A media to inject into a rock mass to stabilise the rock mass, the media including: A Part A including gypsum, an alkaline polymer resin, and a hydration inhibitor comprising at least one of acrylic acid, methacrylic acid, and itaconic acid; and A Part B including: an acidic polymer resin, a filler, and an activator; wherein both components A and B are dispersed in water to create an aqueous dispersion.

19. A media to inject into a rock mass to stabilise the rock mass, the media including: A Part A including a gypsum, an alkaline polymer resin, and a hydration inhibitor comprising at least one of acrylic acid, methacrylic acid, and itaconic acid; and A Part B including an acidic polymer resin, and an activator; wherein both Parts A and B are dispersed in water to create an aqueous dispersion.