AU2006222679A1 - Sealing Techniques in Mining and Related Industries - Google Patents

Description

AUSTRALIA

Patents Act 1990 PROVISIONAL SPECIFICATION Applicant/s: Resin Grouting Technology Invention Title: Sealing Techniques in Mining and Related Industries The invention is described in the following statement: 2 SEALING TECHNIQUES IN MINING AND RELATED INDUSTRIES Field of the Invention The present invention relates to a method and apparatus for sealing various members in roof and wall formations. The invention finds particular application in the mining industry, but also has applications in industries where sealing/fastening in rock and concrete formations is required, such as in the construction industry and in structural and civil engineering applications. Thus, it should be appreciated that the invention has broader applications and is not limited to mining applications.

Background Art In the mining industry, after a tunnelling operation, it becomes necessary to stabilise the tunnel, particularly at the roof and wall surfaces, to prevent tunnel collapse (and to prevent human injury, damage to property, costly excavation, explosion etc).

It is known to stabilise the roof and walls (or ribs) of tunnels by employing cable bolts and roof bolts. A cable bolt acts as a large pin and is fitted in a hole drilled in the roof (or rib) of the tunnel, and is then manually adhered therein using a grout. During application of the grout, however, grout rundown and fallout occurs and this is undesirable.

With roof bolts, once fitted into the roof or rib of a tunnel, it sometimes occurs that the bolt hole penetrates an overlying water table and water seepage and leakage occur through the annular space surrounding the bolt. Roof bolts often hold a metallic plate over the opening to the drilled hole and this plate is urged against the roof (or rib) of the tunnel by a nut attached to a free end of the roof bolt (usually tightly). Water flow, accordingly, not only leaks into the tunnel but can cause corrosion and weakening of parts in the assembly such as the plate.

3 In coal and other mining applications, often large quantities of gas (eg. methane coal gas) and water are dispersed through the site to be mined. Prior to mining the site, it is common to fit gas or water pipes (stand pipes) into walls etc or the ceiling of the site, and then to vacuum extract the gas or water therefrom, leaving the site in a safer and easier state for mining. Such piping is fitted in a similar manner to cable and roof bolts (ie.

using manually applied grout).

Summary of the Invention In a first aspect the present invention provides a method of sealing space around a member when arranged in a formation, comprising the steps of: selecting a curable sealant that is adapted such that it can be injected into the space and, once injected, does not flow, to enable sealant curing to occur; and injecting that sealant into the space.

In various applications, once the sealant has cured, grout can then be introduced (usually pumped) into space around the member beyond the sealant. The sealant then functions as a plug to hold that grout in the space whilst curing. In other applications, the sealant may be the only substance introduced to the space surrounding the member and thus acts as both a sealant and a type of grout.

Preferably the sealant is thixotropic, and more preferably is a two part polyurethane.

Furthermore, it is preferred that the sealant, once injected, is adapted (in addition to being non-flowable) to be non-slumpable (ie. the integrity and position of the sealant is substantially maintained once injected).

In a second aspect the present invention provides apparatus for sealing space around a member when arranged in a formation, or for sealing space in a structure, comprising an injection means that is adapted for injecting 4a curable sealant, that in turn is adapted such that, once injected into the space, the sealant does not flow.

It is preferred that the injector is a syringe, preferably pneumatically driven, but can also be hand mechanically driven. Furthermore, when the sealant is formed by mixing a two part polymer resin (eg. An isocyanate and a polyol, then the injector preferably comprises two separate chambers for each part). Thus, separately or conjunctively movable plungers can be displaced respectively through the chambers, and mixing can take place in a nozzle formation of the injector.

The injector may also be adapted for receiving an extension portion thereon to enable sealant to be injected into space, remote from the opening thereto.

In a third aspect the present invention provides a method of sealing a space in a structure comprising the steps of: selecting a curable sealant that is adapted such that it can be injected into the space, once injected, does not flow, to enable sealant curing to occur; and injecting that sealant into the space.

Such a methos can be used to repair other structures, such as dams (where dam leakage is occurring), waterproofing membranes used in the construction industry etc.

Brief Description of the Drawings Notwithstanding any other forms which may fall within the scope of the present invention, preferred forms of the invention will not be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows a cross-sectional view of apparatus according to the invention when used to seal a cable bolt assembly; Figure 2 shows a cross-sectional view of apparatus according to the invention when used to seal a roof bolt and roof plate assembly.

5 Figure 3 shows a cross-sectional view of apparatus according to the invention when used to seal a stand pipe in a wall formation; Figure 4 shows a cross-sectional view of alternative apparatus according to the invention when used to seal a cable bolt assembly; and Figure 5 shows a cross-sectional view of alternative apparatus according to the invention when used to seal a roof bolt and roof plate assembly.

Modes for Carrying Out the Invention Referring to Figure 1, the sealing of a cable bolt assembly will now be described. A cable bolt 10 is arranged in a drilled shaft 12 in the ceiling C of a tunnel (typically a mining tunnel or other excavated tunnel where cable bolt pinning stability is required). A grout tube 14 (eg. that is 20mm in diameter) and an air breather tube 16 (eg. 5mm in diameter) are positioned next to the cable bolt. (The air breather tube enables air to be exhausted from the annular space when grout is subsequently introduced into the shaft. Note: in the fusing of cable bolts, a cementitious grout is typically used for the bulk of the bolt fixing and only a small amount of the sealant is used at or near the opening to prevent grout runout).

An injector device 26, that is typically pneumatically driven via an air ram mechanism 28 fed by pneumatic air line 29 is positioned adjacent to opening 30 to the shaft 12. The ram mechanism drives a pair of plungers 31, 32, which interact with and slide within respective chambers, 33, 34. The ram mechanism causes the plungers to be driven (usually simultaneously and equidistantly) within each respective chamber, although each plunger may be separately driven to effect different mixing ratios etc. Chamber volumes can also be varied as appropriate.

Chamber 33 can hold part A of a polymeric resin mixture and chamber 34 can hold part B of the mixture. For 6 example, chamber A can hold the polyol component of a polyurethane and chamber 34 can hold the isocyanate component of the urethane.

When the ram mechanism is activated, the plungers are driven forwardly into their respective chambers causing the components A and B to be driven outwardly through the nozzle 24 and via static mixer 36. The static mixer mixes the components so that the sealant leaving the end of the nozzle 24 is thoroughly mixed.

In use, after the cable bolt and tube assembly has been arranged as shown, then the nozzle 24 is positioned so that it extends through opening 30 and partway into shaft 12. The injector device is then activated so that sealant is introduced into the shaft as shown at 40. For preferred thixotropic sealants, the nozzle can be removed as soon as injection has been completed (ie. at a specific volume of material injected) and the as restored, higher viscosity of the sealant then prevents the sealant from running back out opening Typically with fast curing resin mixtures, "creaming" (or reaction time) may be instantaneous or may occur only a few moments after injection. "Gelling" (or hardening) was typically observed to occur some minutes thereafter.

The use of a pneumatic injector device is preferred, but hydraulic, manual, electric, pump driven and other types of actuating devices can be used. The device provides a very rapid and easy to use mechanism for sealing the opening to the shaft 12.

Once the sealing of the opening has occurred, grout to fix the cable bolt can be introduced into space 42 via grout tube 14 (ie. using heavy duty pumps) with air escaping via the air breather tube 16 in the conventional manner. The cured sealant holds the grout in space 42.

After grouting, the grout and air breather tubes are typically cut off with the ends left in situ.

7 Referring to Figure 2 where like reference numerals will be used to denote similar or like parts, the sealing off of a roof bolt 50 will now be described. The roof bolt has already been fastened in shaft 12 and usually there is some annular space around the roof bolt along its length.

However, it is often the case that the shaft intersects with water table systems in the overlying roof structure.

This water leaks down through the annular space and runs out of the shaft opening, often causing corrosion of the bolt system, fatigue of the surrounding structure and water accumulations in the underlying tunnel etc.

With the bolt fitted as shown, the roof plate 52 can then be attached to bolt 50. Typically, the roof bolt extends through a hemispherical portion 54 of roof plate 52. A nut 56 is then threaded onto a threaded end 58 of the roof bolt and engages the underside of the hemispherical portion so that the plate is held and urged against the ceiling C as shown.

The problem of water seepage can be overcome by sealing the opening 30; ie. by positioning the injector adjacent to opening 30 so that the injector nozzle extends through the opening and then injecting sealant 40 into the annular space. Again, the sealant viscosity enables curing to occur before any sealant flowback occurs.

Sealant introduction can be performed either with the plate 52 removed (eg. prior to its attachment to bolt or attached (in which case, an injector hole would need to be made or be present in plate 52 prior to injection).

Referring now to Figure 3 where like reference numerals will be used to denote similar or like parts, the sealing off of a stand pipe 70 in formation F will now be described. Stand pipes are used for both gas and water drainage, particularly in the mining industry. For example, coal seams can have high free methane gas content and/or water content. To effectively and efficiently long wall mine, for example, a coal seam, the methane gas 8 present therein must be bled from the coal to prevent potential explosion and atmospheric air poisoning during mining. A series of holes are drilled the length and width of the long wall block, and individual stand pipes are fitted in each hole. These pipes are connected to a common trunk pipe to which a vacuum is applied to extract the gas from the seam and to carry it from the mine for reclamation.

It is vital to seal around the gas extraction holes and stand pipes in the seam, otherwise it is extremely difficult to pump fluid (gas or liquid) from the seam, due to leakage.

As with cable bolt systems, the fixing of the stand pipe is achieved by a cement grout in slurry form that is pumped around the stand pipe. However, to prevent the cement grout from exiting the opening 30 and furthermore, to ensure a fluid-tight (and gas-tight) seal around the stand pipe at the opening, a sealant is injected at or near the opening.

In Figure 3, it can be seen how sealant 80 is progressively injected near the opening 30 of horizontal shaft 72. The sealant 80 progressively fills up the shaft 72 and, because of its post-injection viscosity, ensures that the entire annular space adjacent to the opening is filled and thus sealed (ie. the sealant does not slump after injection and run out of opening 32).

To ensure a deep penetration of the sealant, an extension tube 82 can be fitted to the end of the injector device and this extension tube can be progressively retracted out from the shaft 72 as the annular space in the shaft fills up with sealant.

Stand pipes are used for mine systems that include water, because it is usually necessary to drain a mined area of water or even to use a previously extracted (and mined) area for temporary water storage. Again, the stand pipes are grouted in, but the presence of water means the 9cement-type slurries used often tend to be "washed-out". By sealing the annular space around the stand pipes at and near the opening with, for example, waterproof sealant, this wash-out can be prevented and a fluid-tight seal can be provided.

In the above application it is preferred that the sealant is thixotropic and some Polymeric resin compounds were found to be suitable for use in this regard.

The most suitable were polyurethane resins. Polyurethane resins were also favoured because of their tendency to expand in volumne during curing and during contact with water, because of their adhesion being unaffected by water contact, and because of their suitable viscosity in use. However, epoxy, phenolic and polyester resins were also investigated. Epoxy resins were observed to be environmentally friendly and less hazardous resins to use in tunnel environments.

Phenolic resins potentially could have superior qualities that are currently being investigated.

In a most preferred method of use, a two part polyurethane resin having a variety (eg. one-to-one) of mix ratios was formulated. For the cable bolt and stand pipe sealing techniques, a polyurethane formula having a high expansion ratio and a high post-injection viscosity was used, whereas for roof bolt water sealing, a polyurethane formula with a low expansion ration was used. Typical high expansion ratios for the polyurethane ranged from 4:1 to 8:1 whereas typical low expansion ratios ranged from 2:1 to 3:1.

A most preferred polyurethane was typically formed from, for component A, a polyol (eg. polyether polyols optional blended with trimonochloro isopropyl phosphate) and, for component B, a 4,4' diphenyl methane diisocyante. The thixotropic properties of the diisocyanate were enhanced by incorporating therein a fumed silica and ensuring that the prepolymer diiocyanate was CFC free.

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c A problem can occur when blending silica fume such as Aerosil R202 or 'Wacka'. The blending process will entrain minute air bubbles which also may contain moisture. If these bubbles remain in the diisocyanate over time the c, moisture will react with the diisocyanate and either affect the expansion ratio when mixed with the polyol or begin an expansion process within the diisocyanate tube which can cause the sealing plug or piston to dislodge.

C To prevent these problems it was found necessary to vacuum the ND diisocynate and polyol in separate pressure vessels to remove minute air particles.

Typical process involved a vacuum of 80 ins water gauge for 8 hours ani 200 litres of diisocyante or polyol.

The two components were provided in separate cartridges (eg. 300ml) capacity cartridges) and the 10 cartridges were then snapped together and secured in the injector device (typically an air driven gun).

It was found that sufficient resin for each application could be injected into the shaft after approximately 10 to 20 seconds. The nozzle was then withdrawn ready for further injections. Varying injection speeds were also tested in order to maximise the effectiveness in each application.

Referring to Figure 4, an alternative sealing of a cable bolt assembly will now be described. A cable bolt is arranged in a drilled shaft 12 in the ceiling C of a tunnel (typically a mining tunnel or other excavated tunnel where cable bolt pinning stability is required). A grout tube 14 (eg. that is 20mm in diameter) and an air breather tube 16 (eg. 5mm in diameter) are positioned next to the cable bolt. (The air breather tube enables air to be exhausted from the annular space when grout is subsequently introduced into the shaft).

A closure in the form of rubber grommet 18 is then positioned to close the opening to the shaft (ie. as shown). The grommet includes a passage 20 through which the cable bolt extends and through which the grout and air breather tubes are passed. In addition, the grommet has a hole 22 formed therethrough to enable nozzle 24 of sealant injector device 26 to also pass through the grommet.

The injector device is typically pneumatically driven via an air ram mechanism 28 fed by pneumatic air line The ram mechanism drives a pair of plungers 31, 32, which interact with and slide within respective chambers, 33, 34.

The ram mechanism causes the plungers to be driven (usually simultaneously and equally) within each respective chamber, although each plunger may be separately driven to effect different mixing ratios etc.

Chamber 33 can hold part A of a polymeric resin mixture and chamber 34 can hold part B of the mixture. For example, chamber A can hold the polyol component of a 11 polyurethane and chamber 34 can hold the isocyanate component of the urethane. Alternatively, chamber A can hold an epoxide monomer and chamber B the hardener or curing agent for an epoxy resin etc.

When the ram mechanism is activated, the plungers are driven forwardly into their respective chambers causing the components A and B to be driven outwardly through the nozzle 24 and via static mixer 36. The static mixer mixes the components so that the sealant leaving the end of the nozzle 24 is thoroughly mixed.

In use, after the cable bolt and tube assembly has been arranged as shown, then the nozzle is positioned within its respective hole 22, and the injector device is activated so that sealant is introduced into the shaft as shown at 40. For a fairly viscous sealant, the nozzle can be removed as soon as injection has been completed (ie. at a specific volume of material injected) and the viscosity of the sealant then prevents the sealant from running back through the hole 22. For less viscous sealants, the nozzle can be held in position at the hole with a positive pressure from the ram mechanism until initial curing starts and then it can be withdrawn. Typically with fast curing resin mixtures this may be instantaneous or only a few moments after injection.

The use of a pneumatic injector device is preferred, but hydraulic, manual, electric, pump driven and other type devices can also be used. The device provides a very rapid and easy to use mechanism for sealing the opening to the shaft 12. Once the sealing of the opening has occurred, grout to fix the cable bolt can be introduced via a grout tube (ie. using heavy duty pumps) with air escaping via the air breather tube in the conventional manner. After grouting, the grout and air breather tubes are typically cut off with the ends left in situ.

Referring to Figure 5 where like reference numerals will be used to describe similar or like parts to those of 12 Figure 4, the sealing off of a roof bolt 50 will.now be described. The roof bolt has already been fastened in shaft 12 and usually there is some annular space around the roof bolt along its length. However, it is often the case that the shaft can intersect with water table systems in the overlying roof structure. This water then leaks down and runs out of the shaft opening, often causing corrosion of the bolt system, fatigue of the surrounding structure and water accumulations in the underlying tunnel etc.

Typically, the roof bolt extends through a hemispherical portion 52 of roof plate 54. A nut 56 is then threaded onto a threaded end 58 of the roof bolt and engages the underside of the hemispherical portion so that the plate is held and urged against the ceiling C as shown.

The problem of water seepage can be overcome by drilling a hole 60 through the roof plate as shown and then passing the injector nozzle through the hole and injecting sealant 40 into the annular space. Again, the nozzle is held in position only sufficiently long for the sealant to initially cure, or alternatively, a viscosity is selected for the sealant which prevents flowback through the hole after the nozzle is removed.

In the alternative method of Figures 4 and 5, a number of preferred polymeric resin compounds were found to be suitable for use as a sealant, including epoxy resins, polyester resins, phenolic resins and polyurethane resins.

A cementious grout was also found to be useful.

Polyurethane resin was found to be the most favoured type of resin because of its tendency to expand in volume during curing and during its contact with water, because of its adhesion being unaffected by water contact and because of its suitable viscosity in use. However, polyester resin was also preferred because it is a more environmentally friendly and less hazardous resin to use in the tunnel environment.

13 IND It was found that with a 10mm diameter hole through O the grommet (or roof bolt plate), sufficient resin could be Sinjected into the shaft and after 10 to 20 seconds approximately the nozzle could then be withdrawn from the 5 grommet ready for further injections. Varying injection speeds were also tested in order to maximise the effectiveness in each application.

ION

The preferred apparatus and methods described can also 1 0 be applied to sealing other structures, such as leaks in

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Sdams and membranes, in water stopping and gas leaking environments etc.

Whilst the invention has been described with reference to a number of preferred embodiments, it should be appreciated that the invention can be embodied in many other forms.

Claims (16)

1. A method of sealing space around a member when arranged in a formation, comprising the steps of: selecting a curable sealant that is adapted such that it can be injected intc the space and, once injected, does not flow, to enable sealant curing to occur; and injecting that sealant into the space.

2. A method as claimed in claim 1, wherein the sealant is thixotropic.

3. A method as claimed in claim 1, wherein the sealant becomes thixotroph immediately Part A (polyol) and Part B (isocynate) in liquid form are blende(' together. This feature is known as delayed thixopthtry. A method as claimed ir claim 1 or claim 2, wherein the sealant is polyurethane resin.

4. A method as claimed in any one of the preceding claims, wherein th( adaptation of the sealant which presents it from flowing also prevents it frorr slumping.

5. A method as claimed in any one of the preceding claims comprising th( step of injecting the sealant in a manner such that a part of the space furthest fron the opening is filled firstly and then the space is progressively filled up to th( opening.

6. A method as claimed in any one of the preceding claims wherein the sealan is formed by mixing two parts, and such that mixing of the two parts takes plac( during injection.

7. A method of sealing space around a member substantially as hereii described with reference to the accompanying drawings.

8. Apparatus for sealing space around a member when arranged in formation, or for sealing space in a structure, comprising an injection means tha is adapted for injecting a curable sealant, that in turn is adapted such that, once injected intc the space, the sealant does not flow.

9. Apparatus as claimed in claim 8 wherein the injector is a syringe.

Apparatus as claimed in claim 8 or claim 9 wherein that injector is pneumatically driven with, for example, a Svenic "Pro Gun" caulking gun Apparatus as claimed in claim 8 or claim 9 wherein the injector is mechanically hac driven with a Svenic "Pro Gun" caulking gun.

11. Apparatus as claimed in any one of claims 8 to 10 that is adapted for injectin, a two part sealant therefrom, the apparatus including two separated chambers, eacl- adapted for holding a respective sealant part.

12. Apparatus as claimed in claim 11, wherein two separated plungers, either independently or simultaneously drivable, each act in a respective chamber to force a sealant part therefrom.

13. Apparatus as claimed in claim 11 or claim 12, wherein at an outlet to each chamber, a common nozzle in fluid communication with each outlet is arranged, and the nozzle is adapted for mixing the two parts of the sealant when forced from their respective chambers, and prior to the sealant being released from the nozzle into the space.

14. Apparatus as claimed in any one of the claims 8 to 13, further including an extension portion adapted for mounting to the injector to enable sealant to be injected into the space remote from the opening.

In a third aspect the present invention provides a method of sealing a space in a structure comprising the steps of: 16 selecting a curable sealant that is adapted such that it can be injected into the space and, once injected, does not flow, to enable sealant curing to occur; and injecting that sealant into the space.

16. Apparatus for sealing around a member substantially as herein described with reference to, the accompanying drawings.