AU730119B2 - A method for stabilising landforms - Google Patents

Description

P/00/01i1 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: A Method for Stabilising Landforms The following statement is a full description of this invention, including the best method of performing it known to us: GH REF: P18535-T:RPW:DC 2 A METHOD FOR STABILISING LANDFORMS The present invention relates to a method for stabilising landforms and, in particular, to the stabilisation of landforms with a Gilsonite based resin.

The invention will hereinafter be described with reference to its use in underground mining structure stabilisation and land fill site stabilisation, but it is to be appreciated that the invention is not limited to these applications.

In the mining industry, and in particular in the coal mining industry, it has been necessary to stabilise the ribs (or walls) of mining roadways, shafts, tunnels, bores, etc. to prevent strata movement, strata exfoliation, strata 15 collapse, strata consolidation and rib internal collapsing.

Structural stabilisation is achieved in part by reinforcing the ribs and some reinforcement methods have involved the injection under pressure of stabilising grouts and adhesives into the rib at varying depths. The most frequently used grout is polyurethane, but polyurethane has many disadvantages, particularly relating to its safe handling. Diphenylmethane Diisocyanate (DMI) is a commonly employed polyurethane monomer and is considered extremely o dangerous to human health, and may cause lung damage in an aerosol form. Furthermore, when DMI is burnt, toxic fumes are liberated and thus the use of polyurethane grout is permitted only to accredited and licensed operators.

Furthermore, the grout is considered expensive and thus its use is limited because of a tendency to detract from the profits of coal/ore mines.

Land fill sites, particularly for waste and toxic waste disposal are becoming more prevalent. A major problem with toxic waste land fill sites relates to the leaching of toxic waste into the often underlying water table by, for example, rain. In preparing a land fill site for toxic waste disposal, plastic sheeting and clay based Spec:18535T 3 materials are currently used to provide a base and a cover of the site, but these materials may not totally contain the land fill site against leaching.

Gilsonite is a naturally occurring hydrocarbon (asphaltite) found only in the United States and Mexico.

The material is mined and is similar to coal in appearance.

It is one of the purest natural bitumins and mixes well with fatty acid pitches in all proportions.

In its current applications, mined Gilsonite is ground to a fine powder of various grades depending upon the application. These applications include use in thin protective coatings, including acid and alkali coatings, printing inks, foundry applications (as a source of lustrous carbon), black and coach varnishes, black 15 lacquers, black baking enamels, asphalt paints, wire insulation compounds, mineral wax, di-electric compounds, battery boxes, linoleum and floor tiling, paving, insulation, fabric saturants and preservatives. Its use in the stabilising of landforms, however, is not known.

The present invention relates to a method for stabilising landforms (as herebelow defined) comprising the steps of: adding Gilsonite to a solvent to form a resinous co.solution; catalysing the solution resulting from for the curing of the Gilsonite resin; and applying the solution resulting from to the landform to be stabilised prior to curing of the resinous solution.

When the term "landform" is used in the present specification it is intended to include both man-made and naturally occurring land formations and includes mining roadways, shafts, tunnels, bores and mined seams, especially in the coal industry; land fill sites including toxic waste dumping sites; open-cut mines; the ribs (the walls) of long wall mining shafts; high wall underground Spec:18535T -4 mining tunnels; high wall open cut mines etc.

Preferably the method of the present invention further comprises a step of applying the solution resulting from into injection bore holes which have been drilled into the landform to be stabilised prior to solution application.

The solution can be applied to the surface of the landform to be stabilised, as well as within the landform itself, and application methods such as sparging, spraying, or pouring onto or injecting into the landform can be used.

The solution can be injected into the injection bore at a pressure and flow rate to facilitate migration and/or infusion through the landform to be stabilised.

Two basic application techniques can be employed, namely, fast curing, wherein the resinous mixture cures within minutes of application for immediate support of the landform to be stabilised; and slow curing wherein the resinous solution cures 20 within predetermined intervals of hours up to days; used for long distance infusion into the material to be stabilised.

The method can be applied to underground mining landform stabilisation, in particular to the ribs or walls 25 of an underground roadway, tunnel, shaft, bore or seam, and more particularly to coal mining landform stabilisation.

Alternatively, the method can be applied to above ground land fill site stabilisation, particularly where the land fill site is used for toxic waste disposal. In this regard, the step of applying the resinous solution comprises covering the land fill site outer surface with the resinous solution prior to filling the site and, after filling with the land fill (eg. toxic waste), covering the site with further resinous solution at a sufficient thickness to resist mechanical and chemical damage.

Spec:18535T 5 The step of catalysing the solution resulting from step can involve either: heating the solution resulting from to cause curing of the resinous solution; or chemically catalysing the solution resulting from by adding a catalyst thereto to at least initiate curing of the resinous solution.

In the case of step it is preferred that the solution resulting from is an emulsified blend of, inter alia, Gilsonite, and tall oil pitch as the solvent.

In this case step preferably involves applying the catalysed solution to land fill sites; eg. toxic waste dumps, dam sites, refuse dumping sites, etc.

In the case of step it is preferred that the 15 solvent is one or more of: glycol acrylate; glycol diacrylate; glycol triacrylate or polyol acrylate. It is then preferred that the catalyst is either one or both of: tin catalyst or an amine catalyst. The choice of solvent and catalyst combinations can be varied to vary reaction times based on the ultimate landform stabilising application. Also the catalyst can be added at the same time as the Gilsonite is added to the solvent.

Alternatively, the catalyst can be selected from one or more of anhydrous aluminium chloride, talc powder, organic titanates, or calcium carbonates. As indicated above, the solvent can be a type of pine oil or blends of various types thereof including mineral turpentine or other fatty acid pitches.

Preferably the Gilsonite is ground to a fine powder prior to its addition and/or dissolution in the solvent.

However, the Gilsonite can be used in any form, be it fine powder, powder chip or lump prior to its dissolution.

Some advantages of using Gilsonite resin are that it is non-toxic and non-flammable and does not have the health restrictions of polyurethane resin grouts. The cost of applying resinous Gilsonite mixtures is surmised to be Spec:18535T 6considerably less than polyurethane.

Notwithstanding any other forms which may fall within the scope of the present invention, a preferred embodiment will now be described by way of example only.

EXAMPLES

Example 1 Mined Gilsonite was crushed and pulverised to produce a Gilsonite powder. Various resinous Gilsonite solutions were then prepared with the following ranges of components.

Grade 400 Gilsonite 58 65 wt% Dypentine 28 34 wt% Organic Titanate 2 5 wt% Calcium Carbonate 2 5 wt% After blending of the various components, the solution 15 was injected into a bore hole drilled within a coal seam rib at a predetermined pressure and flow rate to cause migration and infusion of the resinous solution throughout the rib up to a certain depth. The previously unstable and broken coal mass (ie. due to failure induced by geological and/or mining stresses) following injection (or infusion) S* was rebonded and strengthened.

Further laboratory tests indicated that the catalyst combinations, using catalysts as set forth above, could be varied to change reaction/curing time and mechanical properties (including compressive, tensile and adhesive strengths).

Two of many proposed applications identified for Gilsonite resin were: 1. Fast curing, up to 90 seconds for immediate support of a coal rib.

2. Slow curing, up to 24 hours for long distance coal infusion and stabilisation.

Example 2 A simulated land fill site was prepared and a Gilsonite based formulation was then prepared and blended in such a way that the cured composition had a high Spec:18535T 7 tendency to resist self levelling and had a high compressive strength. The simulated site was thickly and evenly covered with the Gilsonite formulation and allowed to cure. Simulated toxic waste was then deposited thereon.

After this the simulated toxic waste was further covered with the Gilsonite formulation and was permitted to cure before finally covering the site (eg. with earth).

The resulting formulation exhibited fast curing whilst allowing a continuous bonding layer of sufficient thickness to be formed enabling a resistance to mechanical and chemical damage to be provided in the simulated land fill site. It appeared that the tendency for leaching to occur S* was eliminated 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.

Spec:18535T

Claims (21)

1. A method for stabilising landforms (as herein defined) comprising the steps of: adding Gilsonite to a solvent to form a resinous solution; catalysing the solution resulting from for the curing of Gilsonite resin; and applying the solution resulting from to the landform to be stabilised prior to curing of the resinous solution.

2. A method as claimed in claim 1 further comprising a step of applying the solution resulting from (b) into injection bore holes which have been drilled into the landform to be stabilised prior to solution application.

3. A method as claimed in claim 1 or claim 2 wherein the solution is applied to the surface of the landform to be stabilised.

4. A method as claimed in any one of the preceding claims wherein the solution is applied by one or more of 20 sparging, spraying, or pouring onto or injecting into the landform to be stabilised.

A method as claimed in claim 2 wherein the solution is injected into the injection bore at a pressure and flow rate to facilitate migration and/or infusion 25 through the landform to be stabilised.

6. A method as claimed in any one of the preceding claims when applied to underground mining landform stabilisation.

7. A method as claimed in claim 6 wherein the solution is applied to the ribs (or walls) of an underground tunnel, shaft, bore or seam.

8. A method as claimed in any one of the preceding claims when applied to coal mining landform stabilisation.

9. A method as claimed in any one of claims 1 to when applied to above-ground land fill site stabilisation.

Spec:18535T 9 A method as claimed in claim 9 wherein the land fill site is used for toxic waste disposal and the step of applying the resinous solution comprises covering the land fill site surface with the resinous solution at a sufficient thickness to resist mechanical and chemical damage, then depositing toxic waste thereon and subsequently applying a further covering of the resinous solution at said sufficient thickness, to encapsulate the toxic waste.

11. A method as claimed in any one of claims 1 to wherein the step of catalysing the solution resulting from step involves either: heating the solution resulting from to cause curing of the resinous solution; or 15 chemically catalysing the solution resulting from by adding a catalyst thereto to at least initiate curing of the resinous solution.

12. A method as claimed in claim 11, wherein in step the solution resulting from is an emulsified blend including Gilsonite, and tall oil pitch as the -*"*solvent.

13. A method as claimed in claim 11, wherein in step the solvent is one or more of glycol acrylate; glycol diacrylate; glycol triacrylate or polyol acrylate.

14. A method as claimed in claim 13, wherein the catalyst is a tin catalyst and/or an amine catalyst.

A method as claimed in claim 11, wherein in step the catalyst is selected from one or more of anhydrous aluminium chloride, talc powder, organic titanates, and calcium carbonate.

16. A method as claimed in any one of claims 11 or 13 to 15, wherein step is performed simultaneously with step

17. A method as claimed in any one of the preceding claims wherein the solvent is a type of pine oil, or blends of various types of pine oil including mineral turpentine. Spec:18535T 10

18. A method as claimed in any one of the preceding claims wherein the Gilsonite is ground to a fine powder prior to addition and/or dissolution in the solvent.

19. A method as claimed in any one of claims 1 to 17 wherein the Gilsonite is in powder chip or lump form prior to addition and/or dissolution in the solvent.

A method for stabilising landforms substantially as herein described with reference to the Examples.

21. Gilsonite when used in a method as claimed in any one of the preceding claims. Dated this 1 4 th day of December 2000 FOSECO PTY LIMITED By its Patent Attorneys GRIFFITH HACK e S** o*ooo* Spec:18535T