COMPOSITION, METHOD AND SYSTEM FOR STABILISING A ROCK MASS

Abstract

A composition for use in a method or a system to stabilise a material such as geological strata or a rock mass in which initially retarded gypsum is accelerated at the time of introduction or injection into the rock mass. The retarding of the gypsum may be accomplished by a retarder such as a hydration inhibitor mixed with the gypsum and the acceleration may be accomplished by an accelerant added to mixture of the gypsum and retarder. Upon introduction of the accelerant, water is also added to initially reduce the viscosity of the composition so as to be less than the initially retarded gypsum so as to make it more easily pumpable before becoming set within the geological strata or a rock mass.

Claims

1-33. (canceled)

34. A method of stabilising a rock mass including injecting into a hole at pressure an injectable media, the method including: a. Forming a Part AB by mixing at a Part A including water and a hydration inhibitor and a Part B including gypsum such that Part AB remains at a first viscosity below a pumpable viscosity threshold for a first time period; b. Mixing, immediately prior to introduction into the rock mass, the Part AB with a Part C including an activator and water to provide the injectable media having a second viscosity which is initially at least about 2,500 cps less than the first viscosity; and c. Pumping the injectable media into the hole at pressure such that the injectable media moves into and sets within at least one of voids, spaces and cracks of the rock mass, the second viscosity increasing over an injection time period toward a pumpability threshold at which the injectable media is no longer able to be pumped, the injection time period being less than about 5 minutes.

35. The method according to claim 34, wherein the injection time period is in the range of about 2 to 5 minutes.

36. The method according to claim 34, wherein the second viscosity 5,000 cps less than the first viscosity.

37. The method according to claim 34, wherein the first time period is at least about 30 minutes.

38. The method according to claim 34, wherein the pumpable viscosity threshold is about 20,000 cps.

39. The method according to claim 34, wherein the first viscosity is preferably less than about 10,000 cps.

40. The method according to claim 34, wherein the second viscosity is initially less than about 5,000 cps.

41. The method according to claim 34, wherein the second viscosity is initially less than about 2,500 cps.

42. The method according to claim 34, wherein the second viscosity is initially less than about 1,000 cps.

43. The method according to claim 34, wherein the setting time period is less than about 2 hours.

44. The method according to claim 34, wherein the setting time period is less than about 1 hour.

45. The method according to claim 34, wherein the setting time period is preferably in the range of about 4 minutes to 2 hours.

46. The method according to claim 34, wherein the second viscosity increases toward a set viscosity within the hole, the set viscosity being greater than the pumpable viscosity threshold.

47. The method according to claim 46, wherein the set viscosity is greater than 25,000 cps.

48. The method according to claim 47, wherein the set viscosity is greater than 50,000 cps.

49. The method according to claim 34, wherein the hydration inhibitor of Part A is a dispersant.

50. The method according to claim 34, wherein Part B is a dry gypsum powder.

51. The method according to claim 34, wherein the gypsum of Part B is about between 30% to 75%, and preferably 50% to 70%, by weight of the mixed composition.

52. The method according to claim 34, wherein Part AB is a premixed composition.

53. An injectable composition used in a method in accordance with claim 34.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0042] The invention is described, by way of non-limiting example only, by reference to the accompanying figures, in which;

[0043] FIG. 1 is a flow chart illustrating a method of forming a composition for stabilising a rock mass; and

[0044] FIGS. 2 to 7 illustrate a sequence of steps to stabilise a rock mass using a system to mix and inject the composition into the rock mass.

DETAILED DESCRIPTION

[0045] The invention relates to a composition for use in a method and a system to stabilise a rock mass in which initially retarded gypsum is accelerated at the time of introduction or injection into the rock mass. The retarding of the gypsum enables the use of gypsum in the application of the composition as an injectable media. The retarding of the gypsum may be accomplished by a retarder or hydration inhibitor that may be, but not limited to, a dispersant added to the gypsum to form a retarded gypsum mixture. This allow the initial gypsum based mixture to remain stable and able to be pumped prior to mixing with an accelerant.

[0046] The acceleration at the time of introduction or injection into the rock mass may be accomplished by using an accelerant such as, but not limited to, a salt such as aluminium sulphate dissolved in water that is added to the retarded gypsum mixture to form the composition. Upon introduction of the accelerant and water, the viscosity of the composition is initially less than that of the retarded gypsum so as to make it more easily pumpable, and able to enter cracks of the geological strata or the rock mass the before becoming set within the geological strata or the rock mass.

[0047] It has been identified that gypsum by itself has limited suitability for use as an injection media. However, the composition disclosed herein addresses issues with its suitability by initially retarding the gypsum to extend its setting time. Further, additional components such as acrylic polymers in the composition as are further detailed below provide the composition with an improved bond strength and improved resistance to water degradation.

[0048] In more detail, the present invention relates to a three-part composition for use as an injectable media to stabilise a rock mass such as, but not limited, to a roof of a mine road way or the like. The composition may include a Part A including water and a hydration inhibitor, a Part B including gypsum that may be in powdered form, and a Part C that includes an activator and water. Accordingly, Part A and C are initially liquid mixtures and Part B may be a solid powder.

[0049] The Part A, Part B and Part C may be combined during use to provide a setting injectable media or composition including generally four components (once combined) being the gypsum, the water, the hydration inhibitor and the activator. An example of % by weight of these components may be, Gypsum 40% to 80%, Water20% to 60%, hydration inhibitor 0.01% to 5% and activator 0.01% to 5%.

[0050] Another example of water associated with Part A and Part C is about between 5% to 40%, and preferably about 10% to 30%, by weight of the mixed composition. The gypsum of Part B is about between 30% to 75%, and preferably 50% to 70%, by weight of the mixed composition.

[0051] The gypsum may be a powdered gypsum in a semi-hydrate state, the hydration inhibitor may be hydrophilic copolymer pigment dispersant such as OROTAN 1288 and the activator may be a salt such as aluminium Sulphate dissolved in water. It is noted that other suitable hydration inhibitors and activators may also be used, and the present composition, system and method are not limited to the specific example constituents disclosed herein.

[0052] The composition and mixing method as further detailed below function to inhibit or retard the hydration of gypsum upon mixing, and then activate the gypsum with an initially lowered viscosity for setting immediately prior to entering the rock mass.

General Viscosity Properties as a Function of Time

[0053] Referring to Graph 1 below, Part A and Part B may be initially combined to provide a gypsum mixture that is retarded to remain in a pumpable state. Depending on the type and capacity of the pump, the pumpable state may be where the viscosity is less than about 20,000 cps (where cps stands for a Centipoise). The hydration inhibitor may be used to control the viscosity and maintain mixture AB in the pumpable state.

[0054] In this example, the pumpable state may include the AB mixture having a relatively stable first viscosity over a first time period. The first viscosity may be less a pump threshold viscosity, which may be about 20,000 cps, and preferably less an about 10,000 cps. The first time period may be at least about 10 minutes, but preferably at least about 30 minutes. For example, AB may be adapted to remain stable with a viscosity of about 8,000 cps for a period of at least about 30 minutes prior to being combined with Part C as shown in Graph 1.

Graph 1Composition Viscosity as a Function of Time

[0055] When Part AB is mixed with Part C, to form the composition (i.e ABC as shown in Graph 1) the viscosity changes and preferably undergoes an initially significant drop, dropping by more than about 1,000 cps and in some examples dropping in the range of about 5,000 to 10,000 cps. The viscosity of the finally mixed composition, then increases as a function of time to become set or considered set, in which the setting or set composition may have a viscosity over about 25,000 cps and preferably over at least about 50,000 cps.

[0056] In more detail, the viscosity drop allows the composition to more readily progress into cracks and crevasses of the rock material before the viscosity increases. This may be referred to as the composition being in an injectable state. For example, when Part AB is mixed with Part C, the viscosity of the composition may drop to a second or initial mixture viscosity that may be in the range about 500 cps to 5,000 cps and may be about 1,000 cps. This second or initial mixture viscosity in which the composition is in an injectable state is controllable by the amount of water in Part C. This also provides a lower viscosity starting point which may allow more activator to be used to provide a faster setting ratewith the lower starting point still allowing the composition to be in an injectable state for a suitable time period.

[0057] The setting time of the composition is controlled by increasing/decreasing the activator and also increasing/decreasing inhibitor. For example, increasing the activator will steepen then setting viscosity curve (i.e the setting rate) shown in Graph 1 whereas increasing the inhibitor will flatten the curve shown in Graph 1. Preferably, the composition remains in a pumpable state, with its viscosity less than about 20,000 cps for at least about 1 minute and in some examples up to about 10 minutes, and approaches or is in a set state within about 2 hours. In some preferred examples, the pumpable state is maintained for about 4 minutes. The set state may be defined as the composition having a viscosity of at least about 25,000 to 50,000 cps, or greater.

[0058] Preferably, the composition (i.e. the mixture of Part AB and Part C) remains in the injectable state, having a relatively lower viscosity, that is lower than AB, in the range of about 500 to 5,000 cps for at least about 1 to 4 minutes to allow the composition to be easily pumped and enter cracks and crevasses of the rock mass. A preferred formulation of the composition exceeds 20,000 cps at about 4 minutes.

[0059] The composition then sets within the cracks and crevasses of the rock mass which may occur any time after it has become deposited and preferably in less than about 2 hours. Again, the set state may have a viscosity of at least about 25,000 to 50,000 cps, and the viscosity of the setting composition may increase as a function of time as it solidifies.

First Preferred Composition Example

[0060] In more detail, as best shown in Table 1 below, Part A may contain polymers, in particular acrylic emulsion polymers, hydration inhibitors, surfactants, dispersants, solvents and defoamer. Examples of the components of Part A include a polymer such as PRIMAL AC-339 which is a hydrophobic acrylic polymer, a defoamer such as Nopco NXZ, a surfactant such as Triton X-405, 70%, a dispersant such as OROTAN 1288, a further polymer such as Primal ECO-16 which is a binding or cross-linking polymer, a coalescent such as Butyl Carbitol, 100%, water and an alkaline Agent such as Ca(OH).sup.2. Part B may simply be the gypsum powder and Part C includes the activator in the form of Aluminium Sulphate [(AL.sup.2(SO4).sup.3*14H20] dissolved in water.

TABLE-US-00001 TABLE 1 First Composition Example % By Parts by Weight weight Part A Premix 30% Polymer - PRIMAL AC-339 (Hydrophobic 8.72% 138.2 Acrylic Polymer) Defoamer - Nopco NXZ 0.19% 3 Surfactant - Triton X-405, 70% 0.32% 5.1 Dispersant - OROTAN 1288 0.37% 5.9 Polymer - Primal ECO-16 (Acrylic 4.99% 79.1 Binding/cross-linking Polymer) Coelesctent - Butyl Carbitol, 100% 0.50% 8 Water 14.75% 233.8 Alkaline Agent - Ca(OH)2 0.06% 1 Part B Solids 64% Gypsum 64.03% 1014.9 Part A and Part B Combined 94% 1489 Part C 6% Activator (AL2(SO4)3*14H20 0.29% 4.6 Water 6% 91.4

[0061] Prior to use, Part A and Part B are mixed, preferably to form Part AB using a mixer (not shown) such as, but not limited to, a ChemGrout CG-460 High Pressure Colloidal Series. The Part AB (now a pumpable mixture) may then be combined with Part C which activates and causes the setting of the composition, now including Part AB and C, as defined above. The system and method of the use of Part AB and Part C to provide the injectable media for rock stabilisation is now further described below with reference to FIGS. 1 to 7.

[0062] In more general terms, some of the functional aspects of the components of the composition are further detailed below. Firstly, the inclusion of acrylic polymers provides increased bond strength. Without acrylic polymers the gypsum may have low bond strength and be susceptible to water degradation. Acrylic polymers may not normally set within an acceptable timeframe in an underground rockmass due to the high humidity and lack of air flow as they set by drying.

[0063] However, the gypsum is originally in a semi-hydrate state and requires water to crystallise. The gypsum after activation, quickly extracts water from the emulsified polymers to crystallise. This also causes the polymers to set and provide advantageous qualities such as bond strength, elastic deformation and water resistance. If the total amount of water in the mix is formulated to be stochiometric for gypsum crystallisation i.e. no excess water in the mix than is needed to fully crystalise the gypsum, then higher strengths, faster setting and better hardening of the gypsum and polymers occurs.

[0064] In relation to the binding or cross-linking polymers, it is noted that polymers do not essentially need to be self-cross-linking. However, the inclusion of a self-cross linking acrylic leads to improved mechanical properties (durability, bond strength, flexibility etc).

[0065] In relation to the water resistance or waterproofing. Gypsum by itself can be degraded by water. The inclusion of the hydrophobic acrylic polymers greatly enhances the materials water resistance. Water is typically present in underground rock masses. The acrylic polymers are APEO free providing advantages in chemical disposing and much lower risk to environment. APEO containing products are more toxic and bioaccumulate.

[0066] Finally, gypsum is notoriously fast setting compared to most cementitious materials. The use of the retarder, in this example the hydration inhibitor, allows longer workability of the mix prior to injection and the activator allows a rapid gain of strength to provide fast support to unstable ground. The addition of the above polymers enhances the materials properties to a point that the material becomes suitable as an injection media for rock mass stabilisation and may be used in the method and system as are further detailed below.

Second Preferred Example Composition

TABLE-US-00002 TABLE 2 Second Composition Example with Activator Variations Test No. 1 2 Parts by Parts by weight (g) Percentage weight (g) Percentage Part A Polymer - 105.4 5.27% 105.4 5.27% Primal ECO-16 Water 192.3 9.61% 192.3 9.61% Polymer - 184.1 9.20% 184.1 9.20% PRIMAL AC- 339 Defoamer - 4 0.20% 4 0.20% Nopco NXZ Surfactant - 6.8 0.34% 6.8 0.34% Triton X-405, 70% Dispersant - 7.86 0.39% 7.86 0.39% OROTAN 1288 Coelesctent - 10.7 0.53% 10.7 0.53% Butyl Carbitol, 100% Part B Gypsum 1352 67.60% 1352 67.59% Parts by weight (g)/ Parts by weight (g)/ Part C Activator % Activator % Activator 3.36%* 4.45** 0.22%*** 3.57%* 4.73** 0.24%*** (AL2(SO4)3*14H20 Water 132.5 6.62% 132.5 6.62% Test No. 3 4 Parts by Parts by weight (g) Percentage weight (g) Percentage Part A Polymer - 105.4 5.27% 105.4 5.27% Primal ECO-16 Water 192.3 9.62% 192.3 9.62% Polymer - 184.1 9.21% 184.1 9.21% PRIMAL AC- 339 Defoamer - 4 0.20% 4 0.20% Nopco NXZ Surfactant - 6.8 0.34% 6.8 0.34% Triton X-405, 70% Dispersant - 7.86 0.39% 7.86 0.39% OROTAN 1288 Coelesctent - 10.7 0.54% 10.7 0.54% Butyl Carbitol, 100% Part B Gypsum 1352 67.60% 1352 67.61% Parts by weight (g)/ Parts by weight (g)/ Part C Activator % Activator % Activator 3.25%* 4.3** 0.22%*** 3.00%* .sup.3.99** 0.20%*** (AL2(SO4)3*14H20 Water 132.5.sup. 6.63% 132.5.sup. 6.63%

[0067] Table 2 shows a second a preferred example of the composition with the formulation of Parts A, B and C. The formulation is similar to the first example and the components are not again described here. However, in this example, the amount of the activator was varied to observe the effect on the viscosity of the composition as a function of time as shown in Graph 2 below which shows the results of the above test data shown in Table 2.

[0068] It is noted that for Part C as shown in Table 2, the percent of activator in relation to only Part C is indicated with a *, the weight in grams within Part C is indicated with a ** and amount of activator as a % by weight of the overall composition is indicated by ***.

Graph 2Viscosity as a Function of Time for Composition (Part AB and Part C when mixed).

[0069] In this example, the preferred salt percentage is 3.36% of the Part C weight (which was tested twice as indicated by Test 1 and Test 2). It can be seen that with the salt percentage of about 3.36%, the viscosity remained relatively low, less than about 5,000 cps for about 2 minutes before starting to set with the viscosity increasing to above about 20,000 cps after about 5 mins which means the composition may no longer be pumpable. Higher salt amounts pushed the viscosity higher more quickly which may be suitable in some use cases and lower salt amounts kept the viscosity lower for more than 8 minutes.

[0070] In this example, for injecting through a drill rod and into a rock mass it was found that keeping the viscosity in the range of about 5,000 to 10,000 cps, or less, for a time of about 2 to 4 minutes was preferable as this allows enough time for pumping whilst after about 2 to 4 minutes the composition starts to set to retain itself within the rock mass as it sets.

Experimental Data

[0071] Referring to Table 3 below, a summary of experimental results is provided indicating broadly if a particular combination was suitable or not suitable. The % data provided are a % by weight of the overall mixture (ABC).

[0072] The suitability criteria (suitable/not suitable) was generally set as followsPart AB needs to stay below 20,000cps for at least 30 minutes, preferably an even lower viscosity and preferably for much longer than 30 minutes, hours, weeks or even longer. This AB upper limit has been based on the application pump rating of 20,000 cps (Viscosity going through the pump pistons not downstream).

[0073] The combining of Part C to form the composition ABC will initially drop the viscosity to a value below the AB viscosity of (20,000 cps max); however the addition of C needs to cause the rapid viscosity increase between 1 minute and 60 minutes heading to unmeasurable as it solidifies. It needs to have measurable strength at within about 1 to 2 hours.

[0074] It is noted in these examples the dispersant, solvent, defoamer and activator etc are the same as those described above in relation to preferred examples 1 and 2. Tables 4 to 22 below provide examples of the composition viscosity as a function of time for each of the examples shown in Table 3.

TABLE-US-00003 TABLE 3 Summary of Experimental Results Test 1.1 1.2 1.3 1.4.1 1.4.2 2.1.1 2.1.2 2.2.1 2.2.2 2.3.1 Suitable Yes Yes Yes Yes Yes No Yes No Yes No Ingredient Part A Eco-16 5.28% 5.29% 5.30% 5.30% 5.30% 5.19% 5.21% 5.19% 5.12% 4.91% Water 9.63% 9.64% 9.69% 9.70% 9.69% 9.56% 9.50% 9.43% 9.40% 8.91% AC-339 9.22% 9.23% 9.23% 9.30% 9.23% 9.16% 9.07% 9.03% 8.96% 8.50% Defoamer 0.20% 0.20% 0.25% 0.20% 0.20% 0.22% 0.21% 0.29% 0.30% 0.19% Surfactant 0.34% 0.34% 0.37% 0.40% 0.36% 0.36% 0.40% 0.37% 0.36% 0.33% Dispersant 0.20% 0.10% 0.05% 0.02% 0.02% 1.02% 1.01% 2.01% 2.01% 4.85% Solvent 0.53% 0.53% 0.56% 0.56% 0.57% 0.53% 0.55% 0.55% 0.54% 0.57% Part B Gypsum 67.74% 67.81% 67.72% 67.88% 67.78% 67.11% 66.76% 66.30% 65.77% 65.10% Part C Activator 0.22% 0.22% 0.22% 0.01% 0.22% 0.22% 0.70% 0.22% 0.99% 0.22% Water 6.63% 6.63% 6.61% 6.64% 6.62% 6.62% 6.59% 6.61% 6.56% 6.42% Test 2.3.2 3.1 3.2 3.3 3.4 3.5 3.6 3.7 Suitable No Yes Yes Yes Yes Yes No Yes Ingredient Part A Eco-16 4.9% 5.50% 4.13% 2.94% 9.71% 8.21% 3.28% 0.0% Water 9.1% 5.89% 27.7% 40.81% 17.73% 14.73% 9.57% 20.1% AC-339 8.7% 9.69% 7.20% 5.18% 17.48% 14.06% 5.66% 0.0% Defoamer 0.2% 0.27% 0.19% 0.11% 0.36% 0.34% 0.16% 0.0% Surfactant 0.3% 0.36% 0.27% 0.21% 0.62% 0.62% 0.24% 0.0% Dispersant 5.0% 0.42% 0.30% 0.23% 0.71% 0.67% 0.20% 0.4% Solvent 0.5% 0.60% 0.44% 0.30% 0.97% 0.81% 0.26% 0.0% Part B Gypsum 63.7% 70.44% 52.86% 43.76% 39.81% 49.69% 79.97% 72.0% Part C Activator 1.0% 0.22% 0.23% 0.23% 0.42% 0.35% 0.16% 0.2% Water 6.6% 6.60% 6.61% 6.22% 12.19% 10.50% 0.50% 7.2%

[0075] An interesting result that has arisen was test 3.7 in which most components were removed leaving Part A with just water and the dispersant, Part B the Gypsum, and Part C the activator and water. This formulation was found to be suitable to meet the initially pumping state criteria, and then set in a suitable timeframe as is further shown below in the graphs.

[0076] It is noted these graphs measure the viscosity at the mixing of Parts AB, and Part C. It is further noted that Part AB was measured before each test and was generally found to be in the range of 6,000 to 12,000 cps. However, in some cases, such as using 0.01% of the dispersantPart AB was found to be too viscous such as having a viscosity of about 20,000 cps after only 10 minutes and therefore these samples where not tested further.

TABLE-US-00004 TABLE 4 Test Composition 1.1 Test 1.1 - 0.2% Dispersant Time seconds Viscosity (cps) 20 843 25 1157 30 1224 35 1328 40 1439 45 1563 50 1709 55 1878 60 2085 150 25,220 160 61,998 170 >100,000

TABLE-US-00005 TABLE 5 Test Composition 1.2 Test 1.2 - 0.1% Dispersant Time (Sec) Viscosity (cps) 20 948 25 958 30 999 35 1055 40 1124 45 1211 50 1316 55 1443 60 1602 65 1795 70 2026 130 8,466 140 14,154 145 30,976 150 >100,000

TABLE-US-00006 TABLE 6 Test Composition 1.3 Test 1.3 - 0.5% Dispersant Time (sec) Viscosity (cps) 20 736 30 808 40 900 50 1031 60 1200 70 1434 80 1779 90 2014 130 Not flowing / Set

TABLE-US-00007 TABLE 7 Test Composition 1.4.1 Test 1.4.1 - 0.02% Dispersant (inhibitor) & Low Activator 0.01% Time (sec) Time (min) Viscosity (cps) 30 0.5 950 90 1.5 931 150 2.5 1016 260 4.3 1093 330 5.5 1004 390 6.5 917 570 9.5 1211 800 13.3 1250 825 13.8 1483 920 15.3 1374 1020 17.0 1735 1100 18.3 1248 1180 19.7 1528 1320 22.0 1535 1430 23.8 1644 1520 25.3 1955 1620 27.0 3695 1710 28.5 3981 1780 29.7 3100 1860 31.0 5170 1920 32.0 6523

TABLE-US-00008 TABLE 8 Test Composition 1.4.2 Test 1.4.2 - 0.02% Dispersant (inhibitor) & normal Activator 0.02% Time (sec) Time (min) Viscosity (cps) 20 0.33 1720 35 0.58 1793 40 0.67 1878 45 0.75 1981 50 0.83 2101 90 1.5 8215 134 2.2 11912 150 2.5 14556 155 2.58 20057 165 2.75 29046

TABLE-US-00009 TABLE 9 AB Viscosity only for Test Composition 1.4.2 AB only viscosity for Test case 1.4.2 Time (sec) Tim (Min) Viscosity (cps) 120 2 5929 240 4 5917 360 6 5964 1140 19 7240 1260 21 6567 1380 23 7304 1440 24 6974 1560 26 7288 2280 38 7939 1920 32 8304 2040 34 7975 2160 36 8466 2280 38 10112 2340 39 10942 2400 40 11960 2460 41 15087 2580 43 23335 2640 44 53479 2700 45 316129

TABLE-US-00010 Test 1.5 - AB only for Dispersant 0.01% Time (sec) Time (min) Viscosity 180 3 6,599 780 13 8,343 960 16 22,000 1020 17 36,139 1080 18 67,139 1200 20 151,334

[0077] In relation to test composition 1.4.2, it is noted that with the dispersant at 0.01% the pot life of AB is not usable to then mix ABC underground. It appears that 0.02% when using the dispersant (Orotan 1288) is the lower limit. However, another dispersant may be usable at 0.01%.

[0078] It is noted a test 1.6 was also performed with 0% dispersant (inhibitor) in AB, and it was found that AB alone set within 10 minutes which is not considered suitable. As such, it is believed the dispersant (inhibitor) in AB is required for most examples.

Table 10AB Viscosity Only for Text Composition 1.5

TABLE-US-00011 Test 2.1.1 - 1% Dispersant and 0.2% Activator Time (sec) Time (hrs) Viscosity (cps) 20 0 898 6540 1.8 1,263 16380 4.55 722 41400 11.5 898

[0079] It is noted a test 2.1.1 did not set within a suitable time limit (less than about 2 hours) and therefore requires a higher activator.

Table 11Test Composition 2.1.1

TABLE-US-00012 TABLE 12 Test Composition 2.1.2 Test 2.1.2 - 1% Dispersant and 0.7% Activator Time (sec) Time (min) Viscosity (cps) 10 0.17 898 60 1 Butter consistency, set

TABLE-US-00013 TABLE 13 Test Composition 2.2.1 Test 2.2.1 - 2% Dispersant and 0.2% Activator Time (sec) Time (hrs) Viscosity 15600 4.33 1,302 76788 21.33 1,057

TABLE-US-00014 TABLE 14 Test Composition 2.3.1 Test 2.3. 1 - 5% Dispersant and 0.2% Activator Time (sec) Time (hrs) Viscosity (cps) 0 0 32,995 4788 1.33 30,512 15012 4.17 26,607 81720 22.7 19,448

[0080] In relation to test 2.2.1, the composition was too viscous to be practical for the application and also did not set within a suitable time frame, and therefore appeared to require more activator.

TABLE-US-00015 TABLE 15 Test Composition 2.3.2 Test 2.3.2 - 5% Dispersant and 1% Activator Time (sec) Time (min) Viscosity (cps) 160 2.67 50134 205 3.42 99315 230 3.83 111256

[0081] In relation to test 2.3.2, the composition set in reasonable time but started too viscous and was therefore may not be able to be pumped.

TABLE-US-00016 TABLE 16 Dispersant/Activator Summary Table Dispersant Activator Summary Dispersant Salt/Activator Suitable Reason 0.00% 0% No Set-time on AB too short 0.01% 0% No Set-time on AB too short <40 min 0.02% 0.01% Yes Suitable Set-time, Low initial viscosity 0.02% 0.22% Yes Suitable Set-time, Low initial viscosity 0.05% 0.22% Yes Suitable Set-time, Low initial viscosity 0.1%.sup. 0.22% Yes Suitable Set-time, Low initial viscosity 0.2%.sup. 0.22% Yes Suitable Set-time, Low initial viscosity 1% 0.22% No Did not set in suitable time, criteria <2 hrs 1% 0.7% Yes Suitable Set-time, Low initial viscosity 2% 0.22% No Did not set in suitable time, criteria 2% 1% Yes Suitable Set-time, Low initial viscosity 5% 0.22% No Starting Viscosity too high 5% 1% No Starting Viscosity too high

TABLE-US-00017 TABLE 17 Test Composition 3.1 Water/Gypsum variation Test 3.1 - 20% total associated water, 70% Gypsum Time (sec) Viscosity (cps) 35 2018 40 1916 50 1898 60 1930 65 2017 70 2063 75 2114 85 2167 90 2298 100 2369 105 2459 110 2672 115 2810 120 2966 125 3149 130 3353 135 3600 140 3864 145 4179 150 4558 155 4978 160 5491 170 6123 175 7009 180 8356 185 10000 315 45079 370 67796

TABLE-US-00018 TABLE 18 Test Composition 3.2 Water/Gypsum variation 3.2. 40% total associated water, 53% Gypsum Time (sec) Viscosity (cps) 35 66 40 65 50 65 60 65 70 66 80 68 90 76 100 84 110 94 120 106 130 118 140 134 150 147 160 172 170 194 180 223 190 250 200 300 210 333 220 414 230 474 240 561 250 664 260 800 285 1600 300 4042 405 10183 520 84103 540 133873

TABLE-US-00019 TABLE 19 Test Composition 3.3 Water/Gypsum variation 3.3 - 54% total associated water, 40% Gypsum Time (sec) Viscosity (cps) 55 55 60 40 100 39 120 39 130 40 150 50 160 58 170 70 180 80 190 90 200 104 210 117 220 129 230 141 240 156 250 177 260 205 270 247 280 299 390 347 420 424 430 122 450 161 470 181 480 227 500 272 550 304 560 393 570 1289 580 1294 800 4301 810 6662 820 8246 835 8999 840 9922 850 9183 940 68884

TABLE-US-00020 TABLE 20 Test Composition 3.4 Water/Gypsum variation 3.4 - 40% Gypsum Time (sec) Viscosity (cps) 10 46 30 45 40 45 50 45 60 46 80 48 100 52 120 55 140 57 170 63 180 67 190 73 200 77 210 80 230 91 240 96 260 110 270 120 350 72 380 93 390 101 400 108 410 116 420 125 430 137 440 148 450 156 460 170 470 183 480 197 490 210 500 226 510 250 530 280 540 301 550 329 570 553 580 620 590 691 600 767 620 1773 640 3244 700 17011 720 7203 735 15182 755 25756 830 48084 850 57074 875 124716

TABLE-US-00021 TABLE 21 Test Composition 3.4 Water/Gypsum variation Test 3.5 50% Gypsum Time (sec) Viscosity (cps) 60 75 70 78 80 74 100 70 120 69 150 68 180 70 210 73 270 80 300 85 330 89 360 92 390 96 420 101 450 104 510 119 540 122 600 132 660 142 780 166 840 176 900 189 960 205 1800 264 2640 730 3180 9392 3240 10442

[0082] It is noted that for test composition 3.6, that mixture AB was too viscous and dry to pump with the viscosity of about being about 47,379 cps, and the mixed ABC viscosity being approximately 40,000 cps.

TABLE-US-00022 TABLE 22 Test Composition 3.7 Test 3.7 - Water, Dispersant, Gypsum & Activator only mix Time (sec) Viscosity (cps) 20 3017 40 3611 90 6984 110 7988 Changed instrument Considered Set settings

[0083] As aforesaid, test composition 3.7 was found to be suitable, in terms of pumping viscosity and set times, having only water, the dispersant, gypsum and activator. However, as noted in relation to the preferred composition examples there are other components such as the polymers that assist with bond strength when the material is set, and these additional components further improve the performance of the composition beyond the base form of the composition as shown in example 3.7.

Example Method of Use

[0084] Referring to FIG. 1, a method 100 to form the composition for stabilising a rock mass may include, at step 110, providing, at site, Part A including water and a hydration inhibitor, a Part B including gypsum, and a Part C including an activator and water. At step 120, Part A and Part B are mixed at or just prior to the time of use to provide Part AB. As discussed above, the mixture of AB is formulated so as to be in the pumpable state and have a fairly stable and pumpable viscosity for the first time period that may be, but not limited to, at least above 30 minutes.

[0085] At step 130, Part AB and Part C immediately prior to introduction into the rock mass in which Part C activates Part AB to set the composition once it has been injected into the rock mass as is further detailed below. It is noted that in some examples, the Part AB may be pre-made on or off-site, and the Part AB may be combined with Part C just prior to use. As such, in this example, the composition may be considered to be formed using two-parts as opposed to the three-parts as has been detailed below.

[0086] Turning to now FIGS. 2 to 7, the composition, indicated in the drawing by reference numeral 11, may be used in a system 5 in a method for stabilising a rock mass 9. 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 AB composition and a Part C composition (located in containers or the like, not shown, in communication with the pump 16), and associated Part AB and Part C conduits 18, 20 to communicate the Part AB and Part C 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 AB and the Part C to form the composition.

[0087] 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 5 to 50 mm. The pump 16 may be any suitable pump capable to pumping a two-part viscous material quantity in the range of 1 litres to 1000 litres per hole and more usually 50 to 500 litres per hole to a predetermined pressure that may be a predetermined value or the maximum pressure of the pump. In some cases, it is noted the hole may take relatively small volume of the composition if there are no or few cracks.

[0088] The pressure at the pump may be in the range of about 100 BAR to 500 BAR, and may be 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. It is noted that in the example application disclosed herein, pumping may be stopped at about t 110 BAR pressure at the Hole Collar, otherwise damage to strata can occur i.e. fracking/jacking. This pressure may be higher for hardrock mines with stronger surrounding coal. The pressure at the collar also increases from 0 BAR at the commencement of injection to a self-imposed stop point at 110 BAR when the strata material is, for example, coal.

[0089] The pump 16 may be a high-pressure pump capable of providing a pressure of about 300 BAR which allows it to pump up to about a victory of 20,000 cps which sets a pump viscosity threshold. A suitable pump is model XP-hf available from Graco. 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 Stamixco. Of course, other suitable seals may be utilised.

[0090] Turning now to a more detailed method for stabilising a rock mass 9 using the system 5 and 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. However, it is noted that the packer 14 may be positioned at any depth within the hole 12.

[0091] The Part A and Part B are mixed, preferably onsite, at or just prior to being used to form Part AB. The Part AB may be temporarily stored in a container such as for at least about 30 minutes perhaps as long as a several hours or days.

[0092] The Part AB and Part C 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 AB and Part C 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.

[0093] 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. It is noted that in this example, pressure is measured at the hole collar to indicate when pumping should be stopped to limit damage to surrounding strata. In this example, pumping may be stopped at around 110 BAR at the collar. The pressure at the pump will be higher than this but dependent on the length of hoses from the mixing/pumping site to the hole site.

[0094] 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. It is noted that there is a lesser pressure at the Y piece. The set relief pressure of the pump may be based on the rock type and inherent properties of the rock. If the set pressure is exceeded the rockmass could be further fractured rather than glued, which may be undesirable. It is further noted that The set relief on the pump can be set to the rating of the hoses for safety; or calibrated to account for the pressure in the hoses to relief when the hole collar pressure is at around 110 BAR or lower or higher. i.e. the pressure at the pump may be reading 300 BAR and the pressure at the collar may be reading 110 BAR then relief at the pump can be set at 300 BAR, being calibrated to the collar pressure, providing no further changes to the hose length or orifice size.

Advantages

[0095] Advantageously, there has been described a composition including a Part A, Part B and Part C. Part A including water and the hydration inhibitor and Part B including gypsum that may be in powdered form are adapted to be mixed to provide Part AB, which is a polymer modified gypsum composition, just prior to use onsite which alleviates issues relating to settlement of the product in containers. The ratio of the mixture of Part AB allows the quantity of the components such as gypsum to be controlled and allow adjustment, for example, of the strength of the final set media. Part C that includes an activator and water, may be combined then with Part AB to provide the settable media that is injected into the rock mass for stabilisation.

[0096] Part AB is formulated to remain stable at a pumpable viscosity for a time period that may be about 30 minutes or longer. When Part C is introduced with the activator, water is also added which temporarily lowers the viscosity which allow the mixed composition comprising Parts A, B, C to be more easily pumped into cracks and crevasses of the rock. Moreover, by lowering the starting viscosity of the composition, more time is provided before the composition becomes unable to be pumped and/or sets. This may allow more activator to be used to lower the overall set time as the lower initial viscosity provides a time window in which the composition is pumpable and injectable into the mediawhich may the quite rapidly set so as to be retained in the rock.

[0097] Further advantageously, there has been described a method, a system and media for stabilising a rock mass in which media is injected 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.

[0098] Further still 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 many products that have a significant exothermic reaction. In industry, this value may be around 350 Litres per hole. The present media may 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 or maximum allowable pressure within the rockmass for the rock type. 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.