BLASTHOLE STEMMING BASED ON FORMALDEHYDE RESINS, SYSTEM AND CHARGING METHOD

Abstract

The invention relates to a method for forming blasthole stemming for mining, which comprises charging a blasthole with a two-component mixture of resin and catalyst, wherein the two-component mixture produces a stiff foam in situ, and once hardened, the two-component mixture is then detonated. The invention also relates to a system for forming blasthole stemming for mining in order to carry out the method; the mixture used as blasthole stemming for mining that comprises the two-component mixture of resin and catalyst, wherein the resins are based on formaldehyde; and to a method for charging and detonating a mining blasthole by using the two-component mixture.

Claims

1. A Method for forming in situ mining blast hole plugs comprising: loading a blast hole with a bi-component mixture of formaldehyde-based resin-catalyst on an explosive separated by a layer of drill cutting, where the bi-component mixture is produced in situ in the hole forming a foam, where the formaldehyde-based resins contained in a first pond are-is selected from phenol-formaldehyde (PF) resins, urea-formaldehyde (UF) resins, melamine-formaldehyde (MF) resins, melamine-urea-formaldehyde (MUF) resins, phenol-resorcinol-formaldehyde (PRF) resins, modified formaldehyde-based resins with lignin or tannins, and their derivatives; and the catalyst contained in a second pond is selected from acidic, basic or based on cross-linking agent catalysts; allowing the foam to set, forming a rigid foam with a density between about 0.2 and about 0.3 Kg/m.sup.3 and in which the reaction temperature is less than about 55 C., generating an expansion volume of about 3 to 5 times a loaded volume of the bi-component mixture; after the bi-component mixture has set, initiating detonation.

2. The method for forming blast hole plugs according to claim 1, wherein the catalysts is an acidic catalyst selected from mineral acids, sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, or mixtures thereof, and/or organic acids, formic acid, lactic acid, benzenesulfonic acid derivatives, citric acid, acetic acid, or mixtures thereof.

3. The method for forming blast hole plugs according to claim 2, wherein the catalysts is a basic catalyst selected from mineral bases, such as-potassium hydroxide, barium hydroxide, sodium hydroxide, calcium hydroxide, or mixtures thereof and/or organic bases, diethylamine, triethylamine, ethanolamine or mixtures thereof.

4. The method for forming blast hole plugs according to claim 2, wherein the catalysts is based on cross-linking or hardening agents are-and is selected from Polymethyldiisocyanate (pMDI), erythritol and its derivatives, polyols, acrylic resins, polyvinyl alcohols, formaldehyde, succinic derivatives, alkaline formaldehydes, glycidol and epoxides derivatives, or mixtures thereof.

5. The method for forming blast hole plugs according to claim 1, wherein the weight proportions between resin and catalyst is in a range of about 9:1 to about 1:9.

6. The method for forming blast hole plugs according to claim 1 further comprising optionally applying rheological modifiers, surfactants, buffers or pH regulators, gasifying agents, expanding agents and mixtures thereof.

7. A system for forming mining blast hole plugs to carry out the method of claim 1, wherein the system allows the in situ formation of rigid foam blocks using a bi-component mixture of resin-catalyst, comprising a first pond containing the formaldehyde-based resin, selected from phenol-formaldehyde (PF) resins, urea-formaldehyde (UF) resins, melamine-formaldehyde (MF) resins, melamine urea formaldehyde (MUF) resins, phenol-resorcinol formaldehyde (PRF) resins, modified formaldehyde-based resins with lignin or tannins, and their derivatives, a second pond containing the catalyst selected from acidic, basic or based on cross-linking agent catalysts, a mixer-applicator for homogenization and application of the bi-component mixture, pumps and valves that allow the loading of the plug into the blast hole, a monitoring system.

8. A mixture to be used in situ as a blasting plug in mining blastholes forming a rigid foam according to the method of claim 1, comprising a bi-component mixture of resin-catalyst where the resins is formaldehyde-based and is selected from phenol-formaldehyde (PF) resins, urea-formaldehyde (UF) resins, melamine-formaldehyde (MF) resins, melamine urea formaldehyde (MUF) resins, phenol-resorcinol formaldehyde (PRF) resins, modified formaldehyde-based resins with lignin or tannins, and their derivatives, and the catalyst is selected from acidic, basic or based on cross-linking agent catalysts; where a rigid foam formed with the be-component mixture has a density between about 0.2 and about 0.3 Kg/m.sup.3 and in which the reaction temperature is less than about 55 C., generating an expansion volume of about 3 to about 5 times a loaded volume of the bi-component mixture.

9. The mixture according to claim 8, wherein the catalysts is an acidic catalyst selected from mineral acids, such as sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, or mixtures thereof, and/or organic acids, formic acid, lactic acid, benzenesulfonic acid derivatives, citric acid, acetic acid, or mixtures thereof.

10. The mixture according to claim 8, wherein the catalysts is a basic catalyst selected from mineral bases, potassium hydroxide, barium hydroxide, sodium hydroxide, calcium hydroxide, or mixtures thereof and/or organic bases, diethylamine, triethylamine, ethanolamine or mixtures thereof.

11. The mixture according to claim 8, wherein the catalysts is based on crosslinking or hardening agents and is selected from Polymethyldiisocyanate (pMDI), erythritol and its derivatives, polyols, acrylic resins, polyvinyl alcohols, formaldehyde, succinic derivatives, alkaline formaldehydes, glycidol and epoxides derivatives, or mixtures thereof.

12. The mixture according to claim 8, wherein the weight proportions between resin and catalyst is in the range of about 9:1 to about 1:9.

13. The mixture according to claim 8, wherein the mixture further comprises rheological modifiers, surfactants, buffers or pH regulators, gasifying agents, expanding agents, and mixtures thereof.

14. Use of a bi-component mixture of resin-catalyst according to claim 8, wherein it is to form a blasting plug in mining blastholes to reduce the loading time of a plug, increase rock fragmentation, reduce the noise of blasting and contain particulate material produced by the blasting.

15. The method for loading and blasting a mining blasthole comprising the use the mixture of claim 11, and comprising the following steps: installing an explosive in a blast hole, adding a layer of drill cutting over the explosive, loading a bi-component mixture of resin-catalyst to form a foam in situ, onto the drill cutting layer, where the resins is formaldehyde-based and is selected from phenol-formaldehyde (PF) resins, urea-formaldehyde (UF) resins, melamine-formaldehyde (MF) resins, melamine urea formaldehyde (MUF) resins, phenol-resorcinol formaldehyde (PRF) resins, modified formaldehyde-based resins with lignin or tannins, and their derivatives, and the catalyst is selected from acidic, basic or based on cross-linking agent catalysts; allowing the foam formed to set, obtaining the blasting plug by a rigid foam formed in situ wherein the rigid foam has a density between about 0.2 and about 0.3 Kg/m.sup.3 and in which the reaction temperature is less than about 55 C., generating an expansion volume of about 3 to about 5 times the a loaded volume of the bi-component mixture, and blasting the explosive, where the drill cutting layer acts as a separation medium between the explosive and the bi-component mixture, preventing the mixture from diffusing into the explosive.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0046] FIG. 1: shows photographs of the experimental laboratory results of the bi-component mixture of resin/catalyst, where the following resins were tested in polycarbonate tubes: (1) PHENOLIC Resin: PF phenol formaldehyde, in molar ratio 1.6; (2) PUR: Polyurethane Resin; (3) pMDI: Polymethyldiisocyanate (Durapro); (4) pMDI-LS: Low reactivity polymethyl diisocyanate (Durapro); (5): PRF: Formaldehyde Resin/(Resorcinol+Phenol) in a molar ratio of 0.8 to 1.0; (6) MUF-1: Formaldehyde Resin/(Melanin+Urea) in a molar ratio of 1.2 to 1.8 (low viscosity); (7) MUF-2: Formaldehyde Resin/(Melanin+Urea) in a molar ratio of 1.2 to 1.8 (high viscosity).

[0047] FIG. 2: Evolution of surface temperature as a function of time measured in the formation of rigid foam of PHENOLIC Resin: PF phenol formaldehyde, in molar ratio 1.6; PUR: Pylourethane Resin; pMDI: Polymethyldiisocyanate (Durapro); pMDI-LS: Low reactivity polymethyldiisocyanate (Durapro); PRF: Formaldehyde Resin/(Resorcinol+Phenol) in a molar ratio of 0.8 to 1.0; MUF-1: Formaldehyde Resin/(Melanin+Urea) in a molar ratio of 1.2 to 1.8 (low viscosity); MUF-2: Formaldehyde Resin/(Melanin+Urea) in a molar ratio of 1.2 to 1.8 (high viscosity).

[0048] FIG. 3: represents a diagram of the configuration and design of the blast holes compared to a conventional plug scheme according to the parameters in Table 3.

[0049] FIG. 4: Flowchart of blast hole loading with the resin-catalyst mixture of the present invention.

[0050] FIG. 5: Graph of surface exothermicity during foaming of the present invention, measured over time (seconds), at room temperature of 20 C.

[0051] FIG. 6: Photographic sequences of blasting at time 0, 30 and 50 milliseconds. Top: conventional blasting with debris plugs; Bottom: blasting with phenolic resin plugs of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0052] The present invention corresponds to a method of producing plugs made of rigid polymeric materials in blastholes previously loaded with explosive, where these plugs are produced in situ, through the chemical reaction of formaldehyde-based resins, a catalytic agent and additives that confer different properties of density, hardness, pH, etc. to the material to be used. The resins are of the phenol-formaldehyde (PF), phenol-resorcinol-formaldehyde (PRF), melamine-urea-formaldehyde (MUF) and/or lignin-formaldehyde type.

[0053] The technical problem, which the present invention solves, has been addressed in different ways in the state of the art. However, the solution proposed in the present invention, related to a method for forming plugs in situ from formaldehyde-based resins, is not disclosed in the prior art.

[0054] The method for in situ formation consists of filling the blast hole to a certain height with the reactive agents, the reaction taking place at the time of mixing, which gives the advantage that this method requires a very short time for the formation of the plug. The in-situ formed plug allows the energy of the explosion to be contained and the transfer of this energy to the rock to be maximized, which results in greater fragmentation of the rock, considerably reducing the operational costs of the production stages after extraction. Additionally, the plugs obtained by the method of the invention have the additional advantage of reducing the undesirable environmental effects of noise and particulate material emissions, which could affect the workers at the site and the communities surrounding the mining operation.

[0055] The system that enables the method of applying rigid foam-forming agents consists of a mixer-applicator capable of handling highly corrosive substances and mixing the reagents homogeneously, in the necessary and optimal concentrations to form the materials that will serve as blasting plugs.

[0056] The method of constructing the blasting plugs obtained by means of the present invention, using polymeric materials derived from formaldehyde and phenolic compounds, has surprisingly allowed to increase the fragmentation of the rock by at least 25%, to decrease the reduction of air pressure in the monitoring systems, and to decrease the decibels of the detonation and particulate material by at least 50%, compared to the methods normally used in said mining operations.

[0057] It is known that phenol-formaldehyde based resins can be produced in such a way that their setting temperature and time (hardening process) are determined by the different physicochemical parameters that characterize it, such as the amount of total solids, pH, the molar ratio between formalin/phenol and/or urea, melamine, resorcinol, the size of the polymer and alkalinity. If this resin is mixed with additives capable of generating a gas during the setting process, a highly porous material (foam) can be obtained, which can present different characteristics of elasticity, hardness, toughness, and plasticity. These characteristics, besides depending on the internal composition of the resin used, may be a reflection of the quantity and speed of the reaction at the time of setting, which is dictated by the type, concentration and quantity of catalyst added to the reactive mixture.

[0058] In addition, other additives can be added to the formaldehyde-based resin, such as foaming agents, surfactants, fillers, buffers, or any other additive compatible with the setting characteristics required for the application. Therefore, by controlling the composition of a formaldehyde-based resin mixed with specific additives, which form a specially designed catalyst, materials with characteristics suitable for use as plugs in mining blast holes are obtained.

[0059] The material constituting the blasting plug of the present invention is formed from a bi-component composition or mixture comprising a formaldehyde-based resin and a catalyst suitable for said resin.

[0060] The resins used as the material forming the plug are synthesized based on formaldehyde and another co-monomer capable of forming a stable co-polymer with formaldehyde and with characteristics appropriate to the desired use. Such co-monomers may be chosen from (but not limited to) phenol, urea, melamine, resorcinol, etc. Additionally, blocks of semi-polymerized materials such as pMDI (Polymethyldiisocyanate), or any petroleum-based material capable of reacting with formaldehyde, may be used. In addition, renewable materials such as tannins, lignin, or any other lignocellulosic material capable of copolymerizing with formaldehyde can be used.

[0061] The copolymers mentioned above can also be used as blends. Formaldehyde-based polymers can be used in different molar ratios, with various sizes and degrees of polymerization, viscosities, pH conditions and total solids content suitable for use as plug material.

[0062] The resin compositions mentioned may contain other types of substances that incorporate desired characteristics to the material that will be used as a plug, such as (but not limited to): [0063] Rheology modifiers that provide particular flow or rheology characteristics, for example, acrylic polymers or prepolymers, urethanes, carbohydrates, lignocellulosic materials, etc. [0064] Surfactants that give the material antifoaming or foaming characteristics. [0065] Buffers or pH regulators suitable for setting of the material; said buffers can be inorganic or organic. [0066] Gasifying agents, such as pentane, hexane, dichloromethane or any other additive that generates gas during the setting reaction of the material to be used as a plug. [0067] Expanding agents such as carbonated or polycarbonate salts, organic solvents miscible with phenolic resin, melamine resin (MUF) or PRF with a chain of no more than 6 carbons.

[0068] The resins described above are reacted with a catalyst, depending on the type of resin to be used.

[0069] The catalysts are chosen taking into consideration the type of resin, so acidic, basic or cross-linking agent-based catalysts can be used to generate a material suitable for use as a plug.

[0070] Acidic catalysts may be selected from (but not limited to) mineral acids such as sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, or mixtures thereof. Catalysts may also be selected from organic acids such as formic acid, lactic acid, benzenesulfonic acid derivatives, citric acid, acetic acid, or mixtures thereof. As mentioned, acids can be used in mixtures in proportions suitable for the setting reaction of the resin to be used.

[0071] Basic catalysts may be selected from (but not limited to) mineral bases such as potassium hydroxide, barium hydroxide, sodium hydroxide, calcium hydroxide, or mixtures thereof. Catalysts may also be chosen from organic bases such as diethylamine, triethylamine, ethanolamine, or mixtures thereof. As mentioned, acids bases can be used in mixtures in proportions suitable for the setting reaction of the resin to be used.

[0072] Catalysts based on cross-linking or hardening agents may be selected from (but not limited to) pMDI, erythritol and its derivatives, polyols, acrylic resins, polyvinyl alcohols, formaldehyde, succinic derivatives, alkaline formaldehydes such as Resorplus, glycidol and epoxides derivatives or mixtures thereof or any bi or multi-functional compound capable of hardening the aforementioned resin. Each of these components or their mixtures can be used synergistically with one or more of the acidic or basic catalysts mentioned in the previous paragraphs.

[0073] Catalysts may consist of one or more of the agents mentioned above.

[0074] The weight/weight ratio of the bi-component mixture of resin respect to the catalyst (resin/catalyst) is in the range of 9:1 to 1:9; preferably between 3:1 and 1:3. Depending on the type of system and catalyst used, it can even be 2:1 to 1:2, in such a way as to generate a rigid foam material with hardness between 1 to 10 N/mm.sup.2.

[0075] In particular, the bi-component composition or mixture of the present invention is constituted by a phenol-formaldehyde (PF) resin or a melamine-urea-formaldehyde (MUF) resin, in a proportion of the resin components of 5020% by weight, which means a proportion of 30 to 70% of one component and 70 to 30% of the other resin component. This resin mixture is reacted in situ, that is, in the same blast hole with the catalyst, preferably in a proportion of 5020% based on the weight of the total mixture, and additives in the required proportions.

EXAMPLES

Example 1

[0076] Laboratory-scale plugs were constructed in order to demonstrate the physicochemical and mechanical properties of the bi-component mixture of resin and catalyst of the present invention compared to plugs produced with components used in the state of the art. Plugs formed with the following resins were tested:

[0077] PF: Phenol formaldehyde resin, in molar ratio 1.6 (invention). [0078] PUR: Polyurethane resin (comparative); [0079] pMDI: Polymethyldiisocyanate (Durapro) (comparative); [0080] pMDI-LS: Polymethyldiisocyanate with low reactivity (Durapro) (comparative); [0081] PRF: Formaldehyde Resin/(Resorcinol+Phenol) in a molar ratio of 0.8 to 1.0 (invention); [0082] MUF-1: Formaldehyde Resin/(Melamine+Urea) in a molar ratio of 1.2 to 1.8 (low viscosity) (invention); [0083] MUF-2: Formaldehyde Resin/(Melamine+Urea) in a molar ratio of 1.2 to 1.8 (high viscosity) (invention); [0084] Table No. 1 describes the bi-component mixtures of resin-catalyst of the present invention and foams produced with commercial resins as a comparison, and Table 2 shows the compositions of the catalysts used.

TABLE-US-00001 TABLE 1 Composition of foams produced with resins and catalysts according to the present invention compared to other commercial foams. Bi-component mixture of resin PF PRF MUF-1 MUF-2 PUR pMDI pMDI-LS Catalyst D E D D A B C Catalyst/ 2:1 2.3:1 1:1 1:1 1:1 1:1 1:1 Resin Ratio

TABLE-US-00002 TABLE 2 Catalysts used for the formation of the bi-component mixture of Table 1. Catalyst A B C D E Polyethylene glycol 400 94.79 90 87.5 0 Linear sulfonic acid 0.47 2.5 2.5 0 Triethanolamine 75% 4.74 7.5 7.5 0 NaK lignosulfonate 0 0 5.5 0 p-toluenesulfonic acid 0 0 0 50 Sulfuric acid 0 0 0 25 RESORPLUS 30 Water 0 0 0 25 TOTAL 100 100 100 100

[0085] Tests were carried out in transparent polycarbonate tubes of 40 cm long and 10 cm in diameter. These tubes were filled with gravel to a height of 22 cm, and 300 g of resin-catalyst mixture was poured over the gravel, as shown in FIG. 1.

[0086] Measurements were taken to record the degree of diffusion of the bi-component mixture within the gravel, setting time, degree of expansion and the maximum temperature reached by the mixture at the surface and bottom.

[0087] Table N3 shows a summary of the average results obtained from the various laboratory tests. The numbering 1 to 7 of the columns correlates with the numbering of the photograph in FIG. 1.

TABLE-US-00003 TABLE NO. 3 Summary of the results obtained from the laboratory tests. Diffu- Set- Maximum Bicomponent sion in Equivalent Expan- Volume ting temper- resin-catalyst gravel diffusion sion change time ature mixture (cm) (m) (cm) (%) (min) ( C.) (1) PF 8 1.46 10 500 2 40 Invention (2) PUR 10.5 1.91 10.5 300 20 56 (3) pMDI Total 4 14.5 500 15 115 (4) pMDI-LS 12 2.18 >20 800 15 95 (5) PRF 4 0.73 6.5 300 2 40 Invention (6) MUF-1 3.5 0.64 10 500 2 35 Invention (7) MUF-2 1.5 0.28 10 500 2 55 Invention

[0088] As it can be seen from the results shown in Table 3, the expansion and volume change parameters of the resins formed allow establishing a control for the formation of the plug, in order to extrapolate it to a blast hole and not exceed the volume limits that the hole can contain when forming the plug.

[0089] It is also possible to appreciate that the setting time of the bi-component mixture of the present invention represents a considerably shorter time than the formation of rigid foams formed with the other resins tested.

[0090] When reacting the resins and catalysts for the formation of the plug, the evolution of temperature as a function of time was measured, as shown in FIG. 2, where it was found that the bottom temperatures remained constant except for the pMDI mixture (comparative), which reached more than 100 C. Therefore, it is possible to establish that the compositions of the present invention have the advantage of maintaining a temperature equal to or lower than 40 C., which gives an advantage in the detonation operation, since the detonation wires have limits and safety standards which cannot operate at temperatures higher than 55, since above this temperature the wires can present failures, which can inhibit a correct detonation, with all the problems associated with the so-called misfire, which implies risk situations in the mine due to latent explosives. Therefore, exothermic temperatures below 40 Celsius is a highly desirable condition.

Example 2

[0091] The physicochemical properties of the experimental formulas were optimized at the laboratory scale of Example 1, in order to generate stable compounds to be used in field blasting with explosive material, to verify the feasibility and possible scalability of the prototype.

[0092] A test of the invention was carried out to evaluate the method of forming a blasting plug based on a formaldehyde resin and a catalyst of the invention, which when applied in-situ, i.e. in the field, react and generate the rigid foam. The test included a comparison with conventional plugs.

[0093] The mixture of formaldehyde resin-catalyst is loaded directly into the holes in the required amount, according to the diameter and depth of the hole, that is, in the order of 2 to 100 kg, considering an expansion volume of 3 to 5 times the loaded volume of the mixture. The time it takes to load the hole is around 30 seconds to 5 minutes, depending on the loading volume, and the foaming formation time is in the order of 3 to 10 minutes, also depending on the loading volume.

[0094] For the field example, holes with plugs based on the bi-component mixture of phenolic resin-catalyst of the present invention and conventional holes with drill cuttings were considered. Drill cuttings refers to the ground material obtained from drilling the ore during hole construction, used as the sole constituent for a conventional plug. The holes with plugs of the present invention have drill cuttings at a proportionally minimum fraction in their design.

[0095] The perforation design, load configuration and detonation were kept constant. Table 4 shows the drilling and blasting design parameters for the blast holes.

TABLE-US-00004 TABLE 4 Drilling and blasting design parameters Parameters Values Type of Explosive ANFO Diameter 11.5 cm (4.5 inches) Blasting cap 0.5 meters Charge length 5.5 meters Plug length 2 meters Density explosive 0.8 g/cm.sup.3 Linear charge 8.21 kg/m Explosive column charge 28.7 kg Load factor 199 g/ton Length of conventional drill cutting plug 2.0 meters Length of drill cutting of invention 0.5 meters (maximum) Length of plug of resin mix of invention 1.5 meters (minimum)

[0096] FIG. 3 represents a scheme of the configuration and design of the blasting holes according to the parameters defined in the previous table.

[0097] FIG. 4 shows a flow chart of the preferred embodiment of the method of applying the bi-component mixture of resin-catalyst of the present invention, which is mounted on a truck to provide mobility to the system.

[0098] The application system comprises a first pond containing the resin and a second pond containing the catalyst. In the preferred embodiment, the ponds have a volume of approximately 1 m.sup.3.

[0099] A first flow originates from the first pond to a first pump. The first pump can be a screw or centrifugal pump, being driven, for example, by a motor powered by a generator. The first pond may also comprise an internal mechanical agitator, for homogenization and recirculation of the resin, and may also include a heater to maintain the necessary temperature in low ambient temperature conditions. Alternatively, the second pond may also include such features (not shown in FIG. 4).

[0100] A second flow originates from the second pond, by means of a second pump. The second pump can be a pneumatic pump, driven, for example, by a compressor that is also powered by the generator.

[0101] Both flows are standardized to a predetermined ratio (resin to catalyst) ranging from 3:1 to 1:3.

[0102] As shown in FIG. 4, the first flow and the second flow are directed through various valves to a mixer, for example, a static mixer, achieving homogenization of the catalyst and resin. Once the mixture has been mixed, it is deposited directly into the blast hole.

[0103] FIG. 4 also shows that the preferred embodiment of the application method has various valves, which open or close the passage of flows. Both the first and second flow can be redirected to their corresponding ponds by means of, for example, relief valves in case the pressures are high enough and/or the other valves are closed.

[0104] The compressor is additionally used to provide an air flow when stopping the system or terminating the application of the mixture. This air flow allows the cleaning of pipes, and particularly to avoid the deposition of residues of the homogenized and solidified mixture in the static mixer.

[0105] The first and second flows and air flow can be regulated manually, by reading of various mass flow meters, or automatically, by means of a programmable logic controller (PLC).

[0106] The amount of resin-catalyst mixture to be loaded into the blast holes is calculated according to the diameter and height of the hole, considering an expansion of 3 to 5 times the foam formation volume. The loading time of a hole is approximately 30 seconds to 1 minute and with a foaming time of the order of 40 to 60 seconds.

[0107] The mixer used in the test corresponds to a static mixer of 30 cm long, 1 inch wide (2.54 cm) with a flow rate design ranging from 1 to 200 L/minute.

[0108] The procedure for carrying out the formation of the plug and subsequent detonation and blasting with the rigid foam of the present invention comprises the following steps: [0109] load the explosive to the bottom of each of the holes, 28.7 Kg of ANFO (Ammonium Nitrate [0110] Fuel Oil), [0111] load with a layer of drill cutting or stone (1-2 kg of material equivalent to 0.5 m) to seal and prevent contact of the foam of the invention with the explosive, [0112] load 3.5 kg of the invention foam according to the method described above, in a time of 30 seconds to 1 minute, [0113] setting of the foam of the invention, which lasts between 1 to 3 minutes. [0114] once the hole filling operation is completed, the area is evacuated and the holes are detonated.

[0115] For comparison, conventional holes were loaded with 2 meters of drill cuttings, without the foam of the present invention. The loading time of these conventional holes was on average 5 minutes.

[0116] After detonation, air pressure measurements and aerial camera inspections are carried out to determine dust emissions and the height of smoke columns.

[0117] The total reaction time of setting for the rigid foam of the present invention ranged from 1 to 3 minutes, that is, the time in which the rigid foam reached the final hardness. The reaction therefore reaches its end very quickly, which provides a highly efficient performance in the loading of plug and explosives in the blasting area.

[0118] The density of the foam obtained was of the order of 0.25 g/m and its stiffness was of the order of 2 N/mm.sup.2. These values obtained from the foam improved the performance of the blasting, allowing for a greater amount of noise and energy expansion to be retained at the time of detonation, and also allowing for greater rock fragmentation, compared to traditional holes.

[0119] The test carried out in the field showed a maximum exothermicity at 6.5 seconds, with the maximum temperature reached on the surface of the foam being 40.6 C., as shown in FIG. 5, providing safety and the advantage of keeping the wires in good condition and not being damaged by the effect of temperature.

[0120] By using slow motion recording images, at a speed of 240 frames per second, it was possible to obtain the retention time and ejection height of the detonation. Retention time is also known as explosive velocity, and corresponds to the speed at which the shock wave front travels through a detonating explosive.

[0121] The recording images demonstrated that the test conducted in the field allowed containment of gases in the blast holes with plugs formed with the phenolic resin of the present invention, with an ejection delay of 50 milliseconds with respect to the detonation initiation point marked by an electronic system in the conventional hole without foam, and a decrease in the height of the ejection from 15 meters height for the conventional plugs compared to 5 meters height for plugs of the invention.

[0122] FIG. 6 shows photographs that were taken at the same comparative times when making a blasting with and without plugs of the invention. Both the upper (conventional blasting) and lower (blasting with the resin plug of the present invention) photographs were captured with a drone during the operation at times 0, 30 and 50 milliseconds.

[0123] In addition to the height measured in both cases, at the time of blasting, the density of smoke and dust is clearly observed in the upper photographs, compared to the lower photographs, where a lower density of smoke can be seen and there are even sectors of the blasting where there is no dust ejection from the blast holes.

[0124] On the other hand, the blasting with the invention's plugs produced a blast zone with greater fragmentation, compared to a conventional blasting plug, where the percentages of rock size decrease ranged between 30-50% with respect to conventional blasting.

[0125] The reduction in air pressure was also measured, which is mathematically correlated by software with the sound intensity during blasting, resulting in a reduction of between 50 and 90% of decibels with respect to conventional blasting.

[0126] To determine the behavior of the explosives and the decibel measurement, two conventional blasts were considered, with the same configuration of blast hole designs defined in this example. Likewise, 3 blasting operations were carried out with the invention's plugs, under the same conditions to compare with the noise behavior of conventional plugs. Table N5 provides a summary of the measurements taken.

TABLE-US-00005 TABLE 5 Field measurements for determination of noise reduction in blasting with plugs loaded with the bi-component mixture of the present invention (PF + catalyst) in comparison with plugs loaded with drill cuttings in conventional blasting. Number Pressure Sound Noise Blasting type of holes (Pa) intensity reduction Conventional 1 24 4.79 107.7 0% Convenctional 2 20 6.28 110.1 0% Invention 1 30 1.18 102.2 79% Invenction 2 16 0.53 98.3 90% Invention 3 30 2.47 104.9 55%