Methods and apparatus for hybrid electromagnetic-ultrasonic fragmenting of rock surfaces

Abstract

Apparatus and methods for in situ fragmentation of a rock formation. The apparatus and methods comprising propagating ultrasonic radiation into a working face of a rock formation with an ultrasonic horn, while simultaneously propagating electromagnetic energy into the rock formation with an electromagnetic applicator, the electromagnetic applicator shaped and / or located such that a location of maximal flux of the electromagnetic radiation on the working face is within the footprint.

Description

METHODS AND APPARATUS FOR HYBRID ELECTROMAGNETIC-ULTRASONIC FRAGMENTING OF ROCK SURFACESReference to Related Applications

[0001] This application claims priority from, and the benefit under 35 USC 119 in relation to, US application No. 63 / 754760 filed 6 February 2025, which is hereby incorporated herein by reference for all purposes.Technical Field

[0002] This disclosure relates to systems and methods for mining. Particular embodiments of this disclosure provide methods and apparatus for hybrid electromagnetic-ultrasonic fragmentation of rock formations.Background

[0003] Conventional hard rock mining relies heavily on drilling and blasting to excavate rocks and extract ore from natural deposits. The “drill and blast” process is cyclic and involves stages of drilling, drill hole preparation, explosive loading, and detonation to achieve fragmentation of rock formations.

[0004] The cyclic nature of the “drill and blast” process necessitates significant interruptions between each stage resulting in inefficient hard rock mining operations. Interruptions may result in opportunity costs associated with idle equipment and / or reduce the output of a mine relative to a continuous mining process.

[0005] Additionally, the run-of-mine material produced by “drill and blast” processes comprises valuable minerals disseminated within and closely interlocked with gangue. Effective liberation of valuable minerals from the gangue is typically achieved in subsequent processing through a sequence of comminution stages.

[0006] Comminution stages involve crushing and grinding the run-of-mine ore to a size where valuable ore minerals are separated from gangue, yielding a finely ground product (typically with a dso size below 0.1 mm) of relatively clean, relatively liberated mineral and gangue particles.

[0007] Comminution is typically carried out in two or three stages of crushing followed by grinding (milling)

[0008] In the primary crushing stage, run-of-mine ore, with particle sizes up to 1.5 m, is reduced to a product with a dso size of 100-200 mm particles. Secondary crushing further reduces the product to a dso size of 37-50 mm, and tertiary crushing yields pebbled particles sized between a dso of 5-20 mm.

[0009] Subsequent grinding is performed in mills, where particles are reduced by a combination of impact and abrasion. Tumbling mills initially reduce particle dso sizes to between 25-300 pm, followed by stirred mills that refine particles to dso sizes below 25 pm.

[0010] In a typical open-pit mine-to-mill sequence, comminution may consume up to 70% of the mine's total electrical energy.

[0011] Ultrasonic systems for pre-conditioning rocks in mining applications have been explored by the industry. However, such systems have necessitated significant time and energy to achieve results. See for example Zhao, D., Zhang, S., Zhao, Y., & Wang, M. (2019). Experimental study on damage characteristics of granite under ultrasonic vibration load based on infrared thermography. Environmental Earth Sciences, 78, 1-12., Zhang, C., Zhang, S., & Zhao, D. (2022). Effect of Amplitude and Confining Pressure on Granite Failure under Ultrahigh Frequency (UHF) Impact Based on Radiation Temperature.Geofluids, 1, 4817269.; and Tang, Q., Zhou, Y., Zhang, C., Zhang, S., Xu, X., Sun, H., & Zhao, D. (2024). Effect of confining pressure on the damage characteristics and mechanism of granite under ultra-high-frequency impact. Geoenergy Science and Engineering, 238, 212842.

[0012] Ultrasonic pre-conditioning of rocks has been found to require significant energy input to fracture rocks. For example, Tang et al referenced above, found that it requires approximately 220 kWh / t of ultrasonic energy to fracture granite.

[0013] Ultrasonic systems and their use in mining remain inconsistent and are challenging to implement in large-scale mining due to the energy requirements of ultrasonic systems, high cutting tool wear rates, frequent equipment downtime and maintenance needs. These limitations contribute to reduced system availability, suboptimal production rates, and increased operational costs.

[0014] The use of microwave heating of rocks to reduce the strength of rocks has also been investigated by the industry. The use of microwave irradiation to substantially reduce rock strength requires energy input comparable to the combination of conventional excavation and comminution processes. See for example Hassani, F., Shadi, A., Rafezi, H., Sasmito, A.P., & Ghoreishi-Madiseh, S.A. (2020). Energy analysis of the effectiveness of microwave-assisted fragmentation. Minerals Engineering, 159, 106642, which is hereby incorporated by reference in its entirety.

[0015] CN118080114A discloses a method of simultaneously applying ultrasonic energy and microwave radiation to ore previously extracted from a rock formation to perform auxiliary crushing of the previously extracted ore. CN118080114A discloses that further mechanical crushing is necessary after their auxiliary crushing method. The need for additional mechanical crushing indicates that products produced by the CN118080114A method are likely at least several centimeters in diameter. CN118080114 teaches the use of an ultrasonic cutting tool and a microwave port radially spaced apart from the cutting tool. The CN118080114 microwave port receives microwave radiation via a waveguide depicted to be located at a particular angular position relative to the cutting tool.

[0016] There is a general desire for mining systems and processes which allow for continuous mining of hard rock formations in a cost-effective manner.

[0017] There is a general desire for mining systems and processes which allow for continuous in situ fragmentation of a rock formation in a cost-effective manner.

[0018] There is a general desire mining systems and processes which mitigate the cost and time spent on comminution of run-of-mine ore.

[0019] The foregoing examples of the related art and limitations related thereto are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.Summary

[0020] The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools and methods which are meant to be exemplary and illustrative, not limiting in scope. In various embodiments, one or more of the above-described problems have been reduced or eliminated, while other embodiments are directed to other improvements.

[0021] One aspect of the invention provides an apparatus for in situ fragmentation of a rock formation. The apparatus comprises: an ultrasonic horn comprising a contact surface that contacts a working face of the rock formation, a perimeter of the contact surface defining an outer footprint of the ultrasonic horn on the working face, the ultrasonic horn moveable against the working face to thereby propagate ultrasonic energy into the rock formation; and an electromagnetic applicator for emitting electromagnetic radiation into the rock formation, the electromagnetic applicator shaped and / or located such that a location of maximal flux of the electromagnetic radiation on the working face is within the outer footprint.

[0022] The electromagnetic applicator may be shaped to emit the electromagnetic radiation such that the electromagnetic radiation has a direction of maximum flux extending from the electromagnetic applicator to the working face and intersecting the working face within the outer footprint.

[0023] The ultrasonic horn may be moveable against the working face in an axial direction normal to the working face to thereby propagate ultrasonic energy into the rock formation in the axial direction. The horn may also optionally be moveable in one or more angular directions about the axial direction.

[0024] The electromagnetic applicator may be shaped and / or located to propagate electromagnetic radiation into a fragmentation volume of the rock formation, the fragmentation volume being a volume of the rock formation extending into the rock formation in the axial direction from the outer footprint of the ultrasonic horn.

[0025] The ultrasonic horn may comprise a bore-defining surface which defines a bore that extends in the axial direction at least partially through the ultrasonic horn.

[0026] The ultrasonic horn may comprise a contact surface for contacting the rock formation, the contact surface defining an opening into the bore.

[0027] At least a portion of the electromagnetic applicator from which the electromagnetic radiation is emitted may be located inside the bore.

[0028] The bore defining surface may comprises a bore defining surface cross-section in a cross-sectional plane orthogonal to the axial direction. The at least a portion of theelectromagnetic applicator mat comprise an electromagnetic applicator cross-section in the cross-sectional plane. The bore defining surface cross-section may surround the electromagnetic applicator cross-section.

[0029] The electromagnetic applicator may comprise a waveguide. A portion of the waveguide may comprise a portion of the bore defining surface.

[0030] The ultrasonic horn and the electromagnetic applicator may be operative to simultaneously propagate the ultrasonic energy and the electromagnetic energy into the rock formation.

[0031] The apparatus may comprise a debris removal system for removing debris from the working face.

[0032] The debris removal system may be operative to remove debris while (e.g. at the same time as) the ultrasonic horn propagates the ultrasonic energy into the rock formation, and the electromagnetic applicator emits the electromagnetic radiation into the rock formation.

[0033] The debris removal system may comprise a collection system for collecting fragments fragmented by the apparatus from the rock formation.

[0034] The apparatus may comprise a backforce mechanism connected to the ultrasonic horn to apply a force to the ultrasonic horn, the force comprising a directional component in the axial direction.

[0035] The electromagnetic applicator may comprise a microwave applicator.

[0036] The apparatus may comprise a propulsion system connected to move the apparatus relative to the working face while (e.g. at the same time as) the apparatus is fragmenting the rock formation (e.g. by the ultrasonic horn propagating the ultrasonic energy into the rock formation and the electromagnetic applicator emitting the electromagnetic radiation into the rock formation).

[0037] The propulsion system may be connected to move the apparatus in the axial direction while the apparatus is fragmenting the rock formation.

[0038] The propulsion system may be connected to move the apparatus in a transverse direction having at least a component that is orthogonal to the axial direction while the apparatus is fragmenting the rock formation.

[0039] The propulsion system may be connected to pivot the apparatus (e.g. the ultrasonic horn and the electromagnetic applicator) relative to the rock formation while the apparatus is fragmenting the rock formation.

[0040] The ultrasonic energy may create a stress field within the rock formation, wherein an ultrasonically excited volume of the rock formation comprises regions of the stress field having a tensile stress greater than 70% of a maximum tensile stress of the stress field. The electromagnetic applicator may be shaped and / or located such that the electromagnetic radiation creates an irradiated volume of the rock formation wherein an electromagnetic power density of an electromagnetic field created by the electromagnetic applicator in the irradiated volume is greater than 25% of a maximum electromagnetic power density of the electromagnetic field. The irradiated volume may be contiguous with the ultrasonically excited volume.

[0041] The ultrasonic energy may create a stress field within the rock formation, wherein an ultrasonically excited volume of the rock formation comprises regions of the stress field having a tensile stress greater than 70% of a maximum tensile stress of the stress field. The electromagnetic applicator may be shaped and / or located such that the electromagnetic radiation creates an irradiated volume of the rock formation wherein an electromagnetic power density of an electromagnetic field created by the electromagnetic applicator in the irradiated volume is greater than 25% of a maximum electromagnetic power density of the electromagnetic field. The irradiated volume may overlap with the ultrasonically excited volume.

[0042] The ultrasonic energy may create a stress field within the rock formation, wherein an ultrasonically excited volume of the rock formation comprises regions of the stress field having a tensile stress greater than 70% of a maximum tensile stress of the stress field. The electromagnetic applicator may be shaped and / or located such that the electromagnetic radiation creates an irradiated volume of the rock formation wherein an electromagnetic power density of an electromagnetic field created by the electromagnetic applicator in the irradiated volume is greater than 25% of a maximum electromagnetic power density of the electromagnetic field. The irradiated volume may be contained within a volume defined by a transverse-most extent of and axial-most extent of the ultrasonically excited volume.

[0043] The ultrasonically excited volume of the rock formation may comprise regions of the stress field comprising tensile stress greater than 80% of the maximum tensile stress of the stress field or, optionally, greater than 90% of the maximum tensile stress of the stress field.

[0044] The irradiated volume of the rock formation may comprise regions of the electromagnetic field comprising an electromagnetic power density greater than 50% of the maximum electromagnetic power density of the electromagnetic field or, optionally, greater than 80% of the maximum electromagnetic power density of the electromagnetic field, or, further optionally, greater than 90% of the maximum electromagnetic power density of the electromagnetic field or, still further optionally, greater than 99% of the maximum electromagnetic power density of the electromagnetic field or, still further optionally, greater than 99.9% of the maximum electromagnetic power density of the electromagnetic field.

[0045] The apparatus may comprise an ultrasonic transducer coupled to the ultrasonic horn to move the ultrasonic horn and thereby propagate the ultrasonic energy into the rock formation.

[0046] The ultrasonic energy may create a stress field within the rock formation, wherein an ultrasonically excited volume of the rock formation comprises regions of the stress field having a tensile stress greater than 50% of a maximum tensile stress of the stress field. The electromagnetic applicator may be shaped and / or located such that the electromagnetic radiation creates an irradiated volume of the rock formation wherein an electromagnetic power density of an electromagnetic field created by the electromagnetic applicator in the irradiated volume is greater than 50% of a maximum electromagnetic power density of the electromagnetic field. The ultrasonically excited volume may overlap the irradiated volume.

[0047] The electromagnetic applicator may be shaped and / or located such that a direction of maximal flux of the electromagnetic radiation is orthogonal to the working face is within the outer footprint.

[0048] Another aspect of the invention provides a method of in situ fragmentation of a rock formation. The method comprises: propagating ultrasonic energy into the rock formation through a first area of a working face of the rock formation; and simultaneously propagating electromagnetic radiation into the rock formation through the working face, wherein a location of maximal flux of the electromagnetic radiation on the working face is within the first area. Simultaneously propagating the electromagnetic radiation and the ultrasonicenergy into the rock formation induces fragmentation of a portion of the rock formation into a plurality of fragments.

[0049] Propagating the electromagnetic radiation may comprise emitting the electromagnetic radiation from an electromagnetic applicator such that that the electromagnetic radiation has a direction of maximum flux extending from the electromagnetic applicator to the working face and intersecting the working face within the first area.

[0050] The first area may be defined by a perimeter of a contact surface of an ultrasonic horn, the contact surface contacting a working face of the rock formation

[0051] Propagating the ultrasonic energy into the rock formation may comprise propagating the ultrasonic energy in an axial direction normal to the working face, or, optionally, in the axial direction and an angular direction about the axial direction.

[0052] Propagating the electromagnetic radiation into the rock formation may comprise propagating the electromagnetic radiation into a fragmentation volume of the rock formation, the fragmentation volume being a volume of the rock formation projecting axially into the rock formation from the first area.

[0053] The plurality of fragments may have a dso of 1 mm or less, or, optionally, 800 pm or less, or, further optionally, 600 pm or less, or, still further optionally 500 pm or less or, yet still further optionally, 400 pm or less.

[0054] The method may comprise conveying the plurality of fragments away from the rock formation.

[0055] The method may comprise simultaneously: propagating the electromagnetic radiation into the rock formation; propagating the ultrasonic energy into the rock formation; and conveying the plurality of fragments away from the rock formation.

[0056] The method may moving, relative to the working face, an apparatus for performing the method simultaneously with propagating the electromagnetic radiation into the rock formation and propagating the ultrasonic energy into the rock formation.

[0057] Moving the apparatus relative to the working face may comprise advancing the apparatus in an axial direction orthogonal to the working face.

[0058] Moving the apparatus relative to the working face may comprise moving the apparatus in a transverse direction having at least a component that is orthogonal to the axial direction.

[0059] Moving the apparatus relative to the working face may comprise pivotal movement of the apparatus (e.g. about one or more pivot axes) relative to the rock formation.

[0060] Propagating the electromagnetic radiation into the rock formation may comprise propagating the electromagnetic radiation into the rock formation continuously.

[0061] Propagating the electromagnetic radiation into the rock formation may comprise propagating the electromagnetic radiation into the rock formation in pulses.

[0062] Propagating the electromagnetic radiation into the rock formation may comprise propagating the electromagnetic radiation into the rock formation until intergranular microcracks are nucleated in the rock formation.

[0063] Propagating the electromagnetic radiation into the rock formation in pulses may comprise propagating the electromagnetic radiation into the rock formation in pulses comprising a pulse width of one second or less.

[0064] Propagating ultrasonic energy into the rock formation may comprise propagating the ultrasonic energy into the rock formation continuously.

[0065] Propagating ultrasonic energy into the rock formation may comprise propagating the ultrasonic energy into the rock formation in pulses.

[0066] Propagating ultrasonic energy into the rock formation may comprise propagating ultrasonic energy into the rock formation until the ultrasonic energy propagates the intergranular microcracks nucleated by the electromagnetic radiation to coalesce the microcracks and thereby fracture the rock formation.

[0067] Propagating the ultrasonic energy into the rock formation in pulses may comprise propagating the ultrasonic energy into the rock formation in pulses comprising a pulse width of 1 second or less.

[0068] The ultrasonic energy may be applied in a range of 20 kHz to 2 MHz.

[0069] The method may comprise varying a frequency of the ultrasonic energy based on a material response to propagating the ultrasonic energy into the rock formation to identify aresonance mode. Propagating the ultrasonic energy into the rock formation may comprise propagating the ultrasonic energy at a frequency corresponding to the resonance mode.

[0070] The material response may comprise one or more of a change in temperature, absorbed thermal energy, and microwave efficiency.

[0071] The method may comprise varying a power of the ultrasonic energy based on an expected change in strength and / or expected elastic modulus of the rock formation.

[0072] The power of the ultrasonic energy may be varied between 10 W and 100 kW.

[0073] The electromagnetic radiation may be microwave radiation.

[0074] Propagating ultrasonic energy into the rock formation may create a stress field within the rock formation, wherein an ultrasonically excited volume of the rock formation comprises regions of the stress field having a tensile stress greater than 70% of a maximum tensile stress of the stress field. Propagating electromagnetic radiation into the rock formation may create an irradiated volume of the rock formation, wherein an electromagnetic power density of an electromagnetic field created by the electromagnetic applicator in the irradiated volume is greater than 25% of a maximum electromagnetic power density of the electromagnetic field. The irradiated volume may be contiguous with the ultrasonically excited volume.

[0075] Propagating ultrasonic energy into the rock formation may create a stress field within the rock formation, wherein an ultrasonically excited volume of the rock formation comprises regions of the stress field having a tensile stress greater than 70% of a maximum tensile stress of the stress field. Propagating electromagnetic radiation into the rock formation may create an irradiated volume of the rock formation, wherein an electromagnetic power density of an electromagnetic field created by the electromagnetic applicator in the irradiated volume is greater than 25% of a maximum electromagnetic power density of the electromagnetic field. The irradiated volume may overlap with the ultrasonically excited volume.

[0076] Propagating ultrasonic energy into the rock formation may create a stress field within the rock formation, wherein an ultrasonically excited volume of the rock formation comprises regions of the stress field having a tensile stress greater than 70% of a maximum tensile stress of the stress field. Propagating electromagnetic radiation into the rock formation maycreate an irradiated volume of the rock formation wherein an electromagnetic power density of an electromagnetic field created by the electromagnetic applicator in the irradiated volume is greater than 25% of a maximum electromagnetic power density of the electromagnetic field. The irradiated volume may be contained within a volume defined by a traverse-most extent of and an axial-most extend of the ultrasonically excited volume.

[0077] The ultrasonically excited volume of the rock formation may comprise regions of the stress field comprising a tensile stress greater than 80% of a maximum tensile stress of the stress field or, optionally, greater than 90% of the maximum tensile stress of the stress field.

[0078] The irradiated volume of the rock formation may comprise regions of the electromagnetic field comprising an electromagnetic power density greater than 50% of the maximum electromagnetic power density of the electromagnetic field or, optionally, greater than 80% of the maximum electromagnetic power density of the electromagnetic field, or, further optionally, greater than 90% of the maximum electromagnetic power density of the electromagnetic field or, still further optionally, greater than 99% of the maximum electromagnetic power density of the electromagnetic field or, still further optionally, greater than 99.9% of the maximum electromagnetic power density of the electromagnetic field.

[0079] Propagating ultrasonic energy into the rock formation may create a stress field within the rock formation, wherein an ultrasonically excited volume of the rock formation comprises regions of the stress field having a tensile stress greater than 50% of a maximum tensile stress of the stress field. Propagating electromagnetic radiation into the rock formation may create an irradiated volume of the rock formation wherein an electromagnetic power density of the electromagnetic field in the irradiated volume is greater than 50% of a maximum electromagnetic power density of the electromagnetic field. The ultrasonically excited volume may overlap the irradiated volume.

[0080] Another aspect of the invention provides an apparatus comprising: an ultrasonic horn comprising a contact surface that contacts a working face of the rock formation, a perimeter of the contact surface defining a footprint of the ultrasonic horn on the working face, the ultrasonic horn moveable against the working face to thereby propagate ultrasonic energy into the rock formation; and an electromagnetic applicator for emitting electromagnetic radiation into the rock formation, the electromagnetic applicator shaped and / or located such that when the ultrasonic horn is in contact with the working face theelectromagnetic radiation is propagated through the footprint. The apparatus may comprise any of the features, combinations of features and / or sub-combinations of features of the other apparatus and methods described herein.

[0081] Other aspects of the invention provide apparatus comprising any feature(s), combinations of feature(s) and / or subcombinations of feature(s) disclosed herein.

[0082] Other aspects of the invention provide methods comprising any feature(s), combinations of feature(s) and / or subcombinations of feature(s) disclosed herein.

[0083] In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following detailed descriptions.Brief Description of the Drawings

[0084] Exemplary embodiments are illustrated in referenced figures of the drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive.

[0085] Figure 1 is a flow chart representation of a conventional mine-to-mill process.

[0086] Figure 2 is a chart of fracture stages of rock undergoing an ultrasonic treatment as measured through temperature of the rock plotted against time.

[0087] Figure 3 is a chart of uniaxial compressive strength of a rock plotted against applied microwave energy at various microwave power levels.

[0088] Figure 4 is a schematic diagram of an exemplary hybrid electromagnetic-ultrasonic mining apparatus according to an exemplary embodiment.

[0089] Figure 5 is a schematic diagram of an axial plan view of regions excited by ultrasonic energy and electromagnetic radiation according to the Figure 4 embodiment of the invention.

[0090] Figure 6A is a 3D stress model of a volume of basalt undergoing an ultrasonic treatment.

[0091] Figure 6B is the same 3D stress model of a volume of basalt undergoing an ultrasonic treatment as depicted in Figure 6A depicted in greyscale. Figure 6A and 6B are referred to collectively as Figure 6.

[0092] Figure 7 is a graph of the modulus of elasticity of a rock plotted against absorbed microwave radiation at various power densities.

[0093] Figure 8A is a 3D model of the elastic modulus of a volume of basalt undergoing a microwave treatment, depicted using contour lines.

[0094] Figure 8B is the same 3D model of the elastic modulus of a volume of basalt undergoing a microwave treatment as depicted in Figure 8A, depicted in greyscale.

[0095] Figure 8C is a 3D model of an electromagnetic power density field within of a volume of basalt undergoing a microwave treatment, depicted using contour lines.

[0096] Figure 8D is a is an enlarged view of a portion of the 3D model of Figure 8C. Figure 8A, 8B, 8C and 8D are referred to collectively as Figure 8.

[0097] Figure 9A is a 3D stress model of a volume of basalt undergoing a hybrid microwave-ultrasonic treatment, depicted using contour lines.

[0098] Figure 9B is the same 3D stress model of a volume of basalt undergoing a hybrid microwave-ultrasonic treatment as depicted in Figure 9A, depicted in greyscale. Figure 9A and 9B are referred to collectively as Figure 9.

[0099] Figure 10A is an image of fragments produced by fragmenting a rock sample using an exemplary hybrid ultrasonic-electromagnetic process of the type implemented by the Figure 4 apparatus.

[0100] Figure 10B is an image of fragments produced by fragmenting a rock sample using a conventional ultrasonic process.

[0101] Figure 11 is a particle size distribution chart plotting percent of particles passing through a sieve against the sieve size after undergoing ultrasonic treatments, microwave treatments or hybrid ultrasonic-electromagnetic process of the type implemented by the Figure 4 apparatus.

[0102] Figure 12 is a flow chart representing a fragmentation process using a hybrid ultrasonic-electromagnetic process of the type implemented by the Figure 4 apparatus according to a particular embodiment.

[0103] Figure 13 is a flow chart representing a mine-to-mill process using a hybrid ultrasonic-electromagnetic process of the type implemented by the Figure 4 apparatus according to a particular embodiment.

[0104] Figure 14 is a schematic representation of a control system of the Figure 4 apparatus according to a particular embodiment.

[0105] Figure 15 is a schematic diagram of an exemplary hybrid electromagnetic-ultrasonic mining apparatus according to an exemplary embodiment.Description

[0106] Throughout the following description specific details are set forth in order to provide a more thorough understanding to persons skilled in the art. However, well known elements may not have been shown or described in detail to avoid unnecessarily obscuring the disclosure. Accordingly, the description and drawings are to be regarded in an illustrative, rather than a restrictive, sense.

[0107] Figure 1 depicts a conventional prior art mine-to-mill process 20. Conventionally, hard rock mining begins with drilling a blast hole into a rock formation (step 22) followed by using explosives placed in the drilled blast hole to blast the rock formation into extractable run-of-mine ore (step 24). The ore extracted by conventional blasting methods may have a top size of 1.5 m or more. The ore is then extracted and loaded into haul trucks (step 26) which transport the ore (step 28) to comminution equipment. Drilling (step 22), blasting (step 24) and extracting (step 26) cannot be performed simultaneously due to blasting being inherently incompatible with operating equipment within a blast zone.

[0108] Comminution stages begin with primary crushers which may crush the ore from a Fso size of 1.5 m to a Pso size of 100-200 mm (step 30). Crushed ore is then transferred to secondary crushers which crush the ore from a Fso size of 100-200 mm down to a crushed product with a Pso size of 37-50 mm (step 32). The crushed product is then transferred to tertiary crushers which crush the crushed product down to a Pso size of 5-20 mm (step 34).The crushed product is then transferred to mills beginning with a tumbling mill to reduce the crushed product to a milled product with a Psosize of 25-300 pm (step 36) and then to a stirred mill to reduce the milled product to a Pso size of less than 25 pm (step 38). After the milling process the milled product is ready to be further processed for beneficiation and mineral processing to extract valuable minerals (step 40).

[0109] Figure 2 is a chart 50 which plots temperature variations of a granite sample undergoing an ultrasonic treatment against time the ultrasonic treatment is applied to the granite sample. Temperature variations of the sample may be used as an indicator of dominant cracking regimes within the granite.

[0110] Stage I of Figure 2 is known as the elastic regime where the granite sample is able to accumulate energy without substantial nucleation or propagation of cracks. Without wishing to be bound by theory, the inventors posit that during this zone, ultrasonic energy is dissipated within the granite sample relatively effectively (as compared to zone II as discussed next). Within stage I the temperature curves increase in a generally linear manner due to the accumulation of energy.

[0111] Stage II of Figure 2 is the plastic regime. Within the plastic regime microcracks are nucleated in the rock. Without wishing to be bound by theory, the inventors posit that friction generated by motion of micro-crack surfaces generate significant heat as compared to heat accumulated in the granite sample from the ultrasonic energy. The heat generated by friction is significantly greater than that consumed by microcrack nucleation and propagation, leading to the temperature-time curve increasing rapidly in stage II compared to stage I.

[0112] Stage III is the failure regime. Within the failure regime the dominant cracking regime is granite undergoing failure wherein microcracks propagate and / or coalesce into macro cracks and macro-crack networks thereby fracturing the granite. Without wishing to be bound by theory, the inventors posit that the propagation of cracks and the fragmentation of rock particles consume significant energy as compared to the accumulated ultrasonic energy, causing sharp fluctuations in the temperature-time curves in Stage III.

[0113] Figure 2 shows that significant time is spent in the elastic regime (Stage I) and plastic regime (Stage II) prior to entering the failure regime (Stage III). In the case depicted in Figure 2, almost two minutes are required to induce the granite sample to fail usingultrasonic vibrations. The energy cost and time to induce failure within samples under ultrasonic excitation have reduced the applicability of ultrasonic methods to industrial mining operations.

[0114] Figure 3 depicts the uniaxial compressive strength (UCS) of a kimberlite sample as a function of applied microwave energy in kilo-Watt hours per ton of kimberlite for various microwave treatments.

[0115] The UCS of the kimberlite sample undergoing a 5 kW microwave treatment as shown by line 62 decreased from 75 MPa to approximately 63 MPa with the application of 200 kWh / t of microwave energy.

[0116] The UCS of the kimberlite sample undergoing a 10 kW microwave treatment as shown by line 64 decreased from 75 MPa to approximately 39 MPa with the application of approximately 134 kWh / t of microwave energy .

[0117] The UCS of the kimberlite sample undergoing a 15 kW microwave treatment as shown by line 66 decreased from 75 MPa to approximately 0 MPa with the application of approximately 119 kWh / t of microwave energy.

[0118] The application of microwave energy to reduce the strength of rock samples as shown in Figure 3 may be time and cost inefficient compared to conventional mining methods.

[0119] Figure 4 depicts a hybrid electromagnetic-ultrasonic mining apparatus 100 according to an example embodiment of the invention. Apparatus 100 may be used for in-situ fragmentation of a rock formation 10 of a mine. In-situ fragmentation may comprise a mining process applied to a working face of a rock formation that is still in formation - e.g. is in its natural state and / or has not been separated from surrounding rock. In the particular case of apparatus 100 (Figure 4), apparatus 100 may operate at a working face 12 of rock formation 10.

[0120] Apparatus 100 may be used for continuous fragmentation of a rock formation 10 of a mine. In some embodiments where apparatus 100 continuously fragments rock formation 10, apparatus 100 may be self-propelled or otherwise propelled by a suitable movement system (not shown) to continuously advance or move along working face 12. In some embodiments where apparatus 100 continuously fragments rock formation 10, apparatus100 may be connected to a vehicle or propulsion system (not shown in Figure 4) which moves apparatus 100 along working face 12. In some embodiments, depending on the shape of working face 12, apparatus 100 may be pivotable and / or translatable to move along working face 12.

[0121] Rock formation 10 may comprise a natural formation (or a portion of a natural formation) of rock which is being mined to extract ore and / or has not been separated from surrounding rock. Rock formation 10 may comprise one or more mineral deposits comprising valuable ore which may be desirable to liberate from rock formation 10.

[0122] Working face 12 of rock formation 10 may comprise an exposed face of rock formation 10 upon which mining operations to extract ore from the rock formation are performed.

[0123] Apparatus 100 comprises an ultrasonic horn 120. Ultrasonic horn 120 is movable against working face 12 to propagate ultrasonic energy 202 (Figure 12) into rock formation 10. Ultrasonic energy 202 propagated into rock formation 10 may comprise frequencies between 20 kHz and 2 MHz. Ultrasonic energy 202 propagated into rock formation 10 may comprise amplitudes between: 0.1 pm and 100 pm. Ultrasonic horn 120 may output between 10 W and 100 kW of power into rock formation 10. Ultrasonic horn 120 may propagate ultrasonic energy 202 into rock formation 10 by contacting a working face 12 of rock formation 10 (such contact is not expressly shown in Figure 4) and vibrating at an ultrasonic frequency. Vibrating may comprise repeated engagement and disengagement of ultrasonic horn 120 with working face 12. Ultrasonic horn 120 may extend in an axial direction 2. Ultrasonic horn 120 may be generally symmetric about its axis 2. Ultrasonic horn 120 may be configured to vibrate in directions parallel to its axis 2. Ultrasonic horn 120 may be configured to vibrate torsionally about axis 2. Ultrasonic horn 120 may be configured to vibrate both axially and torsionally. Ultrasonic horn 120 may be brought into contact with working face 12 such that its axis 2 is generally normal to working face 12, so that vibration of ultrasonic horn 120 propagates ultrasonic energy 202 (Figure 12) into rock formation 10. Ultrasonic horn 120 may be brought into contact with working face 12 such that its axis 2 is generally normal to working face 12, so that vibration of ultrasonic horn 120 in axial directions propagates ultrasonic energy 202 (Figure 12) into rock formation 10 in an axial direction 2 which is generally normal to working face 12.

[0124] An outer perimeter 120B of contact surface 120A of ultrasonic horn 120 that contacts working face 12 may define an outer footprint 124 on working face 12 of rock formation 10 (as shown in Figure 5) to be an area of working face 12 that is interior to where outer perimeter 120B contacts working face 12. Outer perimeter 120B may be the perimeter of contact surface 120A that is most transversely distal from axis 2, where transverse directions are generally orthogonal to axis 2.

[0125] An inner perimeter 120C of contact surface 120A of ultrasonic horn 120 that contacts working face 12 may define an inner footprint 128 on working face 12 of rock formation 10 (as shown in Figure 5) to be an area of working face 12 that is interior to where inner perimeter 120C contacts working face 12. Inner perimeter 120C may be the perimeter of contact surface 120A that is transversely closest to axis 2.

[0126] The movement of ultrasonic horn 120 against working face 12 may induce an ultrasonic induced stress field 138 within rock formation 10. Tensile stresses may be highest at working face 12. Specifically, tensile stresses may be highest within the area of footprint 128 on working face 12. Tensile stresses may generally decrease with axial distance from working face 12. Tensile stresses may generally decrease with transverse distance from axis 2.

[0127] An ultrasonically excited volume 134 may be defined as a volume comprising the regions of ultrasonic induced stress field 138 which have tensile stresses greater than 50% or 70% or 80% or 90% or 95% or 99% of a maximum tensile stress of ultrasonic induced stress field.

[0128] A fragmentation volume 154 may be a volume extending axially into rock formation 10 from footprint 124. In some embodiments, ultrasonically excited volume 134 may be within fragmentation volume 154. A working volume 156 may be a volume extending axially into rock formation 10 from footprint 128. In some embodiments, ultrasonically excited volume 134 may be within fragmentation volume 154. A compression volume 132 may be a volume extending axially into rock formation 10 from contact surface 120A, compression volume 132 may contain regions of stress field 138 which are in compression as described below.

[0129] Apparatus 100 comprises an electromagnetic applicator 122. Electromagnetic applicator 122 may comprise one or more waveguides, antennas and / or the like.Electromagnetic applicator 122 may comprise a microwave applicator. Electromagnetic applicator 122 may emit electromagnetic radiation 204 (Figure 12) that propagates into rock formation 10. Electromagnetic radiation 204 propagated into rock formation 10 may comprise frequencies in the range of 300 MHz to 300 GHz. Electromagnetic radiation 204 propagated into rock formation 10 may comprise power in the range of 100 W to 400 kW.

[0130] Electromagnetic applicator 122 may be shaped and / or located to emit electromagnetic radiation 204 such that a direction of maximum flux of the electromagnetic radiation 204 extends from electromagnetic applicator 122 to working face 12 and intersects working face 12 within footprint 124 and, in some embodiments, within footprint 128.Electromagnetic applicator 122 may be shaped and / or located to emit electromagnetic radiation 204 such that a direction of maximum flux of the electromagnetic radiation 204 is axial direction 2. Electromagnetic applicator 122 may be shaped and / or located such that a location of maximal flux 146 of the electromagnetic radiation 204 on the working face is within footprint 124 and, in some embodiments, within footprint 128. Electromagnetic applicator 122 may be shaped and / or located such that a location of maximal flux 146 of the electromagnetic radiation 204 on the working face is centered within footprint 128 (e.g. in the location of axis 2 as shown in Figure 5), but this is not necessary.

[0131] In embodiments where electromagnetic applicator 122 is a microwave applicator, electromagnetic applicator 122 may propagate microwave radiation into rock formation 10.

[0132] Electromagnetic applicator 122 may comprise a microwave lens. Microwave lens may allow an electromagnetic field distribution produced by electromagnetic applicator 122 to be adjusted.

[0133] Electromagnetic applicator 122 may create an electromagnetic field 172 within rock formation 10. Electromagnetic field 172 may be described in terms of electromagnetic power density field 174. Electromagnetic applicator 122 may be shaped and / or located such that electromagnetic radiation 204 of electromagnetic field 172 creates an irradiated volume 136 of rock formation 10. Irradiated volume 136 may comprise regions of electromagnetic power density field 174 wherein an electromagnetic power density is greater than 25% or 30% or 40% 50% or 70% or 80% or 90% or 95% or 99% or 99.9% or 99.99% of a maximum electromagnetic power density of electromagnetic power density field 174.

[0134] Figure 5 depicts footprint 124 on working face 12 of rock formation 10. An irradiated area 126 depicted within footprint 124 may be defined as an area where irradiated volume 136 intersects working face 12. In some embodiments irradiated area 126 may be the same as footprint 128.

[0135] In some embodiments, irradiated area 126 may be co-centric with footprint 124. In some embodiments, irradiated area 126 may be fully enclosed by footprint 124 or , in some embodiments, footprint 128. In some embodiments, irradiated area 126 may be fully enclosed by footprint 128. In some embodiments footprint 124 and irradiated area 126 may only partially overlap. In some embodiments footprint 124 and irradiated area 126 may be the same area.

[0136] The propagation of electromagnetic field 172 into rock formation 10 may heat rock formation 10.

[0137] Ultrasonic horn 120 may comprise a bore-defining surface 120D that is shaped to define a bore 120E. Bore-defining surface 120D (and bore 120E) may extend axially from contact surface 120A and at least partially through ultrasonic horn 120. Ultrasonic horn 120 comprising a bore 120E may be referred to herein a hollow ultrasonic horn. The intersection of bore defining surface 120D and contact surface 120A may define an opening 120F into bore 120E. Ultrasonic horn 120 comprising a contact surface 120A defining an opening 120F may be referred to herein an open-ended ultrasonic horn.

[0138] The inventors have determined that in the case of a hollow, open ended ultrasonic horn 120, tensile stresses are largest at working face 12 within footprint 128 and generally decreases with axial depth into rock formation 10. Tensile stresses have been determined to generally decrease with transverse distance from axis 2.

[0139] In embodiments where ultrasonic horn 120 is hollow, electromagnetic applicator 122 may be positioned within bore 120E of ultrasonic horn 120. Positioning electromagnetic applicator 122 within bore 120E may ensure that electromagnetic applicator 122 is located to emit electromagnetic radiation 204 such that a direction of maximum flux of the electromagnetic radiation 204 extends from electromagnetic applicator 122 to working face 12 and intersects working face 12 within footprint 124 and, in some embodiments, within footprint 128. In some embodiments, the direction of maximum flux is in an axial direction 2. Positioning electromagnetic applicator 122 within bore 120E may ensure thatelectromagnetic applicator 122 is located to emit electromagnetic radiation 204 such that a location of maximal flux 146 of the electromagnetic radiation 204 on the working face is within footprint 124 and, in some embodiments, within footprint 128. Positioning electromagnetic applicator 122 within bore 120E of ultrasonic horn 120 may ensure that irradiated volume 136 overlaps with ultrasonically excited volume 134. Ultrasonically excited volume 134 may overlap at least 50% or 60% or 70% or 80% or 90% of irradiated volume 136. Positioning electromagnetic applicator 122 within bore 120E of ultrasonic horn 120 may ensure that irradiated volume 136 is contained within ultrasonically excited volume 134. Ultrasonically excited volume 134 may contain at least 50% or 60% or 70% or 80% or 90% of irradiated volume 136 within ultrasonically excited volume 134. Positioning electromagnetic applicator 122 within bore 120E of ultrasonic horn 120 may ensure that a portion of a surface of irradiated volume 136 is a portion of a surface of ultrasonically excited volume 134. Positioning electromagnetic applicator 122 within bore 120E of ultrasonic horn 120 may ensure irradiated volume 136 is contiguous with ultrasonically excited volume 134. Positioning electromagnetic applicator 122 within bore 120E of ultrasonic horn 120 may ensure that irradiated volume 136 is contained within a volume defined by a transverse-most extent of, and axial-most extent of, ultrasonically excited volume 134.

[0140] Ultrasonic horn 120 may be formed from any suitably tough and / or strong material capable of withstanding stresses associated with pressing ultrasonic horn 120 against working face 12 and generating the ultrasonic energy 202 described herein without ultrasonic horn 120 failing. For example, ultrasonic horn 120 may be formed from tungsten carbide, titanium, various types of steel, other metals, ceramic-metal composite materials, metal alloys and / or the like.

[0141] Generally, suitable metals or ceramic-metal composite materials for ultrasonic horn 120 will block the transmission of microwave radiation through the body of horn (either from an exterior surface 120G of horn 120 into bore 120E or vice versa). A person of skill in the art will recognize that to locate irradiated area 126 within footprint 128, electromagnetic applicator 122 may be located to transmit electromagnetic radiation 204 within bore 120E. Were electromagnetic applicator 122 not located to transmit electromagnetic radiation 204 within bore 120E, ultrasonic horn 120 would prevent electromagnetic field 172 from extending into bore 120E and entering rock formation 10 through footprint 128. Wereelectromagnetic applicator 122 not located to transmit electromagnetic radiation 204 within bore 120E, ultrasonic horn 120 would prevent electromagnetic field 172 from having a location of maximal flux 146 of electromagnetic radiation 204 within footprint 124 and / or within footprint 128.

[0142] Further, a person skilled in the art will recognize that the penetration depth of microwave radiation into rock can be as low as several millimeters. Consequently, electromagnetic applicator 122 may be located and / or shaped to transmit microwave radiation within bore 120E to locate irradiated volume 136 within a fragmentation volume 154 extending axially into rock formation 10 from footprint 124. Were electromagnetic applicator 122 not located and / or shaped to transmit microwave radiation within bore 120E ultrasonic horn 120 would prevent electromagnetic field 172 from extending into bore 120E and through footprint 124, which combined with a low penetration depth of microwave radiation in rock formation 10 may prevent irradiated volume 136 from overlapping with fragmentation volume 154 and / or working volume 156.

[0143] Locating irradiated volume 136 within a fragmentation volume 154 and / or working volume 156 may allow irradiated volume 136 and ultrasonically excited volume 134 to at least partially overlap. Irradiated volume 136 and ultrasonically excited volume 134 at least partially overlapping may facilitate simultaneous applications of ultrasonic energy 202 and electromagnetic energy 204 to the same volume of rock formation 10. The inventors have determined that such simultaneous applications of ultrasonic energy 202 and electromagnetic energy 204 to the same volume of rock formation 10 fragments rock formation 10.

[0144] Figure 6A depicts a model 350 of tensile stresses in an ultrasonic induced stress field 138 in a 25cm x 25cm x 11cm rock formation 10 formed from basalt of the type that may be created by apparatus 100 (Figure 4) comprising a hollow, open ended ultrasonic horn with a footprint 128 having a diameter of 2.5 inches, in the absence of microwave radiation. Figure 6A depicts model 350 using contour lines. Apparatus 100 has been omitted from Figure 6A for clarity. Model 350 is positioned with axial direction 2 being in the Z direction 2 of a cartesian coordinate system. Rock formation 10 has been depicted sectioned in in the X-Z and Y-Z planes to show ultrasonic induced stress field 138 extending into rock formation 10.

[0145] In model 350, a compressed volume 132 of rock formation 10 extending axially into rock formation 10 from contact surface 120A (not shown) experiences compressive stress during operation of apparatus 100. A top surface 132A of compressed volume 132 conforms generally to the area of working face 12 contacted by contact surface 120A of apparatus 100 (i.e. shaded region 120A of Figure 5).

[0146] In model 350, working volume 156 extending axially into rock formation 10 from footprint 128 exhibits the largest tensile stresses induced within rock formation 10. Tensile stress within fragmentation volume 154 are highest at working surface 12 and generally decreases with axial depth into rock formation 10.

[0147] Ultrasonic induced stress field 138 depicted in Figure 6A is the stress field modeled as created within rock formation 10 formed from basalt. Rock formation 10 was modeled to be excited by a 30 kHz ultrasonic actuator equipped with a hollow ultrasonic horn 120 with a bore 120E having a circular cross-section, an internal diameter of 2.5 in and an external diameter of 3.5 in. Ultrasonic horn 120 was modeled to deliver 1500±35 W of ultrasonic power to footprint 124 over a duration of one second.

[0148] The maximum tensile stress experienced by rock formation 10 under the Figure 6A modeled conditions was approximately 12.6 MPa. The ultimate tensile strength of basalt is approximately 15 MPa. Consequently, model 350 indicates that ultrasonic treatment alone under the modeled conditions is insufficient to fragment a basalt rock formation 10.

[0149] Figure 6B depicts the same model 350 as Figure 6A, but without the contour lines and the contrast of the model increased to better depict the stress field within fragmentation volume 154.

[0150] Figure 7 is a plot of the elastic modulus of basalt under various microwave treatments.

[0151] Line 182 depicts the response of the modulus of elasticity of basalt over time when irradiated by microwave energy with a power density of 1.14 x 107W / m3. Line 184 depicts the response of the modulus of elasticity of basalt over time when irradiated by microwave energy with a power density of 2.68 x 107W / m3. Line 186 depicts the response of the modulus of elasticity of basalt over time when irradiated by microwave energy with a power density of 4.60 x 107W / m3. Line 188 depicts the response of the modulus of elasticity of basalt over time when irradiated by microwave energy with a power density of 9.58 x 107W / m3. Line 192 depicts the response of the modulus of elasticity of basalt over time when irradiated by microwave energy with a power density of 1.92 x 108W / m3.

[0152] As shown in Figure 7, the modulus of elasticity of rock (basalt in the case of Figure 7) decreases with the application of microwave radiation. In particular, higher power densities of microwave radiation reduce the modulus of elasticity of an irradiated rock to a greater degree than lower power densities of microwave radiation for the same cumulative microwave radiation absorbed by the irradiated rock.

[0153] As shown in Figure 7 the modulus of elasticity of untreated basalt is approximately 60 GPa. Absorption of approximately 51 kilowatt-hour per tonne (kWh / t) of microwave radiation reduces the modulus of elasticity of basalt to approximately the following values at each of the following microwave radiation power densities:

[0154] Figure 8A depicts a model 450 model 450 depicting an electromagnetic power density field 174 within a 25cm x 25cm x 11 cm rock formation 10 formed from basalt when irradiated for one second by microwave radiation of the type that may be created by electromagnetic applicator 122 (Figure 4) in the absence of ultrasonic energy 202. Figure 8A depicts how the power density of electromagnetic power density field 174 attenuates rapidly with axial and transverse distance from a location of maximal flux 146.

[0155] Figure 8B is an enlarged view of region 410 of Figure 8C.

[0156] Figure 8C is a model 400 depicting the modeled change in modulus of elasticity of a 25cm x 25cm x 11cm rock formation 10 formed from basalt when irradiated for one second by microwave radiation of the type that may be created by apparatus 100 (Figure 4) in theabsence of ultrasonic energy. Figure 8C depicts the modulus of elasticity using contour lines. Electromagnetic applicator 122 (in this case a microwave applicator) was shaped and located such that a location of maximal flux 146 of electromagnetic radiation 204 on working face 12 was within footprint 128. Apparatus 100 has been omitted from Figure 8A for clarity. Model 400 is positioned with axial direction 2 being in the Z direction 2 of a cartesian coordinate system. Rock formation 10 has been depicted sectioned in in the X-Z and Y-Z planes to show ultrasonic induced stress field 138 extending into rock formation 10.

[0157] As depicted in Figure 8C, an irradiated volume 136 of rock formation 10 irradiated by microwave radiation was modeled to undergo a reduction of the modulus of elasticity from about 60 GPa to below 1 GPa after a one second microwave treatment of 15kW. The modeled volume of Figure 8C within which the elastic modulus is reduced to less than 1 GPa corresponds generally to the contour line of 0.64 GW / m3in figures 8A and 8B. The modeled volume of Figure 8C within which the elastic modulus reduces appreciably below 60 GPa corresponds generally to the contour line of an electromagnetic power density of 0.46 GW / m3in figures 8A and 8B. As the maximum electromagnetic power density modeled in model 450 was an electromagnetic power density of 1.88 GW / m3, irradiated volume 136 of Figure 8C may be the volume within which the electromagnetic power density of electromagnetic power density field 174 is greater than approximately 25% of the maximum electromagnetic power density within rock formation 10.

[0158] Without intending to be bound by theory, the inventors posit that the high-intensity microwave radiation in irradiated volume 136 nucleates microcracks within irradiated volume 136. Such microcracks may be formed along grain boundaries within irradiated volume 136. Microcracks formed by brief microwave irradiation (e.g. irradiation of rock formation 10 for one second through footprint 128) may generally be isolated from each other.

[0159] Without intending to be bound by theory, the inventors posit that irradiating rock formation 10 through footprint 128 with microwave radiation causes high temperature zones within irradiated volume 136. Specifically, high temperature zones may be induced along grain boundaries, thereby inducing a plastic state at the grain boundaries.

[0160] Figure 8D depicts the same model 400 as Figure 8C, but with increased contrast and without the contour lines to more clearly show the relationship of irradiated volume 136 and footprint 128.

[0161] Figure 9A is a model 500 depicting the effect of spatiotemporally aligned applications of ultrasonic energy 202 and electromagnetic radiation 204 to a 25cm x 25cm x 11cm rock formation 10 as may be applied by apparatus 100 (Figure 4) comprising a hollow, open ended ultrasonic horn with a footprint 128 having a diameter of 2.5 inches. As used herein, spatiotemporally aligned refers to the simultaneous application of ultrasonic energy 202 and electromagnetic radiation 204 to overlapping volumes of rock formation 10. Apparatus 100 has been omitted from Figure 9A for clarity. Model 500 is positioned with axial direction 2 being in the Z direction 2 of a cartesian coordinate system. Rock formation 10 has been depicted sectioned in in the X-Z and Y-Z planes to show ultrasonic induced stress field 138 extending into rock formation 10. Figure 9A depicts ultrasonically induced stress field 138 within rock formation 10 using contour lines.

[0162] Fragmentation volume 154 extending into rock formation 10 from footprint 124 exhibits the highest tensile stresses within rock formation 10. Specifically, tensile stresses proximate to the surface of irradiated volume 136 created by the simultaneous application of ultrasonic energy 202 and electromagnetic energy 204 are amplified relative to tensile stresses created by ultrasonic energy 202 alone. In the Figure 9 model 500 fragmentation volume 154 experiences a maximum tensile stress of 16.2 MPa while in the Figure 6 Model 350 fragmentation volume 154 experiences a maximum tensile stress of 12.6 MPa. The simultaneous application of electromagnetic energy 204 and ultrasonic energy 202 resulted in a 28.6% increase in maximum tensile stress experienced by rick formation 10 within fragmentation volume 154. Compressed volume 132 extending axially into rock formation 10 from surface 132A exhibits the highest compressive stresses.

[0163] Model 500 depicts the simultaneous application of ultrasonic excitation of model 350 and the microwave irradiation of model 400 for one second. In model 500, the maximum tensile stress modeled within rock formation 10 was approximately 16.2 MPa. Since 16.2 MPa exceeds the ultimate tensile strength of basalt (approximately 15 MPa), rock formation 10 would fragment under the modeled conditions.

[0164] The inventors have found that applying spatiotemporally aligned electromagnetic radiation 204 and ultrasonic energy 202 to the same volumes of rock formation 10 at the same time effectively fragments rock formation 10.

[0165] The inventors have further found that applying spatiotemporally aligned electromagnetic radiation 204 and ultrasonic energy 202 fragments a volume of rock of the diameter of footprint 128 and a depth of at least a centimeter in less than a second.

[0166] Fragmentation of a portion of fragmentation volume 154 in less than a second may facilitate continuous mining of rock formation 10 wherein an apparatus 100 is continuously repositioned to fragment new regions of working face 12.

[0167] Without intending to be bound by theory, the inventors posit that microwave irradiation may introduce significant thermal gradients within rock formation 10 which in turn may cause stress in rock formation 10 and nucleate intergranular microcracks. Intergranular microcracks may be nucleated in a manner which is positively correlated with the magnitude of the thermal gradient introduced into rock formation 10 at any particular location.Intergranular microcracks may in turn weaken the rock formation 10. Microwave irradiation may induce a plastic state along grain boundaries within irradiated volume 136 and / or reduce the modulus of elasticity within irradiated volume 136. Ultrasonic energy 202 spatiotemporally aligned with the microwave radiation may then propagate microcracks formed by the microwave radiation and / or allow easier nucleation and propagation of microcracks within fragmentation volume 154 excited by ultrasonic energy 202. Microcracks propagated by spatiotemporally aligned ultrasonic and microwave radiation may coalesce to fragment rock formation 10. Coalescing of microcracks as used herein refers to the propagation of disconnected microcracks to form a network of connected cracks.

[0168] Figure 9B depicts the same model 500 as Figure 9A, but without the contour lines and with higher contrast to more clearly show ultrasonically induced stress field 138 within fragmentation volume 154.

[0169] Figure 10A depicts fragments 14 fragmented from rock formation 10 using apparatus 100. Fragments 14 have diameters of a few millimeters to less than several hundred microns. Fragments 14 produced using apparatus 100 are about the size of products produced by a tertiary crushing in a conventional mining process.

[0170] Fragmenting rock formation 10 using apparatus 100 may allow mine operations to omit some of the crushing steps conventionally performed after a conventional “drill-and-blast” mining process.

[0171] Figure 10B depicts fragments 16 fragmented from rock formation 10 using ultrasonic energy 202 without the application of electromagnetic energy 204. Fragments 16 have diameters ranging from several hundred microns to several centimeters (e.g. fragments 16-1 and 16-2). Fragments 16 produced using ultrasonic energy 202 without the application of electromagnetic energy 204 are on the order of the size of products produced by primary crushing in a conventional mining process.

[0172] Figure 11 is a particle size distribution chart plotting percent of particles passing through a sieve against the sieve size under various treatments. Fragments 14 produced using an ultrasonic horn 120 and an electromagnetic application 122 exhibit a dso diameter of approximately 800 pm as indicated by line 194. Fragments 16 produced using an ultrasonic horn 120 without the use of electromagnetic applicator 122 exhibit a dso diameter of approximately 11 mm, as indicated by line 196, over an order of magnitude larger than the dso of fragments 14. Microwave irradiation alone applied by electromagnetic applicator 122 , failed to fragment the rock formation as indicated by point 198.

[0173] Returning to Figure 4, apparatus 100 may comprise an electromagnetic (“EM”) power generator 110. EM power generator 110 may provide power to electromagnetic applicator 122. EM power generator 110 may operate at a single frequency in the range of 300 MHz to 300 GHz. EM power generator 110 may operate at variable frequencies in the range of 300 MHz to 300 GHz. EM power generator 110 may operate at a fixed power level. EM power generator 110 may operate at variable power levels. EM power generator 110 may operate in a continuous mode. EM power generator 110 may operate in a pulsing mode. EM power generator 110 may generate electromagnetic radiation 204 which may be conveyed to electromagnetic applicator 122 by a waveguide. EM power generator 110 may include an EM tuner. The EM tuner may tune the electromagnetic radiation 204 applied by electromagnetic applicator 122 to apply a desired frequency of electromagnetic radiation 204 and / or a desired power of electromagnetic radiation 204. EM power generator 110 may comprise a reflection sensor. A reflection sensor may measure electromagnetic radiation 204 reflected back to apparatus 100 from rock formation 10. The reflection sensor and / or other suitable sensors may monitor the susceptibility of rock formation 10 to microwaveirradiation and / or may be used to provide feedback to a suitable control system which may comprise a suitably configured processor (not expressly shown in Figure 4) and may be used to control EM power generator 110 and / or the EM tuner (e.g. to control corresponding EM power, frequency and / or the like) based on feedback from such sensors.

[0174] Apparatus 100 may comprise an ultrasonic generator 130. Ultrasonic generator 130 may power ultrasonic horn 120. Apparatus 100 may comprise an ultrasonic transducer 140. Ultrasonic transducer 140 may convert electrical energy produced by ultrasonic generator 130 into mechanical vibrations in the range of 20 kHz to 2 MHz. In some non-limiting embodiments, ultrasonic transducer 140 comprises a piezoelectric transducer. Mechanical vibrations produced by ultrasonic transducer 140 may be conducted into ultrasonic horn 120 for application to rock formation 10. Apparatus 100 may comprise an ultrasonic amplifier 150. Ultrasonic amplifier 150 may amplify energy transmitted to ultrasonic transducer 140. Ultrasonic amplifier 150 may amplify vibrations transmitted from ultrasonic transducer 140 to ultrasonic horn 120.

[0175] Apparatus 100 may comprise a control system 160 (depicted in Figure 14) for controlling apparatus 100. Control system 160 may adjust operational parameters of electromagnetic and / or ultrasonic excitations (for example, sequence, duration, power, amplitude, frequencies, contact force (pressure), etc.). Control system 160 may comprise active configurations. Active configurations may incorporate one or more feedback control loop(s) for real-time adjustment of electromagnetic and / or ultrasonic excitations. Control system 160 may be adaptable to integrate feedback loops for temperature sensing, vibration sensing, electromagnetic sensing and / or other types of sensors for sensing other parameters. Feedback loops for temperature sensing, vibration sensing, electromagnetic sensing, and / or other types of sensing may allow for adjustments to the operational parameters of ultrasound transmission (e.g. via control of ultrasonic generator 130 and / or ultrasonic amplifier 150) and / or electromagnetic transmission (e.g. via control of EM power generator 110 and / or the EM tuner) based on real-time environmental and / or system conditions. Feedback control of electromagnetic applicator 122 may comprise measurements of reflected power. Feedback control of ultrasonic horn 120 may comprise measurements of power, amplitude and / or frequency of output ultrasonic energy 202.Control system 160 may comprise passive configurations. Passive configurations may be useful where no feedback control loops are available.

[0176] Control system 160 may be implemented by, or may otherwise comprise, one or more programmable data processors suitably configured using applicable software.

[0177] Control system 160 may additionally or alternatively use data received from sensor(s) 162A, 162B...162N (collectively sensors 162) to control apparatus 100 via control module(s) 164A, 164B ... 164N (collectively and individually, control modules 164). Although shown separately in Figure 14, control modules 164 may be implemented in whole or part by controller 168. Sensors 162 may sense for example power, amplitude and / or frequency of output ultrasonic energy 202, temperature or vibration of rock formation 10, reflected electromagnetic power or any other measurable parameter as may be applicable to the control of apparatus 100. Sensors 162 may be configured for machine vision. Specifically, control modules 164 receive commands from controller 168 and use various forms of communications interface(s) and protocol(s) to provide particular commands to apparatus 100 to thereby control or otherwise interact with apparatus 100. By way of non-limiting example, control modules 164 may comprise Bluetooth communications protocols, USB dongles, LAN communications interfaces, WiFi communications interfaces, data communication protocols / means (e.g. serial com interfaces) and / or the like. In some embodiments, some or all of control modules 164 may be implemented in whole or in part by controller 160.

[0178] Control system 160 comprises one or more processing units 166. Control system 160 processes data obtained by sensors 162 and based on this information, control system 160 may send commands to one or more of ultrasonic horn 120, electromagnetic applicator 122, EM power generator 110, EM tuner, ultrasonic generator 130, ultrasonic transducer 140 and / or ultrasonic amplifier 150 via appropriate control module(s) 164.

[0179] Control modules 164 interface with one or more of ultrasonic horn 120, electromagnetic applicator 122, EM power generator 110, ultrasonic generator 130, ultrasonic transducer 140 and / or ultrasonic amplifier 150 to pass on commands from controller 168. Specifically, control modules 164 may receive electronic commands from controller 168 via any suitable wired or wireless communication protocol, translate such commands into specific control signals corresponding to one or more of ultrasonic horn 120, electromagnetic applicator 122, EM power generator 110, EM tuner, ultrasonic generator 130, ultrasonic transducer 140 and / or ultrasonic amplifier 150 and communicate these specific control commands to one or more of ultrasonic horn 120, electromagnetic applicator122, EM power generator 110, ultrasonic generator 130, ultrasonic transducer 140 and / or ultrasonic amplifier 150.

[0180] One or more components of control system 160 may be located remotely from apparatus 100. For example controller 168 may be located in a control room and communicate wirelessly with sensors 162 and / or control modules 164.

[0181] Referring back to Figure 4, apparatus 100 may comprise a backforce mechanism 170. Backforce mechanism 170 may apply a force to ultrasonic horn 120 to maintain a contact force between rock formation 10 and ultrasonic horn 120. Backforce mechanism 170 may facilitate advancement (e.g. in axial direction 2) of apparatus 100 into rock formation 10 as rock formation 10 is fragmented by apparatus 100. Backforce mechanism 170 may actively apply a mechanical force (e.g. hydraulic, pneumatic, electric motor or electromagnetic) which force may be regulated or controlled by a suitable control system (not shown). In some embodiments, control system 160 described above, may incorporate suitable functionality to control backforce mechanism 170. Backforce mechanism 170 may passively apply a non-regulated load (e.g., using a deadweight, spring, or other passive loading mechanisms).

[0182] Apparatus 100 may comprise a propulsion system 190. Propulsion system 190 may facilitate movement of apparatus 100. Propulsion system 190 may facilitate the advancement (e.g. in axial direction 2) of apparatus 100 into rock formation 10 as rock formation 10 is fragmented by apparatus 100. Propulsion system 190 may facilitate the pivotal movement and / or translational movement of apparatus 100 to facilitate movement of apparatus 100 along working surface 12 of rock formation 10. Propulsion system 190 may facilitate the repositioning of apparatus 100. Propulsion system 190 may comprise one or more of tires, treads, rollers. Propulsion system 190 may comprise a vehicle.

[0183] Apparatus 100 may be propelled by one or more of backforce mechanism 170 and / or propulsion system 190 at a speed of up to 0.1 m / s or 0.2m / s or 0.5m / s along working face 12 while (at the same time as) actively fragmenting rock formation 10 by propagating ultrasonic energy and electromagnetic energy into rock formation 10.

[0184] Apparatus 100 may comprise a debris removal system 180. Debris removal system 180 may remove fragments 14 and any other debris from rock formation 10. Debris removal system 180 may comprise a vacuum system for vacuuming debris away from rockformation 10. Debris removal system may comprise a sweeping system for sweeping debris away from rock formation 10. In some embodiments, the debris removal system may collect fragments 14 to be conveyed away from working face 12. Debris removal system 180 may remove fragments and / or any other debris from rock formation 10 while (at the same time as) actively fragmenting rock formation 10 by propagating ultrasonic energy and electromagnetic energy into rock formation 10.

[0185] Figure 12 depicts an exemplary method 200 of using apparatus 100 for in situ fragmentation of rock formation 10 according to a particular embodiment. Method 200 begins with energy application step 210. Ultrasonic energy 202 and electromagnetic radiation 204 are applied simultaneously to overlapping volumes (e.g. ultrasonically excited volume 134 and irradiated volume 136) of rock formation 10.

[0186] One or more of electromagnetic radiation 204 and ultrasonic energy 202 may be pulsed as notionally depicted in optional step 220. Electromagnetic radiation 204 and ultrasonic energy 202 may be pulsed at any frequency as appropriate to fragment rock formation 10. Electromagnetic radiation 204 and ultrasonic energy 202 may be pulsed with a period between 2 ps and 128 ms and a pulse width of 1 ps and 65 ms.

[0187] In some embodiments, an expected material response to ultrasonic energy 202 may optionally be determined at step 230 (e.g. based on sensor feedback, suitable modelling and / or the like). Without limitation, material response determined at step 230 may comprise a frequency response (e.g. indicative of a resonance frequency), the expected strength, elastic modulus and / or the like of rock formation 10 within one or more of ultrasonically excited volume 134, fragmentation volume 154 and compressed volume 132.

[0188] In some embodiments, a material response to electromagnetic radiation 204 may be determined at step 240 (e.g. based on sensor feedback, suitable modelling and / or the like). Without limitation, material response determined in block 240 may comprise one or more of surface temperature, absorbed thermal energy, microwave efficiency, microwave power or intensity, and / or the like.

[0189] In some embodiments, the application of ultrasonic energy 202 may be modified, at step 250, based on the material response determined at one or both of optional steps 230, 240.

[0190] In some embodiments, the application of electromagnetic radiation 204 may be modified, at step 260, based on the material response determined at one or both of optional steps 230, 240.

[0191] The spatiotemporally aligned application of ultrasonic energy 202 and electromagnetic radiation 204 to rock formation 10 in step 210 fragments rock formation 10 into fragments 14 at step 270.

[0192] Fragments 14 may be characterized by a dso of less than 1 mm or less than 800 pm or less than 600 pm or less than 400 pm.

[0193] Apparatus 100 may be moved along working face 12 of rock formation by propulsion system 190 at step 280. The step 280 movement along working face 12 may comprise translational movement and / or pivotal movement as described elsewhere herein. In some embodiments, apparatus 100 may be moved along working face 12 of rock formation 10 by propulsion system 190 concurrently to fragmenting rock formation 10 in step 210. In some embodiments, apparatus 100 may be continuously moved along working face 12 of rock formation 10 by propulsion system while simultaneously continuously fragmenting rock formation 10 in step 210.

[0194] Figure 13 depicts an exemplary mining process 600 incorporating the use of apparatus 100 according to a particular example embodiment. Process 600 begins with excavation step 610. Step 610 comprises in-situ fragmentation of rock formation 10 of a mine using apparatus 100. Step 610 may comprise continuous motion of apparatus 100 relative to rock formation 10. Continuous motion of apparatus 100 may comprise pivotal and / or translational motion of apparatus 100 along working face 12 of rock formation 120 and / or motion in an axial direction as rock formation 10 is fragmented.

[0195] Step 610 may fragment rock formation 10 to generate fragments 14 of rock formation with dso diameters of less than 1mm, or less than 800 pm, or less than 600 pm, or less than 400 pm.

[0196] Excavated fragments 14 may then be conveyed away from rock formation 10 at material handling step 620. In some non-limiting embodiments, fragments 14 may be suitably conveyed in step 620 by electronic conveyors. Electronic conveyors generally are suitable for fragments with a dso size on the order of centimeters or less. Conventional “drill-and-blast” mining methods typically produce ore on the scale of tens of centimeters tometers which necessitates haul trucks to move the blasted ore away from rock formation 10. Mitigating the need for haul trucks may reduce material handling costs of a mining operation as electric conveyors may be less expensive to operate than haul trucks.Mitigating the need for haul trucks may improve air quality in mines as diesel fumes may be a significant contributor to poor air quality in some mines. Mitigating the need for haul trucks may reduce the need for air purification systems which may in turn reduce air purification costs.

[0197] Method 600 may proceed to comminution step 630. Comminution step 630 may comprise milling fragments 14 to a dso diameter appropriate for beneficiation of the particular ore being mined. In some embodiments comminution step 630 may comprise milling fragments 14 to a dso diameter of 25 pm or less. In some embodiments milling fragments 14 may comprise stirred milling.

[0198] After performing any necessary comminution at step 630 process 600 may proceed to any known beneficiation process as shown as step 640 of process 600.

[0199] While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are consistent with the broadest interpretation of the specification as a whole. For example, Figure 15 depicts a hybrid electromagnetic-ultrasonic mining apparatus 300 similar to apparatus 100 described above, except that ultrasonic horn 120 and electromagnetic applicator 122 are combined into a single applicator 320. Applicator 320 comprises an ultrasonic horn 120 with a bore defining surface 120D where bore defining surface 120D is at least a portion of a waveguide of electromagnetic application 122.Interpretation of Terms

[0200] Where a component (e.g. a temperature sensor, a ultrasonic transducer, a ultrasonic horn, etc.) is referred to herein, unless otherwise indicated, reference to that component (including a reference to a “means”) should be interpreted as including as equivalents of that component any component which performs the function of the described component(i.e. , that is functionally equivalent), including components which are not structurally equivalent to the disclosed structure which performs the function in the illustrated exemplary embodiments of the present technology.

[0201] Unless the context clearly requires otherwise, throughout the description and the claims:• “comprise”, “comprising”, and the like are to be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”;• “connected”, “coupled”, or any variant thereof, means any connection or coupling, either direct or indirect, between two or more elements; the coupling or connection between the elements can be physical, logical, or a combination thereof;• “herein”, “above”, “below”, and words of similar import, when used to describe this specification, shall refer to this specification as a whole, and not to any particular portions of this specification;• “or”, in reference to a list of two or more items, covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list;• the singular forms “a”, “an”, and “the” also include the meaning of any appropriate plural forms. These terms (“a”, “an”, and “the”) mean one or more unless stated otherwise;• “and / or” is used to indicate one or both stated cases may occur, for example A and / or B includes both (A and B) and (A or B);• “approximately” when applied to a numerical value means the numerical value ± 10%;• where a feature is described as being “optional” or “optionally” present or described as being present “in some embodiments” it is intended that the present disclosure encompasses embodiments where that feature is present and other embodiments where that feature is not necessarily present and other embodiments where that feature is excluded. Further, where any combination of features is described in this application this statement is intended to serve as antecedent basis for the use of exclusive terminology such as "solely," "only" and the like in relation to thecombination of features as well as the use of "negative" limitation(s)” to exclude the presence of other features; and• “first” and “second” are used for descriptive purposes and cannot be understood as indicating or implying relative importance or indicating the number of indicated technical features.

[0202] Words that indicate directions such as “vertical”, “transverse”, “horizontal”, “upward”, “downward”, “forward”, “backward”, “inward”, “outward”, “left”, “right”, “front”, “back”, “top”, “bottom”, “below”, “above”, “under”, and the like, used in this description and any accompanying claims (where present), depend on the specific orientation of the apparatus described and illustrated. The subject matter described herein may assume various alternative orientations. Accordingly, these directional terms are not strictly defined and should not be interpreted narrowly.

[0203] Where a range for a value is stated, the stated range includes all sub-ranges of the range. It is intended that the statement of a range supports the value being at an endpoint of the range as well as at any intervening value to the tenth of the unit of the lower limit of the range, as well as any subrange or sets of sub ranges of the range unless the context clearly dictates otherwise or any portion(s) of the stated range is specifically excluded. Where the stated range includes one or both endpoints of the range, ranges excluding either or both of those included endpoints are also included in the invention.

[0204] Certain numerical values described herein are preceded by "about". In this context, "about" provides literal support for the exact numerical value that it precedes, the exact numerical value ±5%, as well as all other numerical values that are near to or approximately equal to that numerical value. Unless otherwise indicated a particular numerical value is included in “about” a specifically recited numerical value where the particular numerical value provides the substantial equivalent of the specifically recited numerical value in the context in which the specifically recited numerical value is presented. For example, a statement that something has the numerical value of “about 10” is to be interpreted as: the set of statements:• in some embodiments the numerical value is 10;• in some embodiments the numerical value is in the range of 9.5 to 10.5;and if from the context the person of ordinary skill in the art would understand that values within a certain range are substantially equivalent to 10 because the values with the rangewould be understood to provide substantially the same result as the value 10 then “about 10” also includes:• in some embodiments the numerical value is in the range of C to D where C and D are respectively lower and upper endpoints of the range that encompasses all of those values that provide a substantial equivalent to the value 10.

[0205] Specific examples of systems, methods and apparatus have been described herein for purposes of illustration. These are only examples. The technology provided herein can be applied to systems other than the example systems described above. Many alterations, modifications, additions, omissions, and permutations are possible within the practice of this invention. This invention includes variations on described embodiments that would be apparent to the skilled addressee, including variations obtained by: replacing features, elements and / or acts with equivalent features, elements and / or acts; mixing and matching of features, elements and / or acts from different embodiments; combining features, elements and / or acts from embodiments as described herein with features, elements and / or acts of other technology; and / or omitting combining features, elements and / or acts from described embodiments.

[0206] As will be apparent to those of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any other described embodiment(s) without departing from the scope of the present invention.

[0207] Any aspects described above in reference to apparatus may also apply to methods and vice versa.

[0208] Any recited method can be carried out in the order of events recited or in any other order which is logically possible. For example, while processes or blocks are presented in a given order, alternative examples may perform routines having steps, or employ systems having blocks, in a different order, and some processes or blocks may be deleted, moved, added, subdivided, combined, and / or modified to provide alternative or subcombinations. Each of these processes or blocks may be implemented in a variety of different ways. Also, while processes or blocks are at times shown as being performed in series, these processes or blocks may instead be performed in parallel, simultaneously or at different times.

[0209] Various features are described herein as being present in “some embodiments”. Such features are not mandatory and may not be present in all embodiments. Embodimentsof the invention may include zero, any one or any combination of two or more of such features. All possible combinations of such features are contemplated by this disclosure even where such features are shown in different drawings and / or described in different sections or paragraphs. This is limited only to the extent that certain ones of such features are incompatible with other ones of such features in the sense that it would be impossible for a person of ordinary skill in the art to construct a practical embodiment that combines such incompatible features. Consequently, the description that “some embodiments” possess feature A and “some embodiments” possess feature B should be interpreted as an express indication that the inventors also contemplate embodiments which combine features A and B (unless the description states otherwise or features A and B are fundamentally incompatible).This is the case even if features A and B are illustrated in different drawings and / or mentioned in different paragraphs, sections or sentences.

[0210] It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions, omissions, and sub-combinations as may reasonably be inferred. The scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.

Claims

CLAIMS:

1. An apparatus for in situ fragmentation of a rock formation, the apparatus comprising:an ultrasonic horn comprising a contact surface that contacts a working face of the rock formation, a perimeter of the contact surface defining an outer footprint of the ultrasonic horn on the working face, the ultrasonic horn moveable against the working face to thereby propagate ultrasonic energy into the rock formation;an electromagnetic applicator for emitting electromagnetic radiation into the rock formation, the electromagnetic applicator shaped and / or located such that a location of maximal flux of the electromagnetic radiation on the working face is within the outer footprint.

2. The apparatus of claim 1 or any other claim herein wherein the electromagnetic applicator is shaped to emit the electromagnetic radiation such that the electromagnetic radiation has a direction of maximum flux extending from the electromagnetic applicator to the working face and intersecting the working face within the outer footprint.

3. The apparatus of any one of claims 1 to 2, or any other claim herein, wherein the ultrasonic horn is moveable against the working face in an axial direction normal to the working face to thereby propagate ultrasonic energy into the rock formation in the axial direction and wherein, optionally, the horn is also moveable in one or more angular directions about the axial direction.

4. The apparatus of claim 3, or any other claim herein, wherein the electromagnetic applicator is shaped and / or located to propagate electromagnetic radiation into a fragmentation volume of the rock formation, the fragmentation volume being a volume of the rock formation extending into the rock formation in the axial direction from the outer footprint of the ultrasonic horn.

5. The apparatus of any one of claims 3 to 4, or any other claim herein, wherein the ultrasonic horn comprises a bore-defining surface which defines a bore that extends in the axial direction at least partially through the ultrasonic horn.

6. The apparatus of claim 5 wherein the ultrasonic horn comprises a contact surface for contacting the rock formation, the contact surface defining an opening into the bore.

7. The apparatus of any one of claims 5 to 6, or any other claim herein, wherein at least a portion of the electromagnetic applicator from which the electromagnetic radiation is emitted is located inside the bore.

8. The apparatus of claim 7, or any other claim herein, wherein:the bore defining surface comprises a bore defining surface cross-section in a cross-sectional plane orthogonal to the axial direction;the at least a portion of the electromagnetic applicator comprises an electromagnetic applicator cross-section in the cross-sectional plane; andthe bore defining surface cross-section surrounds the electromagnetic applicator cross-section.

9. The apparatus of any one of claims 1 to 8, or any other claim herein, wherein the electromagnetic applicator comprises a waveguide.

10. The apparatus of any one of claims 5 to 8, or any other claim herein, wherein the electromagnetic applicator comprises a waveguide, and a portion of the waveguide comprises a portion of the bore defining surface.

11. The apparatus of any one of claims 1 to 10 wherein the ultrasonic horn and the electromagnetic applicator are operative to simultaneously propagate the ultrasonic energy and the electromagnetic energy into the rock formation.

12. The apparatus of any one of claims 1 to 11 , or any other claim herein, comprising a debris removal system for removing debris from the working face.

13. The apparatus of claim 12, or any other claim herein, wherein the debris removal system is operative to remove debris while (e.g. at the same time as) the ultrasonic horn propagates the ultrasonic energy into the rock formation, and the electromagnetic applicator emits the electromagnetic radiation into the rock formation.

14. The apparatus of any one of claims 12 to 13, or any other claim herein, wherein the debris removal system comprises a collection system for collecting fragments fragmented by the apparatus from the rock formation.

15. The apparatus of any one of claims 3 to 14, or any other claim herein, comprising a backforce mechanism connected to the ultrasonic horn to apply a force to the ultrasonic horn, the force comprising a directional component in the axial direction.

16. The apparatus of any one of claims 1 to 15, or any other claim herein, wherein the electromagnetic applicator is a microwave applicator.

17. The apparatus of any one of claims 3 to 16, or any other claim herein, comprising a propulsion system connected to move the apparatus relative to the working face while (e.g. at the same time as) the apparatus is fragmenting the rock formation (e.g. by the ultrasonic horn propagating the ultrasonic energy into the rock formation and the electromagnetic applicator emitting the electromagnetic radiation into the rock formation).

18. The apparatus of claim 17, or any other claim herein, wherein the propulsion system is connected to move the apparatus in the axial direction while the apparatus is fragmenting the rock formation.

19. The apparatus of any one of claims 17 to 18, or any other claim herein, wherein the propulsion system is connected to move the apparatus in a transverse direction having at least a component that is orthogonal to the axial direction while the apparatus is fragmenting the rock formation.

20. The apparatus of any one of claims 17 to 19, or any other claim herein, wherein the propulsion system is connected to pivot the apparatus (e.g. the ultrasonic horn and the electromagnetic applicator) relative to the rock formation while the apparatus is fragmenting the rock formation.

21. The apparatus of any one of claims 1 to 20, or any other claim herein, whereinthe ultrasonic energy creates a stress field within the rock formation, wherein an ultrasonically excited volume of the rock formation comprises regions of the stress field having a tensile stress greater than 70% of a maximum tensile stress of the stress field; the electromagnetic applicator is shaped and / or located such that the electromagnetic radiation creates an irradiated volume of the rock formation wherein an electromagnetic power density of an electromagnetic field created by the electromagnetic applicator in the irradiated volume is greater than 25% of a maximum electromagnetic power density of the electromagnetic field; andthe irradiated volume is contiguous with the ultrasonically excited volume.

22. The apparatus of any one of claims 1 to 20, or any other claim herein, wherein the ultrasonic energy creates a stress field within the rock formation, wherein an ultrasonically excited volume of the rock formation comprises regions of the stress field having a tensile stress greater than 70% of a maximum tensile stress of the stress field; the electromagnetic applicator is shaped and / or located such that the electromagnetic radiation creates an irradiated volume of the rock formation wherein an electromagnetic power density of an electromagnetic field created by the electromagnetic applicator in the irradiated volume is greater than 25% of a maximum electromagnetic power density of the electromagnetic field; andthe irradiated volume overlaps with the ultrasonically excited volume.

23. The apparatus of any one of claims 1 to 20, or any other claim herein, wherein the ultrasonic energy creates a stress field within the rock formation, wherein an ultrasonically excited volume of the rock formation comprises regions of the stress field having a tensile stress greater than 70% of a maximum tensile stress of the stress field; the electromagnetic applicator is shaped and / or located such that the electromagnetic radiation creates an irradiated volume of the rock formation wherein an electromagnetic power density of an electromagnetic field created by the electromagnetic applicator in the irradiated volume is greater than 25% of a maximum electromagnetic power density of the electromagnetic field; andthe irradiated volume is contained within a volume defined by a transverse-most extent of and axial-most extent of the ultrasonically excited volume.

24. The apparatus of any one of claims 21 to 23, or any other claim herein, wherein the ultrasonically excited volume of the rock formation comprises regions of the stress field comprising tensile stress greater than 80% of the maximum tensile stress of the stress field or, optionally, greater than 90% of the maximum tensile stress of the stress field.

25. The apparatus of claim any one of claims 21 to 24, or any other claim herein, wherein the irradiated volume of the rock formation comprises regions of the electromagnetic field comprising an electromagnetic power density greater than 50% of the maximum electromagnetic power density of the electromagnetic field or, optionally, greater than 80% of the maximum electromagnetic power density of the electromagnetic field, or, further optionally, greater than 90% of the maximum electromagnetic power density of the electromagnetic field or, still further optionally, greater than 99% of the maximum electromagnetic power density of the electromagnetic field or, still further optionally, greater than 99.9% of the maximum electromagnetic power density of the electromagnetic field.

26. The apparatus of any one of claims 1 to 25, or any other claim herein comprising an ultrasonic transducer coupled to the ultrasonic horn to move the ultrasonic horn and thereby propagate the ultrasonic energy into the rock formation.

27. The apparatus of any one of claims 1 to 26, or any other claim herein, wherein the ultrasonic energy creates a stress field within the rock formation, wherein an ultrasonically excited volume of the rock formation comprises regions of the stress field having a tensile stress greater than 50% of a maximum tensile stress of the stress field; the electromagnetic applicator is shaped and / or located such that the electromagnetic radiation creates an irradiated volume of the rock formation wherein an electromagnetic power density of an electromagnetic field created by the electromagnetic applicator in the irradiated volume is greater than 50% of a maximum electromagnetic power density of the electromagnetic field; andthe ultrasonically excited volume overlaps the irradiated volume.

28. The apparatus of any one of claims 1 to 27 wherein the electromagnetic applicator is shaped and / or located such that a direction of maximal flux of the electromagnetic radiation is orthogonal to the working face is within the outer footprint.

29. A method of in situ fragmentation of a rock formation, the method comprising: propagating ultrasonic energy into the rock formation through a first area of a working face of the rock formation;simultaneously propagating electromagnetic radiation into the rock formation through the working face, wherein a location of maximal flux of the electromagnetic radiation on the working face is within the first area; andwherein simultaneously propagating the electromagnetic radiation and the ultrasonic energy into the rock formation induces fragmentation of a portion of the rock formation into a plurality of fragments.

30. The method of claim 29, or any other claim herein, wherein propagating the electromagnetic radiation comprises emitting the electromagnetic radiation from an electromagnetic applicator such that that the electromagnetic radiation has a direction of maximum flux extending from the electromagnetic applicator to the working face and intersecting the working face within the first area.

31. The method of any one of claims 29 to 30, or any other claim herein, wherein the first area is defined by a perimeter of a contact surface of an ultrasonic horn, the contact surface contacting a working face of the rock formation32. The method of any one of claims 29 to 31 , or any other claim herein, wherein propagating the ultrasonic energy into the rock formation comprises propagating the ultrasonic energy in an axial direction normal to the working face, or, optionally, in the axial direction and an angular direction about the axial direction.

33. The method of any one of claims 29 to 32, or any other claim herein, wherein propagating the electromagnetic radiation into the rock formation comprises propagating the electromagnetic radiation into a fragmentation volume of the rock formation, the fragmentation volume being a volume of the rock formation projecting axially into the rock formation from the first area.

34. The method of any one of claims 29 to 33, or any other claim herein, wherein the plurality of fragments have a dso of 1 mm or less, or, optionally, 800 pm or less, or, further optionally, 600 pm or less, or, still further optionally 500 pm or less or, yet still further optionally, 400 pm or less.

35. The method of any one of claims 29 to 34, or any other claim herein, comprising conveying the plurality of fragments away from the rock formation.

36. The method of claim 35, or any other claim herein, comprising simultaneously: propagating the electromagnetic radiation into the rock formation; propagating the ultrasonic energy into the rock formation; and conveying the plurality of fragments away from the rock formation.

37. The method of any one of claims 29 to 36, or any other claim herein, comprising moving, relative to the working face, an apparatus for performing the method of claim 30 simultaneously with propagating the electromagnetic radiation into the rock formation and propagating the ultrasonic energy into the rock formation.

38. The method of claim 37, or any other claim herein, wherein moving the apparatus relative to the working face, comprises advancing the apparatus in an axial direction orthogonal to the working face.

39. The method of any one of claims 37 to 38, or any other claim herein, wherein moving the apparatus relative to the working face, comprises moving the apparatus in a transverse direction having at least a component that is orthogonal to the axial direction.

40. The method of any one of claims 37 to 39, or any other claim herein, wherein moving the apparatus relative to the working face, comprises pivotal movement of the apparatus (e.g. about one or more pivot axes) relative to the rock formation.

41. The method of any one of claims 29 to 40, or any other claim herein, wherein propagating the electromagnetic radiation into the rock formation comprises propagating the electromagnetic radiation into the rock formation continuously.

42. The method of any one of claims 29 to 41 , or any other claim herein, wherein propagating the electromagnetic radiation into the rock formation comprises propagating the electromagnetic radiation into the rock formation in pulses.

43. The method of any one of claims 29 to 42, or any other claim herein, wherein propagating the electromagnetic radiation into the rock formation comprises propagating the electromagnetic radiation into the rock formation until intergranular microcracks are nucleated in the rock formation.

44. The method of claim 42, or any other claim herein, wherein propagating the electromagnetic radiation into the rock formation in pulses comprises propagating the electromagnetic radiation into the rock formation in pulses comprising a pulse width of one second or less.

45. The method of any one of claims 29 to 44, or any other claim herein, wherein propagating ultrasonic energy into the rock formation comprises propagating the ultrasonic energy into the rock formation continuously.

46. The method of any one of claims 29 to 44, or any other claim herein, wherein propagating ultrasonic energy into the rock formation comprises propagating the ultrasonic energy into the rock formation in pulses.

47. The method of claim 43, or any other claim herein, wherein propagating ultrasonic energy into the rock formation comprises propagating ultrasonic energy into the rock formation until the ultrasonic energy propagates the intergranular microcracks nucleated by the electromagnetic radiation to coalesce the microcracks and thereby fracture the rock formation.

48. The method of claim 46, or any other claim herein, wherein propagating the ultrasonic energy into the rock formation in pulses comprises propagating the ultrasonic energy into the rock formation in pulses comprising a pulse width of 1 second or less.

49. The method of any one of claims 29 to 48, or any other claim herein, wherein the ultrasonic energy is applied in a range of 20 kHz to 2 MHz.

50. The method of any one of claims 29 to 49, or any other claim herein, comprising varying a frequency of the ultrasonic energy based on a material response to propagating the ultrasonic energy into the rock formation to identify a resonance mode and wherein propagating the ultrasonic energy into the rock formation comprises propagating the ultrasonic energy at a frequency corresponding to the resonance mode.

51. The method of claim 50, or any other claim herein, wherein the material response comprises one or more of a change in temperature, absorbed thermal energy, and microwave efficiency.

52. The method of any one of claims 29 to 51 , or any other claim herein, comprising varying a power of the ultrasonic energy based on an expected change in strength and / or expected elastic modulus of the rock formation.

53. The method of claim 52, or any other claim herein, wherein the power of the ultrasonic energy is varied between 10 W and 100 kW.

54. The method of any one of claims 29 to 53, or any other claim herein, wherein the electromagnetic radiation is microwave radiation.

55. The method of any one of claims 29 to 54, or any other claim herein, wherein:propagating ultrasonic energy into the rock formation creates a stress field within the rock formation, wherein an ultrasonically excited volume of the rock formation comprises regions of the stress field having a tensile stress greater than 70% of a maximum tensile stress of the stress field;propagating electromagnetic radiation into the rock formation creates an irradiated volume of the rock formation, wherein an electromagnetic power density of an electromagnetic field created by the electromagnetic applicator in the irradiated volume is greater than 25% of a maximum electromagnetic power density of the electromagnetic field; andthe irradiated volume is contiguous with the ultrasonically excited volume.

56. The method of any one of claims 29 to 54, or any other claim herein, wherein:propagating ultrasonic energy into the rock formation creates a stress field within the rock formation, wherein an ultrasonically excited volume of the rock formation comprises regions of the stress field having a tensile stress greater than 70% of a maximum tensile stress of the stress field;propagating electromagnetic radiation into the rock formation creates an irradiated volume of the rock formation, wherein an electromagnetic power density of an electromagnetic field created by the electromagnetic applicator in the irradiated volume is greater than 25% of a maximum electromagnetic power density of the electromagnetic field;the irradiated volume overlaps with the ultrasonically excited volume.

57. The method of any one of claims 29 to 54, or any other claim herein, wherein:propagating ultrasonic energy into the rock formation creates a stress field within the rock formation, wherein an ultrasonically excited volume of the rock formation comprises regions of the stress field having a tensile stress greater than 70% of a maximum tensile stress of the stress field;propagating electromagnetic radiation into the rock formation creates an irradiated volume of the rock formation wherein an electromagnetic power density of an electromagnetic field created by the electromagnetic applicator in the irradiated volume is greater than 25% of a maximum electromagnetic power density of the electromagnetic field;the irradiated volume is contained within a volume defined by a traverse-most extent of and an axial-most extend of the ultrasonically excited volume.

58. The method of any one of claims 55 to 57, or any other claim herein, wherein the ultrasonically excited volume of the rock formation comprises regions of the stress field comprising a tensile stress greater than 80% of a maximum tensile stress of the stress field or, optionally, greater than 90% of the maximum tensile stress of the stress field.

59. The method of any one of claims 55 to 57, or any other claim herein, wherein the irradiated volume of the rock formation comprises regions of the electromagnetic field comprising an electromagnetic power density greater than 50% of the maximumelectromagnetic power density of the electromagnetic field or, optionally, greater than 80% of the maximum electromagnetic power density of the electromagnetic field, or, further optionally, greater than 90% of the maximum electromagnetic power density of the electromagnetic field or, still further optionally, greater than 99% of the maximum electromagnetic power density of the electromagnetic field or, still further optionally, greater than 99.9% of the maximum electromagnetic power density of the electromagnetic field.

60. The method of any one of claims 29 to 59, or any other claim herein, wherein propagating ultrasonic energy into the rock formation creates a stress field within the rock formation, wherein an ultrasonically excited volume of the rock formation comprises regions of the stress field having a tensile stress greater than 50% of a maximum tensile stress of the stress field;propagating electromagnetic radiation into the rock formation creates an irradiated volume of the rock formation wherein an electromagnetic power density of the electromagnetic field in the irradiated volume is greater than 50% of a maximum electromagnetic power density of the electromagnetic field; andthe ultrasonically excited volume overlaps the irradiated volume.

61. An apparatus for in situ fragmentation of a rock formation, the apparatus comprising:an ultrasonic horn comprising a contact surface that contacts a working face of the rock formation, a perimeter of the contact surface defining a footprint of the ultrasonic horn on the working face, the ultrasonic horn moveable against the working face to thereby propagate ultrasonic energy into the rock formation;an electromagnetic applicator for emitting electromagnetic radiation into the rock formation, the electromagnetic applicator shaped and / or located such that when the ultrasonic horn is in contact with the working face the electromagnetic radiation is propagated through the footprint.

62. The apparatus of claim 61 comprising any of the features, combinations of features and / or sub-combinations of features of any of the other claims recited herein.

63. Apparatus comprising any feature(s), combinations of feature(s) and / or subcombinations of feature(s) disclosed herein.

64. Methods comprising any feature(s), combinations of feature(s) and / or subcombinations of feature(s) disclosed herein.

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