Patent ID: 12196082

DESCRIPTION OF THE EMBODIMENTS

The following description of embodiments of the disclosure is not intended to limit the disclosure to these embodiments but rather to enable a person skilled in the art to make and use this disclosure. Variations, configurations, implementations, example implementations, and examples described herein are optional and are not exclusive to the variations, configurations, implementations, example implementations, and examples they describe. The disclosure described herein can include any and all permutations of these variations, configurations, implementations, example implementations, and examples.

Methods

As shown inFIG.1, a method S100for boring can include: at a first time, driving a non-contact boring element, facing a bore face, to a target standoff distance from the bore face in Block S110; actuating the non-contact boring element to remove material from the bore face in Block S120; detecting a first profile of the bore face in Block S130; and adjusting the target standoff distance to a second target standoff distance in Block S140. As shown inFIG.1, the method S100can include: in response to the first profile exhibiting a first gradient less than a target gradient range, decreasing the target standoff distance to the second target standoff distance in Block S150; or, in response to the first profile exhibiting the first gradient greater than the target gradient range, increasing the target standoff distance to the second target standoff distance in Block S160. The method S100can also include at a second time, repositioning the non-contact boring element toward the bore face according to the second target standoff distance in Block S170.

As shown inFIG.3, a second method S200for boring with plasma can include: at a first time, driving a plasma torch, facing a bore face, to a target standoff distance from the bore face in Block S210; actuating the plasma torch to remove material from the bore face in Block S220; detecting a first profile of the bore face in Block S230; and adjusting the target standoff distance to a second target standoff distance in Block S240. As shown inFIG.3, the method S200can include, in response to the first profile exhibiting a first gradient less than a target gradient range, decreasing the target standoff distance to the second target standoff distance in Block S250; or, in response to the first profile exhibiting the first gradient greater than the target gradient range, increasing the target standoff distance to the second target standoff distance in Block S260. The method S200can also include: at a second time, repositioning the plasma torch toward the bore face according to the second target standoff distance in Block S270.

As shown inFIG.5, a third method S300for boring with a cutterhead including a jet engine can include: at a first time, driving a cutterhead, facing a bore face to a target standoff distance from the bore face in Block S310; actuating the cutterhead to direct exhaust gases at a target exhaust gas temperature from a nozzle toward the bore face to remove material from the bore face in Block S320; detecting a first temperature of the exhaust gases directed at the bore face in Block S330; and adjusting the first temperature of the exhaust gases directed at the bore face in Block S340. As shown inFIG.5the method S300can also include: directing a fuel metering unit to regulate a rate of fuel entering a combustor to maintain the temperature of exhaust gases exiting the nozzle proximate the target exhaust gas temperature in Block S350; and directing an air metering unit to regulate a mass of air entering the combustor to maintain the temperature of exhaust gases existing the nozzle at or near the target exhaust gas temperature in Block S360.

Variation of the methods S100, S200, S300can include: at a first time, driving a non-contact boring element, facing a bore face, to target standoff distance from the bore face; actuating the non-contact boring element to remove material from the bore face; detecting a first standoff distance from the non-contact boring element to the bore face; calculating a first removal rate from the bore face based on a first difference between the target standoff distance at the first time and the first standoff distance; in response to the first removal rate falling below a target removal rate, increasing the target standoff distance; at a second time succeeding the first time, driving the non-contact boring element to the target standoff distance; actuating the non-contact boring element to remove material from the bore face; detecting a second standoff distance from the non-contact boring element to the bore face; calculating a second removal rate from the bore face based on a second difference between the target standoff distance at the second time and the second standoff distance; and, in response to the second removal rate falling below the first removal rate, decreasing the target standoff distance.

Systems

As shown inFIG.2, a system100for non-contact boring can include: a chassis110; a propulsion system120arranged with the chassis110to advance the chassis110in a first direction toward a bore face200and retract the chassis110in a second direction away from the bore face; a non-contact boring element130connected to the chassis110and configured to operate in response to a set of boring parameters; and a depth sensor190configured to measure a standoff distance between the chassis110and the bore face200. The system100can also include a controller180connected to the propulsion system120, the non-contact boring element130, and the depth sensor190and configured to control the propulsion system120, the non-contact boring element130, and the depth sensor190in response to the depth sensor190measuring the standoff distance between the chassis110and the bore face200.

In one variation of the system100shown inFIGS.4A and4B, the system100can include: a chassis110; a propulsion system120arranged with the chassis110to advance the chassis110in a first direction toward a bore face200and retract the chassis110in a second direction away from the bore face200; a plasma torch132connected to a power supply134and a gas supply136; and a plasma torch ram170connecting the plasma torch132to the chassis110. As shown inFIGS.4A and4B, the plasma torch ram170can be configured to: locate the plasma torch132on the chassis110; advance and retract the plasma torch132along the chassis110along a longitudinal axis (X-axis) substantially parallel to the first direction and the second direction; tilt the plasma torch132along a pitch angle relative to the longitudinal axis and a yaw angle relative to the longitudinal axis; lift the plasma torch132vertically along a vertical axis (Z axis) substantially perpendicular to the longitudinal axis; and shift the plasma torch132laterally along a horizontal axis substantially perpendicular to the longitudinal axis and the vertical axis. As shown inFIGS.2,4A, and4B, the system100can also include a depth sensor190configured to measure a standoff distance between the chassis110and the bore face200; and a spoil evacuator configured to draw waste from a first location between the chassis110and the bore face200to a second location. In this variation of the exemplary implementation, the system100can also include a controller180connected to the propulsion system120, the plasma torch132, the plasma torch ram170, and the depth sensor190and configured to drive the propulsion system120, the plasma torch132, the plasma torch ram170, and the depth sensor190in response to the depth sensor190measuring the standoff distance between the chassis110and the bore face200.

In another variation of the system100shown inFIG.6, the system100can include a chassis110, and a cutterhead140including: a compressor142configured to compress air inbound from an above-ground fresh air supply; a combustor144configured to mix compressed air exiting the compressor142with a fuel inbound from an above-ground fuel supply and to ignite the fuel; a turbine154configured to extract energy from combusted fuel and compressed air exiting the combustor144to rotate the compressor142; and a nozzle160configured to direct exhaust gases220exiting the turbine154to induce an area of jet impingement at a bore face200. As shown inFIG.6, the system100can also include a cutterhead ram170connected to the cutterhead140and configured to position the cutterhead140relative to the bore face200; a temperature sensor156; and a controller180connected to the cutterhead140, the temperature sensor156, and the cutterhead ram170. In this variation of the system100of the example implementation, the controller180can be configured to: track a temperature of exhaust gases220exiting the nozzle160based on a signal output by the temperature sensor156; and to regulate a rate of fuel entering the combustor144to maintain the temperature of exhaust gases220exiting the nozzle160below a melting temperature and above a spallation temperature of a geology present in the bore. As shown inFIGS.2and6, the system100can also include a propulsion system120connected to the controller180and arranged with the chassis110to advance the chassis in a first direction toward a bore face200and retract the chassis110in a second direction away from the bore face200.

Applications

Generally, one or more variations of the system100can execute Blocks of the methods S100, S200, S300to bore or tunnel through various geologies in an autonomous or substantially autonomous manner while increasing efficiencies in boring rate and power (fuel, electricity, combustible gases) consumption. Generally, the system100can include one or more non-contact boring elements that direct energy (e.g., through high temperatures, pressures, electromagnetic radiation, etc.) at the bore face to remove material from the bore face through fracture, spallation, and removal of the material. In order to operate in an autonomous or substantially autonomous manner, the system100can automatically execute Blocks of the methods S100, S200, S300to control a set of boring parameters (electrical power, gas flow, air flow, fuel flow, etc.) that affect the flux of energy directed at the bore face. Moreover, the system100can automatically execute Blocks of the methods S100, S200, S300to: monitor, direct, maintain, and/or adjust a set of boring controls, including for example a standoff distance between the system100and the bore face, a temperature of exhaust gases directed at the bore face, a removal rate of material from the bore face, and/or a thermal or topological characterization of the bore face during boring operations. Applications of example implementations of a non-contact boring system100are described below with reference to the FIGURES.

Applications: Plasma Boring Variation

Generally, the methods S100and S200can be executed by a plasma boring system100(hereinafter the “system100”) during a plasma boring operation to modulate plasma torch power, gas flow rate, orientation, advance rate, and standoff distance as a function of bore shape (or “profile”) and material removal rate from the bore face in order to maintain a bore geometry and efficient boring. More specifically, the system100can execute Blocks of the methods S100and S200to: track actual standoff distance from the plasma torch to the bore face; implement closed-loop controls to maintain actual standoff distance at a target standoff distance; characterize boring efficacy based on differences between actual and predicted standoff distance as a function of power and gas flow rate input to the plasma torch; derive a bore face profile based on standoff distances at various positions across the bore face; modify the target standoff distance and plasma torch orientation to increase boring efficiency and maintain a target bore face profile across the bore face; and to modulate power and gas flow rate to the plasma torch to maintain high boring efficiency given the target standoff distance and plasma torch orientation over time throughout a boring operation.

For example, the system100can: monitor the bore face profile (or “shape”) of the bore based on standoff distances measured by the system100across the bore face; and then increase the target standoff distance if the bore profile exhibits a high gradient (e.g., is steep, is highly concave) or decrease the target standoff distance if the bore profile exhibits a low gradient (e.g., is shallow, is minimally concave, exhibits local convexity). The system100can also increase gas flow rate and power to the plasma torch and/or slow an advance (or “feed”) rate of the plasma torch responsive to detecting a narrow bore cross-section in order to widen the bore; and decrease gas flow rate and power to the plasma torch and/or slow an advance rate of the plasma torch responsive to detecting a broad bore cross-section in order to maintain a desired bore width or reduce the size of the cross section of the bore. Furthermore, the system100can orient (or “tilt”) the plasma torch toward a region of the bore face nearest the leading end of the system100—which may exhibit low removal rate at current operating parameters of the system100due to a change in geology—and adjust power and/or gas flow rate to the torch to preferentially remove material from this region of the bore face.

Therefore, by monitoring a single standoff distance between the torch and the bore face, the system100can: track material removal rate from the bore face; adjust target standoff distance based on this removal rate; and adjust power and gas flow to the plasma torch to compensate for this target standoff distance and thus maintain high removal rate from the bore face. Furthermore, by monitoring multiple standoff distances between the system100and regions across the bore face, the system100can: characterize a profile of the bore face; adjust target standoff, power, and gas flow rates to maintain a target shape of the bore; detect low-yield (or high-resilience) regions across the bore face; and adjust plasma torch orientation, target standoff, power, and gas flow rates to preferentially target removal of material from such low-yield regions.

The methods S100, S200are described herein as executed by the system100during a horizontal boring operation. However, the system100can additionally or alternatively execute Blocks of the methods S100, S200during vertical and angled boring operations.

Generally, the system100executes Blocks of the methods S100, S200while boring through underground geologies with plasma in order to avoid melting rock (e.g., creating lava) and instead maintain spoil in the form of a gas (e.g., gaseous carbonate) with spall (e.g., rock flakes), thereby enabling a spoil evacuator within the system100to draw spoil—removed from the bore face—rearward and out of the bore with limited spoil entrapment between the system100and the bore face and with limited collection of spoil along the spoil evacuator (e.g., due to condensation of molten rock or “slag” on cooler surfaces within the spoil evacuator). Additionally or alternatively, the system100modulates power, gas flow rate, and/or standoff distances according to Blocks of the methods S100, S200in order to achieve a target rate of lava creation (e.g., a target lava volume creation rate), such as in preparation for applying lava to the surface of the bore to form a lava tube of target thickness and profile.

In particular, various geologies may contain crystals (e.g., SiO2) in large proportions, such as sandstone, granite, and basalt. For example, basalt commonly contains 30-40% SiO2 by volume and may contain as much as 80% SiO2 by volume. SiO2 exhibits relatively a low melting temperature. However, the crystalline structure of SiO2 may decompose below the melting temperature of SiO2. Therefore, the system100can implement Blocks of the methods S100, S200to control the temperature of material at the bore face near the crystalline decomposition temperature of SiO2—and below the melting temperature of SiO2—in order to decompose the crystalline structure of material across the bore face and to thus fracture (or disintegrate) this material while not melting this material (or controlling a volume of melted material per unit distance bored by the system100).

More specifically, the system100executes Blocks of the methods S100, S200in order to fracture and disintegrate rock (and soil, etc.) at the bore face before these materials melt. By fracturing material at the face of the bore rather than melting this material, the system100can remove less complex spoil (e.g., e.g., gas and solid rock spall only rather than gas, spall, and lava) with less heat, which may extend the operating life of components of the system100, reduce energy consumption per unit distance (or volume) bored, and reduce overall expenses associated with boring operations through increased efficiency and longevity of the system100.

Furthermore, the effectiveness of fracturing material at the bore face (e.g., via thermal shock) may be a function of pressure and heat. To increase pressure at the bore face, the system100can: decrease the distance from the plasma torch to the bore face (hereinafter “standoff distance”) and/or increase gas flow rate through the plasma torch; the system100can also increase plasma torch power to compensate for increased gas flow rate. Similarly, to increase temperature at the bore face, the system100can: decrease bore speed or increase dwell time; decrease the standoff distance; and/or increase torch power and gas flow rate.

The methods S100, S200are described herein as executed by the system100to bore through felsic geologies containing high proportions of crystals, such as SiO2. However, the system100can additionally or alternatively execute Blocks of the methods S100, S200to bore through other igneous, metamorphous, and sedimentary geologies such as intermediate, mafic, and ultramafic geologies; sand, soil, silty sand, clay, cobbles, loam, etcetera.

Furthermore, the methods S100, S200are described here as executed by the system100to remove material from a bore face via spallation and gasification (or vaporization) while minimizing or eliminating melting of material at the bore face. However, the system100can additionally or alternatively execute Blocks of the method S100to control a rate or volume of melting of material at the bore face, such as to achieve a target thickness of a glassified layer of rock lining the wall of the bore.

Applications: Jet Thrust Boring Variation

Generally, a jet-thrust type variation of the system100includes: a chassis; a propulsion subsystem (e.g., a set of driven wheels or tracks) configured to advance the chassis forward through an underground bore; and a fully-contained cutterhead including a Brayton-cycle turbojet engine (hereinafter the “engine”) mounted to the chassis and configured to compress fresh air from an above-ground air supply within a compressor, to mix this compressed air with fuel from an above-ground fuel source, to combust this mixture, to extract energy from these combustion products to drive the compressor, and to exhaust these high-temperature, high-mass-flowrate exhaust gases toward a face of an underground bore. These high-temperature, high-mass-flowrate exhaust gases—reaching the bore face within a jet impingement area—can thermally shock geologies at the bore face, thus leading to spallation of geologies and removal of rock spall from the bore face.

Furthermore, vitrification at the bore face may lessen or inhibit thermal spallation at the bore face and thus yield a reduction in rock removal per unit time and per unit energy consumed by the system100relative to rock removal via spallation. Therefore, the system100can further include: a temperature sensor configured to output a signal representing a temperature of these exhaust gases; and a controller configured to vary fuel flow rate into the engine (e.g., a “throttle position”) and/or other boring parameters within the engine in order to maintain the temperature of these exhaust gases below the minimum melting temperature of all geologies present at the face (e.g., less than 1400° C.) or below the melting temperature of a particular geology detected at the bore face in order to prevent vitrification of the surface of the bore face, maintain spallation across the bore face, and maintain a high volume of rock removal per unit time and per unit energy consumed by the system100.

In particular, the system100can execute Blocks of the methods S100, S300to bore through rock via thermal spallation by directing a high-energy (e.g., high-temperature and/or and high-mass flow rate) stream of exhaust gases toward a bore face. These high-energy exhaust gases rapidly transfer thermal energy into the surface of the bore face, thus resulting in a rapid thermal expansion of a thin layer of rock at the surface of the bore face. Expansion and local stresses occur along natural discontinuities and nonuniformities that exist in the microstructure of rock matrix, causing differential expansion of the minerals of which the rock matrix is composed, in turn causing stresses and strains along and between mineral grains. Because geologies are typically brittle, rapid thermal expansion of rock at the surface of the bore face causes this thin, hot surface layer of rock to fracture from the cooler rock behind the bore face. This thin, hot surface layer of rock may therefore break into rock fragments (or spall) and separate from the surface of the bore face during this spallation process. The mechanism of fracturing or induction of micro-stresses at the surface of the bore face may vary across lithologies based on mineralogy, material properties, chemical properties, and physical properties of the surface subjected to these exhaust gases.

However, if temperature of the exhaust gases reaching the bore face exceed the melting temperature of the geology at the surface of the bore face, the surface of the bore face may melt and flow down the bore face rather than fracture and release from the bore face. Molten rock may: absorb more energy per unit mass than spall; flow slowly down the bore face rather than breaking and releasing from the surface of the bore face like spall; and thermally shield non-molten material on the bore face (e.g., material directly behind or around the area of molten material) from energy carried by the exhaust gases output by the engine. Therefore, relative to spallation, molten rock at the bore face may result in immediate reduction in the volume or mass of rock removed from the bore face per unit time and per unit energy consumed by the engine, for example because energy consumed by the engine is thus directed to changing the phase of rock at the bore face rather than sequentially fracturing thin layers of rock from the bore face.

Thus, the system100can include a Brayton-cycle turbojet engine—with its outlet nozzle facing toward the bore face—to generate high-temperature exhaust gases and to direct these exhaust gases at a high-volume flow rate in order to maintain a high pressure and a high total heat flux at the bore face and to achieve rapid spallation and material removal from the bore face. The system100can also implement closed-loop controls to maintain the temperature of these exhaust gases below the melting temperature of all geologies (e.g., 825° C. to compensate for melting temperatures between 900° C. and 1400° C. for most geologies) or below a particular geology detected at the bore face. A geology at the bore face may therefore be unlikely to melt in the presence of these exhaust gases from the engine. The system100can also maintain a high mass flow rate in order to compensate for sub-melting-temperature exhaust temperatures in order to generate high heat flux at the bore face—and therefore high rate of spallation of rock at the bore face—with low risk of melting the bore face over a wide range of geologies.

Furthermore, the engine can approach transformation of nearly one hundred percent of the energy contained in supplied fuel (e.g., liquid diesel) into heat and kinetic energy of the exhaust gases, which the system100then directs toward the bore face to spall the rock. In one example implementation, the engine includes: a combustor that burns fuels; a turbine that transforms pressure and thermal energy of gases exiting the combustor into mechanical rotation of a driveshaft; and an integrated axial compressor that is powered by the turbine via the driveshaft to draw air into the engine, to compress this air, and to feed this air into the combustor.

The engine may therefore be fully contained and may require no or minimal external (i.e., above-ground) support systems in order to bore an underground tunnel through various geologies. In particular, the system100can be connected solely to: an air supply that feeds fresh, unconditioned, above-ground air at any temperature and humidity into the compressor; a fuel supply that feeds fuel from an above ground supply (e.g., a fuel tank) into a fuel metering unit within the engine; and/or an above-ground monitoring system or remote control via low-power sensor and data lines.

Therefore, substantially all energy consumed during a boring operation may be consumed at the bore face by the engine to convert chemical energy in the fuel into: heat at the bore face; kinetic energy of exhaust gases producing pressure at the bore face; kinetic energy of exhaust gases moving off of the bore face and drawing spall rearward behind the engine; and kinetic energy to rotate the turbine and compressor. In particular, because the compressor and combustor are fully integrated into the engine and because the engine is configured to function solely on (unconditioned) air and fuel supplies, the system100may require that no or minimal energy be consumed by fans, pumps, cooling systems, etc. to power and cool above-ground subsystems or to pump air to the engine.

The system100can therefore require minimal setup time and complexity in order to bore an underground tunnel. For example, an operator may: dig a shallow trench at the start of the tunnel; place the system100in the trench; connect a fuel supply line extending rearward from the system100to an above-ground fuel reservoir (e.g., a mobile fueling rig); locate an end of an air supply line—extending rearward from the system100—in an unobstructed above-ground location; and start the engine, for example with a small electric starter motor integrated into the system100.

The engine can then: draw air into the compressor via the air supply line; combust pressurized air and fuel in the combustor; extract some energy from the resulting exhaust gases at the turbine to power the compressor; and eject hot gases at high mass flow rate toward the bore face to spall and remove material from the bore face. Concurrently, the propulsion subsystem can move the engine forward at a rate proportional to material removal from the bore face in order to maintain a standoff distance between the nozzle and the bore face. Additionally or alternatively, the propulsion subsystem can move the engine forward based on material removal from the bore face, the temperature and velocity of the exhaust gases exiting the nozzle, raster rate of the nozzle across the bore face, and/or the standoff distance in order to maintain consistent heat flux across the bore face.

Thus, the system100can execute Blocks of the methods S100, S300to remove material from the bore face without substantive above-ground air and power support systems, thereby simplifying setup and deployment of the system100to bore an underground tunnel.

Boring Initialization

To initiate a boring operation, the system100is located at a bore entry. For example, for a horizontal boring operation, a ground opening (or “launch shaft”) is dug (e.g., manually) at a start depth of the bore and at a width and length sufficient to accommodate the system100in a horizontal orientation. With the system100located at the bore entry and the torch adjacent a bore face, the controller can: implement methods and techniques described below to measure the standoff distance from the torch to the bore face; implement closed-loop controls to drive the torch to a nominal standoff distance (e.g., 6″); and then activate the torch by ramping the torch to a baseline power setting and to a baseline gas flow rate.

Closed-Loop Controls

As described below, during phases of the boring operation, the controller180can receive data, monitor sensors, measure parameters, determine states of the system100, calculate corrections, adapt to changes in the geology of the bore face200, and transmit instructions and direction to one or more components, subsystems, actuators, or sensors of the system100in order to improve or optimize system100performance (e.g., boring rate) at the bore face200in an autonomous or substantially autonomous manner.

The closed-loop controls described herein can be generally applied to any type of non-contact boring element130. In example implementations, the system100can include a non-contact boring element130that is configured to displace material from the bore face200through temperature, pressure, air flow, or a combination thereof. In specific example implementations, the non-contact boring element130includes a plasma torch, a cutterhead including a Brayton-style jet engine, or a flame jet. However, the system100can alternatively or additionally include any other thermal and/or pressure inducing non-contact boring element130.

Standoff Distance

In one implementation shown inFIG.2, the system100includes a single depth sensor190arranged near the leading face of the system100near the non-contact boring element130and including: a contact probe192; a linear actuator194configured to extend the contact probe192toward the bore face200and to retract the contact probe192, such as into a thermally-shielded housing; and an encoder or other sensor configured to track the length of the contact probe192extending from the leading face of the system100.

In this implementation, the controller180can intermittently trigger the depth sensor190to execute a standoff measurement cycle, such as once per minute. During a standoff measurement cycle, the controller180can: direct the linear actuator194to extend the contact probe192out of the housing; read a length measurement from the sensor once resistance on (or current draw from) the actuator reaches a threshold resistance (or threshold stall current); return this length measurement to the controller180; and trigger the linear actuator194to retract the contact probe192back into the housing.

Furthermore, when the contact probe192is extended out of the depth sensor190housing during a standoff measurement cycle, the controller180can adjust a boring parameter (e.g., air flow, fuel flow, gas flow, electrical power) of the non-contact boring element130in order to reduce surface temperature at the bore face200and thus reduce thermal shock and/or heat-induced warpage of the contact probe192. The controller180can subsequently readjust or modify the boring parameter of the non-contact boring element130to resume boring by increasing the surface temperature at the bore face200once the linear actuator194returns the contact probe192to the housing.

Upon receipt of a length measurement from the depth sensor190, the controller180can store this length measurement as a current standoff distance. The controller180can also: calculate a ram reset distance based on the current longitudinal position of the non-contact boring element ram170; reset the non-contact boring element ram170to a home position over a reset distance; and actuate the propulsion system120to move the system100forward by a sum of the ram reset distance and a difference between the current standoff distance and a current target standoff distance, thereby locating the non-contact boring element130at the target standoff distance.

In another implementation, the contact probe192can be spring loaded on the linear actuator194and/or the depth sensor housing is spring-loaded on the chassis110. During a standoff measurement cycle, the controller180triggers the depth sensor190to extend the contact probe192to the current target standoff distance. If the contact probe fails to meet resistance at this target standoff distance, the controller180: retracts the non-contact boring element ram170to the home position; advances the propulsion system120forward until the contact probe192meets resistance (i.e., contacts the bore face200), thereby setting the non-contact boring element130at the target standoff distance; records a bore distance since a last standoff measurement cycle based on the distance traversed by the non-contact boring element ram170and the propulsion system120within the bore; and then triggers the depth sensor190to retract the contact probe192.

In this implementation, after recording a standoff distance and resetting the non-contact boring element130to the target standoff distance during a standoff measurement cycle, the controller180can: implement dead-reckoning techniques to estimate the current standoff distance as a function of the last measured standoff distance, boring parameters associated with the non-contact boring element130; and implement closed-loop controls to adjust the non-contact boring element ram170position and/or advance the propulsion system120to maintain the estimated current standoff distance at the target standoff distance. The controller180can then trigger a next standoff measurement cycle once the estimated bore distance completed by the system100exceeds a threshold distance (e.g., one inch) or after a threshold duration of time.

For example, after recording a standoff distance during a standoff measurement cycle, the controller180can sum this standoff length measurement with changes in non-contact boring element ram170and propulsion system120position since the preceding standoff measurement cycle in order to calculate the total boring distance over a boring interval between the current and preceding standoff measurement cycles. In this example, the controller180can also: record boring parameters during this boring interval; and calculate or refine a standoff distance model linking linear boring distance to boring parameters and standoff distance as a function of time based on data collected over this boring interval (and during preceding boring intervals). The controller180can then: implement dead reckoning techniques to estimate linear bore distance over a next boring interval based on the standoff distance model, boring parameters during the boring interval, and the last measured standoff distance; re-estimate the standoff distance based on this linear bore distance; and advance the non-contact boring element ram170and/or the propulsion system120forward during this boring interval in order to maintain the actual standoff distance between the non-contact boring element130and the bore face200at the target standoff distance.

As shown inFIGS.4A and4B, in one variation of the example implementation the non-contact boring element130is a plasma torch132. In this variation, the contact probe192can be electrically shielded, and the system100can regularly or continuously read a standoff distance from the depth sensor190. For example, the contact probe192can include a stainless steel or low-alloy steel shaft and can be driven to a reference voltage—such as to the same voltage as the cathode in the plasma torch132or to the average voltage of the cathode and anode in the plasma torch132—thereby creating an electric field around the contact probe192that repels charged plasma, gas, and spall flowing between the plasma torch132and the bore face200.

Therefore, in this implementation, the controller180can drive the contact probe192forward to maintain continuous or substantially continuous contact with the bore face200, and the controller180can drive the plasma torch ram170and/or the propulsion system120forward to maintain a target standoff distance between the plasma torch132and the bore face200based on a standard distance read and output by the depth sensor190.

Alternatively, the depth sensor190can regularly or continuously oscillate the contact probe192fore and aft (e.g., along the X-axis shown inFIG.4B) during operation, such as: by partially retracting the contact probe192to enable fracture and spallation of rock at the bore face200ahead of the contact probe192or by fully retracting the contact probe192into a thermally-shielded housing within the chassis110to enable the contact probe192to cool; and then advancing the contact probe192forward and into contact with the bore face200. Once the contract probe192makes contact with the bore face200, the controller180can determine or calculate a current standoff distance as described above.

The controller180can also regularly drive the plasma torch ram170and/or the propulsion system120forward to maintain a target standoff distance between the plasma torch132and the bore face200based on a measured length of the contact probe192upon last contact with the bore face200. Furthermore, the controller180can implement dead-reckoning techniques to estimate current standoff distance, adjust the plasma torch ram170position, and/or advance the propulsion system120to maintain this estimated current standoff distance at the target standoff distance, and adjust boring parameters such as electrical power and gas flow rates to the plasma torch132, in time intervals between consecutive standoff distance measurements with the contact probe192.

In another variation of the example implementation, the system100includes multiple contact-based depth sensors190, each configured to extend from the leading face of the system100and to measure a distance from its position on the leading face of the system100to a corresponding position on the bore face.

In one implementation, the system100includes a set of contact-based depth sensors190arranged in a pattern about the perimeter of the leading face of the system100. The set of contact-based depth sensors190can include two or more depth sensors190arranged such that they cooperate to determine a range of depths to the bore face200, and from which the controller180can estimate or interpolate a topography of the bore face200. For example, a set of three, four, five, six, etcetera contact-based depth sensors190can be arranged symmetrically or asymmetrically about the leading face of the system100to provide three, four, five, six, etcetera points of depth measurement along the bore face200, from which the controller180can determine a generalized topography of the bore face200, and based on which the controller180can implement closed-loop controls to manage and optimize system performance.

In this variation of the example implementation, the system100implements methods and techniques described above to regularly or intermittently measure a distance from each contact-based depth sensor190to the bore face200. The controller180then: identifies a particular contact probe192indicating a shortest distance to the bore face200, which can generally represent a location of a low-yield (or most-resilient) region at the bore face200; and advances the plasma torch ram170and/or the propulsion system120forward toward the bore face200in order to set the standoff distance between the particular contact probe192and the corresponding low-yield region of the bore face200to the target standoff distance.

As shown inFIG.4B, the controller180can also tilt (e.g., pitch, yaw) the plasma torch ram170in the direction of the depth sensor190, such as by an angular distance proportional to a difference between the shortest standoff distance300and longest standoff distance302measured by the set of depth sensors190. With the axis of the plasma torch132now oriented nearer the low-yield region at the bore face, the system100can preferentially heat and fracture this low-yield region of the bore face200. The controller180can also: implement dead reckoning to predict removal of material from the bore face200, such as described above; and transition the plasma torch132back to its centered position coaxial with the bore as the controller180predicts removal of material from the low-yield region at the bore face200and flattening or smoothing of the bore face200.

In a similar implementation, after measuring a standoff distance at each depth sensor190, the controller180can: interpolate a depth profile around the perimeter of the bore based on these standoff measurements and known positions of these depth sensors190on the leading face of the system100. Generally, a shallowest section of the depth profile represents a low-yield region at the bore face200, and a deepest section of the depth profile represents a highest-yield region at the bore face200given the current position of the system100relative to the bore face200. Therefore, given current operating parameters of the plasma torch132, the controller180can: tilt the plasma torch132in the direction of a shallowest section of the depth profile, such as by an angular distance proportional to a distance between the shallowest section and the deepest section in the depth profile or proportional to a distance between the shallowest section in the depth profile and a nominal bore face plane; and continue or resume actuation of the plasma torch132with the axis of the plasma torch132now oriented toward the low-yield region at the bore face200in order to preferentially heat and fracture this low-yield region of the bore face200. In order to focus material removal in this low-yield region, the controller180can also decrease the target standoff distance; maintain (or increase) gas flow rate and/or power to the plasma torch132in order to prevent melting of material at this low-yield region while increasing pressure at this low-yield region of the bore face200. The controller180can then implement dead reckoning to predict removal of material from the bore face and/or measure a change in bore profile directly, as described above. As the controller180predicts or measures removal of material from this low-yield region toward the nominal bore face shape, the controller180can tilt the plasma torch132toward a next-shallowest section in the depth profile and repeat the foregoing process to level the bore face200to the nominal bore face shape before re-centering the plasma torch132to zero degree pitch and yaw positions and resuming longitudinal boring parallel to the axis of the bore.

Therefore, in this variation, the system100can scan the torch to different angular positions relative to the longitudinal axis of the bore to selectively increase material removal from low-yield regions of the bore face200based on standoff distances from the leading end of the system100to the perimeter of the bore face200.

In a similar variation, the system100further includes a center contact-based depth sensor190inset from the outer set of contact-based depth sensors190, such as arranged near an axial center of the leading face of the system100. Accordingly, the controller180can fuse a standoff measurement from the center depth sensor190with concurrent standoff measurements from the set of perimeter depth sensors190to interpolate a bore profile across the bore face200.

For example, if the bore profile represents a gradient from a perimeter of the bore face200to a center of the bore face200that is less than a target depth range (i.e., if the bore face is overly planar), the controller180can predict that the bore is oversized. Accordingly, the controller180can: reduce the target standoff distance from the center depth sensor190to the center of the bore face200to reduce thermal material removal at the perimeter of the bore; and reduce power to the plasma torch132in order to prevent melting near the center of the bore face200given this reduced target standoff distance. In this example, the controller180can additionally or alternatively increase the advance speed of the propulsion system120and/or the plasma torch ram170, such as in response to calculating a high removal rate concurrently with a shallow gradient across the bore face.

Conversely, if the gradient from the perimeter of the bore face200to the center of the bore face200is greater than the target depth range (i.e., the bore face200is overly conical), the controller180can predict that the bore is undersized and therefore too narrow for the system100to advance. Accordingly, the controller180can increase the target offset distance, power, and gas flow rates in order to achieve greater pressure and energy at the perimeter of the bore. In this example, the controller180can additionally or alternatively decrease the advance speed of the propulsion system120and/or the plasma torch ram170, such as in response to calculating a low removal rate (as described below) concurrently with a steep gradient across the bore face200.

Therefore, in this variation, the system100can scan or raster the plasma torch132to different positions across the bore face200(e.g., pitch, yaw, elevation along the Z-axis, translation along the Y-axis) in order to selectively increase material removal from low-yield regions of the bore face200based on a profile of the bore face200derived from standoff distances between from the leading end of the system100and multiple positions across the bore face200.

In another variation of the example implementation shown inFIG.2, the system100includes one or more single-point contactless depth sensors190.

In one implementation, the system100includes: a thermally shielded sensor housing; a thermally shielded shutter arranged across an opening in the shutter housing; and a single-point depth sensor190arranged in the housing behind the shutter, such as a radar-based depth sensor (e.g., a millimeter-wave radar sensor), an infrared sensor, an ultrasonic sensor, a laser (e.g., LIDAR, time of flight) sensor, etcetera.

Throughout operation, the controller180can: open the shutter; sample the depth sensor190to capture a depth measurement at a point on the bore face200; and then close the shutter to shield the depth sensor190from excess heat. For example, the controller180can intermittently trigger the depth sensor190to execute a standoff measurement cycle, such as once per minute as described above.

Alternatively, the system100can include a temperature sensor within the sensor housing. During operation, the controller180can: regularly sample this temperature sensor; open the shutter and read standoff measurements from the depth sensor190when the temperature in the housing is below an operating temperature range; and close the shutter and cease standoff measurements when the temperature in the housing is above the operating temperature range.

In this variation, the system100can implement methods and techniques described above to verify the standoff distance from the non-contact boring element130to the bore face200based on outputs of the depth sensor190and to reposition the non-contact boring element ram170and/or the propulsion system120accordingly to maintain the target standoff distance.

In this variation, the system100can also: include multiple single-point contactless depth sensors190; implement methods and techniques described above to calculate a bore perimeter or bore face profile; and then implement methods and techniques described herein to adjust the orientation of the non-contact boring element130and associated boring parameters according to this bore perimeter or bore face profile.

In another variation of the example implementation, the system100includes: a thermally shielded sensor housing; a thermally shielded shutter arranged across an opening in the shutter housing; and a multi-point depth sensor190arranged in the housing behind the shutter, such as a radar-based depth sensor190, such as a multi-point millimeter-wave radar sensor, a 2D depth camera, or a 3D LIDAR camera. In this implementation, the controller180can: open the shutter and sample the depth sensor190during a standoff measurement cycle; derive a bore face profile from an output of the depth sensor190during this standoff measurement cycle; and adjust operation of the system100accordingly, as described above.

For example, the controller180can: interpolate a 3D profile of the bore face200directly from an output of the depth sensor190including multiple depth measurements to multiple points on the bore face200; tilt the non-contact boring element130in an orientation corresponding to a shallowest region represented in the bore face profile, thereby bringing the non-contact boring element130nearer a corresponding low-yield region at the bore face200; reduce the target standoff distance at this low-yield region of the bore face proportional to a gradient from this low-yield region to the center of the bore; and adjust a boring parameter of the non-contact boring element130in order to prevent melting of material at this low-yield region of the bore face200.

In this variation of the example implementation, the controller180can: continue to sample the depth sensor190, such as intermittently or continuously while removing material from this low-yield region of the bore face200; recalculate the bore face profile accordingly; and reorient the non-contact boring element130to align with the lowest-yield region detected in each subsequent bore face profile thus calculated by the controller180. In particular, as the gradient across the bore face profile lessens, the controller180can re-center the longitudinal axis of the non-contact boring element130with the longitudinal axis of the bore, increase standoff distance, and adjust boring parameters of the non-contact boring element130in order to achieve more uniform fracturing, gasification, spallation, and general removal of material across the bore face200.

In other variations of the example implementation, the system100can include a set of depth sensors190including a combination of contact sensors and non-contact sensors. Furthermore, in still other variations of the example implementation, the system can include a non-contact depth sensor190that includes subcomponents or functionality (e.g., an optical camera paired with a LIDAR range finder) to provide optical or topological data regarding a temperature profile or topological profile of the bore face200, as described in more detail below.

Closed-Loop Control: Temperature Control

As shown inFIG.6, in one variation of the example implementation, the non-contact boring element130includes a cutterhead140including a Brayton-style turbojet engine. In this variation of the example implementation, the controller180can employ closed-loop controls to maintain a target temperature of the exhaust gases220directed at the bore face200. Alternatively, the closed-loop temperature controls described herein can be applied to other types of non-contact boring elements130, including one or more plasma torches132and/or flame jets.

As shown inFIG.6, this variation of the system100can include: a controller180; a temperature sensor156(e.g., a thermocouple) arranged near an exit of the nozzle160(e.g., near an exit of the nozzle160or between the nozzle160and the bore face200); and a fuel metering unit146configured to adjust a rate of fuel injected into the flame tube. Generally, during operation, the controller180can: track a temperature of exhaust gases220exiting the nozzle160based on a signal output by the temperature sensor156; and regulate a rate of fuel entering the combustor144—via the fuel metering unit146—to maintain the temperature of exhaust gases220exiting the nozzle160below the melting temperatures of all geologies or below the melting temperature of a particular geology predicted or detected at the bore face200.

In particular, the controller180can: set a target exhaust gas temperature, such as described below; sample the temperature sensor156to track the temperature of exhaust gases220exiting the nozzle160; and then implement closed-loop controls to adjust the fuel metering unit146to increase the rate of fuel injected into the combustor144if the temperature of these exhaust gases220is less than the target temperature; and adjust the fuel metering unit146to decrease the rate of fuel injected into the combustor144if the temperature of the exhaust gases220is more than the target temperature. For example, the controller180can: read the temperature of exhaust gases220at a frequency of10Hz; and then calculate an average of these temperatures and update the fuel flow rate based on this average temperature at a frequency of1Hz.

In one variation of the example implementation, the system100further includes an air metering unit148configured to vary a dilution ratio of: the first portion of compressed air entering the primary zone of the combustor144to the second portion of compressed air entering the dilution zone of the combustor144.

In one implementation, the air metering unit148includes a sleeve150configured to slide over a range of positions along the combustor144, such as including: a 1:0 dilution ratio position in which the sleeve150fully exposes the first set of perforations and fully encloses the second set of perforations in the combustor144; a 2:1 dilution ratio position in which the sleeve150predominantly exposes the first set of perforations and predominantly encloses the second set of perforations in the combustor144; a 1:1 dilution ratio position in which the sleeve150similarly exposes the first and second sets of perforations in the combustor144; and a 1:2 dilution ratio position in which the sleeve150predominantly encloses the first set of perforations and predominantly exposes the second set of perforations in the combustor144.

In this variation of the example implementation, the air metering unit148can also include an actuator152configured to transition the sleeve150along this range of positions. Thus, during operation, the controller180can set a target exhaust gas temperature, such as described below, detect a temperature of the exhaust gases220exiting the nozzle160, and implement closed-loop controls to: adjust the air metering unit148to increase the dilution ratio-and increase the fuel flow rate accordingly to maintain a target air-fuel ratio-if the temperature of the exhaust gases220is less than the target temperature; and adjust the air metering unit148to decrease the dilution ratio—and decrease the fuel flow rate accordingly to maintain the target air-fuel ratio—if the temperature of the exhaust gases220is more than the target temperature.

Generally, the controller180can: set a target exhaust gas temperature based on nominal bore geologies or based on real-time boring characteristics; and then implement closed-loop controls to adjust fuel flow rate and/or dilution ratio within the combustor144based on a difference between the measured and target temperatures of exhaust gases220exiting the nozzle160.

For example, in the foregoing implementations, the controller can set and implement a fixed target exhaust gas temperature of 825° C.—that is, less than the minimum melting temperature of most geologies.

The controller180can also regularly implement temperature test loops, including: increasing the target exhaust gas temperature; adjusting fuel flow rate and/or dilution ratio to achieve this exhaust gas temperature; measuring standoff distances as described above; and calculating a current boring rate and repeating this temperature test loop. If the current boring rate is greater than the previous boring rate at a lower target temperature (e.g., if material at the bore face is now spalling and releasing from the bore face at a greater rate), the controller180can further increase the target exhaust gas temperature and repeat the process. However, if the current boring rate is less than the previous boring rate at the lower target temperature (e.g., if material at the bore face is now melting rather than spalling), the controller180can decrease the target exhaust gas temperature and repeat this temperature test loop. Thus, in this example, the controller180can adjust the target exhaust gas temperature based on real-time boring rate, such as including: increasing the target exhaust gas temperature to maintain high thermal shock and spallation of harder geologies; and decreasing the target exhaust gas temperature to prevent melting of softer geologies, thereby maintaining the exhaust temperature above the average spallation temperature of the surface and below the minimum melting temperature of any point on the surface and thus maximizing material remove from the bore face200.

Closed-Loop Control: Removal Rate

The system100can additionally or alternatively calculate removal rate and adjust power, gas flow rate, and/or target standoff distance, etc. based on a difference between this removal rate and a target removal rate (or target removal rate range). In particular, the controller180can implement closed-loop controls to modulate standoff distance, non-contact boring element orientation, and boring parameters, as described above, in order to maintain uniform fracturing and spallation of rock at the bore face200without melting while maintaining a minimum removal rate from (or minimum advance through) the bore.

For example, in a plasma torch132configuration, increasing power to the plasma torch132may support greater gas flow rate though the plasma torch132and therefore greater pressure at the bore face200and greater removal rate. However, greater power and gas flow rate through the plasma torch132may: non-linearly reduce operating life of plasma torch132components; reduce total bore volume removal with these plasma torch132components; require more-frequent withdrawal of the system100from the bore for maintenance; require a larger power and gas supply; and reduce overall operating efficiency of the system100.

Similarly, in a jet engine cutterhead configuration, increasing air flow, fuel flow, and afterburner use can increase the temperature and pressure at the bore face200, yielding a temporarily higher removal rate. However, a full burn scenario for the cutterhead140may also: result in temperature spikes at the bore face200that result in melting of material; generate large spall fragments that impede further progress of the system100through the bore; induce increased wear and replacement rates for the cutterhead140components; and greatly increase the operating costs of the system100while lowering the overall operating efficiency of the system100. Therefore, the controller180can implement closed-loop controls to adjust operating parameters of the system100to maintain both a minimum removal rate from the bore and high overall operating efficiency.

In the variation of the system100that includes one single-point depth sensor190, the controller180implements methods and techniques described above to calculate an advance rate of the bore face200by: summing changes in standoff measurement, non-contact boring element ram170advancement, and chassis110advancement over a time interval (e.g., between two standoff measurement cycles); and dividing this sum by the duration of this time interval. The controller180can then calculate a removal rate (e.g., material volume) from the bore face200by multiplying the advance rate by a nominal or target cross-sectional area of the bore.

Alternatively, in the variation of the system100that includes multiple single-point depth sensors190and/or a multi-point depth sensor190, the controller180can: implement methods and techniques described above to calculate bore face profiles during consecutive standoff measurement cycles; calculate an offset distance between two consecutive bore face profiles based on a sum of changes in standoff measurement, non-contact boring element ram170advancement, and chassis110advancement over a time interval between these standoff measurement cycles; calculate a volume between these bore face profiles based on this offset distance; and then calculate a removal rate during this time interval by dividing this volume by the duration of this time interval.

In this variation, the controller180can access a single target removal rate for the bore and then implement closed-loop controls to adjust boring parameters, including electrical power, gas flow rate, fuel flow rate, air flow rate, exhaust gas temperature, and/or target standoff distance, based on the target removal rate.

Alternatively, an operator may: aggregate core samples at a target depth of the bore and at intervals along a planned path of the bore; process these core samples to derive geologies along the planned path; and generate a target removal rate schedule based on these geologies. For example, the operator may specify: a high target removal rate along sections of the planned path characterized by loose soil; a moderate-to-high target removal rate along sections of the planned path characterized by sandstone; a moderate target removal rate along sections of the planned path characterized by limestone; and a low target removal rate along sections of the planned path characterized by granite in the target removal rate schedule.

Accordingly, during operation, the controller180can: track its location along the planned path of the bore; query the target removal rate schedule for a target removal rate at a bore section currently occupied by the system100; and then load this target removal rate.

During operation, the controller180can compare the current removal rate to the target removal rate and adjust boring parameters based on this difference.

In particular, a decrease in removal rate below the target removal rate may result from: melting of rock at the bore face200rather than fracture and spallation of the bore face200; or from a change in geology at the bore face (e.g., to a material with less SiO2). If the former, the controller180can adjust boring parameters, for example by reducing power and gas flow rates and/or increasing standoff distance in a plasma torch132configuration, in order to reduce melting at the bore face. If the latter, the controller180can adjust boring parameters, for example by increasing power and gas flow rates and/or decreasing standoff distance in a plasma torch132configuration, in order to increase pressure at the bore face200and thus increase fracture and spallation at the bore face200. In a cutterhead140configuration, the controller180can similarly adjust boring parameters, for example fuel flow rate, air flow rate, exhaust temperature, and/or standoff distance, to decrease or increase pressure and/or temperature at the bore face200to adjust to changing geologies.

In one example implementation, if the current removal rate is less than the target removal rate, the controller180can first increase the target standoff distance (e.g., by a step width of 0.500″) and thus retract the non-contact boring element ram170while maintaining other boring parameters over a first time interval. The controller180can then execute a standoff measurement cycle and recalculate a removal rate from the bore face200. If this removal rate has increased, the controller180can further increase the target standoff distance, retract the non-contact boring element ram170accordingly (e.g., by an additional step width of 0.500″), and retest the current removal rate. The controller180can repeat this process until the removal rate decreases or decreases below a threshold change in removal rate, at which time the controller180can reduce the target standoff distance, advance the non-contact boring element ram170, and implement similar methods and techniques to test effects of adjusted boring parameters on removal rate.

Therefore, in this implementation, the controller180can first increase the target standoff distance in order to preempt a decrease in removal rate due to melting of the bore face200. If increase in the standoff distance between the non-contact boring element130and the bore face200increases removal rate, the controller180can verify that the decrease in removal rate was due to melting of material at the bore face200and iteratively increase the standoff distance in order to further increase removal rate and further reduce melting at the bore face200before increasing any boring parameters that would result in further material melting.

However, if increasing the standoff distance reduces or fails to affect the removal rate, the controller180can predict that the decrease in removal rate is due to a change in geology at the bore face200. Accordingly, the controller180can reduce the target standoff distance, adjust boring parameters as necessary in order to increase pressure at the bore face200. For example, the controller can iteratively decrease the standoff distance, execute standoff measurement cycles, recalculate removal rate, and verify increase in removal rate responsive to reduction in standoff distance. Upon verifying increase in removal rate responsive to reduction in standoff distance, the controller can: iteratively adjust boring parameters to increase pressure at the bore face200; recalculate removal rate; and then readjust or maintain boring parameters once any further increase in pressure at the bore face200results in a decrease in removal rate.

Therefore, in this implementation, the controller180can: first increase the target standoff distance responsive to a decrease in removal rate; verify that this increase in target standoff distance improves removal rate; and then only decrease the target standoff distance upon verifying that increasing the target standoff distance failed to improve removal rate, thereby preempting further melting of the bore face200and generation of slag within the bore and along the evacuation system.

Additionally or alternatively, the controller180can implement similar methods and techniques to: first adjust the boring parameters to reduce pressure at the bore face200responsive to a decrease in removal rate, verify that adjusted boring parameters improve removal rate; and then only readjust or maintain the boring parameters to increase pressure at the bore face200upon verifying that the prior decrease in pressure at the bore face200failed to improve removal rate, thereby preempting further melting of the bore face200and generation of slag within the bore and along the evacuation system.

Closed-Loop Controls: Bore Face Characterization

In another variation of the example implementation shown inFIG.6, the system100includes an optical sensor164directed toward the bore face200and configured to output images (e.g., color images, infrared images) of the jet impingement area at the bore face200. In this example, the controller180: accesses an image of the bore face200captured by the optical sensor164; and scans the image for “bright” (i.e., high intensity, high color value) pixels that indicate molten material at the bore face200. If the controller180thus detects a “bright” region in the image thus indicating molten material at the bore face200, the controller180can reduce the target exhaust gas temperature. Conversely, if the controller180detects no “bright” region in the image thus indicating no molten material at the bore face200, then the controller180can increase the target exhaust gas temperature. The controller180can then adjust the fuel flow rate and/or the dilution ratio at the combustor144to achieve this updated target exhaust gas temperature. The controller180can regularly repeat this process, such as at a frequency of 1 Hz.

In the foregoing example, the controller180can implement similar methods and techniques to detect higher temperature—but not yet molten—regions on the bore face200(e.g., “hot spots”) based on images captured by the optical sensor and to update the target exhaust gas temperature accordingly.

Generally, the optical sensor164is configured to detect frequencies and amplitudes of photons emitted at or near the bore face200during non-contact boring and converting the detected frequencies and amplitudes into an image of the bore face200. In one implementation, the optical sensor164can scan the bore face200at or near the point of non-contact thermal impingement from a nominal standoff distance. Alternatively, the optical sensor164can implement a full-face static scan of the bore face200to detect photons emitted after impingement by the non-contact boring element130. In another alternative implementation, the optical sensor164can follow a raster pattern of the non-contact boring element sub-assembly, for example by being attached to or moving in concert with the non-contact boring element ram170. In variations of the example implementation, the optical sensor164can be paired with a light source (not shown) to illuminate the bore face200during an optical scan of the bore face200.

In one implementation, the optical sensor164can detect and interpret photons emitted and/or reflected at the bore face using a red-green-blue (RGB) camera detector. Using the RGB camera detector, the optical sensor164can generate and store a two-dimensional image representing the photon emissions and/or reflections at the bore face200in an RGB view. In another implementation, the optical sensor164can detect and interpret photons emitted and/or reflected at the bore face using a cyan-magenta-yellow-black (CMYK) camera detector. Using the CMYK camera detector, the optical sensor164can generate and store a two-dimensional image representing the photon emissions and/or reflections at the bore face200in CMYK view. In another implementation, the optical sensor164can detect and interpret photons emitted and/or reflected at the bore face using an infrared (near-infrared or far-infrared) camera detector. Using the infrared camera system, the optical sensor164can generate and store a two-dimensional image of the bore face200in an infrared view.

In another variation, the optical sensor164includes a combination of RGB, CMYK, infrared, multispectral, and hyperspectral detectors to be used in parallel or serially during the boring process. For example, the system can utilize an RGB camera detector in combination with or in sequence with a hyperspectral imager to get a visible light and non-visible light depiction of the bore face200. The controller180can then fuse or integrate the respective images into a fuller-spectrum view of the bore face200indicative of the current or near-current temperature profile of the bore face200.

Additionally or alternatively, the system100can: implement object-tracking techniques to detect and track material moving off the bore face based on features detected in a sequence of images captured by the optical sensor164; and estimate temperatures or phases of this material based on color, brightness, and/or intensity of pixels identified as spall in these images. The controller180can then increase the target exhaust gas temperature if no molten material moving off the bore face200is detected; or conversely decrease the target exhaust gas temperature if molten material moving off the bore face200is detected. The controller180can adjust the target exhaust gas temperature based on any other real-time or near-real time boring characteristic detected or tracked by the sensors or detectors in communication with the controller180.

Example Configurations

Generally, the techniques and methods described herein can be applied to any type or modality of non-contact boring, including but not limited to: plasma torch, jet engine thrust, flame jet, acoustic energy, electromagnetic radiation (e.g., laser, millimeter wave directed energy), or a combination or subcombination thereof. The following example implementations should therefore be understood as non-limiting with respect to the applicability of other types or modalities of non-contact boring elements.

Example: Plasma Torch System

In one variation of the system100shown inFIGS.4A and4B, the system100can include: a chassis110; a propulsion system120arranged with the chassis110to advance the chassis in a first direction toward a bore face200and retract the chassis110in a second direction away from the bore face200; a plasma torch132connected to a power supply134and a gas supply136; and a plasma torch ram170connecting the plasma torch132to the chassis110. As shown inFIGS.4A and4B, the plasma torch ram170can be configured to position the plasma torch132along at least five degrees of freedom. The plasma torch ram170can be configured to: locate the plasma torch132on the chassis110; advance and retract the plasma torch132along the chassis110along a longitudinal axis (X-axis) substantially parallel to the first direction and the second direction; tilt the plasma torch132along a pitch angle relative to the longitudinal axis and a yaw angle relative to the longitudinal axis; lift or surge the plasma torch132vertically along a vertical axis (Z axis) substantially perpendicular to the longitudinal axis; and shift or heave the plasma torch132laterally along a horizontal axis (Y-axis) substantially perpendicular to the longitudinal axis and the vertical axis.

As shown inFIGS.2,4A, and4B, the system100can also include a depth sensor190configured to measure a standoff distance between the chassis110and the bore face200; and a spoil evacuator configured to draw waste from a first location between the chassis110and the bore face200to a second location. In this variation of the exemplary implementation, the system100can also include a controller180connected to the propulsion system120, the plasma torch132, the plasma torch ram170, and the depth sensor190and configured to drive the propulsion system120, the plasma torch132, the plasma torch ram170, and the depth sensor190in response to the depth sensor190measuring the standoff distance between the chassis110and the bore face200. Generally, the controller180can implement closed-loop controls of the type described above (e.g., stand-off distance, temperature controls, removal rate, bore face characterization) to manage and direct the system100in an autonomous or semi-autonomous manner to achieve efficient removal of material from the bore face200.

In one variation of the plasma torch132example implementation, the system100includes multiple plasma torches132, such as arranged in an array on the leading end of the system100. For example, the system100can include: a primary center plasma torch132; and a set of secondary plasma torches132, such as three, five, or seven torches arranged in a symmetrical or asymmetrical pattern about the primary center torch.

In this variation, the controller180can implement methods and techniques described above to monitor the standoff distance to the bore face200, the perimeter profile of the bore face200, and/or the face profile of the bore face200based on outputs of one or more single- or multi-point depth sensors190arranged on the leading end of the system100. Additionally, the controller180can implement additional methods and techniques described above to characterize and interpret a temperature profile of the bore face200; and actuate and direct one or more of the sets of plasma torches to maintain a desired temperature at the bore face200(e.g., sufficient to produce spall, insufficient to produce molten material). Additionally, the controller180can implement additional methods and techniques described above to maintain a target removal rate, autonomously adjust to variations in the calculated removal rate, and autonomously drive or steer the system100along its boring path consistent with the target removal rate.

In this variation, the controller180can also implement Blocks of the method S100to adjust power and gas flow rates to individual torches in the set based on the standoff distance, removal rate, temperature profile, and bore face200profile metrics. For example, rather than tilt a single torch toward a low-yield region detected at the bore face200to increase thermal and material removal in this region, as described above, the controller180can instead increase power and gas flow rate flux to a particular torch (or a subset of torches) nearest this low-yield region in order to break this low-yield region of the bore face200.

In this variation, each plasma torch132can also be mounted to an independently actuated plasma torch ram170. Accordingly, the controller180can: derive a face or perimeter profile of the bore face, as described above; independently actuate the plasma torch rams170to set each plasma torch132at its assigned standoff distance based on a last (or estimated) face or perimeter profile of the bore face200; and independently adjust target standoff distances for these plasma torches132based on material removal rate or detected temperature from corresponding regions of the bore face200.

Example: Jet Engine Cutterhead Variation

In another variation of the system100shown inFIG.6, the system100can include a chassis110, and a cutterhead140including: a compressor142configured to compress air inbound from an above-ground fresh air supply; a combustor144configured to mix compressed air exiting the compressor142with a fuel inbound from an above-ground fuel supply and to ignite the fuel; a turbine154configured to extract energy from combusted fuel and compressed air exiting the combustor144to rotate the compressor142; and a nozzle160configured to direct exhaust gases220exiting the turbine154to induce an area of jet impingement at a bore face200. As shown inFIG.6, the system100can also include a cutterhead ram170connected to the cutterhead140and configured to position the cutterhead140relative to the bore face200; a temperature sensor156; and a controller180connected to the cutterhead140, the temperature sensor156, and the cutterhead ram170. In this variation of the system100of the example implementation, the controller180can be configured to: track a temperature of exhaust gases220exiting the nozzle160based on a signal output by the temperature sensor156; and to regulate a rate of fuel entering the combustor144to maintain the temperature of exhaust gases220exiting the nozzle160below a melting temperature and above a spallation temperature of a geology present in the bore. As shown inFIGS.2and6, the system100can also include a propulsion system120connected to the controller180and arranged with the chassis110to advance the chassis in a first direction toward a bore face200and retract the chassis110in a second direction away from the bore face200.

The system100includes or couples to a fuel supply line. In one implementation, the fuel supply line includes a thermally shielded flexible fuel line that connects to an above-ground fuel reservoir (e.g., a mobile diesel fuel tank), runs through the tunnel, and connects to the cutterhead140to supply fuel to the cutterhead140during operation.

The system100can also include a fuel pump (not shown) integrated into the cutterhead140and configured to draw fuel from the above-ground fuel reservoir through the fuel supply line and to maintain a minimal fuel pressure within the cutterhead140. For example, the system100can include a mechanical fuel pump driven by a power takeoff from the turbine154. Alternatively, the system100can include: an electric fuel pump; and an electric generator (or an electric starter motor operated in a generator mode) driven by a power takeoff from the turbine154and supplying power to the electric fuel pump to draw fuel from the above-ground fuel reservoir.

Additionally or alternatively, the above-ground fuel reservoir can include a fuel pump configured to push fuel toward the engine via the fuel supply line. Furthermore, the system100can include a series of inline fuel pumps arranged along the fuel supply line and configured to boost fuel pressure and maintain fuel flow along the fuel supply line, such as over extended tunnel bore lengths (e.g., dozens, hundreds of feet).

Furthermore, as the fuel supply line runs from the above-ground fuel reservoir, along the tunnel, to the cutterhead140, the fuel supply line may be heated by exhaust gases moving off the bore face200, around the cutterhead140, and rearward though the tunnel toward a tunnel opening behind the cutterhead140. Fuel running through the fuel supply line may therefore be heated by these exhaust gases on its way to the cutterhead140and may thus recapture some thermal energy from these exhaust gases and return this thermal energy to the cutterhead140, which then redirects this recycled heat—with additional heat from burning this fuel—back to the bore face200.

The system100also includes or couples to a fresh air supply line (or “hose”) that includes an inlet above ground, runs through the tunnel behind the cutterhead140, connects to the inlet of the cutterhead140, and supplies fresh air (or “working fluid”) to the compressor142during operation. In particular, the air supply line feeds fresh air from above grade to the cutterhead140, which then compresses this fresh air in the compressor142, mixes this compressed fresh air with fuel received via the fuel supply line, ignites this air-fuel mixture in the combustor144, extracts some energy from combusted and expanding exhaust gases via the turbine154to rotate the compressor142, and then releases these high-temperature, high-mass-flowrate exhaust gases220toward the bore face200to spall and remove material from the bore face200.

For example, the air supply line can include: a flexible duct hose; and heat shielding over a first section of the flexible duct hose immediately trailing the cutterhead140(e.g., a ten-foot section of the air line immediately behind the engine) and configured to shield the flexible duct hose from high-temperature exhaust gases220and spall moving off of the bore face and around the cutterhead140. In this example, the air supply line can also exclude heat shielding over the remainder of the flexible duct hose. Accordingly, this second section of the flexible duct hose may be heated by exhaust gases220moving behind the engine and around the flexible duct hose. Fresh air moving through the duct hose may therefore be heated by these exhaust gases220on its way to the cutterhead140and may thus recapture some thermal energy from these exhaust gases220and return this thermal energy to the cutterhead140, which then redirects this recycled heat—with additional heat from burning fuel—back to the bore face200. Thus, in this implementation, the air supply line can function as a heat exchanger to recycle heat moving off the bore face200and to return this heat to the cutterhead140.

As shown inFIG.6, the compressor142is configured to compress air inbound from the above-ground fresh air supply. Generally, the compressor142is described herein as defining a radial compressor coupled to, driven by, and arranged on the same drive line with the turbine154. For example, the compressor142can include a single- or multi-stage axial compressor including: a set of compressor stator vanes fixedly mounted to the engine; a compressor rotor rotating within the engine; and a set of compressor rotor vanes mounted to the compressor rotor. However, the compressor142can alternatively include a centrifugal compressor. The compressor142can also be be driven by the turbine154via a gearbox, belt drive, or other power transmission subsystem.

As shown inFIG.6, the combustor144is configured to mix compressed air exiting the compressor with fuel inbound from the fuel supply and to ignite this fuel mixture. In one implementation, the combustor144includes one or more flame tubes arranged in parallel with the compressor142and the turbine154, each flame tube defining: a primary zone including a first set of perforations; and a dilution zone including a second set of perforations. In this implementation, the combustor144can also include a fuel injector attached to a fuel metering unit146that sprays fuel into the flame tube ahead of the primary zone. During operation, a first portion of compressed air—exiting the compressor142—moves into the primary zone of the flame tube via the first set of perforations and mixes with the fuel to form an air-fuel mixture at or near a target ratio (e.g., leaner than a stoichiometric ratio). This air-fuel mixture then combusts (nearly completely) within a primary zone of the flame tube at (near) constant pressure and flows into the dilution zone on its way to the turbine154. Concurrently, a second portion of air—exiting the compressor142—moves around and outside of the primary zone of the flame tube, passes through the second set of perforations in the flame tube, and mixes with high-temperature combustion products moving from the primary zone to the dilution zone of the flame tube.

This second portion of compressed air may be much cooler than these high-temperature combustion products and may thus reduce the average temperature of combustion products exiting the combustor and thus reduce the average temperature of exhaust gases subsequently exiting the nozzle160and directed toward the bore face.

As described above, the system100can also control a “dilution ratio” of the first portion of compressed air to the second portion of compressed air entering and diverted around the flame tube, respectively, in order to maintain a target air-fuel mixture within the primary zone of the flame tube and to control exhaust gas temperature when adjusting fuel flow rate into the combustor.

As shown inFIG.6, the turbine154is configured to extract energy from combusted products exiting the combustor144and to rotate the compressor142. In particular, the turbine154can include: a set of turbine stator vanes mounted to the engine; a turbine rotor rotating within the engine and coupled to the compressor rotor (e.g., via a driveshaft and/or gearbox); and a set of turbine rotor vanes mounted to the turbine rotor. Combustion products exiting the combustor144may expand isentropically while moving through the turbine stator and rotor vanes of the turbine154, thus reducing the temperature and pressure of these combustion products and transforming this energy into rotation of the compressor142.

As shown inFIG.6, the nozzle160is coupled to the output of the turbine and is configured to direct exhaust gases220exiting the turbine onto a jet impingement area at the bore face200.

In one implementation, the system100includes a fixed-area nozzle160that directs exhaust gases toward the bore face200to form a jet impingement area of a target size (e.g., a target diameter) on the bore face200at a target standoff distance (or within a narrow range of target standoff distances), as determined by the controller180, between the nozzle160and the bore face200. For example, the fixed-area nozzle160can define a nozzle geometry that yields an impingement area of width approximately ten times the width of the nozzle160in order to achieve: a stream of exhaust gases220that includes a hot center region shielded by a thick boundary layer; an efficient convection within the center region; a high rate of heat transfer from the center stream into the bore face200; and thus a high rate of spallation within the jet impingement area.

As described herein, the controller180can control standoff distance and angular position of the nozzle160on the chassis110via the cutterhead ram170—and therefore relative to the bore face200—to induce a jet impingement of controlled area on the surface of the bore face200and thus evenly excavate one discrete cross-section of the bore face200before advancing forward the chassis110forward.

In one variation of the example implementation, the system100includes a variable-area nozzle160including a variable aperture162through which the exhaust gases220can flow. In this variation, by adjusting the area of the nozzle, the controller180can adjust the jet impingement area at the bore face200and thus control power density (i.e., heat flux per unit area) within the jet impingement area at the bore face200.

Generally, the speed of the compressor142may be correlated with mass flow rate of air through the cutterhead140and thus a pressure within the jet impingement area at the bore face200. Similarly, fuel flow rate may be correlated with exhaust gas temperature and turbine and compressor speeds. Thus, during operation, the controller180can also implement closed-loop controls to: increase fuel flow rate to raise the exhaust gas temperature to a (fixed or variable) target temperature; and increase the nozzle area to compensate for higher compressor speeds resulting from increased fuel flow rate and thus maintain a controlled (e.g., constant) pressure across the jet impingement area. Similarly, the controller180can further implement closed-loop controls to: decrease fuel flow rate to decrease the exhaust gas temperature to a (fixed or variable) target temperature; and decrease the nozzle area to compensate for lower compressor speeds resulting from decreased fuel flow rate and thus maintain a controlled (e.g., constant) pressure across the jet impingement area.

In a similar example, the controller180can implement additional closed-loop controls to increase the nozzle area at higher compressor speeds in order to reduce the velocity of exhaust gases exiting the nozzle and thus maintain the exhaust gas stream at subsonic speeds.

Conversely, the controller180can adjust the nozzle area to: maintain a supersonic exhaust gas stream; and locate a first shock diamond (i.e., an abrupt change in local density and pressure) in the exhaust gas stream at the bore face200. The complex flow of exhaust gases220within and around this shock diamond—positioned at the bore face by the system100—may result in a high rate of heat transfer, thermal shock, and pressure shock across the jet impingement area, which may yield a high rate of spallation and material removal from the jet impingement area. Thus, in this implementation, the controller can: monitor a standoff distance from the engine to the bore face200through any of the methods or techniques described herein; and adjust the nozzle area based on the current exhaust gas temperature, the current air flow rate (or compressor speed, turbine speed) through the cutterhead140, and the current standoff distance in order to locate a shock diamond (e.g., the first shock diamond) in the exhaust gas flow at the current standoff distance and thus produce thermal and pressure shocks at the bore face200that yield an increased rate of material removal.

In another example of closed-loop control of a variable area nozzle160, the controller180can reduce the nozzle area when hard geologies (e.g., igneous and metamorphic rocks) are present at the bore face200in order to: achieve greater energy density within the jet impingement area and maintain a high rate of spallation within the jet impingement area despite these harder geologies; while also maintaining exhaust gas temperatures below the low melting temperatures of softer geologies in order to prevent melting at the bore face200under mixed-geology bore face conditions or during transitions from harder geologies to softer geologies along the tunnel. Similarly, in this example, the controller180can increase the nozzle area when soft geologies (e.g., sedimentary rocks) are present at the bore face in order to increase the size of the jet impingement area and thus maintain a high rate of spallation over a wider bore area with more uniform rock removal across the width and height of the bore.

As shown inFIG.6, the system100also includes: a temperature sensor156(e.g., a thermocouple) arranged near an exit of the nozzle160(e.g., between the nozzle160and the bore face200); and a fuel metering unit146configured to adjust a rate of fuel injected into the combustor144. Generally, during operation, the controller180can: track a temperature of exhaust gases220exiting the nozzle160based on a signal output by the temperature sensor156; and regulate a rate of fuel entering the combustor144—via the fuel metering unit146—to maintain the temperature of exhaust gases220exiting the nozzle160below the melting temperatures of all geologies or below the melting temperature of a particular geology predicted or detected at the bore face200.

As described herein, the controller180can: set a target exhaust gas temperature, such as described above; sample the temperature sensor156to track the temperature of exhaust gases220exiting the nozzle160; and then implement closed-loop controls to adjust the fuel metering unit146to increase the rate of fuel injected into the flame tube if the temperature of these exhaust gases220is less than the target temperature; and adjust the fuel metering unit146to decrease the rate of fuel injected into the combustor144if the temperature of the exhaust gases220is more than the target temperature.

As shown inFIG.6, the system100includes an air metering unit148configured to vary a dilution ratio of: the first portion of compressed air entering the primary zone of the combustor144to the second portion of compressed air entering the dilution zone of the combustor144.

In one implementation, the air metering unit148includes a sleeve150configured to slide over a range of positions along the combustor144, such as including: a 1:0 dilution ratio position in which the sleeve150fully exposes the first set of perforations and fully encloses the second set of perforations in the combustor144; a 2:1 dilution ratio position in which the sleeve150predominantly exposes the first set of perforations and predominantly encloses the second set of perforations in the combustor144; a 1:1 dilution ratio position in which the sleeve150similarly exposes the first and second sets of perforations in the combustor144; and a 1:2 dilution ratio position in which the sleeve150predominantly encloses the first set of perforations and predominantly exposes the second set of perforations in the combustor144.

In this variation of the example implementation, the air metering unit148can also include an actuator152configured to transition the sleeve150along this range of positions. Thus, during operation, the controller180can set a target exhaust gas temperature, such as described below, detect a temperature of the exhaust gases220exiting the nozzle160, and implement closed-loop controls to: adjust the air metering unit148to increase the dilution ratio—and increase the fuel flow rate accordingly to maintain a target air-fuel ratio—if the temperature of the exhaust gases220is less than the target temperature; and adjust the air metering unit148to decrease the dilution ratio—and decrease the fuel flow rate accordingly to maintain the target air-fuel ratio—if the temperature of the exhaust gases220is more than the target temperature.

Generally, the controller180can: set a target exhaust gas temperature based on nominal bore geologies or based on real-time boring characteristics; and then implement closed-loop controls to adjust fuel flow rate and/or dilution ratio within the combustor144based on a difference between the measured and target temperatures of exhaust gases220exiting the nozzle160.

Additionally, as shown inFIG.6, the system100can also include an afterburner158configured to inject fuel into exhaust gases220exiting the turbine154in order to rapidly increase temperature and pressure of exhaust gases reaching the bore face200. The controller180can be configured to: selectively actuate the afterburner158(through ignition and control of fuel flow rate) to rapidly increase the temperature of the exhaust gases220and the pressure of the exhaust gases220impinging upon the bore face200. In use, the afterburner158can define a recirculation zone proximate its terminus to anchor the afterburner flame. The afterburner158can further include a spark plug, glow plug, or other electrical or electromagnetic starter to ignite the afterburner flame and initialize vaporization of the injected fuel. In another variation of the example implementation, when adjusting the temperature and/or pressure of the exhaust gases220upon the bore face200, the controller180can be configured to: first adjust an activation and/or fuel flow rate to the afterburner158; then if necessary adjust a fuel flow rate or dilution rate through methods and techniques described above.

In one variation of the example implementation, the afterburner158can be fed with fuel from the primary fuel supply line, for example liquid diesel fuel. Alternatively, the afterburner158can be fed by a separate fuel line and with a separate type of fuel (e.g., a mixture of kerosene and gasoline, biodiesel, etcetera). Moreover, the controller180can: selectively increase or decrease a nozzle area of a variable area nozzle160in coordination with actuation of the afterburner158in order to maintain consistent pressure within the nozzle160.

In another variation of the example implementation, the system100further includes: a compressor tap (not shown) arranged between the compressor142and the combustor144; and a low-temperature jet coupled to the compressor tap, arranged near the bore face200, and configured to blow spall—removed from the bore face200by high-temperature exhaust gases output from the nozzle160—away from the bore face200and rearward behind the cutterhead140.

For example, the low-temperature jet can be arranged below the nozzle160and can face downwardly and/or toward a bottom corner of the bore face200such that compressed air discharged by the low-temperature jet displaces spall—falling from the bore face and collecting in this bottom corner of the bore face—rearward, thereby exposing the bottom of the bore face200to spallation by exhaust gases220discharged from the nozzle160. The system100can thus: bleed a third portion of compressed air from the output of the compressor142via the compressor tap and feed this compressed air to the low-temperature jet; blast this third portion of compressed air toward the bottom region of the bore face200; draw spall and larger rock fragments—that may otherwise collect along the bottom of the bore face200—rearward; and thus expose the bottom corner of the bore face200to the nozzle160for further spallation.

Additionally or alternatively, in this variation, the system100can include a set of low-temperature jets arranged about the outer casing of the cutterhead140near the nozzle160, facing reward on the cutterhead (i.e., opposite the bore face), and connected to the compressor tap. In this implementation, the set of low-temperature jets can direct low-temperature air along the outer casing of the cutterhead140in order to form a cool boundary layer along the chassis110, which may thermally shield the chassis110from hot exhaust gases and spall moving off of the bore face200and flowing around the cutterhead140during operation.

In another variation, the system100further includes a fan: arranged inline and ahead of the compressor142; coupled to the air supply line; driven by the turbine154(e.g., in a high-bypass fan configuration); and configured to output a second stream of low-temperature compressed air separate from the compressor142, the combustor144, and the nozzle160. In this variation, the system100can also include a flow reversal subsystem (e.g., in a clamshell configuration) configured to direct this second stream of low-temperature compressed air rearward and away from the bore face200to draw spall —moving off of the bore face200—away from the bore face, past the cutterhead140, and out of the tunnel. For example, the flow reversal subsystem can: direct the second stream of low-temperature compressed air rearward (i.e., away from the bore face200; opposite the direction of air flowing from the air supply into the cutterhead140); thus creating a lower-pressure region between the rear of the cutterhead140and the bore face200in order to increase flow rate of exhaust gases220and spall around and past the cutterhead; and cool the chassis110of the system100.

As shown inFIGS.2and6, the cutterhead140can be mounted on the chassis110, and the propulsion system120can advance the chassis110and the cutterhead140forward toward the newly exposed surface of the bore face200as the system100bores the tunnel.

For example, the chassis110and the propulsion system120can form a wheeled or tracked cart driven by electric, hydraulic, or pneumatic motors powered via a generator, pump, or compressed air tap, etc. connected to the cutterhead140. The chassis110can also include a cutterhead ram170configured to move the cutterhead140in at least five degrees of freedom. The cutterhead ram170can be configured: to locate the cutterhead140on the chassis110; to advance and retract the cutterhead140longitudinally (e.g., along an X-axis) along the chassis110in order to maintain a standoff distance between the nozzle160and the bore face200; to pitch and yaw the cutterhead140on the chassis110(e.g., by up to +/−10° in pitch and yaw) in order to scan (or “raster”) the jet impingement area across the bore face200; and/or to lift or surge the cutterhead140vertically along a Z-axis and shift or heave the cutterhead140laterally along a Y-axis on the chassis110in order to scan the jet impingement area across the bore face200.

In this example implementation, the controller180can implement one or more closed-loop controls to: fully retract the cutterhead ram170; advance the propulsion system120forward to locate the nozzle160at (approximately) a target standoff distance from the bore face200; raster the nozzle160across the bore face200in order to spall and remove the rock over a bore face area larger than the jet impingement area and the cross-section of the system100; selectively pause (or “dwell”) the nozzle160to locate the jet impingement area at a low boring rate region of the bore face200; and advance the cutterhead ram170forward according to a removal rate calculated during this raster cycle.

The controller180can repeat the closed-loop process over multiple raster cycles until the cutterhead ram170reaches the apex of its forward travel, at which time the controller180can fully retract the cutterhead ram170and advance the propulsion system120forward to locate the nozzle160at (approximately) the target standoff distance from the bore face200before repeating this process. Furthermore, in this example, the controller180can: maintain a consistent fuel flow rate through the combustor144and/or afterburner158and thus maintain a consistent temperature and pressure of exhaust gases220exiting the nozzle; and modulate a scan rate through which the system100rasters the nozzle160across the bore face200in order to achieve a target bore size (e.g., width and height) and a target bore profile (e.g., a D-shape) over the length of the bore.

CONCLUSION

The systems and methods described herein can be embodied and/or implemented at least in part as a machine configured to receive a computer-readable medium storing computer-readable instructions. The instructions can be executed by computer-executable components integrated with the application, applet, host, server, network, website, communication service, communication interface, hardware/firmware/software elements of a user computer or mobile device, wristband, smartphone, or any suitable combination thereof. Other systems and methods of the embodiment can be embodied and/or implemented at least in part as a machine configured to receive a computer-readable medium storing computer-readable instructions. The instructions can be executed by computer-executable components integrated by computer-executable components integrated with apparatuses and networks of the type described above. The computer-readable medium can be stored on any suitable computer readable media such as RAMs, ROMs, flash memory, EEPROMs, optical devices (CD or DVD), hard drives, floppy drives, or any suitable device. The computer-executable component can be a processor but any suitable dedicated hardware device can (alternatively or additionally) execute the instructions.

As a person skilled in the art will recognize from the previous detailed description and from the figures and claims, modifications and changes can be made to the embodiments of the disclosure without departing from the scope of this disclosure as defined in the following claims.