Hybrid tunnel boring using combination of thermal and mechanical processes
Novel hybrid tunnel boring methods, systems, and apparatuses are described. Example hybrid methods integrate (a) thermal processing, e.g., preconditioning and/or thermal spallation (which may be used as pre-treatment), and (b) mechanical processing while boring tunnels in rock and other formations. Thermal processing and mechanical processing may be used alternatively or simultaneously. For example, the preconditioning may use thermal energy to induce thermal shock and weaken the rock (e.g., cause expansion stress, micro-fractures, thermal spallation, etc.). This preconditioning changes the relevant properties of the rock relative to the additional (e.g., mechanical) excavation, including, among other things, effective compressive stress, abrasion properties, and hardness. This preconditioned rock can therefore be efficiently removed using mechanical drilling tools, resulting in, for example, faster boring speeds, reduced tool wear, enhanced precision, and longer deployment lengths (e.g., in comparison to conventional TBM and especially MTBM approaches).
1 . A hybrid boring head defined by a primary axis and configured for boring an underground tunnel through ground comprising both soil and rock using different ones of multiple operating modes of the hybrid boring head, the hybrid boring head comprising:
a frame configured to rotate about the primary axis and to advance along the primary axis while boring the underground tunnel, the frame comprising:
a spoil drain opening,
a thermal unit opening extending through the frame and comprising a front orifice and a back orifice, and
a thermal-opening valve positioned within the thermal unit opening and configured to move between an open position and a shut position;
a thermal torch device positioned within the thermal unit opening between the thermal-opening valve and back orifice, wherein:
the thermal torch is configured to generate a thermal stream at least along a thermal stream axis directed to a bore face formed by the hybrid boring head in the underground tunnel while boring the underground tunnel,
the thermal torch device is selected from the group consisting of a burner, a turbine, and a plasma torch,
the thermal-opening valve, while in the shut position, isolates the thermal torch from the front orifice, and
the thermal-opening valve, while in the open position, opens the thermal torch to the front orifice; and
a set of mechanical boring implements attached to the frame and configured to contact and remove the ground from the bore face while boring the underground tunnel, wherein the set of mechanical boring implements is selected from the group consisting of mechanical rollers, mechanical teeth, and hard-faced structural elements.
2 . The hybrid boring head of claim 1 , wherein:
the thermal stream axis is not parallel to the primary axis, thereby enabling location control of an interface between the thermal stream and the bore face, and
the location control is provided by a rotational angle of the hybrid boring head about the primary axis.
3 . The hybrid boring head of claim 1 , wherein:
the front orifice is configured to direct the thermal stream to the bore face, and
the back orifice is configured to house one or more lines for operating the thermal torch device positioned in the thermal unit opening.
4 . The hybrid boring head of claim 1 , wherein the thermal torch device is recessed into the thermal unit opening away from the front orifice.
5 . The hybrid boring head of claim 1 , wherein an offset of the thermal torch device relative to the front orifice determines a spread angle of the thermal stream as the thermal stream exits the thermal unit opening and is directed to the bore face.
6 . The hybrid boring head of claim 5 , wherein the hybrid boring head is steerable when forming a portion of the underground tunnel through the rock by controlling a dwell time of the thermal stream on portions of the bore face during rotation.
7 . The hybrid boring head of claim 1 , wherein position of the thermal torch device within the thermal unit opening relative to the frame is adjustable.
8 . The hybrid boring head of claim 1 , wherein the thermal torch device is pivotable relative to the frame, thereby changing an angle between the primary axis and the thermal stream axis.
9 . The hybrid boring head of claim 1 , wherein the thermal torch device is axially movable within the thermal unit opening, thereby changing a spread angle of the thermal stream as the thermal stream exits the thermal unit opening and is directed to the bore face.
10 . The hybrid boring head of claim 1 , wherein a power output of the thermal torch device is adjustable and is different for the different ones of the multiple operating modes of the hybrid boring head.
11 . The hybrid boring head of claim 1 , further comprising one or more additional thermal torch devices attached to the frame and configured to generate additional thermal stream directed to the bore face, wherein a path of the thermal stream axis on the bore face is offset relative to paths of additional thermal stream axis.
12 . The hybrid boring head of claim 1 , wherein the frame comprises a steering surface that is not colinear or parallel to the primary axis thereby enabling steering of the hybrid boring head while forming the underground tunnel through the soil using a combination a rotational angle of the hybrid boring head about the primary axis and an axial movement of the hybrid boring head along the primary axis.
13 . The hybrid boring head of claim 1 , wherein the frame further comprises a spoil intake defined by an intake angle and extending between an outer perimeter of the frame and at least one of the spoil drain opening.
14 . The hybrid boring head of claim 1 , wherein:
the set of mechanical boring implements are mechanical teeth comprising a front set, a reaming set, and a crushing set,
the front set is configured to form the bore face,
the reaming set is configured to form a tunnel wall, and
the crushing set is configured to assist the ground to pass through the drain openings.
15 . The hybrid boring head of claim 1 , wherein the set of mechanical boring implements comprises abrasion-resistant coatings or inserts comprising one or more materials selected from the group consisting of tungsten carbide, boron carbide, and polycrystalline diamond.
16 . The hybrid boring head of claim 1 , wherein the set of mechanical boring implements is offset relative to the thermal stream axis such that the thermal stream does not contact the set of mechanical boring implements.
17 . The hybrid boring head of claim 1 , further comprising one or more sensors configured to measure one or more of (a) torque between the hybrid boring head and the head actuating unit, (b) thrust between the hybrid boring head and the head actuating unit, (c) pressure inside the underground tunnel, and (d) temperature of one or more components of the hybrid boring head.
18 . The hybrid boring head of claim 1 , wherein:
the frame comprises a drain-opening valve positioned within the spoil drain opening,
the drain-opening valve, when shut, prevents flow through the spoil drain opening, and
the drain-opening valve, when open, allows the flow through the spoil drain opening.
19 . The hybrid boring head of claim 18 , wherein:
the frame comprises seeping holes, extending between the spoil drain opening and the set of the mechanical boring implements, and
when the drain-opening valve is shut, a drilling fluid is configured to be evenly distributed through the seeping holes from the spoil drain opening.