A method for excavating a connecting passage using a shape memory alloy device

Abstract

The application discloses a method for excavating a connecting passage by using a shape memory alloy device, and comprises the following steps: drilling a fracturing hole and a cavity hole on an excavation surface of the connecting passage; the fracturing hole and the cavity hole are arranged into a plurality of fracturing units, and the fracturing units are located in a closed circle formed by an excavation contour line of the connecting passage; a vertical line between a vault top point and a midpoint of a bottom side of the excavation contour line is taken as a central axis, the fracturing units are axially symmetrical about the central axis, and a plurality of the cavity holes are arranged in a vertical direction at the central axis; a memory alloy device is installed in the fracturing hole; the memory alloy device is heated, so that the memory alloy device is expanded and cracks the frozen soil; and the cracked frozen soil is secondarily crushed. The method has the advantages of reusable device, high operation stability, environmental protection and safety, and is particularly suitable for the excavation of a frozen wall of a subway connecting passage in a densely populated area and the subsequent construction of a supporting structure.

Description

Technical Field

[0001] This invention relates to the field of subway connecting passage construction technology. Specifically, it is a method for excavating connecting passages using a shape memory alloy device. Background Technology

[0002] In urban rail transit construction, the excavation of subway connecting passages is a crucial engineering step. Currently, the common methods for excavating connecting passages mainly rely on a combination of artificial freezing and pneumatic excavation. Specifically, artificial freezing is used to isolate groundwater and maintain the stability of the construction area, followed by the use of pneumatic drills to break up and excavate the frozen soil.

[0003] However, the traditional method of manually excavating frozen soil with pneumatic picks is slow, has a long construction period, and affects the overall project progress. This method is inefficient, operates under harsh conditions, and increases labor and equipment costs. Furthermore, pneumatic pick excavation generates significant noise and vibration, potentially impacting the surrounding environment, especially in densely populated urban areas. Therefore, a more efficient, safe, and environmentally friendly method for excavating frozen soil for connecting passages is urgently needed to optimize the construction process, improve project quality, and reduce construction costs. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to provide a method for excavating connecting passages using a shape memory alloy device.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] A method for excavating a connecting tunnel using a shape memory alloy device includes the following steps:

[0007] S1. Fracturing holes and voids are drilled on the excavation surface of the connecting passage; the fracturing holes and voids are arranged into multiple fracturing units, and the fracturing units are all located within the closed circle enclosed by the excavation outline of the connecting passage; the line perpendicularly connecting the top apex and the midpoint of the bottom edge of the excavation outline is taken as the central axis, the fracturing units are symmetrical about the central axis, and multiple voids are arranged at intervals along the vertical direction at the central axis;

[0008] S2. Install a shape memory alloy device in the fracturing hole;

[0009] S3. Simultaneously heat the shape memory alloy device in all the fracturing holes, causing the shape memory alloy device to expand and crack the frozen soil;

[0010] S4. Secondary crushing of the fractured frozen soil;

[0011] S5. Repeat steps S1 to S4 until the communication channel is completed.

[0012] S6. Construct a waterproof layer in the connecting passage and provide permanent support for the passage wall.

[0013] The above-described method for excavating connecting passages using shape memory alloy devices, in step S1, the fracturing unit is divided into a central fracturing unit, a peripheral fracturing unit, and a bottom edge fracturing unit; wherein:

[0014] The fracturing holes and voids in the central fracturing unit are arranged in a matrix at intervals.

[0015] There are multiple surrounding fracturing units, which are arranged at equal intervals. The fracturing holes and voids in any surrounding fracturing unit are arranged alternately in an inverted "U" shape, and the surrounding fracturing units are all parallel to the excavation outline. The central fracturing unit is located inside the inverted "U" shape of the surrounding fracturing units.

[0016] The fracturing holes and voids in the bottom edge fracturing unit are arranged in a straight line parallel to the bottom edge of the excavation outline and are adjacent to the bottom edge of the excavation outline.

[0017] In the above-described method for excavating connecting passages using a shape memory alloy device, in step S1, the hollow holes and the fracturing holes in the central fracturing unit are respectively central hollow holes and central fracturing holes. The central hollow holes are arranged vertically at intervals in a row on the central axis, and the central fracturing holes are arranged symmetrically about the central axis in two rows, with the two rows of central fracturing holes being symmetrical about the central axis. The central fracturing holes on both sides of each central hollow hole are located on the same horizontal line as the central hollow hole.

[0018] In the above-described method for excavating connecting passages using a shape memory alloy device, in step S1, the hollow holes and the fracturing holes in the bottom edge fracturing unit are respectively bottom edge auxiliary hollow holes and bottom edge fracturing holes; in the bottom edge fracturing unit: the bottom edge auxiliary hollow holes and the bottom edge fracturing holes are arranged alternately, the bottom edge auxiliary hollow holes located on both sides of the central axis are symmetrical to each other, the bottom edge fracturing holes located on both sides of the central axis are symmetrical to each other, and one bottom edge fracturing hole is located on the central axis.

[0019] In the above-described method of excavating connecting passages using a shape memory alloy device, each of the central fracturing holes in a row is vertically aligned with one of the bottom auxiliary holes.

[0020] The above-described method for excavating connecting passages using shape memory alloy devices comprises a first surrounding fracturing unit, a second surrounding fracturing unit, and a third surrounding fracturing unit arranged sequentially in the direction from the central fracturing unit to the excavation outline; wherein, the ends of the two inverted "U"-shaped arms of the third surrounding fracturing unit are fracturing holes, and the ends of the two inverted "U"-shaped arms of the first surrounding fracturing unit and the ends of the two inverted "U"-shaped arms of the second surrounding fracturing unit are hollow holes.

[0021] In the above-described method for excavating connecting passages using a shape memory alloy device, the holes at the ends of the inverted "U"-shaped arms of the first peripheral fracturing unit are vertically aligned with the two bottom fracturing holes in the bottom fracturing unit; the holes at the ends of the inverted "U"-shaped arms of the second peripheral fracturing unit are vertically aligned with the two bottom auxiliary holes in the bottom fracturing unit; and the fracturing holes at the ends of the inverted "U"-shaped arms of the third peripheral fracturing unit are vertically aligned with the two bottom fracturing holes at both ends of the bottom fracturing unit.

[0022] In the above-described method for excavating connecting passages using a shape memory alloy device, the cavities and fracturing holes in the surrounding fracturing unit are respectively surrounding auxiliary cavities and surrounding fracturing holes; the first surrounding fracturing unit includes 6 surrounding auxiliary cavities and 5 surrounding fracturing holes;

[0023] The second peripheral fracturing unit includes five peripheral auxiliary voids and four peripheral fracturing holes;

[0024] The third peripheral fracturing unit includes 8 peripheral auxiliary voids and 8 peripheral fracturing holes;

[0025] Furthermore, in both the first and third peripheral fracturing units, there is one peripheral fracturing hole located on the central axis.

[0026] In the above-described method for excavating connecting passages using shape memory alloy devices, the spacing between the central fracturing holes arranged vertically in the central fracturing unit is 0.7m to 0.9m.

[0027] In the first peripheral fracturing unit, the distance between the peripheral fracturing hole and the peripheral auxiliary hole is 0.6m to 0.8m; in the second peripheral fracturing unit, the distance between the peripheral fracturing hole and the peripheral auxiliary hole is 1.0m to 1.2m; in the third peripheral fracturing unit, the distance between the peripheral fracturing hole and the peripheral auxiliary hole is 0.6m to 0.8m.

[0028] The distance between two adjacent surrounding fracturing units is 0.5m to 0.7m; the distance between the excavation outline and the third surrounding fracturing unit is 0.3m to 0.4m.

[0029] In the above method of excavating connecting passages using a shape memory alloy device, in S1, the diameter of the fracturing hole and the hollow hole are both 50-60 mm, and the hole depth is both 0.45-0.55 m; in S2, the shape memory alloy device is the shape memory rock breaking device in the literature "Yang Dabing, Shao Peng, Fan Zhiyu, et al. Research on shape memory rock breaking device [J]. Blasting, 2012, 29(3): 104-108".

[0030] The technical solution of the present invention achieves the following beneficial technical effects:

[0031] 1. The method for excavating connecting passages using a shape memory alloy device provided by this invention achieves efficient, safe, and environmentally friendly excavation of frozen soil for connecting passages through the combination of the shape memory alloy device, layered fracturing units, and the void effect. Within the excavation outline, the central fracturing unit, the first surrounding fracturing unit, the second surrounding fracturing unit, the third surrounding fracturing unit, and the bottom fracturing unit are all arranged symmetrically about the central axis. The three surrounding fracturing units are evenly spaced, and the voids and fracturing holes in each fracturing unit are aligned vertically. When all shape memory alloy devices are simultaneously powered on and heated, the Ti-Ni shape memory alloy body expands almost simultaneously, outputting static fracturing force that is instantly superimposed across the entire excavation face. This allows for the effective generation of cracks on the excavation face with minimal vibration. With the scientifically designed arrangement of the fracturing units, an initial cracking zone with transversely extending cracks is formed first in the middle of the excavation face. Pressure-dense zones are formed above and below the initial cracking zone, pushing the cracks to simultaneously penetrate to the top and bottom of the excavation outline. This creates a continuous and blind-zone-free crack grid within the closed loop, with the crack grid extending uniformly parallel to the excavation outline. This splits the frozen soil into several relatively independent blocks with controllable dimensions. Manual pneumatic picks can then perform low-intensity secondary crushing of the frozen soil blocks, significantly improving stripping efficiency and reducing labor intensity.

[0032] 2. In the method for excavating connecting passages using a shape memory alloy device provided by this invention, the cavities and fracturing holes in each fracturing unit are aligned vertically, which not only prevents disorderly crack propagation but also effectively reduces residual ridges. The transverse cracks formed by the bottom fracturing holes and the bottom auxiliary cavities intersect with the cracks in the central fracturing unit and the surrounding fracturing units to form an inverted "T"-shaped connecting channel, ensuring that the residual frozen soil at the bottom does not restrain the fracturing above and preventing the disorderly extension of cracks to the frozen wall. In addition, the two surrounding fracturing holes located at the ends of the inverted "U"-shaped arms of the third surrounding fracturing unit are vertically aligned with the corresponding bottom fracturing holes in the bottom fracturing unit, forming stress concentration zones at the bottom corners of the excavation face, effectively preventing the generation of residual ridges at the bottom corners.

[0033] 3. The Ti-Ni shape memory alloy device used in this invention is wear-resistant, corrosion-resistant, and fatigue-resistant, maintaining stable performance during multiple fracturing cycles without the use of any chemical or explosive media, significantly extending its service life. The reusability of this device not only reduces the investment and replacement frequency of auxiliary equipment but also lowers construction costs and improves economic efficiency. Furthermore, the method provided by this invention involves a smoke-free, jet-free, and vibration-free construction process, minimizing environmental impact and making it particularly suitable for excavating frozen walls in subway connecting passages in densely populated areas. Attached Figure Description

[0034] Figure 1 A schematic diagram illustrating the positional relationship between the frozen wall and the excavation outline in an embodiment of the present invention;

[0035] Figure 2 A schematic diagram showing the location of the central fracturing unit in this embodiment of the invention;

[0036] Figure 3 A schematic diagram showing the specific arrangement of the surrounding fracturing units in an embodiment of the present invention;

[0037] Figure 4 A schematic diagram showing the specific arrangement of the bottom edge fracturing units in an embodiment of the present invention;

[0038] Figure 5 A schematic diagram showing the specific arrangement of the first, second, and third surrounding fracturing units in an embodiment of the present invention;

[0039] Figure 6 A schematic diagram of the completed communication channel in an embodiment of the present invention.

[0040] The reference numerals in the figure are as follows: 1-Frozen wall; 2-Central fracturing unit; 201-Central void; 202-Central fracturing hole; 3-Surrounding fracturing unit; 301-Surrounding auxiliary void; 302-Surrounding fracturing hole; 31-First surrounding fracturing unit; 32-Second surrounding fracturing unit; 33-Third surrounding fracturing unit; 4-Bottom fracturing unit; 401-Bottom auxiliary void; 402-Bottom fracturing hole; 5-Excavation outline; 6-Support structure. Detailed Implementation

[0041] This embodiment provides a method for excavating a connecting passage using a shape memory alloy device. The excavation surface of the connecting passage is located within the enclosure of a frozen wall 1, and the center of the excavation surface is the center of the excavation outline 5. Figure 1 As shown. The method includes the following steps:

[0042] 1. Fracturing holes and voids are drilled on the excavation surface of the connecting passage. The fracturing holes and voids are arranged into multiple fracturing units, all located within a closed loop enclosed by the excavation outline 5 of the connecting passage. Using the vertical line connecting the apex of the excavation outline 5 (i.e., the highest point of the arch of the excavation outline 5) and the midpoint of its bottom edge as the central axis, all fracturing units are symmetrical about this central axis. Multiple voids are arranged vertically at intervals along the central axis, such as... Figure 5 As shown.

[0043] Specifically, the fracturing unit is divided into a central fracturing unit 2, a peripheral fracturing unit 3, and a bottom fracturing unit 4. The fracturing holes and voids in the central fracturing unit 2 are central fracturing holes 202 and central voids 201, respectively, arranged in a matrix at intervals. The central voids 201 are arranged vertically at intervals along the central axis, and the central fracturing holes 202 are symmetrically arranged in pairs at the same height on both sides of each central void 201, meaning that the central fracturing holes 202 on both sides of each central void 201 are located on the same horizontal line as that central void 201. The central fracturing holes 202 are arranged symmetrically about the central axis in two rows. Figure 2 As shown.

[0044] like Figure 3 As shown, the surrounding fracturing units 3 contain surrounding fracturing holes 302 and surrounding auxiliary holes 301, arranged in multiple nested inverted "U" shapes. The curves of the inverted "U" shapes are parallel to the excavation outline 5, and adjacent surrounding fracturing units 3 are spaced equally. Within each inverted "U" shape (i.e., within each surrounding fracturing unit 3), the surrounding fracturing holes 302 and surrounding auxiliary holes 301 are arranged alternately. The central fracturing unit 2 is located within the opening of the inverted "U" shape of the surrounding fracturing unit 3.

[0045] like Figure 4As shown, the hollow holes and fracturing holes in the bottom edge fracturing unit 4 are bottom edge fracturing holes 402 and bottom edge auxiliary hollow holes 401, respectively, arranged in a straight line, parallel to the bottom edge of the excavation outline 5, and adjacent to the bottom edge of the excavation outline 5. In this embodiment, the bottom edge fracturing unit contains a total of 4 bottom edge auxiliary hollow holes 401 and 5 bottom edge fracturing holes 402, and one of the bottom edge fracturing holes 402 is located on the central axis. The bottom edge auxiliary hollow holes 401 and bottom edge fracturing holes 402 in the bottom edge fracturing unit are symmetrically distributed about the central axis.

[0046] The diameter of both the fracturing hole and the empty hole is 40 mm, and the hole depth is 0.5 m.

[0047] like Figure 5 As shown, in this embodiment, a first surrounding fracturing unit 31, a second surrounding fracturing unit 32, and a third surrounding fracturing unit 33 are arranged sequentially in the direction from the central fracturing unit 2 to the excavation outline 5. The first surrounding fracturing unit 31 includes six surrounding auxiliary holes 301 and five surrounding fracturing holes 302. The two ends of its inverted "U"-shaped arms are two surrounding auxiliary holes 301, which are vertically aligned with the two bottom fracturing holes 402 in the bottom fracturing unit 4. The second surrounding fracturing unit 32 includes five surrounding auxiliary holes 301 and four surrounding fracturing holes 302. The two ends of its inverted "U"-shaped arms are two surrounding auxiliary holes 301, which are vertically aligned with the two bottom auxiliary holes 401 in the bottom fracturing unit 4. The third peripheral fracturing unit 33 includes eight peripheral auxiliary holes 301 and eight peripheral fracturing holes 302. The top of its inverted "U"-shaped arms forms two peripheral fracturing holes 302, which are vertically aligned with the two bottom fracturing holes 402 in the bottom fracturing unit 4. Furthermore, in the first peripheral fracturing unit 31, one peripheral fracturing hole 302 is located on the central axis; in the second peripheral fracturing unit 32, one peripheral auxiliary hole 301 is located on the central axis; and in the third peripheral fracturing unit 33, one peripheral fracturing hole 302 is located on the central axis.

[0048] In this embodiment, the spacing between the central fracturing holes 202 arranged vertically in the central fracturing unit 2 is 0.8m, and the spacing of the central hollow holes 201 in the central fracturing unit 2 in the vertical direction is the same as the spacing of the central fracturing holes 202 in the vertical direction.

[0049] In the first peripheral fracturing unit 31, the distance between the peripheral fracturing holes 302 and the peripheral auxiliary holes 301 is 0.6m; in the second peripheral fracturing unit 32, the distance between the peripheral fracturing holes 302 and the peripheral auxiliary holes 301 is 1.0mm; and in the third peripheral fracturing unit 33, the distance between the peripheral fracturing holes 302 and the peripheral auxiliary holes 301 is 0.6m. The first peripheral fracturing unit is close to the center and experiences a large clamping force, so a small hole spacing in the first peripheral fracturing unit is beneficial for fracturing. The clamping force in the second peripheral fracturing unit is slightly less than that in the first peripheral fracturing unit, so the hole spacing in the second peripheral fracturing unit is slightly larger than that in the first peripheral fracturing unit, which can save construction costs. The third peripheral fracturing unit is adjacent to the outline, and its smaller hole spacing design is conducive to forming circumferential through-cracks and preventing cracks from developing towards the frozen wall.

[0050] The distance between two adjacent surrounding fracturing units 3 is 0.5m; the distance between the excavation outline 5 and the third surrounding fracturing unit 3 is 0.4m.

[0051] 2. Install shape memory alloy devices in all fracturing holes. The shape memory alloy device consists of a shape memory alloy body, a pressure transmission body and a heating element. It has a diameter of 30 mm and a length of 0.5 m. The material is Ti-Ni shape memory alloy. Its specific structure is designed according to the shape memory rock breaking device in the literature "Yang Dabing, Shao Peng, Fan Zhiyu, et al. Research on shape memory rock breaking device [J]. Blasting, 2012, 29(3): 104-108".

[0052] 3. The shape memory alloy devices within all the fracturing holes are electrically heated, causing them to expand and generate pressure. This pressure is then applied to the frozen soil within the area surrounded by the freezing wall 1 via a pressure transmission body, causing the frozen soil within this area to fracture, i.e., the frozen soil undergoes fracturing. In this embodiment, a Ti-Ni shape memory alloy device is used. This device operates at 170℃ and can complete the opening of the fracturing holes and the fracturing of the frozen soil within 30 seconds, with minimal thawing of the frozen soil on the excavation surface. During electrical heating, all the shape memory alloy devices are simultaneously energized. The uniform shape recovery speed of these devices allows the fracturing force on each fracturing hole to increase synchronously in a short time and to superimpose, generating a large number of fractures in an almost "static" manner. Furthermore, with the scientific arrangement of the fracturing holes and auxiliary voids in each fracturing unit, the fractures will extend into regular and uniform cracks on the excavation surface.

[0053] The pressure generated by the final shape memory alloy device will cause the frozen soil to fracture into several layers. Specifically, the frozen soil inside frozen wall 1 will split into multiple relatively independent blocks. Since each fracturing unit is symmetrical about the central axis, the frozen soil on both sides of the central axis will experience similar stress, resulting in roughly similar-sized fractured blocks with relatively clear boundaries. During secondary fracturing with a pneumatic hammer, only a light tap on the crack surface is needed to achieve rapid block removal, further improving construction efficiency.

[0054] 4. After checking the fracturing effect, use a manual pneumatic hammer to further break up the fractured frozen soil.

[0055] Repeat steps S1 to S4 until the entire cross-section of the connecting passage is completed. After excavation, waterproofing layer construction can be carried out, followed by construction of the reinforced concrete support structure 6 to complete the permanent support of the entire connecting passage. Figure 6 The cross section of the connecting passage after the completion of the support structure 6.

[0056] This invention achieves efficient and controllable fracture network construction by arranging a central fracturing unit 2, a first surrounding fracturing unit 31, a second surrounding fracturing unit 32, a third surrounding fracturing unit 33, and a bottom edge fracturing unit 4 on a frozen wall 1, and installing Ti-Ni shape memory alloy devices in each fracturing hole. It employs a process combining static fracturing and secondary crushing with pneumatic hammers. After heating, the shape memory alloy devices expand within each fracturing hole and output uniform static pressure outwards, causing the frozen soil within the closed circle enclosed by the excavation outline 5 to symmetrically develop cracks along a predetermined central axis. This allows for initial crushing without blasting, significantly reducing vibration and flyrock risks, while simultaneously keeping construction noise and environmental interference at extremely low levels.

[0057] Specifically, when all shape memory alloy devices are simultaneously heated, the shape memory alloy in each fracturing hole expands with the same temperature curve, and the output pressure is almost completely synchronized and instantaneously superimposed across the entire excavation surface. The reason for using "all-round" simultaneous fracturing is that the output force of a single shape memory alloy device is relatively small. If fracturing is performed hole by hole, the pressure cannot be superimposed, making it difficult to form a through crack on the excavation surface, resulting in poor fracturing effect.

[0058] In conjunction with this, in this embodiment, the central fracturing unit 2, the surrounding fracturing units 3, and the bottom fracturing unit 4 are all symmetrically arranged about the central axis. The three surrounding fracturing units 3 are evenly spaced and are in an inverted "U" shape. The holes on the two arms of the inverted "U" shape are precisely aligned vertically with the holes of the bottom fracturing unit 4. This arrangement of fracturing units allows the pressure generated by the expansion of the shape memory alloy devices in each fracturing hole to be effectively superimposed across the entire excavation surface, promoting the parallel development of cracks. It also facilitates the formation of multi-layered cracks with relatively uniform extension directions parallel to the excavation outline 5 on the excavation surface during fracturing. The extension of cracks on the excavation surface is regular and without blind spots, ultimately causing the frozen soil within the closed circle enclosed by the excavation outline to crack into several layers, forming multiple relatively independent frozen soil blocks, which facilitates manual crushing.

[0059] In this integrated fracturing mode, the central hollow holes 201 arranged vertically on the central axis first provide the lowest resistance initiation channel for the initial crack; the central fracturing holes 202 on both sides are symmetrically fracturing at the same height, so that the initial crack area is formed first in the middle of the excavation face (between the two rows of central fracturing holes 202).

[0060] Furthermore, in this embodiment, the distance between the central fracturing unit 2 and the bottom fracturing unit 4 is 0.5m. This distance is calculated based on the distance between the central fracturing hole 202 located at the bottommost point of the central fracturing unit 2 and the bottom auxiliary hole 401 that is adjacent to it and directly opposite it in the vertical direction. The distances between the first surrounding fracturing unit 31 and the bottom fracturing unit 4, the distances between the second surrounding fracturing unit 32 and the bottom fracturing unit 4, and the distances between the third surrounding fracturing unit 33 and the bottom fracturing unit 4 are 1.01m, 1.06m, and 0.69m, respectively. These distances are calculated based on the distance between the fracturing hole or hole at the end of the inverted "U" shaped arms of the corresponding surrounding fracturing unit (located at the bottommost point of the inverted "U" shaped arms) and the bottom fracturing hole 402 or bottom auxiliary hole 401 that is directly opposite the fracturing hole or hole in the vertical direction.

[0061] In other words, in this embodiment, the distance between the central fracturing unit 2 and the bottom fracturing unit 4 is relatively small. Therefore, in the bottom fracturing unit 4, the bottom fracturing hole 402 located on the central axis and the two lowest fracturing holes of the central fracturing unit 2 are more likely to generate stress superposition, forming a stress concentration zone below the initial fracturing region. At the same time, above the initial fracturing region, the three peripheral fracturing holes 302 of the arch of the first peripheral fracturing unit 31 will also generate stress superposition with the two uppermost central fracturing holes 202 of the central fracturing unit, forming another stress concentration zone.

[0062] These two stress concentration zones reinforce and push the frozen soil at the upper and lower ends of the cracks, causing the cracks to spread preferentially in the middle of the excavation face and continuously propagate along the central axis to the top and bottom of the excavation outline 5. This ultimately achieves a through-type crack network that runs synchronously from the center upwards and downwards. This not only ensures a dense distribution of cracks in the central area of ​​the entire excavation face, but also provides additional "pressure reinforcement" to the stress concentration zones at the top and bottom of the excavation face, which is more conducive to the comprehensive breaking of the frozen soil in these difficult-to-break areas.

[0063] After being fracturing, the bottom edge fracturing holes 402 and the bottom edge auxiliary voids 401 will form transverse cracks, quickly tearing open the bottom edge area and preventing the residual frozen soil from restraining the upper cracks. Since the holes on the inverted "U"-shaped arms of each surrounding fracturing unit 3 are aligned vertically with the holes between the bottom edge fracturing units, and the central fracturing holes are also aligned vertically with the bottom edge fracturing voids in the bottom edge fracturing units, the transverse cracks of the bottom edge fracturing unit 4 intersect with the cracks transmitted from the central fracturing unit 2 and the surrounding fracturing units 3, forming several inverted "T"-shaped connecting channels. This restricts the uncontrolled extension of cracks towards the frozen wall 1 and improves the safety of construction.

[0064] Specifically, the two peripheral fracturing holes 302 located at the ends of the inverted "U"-shaped arms of the third peripheral fracturing unit 33 are vertically aligned with a bottom fracturing hole 402, which creates a stress concentration zone at the bottom corner of the excavation face, preventing the formation of residual embankments at the bottom corner.

[0065] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A method for excavating connecting tunnels using a shape memory alloy device, characterized in that, Includes the following steps: S1. Fracturing holes and voids are drilled on the excavation surface of the connecting passage; the fracturing holes and voids are arranged into multiple fracturing units, and the fracturing units are all located within the closed circle enclosed by the excavation outline (5) of the connecting passage; the fracturing units are symmetrical about the central axis with the vertical line connecting the top of the arch and the midpoint of the bottom edge of the excavation outline (5) as the central axis, and multiple voids are arranged at intervals along the vertical direction at the central axis; S2. Install a shape memory alloy device in the fracturing hole; S3. Simultaneously heat the shape memory alloy device in all the fracturing holes, causing the shape memory alloy device to expand and crack the frozen soil; S4. Secondary crushing of the fractured frozen soil; S5. Repeat steps S1 to S4 until the communication channel is completed. S6. Construct a waterproof layer in the connecting passage and provide permanent support for the passage wall; In step S1, the fracturing unit is divided into a central fracturing unit (2), a peripheral fracturing unit (3), and a bottom edge fracturing unit (4); wherein: The fracturing holes and the voids in the central fracturing unit (2) are arranged in a matrix at intervals; There are multiple surrounding fracturing units (3), and the multiple surrounding fracturing units (3) are arranged at equal intervals; the fracturing holes and the voids in any surrounding fracturing unit (3) are arranged alternately in an inverted "U" shape, and the surrounding fracturing units (3) are all parallel to the excavation outline (5); the central fracturing unit (2) is located in the inverted "U" shape opening of the surrounding fracturing unit (3); The fracturing holes and the voids in the bottom edge fracturing unit (4) are arranged in a straight line parallel to the bottom edge of the excavation outline (5) and adjacent to the bottom edge of the excavation outline (5). In step S1, the hollow holes and fracturing holes in the central fracturing unit (2) are central hollow holes (201) and central fracturing holes (202), respectively. The central hollow holes (201) are arranged in a row at vertical intervals on the central axis, and the central fracturing holes (202) are arranged in two rows symmetrical about the central axis, and the two rows of central fracturing holes (202) are symmetrical about the central axis. The central fracturing holes (202) on both sides of each central hollow hole (201) are located on the same horizontal line as the central hollow hole (201). In step S1, the hollow hole and the fracturing hole in the bottom edge fracturing unit (4) are respectively the bottom edge auxiliary hollow hole (401) and the bottom edge fracturing hole (402); in the bottom edge fracturing unit (4): the bottom edge auxiliary hollow hole (401) and the bottom edge fracturing hole (402) are arranged alternately, the bottom edge auxiliary hollow holes (401) located on both sides of the central axis are symmetrical to each other, the bottom edge fracturing holes (402) located on both sides of the central axis are symmetrical to each other, and one of the bottom edge fracturing holes (402) is located on the central axis.

2. The method for excavating connecting passages using a shape memory alloy device according to claim 1, characterized in that, Each of the central fracturing holes (202) is vertically aligned with one of the bottom auxiliary holes (401).

3. The method for excavating connecting passages using a shape memory alloy device according to claim 1, characterized in that, In the direction from the central fracturing unit (2) to the excavation outline (5), a first surrounding fracturing unit (31), a second surrounding fracturing unit (32), and a third surrounding fracturing unit (33) are arranged in sequence; wherein, the ends of the two inverted "U"-shaped arms of the third surrounding fracturing unit (33) are fracturing holes, and the ends of the two inverted "U"-shaped arms of the first surrounding fracturing unit (31) and the ends of the two inverted "U"-shaped arms of the second surrounding fracturing unit are hollow holes.

4. The method for excavating connecting passages using a shape memory alloy device according to claim 3, characterized in that, The holes at the ends of the inverted "U"-shaped arms of the first peripheral fracturing unit (31) are vertically aligned with the two bottom fracturing holes (402) in the bottom fracturing unit (4); the holes at the ends of the inverted "U"-shaped arms of the second peripheral fracturing unit (32) are vertically aligned with the two bottom auxiliary holes (401) in the bottom fracturing unit (4); and the fracturing holes at the ends of the inverted "U"-shaped arms of the third peripheral fracturing unit (33) are vertically aligned with the two bottom fracturing holes (402) at both ends of the bottom fracturing unit (4).

5. The method for excavating connecting passages using a shape memory alloy device according to claim 4, characterized in that, The cavities and fracturing holes in the surrounding fracturing unit (3) are respectively surrounding auxiliary cavities (301) and surrounding fracturing holes (302); the first surrounding fracturing unit (31) includes 6 surrounding auxiliary cavities (301) and 5 surrounding fracturing holes (302). The second peripheral fracturing unit (32) includes five peripheral auxiliary cavities (301) and four peripheral fracturing cavities (302). The third peripheral fracturing unit (33) includes eight peripheral auxiliary cavities (301) and eight peripheral fracturing cavities (302). Furthermore, in the first peripheral fracturing unit (31) and the third peripheral fracturing unit (33), there is a peripheral fracturing hole (302) located on the central axis.

6. The method for excavating connecting passages using a shape memory alloy device according to claim 5, characterized in that, In the central fracturing unit (2), the spacing between the central fracturing holes (202) arranged in the vertical direction is 0.7m to 0.9m; In the first peripheral fracturing unit (31), the distance between the peripheral fracturing hole (302) and the peripheral auxiliary hole (301) is 0.6m to 0.8m; in the second peripheral fracturing unit (32), the distance between the peripheral fracturing hole (302) and the peripheral auxiliary hole (301) is 1.0m to 1.2m; in the third peripheral fracturing unit (33), the distance between the peripheral fracturing hole (302) and the peripheral auxiliary hole (301) is 0.6m to 0.8m. The distance between two adjacent surrounding fracturing units (3) is 0.5m to 0.7m; the distance between the excavation outline (5) and the third surrounding fracturing unit (33) is 0.3m to 0.4m.

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