A deep underground space excavation supporting structure and an excavation construction method

Abstract

This invention belongs to the field of underground engineering construction technology, and particularly relates to a deep underground space tunneling support structure and construction method. The structure includes a surrounding enclosure, multiple enlarged head piles arrayed inside the enclosure, and multiple layers of arched body groups arranged from bottom to top. The enlarged head piles have multiple layers of outwardly protruding enlarged heads on their pile bodies, and each layer of arched body group is located above and connected to the enlarged head of a corresponding layer. The construction method includes: first constructing the enclosure and enlarged head piles, and then forming multiple layers of arched body groups; subsequently, excavating the soil layer by layer from bottom to top and constructing the permanent main structure of each layer; when the Nth layer of main structure is completed and the N+1th layer of soil is excavated, the arched body group of the Nth layer is removed, and this cycle is repeated until completion, while retaining the topmost arched body group. This invention can achieve advanced support, effectively control deformation, save underground space, and improve construction efficiency and safety.

Description

Technical Field

[0001] This invention belongs to the field of underground engineering construction technology, and in particular relates to a deep underground space tunneling support structure and tunneling construction method. Background Technology

[0002] With the deepening of global urbanization, urban land resources are becoming increasingly scarce, and expanding into underground space has become a key path to enhance urban functions and achieve sustainable development. The development of deep underground space, such as the construction of large-scale underground transportation hubs, integrated utility tunnels, or commercial complexes, faces complex geological conditions, stringent environmental protection requirements, and high standards for construction safety and efficiency. Against this backdrop, how to safely, efficiently, and economically complete the excavation and support of deep, long-span underground spaces is a core technical challenge that urgently needs to be solved in the field of underground engineering.

[0003] Currently, deep underground space excavation commonly employs techniques such as open-cut excavation, traditional tunneling, and shield tunneling. Open-cut excavation requires large-scale surface excavation, causing significant disruption to urban traffic, the environment, and existing infrastructure, making it difficult to apply in urban core areas. While traditional tunneling can reduce surface impact, its support systems, such as multi-layer internal bracing or anchor bolt support, are typically complex, occupying substantial usable building space, limiting the flexibility of underground space layout, and involving cumbersome construction procedures and long cycles. Particularly during the removal of temporary supports, stress redistribution in the surrounding rock can easily occur, leading to secondary deformation of the foundation pit and increasing the risk of ground settlement and damage to surrounding structures. Furthermore, existing support methods often focus on the structural bearing capacity itself, failing to fully guide and utilize the bearing capacity of the surrounding rock, resulting in high material consumption and construction costs for the support structure. Moreover, there is often a lack of effective collaborative stress-bearing mechanisms between temporary supports and the permanent main structure, leaving room for improvement in the long-term stability and economy of the overall structure.

[0004] Therefore, there is an urgent need for a multi-layer pre-arch support system for deep underground space excavation to solve the above problems and achieve the goals of optimizing the utilization rate of underground space, shortening the construction period and reducing the project cost under the premise of strictly controlling stratum deformation and ensuring construction safety. Summary of the Invention

[0005] The purpose of this invention is to provide a support structure and a method for tunneling in deep underground spaces to solve the above-mentioned problems.

[0006] To achieve the above objectives, the present invention provides the following solution: A deep underground space tunneling support structure includes: Enclosures are set up around the perimeter of the space to be excavated; Multiple flared piles are arranged in an array on the inner side of the enclosure. The flared piles are vertically arranged, and multiple outwardly protruding flared heads are arranged at equal intervals from bottom to top on the pile body. A multi-layered arched body assembly is arranged at equal intervals from bottom to top. The arched body assembly is arranged corresponding to multiple expansion heads located on the same layer, and the arched body assembly is located above the expansion heads.

[0007] Preferably, the top and bottom surfaces of the expansion head are both provided with load-bearing inclined surfaces in the circumferential direction, the outer edges of the two load-bearing inclined surfaces are close to each other, and the arched body assembly is arranged on the load-bearing inclined surfaces.

[0008] Preferably, the arched body assembly includes a central arch and side arches. The central arch is disposed between the four enlarged piles forming a rectangle, and the side arches are disposed between the enlarged piles and the inner wall of the enclosure. The bottom ends of the central arch and the side arches are both disposed on the load-bearing inclined surface of the top surface of the enlarged pile.

[0009] Preferably, the central arch and the side arch are constructed using high-pressure jet grouting pile technology, employing a triple-pipe method for layered construction from bottom to top.

[0010] Preferably, the enclosure includes a continuous wall surrounding the space to be excavated, and the side arch is disposed between the continuous wall and the expansion pile.

[0011] A method for deep underground space excavation based on the aforementioned deep underground space tunnel support structure includes the following steps: S1. Excavate a working shaft to be used as a transportation channel; S2. Excavate the soil layer by layer from bottom to top. After each layer of soil is excavated, construct the permanent main structure. S3. When the permanent main structure of the Nth floor is completed and reaches the design strength, and the soil excavation of the N+1th floor is completed, the arched body of the Nth floor is demolished, where N≥1; S4. Repeat steps S2 to S3 until construction is complete, retaining the arched body group at the top layer.

[0012] Preferably, the permanent main structure includes a base slab and multiple underground beams. The base slab is located above the soil in the lowest space, and the multiple underground beams and the multiple expansion heads are arranged in a one-to-one correspondence.

[0013] Compared with the prior art, the present invention has the following advantages and technical effects: This invention provides a support structure and construction method for deep underground space excavation. By setting up a perimeter enclosure around the space to be excavated, and arranging enlarged piles with multiple enlarged heads on their inner side, a multi-layered arched structure connected to the enlarged heads is constructed layer by layer from bottom to top using high-pressure jet grouting, forming a pre-support system before excavation. During construction, the soil is excavated layer by layer from bottom to top, and the permanent main structure is constructed simultaneously. Each time a layer of the main structure is completed and the soil above it is excavated, the arched structure of that layer is dismantled, while the topmost arch is retained. This invention uses thin-walled arches instead of traditional bulky supports, significantly saving underground space; the layered arch dismantling process simplifies the process, shortens the construction period, and avoids the settlement risk of overall support dismantling; it fully utilizes the soil arch effect to transfer the load to the enlarged piles and enclosure, reducing the burden on the support structure itself and saving costs; at the same time, the permanently retained top arch works in conjunction with the main structure, enhancing overall stability, thus achieving safe, efficient, and economical underground space development. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort: Figure 1 This is an overall schematic diagram of the support structure before excavation in this invention; Figure 2 This is a schematic diagram of the support structure before excavation in this invention; Figure 3 This is a schematic diagram of the support structure after excavation is completed in this invention; Among them, 1. Expanded head pile; 2. Expanded head; 3. Central arch; 4. Side arch; 5. Underground beam; 6. Base slab; 7. Continuous wall. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] In this invention, the expanded head pile 1, as a key load-bearing component in the underground structure system, integrates multiple core functions such as vertical bearing, anti-buoyancy, anti-lateral displacement, foundation reinforcement, deformation restraint, and seismic damping. It can effectively transfer the load of the superstructure to the deep bearing layer, resist the buoyancy of groundwater and the action of horizontal loads, improve the mechanical properties of the foundation soil, control the overall and local deformation of the structure, and dissipate energy and reduce the structural response under seismic action. It is a core technical component to ensure the vertical and horizontal stability of the underground structure and enhance the overall safety reserve and durability of the project. The enlarged head 2 forms a stable bearing interface. Its core function is to bear all the loads transmitted by the soil arch and to transmit the loads stably, reliably and evenly to the surrounding stable soil. It effectively expands the load diffusion range and reduces local soil stress concentration. It is equivalent to the key load-bearing support of the soil arch structure, providing reliable support for the continuous performance and stable transmission of the soil arch effect, and ensuring the mechanical continuity and overall stability of the soil arch system under long-term loads and complex working conditions. The central arch 3 and the side arch 4 work together with the stable soil in their respective areas to form and strengthen the soil arch effect, optimize the stress transmission path, and efficiently transfer the soil's self-weight and additional load to the pile heads or continuous walls and piles on both sides through the arch-shaped force transmission mechanism, forming a stable arch-shaped force system. This significantly improves the overall stability of the soil between piles and between walls and piles, and effectively curbs soil slippage, collapse and other unstable damage. As a crucial lateral force-transmitting component of the underground structural system, underground beam 5 serves multiple functions, including load-bearing and force transmission, auxiliary lateral resistance, structural connection, deformation control, functional adaptation, and construction assurance. Through its own stiffness and reasonable reinforcement, it effectively bears and transmits superimposed and lateral loads, coordinates the force distribution of adjacent components such as piles, soil arches, and side walls, reduces uneven structural deformation and internal force concentration, enhances the overall spatial coordination and overall stiffness of the structure, and provides a reliable guarantee for the stable operation of the underground structure under vertical and horizontal loads. As the core load-bearing and force-transmitting component of the underground structure, the base plate 6 mainly bears and evenly transmits various vertical loads such as those from the superstructure, backfill, and construction. At the same time, it effectively resists the buoyancy of groundwater and the arching pressure of the soil. Through the coordinated work with components such as side walls, piles, and underground beams, it forms a complete load-bearing system with closed space, clear force distribution, and overall coordination. This significantly improves the overall stiffness, buoyancy resistance, and deformation resistance of the underground structure, providing a solid foundation for the overall stability and safe operation of the underground structure under long-term service and complex working conditions. As the core support and water-stopping component for underground space excavation and main structure construction, the continuous wall 7, with its excellent overall rigidity and structural strength, effectively bears and resists the active earth pressure, water pressure and additional lateral load generated by the side wall soil after underground space excavation. It reliably prevents the surrounding soil from collapsing, sliding and lateral deformation, while also having good water-stopping and seepage prevention performance. It provides a safe, stable and closed working space for layered excavation, main structure pouring and subsequent construction processes in underground space. It is a key technical measure to ensure the safety of underground engineering construction, control stratum deformation and protect the surrounding environment.

[0018] Reference Figures 1 to 3 This invention discloses a support structure for deep underground space excavation, comprising: Enclosures are set up around the perimeter of the space to be excavated; Multiple enlarged piles 1 are arranged in an array on the inner side of the enclosure. The enlarged piles 1 are set vertically, and multiple outwardly protruding enlarged heads 2 are set at equal intervals from bottom to top on the pile body of the enlarged pile 1. The multi-layered arched body group is arranged at equal intervals from bottom to top. The arched body group is arranged in correspondence with multiple expansion heads 2 located on the same layer, and the arched body group is located above the expansion heads 2.

[0019] Before excavating deep underground spaces, a perimeter fence is constructed around the area to be excavated for boundary protection. Then, multiple vertical, enlarged-head piles 1 are arrayed inside the fence, each pile 1 having multiple outwardly protruding enlarged heads 2 at equal intervals. Next, multi-layered arched body assemblies are constructed from bottom to top, corresponding to the layers of enlarged heads 2. Each layer of arched body assembly is located above the corresponding layer of enlarged heads 2, thus pre-forming a multi-layered arched support network in the soil. This invention utilizes the cooperation between the arched body assemblies and the enlarged heads 2 to fully leverage the soil arching effect, transmitting the soil pressure released during excavation through the arches to the enlarged-head piles 1 and the fence, achieving advanced support and deformation control of the soil in the excavation area, and providing a safe and stable working environment for subsequent bottom-up tunneling construction.

[0020] The scheme was further optimized by providing load-bearing inclined surfaces on both the top and bottom surfaces of the expanded head 2. The outer edges of the two load-bearing inclined surfaces are close to each other, and the arched body assembly is set on the load-bearing inclined surfaces.

[0021] The top and bottom of the expanded head 2 are circumferentially formed with mutually close outer edge bearing ramps. During the construction of the arch assembly, the bottom of the arch assembly is supported and attached to these bearing ramps. The bearing ramps provide a stable and reliable support surface for the arch assembly, increase the contact area between the arch foot and the expanded head 2, and allow the load transmitted from the arch to be more evenly and smoothly distributed to the expanded head 2 and the pile body. This optimizes the force transmission path and enhances the reliability of the connection between the arch and the pile and the stability of the overall structure.

[0022] The inclined plane has an inclination angle of 45° and a generatrix length of 1m.

[0023] Setting the inclination angle of the load-bearing slope to 45° allows for a more reasonable decomposition of forces when bearing the oblique pressure transmitted from the arch. It also facilitates construction positioning and quality control, ensuring that the expansion head 2 is in a good stress state, balancing the horizontal and vertical components of the force, preventing stress concentration, and thus further improving the mechanical properties and force transmission efficiency of the support interface.

[0024] Further optimization of the scheme: the arch body group includes a central arch 3 and a side arch 4. The central arch 3 is set between the four enlarged piles 1 that form a rectangle, and the side arch 4 is set between the enlarged piles 1 and the inner wall of the enclosure. The bottom ends of the central arch 3 and the side arch 4 are both set on the load-bearing inclined surface of the top surface of the enlarged pile 2.

[0025] The arched structure specifically comprises a central arch 3 and side arches 4. The central arch 3 is constructed above the center of the rectangular area enclosed by four enlarged head piles 1; the side arches 4 are constructed in the area between the enlarged head piles 1 and the inner wall of the retaining wall. The bottom ends of both types of arches are supported on the load-bearing inclined surfaces of the top surfaces of the corresponding enlarged head piles 2. The central arch 3 and side arches 4 are designed to address the different stress and constraint conditions between piles within the underground space and between the edge piles and walls, achieving full coverage and refined design of the support system. Working together, they transmit the earth pressure across the entire excavation surface to the surrounding enlarged head piles 1 and the retaining wall through the arch effect, forming a complete and efficient pre-support system.

[0026] To further optimize the plan, the central arch 3 and the side arch 4 were constructed using high-pressure jet grouting pile technology, employing a triple-pipe method for layered construction from bottom to top.

[0027] The spray-jet arching material uses cement, but can also be replaced with cement-water glass dual-liquid slurry, which is suitable for soft soil geological scenarios that require rapid curing.

[0028] The triple-tube jet grouting process can be replaced by the five-tube jet grouting process, which adds high-pressure cutting teeth and secondary grouting channels to further improve the cutting efficiency of hard soil layers and the anti-seepage performance of the arch, making it suitable for large-span deep underground space projects with a span of ≥15m.

[0029] During the construction of the central arch (3) and the side arches (4), high-pressure jet grouting was employed, specifically using the triple-tube method. The jet grouting was carried out layer by layer from bottom to top, allowing the grout to mix with the soil and solidify to form the designed arch structure. High-pressure jet grouting enables the formation of a high-strength, high-integrity cement-soil arch in situ underground without prior excavation, achieving both "underground excavation" and "pre-support." The triple-tube method effectively controls the quality and dimensions of the arch, while the layered construction from bottom to top ensures the sequential formation and integrity of the multi-layered arch structure.

[0030] The scheme was further optimized, and the enclosure includes a continuous wall 7, which is set around the perimeter of the space to be excavated, and the side arch 4 is set between the continuous wall 7 and the enlarged head pile 1.

[0031] The enclosure uses a continuous wall 7, which is installed around the perimeter of the space to be excavated. One end of the side arch 4 is supported on the enlarged head 2 of the enlarged head pile 1, while the other end is supported or embedded in the continuous wall 7. The continuous wall 7 itself has high rigidity and good water-stopping performance, which can effectively bear the soil pressure transmitted from the side arch 4, and together with the enlarged head pile 1, it forms a stable vertical support boundary. This makes the entire pre-arch support system closely integrated with the outer permanent retaining structure continuous wall 7, forming a closed and rigid load-bearing frame, which greatly enhances the overall stability of the foundation pit.

[0032] A method for deep underground space tunneling construction based on a deep underground space tunneling support structure, comprising the following steps: S1. Excavate a working shaft to be used as a transportation channel; S2. Excavate the soil layer by layer from bottom to top. After each layer of soil is excavated, construct the permanent main structure. S3. When the permanent main structure of the Nth floor is completed and reaches the design strength, and the soil excavation of the N+1th floor is completed, the arched body of the Nth floor is demolished, where N≥1; S4. Repeat steps S2 to S3 until construction is complete, retaining the arched body group at the top layer.

[0033] First, a working shaft is excavated as a passage for materials and personnel. Then, starting from the bottom, the soil is excavated layer by layer from bottom to top. After each layer is excavated, the permanent main structure of that layer is immediately constructed. When the permanent main structure of the Nth layer is completed and reaches the required strength, and the soil of the N+1th layer has also been excavated, the arch assembly of the Nth layer can be safely dismantled. This cycle of "excavating one layer, constructing one layer of structure, excavating the next layer, and dismantling one layer of arch" is continued layer by layer until the construction is completed, retaining the topmost arch assembly as part of the permanent structure. This invention achieves seamless connection and smooth load transfer between the temporary support arch assembly and the permanent structure construction. "Layered arch dismantling" avoids the concentrated risks of removing all temporary supports at once, resulting in high construction safety. The bottom-up sequence is consistent with the structural construction sequence, with clear logic, which helps to shorten the construction period. Retaining the top arch further enhances the load-bearing capacity of the permanent structure.

[0034] The excavation process can also be replaced by first excavating to the intermediate layer, constructing the intermediate structure, and then excavating downwards to the bottom layer and upwards to the top layer.

[0035] The scheme was further optimized. The permanent main structure includes a base slab 6 and multi-layer underground beams 5. The base slab 6 is located above the soil in the lowest space, and the multi-layer underground beams 5 and multi-layer extensions 2 are set up in a one-to-one correspondence.

[0036] The permanent main structure constructed in step S2 includes a base slab 6 located above the lowest soil layer, and underground beams 5 arranged in a one-to-one correspondence with the multi-layered expansion heads 2. During construction, each underground beam 5 is reliably connected to the corresponding expansion head 2 and the completed main structure of that layer, such as columns and walls. The base slab 6 bears the vertical load and resists buoyancy, while the multi-layered underground beams 5 effectively transfer and distribute the loads of each layer to the arrayed expansion head piles 1. Together with the expansion head piles 1, the continuous wall 7, and the retained top-level arch, they form a permanent frame structure system with high spatial stiffness and clear stress distribution, ensuring the long-term stability and safe use of the underground space after its completion.

[0037] One specific example: The underground space project has a total height of 16 meters, designed in four layers, with a net height of 4 meters per layer. The construction sequence follows the principle of "support first, excavation second, structure third, excavation of the next layer, and removal of the arch of the next layer," and the specific process is as follows: 1. Construct a 2m thick underground continuous wall 7 with a wall depth of 25.0m, including an underground buried section of 17.0m and a bearing layer embedded at a depth of 8.0m, as a permanent support structure around the project to complete the boundary enclosure of the overall space; 2. Construct 15 enlarged head piles 1, with a pile diameter of 1.5m and a total height of 23m. Among them, the underground buried section is 17m deep and the bearing layer is embedded to a depth of 6m, which are precisely driven into the design depth to provide core vertical support for the subsequent construction of the arch body; the distance between the edges of the two bearing inclined surfaces of the enlarged head 2 is 0.1m.

[0038] 3. A circular cap-shaped arch is formed using high-pressure jet grouting technology. The triple-pipe method is employed, with an effective cutting radius of 1.0~2.0m under conventional construction, which can be increased to 2.0~2.5m through parameter optimization. The jet grouting is performed in four layers from bottom to top. After the central arch 3 and side arch 4 are formed, their outlines coincide with the 45° inclined edge of the expanding head 2, forming a support system by closely fitting the inclined edge of the expanding head 2. The thickness of the central arch 3 and the side arch 4 is 1m.

[0039] 4. Excavate an 8m×10m working shaft as a vertical transportation channel for personnel, equipment and materials during construction; 5. Carry out soil excavation work, starting from the bottom layer and proceeding layer by layer in the order of "from bottom to top". After the excavation of each layer of soil is completed, the construction of the permanent main structure of that layer shall be carried out simultaneously. The construction of the permanent main structure shall also be carried out layer by layer from the bottom layer. The bottom slab 6 is designed to be 1m thick. 6. After the permanent main structure of each floor is completed and reaches the design strength, and after the excavation of the soil of the previous floor is completed, the jet grouting arch of the next floor is dismantled. The closed-loop process of "excavation of the previous floor → dismantling of the next floor arch" is completed in the order of "excavation of the previous floor → structure → excavation of the previous floor → dismantling of the arch" for each floor.

[0040] Ground settlement was effectively controlled, fully complying with current standards and design requirements, and strongly ensuring the safety and stability of surrounding buildings, underground pipelines, and the site itself. Compared to traditional support schemes, this invention significantly optimizes support material consumption, greatly reducing material procurement, transportation, and on-site processing costs; it also effectively shortens the construction period, improves overall project construction efficiency, and creates favorable conditions for earlier intervention in subsequent processes. Furthermore, the underground structural system adopted in this invention is flexible and adaptable, fully matching the functional requirements and spatial layout characteristics of storage facilities. While ensuring overall structural rigidity and load-bearing capacity, it maximizes space utilization efficiency; the structure itself exhibits excellent stability, effectively resisting various loads and deformation effects during construction and use, possessing good long-term safety and reliability, and providing a solid guarantee for the safe operation of storage facilities.

[0041] This invention has the following advantages: 1. Multi-layer underground arch construction technology: It adopts the core mode of "arch first, layered advancement" and takes the bottom-up construction logic as the overall construction logic - first, the arch support system is constructed layer by layer from bottom to top to form an early stable load-bearing structure; then, with the arch as support, the earthwork excavation and main structure construction are promoted simultaneously from bottom to top, realizing the integrated collaborative operation of "support first, excavation follow, and structure forming", effectively controlling the deformation of the strata and ensuring construction safety and efficiency; 2. A technical solution for constructing underground multi-layered concealed arches using triple-tube jet grouting technology, including the coordinated adaptation of composite jetting parameters (such as pressure, flow rate, and velocity), borehole layout, slurry ratio, and concealed arch forming design; 3. The construction process of "layered construction and layered arch removal" is as follows: After the main structure of each layer is completed and passes inspection, and the soil of the previous layer is excavated to the design elevation, the temporary hidden arch of the next layer is removed; the hidden arch of the top layer is retained and used as a permanent support structure. 4. The construction technology of multi-layer hidden arches in deep underground spaces adopts the jet grouting method to form the arch structure. The key is to ensure the quality of arch formation and structural integrity by precisely controlling the cutting radius of the jet grouting method. Specifically, it also includes the reasonable layout of the underground excavation face and the precise control of key parameters in each stage. At the same time, it clarifies the technical points of the connection between the top permanent hidden arch and the main structure.

[0042] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0043] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A support structure for deep underground space excavation, characterized in that, include: Enclosures are set up around the perimeter of the space to be excavated; Multiple enlarged piles (1) are arranged in an array on the inner side of the enclosure. The enlarged piles (1) are vertically set, and multiple outwardly protruding enlarged heads (2) are arranged at equal intervals from bottom to top on the pile body of the enlarged piles (1). The multi-layered arched body group is arranged at equal intervals from bottom to top. The arched body group is arranged in correspondence with the multiple expansion heads (2) located on the same layer. The arched body group is located above the expansion heads (2).

2. The deep underground space tunneling support structure according to claim 1, characterized in that, The top and bottom surfaces of the expansion head (2) are both provided with load-bearing inclined surfaces in the circumferential direction. The outer edges of the two load-bearing inclined surfaces are close to each other, and the arched body assembly is set on the load-bearing inclined surfaces.

3. The deep underground space tunneling support structure according to claim 2, characterized in that, The arched body assembly includes a central arch (3) and side arches (4). The central arch (3) is located between the four enlarged piles (1) forming a rectangle. The side arches (4) are located between the enlarged piles (1) and the inner wall of the enclosure. The bottom ends of the central arch (3) and the side arches (4) are both located on the load-bearing inclined surface of the top surface of the enlarged head (2).

4. The deep underground space tunneling support structure according to claim 3, characterized in that, During construction, the central arch (3) and the side arch (4) are constructed using high-pressure jet grouting pile technology and the triple-pipe method, which is used to construct them layer by layer from bottom to top.

5. The deep underground space tunneling support structure according to claim 3, characterized in that, The enclosure includes a continuous wall (7) which surrounds the space to be excavated, and the side arch (4) is located between the continuous wall (7) and the expansion pile (1).

6. A method for deep underground space excavation based on the deep underground space excavation support structure according to any one of claims 1-5, characterized in that, The steps are as follows: S1. Excavate a working shaft to be used as a transportation channel; S2. Excavate the soil layer by layer from bottom to top. After each layer of soil is excavated, construct the permanent main structure. S3. When the permanent main structure of the Nth floor is completed and reaches the design strength, and the soil excavation of the N+1th floor is completed, the arched body of the Nth floor is demolished, where N≥1; S4. Repeat steps S2 to S3 until construction is complete, retaining the arched body group at the top layer.

7. The method for deep underground space excavation according to claim 6, characterized in that, The permanent main structure includes a base plate (6) and multiple underground beams (5). The base plate (6) is located above the soil in the lowest space. The multiple underground beams (5) and the multiple expansion heads (2) are set in a one-to-one correspondence.

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