Underground space expansion method based on pre-cut groove and load underpinning system and its structure

Abstract

This invention relates to a method and structure for underground space expansion based on a pre-cut groove and load-bearing system. Underground expansion projects may cause ground displacement, posing safety hazards to the surrounding environment. This method involves opening holes in the sidewalls of existing underground structures, removing reinforcing steel from the sidewalls and retaining structures according to the outline of the pre-cut groove; drilling laterally at the opening location, then longitudinally extending and cutting to form the pre-cut groove, simultaneously injecting concrete into the pre-cut groove; excavating small pilot tunnels and shafts below the cover plate; constructing support piles within the shafts; fully excavating and constructing the bottom slab, sidewalls, and top slab; pouring a ring beam, and integrally superimposing the ring beam with the cover plate, top slab, sidewalls, and longitudinal beams. In this invention, the cover plate injection and pre-cut groove construction are synchronized, achieving the effect of cutting and constructing simultaneously. Furthermore, a high-rigidity pipe roof is installed within the cover plate thickness to achieve cover plate-type advanced support. The support piles and cover plate form a vertical plate-column type advanced support force transmission system, effectively avoiding ground displacement that may occur during underground project expansion.

Description

Technical Field

[0001] This invention relates to the field of underground engineering construction technology, specifically to a method and structure for expanding underground space based on pre-cut grooves and load-bearing systems. Background Technology

[0002] In recent years, with changes in climate and the development of underground space, various underground renovation and expansion projects have been increasing. For example, due to the significant impact of surface transportation on the surrounding environment and its susceptibility to external climate factors, underground transportation and road projects offer greater advantages, involving numerous urban underpass reconstruction projects. Furthermore, with the continuous advancement of TOD (transit-oriented development) projects based on rail transit stations, various expansion projects of rail transit stations are commonplace. Since the surrounding environment of key stations is generally complex, the expansion of existing underground projects is difficult and risky, urgently requiring new expansion concepts and technologies to support underground engineering expansion. Therefore, underground engineering expansion technologies based on the needs of surrounding environmental protection have attracted widespread attention in the industry.

[0003] The expansion of existing underground engineering projects generally involves excavating the strata first and then constructing the support structure. This is not substantially different from the construction method of general underground engineering. However, due to the relatively harsh surrounding environment and the need to protect existing structures, the expansion of existing projects typically faces challenges. Currently, high-rigidity pipe roofs and pre-grouting reinforcement are commonly used. While these methods can pre-reinforce the strata, they suffer from uncontrollable reinforcement effects. Ground displacement and deformation caused by excavation cannot be effectively controlled, and the safety of the surrounding environment cannot be guaranteed. To ensure the safety of the project itself and the surrounding environment, it is necessary to take measures to provide effective support to the strata before expansion excavation.

[0004] Given that existing advanced ground reinforcement techniques and their effectiveness cannot be effectively improved, and considering current underground engineering excavation methods, the risks to ground displacement and the surrounding environment caused by underground engineering expansion cannot be effectively mitigated. Therefore, there is an urgent need to design new advanced ground support techniques for underground engineering expansion, especially in situations where environmental protection requirements are relatively stringent and safety margins are relatively small. Summary of the Invention

[0005] The purpose of this invention is to provide a method and structure for underground space expansion based on pre-cut grooves and load replacement system, so as to solve the problems of ground displacement and safety hazards of the surrounding environment that may be caused during the expansion of underground engineering projects.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for expanding underground space based on pre-cut grooves and load-bearing systems, the method comprising:

[0008] According to the design location of the expanded underground space, holes are made in the side walls of the existing underground works, and the steel bars in the side walls and the enclosure structure are removed according to the outline of the pre-cut groove.

[0009] After drilling laterally to the designed depth at the opening position, longitudinally extend and cut to form a pre-cut groove. Simultaneously, during the formation of the pre-cut groove, press-in the cover plate concrete into the space of the pre-cut groove.

[0010] Excavate a small horizontal pilot tunnel under the cover plate, and excavate a vertical shaft downward at the end of the pilot tunnel;

[0011] Construct support piles inside the shaft;

[0012] The top of the support pile is supported by a cover plate, forming a vertical load transmission system. Under the protection of the vertical load transmission system, the underground space is fully excavated and expanded.

[0013] After the excavation of the expanded underground space is completed, the base slab, side walls, and roof slab of the expanded underground space are constructed.

[0014] The L-shaped ring beam is poured after the main structure is poured, and then the L-shaped ring beam is superimposed on the cover plate, the top slab of the expanded underground space, and the side walls and longitudinal beams of the existing underground works.

[0015] Furthermore, the method also includes:

[0016] After the concrete of the cover plate reaches its initial setting strength, a transverse high-rigidity pipe shed is installed in the cover plate.

[0017] Furthermore, reinforcing steel bars are inserted into the high-rigidity pipe shed, and micro-expansion cement mortar is injected.

[0018] Furthermore, the method also includes:

[0019] Within the shaft area, concrete is sprayed into the gap between the support piles and the end wall of the small pilot tunnel to form concrete backfill.

[0020] Furthermore, the method also includes:

[0021] During the construction of the pilot tunnel and the vertical shaft, grouting anchor pipes were used as temporary supports.

[0022] Furthermore, the method also includes:

[0023] The top of the side wall of the expanded underground space is connected to the cover plate using rebar and epoxy grout.

[0024] Furthermore, the construction of the roof slab for the expanded underground space includes:

[0025] Reinforcing bars were installed at the bottom of the cover plate, and the top slab of the extended underground space was poured. The top slab of the extended underground space and the cover plate were treated as composite components.

[0026] On the other hand, an underground space expansion structure based on a pre-cut groove and load-bearing system is provided. The structure is obtained by the method described above and includes a cover plate, support piles, an underground space expansion base plate, an underground space expansion side wall, and an underground space expansion top plate.

[0027] The extended underground space consists of the base slab, the side walls, and the top slab, and is connected to the existing underground works at the side walls.

[0028] The cover plate is located above the top slab of the expanded underground space, and the top of the support pile supports the cover plate and is located on the lateral outer side of the side wall of the expanded underground space.

[0029] Furthermore, the structure also includes a post-cast L-shaped ring beam, which is superimposed and connected to the cover plate, the top slab of the extended underground space, and the side walls and longitudinal beams.

[0030] Furthermore, concrete backfill is applied to the lateral outer side of the support pile.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] This invention provides a method and structure for underground space expansion based on a pre-cut groove and load-bearing system. The structure includes a cover plate based on a pre-cut groove, with concrete pouring for the cover plate and pre-cut groove construction carried out simultaneously to achieve a "cut-and-build" effect. A high-rigidity pipe roof is installed within the cover plate thickness to achieve "cover plate-type pre-support." Support piles are installed at certain intervals below the cover plate, and these support piles provide working space through a small tunnel and an internal shaft. The support piles and the cover plate form a vertical "plate-column-type pre-support" force transmission system. Finally, large-area excavation of the expansion space is carried out, followed by the pouring of the lining structure. This invention, based on the "plate-column-type pre-support" load system, realizes a "support-before-excavation" expansion process for underground space, effectively avoiding potential ground displacement during underground engineering expansion. The concept is clear, the process is convenient and safe, and the results are controllable and significant. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art 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 embodiments can be obtained from these drawings without creative effort.

[0034] Figure 1This is a schematic diagram of the horizontal expansion construction based on underground engineering in the method of the present invention.

[0035] Figure 2 This is a schematic diagram of the longitudinal distribution of the cover plate and supporting piles in the structure of this invention.

[0036] Figure 3 This is a schematic diagram of the full-section excavation and expansion of the vertical load transmission system in the structure of this invention.

[0037] Figure 4 This is a cross-sectional view of the expanded underground space after the lateral expansion construction using the method of this invention.

[0038] The diagram is labeled as follows:

[0039] 1-Building, 2-Pile foundation, 3-Enclosure structure, 4-Existing underground works, 5-Cover plate, 6-High rigidity pipe shed, 7-Small pilot tunnel, 8-Shaft, 9-Grouting anchor pipe, 10-Support pile, 11-Concrete backfill, 12-Shaft bottom outline, 13-Expanding underground space, 14-Post-cast L-shaped ring beam;

[0040] 41-Top slab, 42-Middle slab, 43-Bottom slab, 44-Side wall, 45-Central column, 46-Longitudinal beam;

[0041] 131 - Expand the base slab of the underground space; 132 - Expand the side walls of the underground space; 133 - Expand the top slab of the underground space. Detailed Implementation

[0042] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0043] In the description of this invention, it should be understood that the terms "vertical", "horizontal", "longitudinal", "lateral", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0044] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connection," "setting," etc., should be interpreted broadly. For example, they can refer to a fixed connection or setting, a detachable connection or setting, or an integral connection or setting. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0045] In a specific implementation, Figure 1 The direction from left to right is defined as horizontal, and the direction perpendicular to the horizontal is defined as vertical.

[0046] like Figure 1 The existing underground structure 4 mainly consists of a top slab 41, a middle slab 42, a bottom slab 43, central columns 44, and longitudinal beams 45, and also has an external enclosure structure 3. Due to the need for underground space development, lateral expansion construction is required at specific locations. This invention provides an underground space expansion method based on a pre-cut groove and load-bearing system, which is applicable to the construction of an expanded underground space 13 for the existing underground structure 4.

[0047] First, dewatering operations are carried out according to design requirements. Construction begins once the groundwater level has been lowered to the required depth. Figure 1-4 The method includes:

[0048] S1: According to the design location of the expanded underground space 13, make a hole in the side wall 44 of the existing underground project 4, and remove the steel bars in the side wall 44 and the enclosure structure 3 according to the outline of the pre-cut groove.

[0049] The outline and scope of the excavation must be strictly controlled, and static cutting with a wire saw should be used. Before cutting, necessary temporary support should be provided for the existing underground works according to the cutting scope, such as the erection of steel columns.

[0050] S2: After drilling laterally to the designed depth at the opening location, longitudinally extend and cut to form a pre-cut groove. During the formation of the pre-cut groove, concrete for the cover plate 5 is simultaneously injected into the space of the pre-cut groove. After the concrete for the cover plate 5 reaches its initial setting strength, transverse high-rigidity pipe sheds 6 are installed in the cover plate 5 at certain intervals along the longitudinal direction. Reinforcing steel bars are inserted into the high-rigidity pipe sheds 6, and micro-expansion cement mortar is injected.

[0051] A hinged trenching device is used for trenching construction. This device consists of a main arch frame, a cutter holder, and a movable chain cutter. The entire device can move on a set track or step beam structure. First, the chain cutter is used to drill laterally from position 44 of the side wall to the designed depth. Then, longitudinal cutting is performed. During the longitudinal movement of the hinged trenching device and the chain cutter, concrete for the cover plate 5 is simultaneously poured, completing the cover plate pouring within the underground expansion area. The hinged trenching device and chain cutter can achieve continuous cutting and excavation in a near-horizontal direction. The pre-cut trench excavation and cover plate 5 pouring can be carried out continuously in one operation along the longitudinal direction of the underground project 4.

[0052] The high-rigidity pipe shed 6 is generally about 3-5m longer than the cover plate 5. After inserting reinforcing steel bars into the high-rigidity pipe shed 6 and injecting micro-expansion cement mortar, it can increase the overall bending stiffness of the cover plate 5, reduce deformation, and form a "thin shell" cover plate structure with specific bending resistance.

[0053] The distance between the pre-cut groove outline and the upper part of the cover plate 5 and the existing underground engineering longitudinal beam 46 is determined by the operating space of the hinged grooving equipment and the chain cutter. The longitudinal spacing of the high-rigidity pipe shed 6 can generally be considered to be around 300mm.

[0054] The specific dimensions of the cover plate 5 should be designed specifically according to the project conditions. Its width is generally determined by the trenching equipment and chain cutter, but should not be less than 250mm. Its transverse length is generally determined by the range of the underground space 13 to be expanded, and should generally exceed the width of the bottom plate 131 of the underground space by at least 3m. In addition, the length of the high-rigidity pipe shed 6 exceeding the cover plate 5 by at least 4m can basically cover the range of stratum deformation during the excavation of the underground space 13. If the underground space 13 is a multi-story structure, the dimensions need to be adjusted accordingly.

[0055] S3: Excavate transverse pilot tunnels 7 at regular intervals along the longitudinal direction of the underground space below the cover plate 5. The width and height of the pilot tunnels 7 can be considered to be about 2m. At the end of the pilot tunnels 7, excavate a vertical shaft 8 downwards to the bottom outline 12. The depth of the shaft 8 can be considered to be about 4m. The specific dimensions of the shaft 8 should meet the needs of the pile foundation construction. During the construction of the pilot tunnels 7 and the shaft 8, grouting anchor pipes 9 are used as temporary support.

[0056] S4: Construct support piles 10 within shaft 8. Within the area of ​​shaft 8, spray concrete into the gap between support piles 10 and the end wall of the small guide tunnel 7 to form concrete backfill 11.

[0057] The construction of support pile 10 uses a small drilling rig for pile foundation drilling. Depending on the specific geological conditions, mud slurry is used for drilling when necessary. After reaching the predetermined depth, the hole is cleaned, and then a reinforcing cage is placed and concrete is poured. The pile foundation within the depth range of the shaft is constructed using formwork casting. The construction of support pile 10 is completed, and the top of support pile 10 is secured to the cover plate 5 with steel wedges.

[0058] The support piles 10 are arranged longitudinally at certain intervals. The support piles 10 are mainly provided by the small guide tunnel 7 and the vertical shaft 8. The distance between the bottom outline 12 of the vertical shaft and the cover plate 5 is generally about 4m, which is determined by the working height of the drilling machinery.

[0059] S5: A steel wedge needs to be inserted between the top of the support pile 10 and the cover plate 5 to ensure stable force transmission. After all the support piles 10 are installed, they form a vertical load transmission system with the cover plate 5. Under the protection of the vertical load transmission system, the underground space 13 is fully excavated and expanded.

[0060] like Figure 3 Under the protection of the vertical load transmission system formed by the support piles 10 and the cover plate 5, the expansion of the underground project can be carried out by using the step method or the full-section excavation method to excavate the strata, which can speed up the construction progress to the greatest extent, while ensuring that the settlement and deformation of the strata meet the requirements of the surrounding environmental protection.

[0061] S6: After the excavation of the expanded underground space 13 is completed, the expanded underground space floor slab 131, expanded underground space side walls 132, and expanded underground space roof slab 133 are constructed. The top of the expanded underground space side walls 132 is connected to the cover plate 5 using rebar anchoring and epoxy grout. When constructing the expanded underground space roof slab 133, rebar anchoring is carried out at the bottom of the cover plate 5, and the expanded underground space roof slab 133 is poured. The expanded underground space roof slab 133 and the cover plate 5 are treated as composite components.

[0062] The length of the support pile 10 is generally no less than 5m below the bottom slab 131 of the underground space. The specific length can be appropriately increased according to the stratum conditions, or the pile with an enlarged bottom can be used to further increase the vertical bearing capacity of the pile foundation.

[0063] A waterproof layer also needs to be laid below the base slab 131 of the expanded underground space. The support piles 10 are sprayed with mortar and smoothed, then the waterproof membrane is adhered and the side wall 132 of the expanded underground space is poured.

[0064] S7: Cast the post-cast L-shaped ring beam 14, and integrate the post-cast L-shaped ring beam 14 with the cover plate 5, the top plate 133 of the expanded underground space, and the side wall 44 and longitudinal beam 46 of the existing underground works 4 to ensure the formation of an integral load-bearing node.

[0065] The side walls 132 and the top slab 133 of the expanded underground space, as well as the cover plate 5, must be considered as composite components to enhance the safety of the expanded underground space structural system. Finally, a post-cast L-shaped ring beam 14 is used to connect the cover plate 5, the top slab 133 of the expanded underground space, the side walls 44 and longitudinal beams 45 of the existing underground space 4 into a structural node that bears the load as a whole, forming a "strong node" design scheme to ensure the safety and stability of the node.

[0066] The above-described method resulted in an underground space expansion structure based on a pre-cut groove and load-bearing system. This structure includes a cover plate 5, support piles 10, an expanded underground space base slab 131, expanded underground space side walls 132, and expanded underground space top slab 133. The expanded underground space base slab 131, expanded underground space side walls 132, and expanded underground space top slab 133 together form the expanded underground space 13, which connects to the existing underground structure 4 at side wall 44. The cover plate 5 is located above the expanded underground space top slab 133, and the support piles 10 support the cover plate 5 at their tops and are located laterally outside the expanded underground space side walls 132.

[0067] The structure also includes a post-cast L-shaped ring beam 14, which is superimposed and connected to the cover plate 5, the top slab 133 of the extended underground space, and the side walls 44 and longitudinal beams 46. Concrete backfill 11 is applied to the transverse outer side of the support piles 10.

[0068] Above the opening at sidewall 44 is a pre-cut groove, and above the pre-cut groove is a cover plate 5. A high-rigidity pipe roof 6 is installed inside the cover plate 5, together forming the "upper cover" structure of the vertical load transfer system. Below the cover plate 5 are support piles 10, which, together with the cover plate 5, form an "advanced cover plate type" vertical load transfer system. During the construction of the pre-cut groove and cover plate 5, the concrete pouring of the cover plate 5 is carried out simultaneously with the longitudinal pre-cut groove excavation, ensuring that the underground "thin shell" space formed by the pre-cut groove construction is effectively filled immediately, minimizing ground stress release and settlement deformation.

[0069] In the above structure, Q235 steel can be used for the high-rigidity pipe shed 6 and the grouting anchor pipe 9, while C35 or higher grade concrete can be used for various plate wall columns, support piles 10, and L-shaped ring beams 14. Ordinary HRB335 steel bars can be used for the steel bars in various plate wall columns, and ordinary Portland cement can be considered for the cement mortar injected in the high-rigidity pipe shed 6 and the grouting anchor pipe 9.

[0070] The method provided by this invention requires the following attention during implementation:

[0071] 1. The specific dimensions of the cover plate 5 and the support pile 10 should generally be based on the overall stress calculation and analysis. It can be analyzed according to the most unfavorable working condition after the excavation of the entire underground space 13 is completed. Under normal circumstances, the thickness of the cover plate 5 should not be less than 250mm, and the lateral range of the cover plate should exceed the width of the bottom plate 131 of the underground space by 3m.

[0072] 2. The construction accuracy of the trenching equipment and chain cutter is basically guaranteed by the guide rail or traveling rail installed on the existing underground engineering 4 bottom plate 43. The longitudinal cutting speed of the chain cutter should not be too fast. The specific speed should be determined comprehensively based on the geological conditions, concrete injection of the cover plate 5, etc.

[0073] 3. The length of the high-rigidity pipe shed 6 inside the cover plate 5 should exceed the edge of the cover plate 5 by at least 4m to ensure a tight "interlocking" effect between the cover plate 5 and the surrounding strata. The high-rigidity pipe shed 6 can significantly improve the load-bearing capacity and bending stiffness of the cover plate 5. The diameter of the high-rigidity pipe shed 6 is generally not less than 109mm, and can be appropriately increased depending on the situation, but it should be ensured that the diameter of the high-rigidity pipe shed 6 does not exceed 50% of the thickness of the cover plate 5.

[0074] 4. The dimensions of the small pilot tunnel 7 and the vertical shaft 8 shall be based on the premise of the construction of the support piles 10. Under this premise, the excavation range shall be minimized as much as possible to reduce the release of ground stress and settlement deformation. During the excavation of the small pilot tunnel 7 and the vertical shaft 8, grouting anchor pipes 9 shall be used for temporary support. The tunnel wall or shaft wall may be appropriately sloped as appropriate.

[0075] The structure of the present invention has the following features and advantages:

[0076] 1) Based on the concept of “bearing and supporting, supporting before excavation”, this invention achieves synchronous pouring of the pre-cut slab through pre-cut groove, and then uses small guide tunnels and shafts to achieve the construction of support piles. Under the “supporting” effect of the support piles and the pre-cut slab, the underground space is then expanded and excavated. This can meet the strict control of ground displacement during the expansion of underground space and meet the stringent protection requirements of the surrounding environment.

[0077] 2) The trenching equipment and chain cutter for pre-cutting can be specifically designed according to the working space available for the underground project. At the same time, the rigidity and size of the chain cutter can also be optimized and adjusted according to the geological conditions. For example, if the geological strength is high, especially in gravel strata, the rigidity and cutting capacity of the chain cutter need to be increased accordingly to ensure the smooth cutting of the strata and reduce the disturbance of the strata during the cutting process.

[0078] 3) The dimensions of the pilot tunnel and shaft required for the construction space of the support pile should be determined according to the operating space of the support pile drilling machinery. Generally, the size of the pilot tunnel can be controlled at 2m, and the height of the shaft can be controlled at 4-5m. Due to the limited space, and in order to facilitate the rigid connection between the top of the support pile and the cover plate, the support pile can be made of steel pipe concrete pile. The sections of steel pipe are connected by threaded mechanical connection, and anchor nails are set around the steel pipe wall to ensure that the overall shear resistance and stress meet the requirements after the concrete is poured later.

[0079] 4) The “plate-column type advanced support” based on the pre-cut groove and load replacement system described in this invention can meet the stringent protection requirements of the surrounding environment during the expansion of underground space. The solution is clear, simple in process and easy to construct, with high economic and social benefits. It has broad application prospects in structural engineering projects such as urban underground space development, rail transit and railway projects.

[0080] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the principles of this invention.

Claims

1. A method for expanding underground space based on pre-cut grooves and load-bearing replacement systems, characterized in that: The method includes: According to the design location of the expanded underground space (13), an opening is made in the side wall (44) of the existing underground project (4), and the steel bars in the side wall (44) and the enclosure structure (3) are removed according to the outline of the pre-cut groove. After drilling laterally to the designed depth at the opening position, longitudinally extend and cut to form a pre-cut groove. Simultaneously, press the cover plate (5) concrete into the pre-cut groove space during the formation of the pre-cut groove. A small horizontal guide tunnel (7) is excavated below the cover plate (5), and a vertical shaft (8) is excavated downward at the end of the small guide tunnel (7). Construct support piles (10) inside the vertical shaft (8); The top of the support pile (10) is supported by the cover plate (5), forming a vertical load transmission system. Under the protection of the vertical load transmission system, the underground space (13) is fully excavated and expanded. After the excavation of the underground space (13) is completed, the underground space floor slab (131), the underground space side walls (132) and the underground space roof slab (133) are constructed. Cast the L-shaped ring beam (14) after casting, and then combine the L-shaped ring beam (14) with the cover plate (5), the top plate of the expanded underground space (133), and the side wall (44) and longitudinal beam (46) of the existing underground works (4) as a whole; The method further includes: Within the vertical shaft (8), concrete is sprayed into the gap between the support pile (10) and the end wall of the small guide tunnel (7) to form concrete backfill (11).

2. The underground space expansion method based on pre-cut grooves and load-bearing system according to claim 1, characterized in that: The method further includes: After the concrete of the cover plate (5) reaches its initial setting strength, a transverse high-rigidity pipe shed (6) is installed in the cover plate (5).

3. The underground space expansion method based on pre-cut grooves and load-bearing system according to claim 2, characterized in that: Reinforcing steel bars are inserted into the high-rigidity pipe shed (6), and micro-expansion cement mortar is injected.

4. The underground space expansion method based on pre-cut grooves and load-bearing system according to claim 3, characterized in that: The method further includes: During the construction of the small pilot tunnel (7) and the vertical shaft (8), grouting anchor pipes (9) were used as temporary supports.

5. The underground space expansion method based on pre-cut grooves and load-bearing system according to claim 4, characterized in that: The method further includes: The top of the side wall (132) of the underground space expansion is connected to the cover plate (5) by anchoring and epoxy grouting.

6. The method for expanding underground space based on pre-cut grooves and load-bearing system according to claim 5, characterized in that: Constructing the roof slab (133) for the expanded underground space, including: Reinforcing bars are installed at the bottom of the cover plate (5), and the top slab (133) of the underground space is poured. The top slab (133) of the underground space and the cover plate (5) are treated as composite components.

7. An underground space expansion structure based on a pre-cut groove and load-bearing system, characterized in that: The structure is obtained by the method described in claim 6, including a cover plate (5), support piles (10), an extended underground space bottom plate (131), an extended underground space side wall (132), and an extended underground space top plate (133). The base slab (131) of the expanded underground space, the side wall (132) of the expanded underground space and the top slab (133) of the expanded underground space constitute the expanded underground space (13), and the expanded underground space (13) is connected to the existing underground project (4) at the side wall (44); The cover plate (5) is located above the top plate (133) of the expanded underground space, and the top of the support pile (10) supports the cover plate (5) and is located on the lateral outside of the side wall (132) of the expanded underground space.

8. The underground space expansion structure based on pre-cut grooves and load-bearing system according to claim 7, characterized in that: The structure also includes a post-cast L-shaped ring beam (14), which is superimposed and connected to the cover plate (5), the top plate (133) of the extended underground space, and the side wall (44) and the longitudinal beam (46).

9. The underground space expansion structure based on pre-cut grooves and load-bearing system according to claim 8, characterized in that: The outer side of the support pile (10) is filled with concrete (11).

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