Underground space vertical extension construction method and structure

Abstract

The invention relates to an underground space vertical extension construction method and structure, the structure comprises a compensation pile, an anchoring assembly, a truss, a back shore supporting system and a newly added foundation, and the compensation pile is vertically arranged on the outer side of a projection line of an existing building outer wall; the anchoring assembly is fixed to the upper middle portion of an existing structural column in an original first underground layer in a surrounding mode to form a high-position load stress node, the inner end of the truss is fixedly connected with the anchoring assembly, and the outer end of the truss penetrates through an existing side wall of the original first underground layer and is fixed to the pile top of the compensation pile to form a suspension type supporting system. The newly-added foundation is arranged below the extension space below the original first underground layer, and a stress foundation of the extension structure is formed. The design is ingenious, deep expansion of the underground space is achieved, stress is clear, construction is controllable, combination of a new structure and an old structure is reliable, and applicability is high.

Description

Technical Field

[0001] This invention relates to the field of underground space construction technology in building engineering, specifically to a method and structure for vertical expansion construction of underground space. Background Technology

[0002] As the population continues to grow in major cities across my country, the existing above-ground building capacity is no longer sufficient to meet the needs of residents' production and daily life. Commercial, residential, and municipal facilities such as shopping malls, subway stations, and integrated transportation hubs are gradually expanding into deeper underground spaces. However, many existing buildings did not make overall plans for the long-term use of underground space during the initial construction phase, resulting in a small number of underground floors and limited space that does not match current usage needs.

[0003] Currently, the main methods for expanding the underground space of existing buildings are demolition and reconstruction or horizontal expansion. However, demolition and reconstruction are costly and time-consuming, and the building loses its functionality during construction. Horizontal expansion, whether it is open excavation or tunneling, has problems such as large land area, complex connection nodes between new and old structures, and large construction disturbance.

[0004] Patent "CN118793298A" discloses a method for underground extension of existing buildings in operation. The scheme utilizes the remaining bearing capacity of existing pile foundations to excavate a construction space below the existing foundation, constructs and replaces the pile foundations and extends the upper columns, sets hydraulic jacks between the basement conversion roof slab and the existing foundation, disconnects the existing pile foundations from the foundation through the lifting force of the jacks, and adjusts the building deformation according to monitoring data, ultimately realizing the underground extension of existing buildings.

[0005] However, this scheme has the following problems in actual construction: Because jacks are installed on the conversion slab, the conversion slab will undergo bending deflection deformation after being loaded. This deflection deformation will be directly superimposed on the jacks, resulting in uncontrollable initial settlement of the existing building during load transfer. Moreover, since the jacks must be installed in the narrow gap between the existing foundation and the new conversion slab, the supporting equipment, hydraulic pipelines, etc. are densely distributed above the excavation area. This layout will directly limit the construction space and thus directly restrict the construction efficiency of building multiple floors downward. In addition, the scheme mentions that the jacks can adjust the elevation of the existing building in real time according to settlement monitoring data, which is a passive compensation mechanism. Therefore, it cannot actively balance the uneven deformation of large-span support components caused by complex stratum stress, and has a certain degree of response lag and adjustment limitations.

[0006] Therefore, it is necessary to study a construction method and structure for vertical expansion of underground space. Summary of the Invention

[0007] Therefore, the purpose of this invention is to provide a method and structure for vertical expansion of underground space, which can effectively solve the problems existing in the prior art.

[0008] To achieve the above objectives, the technical solution adopted by this invention is as follows: a construction structure for vertical expansion of underground space, comprising compensating piles, anchoring components, trusses, a top-support system, and a new foundation. The compensating piles are vertically arranged outside the projection line of the existing building's exterior wall, with the pile bottom embedded in the bearing layer of the underground soil. The anchoring components are fixed to the upper middle part of the existing structural columns within the original basement level, forming a high-level load-bearing node. The truss is arranged horizontally, with its inner end fixedly connected to the anchoring components, and its outer end passing through the existing side wall of the original basement level and fixed to the top of the compensating piles. The top-support system includes jacks located at the bottom of the inner end of the truss and at the top of the compensating piles, with the inner jacks supporting the left and right ends of the truss to form a suspended support system. The new foundation is located below the expansion space below the original basement level, forming the load-bearing foundation of the expansion structure.

[0009] Furthermore, the anchoring assembly includes a friction lining, a shell, and a support bracket. The two sets of shells are interlocked and fixed to the existing structural column. The friction lining is adapted and fixed to the inner side of the shell. When the shells are fixed together, the friction lining is fitted to the existing structural column. The support bracket is welded and fixed to the outer wall of the shell for fixed connection with the truss.

[0010] Furthermore, multiple reinforcing ribs are uniformly fixed on the outer wall of the shell.

[0011] Furthermore, the existing side wall is provided with through-wall openings, and steel through-wall boxes are installed in the openings; the truss passes through the boxes and is interlocked with them, so that the truss load does not directly act on the existing side wall.

[0012] Furthermore, the area around the truss opening in the side wall is reinforced with carbon fiber cloth.

[0013] Furthermore, the new foundation includes a new pile foundation located at the bottom of the expanded space, a new pile cap located on top of the new pile foundation, and a new load-bearing column connecting the new pile cap with the cut section of the existing structural column.

[0014] Furthermore, the new load-bearing column is coaxially aligned with the existing structural column, and the two are connected by longitudinal steel bars and integrally cast with high-strength grout to form an integrated vertical load-bearing component.

[0015] This invention also provides a method for vertical expansion of underground space, comprising the following steps: Step 1: Lay out the location of the compensation piles outside the projection line of the existing building's exterior wall, and construct the compensation piles to form an external rigid support foundation; Step 2: Install anchoring components in the upper part of the existing structural column to form a high-level load-bearing pipe joint with the existing structural column. Step 3: Construct a steel truss, rigidly connect one end of the truss to the anchoring components, and let the other end pass through the side wall laterally and be supported on the top of the compensation pile to form a suspension system, so that the load can be transferred to the external compensation pile through the truss; Step 4: Install jacks on the inside of the truss and on the top of the compensation piles, and control the inner and outer jacks to lift synchronously in stages to realize the conversion of the load path from the existing structural column bottom bearing to the high-level suspended bearing; Step 5: After the suspension system is stable, cut the existing structural column bases, partially closed sections of the original base plate, and abandoned existing pile foundations in the expansion area; Step 6: Excavate the earthwork layer by layer from top to bottom to the foundation elevation, and then carry out new structural construction, including the construction of new pile foundations, new pile caps and new base slabs, to build a permanent bottom load-bearing system; Step 7: Construct new load-bearing columns, so that the new load-bearing columns, existing structural columns, and new foundations form an integrated vertical load-bearing component; Step 8: Using the new pile foundation, new pile cap, and new load-bearing columns as supports, construct the new structural beams and slabs, side walls, and supporting waterproofing and electromechanical pre-embedded works of the underground expansion layer from bottom to top in reverse construction. Step 9: After the strength of the new structure meets the standard, control the jacks to reduce the pressure in stages and transfer the upper load to the permanent load-bearing system. Then, dismantle the temporary suspension structure and seal the soil extraction port to complete the vertical expansion of the underground space.

[0016] Furthermore, in the aforementioned steps, fiber Bragg grating sensors are pre-embedded on the surface of the existing structural columns. During the jacking process and the load transfer process, the structural stress and displacement changes are monitored in real time by the fiber Bragg grating sensors, and the jacking amount or pressure reduction amount of the jacks is adjusted in real time based on the monitoring data.

[0017] Furthermore, in the aforementioned steps, the jacks at both ends of the truss are controlled to lift synchronously in stages, and the lifting amount is adjusted in real time to balance the inward and outward moments of the truss until the residual reaction force at the base of the existing structural column is reduced to 5%-8% of the initial value and the displacement is stable.

[0018] The beneficial effects of the above technical solution are: the construction method and structure for vertical expansion of underground space provided by the present invention set up anchoring nodes in the upper part of the existing structural columns, and shifted the building load outward as a whole through the outer compensation piles and steel trusses, so as to avoid problems such as delayed stress release, uncontrollable settlement, and disturbance of the original foundation caused by bottom underpinning.

[0019] This invention only cuts the column bases, base plates, and abandoned pile foundations within the expansion area, while preserving the jack support area and the integrity of the surrounding structure. Under suspended balance, it forms a large space without temporary support or obstruction, allowing large equipment to be directly deployed for efficient excavation and construction, significantly improving construction efficiency and safety.

[0020] In this invention, the newly added vertical load-bearing column is precisely aligned with the existing column, the steel bars are connected through the column, and the whole structure is grouted together to form an integrated vertical load-bearing component. A permanent pile foundation penetrating to the bearing layer is re-installed below the new column to form a complete permanent load-bearing system. After the new structure is formed, the load will be smoothly returned, the temporary suspension system will be removed and the structure will be repaired. Finally, without affecting the normal use of the existing building, the vertical expansion of the underground space and the integrated connection between the old and new structures are completed. Attached Figure Description

[0021] Figure 1 A schematic diagram of the existing building and the original basement level construction structure; Figure 2 This is a schematic diagram of the construction structure during steps 1 and 2 of the present invention; Figure 3 This is a schematic diagram of the construction structure during step 3 of the present invention; Figure 4 This is a schematic diagram of the construction structure during steps 4-6 of the present invention; Figure 5 This is a schematic diagram of the construction structure during step 7 of the present invention; Figure 6 This is a schematic diagram of the construction structure during steps 8 and 9 of the present invention; Figure 7 This is a schematic diagram of the structure after the completion of step 10 of the present invention; Figure 8 This is a schematic diagram of the implementation structure of the anchoring component of the present invention.

[0022] Attached reference numerals: 1-Existing building, 2-Original basement level, 3-Existing structural column, 4-Existing pile foundation, 5-Side wall, 6-Compensation pile, 7-Anchoring component, 8-Original base plate, 9-Truss, 10-Jack, 11-New pile foundation, 12-New pile cap, 13-New base plate, 14-New load-bearing column, 15-New structural beam and slab, 16-Friction lining, 17-Shell, 18-Supporting bearing, 19-Ear plate. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: Example 1: This example aims to provide a construction method and structure for vertical expansion of underground space, which is used to vertically expand the existing underground structure of existing buildings to achieve deep expansion of underground space, thereby increasing usable space and improving land use efficiency.

[0024] See Figure 1-7 The underground space vertical expansion construction method provided in this embodiment specifically includes the following construction steps: Step 1: Based on the existing building 1 and the original basement 2 space, mark the pile positions of the compensation piles 6 outside the projection line of the exterior wall of the existing building 1, avoiding existing underground pipelines and the original foundation; then use a low-disturbance rotary drilling rig to drill holes, the drilling depth penetrating the soft strata to be expanded and entering the solid bearing layer such as rock, to meet the requirements of vertical heavy load and pull-out bearing capacity. For the needs of multi-level expansion, such as the construction of the third basement level, the pile depth penetrates at least twice the expansion depth below the bottom slab of the third basement level; then lower the steel cage and pour concrete, forming an external rigid support foundation after molding, so that the upper load of the existing building 1 can be transferred to the outside of the building, avoiding additional foundation stress on the internal expansion area.

[0025] Step 2: Clean the surface of the original basement level 2 structural column, and then wrap the anchoring component 7 around the existing structural column 3 at a predetermined height, so that it tightly interlocks with the structural column. By circumferentially tensioning its prestressed tendons, the anchoring is fixed under uniform radial pressure. Through the friction lining, a tight and non-destructive interlock is achieved with the structural column, forming a non-destructive friction bearing section, thereby establishing a high-level load-bearing joint node, so that the load is transferred from the upper part of the structural column.

[0026] Step 3: A high-rigidity steel truss 9, prefabricated in the factory and assembled on site, is hoisted into place in sections. One end is rigidly connected to the anchoring component 7, and the other end passes through the original basement side wall 5 and is supported at the top of the compensation pile 6 on the outside. Specifically, during the construction of the truss 9, the area around the opening to be made in the basement side wall 5 is first reinforced with carbon fiber cloth to expand the reinforcement range and improve the shear and tensile strength of the side wall 5 after the opening is made. Then, at the position of the compensation pile 6 in the existing side wall 5, a through hole with a cross-sectional diameter slightly larger than that of the truss 9 is cut, and a steel casing is inserted into the hole. The gap between the casing and the side wall 5 is filled with non-shrink high-strength grout to make the casing and the existing side wall 5 form an integral load-bearing structure to ensure the shear strength and structural integrity of the side wall 5.

[0027] Furthermore, after truss 9 is in place, its inner end is fixed to anchoring component 7, and its middle section passes through the through-wall sleeve, with the two being intermittently fitted. Truss 9 does not directly bear force on side wall 5, thus avoiding the building load support pressing on the existing side wall 5. The outer end of truss 9 extends out of the sleeve and is located above the top of the outer compensating pile 6. Ten sets of hydraulic jacks are arranged between the outer end of truss 9 and the top surface of compensating pile 6, and corresponding hydraulic jacks 10 are also installed at the bottom of the inner end of truss 9 near anchoring component 7. Fiber optic grating sensors can also be installed on the surface of the existing structural column 3 to extract the initial stress field distribution data of the building under operational conditions, and to monitor the column top displacement, column base reaction force, and structural stress changes in real time during the jacking process through pre-embedded FBG fiber optic grating sensors, thereby enabling real-time feedback of load changes.

[0028] Step 4: Control jack 10 to start the jacking operation, control both ends of jack 10 to lift slowly and synchronously in stages, and adjust the lifting amount at both ends in real time to control the inward and outward moments of truss 9. Combined with the structure of truss 9, this effectively reduces the mid-span deflection caused by the load. Stop when the residual reaction force at the column foot of the structure drops to 5%-8% of the initial value and the displacement remains stable and unchanged. This completes the conversion of the load path from the existing structural column 3 bottom bearing to the high-level suspended bearing, thereby effectively solving the problems of stress release lag and uncontrollable settlement that exist in traditional bottom support.

[0029] Step 5: After the entire suspension system reaches a stable equilibrium state, the structure has no additional stress, and all monitoring data remain normal, use the existing low-disturbance static cutting equipment to cut the existing structural column 3 column base, the partial closed section in the middle of the original basement 2 floor corresponding to the expansion area, and the existing load-bearing pile foundations at the bottom of the original building that are located within the expansion space and have completed load withdrawal. These existing pile foundations 4 occupy the new underground space and no longer bear the load, and are considered abandoned pile foundations. They must all be cut and removed to free up space for vertical expansion operations.

[0030] Step 6: After completing the local cutting, under suspended and pressureless conditions, excavate the earthwork layer by layer from top to bottom with the soil intake as the center. After excavating to the design foundation elevation of the third underground floor, inspect, level, and construct the foundation layer. Using the positioning axis of the newly added vertical load-bearing column as a reference, construct the new permanent load-bearing pile foundation using rotary drilling below the corresponding column position. The new pile foundation 11 penetrates below the design elevation of the third underground floor slab and extends to the original solid bearing layer to meet the overall vertical bearing capacity and settlement control requirements after the expansion. After the construction of the new pile foundation 11 is completed and reaches the design strength, pour the new pile cap 12 at the top of the pile and the pre-embedded column foot connector. Then tie the reinforcement of the new third underground floor foundation slab, reliably anchor the reinforcement of the new load-bearing column 14 to the pile cap reinforcement, and pour the whole to form a closed rigid base slab, constructing a permanent bottom load-bearing system.

[0031] Step 7: After the new pile foundation 11 and the new pile cap 12 pass the acceptance inspection, a new vertical load-bearing column is constructed. The upper end of the new load-bearing column 14 is coaxially aligned with the cut section of the existing structural column 3, and the lower end extends vertically downward and is anchored to the new pile cap 12. High-strength concrete is used to integrally pour the cut point of the existing structural column 3 and the top of the load-bearing column. After the grout and the column concrete reach the design strength, the existing structural column 3 and the new load-bearing column 14 are connected by longitudinal reinforcement and integrally interlocked with concrete to form a coaxial, seamless, and continuously load-bearing integrated vertical load-bearing component. This allows the upper load to be reliably transferred to the lower new load-bearing column 14, the new pile cap 12, and the new permanent pile foundation, realizing the complete integration of the old and new columns into an integral load-bearing structure.

[0032] Step 8: Construct the new foundation slab 13 at the bottom. After the strength of the three underground foundation slabs reaches the standard, construct the second underground beam and slab structure, side wall 5 structure, waterproofing, and electromechanical pre-embedded works from bottom to top, using the newly added permanent pile foundation, pile cap, and vertical load-bearing columns as the support system. The entire process is carried out through a special soil extraction port to complete the earthwork transportation and material delivery.

[0033] Step 9: After the construction of each underground floor expansion is completed, the pressure of the jacks 10 on both sides is reduced synchronously and in stages to smoothly transfer the load of the upper building from the suspended truss 9 system to the permanent load-bearing system composed of the newly added vertical load-bearing columns, permanent pile foundations and the new base plate 13 of the expansion floor. During this process, stress and displacement changes are continuously monitored by sensors. After the load transfer is completed and the monitoring data is stable, the jacks 10 on both sides of the truss 9 are removed in sequence, followed by the removal of the space conversion truss 9, the force-shaping anchoring components 7 and the through-wall sleeve. The high-level anchoring parts of the original two columns on the first underground floor are repaired with concrete, the surface is leveled and waterproofed. The through-wall holes are sealed with non-shrinkage high-strength grout. Waterproof membrane is laid to restore the waterproofing system of the basement side wall 5. The compensation piles 6 constructed on the outside of the building can be retained as permanent anti-lateral displacement piles and outer protective piles without being removed to improve the overall stability of the underground structure. Alternatively, they can be backfilled to the ground and the soil cover and ground level restored.

[0034] Step 10: After the temporary structure is demolished and repaired, the special soil extraction port is sealed. After acceptance, the complete integration of the old and new structural load-bearing systems is completed, and the vertical expansion of the existing underground structure of the existing building 1 can be realized.

[0035] The underground space vertical expansion construction method provided in this embodiment uses newly added permanent pile foundations, pile caps, and vertical load-bearing columns as the support system. It continues to construct the underground second-floor beam and slab structure, side wall structure, and supporting waterproofing and electromechanical pre-embedded pipelines in reverse. The entire process is completed through the soil extraction port for soil removal and material transportation until the permanent expansion structure of the second and third underground floors is completed and reaches the design strength. This forms a complete permanent load-bearing system composed of newly added permanent pile foundations, vertical load-bearing columns, and the bottom slabs and beams of each floor. It can safely bear the entire load of the superstructure and lay a complete structural foundation for the smooth return of subsequent loads, unloading of the hydraulic system, and removal of temporary suspension trusses and anchoring components.

[0036] Example 2, based on Example 1, provides a construction structure for vertical expansion of underground space, which is implemented by the construction method for vertical expansion of underground space described in Example 1, and is used to realize the vertical expansion of the original underground structure.

[0037] In the specific implementation structure, the underground space vertical expansion construction structure provided in this embodiment includes external compensation piles 6, anchoring components 7, trusses 9, new pile foundations 11, and new load-bearing columns. The external compensation piles 6 are arranged along the outer side of the projection line of the existing building 1's exterior wall, avoiding existing underground pipelines and the original foundation. The piles penetrate the soft stratum to be expanded and embed into the original solid bearing layer. The pile bottom elevation is at least twice the expansion depth below the third basement floor slab, forming an external rigid support foundation during the construction phase. The high-level anchoring components 7 are fixed to the pre-set high position of the existing basement first-floor structural column, tightly interlocking with the column to form a high-level load-bearing connection node. One end of the spatial conversion steel truss 9 is rigidly connected to the high-level anchoring component 7, and the other end passes through the existing basement side wall 5 and is supported on the top of the external compensation piles 6. A steel through-wall sleeve is provided between the truss 9 and the side wall 5. The sleeve and the side wall 5 are filled with high-strength grout to form an integral whole. A gap is left between the truss 9 and the sleeve and a flexible waterproof sealing structure is set to prevent the load of the truss 9 from acting directly on the existing side wall 5. The jacking support system includes an inner jack 10 located between the bottom of the inner end of the truss 9 and the non-cut and retained bottom slab of the first basement level, and an outer jack 10 located between the outer end of the truss 9 and the top of the compensation piles 6. The inner and outer jacks 10 work together to achieve the smooth transfer and suspension of the upper load.

[0038] like Figure 8As shown, the anchoring assembly 7 includes a friction lining 16, a housing 17, and a support 18. Two sets of housings 17 are interlocked and fixed to the existing structural column 3. The high-strength friction lining 16 is adapted and fixed to the inner side of the housing 17. The high-strength friction lining 16 is a special high-strength friction plate, such as a thin steel plate with a diamond-like surface or a high-hardness anti-slip rubber pad. The housing 17 has symmetrical ear plates 19 on both sides. The two housings 17 are fixed together through the ear plates 19. When the housings 17 are fixed together, the friction lining 16 is set to fit against the existing structural column 3. The support 18 is welded and fixed to the outer wall of the housing 17. Multiple reinforcing ribs are evenly arranged on the outer wall of the housing 17 to enhance the structural strength of the anchoring housing 17. The inner end of the truss 9 is fixed to the upper surface of the support 18 by bolts.

[0039] The underground space vertical expansion construction structure provided in this embodiment forms a suspended force system during construction through external compensation pile foundations, high-level anchoring components and space conversion steel trusses. Without interrupting the use of the existing structure, it completes the cutting of existing local components, earthwork excavation and construction of new permanent structures, and finally forms an integrated vertical expansion space composed of the existing retained structure and the new underground expansion structure. It has the advantages of clear force, controllable construction, reliable combination of old and new structures and strong applicability.

[0040] The embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. The basic concept of the present invention lies in transferring the load of the existing building from the bottom of the column to the middle and upper part and then moving the support outward by setting up a suspended load-bearing system, thereby achieving a safe expansion environment without additional stress and settlement risk. Ultimately, without affecting the normal use of the existing building, the vertical expansion of the underground space and the integrated connection between the old and new structures are completed. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A construction structure for vertical expansion of underground space, characterized in that: The structure includes compensating piles, anchoring components, trusses, a top-support system, and a new foundation. The compensating piles are vertically arranged outside the projection line of the existing building's exterior wall, with the pile bottom embedded in the bearing layer of the underground soil. The anchoring components are fixed to the upper middle part of the existing structural columns within the original basement level, forming a high-level load-bearing node. The trusses are arranged horizontally, with their inner ends fixedly connected to the anchoring components and their outer ends passing through the existing sidewalls of the original basement level and fixed to the top of the compensating piles. The top-support system includes jacks located at the bottom of the inner end of the truss and at the top of the compensating piles. The inner jacks support the left and right ends of the truss, forming a suspended support system. The new foundation is located below the expanded space below the original basement level, forming the load-bearing foundation of the expanded structure.

2. The underground space vertical expansion construction structure according to claim 1, characterized in that: The anchoring assembly includes a friction lining, a shell, and a support bracket. The two sets of shells are interlocked and fixed to the existing structural column. The friction lining is adapted and fixed to the inner side of the shell. When the shells are fixed together, the friction lining is fitted to the existing structural column. The support bracket is welded and fixed to the outer wall of the shell for fixed connection with the truss.

3. The underground space vertical expansion construction structure according to claim 2, characterized in that: Multiple reinforcing ribs are evenly fixed on the outer wall of the shell.

4. The underground space vertical expansion construction structure according to claim 1, characterized in that: The existing side wall has through-wall openings, and steel through-wall boxes are installed inside the openings; the truss passes through the boxes and is interlocked with them, so that the truss load does not directly act on the existing side wall.

5. The underground space vertical expansion construction structure according to claim 4, characterized in that: The area around the truss openings in the side wall is reinforced with carbon fiber cloth.

6. The underground space vertical expansion construction structure according to claim 1, characterized in that: The new foundation includes a new pile foundation at the bottom of the expanded space, a new pile cap at the top of the new pile foundation, and a new load-bearing column connecting the new pile cap to the cut section of the existing structural column.

7. The underground space vertical expansion construction structure according to claim 6, characterized in that: The new load-bearing column is coaxially aligned with the existing structural column. The two are connected by longitudinal steel bars and integrally cast with high-strength grout to form an integrated vertical load-bearing component.

8. A method for vertical expansion of underground space, using the underground space vertical expansion construction structure described in any one of claims 1-7, characterized in that: Includes the following steps: Step 1: Lay out the location of the compensation piles outside the projection line of the existing building's exterior wall, and construct the compensation piles to form an external rigid support foundation; Step 2: Install anchoring components in the upper part of the existing structural column to form a high-level load-bearing pipe joint with the existing structural column. Step 3: Construct a steel truss, rigidly connect one end of the truss to the anchoring components, and let the other end pass through the side wall laterally and be supported on the top of the compensation pile to form a suspension system, so that the load can be transferred to the external compensation pile through the truss; Step 4: Install jacks on the inside of the truss and on the top of the compensation piles, and control the inner and outer jacks to lift synchronously in stages to realize the conversion of the load path from the existing structural column bottom bearing to the high-level suspended bearing; Step 5: After the suspension system is stable, cut the existing structural column bases, partially closed sections of the original base plate, and abandoned existing pile foundations in the expansion area; Step 6: Excavate the earthwork layer by layer from top to bottom to the foundation elevation, and then carry out new structural construction, including the construction of new pile foundations, new pile caps and new base slabs, to build a permanent bottom load-bearing system; Step 7: Construct new load-bearing columns, so that the new load-bearing columns, existing structural columns, and new foundations form an integrated vertical load-bearing component; Step 8: Using the new pile foundation, new pile cap, and new load-bearing columns as supports, construct the new structural beams and slabs, side walls, and supporting waterproofing and electromechanical pre-embedded works of the underground expansion layer from bottom to top in reverse construction. Step 9: After the strength of the new structure meets the standard, control the jacks to reduce the pressure in stages and transfer the upper load to the permanent load-bearing system. Then, dismantle the temporary suspension structure and seal the soil extraction port to complete the vertical expansion of the underground space.

9. The method for vertical expansion of underground space according to claim 8, characterized in that: In step 3, fiber optic grating sensors are pre-embedded on the surface of the existing structural column. During the jacking process in step 4 and the load transfer process in step 9, the structural stress and displacement changes are monitored in real time by the fiber optic grating sensors, and the jacking amount or pressure reduction amount of the jacks is adjusted in real time according to the monitoring data.

10. The method for vertical expansion of underground space according to claim 8, characterized in that: In step 4, the jacks at both ends of the truss are controlled to lift synchronously in stages, and the lifting amount is adjusted in real time to balance the inward and outward moments of the truss until the residual reaction force at the base of the existing structural column is reduced to 5%-8% of the initial value and the displacement is stable.

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