Equipment raft foundation underpinning frame with underground cavity and reinforcing method

Abstract

The invention discloses an equipment raft foundation underpinning frame with underground cavities and a reinforcing method, and belongs to the technical field of industrial equipment foundation reinforcing and deviation rectifying, the equipment raft foundation underpinning frame comprises a plurality of vertical bearing structures, the vertical bearing structures are distributed in the area with the underground cavities in an array mode, reinforced concrete connecting beams are connected between the vertical bearing structures in the same row, and the reinforced concrete connecting beams are connected between the vertical bearing structures in the same row. Dragging and replacing steel beams are connected between the vertical bearing structures in the same row, and a foundation raft is borne on the dragging and replacing steel beams. An assembly type construction thought is innovatively adopted, and a steel-concrete composite structure thought is proposed for underpinning, namely, the characteristic that the vertical bearing capacity of a concrete structure is high is fully utilized, and a vertical bearing structure is constructed. The flexural capacity of a steel structure is fully utilized, and the steel structure is adopted as an underpinning cross beam. According to the innovative scheme, standardized design, factory-like batch production and on-site assembly type construction can be achieved, the project construction progress is improved, the project quality is convenient to control, and the modules can be reused.

Description

Technical Field

[0001] The present invention belongs to the technical field of industrial equipment foundation reinforcement and deviation correction, and relates to a replacement frame and reinforcement method for the raft foundation of equipment with underground cavities. Background Art

[0002] With the improvement of industrial production technology level, industrial equipment is developing towards the direction of large-scale, integrated and skid-mounted. Among them, the raft foundation has become a common foundation form for industrial equipment. For the stations located in collapsible loess areas, due to the influence of geological structure, station site selection and heavy rain weather, etc., the soil layer below the bearing layer of the raft foundation is extremely easy to be soaked with water to form loess cavities, underground seepage channels or even sinkholes, etc., resulting in the collapse of the equipment raft foundation below, causing uneven settlement and inclination of the foundation. It causes economic losses to industrial production, and even causes large accidents and secondary disasters.

[0003] In addition, due to the influence of the terrain of the station, some equipment raft foundations are built in the filled areas of the station. For the large vibrating equipment in the filled area, the bearing layer and the soil layer below the raft foundation of the equipment will gradually become dense under the long-term vibration, resulting in vibration voids in the soil layer. It causes the raft foundation of the equipment to be separated from and suspended above the bearing layer. It causes economic losses to industrial production, and even causes large accidents and secondary disasters. Summary of the Invention

[0004] In order to overcome the shortcomings of the above-mentioned technology, the purpose of the present invention is to provide a replacement frame and reinforcement method for the raft foundation of equipment with underground cavities, and solve the geological disaster situation of uneven settlement and inclination of the foundation caused by the existence or emergence of cavities, water holes, etc. below the foundation.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions to implement:

[0006] A replacement frame for the raft foundation of equipment with underground cavities, comprising: a plurality of vertical supporting structures, the vertical supporting structures are arranged in an array in the area with underground cavities, a reinforced concrete tie beam is connected between the vertical supporting structures in the same row, a replacement steel beam is arranged above the vertical supporting structures in the same column, and the foundation raft is supported on the replacement steel beam.

[0007] Preferably, the vertical supporting structure includes a jet grouting pile body and an internal steel profile connector. A steel casing is arranged above the jet grouting pile body, a concrete connection section is poured inside the steel casing, a rigid enlarged bearing platform is arranged above the concrete connection section, connection structure dowels are arranged inside the concrete connection section and the rigid enlarged bearing platform, the internal steel profile connector penetrates through the concrete connection section and the rigid enlarged bearing platform and extends into the jet grouting pile body and is located inside the three, and its upper end is connected to the replacement steel beam.

[0008] Preferably, a connecting ear is provided at the upper end of the built-in steel section connector, and the connecting ear is hinged to the underpinning steel beam.

[0009] Preferably, the length of the built-in steel section connector extending into the jet grouting pile body is not less than 500 mm; the length extending out of the rigid enlarged head bearing platform is not less than 500 m

[0010] Preferably, a polytetrafluoroethylene plate is provided on the contact surface between the underpinning steel beam and the vertical supporting structure.

[0011] Preferably, within the contact length range between the underpinning steel beam and the vertical supporting structure, underpinning beam stiffeners are arranged at equal intervals.

[0012] A method for underpinning and strengthening the raft foundation of equipment with underground cavities specifically includes the following steps:

[0013] Vertical supporting structures are arranged around the raft foundation with underground cavities;

[0014] Reinforced concrete tie beams and underpinning steel beams are connected between the vertical supporting structures;

[0015] The foundation raft is supported on the underpinning steel beam.

[0016] Preferably, the vertical supporting structure includes: jet grouting pile body, steel casing, rigid enlarged head bearing platform, concrete connection section, connecting structural reinforcement bars and built-in steel section connectors; the specific steps of arranging the vertical supporting structure around the raft foundation with underground cavities are as follows:

[0017] S101: Jet grouting pile bodies are arranged around the raft foundation with underground cavities. Before the jet grouting pile mixture starts to set, steel casings and built-in steel section connectors are inserted;

[0018] S102: After the jet grouting pile mixture starts to set, concrete is added into the steel casing to form a concrete connection section, and connecting structural reinforcement bars are inserted into the concrete connection section;

[0019] S103: After the concrete connection section reaches final set, formwork is supported above it to pour the rigid enlarged head bearing platform, and after it reaches final set, a vertical supporting structure is formed.

[0020] Preferably, in S103, after the concrete connection section reaches final set, its upper surface is roughened to form a roughened layer, and then formwork is supported to pour the rigid enlarged head bearing platform.

[0021] Preferably, a connecting ear is provided on the side of the built-in steel section connector, and a hinge structure is constructed with the underpinning steel beam by means of a pin bolt. The reinforced concrete tie beam is used to effectively connect with the vertical supporting structure, so that the underpinning structure forms a stable structure.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. Innovatively adopt the prefabricated construction concept, and propose the steel-concrete composite structure concept for underpinning, that is, make full use of the characteristics of high vertical bearing capacity of the concrete structure to construct the vertical supporting structure. The steel structure with high flexural bearing capacity can be used as the underpinning cross beam.

[0024] 2. For the construction of the vertical supporting structure, innovatively adopt the structural form of jet grouting pile + concrete in the middle section of the steel structure casing + rigid enlarged head bearing platform. Make full use of the simple technological process and investment-saving characteristics of the jet grouting pile to compact and reinforce the soil around the equipment foundation, and at the same time play a role in vertically conducting the upper load of the structure.

[0025] 3. Provide a new idea for the coupling structure of the vertical supporting structure: the concrete in the middle section of the steel structure casing plays a connecting role between the upper and lower parts. Through the preset internal steel connectors, the effective connection between the lower jet grouting pile and the middle section concrete is ensured; the middle section concrete is connected to the upper rigid enlarged head bearing platform through structural reinforcement bars. Ensure the reliability of the vertical load transfer of the overall supporting structure.

[0026] 4. The innovative solution can realize the standardized design of the vertical supporting structure, the factory batch production of the internal steel connectors, and the on-site prefabricated construction of the horizontal underpinning steel beam, improve the construction progress of the project, facilitate the control of the project quality, and the modules can be reused.

[0027] 5. Adopt the idea of separating the design of the horizontal supporting body and the vertical supporting body: the two adopt a structural hinge structure, and a sliding material of polytetrafluoroethylene plate is set on the contact surface to minimize the friction force and reduce the transfer of unbalanced bending moment.

[0028] The concrete in the middle section of the innovative structure casing plays a connecting role between the upper and lower parts, and can bear a certain amount of horizontal shear force, effectively avoiding the characteristics that due to the structural reasons of the jet grouting pile (no steel bars are configured, and the structure is a bonded body of cement, soil and a small amount of gravel), it can only bear vertical loads and cannot bear the shear force of the transfer of the top unbalanced bending moment and has insufficient bearing capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is the structural plan view of the present invention;

[0030] Figure 2 It is the top view of the vertical supporting structure of the present invention;

[0031] Figure 3 It is the schematic view of the vertical supporting structure of the present invention in the 1-1 direction;

[0032] Figure 4 It is the structural schematic view of Embodiment 2 of the present invention;

[0033] Figure 5 This is a schematic structural diagram of Embodiment 3 of the present invention.

[0034] Wherein: 1 - vertical supporting structure; 2 - reinforced concrete connecting beam; 3 - foundation raft; 4 - underpinning steel beam; 5 - jet grouting pile body; 6 - steel casing; 7 - roughening; 8 - rigid enlarged head bearing platform; 9 - middle section concrete connecting section of the casing; 10 - connecting construction inserted steel bars; 11 - polytetrafluoroethylene plate; 12 - built-in steel section connector; 13 - connecting ear; 14 - stiffening rib of the underpinning beam; 15 - underground cavity; 16 - outer contour of the vibration equipment; 17 - independent foundation of the house. Detailed implementation manners

[0035] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0036] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0037] The present invention will be further described in detail below with reference to the accompanying drawings:

[0038] See Figure 1, this application discloses a frame for underpinning the raft foundation of an equipment with underground cavities, which is characterized by including: a number of vertical supporting structures 1, which are arranged in an array in the area with underground cavities 14. Reinforced concrete tie beams 2 are connected between the vertical supporting structures 1 in the same row. A jacking steel beam 4 is provided above the vertical supporting structures 1 in the same column, and the foundation raft 3 is supported on the jacking steel beam 4. The innovative use of the prefabricated construction idea proposes the steel-concrete composite structure idea for underpinning, that is, making full use of the characteristics of the high vertical bearing capacity of the concrete structure to construct the vertical supporting structure. Making full use of the flexural bearing capacity of the steel structure, using the steel structure as the underpinning cross beam. Using this structure can not only carry out the overall underpinning of the equipment raft foundation. The reinforced concrete tie beam 2 is effectively connected with the vertical supporting structure 1 to form a stable system for the underpinning structure; in addition, since the lower part of the vertical supporting structure uses the jet grouting method to form piles, it can also compact and reinforce the non-compact soil around the foundation to solve the problem of non-compact soil in the filled area. Solve the geological disaster situation of uneven settlement and inclination of the foundation caused by the existence or emergence of cavities, water drop holes, etc. below the foundation.

[0039] In some embodiments, referring to Figure 2 , Figure 3 , the vertical supporting structure 1 includes a jet grouting pile body 5 and an internal steel connector 12. A steel casing 6 is arranged above the jet grouting pile body 5. A concrete connection section 9 is poured inside the steel casing 6. A rigid enlarged bearing platform 8 is arranged above the concrete connection section 9. Connecting structural dowels 10 are arranged inside the concrete connection section 9 and the rigid enlarged bearing platform 8. The internal steel connector 12 penetrates through the concrete connection section 9 and the rigid enlarged bearing platform 8 and extends into the jet grouting pile body 5 and is located inside the three, and its upper end is connected to the jacking steel beam 4. Around the equipment foundation to be reinforced and underpinned, the jet grouting pile technology is adopted to form the lower jet grouting pile body 5 by using high-pressure rotation cutting. It plays the role of reinforcing the soil and forming the lower bearing structure; before the jet grouting pile mixture starts to set, insert the steel casing 6. The depth of the steel casing extending into the jet grouting pile body shall not be less than 500mm. After the jet grouting pile mixture starts to set, add concrete into the steel casing to form the concrete connection section 9. Insert the connecting structural dowels 10 to effectively anchor and connect with the rigid enlarged head bearing platform 8. An internal steel connector 12 is arranged inside the jet grouting pile body 5, the middle section steel casing concrete connection section 9, and the rigid enlarged head bearing platform 8 to connect the above three components into the vertical supporting structure 1.

[0040] In some embodiments, a connection ear 13 is arranged at the upper end of the internal steel connector 12, and the connection ear 13 is hinged to the jacking steel beam 4. It is hinged to the jacking steel beam 4 by a pin bolt. The equipment foundation raft 3 is supported on the upper part of the jacking steel beam 4.

[0041] In some embodiments, the length of the built-in steel connector 12 extending into the jet grouting pile body 5 is not less than 500 mm; the length extending out of the rigid enlarged head bearing platform 8 is not less than 500 m

[0042] In some embodiments, a polytetrafluoroethylene plate 11 is provided on the contact surface between the underpinning steel beam 4 and the vertical supporting structure 1. The polytetrafluoroethylene plate-flexible sliding material 11 is laid to reduce friction. Within the contact length range between the underpinning steel beam 4 and the vertical supporting structure 1, underpinning beam stiffeners are arranged at equal intervals to improve the bearing capacity of the underpinning steel beam 4.

[0043] The present application also discloses a method for underpinning and strengthening the raft foundation of equipment with underground cavities, which specifically includes the following steps:

[0044] S1: Set up a vertical supporting structure 1 around the raft foundation with an underground cavity 14;

[0045] S2: Connect a reinforced concrete tie beam 2 and an underpinning steel beam 4 between the vertical supporting structures 1;

[0046] S3: The foundation raft 3 is supported on the underpinning steel beam 4.

[0047] In some embodiments, the vertical supporting structure 1 includes: a jet grouting pile body 5, a steel casing 6, a rigid enlarged bearing platform 8, a concrete connection section 9, a connecting structural reinforcement 10, and a built-in steel connector 12; the specific steps for setting up the vertical supporting structure 1 around the raft foundation with an underground cavity 14 include the following:

[0048] S101: Set up jet grouting pile bodies 5 around the raft foundation with an underground cavity 14, and insert the steel casing 6 and the built-in steel connector 12 before the initial setting of the jet grouting mixture;

[0049] S102: After the initial setting of the jet grouting mixture, add concrete into the steel casing to form a concrete connection section 9, and insert the connecting structural reinforcement 10 into the concrete connection section 9;

[0050] S103: After the final setting of the concrete connection section 9, formwork and pour the rigid enlarged head bearing platform 8 above it, and form the vertical supporting structure 1 after its final setting.

[0051] In some embodiments, in S103, after the final setting of the concrete connection section 9, the upper surface is roughened to form a roughened layer 7, and then formwork is used to pour the rigid enlarged head bearing platform 8.

[0052] In some embodiments, a connection ear 13 is provided on the side of the built-in steel connector 12, and it is hinged to the underpinning steel beam 4 by a pin bolt. A reinforced concrete tie beam 2 is used to construct a hinged structure with the vertical supporting structure 1 to make the underpinning structure form a stable structure. Specific embodiments:

[0054] Taking the hidden danger treatment of a certain oilfield in industrial production as an example: it is applicable not only to raft foundations but also to saddle foundations of large horizontal vessels.

[0055] For a certain station located in the collapsible loess area, due to the influence of geological structure, station location and heavy rain weather, etc., the soil layer below the bearing stratum of the raft foundation is extremely easy to be flooded to form loess cavities, underground seepage channels and even sinkholes, etc., which will cause the collapse under the raft foundation of the equipment, resulting in uneven settlement and inclination of the foundation.

[0056]

Example 1

[0057] See Figure 1 , adopting the structure of the present invention, a vertical supporting structure is arranged around the raft foundation. Before the initial setting of the jet grouting pile mixture, the steel casing 6 is inserted. The depth of the steel casing extending into the jet grouting pile body shall not be less than 500 mm. After the initial setting of the jet grouting pile mixture, concrete is added into the steel casing to form the concrete connection section 9. The connecting structure reinforcing bars 10 are inserted into the middle-section casing concrete connection section 9 to achieve effective anchoring connection with the rigid enlarged head bearing platform 8. After the final setting of the middle-section casing concrete connection section 9, the upper surface thereof is roughened to form the roughened layer 7. And formwork is supported to pour the rigid enlarged head bearing platform 8. The jet grouting pile body 5, the middle-section casing concrete connection section 9, the rigid enlarged head bearing platform 8, and the internal full-length steel section connectors 12 are arranged to connect the above three components into the vertical supporting structure 1. The length of the internal steel section connector extending into the jet grouting pile body is not less than 500 mm. The length extending out of the rigid enlarged head bearing platform 8 is not less than 500 mm. Connection ears 13 are arranged on the side of the internal steel section connector 12 and are hinged with the underpinning steel beam 4 by bolts. The upper part of the underpinning steel beam 4 supports the equipment foundation raft 3, and the lower part spans the cavity and / or loess cave 14 under the raft. Subsequently, the reinforced concrete tie beam 2 is effectively connected with the vertical supporting structure 1 to form a stable system for the underpinning structure. A polytetrafluoroethylene sheet - flexible sliding material 11 is padded between the underpinning steel beam 4 and the vertical supporting structure 1 to play a role in reducing friction. Finally, underpinning beam stiffeners are arranged at equal intervals within the contact length range between the underpinning steel beam 4 and the vertical supporting structure 1 to improve the bearing capacity of the underpinning steel beam 4.

[0058] Due to the influence of the station terrain, part of the equipment raft foundation is built in the filled area of the station. For large vibrating equipment in the filled area, the bearing stratum and the soil layer below the raft foundation will gradually become dense under the long-term vibration, resulting in voids in the soil layer. This will cause the equipment raft foundation to be separated from and suspended above the bearing stratum, causing economic losses to industrial production, and even causing large accidents and secondary disasters.

[0059]

Example 2

[0060] See Figure 4 , with the structure of the present invention, a vertical supporting structure is arranged around and inside the foundation of the horizontal saddle. Before the initial setting of the jet grouting pile mixture, the steel casing 6 is inserted. The depth of the steel casing extending into the jet grouting pile body shall not be less than 500 mm. After the initial setting of the jet grouting pile mixture, concrete is added into the steel casing to form the concrete connection section 9. The connecting structure reinforcing bars 10 are inserted into the middle section casing concrete connection section 9 to effectively anchor and connect with the rigid enlarged head bearing platform 8. After the final setting of the middle section casing concrete connection section 9, the upper surface is roughened 7. And formwork is supported and the rigid enlarged head bearing platform 8 is poured. The jet grouting pile body 5, the middle section casing concrete connection section 9, and the rigid enlarged head bearing platform 8 are internally provided with steel section connectors 12 throughout the length to connect the above three components into a vertical supporting structure 1. The length of the internal steel section connector extending into the jet grouting pile body is not less than 500 mm. The length extending out of the rigid enlarged head bearing platform 8 is not less than 500 mm. Connection ears 13 are arranged on the side of the internal steel section connector 12 and are hinged with the underpinning steel beam 4 by bolts. The upper part of the underpinning steel beam 4 supports the horizontal equipment saddle foundation 3, and the lower part spans the void under the raft and / or the loess cave 14. Subsequently, a reinforced concrete tie beam 2 is effectively connected with the vertical supporting structure 1 to form a stable system for the underpinning structure. A polytetrafluoroethylene sheet-flexible sliding material 11 is provided between the underpinning steel beam 4 and the vertical supporting structure 1 to reduce friction. Finally, underpinning beam stiffeners are arranged at equal intervals within the contact length range between the underpinning steel beam 4 and the vertical supporting structure 1 to improve the bearing capacity of the underpinning steel beam 4.

[0061]

Example 3

[0062] See Figure 5, with the structure of the present invention, vertical supporting structures are arranged around and inside the independent foundation of the house. Before the initial setting of the jet grouting pile mixture, the steel casing 6 is inserted. The depth of the steel casing extending into the jet grouting pile body shall not be less than 500 mm. After the initial setting of the jet grouting pile mixture, concrete is added into the steel casing to form the concrete connection section 9. The connecting structure reinforcing bars 10 are inserted into the middle-section casing concrete connection section 9 to effectively anchor and connect with the rigid enlarged head bearing platform 8. After the final setting of the middle-section casing concrete connection section 9, the upper surface thereof is roughened 7. And formwork is supported and the rigid enlarged head bearing platform 8 is poured. The jet grouting pile body 5, the middle-section casing concrete connection section 9, and the rigid enlarged head bearing platform 8 are provided with steel section connectors 12 arranged longitudinally throughout to connect the above three components into the vertical supporting structure 1. The length of the built-in steel section connector extending into the jet grouting pile body is not less than 500 mm. The length extending out of the rigid enlarged head bearing platform 8 is not less than 500 mm. Connection ears 13 are arranged on the side of the built-in steel section connector 12 and are hinged to the underpinning steel beam 4 by bolts. The upper part of the underpinning steel beam 4 supports the independent foundation 3 of the house, and the lower part spans the void under the raft and / or the loess cave 14. Subsequently, the reinforced concrete tie beam 2 is effectively connected with the vertical supporting structure 1 to form a stable system for the underpinning structure. A polytetrafluoroethylene plate-flexible sliding material 11 is provided between the underpinning steel beam 4 and the vertical supporting structure 1 to reduce friction. Finally, underpinning beam stiffeners are arranged at equal intervals within the contact length range between the underpinning steel beam 4 and the vertical supporting structure 1 to improve the bearing capacity of the underpinning steel beam 4.

[0063] The above content is only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. An equipment raft foundation underpinning frame with underground cavities, Characterized in that, Comprising: A number of vertical supporting structures (1), the vertical supporting structures (1) are arranged in an array in the area with underground cavities (14). Reinforced concrete tie beams (2) are connected between the vertical supporting structures (1) in the same row. A jacking steel beam (4) is arranged on the vertical supporting structures (1) in the same column, and the foundation raft (3) is supported on the jacking steel beam (4).

2. An equipment raft foundation underpinning frame with underground cavities according to claim 1, Characterized in that, The vertical supporting structure (1) includes a jet grouting pile body (5) and an internal steel section connecting member (12). A steel casing (6) is arranged above the jet grouting pile body (5). A concrete connecting section (9) is poured inside the steel casing (6). A rigid enlarged bearing platform (8) is arranged above the concrete connecting section (9). Connecting structural dowels (10) are arranged inside the concrete connecting section (9) and the rigid enlarged bearing platform (8). The internal steel section connecting member (12) penetrates through the concrete connecting section (9) and the rigid enlarged bearing platform (8) and extends into the jet grouting pile body (5) and is located inside the three, and its upper end is connected to the jacking steel beam (4).

3. An equipment raft foundation underpinning frame with underground cavities according to claim 2, Characterized in that, A connecting ear (13) is arranged at the upper end of the internal steel section connecting member (12), and the connecting ear (13) is hinged to the jacking steel beam (4).

4. An equipment raft foundation underpinning frame with underground cavities according to claim 2, Characterized in that, The length of the internal steel section connecting member (12) extending into the jet grouting pile body (5) is not less than 500 mm; the length extending out of the rigid enlarged head bearing platform (8) is not less than 500 m.

5. An equipment raft foundation underpinning frame with underground cavities according to claim 1, Characterized in that, A polytetrafluoroethylene plate (11) is arranged on the contact surface between the jacking steel beam (4) and the vertical supporting structure (1).

6. An equipment raft foundation underpinning frame with underground cavities according to claim 1, Characterized in that, In the contact length range between the jacking steel beam (4) and the vertical supporting structure (1), jacking beam stiffeners (14) are arranged at equal intervals.

7. An equipment raft foundation underpinning and strengthening method with underground cavities, Characterized in that, The equipment raft foundation underpinning frame described in any one of claims 1 to 6 is adopted, and specifically includes the following steps: Vertical supporting structures (1) are arranged around the raft foundation with underground cavities (14); Reinforced concrete tie beams (2) and jacking steel beams (4) are connected between the vertical supporting structures (1); The foundation raft (3) is supported on the jacking steel beam (4).

8. An equipment raft foundation underpinning and strengthening method with underground cavities according to claim 7, Characterized in that, The vertical supporting structure (1) includes: jet grouting piles (5), steel casing (6), rigid enlarged cap (8), concrete connection section (9), connecting structure reinforcing bars (10), and built-in steel connectors (12); the specific steps of setting the vertical supporting structure (1) around the raft foundation with underground cavities (14) are as follows: S101: Set jet grouting piles (5) around the raft foundation with underground cavities (14). Before the initial setting of the jet grouting pile mixture, insert the steel casing (6) and the built-in steel connectors (12). S102: After the initial setting of the jet grouting pile mixture, add concrete into the steel casing to form the concrete connection section (9), and insert the connecting structure reinforcing bars (10) into the concrete connection section (9). S103: After the final setting of the concrete connection section (9), formwork and pour the rigid enlarged head cap (8) above it. After its final setting, the vertical supporting structure (1) is formed.

9. According to the method for underpinning and strengthening the equipment raft foundation with underground cavities described in claim 8, characterized in that, in S103, after the final setting of the concrete connection section (9), roughen its upper surface to form a roughened layer (7), and then formwork and pour the rigid enlarged head cap (8).

10. According to the method for underpinning and strengthening the equipment raft foundation with underground cavities described in claim 8, characterized in that, connection ears (13) are arranged on the side of the built-in steel connector (12), and a hinge structure is constructed with the underpinning steel beam (4) using pin bolts. An effectively connected structure is formed by using the reinforced concrete tie beam (2) and the vertical supporting structure (1), so that the underpinning structure becomes a stable structure.

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