Construction method for adding storey to lower portion of subway station structure

Abstract

The invention discloses a construction method for storey adding on the lower portion of a subway station structure, solves the problem of poor supporting stability in storey adding construction in the prior art, and has the beneficial effects of being integrated with an existing structure and improving construction safety. Comprising the following steps that grouting reinforcement is conducted on a foundation under the existing structure of the subway, a grouting reinforcement area is formed after grouting is completed, and storey-adding supporting components are implanted into the two opposite sides of the grouting reinforcement area correspondingly; side walls on the lower portions of the two sides of the existing structure are cut, inclined inserting supporting piles are implanted from the cutting positions, the inclined inserting supporting piles are implanted between fender posts of the side walls of the existing structure and located on the outer sides of storey-adding supporting components, and the tops of the storey-adding supporting components and the tops of the inclined inserting supporting piles are connected with underpinning beams. A bearing arch cover is built through underpinning beams on the two sides and middle columns of an existing structure, a bottom plate of the existing structure is broken, and a foundation pit of the storey-adding structure is excavated in a layered and segmented mode.

Description

Technical Field

[0001] The present invention relates to the technical field of underground space development engineering, and in particular to a construction method for adding a layer under the structure of a subway station. Background Technique

[0002] The statements in this part only provide background technical information related to the present invention and do not necessarily constitute prior art.

[0003] With the advancement of the urbanization process and the increasing scale of the construction of urban rail transit systems, many early subway stations did not consider the need for future layer addition and expansion during construction. Facing the increase in newly built rail transit lines and passenger volume, the demand for increasing the number of floors of operating subway stations is gradually emerging. Traditional construction methods for adding layers to subway stations mostly rely on pouring replacement caissons to replace the columns of the existing structure. That is to say, replacement piles and retaining piles are set up. Both the replacement piles and the retaining piles are vertically arranged, without making full use of the support system of the existing subway structure. The replacement piles and the retaining piles are connected by a replacement beam slab to form a replacement system. The replacement system is arranged on both sides of the existing structure, and there is no connection relationship between the replacement systems on both sides, resulting in poor support stability, greater impact on the existing structure, and the need for high-frequency monitoring of the deformation of the existing structure, pile foundation settlement, and soil stability during construction, with a large difficulty in risk control;

[0004] In addition, during the construction of the existing replacement system, it is necessary to construct again outside the subway and re-excavate the foundation pit, resulting in high construction complexity and a long construction period. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a construction method for adding a layer under the structure of a subway station, which has little impact on the existing structure, enables the reasonable force of the existing upper structure, is simple in construction, and saves costs.

[0006] In order to achieve the above purpose, the present invention is realized through the following technical solutions:

[0007] A construction method for adding a layer under the structure of a subway station includes the following contents:

[0008] Grout and reinforce the foundation under the existing subway structure. After grouting is completed, a grout reinforcement area is formed, and layer-adding support components are respectively implanted on the opposite sides of the grout reinforcement area;

[0009] Cut the lower side walls on both sides of the existing structure respectively, and implant inclined support piles from the cutting points. The inclined support piles are implanted between the retaining piles of the side walls of the existing structure. The inclined support piles are located outside the layer-adding support components. The tops of the layer-adding support components and the tops of the inclined support piles are connected to the replacement beam. The supporting arch cover is built through the replacement beams on both sides and the middle columns of the existing structure;

[0010] Demolish the existing structural floor slab, excavate the foundation pit of the additional story structure in layers and sections, construct the additional story middle column in the foundation pit, drive the additional story middle column downward into the foundation, and the additional story middle column supports the existing structure middle column;

[0011] Continue to excavate in the foundation pit to form a complete additional story space, construct the additional story structure, remove the supporting arch cover, and complete the additional story construction of the subway station.

[0012] For a construction method for adding an additional story to the lower part of a subway station structure as described above, a hollow section is provided at the top of the additional story support component, a steel bar mesh is arranged in the hollow section, the first anchoring steel bars in the steel bar mesh extend beyond the hollow section, and the part of the first anchoring steel bars extending beyond the hollow section is used to connect with the said underpinning beam. The part of the first anchoring steel bars used to connect with the underpinning beam is bent in a direction away from the central axis of the hollow section to improve the connection stability between the additional story support component and the underpinning beam.

[0013] For a construction method for adding an additional story to the lower part of a subway station structure as described above, a mechanical conversion joint is provided at the top of the inclined inserted support pile, the mechanical conversion joint is connected with the second anchoring steel bars, the second anchoring steel bars are used to connect with the said underpinning beam, and the top end of the second anchoring steel bars is bent to ensure the connection stability with the underpinning beam.

[0014] For a construction method for adding an additional story to the lower part of a subway station structure as described above, one side of the underpinning beam extends beyond the additional story support component, the width of the underpinning beam is 1 / 15 - 1 / 12 of the width of the existing structural floor slab, first connecting planted steel bars are arranged in the underpinning beam, and the underpinning beam is connected with the said supporting arch cover through the first connecting planted steel bars;

[0015] The supporting arch cover is divided into multiple sections, and the end parts of each section of the supporting arch cover are respectively connected with the said existing structure middle column through second connecting planted steel bars.

[0016] For a construction method for adding an additional story to the lower part of a subway station structure as described above, after the construction of the steel bar mesh is completed, the waterproof system of the existing structure is repaired and lapped. After the repair and lapping are completed, the said underpinning beam is constructed, and the underpinning beam contacts the waterproof system after the repair and lapping.

[0017] For a construction method for adding an additional story to the lower part of a subway station structure as described above, the repair and lapping of the waterproof system of the existing structure includes the following contents:

[0018] A water stop ring is arranged at the joint between the pile head of the inclined inserted support pile and the existing structural floor slab, and water swelling water stop rubber is filled in the joint. The interface is plugged with waterproof coating;

[0019] Lap waterproofing membranes are provided at the cutting position of the lower side wall, and the lap waterproofing membranes are laid from the cutting position of the lower side wall to the top of the inclined inserted support piles and the additional story support components.

[0020] Waterstop plates are arranged at the top of the additional story support components. Lap waterproofing membranes are laid on both sides of the waterstop plates, and the waterstop plates are vertically arranged on the surface of the additional story support components.

[0021] In a construction method for adding an additional story to the lower part of a subway station structure as described above, the supporting arch cover adopts a two-way prestressed reinforced concrete shell structure, which can give full play to the compressive performance of concrete.

[0022] In a construction method for adding an additional story to the lower part of a subway station structure as described above, after the foundation pit excavation is completed, shotcreting operations are carried out on the slope surface of the foundation pit. After the shotcreting is completed, anchor bolts are set to carry out anchor shotcrete support for the foundation pit.

[0023] In a construction method for adding an additional story to the lower part of a subway station structure as described above, the additional story middle column is driven into the foundation. The top of the additional story middle column is set as an inverted frustum shape, and the additional story middle column is fixedly connected to the existing structure middle column.

[0024] In a construction method for adding an additional story to the lower part of a subway station structure as described above, after the additional story space is formed, waterproof components are laid in the additional story space.

[0025] The additional story structure includes an additional story floor slab, additional story side walls, and an additional story roof slab. After the waterproof components are laid, the additional story floor slab is constructed first, then the additional story side walls are constructed, and after the construction of the additional story side walls is completed, the additional story roof slab, that is, the existing structure floor slab, is constructed.

[0026] The beneficial effects of the present invention are as follows:

[0027] 1) In the construction method provided by the present invention, the foundation under the existing structure is first grouted and reinforced to ensure the structural stability of the foundation. Additional story support components are implanted on the side of the grouting reinforcement area as the support structure of the additional story structure. The lower side wall is cut, and inclined inserted support piles are implanted from the cutting position. The inclined inserted support piles are implanted between the existing structure side wall retaining piles. The inclined inserted support piles are obliquely implanted between the existing structure side wall retaining piles. Even if minor structural settlement and shaking occur during subsequent construction, under the support and restriction of the existing structure side wall retaining piles, the stability of the additional story maintenance structure can be provided; the transfer beam, the inclined inserted support piles, and the additional story support components are connected, solving the misalignment problem between the additional story side wall and the existing structure side wall. The setting of the transfer beam is beneficial to resisting the bending and shear forces generated by the existing structure side wall. By connecting the transfer beams on both sides and the existing structure middle column through the supporting arch cover, a stable structural system is formed between the transfer beams on both sides and the existing structure, which is beneficial to the smooth construction of the additional story structure and has less impact on the existing structure. In this way, the safety risks during construction are reduced, and there is no need for high-frequency monitoring of pile foundation settlement, soil body stability, etc.

[0028] 2) The overall construction idea of the present invention is simple. First, construct the additional story support components, the obliquely inserted support piles, and the underpinning beams, and then construct the supporting arch cover, so that the retaining structure of the additional story structure and the existing structure of the subway become an integrated whole, ensuring the overall stability. Then, excavate downward to construct the additional story structure. The construction is carried out within the existing underground station, which not only avoids the disadvantages of the long construction period and high complexity of the conventional pile foundation underpinning cap method, but also ensures the construction safety, effectively reduces the disturbance to the existing upper station structure during construction, and is conducive to improving the usable space of the subway station.

[0029] 3) In the present invention, a hollow section is provided at the top of the additional story support component, and a steel mesh is arranged in the hollow section. The first anchoring steel bars in the steel mesh extend beyond the hollow section for connection with the underpinning beam, effectively improving the connection stability between the additional story support component and the underpinning beam. The top of the inclined support is connected to the second anchoring steel bar through a mechanical conversion joint, and the top end of the second anchoring steel bar is bent to ensure the connection stability between the obliquely inserted support pile and the underpinning beam.

[0030] 4) In the present invention, the supporting arch cover is reasonably set to adopt a two-way prestressed reinforced concrete shell structure, which can give full play to the compressive performance of concrete and form a spatial thin-shell force transmission system. The supporting arch cover connects the underpinning beams on both sides, and the underpinning beams are connected to the obliquely inserted support piles and the additional story support components, so that the additional story support system and the existing structure are connected as an integrated whole to jointly form a stable support system; the supporting arch cover is divided into multiple sections, and each section is stably connected to the middle column of the existing structure to ensure the connection stability between the supporting arch cover and the existing structure of the subway.

[0031] 5) In the present invention, considering the damage to the waterproof system during the construction process, it is necessary to repair and lap the waterproof system of the existing structure. By setting structures such as a water stop ring at the pile head of the obliquely inserted support pile, lapping waterproof coiled materials are set at the cutting part of the lower side wall. The lapping waterproof coiled materials are reasonably set, and a water blocking plate is set at the top of the additional story support component to ensure the waterproofness of the subway station as a whole and effectively prevent water seepage from pouring into the subway station. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The specification drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0033] Figure 1 is a sectional view of the existing structure of the subway station in the prior art.

[0034] Figure 2 is a schematic diagram of ground grouting reinforcement in a construction method for adding a story to the lower part of the subway station structure according to one or more embodiments of the present invention.

[0035] Figure 3 Schematic diagram of constructing a supporting beam by cutting the side wall of the existing structure in a construction method for adding a story to the lower part of the subway station structure according to one or more embodiments of the present invention.

[0036] Figure 4 It is the present invention Figure 3 Enlarged view of the structure at location A in the present invention.

[0037] Figure 5 It is the present invention Figure 5 Enlarged view of the structure at location B in the present invention.

[0038] Figure 6 It is the present invention Figure 5 Enlarged view of the structure at location C in the present invention.

[0039] Figure 7 Schematic diagram of the connection between the supporting arch cover and the existing middle column in a construction method for adding a story to the lower part of the subway station structure according to one or more embodiments of the present invention.

[0040] Figure 8 Schematic diagram of excavating the foundation pit and constructing the additional middle column in a construction method for adding a story to the lower part of the subway station structure according to one or more embodiments of the present invention.

[0041] Figure 9 Schematic diagram of excavating the soil on both sides of the foundation pit and constructing the additional floor slab and additional side wall in a construction method for adding a story to the lower part of the subway station structure according to one or more embodiments of the present invention.

[0042] Figure 10 Schematic diagram of restoring the floor slab of the existing structure layer after the completion of the construction method for adding a story to the lower part of the subway station structure according to one or more embodiments of the present invention.

[0043] In the figure: The distances or dimensions between each part are exaggerated for showing the positions of each part, and the schematic diagram is only for illustration.

[0044] Among them: 1. Grouting reinforcement area; 2. Vertical steel pipe pile; 3. Inclined steel pipe pile; 4. Supporting beam; 5. Original waterproof coiled material; 6. Lapped waterproof coiled material; 7. Waterstop steel ring; 8. Water-swelling waterstop rubber; 9. Polyurethane waterproof coating; 10. Waterstop board; 11. Supporting arch cover; 12. Mechanical adapter; 13. Second anchoring steel bar; 14. First anchoring steel bar; 15. Stirrup; 16. Core filling concrete; 17. First connecting planted bar; 18. Second connecting planted bar; 19. Shotcrete protective layer; 20. Locking foot bolt; 21. Additional middle column; 22. Waterproof coiled material; 23. Additional floor slab; 24. Additional side wall. Detailed implementation manners

[0045] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0046] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless otherwise clearly indicated in the present invention, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "include" and / or "comprising" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or their combinations;

[0047] As introduced in the background technology, in the prior art, there is a problem of poor support stability in the construction of adding floors to subway stations. In order to solve the above technical problems, the present invention proposes a construction method for adding floors to the lower part of a subway station structure.

[0048] In a typical embodiment of the present invention, a construction method for adding a floor to the lower portion of a subway station structure includes the following:

[0049] refer to Figure 1 and Figure 2 As shown, grouting reinforcement is performed on the foundation under the existing structure of the subway to improve the bearing capacity of the foundation during the excavation of the additional structure. After the grouting is completed, a grouting reinforcement area 1 is formed, and additional support components are implanted on the opposite sides of the grouting reinforcement area 1.

[0050] Cut the lower side walls on both sides of the existing structure respectively, and plant oblique support piles from the cut points. The oblique support piles are planted between the existing structure side wall retaining piles. The oblique support piles are located on the outside of the added-story support components and are planted obliquely between the existing structure side wall retaining piles. Even if slight structural settlement and shaking occur during subsequent construction, the stability of the added-story retaining structure can be provided under the support and restriction of the existing structure side wall retaining piles. The top of the added-story support components and the top of the oblique support piles are connected to the underpinning beams, and the supporting arch cover is constructed through the underpinning beams on both sides and the center column of the existing structure.

[0051] Remove the existing structural base plate, excavate the foundation pit for the additional structure in layers and sections, construct additional center columns in the foundation pit, drive the additional center columns down into the foundation, and support the existing center columns;

[0052] Continue excavating in the foundation pit to form a complete additional floor space, construct the additional floor structure, remove the supporting arch cover, and complete the additional floor construction of the subway station.

[0053] Among them, it should be noted that the additional story support component is a vertical support pile. The vertical support pile serves as the support structure for the additional story structure, and the construction of the additional story side wall is carried out subsequently along the inner side of the vertical support pile. The vertical support pile is specifically a vertical steel pipe pile 2, and the inclined support pile is an inclined steel pipe pile 3.

[0054] Reference Figure 3 As shown in the reference, after the lower side walls on both sides of the existing structure are cut, the inclined steel pipe piles 3 are driven into the spaces between the retaining piles of the existing structure side wall. The inclined steel pipe piles 3 penetrate through the existing structure floor slab, causing partial damage to the original waterproof system. At the same time, the cutting of the lower side walls exposes the original waterproof coiled material 5 outside the existing structure side wall. Therefore, it is necessary to repair and lap the waterproof system to ensure the waterproof requirements of the overall structure during construction. Considering that the transfer beam needs to be connected to the vertical steel pipe pile 2 and the inclined steel pipe pile 3, the steel mesh and the second anchoring steel bars are set first, and then the waterproof system is repaired and lapped.

[0055] It should be explained that because the additional story support component is located inside the retaining piles of the existing structure side wall, which causes a dislocation between the additional story side wall and the existing structure side wall. Therefore, in order to achieve the safe transfer of the load of the existing structure side wall downward and resist the bending and shear forces generated by the upper and lower side walls of the existing structure side wall and the additional story structure side wall, it is necessary to set a transfer beam 4 between the existing structure side wall and the new additional side wall.

[0056] Reference Figure 5 As shown in the reference, the key load-bearing component, the supporting arch cover 11, is constructed. The supporting arch cover 11 adopts a two-way prestressed reinforced concrete shell structure, which can give full play to the compressive performance of concrete and form a spatial thin-shell load-bearing system. The supporting arch cover 11 connects the two sides of the transfer beam 4 to further support the existing structure. The transfer beam 4 is connected to the vertical steel pipe pile 2 and the inclined steel pipe pile 3, making the additional story support system and the existing structure connected as a whole, jointly forming a stable support system to prevent the existing structure from settling during the excavation of the additional story structure. Through this innovative composite support technology system, the stable replacement and protection of the existing structure are realized.

[0057] In this embodiment, the transfer beam 4 serves as a support member and a load-bearing member. One side of the transfer beam 4 contacts the waterproof system after the repair and lapping, and the other side of the transfer beam 4 extends beyond the vertical steel pipe pile 2. The width of the transfer beam 4 is 1 / 15 - 1 / 12 of the width of the existing structure floor slab.

[0058] It is easy to understand that the three components, the supporting arch cover 11, the vertical steel pipe pile 2, and the inclined steel pipe pile 3, are connected to the transfer beam 4 through a reasonable method. For the specific connection method, refer to Figure 6As shown, the vertical steel pipe piles 2 and the underpinning beam 4 are connected by cast-in-place with a steel mesh. The vertical steel pipe piles 2 are provided with hollow sections, and steel meshes are tied inside the hollow sections. The steel meshes include first anchoring steel bars 14 and stirrups 15. Multiple stirrups 15 are arranged circumferentially around multiple first anchoring steel bars 14, and adjacent two first anchoring steel bars 14 are arranged at an interval. The first anchoring steel bars 14 extend beyond the top end of the hollow section, and the part of the first anchoring steel bars 14 that extends beyond the hollow section is used to connect with the underpinning beam 4. The uplift force is transmitted between the pile top of the vertical steel pipe piles 2 and the underpinning beam through the steel mesh, and core filling concrete 16 is injected into the hollow section to ensure its high bearing capacity requirements.

[0059] In addition, the supporting arch cover 11 and the underpinning beam 4 are connected by post-inserted reinforcing bars. When constructing the supporting arch cover 11, holes are drilled into the underpinning beam 4 to insert first connecting post-inserted reinforcing bars 17, and the first connecting post-inserted reinforcing bars 17 are cast-in-place and connected with one end of the supporting arch cover 11. One end of the supporting arch cover 11 is provided with an inclined surface, and the inclined surface is in full contact with the top of the underpinning beam 4. The first connecting post-inserted reinforcing bars 17 can be arranged perpendicular to the underpinning beam, and there can be multiple first connecting post-inserted reinforcing bars 17, and adjacent two first connecting post-inserted reinforcing bars 17 are arranged at an interval.

[0060] It should be noted that a mechanical conversion joint 12 is arranged at the pile head of the inclined steel pipe pile 3. The mechanical conversion joint 12 can be an existing anchoring nut, and the anchoring nut is bonded to the top of the inclined steel pipe pile 3 to conduct the uplift force through the mechanical conversion joint. The mechanical conversion joint 12 is connected with multiple second anchoring steel bars 13 to realize the effective connection between the second anchoring steel bars 13 and the pile top of the inclined steel pipe pile 3, avoid the stress concentration or damage that may be caused by directly welding the steel bars and the pile body, enhance the connection reliability, and improve the construction efficiency.

[0061] Among them, it should be noted that the part of the first anchoring steel bars 14 located in the underpinning beam is arranged to open outwards, so that the part of the first anchoring steel bars that extends beyond the hollow section is in a flared shape; the second anchoring steel bars 13 are in an L shape, that is, the top ends of the second anchoring steel bars are bent to ensure the stability of the connection between the inclined steel pipe pile 3 and the underpinning beam 4.

[0062] It is easy to understand that after the construction of the steel mesh and the second anchoring steel bars 13, the waterproof system is constructed. Refer to Figure 4As shown in the figure, after driving the inclined steel pipe piles 3, the original waterproof structure of the existing structure floor slab is damaged. To prevent groundwater from seeping in, a water stop ring such as the water stop steel ring 7 is set at the joint between the pile head of the inclined steel pipe pile 3 and the floor slab, and a water-swelling water stop rubber 8 is filled in the joint. The interface is plugged with polyurethane waterproof coating 9. The cutting of the lower side wall exposes the original waterproof coiled material 5 outside the side wall. A lapped waterproof coiled material 6 is set at the cutting position of the lower side wall to make it an integral part with the original waterproof coiled material 5. The lapped waterproof coiled material 6 is laid from the cutting of the side wall to the top of the vertical steel pipe pile 2 and the inclined steel pipe pile 3. A water stop plate such as the water stop steel plate 10 is set at the pile head of the vertical steel pipe pile 2. Lapped waterproof coiled materials are laid on both sides of the water stop plate. The water stop plate is arranged avoiding the first anchor bar 14 and is vertically arranged on the surface of the additional story support component to prevent water seepage from flowing in.

[0063] It should be noted that in a certain longitudinal section, there are multiple existing structure middle columns, usually two. Therefore, the supporting arch cover 11 is divided into multiple sections, and the end parts of each section of the supporting arch cover are respectively connected to the existing structure middle columns through the second connecting implanted bars.

[0064] In this embodiment, the connection between the supporting arch cover 11 and the existing structure middle column refers to Figure 7 As shown in the figure, the method of connecting the supporting arch cover 11 and the existing structure middle column by implanted bars is adopted. Before constructing the supporting arch cover 11, the prefabricated second implanted bar steel bars 18 are horizontally inserted into the holes of the existing structure middle column to ensure the stability of the second implanted bar steel bars 18 in the holes and completely sink them into the existing structure middle column. When constructing the supporting arch cover 11, the second implanted bar steel bars 18 implanted in the existing structure middle column are connected to the supporting arch cover 11 to ensure the stable and reliable connection.

[0065] Among them, the second implanted bar steel bars 18 are arranged along the radial direction of the existing structure middle column, and multiple, such as 3, second implanted bar steel bars are respectively arranged on both sides of the existing structure middle column.

[0066] Refer to Figure 8 As shown in the figure, the existing structure floor slab is demolished, and the foundation pit of the additional story structure is excavated in layers and sections. The foundation pit is sprayed with anchor support. After the foundation pit excavation is completed, the loose materials and floating soil on the slope surface are cleaned to ensure that the shotcrete and anchor bolts can be firmly attached. Shotcrete operation is carried out by spraying concrete on the slope surface of the foundation pit. The thickness of the shotcrete is generally 5 - 8 cm to form a shotcrete protective layer 19 to ensure that the shotcrete layer has sufficient strength and stability. Lock foot anchor bolts 20 are set deep into the slope surface along the foundation pit slope. There are multiple lock foot anchor bolts 20. The shotcrete protective layer 19 and the anchor bolt support 20 act together to form a stable support system for the foundation pit, so as to ensure the stability during the construction of the additional story middle column 21.

[0067] After the foundation pit shotcrete-bolting support is completed, the additional story middle column 21 is constructed in the foundation pit. The additional story middle column is fixedly connected to the existing structure middle column, so that the load of the existing structure middle column above is transferred to the additional story middle column 21. The additional story middle column 21 is driven into the foundation. The top of the additional story middle column 21 is set as an inverted frustum shape, and the top of the additional story middle column 21 is in a horn shape to stably support the existing structure middle column.

[0068] Reference Figure 9 As shown, after the additional story middle column 21 is constructed, the remaining soil is excavated to both sides in the foundation pit to form a complete additional story space. New waterproof components are constructed in the additional story space, and waterproof components such as waterproof coiled material 22 are laid. After the waterproof coiled material 22 is completely laid, the additional story floor slab 23 is poured, and the additional story side wall 24 is constructed.

[0069] Reference Figure 10 As shown, the floor slab 25 of the existing structure layer, that is, the top slab of the additional story structure, is constructed. After the construction of the top slab of the additional story structure is completed, the supporting arch cover is removed to restore the complete space of the existing structure layer, and the additional story construction of the subway station is completed.

[0070] In summary, for the construction method provided in this embodiment, by connecting the supporting arch cover to the underpinning beams on both sides and the existing structure middle column, the underpinning beams on both sides and the existing structure form a stable structural system, which is beneficial to the smooth construction of the additional story structure, has less impact on the existing structure, thus reducing the safety risks during the construction process. The construction is carried out downward from the inside of the subway station as a whole, without the need to excavate from the outside of the subway. First, the additional story support components, inclined inserted support piles, and underpinning beams are constructed, and then the supporting arch cover is constructed, so that the retaining structure of the additional story structure and the existing subway structure become an integral body to ensure the overall stability. Then, excavation is carried out downward for the construction of the additional story structure. This not only avoids the disadvantages of the long construction period and high complexity of the previous pile foundation underpinning cap method, but also ensures the construction safety, effectively reduces the disturbance to the existing upper station structure during the construction, and is beneficial to improving the usable space of the subway station.

[0071] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A construction method for adding floors to the lower part of the subway station structure, characterized in that, It includes the following contents: The foundation under the existing subway structure is grouted and reinforced. After the grouting is completed, a grouting reinforcement area is formed. Reinforcement components for additional storeys are implanted on the opposite sides of the grouting reinforcement area respectively; The lower side walls on both sides of the existing structure are cut respectively. Inclined inserted support piles are implanted from the cutting positions. The inclined inserted support piles are implanted between the retaining piles of the side walls of the existing structure. The inclined inserted support piles are located outside the reinforcement components for additional storeys. The tops of the reinforcement components for additional storeys and the tops of the inclined inserted support piles are connected to the underpinning beams. The supporting arch cover is built through the underpinning beams on both sides and the middle columns in the existing structure; The existing structure floor slab is demolished. The foundation pit for the additional storey structure is excavated in layers and sections. Additional storey middle columns are constructed in the foundation pit. The additional storey middle columns are driven into the foundation downward. The additional storey middle columns support the middle columns in the existing structure; The foundation pit is continuously excavated in the foundation pit to form a complete additional storey space. The additional storey structure is constructed. The supporting arch cover is demolished, and the additional storey construction of the subway station is completed.

2. The construction method for adding a lower story to the structure of a subway station according to claim 1, characterized in that, A hollow section is arranged at the top of the reinforcement component for additional storeys. A steel mesh is arranged in the hollow section. The first anchoring steel bars in the steel mesh extend beyond the hollow section. The part of the first anchoring steel bars extending beyond the hollow section is used to connect with the underpinning beam mentioned above. The part of the first anchoring steel bars used to connect with the underpinning beam is bent in the direction away from the central axis of the hollow section.

3. The construction method for adding a story to the lower part of the subway station structure according to claim 1, characterized in that A mechanical conversion joint is arranged at the top of the inclined inserted support pile. The mechanical conversion joint is connected with the second anchoring steel bars. The second anchoring steel bars are used to connect with the underpinning beam mentioned above. The top ends of the second anchoring steel bars are bent.

4. The construction method for adding a storey to the lower part of the subway station structure according to claim 1, characterized in that, One side of the underpinning beam extends beyond the reinforcement component for additional storeys. The width of the underpinning beam is 1 / 15 - 1 / 12 of the width of the existing structure floor slab. First connecting implanted steel bars are arranged in the underpinning beam. The underpinning beam is connected with the supporting arch cover through the first connecting implanted steel bars; The supporting arch cover is divided into multiple sections. The end parts of each section of the supporting arch cover are respectively connected with the middle columns in the existing structure through second connecting implanted steel bars.

5. A construction method for adding a lower layer to the structure of a subway station according to claim 2, characterized in that, After the construction of the steel mesh is completed, the waterproof system of the existing structure is repaired and lapped. After the repair and lapping are completed, the underpinning beam is constructed. The underpinning beam contacts with the waterproof system after the repair and lapping.

6. A construction method for adding a lower story to the structure of a subway station according to claim 5, characterized in that, The repair and lapping of the waterproof system of the existing structure includes the following contents: A water stop ring is arranged at the joint between the pile head of the inclined inserted support pile and the existing structure floor slab, and water swelling water stop glue is filled in the joint. The interface is plugged with waterproof coating; Lapped waterproof coiled materials are arranged at the cutting positions of the lower side walls. The lapped waterproof coiled materials are laid from the cutting positions of the lower side walls to the tops of the inclined inserted support piles and the reinforcement components for additional storeys; A water blocking plate is arranged at the top of the reinforcement component for additional storeys. Lapped waterproof coiled materials are laid on both sides of the water blocking plate. The water blocking plate is vertically arranged on the surface of the reinforcement component for additional storeys.

7. A construction method for adding a lower storey to the structure of a subway station according to claim 1, characterized in that, The supporting arch cover adopts a two-way prestressed reinforced concrete shell structure.

8. A construction method for adding a lower storey to the structure of a subway station according to claim 1, characterized in that, After the excavation of the foundation pit is completed, shotcreting operation is carried out on the slope surface of the foundation pit. After the shotcreting is completed, anchor rods are set to carry out anchor shotcrete support for the foundation pit.

9. The construction method for adding a lower storey to the structure of a subway station according to claim 1, wherein, The additional storey middle columns are driven into the foundation downward. The tops of the additional storey middle columns are set as inverted frustum shapes. The additional storey middle columns are fixedly connected with the middle columns in the existing structure.

10. The construction method for adding a story to the lower part of the subway station structure according to claim 1, characterized in that, After the additional storey space is formed, waterproof components are laid in the additional storey space; The additional floor structure includes an additional floor slab, additional side walls, and an additional roof slab. After the waterproof components are laid and in contact, the additional floor slab is constructed first, followed by the additional side walls. After the construction of the additional side walls is completed, the additional roof slab, which is the existing structure floor slab, is constructed.

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