UHPC-RC formwork assembly type subway station cover and excavation semi-reverse construction method and device

Abstract

The invention provides a cover and excavation semi-reverse construction method and device for a UHPC-RC formwork assembly type subway station. The cover and excavation semi-reverse construction method comprises the steps that a formwork is used as a permanent formwork, and the formwork and common concrete used for being poured into the formwork jointly form a bearing structure; the formwork is of an ultra-high-performance reinforced concrete structure, and the construction method comprises the following steps that firstly, a middle stand column is constructed, then a superimposed top plate is constructed, then backfilling and earthing are conducted to recover a road surface, downward excavation is conducted to the position below a cast-in-place bottom plate, and then the structure is constructed in sequence from bottom to top. According to the cover and excavation semi-reverse construction method and device for the UHPC-RC formwork assembly type subway station, the structure size is reduced, the available building space is increased, the self weight of the structure is reduced, the formwork erecting and removing procedures are reduced, the durability of the structure is improved, and the effects that the interior of the structure of the subway station is solid, the exterior of the structure of the subway station is beautiful, and seepage and leakage are avoided are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of underground engineering, and in particular relates to a method and a device for semi-reverse construction of a UHPC-RC formwork assembled subway station. Background Art

[0002] As the construction of urban rail transit slows down, the concept of urban rail transit construction has gradually shifted from the pursuit of construction scale to the pursuit of quality and efficiency. Underground projects have been in a water environment for a long time. The poor impermeability of traditional concrete leads to serious groundwater leakage, and the internal steel bars are prone to corrosion, which seriously affects the life of underground stations. Ultra-high performance concrete has excellent properties such as ultra-high strength, high toughness, low permeability and high volume stability. Ultra-high performance concrete is very expensive while having high performance. If ultra-high performance concrete is used entirely for the overall structure casting, the cost is too expensive and does not conform to the concept of green construction. At the same time, for the core areas of the city, the ground space is limited, which will cause serious inconvenience to surrounding traffic, residents' lives, and commercial activities during the construction period. Summary of the invention

[0003] The purpose of the present invention is to provide a UHPC-RC formwork assembled subway station cover excavation semi-reverse construction method and device, aiming to solve the technical problems existing in the above-mentioned background technology.

[0004] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: to provide a UHPC-RC formwork assembled subway station cover and excavation semi-reverse construction method, using the formwork as a permanent formwork, and the membrane shell and ordinary concrete used to be poured in the membrane shell together constitute a bearing structure; the formwork is an ultra-high performance reinforced concrete structure, including the following steps: first constructing a central column, then constructing a composite top plate, and then backfilling and covering the soil to restore the road surface, and then excavating downward to under the cast-in-place bottom plate, and then constructing the structure from bottom to top.

[0005] Preferably, the method comprises the following steps:

[0006] Pretreatment of the construction site: construction of station center column piles;

[0007] Temporary supports are set up on both sides of the foundation pit, prefabricated assembled UHPC top longitudinal beams are installed, and prefabricated UHPC top plate formwork is hoisted. The top longitudinal beams and temporary supports support both ends of the prefabricated UHPC top plate formwork; then cast-in-place ordinary concrete top plate is poured on the prefabricated UHPC top plate formwork; after the construction is completed, the composite top plate is supported by the crown beam and the top longitudinal beam to form a cover plate; after the concrete of the composite top plate solidifies, the upper part is backfilled with soil to restore the road surface;

[0008] Excavate downwards to the lower elevation of the cast-in-place slab;

[0009] Carry out construction pretreatment on the foundation pit, and then construct the cast-in-place bottom slab and cast-in-place bottom longitudinal beam;

[0010] Install the prefabricated UHPC side wall formwork for the second underground floor, and then pour the ordinary concrete side wall in the formwork; install the brackets of the central column of the second underground floor, and hoist the prefabricated assembled UHPC middle longitudinal beam onto the brackets; hoist the prefabricated UHPC middle plate formwork, and support the two ends of the prefabricated UHPC middle plate formwork with the prefabricated assembled UHPC middle longitudinal beam and temporary supports;

[0011] Casting a cast-in-place ordinary concrete middle plate on the installed prefabricated UHPC middle plate formwork; wherein the second connection node is cast together with the cast-in-place ordinary concrete middle plate;

[0012] Install the prefabricated UHPC side wall formwork for the underground first floor, connect the steel bars at the first connection node into the formwork, and then pour ordinary concrete side walls in the prefabricated UHPC side wall formwork.

[0013] Preferably, the construction of the station center column piles includes the following steps:

[0014] Construction preparation: lay out the lines to determine the pile position; empty the borehole, and hang the steel casing and steel cage; pour the pile foundation concrete to the predetermined position for the first time; chisel out the concrete in the center of the pile after the initial setting of the first pouring of concrete to form a cup; level the pile head of the center column pile foundation, and hang the center column; pour the cup concrete to the top elevation of the pile foundation; recover the steel casing, and backfill the area around the center column with crushed stone and dry sand.

[0015] Preferably, the construction of the station center column piles includes: the differential settlement between the center column piles and between the center column piles and the bored cast-in-place piles meets the following requirements: the cumulative settlement of the column top is ≤20mm, the differential settlement is ≤15mm, and the differential settlement of adjacent column piles is ≤10mm.

[0016] Preferably, the construction site pretreatment comprises the following steps:

[0017] Level the site and construct bored piles on both sides;

[0018] After excavating downwards to the bottom elevation of the prefabricated UHPC top and longitudinal beams, the surface is chiseled and cleaned to the designed elevation, and then the cap beam and retaining wall are constructed.

[0019] Preferably, the pouring of the cast-in-place ordinary concrete middle plate on the installed prefabricated UHPC middle plate formwork comprises:

[0020] When constructing the node between the prefabricated UHPC middle longitudinal beam and the middle column, the third steel pipe section is welded with steel hoops up and down, and the tensile steel plates are welded up and down along the axial direction. Steel bars are laid in the recess of the prefabricated middle longitudinal beam at a certain distance outside the beam-column node along the axial direction, the main bars are welded to the tensile steel plates, the waist bars are welded to the steel hoops, and concrete is poured.

[0021] Preferably, the pouring of the cast-in-place ordinary concrete middle plate on the installed prefabricated UHPC middle plate formwork comprises:

[0022] When constructing the node between the composite middle plate and the central column, the tensile steel plate is welded horizontally on top, and the main reinforcement of the composite middle plate is welded to the tensile steel plate and the steel hoop.

[0023] Preferably, the pre-treatment of the foundation pit and then the construction of the cast-in-place bottom plate and cast-in-place bottom longitudinal beams include:

[0024] When constructing the cast-in-place bottom longitudinal beam, cast-in-place bottom slab and central column nodes, the second steel pipe section is welded with steel hoops and tensile steel plates at the top and bottom respectively, which are used to weld with the steel bars of the cast-in-place bottom longitudinal beam and cast-in-place bottom slab.

[0025] The UHPC-RC formwork assembled subway station device is manufactured based on the steps in the UHPC-RC formwork assembled subway station cover excavation semi-reverse construction method as described in any one of the above, and the structure is an open-cut rectangular double-layer two-span station, including:

[0026] The station body comprises a cast-in-place bottom plate, a side wall structure connected to the side of the cast-in-place bottom plate, and a composite top plate connected to one end of the side wall structure away from the cast-in-place bottom plate;

[0027] A laminated middle plate is arranged in the side wall structure; the side surfaces of the laminated middle plate are respectively connected and fixed to the inner wall surfaces of the side wall structure;

[0028] A central column, one end of which is connected to the composite top plate, and the other end of which penetrates the composite middle plate and the cast-in-place bottom plate in sequence and extends into and is connected and fixed to the central column pile foundation buried in the foundation pit;

[0029] The prefabricated UHPC middle longitudinal beam has two ends respectively connected and fixed to the side wall structure; the prefabricated UHPC middle longitudinal beam is connected and fixed to the middle column; the prefabricated UHPC middle longitudinal beam is connected and fixed to the composite middle plate;

[0030] The prefabricated UHPC top longitudinal beam is arranged above the prefabricated UHPC middle longitudinal beam; the two ends of the prefabricated UHPC top longitudinal beam are respectively connected and fixed to the side wall structure; the prefabricated UHPC top longitudinal beam is connected and fixed to the middle column; the prefabricated UHPC top longitudinal beam is connected and fixed to the composite top plate.

[0031] Preferably, the center column comprises:

[0032] The steel casing section includes a first steel pipe section, a second steel pipe section and a third steel pipe section; the first steel pipe section is used to connect with the pile foundation of the middle column; the second steel pipe section is used to weld with the beam and slab steel bars when constructing the beam and slab column node; the third steel pipe section is used to weld the plate steel bars when constructing the beam and slab column node

[0033] The UHPC segment includes a first UHPC segment and a second UHPC segment; the first UHPC segment is a portion from the top elevation of the cast-in-place bottom longitudinal beam to the bottom elevation of the prefabricated UHPC middle longitudinal beam; the second UHPC segment is a portion from the top elevation of the composite middle plate to the bottom elevation of the prefabricated UHPC top longitudinal beam.

[0034] The beneficial effects of the UHPC-RC formwork assembly type subway station cover excavation semi-reverse construction method and device provided by the present invention are: compared with the prior art, the UHPC-RC formwork assembly type subway station cover excavation semi-reverse construction method and device of the present invention reduce the structural size, increase the available building space, reduce the structural deadweight, reduce the formwork and demolding process, improve the structural durability, and help to achieve the subway station structure is solid inside and beautiful outside, no seepage and no leakage. The UHPC-RC formwork components have the characteristics of versatility and assembly, and can realize the factory prefabrication of components, which is conducive to improving the level of building industrialization and saving construction period; the UHPC-RC formwork has high strength and good volume stability, and the light and thin design can achieve better template function; the UHPC-RC formwork as a permanent formwork reduces the demolding process, and the factory prefabrication of components can shorten the construction period. The UHPC-RC formwork as a permanent formwork and cast-in-place ordinary concrete structure jointly bear and resist seepage, which can reduce the amount of ordinary concrete, reduce the structural size, and improve the structural durability while realizing a larger available building space. According to the stress characteristics of the structure, UHPC materials are only used locally to reduce the stress redundancy of high-strength materials, which can save engineering costs. The cover-excavation semi-reverse construction method can be constructed in a limited space, and after the construction of the central column, top longitudinal beam and top plate is completed, the road surface can be immediately backfilled and covered with soil to minimize traffic interruption and environmental impact. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 This is the structural diagram of the UHPC-RC formwork-assembled subway station;

[0037] Figure 2 This is a schematic diagram of the structural truss reinforcement;

[0038] Figure 3 It is a detailed view of the composite side wall structure; the left picture is a front view; the right picture is a top view;

[0039] Figure 4 It is the elevation and section view of the laminated middle plate, where the left side is the side wall side and the right side is the column side;

[0040] Figure 5 It is the elevation and section view of the composite top plate, where the left side is the side wall side and the right side is the column side;

[0041] Figure 6 This is the cross-section of the longitudinal beam in the prefabricated UHPC;

[0042] Figure 7 This is the cross-section of the prefabricated UHPC top and longitudinal beam;

[0043] Figure 8 This is a construction sequence diagram of the semi-reverse construction method of UHPC-RC formwork prefabricated subway station; A represents the excavation surface; B represents the drilling of the middle column pile; C represents backfilling and soil restoration; D represents the excavation surface;

[0044] Fig. 9 It is a detailed drawing of the bottom longitudinal beam and column node of the UHPC-RC formwork assembled subway station; the left figure shows the axial section of the bottom longitudinal beam and column node; the right figure shows the transverse section of the bottom longitudinal beam and column node, A represents the waist reinforcement of the bottom longitudinal beam; B represents the main reinforcement of the bottom plate; C represents the main reinforcement of the bottom longitudinal beam;

[0045] Fig.10 The detailed drawing of the longitudinal beam and column node of the UHPC-RC formwork assembled subway station, where the left figure shows the axial section of the longitudinal beam and column node; the right figure shows the transverse section of the longitudinal beam and column node, A represents the 100mm UHPC post-cast layer; B represents the local pouring of concrete; C represents the local laying of steel bars;

[0046] Fig.11 It is a detailed drawing of the top longitudinal beam and column node of the UHPC-RC formwork assembled subway station. The left figure shows the axial section of the top longitudinal beam and column node; the right figure shows the transverse section of the top longitudinal beam and column node; A represents the 100mm UHPC post-cast layer; B represents the local pouring of concrete; C represents the local laying of steel bars.

[0047] In the figure: 1, cast-in-place bottom plate; 2, cast-in-place bottom longitudinal beam; 3, composite side wall; 31, prefabricated UHPC side wall formwork; 311, UHPC thin plate; 312, tension steel bars; 32, cast-in-place ordinary concrete side wall; 4, central column; 41, central column pile foundation; 42a, first steel pipe section; 42b, second steel pipe section; 42c, third steel pipe section; 43a, first UHPC section; 43b, second UHPC section. 5. Prefabricated UHPC middle longitudinal beam; 6. Composite middle plate; 61. Prefabricated UHPC middle plate formwork; 62. Cast-in-place ordinary concrete middle plate; 63. Second connection node; 7. Prefabricated UHPC top longitudinal beam; 8. Composite top plate; 81. Prefabricated UHPC top plate formwork; 82. Cast-in-place ordinary concrete top plate; 83. First connection node; 9. Truss reinforcement; 91. Upper chord reinforcement; 92. Lower chord reinforcement; 93. Web reinforcement; 10. Bored piles; 11. Crown beam; 12. Retaining wall; 13. Temporary support; 14. Corbel; 15. Steel nails; 16. Steel hoop; 17. Tensile steel plate. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0049] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0050] Ultra-high performance materials and prefabricated construction technology are the hot spots for improving the quality and efficiency of urban rail. Ultra-high performance concrete (UHPC) has excellent properties such as ultra-high strength, high toughness, low permeability and high volume stability. UHPC is very suitable for the demand for building materials in subway stations, but it is very expensive at the same time as high performance. If UHPC is used for overall structural casting, the cost is too expensive and does not conform to the concept of green construction. At the same time, for the core area of ​​the city, the ground space is limited, and construction often needs to consider factors such as surrounding traffic, residents' lives and commercial activities. Therefore, the project team constructively proposed the idea of ​​combining ultra-high performance reinforced concrete structure (UHPC-RC) as a permanent formwork with cast-in-place ordinary concrete, designed an assembled UHPC-RC formwork subway station structure, and invented a cover-excavation semi-reverse construction method for assembled UHPC-RC formwork subway stations. After the upper structure is completed, the excavation surface is covered, which can effectively reduce noise, dust and traffic interference.

[0051] Reference Figures 1 to 11 , the semi-reverse construction method of the UHPC-RC formwork assembled subway station provided by the present invention is now described. The semi-reverse construction method of the UHPC-RC formwork assembled subway station first constructs the central column 4 and the superimposed top plate 8, backfills the soil to restore the road surface after constructing the central column 4 and the superimposed top plate 8, and then excavates downward to the cast-in-place bottom plate 1, and then constructs the structure from bottom to top; wherein, the UHPC-RC formwork is used as a permanent formwork and cast-in-place ordinary concrete to form a bearing structure. Specifically, the formwork is used as a permanent formwork, and the membrane shell and the ordinary concrete used to be cast in the membrane shell together form a bearing structure; wherein the formwork is an ultra-high performance reinforced concrete structure. The construction method comprises the following steps:

[0052] Step S1, pretreatment of the construction site.

[0053] The implementation of this step includes:

[0054] Step S1.1, reference Figure 8 (a) Level the site and construct 10 bored piles on both sides;

[0055] Step S1.2, reference Figure 8 (b) After excavating downward to the bottom elevation of the prefabricated UHPC top longitudinal beam 7, reliable protection measures are taken for the outer side of the foundation pit, and the residue, loose soil and water of the pile are cleaned, and the surface is roughened and cleaned to the design elevation, and then the cap beam 11 and retaining wall 12 are constructed. The cap beam 11 is a concrete structure.

[0056] Step S2, reference Figure 8(c) Construct the center column piles of the station; during the construction, the differential settlement between the center column piles and between the center column piles and the bored cast-in-place piles shall be strictly controlled, requiring the cumulative settlement of the column top to be ≤20mm, the differential settlement to be ≤15mm, and the differential settlement of adjacent column piles to be ≤10mm.

[0057] The implementation of this step includes:

[0058] Step S2.1, construction preparation, laying out and determining pile positions;

[0059] Step S2.2, empty the borehole, and hang the wall protection steel casing and steel cage;

[0060] Step S2.3: pouring pile foundation concrete to a predetermined position for the first time, wherein the predetermined position is located at least 1500 mm below the top elevation of the middle column pile foundation 41 .

[0061] Step S2.4, after the concrete is poured, the mud in the bored pile is promptly pumped out with a mud pump, and after the first pouring of concrete is initially set, the concrete in the center of the pile is chiseled out to form a cup mouth; the structure formed after the concrete solidifies is the central column pile foundation 41;

[0062] Step S2.5, leveling the pile head of the center column pile foundation 41, and hanging the center column 4;

[0063] Step S2.6, pouring cup-mouth concrete to the top elevation of the pile foundation;

[0064] Step S2.7, reclaim the wall protection steel casing, and backfill gravel and dry sand around the middle column 4.

[0065] Step S3, reference Figure 8 (d) Temporary supports 13 are set up on both sides of the foundation pit. To ensure the stability of the support, avoid the position of the armpit. Install the prefabricated assembled UHPC top longitudinal beam 7, hoist the prefabricated UHPC top plate formwork 81, and support the two ends of the prefabricated UHPC top plate formwork 81 with the top longitudinal beam 7 and temporary supports 13. During construction, attention should be paid to symmetrical hoisting and appropriate temporary fixing to avoid overturning.

[0066] Cast in-situ ordinary concrete top slab 82 on the installed prefabricated UHPC top slab formwork 81. A 100mm high UHPC post-cast layer is reserved for the cast-in-situ ordinary concrete top slab 82 at the top above the prefabricated assembled UHPC top longitudinal beam 7. Steel bars connected to the composite side wall 3 are reserved at the connection node (i.e., the first connection node 83) between the composite side wall 3 and the composite top slab 8 of the underground floor. After the construction is completed, the composite top slab 8 is supported by the crown beam 11 and the top longitudinal beam 7 to form a cover plate.

[0067] After the concrete of the composite top plate 8 solidifies, backfill the upper part with soil to restore the road surface, completing the construction of the center column 4 and the composite top plate 8;

[0068] Step S4, reference Figure 8 (e) Excavate downward to the lower elevation of the cast-in-place bottom plate 1, support as you dig, and select internal support or anchor support according to geological conditions;

[0069] Step S5, reference Figure 8 (f) Level the foundation pit, drain the water in the pit, and promptly construct the bottom plate waterproof layer and cushion layer, and construct the cast-in-place bottom plate 1 and cast-in-place bottom longitudinal beam 2. In particular, when constructing the cast-in-place bottom longitudinal beam 2, cast-in-place bottom plate 1, and the middle column 4 node, the second steel pipe section 42b is welded with steel hoops 16 and tensile steel plates 17 at the top and bottom, respectively, for welding with the steel bars of the bottom longitudinal beam 2 and the bottom plate 1.

[0070] Step S6: Reference Figure 8 (g) Install the prefabricated UHPC side wall formwork 31 of the second underground floor, and then cast the ordinary concrete side wall 32 in the formwork. Install the corbels of the middle column 4 of the second underground floor, and hoist the prefabricated assembled UHPC middle longitudinal beam 5 onto the corbels.

[0071] Temporary supports 13 are set up on the inner side of the composite side walls 3 on both sides of the second underground floor. In order to ensure the stability of the support, avoid the haunch position. The prefabricated UHPC middle plate formwork 61 is hoisted, and the two ends of the prefabricated UHPC middle plate formwork 61 are supported by the prefabricated assembled UHPC middle longitudinal beam 5 and the temporary supports 13. During construction, attention should be paid to symmetrical hoisting and appropriate temporary fixing to avoid overturning.

[0072] Step S7, reference Figure 8 (h) Cast in-situ ordinary concrete middle plate 62 on the installed prefabricated UHPC middle plate formwork 61. The connection node (i.e., the second connection node 63) between the underground second floor composite side wall 3 and the composite middle plate 6 should be cast together with the cast-in-situ ordinary concrete middle plate 62. A 100 mm high UHPC post-casting layer is reserved at the top of the cast-in-situ ordinary concrete middle plate 62 above the prefabricated assembled UHPC middle longitudinal beam 5.

[0073] In this step, when constructing the node between the prefabricated and assembled UHPC middle longitudinal beam 5 and the center column 4, the third steel pipe section 42c is welded with steel sleeves 16 up and down, and the tensile steel plate 17 is welded up and down along the axial direction, and steel bars are laid in the recess of the prefabricated and assembled middle longitudinal beam 5 within 1000mm outside the beam-column node along the axial direction, the main bars are welded to the tensile steel plate 17, the waist bars are welded to the steel sleeves 16, and concrete is poured to 100mm below the top elevation of the composite middle plate; when constructing the node between the composite middle plate 6 and the center column 4, the tensile steel plate 17 is welded on the top along the horizontal direction, and the main bars of the composite middle plate 6 are welded to the tensile steel plate 17 and the steel sleeves 16.

[0074] After the initial setting of the composite middle plate 6 concrete meets the construction requirements, pour the 100mm thick UHPC post-casting layer.

[0075] Step S8, reference Figure 8 (i) Install the prefabricated UHPC side wall formwork 31 of the underground first floor, connect the steel bars at the connection node (i.e., the first connection node 83) between the underground first floor composite side wall 3 and the composite top plate 8 into the formwork, and then cast the ordinary concrete side wall 32 in the prefabricated UHPC side wall formwork 31.

[0076] The present invention also provides a UHPC-RC formwork assembly type subway station device, referring to Figures 1 to 11 , which is manufactured based on the steps in the semi-reverse construction method of the UHPC-RC formwork assembled subway station as described in any one of the above items, and the structural form is an open-cut rectangular double-layer two-span station, including: a cast-in-place bottom plate 1, a cast-in-place bottom longitudinal beam 2, a composite side wall 3, a central column 4, a prefabricated assembled UHPC middle longitudinal beam 5, a composite middle plate 6, a prefabricated assembled UHPC top longitudinal beam 7 and a composite top plate 8. More specifically, it includes: a central column pile foundation 41 buried in the foundation pit; the station body includes a cast-in-place bottom plate 1, a side wall structure connected to the side of the cast-in-place bottom plate 1, and a composite top plate 8 connected to one end of the side wall structure away from the cast-in-place bottom plate 1; a composite middle plate 6 is arranged in the side wall structure; the sides of the composite middle plate 6 are respectively connected and fixed to the inner wall surface of the side wall structure; one end of the central column 4 is connected to the composite top plate 8, and the other end penetrates the composite middle plate 6 and the cast-in-place bottom plate 1 in turn and extends into and is connected and fixed to the central column pile foundation 41 buried in the foundation pit; prefabricated assembly The two ends of the prefabricated UHPC middle longitudinal beam 5 are respectively connected and fixed to the side wall structure; the prefabricated UHPC middle longitudinal beam 5 is connected and fixed to the center column 4; the prefabricated UHPC middle longitudinal beam 5 is connected and fixed to the composite middle plate 6; the prefabricated UHPC top longitudinal beam 7 is arranged above the prefabricated UHPC middle longitudinal beam 5; the two ends of the prefabricated UHPC top longitudinal beam 7 are respectively connected and fixed to the side wall structure; the prefabricated UHPC top longitudinal beam 7 is connected and fixed to the center column 4; the prefabricated UHPC top longitudinal beam 7 is connected and fixed to the composite top plate 8. The composite middle plate 6 is arranged between the cast-in-place bottom plate 1 and the composite top plate 8, and the composite middle plate 6 is used to divide the space of the station body into upper and lower layers; the bottom plate 1 is connected and fixed to the center column pile foundation 41; the lower end surface of the bottom plate 1 is connected to the bottom surface of the foundation pit;

[0077] In some feasible embodiments, the side wall structure is assembled from a plurality of stacked side walls 3. Adjacent stacked side walls 3 are connected and fixed.

[0078] In some feasible embodiments, the laminated side wall 3 is embedded with truss steel bars 9. The laminated middle plate 6 is embedded with truss steel bars 9. The laminated top plate 8 is embedded with truss steel bars 9. The use of truss steel bars 9 can effectively ensure the firmness and reliability of the component. The truss steel bars 9 are composed of three parts: upper chord steel bars 91, lower chord steel bars 92 and web steel bars 93. The provision of truss steel bars 9 can effectively ensure the performance of the laminated component.

[0079] In some achievable embodiments, the center column 4 includes: a steel casing section and a UHPC section; the steel casing section includes a first steel pipe section 42a, a second steel pipe section 42b and a third steel pipe section 42c; the first steel pipe section 42a is used to connect with the center column pile foundation 41; the second steel pipe section 42b is used to weld with the beam-slab steel bars when constructing the beam-slab-column node; the third steel pipe section 42c is used to weld the plate steel bars when constructing the beam-slab-column node. The UHPC section includes a first UHPC section 43a and a second UHPC section 43b; the first UHPC section 43a is the position from the top elevation of the cast-in-place bottom longitudinal beam 2 to the bottom elevation of the prefabricated assembled UHPC middle longitudinal beam 5; the second UHPC section 43b is the position from the top elevation of the composite middle plate 6 to the bottom elevation of the prefabricated assembled UHPC top longitudinal beam 7.

[0080] As a specific implementation of the embodiment of the present invention, refer to Figures 1 to 11 , the composite side wall 3 includes: a prefabricated UHPC side wall formwork 31 and a cast-in-place ordinary concrete side wall 32. The prefabricated UHPC side wall formwork 31 is a non-disassembly formwork. The prefabricated UHPC side wall formwork 31 includes two UHPC sheets 311 arranged at a certain distance; and tension steel bars 312 arranged in the gap between the two UHPC sheets 311 and respectively connected and fixed to the two UHPC sheets 311. Truss steel bars 9 are embedded in the gap between the two UHPC sheets 311. The cast-in-place ordinary concrete side wall 32 is filled in the prefabricated UHPC side wall formwork 31. The tension steel bars 312 connect the two UHPC sheets 311 to form a reliable UHPC side wall formwork 31. The prefabricated UHPC side wall formwork 31 consisting of two UHPC sheets 311 and tension steel bars 312 can effectively ensure the integrity and reliable force performance of the composite side wall 3.

[0081] The upper chord steel bars 91 and the lower chord steel bars 92 of the truss steel bars 9 are respectively embedded in the two UHPC sheets 311, and the web steel bars 93 connect the upper chord steel bars 91 and the lower chord steel bars 92 in the two UHPC sheets 311; after the cast-in-place ordinary concrete side wall 32 is cast, the web steel bars 93 are located in the cast-in-place ordinary concrete side wall 32. The provision of the truss steel bars 9 can ensure that the prefabricated UHPC side wall formwork 31 and the cast-in-place ordinary concrete side wall 32 are tightly connected.

[0082] As a specific implementation of the embodiment of the present invention, refer to Figures 1 to 11, the composite middle plate 6 includes: a prefabricated UHPC middle plate formwork 61 and a cast-in-place ordinary concrete middle plate 62; the cast-in-place ordinary concrete middle plate 62 is filled in the prefabricated UHPC middle plate formwork 61. The shape of the prefabricated UHPC middle plate formwork 61 is an inverted π shape. The prefabricated UHPC middle plate formwork 61 is a non-disassembly formwork. The prefabricated UHPC middle plate formwork 61 is pre-embedded with a lower chord steel bar 92. In this embodiment, the shape of the truss steel bar 9 is a "V" shape, and the truss steel bar 9 includes two lower chord steel bars 92 arranged at a certain distance. Two web bars 93 are respectively connected and fixed to the lower chord steel bars 92, and an upper chord steel bar 91 is simultaneously connected to the two web bars 93. Specifically, two lower chord steel bars 92 are pre-embedded in the prefabricated UHPC middle plate formwork 61. One upper chord steel bar 91 is embedded outside the prefabricated UHPC middle plate formwork 61. The web bar steel bar 93 connects the lower chord steel bar 92 and the upper chord steel bar 91. After pouring the cast-in-place ordinary concrete middle plate 62, the upper chord steel bars 91 and the web steel bars 93 are located in the cast-in-place ordinary concrete middle plate 62, thereby playing the role of connecting the prefabricated UHPC inverted P-shaped middle plate formwork 61 and the cast-in-place ordinary concrete middle plate 62. It can effectively ensure the integrity and reliable force performance of the composite middle plate 6. The second connection node 63 is the connection node between the side wall of the second underground floor and the middle plate.

[0083] As a specific implementation of the embodiment of the present invention, refer to Figures 1 to 11 The composite top plate 8 includes: a prefabricated UHPC top plate formwork 81 and a cast-in-place ordinary concrete top plate 82. The prefabricated UHPC top plate formwork 81 is filled with truss steel bars 9. The cast-in-place ordinary concrete top plate 82 is cast in the prefabricated UHPC top plate formwork 81. The truss steel bars 9 are used to connect and fix with the prefabricated UHPC top plate formwork 81 and the cast-in-place ordinary concrete top plate 82 at the same time. Specifically, the prefabricated UHPC top plate formwork 81 is a non-dismantling formwork. Two lower chord steel bars 92 are embedded in the prefabricated UHPC top plate formwork 81, one upper chord steel bar 91 is outside the prefabricated UHPC top plate formwork 81, and the web steel bars 93 connect the lower chord steel bars 92 and the upper chord steel bars 91. After the cast-in-place ordinary concrete top plate 82 is cast, the upper chord steel bars 91 and the web steel bars 93 are located in the cast-in-place ordinary concrete top plate 82, thereby playing the role of connecting the prefabricated UHPC top plate formwork 81 and the cast-in-place ordinary concrete top plate 82. The integrity and stress-bearing performance of the composite top plate 8 are reliable. The shape of the prefabricated UHPC top plate template 81 is an inverted π shape. The first connection node 83 is the connection node between the side wall of the first underground floor and the top plate.

[0084] As a specific implementation of the embodiment of the present invention, refer to Figures 1 to 11 , the longitudinal beam 5 in the prefabricated UHPC is a notched component. Figure 7 The prefabricated UHPC top longitudinal beam 7 is a hollow component.

[0085] As a specific implementation of the embodiment of the present invention, refer to Figures 1 to 11 The center column 4 is arranged on the center column pile foundation 41. Specifically, the center column 4 is a prefabricated structure and is installed on the center column pile foundation 41. The center column 4 includes a steel casing section and a UHPC section.

[0086] The steel casing sections are mainly distributed at the beam-slab-column nodes. The specific sections are: the bottom elevation of the middle column to the bottom elevation of the bottom plate 1 is the first steel pipe section 42a, see Fig. 9 The first steel pipe section 42a is provided with steel nails 15 for connecting with the middle column pile foundation 41. The elevation from the bottom of the bottom plate 1 to the top of the bottom longitudinal beam 2 is the second steel pipe section 42b. Fig. 9 When constructing the beam-slab-column node, the second steel pipe section 42b is welded with steel hoops 16 and tensile steel plates 17 at the top and bottom, respectively, for welding with the beam-slab reinforcement. The top elevation of the bottom longitudinal beam 2 to the bottom elevation of the prefabricated UHPC longitudinal beam 5 is the first uhpc section 43a. The bottom elevation of the prefabricated UHPC longitudinal beam 5 to the top elevation of the composite middle plate 6 is the third steel pipe section 42c. When constructing the beam-slab-column node, the steel hoops 16 are welded at the top and bottom, and the tensile steel plates 17 are welded at the top and bottom along the axial direction for welding the main beam reinforcement. The top elevation of the composite middle plate 6 to the bottom elevation of the prefabricated UHPC top longitudinal beam 7 is the second UHPC section 43b.

[0087] The beneficial effects of the UHPC-RC formwork assembly type subway station cover excavation semi-reverse construction method and device provided by the present invention are: compared with the prior art, the structural size is reduced, the available building space is increased, the structural deadweight is reduced, the formwork and demolding process are reduced, the structural durability is improved, and it is conducive to realizing the subway station structure to be solid inside and beautiful outside, and leak-proof. The UHPC-RC formwork components have the characteristics of versatility and assembly, and can realize the factory prefabrication of components, which is conducive to improving the level of building industrialization and saving construction period; the UHPC-RC formwork has high strength and good volume stability, and the light and thin design can achieve better template function; the UHPC-RC formwork as a permanent formwork reduces the demolding process, and the factory prefabrication of components can shorten the construction period. The UHPC-RC formwork as a permanent formwork and cast-in-place ordinary concrete structure can jointly bear and resist seepage, which can reduce the amount of ordinary concrete, reduce the structural size, and improve the structural durability while realizing a larger available building space. According to the structural stress characteristics, UHPC materials are only used locally to reduce the stress redundancy of high-strength materials, which can save engineering costs. The cover-excavation semi-reverse construction method can be constructed in a limited space, and after the construction of the central column, top longitudinal beam and top plate is completed, the soil can be immediately backfilled to restore the road surface, minimizing traffic interruption and environmental impact. More specifically, this structure and construction method have the following advantages: First, due to the universality and assembly characteristics of the UHPC-RC formwork components, the components can be prefabricated in the factory; second, the UHPC-RC formwork has high strength and good volume stability, and the light and thin design can achieve better formwork function; third, the UHPC-RC formwork as a permanent formwork can be used together with the cast-in-place ordinary concrete structure to bear and resist seepage, so the amount of ordinary concrete can be reduced, the structure size can be reduced, and the durability of the structure can be improved while achieving a larger usable building space; fourth, the UHPC-RC formwork as a permanent formwork reduces the demoulding process, and the factory prefabrication of the components can shorten the construction period; fifth, the cover-excavation semi-reverse construction method can be constructed in a limited space, and after the construction of the central column, top longitudinal beam and top plate is completed, the soil can be immediately backfilled to restore the road surface, minimizing traffic interruption and environmental impact.

[0088] The UHPC-RC formwork assembly type subway station cover excavation semi-reverse construction method provided by the present invention adopts ultra-high performance concrete to prefabricate the formwork of the middle longitudinal beam, top longitudinal beam and middle column as well as the side wall, middle plate and top plate, and the formwork and the cast-in-place ordinary concrete structure are used as the bearing structure during the service period of the station. The use of high-strength ultra-high performance concrete can reduce the volume of beams, plates, columns and wall structures, which is conducive to improving the lightweight level of buildings and increasing the use space of buildings; the use of partial structural prefabrication can improve the level of building industrialization and speed up construction efficiency. For large-volume structural components such as side walls and plates, the design combining prefabrication and cast-in-place, ultra-high performance concrete and ordinary concrete is conducive to reducing the project cost and saving costs. When casting the cast-in-place ordinary concrete middle plate and the cast-in-place ordinary concrete top plate, a 100mm high UHPC post-casting layer is cast on the top above the prefabricated assembled UHPC middle longitudinal beam and the prefabricated assembled UHPC top longitudinal beam. Because when calculating the main structure of the underground station, the middle plate and the top plate belong to the support position at the position of the middle longitudinal beam and the top longitudinal beam, and the mechanical performance is that the upper part is tensile. Therefore, pouring a 100mm high UHPC post-casting layer on the top of the prefabricated UHPC middle longitudinal beam and the prefabricated UHPC top longitudinal beam can effectively utilize the advantages of UHPC's high tensile strength to prevent the middle plate and the top plate from cracking above the middle longitudinal beam and the top longitudinal beam. Through optimization, the longitudinal beam is designed to be a notch and hollow structure, and steel bars are locally laid and concrete is poured at the node between the longitudinal beam and the column. In the present invention, the prefabricated UHPC middle longitudinal beam is a notch structure, and the prefabricated UHPC middle longitudinal beam is a hollow structure, which can reduce the amount of UHPC and reduce the project cost; laying steel bars and pouring concrete locally at the beam-column node position can ensure stable force transmission and structural safety. In this way, both cost and safety can be taken into account. The cover-excavation semi-reverse method can be constructed in a limited space, and after the construction of the middle column, the top longitudinal beam and the top plate is completed, the road surface can be immediately backfilled and covered with soil to minimize traffic interruption and environmental impact. The neutral column is designed in a segmented form, and the surface of the beam-slab-column node is a steel casing, which is convenient for welding steel hoops and tensile steel plates, so as to facilitate welding and anchoring with the beam and slab steel bars.

[0089] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0090] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or terminal device including the elements.

[0091] The above is a detailed introduction to the UHPC-RC formwork assembled subway station cover excavation semi-reverse construction method and device provided by the present invention. Specific examples are used in this article to illustrate the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. UHPC-RC formwork assembled subway station cover excavation semi-reverse construction method, characterized by: The formwork is used as a permanent formwork, and the membrane shell and ordinary concrete poured in the membrane shell together constitute the load-bearing structure; the formwork is an ultra-high performance reinforced concrete structure, including the following steps: first construct the central column, then construct the composite top plate, then backfill the soil to restore the road surface, and then excavate downward to under the cast-in-place bottom plate, and then construct the structure from bottom to top.

2. The UHPC-RC formwork assembled subway station cover excavation semi-reverse construction method according to claim 1, characterized in that: The following steps are involved: Pretreatment of the construction site: construction of station center column piles; Temporary supports are set up on both sides of the foundation pit, prefabricated assembled UHPC top longitudinal beams are installed, and prefabricated UHPC top plate formwork is hoisted. The top longitudinal beams and temporary supports support both ends of the prefabricated UHPC top plate formwork; then cast-in-place ordinary concrete top plate is poured on the prefabricated UHPC top plate formwork; After the construction is completed, the composite top plate is supported by the crown beam and the top longitudinal beam to form a cover plate; after the concrete of the composite top plate solidifies, the upper part is backfilled with soil to restore the road surface; Excavate downwards to the lower elevation of the cast-in-place slab; Carry out construction pretreatment on the foundation pit, and then construct the cast-in-place bottom slab and cast-in-place bottom longitudinal beam; Install the prefabricated UHPC side wall formwork for the second underground floor, and then pour the ordinary concrete side wall in the formwork; install the brackets of the central column of the second underground floor, and hoist the prefabricated assembled UHPC middle longitudinal beam onto the brackets; hoist the prefabricated UHPC middle plate formwork, and support the two ends of the prefabricated UHPC middle plate formwork with the prefabricated assembled UHPC middle longitudinal beam and temporary supports; Casting a cast-in-place ordinary concrete middle plate on the installed prefabricated UHPC middle plate formwork; wherein the second connection node is cast together with the cast-in-place ordinary concrete middle plate; Install the prefabricated UHPC side wall formwork for the underground first floor, connect the steel bars at the first connection node into the formwork, and then pour ordinary concrete side walls in the prefabricated UHPC side wall formwork.

3. The UHPC-RC formwork assembled subway station cover excavation semi-reverse construction method according to claim 2, characterized in that: The construction of the station center column pile comprises the following steps: Construction preparation: lay out the lines to determine the pile position; empty the borehole, and hang the steel casing and steel cage; pour the pile foundation concrete to the predetermined position for the first time; chisel out the concrete in the center of the pile after the initial setting of the first pouring of concrete to form a cup; level the pile head of the center column pile foundation, and hang the center column; pour the cup concrete to the top elevation of the pile foundation; recover the steel casing, and backfill the area around the center column with crushed stone and dry sand.

4. The UHPC-RC formwork assembled subway station cover excavation semi-reverse construction method as claimed in claim 3, characterized in that: The construction of the station center column piles includes: the differential settlement between the center column piles and between the center column piles and the bored cast-in-place piles meets the following requirements: the cumulative settlement of the column top is ≤20mm, the differential settlement is ≤15mm, and the differential settlement of adjacent column piles is ≤10mm.

5. The UHPC-RC formwork assembled subway station cover excavation semi-reverse construction method as claimed in claim 3, characterized in that: The construction site pretreatment comprises the following steps: Level the site and construct bored piles on both sides; After excavating downwards to the bottom elevation of the prefabricated UHPC top and longitudinal beams, the surface is chiseled and cleaned to the designed elevation, and then the cap beam and retaining wall are constructed.

6. The UHPC-RC formwork assembled subway station cover excavation semi-reverse construction method according to claim 5, characterized in that: The method of pouring a cast-in-place ordinary concrete middle slab on the installed prefabricated UHPC middle slab formwork comprises: When constructing the node between the prefabricated UHPC middle longitudinal beam and the middle column, the third steel pipe section is welded with steel hoops up and down, and the tensile steel plates are welded up and down along the axial direction. Steel bars are laid in the recess of the prefabricated middle longitudinal beam at a certain distance outside the beam-column node along the axial direction, the main bars are welded to the tensile steel plates, the waist bars are welded to the steel hoops, and concrete is poured.

7. The UHPC-RC formwork assembled subway station cover excavation semi-reverse construction method according to claim 6, characterized in that: The method of pouring a cast-in-place ordinary concrete middle slab on the installed prefabricated UHPC middle slab formwork comprises: When constructing the node between the composite middle plate and the central column, the tensile steel plate is welded horizontally on top, and the main reinforcement of the composite middle plate is welded to the tensile steel plate and the steel hoop.

8. The UHPC-RC formwork assembled subway station cover excavation semi-reverse construction method as claimed in claim 7, characterized in that: The said construction pretreatment of the foundation pit and then construction of the cast-in-place bottom plate and cast-in-place bottom longitudinal beams include: When constructing the cast-in-place bottom longitudinal beam, cast-in-place bottom slab and central column nodes, the second steel pipe section is welded with steel hoops and tensile steel plates at the top and bottom respectively, which are used to weld with the steel bars of the cast-in-place bottom longitudinal beam and cast-in-place bottom slab.

9. UHPC-RC formwork assembly type subway station device, characterized in that: The method is based on the steps of the semi-reverse construction method of UHPC-RC formwork assembled subway station as claimed in any one of claims 1 to 8, and the structure is an open-cut rectangular double-layer two-span station, including: The station body comprises a cast-in-place bottom plate, a side wall structure connected to the side of the cast-in-place bottom plate, and a composite top plate connected to one end of the side wall structure away from the cast-in-place bottom plate; A laminated middle plate is arranged in the side wall structure; the side surfaces of the laminated middle plate are respectively connected and fixed to the inner wall surfaces of the side wall structure; A central column, one end of which is connected to the composite top plate, and the other end of which penetrates the composite middle plate and the cast-in-place bottom plate in sequence and extends into and is connected and fixed to the central column pile foundation buried in the foundation pit; The prefabricated UHPC middle longitudinal beam has two ends respectively connected and fixed to the side wall structure; the prefabricated UHPC middle longitudinal beam is connected and fixed to the middle column; the prefabricated UHPC middle longitudinal beam is connected and fixed to the composite middle plate; The prefabricated UHPC top longitudinal beam is arranged above the prefabricated UHPC middle longitudinal beam; the two ends of the prefabricated UHPC top longitudinal beam are respectively connected and fixed to the side wall structure; the prefabricated UHPC top longitudinal beam is connected and fixed to the middle column; the prefabricated UHPC top longitudinal beam is connected and fixed to the composite top plate.

10. The UHPC-RC formwork assembled subway station device according to claim 9, characterized in that: The center column comprises: The steel casing section includes a first steel pipe section, a second steel pipe section and a third steel pipe section; the first steel pipe section is used to connect with the pile foundation of the middle column; the second steel pipe section is used to weld with the beam and slab steel bars when constructing the beam and slab column node; the third steel pipe section is used to weld the plate steel bars when constructing the beam and slab column node The UHPC segment includes a first UHPC segment and a second UHPC segment; the first UHPC segment is a portion from the top elevation of the cast-in-place bottom longitudinal beam to the bottom elevation of the prefabricated UHPC middle longitudinal beam; the second UHPC segment is a portion from the top elevation of the composite middle plate to the bottom elevation of the prefabricated UHPC top longitudinal beam.

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