Rectangular non-column assembly type underground station and construction method adopting foundation pit non-support open caisson type

Abstract

The underground station comprises a bottom plate, a middle plate, a top plate and inclined struts, a lower side wall is arranged between the bottom plate and the middle plate, a first inclined strut is arranged between the lower side wall and the middle plate, an upper side wall is arranged between the middle plate and the top plate, and a second inclined strut is arranged between the upper side wall and the middle plate. According to the invention, the inclined struts are used for replacing a traditional beam column structure, so that the span of the top plate is reduced. The internal space of the station is wider, and the building arrangement is more flexible; the top plate, the middle plate and the side walls are connected to form the triangular rigid frame structure, and the lateral anti-pushing capacity of the station is further enhanced. The invention further provides an open caisson type construction method for realizing support-free excavation of the foundation pit by replacing a traditional maintenance structure with the assembly structure, the construction period is shortened, the excavation width of a station is reduced, and the cost is saved.

Description

Technical Field

[0001] The invention relates to the technical field of rail transit, and in particular to a rectangular column-free assembled underground station and a construction method thereof using a foundation pit unsupported caisson type. Background Art

[0002] Subway stations, as the gathering and distribution points of urban rail transit passenger flow, connect the passenger transportation functions on the ground and underground, and play an increasingly important role. Existing underground stations generally adopt a single-column two-span or double-column three-span structure, and the structure adopts a beam, slab, and column structure, which has the following disadvantages: 1) The layout of the rooms inside the station is affected by the column span and is not flexible; 2) The escalator combination in the public area of ​​the station hall is affected by the column span and the layout is not flexible; 3) The flow of people getting on and off the train in the station is interrupted and blocked by pillars; 4) The view of the station hall and platform is blocked by pillars; 5) When the total width of the station is the same, the effective platform width of the station with columns is about 1.0m less than that of the station without columns; 6) There are longitudinal and transverse beams under the middle plate and top plate of the column station, which is not conducive to the laying of integrated pipelines.

[0003] In addition, the existing prefabricated construction technology for underground stations usually uses the enclosure structure as a temporary support to excavate the foundation pit, and then assembles the prefabricated components after the foundation pit is formed. This method has the following disadvantages: The excavation area of ​​the foundation pit is large. The cumulative width of the maintenance structure, waterproof structure and fertilizer trough structure of the traditional construction method can reach 4m~5m, which is about 20% of the outer width of the main structure of the station of 21m~23m, increasing the implementation width of the station; The construction period is long. The traditional construction method of foundation pit excavation, waterproofing structure and fertilizer tank replacement usually accounts for more than 70% of the total construction period of the station. The investment is large and the environmental impact is great. The traditional method has a large amount of foundation pit work, a long implementation period, and consumes a lot of manpower, equipment and materials on site. Therefore, the investment is large. The traditional method also occupies more urban space. During the construction period, it also interferes with the surrounding roads for a long time, and causes great environmental interference such as noise and garbage.

[0004] Due to the above-mentioned shortcomings of column-mounted stations and traditional assembled station structures, there is a need for an assembled station structure and a supporting construction method that is simple in structure, convenient to implement, and saves investment. Summary of the invention

[0005] In view of this, the problem to be solved by the present invention is to provide a rectangular column-free prefabricated underground station and a construction method thereof using a foundation pit unsupported caisson type. The prefabricated underground station has a simple structure, reduces the column structure, makes the station layout more flexible, reduces the concrete support of the main structure, reduces the amount of building materials, shortens the construction period, and saves costs.

[0006] The present invention solves the above-mentioned technical problems through the following technical means: The present invention provides a rectangular column-free assembled underground station, comprising a bottom plate, a middle plate and a top plate, characterized in that: a lower side wall is arranged between the bottom plate and the middle plate, an upper side wall is arranged between the middle plate and the top plate, a first diagonal brace is arranged between the lower side wall and the middle plate, a second diagonal brace is arranged between the upper side wall and the top plate, an embedded bayonet and a reserved steel bar joint are arranged at the top end of the upper side wall, connecting blocks matching the reserved bayonet are arranged at both ends of the top plate, embedded tenons are arranged at both ends of the middle plate, the lower end surface of the upper side wall and the upper end surface of the lower side wall are respectively provided with slots matching the embedded tenons, the embedded tenons are installed in the slots, side wall limiting tenons are arranged on both sides of the bottom plate, and the lower side wall is installed on the bottom plate through the side wall limiting tenons.

[0007] Furthermore, low side walls are provided on the left and right sides of the base plate, and the side wall limiting tenons are arranged on the upper side surfaces of the low side walls. The side wall limiting tenons are formed by a steel shell and cast-in-place reinforced concrete. A steel anchor box is pre-embedded in the low side wall, and the steel anchor box forms an opening with the low side wall at the bottom inner side of the station. The steel anchor box can be connected to the steel shell as a whole through a steel conduit. Through holes are provided on the steel shell and the steel anchor box. The steel conduit needs to match the through holes of the steel shell and the steel anchor box. An inverted arch backfill layer is provided on the upper side surface of the base plate.

[0008] Furthermore, a prestressed steel cable channel is provided through the lower side wall, and guide holes corresponding to the prestressed steel cable channel are provided on both end surfaces of the lower side wall, and a middle plate prestressed steel cable pipe is provided on the embedded tenon, and the middle plate prestressed steel cable pipe corresponds to the prestressed steel cable channel on the inner side of the lower side wall.

[0009] Furthermore, a first groove is provided on the lower end surface of the lower side wall, a second groove is provided on the upper end surface of the lower side wall, a first corbel is provided on the inner side surface of the lower side wall, the first groove is docked with the side wall limiting tenon, a first diagonal brace is provided on the first corbel, and one end of the first diagonal brace is supported on the first corbel of the lower side wall.

[0010] Furthermore, the top plate includes a prefabricated π beam, a prefabricated composite slab and a post-cast composite concrete layer. The prefabricated composite slab is located within the cavity of the prefabricated π beam. An exposed steel skeleton is embedded on the top surface of the prefabricated π beam. The post-cast composite concrete layer utilizes the exposed steel skeleton to couple with the prefabricated π beam and the prefabricated composite slab to form an overall top plate structure.

[0011] Furthermore, the lower end surface of the upper side wall is provided with a third groove and an exposed steel conduit, the upper end surface of the upper side wall is provided with a fourth groove and an exposed anchor steel bar, and the two end surfaces of the upper side wall are also provided with penetrating connecting steel cable guide holes, and the connecting steel cable guide holes are connected by sleeves to form through holes penetrating the two end surfaces of the upper side wall, and the through holes are used as channels for the later installed anchor cables.

[0012] Furthermore, a second corbel is provided on the inner side of the upper side wall, a second diagonal brace is provided on the second corbel, and the other end of the second diagonal brace is anchored on the lower side of the crossbeam of the prefabricated π beam.

[0013] Furthermore, tenons and anchor cable through holes are provided on both end surfaces of the middle plate, and the tenons are embedded in the cavity formed by the second groove on the upper end surface of the lower side wall and the third groove on the lower end of the upper side wall.

[0014] Furthermore, the first corbel and the second corbel are respectively provided with fastening bolt holes and limiting slots for fastening the first diagonal brace and the second diagonal brace, the bottom of the limiting slot is provided with a diagonal brace limiting pin hole, the first diagonal brace and the second diagonal brace are respectively provided with a diagonal brace limiting tenon matching the limiting slot, the end surface of the diagonal brace limiting tenon is provided with a connecting steel bar matching the diagonal brace limiting pin hole, and overflow holes are also provided on the side surfaces of the second diagonal brace and the first diagonal brace.

[0015] Furthermore, the bottom plate, lower side wall, middle plate and upper side wall are provided with through pipes with matching positions and apertures. The pipes are used to vertically pass prestressed steel cables after the components are installed. The lower ends of the prestressed steel cables are anchored in the steel anchor box in the lower side wall, and the upper ends are anchored to the top surface of the upper side wall.

[0016] The present invention also provides a construction method of a rectangular column-free assembled underground station using a foundation pit without support caisson type, comprising the following steps: the first step: leveling the site where the station is to be built, removing the topsoil, and drilling a row of multiple vertical circular holes in the rock and soil along the side wall of the station, the bottom depth of the circular holes being consistent with the bottom depth of the station structure, the center line of the circular holes being flush with the outer edge of the side wall of the station, and the spacing between adjacent circular holes being twice the diameter of the holes; Step 2: According to the position and size of the segments, temporary steel piles are placed in the circular holes, and fine sand is filled between the temporary steel piles and the circular holes. The fine sand is filled densely by water flushing. When all temporary steel piles are installed, the foundation longitudinal beam is poured on top of them; Step 3: After transporting the lower side wall, middle plate and diagonal bracing components to the site, assemble them and add a temporary internal support system. After the assembly is completed, install the jack at the location where the temporary steel pile support is placed. The jack needs to be hung on the bottom surface of the lower side wall and placed on the top surface of the steel support pile; Step 4: Excavate the foundation pit soil inside the assembled station structure; Step 5: Compress the jack strokes one by one, and promptly extract the next section of temporary steel pile support, then extend the jack until the bottom of the jack contacts the top plate of the remaining temporary steel pile support. After each temporary steel pile support in the same section is extracted, compress the jacks synchronously to make the station structure sink steadily until the jack stroke is compressed to the specified value. Repeat this step until the station structure descends to the set elevation, lock all jacks, and excavate the foundation pit downwards again; Step 6: After the assembled structure sinks to the preset depth, assemble the prefabricated components on it; Step 7: After excavation reaches the designed depth, pour the bottom slab in the area outside the jack position and reach the designed strength, remove the jack and pour the bottom slab in the remaining positions, and complete the excavation and bottom slab pouring of all underground station sections in sequence; Step 8: Remove the rails between the underground station sections, pour concrete at the joints, and perform waterproofing; Step 9: Cast the secondary structural layer of the top plate, pour waterproof and sealing materials into the joint interface of the prefabricated components, and complete the top waterproofing after forming the overall station; Step 10: Backfill the gap between the outer side of the side wall and the foundation pit, and backfill the upper covering soil.

[0017] It can be seen from the above technical scheme that the beneficial effects of the present invention are as follows: the present invention provides a rectangular column-free assembled underground station, comprising a bottom plate, a top plate and a middle plate, a lower side wall is arranged between the bottom plate and the middle plate, an upper side wall is arranged between the middle plate and the top plate, an embedded bayonet and a reserved steel bar joint are arranged at the top of the upper side wall, connecting blocks matching the reserved bayonet are arranged at both ends of the top plate, embedded tenons are arranged at both ends of the middle plate, the lower end surface of the upper side wall and the upper end surface of the lower side wall are respectively provided with slots matching the embedded tenons, the embedded tenons are installed in the slots, side wall limiting tenons are arranged on the upper end surfaces of both sides of the bottom plate, a groove corresponding to the side wall limiting tenon is arranged on the lower end surface of the lower side wall, and the side wall limiting tenon is embedded in the groove on the lower end surface of the lower side wall. It has a simple structure, reduces the column structure, makes the station layout more flexible, reduces the structural columns in the station, reduces the amount of engineering, shortens the construction period and saves costs. Diagonal braces are used to reduce the span of the top plate, and the top plate and side walls are connected to form a triangular rigid frame structure, which enhances the station's lateral thrust resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for the specific embodiments or the description of the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn according to the actual scale.

[0019] Figure 1 A three-dimensional structural diagram of a rectangular column-free assembled underground station device provided by the present invention; Figure 2 for Figure 1 A cross-sectional view of Figure 3 is a schematic diagram of the top plate; Figure 4 is a schematic diagram of the upper side wall; Figure 5 is a schematic diagram of the middle plate; Figure 6 is a schematic diagram of the lower side wall; Figure 7 This is the partial connection diagram between the upper side wall and the top plate; Figure 8 is a partial schematic diagram of the base plate; Fig. 9 It is a schematic diagram of the limiting tenon of the lower side wall; Fig.10 is a schematic diagram of a steel anchor box; Fig.11 is a schematic diagram of the second diagonal brace; Figures 12 to 21 A step diagram of a construction method of a rectangular column-free assembled underground station provided by the present invention using a foundation pit unsupported caisson type; Reference numerals: 1-bottom plate; 11-bottom side wall; 111-side wall limiting tenon; 112-steel anchor box; 1121-steel conduit; 2-top plate; 21-connecting block; 211-first through hole; 22-exposed steel skeleton; 23-prefabricated composite plate; 3-middle plate; 31-embedded tenon; 32-embedded external stirrups; 4-upper side wall; 41-embedded bayonet; 53-slot; 411-limiting pin; 43-connecting cable guide hole; 44-first corbel; 441-first diagonal brace; 4411-overflow hole; 4412-diagonal brace limiting tenon; 442 limiting slot; 4421-diagonal brace limiting hole; 5-lower side wall; 51-vertical connecting plate; 511-boss; 512-bump; 5121-second through hole; 52-prestressed cable channel. DETAILED DESCRIPTION

[0020] The following embodiments of the technical solution of the present invention are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore only used as examples, and cannot be used to limit the protection scope of the present invention.

[0021] See also Figures 1 to 21 The present invention provides a rectangular column-free assembled underground station, wherein a lower side wall is arranged between the bottom plate and the middle plate, an upper side wall is arranged between the middle plate and the top plate, a first diagonal brace is arranged between the lower side wall and the middle plate, a second diagonal brace is arranged between the upper side wall and the top plate, an embedded bayonet and a reserved steel bar joint are arranged at the top of the upper side wall, connecting blocks matching the reserved bayonet are arranged at both ends of the top plate, embedded tenons are arranged at both ends of the middle plate, and card grooves matching the embedded tenons are respectively arranged on the lower end surface of the upper side wall and the upper end surface of the lower side wall, the embedded tenon is installed in the card groove, side wall limiting tenons are arranged on both sides of the bottom plate, and the lower side wall is installed on the bottom plate through the side wall limiting tenons. The bottom plate is provided with short side walls on the left and right sides, the side wall limiting tenons are arranged on the upper side of the short side walls, the side wall limiting tenons are formed by a steel shell and cast-in-place reinforced concrete, a steel anchor box is embedded in the short side wall, the steel anchor box forms an opening with the short side wall at the bottom of the inner side of the station, the steel anchor box can be connected to the steel shell as a whole through a steel conduit, the steel shell and the steel anchor box are provided with through holes, the steel conduit and the through holes of the steel shell and the steel anchor box need to match, and an inverted arch backfill layer is arranged on the upper side of the bottom plate. It has a simple structure, reduces column structures, makes the station layout more flexible, reduces the concrete support of the main structure, reduces the amount of concrete, shortens the construction period, and saves costs.

[0022] As a further improvement to the above technical solution, a steel anchor box 112 is pre-buried in the bottom side wall 11, and a steel conduit 1121 for positioning the prestressed pipe is arranged on the upper side of the steel anchor box 112, and a third through hole is arranged on the steel conduit 1121, and the third through hole is communicated with the steel anchor box 112, and one side of the steel anchor box 112 is arranged as an opening, and the opening passes through the bottom side wall 11. By arranging the steel anchor box 112 in the bottom side wall 11, it is used to position the prestressed pipe and place the lower end anchor head, and one side of the steel anchor box 112 is arranged as an opening, and the opening is arranged on the side of the bottom side wall 11, so as to facilitate the installation and fixation of the connecting steel cable.

[0023] As a further improvement to the above technical solution, the two end faces of the lower side wall 5 are provided with through prestressed steel cable holes, the prestressed steel cable holes correspond to the connecting steel cable guide holes 43, and the embedded tenon 31 is provided with a middle plate 3 prestressed pipe, the middle plate 3 prestressed pipe corresponds to the prestressed steel cable hole on the inner side of the lower side wall 5. The prestressed steel cable holes are provided for installing the connecting steel cables, and the upper side wall 4, the lower side wall 5 and the bottom plate 1 are fastened and connected, so that the connection is more firm.

[0024] As a further improvement to the above technical solution, a limit pin 411 is provided on the embedding bayonet 41 of the upper side wall 4, and a first through hole 211 matching the limit pin 411 is provided on the connecting block 21 of the top plate 2. The limit pin passes through the upper side wall 4, and the two end surfaces of the upper side wall 4 are also provided with connecting cable guide holes 43. A limit bolt installation hole is provided on the inner side surface of the upper side wall 4, and its purpose is to facilitate the installation of fixing bolts from this hole when the side wall is assembled and before the system forms a stable structural system, so as to temporarily lock the lower part of the side wall to prevent the side wall from tipping over.

[0025] Specifically, viewed from the top of the upper side wall 4, the upper side wall 4 is vertically connected to the steel cable anchoring points, a total of 6, and the rest are limit pin holes; viewed from the bottom of the side wall, the upper side wall 4 is vertically connected to the steel cable guide holes 43, a total of 6 on each side wall.

[0026] As a further improvement to the above technical solution, a vertical connection plate 51 is pre-embedded on the lower end surface of the lower side wall 5, and a boss 511 matching the groove is provided on the upper end surface of the vertical connection plate 51, and the boss 511 is set to be hollow, and a convex block 512 is provided on the lower end surface of the vertical connection plate 51, and a second through hole 5121 is provided on the convex block 512, and the second through hole 5121 is connected to the prestressed pipe. The hole on the convex block 512 is elliptical, which provides a certain error redundancy for the side wall installation. By arranging the vertical connection plate 51 to be pre-embedded on the lower end surface of the lower side wall 5, a composite connection node structure is formed by the joint engagement of the limiting tenon, the pin hole and the prestress.

[0027] As a further improvement to the above technical solution, the left and right sides of the middle plate 3 are provided with embedded external stirrups 32, and the adjacent middle plates 3 are connected by cast-in-place concrete at the position of the embedded external stirrups 32. The top plate 2 has embedded top skeleton steel bars, which are used to connect the cast-in-place layer and the prefabricated π beam into a whole, thereby enhancing the structural performance of the station top plate 2; the top exposed steel skeleton 22 is mainly used as the skeleton steel bar of the top 30cm cast-in-place concrete layer after the station is assembled, and at the same time realizes the connection of the cast-in-place layer and the prefabricated π beam into a whole, thereby enhancing the structural performance of the station top plate 2; the first step is to prefabricate the π beam and the prefabricated composite plate 23, the second step is to lay the prefabricated composite plate 23 in the top cavity of the prefabricated π beam, and the third step is to tie the top cast-in-place layer steel cage.

[0028] As a further improvement of the above technical solution, the top plate includes a prefabricated π-beam, a prefabricated composite slab and a post-cast composite concrete layer. The prefabricated composite slab is located within the cavity of the prefabricated π-beam. An exposed steel skeleton is embedded on the top surface of the prefabricated π-beam. The post-cast composite concrete layer utilizes the exposed steel skeleton to couple with the prefabricated π-beam and the prefabricated composite slab to form an overall top plate structure.

[0029] The production process of the π beam is as follows: the first step is to embed the top skeleton steel bars, which are used to connect the cast-in-place layer and the prefabricated π beam into a whole, and enhance the structural performance of the station roof 2. This part of the steel bars is tied together with the π beam steel bars; the second step is to place the prefabricated composite slab 23; the third step is to tie the remaining steel bars on the top of the π beam to form an overall skeleton steel bar structure, and the exposed part is the post-casting layer steel bars.

[0030] As a further improvement of the above technical solution, a first groove is provided on the lower end surface of the lower side wall, a second groove is provided on the upper end surface of the lower side wall, a first corbel is provided on the inner side surface of the lower side wall, the first groove is docked and matched with the side wall limiting tenon, a first diagonal brace is provided on the first corbel, one end of the first diagonal brace is supported on the first corbel of the lower side wall; a second corbel is provided on the inner side of the upper side wall, a second diagonal brace is provided on the second corbel, and the other end of the second diagonal brace is anchored on the lower side of the crossbeam of the prefabricated π beam; the first corbel and The second corbel is provided with fastening bolt holes and limiting slots for fastening the first diagonal brace and the second diagonal brace, respectively. The bottom of the limiting slot is provided with a diagonal brace limiting pin hole. The first diagonal brace and the second diagonal brace are respectively provided with diagonal brace limiting tenons matching the limiting slots. The end faces of the diagonal brace limiting tenons are provided with connecting steel bars matching the diagonal brace limiting pin holes. The sides of the second diagonal brace and the first diagonal brace are also provided with overflow holes. The first corbel 44 and the second corbel are provided to install the second diagonal brace 441 and the first diagonal brace, and the air duct is fixed by the diagonal brace. The bottom plate, the lower side wall, the middle plate and the upper side wall are provided with through pipes with matching positions and apertures. The pipes are used to vertically pass the prestressed steel cable after the components are installed. The lower end of the prestressed steel cable is anchored in the steel anchor box in the lower side wall, and the upper end is anchored to the top surface of the upper side wall.

[0031] As a further improvement to the above technical solution, a diagonal brace limiting corbel is provided on the lower side of the top plate 2, and a fastening bolt hole is provided on the diagonal brace limiting corbel. The first diagonal brace 441 is fastened to the diagonal brace limiting corbel by a screw rod. The first corbel 44 and the second corbel are respectively provided with a limiting slot, and the purpose of providing the limiting slot is to prevent the bottom of the diagonal brace from slipping off and enhance the reliability of the connection between the diagonal brace and the upper side wall 4. A diagonal brace limiting pin hole 4421 is provided at the bottom of the limiting slot, and a diagonal brace limiting tenon 4412 matching the limiting slot is provided on the second diagonal brace 441 and the first diagonal brace, and a connecting steel bar matching the diagonal brace limiting pin hole 4421 is provided on the end surface of the diagonal brace limiting tenon 4412, and a grouting hole 4411 is also provided on the side of the second diagonal brace 441 and the first diagonal brace. When the slurry is densely injected from the bottom, the overflow hole 4411 will overflow upward to check whether the sealing cavity is densely injected. Preferably, a rubber sealing strip is provided at the bottom of the diagonal brace and pasted along the outer edge of the tenon. Its function is that when the diagonal brace is installed on the side wall corbel, grouting is required to fill the gap between the diagonal brace and the corbel groove tightly. This sealing strip can prevent the slurry from flowing out.

[0032] As a further improvement to the above technical solution, an inverted backfill layer is provided on the upper side surface of the base plate 1, a platform layer is provided on the backfill layer, and bottom side walls 11 for installing the lower side wall 5 are provided on the left and right sides of the upper side surface of the base plate 1, and the side wall limiting tenon 111 is provided on the upper end surface of the bottom side wall 11, and a prestressed pipe hole is also provided on the upper end surface of the bottom side wall 11, and the prestressed pipe hole is provided on both sides of the side wall limiting tenon 111. The bottom side wall 11 is provided on the base plate 1 for installing the lower side wall 5, and the side wall limiting tenon 111 is provided on the bottom side wall 11 to limit the relative displacement between the prefabricated side wall and the lower bottom to offset the water and soil pressure behind the side wall, wherein the side wall limiting tenon 111 is a factory-processed steel product, which is pre-buried together with the cast-in-place base plate 1, and its function is to enhance the shear strength of the tenon, regulate and ensure the position of the buried hole, and facilitate the installation of the prefabricated side wall in the later stage. The prestressed pipe hole and the stopper pin 411 hole at the bottom of the side wall can be taken out from the anchor hole on the side of the bottom plate 1 after the prestressed tendons extending from the side wall pass through this hole, and then the anchor can be installed. The bottom plate 1 can be prefabricated or cast in place. The bottom plate 1 can be selected as an arc bottom or a flat bottom according to needs.

[0033] The present invention also provides a construction method of a rectangular column-free assembled underground station using a foundation pit unsupported caisson type, comprising the following steps: S1. Level the site where the station is to be built, remove the topsoil, and drill a row of multiple vertical circular holes in the rock and soil along the side wall of the station. The bottom depth of the circular holes is consistent with the bottom depth of the station structure. The center line of the circular holes is flush with the outer edge of the side wall of the station, so that there is a gap between the outer wall of the side wall of the underground station and the excavated rock wall during the excavation process, reducing the resistance encountered by the underground station during the sinking process. The spacing between adjacent circular holes is twice the diameter of the hole.

[0034] S2. According to the location and size of the underground station segment, temporary steel piles are placed in the circular holes, and fine sand is filled between the temporary steel piles and the circular holes. The fine sand is filled densely by water flushing. When all temporary steel piles are installed, the foundation longitudinal beam is poured on top. In order to reduce the difficulty of controlling the jack system, the rectangular column-free prefabricated underground station is divided into multiple segments. The longitudinal prestressing force is used inside each segment to connect the transverse units in series into a whole. The guide rails are set between the connecting surfaces of adjacent segments to assist the segments to descend vertically one by one. Each segment consists of 10 to 15 transverse units.

[0035] S3. After transporting the lower side wall, middle plate and diagonal bracing components to the site, assemble them and add a temporary internal support system. After the assembly is completed, install the jack at the location where the temporary steel pile support is placed. The jack needs to be hung on the bottom surface of the lower side wall and placed on the top surface of the steel support pile; each segment is set as an independent unit, and more than 3 jacks and temporary steel pile supports are set at the four corners of each segment to enable it to descend stably.

[0036] S4. Excavate the foundation pit soil inside the assembled station structure, with each layer excavated about 2m deep during the excavation process. Control the excavation depth of each layer so that the station segment can sink easily.

[0037] S5. Compress the jack stroke one by one, and promptly extract the next section of temporary steel pile support, then extend the jack until the bottom of the jack contacts the top plate of the remaining temporary steel pile support. After each temporary steel pile support in the same section is extracted, compress the jack synchronously to make the station structure sink steadily until the jack stroke is compressed to the specified value. Repeat this step until the station structure drops about 2m, lock all jacks, and excavate the foundation pit again. Sinking the station section by section makes the station structure sink more steadily and the construction safer.

[0038] S6. After the assembled structure sinks to the set distance, assemble the prefabricated components on it. During the assembly process, it is not advisable to perform other operations under the foundation pit. First, assemble the lower side walls, middle plates and diagonal braces. After the foundation pit is excavated, when the top surface of the lower side walls is about 1m below the ground, the upper side walls, top plates and diagonal braces can be assembled. No excavation is performed during the assembly of the station segment to prevent accidents; the upper side walls, top plates and diagonal braces are assembled when the top surface of the lower side walls is about 1m below the ground, so that there is no need to perform high-altitude operations, the construction is more convenient and safe, and the construction efficiency is improved.

[0039] S7. After excavation to the designed depth, pour the floor slab in the area outside the jack position. After completion, remove the jack and pour the floor slab in the remaining positions. Complete the excavation and floor slab pouring of all underground station sections in sequence. After the station section is sunk to the designed depth, pour the floor slab to complete the entire station.

[0040] S8. Remove the rails between the underground station sections, pour concrete at the joints, and perform waterproofing; S9. Cast the secondary structural layer of the top slab, inject waterproof and sealing materials into the joints of prefabricated components, and complete the top waterproofing after the integral station is formed.

[0041] S10. Backfill the gap between the outer side of the side wall and the foundation pit, and backfill the upper covering soil.

[0042] This construction method uses the assembled station main structure formed on the ground as a maintenance structure during the foundation pit excavation process, excavates a circular hole in the soil and places temporary steel piles and a jack system to assist in assembling the station structure, and uses the assembled station structure to sink downward. As the foundation pit is excavated downward, multiple jacks are used to alternately extend and extract temporary steel pile segments to make the assembled station structure sink downward until it reaches the set position. The use of this construction method improves construction efficiency, reduces construction costs, and makes the construction process safer.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the various implementation cases of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A rectangular column-free assembled underground station, comprising a bottom plate, a middle plate and a top plate, characterized in that: A lower side wall is arranged between the bottom plate and the middle plate, an upper side wall is arranged between the middle plate and the top plate, a first diagonal brace is arranged between the lower side wall and the middle plate, a second diagonal brace is arranged between the upper side wall and the top plate, an embedded snap-in and a reserved steel bar joint are arranged at the top end of the upper side wall, connecting blocks matching the reserved snap-in are arranged at both ends of the top plate, embedded tenons are arranged at both ends of the middle plate, the lower end surface of the upper side wall and the upper end surface of the lower side wall are respectively provided with slots matching the embedded tenons, the embedded tenons are installed in the slots, side wall limiting tenons are arranged on both sides of the bottom plate, and the lower side wall is installed on the bottom plate through the side wall limiting tenons.

2. The rectangular column-free assembled underground station according to claim 1 is characterized in that: The bottom plate is provided with low side walls on the left and right sides, the side wall limiting tenons are arranged on the upper side surfaces of the low side walls, the side wall limiting tenons are formed by a steel shell and cast-in-place reinforced concrete, a steel anchor box is embedded in the low side wall, the steel anchor box forms an opening with the low side wall at the bottom inner side of the station, the steel anchor box can be connected to the steel shell as a whole through a steel conduit, the steel shell and the steel anchor box are provided with through holes, the steel conduit needs to match the through holes of the steel shell and the steel anchor box, and an inverted arch backfill layer is provided on the upper side surface of the bottom plate.

3. The lower side wall according to claim 2, characterized in that: A penetrating prestressed steel cable channel is provided on the lower side wall, guide holes corresponding to the prestressed steel cable channel are provided on both end surfaces of the lower side wall, a middle plate prestressed steel cable pipe is provided on the embedded tenon, and the middle plate prestressed steel cable pipe corresponds to the prestressed steel cable channel on the inner side of the lower side wall.

4. The rectangular column-free assembled underground station according to claim 1 is characterized in that: A first groove is provided on the lower end surface of the lower side wall, a second groove is provided on the upper end surface of the lower side wall, a first corbel is provided on the inner side surface of the lower side wall, the first groove is docked with the side wall limiting tenon, a first diagonal brace is provided on the first corbel, and one end of the first diagonal brace is supported on the first corbel of the lower side wall.

5. The rectangular column-free assembled underground station according to claim 3 is characterized in that: The top plate includes a prefabricated π beam, a prefabricated composite plate and a post-cast composite concrete layer. The prefabricated composite plate is located within the cavity of the prefabricated π beam. An exposed steel skeleton is embedded on the top surface of the prefabricated π beam. The post-cast composite concrete layer utilizes the exposed steel skeleton to couple with the prefabricated π beam and the prefabricated composite plate to form an overall top plate structure.

6. The rectangular column-free assembled underground station according to claim 5 is characterized in that: The lower end surface of the upper side wall is provided with a third groove and an exposed steel conduit, the upper end surface of the upper side wall is provided with a fourth groove and an exposed anchor steel bar, and the two end surfaces of the upper side wall are also provided with penetrating connecting steel cable guide holes, the connecting steel cable guide holes are connected by sleeves to form through holes penetrating the two end surfaces of the upper side wall, and the through holes are used as channels for the later installed anchor cables.

7. The rectangular column-free assembled underground station according to claim 6 is characterized in that: A second corbel is arranged on the inner side of the upper side wall, a second diagonal brace is arranged on the second corbel, and the other end of the second diagonal brace is anchored on the lower side of the crossbeam of the prefabricated π beam.

8. The rectangular column-free assembled underground station according to claim 6 is characterized by: The two end surfaces of the middle plate are provided with tenons and anchor cable through holes, and the tenons are embedded in the cavity formed by the second groove on the upper end surface of the lower side wall and the third groove on the lower end of the upper side wall.

9. The rectangular column-free assembled underground station according to claim 7 is characterized in that: The first corbel and the second corbel are respectively provided with fastening bolt holes and limiting slots for fastening the first diagonal brace and the second diagonal brace, the bottom of the limiting slot is provided with a diagonal brace limiting pin hole, the first diagonal brace and the second diagonal brace are respectively provided with a diagonal brace limiting tenon matching the limiting slot, the end surface of the diagonal brace limiting tenon is provided with a connecting steel bar matching the diagonal brace limiting pin hole, and the side surfaces of the second diagonal brace and the first diagonal brace are also provided with overflow holes.

10. The rectangular column-free assembled underground station according to claim 4, characterized in that: The bottom plate, lower side wall, middle plate and upper side wall are provided with through pipes with matching positions and apertures. The pipes are used to vertically pass prestressed steel cables after the components are installed. The lower ends of the prestressed steel cables are anchored in the steel anchor box in the lower side wall, and the upper ends are anchored to the top surface of the upper side wall.

11. A rectangular column-free assembled underground station adopts a foundation pit unsupported caisson construction method, characterized in that: The steps include: Step 1: Level the site where the station is to be built, remove the topsoil, and drill a row of multiple vertical circular holes in the rock and soil along the side wall of the station. The bottom depth of the circular holes is consistent with the bottom depth of the station structure. The center line of the circular holes is flush with the outer edge of the side wall of the station. The spacing between adjacent circular holes is twice the diameter of the hole. Step 2: According to the position and size of the segments, temporary steel piles are placed in the circular holes, and fine sand is filled between the temporary steel piles and the circular holes. The fine sand is filled densely by water flushing. When all temporary steel piles are installed, the foundation longitudinal beam is poured on top of them; Step 3: After transporting the lower side wall, middle plate and diagonal bracing components to the site, assemble them and add a temporary internal support system. After the assembly is completed, install the jack at the location where the temporary steel pile support is placed. The jack needs to be hung on the bottom surface of the lower side wall and placed on the top surface of the steel support pile; Step 4: Excavate the foundation pit soil inside the assembled station structure; Step 5: Compress the jack strokes one by one, and promptly extract the next section of temporary steel pile support, then extend the jack until the bottom of the jack contacts the top plate of the remaining temporary steel pile support. After each temporary steel pile support in the same section is extracted, compress the jacks synchronously to make the station structure sink steadily until the jack stroke is compressed to the specified value. Repeat this step until the station structure descends to the set elevation, lock all jacks, and excavate the foundation pit downwards again; Step 6: After the assembled structure has sunk to the preset depth, assemble the prefabricated components thereon; Step 7: After excavation reaches the designed depth, pour the bottom slab in the area outside the jack position and reach the designed strength, remove the jack and pour the bottom slab in the remaining positions, and complete the excavation and bottom slab pouring of all underground station sections in sequence; Step 8: Remove the rails between the underground station sections, pour concrete at the joints, and perform waterproofing; Step 9: Cast the secondary structural layer of the top plate, pour waterproof and sealing materials into the joint interface of the prefabricated components, and complete the top waterproofing after the integral station is formed; Step 10: Backfill the gap between the outer side of the side wall and the foundation pit, and backfill the upper covering soil.

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