Water-rich soft soil stratum continuous open caisson underground station prefabricated assembly structure and construction method thereof

Abstract

The invention discloses a water-rich soft soil stratum continuous open caisson underground station prefabricated assembly structure and a construction method thereof. The structure comprises a plurality of open caisson modules; each open caisson module comprises an open caisson, a bottom plate, a middle plate and a top plate, the open caisson is of a structure with the periphery closed and the upper end and the lower end open, at least one closed end of the open caisson is configured to be a temporary blocking wall capable of being dismantled from the open caisson, the bottom plate is arranged in the open caisson, and the middle plate and the top plate are both prefabricated parts. The plurality of steel pipes are sequentially lapped in the open caisson from bottom to top; every two adjacent open caissons are connected through a first cast-in-place concrete body, all plates in the open caissons are connected through a second cast-in-place concrete body, and all the plates, the first cast-in-place concrete body and the second cast-in-place concrete body are connected in a sealed mode through a post-pouring concrete body. The technical problems that the field cast-in-place operation efficiency is low, a waterproof system is separated from a main body structure, construction is complex, the construction process of a connecting section is tedious, and the integrity of the main body structure is damaged are solved.

Description

Technical Field

[0001] This invention relates to the field of underground station construction technology, specifically to a prefabricated assembly structure for a continuous caisson underground station in water-rich soft soil strata and its construction method. Background Technology

[0002] As urban rail transit expands deeper into underground spaces, constructing underground stations in challenging geological conditions such as water-rich soft soil presents significant challenges. Due to their high water content, low strength, and susceptibility to deformation, traditional open-cut methods suffer from large pit deformation, difficult dewatering, and environmental impact. In contrast, the caisson method, which integrates permanent structural support and construction, demonstrates unique advantages in water-rich soft soil strata. By constructing a caisson structure on the ground and sinking it to the design elevation, large-scale slope excavation is avoided, reducing earthwork and groundwater treatment. This method offers strong integrity and good stability.

[0003] Currently, the main method for constructing caissons for underground stations in soft soil strata is cast-in-place casting; that is, multiple rectangular caissons are constructed and sunk in stages using a skip-casting sequence, and finally connected to form a continuous station structure. While this method improves construction efficiency to some extent, it still has the following shortcomings:

[0004] First, the main structures, such as the caisson and internal floor slabs, need to be poured layer by layer on-site, resulting in a large amount of on-site work, complex formwork and support systems, long curing periods, and slow overall construction speed. Especially in water-rich strata, the cast-in-place structures have many construction joints and cold joints, leaving weak points for later waterproofing.

[0005] Secondly, after the main structure is completed, waterproofing is achieved by laying waterproof membranes at construction joints and expansion joints, installing various waterstops, and reinforcing with grout. This "structure first, waterproofing later" construction method is not only complicated, but also makes it difficult to ensure the bonding between the waterproofing materials and the main structure, especially the waterproofing treatment at the connection points.

[0006] Third, in order to connect the independently sunken caissons into a complete station, it is usually necessary to reinforce and waterproof the soil in the narrow space between the two caissons using high-pressure jet grouting (such as the N-Jet method). Then, temporary retaining walls and water barriers are installed while excavating for support, and finally, the connecting section is poured. This process is equivalent to secondary excavation and support on the already completed caisson sidewalls. Not only are the construction steps cumbersome, the cycle long, and the cost high, but it also causes multiple disturbances to the already positioned caisson structure and the surrounding strata, increasing the risk of settlement control and waterproofing failure.

[0007] In addition, although existing technologies have proposed using prefabricated composite components in station structures to improve the degree of assembly, they are mainly applied to local components such as the side walls and floor slabs of caissons. These prefabricated components have many splicing nodes, and waterproofing treatment still relies on complex joint sealing processes, failing to form an efficient waterproofing system integrated with the structure. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a prefabricated assembly structure for underground stations with continuous caissons in water-rich soft soil strata and its construction method, thereby solving the technical problems of low efficiency in on-site casting operations, separation of the waterproofing system from the main structure and complex construction, and cumbersome construction procedures for connecting sections that damage the integrity of the main structure.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A prefabricated assembly structure for a continuous caisson underground station in water-rich soft soil strata includes: multiple caisson modules;

[0011] Multiple caisson modules are spaced apart from each other and independently arranged in the same direction. Each caisson module includes: a caisson, a bottom plate, a middle plate, and a top plate. The caisson is a structure that is closed on all four sides and open at both the top and bottom ends. At least one of its closed ends is configured as a temporary sealing wall that can be removed from the caisson. The bottom plate is set inside the caisson to close its lower open end. The middle plate and the top plate are both prefabricated components and are sequentially overlapped inside the caisson from bottom to top, so that the top plate closes the upper open end of the caisson and the middle plate divides the internal space of the caisson.

[0012] One of two adjacent caisson modules is defined as the first caisson module and the other as the second caisson module. After the temporary sealing walls of the first caisson module and the second caisson module are removed, they are connected by a first cast-in-place concrete main body. The bottom slabs, middle slabs and top slabs of the two modules are connected by a second cast-in-place concrete main body. Furthermore, the bottom slabs, middle slabs, top slabs and corresponding second cast-in-place concrete main bodies of multiple caisson modules are sealed and connected by post-cast concrete main bodies to form a through-type station structure.

[0013] Furthermore, the temporary sealing wall is formed at the opposite ends of two adjacent caissons.

[0014] Furthermore, the temporary sealing wall is a precast reinforced concrete slab.

[0015] Furthermore, the base plate is cast at the lower open end of the caisson;

[0016] The caisson is equipped with supports for connecting the middle plate and the top plate.

[0017] Furthermore, the first cast-in-place concrete main body is poured between the ends of two adjacent caissons, and the end is provided with a first connecting steel bar.

[0018] Furthermore, the second cast-in-place concrete main body is poured between the ends of the bottom slab, middle slab, and top slab of two adjacent caissons, and the ends of the bottom slab, the middle slab, and the top slab are all provided with second connecting steel bars.

[0019] Furthermore, the post-cast concrete body covers the first cast-in-place concrete body and the second cast-in-place concrete body, forming a continuous waterproof layer base surface.

[0020] Furthermore, the middle plate extends towards the bottom plate to form a rail-top air duct, and the rail-top air duct and the middle plate are integrally formed.

[0021] A construction method for a prefabricated and assembled underground station structure with continuous caissons in water-rich soft soil strata includes the following steps:

[0022] Each caisson will be lowered until it reaches the design elevation;

[0023] The middle plate and the top plate are prefabricated and then hoisted into their respective caissons.

[0024] Remove the temporary sealing walls between the two adjacent caissons;

[0025] The first cast-in-place concrete main body is poured between two adjacent caissons, and the second cast-in-place concrete main body is poured between each adjacent bottom slab, middle slab, and top slab.

[0026] The post-cast concrete main body is poured on each slab, the first cast-in-place concrete main body and the second cast-in-place concrete main body to form a through station structure.

[0027] Furthermore, the middle plate is prefabricated using a wooden mold, and the top plate is prefabricated using either a steel mold or a wooden mold.

[0028] Compared to existing technologies, this invention offers the following advantages: A continuous underground station is formed by splicing multiple caisson modules, with removable temporary sealing walls connecting these modules. This not only addresses the unique geological conditions of water-rich soft soil but also accelerates the overall construction progress through independent construction in separate sections, eliminating the need for destructive demolition of the caissons. Furthermore, the middle and top slabs within the caissons are precast components, replacing traditional cast-in-place construction with factory prefabrication and rapid assembly, significantly improving construction efficiency. Simultaneously, the post-cast concrete main body forms a continuous waterproof layer on the overall structural surface, encasing all joints below, achieving an overall seal with the same lifespan as the structure. This prevents leakage in water-rich strata, resulting in a station structure with strong integrity and adaptability, ensuring overall structural rigidity and stability. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the assembly structure according to an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of the structure of a caisson module without a track-top ventilation duct according to an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of the structure of a caisson connection section containing a rail-top ventilation duct according to an embodiment of the present invention.

[0032] The reference numerals in the accompanying drawings include:

[0033] 100. Caisson module;

[0034] 1. Caisson; 2. Base slab; 3. Middle slab; 4. Top slab; 5. Temporary sealing wall; 6. Support; 7. Rail-top ventilation duct. Detailed Implementation

[0035] The present invention will be further described in detail below through specific embodiments:

[0036] In embodiments of the present invention, such as Figure 1 , Figure 2 As shown, the prefabricated assembly structure of the underground station with continuous caissons in water-rich soft soil strata includes: multiple caisson modules 100;

[0037] Multiple caisson modules 100 are spaced apart from each other and independently arranged in the same direction. Each caisson module 100 includes: a caisson 1, a bottom plate 2, a middle plate 3 and a top plate 4. The caisson 1 is a structure that is closed on all four sides and open at both ends. At least one of its closed ends is configured as a temporary sealing wall 5 that can be removed from the caisson 1. The bottom plate 2 is set inside the caisson 1 to close its lower open end. The middle plate 3 and the top plate 4 are both prefabricated components and are sequentially connected to the caisson 1 from bottom to top, so that the top plate 4 closes the upper open end of the caisson 1 and the middle plate 3 divides the internal space of the caisson 1.

[0038] One of two adjacent caisson modules 100 is defined as the first caisson module and the other as the second caisson module. After the temporary sealing walls 5 of the first caisson module and the second caisson module are removed, they are connected by a first cast-in-place concrete main body. The bottom slabs 2, middle slabs 3, and top slabs 4 of the two are connected by a second cast-in-place concrete main body. The bottom slabs 2, middle slabs 3, top slabs 4 and the corresponding second cast-in-place concrete main bodies of the multiple caisson modules 100 are sealed and connected by a post-cast concrete main body to form a through-through station structure.

[0039] Specifically, in this embodiment of the invention, the prefabricated components in the caisson module 100 include at least: a middle slab 3, a top slab 4, and a temporary sealing wall 5. This facilitates the transfer of on-site pouring operations from a humid environment to a controlled environment. On the one hand, this improves the production efficiency of each component; on the other hand, it combines hoisting and splicing with local on-site casting connections, resulting in clear procedures and less cross-interference, thereby shortening the construction cycle of the main structure. Simultaneously, the removable temporary sealing wall 5 can also be a prefabricated reinforced concrete slab, eliminating the need for the traditional process of demolishing the existing caisson 1 wall, complex soil reinforcement, and temporary support during excavation when constructing the connection section between adjacent caisson modules 100. This simplifies the process and avoids damage to the end face of the caisson 1.

[0040] In this embodiment of the invention, a first cast-in-place concrete body is used to connect the end faces of two adjacent caissons 1, a second cast-in-place concrete body is used to connect the corresponding slabs of two adjacent caissons 1, and a post-cast concrete body is used to cover each slab and the second cast-in-place concrete body, forming an integral sealed structure. This improves the overall structural strength and eliminates construction cold joints that are difficult to handle in traditional processes, thus addressing the risk of leakage caused by the special geological features of water-rich soft soil. The post-cast concrete body can enclose all the precast joints and cast-in-place construction joints below, improving its waterproof reliability and making it suitable for water-rich soft soil strata.

[0041] The temporary sealing wall 5 is formed at the opposite ends of two adjacent caissons 1. Specifically, in this embodiment, each caisson 1 is an independent sealed chamber with both ends (or one end) temporarily closed by a removable temporary sealing wall 5 during the sinking stage. After the two caissons 1 are in place, their opposite ends are adjacent to each other. At this time, the construction of the connecting section does not require drilling, cutting, or high-pressure jet grouting reinforcement on the complete sidewalls of the caisson 1 as in traditional methods, but only requires the sequential removal of these two pre-formed temporary sealing walls 5. This allows for the direct removal and connection of the walls instead of opening holes and reinforcing the existing structure; it not only improves construction efficiency and eliminates the complex soil reinforcement and temporary support procedures, but also reduces construction risks and avoids damage to the already positioned caissons 1 and secondary disturbance to the surrounding strata; at the same time, the regular concrete section and pre-embedded connecting bars exposed after removing the temporary sealing wall 5 provide a working surface for the subsequent pouring of the connecting section structure, improving the bonding quality of the old and new concrete and enhancing the structural integrity and waterproof reliability of the connecting node.

[0042] The base slab 2 is cast at the lower open end of the caisson 1. In this embodiment, the base slab 2 is cast-in-place and can seal the bottom of the caisson 1, ensuring that there are no construction cold joints or assembly joints between the base slab 2 and the sidewall of the caisson 1, thus preventing leakage in this area and improving its waterproof reliability. Furthermore, the cast-in-place base slab 2 can accommodate minor posture deviations or unevenness of the foundation that may occur after the caisson 1 sinks. The flow and filling of concrete ensures that the base slab 2 is tightly bonded to the foundation, forming a flat and continuous load-bearing base, thereby enhancing the bottom bearing capacity and overall stability of the entire caisson 1.

[0043] Furthermore, in this embodiment, a support 6 is provided inside the caisson 1 to connect the middle plate 3 and the top plate 4. During construction, the supports 6 for supporting the middle plate 3 and the top plate 4 are pre-embedded to facilitate the precise hoisting of the middle plate 3 and the top plate 4 into place. This allows each plate to be directly placed on its corresponding support 6, eliminating the need for a complex temporary support system on-site, simplifying the installation process, and improving assembly efficiency and accuracy. Moreover, the support 6 can serve as both a temporary support and a permanent structural connection node, ensuring a rigid and reliable force transmission connection between each plate and the caisson wall 1. For water-rich soft soil strata, the caisson structure may experience slight attitude changes after sinking, and the support 6 provides a uniform installation benchmark to compensate for these construction errors.

[0044] The first cast-in-place concrete main body is poured between the ends of two adjacent caissons 1, and the end is provided with a first connecting steel bar. In this embodiment, after the temporary sealing wall 5 of the two adjacent caissons 1 is removed, the first connecting steel bar pre-embedded in the concrete at the end of the caisson 1 can be exposed, so that it can be cast into a whole by relying on the first connecting steel bar and the first cast-in-place concrete main body; that is, through the anchoring of the steel bar and the interlocking of the concrete, a rigid and continuous node is formed with the structure of the two caissons 1 on both sides, ensuring the continuity and stability of the longitudinal structure of the station. At the same time, by pouring the first cast-in-place concrete main body and the first connecting steel bar together, a one-time integral casting is formed to avoid the risk of leakage caused by construction cold joints.

[0045] Similarly, the second cast-in-place concrete main body is poured between the ends of the bottom slab 2, middle slab 3, and top slab 4 of the two adjacent caissons 1. The ends of the bottom slab 2, middle slab 3, and top slab 4 are all provided with second connecting steel bars. In this embodiment, after the two adjacent caissons 1 are in place, the ends of each layer of slabs are aligned with each other, and the gaps between them form a regular cast-in-place space. The second cast-in-place concrete main body, integrally poured within this space, firmly connects the floor slabs of the same floor belonging to the two caissons 1 into a continuous integral load-bearing slab under the synergistic effect of the steel bars. This eliminates the longitudinal weak joints that may be formed due to the independent laying of precast slabs, ensuring the continuity of load transfer and deformation coordination among the floors of the concourse and platform levels.

[0046] Meanwhile, the connection between the second cast-in-place concrete main body and the second connecting steel bars transforms the horizontal longitudinal joints of each layer, which in traditional processes required complex waterproofing treatment, into a single-cast reinforced concrete node. The density of the concrete itself provides a reliable waterproof barrier, while the reinforcing effect of the pre-embedded steel bars further inhibits the formation of cracks, improves the overall rigidity, and eliminates the risk of water seepage at the joints.

[0047] The post-cast concrete body covers the first and second cast-in-place concrete bodies, forming a continuous waterproof base surface. In this embodiment, the post-cast concrete body facilitates the overall pouring of a continuous and dense layer of post-cast concrete, ensuring that all connecting joints beneath it are covered and encased, and waterproofing is performed during the pouring process to prevent water seepage.

[0048] like Figure 3 As shown, the middle plate 3 extends towards the bottom plate 2 to form the rail-top ventilation duct 7, and the rail-top ventilation duct 7 and the middle plate 3 are integrally formed. In this embodiment, by using the rail-top ventilation duct 7 as a structural extension of the middle plate 3 and integrally casting it during the prefabrication stage, its structural rigidity and integrity are ensured, and assembly nodes are reduced. Furthermore, in terms of waterproofing, construction joints between the middle plate 3 and the rail-top ventilation duct 7 can be eliminated to prevent leakage. Simultaneously, the rail-top ventilation duct 7 can be used as a ventilation channel, improving the overall usability of the station.

[0049] In this embodiment of the invention, a construction method for a prefabricated assembly structure of an underground station using a continuous caisson in water-rich soft soil strata includes the following steps:

[0050] Each caisson 1 will be lowered until it reaches the design elevation;

[0051] The middle plate 3 and the top plate 4 are prefabricated and respectively hoisted into the corresponding caissons 1;

[0052] Remove the temporary sealing wall 5 between the two adjacent caissons 1;

[0053] The first cast-in-place concrete main body is poured between two adjacent caissons 1, and the second cast-in-place concrete main body is poured between each adjacent bottom slab 2, each middle slab 3, and each top slab 4.

[0054] The post-cast concrete main body is poured on each slab, the first cast-in-place concrete main body and the second cast-in-place concrete main body to form a through station structure.

[0055] Specifically, in this embodiment, the construction method of caisson 1 and its internal structure includes: dividing multiple caisson modules 100 into 7 sections based on the number of caissons 1, and constructing the top slab 4 and internal structure on a unit basis for each section of caisson 1. Construction of the internal structure and connecting sections is carried out simultaneously after the bottom slab 2 is poured, mainly divided into the following four stages of construction. Stage 1: After the final sinking of caisson 2#, the left upper hot air duct, middle slab 3, and top slab 4 are constructed (construction of the right upper hot air duct is carried out after the conditions for construction are met); Stage 2: The upper hot air ducts and middle slabs 3 of caissons 6#, 4#, 5#, and 3# are constructed in sequence, and the top slabs 4 of caissons 6#, 4#, and 3# are constructed (the shield hoisting holes are reserved in caissons 3# and 5#, and the elevator shaft is constructed in caisson 4# at the same time); Stage 3: The upper hot air ducts, middle slabs 3, and top slabs 4 of caissons 1# and 7# are constructed (after the shield construction is completed); Stage 4: The platform slab and stairs are constructed.

[0056] The construction method for precast slabs includes: the precasting of the middle slab 3 is carried out using wooden molds, and the precasting of the top slab 4 is carried out using steel molds or wooden molds. For example, the top slab 4 can be precast on one side of one caisson 1 and on the top slab 4 of the subsequent caisson 1, while the middle slab 3 is precast on another caisson 1 and its top slab 4; after the top slab 4 is demolded, it is transported to the curing site for curing, while the middle slab 3 can be cured in situ. After the bottom slab 2 of the caisson 1 is completed and the precast slab is ready for hoisting, the precast slab is installed and the post-cast layer is constructed.

[0057] Wooden formwork construction: The wooden formwork for the middle slab 3 uses a full-span disc-lock support frame system, constructed in conjunction with the wooden formwork. The support system material specifications are: disc-lock scaffold uprights φ48*3.2mm, horizontal bars φ48*3.2mm, and diagonal bars φ48*3.2mm. The slab formwork is constructed using a combination of I10 I-beams, 5*10cm square timber, and 12mm plywood. All main formwork ribs are made of I10 I-beams, while secondary ribs are constructed using a combination of square timber and steel pipes. The side wall formwork is constructed using a combination of φ48 double-layer steel pipes, 5*10cm square timber, or φ48 steel pipes, 12mm plywood, and φ16 bolts.

[0058] The wooden formwork for the top slab 4 uses a full-span steel pipe and fastener support frame to form a support system, which is constructed in conjunction with the wooden formwork. The support system material specifications are φ48*3.2mm steel pipes. The precast top slab 4 rib beams are constructed using a combination of φ48 double-jointed steel pipes, 5*10cm square timber, 12mm plywood, and φ16 bolts. The bottom of the slab is constructed using a combination of 5*10cm square timber and 12mm plywood.

[0059] Steel formwork fabrication: The steel formwork for top plate 4 uses 1.5mm thick steel plate with an overall thickness of 5cm. The back of the formwork uses 1.5mm thick steel plate with reinforcement at 20cm intervals. Five channel steels are added to each side for demolding and hoisting beams. After the steel formwork is fabricated, all dimensions must be inspected and accepted before it can be put into use.

[0060] The erection steps are as follows: Install the adjustable base; install the base; install the first layer of horizontal bars; install the first layer of vertical bars; install the second layer of horizontal bars; install the first layer of vertical diagonal bars; install the third layer of horizontal bars; connect the vertical bars; continue to erect upwards according to the previous steps; install the U-shaped adjustable top support.

[0061] After the steel bars for the precast slabs are manufactured in the processing plant, they are transported to the site and installed on the formwork.

[0062] The embedded parts of the middle plate 3 include embedded channels, embedded angle steel at the opening, embedded angle steel bolts at the interface of the rail top ventilation duct 7, and embedded lifting rings; the embedded parts of the top plate 4 are only embedded lifting rings.

[0063] Embedded channels: Embedded channels are made in the formwork of the middle plate 3. Fixing bars are spot-welded on the steel mold for positioning. During the construction of the steel bar binding, care should be taken to protect the embedded parts to prevent them from being touched and causing displacement between the embedded parts.

[0064] Angle steel embedded in the opening: 100mm*8mm equilateral angle steel is embedded in the reinforcing steel and tied firmly to the structural reinforcing steel to prevent displacement caused by contact.

[0065] Pre-embedded angle steel bolts at the interface of the rail top ventilation duct 7: 60mm*5mm equilateral angle steel is pre-embedded on the end reinforcement of the rail top ventilation duct 7 in the precast middle plate 3. M20 bolts with a length of 170mm are welded on the angle steel at 500mm intervals and are tied firmly to the structural reinforcement to prevent displacement of the pre-embedded space due to contact.

[0066] Embedded lifting rings: Φ32 lifting rings are embedded in the precast slab reinforcement at the designed positions, with additional transverse reinforcing bars, and securely tied to the structural reinforcement to prevent displacement caused by contact. Precast rail top ventilation duct 7

[0067] The top ventilation duct 7 is constructed using a full-span scaffold. The bottom slab 2 panel is made of 12mm thick plywood + I10 I-beams + 50mm*100mm square timber @200mm. The side wall formwork is made of 12mm thick plywood + 50mm*100mm square timber @200mm or φ48*2.7mm steel pipe @200mm + double φ48*2.7mm steel pipe + φ16mm tie rods @600 / 900mm + φ48 steel pipe cross bracing.

[0068] Precast Slab 3: After the support frame is installed and the top support elevation is adjusted, install the slab template. The panel template is made of 12mm thick plywood. The main beams are made of No. 10 I-beams, and the secondary beams are made of 5×10cm double-sided planed square timber or No. 10 I-beams @ 20cm. When installing the main beams, ensure that the longitudinal I-beam joints are at the center of the top support of the uprights, and the transverse square timber joints are at the center of the longitudinal I-beams. The joints of the longitudinal square timbers should be staggered from the joints of the transverse I-beams, and the joints of any two adjacent transverse square timbers should not be on the same plane.

[0069] Precast Roof Slab 4: After the support frame is installed and the elevation is adjusted, the slab formwork is installed. The panel formwork is made of 12mm thick plywood, using 5×10cm double-sided planed square timber at 20cm intervals. The joints of the longitudinal square timber are staggered from the joints of the transverse I-beams, and the joints of any two adjacent transverse square timbers are not on the same plane. The rib beams of the precast roof slab 4 have 12mm plywood panels, secondary ribs are made of 5*10cm square timber at 20cm intervals, main ribs are double-splittered φ48 steel pipes, and φ16 threaded rods are spaced 600*600mm apart.

[0070] Concrete pouring, curing before demolding, formwork removal, and hoisting after curing.

[0071] The construction of the connecting section of caisson 1 includes: removing the temporary sealing wall 5 and the temporary sealing beams and columns; sequentially pouring the bottom slab 2, rail top ventilation duct 7, middle slab 3, platform level side walls, top slab 4, and concourse level side walls at the connecting section; pouring the post-cast layers of each floor slab and applying waterproofing treatment; backfilling and restoring the road surface to its original state. This connecting section is constructed using both forward and reverse construction methods.

[0072] Construction procedure: The standard cross-section of the connecting section area is divided into 6 parts from bottom to top, and the construction parts are as follows: construct the longitudinal beams of the top slab 4; construct the longitudinal beams of the middle slab 3; construct the reinforced concrete structure of the bottom slab 2 (including integrated grounding, bedding layer, and waterproof layer); construct the reinforced concrete structure of the track top ventilation duct 7; construct the reinforced concrete structure of the platform level side walls and middle slab 3; construct the reinforced concrete structure of the concourse level side walls and top slab 4.

[0073] Reverse construction method: The standard cross-section of the connecting section is constructed in eight steps from bottom to top, as follows: construct the longitudinal beams of the top slab 4; construct the side walls of the concourse level; construct the longitudinal beams of the middle slab 3; construct the side walls of the platform level; construct the reinforced concrete structure of the bottom slab 2 (including integrated grounding, bedding layer, and waterproof layer); construct the reinforced concrete structure of the rail top ventilation duct 7; construct the reinforced concrete structure of the middle slab 3; construct the reinforced concrete structure of the top slab 4. Among these, the construction of the rail top ventilation duct 7 and the middle slab 3 utilizes full-span scaffolding, with the scaffolding foundation structure being the bottom slab 2, and the concourse level scaffolding foundation being the structural middle slab 3.

Claims

1. A prefabricated assembly structure for a continuous caisson underground station in water-rich soft soil strata, characterized in that, include: Multiple caisson modules; Multiple caisson modules are spaced apart from each other and independently arranged in the same direction. Each caisson module includes: a caisson, a bottom plate, a middle plate, and a top plate. The caisson is a structure that is closed on all four sides and open at both the top and bottom ends. At least one of its closed ends is configured as a temporary sealing wall that can be removed from the caisson. The bottom plate is set inside the caisson to close its lower open end. The middle plate and the top plate are both prefabricated components and are sequentially overlapped inside the caisson from bottom to top, so that the top plate closes the upper open end of the caisson and the middle plate divides the internal space of the caisson. One of two adjacent caisson modules is defined as the first caisson module and the other as the second caisson module. After the temporary sealing walls of the first caisson module and the second caisson module are removed, they are connected by a first cast-in-place concrete main body. The bottom slabs, middle slabs and top slabs of the two modules are connected by a second cast-in-place concrete main body. Furthermore, the bottom slabs, middle slabs, top slabs and corresponding second cast-in-place concrete main bodies of multiple caisson modules are sealed and connected by post-cast concrete main bodies to form a through-type station structure.

2. The prefabricated assembly structure of a continuous caisson underground station in water-rich soft soil strata as described in claim 1, characterized in that, The temporary sealing wall is formed at the opposite ends of two adjacent caissons.

3. A prefabricated assembly structure for a continuous caisson underground station in water-rich soft soil strata as described in claim 1 or 2, characterized in that, The temporary sealing wall is a precast reinforced concrete slab.

4. The prefabricated assembly structure of a continuous caisson underground station in water-rich soft soil strata as described in claim 1, characterized in that, The base plate is cast at the lower open end of the caisson; The caisson is equipped with supports for connecting the middle plate and the top plate.

5. The prefabricated assembly structure of a continuous caisson underground station in water-rich soft soil strata as described in claim 1, characterized in that, The first cast-in-place concrete main body is poured between the ends of two adjacent caissons, and the end is provided with a first connecting steel bar.

6. The prefabricated assembly structure of a continuous caisson underground station in water-rich soft soil strata as described in claim 1, characterized in that, The second cast-in-place concrete main body is poured between the ends of the bottom slab, middle slab, and top slab of two adjacent caissons, and the ends of the bottom slab, the middle slab, and the top slab are all provided with second connecting steel bars.

7. The prefabricated assembly structure of a continuous caisson underground station in water-rich soft soil strata as described in claim 1, characterized in that, The post-cast concrete body covers the first cast-in-place concrete body and the second cast-in-place concrete body, forming a continuous waterproof layer base surface.

8. The prefabricated assembly structure of a continuous caisson underground station in water-rich soft soil strata as described in claim 1, characterized in that, The middle plate extends towards the bottom plate to form a rail-top air duct, and the rail-top air duct and the middle plate are integrally formed.

9. A construction method for a prefabricated underground station structure with continuous caissons in water-rich soft soil as described in any one of claims 1-8, characterized in that, Includes the following steps: Each caisson will be lowered until it reaches the design elevation; The middle plate and the top plate are prefabricated and then hoisted into their respective caissons. Remove the temporary sealing walls between the two adjacent caissons; The first cast-in-place concrete main body is poured between two adjacent caissons, and the second cast-in-place concrete main body is poured between each adjacent bottom slab, middle slab, and top slab. The post-cast concrete main body is poured on each slab, the first cast-in-place concrete main body and the second cast-in-place concrete main body to form a through station structure.

10. The construction method of a prefabricated assembly structure for a continuous caisson underground station in water-rich soft soil strata as described in claim 9, characterized in that, The middle plate is prefabricated using wooden molds, and the top plate is prefabricated using either steel molds or wooden molds.

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