CN117888547A - Composite supporting system for protecting closely attached subway station and construction method - Google Patents

Abstract

The invention discloses a composite support system and a construction method for protecting a closely attached subway station, and belongs to the field of deep foundation pit support; the composite support system comprises a combined steel sheet pile closely fitted to a main body of a subway station, and a guide rail steel plate closely fitted to a main body of a central island, the two are connected by a steel support, and a deep foundation pit and a counter-pressure soil body are formed by excavating the two, and the composite support system adopts a plurality of grouting conduits inserted in the counter-pressure soil body; during the excavation process, cement and water glass slurry materials are injected into the counter-pressure soil body through the grouting conduits, thereby reinforcing the counter-pressure soil body, reducing the deformation of the soil structure caused by the time and space effect during the soil excavation process, improving the strength of the counter-pressure soil body, and effectively controlling the influence of unilateral large-area unloading on the subway station; the principle and structure of the composite support system are simple, easy to implement, can shorten the engineering period, and has good popularization and application value.

Description

A composite support system and construction method for protecting a close-fitting subway station

Technical Field

The invention belongs to the field of deep foundation pit support, and in particular relates to a composite support system and a construction method for protecting a closely attached subway station.

Background technique

At present, the development of urban transportation systems has made great progress, and the subway system plays an important role in it. With the increasing density of buildings in urban areas, it is imperative to carry out new construction close to existing subway stations. The unloading caused by large-scale excavation of the foundation pit soil around the subway station has a great influence on its deformation. Therefore, how to better operate the support system under the premise of protecting the structure of the close-fitting subway station from large deformation is an urgent problem to be solved in the current urban rail transit.

The existing support system scheme for close-fitting subway stations is imperfect, mainly manifested in the following aspects: in the construction of other existing close-fitting projects, the foundation pit support system mostly adopts enclosure structure plus reinforced concrete horizontal internal support or conventional inclined support. The former adopts reinforced concrete horizontal internal support. In the later stage of construction, the concrete support removal process is relatively complicated, and the noise pollution and dust pollution are serious. The project is labor-intensive and the cost is high. The latter adopts conventional inclined support, which leads to large deformation of the foundation pit, and the main structure bottom plate needs to be cut and poured again during the construction process. The construction period is relatively long and the project cost is high. It is difficult for the two conventional support systems to adjust or reinforce the support system in time according to the deformation of the foundation pit and surrounding buildings detected on site. In order to deal with the above problems, the existing project adopts the method of counter-pressure soil auxiliary support, but the problem of insufficient strength of the counter-pressure soil caused by the uncertainty of soil conditions has reduced its application effect. For example, Chinese patent number CN218508448U discloses a central island slope support structure for protecting closely attached subway stations. The structure adopts counter-pressure soil auxiliary support. However, the problem of soil structure deformation caused by time and space effects is not considered in the counter-pressure soil auxiliary support structure, resulting in insufficient strength of the counter-pressure soil, which easily affects the normal operation of the subway station.

It can be seen that the prior art has at least the following deficiencies: the existing counter-pressure soil auxiliary support method cannot effectively control the rebound uplift of the deep foundation pit during the excavation process, causing the soil structure to deform, resulting in insufficient strength of the counter-pressure soil.

Summary of the invention

In order to overcome the above-mentioned technical defects, the present invention provides a composite support system and construction method for protecting closely attached subway stations, which can solve the technical problem that the existing counter-pressure soil auxiliary support method cannot effectively control the rebound uplift of the deep foundation pit during the excavation process, causing the soil structure to deform, resulting in insufficient strength of the counter-pressure soil.

In order to achieve the above object, the present invention adopts the following technical contents:

The close-fitting subway station uses a combined steel plate with reserved pulley guide rails as the pile foundation, and the horizontal steel support is erected in combination with the center island method. During the excavation of the foundation pit, cement and water glass slurry materials are injected into the counter-pressure soil through the grouting pipe to reinforce the counter-pressure soil to achieve composite support. Assisted by axial force detection systems and displacement meters, etc., the pre-set guide rails are used to realize the rapid erection and adjustment of steel supports, reduce the deformation of the foundation pit and existing buildings, and improve the resilience and adaptability of the composite support system.

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

The present invention provides a composite support system for protecting a closely attached subway station. The composite support system comprises a combined steel sheet pile tightly fitted to a main body of the subway station and a guide rail steel plate tightly fitted to a main body of a central island. The two are connected by a steel support, and a deep foundation pit and a counter-pressure soil body are formed by excavating the two. The composite support system adopts a plurality of grouting ducts inserted in the counter-pressure soil body. During the excavation process, cement and water glass slurry materials are injected into the counter-pressure soil body through the grouting ducts, thereby reinforcing the counter-pressure soil body, reducing the deformation of the soil structure caused by the time and space effect during the soil excavation process, improving the strength of the counter-pressure soil body, and effectively controlling the influence of unilateral large-area unloading on the subway station. The principle and structure of the composite support system are simple, easy to implement, can shorten the engineering period, and has good promotion and application value.

Preferably, in the present invention, the counter-pressure soil body adopts a two-level slope structure, a concrete layer is laid on the slope surface, and the concrete layer is sprayed twice to reinforce the structure of the counter-pressure soil body and improve the strength of the entire support system.

Preferably, in the present invention, multiple threaded holes are opened on the combined steel sheet piles and the guide rail steel plates, and guide rails are set to facilitate the assembly of steel supports. When in use, the steel supports are transported to the points to be supported by the guide rails, thereby improving work efficiency.

Preferably, in the present invention, the combined steel sheet pile adopts a splicing structure, which is composed of multiple steel sheet pile bodies. After the project is completed, it can be recycled in time, has strong applicability, shortens the construction period, and saves construction costs. In addition, the splicing form of close-fitting steel plates, corrugated steel plates, and counter-pressure steel plates is adopted, which further improves the strength of the combined steel sheet piles and ensures the stability and reliability of the support system.

Preferably, in the present invention, a cylinder servo system and an axial force monitoring system are respectively provided on both sides of the steel support, which are used to monitor the support data and automatically adjust the support force. At the same time, the support data can be fed back to the user, and the user analyzes the support data. The user can strengthen the support for the insufficiently supported position according to the analysis results.

Preferably, in the present invention, the steel support can also adopt a splicing structure, which is convenient for completing the splicing in advance according to the design of the construction site and the force analysis, thereby improving the construction efficiency and facilitating transportation.

The present invention also provides a construction method for a composite support system for protecting a closely fitted subway station. Based on the above-mentioned composite support system for protecting a closely fitted subway station, the method firstly carries out piling installation on the combined steel sheet piles and guide rail steel plates, and installs steel supports, so that the combined steel sheet piles are closely fitted to the main body of the subway station, and the guide rail steel plates are closely fitted to the main body of the center island, and then a deep foundation pit is excavated between the combined steel sheet piles and the guide rail steel plates to form a back-pressure soil body that is closely fitted to the combined steel sheet piles; finally, grouting material is injected into the back-pressure soil body layer by layer from top to bottom through a grouting conduit to reinforce the back-pressure soil body, improve the problem of insufficient stable supporting capacity of the back-pressure soil body, and ensure the strength of the composite support system; the method solves the problem of insufficient strength of the existing support method, avoids the influence of large-scale excavation and unloading of a single-sided deep foundation pit on the structural safety of the operating subway station, and ensures that the normal operation of the subway station is not affected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a structural plan view of a composite support system for protecting a closely attached subway station provided by an embodiment of the present invention;

Fig. 2 is a cross-sectional view taken along the line A-A of Fig. 1;

FIG3 is a schematic structural diagram of a composite steel sheet pile for protecting a composite support system of a closely attached subway station provided by an embodiment of the present invention;

FIG4 is a layout diagram of the guide rail surface of the combined steel sheet pile provided in an embodiment of the present invention;

FIG5 is a schematic diagram of the steel support transportation of the combined steel sheet pile provided by an embodiment of the present invention;

FIG6 is a construction status diagram of construction step 4 of a composite support system for protecting a closely attached subway station provided by an embodiment of the present invention;

FIG. 7 is a construction status diagram of construction step 5 of a composite support system for protecting a closely attached subway station provided by an embodiment of the present invention;

FIG8 is a construction status diagram of construction step 6 of a composite support system for protecting a closely attached subway station provided by an embodiment of the present invention;

FIG9 is a construction status diagram of construction step seven of a composite support system for protecting a closely attached subway station provided by an embodiment of the present invention;

FIG10 is a construction status diagram of construction step eight of a composite support system for protecting a close-fitting subway station provided by an embodiment of the present invention;

FIG. 11 is a construction status diagram of construction step nine of a composite support system for protecting a closely attached subway station provided by an embodiment of the present invention;

FIG. 12 is a construction status diagram of construction step 10 of a composite support system for protecting a closely attached subway station provided in an embodiment of the present invention.

Reference numerals:

Central island body-1, triangular steel support-2, cylinder servo system-3, steel support-4, flange-5, drainage hole-6, axial force monitoring system-7, hook-8, subway station cover-9, subway station body-10, counterpressure soil-11, subway station enclosure structure-12, combined steel sheet piles-13, concrete layer-14, grouting conduit-15, drainage ditch-16, guide rail steel plate-17, central island enclosure structure-18, concrete cushion and foundation slab-19;

Close fitting steel plate-13-1, corrugated steel plate-13-2, splicing groove-13-3, splicing convex groove-13-4, guide rail-13-5, counter-pressure steel plate-13-6, bolt-13-7, first steel support reserved hole-13-8, steel support splicing interface-13-9, triangular support reserved hole-13-10, unreserved groove part-13-11, pointed head-13-12, vertical slide rail entrance-13-13.

Detailed ways

In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail in the following specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not require further definition and explanation in the subsequent drawings.

In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

The present invention is further described in detail below in conjunction with the accompanying drawings:

Example

As mentioned in the background technology, the existing support system solutions for close-fitting subway stations are imperfect, mainly manifested in the following aspects: when constructing other existing close-fitting projects, the foundation pit support system mostly adopts a retaining structure plus a reinforced concrete horizontal internal support or conventional inclined support for the foundation pit. The former adopts reinforced concrete horizontal internal support. In the later stage of construction, the concrete support removal process is relatively complicated, and the noise pollution and dust pollution are serious. The project is labor-intensive and the cost is high. The latter adopts conventional inclined support, which leads to large deformation of the foundation pit, and the main structure bottom plate needs to be cut and poured again during the construction process. The construction period is relatively long and the project cost is high. It is difficult for the two conventional support systems to adjust or reinforce the support system in time according to the deformation of the foundation pit and surrounding buildings detected on site. In order to address the above-mentioned problems, the existing projects have adopted the method of auxiliary support of counter-pressure soil, but there is a defect of insufficient strength of the counter-pressure soil; for example, Chinese patent No. CN218508448U discloses a central island slope support structure for protecting a closely attached subway station, which adopts auxiliary support of counter-pressure soil. Because the auxiliary support structure of counter-pressure soil does not consider the time and space effect problem, it causes deformation of the soil structure, resulting in insufficient strength of the counter-pressure soil, which easily affects the normal operation of the subway station.

In order to solve the above problems, the present invention provides a composite support system and construction method for protecting closely attached subway stations; in the present invention, a combined steel sheet pile with reserved pulley guide rails is used as the pile foundation, and a horizontal steel support is erected in combination with the main body of the central island. The counter-pressure soil platform is reinforced by grouting to realize composite support, and auxiliary axial force detection systems and displacement meters are used for monitoring. Pre-set guide rails are used to realize rapid erection and adjustment of horizontal supports, improve and reinforce the counter-pressure soil, reduce the influence of time and space effects, enhance the strength of the counter-pressure soil, and improve the resilience and adaptability of the support system.

As shown in FIG. 1 and FIG. 2 , this embodiment provides a composite support system for protecting a close-fitting subway station, including:

The central island body 1, triangular steel support 2, cylinder servo system 3, steel support 4, flange 5, drainage hole 6, axial force monitoring system 7, hook 8, subway station cover 9, subway station body 10, counter pressure soil 11, subway station enclosure structure 12, combined steel sheet pile 13, concrete layer 14, grouting duct 15, drainage ditch 16, guide rail steel plate 17 and central island enclosure structure 18, the specific structural relationship and position relationship are as follows:

As shown in FIG3 , in this embodiment, the combined steel sheet pile 13 is composed of a plurality of steel sheet pile bodies, and the steel sheet pile body includes a close-fitting steel plate 13-1, a corrugated steel plate 13-2 and a counter-pressure steel plate 13-6; wherein the middle steel plate is sandwiched between the two corrugated steel plates 13-2, connected by bolts 13-7, and arranged between the close-fitting steel plate 13-1 and the counter-pressure steel plate 13-6; the splicing groove 13-3 and the splicing convex groove 13-4 are respectively arranged on each of the close-fitting steel plate 13-1, the corrugated steel plate 13-2, and the middle steel plate is sandwiched between the two corrugated steel plates 13-2, connected by bolts 13-7, and arranged between the close-fitting steel plate 13-1 and the counter-pressure steel plate 13-6; 3-2 and the left and right ends of the counter-pressure steel plate 13-6 can be spliced and combined, and are easy to disassemble. After the construction is completed, they can be recycled and reused; the close-fitting steel plate 13-1 is close to the subway station enclosure structure 12 of the subway station body 10, and the subway station enclosure structure 12 is the underground continuous wall of the subway station body 10; the combined steel sheet piles 13 are provided with steel support splicing interfaces 13-9 in the horizontal and vertical directions, and a steel support reserved hole 13-8 is reserved at the top for connection with the first steel support 4.

It should be noted that: in order to solve the problem of assembling the steel support 4, a reserved guide rail design is adopted, that is, multiple guide rails 13-5 are opened in the horizontal and vertical directions of the combined steel sheet pile 13, and pulleys are preset in the guide rails 13-5, which can cooperate with the steel support joint 13-9 to complete the efficient assembly of the steel support 4; the guide rail steel plate 17 at the other end of the steel support 4 is not a combined structure, but is only composed of a high-strength thick flat steel plate with a reserved pulley guide rail, and also adopts the same structural design as the combined steel sheet pile 13, that is, the pulley guide surface size and layout of the two are the same, and the steel support 4 can be transported to any reserved connection position (steel support joint 13-9, during assembly, it is cooperated through the reserved hole 13-10 of the triangular support) in the horizontal or vertical direction through the guide rail 13-5; the problem of inconvenience in assembling the steel support 4 during excavation is solved.

Here, the steel support 4, the combined steel sheet piles 13 and the guide rail steel plate 17 can be prefabricated in sections, and the steel support 4 is spliced into a whole through the flange 5, and then spliced with the two end structures through the hook 8 and the triangular steel support 2 with the help of screw holes.

The bottom of the steel sheet pile body is provided with a pointed head 13-12 for easy insertion into the soil. Meanwhile, the top of the steel sheet pile is close to the subway station cover 9, and the bottom is deep below the underground continuous wall.

As shown in FIG4 , the specific assembly process of the steel support 4 is as follows:

The steel support 4 can be quickly pulled to the installation position by ropes under the action of the guide rails 13-5, and quickly installed under the support of the triangular steel support 2; the steel support 4 is prefabricated in sections and connected to form a whole by welding or flange 5; one side of the steel support 4 is connected to the existing structure of the center island body 1 (i.e., the center island enclosure structure 18) through the cylinder servo system 3, and the other side is connected to the combined steel sheet piles 13 on the side of the subway station body 10 through the axial force detection system 7.

As shown in Figures 1 and 2, in this embodiment, the guide rail steel plate 17 is prefabricated and spliced, and its height is the same as the height of the combined steel sheet piles 13. The triangular steel support 2 is installed after the guide rail steel plate 17 part that is higher than the center island body 1, which further improves the reinforcement effect.

The counter-pressure soil body 11 is set up close to the combined steel sheet piles 13 on one side of the subway station body 10 and is treated with two-level slope reduction. A mesh structure is set up on the slope surface of the counter-pressure soil body 11, and a steel wire mesh is used. The broken surface is treated with sprayed concrete twice to form a concrete layer 14. The counter-pressure soil body 11 is located below the first steel support 4.

In this embodiment, during the construction process, as shown in Figure 10, the back pressure soil 11 is excavated in layers, and grouting is performed layer by layer through the grouting pipe 15 before excavation; the grouting material is a cement-water glass slurry material with AJG composite additive added; when the excavation reaches the base elevation, the concrete cushion layer and the foundation bottom plate 19 are poured, which plays a role in stabilizing and reinforcing, and also reduces the exposure time of a large area of the foundation pit, controls the rebound uplift of the foundation pit, and further improves the reinforcement effect.

In this embodiment, the cylinder servo system 3 automatically adjusts the output state to provide supporting force based on the support data obtained through the monitoring of the axial force detection system 7, and the axial force detection system 7 feeds back the monitoring data to the user, who can strengthen the support for the insufficiently supported position after analyzing the situation.

This embodiment also provides a construction method for protecting a composite support system close to a subway station, comprising the following steps:

Step 1: According to the design of the construction site and the force analysis, the prefabrication size and construction position of the combined steel sheet pile 13, the steel support 4 and the guide rail steel plate 17 are determined. The guide rail and theodolite are set at the selected position on the top of the subway station enclosure structure 12.

Step 2: Prefabricated composite steel sheet piles 13, support structure 4 and guide rail steel plates 17 are brought in for assembly, and piles are driven accurately close to the subway station enclosure structure 12 with the aid of a theodolite and guide rails.

Step 3: excavate the center island body 1 in the middle of the foundation pit, reserve graded counter-pressure soil 11 on the side of the combined steel sheet pile 13, and form a foundation pit with the counter-pressure soil 11. Set drainage holes 6 and drainage ditches 16 at the bottom of the slope of the counter-pressure soil 11. Hang a mesh on the slope of the reserved counter-pressure soil slope and spray concrete. The concrete is sprayed twice, with a thickness of 30mm for the first spray and 30mm for the second spray. The slope mesh is made of steel wire mesh, which is fixed by vertical (planar plum blossom arrangement) dowels with a length of L=1m; finally, a concrete layer 14 of the counter-pressure soil 11 is formed.

Step 4, as shown in FIG6 , according to the layered principle, cement water glass grouting material with AJG composite additive is injected into the reserved counter-pressure soil 11 on one side of the subway station layer by layer from top to bottom through the grouting conduit 15 to reinforce the soil.

Step 5, as shown in Figure 7, the underground structure of the central island is completed by sequential construction, and the foundation pit is constructed except for the back pressure soil 11. After the construction of the central island body 1 is completed, the guide rail steel plate 17 parallel to the subway station side is arranged on the central island enclosure structure 18 according to actual needs with the help of measuring instruments.

Step six, as shown in FIG8 , erect a triangular steel support 2 after the guide rail steel plate 17 is higher than the portion of the center island main structure 1 .

Step seven, as shown in Figure 9, install the first steel support 4, which is connected into a whole through the flange 5. One side of the steel support 4 is connected to the reserved steel plate 17 on the existing structure of the central island through the cylinder servo system 3, and the other side is connected to the reserved hole 13-8 of the first steel support on the upper part of the combined steel sheet pile 13 on the side of the subway station through the axial force detection system 7.

Step eight, as shown in Figure 10, excavate the counter-pressure soil on one side of the subway station, follow the principle of "layered, block, symmetrical and balanced excavation", and before excavating the soil to the designed height for the installation of the second steel support, analyze the data fed back by the axial force detection system 7 and the cylinder servo system 3, and add steel supports 4 to the required position through the preset guide rails 13-5 at any time according to needs; as shown in Figures 4 and 5, temporarily add steel supports 4 through the vertical slide rail entrance 13-13, and transport them to the installation position with the help of pulleys. When the steel support 4 needs to be transported vertically to horizontal transportation, the triangular steel support 2 can be horizontally installed at the triangular support reserved hole 13-10 set below the turning port steel support 4 to form a transverse track to complete the turning transportation.

Step nine, as shown in Figure 11, further excavate the counter-pressure soil 11 on one side of the subway station. When the excavation reaches the designed foundation pit depth for installing the second steel support 4, the second steel support 4 is transported to the designated position for installation through the guide rail 13-5. It should be noted that during the excavation process, multiple arrangements of the steel supports 4 are performed according to actual conditions. In this step, the arrangement of the second steel support is taken as an example, and is not limited to arranging only two steel supports.

Step 10, as shown in Figure 12, according to the deformation of the on-site support structure and the subway station structure, the position of the steel support 4 is adjusted and increased or decreased in time through the reserved guide rail 13-5. After the counter-pressure soil 11 is further excavated to the base elevation, the concrete cushion layer and the foundation bottom plate 19 are poured in time, thereby reducing the exposure time of a large area of the foundation pit and controlling the rebound uplift of the foundation pit.

The composite support system and construction method provided in this embodiment for protecting a close-fitting subway station have the following advantages:

This support system and construction method can promptly reinforce and adjust the existing support structure according to the data monitored by the actual project, thereby reducing the deformation of the foundation pit. The problem of insufficient support capacity of the counter-pressure soil can be improved by using steel supports inside the foundation pit and reinforcing the counter-pressure soil, avoiding the impact of large-scale excavation and unloading of a single-sided deep foundation pit on the structural safety of the operating subway station, and ensuring that the normal operation of the subway station is not affected. Steel supports, combined steel sheet piles, and guide rail steel plates can be reused after the project is completed, reducing the project cost. It effectively shortens the time for deep foundation pit excavation and support erection, avoiding the complexity of disassembly of reinforced concrete horizontal supports, as well as pollution problems such as dust caused by the disassembly process.

In other words, this system solves the problems of insufficient support, difficulty in timely adjustment or reinforcement according to actual monitoring data, and insufficient strength of counter-pressure soil in traditional support systems when excavating large areas of single-sided foundation pits close to existing buildings through design optimization. This system is highly adjustable. Compared with traditional support systems, it can quickly reinforce and adjust the support structure according to actual monitoring data to reduce foundation pit deformation and improve the resilience and adaptability of the support system. In addition, most of the components of the optimized composite support system are assembled in an assembled manner, which greatly simplifies the construction process. After the project is completed, these components can be recycled in time, which helps to shorten the construction period and reduce construction costs, which is in line with the concept of sustainable development.

In summary, the present invention provides a composite support system and construction method for protecting a closely attached subway station. The composite support system includes a combined steel sheet pile tightly fitted to the main body of the subway station and a guide rail steel plate tightly fitted to the main body of the center island. The two are connected by a steel support, and a deep foundation pit and a back-pressure soil body are excavated between the two. The composite support system adopts a plurality of grouting ducts inserted in the back-pressure soil body. During the excavation process, cement and water glass slurry materials are injected into the back-pressure soil body through the grouting ducts, thereby reinforcing the back-pressure soil body, reducing the deformation of the soil structure caused by the time and space effect during the soil excavation process, improving the strength of the back-pressure soil body, and effectively controlling the influence of unilateral large-area unloading on the subway station. The principle and structure of the composite support system are simple, easy to implement, can shorten the engineering period, and has good promotion and application value.

The above embodiment is only one of the implementation methods that can realize the technical solution of the present invention. The scope of protection claimed by the present invention is not limited only to this embodiment, but also includes changes, replacements and other implementation methods that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention.

Claims (10)

1. A composite support system for protecting a close-fitting subway station, characterized in that it comprises a combined steel sheet pile (13) and a guide rail steel plate (17); The combined steel sheet piles (13) are arranged to fit closely to the main body of the subway station (10) and are inserted into the soil; The guide rail steel plate (17) is arranged to fit tightly against the central island body (1); A deep foundation pit and a counter-pressure soil body (11) are excavated between the combined steel sheet piles (13) and the guide rail steel plates (17), and the counter-pressure soil body (11) is tightly fitted to the combined steel sheet piles (13); The combined steel sheet pile (13) and the guide rail steel plate (17) are connected via a steel support (4), and the counter-pressure soil body (11) is located below the steel support (4); A plurality of grouting conduits (15) are inserted into the counter-pressure soil body (11). 2. According to claim 1, a composite support system for protecting a closely attached subway station is characterized in that the counter-pressure soil body (11) adopts a secondary slope structure, and a concrete layer (14) is laid on the slope surface; the grouting conduit (15) passes through the concrete layer (14) and is inserted into the counter-pressure soil body (11). 3. According to claim 1, a composite support system for protecting a closely attached subway station is characterized in that a plurality of threaded holes are provided on the combined steel sheet piles (13) and the guide rail steel plates (17) for connecting the two sides of the steel support (4); the threaded holes are arranged in an array on the combined steel sheet piles (13) and the guide rail steel plates (17), and a plurality of guide rails (13-5) are provided in the horizontal and vertical directions of the combined steel sheet piles (13) and the guide rail steel plates (17), and the steel support (4) can slide to the threaded holes at any position through the guide rails (13-5). 4. A composite support system for protecting a close-fitting subway station according to claim 1 or 3, characterized in that the combined steel sheet pile (13) is formed by combining and splicing a plurality of steel sheet pile bodies, wherein the steel sheet pile body comprises a close-fitting steel plate (13-1), a corrugated steel plate (13-2), a splicing groove (13-3), a splicing convex groove (13-4), a guide rail (13-5) and a counter-pressure steel plate (13-6); wherein the close-fitting steel plate (13-1) is arranged in contact with the subway station body (10), and the counter-pressure steel plate (13-6) ) is arranged in close contact with the counter-pressure soil body (11); a plurality of corrugated steel plates (13-2) are connected by bolts (13-7) and are arranged between the close contact steel plate (13-1) and the counter-pressure steel plate (13-6); the close contact steel plate (13-1), the corrugated steel plate (13-2) and the counter-pressure steel plate (13-6) are all provided with a splicing groove (13-3) on one side and a splicing convex groove (13-4) on the other side for splicing a plurality of steel sheet pile bodies; a plurality of guide rails (13-5) are provided on the counter-pressure steel plate (13-6) in the horizontal and vertical directions. 5. According to claim 4, a composite support system for protecting a closely attached subway station is characterized in that the combined steel sheet pile (13) is closely fitted to the underground continuous wall of the subway station body (10); the steel sheet pile body connection tip (13-12) located at the bottom of the combined steel sheet pile (13); the tip (13-12) is inserted into the soil, and the insertion position is lower than the bottom of the underground continuous wall. 6. According to claim 1, a composite support system for protecting closely attached subway stations is characterized in that one side of the steel support (4) is connected to the guide rail steel plate (17) through a cylinder servo system (3), and the other side is connected to the combined steel sheet pile (13) through an axial force monitoring system (7); the axial force monitoring system (7) is used to monitor support data and feed back the support data to the cylinder servo system (3) and the user; the cylinder servo system (3) is used to automatically adjust the support force according to the support data. 7. According to claim 1, a composite support system for protecting a closely attached subway station is characterized in that the guide rail steel plate (17) is tightly fitted with the central island enclosure structure (18) of the central island body (1), and a triangular steel support (2) is provided at the top connection between the central island enclosure structure (18) and the central island body (1); the steel support (4) is connected to the combined steel sheet pile (13) by a hook (8), and is fixed to the triangular steel support (2) by the guide rail steel plate (17). 8. A composite support system for protecting a closely attached subway station according to claim 1, characterized in that the steel support (4) comprises a plurality of steel support bodies, and the plurality of steel support bodies are spliced and connected via flanges (5). 9. A construction method for protecting a composite support system close to a subway station, characterized by comprising: Step 1: According to the design and stress analysis of the construction site, the combined steel sheet piles (13) and the guide rail steel plates (17) are piled and installed so that the combined steel sheet piles (13) are closely attached to the subway station body (10), and the guide rail steel plates (17) are closely attached to the center island body (1), and the steel supports (4) are installed between the combined steel sheet piles (13) and the guide rail steel plates (17); Step 2: excavating a deep foundation pit between the combined steel sheet piles (13) and the guide rail steel plate (17) to form a counter-pressure soil body (11) that is closely attached to the combined steel sheet piles (13); Step 3: injecting grouting material into the counter-pressure soil body (11) layer by layer from top to bottom through the grouting conduit (15) to reinforce the counter-pressure soil body (11). 10. The construction method for a composite support system for protecting a close-fitting subway station according to claim 9, characterized in that it also includes: Step 4: excavating the counter-pressure soil (11) until the base is reached; wherein, during the excavation of the counter-pressure soil (11), a plurality of steel supports (4) are continuously installed between the combined steel sheet piles (13) and the guide rail steel plate (17) to reinforce one side of the subway station body (10).