A subway station main body deep and large foundation pit anti-disturbance support construction method

Abstract

This invention provides a method for constructing a disturbance-proof support structure for a deep foundation pit of a subway station, comprising: Step S1, constructing a temporary partition in the middle of the foundation pit and simultaneously constructing on both sides of the temporary partition; Step S2, constructing a diaphragm wall; Step S3, performing dewatering treatment; Step S4, installing formwork and pouring concrete for the capping beam; Step S5, constructing a retaining wall on top of the capping beam; Step S6, excavating from the temporary partition towards both ends of the foundation pit, longitudinally segmented and vertically layered, using a supported excavation method; Step S7, simultaneously removing the temporary partition and excavating to the foundation as the excavation progresses. Dividing the foundation pit using temporary partitions achieves regionalized excavation. The stability of the foundation pit is ensured by the support provided by the temporary partitions during excavation. Simultaneous excavation on both sides significantly improves construction efficiency. Simultaneous removal of the temporary partitions during excavation ensures the reliability and stability of the foundation pit support structure system.

Description

Technical Field

[0001] This invention belongs to the field of subway foundation pit construction technology, specifically relating to a method for preventing disturbance and supporting the construction of deep foundation pits for subway stations. Background Technology

[0002] Subways are mostly located near existing buildings, and due to space constraints, subway foundation pits are becoming increasingly deep. Therefore, the difficulty of foundation pit construction is constantly increasing. For deep and large foundation pits, traditional construction methods are insufficient to guarantee safe excavation and construction of underground structures, nor can they guarantee the safety of existing above-ground building structures.

[0003] Therefore, there is a need to provide an improved technical solution that addresses the shortcomings of the existing technology. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art. This invention provides a method for preventing disturbance to the construction of a deep foundation pit for a subway station.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for constructing a disturbance-proof support system for a deep foundation pit of a subway station, comprising:

[0007] Step S1: Construct a temporary partition in the middle of the foundation pit, and carry out simultaneous construction on both sides of the temporary partition;

[0008] Step S2: Construct the diaphragm wall;

[0009] Step S3: Drilled cast-in-place piles are used as both tension piles and column piles, and multiple dewatering wells are set up for dewatering treatment.

[0010] Step S4: Excavate the earthwork above the bottom of the cap beam in sections in one go, remove the over-poured concrete of the underground continuous wall pile heads, and after the underground continuous wall pile heads are chiseled to the bottom elevation of the cap beam, pour a concrete cushion layer as the bottom formwork of the cap beam, and then carry out the reinforcement binding, formwork installation and cap beam concrete pouring.

[0011] Step S5: After the capping beam construction is completed, the retaining wall at the top of the capping beam is constructed. The vertical steel bars of the retaining wall are pre-embedded before the capping beam concrete is poured.

[0012] Step S6: Excavate from the temporary partition towards both ends of the foundation pit, dividing it longitudinally into sections and vertically into layers, and excavate the foundation pit sequentially using a supported excavation method.

[0013] Step S7: During the excavation of the foundation pit, the temporary partitions are removed in sync with the excavation progress. When the foundation elevation is 300mm above the foundation level, manual excavation is used to excavate to the foundation level.

[0014] Preferably, at the transfer node, the support members are supported at the end and side of the pit by diagonal bracing from the end of the pit, and a connecting beam is provided between two adjacent support members.

[0015] Preferably, at non-transfer nodes, the supporting components include concrete supports and steel supports, and the supporting components of the foundation pit from top to bottom are alternating between concrete supports and steel supports;

[0016] The longitudinally adjacent concrete and steel supports are reinforced by scissor bracing arranged in an X-shape.

[0017] Preferably, the foundation pit is L-shaped, intersecting with the transfer metro line, and the foundation pits on both sides of the transfer node are excavated simultaneously. All supporting components at the transfer node are concrete supports, and at least two supporting components of the transfer metro line near the transfer node are concrete supports.

[0018] Preferably, the underground continuous wall is provided with concrete lintels corresponding to each supporting component;

[0019] The concrete lintel beam and concrete bracing are interwoven and tied together at their intersections, and concrete corner bracing is installed at the inside corners.

[0020] A concrete brace support is installed at the intersection of the steel support diagonal brace and the concrete waist beam. The concrete surface of the concrete brace support is parallel, and the center line of the steel support diagonal brace is perpendicular to the surface of the brace support.

[0021] Preferably, the inner wall of the diaphragm wall is provided with embedded steel bars for connecting the concrete waist beam, and the corresponding position of the concrete waist beam is roughened. Tie bars are provided on the steel cage of the concrete waist beam. The tie bars are connected to the side of the steel cage of the concrete waist beam away from the diaphragm wall. The upper end of the tie bar is anchored in the diaphragm wall by anchor bolts. The lower end of the tie bar is bent from the bottom of the steel cage of the concrete waist beam toward the diaphragm wall. The bent part is fixed to the steel cage of the concrete waist beam by welding or binding.

[0022] Preferably, the foundation pit is excavated by longitudinal segmentation and vertical layering on both sides of the temporary partition.

[0023] Preferably, in step S3, there are multiple dewatering wells, which are distributed along preset points within the foundation pit. The construction steps include:

[0024] Well locations are marked out according to the preset points, and the bottom of the protective pipe is inserted into the original soil layer according to the preset points. The outside of the pipe is sealed with the original soil layer through cohesive soil.

[0025] After the drilling rig is installed, a hole is drilled. After the hole is drilled, the well casing is installed. In aquifers with high permeability, the well casing is a filter pipe.

[0026] Gravel is filled into the well casing as filter material. After the filter material is filled, the well is flushed, and then the water pump is used to dewater the area.

[0027] Preferably, the dewatering wells are in dewatering operation during the construction of the foundation pit, continuously pumping water out of the strata at the bottom of the foundation pit to keep the water level below the base elevation of 1.5m.

[0028] When carrying out the foundation construction, the well is sealed, a waterproof sleeve is fitted to the outside of the well pipe, the bottom of the waterproof sleeve is inserted below the foundation, and then impermeable concrete is poured into the well.

[0029] A water-stop flange is installed on the outside of the waterproof sleeve, which is cast into the base slab concrete. Water-stop adhesive is applied to the water-stop flange.

[0030] The base plate concrete is provided with a groove corresponding to the top of the waterproof sleeve. The top of the waterproof sleeve extends out of the bottom surface of the groove and is sealed by the top plate flange cover.

[0031] The groove is integrally formed with the base slab concrete of the foundation by impermeable concrete.

[0032] Beneficial effects: The foundation pit is divided into sections by temporary partitions, thereby achieving regionalized foundation pit excavation. During the excavation process, the stability of the foundation pit is ensured by the support of the temporary partitions. At the same time, simultaneous excavation on both sides can greatly improve construction efficiency. Excavation is carried out from the temporary partitions to both ends, and the temporary partitions are removed simultaneously during the excavation process, ensuring the reliability and stability of the foundation pit retaining structure system. Attached Figure Description

[0033] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Wherein:

[0034] Figure 1 This is a schematic diagram showing the distribution of support components in an L-shaped arrangement between the transfer station and the foundation pit in a specific embodiment of the present invention.

[0035] Figure 2 This is a schematic diagram showing the distribution of V-shaped support components in a specific embodiment of the present invention.

[0036] Figure 3 This is a schematic diagram of the longitudinal distribution of the support components in a specific embodiment of the present invention.

[0037] In the diagram: 1. Temporary partition; 2. Cast-in-place pile; 3. Supporting component; 4. Transfer subway line; 5. Diaphragm wall; 6. Connecting beam; 7. Steel structure column; 301. Concrete support; 302. Steel support. Detailed Implementation

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0039] In the description of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and do not require the invention to be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. The terms "connected" and "linked" used in this invention should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; they can refer to a direct connection or an indirect connection through intermediate components. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0040] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0041] like Figure 1-3 As shown, a method for preventing disturbance during the construction of a deep foundation pit for a subway station includes: Step S1, constructing a temporary partition 1 in the middle of the foundation pit, and simultaneously constructing on both sides of the temporary partition 1; simultaneous excavation on both sides can significantly improve construction efficiency; Step S2, constructing a diaphragm wall 5, which is constructed simultaneously from both ends of the temporary partition 1 towards both ends of the foundation pit. During the construction of the diaphragm wall 5, the main components of the mud are bentonite, CMC, soda ash, and water. The mud mix ratio is determined based on the geological conditions and the sediment at the bottom of the borehole. The mud is mixed using a high-speed rotary mixer, and the mixed mud should be placed in a storage tank and allowed to stand for at least 24 hours to allow the bentonite particles to fully hydrate and expand, ensuring the quality of the mud.

[0042] Step S3: Drilled cast-in-place piles 2 are used as both tension piles and column piles, and multiple dewatering wells are set up for dewatering treatment. The cast-in-place piles 2 are installed before the foundation pit is excavated. As the foundation pit is excavated, the cast-in-place piles 2 are cut down to the bottom of the first support member 3 (concrete support 301) to serve as column piles. When the foundation pit is excavated to the second support member 3 (steel support 302), the portion of the cast-in-place piles 2 between the first and second support members 3 is cut off. Then, steel structure columns 7 (which can be steel column piles) are installed between the second and first support members 3. The support members 3 are installed one by one downwards. As the foundation pit is excavated, the cast-in-place piles 2 are cut down to the bottom of the foundation pit body to serve as tension piles.

[0043] The main reinforcing bars of the steel cage for pile 2 are inserted downwards 25-30m into the bottom of the foundation pit. First, pre-set points are installed for pile 2 measurement and positioning. Protective piles are then installed 2m away from the center of the pile location on all sides as control and inspection points during drilling, allowing for continuous monitoring of the pile's center and elevation. The geological conditions are determined before drilling. The borehole casing is made of 5mm thick steel plate, with an inner diameter 100mm larger than the drill bit diameter, and has 1-2 overflow holes at the top. The casing must be inserted into the original soil, and the outer side is backfilled and compacted with clay.

[0044] Determine the drill bit, drilling speed, and wall-protecting mud concentration. When the drill bit reaches the bottom of the casing, remove it and install the casing as specified. After the casing is installed, continue drilling. Add wall-protecting mud into the hole during drilling. The drilling depth is controlled by the drilling depth controller in the drilling rig's operating room. Stop drilling after reaching the design elevation.

[0045] During borehole cleaning, fresh mud should be injected into the borehole promptly to maintain the water level 1.0m above the groundwater level and prevent borehole collapse. After the cleaning work is completed, the borehole depth, position, verticality, and pile position deviation should be checked. After acceptance, the reinforcing cage should be hoisted and lowered. Concrete should be poured immediately after the reinforcing cage is lowered, with an interval not exceeding 4 hours.

[0046] Step S4: After breaking up the hardened road above the foundation pit and removing construction waste and materials, the earthwork above the bottom of the capping beam is excavated in sections in one go. The over-poured concrete of the diaphragm wall pile heads 5 is removed. After the diaphragm wall pile heads 5 are excavated to the bottom elevation of the capping beam, a concrete cushion layer is poured above the diaphragm wall 5 as the bottom formwork of the capping beam. Then, the reinforcement is tied, the formwork is installed, and the capping beam concrete is poured. Preferably, the excavation is carried out to 5cm below the first supporting member 3, and then the concrete cushion layer is constructed as the bottom formwork of the capping beam.

[0047] Step S5: After the capping beam construction is completed, the retaining wall on top of the capping beam is constructed. Before the capping beam concrete is poured, the vertical steel bars of the retaining wall are pre-embedded. The retaining wall is constructed on top of the capping beam and is poured as an integral part of the capping beam.

[0048] Step S6: Excavation begins from temporary partition 1 towards both ends of the foundation pit. Starting from temporary partition 1, the foundation pit is excavated in a longitudinally segmented and vertically layered manner towards both sides of the foundation pit. Specifically, on any side of temporary partition 1, the length of each excavation section is 20-25m. Vertically, the foundation pit is divided into multiple layers, with each layer having an excavation depth of 1.4-1.8m. Excavation is carried out in one go, with a 1:1.5 slope between each section. The foundation pit is equipped with supporting components 3, and the multi-layer foundation pit excavation is carried out sequentially using a supported excavation method.

[0049] Step S7: During the excavation of the foundation pit, the temporary partition 1 is cut off as the excavation progresses. When the foundation elevation is 300mm above the foundation elevation, manual excavation is used to excavate to the foundation.

[0050] In an optional embodiment, at the transfer node or both ends of the pit, the support member 3 is supported at the end and side of the pit by means of diagonal bracing. Specifically, at the end of the transfer node, the support member 3 supports layer by layer from the middle to both sides. The support member 3 corresponding to the non-transfer node of the pit is perpendicular to the main body of the pit, thereby forming a V-shaped transportation channel at the end of the transfer node to transport the excavated soil outward. In order to increase the structural strength, a connecting beam 6 is provided between two adjacent support members 3.

[0051] In this embodiment, the excavation pit is L-shaped, intersecting with the transfer metro line. At the end of the excavation pit, it connects with another transfer metro line 4, such as... Figure 1 For example, one end of the foundation pit is provided with an L-shaped transfer subway line 4. The transfer node is provided with support members 3 that are distributed parallel and perpendicular to the extension direction of the transfer subway line 4. The parallel support members 3 extend to the end of the transfer subway line 4. Inside the parallel support members of the transfer node, there are inclined support members 3. One end of the inclined support member 3 is cast integrally with the support member 3 of the parallel transfer subway line 4, and the other end is cast on the side of the foundation pit. The support members 3 at the corresponding intersection of the foundation pit are perpendicular to the main body of the foundation pit, thus forming a "U"-shaped transportation channel to transport the excavated soil outward. In order to increase the structural strength, a connecting beam 6 is provided between two adjacent support members 3.

[0052] In this embodiment, at non-transfer nodes, the support member 3 includes a concrete support 301 and a steel support 302. The support members 3 of the foundation pit from top to bottom are alternately made of concrete support 301 and steel support 302. Specifically, taking a 7-story support member 3 as an example, from top to bottom, the first support member 3 is a concrete support 301, the second support member 3 is a steel support 302, the third support member 3 is a concrete support 301, the fourth support member 3 is a steel support 302, the fifth support member 3 is a concrete support 301, the sixth support member 3 is a steel support 302, and the seventh support member 3 is a steel support 302. The concrete supports 301 and steel supports 302 that are adjacent in the longitudinal direction are reinforced by scissor bracing distributed in an X shape. The scissor bracing is a support channel steel.

[0053] In this embodiment, after the steel support 302 is installed, a pre-applied axial force is applied to the steel support 302.

[0054] In this embodiment, the foundation pits on both sides of the transfer node are excavated simultaneously. Specifically, at the transfer node, the transfer subway line on one side of the transfer node and the temporary partition, as well as on the other side of the transfer node, are excavated simultaneously to ensure the stability of the construction.

[0055] The distance between the temporary partitions and the transfer nodes is adapted to the length of the transfer metro line to ensure the balance of excavation. Figure 1 For example, the foundation pits on both sides of the transfer node are of the same length and are excavated simultaneously to ensure the geological stress at the intersection.

[0056] In this embodiment, the supporting components 3 at the transfer node are all concrete supports, and at least two supporting components of the transfer metro line near the transfer node are all concrete supports, so as to ensure the construction stability of the transfer node.

[0057] In an optional embodiment, the diaphragm wall 5 is provided with concrete waist beams corresponding to each supporting member 3; the concrete waist beams are connected to the diaphragm wall 5 by casting, and the reinforcement of the concrete waist beams and concrete supports 301 at the intersection nodes are interlaced and tied together, and concrete corner braces are provided at the inside corners.

[0058] A concrete bracing support is installed at the intersection of the steel support 302 diagonal brace and the concrete waist beam. The concrete surface of the concrete bracing support is parallel, and the center line of the steel support 302 diagonal brace is perpendicular to the surface of the bracing support.

[0059] In this embodiment, embedded reinforcing bars for connecting the concrete waist beam are provided on the inner wall of the diaphragm wall 5. The waist beam reinforcing bars are connected to the embedded reinforcing bars of the diaphragm wall 5 through reserved sleeves. The corresponding positions of the concrete waist beam are roughened. Tie bars are provided on the reinforcing cage of the concrete waist beam. The tie bars are connected to the side of the reinforcing cage of the concrete waist beam away from the diaphragm wall 5. The upper end of the tie bar is anchored in the diaphragm wall 5 by anchor bolts. The anchor bolts are YG2-M20 type expansion bolts. The lower end of the tie bar is bent from the bottom of the reinforcing cage of the concrete waist beam toward the diaphragm wall 5. The bent part is fixed to the reinforcing cage of the concrete waist beam by welding or binding. The diameter of the tie bar is not less than 28mm.

[0060] In an optional embodiment, in step S3, there are multiple dewatering wells, which are distributed in the foundation pit along preset points.

[0061] All well casings for dewatering wells are made of welded steel pipes. The diameter of the filter pipes should be the same as that of the well casing. Filter pipes are installed starting 8m below ground level, with each filter pipe being 3m long and spaced 3m apart. The bottom section of the filter pipe is 5m long. The outside of each filter pipe is wrapped with two layers of 80-100 mesh nylon mesh as a filtration layer. A 2m long sedimentation pipe is installed at the bottom of the filter pipes inside the pit.

[0062] The construction steps include:

[0063] Well locations are marked out according to the preset points, and the bottom of the protective pipe is inserted into the original soil layer according to the preset points. The outside of the pipe is sealed with the original soil layer through cohesive soil.

[0064] After the drilling rig is installed, a hole is drilled. After the hole is drilled, the well casing is installed. In aquifers with high permeability, the well casing is a filter pipe.

[0065] Gravel is filled into the well casing as filter material. After the filter material is filled, the well is flushed, and then the water pump is used to dewater the area.

[0066] In one optional embodiment, the dewatering wells are always in dewatering operation during the construction of the foundation pit, continuously pumping water from the strata at the bottom of the foundation pit to keep the water level below the base elevation of 1.5m. Before the dewatering operation begins, the elevation of each wellhead and the ground is accurately measured, the static water level is measured, and the pumping equipment, cables and drainage pipes are arranged for trial operation to ensure the pumping system is in good working order.

[0067] After the precipitation begins, the dynamic changes in water level should be monitored and measured at all times to understand the settlement of the soil around the foundation pit and its impact on underground pipelines, etc.

[0068] During the construction of the foundation slab, a well is sealed. The bottom of the waterproof casing is inserted below the foundation, and then impermeable concrete is poured inside the well. The waterproof casing is then fitted onto the outside of the well pipe to seal the aquifer around the drainage well. After inspection and confirmation of grout sealing, the well pipe is cut to the bottom of the foundation slab. A water-stop flange is installed on the outside of the waterproof casing, cast into the foundation slab concrete, and water-stop sealant is applied to the water-stop flange. A groove corresponding to the top of the waterproof casing is provided in the foundation slab concrete, with the top of the waterproof casing extending beyond the bottom of the groove and sealed by the top plate flange cover. The groove is integrally cast with the foundation slab concrete using impermeable concrete. There should be no water seepage at the waterproof casing location, and the structural surface should be free of damp stains.

[0069] In this embodiment, the temporary partition 1 extends 21.5m below the foundation pit floor slab, and both sections of the temporary partition 1 extend to the outer side of the diaphragm wall 5. The specific construction method includes:

[0070] Step S101: The main function of the guide wall is to guide the trenching of the temporary partition 1, control the elevation, control the verticality and position of the trench section and the positioning of the steel cage, and prevent the trench opening from collapsing and bearing the load. The guide wall is 2.0m high and 200mm thick. After measurement and layout, the trench is excavated, and then the tied guide wall steel bars are put in. After the formwork is erected, concrete is poured.

[0071] Step S102: Lay out the trench section corresponding to temporary partition 1, set control points and leveling points, and accurately locate the position of temporary partition 1. The unit trench section of temporary partition 1 adopts the intermittent skip construction method. The trench is formed by trenching machine. First, dig the single holes at both ends of the trench section, or dig the first hole and then skip a distance before digging the second hole. Leave a certain width of unexcavated soil between the two single holes. This can make the grab bucket bear the force evenly when digging the single hole, which can effectively correct the deviation and ensure the verticality of the trench.

[0072] In step S103, the steel cage of the temporary partition 1 is fabricated on the steel cage fabrication platform and hoisted in sections, specifically by using a double-machine lifting and aerial straightening method.

[0073] Step S104: Concrete is poured into the temporary partition 1. The concrete pouring should be continuous and not interrupted for a long time to maintain the uniformity of the concrete. As the concrete surface rises, the guide pipe is disassembled, and the bottom end of the guide pipe is buried 2 to 6m below the concrete surface.

[0074] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention shall be within the scope of protection of the pending claims of the present invention.

Claims

1. A method for constructing a disturbance-proof support system for deep foundation pits of subway stations, characterized in that, include: Step S1: Construct a temporary partition in the middle of the foundation pit, and carry out simultaneous construction on both sides of the temporary partition; Step S2: Construct the diaphragm wall; Step S3: Drilled cast-in-place piles are used as both tension piles and column piles, and multiple dewatering wells are set up for dewatering treatment. Step S4: Excavate the earthwork above the bottom of the cap beam in sections in one go, remove the over-poured concrete of the underground continuous wall pile heads, and after the underground continuous wall pile heads are chiseled to the bottom elevation of the cap beam, pour a concrete cushion layer as the bottom formwork of the cap beam, and then carry out the reinforcement binding, formwork installation and cap beam concrete pouring. Step S5: After the capping beam construction is completed, the retaining wall at the top of the capping beam is constructed. The vertical steel bars of the retaining wall are pre-embedded before the capping beam concrete is poured. Step S6: Excavate from the temporary partition towards both ends of the foundation pit, dividing it longitudinally into sections and vertically into layers, and excavate the foundation pit sequentially using a supported excavation method. Step S7: During the excavation of the foundation pit, the temporary partitions are removed in sync with the excavation progress. When the foundation elevation is 300mm above the foundation, manual excavation is used to excavate to the foundation. The foundation pit intersects with the transfer metro line in an L-shape. The foundation pits on both sides of the transfer node are excavated simultaneously. All supporting components at the transfer node are concrete supports. At least two supporting components of the transfer metro line near the transfer node are also concrete supports. At the transfer node, the supporting components are supported at the end and side of the pit by diagonal bracing, and a connecting beam is provided between two adjacent supporting components; At non-transfer nodes, the supporting components include concrete supports and steel supports. From top to bottom, the supporting components of the foundation pit are alternating between concrete supports and steel supports. In the longitudinal direction, adjacent concrete supports and steel supports are reinforced by scissor bracing distributed in an X shape. The transfer node is equipped with support components that are distributed parallel to and perpendicular to the extension direction of the transfer metro line. The parallel support components extend to the end of the transfer metro line. Inside the parallel support components of the transfer node, there are inclined support components. One end of the inclined support component is cast integrally with the support component of the parallel transfer metro line, and the other end is cast on the side of the foundation pit. The support components at the corresponding intersection of the foundation pits are perpendicular to the main body of the foundation pit, thus forming a "U"-shaped transportation channel to transport the excavated soil outward.

2. The construction method for preventing disturbance to the deep foundation pit of a subway station as described in claim 1, characterized in that, The underground diaphragm wall is equipped with concrete lintels corresponding to each supporting component; The concrete lintel beam and concrete bracing are interwoven and tied together at their intersections, and concrete corner bracing is installed at the inside corners. A concrete brace support is installed at the intersection of the steel support diagonal brace and the concrete waist beam. The concrete surface of the concrete brace support is parallel, and the center line of the steel support diagonal brace is perpendicular to the surface of the brace support.

3. The method for preventing disturbance to the deep foundation pit of a subway station as described in claim 2, characterized in that, Pre-embedded steel bars for connecting concrete waist beams are provided on the inner wall of the diaphragm wall, and the corresponding positions of the concrete waist beams are roughened. Tie bars are provided on the steel cage of the concrete waist beams. The tie bars are connected to the side of the steel cage of the concrete waist beams away from the diaphragm wall. The upper end of the tie bar is anchored in the diaphragm wall by anchor bolts, and the lower end of the tie bar is bent from the bottom of the steel cage of the concrete waist beams toward the diaphragm wall. The bent part is fixed to the steel cage of the concrete waist beams by welding or binding.

4. The construction method for preventing disturbance to the deep foundation pit of a subway station as described in claim 1, characterized in that, The foundation pit was excavated by longitudinal segmentation and vertical layering on both sides of the temporary partition.

5. The construction method for preventing disturbance to the deep foundation pit of a subway station as described in claim 1, characterized in that, In step S3, there are multiple dewatering wells, which are distributed along predetermined points within the foundation pit. The construction steps include: Well locations are marked out according to the preset points, and the bottom of the protective pipe is inserted into the original soil layer according to the preset points. The outside of the pipe is sealed with the original soil layer through cohesive soil. After the drilling rig is installed, a hole is drilled. After the hole is drilled, the well casing is installed. In aquifers with high permeability, the well casing is a filter pipe. Gravel is filled into the well casing as filter material. After the filter material is filled, the well is flushed and the water pump is lowered to reduce water level.

6. The construction method for preventing disturbance to the deep foundation pit of a subway station as described in claim 5, characterized in that, During the construction of the foundation pit, the dewatering wells were always in dewatering operation, continuously pumping water out of the strata at the bottom of the foundation pit to keep the water level 1.5m below the base elevation; When carrying out the foundation construction, the well is sealed, a waterproof sleeve is fitted to the outside of the well pipe, the bottom of the waterproof sleeve is inserted below the foundation, and then impermeable concrete is poured into the well. A water-stop flange is installed on the outside of the waterproof sleeve, which is cast into the base slab concrete. Water-stop adhesive is applied to the water-stop flange. The base plate concrete is provided with a groove corresponding to the top of the waterproof sleeve. The top of the waterproof sleeve extends out of the bottom surface of the groove and is sealed by the top plate flange cover. The groove is integrally formed with the base slab concrete of the foundation by impermeable concrete.

Images