Construction method for replacing the bottom slab of the foundation pit

Abstract

This invention relates to the field of building construction technology, and provides a method for replacing the support plate at the bottom of a foundation pit. The method includes: excavating the earth to the bottom of the foundation pit; reserving undisturbed soil adjacent to the retaining piles to support the replacement support plate; installing the replacement support plate at the undisturbed soil; and laying a cushion layer, a leveling layer, a waterproof layer, a waterproof protective layer, and a foundation slab sequentially from bottom to top on the side of the replacement support plate away from the retaining piles. This invention, by installing the replacement support plate and adopting a "7"-shaped sidewall structure, avoids the possibility of insufficient strength of the replacement support plate affecting the removal of the supporting structure, ensuring the stability of the foundation pit structure, simplifying construction procedures, reducing the construction period, and reducing the use time of manpower and equipment, thereby reducing construction costs and improving construction efficiency. This invention can effectively avoid the difficulty of fixing in soft soil foundation conditions, reduce uncertainties in foundation pit construction, reduce engineering risks, and ensure construction safety. This invention provides an innovative direction for the research of deep foundation pit support structures and has broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, and in particular to a method for replacing the support of the foundation pit bottom slab. Background Technology

[0002] Horizontal bracing structures for deep foundation pits can withstand the soil and water pressure transmitted by retaining walls. However, the installation of these bracing structures creates some inconvenience for the formwork and pouring of the basement structure, necessitating replacement bracing. Replacement bracing involves installing a force-transferring structure between the underground structure and the retaining wall, utilizing the rigidity of the main structural beams and floor slabs to bear the water and soil pressure. This allows for the gradual replacement of horizontal bracing layer by layer from bottom to top as the structure is constructed. However, when the deep foundation pit is located in a soft geological condition, the construction of the foundation slab replacement bracing on soft ground presents significant challenges due to the low strength, high compressibility, and low permeability of soft soil.

[0003] The horizontal support structure can withstand the soil pressure and water pressure transmitted by the retaining wall. It has a reasonable stress distribution, is safe and reliable, and can effectively control the deformation of the retaining wall, reduce the span of the retaining components, reduce internal forces and deformation, and make the support system economical and stress-reasonable.

[0004] The replacement support technology involves setting up a force-transfer structure between the underground structure and the retaining wall, using the rigidity of the main structural beams and floor slabs to withstand water and soil pressure, thereby replacing the horizontal supports layer by layer from bottom to top as the structure is constructed.

[0005] The existing construction process typically involves: excavation and trench cleaning → foundation layer construction to the edge of the retaining structure → waterproof membrane construction to the edge of the retaining structure → protective layer construction → simultaneous pouring of the replacement support slab and raft foundation. The existing technology has the following technical problems:

[0006] Construction with replacement support plates and soft soil foundation is challenging, especially the installation of formwork for replacement support plates.

[0007] The foundation slab requires a large number of brick formwork pieces on its sides, resulting in high labor costs.

[0008] This construction sequence will delay the construction period due to insufficient strength of the strip;

[0009] The project involves additional work and labor costs for the subbase, waterproofing layer, and protective layer, and also presents the issue of secondary backfilling later on. Summary of the Invention

[0010] The purpose of this invention is to solve at least one technical problem in the background art and to provide a method for replacing the support of the foundation pit bottom slab.

[0011] To achieve the above objectives, the present invention provides a method for replacing the support structure of a foundation pit bottom slab, characterized by comprising:

[0012] When the earthwork is excavated to the bottom of the foundation pit, the original soil is reserved next to the support piles to support the replacement support plate belt;

[0013] Install replacement support strips at the original soil surface;

[0014] On the side of the replacement support plate away from the support pile, from bottom to top, lay the pad layer, leveling layer, waterproof layer, waterproof protective layer and foundation plate in sequence.

[0015] According to one aspect of the present invention, the support plate belt includes: a first support portion and a second support portion;

[0016] The first support portion is supported above the undisturbed soil mass;

[0017] The second support is perpendicularly connected to the first support and is supported on the side wall of the undisturbed soil on the side away from the retaining pile.

[0018] According to one aspect of the present invention, the provision of the replacement support strip at the undisturbed soil site includes:

[0019] Multiple first positioning structures are set on the support piles along the vertical direction;

[0020] Measure and determine the location of the template for setting the support plate belt and erect and fix the template;

[0021] Concrete is poured between the formwork and the support piles to form a replacement support plate strip.

[0022] According to one aspect of the present invention, the supporting and fixing template includes:

[0023] Assemble multiple unit templates into a template and apply a release agent to make the template flat;

[0024] Reinforce the joints between the unit templates with wooden blocks and attach sponge strips to ensure that the unit templates are tightly joined together.

[0025] A keel structure is provided on the side of the template away from the support piles. The keel structure is arranged vertically and supports the template.

[0026] Multiple secondary positioning structures are horizontally supported between the support piles and the formwork;

[0027] One end of the horizontally positioned connector is connected to the first positioning structure, and the other end passes through the template to connect to the keel structure.

[0028] According to one aspect of the invention, the second positioning structure is provided in two parts, respectively supported on the upper and lower sides between the support pile and the formwork;

[0029] The first positioning structure is configured as two, respectively located on the upper and lower sides of the support pile;

[0030] The connector is configured as two, with one end of each connector connected to one of the first positioning structures, and the other end passing through the template to connect to the keel structure.

[0031] According to one aspect of the present invention, the keel structure comprises:

[0032] The first keel is supported vertically and spaced apart from the template;

[0033] Multiple second keels are arranged at intervals between the first keel and the template, with one end fixedly installed on the first keel and the other end abutting against the template.

[0034] According to one aspect of the present invention, the first keel is a steel pipe with a diameter of 48 mm, and the second keel is a 40 mm × 80 mm timber.

[0035] According to one aspect of the present invention, the waterproof layer comprises a first waterproof layer and a second waterproof layer;

[0036] The first waterproof layer is a 4.0mm thick SBS modified bitumen waterproof membrane;

[0037] The second waterproof layer is a 3.0mm thick SBS modified bitumen waterproof membrane;

[0038] The first waterproof layer is formed by loose laying or spot bonding.

[0039] The second waterproof layer is formed using a full-adhesion method.

[0040] According to one aspect of the invention, the waterproof layer is laid above the leveling layer, on the sidewall of the replacement support strip, and above the replacement support strip;

[0041] The waterproof layer located above the support plate is configured to be waterproof.

[0042] According to one aspect of the invention, the waterproof protective layer is laid on top of the waterproof layer and on the sidewall of the support plate;

[0043] The waterproof protective layer laid on the side wall of the support plate is a cement pressure board.

[0044] According to one aspect of the present invention, setting a replacement support strip at the undisturbed soil surface includes: setting multiple first positioning structures on the support piles along the vertical direction; measuring and determining the position of the template for setting the replacement support strip and erecting and fixing the template; and pouring concrete between the template and the support piles to form the replacement support strip. This arrangement ensures the structural stability of the replacement support strip and facilitates rapid construction by pouring the replacement support strip between the template and the support piles, effectively reducing construction difficulty.

[0045] According to one aspect of the present invention, the method of setting up a fixed template includes: assembling multiple unit templates into a template and applying a release agent to make the template flat; reinforcing the joints between the unit templates with wooden blocks and attaching sponge strips to ensure a tight connection between the unit templates; setting a keel structure on the side of the template away from the support piles, the keel structure being set vertically and supporting the template; horizontally supporting multiple second positioning structures between the support piles and the template; and connecting one end of a horizontally set connector to the first positioning structure and the other end passing through the template to connect to the keel structure. This arrangement ensures the verticality of the template by having the keel structure support it from behind, thereby ensuring the vertical accuracy of the poured replacement support strip. Simultaneously, the connection of the first positioning structure ensures the stability of the keel structure, further guaranteeing the stability and accuracy of the replacement support strip during construction, preventing compression deformation and exceeding the pouring range during the pouring process, and ensuring both construction effectiveness and speed. Furthermore, the second positioning structure can better ensure the distance between the support piles and the formwork, and ensure the stability of the position and posture of the formwork, thereby further ensuring the smooth construction of the replacement support strip and ensuring the vertical accuracy and pouring range accuracy of the replacement support strip.

[0046] According to one aspect of the present invention, two second positioning structures are configured, respectively supported on the upper and lower sides between the support pile and the formwork; two first positioning structures are configured, respectively positioned on the upper and lower sides of the support pile; two connectors are configured, with one end of each connector connected to one of the first positioning structures, and the other end passing through the formwork and connecting to the keel structure. This configuration ensures uniform support between the support pile and the formwork, guarantees that the distance between the two ends of the support pile and the formwork is the same, and ensures that the posture of the formwork does not change, thereby guaranteeing the construction accuracy of the support plate belt.

[0047] According to one aspect of the present invention, a keel structure includes: a first keel, supported vertically and spaced apart from the formwork; and a plurality of second keels, spaced apart from each other between the first keel and the formwork, with one end fixedly mounted on the first keel and the other end abutting against the formwork. This arrangement allows the keel structure to uniformly and stably apply a supporting force to the formwork in the vertical direction, ensuring that the back support force on the formwork in the vertical direction is uniform and reliable, thereby ensuring its verticality remains stable, ensuring the stability of the casting range of the support strip formed therefrom, and ensuring the construction accuracy and verticality of the support strip.

[0048] According to the present invention, this invention provides a new approach to the construction of support plate strips under weak geological conditions. By pre-installing the support plates and employing a "7"-shaped sidewall structure, this invention avoids the impact of insufficient support plate strength on the dismantling of the supporting structure, ensuring the stability of the foundation pit structure. Simultaneously, it simplifies construction procedures, shortens the construction period, and reduces the time spent on manpower and equipment, thereby reducing construction costs, improving construction efficiency, and reducing construction difficulty. This invention effectively avoids the difficulties of fixing in soft soil foundation conditions, reduces uncertainties in foundation pit construction, lowers engineering risks, and ensures construction safety. This invention provides an innovative direction for the research of deep foundation pit support structures and has broad application prospects.

[0049] This invention reduces construction difficulty, lowers material input, shortens the construction period, improves working conditions, and ensures construction quality and safety by modifying the structure of the replacement support plate and adjusting the construction sequence. The "7"-shaped sidewall structure serves as the side formwork for the foundation slab, reducing material and labor costs for the side formwork. The adjusted construction sequence prioritizes the replacement support plate, shortening the overall project duration and reducing the need for the construction of the bedding and waterproofing layers at the replacement support plate location. In actual construction, this invention can shorten the construction period by several days compared to other methods and significantly saves costs. Moreover, the larger the foundation pit area, the more pronounced the advantages of this invention, the more significant the economic benefits, and the greater the time reduction.

[0050] The "7"-shaped strip of this invention retains undisturbed soil at the bottom, saving on mechanical construction work involving excavation and backfilling, reducing noise and dust pollution, and thus protecting the environment. The formwork for the replacement strip is secured with wire bracing, further reducing the use of tie bolts and material waste. Proper planning before material delivery minimizes material loss. Civilized construction ensures a clean and orderly site. These measures result in effective energy conservation and environmental protection benefits.

[0051] This invention ensures the safety of the support structure after dismantling, while completing the replacement support measures for the foundation pit bottom slab ahead of time, shortening the overall project duration and improving efficiency. A "7"-shaped sidewall structure is used as the side formwork for the foundation bottom slab, simplifying the construction process. The replacement support structure formwork is fixed by horizontal tie rods (expansion bolts) to the formwork and keel structure using two wires, supplemented by two positioning wooden blocks, reducing the difficulty of fixing under soft soil foundation conditions. Attached Figure Description

[0052] Figure 1 A flowchart illustrating a method for replacing the support of the foundation pit bottom slab according to an embodiment of the present invention is shown.

[0053] Figure 2 This diagram schematically illustrates a foundation pit cleaning process according to an embodiment of the present invention.

[0054] Figure 3This schematic diagram illustrates the structural arrangement of a support plate belt according to one embodiment of the present invention.

[0055] Figure 4 This diagram schematically illustrates a support plate with template according to an embodiment of the present invention.

[0056] Figure 5 This diagram schematically illustrates the laying of a base layer, a leveling layer, a waterproof layer, a waterproof protective layer, and a foundation slab according to one embodiment of the present invention. Detailed Implementation

[0057] The invention will now be discussed with reference to exemplary embodiments. It should be understood that the described embodiments are merely intended to enable those skilled in the art to better understand and thus implement the invention, and are not intended to imply any limitation on the scope of the invention.

[0058] As used herein, the term "comprising" and its variations are to be interpreted as open-ended terms meaning "including but not limited to". The term "based on" is to be interpreted as "at least partially based on". The terms "one embodiment" and "an embodiment" are to be interpreted as "at least one embodiment".

[0059] Figure 1 This is a schematic flowchart illustrating a method for replacing the support structure of a foundation pit floor slab according to an embodiment of the present invention. Figure 1 As shown, in this embodiment, the method for replacing the support on the foundation pit bottom slab includes:

[0060] a. When the earthwork is excavated to the bottom of the foundation pit, the original soil is reserved next to the support piles to support the replacement support plate belt;

[0061] b. Install replacement support strips at the original soil surface;

[0062] c. On the side of the replacement support plate away from the support pile, lay the pad layer, leveling layer, waterproof layer, waterproof protective layer and foundation plate in sequence from bottom to top.

[0063] According to one embodiment of the present invention, such as Figure 2 As shown, in step a above, the earthwork is excavated to the bottom of the foundation pit, leaving 200-300mm for manual cleaning. The original soil is reserved near the support piles of the replacement support strip and leveled and compacted to the bottom elevation of the replacement support strip. A 120mm gap is reserved between the side of the original soil furthest from the support piles and the sidewall of the foundation slab.

[0064] Furthermore, according to one embodiment of the present invention, such as Figure 3 As shown, the support plate belt includes: a first support part 1 and a second support part 2;

[0065] The first support part 1 is supported above the undisturbed soil;

[0066] The second support part 2 is perpendicularly connected to the first support part 1 and is supported on the side wall of the undisturbed soil away from the retaining pile. Therefore, the replacement support strip in this invention is shaped like a "7" (i.e., the first support part 1 and the second support part 2 are perpendicularly connected and bent into a "7" shape). The top of the "7"-shaped replacement support strip is the original "I"-shaped strip, and the sides of the "7"-shaped strip are 120mm of concrete. The specific structure is as follows... Figure 3 As shown, the “7”-shaped sidewall structure can serve as the side formwork for the foundation slab, simplifying the construction process.

[0067] Furthermore, according to one embodiment of the present invention, such as Figure 4 As shown, in step b above, a replacement support strip is installed at the undisturbed soil location, including:

[0068] Along the vertical direction, multiple first positioning structures 3 are set on the support piles;

[0069] Measure and determine the position of the template 4 for setting the support plate belt and erect and fix the template 4;

[0070] Concrete is poured between formwork 4 and the support piles to form a replacement support strip. This arrangement ensures the structural stability of the replacement support strip and facilitates rapid construction by pouring the replacement support strip between formwork 4 and the support piles, effectively reducing construction difficulty.

[0071] Furthermore, in this embodiment, the fixed template 4 includes:

[0072] Assemble multiple unit templates into a template and apply a release agent to make the template flat;

[0073] Reinforce the joints between the unit templates with wooden blocks and attach sponge strips to ensure that the unit templates are tightly joined together.

[0074] A keel structure 5 is installed on the side of the template away from the support piles. The keel structure is installed vertically and supports the template.

[0075] Multiple second positioning structures 6 are horizontally supported between the support piles and the formwork 4;

[0076] One end of the horizontally positioned connector 7 is connected to the first positioning structure 3, and the other end passes through the template 4 and connects to the keel structure 5. This arrangement allows the keel structure 5 to support the template 4 from behind, ensuring the verticality of the template 4 and thus guaranteeing the vertical accuracy of the poured support strip. Simultaneously, the connection through the first positioning structure 3 ensures the stability of the keel structure 5, further guaranteeing the stability and accuracy of the support strip during construction, preventing compression deformation and exceeding the pouring range, and ensuring construction effectiveness and speed. Furthermore, the second positioning structure 6 better maintains the distance between the support piles and the template 4, ensuring the stability of the template 4's position and posture, further guaranteeing smooth construction of the support strip and ensuring its vertical accuracy and pouring range precision.

[0077] Furthermore, such as Figure 4 As shown, in this embodiment, the second positioning structure 6 is configured as two, which are respectively supported on the upper and lower sides between the support pile and the formwork 4;

[0078] The first positioning structure 3 is set in two parts, which are respectively set on the upper side and the lower side of the support pile;

[0079] Two connectors 7 are provided. One end of each connector 7 is connected to one of the first positioning structures 3, and the other end passes through the template 4 and connects to the keel structure 5. This arrangement ensures uniform support between the support piles and the template 4, guarantees that the distance between the two ends of the support piles and the template 4 is the same, and ensures that the posture of the template 4 does not change, thereby ensuring the construction accuracy of the support plate belt.

[0080] Furthermore, such as Figure 4 As shown, in this embodiment, the keel structure 5 includes:

[0081] The first keel 8 is supported vertically and is spaced apart from the template 4;

[0082] Multiple second keels 9 are arranged alternately between the first keel 8 and the formwork 4, with one end (right end in the figure) fixedly installed on the first keel 8 and the other end (left end in the figure) abutting against the formwork 4. This arrangement allows the keel structure 5 to apply a uniform and stable supporting force to the formwork 4 in the vertical direction, ensuring that the back support force on the formwork 4 in the vertical direction is uniform and reliable, thereby ensuring its verticality remains stable, ensuring the stability of the pouring range of the replacement support strip formed by it, and ensuring the construction accuracy and verticality of the replacement support strip.

[0083] Furthermore, in this embodiment, the first keel 8 is a steel pipe with a diameter of 48mm, and the second keel 9 is a 40mm×80mm timber. The spacing between each first keel is 1m, and four second keels 9 are evenly arranged along the height direction. The width of the second keel 9 is 80mm, and one side of it is attached to the template 4.

[0084] Furthermore, in this embodiment, the upper and lower first positioning structures 3 can be respectively: positioning ribs for foundation pit spraying and anchoring and expansion bolts; the second positioning structure 6 can be positioning timber; and the connecting piece 7 can be fixing wire. Of course, the first positioning structure 3, the second positioning structure 6, and the connecting piece 7 can also be any other structure capable of achieving positioning and fixed connection, as long as they satisfy the above-described inventive concept of this invention.

[0085] Based on the above settings, before pouring the replacement support strip, it is still necessary to check the erection of formwork 4 to ensure that the verticality and edge position of formwork 4 meet the requirements. Before pouring, seal the gaps in formwork 4 to ensure that there is no bulging, no grout leakage, and no grout spillage. During pouring, the positioning timbers should be installed and removed as needed.

[0086] Furthermore, according to one embodiment of the present invention, such as Figure 5 As shown, step c above includes:

[0087] Subbase concrete construction:

[0088] After the earthwork unit completes the cleaning of the subbase soil and the replacement of the support plate strip is finished, the subbase elevation is inspected, and the dimensions of the elevator shaft pit and sump pit are checked. Subbase construction then begins. Concrete is poured and smoothed in one go, ensuring a complete finish. The concrete must be troweled at least three times before final setting. The subbase surface should be flat and smooth, meeting the conditions for waterproofing layer construction. Plastic sheeting and straw mats should be used to cover the surface promptly. Personnel can only walk on the concrete and proceed to the next construction step after the concrete strength reaches 4 MPa.

[0089] Waterproofing layer construction:

[0090] In this embodiment, the waterproof layer includes a first waterproof layer and a second waterproof layer;

[0091] The first waterproof layer is a 4.0mm thick SBS modified bitumen waterproof membrane;

[0092] The second waterproof layer is a 3.0mm thick SBS modified bitumen waterproof membrane;

[0093] The first waterproof layer is formed using either the loose-lay method or the spot-adhesive method;

[0094] The second waterproof layer is formed using a full-adhesion method.

[0095] Specifically, the waterproofing layer beneath the foundation slab consists of a 4.0mm thick SBS modified bitumen waterproofing membrane and a 3.0mm thick SBS modified bitumen waterproofing membrane. The first layer is applied using a loose-lay method or a spot-adhesive method, and the second layer is applied using a full-adhesive method. The waterproofing layer should be firm, flat, free of dust and oil. It should be cleaned and swept thoroughly before construction. When the waterproofing reaches the replacement support strip, the waterproofing membrane is laid along the side wall of the "7"-shaped replacement support strip to the top of the replacement support strip. The top waterproofing membrane is a temporary stub: a minimum of 400mm is left; the stub is temporarily covered with a template to protect it.

[0096] Waterproof protective layer construction:

[0097] After the waterproof layer is completed and passes inspection, the waterproof protective concrete can be constructed. During construction, it should be poured, smoothed, and covered simultaneously, with plastic sheeting and straw mats used for insulation. At the same time, the concrete should be properly cured to ensure insulation. The sidewalls of the "7"-shaped support slab use cement pressure board as the waterproof protective layer.

[0098] Foundation slab pouring

[0099] The foundation slab concrete pouring adopts a continuous pouring method involving flat strip pouring, sloping layer pouring, thin-layer pouring, natural flow, sequential advancement, and a single pour to the top. A 60m high-capacity concrete pump is used on site for pouring. During construction, continuous concrete pouring is ensured without cold joints, while excessive vibration is prevented. The concrete vibration time should not be too long, generally 20-30 seconds per point, until the concrete surface is level, no longer significantly subsiding, no longer has air bubbles, and a layer of mortar appears on the surface. During vibration, the vibrator should be inserted quickly and withdrawn slowly, vibrating vertically, with vibration points arranged in a quincunx pattern at 450mm intervals. During vibration, the vibrator should be slightly moved up and down to ensure even vibration. When vibrating the upper layer, the vibrator should be inserted approximately 5cm into the lower layer to eliminate the joint between the two layers. Vibration of the upper layer should be carried out before the lower layer has initially set.

[0100] According to the above-described scheme of this invention, this invention proposes a new approach to the construction of support plate strips under weak geological conditions. By pre-installing the support plates and adopting a "7"-shaped sidewall structure, this invention avoids the impact of insufficient strength of the support plates on the dismantling of the supporting structure, ensuring the stability of the foundation pit structure. Simultaneously, it simplifies construction procedures, shortens the construction period, and reduces the time spent on manpower and equipment, thereby reducing construction costs, improving construction efficiency, and reducing construction difficulty. This invention can effectively avoid the difficulties of fixing in soft soil foundation conditions, reduce uncertainties in foundation pit construction, reduce engineering risks, and ensure engineering construction safety. This invention provides an innovative direction for the research of deep foundation pit support structures and has broad application prospects.

[0101] This invention reduces construction difficulty, lowers material input, shortens the construction period, improves working conditions, and ensures construction quality and safety by modifying the structure of the replacement support plate and adjusting the construction sequence. The "7"-shaped sidewall structure serves as the side formwork for the foundation slab, reducing material and labor costs for the side formwork. The adjusted construction sequence prioritizes the replacement support plate, shortening the overall project duration and reducing the need for the construction of the bedding and waterproofing layers at the replacement support plate location. In actual construction, this invention can shorten the construction period by several days compared to other methods and significantly saves costs. Moreover, the larger the foundation pit area, the more pronounced the advantages of this invention, the more significant the economic benefits, and the greater the time reduction.

[0102] The "7"-shaped strip of this invention retains undisturbed soil at the bottom, saving on mechanical construction work involving excavation and backfilling, reducing noise and dust pollution, and thus protecting the environment. The formwork for the replacement strip is secured with wire bracing, further reducing the use of tie bolts and material waste. Proper planning before material delivery minimizes material loss. Civilized construction ensures a clean and orderly site. These measures result in effective energy conservation and environmental protection benefits.

[0103] This invention ensures the safety of the support structure after dismantling, while completing the replacement support measures for the foundation pit bottom slab ahead of time, shortening the overall project duration and improving efficiency. A "7"-shaped sidewall structure is used as the side formwork for the foundation bottom slab, simplifying the construction process. The replacement support structure formwork is fixed by horizontal tie rods (expansion bolts) to the formwork and keel structure using two wires, supplemented by two positioning wooden blocks, reducing the difficulty of fixing under soft soil foundation conditions.

[0104] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A method for replacing the support structure at the bottom of an excavation pit, characterized in that, include: When the earthwork is excavated to the bottom of the foundation pit, the original soil is reserved next to the support piles to support the replacement support plate belt; Install replacement support strips at the original soil surface; On the side of the replacement support plate away from the support pile, from bottom to top, lay the pad layer, leveling layer, waterproof layer, waterproof protective layer and foundation plate in sequence; The replacement support plate belt includes: a first support part and a second support part; The first support portion is supported above the undisturbed soil mass; The second support is perpendicularly connected to the first support and is supported on the side wall of the undisturbed soil on the side away from the retaining pile. The installation of a replacement support strip at the undisturbed soil site includes: Multiple first positioning structures are set on the support piles along the vertical direction; Measure and determine the location of the template for setting the support plate belt and erect and fix the template; Concrete is poured between the formwork and the support piles to form a replacement support plate strip; The supporting and fixing template includes: Assemble multiple unit templates into a template and apply a release agent to make the template flat; Reinforce the joints between the unit templates with wooden blocks and attach sponge strips to ensure that the unit templates are tightly joined together. A keel structure is provided on the side of the template away from the support piles. The keel structure is arranged vertically and supports the template. Multiple secondary positioning structures are horizontally supported between the support piles and the formwork; One end of the horizontally set connector is connected to the first positioning structure, and the other end passes through the template and is connected to the keel structure. The second positioning structure is configured as two, which are respectively supported on the upper and lower sides between the support pile and the formwork; The first positioning structure is configured as two, respectively located on the upper and lower sides of the support pile; The connector is provided in two parts, one end of each connector is connected to one of the first positioning structures, and the other end passes through the template and connects to the keel structure. The keel structure includes: The first keel is supported vertically and spaced apart from the template; Multiple second keels are arranged at intervals between the first keel and the template, with one end fixedly installed on the first keel and the other end abutting against the template; The waterproof layer includes a first waterproof layer and a second waterproof layer; The first waterproof layer is a 4.0mm thick SBS modified bitumen waterproof membrane; The second waterproof layer is a 3.0mm thick SBS modified bitumen waterproof membrane; The first waterproof layer is formed by loose laying or spot bonding. The second waterproof layer is formed using a full-adhesion method; The waterproof layer is laid on top of the leveling layer, on the side wall of the replacement support strip, and on top of the replacement support strip; The waterproof layer located above the support plate is configured to be waterproof and stubble-proof. The waterproof protective layer is laid on top of the waterproof layer and on the side wall of the replacement support plate; The waterproof protective layer laid on the side wall of the support plate is a cement pressure board.

2. The method for replacing the support of the foundation pit bottom slab according to claim 1, characterized in that, The first keel is a steel pipe with a diameter of 48mm, and the second keel is a 40mm×80mm timber.

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