Pile cap raft foundation elevator shaft pit structure cavity construction method

Abstract

The invention relates to the technical field of foundation elevator shaft pit structures, and discloses a pile cap raft foundation elevator shaft pit structure cavity construction method which specifically comprises the following steps that firstly, a structure cavity is designed, then measurement and paying-off operation are conducted, then earthwork excavation is conducted, waterproof construction is conducted on the structure cavity after earthwork excavation is completed, and the structure cavity is constructed. According to the construction method and the constructed structure, the situation that the elevator shaft pit is located on the bearing platform can be effectively avoided, the construction efficiency is improved, the construction cost is reduced, the construction period is shortened, the construction cost is reduced, and the construction efficiency is improved. The elevation of the whole bearing platform is synchronously reduced along with an elevator shaft pit, a structural cavity is designed between the sinking bearing platform and a basement bottom plate, so that the aims of reducing concrete waste and not increasing the load borne by a pile foundation are achieved, and retaining walls are additionally arranged on the periphery of the cavity in order to prevent underground water on the periphery of the cavity from permeating.

Description

Technical Field

[0001] The invention relates to the technical field of elevator shaft pit structure foundation, and in particular to a method for constructing a cavity of an elevator shaft pit structure with a pile cap raft foundation. Background Art

[0002] With the rapid economic growth of China, urbanization construction is developing continuously. Pile cap raft foundation is a common foundation form for semi-basement buildings. The part of the elevator shaft below the lowest floor station served by the elevator car is called the bottom pit.

[0003] In the prior art, due to the compact layout of the basement, there are situations where the elevator shaft pit, sump and other sunken structures are designed on the cap, resulting in the lowering of the entire cap. Therefore, there will be a height difference between the top of the partially sunken cap and the bottom of the basement floor. In the existing construction method, for this part of the height difference area, in the conventional practice, for the cap drop area, the concrete is filled at one time when the basement floor is poured, or the sunken cap concrete is poured first, and after the cap concrete strength reaches 75% of the design strength, the soil is backfilled and compacted, and then the subsequent basement floor operation is carried out. However, the above traditional construction methods all have the following problems:

[0004] (1) The concrete volume in the area where the foundation is lowered is usually large, exceeding 10m 3 If the basement slab is poured all at once, it will cause a waste of concrete and greatly increase the load on the pile foundation, which is not conducive to structural safety.

[0005] (2) If the concrete of the sinking pedestal is poured first, then the soil is backfilled, and finally the basement floor is constructed, this method will cause delays in the construction period due to waiting for the concrete strength. In addition, since the basement floor and the pedestal are poured separately, it is easy to cause water seepage in the basement floor in the later stage. This is aimed at the area where the entire pedestal sinks with the elevator pit, resulting in a height difference between the top of the partially sunken pedestal and the bottom of the basement floor.

[0006] After searching, it is found that Chinese patent documents disclose an elevator shaft foundation pit and an elevator shaft foundation pit construction method (publication number: CN110670596A). The embodiment of the present invention discloses an elevator shaft foundation pit and an elevator shaft foundation pit construction method. The elevator shaft foundation pit includes a foundation pit main structure; the inner surface of the foundation pit main structure is coated with a cement-based penetrating crystalline waterproof coating; an elevator shaft structure is installed above the foundation pit main structure; the connection between the elevator shaft structure and the foundation pit main structure is coated with the cement-based penetrating crystalline waterproof coating. The elevator shaft foundation pit can improve the construction efficiency of the elevator shaft foundation pit and reduce the maintenance cost of the elevator shaft foundation pit, but it still has the following defects:

[0007] Although the above-mentioned elevator pit and elevator pit construction method can improve the construction efficiency of the elevator pit and reduce the maintenance cost of the elevator pit, there are still problems such as if the basement slab is poured all at once, concrete is wasted, and the load on the pile foundation is greatly increased, which is not conducive to structural safety. If the sinking cap concrete is poured first, then backfilled, and finally the basement slab is operated, this method will cause delays in the construction period due to waiting for the concrete strength, and because the basement slab and cap are poured separately, it is easy to cause water seepage in the basement slab in the later stage. The entire cap sinks with the elevator pit, resulting in a height difference between the top of the partially sunken cap and the bottom of the basement slab. Summary of the invention

[0008] The purpose of the present invention is to provide a method for constructing a cavity of a pile cap raft foundation elevator pit structure, which solves the problem that if the conventional construction method in the background technology is filled all at once with the pouring of the basement floor, concrete waste will be caused, and the load borne by the pile foundation will be greatly increased, which is not conducive to structural safety. If the concrete of the sinking cap is poured first, then the soil is backfilled, and finally the basement floor is operated, this method will cause delays in the construction period due to waiting for the concrete strength, and because the basement floor and the cap are poured separately, it is easy to cause water seepage in the basement floor in the later stage. The problem is that the entire cap sinks with the elevator pit, resulting in a height difference between the top of the partially sunken cap and the bottom of the basement floor.

[0009] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0010] A method for constructing a cavity of a pile cap raft foundation elevator pit structure comprises the following steps:

[0011] S1: Structural cavity design;

[0012] S2: Carry out measurement and line laying operations;

[0013] S3: Carry out earth excavation;

[0014] S4: After the earthwork excavation is completed, waterproofing construction is carried out;

[0015] S5: After the waterproofing work is completed, the reinforcement work is carried out;

[0016] S6: Box making;

[0017] S7: Install the finished box on the prefabricated pad;

[0018] S8: When the box is installed, pour concrete in the structural cavity.

[0019] Preferably, in S1, the position of the structural cavity design is the space between the top of the sunken pedestal and the bottom of the basement floor slab. Since the elevator shaft pit is designed to be above the pedestal, the entire pedestal elevation drops to a specified depth as the elevator shaft pit descends. A structural cavity is designed in the area from part of the pedestal top to the bottom of the basement floor slab. In order to prevent water seepage around the structural cavity, reinforced concrete retaining walls are added around the structural cavity.

[0020] Preferably, in S2, the specific steps of measuring and laying out are:

[0021] S2.1: Substitute the basic plan layout into the general plan coordinates;

[0022] S2.2: Use mapping software to mark the coordinate points of the pedestal and elevator pit, input the coordinates into RTK, and release the coordinate points:

[0023] S2.3: Carry out the line-laying operation and reserve the position of the brick formwork during the line-laying operation.

[0024] Preferably, in the S4, the waterproof material for waterproof construction is SBS modified asphalt waterproof membrane, and before the SBS modified asphalt waterproof membrane waterproof construction work, the water at the bottom of the pit is cleared, the bottom of the pit is dried in the sun and the base layer is cleaned, and then cold primer is sprayed to reduce the influence of floating dust and increase adhesion. Secondly, in the waterproof construction work, the corners are constructed first, and the horizontal width of the corner additional layer is 230mm-270mm, and the vertical width is 230mm-270mm. After the corner construction work is completed, large-surface paving is carried out, and during the large-surface paving process, the long sides overlap by 100mm and the short sides overlap by 150mm.

[0025] Preferably, in S5, the steel bar construction requires laying out the steel bar material and ensuring the anchorage length of the steel bar, as well as the laying out material list obtained through laying out, to complete the processing of the steel bar. After the steel bar processing is completed, it is necessary to inspect it. Before the steel bar material is installed, the laying-out operation is carried out in advance to ensure the accuracy of the position. During the steel bar material binding operation, ensure that the spacing between the steel meshes meets the actual needs. At the same time, according to the protective layer thickness requirements of the water-facing surface and the water-back surface, select an appropriate protective layer to ensure the thickness of the steel bar protective layer.

[0026] Preferably, in S6, the box is made of bamboo plywood, and the secondary ribs are arranged in a wooden square structure and arranged horizontally, while the primary ribs are arranged in a wooden square structure and arranged vertically.

[0027] Preferably, the thickness of the bamboo plywood is 15mm, a plurality of holes are provided at equal intervals on the bottom, the diameter of the holes provided at the bottom end of the bamboo plywood is φ20, and the spacing between the holes is 450mm-500mm, hanging holes are provided on both sides of the bamboo plywood, and the diameter of the hanging holes is φ30, the wooden square structure size used for the secondary ribs is 40mm*800mm, and the vertical spacing of the secondary ribs is 450mm-500mm, the wooden square structure size used for the main ribs is 40mm*800mm, and the lateral spacing of the secondary ribs is 550mm-600mm.

[0028] Preferably, in S7, the specific steps of installing the box are:

[0029] S7.1: Make simple lifting lugs by bending the ends of the steel bars for lifting;

[0030] S7.2: During the lifting process, insert one side of the hook into the lifting hole;

[0031] S7.3: The hook on the other side is tied with wire and wire rope;

[0032] S7.4: Weld four steel bars to the main reinforcement of the pile foundation below the cap;

[0033] S7.5: Move the box into the structural cavity;

[0034] S7.6: Two bars are placed above the box and welded to the main reinforcement of the pile foundation below the cap.

[0035] Preferably, in S7, before the box is installed, in order to ensure the thickness of the protective layer on the top surface of the pedestal below, prefabricated pads are placed on the top of the steel bars, and in order to prevent displacement during concrete pouring, wire binding is used to limit and fix the box. At the same time, in order to prevent the box from shifting during concrete pouring, after the box is installed and calibrated, prefabricated internal support bars are used around the box to tighten the four sides of the box to achieve a limiting effect.

[0036] Preferably, in S8, fine stone concrete with a large slump of 180±20 mm and good fluidity is used in pouring concrete in the structure cavity.

[0037] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0038] 1. Through this construction method and the structure after construction, the present invention can effectively address the situation where the elevator pit is located on the pedestal, lower the elevation of the entire pedestal synchronously with the elevator pit, and design a structural cavity between the sunken pedestal and the basement floor, so as to achieve the purpose of reducing concrete waste and not increasing the load borne by the pile foundation. At the same time, in order to prevent groundwater infiltration around the cavity, retaining walls are added around the cavity. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic diagram of the specific steps of the method for constructing the cavity of the elevator pit structure of the pile cap raft foundation in the present invention;

[0040] Figure 2 It is a schematic diagram of the specific steps of the measurement and wire laying operation in the present invention;

[0041] Figure 3 It is a schematic diagram of specific steps of installing the box in the present invention. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. 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.

[0043] Example 1

[0044] See also Figure 1-3 , a pile cap raft foundation elevator pit structure cavity construction method, comprising the following steps:

[0045] S1: Structural cavity design;

[0046] S2: Carry out measurement and line laying operations;

[0047] S3: Carry out earth excavation;

[0048] S4: After the earthwork excavation is completed, waterproofing construction is carried out;

[0049] S5: After the waterproofing work is completed, the reinforcement work is carried out;

[0050] S6: Box making;

[0051] S7: Install the finished box on the prefabricated pad;

[0052] S8: When the box is installed, pour concrete in the structural cavity.

[0053] In S1, the position of the structural cavity design is the space between the top of the sunken pedestal and the bottom of the basement floor slab. Since the elevator shaft pit is designed to be above the pedestal, the elevation of the entire pedestal drops to a specified depth as the elevator shaft pit descends. A structural cavity is designed in the area from the top of part of the pedestal to the bottom of the basement floor slab. In order to prevent water seepage around the structural cavity, reinforced concrete retaining walls are added around the structural cavity.

[0054] In S1, the design logic of the structural cavity design is that the pile cap raft foundation, the raft slab on the upper part of the cap is counted as the cap and included in the cap height. Because the elevator shaft pit is on the cap, the entire cap is lowered in elevation. The building transfers the vertical load to the cap through the column, and the cap distributes the force to the pile foundation. Since the length, width and height of the cap are not changed, the bearing capacity of the foundation is not affected. The basement floor mainly bears the traffic load and resists the groundwater seepage pressure. Therefore, the structural cavity can be designed in the space from the top of the sinking cap to the bottom of the basement floor to achieve the purpose of reducing concrete waste and not increasing the load borne by the pile foundation.

[0055] In S3, during the earth excavation operation of the foundation and the elevator shaft pit, an appropriate excavator is selected for earth excavation, and the gray line is used for excavation during the excavation process. In the earth excavation process, the management personnel supervise the measurement of the elevation throughout the process, compare the profile diagram, and strictly control the height difference of the sub-platform. When the excavator digs to the target elevation of 1500mm-2500m, manual excavation is performed to avoid over-excavation. If local over-excavation occurs, the original soil is immediately backfilled and compacted. Finally, after the earth excavation is completed, brick formwork and plastering are immediately carried out to prevent sudden rain from soaking and soil collapse caused by rainwater soaking, and the cushion layer is poured in time to prevent rainwater from soaking the soil. If the soil self-stability is poor and the excavation depth is deep, inclined supports can be added to prevent soil collapse.

[0056] In the S4, the waterproof material for waterproof construction is SBS modified asphalt waterproofing membrane, and before the SBS modified asphalt waterproofing membrane waterproofing construction, the water at the bottom of the pit is removed, the bottom of the pit is dried and the base is cleaned, and then cold primer is sprayed to reduce the influence of floating dust and increase the bonding force. Secondly, in the waterproofing construction, the corner is first constructed, and the horizontal width of the corner additional layer is 230mm-270mm, and the vertical width is 230mm-270mm. After the corner construction is completed, the large surface is paved, and in the large surface paving process, the long side overlaps 100mm and the short side overlaps 150mm. At the same time, in the process of paving the SBS modified asphalt waterproofing membrane, first use a spray gun to fully heat the junction between the bottom surface of the membrane and the base, so that the asphalt on the bottom surface of the membrane is fully melted, and then when the SBS modified asphalt waterproofing membrane is heated to a suitable temperature, the membrane is rolled to make the membrane and the base bond firmly.

[0057] In S5, the steel bar construction requires the layout of the steel bar material and the guarantee of the anchorage length of the steel bar, as well as the layout material list obtained through the layout, to complete the processing of the steel bar. After the steel bar processing is completed, it is necessary to inspect it. Before the steel bar material is installed, the layout operation is carried out in advance to ensure the accuracy of the position. During the steel bar material binding operation, ensure that the spacing between the steel meshes meets the actual needs. At the same time, according to the requirements of the protective layer thickness of the water-facing surface and the water-back surface, select an appropriate protective layer to ensure the thickness of the steel bar protective layer.

[0058] In S6, the box is made of bamboo plywood, and the secondary ribs are arranged in a wooden structure and arranged horizontally, while the main ribs are arranged in a wooden structure and arranged vertically.

[0059] The thickness of the bamboo plywood is 15mm, and a plurality of holes are opened at equal intervals on the bottom. The diameter of the holes opened at the bottom end of the bamboo plywood is φ20, and the spacing between the holes is 450mm-500mm. Hoisting holes are opened on both sides of the bamboo plywood, and the diameter of the hoisting holes is φ30. The wooden square structure size used for the secondary ribs is 40mm*800mm, and the vertical spacing of the secondary ribs is 450mm-500mm. The wooden square structure size used for the main ribs is 40mm*800mm, and the horizontal spacing of the secondary ribs is 550mm-600mm.

[0060] In S7, before the box is installed, in order to ensure the thickness of the protective layer on the top surface of the pedestal below, prefabricated pads are placed on the top of the steel bars, and in order to prevent displacement during concrete pouring, wire binding is used to limit and fix the box. At the same time, in order to prevent the box from shifting during concrete pouring, after the box is installed and calibrated, prefabricated internal support bars are used around the box to tighten the four sides of the box to achieve a limiting effect.

[0061] In the above S8, fine stone concrete with a large slump of 180±20mm and good fluidity is used in the concrete pouring at the structure cavity. Because the quality of the concrete forming below the structure cavity cannot be checked later, the required volume of concrete below is calculated in advance before pouring the concrete, and the concrete volume must be sufficient during pouring. Put the concrete next to the retaining wall and vibrate it deeply into the bottom of the wall with a vibrating rod to ensure that the concrete is vibrated and compacted.

[0062] Example 2

[0063] See also Figure 2 , a pile cap raft foundation elevator pit structure cavity construction method, in said S2, the specific steps of measuring and setting out are:

[0064] S2.1: Substitute the basic plan layout into the general plan coordinates;

[0065] S2.2: Use mapping software to mark the coordinate points of the pedestal and elevator pit, input the coordinates into RTK, and release the coordinate points:

[0066] S2.3: Carry out the line-laying operation and reserve the position of the brick formwork during the line-laying operation.

[0067] Example 3

[0068] See also Figure 3 , a pile cap raft foundation elevator pit structure cavity construction method, in said S7, the specific steps of said box installation are:

[0069] S7.1: Make simple lifting lugs by bending the ends of the steel bars for lifting;

[0070] S7.2: During the lifting process, insert one side of the hook into the lifting hole;

[0071] S7.3: The hook on the other side is tied with wire and wire rope;

[0072] S7.4: Weld four steel bars to the main reinforcement of the pile foundation below the cap;

[0073] S7.5: Move the box into the structural cavity;

[0074] S7.6: Two bars are placed above the box and welded to the main reinforcement of the pile foundation below the cap.

[0075] In said S7.1, the angle of the bend at both ends of the steel bar is 125° to 135°.

[0076] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and alterations may be made to the embodiments without departing from the principles and spirit thereof, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for constructing a cavity of a pile cap raft foundation elevator pit structure, characterized in that: The following steps are involved: S1: Structural cavity design; S2: Carry out measurement and line laying operations; S3: Carry out earth excavation; S4: After the earthwork excavation is completed, waterproofing construction is carried out; S5: After the waterproofing work is completed, the reinforcement work is carried out; S6: Box making; S7: Install the finished box on the prefabricated pad; S8: When the box is installed, pour concrete in the structural cavity.

2. A pile cap raft foundation elevator pit structure cavity construction method according to claim 1, characterized in that: In S1, the position of the structural cavity design is the space between the top of the sunken pedestal and the bottom of the basement floor slab. Since the elevator shaft pit is designed to be above the pedestal, the elevation of the entire pedestal drops to a specified depth as the elevator shaft pit descends. A structural cavity is designed in the area from the top of part of the pedestal to the bottom of the basement floor slab. In order to prevent water seepage around the structural cavity, reinforced concrete retaining walls are added around the structural cavity.

3. The method for constructing a cavity of a pile cap raft foundation elevator pit structure according to claim 1, characterized in that: In S2, the specific steps of measuring and laying out are as follows: S2.1: Substitute the basic plan layout into the general plan coordinates; S2.2: Use mapping software to mark the coordinate points of the pedestal and elevator pit, input the coordinates into RTK, and release the coordinate points: S2.3: Carry out the line-laying operation and reserve the position of the brick formwork during the line-laying operation.

4. The method for constructing a cavity of a pile cap raft foundation elevator pit structure according to claim 1, characterized in that: In the S4, the waterproof material for waterproof construction is SBS modified asphalt waterproof membrane, and before the SBS modified asphalt waterproof membrane waterproof construction work, the water at the bottom of the pit is cleared, the bottom of the pit is dried in the sun and the base is cleaned, and then cold primer is sprayed to reduce the influence of floating dust and increase adhesion. Secondly, in the waterproof construction work, the corners are first constructed. The horizontal width of the corner additional layer is 230mm-270mm, and the vertical width is 230mm-270mm. After the corner construction work is completed, the large surface is paved, and during the large surface paving process, the long side overlaps 100mm and the short side overlaps 150mm.

5. The method for constructing a cavity of a pile cap raft foundation elevator pit structure according to claim 1, characterized in that: In S5, the steel bar construction requires the layout of the steel bar material and the guarantee of the anchorage length of the steel bar, as well as the layout material list obtained through the layout, to complete the processing of the steel bar. After the steel bar processing is completed, it is necessary to inspect it. Before the steel bar material is installed, the layout operation is carried out in advance to ensure the accuracy of the position. During the steel bar material binding operation, ensure that the spacing between the steel meshes meets the actual needs. At the same time, according to the requirements of the protective layer thickness of the water-facing surface and the water-back surface, select an appropriate protective layer to ensure the thickness of the steel bar protective layer.

6. The method for constructing a cavity of a pile cap raft foundation elevator pit structure according to claim 1, characterized in that: In S6, the box is made of bamboo plywood, and the secondary ribs are arranged in a wooden square structure and arranged horizontally, while the main ribs are arranged in a wooden square structure and arranged vertically.

7. The method for constructing a cavity of a pile cap raft foundation elevator pit structure according to claim 6, characterized in that: The thickness of the bamboo plywood is 15mm, and a plurality of holes are opened at equal intervals on the bottom. The diameter of the holes opened at the bottom end of the bamboo plywood is φ20, and the spacing between the holes is 450mm-500mm. Hoisting holes are opened on both sides of the bamboo plywood, and the diameter of the hoisting holes is φ30. The wooden square structure size used for the secondary ribs is 40mm*800mm, and the vertical spacing of the secondary ribs is 450mm-500mm. The wooden square structure size used for the main ribs is 40mm*800mm, and the horizontal spacing of the secondary ribs is 550mm-600mm.

8. The method for constructing a cavity of a pile cap raft foundation elevator pit structure according to claim 1, characterized in that: In S7, the specific steps of installing the box are: S7.1: Make simple lifting lugs by bending the ends of the steel bars for lifting; S7.2: During the lifting process, insert one side of the hook into the lifting hole; S7.3: The hook on the other side is tied with wire and wire rope; S7.4: Weld four steel bars to the main reinforcement of the pile foundation below the cap; S7.5: Move the box into the structural cavity; S7.6: Two bars are placed above the box and welded to the main reinforcement of the pile foundation below the cap.

9. The method for constructing a cavity of a pile cap raft foundation elevator pit structure according to claim 1, characterized in that: In S7, before the box is installed, in order to ensure the thickness of the protective layer on the top surface of the pedestal below, prefabricated pads are placed on the top of the steel bars, and in order to prevent displacement during concrete pouring, wire binding is used to limit and fix the box. At the same time, in order to prevent the box from shifting during concrete pouring, after the box is installed and calibrated, prefabricated internal support bars are used around the box to tighten the four sides of the box to achieve a limiting effect.

10. The method for constructing a cavity of a pile cap raft foundation elevator pit structure according to claim 1, characterized in that: In the above S8, fine stone concrete with a large slump of 180±20 mm and good fluidity is used in the concrete pouring at the structure cavity.

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