A method for constructing a basement in stages

Abstract

The present invention belongs to the technical field of underground structures. The present invention discloses a construction method for constructing a basement in stages. A first-stage basement is built, and then a second-stage basement is constructed and connected to the first-stage basement. While constructing the outer wall of the first stage, support columns are constructed according to the position of the second-stage internal support beams; formwork is supported and the retaining wall concrete is poured before backfilling the fat pocket; an additional pre-laid and self-adhered waterproof membrane is added at the junction of the first and second-stage basements; the external wall waterproofing at the junction of the first and second-stage basements uses a combination of polymer asphalt waterproof membrane and cement-based penetrating crystalline; the reserved joints of the horizontal steel bars at the junction of the first and second-stage basements use stainless steel anti-corrosion steel bars; the floor slab at the junction of the first and second-stage basements uses corrugated pipes embedded in the first-stage floor slab, and the prestressed joint of the floor slab directly installs prestressed tendons in the first stage; it is fixed to the civil air defense door frame through a civil air defense door frame U-shaped connector. The method of the present invention has the advantages of being simple and easy to implement.

Description

Technical Field

[0001] The present invention relates to the technical field of underground structures, and particularly relates to a construction method for constructing a basement in stages and phases. Background Art

[0002] The description of the background art in the present invention belongs to the related art related to the present invention, and is only used to illustrate and facilitate the understanding of the content of the present invention, and should not be construed as the applicant clearly believing or presuming that the applicant believes it is the prior art on the filing date of the first application of the present invention.

[0003] Although there are the above-mentioned advantages in constructing hospitals and schools in stages, there are many technical problems in constructing basements in stages. Generally speaking, there are the following points:

[0004] 1. The problem of foundation pit support conversion at the junction of the first and second stages

[0005] At present, the external wall of the basement in the first stage is usually used as the retaining wall for the foundation pit support in the second stage. However, since the external wall of the basement is used as the retaining wall for the foundation pit support, it will bear the huge earth pressure transmitted by the internal support. Therefore, the thickness and reinforcement of the external wall of the basement at the junction of the first and second stages need to be increased several times. On the one hand, this approach causes huge cost waste. On the other hand, due to the thickening of the wall, the usable area of the basement of the hospital and school decreases under the same floor area, further affecting the use function. At the same time, at present, the support problem at the first-stage cushion pit (the gap between the first-stage foundation pit support and the external wall of the basement in the first stage, generally 2m to 2.5m) is often overlooked in the phased construction of the basement foundation pit support. The cushion pit causes the second-stage foundation pit support not to form a closed loop. At present, the cushion pit is generally treated by backfilling soil and sloping. The disadvantages of this approach are: first, it is relatively dangerous. Without support, the backfilled soil in the first-stage cushion pit will gradually flow into the second stage. Second, the foundation pit support does not form a closed loop and lacks integrity, greatly reducing the foundation pit safety. Third, the backfilled soil at the sloping part needs to be backfilled again after the construction of the second-stage basement is completed, resulting in waste, soil loss and cost increase.

[0006] 2. The problem of waterproof jointing of the basement floor and external wall at the junction of the first and second stages

[0007] At present, when constructing the waterproofing of the basement floor in stages, the new material of polymer pre-laid and self-adhered technology is usually adopted. This material has the advantages that no waterproof protective layer is required and after pouring concrete, it will be tightly adhered to the concrete through the hydration heat reaction and form a whole. However, when using this material for the waterproofing of the basement floor in stages, the waterproofing of the first and second stages cannot be jointed, and the waterproofing of the first and second stage floors can never form a whole, and leakage and water seepage will occur at the junction of the first and second stages. At present, the general method is to plug the leakage points by post-grouting in the later stage, but this method cannot fundamentally solve the technical problem that the waterproofing of the basement floor in stages cannot be closed into a whole.

[0008] At present, when constructing the waterproofing of the basement exterior wall in stages, flexible waterproof coiled materials such as polymer asphalt waterproof coiled materials are usually used. Since the horizontal steel bars at the junction of the first and second stages of the basement need to reserve joints for the connection of the steel bars in the second stage during the staged construction of the basement, when encountering the reserved steel bars between layers, the flexible waterproof coiled materials such as polymer asphalt waterproof coiled materials will be punctured by the steel bars and cannot achieve the waterproof effect of the exterior wall. There may be a leakage point at each steel bar. At present, the general method is to plug the leakage points by post-grouting in the later stage, but this method cannot fundamentally solve the technical problem that the waterproofing of the basement exterior wall in stages cannot be closed into a whole.

[0009] 3. Anti-corrosion protection problem of the reserved joints of the horizontal steel bars of the beams, slabs and walls at the junction of the first and second stages

[0010] At present, the reserved joints of the horizontal steel bars of the beams, slabs and walls at the junction of the first and second stages are usually wrapped and protected with C15 concrete. The first disadvantage of this method is that the construction difficulty is extremely high. It is necessary to backfill and tamp one layer at a time, and then support the formwork to pour C15 concrete for protection. The working time of workers in the confined space of the backfill trench is greatly increased, and the corresponding safety risks also increase. Second, due to the obstruction of the reserved joints of the horizontal steel bars of the beams, slabs and walls layer by layer, the chutes for the backfill soil cannot be installed, and the backfill soil will be directly poured from the top plate, which will cause great damage to the waterproofing of the exterior wall. Third, a large amount of manpower is required to break the C15 concrete during the construction of the second stage, resulting in huge material and resource waste.

[0011] 4. Treatment problem of the prestressed joints of the basement floor and floor slabs at the junction of the first and second stages

[0012] At present, especially in large public hospitals and schools, in order to prevent the concrete from cracking due to temperature stress in the basement floor slab and roof slab, prestress is usually added in the basement floor slab and roof slab. For the construction joint at the junction of the first and second phases, prestress is even more needed to reduce cracking. At present, it is usually adopted that some prestressed tendons connected to the second-phase part are bent into coils and left in the fat groove. During the construction of the second phase, the reserved prestress is installed into the floor slab or roof slab. The first disadvantage of this method is that it is easy to be damaged during the backfilling process, and some steel strands cannot meet the design requirements during the second phase; the second disadvantage is that it is not applicable to the slow-bonded prestressed tendons, because generally the longest time of the slow-bonded prestressed tendons is 240 days. If the tendons are not tensioned after 240 days, the slow-bonded prestressed tendons cannot be used continuously.

[0013] 5. Waterproofing at the civil air defense door frame at the junction of the first and second phases, plugging inside the first-phase door frame, and the problem of removing the plugging of the second-phase door frame

[0014] At present, civil air defense is designed in the basement. Due to the special technological requirement of integral pouring for civil air defense, when there is a civil air defense door frame on the external wall of the first-phase basement civil air defense, if the civil air defense door frame is not installed in the first phase, the concrete at the door frame will be broken in the second phase and then the civil air defense door frame will be installed. This method will result in relatively weak concrete at the civil air defense door frame and may not pass the acceptance; if the civil air defense door frame is installed in the first phase, the steel bars of the external wall of the civil air defense will be cut off by the door frame, and the stiffness of the external wall of the first phase cannot be guaranteed, and it may be squeezed and cracked by the huge earth pressure. At present, it is usually adopted that the external wall of the first-phase basement is constructed normally without installing the civil air defense door frame. During the construction of the second phase, a 500-mm range outside the civil air defense door frame is cut off with a rope saw, and then the civil air defense door frame is installed and concrete is poured. Summary of the Invention

[0015] The purpose of the embodiment of the present invention is to provide a construction method for a basement constructed in stages. The method of the present invention solves technical problems such as the conversion of foundation pit support at the junction of the first and second phases, the waterproof joint of the basement floor slab and external wall, the anti-corrosion protection of the reserved joints of the horizontal steel bars of beams, slabs, and walls, the treatment of the prestress joints of the floor slab and floor, the waterproofing at the civil air defense door frame, the plugging inside the first-phase door frame, and the problem of removing the plugging of the second-phase door frame.

[0016] The purpose of the embodiment of the present invention is achieved through the following technical solutions:

[0017] A construction method for a basement constructed in stages and phases, which constructs the first-phase basement and then constructs the second-phase basement to connect with the first-phase basement; during the construction of the external wall of the first phase, the support columns are constructed according to the position of the second-phase internal support beams, and the horizontal steel bars of the retaining wall are reserved from the external wall of the first phase, and the other end of the horizontal steel bars is connected to the anchor piles of the first-phase foundation pit support through chemical anchoring;

[0018] Before backfilling the fat groove, formwork is supported and the retaining wall concrete is poured;

[0019] An additional pre-laid and self-adhered waterproofing membrane is added on top of the original pre-laid and self-adhered waterproofing membrane at the junction of the first-phase basement and the second-phase basement.

[0020] For the external wall waterproofing at the reserved joints of the horizontal steel bars of the beams, slabs, and walls at the junction of the first-phase basement and the second-phase basement, a combination of polymer modified asphalt waterproofing membrane and cementitious capillary crystalline waterproofing material is adopted.

[0021] Stainless steel anti-corrosion steel bars are used for the reserved joints of the horizontal steel bars of the beams, slabs, and walls at the junction of the first-phase basement and the second-phase basement.

[0022] For the treatment of the prestressed joints of the basement floor at the junction of the first-phase basement and the second-phase basement, corrugated pipes are embedded in the first-phase basement floor. For the treatment of the prestressed joints of the floor slab at the junction of the first-phase basement and the second-phase basement, prestressed tendons are directly installed in the first phase.

[0023] At the junction of the first-phase basement and the second-phase basement, it is fixed to the air defense door frame through the U-shaped connector of the air defense door frame.

[0024] Furthermore, for stainless steel anti-corrosion steel bars with a diameter greater than or equal to 18mm, threading is carried out in advance and protective caps are installed. In the second phase, they are connected by 100% straight thread grade I joints. For stainless steel anti-corrosion steel bars with a diameter of 16mm and below, the steel bars are reserved inside the foundation pit retaining piles of the first phase, and then 100% lap welding is adopted in the second phase, with a welding length of 12d.

[0025] Furthermore, during the construction of the second phase, the prestressed tendons are passed through the embedded corrugated pipes. After the concrete construction of the second phase is completed and the concrete strength reaches 75%, tensioning is carried out, and then the corrugated pipes are blocked.

[0026] The prestressed tendons extend out of the external wall and are reserved to a length of not less than 150mm in the second phase, and then are connected to the prestressed tendons of the second phase through prestressed tendon connectors.

[0027] Furthermore, steel bar couplers are welded on the U-shaped connector of the air defense door frame according to the spacing of the horizontal steel bars of the external wall. The steel bar couplers are connected to the horizontal steel bars of the external wall by straight threads, and then formwork is set up to pour the concrete in the shaded parts inside the external wall and the air defense door frame.

[0028] Furthermore, the side height of the additional pre-laid and self-adhered waterproofing membrane is the same as the thickness of the basement floor slab. The lower end extends 2m towards the first-phase basement floor slab, and a layer of cementitious capillary crystalline waterproofing material is applied at the end of the additional pre-laid and self-adhered waterproofing membrane.

[0029] Furthermore, for the horizontal steel bars of beams, slabs, and walls at the junction of the first and second phases, joints need to be reserved. Cementitious capillary crystalline is applied, and the application range is 250 mm above and below the joints reserved for the horizontal steel bars of beams, slabs, and walls at the junction of the first and second phases. At the junction of each layer of polymer modified bitumen waterproofing membrane and the cementitious capillary crystalline, stainless steel pressure bars are nailed to prevent the polymer modified bitumen waterproofing membrane from moving downwards.

[0030] Furthermore, the prestressing tendon connector consists of wedge-shaped anchors, circlips, anchor rings, and joints.

[0031] Furthermore, the civil air defense doorframe U-shaped connector is cold-connected to the civil air defense doorframe by rotating the hexagonal bolt. Rebar couplers are welded on the civil air defense doorframe U-shaped connector according to the spacing of the exterior wall horizontal steel bars, and the rebar couplers are connected to the exterior wall horizontal steel bars by straight threads.

[0032] Furthermore, during the second construction phase, the concrete in the shaded part inside the civil air defense doorframe is cut off by a wire saw. There is a gap reserved between the civil air defense doorframe and the civil air defense doorframe U-shaped connector, so the civil air defense doorframe will not be damaged during the wire saw cutting process.

[0033] The embodiments of the present invention have the following beneficial effects:

[0034] The method of the present invention solves the problem of foundation pit support conversion at the junction of the first and second phases by setting support columns instead of doubling the thickness and steel reinforcement of the basement exterior wall at the junction of the first and second phases; solves the problem of waterproof jointing of the basement floor and exterior wall at the junction of the first and second phases by adding an additional pre-laid and self-adhered waterproofing membrane on top of the original pre-laid and self-adhered waterproofing membrane at the junction of the first and second phases; solves the problem of anti-corrosion protection of the reserved joints of the horizontal steel bars of beams, slabs, and walls at the junction of the first and second phases by using new material stainless steel anti-corrosion steel bars for the reserved joints of the horizontal steel bars; solves the problem of prestressing joint treatment of the floor slab at the junction of the first and second phases by embedding corrugated pipes in the first-phase floor slab and directly installing prestressing tendons in the first phase; solves the problems of waterproofing at the civil air defense doorframe at the junction of the first and second phases, plugging inside the first-phase doorframe, and demolition of the plugging in the second-phase doorframe through a special civil air defense doorframe U-shaped connector. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic plan view of the foundation pit support conversion at the junction of the first and second phases in the embodiment of the present invention;

[0036] Figure 2 It is a schematic sectional view of the support column and the internal support beam in the embodiment of the present invention ( Figure 1 sectional view taken along line 1-1);

[0037] Figure 3Schematic diagram of the connection between the retaining wall, the first-stage foundation pit support, and the first-stage exterior wall in the embodiment of the present invention ( Figure 1 Cross-sectional view taken along line 2-2);

[0038] Figure 4 Schematic diagram of partial demolition of the support columns in the embodiment of the present invention;

[0039] Figure 5 Schematic diagram of waterproof construction of the first-stage floor slab in the embodiment of the present invention;

[0040] Figure 6 Schematic diagram of waterproof construction of the second-stage floor slab in the embodiment of the present invention;

[0041] Figure 7 Schematic diagram of waterproof construction of the exterior wall at the joint of the horizontal steel bars of the beam, slab, and wall at the first and second stages in the embodiment of the present invention;

[0042] Figure 8 Schematic diagram of the treatment of the prestressed joints of the floor slab and the floor at the joint of the first and second stages in the embodiment of the present invention;

[0043] Figure 9 Schematic diagram of the connector in the embodiment of the present invention;

[0044] Figure 10 Schematic diagram of the construction at the civil air defense door frame at the joint of the first and second stages in the embodiment of the present invention. Detailed implementation manners

[0045] The present application will be further introduced below in conjunction with the embodiments.

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, in the following description, different "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. Different embodiments can be replaced or combined. For those of ordinary skill in the art, without creative efforts, other implementation manners can also be obtained based on these embodiments.

[0047] A construction method for a basement constructed in stages, in combination with the attached Figure 1-10 , construct the first-stage basement, and then connect the second-stage basement to the first-stage basement; while constructing the first-stage exterior wall 5, construct the support columns 1 according to the position of the second-stage internal support beam 6, and reserve the horizontal steel bars 8 of the retaining wall 7 from the first-stage exterior wall 5. The other end of the horizontal steel bars 8 is connected to the anchor piles 3 of the first-stage foundation pit support through chemical anchoring;

[0048] Before backfilling the side trench, formwork and pour the concrete of the retaining wall 7;

[0049] An additional pre-laid and self-adhered waterproofing membrane 102 is added on top of the original pre-laid and self-adhered waterproofing membrane 101 at the junction of the first-phase basement and the second-phase basement;

[0050] For the waterproofing of the horizontal steel bar reserved joints 16 of the beams, slabs and walls at the junction of the first-phase basement and the second-phase basement, a combination of a polymer modified asphalt waterproofing membrane 15 and a cementitious capillary crystalline waterproofing material 103 is adopted ( Figure 5 In the figure, reference numeral 14 is the floor slab of the adjacent second-phase basement);

[0051] The horizontal steel bar reserved joints 16 of the beams, slabs and walls at the junction of the first-phase basement and the second-phase basement are made of stainless steel anti-corrosion steel bars;

[0052] For the treatment of the prestressed joint at the bottom slab at the junction of the first-phase basement and the second-phase basement, a corrugated pipe 18 is embedded in the first-phase bottom slab 9. For the treatment of the prestressed joint at the floor slab at the junction of the first-phase basement and the second-phase basement, prestressed steel bars 19 are directly installed in the first-phase;

[0053] At the junction of the first-phase basement and the second-phase basement, it is fixed to the air defense door frame through the air defense door frame U-shaped connector 21.

[0054] In order to solve the problem of the foundation pit support conversion at the junction of the first and second stages, in some embodiments of the present invention, at the part with an internal support beam, a support column 1 is provided to replace the traditional method of doubling the thickness and reinforcement of the basement exterior wall at the junction of the first and second stages. The cross-sectional size of the support pile 1 is 1400*1800, and the reinforcement is 36C32+34C20 (the cross-section and reinforcement of the support column 1 can be adjusted according to the depth of the foundation pit, and the reinforcement noted in the present invention is applicable to a three-story basement). For the case where there is no support at the first-stage backfill trench, a reinforced concrete retaining wall 7 is added. The retaining wall 7 is connected to the first-stage basement exterior wall 5 and the first-stage foundation pit support pile 3 through steel bars to form a closed second-stage foundation pit. The specific method is as follows: While constructing the first-stage exterior wall 5, construct the support column 1 according to the position of the second-stage internal support beam 6, and reserve the horizontal steel bars 8 of the retaining wall 7 from the first-stage exterior wall 5. The other end of the horizontal steel bars 8 is connected to the first-stage foundation pit support pile 3 through chemical anchoring, and the concrete of the retaining wall 7 is poured by formwork before the backfill trench is backfilled. During the construction of the second-stage foundation pit, first demolish all the first-stage foundation pit support piles, and then fix one end of the internal support beam 6 at the position of the second-stage foundation pit support pile 4 according to the design drawing, and the other end is fixed on the first-stage exterior wall 5. The position of the internal support beam 6 just abuts on the support column 1. After the construction of the second-stage basement main structure is completed, since the cross-sectional size of the support column 1 is too large, the support column 1 needs to be cut. If there is only the exterior wall 5 at the position of the support column 1, use a wire saw to cut off the part of the support column 1 protruding from the exterior wall 5; if the position of the support column 1 conflicts with the exterior wall buttress column 13, use a wire saw to cut off the part of the support column 1 protruding from the exterior wall 5 and the exterior wall buttress column 13 to ensure the use function of the basement ( Figure 4 In the figure, the reference numerals 11 and 13 are the reserved parts of the support column, and the reference numeral 12 is the cut-off part of the support column 1).

[0055] In order to better solve the problem of the waterproof joint of the basement floor slab and the external wall at the junction of the first and second stages, in some other embodiments of the present invention, an additional pre-laid and self-adhered waterproof coiled material 102 is added on top of the original pre-laid and self-adhered waterproof coiled material 101 at the junction of the first and second stages. The side height of the additional pre-laid and self-adhered waterproof coiled material 102 is the same as the thickness of the basement floor slab 9, and the lower end extends 2 m towards the basement floor slab 9 of the first stage. A cementitious capillary crystalline 103 is applied at the end of the additional pre-laid and self-adhered waterproof coiled material 102. The additional pre-laid and self-adhered waterproof coiled material 102 is bonded to the basement floor slab 9 of the first stage through a hydration heat reaction to form a whole. On the other hand, the additional pre-laid and self-adhered waterproof coiled material 102 protects the original pre-laid and self-adhered waterproof coiled material 101. During the waterproof construction of the second-stage floor slab, the reserved original pre-laid and self-adhered waterproof coiled material 101 is laid flat at the second-stage floor slab as the waterproof joint of the second-stage floor slab. Then, the additional pre-laid and self-adhered waterproof coiled material 102 that has been bonded to the basement floor slab 9 of the first stage through a hydration heat reaction is removed from the side of the basement floor slab 9, simultaneously achieving the effect of roughening the joint between the new and old concretes, so as to ensure the overall closure of the waterproofing of the basement floor slab at the first and second stages.

[0056] For the horizontal steel bars of the beams, slabs, and walls at the junction of the first and second stages, 16 joints need to be reserved. For the external wall waterproofing, a new waterproof method combining a polymer-modified asphalt waterproof coiled material 15 and a cementitious capillary crystalline 103 is adopted. For the 16 joints that need to be reserved for the horizontal steel bars of the beams, slabs, and walls at the junction of the first and second stages, the cementitious capillary crystalline 103 is applied, and the application range is 250 mm above and below each of the 16 joints that need to be reserved for the horizontal steel bars of the beams, slabs, and walls at the junction of the first and second stages. Due to the fault phenomenon of the lower waterproof coiled layer, in order to prevent the polymer-modified asphalt waterproof coiled material 15 from moving downward due to friction during the backfilling process and causing quality hazards, a stainless steel pressing strip is also required at the closing of each layer of the polymer-modified asphalt waterproof coiled material 15 and the cementitious capillary crystalline 103 to prevent the polymer-modified asphalt waterproof coiled material 15 from moving downward.

[0057] In order to better solve the problem of anti-corrosion protection for the reserved joints of horizontal steel bars in beams, slabs and walls at the junction of the first and second stages, in some embodiments of the present invention, for the horizontal steel bars in beams, slabs and walls at the junction of the first and second stages where reserved joints 16 are required, new material stainless steel anti-corrosion steel bars are used. On the premise of meeting all the mechanical properties of steel bars with the same diameter, the stainless steel anti-corrosion steel bars also have the property of anti-corrosion. For steel bars with a diameter greater than or equal to 18 mm, thread cutting is carried out in advance and a protective cap is provided, and 100% connection is achieved through straight thread grade I joints in the second stage; for steel bars with a diameter of 16 mm and below, the steel bars are reserved to the inner side of the foundation pit support piles 3 in the first stage, and then 100% lap welding is adopted in the second stage, and the welding length is 12d. Since the reserved steel bars are too dense, it is impossible to implement the backfilling of cement stone powder with ordinary chutes or tremies. In order to avoid damage to the reserved joints 16 of the horizontal steel bars in beams, slabs and walls at the junction of the first and second stages during the backfilling process, the present invention uses fluidized solidified soil for backfilling the fat groove. Although this process is a new process, the technology is relatively mature, so it will not be elaborated in the present invention and is not within the protection scope of the present invention.

[0058] In order to further better solve the problem of prestressed joint treatment for the floor slab and the bottom slab at the junction of the first and second stages, in some other embodiments of the present invention, for the prestressed joint treatment of the bottom slab at the junction of the first and second stages, a corrugated pipe 18 is embedded in the bottom slab 9 in the first stage. The oval outer diameter of the corrugated pipe 18 is 76*22. Both ends of the corrugated pipe are tightly plugged with rubber plugs and sealed with tape to prevent concrete from entering the corrugated pipe. During the construction of the second stage, the prestressed tendon is passed through the embedded corrugated pipe 18, and tensioning is carried out after the concrete construction of the second stage is completed and the concrete strength reaches 75%, and then the corrugated pipe 18 is sealed immediately.

[0059] In some embodiments, for the prestressed joint treatment of the floor slab at the junction of the first and second stages, since the thickness of the floor slab is generally 120 mm - 180 mm and the corrugated pipe cannot be embedded, the prestressed tendon 19 is directly installed in the first stage. The prestressed tendon 19 must extend out of the outer wall 5 and be reserved to the second stage with a length of not less than 150 mm, and then it is connected to the prestressed tendon in the second stage through the prestressed tendon connector 20. The prestressed tendon connector 20 is composed of a wedge 201, a snap ring 202, an anchor ring 203 and a joint 204.

[0060] In order to further and better solve the problems of waterproofing at the civil air defense door frame at the junction of the first and second stages, the plugging inside the first-stage door frame, and the removal of the plugging of the second-stage door frame. In some embodiments of the present invention, the special civil air defense door frame U-shaped connector 21 and the hexagon bolt 211 on the U-shaped connector 21 are fixed to the civil air defense door frame. By rotating the hexagon bolt 211, the civil air defense door frame U-shaped connector 21 can be cold-connected to the civil air defense door frame 24, rather than by welding, so as to avoid the change of the material properties of the civil air defense door frame due to excessive welding temperature. Reinforcement couplers 22 are welded on the civil air defense door frame U-shaped connector 21 according to the spacing of the horizontal steel bars 23 of the exterior wall 5. The reinforcement couplers 22 are connected to the horizontal steel bars 23 of the exterior wall 5 through straight threads. Then, formwork is set up and the concrete of the exterior wall 5 and the shaded part 25 inside the civil air defense door frame is poured. Since the concrete of the wall 5 and the shaded part 25 inside the civil air defense door frame is poured at the same time, there will be no water seepage phenomenon at the civil air defense door frame. During the construction of the second stage, it is only necessary to use a rope saw to cut the concrete of the shaded part 25 inside the civil air defense door frame. Moreover, since there is a gap reserved between the civil air defense door frame 24 and the civil air defense door frame U-shaped connector 21, the civil air defense door frame 24 will not be damaged during the rope saw cutting process.

[0061] It should be noted that the above embodiments can be freely combined according to needs. The above introduction is only the preferred embodiments of the present invention and is not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A construction method for building a basement in stages, which involves building a first-stage basement and then connecting it to a second-stage basement; characterized in that, while constructing the external wall (5) of the first stage, support columns (1) are constructed according to the position of the internal support beams (6) of the second stage, and horizontal reinforcement bars (8) of the retaining wall (7) are reserved from the external wall (5) of the first stage. The other end of the horizontal reinforcement bars (8) of the retaining wall (7) is connected to the foundation pit support piles (3) of the first stage through chemical anchoring. Before backfilling the side trench, formwork is supported and the concrete of the retaining wall (7) is poured. An additional pre-laid and self-adhered waterproof membrane (102) is added on top of the original pre-laid and self-adhered waterproof membrane (101) at the junction of the first-stage basement and the second-stage basement. At the reserved joint (16) of the horizontal reinforcement bars of the beams, slabs, and walls at the junction of the first-stage basement and the second-stage basement, the external wall waterproofing adopts a combination of polymer asphalt waterproof membrane (15) and cementitious capillary crystalline (103). The reserved joints (16) of the horizontal reinforcement bars of the beams, slabs, and walls at the junction of the first-stage basement and the second-stage basement use stainless steel anti-corrosion reinforcement bars. For the treatment of the prestressed joints at the bottom slab at the junction of the first-stage basement and the second-stage basement, corrugated pipes (18) are embedded in the bottom slab (9) of the first stage. For the treatment of the prestressed joints at the floor slab at the junction of the first-stage basement and the second-stage basement, prestressed tendons (19) are directly installed in the first stage. At the junction of the first-stage basement and the second-stage basement, it is fixed to the air defense door frame through the air defense door frame U-shaped connector (21).

2. The staged and phased construction method of a basement according to claim 1, characterized in that For stainless steel anti-corrosion reinforcement bars with a diameter greater than or equal to 18mm, thread cutting is carried out in advance and protective caps are put on. In the second stage, they are connected by 100% straight thread grade I joints. For stainless steel anti-corrosion reinforcement bars with a diameter of 16mm and below, the reinforcement bars are reserved to the inner side of the foundation pit support piles (3) of the first stage, and then in the second stage, 100% lap welding is adopted, and the welding length is 12d.

3. The staged and phased construction method of the basement according to claim 1, characterized in that, During the construction of the second stage, the prestressed tendons pass through the embedded corrugated pipes (18). After the concrete construction of the second stage is completed and the concrete strength reaches 75%, tensioning is carried out, and then the corrugated pipes (18) are blocked. The prestressed tendons (19) extend out of the external wall (5) and are reserved to a length of not less than 150mm in the second stage, and then are connected to the prestressed tendons of the second stage through the prestressed tendon connector (20).

4. The staged and phased construction method of the basement according to claim 1, characterized in that, On the air defense door frame U-shaped connector (21), reinforcement couplers (22) are welded according to the spacing of the horizontal reinforcement bars (23) of the external wall (5). The reinforcement couplers (22) are connected to the horizontal reinforcement bars (23) of the external wall (5) through straight threads. Then formwork is supported, and the concrete of the external wall (5) and the shaded part (25) inside the air defense door frame is poured.

5. The construction method of the basement with staged and phased construction according to claim 1, characterized in that, The side height of the additional pre-laid and self-adhered waterproof membrane (102) is the same as the thickness of the basement bottom slab (9), and the lower end extends 2m in the direction of the bottom slab (9) of the first-stage basement. A layer of cementitious capillary crystalline (103) is applied at the end of the additional pre-laid and self-adhered waterproof membrane (102).

6. The construction method of the basement constructed in installments and stages according to claim 1, characterized in that, For the horizontal steel bars of beams, slabs and walls at the junction of the first and second phases, joints (16) need to be reserved. Apply cementitious capillary crystalline (103) coating. The coating range is 250 mm above and below the joints (16) of the horizontal steel bars of beams, slabs and walls at the junction of the first and second phases. At the closing of each layer of polymer modified bitumen waterproofing membrane (15) and cementitious capillary crystalline (103), nail stainless steel pressing strips to prevent the polymer modified bitumen waterproofing membrane (15) from moving downwards.

7. The staged and phased basement construction method according to claim 3, characterized in that The prestressed tendon connector (20) described above consists of wedge grips (201), snap rings (202), anchor rings (203) and joints (204).

8. The construction method of the basement constructed in installments and in stages according to claim 4, characterized in that, Cold connect the civil air defense doorframe U-shaped connector (21) to the civil air defense doorframe (24) by rotating the hexagonal bolt (211). Weld the steel bar couplers (22) on the civil air defense doorframe U-shaped connector (21) according to the spacing of the horizontal steel bars (23) of the external wall (5). Connect the steel bar couplers (22) and the horizontal steel bars (23) of the external wall (5) by straight threads.

9. The construction method of the basement constructed in installments and stages according to claim 8, characterized in that, During the second construction phase, use a wire saw to cut the concrete of the shaded part (25) inside the civil air defense doorframe. There is a gap reserved between the civil air defense doorframe (24) and the civil air defense doorframe U-shaped connector (21). Therefore, the civil air defense doorframe (24) will not be damaged during the wire saw cutting process.

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