CN113832983A - Construction method for supporting foundation pit by adopting variable-cross-section underground continuous wall - Google Patents

Construction method for supporting foundation pit by adopting variable-cross-section underground continuous wall Download PDF

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Publication number
CN113832983A
CN113832983A CN202111068321.1A CN202111068321A CN113832983A CN 113832983 A CN113832983 A CN 113832983A CN 202111068321 A CN202111068321 A CN 202111068321A CN 113832983 A CN113832983 A CN 113832983A
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China
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section
underground continuous
continuous wall
foundation pit
reinforcement cage
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CN202111068321.1A
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Inventor
朱敏
冯东阳
陈涛
梅若非
夏磊
宋涛
茹文恺
孙盼
赵小虎
唐建一
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Changjiang Institute of Survey Planning Design and Research Co Ltd
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Changjiang Institute of Survey Planning Design and Research Co Ltd
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Priority to CN202111068321.1A priority Critical patent/CN113832983A/en
Publication of CN113832983A publication Critical patent/CN113832983A/en
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    • EFIXED CONSTRUCTIONS
    • E02HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02DFOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D17/00Excavations; Bordering of excavations; Making embankments
    • E02D17/02Foundation pits
    • E02D17/04Bordering surfacing or stiffening the sides of foundation pits
    • EFIXED CONSTRUCTIONS
    • E02HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02DFOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D5/00Bulkheads, piles, or other structural elements specially adapted to foundation engineering
    • E02D5/18Bulkheads or similar walls made solely of concrete in situ
    • EFIXED CONSTRUCTIONS
    • E02HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02DFOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D5/00Bulkheads, piles, or other structural elements specially adapted to foundation engineering
    • E02D5/18Bulkheads or similar walls made solely of concrete in situ
    • E02D5/187Bulkheads or similar walls made solely of concrete in situ the bulkheads or walls being made continuously, e.g. excavating and constructing bulkheads or walls in the same process, without joints

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  • Engineering & Computer Science (AREA)
  • Structural Engineering (AREA)
  • Mining & Mineral Resources (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Paleontology (AREA)
  • Civil Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Bulkheads Adapted To Foundation Construction (AREA)

Abstract

The invention discloses a construction method for supporting a foundation pit by adopting a variable-section underground continuous wall, which comprises the following steps of: s1, conducting guide wall construction, trenching, slurry wall protection and groove bottom hole cleaning in sequence according to construction requirements to obtain a constructed groove hole; s2, fixedly arranging a foam board on at least part of the upper section of the reinforcement cage of the prefabricated underground continuous wall, so that the section sizes of the reinforcement cage with the foam board are consistent in the width direction; s3, placing the reinforcement cage with the foam board into the slotted hole, then placing a guide pipe into the reinforcement cage, and injecting concrete into the slotted hole along the guide pipe until the underground continuous wall with the variable cross section is formed; s4, excavating a foundation pit to the section change position of the underground continuous wall, synchronously removing the foam boards, and then respectively pouring a crown beam and a structural top plate on the top of the underground continuous wall and the section change position until the construction is finished. The invention has the characteristics of simple process, small construction difficulty and small engineering investment, and is suitable for the engineering with compact site conditions and short construction period.

Description

Construction method for supporting foundation pit by adopting variable-cross-section underground continuous wall
Technical Field
The invention relates to the field of foundation pit excavation supporting engineering, in particular to a construction method for supporting a foundation pit by adopting a variable-section underground continuous wall.
Background
The underground continuous wall is a commonly used supporting structure in foundation pit engineering, under the condition of slurry wall protection, a long and narrow deep groove is dug on the ground, a reinforcement cage is hung after the groove is cleaned, underwater concrete is poured by using a conduit method to form a unit groove section, and the steps are carried out section by section in this way, and a continuous reinforced concrete wall is built underground.
At present, the common method for subway station construction in China comprises the following steps: open-cut method, cover-cut method and underground method. The four construction methods have the advantages and disadvantages of the applicable conditions, and are mainly determined according to the surrounding environment, geological conditions, construction period, construction cost, construction difficulty and the like of the station.
The enclosure system of the cover-excavation reverse construction method has the advantages of high rigidity, small deformation, high safety, small interference to ground functions, easiness in pipeline relocation, capability of greatly saving the mounting and dismounting of temporary support systems and the like, and the main defects of the construction method are that the process is complex, the construction period is long, and the enclosure system is preferentially selected in areas with high requirements on environmental civilization and deformation control, such as weak strata, central blocks, commercial and luxurious areas and the like.
The underground continuous wall is used as a supporting structure for cover-excavation reverse construction, and is preferably used as a supporting structure scheme by virtue of large rigidity and good water stopping under the geological conditions of soft stratum and high confined water.
The conventional construction method for the top plate of the cover-excavation top-down structure comprises three steps:
a. slope-laying excavation
When the site condition is wide, slope excavation can be carried out within the excavation depth range of the structural top plate (marked with the number 3), so that the structural top plate is lapped on the enclosing structure crown beam during construction of the structural top plate. The method has simple process, but has requirements on site conditions, large earth excavation backfill amount, moderate engineering investment and detailed figure 1 (a).
b. Additionally provided with an enclosure structure
When the field conditions are limited, slope releasing is not allowed, a row of drilled piles (reference number 4) can be additionally arranged on the outer side of the existing underground diaphragm wall, and a cantilever structure formed by the drilled piles keeps water and soil, so that the structural roof is lapped on the building envelope crown beam when the structural roof is constructed. The method has simple process, but needs to be additionally provided with a building envelope, and has high engineering investment, and the detailed process is shown in figure 1 (b).
c. Mortise enclosure structure
When the site condition is limited and the drilled pile is not allowed to be arranged, a certain range can be chiseled out from the inner side of the underground continuous wall within the height range of the structural top plate, so that the structural top plate is embedded and fixed on the underground continuous wall during the construction of the structural top plate, and a tongue-and-groove (reference number 5) structure is formed. The method has the advantages of complex process, high construction difficulty and small engineering investment, and is shown in figure 1 (c).
The conventional cover-excavation top-down construction process has advantages and disadvantages, so that a process which is simple, low in construction difficulty and low in engineering investment needs to be researched.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a construction method for supporting a foundation pit by adopting an underground continuous wall with a variable cross section. According to the invention, the section of the upper part of the underground continuous wall of the foundation pit supporting structure which is covered and dug in a reverse-working mode is filled with the foam board, the variable section is formed on the upper part of the underground continuous wall when underwater concrete is poured, and the structural top plate of the covering and digging reverse-working method is overlapped at the section change part, so that the 'one-wall dual-purpose' of the underground continuous wall is achieved, namely the underground continuous wall is used as a horizontal soil-retaining structure and a vertical top plate bearing structure, and the underground continuous wall has the characteristics of simple process, small construction difficulty and small engineering investment, and is suitable for engineering with compact site conditions and short construction period.
In order to solve the technical problems, the invention is realized by the following technical scheme:
a construction method for supporting a foundation pit by adopting an underground continuous wall with a variable cross section comprises the following steps:
s1, conducting guide wall construction, trenching, slurry wall protection and groove bottom hole cleaning in sequence according to construction requirements to obtain a constructed groove hole;
s2, fixedly arranging a foam board on at least part of the upper section of the reinforcement cage of the prefabricated underground continuous wall, so that the section sizes of the reinforcement cage with the foam board are consistent in the width direction;
s3, placing the reinforcement cage with the foam board into the slotted hole, then placing a guide pipe into the reinforcement cage, and injecting concrete into the slotted hole along the guide pipe until the underground continuous wall with the variable cross section is formed;
s4, excavating a foundation pit to the section change position of the underground continuous wall, synchronously removing the foam boards, and then respectively pouring a crown beam and a structural top plate on the top of the underground continuous wall and the section change position until the construction is finished.
Preferably, in step S2, a structural reinforcement is added to the reinforcement cage section corresponding to the foam board.
In order to meet the structural requirements of the upper underground continuous wall structure during the construction of the underground continuous wall crown beam, the structural steel bars are additionally arranged on the steel bar cage section corresponding to the foam board because the thickness of the variable cross-section at the upper part of the underground continuous wall is thinned, so that the integral stability and the rigidity requirements of the upper underground continuous wall structure are ensured.
It is further preferred that the construction rebar comprises vertical and horizontal rebars adjacent one side of the foam slab, the vertical and horizontal rebars being welded together.
The constructional steel bar is close to cystosepiment one side setting, can regard as the foundation structure of ligature cystosepiment, further reduces and pours the influence of in-process cystosepiment come-up to steel reinforcement cage structural stability at underground continuous wall. The vertical reinforcing steel bars and the horizontal reinforcing steel bars are welded together in a crossed manner, so that the integral stability and rigidity requirements of the upper underground continuous wall structure can be met.
Preferably, in step S2, the foam board is disposed in a range from a top of the reinforcement cage to a cross-sectional change of the reinforcement cage in a direction of the foundation pit. The foam board is arranged to help the upper part of one side of the underground continuous wall close to the foundation pit form a variable cross section.
It is further preferred that the foam boards are formed into blocks by splicing and bound to the reinforcement cage by using iron wires. The foam board is divided into a plurality of splicing blocks, so that constructors can conveniently use steel wire for binding, and meanwhile, later-stage dismantling is facilitated.
Preferably, in step S2, a plurality of positioning pads are welded to both sides of the reinforcement cage in the length direction, and the positioning pads are longitudinally spaced. The thickness of the reinforcing steel bar protection layer can be ensured by the arrangement of the positioning blocks.
Preferably, in the step S2, the top of the reinforcement cage is filled with a foam board in the width direction. The requirement that the top of the underground continuous wall needs to be provided with a groove to pass through a drainage pipeline can be met, and the reinforced concrete structure is prevented from being broken in the later period of manpower.
Preferably, in step S3, the concrete is poured at a higher speed, so that the sediment at the bottom of the groove rises along with the surface of the concrete, and the concrete is poured slowly when the top height of the concrete is close to the foam board. The speed is fast when the concrete is poured just beginning, so that the sediment at the bottom of the groove rises along with the surface of the concrete, and when the top elevation of the concrete is close to the foam board, the concrete is poured slowly to ensure that the concrete at the bottom of the foam board is poured compactly and prevent the concrete from rising underwater to influence the fixation of the foam board.
Preferably, in step S4, the foam board is manually broken during excavation of the foundation pit to be peeled off from the underground continuous wall.
Preferably, in step S4, the crown beam is cast before the structural roof is cast at the section change of the underground continuous wall. The crown beam is poured at the section change position of the underground continuous wall, so that the structural stability of the structural top plate and the section change position of the underground continuous wall can be further enhanced.
Compared with the prior art, the invention has the following advantages and beneficial effects:
the invention can form the underground continuous wall with the variable cross section by only binding the foam board which is easy to remove and has low cost on the upper part of the reinforcement cage, and can form the underground continuous wall with the variable cross section by one-step pouring, has simple process, small construction difficulty and small engineering investment (taking a ground continuous wall with a plane length of 6000mm, a thickness of 1200mm and a height of 4000mm as an example, when the set foam board is 500mm thick, one ground continuous wall can save the pouring and the removing of concrete by 12.0m3And 1.2 ten thousand yuan of engineering investment is saved).
The invention adopts the variable cross-section underground continuous wall which is formed by one-time pouring, can meet the conditions of constructing the crown beam and the structural top plate, simultaneously is used for preventing soil outside the foundation pit from entering the foundation pit, does not need to additionally build a building enclosure, and is suitable for the engineering with compact site conditions and short construction period (the dismantling time can be saved by 7 d).
The invention can fill the foam board in the width direction of the underground continuous wall, can meet the requirement that the top of the underground continuous wall needs to be provided with a groove to pass through a drainage pipeline, and avoids breaking the reinforced concrete structure in the later period of manpower.
Drawings
FIG. 1 is a schematic diagram of a conventional cover-excavation top-down construction in the background art, wherein (a) is a slope-making excavation structure, (b) is an additional enclosure, and (c) is a mortise enclosure;
FIG. 2 is a schematic diagram of an exemplary cross-sectional configuration of the present invention;
FIG. 3 is a schematic structural view of the underground diaphragm wall with the foam board of the present invention;
FIG. 4 is a sectional view taken along line A-A of FIG. 3;
FIG. 5 is a cross-sectional view taken along line B-B of FIG. 3;
FIG. 6 is a cross-sectional view taken along line C-C of FIG. 3;
FIG. 7 is a floor plan of the underground diaphragm wall and pipeline of the present invention;
FIG. 8 is a schematic view of the construction of the underground diaphragm wall and pipeline of the present invention in elevation.
Reference numerals: 1-underground diaphragm wall; 11-a reinforcement cage; 2-a crown beam; 3-a structural ceiling; 4-drilling a pile; 5-mortising; 6-foam board; 7-constructing a steel bar; 71-vertical reinforcing steel bars; 72-horizontal reinforcing steel bars; 8-a catheter; 9-pipeline.
Detailed Description
In order that those skilled in the art will better understand the technical solutions of the present invention, the following description of the preferred embodiments of the present invention is provided in conjunction with specific examples, but it should be understood that the drawings are for illustrative purposes only and should not be construed as limiting the patent; for the purpose of better illustrating the embodiments, certain features of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted. The positional relationships depicted in the drawings are for illustrative purposes only and are not to be construed as limiting the present patent.
The present invention will be further described with reference to the following examples and figures 2-8, but the invention is not limited thereto.
The embodiment provides a construction method for supporting a foundation pit by using an underground continuous wall with a variable cross section, which comprises the following steps:
firstly: and (4) conducting guide wall construction, trenching and excavating, slurry wall protection and cleaning holes at the bottom of the groove in sequence according to construction requirements to obtain the constructed groove holes.
The grooving technical parameters of the underground continuous wall are as follows:
1) in the excavation process of the groove section of the underground continuous wall 1, the groove is always filled with slurry to keep the groove wall stable; 2) the stability of the groove section excavation is enhanced, if the groove wall is seriously locally collapsed, the groove section excavation is backfilled in time and properly processed; 3) during construction, slurry leakage should be timely supplemented, and the required liquid level height is always kept. The quality of the slurry is checked regularly, and the index of the slurry is adjusted in time; 4) after the groove section is excavated, the groove position, the groove depth, the groove width and the groove wall verticality are checked, and the groove cleaning and slurry changing work can be carried out after the groove section is qualified; 5) the control of the final groove depth of the groove section meets the following requirements: a. the final groove depth of the groove section must ensure the design depth, and in the same groove section, the excavation depth of the groove bottom is consistent and kept flat; b. the excavation depth of the groove bottom of the underground continuous wall 1 of the extension section in the same groove section is consistent with that of the groove bottom of the first-stage groove section; 6) the length, thickness, inclination, etc. of the groove sections should meet the following requirements: a. the allowable deviation of the length of the groove section is +/-2.0 percent; b. the allowable deviation of the thickness of the groove section is +/-10 mm; c. the allowable deviation of the perpendicularity of the groove section is +/-1/300; d. the local projection of the wall surface is not more than 100 mm; e. the position deviation of the embedded part on the wall surface is not more than 100 mm; f. deviation of the center line of the wall top: less than or equal to 30 mm; g. the areas of the holes, exposed ribs and honeycombs are not more than 5% of the exposed area of the unit groove section; h. the joint of the groove sections has no mud inclusion and no water leakage; 7) and cleaning impurities such as sediments at the bottom of the tank after the tank digging is finished, wherein the specific gravity of the slurry within 500mm of the bottom of the tank is not more than 1.15 and the thickness of the sediments is not more than 100mm after the tank bottom is cleaned and the slurry is replaced for 1 hour.
Secondly, the method comprises the following steps: the foam plate 6 is fixedly arranged on at least part of the upper section of the reinforcement cage 11 of the prefabricated underground continuous wall 1, so that the section of the reinforcement cage 11 with the foam plate 6 is uniform in the width direction, as shown in fig. 3 to 6.
The arrangement range of the foam plate 6 is from the top of the reinforcement cage 11 close to the foundation pit direction to the section change position of the reinforcement cage 11. The foam plates 6 are spliced into blocks and bound on the reinforcement cage 11 by adopting iron wires. Because the density of the foam board 6 is small, the foam board 6 needs to be firmly bound to prevent the foam board 6 from floating upwards in the process of placing the reinforcement cage 11 downwards and pouring underwater concrete. The foam board 6 is directly stripped from the underground continuous wall 1 in a manual breaking mode during foundation pit excavation.
The reinforcement cage 11 is manufactured as follows:
1) the construction requirements of the structure of the upper underground continuous wall 1 are met when the crown beam 2 of the underground continuous wall 1 is constructed. And a construction steel bar 7 is additionally arranged on the section of the steel bar cage 11 corresponding to the foam board 6, the construction steel bar 7 comprises a vertical reinforcing steel bar 71 and a horizontal reinforcing steel bar 72 which are adjacent to one side of the foam board 6, and the vertical reinforcing steel bar 71 and the horizontal reinforcing steel bar 72 are welded together.
2) The main reinforcement of the reinforcement cage 11 should be welded or mechanically connected, the number of joints in the same connection section should not be greater than 50%, and the joints should be placed at positions with small stress as much as possible. The intersection points of the longitudinal and transverse steel bar trusses and the steel bar cage 11 are all spot-welded, and the intersection points of the main bars and the distribution bars can be spot-welded at intervals. The reinforcement cages 11 of the unit groove sections of the underground continuous wall 1 are preferably assembled into a whole; when the segments are required to be segmented, mechanical connection is adopted, and joints are staggered with each other.
3) In order to ensure the thickness of the steel bar protection layer, positioning blocks are welded on two sides of the steel bar cage 11, two rows are arranged on each side of the steel bar cage 11 in the width direction, and the longitudinal distance between every two positioning blocks is 4 m.
And furthermore: and (3) lowering the reinforcement cage 11 with the foam plates 6 into the slotted hole, then placing the guide pipe 8 into the reinforcement cage 11, and injecting concrete into the slotted hole along the guide pipe 8 until the underground continuous wall 1 with the variable cross section is formed. In order to smoothly pour the underwater concrete, the arrangement of the guide pipe 8 needs to be adjusted to the middle of the variable cross section of the underground continuous wall 1, as shown in fig. 4.
Hoisting and embedding embedded parts of the steel reinforcement cage 11:
1) when the steel reinforcement cage 11 is put into the groove to the designed elevation, the channel steel penetrates into the suspension loop at the upper end of the vertical truss of the steel reinforcement cage 11 and is placed on the guide wall.
2) The manufacturing and hoisting deviation control requirements of the reinforcement cage 11 are as follows:
the distance deviation of the vertical main ribs is not more than 10mm, and the distance deviation of the horizontal main ribs is not more than 20 mm; the position deviation of the embedded part is not more than 10 mm; the central position of the steel reinforcement cage 11 hung in the groove is not more than 10 mm; the verticality of the steel reinforcement cage 11 in the hanging groove is not more than 2 per thousand; the elevation deviation of the steel reinforcement cage 11 in the hanging groove is not more than 10 mm.
Pouring concrete:
1) the diameter, the distance and the position of the concrete guide pipes 8 are staggered with respect to the plane of the foam plate 6.
2) The mixing proportion of the concrete meets the design strength requirement, and the concrete poured in the slurry by adopting the guide pipe 8 has good workability, large fluidity and delayed coagulation; the density difference between the concrete and the slurry is more than 1.1.
3) Before concrete pouring, the conduit 8 can be used for circulating the slurry for more than 15min so as to improve the quality of the slurry in the groove.
4) The concrete should begin to pour in the 11 inslots of steel reinforcement cage 6h, and speed will be fast when just beginning to pour, makes the tank bottom sediment rise along with the concrete surface together, treats when the top standard height of concrete closes on cystosepiment 6, should pour slowly to ensure that cystosepiment 6 bottom concrete placement is closely knit, and prevent that the rising of concrete under water from influencing cystosepiment 6's fixed.
In addition, the foam board 6 can be filled in the width direction of the top of the reinforcement cage 11, so that the requirement that a groove needs to be arranged at the top of the underground continuous wall 1 to penetrate through the drainage pipeline 9 can be met, and the reinforced concrete structure is prevented from being broken in a later period manually, as shown in fig. 7 and 8.
And finally: and excavating a foundation pit to the section change position of the underground continuous wall 1, synchronously removing the foam plate 6, then pouring the top beam 2 on the top of the underground continuous wall 1 and the section change position, and then pouring the structural top plate 3 on the top beam 2 at the section change position until the construction is finished. During the excavation of the foundation pit, the foam board 6 is directly stripped from the underground continuous wall 1 in a manual breaking mode, and the variable cross section of the underground continuous wall 1 forms a retaining structure, as shown in fig. 2.
The variable cross section at the upper part of the underground continuous wall 1 adopts a foam filling mode, when underwater concrete is poured, the variable cross section can be formed at the upper part of the underground continuous wall 1, and the change part of the cross section can be provided with a reinforced concrete crown beam 2 and a structural top plate 3 which is covered and excavated by a reverse method, so that the purpose of one wall and two purposes is achieved, and the condition that a support structure such as a bored pile 4, a steel sheet pile and the like is separately arranged outside the underground continuous wall 1 is avoided.
According to the description and the drawings of the invention, a person skilled in the art can easily manufacture or use the construction method for supporting the foundation pit by using the underground continuous wall with the variable cross section, and can generate the positive effects recorded by the invention.
Unless otherwise specified, in the present invention, if there is an orientation or positional relationship indicated by terms of "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., based on the orientation or positional relationship shown in the drawings, it is only for convenience of describing the present invention and simplifying the description, rather than to indicate or imply that the device or element so referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore, the terms describing orientation or positional relationship in the present invention are for illustrative purposes only, and should not be construed as limiting the present patent, specific meanings of the above terms can be understood by those of ordinary skill in the art in light of the specific circumstances in conjunction with the accompanying drawings. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated.
Unless expressly stated or limited otherwise, the terms "disposed," "connected," and "connected" are used broadly and encompass, for example, being fixedly connected, detachably connected, or integrally connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and all simple modifications and equivalent variations of the above embodiments according to the technical spirit of the present invention are included in the scope of the present invention.

Claims (10)

1. A construction method for supporting a foundation pit by using an underground continuous wall with a variable cross section is characterized by comprising the following steps:
s1, conducting guide wall construction, trenching, slurry wall protection and groove bottom hole cleaning in sequence according to construction requirements to obtain a constructed groove hole;
s2, fixedly arranging a foam plate (6) on at least part of the upper section of the reinforcement cage (11) of the prefabricated underground continuous wall (1), so that the section sizes of the reinforcement cage (11) with the foam plate (6) are consistent in the width direction;
s3, placing the reinforcement cage (11) with the foam plate (6) into the slot, then placing the guide pipe (8) into the reinforcement cage (11), and injecting concrete into the slot along the guide pipe (8) until the underground continuous wall (1) with the variable cross section is formed;
s4, excavating a foundation pit to the section change position of the underground continuous wall (1), synchronously removing the foam board (6), and then respectively pouring the top beam (2) and the structural top plate (3) at the top of the underground continuous wall (1) and the section change position until the construction is finished.
2. The construction method of the underground continuous wall supporting foundation pit with the variable cross section as claimed in claim 1, wherein: in the step S2, the structural steel bars (7) are additionally arranged on the section of the steel bar cage (11) corresponding to the foam board (6).
3. The construction method for supporting the foundation pit by using the variable cross-section underground continuous wall as claimed in claim 2, wherein: the construction steel bar (7) comprises a vertical reinforcing steel bar (71) and a horizontal reinforcing steel bar (72) which are close to one side of the foam board (6), and the vertical reinforcing steel bar (71) and the horizontal reinforcing steel bar (72) are welded together.
4. The construction method of the underground continuous wall supporting foundation pit with the variable cross section as claimed in claim 1, wherein: in the step S2, the arrangement range of the foam board (6) is from the top of the reinforcement cage (11) in the direction of the reinforcement cage (11) adjacent to the foundation pit to the section change position of the reinforcement cage.
5. The construction method of the underground continuous wall supporting foundation pit with the variable cross section as claimed in claim 4, wherein: the foam plates (6) are spliced into blocks and bound on the reinforcement cage (11) by adopting iron wires.
6. The construction method of the underground continuous wall supporting foundation pit with the variable cross section as claimed in claim 1, wherein: in the step S2, a plurality of positioning cushion blocks are welded on both sides of the reinforcement cage (11) in the length direction, and the positioning cushion blocks are longitudinally arranged at intervals.
7. The construction method of the underground continuous wall supporting foundation pit with the variable cross section as claimed in claim 1, wherein: in the step S2, the foam board (6) is filled in the top width direction of the reinforcement cage (11).
8. The construction method of the underground continuous wall supporting foundation pit with the variable cross section as claimed in claim 1, wherein: in the step S3, the speed is increased when the concrete is poured, so that the sediment at the bottom of the groove rises along with the surface of the concrete, and when the top height of the concrete is close to the foam board (6), the concrete is poured slowly.
9. The construction method of the underground continuous wall supporting foundation pit with the variable cross section as claimed in claim 1, wherein: in the step S4, the foam board (6) is peeled from the underground continuous wall (1) in a manual breaking mode during excavation of the foundation pit.
10. The construction method of the underground continuous wall supporting foundation pit with the variable cross section as claimed in claim 1, wherein: in the step S4, the crown beam (2) is poured at the section change position of the underground continuous wall (1) and then the structural top plate (3) is poured.
CN202111068321.1A 2021-09-13 2021-09-13 Construction method for supporting foundation pit by adopting variable-cross-section underground continuous wall Pending CN113832983A (en)

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