CN112832252B - Deep foundation pit supporting construction method with large height difference of two sides - Google Patents
Deep foundation pit supporting construction method with large height difference of two sides Download PDFInfo
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- CN112832252B CN112832252B CN202110015169.4A CN202110015169A CN112832252B CN 112832252 B CN112832252 B CN 112832252B CN 202110015169 A CN202110015169 A CN 202110015169A CN 112832252 B CN112832252 B CN 112832252B
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Abstract
The invention relates to the technical field of constructional engineering, and discloses a deep foundation pit supporting construction method with large height difference of two sides, which comprises the following steps: s01: constructing a filling pile, constructing a vertical column pile, excavating soil to a designed elevation according to a temporary excavation surface, and constructing a first inclined strut waist beam, a first support beam, a concrete panel and a first steel pipe inclined strut; s02: excavating earthwork under the first steel pipe inclined strut; s03: excavating layer by layer, constructing a second support beam, and excavating to the bottom of the pit; s04: constructing a bottom plate and a top plate, and dismantling the second support beam; s05: constructing a top plate layer, and removing a first support beam and a first steel pipe inclined strut; s06: constructing a layer of top plate again, and dismantling the upright post pile; and then, the construction of the top plate of the upper layer is carried out, and the construction of the basement structure is completed. The novel asymmetric supporting system adopts the inclined strut and the inner supporting beam to form an integral stress system, so that the shearing resistance and the bending resistance of the side wall protecting structure with higher terrain are obviously improved, and the construction cost is also saved.
Description
Technical Field
The invention relates to the technical field of constructional engineering, in particular to a deep foundation pit supporting construction method with large height difference of two sides.
Background
The deep foundation pit refers to an engineering with excavation depth of more than 5 meters (including 5 meters) or more than three layers (including three layers) of a basement, or a construction with excavation depth of less than 5 meters, but particularly complex geological conditions, surrounding environment and underground pipelines. The foundation pit engineering mainly comprises foundation pit supporting system design and construction and earthwork excavation, and is a system engineering with strong comprehensiveness. It requires close cooperation between geotechnical engineering and structural engineering technicians. The foundation pit supporting system is a temporary structure and is not needed after the construction of underground engineering is finished. The foundation pit engineering is to excavate an underground space from the ground downwards, and the periphery of a deep foundation pit is generally provided with a vertical soil retaining enclosure structure. The deep foundation pit support is a measure of supporting, reinforcing and protecting the side wall of the deep foundation pit and the surrounding environment in order to ensure the safety of the construction of an underground structure and the surrounding environment of the foundation pit.
At present, the commonly used deep foundation pit supporting structure mainly comprises a pile arrangement structure, a pile anchor structure, a double-row pile structure, a pile support structure and the like. In coastal cities with poor geological conditions, abundant underground water and dense buildings, a pile support supporting mode is generally selected when the excavation depth of a foundation pit exceeds 12 m. The pile supports are symmetrical supporting structures, and when the terrains on the two sides of the foundation pit are different and have large height difference, the arrangement of the pile supports is difficult.
As shown in fig. 1, it is a common deep foundation pit site and surrounding environment.
The first conventional supporting scheme is as follows: as shown in FIG. 2, the design scheme is based on the support elevation on the side with low terrain. According to the scheme, the cantilever of the grouting pile on the high side of the terrain is higher (the height is H), so that the displacement of the foundation pit on the side is overlarge. When the first support is removed, the height of the cantilever formed on the high side of the terrain is increased to H + S, and the height of the cantilever of the cast-in-place pile is the largest at the moment, as shown in FIG. 3.
And a second conventional supporting scheme: as shown in fig. 4, the support elevation on the low side of the terrain is increased, and the support structure on the low side of the terrain is raised above the ground surface. The supporting mode increases the amount of foundation pit supporting engineering, causes waste of certain resources and improves the engineering cost.
If the inner supports are arranged by taking one side with low terrain of the foundation pit as a reference, the side supporting structure with high terrain has a high cantilever, so that the cantilever pile on the side is over stressed and difficult to control deformation. Usually, in order to control the height of a cantilever of a cast-in-place pile in a high-terrain area, the deformation is prevented from being too large, the stress requirement of one side with high terrain is met, and one internal support needs to be arranged. Therefore, the elevation of the support at the lower side of the terrain needs to be properly increased, so that the cast-in-place piles and the inner supporting beams are higher than the external ground in the area with lower terrain, and the engineering quantity of the cast-in-place piles and the inner supports is increased. At present, the conventional internal bracing structure cannot take account of the problems of foundation pit stress and construction cost.
Disclosure of Invention
The invention aims to provide a deep foundation pit supporting construction method with large height difference of two sides, and aims to solve the problem that in the prior art, when the topography of two sides of a deep foundation pit is different and large height difference exists, the stress of a conventional internal bracing structure foundation pit is insufficient.
The invention is realized in this way, a deep foundation pit supporting construction method with large height difference at two sides comprises the following steps:
s01: constructing filling piles around a deep foundation pit, constructing a vertical column pile inside the deep foundation pit, excavating soil to a designed elevation according to a temporary excavation surface, arranging a first inclined support waist beam on the filling pile at the higher side of the deep foundation pit, constructing a first support beam above the vertical column pile, pouring a concrete panel above the first support beam, arranging a connecting part between the vertical column pile and the first support beam, and arranging a first steel pipe inclined support between the first inclined support waist beam and the connecting part;
s02: excavating earthwork under the first steel pipe inclined strut, and extending the first support beam to the cast-in-place pile on the higher side of the deep foundation pit;
s03: excavating layer by layer, constructing a second support beam, connecting the second support beam with the upright post pile, and excavating to the bottom of the pit;
s04: constructing a bottom plate at the bottom of the pit, constructing a top plate of the basement at the lowest layer, and removing the second support beam when the top plate reaches 100% strength;
s05: constructing a top plate of the penultimate basement, and removing the first supporting beam and the first steel pipe inclined strut when the top plate of the penultimate basement reaches 100% strength;
s06: constructing a top plate of the last but one layer of basement, and dismantling the upright post pile when the top plate of the last but one layer of basement reaches 100% strength; and then the construction of the top plate of the basement at the last fourth floor is carried out, and the construction of the basement structure is finished.
Further, in step S05, before the first supporting beam and the first steel pipe diagonal brace are removed, a second steel pipe diagonal brace is added to a connection position between a top plate of the penultimate basement and another upright post pile; then removing the first support beam and the first steel pipe diagonal brace;
and constructing a top plate of the upper layer of basement, and dismantling the second steel pipe inclined strut when the top plate of the upper layer of basement reaches 100% strength.
Furthermore, a second inclined support waist beam is arranged on the cast-in-place pile, one end of the second steel pipe inclined support is connected with the second inclined support waist beam, and the other end of the second steel pipe inclined support is connected to the top plate of the basement on the second layer from the bottom and the other connecting position of the upright post pile.
Further, in steps S03-S04, after the second support beam construction is completed, earth is excavated to a certain depth, and a third support beam is constructed, so that the third support beam is connected to the stud pile and the earth is excavated to the pit bottom;
constructing a bottom plate at the bottom of the pit, constructing a top plate of the basement at the lowest layer, and removing the third support beam when the top plate reaches 100% strength;
and continuously constructing a top plate of the upper layer of basement, and removing the second support beam after the top plate reaches 100% strength.
Further, in step S01, a third diagonal bracing wale is provided on the cast-in-place pile on the higher side of the deep foundation pit, the number of the upright piles is multiple, another connecting portion is provided between another upright pile and the first supporting beam, and a third steel pipe diagonal bracing is provided between the third diagonal bracing wale and the another connecting portion.
Further, in step S06, after the top plate of the penultimate basement reaches 100% strength, the top plate of the penultimate basement is constructed, and then the stud is removed; and then, the construction of the top plate of the basement at the first floor is carried out, and the construction of the basement structure is completed.
Furthermore, a side plate is arranged between each basement floor and close to the cast-in-place pile, and graded broken stones or medium coarse sand are backfilled between the cast-in-place pile and the side plate.
Furthermore, a steel plate is embedded in the first inclined strut waist beam, and the first steel pipe inclined strut is connected with the steel plate.
Furthermore, the connecting part is provided with an inclined plane, and the first steel pipe inclined strut is vertically arranged on the inclined plane.
Furthermore, a plurality of supporting blocks are arranged around the end part of the first steel pipe inclined strut, the supporting blocks are arranged in a right triangle shape, one right-angle side of each supporting block is connected with the outer side wall of the first steel pipe inclined strut, and the other right-angle side of each supporting block is connected with the end face of the first steel pipe inclined strut.
Compared with the prior art, the deep foundation pit supporting construction method with the large height difference of the two sides, provided by the invention, has the advantages that the first inclined-support waist beam is arranged on the cast-in-place pile at the higher side of the deep foundation pit, the first steel pipe inclined support is arranged between the first inclined-support waist beam and the first support beam, and the novel asymmetric supporting system can obviously improve the shearing resistance and bending resistance of the side-wall supporting structure with higher terrain by adopting the inclined support and the inner support beam to form an integral stress system. The problems that the pressure on two sides of the cast-in-place pile is unbalanced and deformation is large due to overhigh cantilever of the cast-in-place pile on the higher side of the ground in earth excavation are solved, and the problems that the cast-in-place pile cantilever is high when a supporting beam is disassembled and replaced can be effectively solved. On the other hand, due to the adoption of the mode of combining the inclined strut with the inner supporting beam, the supporting elevation on the low side of the ground potential of the deep foundation pit does not need to be increased, the cast-in-place pile and the inner supporting beam do not need to be higher than the outer bottom surface in the area with the low ground potential, the increase of the engineering quantity of the cast-in-place pile and the inner supporting beam is avoided, and the engineering cost is saved.
Drawings
FIG. 1 is a schematic cross-sectional view of a conventional deep foundation pit site and surrounding environment;
FIG. 2 is a schematic design diagram of a conventional supporting scheme based on the supporting elevation of the side with low terrain;
FIG. 3 is a schematic diagram of a conventional supporting scheme for dismantling a first inner support based on a side support elevation with low terrain
FIG. 4 is a schematic view of a design of a support elevation on one side with a low elevation of a conventional supporting scheme;
FIG. 5 is a schematic view of a deep foundation pit supporting construction method working condition 1 with a large height difference at two sides provided by the invention;
FIG. 6 is a schematic view of a deep foundation pit supporting construction method working condition 2 with a large height difference at two sides provided by the invention;
FIG. 7 is a schematic view of a deep foundation pit supporting construction method working condition 3 with a large height difference at two sides provided by the invention;
FIG. 8 is a schematic view of a deep foundation pit supporting construction method working condition 4 with a large height difference at two sides provided by the invention;
FIG. 9 is a schematic view of a deep foundation pit supporting construction method working condition 5 with a large height difference at two sides provided by the invention;
FIG. 10 is a schematic view of a deep foundation pit supporting construction method working condition 6 with a large height difference at two sides provided by the invention;
FIG. 11 is a schematic view of a deep foundation pit supporting construction method working condition 7 with a large height difference at two sides provided by the invention;
FIG. 12 is a schematic view of a steel pipe diagonal brace and the connection relationship thereof in the deep foundation pit supporting construction method with large height difference at two sides provided by the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The following describes the implementation of the present invention in detail with reference to specific embodiments.
The same or similar reference numerals in the drawings of the present embodiment correspond to the same or similar components; in the description of the present invention, it should be understood that if there is an orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", 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, but it is not intended to indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and are not to be construed as limiting the present patent, and the specific meaning of the terms may be understood by those skilled in the art according to specific circumstances.
Referring to fig. 5-12, preferred embodiments of the present invention are provided.
A deep foundation pit supporting construction method with large height difference of two sides comprises the following steps:
s01: constructing cast-in-place piles 10 around a deep foundation pit, constructing a vertical column pile 20 in the deep foundation pit, excavating soil to a designed elevation 60 according to a temporary excavation surface, arranging a first inclined support waist beam 31 on the cast-in-place pile 10 on the higher side of the deep foundation pit, constructing a first support beam 40 above the vertical column pile 20, pouring a concrete panel 50 above the first support beam 40, arranging a connecting part 41 between the vertical column pile 20 and the first support beam 40, and arranging a first steel pipe inclined support 30 between the first inclined support waist beam 31 and the connecting part 41;
s02: excavating earthwork below the first steel pipe inclined strut 30, and extending the first support beam 40 to the cast-in-place pile 10 at the higher side of the deep foundation pit;
s03: excavating layer by layer, constructing a second support beam 70, connecting the second support beam 70 with the upright post pile 20, and excavating to the bottom of the pit;
s04: constructing a bottom plate at the pit bottom, constructing a top plate of the basement at the lowest layer, and removing the second support beam 70 when the top plate reaches 100% strength;
s05: constructing a top plate of the penultimate basement, and removing the first supporting beam 40 and the first steel pipe inclined strut 30 after the top plate of the penultimate basement reaches 100% strength;
s06: constructing the top plate of the last but one layer of basement, and dismantling the upright post piles 20 when the top plate of the last but one layer of basement reaches 100% strength; and then the construction of the top plate of the basement at the last fourth floor is carried out, and the construction of the basement structure is finished.
According to the deep foundation pit supporting construction method with the large height difference of the two sides, the first inclined strut waist beam 31 is arranged on the cast-in-place pile 10 on the higher side of the deep foundation pit, the first steel pipe inclined strut 30 is arranged between the first inclined strut waist beam 31 and the first supporting beam 40, and the novel asymmetric supporting system can remarkably improve the shearing resistance and the bending resistance of the side wall protecting structure with the higher terrain by adopting an integral stress system formed by the inclined strut and the inner supporting beam. The problems that the pressure on two sides of the cast-in-place pile 10 on the higher side of the ground potential is unbalanced and the deformation is large due to overhigh cantilever in the earth excavation are solved, and the problems that the cast-in-place pile 10 cantilever is high and the like when a supporting beam is disassembled and replaced can be effectively solved. On the other hand, due to the adoption of the mode of combining the inclined strut and the inner supporting beam, the supporting elevation on the low side of the ground potential of the deep foundation pit does not need to be increased, the cast-in-place pile 10 and the inner supporting beam do not need to be higher than the outer bottom surface in the area with the low ground potential, the increase of the engineering quantity of the cast-in-place pile 10 and the inner supporting beam is avoided, and the engineering cost is saved.
In actual concrete engineering construction, the number of the basement includes four layers but is not limited to four layers.
In step S05, before the first supporting beam 40 and the first steel pipe diagonal brace 30 are removed, a second steel pipe diagonal brace 90 is added to the connecting position of the top plate of the penultimate basement and another upright post 20; specifically, a second inclined strut wale 91 is arranged on the cast-in-place pile 10, one end of the second steel pipe inclined strut 90 is connected with the second inclined strut wale 91, and the other end is connected to the connecting position of the top plate of the penultimate basement and the other upright post pile 20.
Then, removing the first support beam 40 and the first steel pipe diagonal brace 30;
and then constructing a top plate of the upper layer of basement, and dismantling the second steel pipe inclined strut 90 after the top plate of the upper layer of basement reaches 100% strength.
Before the first supporting beam 40 and the first steel pipe inclined strut 30 are dismantled, the newly-added second steel pipe inclined strut 90 continuously provides support for the cast-in-place pile 10 on the higher side of the deep foundation pit, and the situation that the deformation is large due to unbalanced stress on two sides of the cast-in-place pile 10 after the first supporting beam 40 and the first steel pipe inclined strut 30 are dismantled is avoided, so that the construction safety of the whole engineering is improved.
In steps S03-S04, after the second support beam 70 is constructed, earth is excavated to a certain depth, and a third support beam is constructed so that the third support beam is connected to the stud 20 and the earth is excavated to the pit bottom;
constructing a bottom plate at the pit bottom, constructing a top plate of the basement at the lowest layer, and removing a third supporting beam when the top plate reaches 100% strength;
and (5) continuing constructing the top plate of the basement on the upper layer, and removing the second support beam 70 when the strength of the top plate reaches 100%.
When the deep foundation pit is deep, a second supporting beam 70, a third supporting beam … … and an Nth supporting beam need to be arranged at different depths, and the N supporting beams and the plurality of upright posts 20 form an integral internal supporting structure, so that a multi-layer basement is conveniently built in the deep foundation pit.
In step S01, a plurality of steel pipe braces may be provided to sufficiently support the cast-in-place pile 10 at the higher side of the deep foundation pit. For example, a third diagonal brace wale is provided on the cast-in-place pile 10 on the higher side of the deep foundation pit, a plurality of upright piles 20 are provided, another connecting portion is provided between another upright pile 20 and the first support beam 40, and a third steel pipe diagonal brace is provided between the third diagonal brace wale and the other connecting portion.
When the first steel pipe inclined strut 30 and the third steel pipe inclined strut participate in supporting the cast-in-place pile 10 at the higher side of the deep foundation pit, the stress balance at the two sides of the cast-in-place pile 10 is easier to achieve. In this case, the angle between the first steel pipe diagonal brace 30 and the first support beam 40 is equal to or smaller than the angle between the third steel pipe diagonal brace and the first support beam 40, and the third diagonal brace waist beam is located above the first diagonal brace waist beam 31.
More steel pipe inclined struts can be arranged according to the requirements of actual situations.
In step S06, when the last but one floor of the basement roof reaches 100% strength, the construction of the last but one floor of the basement roof is performed, and then the stud 20 is removed; and then, the construction of the top plate of the basement at the first floor is carried out, and the construction of the basement structure is completed.
Under the condition that the stress condition of the cast-in-place pile 10 allows, before the upright post pile 20 is dismantled, the construction of two layers of basements is carried out, the arrangement of supporting beams is reduced, and the cost is saved.
The steel plate 311 is embedded in the end surface of the first inclined strut waist beam 31, and the first steel pipe inclined strut 30 is connected with the steel plate 311 by adopting the modes of bolt connection, welding, riveting and the like. The first steel pipe inclined strut 30 is connected with the steel plate 311, so that the joint is not easy to wear, and the connection reliability is enhanced.
The connection part 41 of the first steel pipe diagonal brace and the stud pile 20 has an inclined surface, and the first steel pipe diagonal brace 30 is arranged perpendicular to the inclined surface. The end face of the steel pipe inclined strut and the inclined face of the connecting portion 41 are more easily and stably connected and are not easy to slip. An extension part is formed at the part of the connecting part 41 deviating from the inclined surface, so that the conduction of the steel pipe inclined supporting force is better, and the connecting part 41 is not easy to be broken by force.
Be equipped with a plurality of supporting shoe 301 around the tip of the both ends of first steel pipe bracing 30, supporting shoe 301 is right triangle and arranges, and a right-angle side of supporting shoe 301 is connected with the lateral wall of first steel pipe bracing 30, and another right-angle side is connected with the terminal surface of first steel pipe bracing 30. Due to the action of the end supporting block 301, the end of the steel pipe diagonal brace has a stable structure and is not easy to deform under stress.
In a specific embodiment, a deep foundation pit supporting construction method with large height difference of two sides comprises the following steps:
s01: firstly constructing cast-in-place piles 10 around a deep foundation pit, constructing a plurality of upright piles 20 in the deep foundation pit, excavating soil to a designed elevation 60 according to a temporary excavation surface, arranging a first inclined support waist beam 31 on the cast-in-place pile 10 at the higher side of the deep foundation pit, constructing a first support beam 40 above the upright piles 20, pouring a concrete panel 50 with the thickness of 300mm above the first support beam 40, arranging a connecting part 41 between the upright piles 20 and the first support beam 40, and arranging a first steel pipe inclined support 30 between the first inclined support waist beam 31 and the connecting part 41.
The upright post 20 is a steel pipe concrete upright post, which has the properties of two materials, namely steel pipe and concrete, due to the structural characteristics. The outside parcel steel pipe material of tubular column promptly, the inside concrete material that fills of tubular column, because of the rigid restraint effect that the steel pipe wall formed to intraductal concrete, prevented the brittle failure of intraductal concrete. The steel pipe concrete column is mainly used as a building component of a pressure pipe column in the building engineering, and forms a frame structure system of a building together with a steel beam, a beam column node and the like.
In the construction process of the upright post pile 20, the bottom of the pile hole is arranged below the bottom of the basement, a sleeve can be arranged at the bottom of the pile hole, and the bottom of the upright post pile 20 is inserted into the sleeve for fixation, so that the fixation of the upright post pile is more stable, and the pile hole is not easy to be damaged or crushed; it is also much more convenient to extract the bottom of the post 20 from the sleeve when it is desired to remove the post 20.
A slope surface 61 of the temporary excavation surface is provided with a concrete protective surface sprayed with steel mesh, and the concrete protective surface is used as a supporting structure, for example, the slope surface 61 is hung with steel mesh phi 8@200 multiplied by 200, and the protective surface sprayed with C20 concrete with the thickness of 100 is used, so that potential safety hazards caused by slope surface 61 landslide are avoided.
The included angle between the first steel pipe inclined strut 30 and the first support beam 40 is an acute angle, preferably 27-31 °.
S02: and excavating earthwork below the first steel pipe inclined strut 30, extending the first support beam 40 to the cast-in-place pile 10 at the higher side of the deep foundation pit, and pouring a concrete panel 50 with the thickness of 300mm above the extended support beam.
The ends of the first support beams 40 are connected to the cast-in-place pile 10 by reinforced concrete, or connecting beams may be provided for connection.
S03: and excavating the soil layer by layer, and constructing a second support beam 70, so that the second support beam 70 is connected with the upright piles 20 and the soil is excavated to the bottom of the pit.
At this time, the first steel pipe diagonal bracing 30, the first support beam 40, the second support beam 70, the stud pile 20 and the like form a diagonal bracing and inner support beam system, so that the cast-in-place pile 10 at the higher side of the deep foundation pit is better supported.
S04: and constructing a bottom plate B4 at the pit bottom, constructing a top plate B3 of the lowest basement, and removing the second support beam 70 after the strength of the top plate B3 reaches 100%.
The joint of the bottom plate B4 of the pit bottom and the cast-in-place pile 10 is made of C20 concrete with the thickness of 1000mm and the strength grade of C20, and the concrete refers to: the standard cube compressive strength is 20MPa, namely 15MPa is more than or equal to fcu and less than 25 MPa. According to the relevant standards, the building material strength is uniformly expressed by the symbol "f". The concrete cube compressive strength is "fcu". Wherein "cu" means a cube.
The joint 83 between the top plate B3 of the basement at the lowest layer and the cast-in-place pile 10 is connected by C20 concrete, and the joint is 300mm higher than the top plate B3, so that the connection strength is enhanced, and the side plate 81 is prevented from falling to the outside.
Between the top plate B3 and the bottom plate B4 of the basement at the lowest layer and near the cast-in-place pile 10, a side plate 81 is arranged, wherein the side plate 81 is usually the outer wall of the basement and is built up layer by layer along with the basement; graded crushed stone or medium grit 82 is backfilled between the cast-in-place pile 10 and the side plate 81.
S05: constructing a top plate B2 of the penultimate basement, adding a second steel pipe inclined strut 90 to the top plate B2 of the penultimate basement and a pre-constructed upright post pile 20 when the strength of the top plate B2 of the penultimate basement reaches 100%, and then dismantling the first support beam 40, the first steel pipe inclined strut 30 and the first inclined strut waist beam 31;
when the top plate of each basement is constructed, C20 concrete is adopted to connect the joint 83 between the top plate of the basement and the cast-in-place pile 10, the joint is 300mm higher than the top plate, and the connecting strength is enhanced.
In the process of newly adding the second steel pipe diagonal brace 90, the second diagonal brace wale 91 is arranged above the first diagonal brace wale 31 of the cast-in-place pile 10, so that one end of the newly added second steel pipe diagonal brace 90 is connected with the second diagonal brace wale 91, the other end of the newly added second steel pipe diagonal brace 90 is connected with the connecting part 41 of the penultimate basement top plate B2 and the other upright post pile 20, and the cast-in-place pile 10 on the higher side of the deep foundation pit is supported. Holes are reserved in the concrete panel 50 with the thickness of 300mm in advance, and a second steel pipe inclined strut 90 is newly added to penetrate through the concrete panel 50.
S06: and constructing a top plate B1M of the last but one layer of basement, and removing the newly added second steel pipe inclined strut 90 and the second inclined strut waist beam 91 when the strength of the top plate B1M of the last but one layer of basement reaches 100%.
When a top plate B1M of a penultimate basement is constructed, holes need to be reserved for a newly added second steel pipe inclined strut 90; and when the newly added second steel pipe inclined strut 90 is detached, the reserved hole is plugged.
S07: constructing a top plate F1 of the penultimate basement, and removing the upright post piles 20 when the strength of the top plate F1 of the penultimate basement reaches 100%; and then, the construction of the top plate of the basement at the first floor is carried out, and the construction of the 5-floor basement structure of the deep foundation pit is completed.
The diagonal wale of the cast-in-place pile 10 is of a reinforced concrete structure, and contains a plurality of reinforcing steel bars and stirrups, so that sufficient strength is provided for the diagonal wale. The end face of the inclined strut waist beam is arranged in a downward inclined mode, a steel plate 311 is embedded in the end face of the inclined strut waist beam, the upper end of the first steel pipe inclined strut 30 is perpendicular to the end face of the inclined strut waist beam, the upper end of the first steel pipe inclined strut 30 is connected with the steel plate 311, and generally, the first steel pipe inclined strut 30 can be connected through screws and studs or welded, riveted and the like.
The connection portion 41 between the first support beam 40 and the stud 20 is a reinforced concrete structure, and contains a tie bar 411 arranged in a quincunx shape. The connecting portion 41 has an inclined surface, the lower end of the first steel pipe inclined strut 30 is perpendicular to the inclined surface of the connecting portion 41, and the direction in which the connecting portion 41 deviates from the inclined surface has an extending portion, so that powerful support is provided for the connecting portion 41, and the connecting portion 41 is prevented from being broken under stress. The inclined surface and the extended portion each contain reinforcing bars to reinforce the strength of the connecting portion 41.
Be equipped with a plurality of supporting shoes 301 around the tip of first steel pipe bracing 30, supporting shoe 301 is right triangle and arranges, and a right-angle side of supporting shoe 301 is connected with the lateral wall of first steel pipe bracing 30, and another right-angle side is connected with the terminal surface of first steel pipe bracing 30. Due to the action of the end supporting block 301, the end of the steel pipe diagonal brace has a stable structure and is not easy to deform under stress.
In this embodiment, 1, an inclined strut is arranged on the high side of the terrain, and the bottom of the inclined strut is connected with the pile top of the upright post 20 to form an integral structural stress system. The problems that the cast-in-place pile 10 is high in cantilever, the supporting structure is large in bending moment, and the soil body around the foundation pit is large in displacement during excavation of high-side soil in the terrain are solved.
2. The deep foundation pit supporting construction method fully utilizes the poured building floor slab, the upright post piles 20 and the temporary steel pipe inclined struts to form a structural stress system, and solves the problem that the cast-in-place piles 10 are high in cantilever when the first supporting system is dismantled.
3. The construction method is a novel deep foundation pit supporting construction method, is reasonable in structure, safe and reliable, and can save a large amount of engineering cost.
4. The construction method is simple, convenient to construct and easy to popularize and use.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (6)
1. A deep foundation pit supporting construction method with large height difference of two sides is characterized by comprising the following steps:
s01: constructing filling piles around a deep foundation pit, constructing a vertical column pile inside the deep foundation pit, excavating soil to a designed elevation according to a temporary excavation surface, arranging a first inclined support waist beam on the filling pile at the higher side of the deep foundation pit, constructing a first support beam above the vertical column pile, pouring a concrete panel above the first support beam, arranging a connecting part between the vertical column pile and the first support beam, and arranging a first steel pipe inclined support between the first inclined support waist beam and the connecting part; the included angle between the first steel pipe inclined strut and the first support beam is 27-31 degrees;
s02: excavating earthwork under the first steel pipe inclined strut, and extending the first support beam to the cast-in-place pile on the higher side of the deep foundation pit;
s03: excavating layer by layer, constructing a second support beam, connecting the second support beam with the upright post pile, and excavating to the bottom of the pit;
s04: constructing a bottom plate at the bottom of the pit, constructing a top plate of the basement at the lowest layer, and removing the second support beam when the top plate reaches 100% strength;
s05: constructing a top plate of the penultimate basement, and removing the first supporting beam and the first steel pipe inclined strut when the top plate of the penultimate basement reaches 100% strength;
s06: constructing a top plate of the last but one layer of basement, and dismantling the upright post pile when the top plate of the last but one layer of basement reaches 100% strength; then, the construction of the top plate of the basement at the fourth last floor is carried out, and the construction of the basement structure is completed;
in step S05, before removing the first support beam and the first steel pipe diagonal brace, adding a second steel pipe diagonal brace to a connection position between a top plate of the penultimate basement and another upright post; then removing the first support beam and the first steel pipe diagonal brace;
constructing a top plate of the upper layer of basement, and removing the second steel pipe inclined strut when the top plate of the upper layer of basement reaches 100% strength;
a second inclined support waist beam is arranged on the cast-in-place pile, one end of the second steel pipe inclined support is connected with the second inclined support waist beam, and the other end of the second steel pipe inclined support is connected to the connecting position of the top plate of the basement on the second layer from the bottom to the top and the other upright post pile;
in steps S03-S04, after the second support beam construction is completed, earth is excavated to a certain depth, a third support beam is constructed, so that the third support beam is connected with the upright pile, and earth is excavated to the pit bottom;
constructing a bottom plate at the bottom of the pit, constructing a top plate of the basement at the lowest layer, and removing the third support beam when the top plate reaches 100% strength;
continuing to construct the top plate of the upper layer of basement, and removing the second support beam when the top plate reaches 100% strength;
in step S06, when the last-but-one floor basement roof reaches 100% strength, the construction of the last-but-one floor basement roof is performed, and then the stud is removed; and then, the construction of the top plate of the basement at the first floor is carried out, and the construction of the basement structure is completed.
2. A deep foundation pit supporting construction method with large difference in height between two sides as claimed in claim 1, wherein in step S01, a third diagonal bracing wale is provided on the cast-in-place pile on the higher side of the deep foundation pit, a plurality of said vertical piles are provided, another connecting portion is provided between another one of said vertical piles and said first supporting beam, and a third steel pipe diagonal bracing is provided between said third diagonal bracing wale and said another connecting portion.
3. The deep foundation pit supporting construction method with the large height difference of two sides according to any one of claims 1-2, characterized in that a side plate is arranged between each basement floor and close to the cast-in-place pile, and graded broken stones or medium coarse sand are backfilled between the cast-in-place pile and the side plate.
4. The deep foundation pit supporting construction method with the large height difference of two sides according to any one of claims 1-2, wherein a steel plate is pre-embedded in the first inclined strut waist beam, and the first steel pipe inclined strut is connected with the steel plate.
5. The deep foundation pit supporting construction method with the large height difference of two sides according to any one of claims 1-2, wherein the connecting part is provided with an inclined surface, and the first steel pipe diagonal brace is arranged perpendicular to the inclined surface.
6. The deep foundation pit supporting construction method with the large height difference of two sides according to claim 5, wherein a plurality of supporting blocks are arranged around the end part of the first steel pipe inclined strut, the supporting blocks are arranged in a right triangle, one right-angle side of each supporting block is connected with the outer side wall of the first steel pipe inclined strut, and the other right-angle side of each supporting block is connected with the end face of the first steel pipe inclined strut.
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