CN110644501A - Foundation pit supporting and underpinning bearing platform combined construction method with zero distance from original building - Google Patents

Foundation pit supporting and underpinning bearing platform combined construction method with zero distance from original building Download PDF

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Publication number
CN110644501A
CN110644501A CN201910926045.4A CN201910926045A CN110644501A CN 110644501 A CN110644501 A CN 110644501A CN 201910926045 A CN201910926045 A CN 201910926045A CN 110644501 A CN110644501 A CN 110644501A
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CN
China
Prior art keywords
foundation pit
pile
bearing platform
foundation
support
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Pending
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CN201910926045.4A
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Inventor
倪德兴
彭涛
何蕃民
邓安
徐建骁
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CREEC Chengdu Survey Design and Research Co Ltd
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CREEC Chengdu Survey Design and Research Co Ltd
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Priority to CN201910926045.4A priority Critical patent/CN110644501A/en
Publication of CN110644501A publication Critical patent/CN110644501A/en
Pending legal-status Critical Current

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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
    • E02D5/22Piles
    • E02D5/64Repairing piles
    • 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
    • E02D5/74Means for anchoring structural elements or bulkheads
    • E02D5/76Anchorings for bulkheads or sections thereof in as much as specially adapted therefor

Abstract

The invention belongs to the technical field of foundation pit supporting, discloses a zero-distance foundation pit supporting and underpinning bearing platform combined construction method for an original building, solves the problems that the foundation pit supporting method in the prior art cannot meet zero-distance foundation pit excavation of a nearby building, the depth of a foundation pit is larger than that of an original foundation pile of the original building, the weight of the original building is large, and the design allowable inclination value is very low, and provides a new supporting method for the foundation pit supporting with special requirements.

Description

Foundation pit supporting and underpinning bearing platform combined construction method with zero distance from original building
Technical Field
The invention belongs to the technical field of foundation pit supporting, and particularly relates to a zero-distance foundation pit supporting and underpinning bearing platform combined construction method from an original building.
Background
In some cases, the adjacent building beside the original building needs to be dismantled and rebuilt, in some special cases, the adjacent building not only fits closely to the original bearing platform of the original building (that is, the distance between the adjacent building and the original bearing platform of the original building is zero), but also the depth of the foundation pit of the rebuilt adjacent building is deeper than the depth of the original foundation pile of the original building, and the original building has a heavy weight (for example, the original building has a weight of 1300 tons or more), and the design of the original building allows the inclination value to be very low (for example, the allowed inclination value is 0.2 per thousand, and if the height of the original building is 87m, the allowed inclination of the original building is about 16 mm). Because the depth of the foundation pit of the rebuilt side adjacent building is larger than the depth of the original foundation pile of the original building, the excavation of the foundation pit can cause the original building to be suspended, and the existing foundation pit supporting mode can not meet the construction requirement at all.
Disclosure of Invention
The invention provides a zero-distance foundation pit supporting and underpinning bearing platform combined construction method for solving the problems that the existing foundation pit supporting method cannot meet the zero-distance foundation pit excavation of a nearby building, the depth of a foundation pit is larger than that of an original foundation pile of an original building, the weight of the original building is heavy, and the design allowable inclination value is very low.
In order to solve the technical problem, the technical scheme adopted by the invention is as follows:
a zero-distance foundation pit supporting and underpinning bearing platform combined construction method from an original building is characterized by comprising the following steps:
(1) firstly, constructing a first reinforcing foundation pile of an original bearing platform close to the side of a foundation pit; after the first reinforced foundation pile is poured, constructing a second reinforced foundation pile of the original bearing platform far away from the side of the foundation pit, wherein the pile top of the second reinforced foundation pile is positioned below the lower end surface of the original bearing platform; after the second reinforced foundation pile is poured, constructing cushion cap supporting piles on the peripheries of the first reinforced foundation pile and the second reinforced foundation pile; the method comprises the following steps that a foundation pit of a rebuilt side adjacent building comprises a first foundation pit section and a second foundation pit section, the first foundation pit section is tightly attached to an original bearing platform, the second foundation pit section is a part of the foundation pit except the first foundation pit section (namely, the second foundation pit section is a foundation pit part which is not tightly attached to the original bearing platform), when a bearing platform support pile is constructed, a second support pile is constructed at the periphery of the second foundation pit section, the pile top elevation of the second support pile is positioned below the ground, and the pile bottom elevations of the first reinforced foundation pile, the second reinforced foundation pile, the bearing platform support pile and the second support pile are smaller than the elevation of the foundation pit (namely, the pile bottom depths of the first reinforced foundation pile, the second reinforced foundation pile, the bearing platform support pile and the second support pile are all larger than the foundation pit depth of the rebuilt side adjacent building);
(2) exposing the pile top of the second support pile after the foundation pit is excavated to a distance below the ground, pouring a crown beam on the pile top of the second support pile, arranging a first steel support in the foundation pit area corresponding to the original bearing platform, and adapting the installation height of the first steel support to the position of the original bearing platform;
(3) continuously downwards excavating the foundation pit for a certain distance until the bottom position of the foundation pit is lower than the pile top position of a second reinforced foundation pile, pouring a second underpinning bearing platform between the original bearing platform and the second reinforced foundation pile, pouring a first underpinning bearing platform between the original bearing platform and a first processed foundation pile, arranging a second steel support in the foundation pit area corresponding to the original bearing platform below the first steel support, and enabling the installation height of the second steel support to be matched with the position of the first underpinning bearing platform;
(4) and continuously downwards excavating the foundation pit for a certain distance until a distance is reserved between the foundation pit and the first underpinning bearing platform, pouring a first support pile below the first underpinning bearing platform, and connecting the top of the first support pile with the lower part of the first underpinning bearing platform after the first support pile is poured.
And further, continuously excavating the foundation pit downwards for a distance, and arranging a third steel support in the area of the foundation pit corresponding to the original bearing platform.
Furthermore, the periphery of the foundation pit is fixed through anchor cables.
Furthermore, at least one group of anchor cables are arranged in a foundation pit area corresponding to the original bearing platform, the installation height positions of the anchor cables in the group of anchor cables are the same, and at least one steel support is arranged between the two groups of anchor cables which are adjacent up and down.
Furthermore, the anchor cable is in a shape of a Chinese character 'ba' along two opposite side walls of the foundation pit.
And further, continuously excavating the foundation pit downwards for a certain distance, and arranging a first group of anchor cables below the third steel support.
And further, continuously excavating the foundation pit downwards for a distance, and arranging a fourth steel support below the first group of anchor cables.
And further, continuously excavating the foundation pit downwards for a distance, and arranging a second group of anchor cables below a fourth steel support.
And further, continuously excavating the foundation pit downwards for a certain distance, and arranging a fifth steel support below the second group of anchor cables.
Furthermore, the first steel support, the second steel support, the third steel support, the fourth steel support and the fifth steel support comprise parallel steel supports parallel to the original bearing platform and inclined steel supports with inclination angles with the original bearing platform, the inclined steel supports are connected to two adjacent foundation pit side walls in a foundation pit area corresponding to the original bearing platform, and the parallel steel supports are connected to two opposite foundation pit side walls in the foundation pit area corresponding to the original bearing platform.
Compared with the prior art, the invention has the following beneficial effects:
according to the foundation pit supporting and underpinning bearing platform combined construction method with the zero distance from the original building, the underpinning bearing platform is arranged and used for bearing the load of the original building after being formed, and the load is transmitted to the pile bottom and below the foundation pit, so that the safety of the original building is ensured; the foundation pit support and the underpinning bearing platform are organically combined, the original support pile of the original building and the reinforced foundation pile of the underpinning bearing platform are both used as the support pile of the foundation pit, the newly-poured first support pile and the underpinning bearing platform are mutually connected and used as the foundation pile of the underpinning bearing platform, the dual-purpose of one pile is realized, the conversion of horizontal stress and vertical stress is effectively solved, the purpose of supporting the original building is achieved, the problem that the original building is suspended due to the fact that the depth of the foundation pit of the newly-built nearby building is larger than that of the original foundation pile of the original building is solved, meanwhile, the steel support is supported on the original bearing platform and the underpinning bearing platform, the inclined deformation of the original building is effectively controlled, finally, the problems that the foundation pit supporting method in the prior art cannot meet zero-distance foundation pit excavation of a nearby building, the depth of the foundation pit is larger than that of an original foundation pile of an original building, the original building is heavy, and the design allowable inclination value is very low are solved. Provides a new supporting method for the foundation pit supporting with special requirements.
According to the invention, the areas corresponding to the original bearing platform are supported in a supporting pile, steel support and anchor cable mode, the rest areas are supported in a supporting pile and anchor cable mode, different supporting modes are adopted for different stress areas of the foundation pit, the construction can be ensured to meet the construction requirement, and meanwhile, the construction cost can be reduced to the maximum extent.
Drawings
Fig. 1 is a schematic top view of an embodiment of the present invention, and it can be seen from fig. 1 that an original bearing platform of an original building and a foundation pit are tightly attached to each other without a gap (i.e., a gap between the original building and the foundation pit is zero);
fig. 2 is a schematic view of the state of the cast-in foundation pile, the pile cap support pile and the pile cap support pile, as can be seen from fig. 2, the depth of the foundation pit is greater than that of the original foundation pile of the original building, and the depths of the foundation pile and the pile cap support pile are greater than that of the foundation pit;
FIG. 3 is a schematic view of a state when a crown beam is poured on a second supporting pile and a first steel support is installed;
FIG. 4 is a schematic view of a second steel support installed on the first underpinning platform after the first and second underpinning platforms are poured;
FIG. 5 is a schematic view of a situation in which a first fender post is cast under the first underpinning platform and is connected to the first underpinning platform;
FIG. 6 is a schematic view of the third steel support in the installed state;
FIG. 7 is a schematic view of the first set of anchor cables and the fourth steel support when they are installed;
FIG. 8 is a schematic view of the second set of anchor cables and a fifth steel support when installed;
FIG. 9 is a schematic cross-sectional view taken at A-A of FIG. 8;
the labels in the figure are: 01. the method comprises the following steps of (1) an original building, 02, an original bearing platform, 03, an original supporting pile, 04 and an original foundation pile;
1. the foundation pit comprises a foundation pit body, 2, a first reinforced foundation pile, 3, a second reinforced foundation pile, 4, a bearing platform support pile, 5, a second support pile, 6, a first support pile, 7, a crown beam, 8, a first underpinning bearing platform, 9, a second underpinning bearing platform, 10, an inclined steel support, 11, a horizontal steel support, 12, a first steel support, 13, a second steel support, 14, a steel purlin, 15, a third steel support, 16, a first group of anchor cables, 17, a fourth steel support, 18, an anchor cable steel waist beam, 19, a second group of anchor cables, 20 and a fifth steel support.
Detailed Description
The present invention will be further described with reference to the following examples, which are intended to illustrate only some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, other embodiments used by those skilled in the art without any creative effort belong to the protection scope of the present invention.
The invention relates to a foundation pit supporting and underpinning bearing platform combined construction method with zero distance to the original building, which comprises the following steps:
with reference to fig. 1 and fig. 2, a first reinforced foundation pile 2 of an original bearing platform 02 close to a side of a foundation pit 1 is constructed, wherein an upper surface of the original bearing platform 02 is located below the ground, the elevation described in the present application is based on the upper surface (± 0.00 m) of the original bearing platform 02, and the elevation of the pile top of the first reinforced foundation pile 2 is ± 0.00m, that is, the pile top of the first reinforced foundation pile is flush with the upper surface of the original bearing platform 02, and in some embodiments, the pile top of the first reinforced foundation pile may be higher than the upper surface of the original bearing platform 02; after the first reinforced foundation pile 2 is poured, constructing a second reinforced foundation pile 3 of the original bearing platform 02 far away from the side of the foundation pit 1, wherein the pile top of the second reinforced foundation pile 3 is positioned below the lower end face of the original bearing platform 02, and the first reinforced foundation pile 2 and the second reinforced foundation pile 3 are positioned on the periphery of the original bearing platform 02 of the original building 01; after the second reinforced foundation pile 3 is poured, constructing cushion cap supporting piles 4 on the peripheries of the first reinforced foundation pile 2 and the second reinforced foundation pile 3; the reconstructed foundation pit 1 of the adjacent building comprises a first foundation pit section and a second foundation pit section, wherein the first foundation pit section is tightly attached to the original bearing platform 02, the second foundation pit section is the part of the foundation pit 1 except the first foundation pit section (namely the second foundation pit section is the part of the foundation pit which is not tightly attached to the original bearing platform 02), when the bearing platform support piles 4 are constructed, the second support piles 5 are constructed on the periphery of the second foundation pit section, wherein the periphery of the foundation pit is provided with marked lines, the second supporting piles 5 are poured along the marked lines, the pile top elevation of the second supporting piles 5 is positioned below the ground, and the pile bottom elevations of the first reinforced foundation pile 2, the second reinforced foundation pile 3, the bearing platform support pile 4 and the second support pile 5 are smaller than the elevation of the foundation pit (namely the pile bottom average depth of the first reinforced foundation pile 2, the second reinforced foundation pile 3, the bearing platform support pile 4 and the second support pile 5 is larger than the depth of the foundation pit 1 of the rebuilt nearby building).
With reference to fig. 3, after the foundation pit 1 is excavated to a distance below the ground, the pile top of the second supporting pile 5 is exposed, that is, the excavation depth of the foundation pit 1 is greater than the distance from the pile top of the second supporting pile 5 to the ground, a crown beam 7 is poured on the pile top of the second supporting pile 5, a first steel support 12 is arranged in the area of the foundation pit 1 corresponding to the original bearing platform 2, and the installation height of the first steel support 12 is matched with the position of the original bearing platform 02; namely, one end of the first steel support clinging to the original bearing platform 02 side is connected to the original bearing platform 02, and the other end of the first steel support 12 is connected to the crown beam 7; and two ends of the first steel support 12 between two adjacent foundation pit edges which are not tightly attached to the original bearing platform are connected to the crown beam 7.
With reference to the attached drawing 4, the foundation pit 1 is continuously excavated downwards for a certain distance until the bottom position of the foundation pit 1 is lower than the pile top position of the second reinforced foundation pile 3, a second underpinning bearing platform 9 is poured between the original bearing platform 02 and the second reinforced foundation pile 3, a first underpinning bearing platform 8 is poured between the original bearing platform 02 and the first machined foundation pile 2, a second steel support 12 is arranged in the area of the foundation pit 1 below the first steel support 12 and corresponding to the original bearing platform 02, and the installation height of the second steel support 12 is matched with the position of the first underpinning bearing platform 8; wherein the second steel support 13 is located below the first steel support 12.
In some embodiments, in order to improve the connection tightness between the original bearing platform 02 and the first and second underpinning bearing platforms, the lower end surface of the original bearing platform 02 is roughened to improve the connection between the original bearing platform 02 and the first and second underpinning bearing platforms, and meanwhile, the lower end surface of the original bearing platform 02 is subjected to a certain shrinkage after concrete is solidified, after the first and second underpinning bearing platforms are poured, high-strength and high-fluidity chemical grout is adopted between the original bearing platform and the first and second underpinning bearing platforms for grouting, so that the connection tightness between the original bearing platform and the first and second underpinning bearing platforms is further improved.
And (3) continuously excavating the foundation pit 1 downwards for a certain distance until a distance is reserved between the foundation pit 1 and the first underpinning bearing platform 8, pouring the first fender pile 2 below the first underpinning bearing platform 8 at the moment, and connecting the top of the first fender pile 2 and the lower part of the first underpinning bearing platform 8 together after the pouring of the first fender pile 2 is finished. In some embodiments, the first fender pile 2 is also cast under the second underpinning platform 9 (with a distance between the first fender pile under the second underpinning platform 9 and the foundation pit), and then the first fender pile 2 and the second underpinning platform 9 are connected together.
With reference to fig. 6-9, in some embodiments, the excavation of the foundation pit 1 continues for a distance downward, and a third steel support 15 is provided in the area of the foundation pit corresponding to the original bearing platform 02.
In some embodiments, the periphery of the foundation pit 1 is further fixed by anchor cables, and the foundation pit supporting capability is further improved by the anchor cables; in some embodiments, the periphery of the second foundation pit section is subjected to 1:1 slope releasing treatment, and in some embodiments, slope releasing treatment can also be performed by adopting different slopes according to the soil quality conditions around the foundation pit.
Further, at least one group of anchor cables are arranged in a foundation pit area corresponding to the original bearing platform 02, the installation height positions of the anchor cables in the group of anchor cables are the same, and at least one steel support is arranged between two adjacent groups of anchor cables.
Furthermore, the anchor cable is in a shape of a Chinese character 'ba' along two opposite side walls of the foundation pit.
In some embodiments, excavation of the excavation pit 1 continues for a distance downward, and a first set of anchor lines 16 is provided below a third steel support 15.
In some embodiments, excavation of foundation pit 1 continues for a distance downward, and a fourth steel support 17 is positioned below first set of anchor lines 16.
In some embodiments, continuing to excavate the excavation 1 a distance down, a second set of anchor lines 19 is provided beneath the fourth steel support 17.
In some embodiments, the excavation continues down the excavation 1 for a distance, and a fifth steel support 20 is provided beneath the second set of anchor lines 19.
The foundation pit area corresponding to the original platform 02 taught in the present application refers to: the projection area of original cushion cap 02 on foundation ditch 1, that is to say, first way steel shotcrete, second way steel shotcrete, third way steel shotcrete, fourth way steel shotcrete and fifth way steel shotcrete in this application all are located in the foundation ditch 1 region corresponding with original cushion cap 02.
According to the supporting method, different supporting modes are adopted for different areas of the foundation pit, different bearing conditions of all areas of the foundation pit are fully met, and meanwhile, the construction cost is reduced to the greatest extent. Namely, the first foundation pit section adopts the combined action of the support piles, the anchor cables and the steel supports to realize foundation pit support, and the second foundation pit section adopts the combined support mode of the support piles and the anchor cables.
In some embodiments, the number of steel struts may be determined according to the depth of the foundation pit 1 and the weight of the original building 01.
In some embodiments, the first steel support, the second steel support, the third steel support, the fourth steel support and the fifth steel support are provided with steel purlins 14, that is, the ends of the steel supports are connected through the steel purlins 14; one end of the anchor cable is connected with the first support pile through the anchor cable steel waist beam 18, the other end of the anchor cable can be fastened in a soil body in modes of anchor spraying, grouting locking and the like, wherein locking of the anchor cable belongs to the prior art, and the anchor cable can be understood and understood by technicians in the field, and is not described in detail herein.
Referring to fig. 1, in some embodiments, the first steel support, the second steel support, the third steel support, the fourth steel support and the fifth steel support each include a parallel steel support 11 parallel to the original bearing platform 02 and an inclined steel support 10 having an inclined angle with the original bearing platform, the inclined steel supports 10 are connected to two adjacent sidewalls of the foundation pit in the area of the foundation pit corresponding to the original bearing platform 02, and the parallel steel supports 11 are connected to two opposite sidewalls of the foundation pit in the area of the foundation pit corresponding to the original bearing platform 02. That is to say, each steel support consists of a plurality of horizontal steel supports and inclined steel supports.
In some embodiments, only the parallel steel supports 11 may be arranged according to the stress condition around the foundation pit.
Example one
The original building 01 of the embodiment has the height of 87m and the weight of 1300 tons, the original building 01 has 28 original foundation piles 04 with the pile bottom elevation of-18.50 m and a plurality of original supporting piles, the thickness of the original bearing platform 02 is 2.5m, and the upper surface of the original bearing platform 02 is 2.5m below the ground. The side-facing building is of a groove structure, the upper end face of the side-facing building is flush with the upper end face of the original bearing platform 02, the bottom elevation of the side-facing building is-10 m, the width of the side-facing building is 10m, and the length of the side-facing building is 42 m. The side buildings are closely attached to the original bearing platform 01 (zero distance).
At present, the original side buildings need to be dismantled, the side buildings with larger volume are rebuilt, the rebuilt side buildings are integrally of a groove structure, the bottom elevation is-22.5 m, the width is about 20m, and the length is about 65.6 m.
And the construction requirements for the original building 01 are as follows: the integral inclination deformation value is not more than 0.2 thousandths (16 mm), the column base deformation value is not more than 5mm, namely the deformation of the top of the first foundation pit section of the foundation pit 1 is allowed to be 5.0mm, and the deformation control requirement is very high. The excavation depth of the foundation pit is larger than the pile bottom elevation of the original foundation pile, which means that the foundation excavation of the foundation pit can 'hang' the foundation of the original building.
And the foundation pit supporting mode in the prior art can not meet the construction requirements of the original building 01 by design. Therefore, the foundation pit supporting and underpinning bearing platform combined construction method can meet the construction requirements of the original building through calculation, and solves the problems that the existing foundation pit supporting method cannot meet zero-distance foundation pit excavation of the adjacent building, the depth of the foundation pit is larger than that of the original foundation pile of the original building, the weight of the original building is large, and the design allowable inclination value is very low. The specific operation and construction process comprises the following steps:
1. in order to protect the original building 01, constructing first reinforcing foundation piles 2 from +/-0.00 m, wherein the number of the first reinforcing foundation piles is 8, and the first reinforcing foundation piles 2 are positioned on the periphery of an original bearing platform 02 close to the side of a foundation pit 1; constructing 4 second reinforced foundation piles 3 after the first reinforced foundation pile 2 is poured, wherein the second reinforced foundation piles 3 are positioned at the periphery of the original bearing platform 02 far away from the side of the foundation pit 1, the elevation of the top of the poured pile of the second reinforced foundation pile 3 is-7.00 m, constructing bearing platform supporting piles 4 at the peripheries of the first reinforced foundation pile 2 and the second reinforced foundation pile 3 after the second reinforced foundation pile 3 is poured, and the number of the bearing platform supporting piles 4 is 38; the diameters of the first reinforced foundation pile and the second reinforced foundation pile are 1300mm, and the diameter of the bearing platform support pile 4 is 1200 mm; when constructing the bearing platform support piles 4, constructing 61 second support piles 5 on the second foundation pit section at the same time, wherein the pile top elevation of the second support piles is-2.50 m;
2. excavating the earthwork of the foundation pit to-2.5 m, constructing a pile top crown beam 7 and a first steel support 12 of a second supporting pile 5, and installing the first steel support 12 in a foundation pit area corresponding to the original bearing platform;
3. when the earthwork of the foundation pit is excavated to-7.00 m, the top surface of the original bearing platform 02 needs to be roughened, so that the connection between new and old concrete is convenient, and after the new bearing platform (the first underpinning bearing platform 8 and the second underpinning bearing platform 9) is poured, high-strength and high-fluidity chemical grout is adopted between the new and old bearing platforms for grouting. After the underpinning bearing platform is constructed, manufacturing a steel enclosing purlin 14 at a position of-7.00 m, and installing a second steel support 13;
4. excavating a foundation pit to-10.0 m, wherein an original supporting pile 03, a first reinforced foundation pile and a second reinforced foundation pile of an original building are used as supporting piles, constructing 4 first supporting piles 6 below a first underpinning bearing platform, connecting piles 3.0m upwards after the first supporting piles are formed, and connecting the piles with the underpinning bearing platform to be used as foundation piles of the underpinning bearing platform;
5. excavating a foundation pit to-11.00 m, manufacturing a steel purlin 14, and installing a third steel support 15;
6. excavating a foundation pit to-13.0 m, constructing a first group of anchor cables 16, manufacturing a steel waist beam 18, grouting, tensioning and locking;
7. excavating a foundation pit to-15.00 m, manufacturing a steel purlin 14, and installing a fourth steel support 17;
8. excavating a foundation pit to-17.0 m, constructing a second group of anchor cables 19, manufacturing a steel waist beam, grouting, tensioning and locking;
9. and excavating the foundation pit to-19.00 m, manufacturing a steel purlin, and installing a fifth steel support 20.
Through the monitoring of the whole process in the construction process, the accumulated deformation of the foundation of the original building 01 is 1.2mm, and the accumulated deformation of the top end of the tower is 13.2mm, so that the deformation requirement is met.
The foundation pit support and the underpinning bearing platform are organically combined, the foundation pile of the underpinning bearing platform is used as a foundation pit support retaining wall pile, and meanwhile, the first newly constructed retaining pile is finally connected with the underpinning bearing platform and used as a foundation pile of the underpinning bearing platform. The conversion between horizontal stress and vertical stress is effectively solved. The problems that the existing foundation pit supporting method cannot meet zero-distance foundation pit excavation of a nearby building, the depth of the foundation pit is larger than that of an original foundation pile of an original building, the original building is heavy, and the design allowable inclination value is very low are solved. Provides a new supporting method for the foundation pit supporting with special requirements.

Claims (10)

1. A zero-distance foundation pit supporting and underpinning bearing platform combined construction method from an original building is disclosed, which is characterized by comprising the following steps:
(1) firstly, constructing a first reinforcing foundation pile of an original bearing platform close to the side of a foundation pit; after the first reinforced foundation pile is poured, constructing a second reinforced foundation pile of the original bearing platform far away from the side of the foundation pit, wherein the pile top of the second reinforced foundation pile is positioned below the lower end surface of the original bearing platform; after the second reinforced foundation pile is poured, constructing cushion cap supporting piles on the peripheries of the first reinforced foundation pile and the second reinforced foundation pile; the rebuilt foundation pit of the adjacent building comprises a first foundation pit section and a second foundation pit section, the first foundation pit section is tightly attached to the original bearing platform, the second foundation pit section is a part of the foundation pit except the first foundation pit section, when a bearing platform support pile is constructed, a second support pile is constructed on the periphery of the second foundation pit section, the pile top elevation of the second support pile is positioned below the ground, and the pile bottom elevations of the first reinforced foundation pile, the second reinforced foundation pile, the bearing platform support pile and the second support pile are smaller than the elevation of the foundation pit;
(2) exposing the pile top of the second support pile after the foundation pit is excavated to a distance below the ground, pouring a crown beam on the pile top of the second support pile, arranging a first steel support in the foundation pit area corresponding to the original bearing platform, and adapting the installation height of the first steel support to the position of the original bearing platform;
(3) continuously downwards excavating the foundation pit for a certain distance until the bottom position of the foundation pit is lower than the pile top position of a second reinforced foundation pile, pouring a second underpinning bearing platform between the original bearing platform and the second reinforced foundation pile, pouring a first underpinning bearing platform between the original bearing platform and a first processed foundation pile, arranging a second steel support in the foundation pit area corresponding to the original bearing platform below the first steel support, and enabling the installation height of the second steel support to be matched with the position of the first underpinning bearing platform;
(4) and continuously downwards excavating the foundation pit for a certain distance until a distance is reserved between the foundation pit and the first underpinning bearing platform, pouring a first support pile below the first underpinning bearing platform, and connecting the top of the first support pile with the lower part of the first underpinning bearing platform after the first support pile is poured.
2. The method of claim 1, wherein the excavation is continued a distance down to the excavation site, and a third steel support is provided in the area of the excavation site corresponding to the existing bearing platform.
3. The method of claim 1, wherein the perimeter of the excavation is further secured by anchor cables.
4. The method as claimed in claim 3, wherein at least one anchor cable is installed in the area of the foundation pit corresponding to the existing cap, the anchor cables of one anchor cable group are installed at the same height, and at least one steel support is installed between two adjacent anchor cables.
5. The method as claimed in claim 3 or 4, wherein the anchor cable is in a form of a "V" along two opposite sidewalls of the foundation pit.
6. The method as claimed in claim 2, 3 or 4, wherein excavation is continued for a distance, and a first set of anchor cables is provided below the third steel support.
7. The method of claim 6, wherein the excavation is continued for a distance, and a fourth steel support is provided below the first set of anchor cables.
8. The method of claim 7, wherein the excavation is continued a distance down to the excavation site, and a second set of anchor cables is provided below a fourth steel support.
9. The method of claim 8, wherein the excavation is continued for a distance, and a fifth steel support is provided below the second set of anchor cables.
10. The method of claim 9, wherein the first, second and third, fourth and fifth steel supports each comprise a parallel steel support parallel to the existing support and an inclined steel support having an angle of inclination with respect to the existing support, the inclined steel supports are connected to two adjacent sidewalls of the foundation pit in the area of the foundation pit corresponding to the existing support, and the parallel steel supports are connected to two opposite sidewalls of the foundation pit in the area of the foundation pit corresponding to the existing support.
CN201910926045.4A 2019-09-27 2019-09-27 Foundation pit supporting and underpinning bearing platform combined construction method with zero distance from original building Pending CN110644501A (en)

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