阅读说明：本技术 一种基坑结构及其施工方法 (Foundation pit structure and construction method thereof ) 是由 于廷新 熊大生 张燕 涂启柱 薛峰 储团结 王忠华 彭俊伟 米军 沈峥 涂仁盼 于 2020-12-11 设计创作，主要内容包括：本申请实施例公开了一种基坑结构及其施工方法,包括一期基坑、二期基坑、三期基坑、支护单元、一期地下室、二期地下室以及三期地下室,一期基坑与轨道交通间隔设置,支护单元设置在轨道交通靠近一期基坑的一侧土层中,二期基坑与三期基坑并排设置在一期基坑与支护单元之间；一期地下室包括多个支撑墩以及一期底板、一期中板和一期顶板,多个支撑墩分别固设在一期中板和一期顶板上；二期地下室包括二期底板、二期中板和二期顶板；三期地下室包括三期底板、三期中板和三期顶板；支撑墩与支护单元能够分别作为临时支撑的两端。本申请实施例的一种基坑结构及其施工方法,具有工程造价低的优点。(The embodiment of the application discloses a foundation pit structure and a construction method thereof, and the foundation pit structure comprises a first-stage foundation pit, a second-stage foundation pit, a third-stage foundation pit, a supporting unit, a first-stage basement, a second-stage basement and a third-stage basement, wherein the first-stage foundation pit and a rail transit are arranged at intervals, the supporting unit is arranged in a soil layer on one side of the rail transit, which is close to the first-stage foundation pit, and the second-stage foundation pit and the third-stage foundation pit are arranged between the first-stage foundation pit and the supporting; the first-stage basement comprises a plurality of support piers, a first-stage bottom plate, a first-stage middle plate and a first-stage top plate, wherein the support piers are fixedly arranged on the first-stage middle plate and the first-stage top plate respectively; the second-stage basement comprises a second-stage bottom plate, a second-stage middle plate and a second-stage top plate; the third-stage basement comprises a third-stage bottom plate, a third-stage middle plate and a third-stage top plate; the support piers and the support units can be used as two ends of the temporary support respectively. The foundation pit structure and the construction method thereof have the advantage of low construction cost.)

1. A foundation pit structure is located on one lateral side of a rail transit (9), and is characterized by comprising a first-stage foundation pit (1), a second-stage foundation pit (2), a third-stage foundation pit (3), a supporting unit (5), a first-stage basement (4a) arranged in the first-stage foundation pit (1), a second-stage basement (4b) arranged in the second-stage foundation pit (2), and a third-stage basement (4c) arranged in the third-stage foundation pit (3), wherein the first-stage foundation pit (1) and the rail transit (9) are arranged at intervals, the supporting unit (5) is arranged in a soil layer on one side, close to the first-stage foundation pit (1), of the rail transit (9), and the second-stage foundation pit (2) and the third-stage foundation pit (3) are arranged between the first-stage foundation pit (1) and the supporting unit (5) side by side;

the first-stage basement (4a) comprises a plurality of support piers (47), a first-stage bottom plate (41a), a first-stage middle plate (42a) and a first-stage top plate (43a), wherein the first-stage bottom plate, the first-stage middle plate and the first-stage top plate are horizontally arranged from bottom to top in sequence, and the support piers (47) are fixedly arranged on the first-stage middle plate (42a) and the first-stage top plate (43a) respectively;

the second-stage basement (4b) comprises a second-stage bottom plate (41b), a second-stage middle plate (42b) and a second-stage top plate (43b) which are horizontally arranged from bottom to top in sequence;

the third-stage basement (4c) comprises a third-stage bottom plate (41c), a third-stage middle plate (42c) and a third-stage top plate (43c) which are horizontally arranged from bottom to top in sequence;

the supporting piers (47) and the supporting units (5) can be used as two ends of temporary supports respectively.

2. The foundation pit structure according to claim 1, characterized in that the number of the tertiary foundation pits (3) is two, and the secondary foundation pit (2) is arranged between the two tertiary foundation pits (3).

3. The foundation pit structure of claim 1, wherein the depth of the first stage foundation pit (1) is H, and the distance between the first stage foundation pit (1) and the rail transit (9) is 2H-6H.

4. The foundation pit structure according to claim 1, wherein the second stage basement (4b) comprises a second stage external wall panel (45b) vertically arranged on one side close to the supporting unit (5), and a second stage gap (48b) between the pit wall of the second stage foundation pit (2) and the second stage external wall panel (45b) is filled with concrete, and/or;

the third-stage basement (4c) comprises a third-stage external wall plate (45c) vertically arranged on one side close to the supporting unit (5), and a third-stage gap (48c) between the pit wall of the third-stage foundation pit (3) and the third-stage external wall plate (45c) is filled with concrete.

5. The foundation pit structure according to any one of claims 1 to 4, wherein the supporting unit (5) is a bored pile or an underground diaphragm wall.

6. The foundation pit structure according to any one of claims 1 to 4, wherein the supporting unit (5) comprises a top-mounted crown beam (51), the crown beam (51) and the supporting pier (47) fixed to the first-stage top plate (43a) can be used as both ends of a temporary support; and/or the presence of a gas in the gas,

the support unit (5) comprises a waist beam (52) arranged at the waist, and the waist beam (52) and the support pier (47) fixedly arranged on the first-stage middle plate (42a) can be used as two ends of a temporary support respectively.

7. The foundation pit structure according to any one of claims 1 to 4, wherein the first stage floor (41a), the second stage floor (41b) and the third stage floor (41c) are reinforced concrete structures; and/or the presence of a gas in the gas,

the first-stage middle plate (42a), the second-stage middle plate (42b) and the third-stage middle plate (42c) are of a reinforced concrete structure; and/or the presence of a gas in the gas,

the first-stage top plate (43a), the second-stage top plate (43b) and the third-stage top plate (43c) are of a reinforced concrete structure; and/or the presence of a gas in the gas,

the support pier (47) is of a reinforced concrete structure.

8. The foundation pit structure according to claim 7, wherein the thickness of the concrete layer of the first stage middle plate (42a) and the first stage top plate (43a) in the area where the support pier (47) is fixed is thicker than the thickness of the concrete layer of the other areas;

the diameter of the reinforcing steel bar of the first-stage plate (42a) and the first-stage top plate (43a) in the area where the support pier (47) is fixed is larger than that of the reinforcing steel bar of other areas.

9. A method of constructing a foundation pit structure according to any one of claims 1 to 8, comprising:

driving the supporting unit (5) into the soil layer;

excavating the first stage foundation pit (1);

constructing the first-stage basement (4a) in the first-stage foundation pit (1);

excavating the second stage foundation pit (2), and arranging a temporary support (8) between the support pier (47) and the support unit (5);

constructing the second-stage basement (4b) in the second-stage foundation pit (2);

excavating the third-stage foundation pit (3), and arranging a temporary support (8) between the support pier (47) and the support unit (5);

and constructing the third-stage basement (4c) in the third-stage foundation pit (3).

10. The construction method according to claim 9, wherein the step of excavating the second stage foundation pit (2) and providing temporary supports (8) between the support piers (47) and the support units (5) comprises:

-providing a first temporary support (8) between the shoring unit (5) and the support pier (47) on the primary roof (43 a);

downwards excavating the second-stage foundation pit (2) to a depth corresponding to the first-stage middle plate (42 a);

arranging a second temporary support (8) between the support unit (5) and the support pier (47) on the first-stage plate (42 a);

and continuously downwards excavating the second-stage foundation pit (2) to a preset depth.

11. The construction method according to claim 10, wherein the step of constructing the second stage basement (4b) in the second stage foundation pit (2) comprises in particular:

constructing a second-stage bottom plate (41b) and a second-stage bottom plate replacement support (71b) in the second-stage foundation pit (2), wherein the second-stage bottom plate (41b) is connected with the first-stage bottom plate (41a), and the second-stage bottom plate replacement support (71b) is supported between the second-stage bottom plate (41b) and the supporting unit (5);

constructing the second-stage middle plate (42b) and a second-stage middle plate replacing support (72b) in the second-stage foundation pit (2), wherein the second-stage middle plate (42b) is connected with the first-stage middle plate (42a), and the second-stage middle plate replacing support (72b) is supported between the second-stage middle plate (42b) and the supporting unit (5);

removing the second temporary support (8);

constructing the second-stage top plate (43b) and a second-stage top plate replacement support (73b) in the second-stage foundation pit (2), wherein the second-stage top plate (43b) is connected with the first-stage top plate (43a), and the second-stage top plate replacement support (73b) is supported between the second-stage top plate (43b) and the supporting unit (5);

and (4) removing the first temporary support (8).

12. The construction method according to any one of claims 9 to 11, wherein the step of excavating the tertiary foundation pit (3) and providing temporary supports (8) between the support piers (47) and the support units (5) comprises:

-providing a third temporary support (8) between the shoring unit (5) and the support pier (47) on the primary roof (43 a);

downwards excavating the third-stage foundation pit (3) to a depth corresponding to the first-stage middle plate (42 a);

a fourth temporary support (8) is arranged between the supporting unit (5) and the supporting pier (47) on the first-stage middle plate (42 a);

and continuously downwards excavating the third-stage foundation pit (3) to a preset depth.

13. The construction method according to claim 12, wherein the step of constructing the third stage basement (4c) in the third stage foundation pit (3) comprises in particular:

constructing the third-stage bottom plate (41c) and a third-stage bottom plate replacement support (71c) in the third-stage foundation pit (3), wherein the third-stage bottom plate (41c), the second-stage bottom plate (41b) and the first-stage bottom plate (41a) are connected with each other, and the third-stage bottom plate replacement support (71c) is supported between the third-stage bottom plate (41c) and the supporting unit (5);

constructing the third-stage middle plate (42c) and a third-stage middle plate replacing support (72c) in the third-stage foundation pit (3), wherein the third-stage middle plate (42c), the second-stage middle plate (42b) and the first-stage middle plate (42a) are connected with each other, and the third-stage middle plate replacing support (72c) is supported between the third-stage middle plate (42c) and the supporting unit (5);

removing the fourth temporary support (8);

constructing the third-stage top plate (43c) and a third-stage top plate replacement support (73c) in the third-stage foundation pit (3), wherein the third-stage top plate (43c), the second-stage top plate (43b) and the first-stage top plate (43a) are connected with each other, and the third-stage top plate replacement support (73c) is supported between the third-stage top plate (43c) and the supporting unit (5);

and removing the third temporary support (8).

Technical Field

The application relates to civil engineering, in particular to a foundation pit structure and a construction method thereof.

Background

With the popularization of rail transit (such as high-speed rail, trains, urban rails and the like), foundation pit projects adjacent to the rail transit are increasing day by day, and as the rail transit has extremely strict requirements on displacement and settlement of a foundation, taking the high-speed rail as an example, the high-speed rail only allows millimeter-scale deformation, the foundation pit structure beside the high-speed rail generally adopts a support method of a bored pile or an underground continuous wall combined with a plurality of inner supports to prevent the deformation of the high-speed rail foundation in the foundation pit construction process. However, the foundation pit structure is large or small, and for a large-span foundation pit beside rail transit, if a horizontal temporary support is directly arranged in the foundation pit, on one hand, the deformation cannot be controlled due to too small support rigidity caused by large span; therefore, the density of the temporary support is increased, and the concrete volume is huge, the cost is high and the dismantling is difficult; in addition, the lower part of a large number of temporary supports is difficult to excavate, the construction efficiency is low, and finally, the construction cost is high and the construction period is long.

Disclosure of Invention

In view of this, the embodiments of the present application are expected to provide a foundation pit structure and a construction method thereof, so as to solve the problem of high construction cost.

In order to achieve the above purpose, the technical solution of the embodiment of the present application is implemented as follows:

a foundation pit structure is located on one lateral side of rail transit and comprises a first-stage foundation pit, a second-stage foundation pit, a third-stage foundation pit, a supporting unit, a first-stage basement arranged in the first-stage foundation pit, a second-stage basement arranged in the second-stage foundation pit and a third-stage basement arranged in the third-stage foundation pit, wherein the first-stage foundation pit and the rail transit are arranged at intervals, the supporting unit is arranged in a soil layer on one side, close to the first-stage foundation pit, of the rail transit, and the second-stage foundation pit and the third-stage foundation pit are arranged between the first-stage foundation pit and the supporting unit side by side; the first-stage basement comprises a plurality of support piers, a first-stage bottom plate, a first-stage middle plate and a first-stage top plate which are horizontally arranged from bottom to top in sequence, wherein the support piers are fixedly arranged on the first-stage middle plate and the first-stage top plate respectively; the second-stage basement comprises a second-stage bottom plate, a second-stage middle plate and a second-stage top plate which are horizontally arranged from bottom to top in sequence; the third-stage basement comprises a third-stage bottom plate, a third-stage middle plate and a third-stage top plate which are horizontally arranged from bottom to top in sequence; the support piers and the support units can be used as two ends of temporary supports respectively.

Furthermore, the number of the third-stage foundation pits is two, and the second-stage foundation pit is arranged between the two third-stage foundation pits.

Furthermore, the depth of the first stage foundation pit is H, and the distance between the first stage foundation pit and the rail transit is 2H-6H.

Further, the second-stage basement comprises a second-stage external wall plate vertically arranged on one side close to the supporting unit, and a second-stage gap between the pit wall of the second-stage foundation pit and the second-stage external wall plate is filled with concrete and/or concrete; the third-stage basement comprises a third-stage external wall plate vertically arranged on one side close to the supporting unit, and concrete is filled in a third-stage gap between the pit wall of the third-stage foundation pit and the third-stage external wall plate.

Further, the supporting unit is a bored pile or an underground continuous wall.

Further, the supporting unit comprises a crown beam arranged at the top, and the crown beam and the supporting pier fixedly arranged on the first-stage top plate can be respectively used as two ends of a temporary support; and/or the supporting unit comprises a waist beam arranged at the waist part, and the waist beam and the supporting pier fixedly arranged on the first-stage middle plate can be respectively used as two ends of temporary support.

Further, the first-stage bottom plate, the second-stage bottom plate and the third-stage bottom plate are of reinforced concrete structures; and/or the first-stage middle plate, the second-stage middle plate and the third-stage middle plate are of reinforced concrete structures; and/or the first-stage top plate, the second-stage top plate and the third-stage top plate are of reinforced concrete structures; and/or the support pier is of a reinforced concrete structure.

Further, the thickness of the concrete layer of the first-stage middle plate and the first-stage top plate in the area where the support pier is fixed is thicker than that of the concrete layer of other areas; the diameter of the reinforcing steel bars in the first-stage middle plate and the first-stage top plate in the area for fixing the support piers is larger than that of the reinforcing steel bars in other areas.

A construction method of the foundation pit structure comprises the following steps: driving the supporting unit into the soil layer; excavating the first stage foundation pit; constructing the first-stage basement in the first-stage foundation pit; excavating the second-stage foundation pit, and arranging a temporary support between the support pier and the support unit; constructing the second-stage basement in the second-stage foundation pit; excavating the third-stage foundation pit, and arranging a temporary support between the support pier and the support unit; and constructing the third-stage basement in the third-stage foundation pit.

Further, the step of excavating the second-stage foundation pit and arranging a temporary support between the support pier and the support unit specifically includes: arranging a first temporary support between the supporting unit and the supporting pier on the first-stage top plate; downwards excavating the second-stage foundation pit to a depth corresponding to the first-stage middle plate; a second temporary support is arranged between the supporting unit and the supporting pier on the first-stage middle plate; and continuously downwards excavating the second-stage foundation pit to a preset depth.

Further, the step of constructing the second-stage basement in the second-stage foundation pit specifically includes: constructing a second-stage bottom plate and a second-stage bottom plate support replacement in the second-stage foundation pit, wherein the second-stage bottom plate is connected with the first-stage bottom plate, and the second-stage bottom plate support replacement is supported between the second-stage bottom plate and the supporting unit; constructing the second-stage middle plate and a second-stage middle plate support changing in the second-stage foundation pit, wherein the second-stage middle plate is connected with the first-stage middle plate, and the second-stage middle plate support changing is supported between the second-stage middle plate and the support unit; removing the second temporary support; constructing the second-stage top plate and a second-stage top plate support replacement in the second-stage foundation pit, wherein the second-stage top plate is connected with the first-stage top plate, and the second-stage top plate support replacement is supported between the second-stage top plate and the supporting unit; and removing the first temporary support.

Further, the step of excavating the third-stage foundation pit and arranging a temporary support between the support pier and the support unit specifically includes: arranging a third temporary support between the supporting unit and the supporting pier on the first-stage top plate; downwards excavating the foundation pit in the third stage to the depth corresponding to the middle plate in the first stage; a fourth temporary support is arranged between the supporting unit and the supporting pier on the first-stage middle plate; and continuously downwards excavating the third-stage foundation pit to a preset depth.

Further, the step of constructing the third-stage basement in the third-stage foundation pit specifically includes: constructing the third-stage bottom plate and a third-stage bottom plate support replacement in the third-stage foundation pit, wherein the third-stage bottom plate, the second-stage bottom plate and the first-stage bottom plate are connected with each other, and the third-stage bottom plate support replacement is supported between the third-stage bottom plate and the supporting unit; constructing the third-stage middle plate and a third-stage middle plate support in the third-stage foundation pit, wherein the third-stage middle plate, the second-stage middle plate and the first-stage middle plate are connected with each other, and the third-stage middle plate support is supported between the third-stage middle plate and the support unit; removing the fourth temporary support; constructing the third-stage top plate and a third-stage top plate support replacement in the third-stage foundation pit, wherein the third-stage top plate, the second-stage top plate and the first-stage top plate are connected with each other, and the third-stage top plate support replacement is supported between the third-stage top plate and the supporting unit; and removing the third temporary support.

According to the foundation pit structure and the construction method thereof, the foundation pit originally dug together is changed into the foundation pit dug out three times and the corresponding basement structure is built in batches by arranging the first-stage foundation pit, the second-stage foundation pit, the third-stage foundation pit, the supporting unit, the first-stage basement a arranged in the first-stage foundation pit, the second-stage basement b arranged in the second-stage foundation pit and the third-stage basement c arranged in the third-stage foundation pit. The first-stage foundation pit and the rail transit are arranged at intervals, and the size of the interval is larger due to the fact that areas of the second-stage foundation pit and the third-stage foundation pit are reserved, so that the influence of the first-stage foundation pit excavation on the foundation of the rail transit is very small. Therefore, the first-stage foundation pit can be excavated under the condition that the temporary supports are not arranged or a small amount of temporary supports are arranged, so that the construction period is shortened, and the construction cost is reduced.

In addition, the span of second stage foundation ditch and third stage foundation ditch is little for the rigidity of temporary support is big, and it can corresponding reduction to set up density, saves concrete placement, and the later stage is also conveniently demolishd, reduces construction cost and cost of labor, and on the other hand, the longitudinal length of second stage foundation ditch, third stage foundation ditch is shorter than first stage foundation ditch, and the excavation area is little, and the excavation operation is quick, and is little to the soil layer influence, ensures that second stage foundation ditch, third stage foundation ditch can not make track traffic's ground take place the deformation in the construction process.

Drawings

Fig. 1 is a schematic diagram of a relative position of a foundation pit structure and rail transit according to an embodiment of the present application;

FIG. 2 is a cross-sectional view C-C of FIG. 1;

FIG. 3 is a cross-sectional view taken along line D-D of FIG. 1;

FIG. 4 is a top view of FIG. 2;

fig. 5 is a schematic view showing a connection relationship of the buttress according to the embodiment of the present application;

fig. 6 is a first process schematic for the construction process of the second-stage foundation pit and the second-stage basement according to the embodiment of the present application;

fig. 7 is a second schematic process of the construction process of the second-stage foundation pit and the second-stage basement according to the embodiment of the present application;

fig. 8 is a third process schematic of the construction process of the second-stage foundation pit and the second-stage basement in the embodiment of the present application;

fig. 9 is a fourth process schematic for the construction process of the second-stage foundation pit and the second-stage basement in the embodiment of the present application;

fig. 10 is a fifth schematic process of the construction process of the second-stage foundation pit and the second-stage basement according to the embodiment of the present application;

fig. 11 is a sixth process schematic of the construction process of the second-stage foundation pit and the second-stage basement according to the embodiment of the present application;

fig. 12 is a seventh schematic process of the construction process of the second-stage foundation pit and the second-stage basement according to the embodiment of the present application;

fig. 13 is a process eight illustrating the construction process of the second-stage foundation pit and the second-stage basement according to the embodiment of the present application;

fig. 14 is a ninth process of building a second-stage foundation pit and a second-stage basement according to the embodiment of the present application;

fig. 15 is a process ten illustrating the construction process of the second-stage foundation pit and the second-stage basement according to the embodiment of the present application;

FIG. 16 is a flow chart of a construction method according to an embodiment of the present application;

fig. 17 is a detailed flowchart of the step S40 in fig. 16;

fig. 18 is a detailed flowchart of the step S50 in fig. 16;

fig. 19 is a detailed flowchart of step S60 in fig. 16;

fig. 20 is a detailed flowchart of step S70 in fig. 16.

Detailed Description

It should be noted that, in the case of conflict, the technical features in the examples and examples of the present application may be combined with each other, and the detailed description in the specific embodiments should be interpreted as an explanation of the present application and should not be construed as an improper limitation of the present application.

In the description of the embodiments of the present application, the "up", "down", "left", "right", "front", "back" orientation or positional relationship is based on the orientation or positional relationship shown in fig. 1, it is to be understood that these orientation terms are merely for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore, should not be considered as limiting the present application.

The rail transit 9 may be a high-speed rail, a train, a light rail or a tram. In the prior art, the bottom of the rail transit 9 is provided with a foundation, and a rail is laid on the foundation for passing, so that the rail transit 9 has a high requirement on deformation of the foundation. When a building needs to be constructed near two sides of the rail transit 9, the part of the foundation of the rail transit 9, which is close to a foundation pit of the building, is exposed to the air, and the gravity of the rail transit 9 and the gravity of a passing vehicle are converted into horizontal acting force, so that the foundation is easy to deform, and therefore in the construction process, besides supporting piles and other structures to maintain the stability of an exposed soil body, a temporary support needs to be arranged on the pit wall of the foundation pit to prevent the deformation of the foundation of the rail transit 9. However, when the span of the foundation pit is too large, the supporting capability of the temporary support is limited, and the support stiffness is too small to control the deformation easily. If the density of the temporary support is increased, the concrete quantity is huge, the dismantling is difficult and the cost is high; in addition, the lower part of a large number of temporary supports is difficult to excavate, the construction efficiency is low, and finally, the construction cost is high and the construction period is long.

In the embodiment of the present application, without affecting the technical solution expression and without specification, the basements refer to the first-stage basement 4a, the second-stage basement 4b, and the third-stage basement 4c, the bottom boards refer to the first-stage bottom board 41a, the second-stage bottom board 41b, and the third-stage bottom board 41c, and the middle boards refer to the first-stage middle board 42a, the second-stage middle board 42b, and the third-stage middle board 42 c. The top plates refer to a primary top plate 3a, a secondary top plate 43b, and a tertiary top plate 43 c.

In the embodiment of the present application, as shown in fig. 1 to 18, a foundation pit structure is located on one lateral side of the rail transit 9. I.e. the pit structure, is located on either lateral side of the rail 9. The foundation pit structure comprises a first-stage foundation pit 1, a second-stage foundation pit 2, a third-stage foundation pit 3, a supporting unit 5, a first-stage basement 4a arranged in the first-stage foundation pit 1, a second-stage basement 4b arranged in the second-stage foundation pit 2 and a third-stage basement 4c arranged in the third-stage foundation pit 3.

The supporting unit 5 is vertically arranged in a soil layer on one side of the track traffic 9 close to the first-stage foundation pit 1 to maintain the stability of an adjacent soil body, and the second-stage foundation pit 2 and the third-stage foundation pit 3 are arranged between the first-stage foundation pit 1 and the supporting unit 5 side by side; so that the supporting unit 5 can be used as an acting point of the temporary support 8 to provide protection for the second-stage foundation pit 2 and the third-stage foundation pit 3. The supporting unit 5 may be a bored pile or an underground diaphragm wall according to the site conditions and the construction needs.

The first-stage basement 4a includes a plurality of support piers 47, and a first-stage bottom plate 41a, a first-stage middle plate 42a and a first-stage top plate 43a horizontally arranged from bottom to top in sequence, and the plurality of support piers 47 are respectively and fixedly arranged on the first-stage middle plate 42a and the first-stage top plate 43 a. Of course, a plurality of support columns (not shown) are disposed between the first stage bottom plate 41a, the first stage middle plate 42a and the first stage top plate 43a to connect them into a rigid whole, and the support columns can be disposed according to the specific environment of the site.

The foundation pit dug out together originally is changed into a structure of a basement dug out for three times and corresponding to the basement built in batches. The first-stage foundation pit 1 and the rail transit 9 are arranged at intervals, and the intervals are larger in size due to the fact that areas of the second-stage foundation pit 2 and the third-stage foundation pit 3 are reserved, so that the foundation of the rail transit 9 is slightly affected by excavation of the first-stage foundation pit 1. Therefore, the first-stage foundation pit 1 can be excavated without providing the temporary supports 8 (mentioned below) or with providing a small number of temporary supports 8, thereby speeding up the construction period and reducing the construction cost.

The second-stage basement 4b includes a second-stage bottom plate 41b, a second-stage middle plate 42b, and a second-stage top plate 43b, which are horizontally arranged from bottom to top in sequence. Similarly, a plurality of support columns (not shown) are arranged among the second-stage bottom plate 41b, the second-stage middle plate 42b and the second-stage top plate 43b to connect the two plates into a rigid whole, and the support columns can be arranged according to the specific environment on site.

The third-stage basement 4c comprises a third-stage bottom plate 41c, a third-stage middle plate 42c and a third-stage top plate 43c which are horizontally arranged from bottom to top in sequence; similarly, a plurality of support columns (not shown) are arranged among the third stage bottom plate 41c, the third stage middle plate 42c and the third stage top plate 43c to connect the three stage bottom plate, the third stage middle plate and the third stage top plate into a rigid whole, and the support columns can be arranged according to the specific environment of the site.

It is understood that the planar shapes of the first stage foundation pit 1 and the first stage basement 4a, the second stage foundation pit 2 and the second stage basement 4b, and the third stage foundation pit 3 and the third stage basement 4c should be substantially the same. The sum of the longitudinal lengths of the second stage basement 4b and the third stage basement 4c should be equal to the first stage basement 4 a. The longitudinal length here refers to the length in the direction of travel along the track traffic 9. And establishing a corresponding basement in the corresponding foundation pit, and further constructing a building main body on the basement.

The support piers 47 and the supporting units 5 can be used as both ends of the temporary support, respectively. Specifically, after the first-stage basement 4a is constructed, the second-stage foundation pit 2 and the third-stage foundation pit 3 which are subsequently close to the rail transit 9 can be supported on the support pier 47 and the support unit 5 through the temporary support 8 (mentioned below) in the construction process to form a horizontal support, and the second-stage foundation pit 2 or the third-stage foundation pit 3 is protected by the support unit 5 to prevent the foundation of the rail transit 9 from being deformed in the construction process.

The first-stage foundation pit 1, the first-stage basement 4a, the second-stage foundation pit 2, the second-stage basement 4b, the third-stage foundation pit 3 and the third-stage basement 4c are sequentially constructed.

Specifically, the first-stage foundation pit 1 and the first-stage basement 4a are built, the second-stage foundation pit 2 is dug, and the second-stage basement 4b is built in the second-stage foundation pit 2 after the excavation is completed. During the excavation of the second stage foundation pit 2, the first stage basement 4a can be considered as a fixed soil layer and can provide a corresponding supporting function. The temporary support 8 supports between supporting pier 47 and supporting unit 5, on the one hand, the span of second stage foundation ditch 2 is little, it is relative, the rigidity of temporary support 8 is big, it can corresponding reduction to set up density, save concrete placement, the later stage is also conveniently demolishd, reduce construction cost and cost of labor, on the other hand, the longitudinal length of second stage foundation ditch 2 is shorter than first stage foundation ditch 1, it is little to excavate the area, it is quick to excavate the operation, and it is little to influence the soil layer, ensure that second stage foundation ditch 2 can not make track traffic 9's ground take place deformation at the construction in-process.

In addition, the first-stage foundation pit 1 and the first-stage basement 4a, the second-stage foundation pit 2 and the second-stage basement 4b are built, the third-stage foundation pit 3 is excavated, and the third-stage basement 4c is built in the third-stage foundation pit 3 after excavation is finished. During the excavation of the foundation ditch 3, the first stage basement 4a and the second stage basement 4b can be considered as fixed soil layers and can provide corresponding supporting functions. Similarly, the foundation of the rail transit 9 cannot be deformed in the process of building the foundation pit 3 in the third stage, and details are not repeated here.

The first stage basement 4a, the second stage basement 4b and the third stage basement 4c which are built are connected into a whole. Taking a reinforced concrete structure as an example, a steel bar joint (not shown) should be reserved on the first-stage bottom plate 41a, the first-stage middle plate 42a and the first-stage top plate 43a of the first-stage basement 4 a; when the second-stage bottom plate 41b, the second-stage middle plate 42b and the second-stage top plate 43b of the second-stage basement 4b are constructed, the second-stage basement 4b and the corresponding reserved steel bar joint steel bars of the first-stage basement 4a are bound, welded and then concrete is poured; of course, the second-stage bottom plate 41b, the second-stage middle plate 42b and the second-stage top plate 43b should be provided with a steel bar joint (not shown); when the third-stage bottom plate 41c, the third-stage middle plate 42c and the third-stage top plate 43c of the third-stage basement 4c are constructed, the third-stage basement 4c and the third-stage basement 4c are bound and welded with the reserved steel bar joint steel bars corresponding to the first-stage basement 4a and the second-stage basement 4b, and then concrete pouring is performed. Thereby, the primary base plate 41a, the secondary base plate 41b, and the tertiary base plate 41c are connected to each other and supported on the supporting unit 5; the first-stage middle plate 42a, the second-stage middle plate 42b, and the third-stage middle plate 42c are connected to each other and supported on the supporting unit 5; the primary roof panel 43a, the secondary roof panel 43b, and the tertiary roof panel 43c are connected to each other and supported on the supporting unit 5. Therefore, the first-stage basement 4a, the second-stage basement 4b and the third-stage basement 4c are connected into a whole, and the supporting unit 5 can be effectively supported to prevent the foundation of the rail transit 9 from deforming.

In a possible embodiment, as shown in fig. 1, the number of the third-stage foundation pits 3 is two, and the second-stage foundation pit 2 is disposed between the two third-stage foundation pits 3. On one hand, the longitudinal length of the foundation pit 3 in the third stage and the longitudinal length of the foundation pit 2 in the second stage are small, the longitudinal length of the foundation pit 1 in the first stage is only 33%, the excavating area is small, the excavating operation is rapid, and the influence on the soil layer is small; in addition, when the second-stage foundation pit 2 is excavated, the soil layers corresponding to the two third-stage foundation pits 3 are respectively positioned on two sides of the second-stage foundation pit 2 and are matched with the fixed support of the first-stage basement 4a, so that the foundation of the rail transit 9 cannot deform in the construction process of the second-stage foundation pit 2.

In a possible embodiment, as shown in fig. 1 to 5, the depth B of the first-stage foundation pit 1, the second-stage foundation pit 2 and the third-stage foundation pit 3 is H, and the distance a between the first-stage foundation pit 1 and the track traffic 9 may be selected to be 2H to 6H according to different soil layer properties. For non-soft soil formations, the distance A is preferably 3H; in the range, the excavation area is used as the excavation area of the second-stage foundation pit 2 and the third-stage foundation pit 3, and the later-stage implementation is carried out; for the foundation pit of the soft soil stratum, the distance A is preferably 5H, and the distance A is used as an excavation area of the second-stage foundation pit 2 and the third-stage foundation pit 3 in the range and is implemented in the later stage. It can be understood that the distance E between the second stage foundation pit 2 and the third stage foundation pit 3 close to the side of the rail transit 9 should meet the national regulations to meet the requirements related to the foundation strength, noise and the like. According to the tenth item of the existing railway transportation safety protection regulation, in urban areas, the distance E is not less than 8 meters; in suburban residential areas, the distance E is not less than 10 meters; in the residential areas of the residents in the villages and the towns, the distance E is not less than 12 meters; in other areas, the distance E is not less than 15 meters.

In one possible embodiment, as shown in fig. 1-3, the first stage basement 4a includes a first stage exterior wall panel 45a disposed vertically. The first-stage external wall panel 45a, the supporting columns, the first-stage bottom panel 41a, the first-stage middle panel 42a and the first-stage top panel 43a are connected to form a rigid main body of the first-stage basement 4 a. The second-stage basement 4b comprises a second-stage external wall panel 45b which is vertically arranged, the second-stage external wall panel 45b, a supporting column body, a second-stage bottom plate 41b, a second-stage middle plate 42b and a second-stage top plate 43b are connected to form a rigid main body of the second-stage basement 4 b. The third-stage basement 4c comprises a third-stage external wall panel 45c which is vertically arranged, the third-stage external wall panel 45c, a supporting column body, a third-stage bottom plate 41c, a third-stage middle plate 42c and a third-stage top plate 43c are connected to form a rigid main body of the third-stage basement 4 c.

Wherein, the fat groove (not marked) between the first-stage external wall panel 45a and the pit wall of first-stage foundation pit 1, the fat groove between the second-stage external wall panel 45b and the pit wall of second-stage foundation pit 2, the fat groove between the third-stage external wall panel 45c and the pit wall of third-stage foundation pit 3 should be backfilled with soil layer or concrete, the gravity of rail transit 9 and the gravity of passing vehicles are converted into horizontal acting force and transmitted to the pit wall of foundation pit, and then further transmitted to the rigid basement structure through the fat groove, and finally transmitted to the soil layer on the other side, so that the stress transmission is effectively completed, and the deformation of high-speed rails after the later-stage main structure is completed is prevented.

As the main direction of the stress, the fertilizer tank, i.e., the second-stage gap 48b, vertically disposed between the second-stage external wall panel 45b near one side of the supporting unit 5 and the second-stage foundation pit 2 should be filled with concrete. The fertilizer groove, i.e., the third-stage gap 48c, vertically disposed between the third-stage external wall panel 45c near one side of the supporting unit 5 and the pit wall of the third-stage foundation pit 3 should be filled with concrete. Prevent that basement structure from receiving to trade to prop and influence backfill incompact, avoid causing the high-speed railway to warp after later stage major structure accomplishes.

In one possible embodiment, as shown in fig. 1-3, the basement may include a waterproof layer 46. The waterproof layer 46 covers the bottom plate, the middle plate, the top plate and the outer wall plate of the basement to prevent water from seeping in the soil layer.

In a possible embodiment, as shown in figures 1 to 3, the supporting unit 5 comprises a crown beam 51 arranged on top. The crown beams 51 extend generally along the direction of travel of the track traffic 9; the crown beam 51 and the supporting pier 47 fixed to the first stage ceiling plate 43a can be supported at both ends as the temporary supports 8, respectively. Further, the supporting unit 5 may also include a wale 52 provided at the waist. Wales 52 extend generally in the direction of travel of track traffic 9; the wale 52 and the support pier 47 fixed to the first intermediate plate 42a can be supported by the temporary support 8 at both ends, respectively.

The horizontal acting force from the soil layer borne by the supporting unit 5 is transmitted to the temporary support 8 through the crown beam 51 and the waist beam 52, and then transmitted to the support pier 47 and further transmitted to the top plate and the middle plate of the basement; and then the stress is transmitted to the soil layer through the rigid basement structure, so that the stress transmission is completed, and the deformation of the foundation of the rail transit 9 is effectively prevented.

In one possible embodiment, primary floor 41a, primary floor 42a, primary roof 43a, and support piers 47 may be reinforced concrete structures. The second stage bottom plate 41b, the second stage middle plate 42b, and the second stage top plate 43b may be a reinforced concrete structure. The third stage bottom plate 41c, the third stage middle plate 42c, and the third stage top plate 43c may be a reinforced concrete structure. The connection between the two steel bars is performed by concrete pouring after the steel bars are bundled and welded, so that the building cost is low and the connection strength is good.

As shown in fig. 5, the reinforcing bars 471 in the supporting piers 47 are spaced horizontally and vertically, and are tied and welded with the reinforcing bars in the first floor 41a (the first middle plate 42a) and the reinforcing bars in the temporary supports 8, and then concrete is poured, so that the three are connected into a whole, stress is effectively transmitted, the construction cost is low, and the connection strength is good.

It will be appreciated that the temporary support 8 is necessarily subjected to a large force; the thickness of the concrete layer in the area of the fixed support piers 47 of the first-stage plate 42a and the first-stage top plate 43a is thicker than that in other areas; the diameter of the reinforcing steel bars in the areas of the fixed support piers 47 of the first-stage middle plate 42a and the first-stage top plate 43a is larger than that of the reinforcing steel bars in other areas; so that the whole structure of the basement can meet the use requirement.

A construction method of the above-described foundation pit structure, as shown in fig. 16 to 18, includes:

and S10, driving the supporting unit 5 into the soil layer. The supporting unit 5 should be driven into the soil layer on the side of the rail transit 9 close to the primary foundation pit 1.

And S20, excavating the first-stage foundation pit 1.

And S30, constructing the first stage basement 4a in the first stage foundation pit 1. As shown in fig. 6, after the first stage basement 4a is constructed, a soil layer is formed between the first stage basement and the supporting unit 5.

And S40, excavating the second-stage foundation pit 2, and arranging a temporary support 8 between the support pier 47 and the support unit 5.

And S50, constructing a second stage basement 4b in the second stage foundation pit 2.

And S60, excavating the third-stage foundation pit 3, and arranging a temporary support 8 between the support pier 47 and the support unit 5.

And S70, constructing a third-stage basement 4c in the third-stage foundation pit 3.

As shown in fig. 7 to 10 and 17, the step S40 specifically includes:

s41, as shown in fig. 7, a first temporary support 8 is provided between the supporting unit 5 and the supporting pier 47 on the first ceiling 43 a.

S42, as shown in fig. 8, the second stage foundation pit 2 is excavated downwards to the depth corresponding to the first stage middle plate 42 a.

S43, as shown in fig. 9, a second temporary support 8 is provided between the supporting unit 5 and the support pier 47 on the first intermediate plate 42 a.

And S44, as shown in FIG. 10, continuing to excavate the second stage foundation pit 2 downwards to a preset depth.

As shown in fig. 11 to 15 and 18, the step S50 specifically includes:

s51, as shown in fig. 11, a second stage floor 41b and a second stage floor support 71b are constructed in the second stage foundation pit 2, the second stage floor 41b is connected to the first stage floor 41a, and the second stage floor support 71b is supported between the second stage floor 41b and the support unit 5.

S52, as shown in fig. 12, the second-stage middle plate 42b and the second-stage middle plate support 72b are constructed in the second-stage foundation pit 2, the second-stage middle plate 42b is connected to the first-stage middle plate 42a, and the second-stage middle plate support 72b is supported between the second-stage middle plate 42b and the support unit 5.

S53, as shown in fig. 13, the second temporary support 8 is removed.

S54, as shown in fig. 14, the second-stage roof 43b and the second-stage roof replacement brace 73b are constructed in the second-stage foundation pit 2, the second-stage roof 43b is connected to the first-stage roof 43a, and the second-stage roof replacement brace 73b is supported between the second-stage roof 43b and the support unit 5.

S55, as shown in fig. 15, the first temporary support 8 is removed.

As shown in fig. 19, the step S60 specifically includes:

s61, a third temporary support 8 is provided between the supporting unit 5 and the support pier 47 on the first roof 43 a.

And S62, downwards excavating the foundation pit 3 in the third period to the depth corresponding to the middle plate 42a in the first period.

S63, a fourth temporary support 8 is provided between the support unit 5 and the support pier 47 on the first intermediate plate 42 a.

And S64, continuously excavating the foundation pit 3 in the third period downwards to a preset depth.

It is understood that the third stage basement 4c is similar to the second stage basement 4b in structure, and the structure of the second stage basement 4b in fig. 7 to 10 is changed to the structure of the corresponding third stage basement 4c, which can be referred to as the steps S61-S64.

As shown in fig. 20, the step S70 specifically includes:

s71, constructing a third-stage bottom plate 41c and a third-stage bottom plate support-changing 71c in the third-stage foundation pit 3, wherein the third-stage bottom plate 41c, the second-stage bottom plate 41b and the first-stage bottom plate 41a are connected with each other, and the third-stage bottom plate support-changing 71c is supported between the third-stage bottom plate 41c and the support unit 5;

and S72, constructing a third-stage middle plate 42c and a third-stage middle plate support 72c in the third-stage foundation pit 3, wherein the third-stage middle plate 42c, the second-stage middle plate 42b and the first-stage middle plate 42a are connected with each other, and the third-stage middle plate support 72c is supported between the third-stage middle plate 42c and the support unit 5.

And S73, removing the fourth temporary support 8.

And S74, constructing a third-stage top plate 43c and a third-stage top plate replacement support 73c in the third-stage foundation pit 3, wherein the third-stage top plate 43c, the second-stage top plate 43b and the first-stage top plate 43a are connected with each other, and the third-stage top plate replacement support 73c is supported between the third-stage top plate 43c and the supporting unit 5.

And S75, removing the third temporary support 8.

It can be understood that the third stage basement 4c is similar to the second stage basement 4b in structure, and the structure of the second stage basement 4b in fig. 11 to 15 is changed into the structure of the corresponding third stage basement 4c, which can be used as a reference for construction in steps S71-S75.

In addition, after the step of S30, the method may further include: and S30a, performing waterproofing treatment on the first-stage basement 4 a.

May further include after the step of S50: and S50a, performing waterproof treatment on the second-stage basement 4 b.

May further include after the step of S70: and S70a, performing waterproofing treatment on the third-stage basement 4 c.

The various embodiments/implementations provided herein may be combined with each other without contradiction.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.