A limited height section foundation pit support structure and construction method thereof

Abstract

The present invention provides a limited height section foundation pit support structure and a construction method thereof. The support structure includes a horizontal retaining wall, an inclined purlin, an inner support, a starting working shaft, a horizontal retaining wall construction guide wall, a receiving working shaft and a horizontal retaining wall head wall. The horizontal retaining wall, the inclined purlin and the inner support are arranged in sequence from the outside of the foundation pit to the inside, the horizontal retaining wall construction guide wall is located in the starting working shaft, and the horizontal retaining wall head wall is located in the receiving working shaft. The horizontal retaining wall includes a plurality of horizontal retaining piles, and the two ends of the horizontal retaining piles are anchored into the horizontal retaining wall construction guide wall and the horizontal retaining wall head wall respectively. The inclined purlins are arranged at intervals at a certain angle on the facade of the foundation pit, and the inner support is arranged horizontally, and its two ends are supported on the inclined purlins on both sides of the foundation pit respectively. The support structure and the construction method of the limited height section foundation pit proposed by the present invention have no requirements for the net height at the construction site, and solve the support problem of the foundation pit of the underground project in the limited height section.

Description

Technical Field

[0001] The invention belongs to the technical field of deep foundation pit engineering, and in particular relates to a height-limited section foundation pit support structure and a construction method thereof. Background Art

[0002] Foundation pit support is an important temporary support measure in the construction process of underground projects. The conventional underground project process is: support structure construction -> foundation pit excavation, support -> main structure construction. The foundation pit support structures at home and abroad include steel sheet piles, SMW construction method, TRD wall, bored piles, underground continuous wall, etc., all of which are vertical load-bearing components. Horizontal crown beams (or surrounding purlins) and internal supports or anchor cables at a certain distance are usually set on the inside of the foundation pit. The transmission path of water and soil pressure outside the foundation pit is: vertical load-bearing retaining structure -> horizontal crown beam (or surrounding purlin) -> internal support or anchor cable.

[0003] The traditional foundation pit retaining type has the advantages of fast construction speed and low cost, but the construction of the retaining structure has high requirements for the net height of the construction site, which not only needs to meet the requirements of the height of the construction equipment, but also needs to meet the height required for the hoisting of the steel cage. When the construction height is limited, such as under existing structures such as bridges or high-voltage lines, the traditional foundation pit retaining type will no longer be applicable. At this time, it will have to consider the use of dark excavation construction technology, resulting in increased project investment and construction risks.

[0004] Therefore, it is necessary to propose a foundation pit support structure and a construction method thereof which have no requirements on the net height at the construction site. Summary of the invention

[0005] The invention provides a limited height section foundation pit support structure and a construction method thereof, aiming to solve the problem in the prior art that the net height requirement at the construction site is relatively high during the construction of the enclosure structure.

[0006] The present invention is implemented as follows: a supporting structure for a foundation pit in a height-limited section includes a horizontal retaining wall, a plurality of inclined purlins, a plurality of internal supports, an initial working well, a horizontal retaining wall construction guide wall, a receiving working well and a horizontal retaining wall head wall;

[0007] The horizontal retaining wall, inclined purlin and inner support are arranged in sequence from outside the height-limited section foundation pit to inside the height-limited section foundation pit, the starting working well and the receiving working well are arranged at both ends of the height-limited section foundation pit respectively, the horizontal retaining wall construction guide wall is located on one side of the starting working well close to the height-limited section foundation pit, and the horizontal retaining wall head wall is located on one side of the receiving working well close to the height-limited section foundation pit;

[0008] The horizontal retaining wall comprises a plurality of horizontal retaining piles, and the horizontal retaining wall is arranged on both sides and the bottom of the foundation pit of the height-limited section; the two ends of the horizontal retaining piles are respectively anchored into the construction guide wall of the horizontal retaining wall and the head wall of the horizontal retaining wall;

[0009] The plurality of inclined purlins are arranged at intervals at a certain angle on the vertical surface of the foundation pit of the limited height section, and the internal support is arranged horizontally, with its two ends respectively supported on the inclined purlins on both sides of the foundation pit of the limited height section.

[0010] Furthermore, the horizontal retaining piles are cylindrical pile bodies and are constructed using a trenchless method.

[0011] Furthermore, a steel pipe or a plastic pipe is sleeved on the outside of the horizontal guardrail pile, a concave lock buckle is provided on one side of the steel pipe or the plastic pipe, and a convex lock buckle is provided on the other side, and two adjacent horizontal guardrail piles are connected by the lock buckle structure.

[0012] Furthermore, the top surface of the convex lock buckle is provided with grouting holes arranged at a certain interval, and the cavity formed after the convex lock buckle is connected with the concave lock buckle is filled with micro-expansive cement mortar.

[0013] Furthermore, the horizontal retaining piles are solid or hollow reinforced concrete structures, a plurality of horizontal main bars evenly arranged along the circumferential direction are arranged inside the horizontal retaining piles, spiral stirrups are arranged on the outside of the horizontal main bars, and the horizontal main bars and the spiral stirrups together constitute a steel cage.

[0014] Furthermore, the inclined perimeter purlin adopts a steel structure or a reinforced concrete structure; the inner support adopts a steel structure or a reinforced concrete structure.

[0015] Furthermore, the cross-sectional widths of the starting working well and the receiving working well are both greater than the width of the height-limited section foundation pit, and the bottoms of the starting working well and the receiving working well are both lower than the bottom of the height-limited section foundation pit.

[0016] Furthermore, guide holes for non-excavation construction such as jacking pipes or horizontal directional drilling are reserved in the guide wall for construction of the horizontal retaining wall, and the guide wall for construction of the horizontal retaining wall is connected to the retaining wall of the starting working shaft by using steel bars.

[0017] In order to solve the above technical problems, the present invention also provides a construction method of the above supporting structure, comprising the following steps:

[0018] S1, the starting working well and receiving working well at both ends of the foundation pit in the construction height limit section;

[0019] S2, the horizontal retaining wall construction guide wall at the starting working pit of the construction pipe;

[0020] S3. Use non-excavation methods such as jacking or horizontal directional drilling to construct the steel pipes or plastic pipes of the horizontal retaining wall at the bottom of the height-limited section from the middle to both sides. Two adjacent steel pipes or plastic pipes are overlapped with each other through a locking structure, and micro-expansion cement mortar is poured into the cavity after the convex locking buckle is connected with the concave locking buckle through the convex locking buckle;

[0021] S4. Insert the steel cage into the constructed steel pipe or plastic pipe and pour concrete;

[0022] S5. Use non-excavation methods such as pipe jacking or horizontal directional drilling to construct the steel pipes or plastic pipes of the horizontal retaining walls on both sides of the foundation pit of the height-limited section from bottom to top. Two adjacent steel pipes or plastic pipes are overlapped with each other through a locking structure buckle. Micro-expansion cement mortar is poured into the cavity after the convex locking buckle is connected with the concave locking buckle through the convex locking buckle. Then, a steel cage is inserted into the constructed steel pipe or plastic pipe, and concrete is poured;

[0023] S6, the head wall of the horizontal retaining wall of the construction receiving working well close to the foundation pit surface of the height limit section;

[0024] S7, slope excavation of soil on top of horizontal retaining wall;

[0025] S8. Excavate the lower soil in the height-limited section of the foundation pit vertically in layers and blocks, and construct the inclined purlins and internal supports in sequence, supporting them as they are excavated;

[0026] S9. Excavate the height-limited section foundation pit to the bottom of the pit and pour the pit bottom cushion layer. The cushion layer serves as the bottom support of the height-limited section foundation pit to complete the construction of the height-limited section foundation pit support structure.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention proposes a support structure for a height-limited section foundation pit and a construction method thereof, which do not require large-scale construction equipment on the ground of the height-limited section foundation pit, do not require vertical hoisting of steel cages, and have no requirements for the clear height at the construction site, thereby solving the support problem of the height-limited section underground engineering foundation pit. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the plan layout of a support structure of a foundation pit with a height limit provided by an embodiment of the present invention;

[0030] Figure 2 yes Figure 1 A schematic diagram of the elevation arrangement of the support structure shown;

[0031] Figure 3 yes Figure 1 A schematic cross-sectional view of the construction guide wall of the horizontal retaining wall at the starting working shaft of the support structure shown;

[0032] Figure 4 yes Figure 1 The cross-sectional schematic diagram of the foundation pit at the height-limited section of the support structure shown;

[0033] Figure 5 yes Figure 1 A schematic cross-sectional view of the horizontal retaining piles of the straight section of the support structure shown;

[0034] Figure 6 yes Figure 1 A schematic cross-sectional view of the horizontal retaining piles at the corner of the support structure shown;

[0035] Figure 7 yes Figure 1 Schematic diagram of grouting holes on the top surface of the convex lock buckle of the support structure shown;

[0036] Figure 8 It is a schematic elevational layout diagram of the earth excavation step sequence in the construction method of the height-limited section foundation pit support structure provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0038] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention; the terms "first", "second", and "third" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance; in addition, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be a connection between the two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0039] See also Figure 1 and Figure 2 , showing a preferred embodiment provided by the present invention, a supporting structure for a foundation pit in a height-limited section, comprising a horizontal retaining wall, a plurality of inclined purlins 1, a plurality of internal supports 2, a starting working shaft 3, a horizontal retaining wall construction guide wall 4, a receiving working shaft 5 and a horizontal retaining wall head wall 6.

[0040] The above-mentioned horizontal retaining wall, inclined purlin 1 and inner support 2 are arranged in sequence from outside the height-limited section foundation pit 100 to inside the height-limited section foundation pit 100. The starting working well 3 and the receiving working well 5 are arranged at both ends of the height-limited section foundation pit 100, respectively. The horizontal retaining wall construction guide wall 4 is located on one side of the starting working well 3 close to the height-limited section foundation pit 100, and the horizontal retaining wall head wall 6 is located on one side of the receiving working well 5 close to the height-limited section foundation pit 100.

[0041] See also Figure 4 The horizontal retaining wall includes a plurality of horizontal retaining piles 7, which are arranged on both sides and the bottom of the height-limited section foundation pit 100. The topmost horizontal retaining pile 7 of the horizontal retaining wall is generally about 2m away from the ground surface, and the foundation pit above it adopts a slope type.

[0042] See also Figure 1 and Figure 3 , the two ends of the horizontal retaining pile 7 are anchored into the horizontal retaining wall construction guide wall 4 and the horizontal retaining wall head wall 6 respectively. Specifically, the horizontal retaining wall construction guide wall 4 of this embodiment is reserved along its thickness direction for guide holes 41 for non-excavation construction such as jacking pipe or horizontal directional drilling, and the starting working shaft 3 and the receiving working shaft 5 have a retaining wall 31 and a retaining wall 51 respectively. The horizontal retaining wall construction guide wall 4 is connected to the retaining wall 31 of the starting working shaft 3 by steel bars. The tail end of the horizontal retaining pile 7 is cast in the horizontal retaining wall head wall 6, and the horizontal retaining wall head wall 6 is connected to the retaining wall 51 of the receiving working shaft 5 by steel bars.

[0043] See also Figure 2 and Figure 4 , a plurality of inclined purlins 1 are arranged at intervals at a certain angle on the vertical surface of the height-limited section foundation pit 100, and the inner support 2 is arranged horizontally, and its two ends are respectively supported on the inclined purlins 1 on both sides of the height-limited section foundation pit 100. In this embodiment, the inclined purlin 1 adopts a steel structure or a reinforced concrete structure, and the inner support 2 adopts a steel structure or a reinforced concrete structure.

[0044] Specifically, the horizontal retaining pile 7 of this embodiment is a cylindrical pile body.

[0045] See also Figure 5 and Figure 6 , respectively showing the cross-sectional structure of the straight section and the corner of the horizontal guard pile 7. The outer side of the horizontal guard pile 7 is covered with a steel pipe or a plastic pipe as a shell 71. A concave lock buckle 72 is provided on one side of the steel pipe or the plastic pipe, and a convex lock buckle 73 is provided on the other side. Two adjacent horizontal guard piles 7 are overlapped with each other through the lock buckle structure. Please refer to Figure 7 The top surface of the convex lock buckle 73 is provided with grouting holes 731 arranged at a certain interval, and the cavity formed after the convex lock buckle 73 and the concave lock buckle 72 are connected is filled with micro-expansion cement mortar.

[0046] The horizontal retaining pile 7 is a solid or hollow reinforced concrete structure. A number of horizontal main bars are arranged evenly along the circumferential direction inside the horizontal retaining pile 7, and spiral stirrups are arranged outside the horizontal main bars. The horizontal main bars and the spiral stirrups together form a steel cage 74, and steel cage reinforcement bars 75 are arranged inside the steel cage 74 along its length direction at a certain interval.

[0047] The cross-sectional widths of the starting working shaft 3 and the receiving working shaft 5 are both greater than the width of the height-limited section foundation pit 100 , and the bottoms of the starting working shaft 3 and the receiving working shaft 5 are both lower than the bottom of the height-limited section foundation pit 100 .

[0048] When the groundwater level is lower than the bottom of the height-limited foundation pit 100, the bottom of the height-limited foundation pit 100 may not be provided with a horizontal retaining wall and the horizontal retaining piles 7 may not be provided with a locking structure.

[0049] This embodiment also provides a construction method of the above-mentioned support structure, comprising the following steps:

[0050] S1, the starting working well 3 and the receiving working well 5 at both ends of the foundation pit 100 in the construction height limit section;

[0051] S2, construction guide wall 4 of the horizontal retaining wall at the construction starting working shaft 3;

[0052] S3, using the jacking method to construct the steel pipes or plastic pipes of the horizontal retaining wall at the bottom of the height-limited section foundation pit 100 from the middle to both sides, two adjacent steel pipes or plastic pipes are overlapped with each other through a locking structure, and micro-expansion cement mortar is poured into the cavity after the convex locking buckle 73 is connected with the concave locking buckle 72 through the convex locking buckle 73;

[0053] S4, inserting a steel cage 74 into the constructed steel pipe or plastic pipe and pouring concrete 76;

[0054] S5. Use a non-excavation method such as pipe jacking or horizontal directional drilling to construct the steel pipes or plastic pipes of the horizontal retaining walls on both sides of the height-limited section foundation pit 100 from bottom to top. Two adjacent steel pipes or plastic pipes are overlapped with each other through a locking structure buckle. The convex locking buckle 73 is used to pour micro-expansion cement mortar into the cavity after the convex locking buckle 72 and the concave locking buckle 73 are connected. Then, a steel bar cage 74 is inserted into the constructed steel pipe or plastic pipe, and concrete 76 is poured.

[0055] S6, the horizontal retaining wall head wall 6 of the construction receiving working well 5 close to the height-limited section foundation pit 100;

[0056] S7, slope excavation of soil on top of horizontal retaining wall;

[0057] S8, please refer to Figure 8, excavate the lower soil in the height-limited section foundation pit 100 vertically and block by block, and construct the inclined purlin 1 and the inner support 2 in sequence. After each soil is excavated, the inclined purlin 1 and the inner support 2 within the range are immediately constructed, so that the support is carried out as the soil is excavated;

[0058] S9, excavating the height-limited section foundation pit 100 to the pit bottom, pouring the pit bottom cushion layer 8, the cushion layer 8 serves as the bottom support of the height-limited section foundation pit 100, and completing the construction of the height-limited section foundation pit 100 support structure.

[0059] In summary, the support structure and construction method for the limited height section foundation pit proposed in this embodiment do not need to use large-scale construction equipment on the ground of the limited height section foundation pit 100, do not need to vertically hoist steel cages, and have no requirements for the clear height at the construction site, thereby solving the support problem of the limited height section underground engineering foundation pit.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A support structure for a foundation pit in a height-limited section, characterized in that: It includes a horizontal retaining wall, several inclined purlins, several internal supports, a starting working shaft, a horizontal retaining wall construction guide wall, a receiving working shaft and a horizontal retaining wall head wall; The horizontal retaining wall, inclined purlin and inner support are arranged in sequence from outside the height-limited section foundation pit to inside the height-limited section foundation pit, the starting working well and the receiving working well are arranged at both ends of the height-limited section foundation pit respectively, the horizontal retaining wall construction guide wall is located in the starting working well, and the horizontal retaining wall head wall is located in the receiving working well; The horizontal retaining wall comprises a plurality of horizontal retaining piles, and the horizontal retaining wall is arranged on both sides and the bottom of the foundation pit of the height-limited section; the two ends of the horizontal retaining piles are respectively anchored into the construction guide wall of the horizontal retaining wall and the head wall of the horizontal retaining wall; The plurality of inclined purlins are arranged at intervals at a certain angle on the vertical surface of the limited height section foundation pit, and the internal support is arranged horizontally, with its two ends respectively supported on the inclined purlins on both sides of the limited height section foundation pit; The horizontal retaining piles are cylindrical piles constructed using a trenchless method; the inclined purlins are made of steel structure or reinforced concrete structure; and the inner supports are made of steel structure or reinforced concrete structure.

2. The support structure according to claim 1, characterized in that: A steel pipe or a plastic pipe is sleeved on the outside of the horizontal guardrail pile. A concave lock buckle is provided on one side of the steel pipe or the plastic pipe, and a convex lock buckle is provided on the other side. Two adjacent horizontal guardrail piles are connected via the lock buckle structure.

3. The support structure according to claim 2, characterized in that: The top surface of the convex lock buckle is provided with grouting holes arranged at a certain interval, and the cavity formed after the convex lock buckle is connected with the concave lock buckle is filled with micro-expansion cement mortar.

4. The support structure according to claim 3, characterized in that: The horizontal retaining piles are solid or hollow reinforced concrete structures, and a plurality of horizontal main bars evenly arranged along the circumferential direction are arranged inside the horizontal retaining piles. Spiral stirrups are arranged on the outside of the horizontal main bars, and the horizontal main bars and the spiral stirrups together constitute a steel cage.

5. The supporting structure according to claim 1, characterized in that: The cross-sectional widths of the starting working well and the receiving working well are both greater than the width of the height-limited section foundation pit, and the bottoms of the starting working well and the receiving working well are both lower than the bottom of the height-limited section foundation pit.

6. The supporting structure according to claim 1, characterized in that: A guide hole for trenchless construction is reserved in the guide wall for the construction of the horizontal retaining wall, and the guide wall for the construction of the horizontal retaining wall is connected to the retaining wall of the starting working shaft by using steel bars.

7. A construction method of a supporting structure as claimed in claim 4, characterized in that: The following steps are involved: S1, the starting working well and receiving working well at both ends of the foundation pit in the construction height limit section; S2, the horizontal retaining wall construction guide wall at the starting working pit of the construction; S3. Use a trenchless method to construct the steel pipes or plastic pipes of the horizontal retaining wall at the bottom of the foundation pit at the height-limited section from the middle to both sides. Two adjacent steel pipes or plastic pipes are overlapped with each other through a locking structure, and micro-expansion cement mortar is poured into the cavity after the convex locking buckle is connected with the concave locking buckle through the convex locking buckle; S4. Insert the steel cage into the constructed steel pipe or plastic pipe and pour concrete; S5. Use trenchless method to construct the steel pipes or plastic pipes of the horizontal retaining wall on both sides of the foundation pit of the height-limited section from bottom to top. Two adjacent steel pipes or plastic pipes are overlapped with each other through a locking structure buckle. Micro-expansive cement mortar is poured into the cavity after the convex locking buckle is connected with the concave locking buckle through the convex locking buckle. Then, a steel cage is inserted into the constructed steel pipe or plastic pipe, and concrete is poured. S6, the head wall of the horizontal retaining wall of the construction receiving working well close to the foundation pit surface of the height limit section; S7, slope excavation of soil on top of horizontal retaining wall; S8. Excavate the lower soil in the height-limited section of the foundation pit vertically in layers and blocks, and construct the inclined purlins and internal supports in sequence, supporting them as they are excavated; S9. Excavate the height-limited section foundation pit to the bottom of the pit and pour the pit bottom cushion layer. The cushion layer serves as the bottom support of the height-limited section foundation pit to complete the construction of the height-limited section foundation pit support structure.

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