Deformation control method for implementing foundation pit engineering through reverse construction method

Abstract

The invention belongs to the field of underground space development, and relates to a deformation control method for implementing foundation pit engineering by a reverse construction method, which comprises the following steps of: firstly, constructing a foundation pit support structure, temporary support side columns and middle support piles, and sequentially excavating a foundation pit to be below each layer of reverse construction beam plate to construct the reverse construction beam plate and an outer wall hidden beam; supporting plate structures are arranged on the periphery of the top-down beam plate and used for placing servo jacks in the later period; an inner structure edge beam is arranged on the periphery of the top-down structure beam plate and is connected with the temporary supporting edge column; a servo jack is installed between a reversed structure beam plate and an outer wall hidden beam, and jacking force is applied, so that deformation of an enclosure structure is reduced. The deformation of the foundation pit is controlled, the influence of excavation construction of the foundation pit on surrounding buildings and structures and an underground pipe network is reduced, and the method plays an important role in urban renewal construction projects.

Description

Technical Field

[0001] The invention belongs to the field of underground space development, and in particular relates to a construction method under the condition that the surrounding environment of a foundation pit in a central urban area is complex and the deformation control requirements of a foundation pit retaining structure are very high. Background Art

[0002] With the rapid development of urban underground space, the design and construction of foundation pit projects have also encountered new problems and challenges. Urban underground space has changed from traditional single functions such as commerce and parking to multi-functional underground complexes, and the scale of foundation pit projects has continued to increase. In addition, foundation pit projects in central urban areas are often close to protected objects such as subways, protected buildings, and underground pipelines. The environmental conditions around the foundation pits are becoming more complex and sensitive, and the deformation control requirements for the implementation of the foundation pits are also becoming higher and higher.

[0003] The top-down method is a commonly used support method in foundation pit engineering. In this method, intermediate supporting piles are cast or driven into relevant locations inside the building as supporting structures that bear the deadweight of the upper structure and construction loads before the bottom slab is sealed during construction. The structural beams and slabs of each floor of the basement are excavated downward to serve as horizontal supports for the retaining structure. Compared with the conventional forward excavation method, the top-down method has the following outstanding advantages: (1) Since the structural beams and slabs of the first floor on the ground are completed first, the upper structure can be constructed simultaneously during the downward top-down excavation process, thereby greatly shortening the construction period; (2) It avoids the waste of temporary supports, has significant economic benefits, and is conducive to the green and sustainable development of foundation pit engineering; (3) The horizontal top-down structural beam and slab support has high rigidity and safety.

[0004] Although the top-down construction method has the above advantages, it still has certain shortcomings in controlling foundation pit deformation when the surrounding environmental protection requirements are very high: (1) The construction speed of underground top-down structural beams and slabs is usually slow. In soft soil areas such as Shanghai, soft clay has rheological properties. Before the top-down construction of the beams and slabs is completed and an effective horizontal support is formed, the foundation pit deformation will continue to accumulate and grow over time; (2) In order to ensure the construction quality and dimensional accuracy of the top-down structural beams and slabs, the top-down construction method usually requires the use of a racking method. Therefore, each stage of the foundation pit excavation process requires over-excavation to a certain depth, which is also not conducive to the control of foundation pit deformation.

[0005] At present, the research on the implementation of foundation pit engineering by reverse construction method, especially the technical means to control the deformation of foundation pit retaining structure and reduce the impact of foundation pit on the surrounding environment, is still immature. Summary of the invention

[0006] The present invention provides a deformation control method for implementing foundation pit engineering by reverse construction, which is particularly suitable for the development of large-depth and multi-layer underground spaces under complex and sensitive environmental conditions in central urban areas. This construction method can effectively reduce the impact of the construction process on the surrounding buildings and underground pipelines of the foundation pit in deep foundation pit engineering by reverse construction.

[0007] The specific construction steps are: Step 1: First construct the foundation pit retaining structure, temporary supporting side columns and intermediate supporting piles in the foundation pit. The temporary supporting side columns surround the outer periphery of the intermediate supporting piles; the intermediate supporting piles are set at the permanent structure column position of the basement.

[0008] Step 2: Excavate the foundation pit to below the elevation of the reverse-construction structure beam-slab, and construct the reverse-construction structure beam-slab and the outer wall hidden beam; the outer wall hidden beam is located on the side wall of the foundation pit retaining structure; a post-cast strip is reserved between the reverse-construction structure beam-slab and the outer wall hidden beam for arranging the servo jack; a cantilevered support plate structure is set around the reverse-construction structure beam-slab to hold up the servo jack, and the position of the servo jack is aligned with the structural main beam of the reverse-construction structure beam-slab; the reverse-construction structure beam-slab between the positions of the servo jacks extends to the edge of the outer wall hidden beam as a pier to tighten the foundation pit retaining structure; the reverse-construction structure beam-slab is connected to the middle supporting pile column through the ring beam node structure; the inner structure side beam is set around the reverse-construction structure beam-slab to connect with the temporary supporting side column; in the post-cast strip, the first structural main reinforcement of the outer wall hidden beam is reserved; the second structural main reinforcement of the reverse-construction structure beam-slab is reserved; the servo jack is installed between the reverse-construction structure beam-slab and the outer wall hidden beam and a top thrust is applied to reduce the deformation of the foundation pit retaining structure. The gaps between the piers and the foundation pit retaining structure during the jacking process are filled with grouting materials.

[0009] Step 3: Repeat step 2 to complete the construction of each layer of reverse-constructed structural beams and slabs and the application of the top thrust of each servo jack in sequence; after the construction of the basement foundation slab is completed, remove the servo jacks in stages, connect the main reinforcement of the first structure and the main reinforcement of the second structure to ensure the effective force transmission of the main reinforcement, and construct the remaining reverse-constructed structural beams and slabs at the rear pouring position to complete the entire basement structure.

[0010] Based on the above technical solution: while constructing the exterior wall hidden beam, the exterior wall vertical main reinforcement and water-stop steel plates should be reserved at the top and bottom of the exterior wall hidden beam for the later construction of the basement exterior wall.

[0011] Based on the above technical solution: the hidden beam of the outer wall is connected to the foundation pit retaining structure through hangers.

[0012] The concept of the above technical solution is: in the foundation pit project, the retaining structure is deformed into the foundation pit due to the unloading of earthwork in the foundation pit, which in turn causes the settlement and deformation of the buildings and underground pipelines outside the pit. The deformation of the foundation pit retaining structure is directly related to the settlement and deformation of the surrounding buildings and underground pipelines. Therefore, controlling the deformation of the retaining structure is beneficial to reducing the impact of the foundation pit excavation on the surrounding environment. Post-cast strips are set around the beams and slabs of the high-rigidity reverse-construction structure, and servo jacks are set on the post-cast strips to apply horizontal thrust to the retaining structure, which can effectively reduce the deformation of the foundation pit retaining structure. At the same time, this technical measure does not increase temporary support components and does not require secondary chiseling, thereby avoiding waste of resources and is conducive to the green and sustainable development of foundation pit projects.

[0013] The present invention uses a deformation control method for implementing foundation pit engineering by the reverse construction method, which can effectively control the deformation of the retaining structure of the deep foundation pit engineering by the reverse construction method, thereby reducing the impact of foundation pit excavation construction on surrounding buildings and underground pipelines, and plays an important role in urban renewal construction projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a cross-sectional schematic diagram of setting up a servo system in combination with the foundation pit reverse construction structure beam and slab in the present invention.

[0015] Figure 2 It is a plan view schematic diagram of setting up a servo system in combination with the foundation pit reverse construction structure beam and slab in the present invention.

[0016] The numbers in the figure are as follows: foundation pit retaining structure 1; temporary supporting side column 2; intermediate supporting pile column 3; reverse structure beam slab 4; external wall hidden beam 5; servo jack 6; support plate structure 7; pier 8; external wall vertical main reinforcement 9; water stop steel plate 10; ring beam node structure 11; internal structure side beam 12; hanger bar 13; first structure main reinforcement 14; second structure main reinforcement 15. DETAILED DESCRIPTION

[0017] The specific embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. These embodiments are only used to illustrate the present invention, but not to limit the present invention.

[0018] In the description of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying 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 operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0019] Furthermore, in the description of the present invention, unless otherwise specified, “plurality” means two or more.

[0020] The present invention provides a method for controlling the deformation of a retaining structure for deep foundation pit engineering by reverse construction. In the development of deep and multi-layer underground space under complex and sensitive environmental conditions in the central urban area, the construction method can effectively reduce the impact of the construction process on the surrounding environment of the foundation pit in the reverse construction deep foundation pit engineering. The specific description is as follows in conjunction with the accompanying drawings.

[0021] The construction steps of the technical solution 1 of the present invention are as follows: Figure 1~Figure 2 The specific construction steps are as follows: Step 1: First construct the foundation pit retaining structure 1, temporary supporting side columns 2 and intermediate supporting piles 3. The temporary supporting side columns 2 surround the outer periphery of the intermediate supporting piles 3, and the intermediate supporting piles 3 are set at the permanent structure column position of the basement.

[0022] Step 2: Excavate the foundation pit to below the elevation of the reverse-construction structure beam slab 4, and construct the reverse-construction structure beam slab 4 and the external wall hidden beam 5; the external wall hidden beam 5 is located on the side wall of the foundation pit retaining structure 1; a post-casting strip is reserved between the reverse-construction structure beam slab 4 and the external wall hidden beam 5 for arranging the servo jack 6; a cantilevered support plate structure 7 is set around the reverse-construction structure beam slab 4 to hold up the servo jack 6. The position of the servo jack 6 is aligned with the structural main beam of the reverse-construction structure beam slab 4; the reverse-construction structure beam slab between the positions of the servo jack 6 extends to the side of the external wall hidden beam 5 as a buttress 8 to hold the foundation pit retaining structure 1 tightly; the reverse-construction structure beam slab 4 is connected to the intermediate supporting pile column 3 through the ring beam node structure 11; the internal structure side beam 12 is set around the reverse-construction structure beam slab 4 to connect with the temporary supporting side column 2; in the post-casting strip, the first structural main reinforcement 14 reserved for the external wall hidden beam 5; the second structural main reinforcement 15 reserved for the reverse-construction structure beam slab 4. A servo jack 6 is installed between the top-down structural beam 4 and the outer wall hidden beam 5 to apply a jacking force, thereby reducing the deformation of the foundation pit retaining structure 1. During the jacking process, the gap between the pier 8 and the foundation pit retaining structure 1 should be filled with grouting materials in time.

[0023] Step 3: Repeat step 2 to complete the construction of each layer of top-down structural beams and slabs 4 and the application of top thrust of each servo jack 6 in sequence; after the construction of the basement foundation slab is completed, the servo jack 6 is removed in stages, and the first structural main reinforcement 14 and the second structural main reinforcement 15 are connected to ensure the effective force transmission of the structural main reinforcement. The remaining top-down structural beams and slabs 4 at the post-casting position are constructed to complete the entire basement structure.

[0024] In the above technical solution: while constructing the exterior wall concealed beam 5, exterior wall vertical main reinforcement 9 and water-stop steel plate 10 should be reserved at the top and bottom of the exterior wall concealed beam 5 for later construction of the exterior wall of the basement.

[0025] In the above technical solution: the outer wall hidden beam 5 can be connected to the foundation pit retaining structure 1 through the hanger rod 13.

[0026] In addition, when the track servo jack 6 applies a jacking force, in order to prevent the support plate structure 7 from being damaged, the support plate structure 7 is cantilevered from the periphery of the reverse structural beam plate 4 to transmit force on one side.

[0027] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A deformation control method for implementing foundation pit engineering by reverse construction, characterized in that: Step 1: First, construct a foundation pit retaining structure (1), temporary supporting side columns (2) and intermediate supporting piles (3) in the foundation pit, wherein the temporary supporting side columns (2) surround the periphery of the intermediate supporting piles (3); and the intermediate supporting piles (3) are arranged at the permanent structural column position of the basement; Step 2: Excavate the foundation pit to below the elevation of the reverse-construction structure beam slab (4), and construct the reverse-construction structure beam slab (4) and the external wall hidden beam (5); the external wall hidden beam (5) is located on the side wall of the foundation pit retaining structure (1); a post-cast strip is reserved between the reverse-construction structure beam slab (4) and the external wall hidden beam (5) for arranging the servo jack (6); a cantilevered support plate structure (7) is arranged around the reverse-construction structure beam slab (4) for supporting the servo jack (6), and the position of the servo jack (6) is aligned with the structural main beam of the reverse-construction structure beam slab (4); the reverse-construction structure beam slab between the positions of the servo jack (6) extends to the side of the external wall hidden beam (5) as a buttress (8) to press against the foundation pit retaining structure (1) ; The reverse-construction structural beam plate (4) is connected to the intermediate supporting pile column (3) through a ring beam node structure (11); an inner structural side beam (12) is arranged around the reverse-construction structural beam plate (4) and connected to the temporary supporting side column (2); in the post-cast zone, a first structural main reinforcement (14) is reserved on the side of the external wall hidden beam (5); a second structural main reinforcement (15) is reserved on the side of the reverse-construction structural beam plate (4); a servo jack (6) is installed between the reverse-construction structural beam plate (4) and the external wall hidden beam (5) and a jacking force is applied to reduce the deformation of the foundation pit retaining structure (1); during the jacking process, the gap between the pier (8) and the foundation pit retaining structure (1) is filled with grouting material; Step 3: Repeat step 2 to sequentially complete the construction of the reverse-constructed structural beams and slabs (4) of each layer and the application of the top thrust of each servo jack (6); after the construction of the basement foundation slab is completed, the servo jacks (6) are removed in stages, and the first structural main reinforcement (14) and the second structural main reinforcement (15) are connected; the remaining reverse-constructed structural beams and slabs (4) at the post-casting zone are constructed to complete the entire basement structure.

2. The deformation control method for implementing foundation pit engineering by reverse construction according to claim 1 is characterized in that: While constructing the exterior wall concealed beam (5), exterior wall vertical main reinforcement (9) and water-stop steel plates (10) should be reserved at the top and bottom of the exterior wall concealed beam (5) for later construction of the exterior wall of the basement.

3. The deformation control method for implementing foundation pit engineering by reverse construction according to claim 1 is characterized in that: The outer wall concealed beam (5) is connected to the foundation pit retaining structure (1) via a hanger bar (13).

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