Multi-angle prestressed bracing structure in foundation pit and method for applying prestress to enclosure

Abstract

The application discloses a multi-angle prestressed top support structure in a foundation pit and a method for applying prestress to a retaining structure. The prestressed top support structure comprises a telescopic top support mechanism, which has a telescopic top support end; the telescopic top support mechanism can swing up and down; a load-bearing surrounding purlin (21) is arranged at a position near the bottom of the retaining structure; the telescopic top support mechanism can swing to an angle at which the top support end faces the load-bearing surrounding purlin, and the top support end of the telescopic top support mechanism can extend out and support on the load-bearing surrounding purlin. The method for applying prestress comprises the following steps: constructing the prestressed top support structure before subsequent lower-layer earth excavation, and applying top support prestress to the retaining structure (6) by using the prestressed top support structure. The prestressed top support structure and the method for applying prestress apply top support prestress to the position near the bottom of the retaining structure based on the near-bottom horizontal support (41), and displacement and deformation of the position near the bottom of the retaining structure can be timely controlled.

Description

Technical Field

[0001] This invention relates to the field of foundation pit engineering technology, and more particularly to a multi-angle prestressed top support structure in a foundation pit and a method for applying prestress to the retaining wall. Background Technology

[0002] Excavation of foundation pits can cause settlement and displacement of the surrounding strata, thereby affecting the safety of nearby subway tunnels and buildings. The main reason for this is that excavation of foundation pits leads to displacement and deformation of the surrounding soil.

[0003] Currently, in order to solve this problem, some technical solutions have been proposed by those skilled in the art. For example, a series of patents, represented by "A Support System for Active Control of Foundation Pit Displacement" (CN201810101897.5), propose a solution using "concrete support combined with a force-applying device". The main technical concept is to use the force-applying device to apply a lateral thrust to the retaining structure outward from the foundation pit, which can achieve active control of the displacement and deformation of the retaining structure.

[0004] The current problem is:

[0005] The existing "concrete support combined with reinforcement device" solution can only apply top-support prestress to the upper and middle parts of the retaining structure, but cannot apply top-support prestress to the retaining structure near the bottom of the pit in a timely manner. Especially before the lower-level pit structure is completed, the inability to apply top-support prestress to the retaining structure near the bottom of the pit may cause displacement and deformation of the retaining structure near the bottom of the pit before the lower-level pit structure is completed, which is detrimental to the construction quality of the entire pit project. Summary of the Invention

[0006] The purpose of this invention is to provide a multi-angle prestressed top support structure in the foundation pit. This prestressed top support structure applies top support prestress to the retaining wall near the bottom of the pit based on the horizontal support near the bottom of the pit, so that the displacement deformation of the retaining wall near the bottom of the pit can be controlled in a timely manner.

[0007] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution:

[0008] A multi-angle prestressed top support structure for an excavation pit, wherein a horizontal support near the bottom of the pit is constructed within the excavation pit;

[0009] The prestressed jacking structure includes a telescopic jacking mechanism, which has a jacking end that can extend and retract; the body of the telescopic jacking mechanism is assembled and connected to a horizontal support near the bottom of the pit, and the telescopic jacking mechanism can swing up and down based on the horizontal support near the bottom of the pit.

[0010] A load-bearing waler is installed near the bottom of the pit.

[0011] The telescopic support mechanism can swing to an angle where its support end faces downwards toward the load-bearing waler, and the support end of the telescopic support mechanism can extend downwards and support the load-bearing waler.

[0012] Furthermore, an assembly gap is left between the edge of the horizontal support near the pit bottom and the enclosure structure; the body of the telescopic top support mechanism is assembled and connected to the edge of the horizontal support near the pit bottom through a pin mechanism.

[0013] The telescopic support mechanism can swing to the assembly interval, and the support end of the telescopic support mechanism can extend laterally and support the enclosure structure.

[0014] Furthermore, the prestressed jacking structure also includes an outward-cantilevered support, which is located at the edge of the horizontal support near the bottom of the pit and at the assembly interval; the outward-cantilevered support forms a jacking posture for the retaining structure based on the edge of the horizontal support near the bottom of the pit.

[0015] Furthermore, a waler is provided on the enclosure structure for the horizontal support near the bottom of the pit, and the assembly interval is the space between the edge of the horizontal support near the bottom of the pit and the waler.

[0016] Furthermore, a ring beam is provided at the edge of the horizontal support near the bottom of the pit.

[0017] Furthermore, the part where the telescopic top support mechanism is assembled and connected to the horizontal support near the bottom of the pit is located at the connection point between the horizontal support near the bottom of the pit and the anti-uplift pile.

[0018] Furthermore, the telescopic support mechanism is specifically implemented in the following structural form: a two-section telescopic steel pipe is used as the telescopic support mechanism, and a telescopic hydraulic cylinder for driving telescopic extension is installed inside the telescopic steel pipe.

[0019] Furthermore, the body of the telescopic top support mechanism is assembled and connected to the horizontal support near the bottom of the pit, specifically, the body of the telescopic top support mechanism is assembled and connected to the horizontal support near the bottom of the pit through a pin mechanism.

[0020] Furthermore, the cantilevered support is made of concrete or steel.

[0021] A method for applying prestress to the retaining wall within a foundation pit, the method comprising:

[0022] S1, construct horizontal support near the bottom of the pit;

[0023] S2, a prestressed top support structure is constructed based on the horizontal support near the bottom of the pit, and the construction of the prestressed top support structure is completed before the subsequent excavation of the next layer;

[0024] The constructed prestressed jacking structure includes a telescopic jacking mechanism, which has a jacking end that can extend and retract; the body of the telescopic jacking mechanism is assembled and connected to a horizontal support near the bottom of the pit, and the telescopic jacking mechanism can swing up and down based on the horizontal support near the bottom of the pit.

[0025] A load-bearing waler is installed near the bottom of the pit.

[0026] S3, applying prestressed bracing to the enclosure structure using a prestressed bracing structure, including:

[0027] Apply prestress to the retaining wall near the bottom of the pit using a prestressed jacking structure: Swing the telescopic jacking mechanism to an angle where its jacking end is angled downward toward the load-bearing waler, so that the jacking end of the telescopic jacking mechanism extends downward and supports the load-bearing waler; Control the telescopic jacking mechanism to apply prestress to the retaining wall near the bottom of the pit according to the deformation of the retaining wall near the bottom of the pit.

[0028] Furthermore, an assembly gap is left between the edge of the constructed near-bottom horizontal support and the enclosure structure; the body of the telescopic top support mechanism is assembled and connected to the edge of the near-bottom horizontal support through a pin mechanism.

[0029] The prestressed jacking structure also includes cantilevered supports, which are located at the edge of the horizontal support near the bottom of the pit and at the assembly interval; the cantilevered supports form a jacking posture for the retaining structure based on the edge of the horizontal support near the bottom of the pit.

[0030] The method of applying prestressed support to the enclosure structure using a prestressed support structure also includes:

[0031] Applying transverse prestressing to the enclosure structure using a prestressed bracing structure:

[0032] Swing the telescopic support mechanism to the assembly interval, with the support end of the telescopic support mechanism extending laterally and supporting the enclosure structure; control the telescopic support mechanism to apply support prestress to the enclosure structure according to the deformation of the enclosure structure; inject adhesive grout between the cantilever support and the enclosure structure to connect the cantilever support and the enclosure structure together.

[0033] Furthermore, when constructing the prestressed top support structure, the soil near the bottom of the pit is removed to facilitate the construction of a load-bearing waler near the bottom of the pit.

[0034] A multi-angle prestressed jacking structure for foundation pits, the prestressed jacking structure includes a telescopic jacking mechanism, the telescopic jacking mechanism having a jacking end that can extend and retract; the body of the telescopic jacking mechanism is assembled and connected to a horizontal support near the bottom of the pit, and the telescopic jacking mechanism can swing up and down based on the horizontal support near the bottom of the pit.

[0035] The telescopic support mechanism can swing to an angle where its support end is angled downward toward the bottom of the enclosure near the pit, and the support end of the telescopic support mechanism can extend downward and support the enclosure near the bottom of the pit.

[0036] The main advantages of the prestressed top support structure of the present invention compared with the prior art are as follows:

[0037] After the construction of the horizontal support near the bottom of the pit is completed, the construction of the prestressed top support structure begins immediately and is completed before the subsequent excavation of the next layer. The prestressed top support structure has segmented telescopic steel pipes, which apply top support prestress to the bottom of the retaining wall based on the horizontal support near the bottom of the pit. In this way, the bottom of the retaining wall can receive the applied top support prestress in the first instance, so that the displacement and deformation of the bottom of the retaining wall can be controlled in a timely manner, thereby improving the overall engineering quality of the foundation pit project. Attached Figure Description

[0038] Figures 1 to 3 This is a schematic diagram of the multi-angle prestressed jacking structure within the foundation pit according to the present invention.

[0039] in,

[0040] Figure 1 This is a side view, showing the segmented telescopic steel pipe in a horizontal position.

[0041] Figure 2 This is a side view, showing the segmented telescopic steel pipe at an angle downwards.

[0042] Figure 3 This is a top view of the horizontal support near the bottom of the pit;

[0043] Figure 4 This is a schematic diagram showing the assembly and connection of the segmented telescopic steel pipe with the horizontal support near the bottom of the pit.

[0044] Figures 5 to 7 This is a schematic diagram illustrating the application of prestressed top support structure to the enclosure structure using the prestressed top support structure of the present invention.

[0045] in,

[0046] Figure 5 This is a schematic diagram of applying transverse bracing prestress to the enclosure structure using a prestressed top bracing structure;

[0047] Figure 6 This is a schematic diagram of applying prestressed top support structure to the retaining wall near the bottom of the pit;

[0048] Figure 7 This is a schematic diagram showing the excavation work for the next stage after the top support prestress has been applied to the retaining structure. Detailed Implementation

[0049] First, to facilitate a clear and accurate description of the technical solution later in the text, the following definitions are made in advance:

[0050] Definition 1: The “current pit bottom” mentioned in this article refers to the bottom of the pit during the excavation process of foundation pit construction. The “current pit bottom” is a dynamic concept. Wherever the foundation pit is excavated, that is the “current pit bottom”.

[0051] Definition 2: The “design pit bottom” mentioned in this article refers to the bottom of the foundation pit in the foundation pit engineering design. The “design pit bottom” is a static concept.

[0052] Definition 3: The term "retaining structure near the bottom of the pit" as used in this article refers to the part of the retaining structure that is close to the current pit bottom. This "retaining structure near the bottom of the pit" is a dynamic concept that changes with the current position of the pit bottom. For example, when the "current pit bottom" is excavated to a depth of 1 meter, the upper and lower parts of the retaining structure at the 1-meter depth are the "retaining structure near the bottom of the pit".

[0053] Definition 4: The "near-bottom horizontal support" mentioned in this article refers to the horizontal support structure that has been constructed within the foundation pit and is closest to the current pit bottom. This "near-bottom horizontal support" is a dynamic concept. For example, when the first layer of horizontal support structure is completed, this first layer of horizontal support structure is the near-bottom horizontal support; when the second layer of horizontal support structure is completed, this second layer of horizontal support structure is the near-bottom horizontal support.

[0054] Definition 5: The “retaining support system” mentioned in this article is a broad concept that encompasses all forms of “support structures” and their combinations within the foundation pit that support the retaining structure, such as “upward-sloping support structures” and “horizontal support structures”.

[0055] Definition 6: The "lower-level foundation pit structure" mentioned in this article refers to the deeper foundation pit structure that will be constructed in the next stage of foundation pit construction. This "lower-level foundation pit structure" is a dynamic concept. For example, if the foundation pit is designed with two layers of horizontal support structures, after the first layer of horizontal support structure is constructed, the second layer of horizontal support structure to be constructed next is the lower-level foundation pit structure. After the second layer of horizontal support structure is constructed, the foundation pit bottom structure to be constructed next is also the lower-level foundation pit structure.

[0056] Definition 7: The term "lower-level excavation work" as used in this article refers to the excavation work performed during the construction of a foundation pit before the construction of a deeper layer of the pit structure. This excavation is necessary to create space for the deeper layer of the foundation pit structure. For example, if a foundation pit is designed with two layers of horizontal support structures, after the first layer is completed, excavation is required to create space for the second layer. This excavation work is considered a lower-level excavation operation.

[0057] The main concept of this invention is:

[0058] Based on the horizontal support 41 near the bottom of the pit, a downwardly inclined support component is installed towards the pit retaining structure. This downwardly inclined support component supports the retaining structure near the bottom of the pit. Then, a supporting force-applying mechanism is provided for the downwardly inclined support component, which can drive the downwardly inclined support component to apply supporting prestress to the retaining structure near the bottom of the pit.

[0059] The main concept of this invention is roughly as described above. In this way, prestressed top support can be applied to the retaining wall near the bottom of the pit before the lower-level foundation pit structure is completed, so as to take corresponding measures to deal with the possible displacement and deformation of the retaining wall near the bottom of the pit in a timely manner, thereby improving the overall engineering quality of the foundation pit project.

[0060] The concept of the present invention will be further illustrated below with specific embodiments:

[0061] See Figure 1 The following is a brief introduction to the foundation pit engineering structure involved in this embodiment.

[0062] Those skilled in the art will understand that the overall engineering structure of the foundation pit mainly includes the retaining structure 6 and the retaining support system, the specific structural configuration of which is as follows:

[0063] The retaining structure 6 is constructed around the perimeter of the foundation pit, and the retaining support system is usually set inside the foundation pit to provide support for the retaining structure 6.

[0064] In this embodiment, the retaining support system mainly consists of several layers of horizontal support structures 4, which are set inside the foundation pit and provide support for the retaining structure 6. In this embodiment, the number of horizontal support structures 4 is three.

[0065] For each layer of horizontal support structure 4, a corresponding waler 7 is provided on the retaining structure 6. Except for the waler 7 provided for the pit top horizontal support structure 4, which is located at the top of the retaining structure 6, the other walers 7 are all located on the free side of the retaining structure 6. The upper two layers of horizontal support structures 4 in the pit are connected to the retaining structure 6 through the walers 7, thereby forming a support for the retaining structure 6.

[0066] The third layer of horizontal support structure 4, namely the horizontal support 41 near the bottom of the pit, has a certain gap between its edge and the waler 7. In other words, the two are separated by a gap. This gap is specifically used to install the prestressing mechanism. The edge of the horizontal support 41 near the bottom of the pit is connected to the waler 7 through the installed prestressing mechanism, and then connected to the retaining structure 6 through the waler 7, thereby forming support for the retaining structure 6.

[0067] For ease of subsequent description, the spaced-out area will be referred to as the assembly interval.

[0068] It should be noted that in other embodiments, if the waler 7 is not provided on the enclosure structure 6, then the assembly interval refers to the gap between the edge of the horizontal support 41 near the bottom of the pit and the enclosure structure 6.

[0069] In this embodiment, the retaining support system also includes a certain number of tension piles 5, which are fixedly installed in the foundation pit. Then, the previously mentioned multi-layer horizontal support structure 4 is connected to the tension piles 5 (the connection between the upper two layers of horizontal support structure 4 and the tension piles 5 is not shown in the figure). It should be noted that the tension piles 5 are columns, column piles, etc.

[0070] In this embodiment, a ring beam 3 is provided at the edge of the horizontal support 41 near the bottom of the pit. The ring beam 3 is connected to a number of anti-uplift piles 5. These anti-uplift piles 5 provide vertical support, especially downward support, to the edge of the horizontal support 41 near the bottom of the pit. This provides a strong foundation for the segmented telescopic steel pipe 11, which will be mentioned later. The edge of the horizontal support 41 near the bottom of the pit will not deform due to the reaction force generated by the prestress applied by the segmented telescopic steel pipe 11.

[0071] In addition, in order to facilitate the detection of displacement and deformation of the enclosure structure 6 and obtain the corresponding data, in this embodiment, an inclinometer (existing technology) is pre-embedded inside the enclosure structure 6. The inclinometer can detect and obtain relevant data on displacement and deformation of the enclosure structure 6.

[0072] Those skilled in the art will understand that the above-described foundation pit engineering structure is a structure of the prior art.

[0073] See Figures 1 to 3This embodiment provides a multi-angle prestressed support structure in the foundation pit. The prestressed support structure is set based on the foundation pit engineering structure. The prestressed support structure can apply support prestress to the retaining wall near the bottom of the pit, thereby preventing displacement and deformation of the retaining wall near the bottom of the pit in the first time.

[0074] The prestressed top support structure mainly includes numerous segmented telescopic steel pipes 11, which are equivalent to downward-sloping support components.

[0075] These numerous segmented telescopic steel pipes 11 are all located at the previously mentioned assembly intervals and are evenly and discretely arranged around the edge of the horizontal support 41 near the bottom of the pit.

[0076] See Figure 4 For each segmented telescopic steel pipe 11, the segmented telescopic steel pipe 11 is two-sectioned. For ease of description, one section is called the body section, and the end of the body section is called the body end; the other section is called the top support section, and the end of the top support section is called the top support end. A telescopic hydraulic cylinder 17 is provided in the segmented telescopic steel pipe 11. The body (cylinder body) of the telescopic hydraulic cylinder 17 is connected to the body section of the segmented telescopic steel pipe 11 by a flange connection (or welding). The telescopic end (cylinder head) of the telescopic hydraulic cylinder 17 is connected to the top support section of the segmented telescopic steel pipe 11 by a flange connection (or welding). In this way, the telescopic hydraulic cylinder 17 can drive the segmented telescopic steel pipe 11 to perform telescopic movements.

[0077] In summary, the telescopic hydraulic cylinder 17 is installed in the segmented telescopic steel pipe 11 as a telescopic drive device, and the segmented telescopic steel pipe 11 can apply a supporting force to the outside under the drive of the telescopic drive device.

[0078] The segmented telescopic steel pipe 11 can be understood as a telescopic support mechanism. In other embodiments, other forms of telescopic support mechanisms can be used to replace the segmented telescopic steel pipe 11.

[0079] In summary, the telescopic top support mechanism should have a telescopic top support end (equivalent to the top support end of the segmented telescopic steel pipe 11), and the body of the telescopic top support mechanism (equivalent to the body end of the segmented telescopic steel pipe 11) is assembled and connected to the horizontal support 41 near the bottom of the pit through a pin mechanism.

[0080] In other implementations, for example, an extended jack can be used as a telescopic support mechanism to replace the segmented telescopic steel pipe, achieving the same effect.

[0081] For each section of the telescopic steel pipe 11

[0082] The main body end of the segmented telescopic steel pipe 11 is assembled with the edge of the near-bottom horizontal support 41 via a quick-detachable axle pin mechanism, specifically assembled on the end face of the edge of the near-bottom horizontal support 41. In this way, the segmented telescopic steel pipe 11 can swing up and down based on the edge of the near-bottom horizontal support 41 (or, in other words, rotate around its own main body end at a certain angle).

[0083] For all the segmented telescopic steel pipes 11, a ring of walers is fixedly installed near the bottom of the pit as a load-bearing waler 21. The load-bearing waler 21 has an upwardly inclined load-bearing surface 211, which is used to support the top of the segmented telescopic steel pipes 11.

[0084] The segmented telescopic steel pipe 11 can swing to an azimuth angle where "the top support end of the segmented telescopic steel pipe 11 is obliquely downward toward the load-bearing surface 211 of the load-bearing waler 21" (e.g., Figure 2 (As shown), then control the telescopic hydraulic cylinder 17 to drive the segmented telescopic steel pipe 11 to extend until the top support end of the segmented telescopic steel pipe 11 leans downward against the top support on the bearing surface 211 of the bearing waler 21. Then continue to control the segmented telescopic steel pipe 11 to extend. In this way, the effect of "applying top support prestress to the bottom of the enclosure based on the horizontal support 41 near the bottom of the pit" can be achieved.

[0085] The segmented telescopic steel pipe 11 can not only apply top support prestress to the bottom of the enclosure, but also apply top support prestress laterally to the enclosure structure 6. This can be achieved by simply swinging the segmented telescopic steel pipe 11 to a horizontal azimuth angle (e.g., Figure 1 As shown), at this time, the segmented telescopic steel pipe 11 is at the assembly interval, that is, between the edge of the horizontal support 41 near the bottom of the pit and the retaining structure 6. Then, the top support end of the segmented telescopic steel pipe 11 is supported on the waler 7, and the top support prestress applied by the segmented telescopic steel pipe 11 is applied to the retaining structure 6 through the waler 7.

[0086] The advantage of this setup is that segmented telescopic steel pipes 11 can be used to temporarily apply top-support prestress to the retaining structure 6 in the horizontal direction, and then pad blocks (such as supports, steel sections, etc.) can be placed in the assembly intervals. In this way, the pad blocks can replace the segmented telescopic steel pipes 11 to achieve the effect of "applying transverse top-support prestress to the retaining structure 6 based on the near-bottom horizontal support 41".

[0087] In this embodiment, the prestressed jacking structure also includes numerous cantilevered supports 8.

[0088] The cantilevered supports 8 are installed at the edge of the horizontal support 41 near the bottom of the pit (i.e., at the ring beam 3) by being cast together with the edge of the horizontal support structure 4. These numerous cantilevered supports 8 are all located at the assembly intervals, that is, between the edge of the horizontal support 41 near the bottom of the pit and the waler 7, and are evenly and discretely arranged around the edge of the horizontal support 41 near the bottom of the pit. These numerous cantilevered supports 8 are arranged alternately with numerous segmented telescopic steel pipes 11.

[0089] Each cantilevered support 8 is based on the edge of the horizontal support 41 near the bottom of the pit to form a supporting posture for the waler 7. In essence, the waler 7 forms a supporting posture for the retaining structure 6.

[0090] It should be noted that at this time, the cantilevered support 8 only forms a "supporting posture" and does not come into contact with the waler 7. The two are very close to each other, thus forming a "supporting posture".

[0091] These cantilevered supports 8 essentially function as the pad blocks mentioned earlier.

[0092] When it is necessary to permanently "apply lateral top-support prestress to the retaining structure 6 based on the near-bottom horizontal support 41", the segmented telescopic steel pipe 11 is swung to a horizontal azimuth angle, and then the top-support end of the segmented telescopic steel pipe 11 is supported on the waler 7. The segmented telescopic steel pipe 11 is controlled to apply a large top-support prestress to the retaining structure 6, so that the assembly interval is slightly larger. Then, adhesive grout is injected at the part where the "top-support posture" is formed between the cantilever support 8 and the waler 7. After the adhesive grout has completely solidified, the cantilever support 8 and the waler 7 are truly connected together. The cantilever support 8 is truly based on the near-bottom horizontal support 41 and applies lateral top-support prestress to the retaining structure 6 through the waler 7.

[0093] It should be noted that in other embodiments, if the waler 7 is not provided on the retaining structure 6, then when applying transverse top bracing prestress to the retaining structure 6, the segmented telescopic steel pipe 11 and the cantilevered support 8 directly support the retaining structure 6. For example, when the retaining structure 6 is a continuous wall retaining structure, it is not necessary to provide the waler 7.

[0094] This embodiment also provides a method for applying prestress to the retaining wall within the excavation pit. This method is used to achieve "applying top-support prestress to the retaining wall near the bottom of the pit". In essence, this method uses the previously described prestressed top-support structure concept to achieve "applying top-support prestress to the retaining wall near the bottom of the pit".

[0095] Specifically, the method for applying prestress in this embodiment includes:

[0096] S1, construct a horizontal support 41 near the bottom of the pit at the construction location of the foundation pit.

[0097] It should be noted that the near-bottom horizontal support 41 is constructed based on the pre-built anti-uplift piles 5 in the foundation pit.

[0098] The constructed near-bottom horizontal support 41 is as described above and will not be repeated here.

[0099] S2, after the construction of the near-bottom horizontal support 41 is completed in step S1, the construction of the prestressed top support structure based on the near-bottom horizontal support 41 is immediately started, and the construction of the prestressed top support structure is completed before the subsequent excavation work of the next layer.

[0100] The constructed prestressed top support structure is as described above and will not be repeated here.

[0101] See Figure 5 and Figure 6 It should be noted that when constructing the prestressed jacking structure, it is necessary to first excavate near the bottom of the pit in the retaining wall area to remove the soil in the vicinity of the pit bottom. The purpose of doing this is...

[0102] On the one hand, it is to enable the construction and installation of load-bearing walers 21 near the bottom of the pit.

[0103] On the other hand, it provides operating space for "the segmented telescopic steel pipe 11 to swing downward toward the bearing surface 211 of the bearing waler 21, and then for the top support end of the segmented telescopic steel pipe 11 to abut against the bearing surface 211 of the bearing waler 21".

[0104] It should be noted that "excavating soil near the bottom of the pit" here does not fall under the category of "lower-level excavation work".

[0105] S3, apply prestressed bracing to the enclosure structure 6 using the constructed prestressed bracing structure.

[0106] Step S3 specifically includes S31 to S32.

[0107] S31, apply transverse prestressing to the enclosure structure 6 using a prestressed top support structure.

[0108] Specifically

[0109] The segmented telescopic steel pipe 11 is swung to a horizontal position, i.e., at the assembly interval. Then, the telescopic steel pipe 11 is controlled and adjusted to extend and extend laterally, so that the top support end of the segmented telescopic steel pipe 11 extends laterally and supports the waler 7. The top support prestress applied by the segmented telescopic steel pipe 11 is then applied to the enclosure structure 6 through the waler 7. Existing detection methods are used to detect the deformation condition (deformation data) of the enclosure structure 6. Based on the deformation condition of the enclosure structure 6 and in accordance with the design standards, the segmented telescopic steel pipe 11 is controlled to apply appropriate top support prestress to the enclosure structure 6, so that the deformation condition of the enclosure structure 6 meets the design standards.

[0110] As mentioned above, an outward-cantilevered support 8 is pre-installed at the edge of the horizontal support 41 near the bottom of the pit. Adhesive grout is injected at the location where a "top-support posture" is formed between the outward-cantilevered support 8 and the waler 7. After the adhesive grout has completely solidified, the outward-cantilevered support 8 and the waler 7 are truly connected together. The outward-cantilevered support 8 is truly based on the horizontal support 41 near the bottom of the pit and applies transverse top-support prestress to the retaining structure 6 through the waler 7.

[0111] At this point, the segmented telescopic steel pipe 11 can be controlled to retract, and the cantilever support 8 can play the role of applying lateral top support prestress.

[0112] It should be noted that in other embodiments, if the retaining structure 6 is not equipped with a waler 7, the top support end of the segmented telescopic steel pipe 11 and the cantilever support 8 directly support the retaining structure 6.

[0113] S32, using a prestressed top support structure to apply top support prestress to the area near the bottom of the pit in the retaining structure.

[0114] Specifically

[0115] Swing the segmented telescopic steel pipe 11 to the position angle where "the top support end of the segmented telescopic steel pipe 11 is obliquely downward toward the bearing surface 211 of the bearing waler 21", and then control and adjust the extension and retraction of the segmented telescopic steel pipe 11 so that the top support end of the segmented telescopic steel pipe 11 extends obliquely downward and abuts against the bearing surface 211 of the bearing waler 21. The top support prestress applied by the segmented telescopic steel pipe 11 is then applied to the bottom of the enclosure through the bearing waler 21.

[0116] Existing detection methods are used to detect the deformation of the retaining wall near the bottom of the pit (deformation data). Based on the deformation of the retaining wall near the bottom of the pit and in accordance with the design standards, the segmented telescopic steel pipe 11 is controlled to apply appropriate top support prestress to the retaining wall near the bottom of the pit so that the deformation of the retaining wall near the bottom of the pit meets the design standards.

[0117] After the prestressing method is completed, the next stage of excavation can begin, such as... Figure 7 As shown.

[0118] It should be noted that in this embodiment, numerous inclinometers (existing technology) are installed inside the retaining structure 6. These inclinometers can detect the deformation of the retaining structure 6, including the deformation near the bottom of the pit.

[0119] It should be noted that the material of the cantilever support 8 can be concrete or steel structure.

[0120] It should be noted that the prestressed top support structure can be applied to the entire enclosure structure or to a partial enclosure structure.

[0121] The advantages of the prestressed support structure and prestressing application method in this embodiment are:

[0122] 1) In terms of current technology, it is usually done by first constructing a foundation pit structure of one level, and then applying top support prestress to the horizontal or upper retaining structure based on the constructed foundation pit structure.

[0123] For example, when the foundation pit project is constructed to the designed pit bottom position, the entire pit bottom structure is usually fully constructed first, and then a prestressed structure is built on the basis of the pit bottom structure to apply top support prestress to the retaining structure near the pit bottom.

[0124] This practice means that the retaining wall near the bottom of the pit will not receive prestressed support for a considerable period after the excavation of the next layer. During this time, the displacement and deformation of the retaining wall near the bottom of the pit cannot be controlled in a timely manner, and the effect of applying prestressed support later will be poor, thus affecting the overall quality of the foundation pit project. This situation is particularly prominent in deep foundation pit projects.

[0125] The most significant feature of the prestressed support structure and prestressing application method in this embodiment is that...

[0126] After the construction of the near-bottom horizontal support 41 is completed, the construction of the prestressed top support structure begins immediately and is completed before the subsequent excavation of the next layer. The prestressed top support structure includes segmented telescopic steel pipes 11, which apply prestressing to the near-bottom area of ​​the retaining wall based on the near-bottom horizontal support 41. This ensures that the near-bottom area of ​​the retaining wall receives the applied prestressing immediately, allowing for timely control of displacement and deformation, thereby improving the overall quality of the foundation pit project.

[0127] Furthermore, the prestressed top support structure and the method for applying prestress in this embodiment have the following advantages:

[0128] 2) Prestress can be applied from multiple angles, which makes up for the insufficiency of only being able to apply prestress horizontally;

[0129] 3) The sectional telescopic steel pipe 11 can be flexibly disassembled, which is green and environmentally friendly and saves resources.

[0130] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A multi-angle prestressed top support structure in a foundation pit, wherein a horizontal support (41) is constructed near the bottom of the pit. Its features are: The prestressed top support structure includes a telescopic top support mechanism, which has a telescopic top support end; the body of the telescopic top support mechanism is assembled and connected to the near-bottom horizontal support (41), and the telescopic top support mechanism can swing up and down based on the near-bottom horizontal support (41). A load-bearing waler (21) is installed near the bottom of the pit. The telescopic top support mechanism can swing to an angle where its top support end is obliquely downward toward the load-bearing waler (21), and the top support end of the telescopic top support mechanism can extend obliquely downward and support the load-bearing waler (21); There is an assembly gap between the edge of the near-bottom horizontal support (41) and the enclosure structure (6); the body of the telescopic top support mechanism is assembled and connected to the edge of the near-bottom horizontal support (41) through a shaft pin mechanism. The telescopic top support mechanism can swing to the assembly interval, and the top support end of the telescopic top support mechanism can extend laterally and support the enclosure structure (6); The prestressed top support structure also includes an outward-cantilevered support (8), which is located at the edge of the horizontal support (41) near the bottom of the pit and at the assembly interval; the outward-cantilevered support (8) forms a top support posture for the retaining structure (6) based on the edge of the horizontal support (41) near the bottom of the pit.

2. The multi-angle prestressed jacking structure in the foundation pit according to claim 1, characterized in that: A waler (7) is provided on the enclosure structure (6) for the horizontal support (41) near the bottom of the pit, and the assembly interval is the space between the edge of the horizontal support (41) near the bottom of the pit and the waler (7).

3. The multi-angle prestressed jacking structure in the foundation pit according to claim 1, characterized in that: A ring beam (3) is provided at the edge of the horizontal support (41) near the bottom of the pit.

4. The multi-angle prestressed jacking structure in the foundation pit according to claim 1, characterized in that: The telescopic top support mechanism is assembled and connected to the near-bottom horizontal support (41) at the connection between the near-bottom horizontal support (41) and the pull-out pile (5).

5. The multi-angle prestressed jacking structure in the foundation pit according to claim 1, characterized in that: The specific structural form of the telescopic support mechanism is as follows: a two-section telescopic steel pipe (11) is used as the telescopic support mechanism, and a telescopic hydraulic cylinder (17) for driving telescopic extension is installed inside the telescopic steel pipe (11).

6. The multi-angle prestressed jacking structure in the foundation pit according to claim 1, characterized in that: The telescopic top support mechanism is assembled and connected to the horizontal support (41) near the bottom of the pit. Specifically, the telescopic top support mechanism is assembled and connected to the horizontal support (41) near the bottom of the pit through a shaft pin mechanism.

7. The multi-angle prestressed jacking structure in the foundation pit according to claim 1, characterized in that: The cantilever support (8) is made of concrete or steel.

8. A method for applying prestress to the retaining wall within a foundation pit, the method employing a multi-angle prestressed top support structure within the foundation pit as described in any one of claims 1 to 7, characterized in that: The method for applying prestress includes: S1, construct horizontal support near the bottom of the pit (41). S2, based on the horizontal support (41) near the bottom of the pit, a prestressed top support structure is constructed, and the construction of the prestressed top support structure is completed before the subsequent excavation of the next lower level. The constructed prestressed top support structure includes a telescopic top support mechanism, which has a telescopic top support end; the body of the telescopic top support mechanism is assembled and connected to the near pit bottom horizontal support (41), and the telescopic top support mechanism can swing up and down based on the near pit bottom horizontal support (41). A load-bearing waler (21) is installed near the bottom of the pit. When constructing the prestressed top support structure, first excavate the soil near the bottom of the pit in the retaining wall to remove the soil near the bottom of the pit in the retaining wall, thereby providing operating space for constructing the prestressed top support structure. S3, applying prestressed bracing to the enclosure structure (6) using a prestressed bracing structure, including: Apply prestress to the bottom of the enclosure near the pit using a prestressed top support structure: swing the telescopic top support mechanism to an angle where its top support end is inclined downward toward the load-bearing waler (21), so that the top support end of the telescopic top support mechanism extends obliquely downward and supports the load-bearing waler (21); control the telescopic top support mechanism to apply prestress to the bottom of the enclosure near the pit according to the deformation of the enclosure near the pit.

9. The method for applying prestress to the retaining wall within the foundation pit according to claim 8, characterized in that: An assembly gap is left between the edge of the constructed near-bottom horizontal support (41) and the enclosure structure (6); the body of the telescopic top support mechanism is assembled and connected to the edge of the near-bottom horizontal support (41) through a shaft pin mechanism. The prestressed top support structure also includes an outward-cantilevered support (8), which is located at the edge of the horizontal support (41) near the bottom of the pit and at the assembly interval; the outward-cantilevered support (8) forms a top support posture for the retaining structure (6) based on the edge of the horizontal support (41) near the bottom of the pit. The method of applying prestressed support to the enclosure structure (6) using a prestressed support structure further includes: Apply transverse prestressing to the enclosure structure (6) using a prestressed top bracing structure: Swing the telescopic support mechanism to the assembly interval, and extend the support end of the telescopic support mechanism laterally and support it on the enclosure structure (6); according to the deformation of the enclosure structure (6), control the telescopic support mechanism to apply support prestress to the enclosure structure (6); inject adhesive grout between the cantilever support (8) and the enclosure structure (6) to connect the cantilever support (8) and the enclosure structure (6) together.

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