Multi-angle prestress back shore structure in foundation pit and method for applying prestress to enclosure

Abstract

The invention discloses a multi-angle prestress back shore structure in a foundation pit and a method for applying prestress to an enclosure. The prestressed jacking structure comprises a telescopic jacking mechanism, wherein the telescopic jacking mechanism is provided with a telescopic jacking end; the telescopic jacking mechanism can swing up and down; a bearing enclosing purlin (21) is arranged at the part, close to the pit bottom, of the enclosure; the telescopic jacking and supporting mechanism can swing to the angle that the jacking and supporting end of the telescopic jacking and supporting mechanism faces the force-bearing enclosing purlin, and the jacking and supporting end of the telescopic jacking and supporting mechanism can stretch out and be jacked and supported on the force-bearing enclosing purlin. The prestress applying method comprises the steps that construction of the prestress back shore structure is completed before subsequent digging operation of a lower layer, and back shore prestress is applied to the enclosure structure (6) through the prestress back shore structure. According to the prestress back shore structure and the prestress applying method, back shore prestress is applied to the portion, close to the pit bottom, of the enclosure on the basis of the horizontal support (41) close to the pit bottom, and displacement deformation of the portion, close to the pit bottom, of the enclosure can be controlled in time.

Description

Technical Field

[0001] The invention relates to the technical field of foundation pit engineering, and in particular to a multi-angle prestressed top support structure in a foundation pit and a method for applying prestress to a surrounding wall. Background Art

[0002] Excavation of foundation pits will cause settlement and displacement of surrounding strata, thus affecting the safety of nearby subway tunnels and buildings. The main reason is that excavation of foundation pits will cause displacement and deformation of surrounding soil.

[0003] At present, in order to solve this problem, technicians in this field have proposed some technical solutions. For example, a series of patents represented by "A support system for actively controlling the displacement of a foundation pit" (CN201810101897.5) proposed a solution of "concrete support combined with a force-adding device". The main technical concept is to use the force-adding device to apply a lateral thrust to the retaining structure outside the foundation pit, which can realize active control of the displacement and deformation of the retaining structure.

[0004] The current problem is:

[0005] The solution of "concrete support combined with force-adding device" in the prior art can only apply top support prestress to the middle and upper part of the enclosure structure, but cannot timely apply top support prestress to the enclosure near the bottom of the pit. In particular, before the lower level foundation pit structure is completed, top support prestress cannot be applied to the enclosure near the bottom of the pit. As a result, the enclosure near the bottom of the pit may be displaced and deformed before the lower level foundation pit structure is completed, which is not conducive to the construction quality of the entire foundation pit project. Summary of the invention

[0006] The purpose of the present invention is to provide a multi-angle prestressed top support structure in a foundation pit. The prestressed top support structure applies top support prestress to the surrounding area near the bottom of the pit based on the horizontal support near the bottom of the pit, so that the displacement and deformation of the surrounding area near the bottom of the pit can be controlled in time.

[0007] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0008] A multi-angle prestressed top support structure in a foundation pit, wherein a horizontal support near the bottom of the pit is constructed in the foundation pit;

[0009] 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 with the horizontal support near the pit bottom, and the telescopic top support mechanism can swing up and down based on the horizontal support near the pit bottom;

[0010] A load-bearing purlin is arranged near the bottom of the pit;

[0011] The telescopic supporting mechanism can swing to an angle where its supporting end is inclined downward toward the load-bearing purlin, and the supporting end of the telescopic supporting mechanism can extend obliquely downward and support on the load-bearing purlin.

[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 with the edge of the horizontal support near the pit bottom through a shaft pin mechanism;

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

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

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

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

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

[0018] Furthermore, the telescopic support mechanism is specifically implemented in the form of a structure in which a two-section telescopic steel pipe is used as the telescopic support mechanism, and a telescopic hydraulic cylinder for driving telescopic movement is arranged inside the telescopic steel pipe.

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

[0020] Furthermore, the material of the cantilever pier is concrete or steel structure.

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

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

[0023] S2, constructing a prestressed top support structure based on the horizontal support near the bottom of the pit, and completing the construction of the prestressed top support structure before the subsequent lower level excavation operation;

[0024] 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 with the horizontal support near the pit bottom, and the telescopic top support mechanism can swing up and down based on the horizontal support near the pit bottom;

[0025] A load-bearing purlin is arranged near the bottom of the pit;

[0026] S3, using prestressed top support structure to apply top support prestress to the enclosure structure, including:

[0027] A prestressed top support structure is used to apply top support prestress to the part of the enclosure near the bottom of the pit: the telescopic top support mechanism is swung to an angle where its top support end is obliquely downward toward the load-bearing purlin, so that the top support end of the telescopic top support mechanism extends obliquely downward and supports the load-bearing purlin; according to the deformation condition of the enclosure near the bottom of the pit, the telescopic top support mechanism is controlled to apply top support prestress to the part of the enclosure near the bottom of the pit.

[0028] Furthermore, an assembly interval is left between the edge of the constructed horizontal support near the pit bottom and the enclosure structure; the body of the telescopic top support mechanism is assembled and connected with the edge of the horizontal support near the pit bottom through a shaft pin mechanism;

[0029] The prestressed top support structure also includes an external cantilever pier, which is arranged at the edge of the horizontal support near the pit bottom and is located at the assembly interval; the external cantilever pier forms a top support posture for the enclosure structure based on the edge of the horizontal support near the pit bottom;

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

[0031] Use prestressed top support structure to apply transverse top support prestress to the enclosure structure:

[0032] The telescopic supporting mechanism is swung to the assembly interval, and the supporting end of the telescopic supporting mechanism is extended horizontally and supported on the retaining structure; according to the deformation condition of the retaining structure, the telescopic supporting mechanism is controlled to apply supporting prestress to the retaining structure; the bonding slurry is poured between the cantilevered pier and the retaining structure to connect the cantilevered pier and the retaining 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 and installation of load-bearing purlins at the bottom of the pit.

[0034] A multi-angle prestressed top support structure in a foundation pit, the prestressed top support structure comprising a telescopic top support mechanism, the telescopic top support mechanism having a telescopic top support end; the body of the telescopic top support mechanism is assembled and connected with a horizontal support near the bottom of the pit, and the telescopic top support mechanism can swing up and down based on the horizontal support near the bottom of the pit;

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

[0036] Compared with the prior art, the prestressed top support structure of the present invention has the following main beneficial effects:

[0037] After the construction of the horizontal support near the bottom of the pit is completed, the prestressed top support structure is immediately started, and the construction of the prestressed top support structure is completed before the subsequent lower-level excavation operation; the prestressed top support structure has segmented telescopic steel pipes, which apply top support prestress to the surrounding area near the bottom of the pit based on the horizontal support near the bottom of the pit. In this way, the surrounding area near the bottom of the pit can obtain the top support prestress at the first time, so that the displacement and deformation of the surrounding area near the bottom of the pit can be controlled in time, thereby improving the overall engineering quality of the foundation pit project. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figures 1 to 3 It is a structural schematic diagram of the multi-angle prestressed top support structure in the foundation pit of the present invention,

[0039] in,

[0040] Figure 1 It is a side view, in which the segmented telescopic steel pipe is in a horizontal state;

[0041] Figure 2 It is a side view, in which the segmented telescopic steel pipe is in a downward tilted state;

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

[0043] Figure 4 It is a schematic diagram of the assembly connection between the segmented telescopic steel pipe and the horizontal support near the bottom of the pit;

[0044] Figures 5 to 7 The schematic diagram of applying the prestressed top support structure of the present invention to the enclosure structure is as follows:

[0045] in,

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

[0047] Figure 6 This is a schematic diagram of using a prestressed top support structure to apply top support prestress to the surrounding area near the bottom of the pit;

[0048] Figure 7 Schematic diagram of the lower level excavation work after the top support prestressing is completed on the retaining structure. DETAILED DESCRIPTION

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

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

[0051] Definition 2: The "designed pit bottom" mentioned in this article refers to the pit bottom designed for foundation pit engineering. The "designed pit bottom" is a static concept.

[0052] Definition 3: The "enclosure near the pit bottom" mentioned in this article refers to the part of the enclosure structure near the current pit bottom. The "enclosure near the pit bottom" is a dynamic concept, which changes with the position of the current pit bottom. For example, when the "current pit bottom" is excavated to a depth of 1 meter, the upper and lower parts of the enclosure structure near the depth of 1 meter are the "enclosure near the pit bottom".

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

[0054] Definition 5: The "support system" mentioned in this article is a broad concept, which summarizes all forms of "support structures" and their combinations for the retaining structures in the foundation pit, such as "inclined upward support structure" and "horizontal support structure".

[0055] Definition 6: The "lower level foundation pit structure" mentioned in this article refers to the deeper foundation pit structure to be constructed in the next stage of the foundation pit construction process. The "lower level foundation pit structure" is a dynamic concept. For example, there are two layers of horizontal support structures designed in the foundation pit. When the first layer of horizontal support structure is completed, the second layer of horizontal support structure to be constructed is the lower level foundation pit structure. When the second layer of horizontal support structure is completed, the bottom structure of the foundation pit to be constructed is the lower level foundation pit structure.

[0056] Definition 7: The "lower level excavation" mentioned in this article refers to the process of excavation in the foundation pit before the next stage of the construction of the deeper foundation pit structure, so as to open up the construction space for the deeper foundation pit structure. The excavation process during this period is called "lower level excavation". For example, there are two layers of horizontal support structures in the foundation pit. After the construction of the first layer of horizontal support structure is completed, it is necessary to dig downwards to open up the construction space for the second layer of horizontal support structure. The excavation process during this period is called lower level excavation.

[0057] The main idea of ​​the present invention is:

[0058] Based on the horizontal support 41 near the bottom of the pit, an inclined downward support component is set toward the foundation pit retaining structure, and the inclined downward support component is supported at the position of the retaining near the bottom of the pit. Then, a support force-adding mechanism is set for the inclined downward support component, and the support force-adding mechanism can drive the inclined downward support component to apply support prestress to the position of the retaining near the bottom of the pit.

[0059] The main concept of the present invention is roughly as described above. In this way, the top support prestress can be applied to the bottom of the enclosure near the pit in time before the lower-level foundation pit structure is completed, so that corresponding measures can be taken in time to deal with the displacement and deformation that may occur in the bottom of the enclosure near the pit, thereby improving the overall engineering quality of the foundation pit project.

[0060] The concept of the present invention is further described below with specific embodiments:

[0061] See also Figure 1 , the foundation pit engineering structure involved in this implementation mode is first introduced below.

[0062] Those skilled in the art can understand that the overall engineering structure of the foundation pit mainly includes the enclosure structure 6 and the enclosure support system, and its specific structure is set as follows:

[0063] The retaining structure 6 is constructed around the foundation pit, and the retaining support system is usually arranged inside the foundation pit to support the retaining structure 6 .

[0064] In this embodiment, the enclosure support system is mainly composed of several layers of horizontal support structures 4, which are arranged on the inner side of the foundation pit, and these horizontal support structures 4 support the enclosure 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 purlin 7 is arranged on the retaining structure 6. Except for the purlin 7 arranged for the horizontal support structure 4 on the pit top, which is located at the top of the retaining structure 6, the remaining purlins 7 are arranged on the air-facing side of the retaining structure 6. The upper two layers of horizontal support structure 4 in the foundation pit are connected to the retaining structure 6 through the purlin 7, thereby forming support for the retaining structure 6.

[0066] The third-layer horizontal support structure 4, i.e., the horizontal support 41 near the pit bottom, has a certain spacing distance between its edge and the surrounding purlin 7, that is, the two are separated, and the separated portion is specially used to set up a prestressed mechanism. The edge of the horizontal support 41 near the pit bottom is connected to the surrounding purlin 7 through the set prestressed mechanism, and then connected to the enclosure structure 6 through the surrounding purlin 7, thereby forming support for the enclosure structure 6.

[0067] For the convenience of subsequent description, the spaced apart portion is referred to as an assembly space.

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

[0069] In this embodiment, the enclosure support system also includes a certain number of pull-out piles 5, which are fixedly arranged in the foundation pit, and then the aforementioned several layers of horizontal support structures 4 are connected with the pull-out piles 5 (the connection between the upper two layers of horizontal support structures 4 and the pull-out piles 5 is not shown in the figure). It should be noted that the pull-out 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 pit bottom, and the ring beam 3 is connected to a plurality of pull-out piles 5. These pull-out piles 5 provide vertical support to the edge of the horizontal support 41 near the pit bottom, especially downward support, which provides a strong support basis for the segmented telescopic steel pipe 11 to be mentioned later, and the edge of the horizontal support 41 near the pit bottom will not be deformed due to the "reaction force generated by the top support prestress applied by the segmented telescopic steel pipe 11".

[0071] In addition, in order to conveniently detect the displacement and deformation of the enclosure structure 6 and obtain corresponding data, in this embodiment, an inclinometer (existing technology) is pre-buried inside the enclosure structure 6, through which the displacement and deformation related data of the enclosure structure 6 can be detected and obtained.

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

[0073] See also Figures 1 to 3In this embodiment, a multi-angle prestressed top support structure is provided in a foundation pit. The prestressed top support structure is arranged based on the foundation pit engineering structure. The prestressed top support structure can apply top support prestress to the surrounding area near the bottom of the pit, thereby preventing the surrounding area near the bottom of the pit from displacement and deformation in the first time.

[0074] The prestressed top support structure mainly includes a plurality of segmented telescopic steel pipes 11, and the segmented telescopic steel pipes 11 are equivalent to the oblique downward supporting components.

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

[0076] See also Figure 4 For each segmented telescopic steel tube 11, the segmented telescopic steel tube 11 is a two-section type. For the convenience of description, one section is called the main body section, and the end where the main body section is located is called the main body end; the other section is called the top support section, and the end where the top support section is located is called the top support end; a telescopic hydraulic cylinder 17 is arranged in the segmented telescopic steel tube 11, and the main body (cylinder body) of the telescopic hydraulic cylinder 17 is connected to the main body section of the segmented telescopic steel tube 11 through a flange connection method (it can also be a welding method), and the telescopic end (cylinder head) of the telescopic hydraulic cylinder 17 is connected to the top support section of the segmented telescopic steel tube 11 through a flange connection method (it can also be a welding method). In this way, the telescopic hydraulic cylinder 17 can drive the segmented telescopic steel tube 11 to perform telescopic movements.

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

[0078] The segmented telescopic steel tube 11 can be understood as a telescopic support mechanism. In other embodiments, other forms of telescopic support mechanisms can also be used to replace the segmented telescopic steel tube 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 main body of the telescopic top support mechanism (equivalent to the main body end of the segmented telescopic steel pipe 11) is assembled and connected with the horizontal support 41 near the bottom of the pit through an axle pin mechanism.

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

[0081] For each segmented telescopic steel pipe 11,

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

[0083] For all segmented telescopic steel pipes 11 , a circle of purlins is fixedly provided at the bottom of the enclosure near the pit as a load-bearing purlin 21 . The load-bearing purlin 21 has a load-bearing surface 211 inclined upward, and the load-bearing surface 211 is used to receive the top support of the segmented telescopic steel pipes 11 .

[0084] The segmented telescopic steel pipe 11 can swing to an angle (such as the angle of the top support end of the segmented telescopic steel pipe 11 is tilted downward toward the bearing surface 211 of the bearing purlin 21) Figure 2 As shown), the telescopic hydraulic cylinder 17 is then controlled to drive the segmented telescopic steel pipe 11 to extend until the top support end of the segmented telescopic steel pipe 11 is inclined downward against the top support on the load-bearing surface 211 of the load-bearing purlin 21, and then the segmented telescopic steel pipe 11 is continued to be controlled to extend, so that the effect of "applying top support prestress to the position of the enclosure near the bottom of the pit 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 a top supporting prestress to the bottom of the enclosure, but also apply a top supporting prestress to the enclosure structure 6 laterally. Figure 1 As shown), at this time, the segmented telescopic steel tube 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, and then the top support end of the segmented telescopic steel tube 11 is supported on the purlin 7, and the top support prestress applied by the segmented telescopic steel tube 11 acts on the retaining structure 6 through the purlin 7.

[0086] The advantage of such a configuration is that the segmented telescopic steel pipe 11 can be used to temporarily apply a top supporting prestress to the enclosure structure 6 in the horizontal direction, and then a pad body (such as a pier, steel, etc.) can be placed in the assembly interval. In this way, the pad body can replace the segmented telescopic steel pipe 11 to achieve the effect of "applying a transverse top supporting prestress to the enclosure structure 6 based on the horizontal support 41 near the bottom of the pit".

[0087] In this embodiment, the prestressed top support structure further includes a plurality of cantilevered piers 8 .

[0088] The cantilevered piers 8 are arranged at the edge of the horizontal support 41 near the pit bottom (i.e., at the ring beam 3) by "casting together with the edge of the horizontal support structure 4". These numerous cantilevered piers 8 are all located at the assembly interval, i.e., between the edge of the horizontal support 41 near the pit bottom and the surrounding purlin 7, and are evenly and discretely arranged around the edge of the horizontal support 41 near the pit bottom. These numerous cantilevered piers 8 are arranged at intervals from the numerous segmented telescopic steel pipes 11.

[0089] Each cantilevered pier 8 forms a top support posture for the surrounding purlin 7 based on the edge of the horizontal support 41 near the pit bottom. In essence, the surrounding purlin 7 forms a top support posture for the retaining structure 6.

[0090] It should be noted that at this time, the cantilevered pier 8 only forms a "top supporting posture", and it does not contact with the surrounding purlin 7, but the two are very close to each other, thus forming a "top supporting posture".

[0091] These outwardly projecting piers 8 actually play the role of the cushion blocks mentioned above.

[0092] When it is necessary to permanently "apply transverse supporting prestress to the retaining structure 6 based on the horizontal support 41 near the pit bottom", the segmented telescopic steel tube 11 is swung to a horizontal azimuth angle, and then the supporting end of the segmented telescopic steel tube 11 is supported on the purlin 7, and the segmented telescopic steel tube 11 is controlled to apply a larger supporting prestress to the retaining structure 6, so that the assembly interval becomes slightly larger, and then the bonding slurry is poured at the position where the "supporting posture" is formed between the cantilevered pier 8 and the purlin 7. After the bonding slurry is completely solidified, the cantilevered pier 8 and the purlin 7 are truly connected together, and the cantilevered pier 8 truly applies transverse supporting prestress to the retaining structure 6 based on the horizontal support 41 near the pit bottom and through the purlin 7.

[0093] It should be noted that, in other embodiments, if the enclosure 6 is not provided with the purlin 7, then when the transverse supporting prestress is applied to the enclosure 6, the segmented telescopic steel pipe 11 and the cantilevered pier 8 are directly supported on the enclosure 6. For example, when the enclosure 6 is a continuous wall enclosure structure, the purlin 7 is not required.

[0094] This embodiment also provides a method for applying prestress to the enclosure in the foundation pit, and the prestressing method is used to achieve "applying top support prestress to the enclosure near the bottom of the pit". In essence, the prestressing method adopts the concept of the prestressed top support structure described above to achieve "applying top support prestress to the enclosure 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 foundation pit at the construction location of the foundation pit.

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

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

[0099] S2, after completing the construction of the horizontal support 41 near the pit bottom in step S1, immediately start to construct the prestressed top support structure based on the horizontal support 41 near the pit bottom, and complete the construction of the prestressed top support structure before the subsequent lower level excavation operation.

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

[0101] See also Figure 5 and Figure 6 It should be noted that when constructing the prestressed top support structure, it is necessary to first dig the soil near the bottom of the pit to remove the soil near the bottom of the pit. The purpose of this is to

[0102] On the one hand, it is to be able to construct and set the load-bearing purlin 21 near the bottom of the pit.

[0103] On the other hand, it provides operating space for "swinging the segmented telescopic steel tube 11 downward toward the load-bearing surface 211 of the load-bearing purlin 21, and then making the top support end of the segmented telescopic steel tube 11 rest against the top support on the load-bearing surface 211 of the load-bearing purlin 21".

[0104] It should be noted that the "digging at the bottom of the pit near the enclosure" here does not fall into the category of "lower level digging operations".

[0105] S3, applying top support prestress to the enclosure structure 6 using the constructed prestressed top support structure.

[0106] The step S3 specifically includes S31 to S32.

[0107] S31, applying transverse top supporting prestress to the enclosure structure 6 by using a prestressed top supporting structure.

[0108] Specifically,

[0109] The segmented telescopic steel tube 11 is swung to a horizontal state, that is, at the assembly interval, and then the segmented telescopic steel tube 11 is controlled and adjusted to be telescopic, so that the top support end of the segmented telescopic steel tube 11 is extended horizontally and supported on the purlin 7, and the top support prestress applied by the segmented telescopic steel tube 11 acts on the enclosure structure 6 through the purlin 7. The deformation condition (deformation data) of the enclosure structure 6 is detected by the detection means of the existing technology, and according to the deformation condition of the enclosure structure 6 and the design standard, the segmented telescopic steel tube 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 standard.

[0110] As mentioned above, an outwardly projecting pier 8 is preset at the edge of the horizontal support 41 near the pit bottom, and bonding slurry is poured at the position where a "supporting posture" is formed between the outwardly projecting pier 8 and the surrounding purlin 7. After the bonding slurry is completely solidified, the outwardly projecting pier 8 and the surrounding purlin 7 are truly connected together, and the outwardly projecting pier 8 is truly based on the horizontal support 41 near the pit bottom and applies transverse supporting prestress to the retaining structure 6 through the surrounding purlin 7.

[0111] At this time, the segmented telescopic steel pipe 11 can be controlled to retract, and the externally cantilevered pier 8 is completely responsible for applying the transverse supporting prestress.

[0112] It should be noted that, in other embodiments, if the enclosure purlin 7 is not provided on the enclosure structure 6 , the top supporting end of the segmented telescopic steel pipe 11 and the cantilevered pier 8 are directly supported on the enclosure structure 6 .

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

[0114] Specifically,

[0115] Swing the segmented telescopic steel tube 11 to the azimuth angle of "the top support end of the segmented telescopic steel tube 11 is obliquely downward toward the bearing surface 211 of the load-bearing purlin 21", and then control and adjust the expansion and contraction of the segmented telescopic steel tube 11 so that the top support end of the segmented telescopic steel tube 11 extends obliquely downward and rests against the top support on the bearing surface 211 of the load-bearing purlin 21, and the top support prestress applied by the segmented telescopic steel tube 11 acts on the enclosure near the bottom of the pit through the load-bearing purlin 21.

[0116] The existing detection means are used to detect the deformation condition (deformation data) of the enclosure near the bottom of the pit. According to the deformation condition of the enclosure 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 enclosure near the bottom of the pit, so that the deformation condition of the enclosure near the bottom of the pit meets the design standards.

[0117] After the prestressing method is implemented, the lower level excavation operation can be started. Figure 7 shown.

[0118] It should be noted that, in this embodiment, a large number of inclinometers (existing technology) are provided inside the enclosure structure 6, and the deformation condition of the enclosure structure 6, including the deformation condition of the enclosure near the bottom of the pit, can be detected by these inclinometers.

[0119] It should be noted that the material of the cantilever pier 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 top support structure and the method for applying prestress in this embodiment are:

[0122] 1) As far as the current existing technology is concerned, a foundation pit structure of a layer is usually constructed first, and then the top support prestress is applied to the horizontal direction or the upper retaining structure based on the constructed foundation pit structure.

[0123] For example, when the foundation pit construction reaches the designed pit bottom position, it is usually necessary to first build the entire pit bottom structure completely, and then build a prestressed structure based on the pit bottom structure to apply top support prestress to the retaining structure near the pit bottom.

[0124] This practice will result in the retaining wall near the bottom of the pit not being able to be prestressed for a long period of time after the lower level excavation operation. During this period, the displacement and deformation of the retaining wall near the bottom of the pit cannot be controlled in time, and the effect of applying prestressed top support later will be poor, which will affect the engineering quality of the entire foundation pit project. This situation is particularly prominent in deep foundation pit projects.

[0125] The most significant feature of the prestressed top support structure and the prestressing method of this embodiment is that:

[0126] After the construction of the near-pit-bottom horizontal support 41 is completed, the prestressed top support structure is immediately constructed, and the construction of the prestressed top support structure is completed before the subsequent lower-level excavation operation. The prestressed top support structure has a segmented telescopic steel pipe 11, which applies top support prestress to the near-pit-bottom position of the enclosure based on the near-pit-bottom horizontal support 41. In this way, the near-pit-bottom position of the enclosure can obtain the top support prestress at the first time, so that the displacement deformation of the near-pit-bottom position of the enclosure can be timely controlled, thereby improving the overall engineering quality of the foundation pit project.

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

[0128] 2) Prestress can be applied at multiple angles, making up for the deficiency of only being able to apply prestress horizontally;

[0129] 3) The segmented telescopic steel pipe 11 can be flexibly disassembled, which is green, environmentally friendly and resource-saving.

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

Claims

1. A multi-angle prestressed top support structure in a foundation pit, wherein a horizontal support (41) near the bottom of the pit is constructed in the foundation pit; Features: The prestressed top support structure comprises a telescopic top support mechanism, wherein the telescopic top support mechanism has a telescopic top support end; the body of the telescopic top support mechanism is assembled and connected with a horizontal support (41) near the pit bottom, and the telescopic top support mechanism can swing up and down based on the horizontal support (41) near the pit bottom; A load-bearing purlin (21) is arranged near the bottom of the pit. The telescopic supporting mechanism can swing to an angle where its supporting end is diagonally downward toward the load-bearing purlin (21); the supporting end of the telescopic supporting mechanism can extend diagonally downward and support the load-bearing purlin (21).

2. The multi-angle prestressed top support structure in the foundation pit according to claim 1 is characterized in that: An assembly gap is left between the edge of the horizontal support (41) near the pit bottom and the enclosure structure (6); the body of the telescopic top support mechanism is assembled and connected to the edge of the horizontal support (41) near the pit bottom through a shaft pin mechanism; The telescopic supporting mechanism can swing to the assembly interval, and the supporting end of the telescopic supporting mechanism can extend laterally and support on the enclosure structure (6).

3. The multi-angle prestressed top support structure in the foundation pit according to claim 2 is characterized in that: The prestressed top support structure also includes an outwardly projecting buttress (8), which is arranged at the edge of the horizontal support (41) near the pit bottom and is located at the assembly interval; the outwardly projecting buttress (8) forms a top support posture for the enclosure structure (6) based on the edge of the horizontal support (41) near the pit bottom.

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

5. The multi-angle prestressed top support structure in the foundation pit according to claim 2 is characterized in that: A ring beam (3) is provided at the edge of the horizontal support (41) near the pit bottom.

6. The multi-angle prestressed top support structure in the foundation pit according to claim 1 is characterized in that: The portion where the telescopic top support mechanism is assembled and connected with the horizontal support (41) near the pit bottom is located at the connection portion between the horizontal support (41) near the pit bottom and the anti-pulling pile (5).

7. The multi-angle prestressed top support structure in the foundation pit according to claim 1 is characterized in that: The telescopic support mechanism is specifically implemented in the form of a structure in which a two-section telescopic steel pipe (11) is used as the telescopic support mechanism, and a telescopic hydraulic cylinder (17) for driving telescopic movement is arranged inside the telescopic steel pipe (11).

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

9. The multi-angle prestressed top support structure in the foundation pit according to claim 3, characterized in that: The material of the cantilevered pier (8) is concrete or steel structure.

10. A method for applying prestress to the enclosure in a foundation pit, characterized in that: The method for applying prestress comprises: S1, constructing a horizontal support near the bottom of the pit (41); S2, constructing a prestressed top support structure based on the horizontal support (41) near the bottom of the pit, and completing the construction of the prestressed top support structure before the subsequent lower level excavation operation; The constructed prestressed top support structure comprises a telescopic top support mechanism, wherein the telescopic top support mechanism has a telescopic top support end; the body of the telescopic top support mechanism is assembled and connected with a horizontal support (41) near the pit bottom, and the telescopic top support mechanism can swing up and down based on the horizontal support (41) near the pit bottom; A load-bearing purlin (21) is arranged near the bottom of the pit. S3, applying top support prestress to the enclosure structure (6) by using a prestressed top support structure, including: A prestressed top support structure is used to apply top support prestress to the enclosure near the bottom of the pit: the telescopic top support mechanism is swung to an angle where its top support end is obliquely downward toward the load-bearing purlin (21), so that the top support end of the telescopic top support mechanism extends obliquely downward and supports the load-bearing purlin (21); according to the deformation condition of the enclosure near the bottom of the pit, the telescopic top support mechanism is controlled to apply top support prestress to the enclosure near the bottom of the pit.

11. The method for applying prestress to the enclosure in the foundation pit according to claim 10, characterized in that: An assembly gap is left between the edge of the constructed horizontal support (41) near the pit bottom and the enclosure structure (6); the body of the telescopic top support mechanism is assembled and connected to the edge of the horizontal support (41) near the pit bottom through a shaft pin mechanism; The prestressed top support structure further comprises an externally cantilevered pier (8), which is arranged at the edge of the horizontal support (41) near the pit bottom and is located at the assembly interval; the externally cantilevered pier (8) forms a top support posture for the enclosure structure (6) based on the edge of the horizontal support (41) near the pit bottom; The method of applying a prestressed top support structure to the enclosure structure (6) includes: The prestressed top support structure is used to apply transverse top support prestress to the enclosure structure (6): The telescopic supporting mechanism is swung to the assembly interval, and the supporting end of the telescopic supporting mechanism is extended horizontally and supported on the enclosure structure (6); according to the deformation state of the enclosure structure (6), the telescopic supporting mechanism is controlled to apply supporting prestress to the enclosure structure (6); and bonding slurry is poured between the cantilever pier (8) and the enclosure structure (6) to connect the cantilever pier (8) and the enclosure structure (6) together.

12. The method for applying prestress to the enclosure in the foundation pit according to claim 10, characterized in that: When constructing the prestressed top support structure, the soil near the bottom of the pit is removed to facilitate the construction and installation of a load-bearing purlin (21) at the bottom of the pit.

13. A multi-angle prestressed top support structure in a foundation pit, characterized in that: The prestressed top support structure comprises a telescopic top support mechanism, wherein the telescopic top support mechanism has a telescopic top support end; the body of the telescopic top support mechanism is assembled and connected with a horizontal support (41) near the pit bottom, and the telescopic top support mechanism can swing up and down based on the horizontal support (41) near the pit bottom; The telescopic supporting mechanism can swing to an angle where its supporting end is inclined downward toward the bottom of the enclosure near the pit, and the supporting end of the telescopic supporting mechanism can extend obliquely downward and support the enclosure near the bottom of the pit.

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