Double-support prestress back shore structure in foundation pit and prestress applying method

Abstract

The invention discloses a double-support prestress back shore structure in a foundation pit and a prestress applying method. The prestressed jacking structure comprises a double-telescopic jacking assembly (9), the double-telescopic jacking assembly comprises an upper telescopic jacking mechanism and a lower telescopic jacking mechanism, and the jacking end of the lower telescopic jacking mechanism can obliquely extend downwards and is jacked on a lower bearing enclosing purlin (921); and the jacking end of the upper telescopic jacking mechanism can obliquely and upwards extend out and is jacked on the upper bearing enclosing purlin (922). The prestress applying method comprises the steps that a prestress back shore structure is constructed on the basis of a near-pit-bottom horizontal support (41), and construction of the prestress back shore structure is completed before subsequent digging operation of a lower layer; and the prestress jacking structure is used for applying jacking prestress to the part, close to the pit bottom, of the enclosure. According to the pre-stress back shore structure and the pre-stress applying method, back shore pre-stress can be loaded on the portion, close to the pit bottom, of the enclosure in time based on the horizontal support close to the pit bottom.

Description

Technical Field

[0001] The invention relates to the technical field of foundation pit engineering, and in particular to a double-support prestressed top support structure in a foundation pit and a method for applying prestress. 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 cannot timely apply top support prestress to the bottom of the pit. In particular, before the lower level foundation pit structure is completed, top support prestress cannot be applied to the bottom of the pit. As a result, 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 object of the present invention is to provide a double-support prestressed top support structure and a method for applying prestress in a foundation pit, wherein the prestressed top support structure and the method for applying prestress can load the top support prestress on the surrounding area near the bottom of the pit based on the horizontal support near the bottom of the pit.

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

[0008] A double-support prestressed top support structure in a foundation pit, the prestressed top support structure comprising a double telescopic top support assembly,

[0009] The double telescopic top support assembly comprises an upper telescopic top support mechanism and a lower telescopic top support mechanism, and both the upper telescopic top support mechanism and the lower telescopic top support mechanism have a telescopic top support end;

[0010] The body of the upper telescopic support mechanism is connected to the horizontal support assembly near the pit bottom, and the body of the lower telescopic support mechanism is connected to the horizontal support assembly near the pit bottom;

[0011] A lower load-bearing purlin is arranged near the bottom of the pit, and an upper load-bearing purlin is arranged near the upper part of the bottom support of the enclosure;

[0012] The lower telescopic support mechanism can swing to an angle where its support end is inclined downward toward the lower load-bearing purlin based on the horizontal support near the pit bottom, and the support end of the lower telescopic support mechanism can extend obliquely downward and support on the lower load-bearing purlin;

[0013] The upper telescopic supporting mechanism can swing to an angle where its supporting end is inclined upward toward the upper load-bearing purlin based on the horizontal support near the pit bottom, and the supporting end of the upper telescopic supporting mechanism can extend obliquely upward and support on the upper load-bearing purlin.

[0014] Furthermore, the upper telescopic support mechanism and the lower telescopic support mechanism both use segmented telescopic steel pipes; the segmented telescopic steel pipes are provided with telescopic hydraulic cylinders, and the telescopic hydraulic cylinders can drive the segmented telescopic steel pipes to perform telescopic movements.

[0015] Furthermore, the double telescopic top support assembly also includes a top support base, and the top support base is installed at the edge of the horizontal support near the bottom of the pit;

[0016] The main body of the upper telescopic support mechanism is assembled with the support base through the shaft pin mechanism, so that the main body of the upper telescopic support mechanism is assembled and connected with the horizontal support near the bottom of the pit through the shaft pin mechanism;

[0017] The body of the lower telescopic support mechanism is assembled with the support base through the shaft pin mechanism, so that the body of the lower telescopic support mechanism is assembled and connected with the horizontal support near the bottom of the pit through the shaft pin mechanism.

[0018] Furthermore, an assembly gap is left between the edge of the horizontal support near the pit bottom and the enclosure structure;

[0019] 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;

[0020] A jack accommodating groove is arranged on one side of the cantilevered pier facing the enclosure structure, and the jack accommodating groove is used to accommodate the jack.

[0021] Furthermore, a purlin is provided on the enclosure structure for the horizontal support near the pit bottom, and the assembly interval is the space between the edge of the horizontal support near the pit bottom and the purlin;

[0022] The cantilevered pier is based on the horizontal support edge near the bottom of the pit and forms a top support posture for the enclosure structure through the surrounding purlin.

[0023] Furthermore, a ring beam is provided at the edge of the horizontal support near the pit bottom.

[0024] Furthermore, the lower telescopic top support mechanism and the portion where the lower telescopic top support mechanism is assembled and connected with the horizontal support near the pit bottom are located at the connection portion between the horizontal support near the pit bottom and the anti-pulling pile.

[0025] Furthermore, the body of the upper telescopic support mechanism is connected to the horizontal support near the bottom of the pit. Specifically, the body of the upper telescopic support mechanism is connected to the horizontal support near the bottom of the pit through a shaft pin mechanism.

[0026] The body of the lower telescopic support mechanism is assembled and connected with the horizontal support near the bottom of the pit. Specifically, the body of the lower telescopic support mechanism is assembled and connected with the horizontal support near the bottom of the pit through a shaft pin mechanism.

[0027] A method for applying prestress to a retaining wall in a foundation pit, the method comprising:

[0028] S1, construct horizontal support near the bottom of the pit;

[0029] 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;

[0030] The constructed prestressed top support structure includes a double telescopic top support assembly.

[0031] The double telescopic top support assembly comprises an upper telescopic top support mechanism and a lower telescopic top support mechanism, and both the upper telescopic top support mechanism and the lower telescopic top support mechanism have a telescopic top support end;

[0032] The body of the upper telescopic support mechanism is connected to the horizontal support assembly near the pit bottom, and the body of the lower telescopic support mechanism is connected to the horizontal support assembly near the pit bottom;

[0033] A lower load-bearing purlin is arranged near the bottom of the pit, and an upper load-bearing purlin is arranged near the upper part of the bottom support of the enclosure;

[0034] S3, using prestressed top support structure to apply top support prestress to the enclosure structure, including:

[0035] Apply top support prestressing to the surrounding area near the bottom of the pit:

[0036] The lower telescopic support mechanism is swung to an angle where its support end is obliquely downward toward the lower load-bearing purlin, so that the support end of the lower telescopic support mechanism extends obliquely downward and supports on the lower load-bearing purlin; according to the deformation condition of the enclosure near the bottom of the pit, the lower telescopic support mechanism is controlled to apply support prestress to the enclosure near the bottom of the pit;

[0037] The upper telescopic supporting mechanism is swung to an angle where its supporting end is inclined upward toward the upper load-bearing purlin, so that the supporting end of the upper telescopic supporting mechanism extends obliquely upward and supports on the upper load-bearing purlin.

[0038] Furthermore, the constructed prestressed top support structure also includes an externally cantilevered pier, which is arranged at the edge of the horizontal support near the bottom of the pit and is located at the assembly interval; the externally cantilevered pier forms a top support posture for the enclosure structure based on the edge of the horizontal support near the bottom of the pit;

[0039] A jack receiving groove is arranged on one side of the cantilevered pier facing the enclosure structure;

[0040] The method of applying prestress to the enclosure structure by using the prestressed top support structure also includes:

[0041] Apply transverse top support prestressing to the enclosure structure:

[0042] The jack is placed in the jack receiving groove of the externally projecting pier, so that the body of the jack abuts against the externally projecting pier, and the supporting end of the jack extends horizontally and supports on the enclosure structure.

[0043] According to the deformation condition of the enclosure structure, the jack is controlled to apply top support prestress to the enclosure structure;

[0044] Adhesive slurry is poured between the cantilevered pier and the surrounding structure to connect the cantilevered pier and the surrounding structure together.

[0045] 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 the lower load-bearing purlin at the bottom of the pit.

[0046] A double-support prestressed top support structure in a foundation pit, the prestressed top support structure comprising a double telescopic top support assembly,

[0047] The double telescopic top support assembly comprises an upper telescopic top support mechanism and a lower telescopic top support mechanism, and both the upper telescopic top support mechanism and the lower telescopic top support mechanism have a telescopic top support end;

[0048] The body of the upper telescopic support mechanism is connected to the horizontal support assembly near the pit bottom, and the body of the lower telescopic support mechanism is connected to the horizontal support assembly near the pit bottom;

[0049] A lower load-bearing purlin is arranged near the bottom of the pit, and an upper load-bearing purlin is arranged near the upper part of the bottom support of the enclosure;

[0050] The top support end of the lower telescopic top support mechanism is obliquely downward toward the lower load-bearing purlin, and the top support end of the lower telescopic top support mechanism can be extended obliquely downward and supported on the lower load-bearing purlin;

[0051] The supporting end of the upper telescopic supporting mechanism is obliquely upward toward the upper load-bearing surrounding purlin, and the supporting end of the upper telescopic supporting mechanism can be extended obliquely upward and supported on the upper load-bearing surrounding purlin.

[0052] A double-support prestressed top support structure in a foundation pit, the prestressed top support structure comprising a double telescopic top support assembly,

[0053] The double telescopic top support assembly comprises an upper telescopic top support mechanism and a lower telescopic top support mechanism, and both the upper telescopic top support mechanism and the lower telescopic top support mechanism have a telescopic top support end;

[0054] The body of the upper telescopic support mechanism is connected to the horizontal support assembly near the pit bottom, and the body of the lower telescopic support mechanism is connected to the horizontal support assembly near the pit bottom;

[0055] The lower telescopic support mechanism can swing to an angle where its support end is tilted downward toward the position of the enclosure near the bottom of the pit based on the horizontal support near the bottom of the pit, and the support end of the lower telescopic support mechanism can extend tilted downward and support the enclosure near the bottom of the pit;

[0056] The upper telescopic support mechanism can swing to an angle where its support end is inclined upward toward the upper part of the enclosure support near the bottom based on the horizontal support near the bottom of the pit. The support end of the upper telescopic support mechanism can extend obliquely upward and support the upper part of the enclosure support near the bottom.

[0057] Compared with the prior art, the prestressed top support structure and the method for applying prestress of the present invention have the following main beneficial effects:

[0058] After the construction of the horizontal support near the pit bottom is completed, the prestressed top support structure is immediately constructed based on the horizontal support near the pit bottom, and the construction of the prestressed top support structure is completed before the subsequent lower-level excavation operation; the constructed prestressed top support structure can apply top support prestress to the surrounding area near the pit bottom based on the horizontal support near the pit bottom; in this way, the surrounding area near the pit bottom can obtain the top support prestress at the first time, so that the displacement and deformation of the surrounding area near the pit bottom can be controlled in time, thereby improving the overall engineering quality of the foundation pit project. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figures 1 to 3 It is a structural schematic diagram of the double-braced prestressed top support structure in the foundation pit of the present invention,

[0060] in,

[0061] Figure 1 is a side view,

[0062] Figure 2 This is a top view of the horizontal support near the bottom of the pit.

[0063] Figure 3 It is a schematic diagram of the assembly connection between the double telescopic top support assembly and the horizontal support near the pit bottom;

[0064] Figure 4The figure is a schematic diagram of applying top support prestress to the retaining structure by using the prestressed top support structure of the present invention, and shows the situation of removing the soil near the bottom of the retaining structure. DETAILED DESCRIPTION

[0065] 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:

[0066] 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".

[0067] 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.

[0068] Definition 3: The “protection structure near the pit bottom” mentioned in this article refers to the part of the protection structure close to the current pit bottom (such as Figure 1 The “position of the enclosure near the pit bottom” is a dynamic concept, which 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 position of the enclosure structure near the depth of 1 meter is the “position of the enclosure near the pit bottom”.

[0069] 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.

[0070] Definition 5: The “upper part of the support near the bottom” mentioned in this article refers to the part of the support structure that is adjacent to the horizontal support near the bottom of the pit and is located above the horizontal support near the bottom of the pit (such as Figure 1 (where the arrow A points).

[0071] Definition 6: 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".

[0072] Definition 7: 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.

[0073] Definition 8: 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 a deeper foundation pit structure, so as to open up a 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 structures is completed, it is necessary to excavate downwards to open up a construction space for the second layer of horizontal support structures. The excavation process during this period is called lower level excavation.

[0074] The main idea of ​​the present invention is:

[0075] Based on the horizontal support 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 top support force adding mechanism is set for the inclined downward support component, and the top support force adding mechanism can drive the inclined downward support component to apply top support prestress to the position of the retaining near the bottom of the pit.

[0076] 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.

[0077] The concept of the present invention is further described below with specific embodiments:

[0078] See also Figure 1 , the foundation pit engineering structure involved in this implementation mode is first introduced below.

[0079] 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:

[0080] 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 .

[0081] In this embodiment, the enclosure support system is mainly composed of several layers of horizontal support structures 4. The several layers of horizontal support structures 4 are arranged inside the foundation pit, and these horizontal support structures 4 support the enclosure structure 6; in this embodiment, the number of horizontal support structures 4 arranged is three.

[0082] For each layer of horizontal support structure 4, a corresponding purlin 7 is arranged on the enclosure structure 6. Except for the purlin 7 arranged for the horizontal support structure 4 at the top of the pit, which is at the top of the enclosure structure 6, the other purlins 7 are arranged on the air side of the enclosure structure 6. The upper two layers of horizontal support structure 4 in the foundation pit are connected to the enclosure structure 6 through the purlin 7, thereby forming support for the enclosure structure 6. The third layer of horizontal support structure 4, i.e., the horizontal support 41 near the bottom of the pit, has a certain spacing distance between its edge and the purlin 7, that is, the two are separated, and the separated part is specially used to set up a prestressed mechanism. The edge of the horizontal support 41 near the bottom of the pit is connected to the purlin 7 through the prestressed mechanism, and then connected to the enclosure structure 6 through the purlin 7, thereby forming support for the enclosure structure 6.

[0083] For the convenience of subsequent description, the spaced area is referred to as the assembly space. It should be noted that in other embodiments, if the enclosure structure 6 is not provided with the purlin 7, the assembly space refers to the space between the edge of the horizontal support 41 near the pit bottom and the enclosure structure 6.

[0084] 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.

[0085] 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 double telescopic top support assembly 9 to be mentioned later.

[0086] 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.

[0087] Those skilled in the art can understand that the above-mentioned foundation pit engineering structure is a structure of the prior art.

[0088] See also Figures 1 to 3 This embodiment provides a prestressed top support structure, which is installed based on the foundation pit engineering structure.

[0089] The prestressed top support structure is mainly composed of two substructures, namely the transverse prestressed top support substructure and the oblique prestressed top support substructure.

[0090] The transverse prestressed top support substructure is used to apply transverse top support prestress to the retaining structure 6 based on the horizontal support 41 near the pit bottom.

[0091] The oblique prestressed top support substructure is used to apply oblique top support prestress to the enclosure near the bottom of the pit based on the horizontal support 41 near the bottom of the pit, so as to prevent the enclosure near the bottom of the pit from displacement and deformation in the first place.

[0092] The transverse prestressed top support substructure includes a plurality of cantilever piers 8, and the cantilever piers 8 are arranged at the edge of the horizontal support 41 near the bottom of the pit (i.e., the ring beam 3) by "casting together with the edge of the horizontal support structure 4".

[0093] These numerous externally cantilevered piers 8 are all located at the assembly interval, that is, 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 externally cantilevered piers 8 are arranged at intervals with numerous double telescopic top support assemblies 9 to be mentioned later.

[0094] 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.

[0095] 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".

[0096] See also Figure 2 , for each cantilevered pier 8,

[0097] A groove is provided on one side of the cantilever pier 8 facing the enclosure structure 6 , with the notch of the groove facing the enclosure structure 6 . For the convenience of description, this groove is called a jack receiving groove, which is used to accommodate a jack 81 .

[0098] Specifically, when it is necessary to permanently "apply transverse supporting prestress to the enclosure structure 6 based on the horizontal support 41 near the bottom of the pit", a jack 81 is placed in the jack receiving groove of the externally cantilevered pier 8, the body of the jack 81 is against the externally cantilevered pier 8, and then the supporting end of the jack 81 is supported on the purlin 7, so that a large transverse supporting prestress is applied to the enclosure structure 6 through the purlin 7, and then the bonding slurry is poured at the position where the "supporting state" is formed between the externally cantilevered pier 8 and the purlin 7, and after the bonding slurry is completely solidified, the externally cantilevered pier 8 and the purlin 7 are truly connected together, and the externally cantilevered pier 8 truly applies transverse supporting prestress to the enclosure structure 6 based on the horizontal support 41 near the bottom of the pit and through the purlin 7. At this time, the jack 81 can be removed.

[0099] 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 cantilevered pier 8 and the jack 81 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.

[0100] The oblique prestressed top support substructure mainly includes a plurality of double telescopic top support components 9, wherein the lower segmented telescopic steel pipe 911 is equivalent to the oblique downward support component.

[0101] These numerous double-telescopic top support assemblies 9 are all set at the assembly intervals mentioned above, and are evenly and discretely arranged around the edge of the horizontal support 41 near the pit bottom.

[0102] The double telescopic top support assembly 9 includes a top support base 913 and two segmented telescopic steel pipes.

[0103] The two segmented telescopic steel pipes, wherein:

[0104] A segmented telescopic steel pipe is used as the lower segmented telescopic steel pipe 911,

[0105] Another segmented telescopic steel pipe serves as an upper segmented telescopic steel pipe 912 .

[0106] The lower segmented telescopic steel pipe 911 and the upper segmented telescopic steel pipe 912 are identical in terms of their single body structures.

[0107] See also Figure 3 For each segmented telescopic steel pipe, the segmented telescopic steel pipe is of two sections.

[0108] For the convenience of description,

[0109] One section is called the body section, and one end of the body section is called the body end;

[0110] 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.

[0111] A telescopic hydraulic cylinder 917 is arranged in the segmented telescopic steel pipe, and the main body (cylinder body) of the telescopic hydraulic cylinder 917 is connected to the main body section of the segmented telescopic steel pipe by a flange connection method (it can also be a welding method), and the telescopic end (cylinder head) of the telescopic hydraulic cylinder 917 is connected to the top support section of the segmented telescopic steel pipe by a flange connection method (it can also be a welding method). In this way, the telescopic hydraulic cylinder 917 can drive the segmented telescopic steel pipe to perform telescopic movements.

[0112] In summary, the telescopic hydraulic cylinder 917 is arranged in the segmented telescopic steel pipe as a telescopic driving device, and the segmented telescopic steel pipe can apply a supporting force to the outside under the drive of the telescopic driving device.

[0113] The segmented telescopic steel tube can be understood as a telescopic top support mechanism. In other embodiments, other forms of telescopic top support mechanisms can also be used to replace the segmented telescopic steel tube.

[0114] In summary, the telescopic supporting mechanism should have a supporting end that can be telescopic, which is equivalent to the supporting end of the segmented telescopic steel pipe, and the body of the telescopic supporting mechanism is equivalent to the body end of the segmented telescopic steel pipe.

[0115] 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.

[0116] The lower segmented telescopic steel pipe 911 can be summarized as a lower telescopic top support mechanism, and the body of the lower telescopic top support mechanism is equivalent to the body end of the lower segmented telescopic steel pipe 911;

[0117] The upper segmented telescopic steel tube 912 can be summarized as an upper telescopic support mechanism, and the body of the upper telescopic support mechanism is equivalent to the body end of the upper segmented telescopic steel tube 912.

[0118] For each double telescopic top support assembly 9,

[0119] The supporting base 913 is installed on the edge of the horizontal support 41 near the pit bottom, specifically, it is assembled on the end surface of the edge of the horizontal support 41 near the pit bottom; the main body ends of the lower segmented telescopic steel pipe 911 and the upper segmented telescopic steel pipe 912 are assembled with the supporting base 913 through a quickly detachable axle pin mechanism. In this way, the lower segmented telescopic steel pipe 911 and the upper segmented telescopic steel pipe 912 can swing up and down based on the edge of the horizontal support 41 near the pit bottom (or, rotate around their main body ends at a certain angle).

[0120] After the installation of the double telescopic top support assembly 9, the lower section telescopic steel tube 911 is located below the upper section telescopic steel tube 912, or in other words, the upper section telescopic steel tube 912 is located above the lower section telescopic steel tube 911. In this way, the upper section telescopic steel tube 912 mainly makes an up and down swinging motion at the upper part, while the lower section telescopic steel tube 911 mainly makes an up and down swinging motion at the lower part.

[0121] It should be noted that the top support base 913 is not necessary. In other embodiments, the lower segmented telescopic steel pipe 911 and the upper segmented telescopic steel pipe 912 can also be directly assembled with the edge of the horizontal support 41 near the bottom of the pit through an axle pin mechanism, as long as it can achieve an up and down swinging motion based on the edge of the horizontal support 41 near the bottom of the pit.

[0122] See also Figure 1 For all double-telescopic top support assemblies 9, two circles of ring beams are fixedly arranged on the enclosure structure 6, wherein one circle of ring beams serves as a lower load-bearing purlin 921, and the other circle of ring beams serves as an upper load-bearing purlin 922.

[0123] The lower load-bearing purlin 921 is arranged for the lower segmented telescopic steel pipe 911 , and is arranged near the bottom of the pit. The lower load-bearing purlin 921 has a load-bearing surface inclined upward, and the load-bearing surface is used to bear the top support of the lower segmented telescopic steel pipe 911 .

[0124] The upper load-bearing purlin 922 is arranged for the upper segmented telescopic steel tube 912 , and is arranged at the upper part of the bottom support of the enclosure. The upper load-bearing purlin 922 has a load-bearing surface inclined downward, and the load-bearing surface is used to bear the top support of the upper segmented telescopic steel tube 912 .

[0125] The lower segmented telescopic steel tube 911 can swing downward to the azimuth angle of "the top support end of the lower segmented telescopic steel tube 911 is inclined downward toward the bearing surface of the lower load-bearing purlin 921", and then the telescopic hydraulic cylinder 917 is controlled to drive the lower segmented telescopic steel tube 911 to extend, until the top support end of the lower segmented telescopic steel tube 911 is inclined downward against the top support on the bearing surface of the lower load-bearing purlin 921, and then the lower segmented telescopic steel tube 911 is continued to be controlled to extend, so that the effect of "applying top support prestress to the near-bottom-of-pit retaining position based on the horizontal support 41 near the bottom of the pit" can be achieved.

[0126] The upper segmented telescopic steel tube 912 can swing upward to the azimuth angle of "the top supporting end of the upper segmented telescopic steel tube 912 is inclined upward toward the bearing surface of the upper load-bearing purlin 922", and then the telescopic hydraulic cylinder 917 is controlled to drive the upper segmented telescopic steel tube 912 to extend until the top supporting end of the upper segmented telescopic steel tube 912 is inclined upward against the bearing surface of the upper load-bearing purlin 922, and then the upper segmented telescopic steel tube 912 is continued to be controlled to extend, so that the effect of "applying an oblique downward supporting force to the edge of the horizontal support 41 near the bottom of the pit based on the retaining structure 6 to offset the reaction force of the lower segmented telescopic steel tube 911, thereby preventing the edge of the horizontal support 41 near the bottom of the pit from deforming" can be achieved.

[0127] 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 structure 6", especially 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 structure 6".

[0128] Specifically, the method for applying prestress in this embodiment includes:

[0129] S1, construct a horizontal support 41 near the bottom of the foundation pit at the construction location of the foundation pit.

[0130] 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.

[0131] The constructed horizontal support 41 near the pit bottom is as described above and will not be repeated here.

[0132] 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.

[0133] The constructed prestressed top support structure is as described above and will not be repeated here.

[0134] See also Figure 4 It should be noted that when constructing the inclined 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

[0135] On the one hand, it is to be able to construct and set the load-bearing purlin 921 near the bottom of the pit.

[0136] On the other hand, it provides operating space for "swinging the lower segmented telescopic steel pipe 911 downward toward the bearing surface of the lower load-bearing purlin 921, and then making the top support end of the lower segmented telescopic steel pipe 911 rest against the top support on the bearing surface of the lower load-bearing purlin 921".

[0137] 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".

[0138] S3, applying top support prestress to the enclosure structure 6 using the constructed prestressed top support structure.

[0139] The step S3 specifically includes S31 to S32.

[0140] S31, applying transverse supporting prestress to the enclosure structure 6 by using the transverse prestressed supporting substructure.

[0141] Specifically,

[0142] A jack 81 is placed in the jack receiving groove of the externally cantilevered pier 8, so that the body of the jack 81 is against the externally cantilevered pier 8, and then the supporting end of the jack 81 is controlled to extend and retract, so that the supporting end of the jack 81 is extended horizontally and supported on the surrounding purlin 7, and the supporting prestress applied by the jack 81 acts on the enclosure structure 6 through the surrounding purlin 7;

[0143] The deformation condition (deformation data) of the enclosure structure 6 is detected by using the detection means of the prior art. According to the deformation condition of the enclosure structure 6 and the design standard, the jack 81 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.

[0144] Then, the bonding slurry is poured at the position where the "supporting posture" is formed between the cantilevered pier 8 and the surrounding purlin 7. After the bonding slurry is completely solidified, the cantilevered pier 8 and the surrounding purlin 7 are truly connected together. The cantilevered pier 8 is truly based on the horizontal support 41 near the bottom of the pit and applies transverse supporting prestress to the retaining structure 6 through the surrounding purlin 7.

[0145] Finally, the jack 81 is disassembled, and the outer cantilever pier 8 is used to exert the transverse supporting prestress.

[0146] It should be noted that, in other embodiments, if the enclosure purlin 7 is not provided on the enclosure structure 6 , the supporting end of the jack 81 and the cantilevered pier 8 are directly supported on the enclosure structure 6 .

[0147] S32, using an inclined prestressed top support substructure to apply top support prestress to the surrounding area near the bottom of the pit.

[0148] Specifically,

[0149] The lower segmented telescopic steel pipe 911 is swung downward to the azimuth angle of "the top support end of the lower segmented telescopic steel pipe 911 is obliquely downward toward the bearing surface of the lower load-bearing purlin 921", and then the lower segmented telescopic steel pipe 911 is controlled and adjusted to be telescopic, so that the top support end of the lower segmented telescopic steel pipe 911 extends obliquely downward and abuts against the top support on the bearing surface of the lower load-bearing purlin 921, and the top support prestress applied by the lower segmented telescopic steel pipe 911 acts on the bottom of the enclosure near the pit through the lower load-bearing purlin 921;

[0150] Existing detection methods 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 lower segmented telescopic steel pipe 911 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.

[0151] Swing the upper segmented telescopic steel tube 912 upward to the azimuth angle of "the top support end of the upper segmented telescopic steel tube 912 is obliquely upward toward the load-bearing surface of the upper load-bearing purlin 922", and then control and adjust the expansion and contraction of the upper segmented telescopic steel tube 912 so that the top support end of the upper segmented telescopic steel tube 912 extends obliquely upward and rests against the top support on the load-bearing surface of the upper load-bearing purlin 922.

[0152] After the prestressing method is implemented, the lower level excavation operation can begin.

[0153] 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.

[0154] It should be noted that the prestressed top support structure and the method for applying prestress in this embodiment are not only implemented for one-layer horizontal support structure 4, but can also be implemented for multiple-layer horizontal support structures 4.

[0155] It should be noted that the prestressed top support structure can be applied to the entire enclosure structure or to a partial enclosure structure.

[0156] It should be noted that, in other embodiments, the lower segmented telescopic steel pipe 911 and the upper segmented telescopic steel pipe 912 can also be fixed together with the edge of the horizontal support 41 near the pit bottom by means of a fixed assembly connection.

[0157] The advantages of the prestressed top support structure and the method for applying prestress in this embodiment are:

[0158] 1) After the construction of the horizontal support 41 near the pit bottom is completed, the prestressed top support structure is immediately constructed based on the horizontal support 41 near the pit bottom, and the construction of the prestressed top support structure is completed before the subsequent lower level excavation operation;

[0159] The constructed prestressed top support structure has a double telescopic top support assembly 9, which includes a lower segmented telescopic steel pipe 911; the lower segmented telescopic steel pipe 911 can be supported at the position of the enclosure near the bottom of the pit based on the horizontal support 41 near the bottom of the pit, and can apply top support prestress to the position of the enclosure near the bottom of the pit;

[0160] In this way, the top support prestress can be applied to the part of the retaining wall near the bottom of the pit in the first place, so that the displacement and deformation of the part of the retaining wall near the bottom of the pit can be controlled in time, thereby improving the overall engineering quality of the foundation pit project.

[0161] 2) The double telescopic support assembly 9 also includes an upper segmented telescopic steel pipe 912, which can apply an oblique downward support force to the edge of the horizontal support 41 near the pit bottom based on the enclosure structure 6 to offset the reaction force of the lower segmented telescopic steel pipe 911, thereby preventing the edge of the horizontal support 41 near the pit bottom from being deformed;

[0162] 3) The constructed prestressed top support structure has an outward-projecting buttress 8, which can apply transverse top support prestress to the enclosure structure 6 based on the horizontal support 41 near the pit bottom (with the help of the jack 81), so that the displacement deformation of the enclosure structure portion corresponding to the horizontal support 41 near the pit bottom can be timely controlled;

[0163] 4) The double telescopic top support assembly 9 in the prestressed top support structure can be flexibly disassembled, which is green, environmentally friendly and resource-saving.

[0164] 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 double-braced prestressed top support structure in a foundation pit, characterized in that: The prestressed top support structure comprises a double telescopic top support assembly (9), The double telescopic top support assembly (9) comprises an upper telescopic top support mechanism and a lower telescopic top support mechanism, and both the upper telescopic top support mechanism and the lower telescopic top support mechanism have a telescopic top support end; The body of the upper telescopic support mechanism is assembled and connected with the horizontal support (41) near the bottom of the pit, and the body of the lower telescopic support mechanism is assembled and connected with the horizontal support (41) near the bottom of the pit; A lower load-bearing purlin (921) is arranged at the position of the enclosure near the bottom of the pit, and an upper load-bearing purlin (922) is arranged at the upper part of the enclosure near the bottom support; The lower telescopic supporting mechanism can swing based on the horizontal support (41) near the pit bottom to an angle where its supporting end is tilted downward toward the lower load-bearing purlin (921), and the supporting end of the lower telescopic supporting mechanism can extend tilted downward and support the lower load-bearing purlin (921); The upper telescopic supporting mechanism can swing to an angle where its supporting end is inclined upward toward the upper load-bearing purlin (922) based on the horizontal support (41) near the pit bottom, and the supporting end of the upper telescopic supporting mechanism can extend obliquely upward and support on the upper load-bearing purlin (922).

2. The double-braced prestressed top support structure in the foundation pit according to claim 1 is characterized in that: The upper telescopic support mechanism and the lower telescopic support mechanism both use segmented telescopic steel pipes; a telescopic hydraulic cylinder (917) is arranged in the segmented telescopic steel pipe, and the telescopic hydraulic cylinder (917) can drive the segmented telescopic steel pipe to perform telescopic movements.

3. The double-braced prestressed top support structure in the foundation pit according to claim 2 is characterized in that: The double telescopic top support assembly (9) further comprises a top support base (913), wherein the top support base (913) is installed at the edge of the horizontal support (41) near the pit bottom; The main body of the upper telescopic support mechanism is assembled with the support base (913) through the shaft pin mechanism, so that the main body of the upper telescopic support mechanism is assembled and connected with the horizontal support (41) near the bottom of the pit through the shaft pin mechanism; The body of the lower telescopic support mechanism is assembled with the support base (913) through the axle pin mechanism, so that the body of the lower telescopic support mechanism is assembled and connected with the horizontal support (41) near the bottom of the pit through the axle pin mechanism.

4. The double-braced 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 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; A jack receiving groove is provided on one side of the cantilevered pier (8) facing the enclosure structure (6), and the jack receiving groove is used to accommodate a jack (81).

5. The double-braced prestressed top support structure in the foundation pit according to claim 4 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); The cantilevered pier (8) is based on the edge of the horizontal support (41) near the bottom of the pit and forms a top support posture for the enclosure structure (6) through the surrounding purlin (7).

6. The double-braced prestressed top support structure in the foundation pit according to claim 4, characterized in that: A ring beam (3) is provided at the edge of the horizontal support (41) near the pit bottom.

7. The double-braced prestressed top support structure in the foundation pit according to claim 1 is characterized in that: The lower telescopic support mechanism and the assembly connection portion of the lower telescopic support mechanism and the near-pit-bottom horizontal support (41) are located at the connection portion of the near-pit-bottom horizontal support (41) and the anti-pulling pile (5).

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

9. 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 double telescopic top support assembly (9), The double telescopic top support assembly (9) comprises an upper telescopic top support mechanism and a lower telescopic top support mechanism, and both the upper telescopic top support mechanism and the lower telescopic top support mechanism have a telescopic top support end; The body of the upper telescopic support mechanism is assembled and connected with the horizontal support (41) near the bottom of the pit, and the body of the lower telescopic support mechanism is assembled and connected with the horizontal support (41) near the bottom of the pit; A lower load-bearing purlin (921) is arranged at the position of the enclosure near the bottom of the pit, and an upper load-bearing purlin (922) is arranged at the upper part of the enclosure near the bottom support; S3, applying top support prestress to the enclosure structure (6) by using a prestressed top support structure, including: Apply top support prestressing to the surrounding area near the bottom of the pit: The lower telescopic support mechanism is swung to an angle where its support end is obliquely downward toward the lower load-bearing purlin (921), so that the support end of the lower telescopic support mechanism extends obliquely downward and supports on the lower load-bearing purlin (921); according to the deformation condition of the enclosure near the bottom of the pit, the lower telescopic support mechanism is controlled to apply support prestress to the enclosure near the bottom of the pit; The upper telescopic supporting mechanism is swung to an angle where its supporting end is inclined upward toward the upper load-bearing purlin (922), so that the supporting end of the upper telescopic supporting mechanism extends obliquely upward and supports on the upper load-bearing purlin (922).

10. The method for applying prestress to the enclosure in the foundation pit according to claim 9, characterized in that: The constructed prestressed top support structure also includes an externally 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 externally 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; A jack receiving groove is provided on one side of the cantilevered pier (8) facing the enclosure structure (6); The method of applying a prestressed top support structure to the enclosure structure (6) includes: Apply transverse top support prestressing force to the enclosure structure (6): A jack (81) is placed in the jack receiving groove of the externally projecting pier (8), so that the body of the jack (81) abuts against the externally projecting pier (8), and the supporting end of the jack (81) extends horizontally and supports on the enclosure structure (6). According to the deformation condition of the enclosure structure (6), the jack (81) is controlled to apply a top supporting prestress to the enclosure structure (6); Adhesive slurry is poured between the externally projecting buttress (8) and the surrounding structure (6) to connect the externally projecting buttress (8) and the surrounding structure (6) together.

11. The method for applying prestress to the enclosure in the foundation pit according to claim 9, 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 the lower load-bearing purlin (921) at the bottom of the pit.

12. A double-braced prestressed top support structure in a foundation pit, characterized in that: The prestressed top support structure comprises a double telescopic top support assembly (9), The double telescopic top support assembly (9) comprises an upper telescopic top support mechanism and a lower telescopic top support mechanism, and both the upper telescopic top support mechanism and the lower telescopic top support mechanism have a telescopic top support end; The body of the upper telescopic support mechanism is assembled and connected with the horizontal support (41) near the bottom of the pit, and the body of the lower telescopic support mechanism is assembled and connected with the horizontal support (41) near the bottom of the pit; A lower load-bearing purlin (921) is arranged at the position of the enclosure near the bottom of the pit, and an upper load-bearing purlin (922) is arranged at the upper part of the enclosure near the bottom support; The top support end of the lower telescopic top support mechanism is obliquely downwardly directed toward the lower load-bearing purlin (921), and the top support end of the lower telescopic top support mechanism can be extended obliquely downwardly and supported on the lower load-bearing purlin (921); The supporting end of the upper telescopic supporting mechanism is obliquely upward toward the upper load-bearing purlin (922), and the supporting end of the upper telescopic supporting mechanism can be extended obliquely upward and supported on the upper load-bearing purlin (922).

13. A double-braced prestressed top support structure in a foundation pit, characterized in that: The prestressed top support structure comprises a double telescopic top support assembly (9), The double telescopic top support assembly (9) comprises an upper telescopic top support mechanism and a lower telescopic top support mechanism, and both the upper telescopic top support mechanism and the lower telescopic top support mechanism have a telescopic top support end; The body of the upper telescopic support mechanism is assembled and connected with the horizontal support (41) near the bottom of the pit, and the body of the lower telescopic support mechanism is assembled and connected with the horizontal support (41) near the bottom of the pit; The lower telescopic support mechanism can swing to an angle where its support end is tilted downward toward the position of the enclosure near the bottom of the pit based on the horizontal support (41) near the bottom of the pit, and the support end of the lower telescopic support mechanism can extend tilted downward and support the position of the enclosure near the bottom of the pit; The upper telescopic support mechanism can swing to an angle where its support end is inclined upward toward the upper part of the enclosure support near the bottom based on the horizontal support (41) near the bottom of the pit, and the support end of the upper telescopic support mechanism can extend obliquely upward and support the upper part of the enclosure support near the bottom.

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