Inclined downward advanced prestress back shore structure in foundation pit and prestress applying method

Abstract

The invention discloses an obliquely downward advanced prestress back shore structure in a foundation pit and a prestress applying method. The obliquely-downward advanced prestress back shore structure comprises an obliquely-downward supporting component, and the obliquely-downward supporting component is based on a near-pit-bottom horizontal support (16) and is arranged at the near-pit-bottom part of an enclosure in a back shore mode; the back shore stress application mechanism drives the inclined downward supporting component to apply back shore prestress to the portion, close to the pit bottom, of the enclosure based on the horizontal support close to the pit bottom. The method for applying the prestress in advance comprises the following steps: constructing an inclined downward advance prestress back shore structure, and completing the construction of the inclined downward advance prestress back shore structure before the subsequent digging operation of a lower layer; and the constructed obliquely-downward advanced prestress jacking structure is used for applying jacking prestress to the portion, close to the pit bottom, of the enclosure. According to the obliquely downward advanced prestress back shore structure and the advanced prestress applying method, the measure of applying the back shore prestress can be taken at the first time when displacement deformation possibly happens to the portion, close to the pit bottom, of the enclosure.

Description

Technical Field

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

[0002] With the acceleration of urbanization, the development and utilization of urban underground space has become an effective way to alleviate urban pressure and enhance the comprehensive carrying capacity of cities. In this context, deep foundation pit excavation technology has been widely used. However, deep foundation pit excavation will have a certain impact on the surrounding environment, and may cause settlement and displacement of surrounding strata, thereby affecting the safety of adjacent subway tunnels, buildings, etc. In order to solve this problem, the prior art proposes a solution of using a concrete support force device. Its main technical concept is to "use a force device to apply a lateral thrust to the retaining structure outside the foundation pit to achieve active control of the displacement of the retaining structure (see the Chinese patent "A support system for actively controlling foundation pit displacement and its design method-CN108130910A").

[0003] The current problem is:

[0004] The active control of the displacement of the retaining structure currently achieved can only apply lateral top support prestressing to the excavation surface of the retaining structure, but cannot apply top support prestressing to the retaining near the bottom of the pit in advance, especially before the lower level foundation pit structure is completed. As a result, the retaining near the bottom of the pit may produce displacement and deformation before the lower level foundation pit structure is completed, thereby failing to effectively control the deformation of the foundation pit. Summary of the invention

[0005] The purpose of the present invention is to provide a 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 in advance can take measures to apply top support prestress at the first time when displacement and deformation may occur at the surrounding area near the bottom of the pit.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0007] A prestressed top support structure inclined downward in a foundation pit, the prestressed top support structure inclined downward includes a downward inclined support component, the downward inclined support component is based on a horizontal support near the bottom of the pit and is supported at a position near the bottom of the pit.

[0008] Furthermore, a top support force-adding mechanism is arranged for the oblique downward support component, and the top support force-adding mechanism can drive the oblique downward support component to 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.

[0009] Furthermore, the oblique downward supporting member is a lower oblique supporting pile, one end of the lower oblique supporting pile serves as a top supporting end, and the other end of the lower oblique supporting pile serves as a force-applying end;

[0010] The downward oblique support component is based on the horizontal support near the bottom of the pit and is supported at the bottom of the pit near the enclosure. The specific structural form is: the force-adding end of the lower oblique support pile is based on the horizontal support near the bottom of the pit, and the top support end of the lower oblique support pile is supported obliquely downward at the bottom of the pit near the enclosure;

[0011] The downward inclined support component is provided with a top support force-adding mechanism, which can drive the downward inclined support component to apply top support prestress to the surrounding pit bottom position based on the horizontal support near the pit bottom. The specific structural form is: a top support force-adding mechanism is arranged at the position of the lower inclined support pile based on the horizontal support near the pit bottom, and the top support force-adding mechanism can apply thrust to the force-adding end of the lower inclined support pile based on the horizontal support near the pit bottom, so that the top support end of the lower inclined support pile applies top support prestress to the surrounding pit bottom position.

[0012] Further, the jacking force-adding mechanism is a corbel-based reaction mechanism, and the corbel-based reaction mechanism includes a reaction corbel, a first jack and a reaction frame;

[0013] The reaction bullneck is arranged on a horizontal support near the bottom of the pit, the reaction frame has a reaction beam, the reaction frame is fixed on the reaction bullneck, a jack retention space is reserved between the reaction beam of the reaction frame and the reaction bullneck, the first jack is placed in the jack retention space, the first jack is between the reaction beam of the reaction frame and the force-applying end of the lower oblique support pile, the first jack can apply a thrust to the force-applying end of the lower oblique support pile based on the reaction beam of the reaction frame, thereby realizing that the top support force-applying mechanism can apply a thrust to the force-applying end of the lower oblique support pile based on the horizontal support near the bottom of the pit.

[0014] Further, the jacking force adding mechanism is a casing-based reaction mechanism, and the casing-based reaction mechanism includes a casing and a second jack;

[0015] One end of the sleeve is used as an oblique end, and the other end of the sleeve is used as a reaction end, and a jack accommodation space is provided at the reaction end of the sleeve;

[0016] The casing is fixed on a horizontal support near the pit bottom, the force-adding end of the lower oblique support pile is passed through the casing, the second jack is arranged in the jack accommodating space, and a reaction steel is arranged in the jack accommodating space. The second jack applies a thrust to the force-adding end of the lower oblique support pile based on the reaction steel, thereby realizing that the top support force-adding mechanism can apply a thrust to the force-adding end of the lower oblique support pile based on the horizontal support near the pit bottom.

[0017] Furthermore, the top support end of the lower oblique support pile is fixedly connected to the surrounding area near the bottom of the pit by bonding with adhesive slurry.

[0018] Furthermore, a grouting passage is provided in the lower oblique support pile, and the grouting passage is used to: pour the bonding slurry to the position between the top support end of the lower oblique support pile and the position of the enclosure near the bottom of the pit through the grouting passage, so as to bond the top support end of the lower oblique support pile and the position of the enclosure near the bottom of the pit together.

[0019] Furthermore, a claw tooth head is provided at the top supporting end of the lower oblique support pile. When the top supporting end of the lower oblique support pile is supported at the position of the enclosure near the bottom of the pit, the claw tooth head can firmly grasp the enclosure structure.

[0020] Further, the claw tooth head is fixed at the top supporting end of the lower oblique supporting pile; or, the claw tooth head is assembled at the top supporting end of the lower oblique supporting pile through a hinge.

[0021] Furthermore, an inclinometer is provided in the retaining structure of the foundation pit.

[0022] Furthermore, a device assembly interval is left between the edge of the horizontal support near the pit bottom and the surrounding structure;

[0023] The oblique downward advanced prestressed supporting structure also includes a transverse supporting mechanism, which is arranged at the device assembly interval. The transverse supporting mechanism applies transverse supporting prestress to the enclosure structure based on the edge of the horizontal support near the pit bottom.

[0024] Furthermore, the lower diagonal support piles are steel pipes, precast concrete structures, composite steel sections or steel rods.

[0025] Furthermore, there is an anti-pullout device in the foundation pit, and the anti-pullout device is a column pile, an anti-pullout anchor rod or a pile load under the support system.

[0026] Furthermore, a mechanical passage is provided in the lower diagonal support pile, and the mechanical passage is used for subsequent mechanical equipment to enter the connection position between the lower diagonal support pile and the surrounding structure to carry out partial reinforcement and subsequent maintenance work at this position.

[0027] Furthermore, an axial force monitoring device is provided on the horizontal support near the pit bottom, and the axial force monitoring device is used to monitor the support axial force of the horizontal support near the pit bottom.

[0028] Furthermore, the lower oblique support piles extend below the soil at the bottom of the pit.

[0029] A method for applying prestress to a retaining wall in advance in a foundation pit, the method comprising:

[0030] S1, construct horizontal support near the bottom of the pit;

[0031] S2, constructing a prestressed top support structure that is inclined downward and completed before the subsequent lower level excavation operation;

[0032] The constructed oblique downward advanced prestressed top support structure includes an oblique downward support component, which is based on the horizontal support near the bottom of the pit and is supported at the position of the enclosure near the bottom of the pit;

[0033] A top support force adding mechanism is arranged for the oblique downward support component, and the top support force adding mechanism can drive the oblique downward support component to 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;

[0034] S3, using the constructed oblique downward advanced prestressed top support structure to apply top support prestress to the surrounding area near the bottom of the pit.

[0035] Furthermore, the oblique downward supporting component adopts a lower oblique supporting pile, one end of the lower oblique supporting pile serves as a top supporting end, and the other end of the lower oblique supporting pile serves as a force-applying end;

[0036] The method for constructing the oblique downward advanced prestressed top support structure specifically includes:

[0037] S21, presetting support holes on the horizontal support near the pit bottom;

[0038] S22, using an inclined pile driver to obliquely drive the lower inclined support pile from the support through hole on the horizontal support near the bottom of the pit into the soil until the top support end of the lower inclined support pile contacts the top support to the retaining structure; the constructed lower inclined support pile, the top support end of which supports the retaining structure, is located in the soil below the current bottom of the foundation pit;

[0039] S23, connecting the top support end of the lower diagonal support pile with the retaining structure;

[0040] S24, installing a top support force-adding mechanism based on the horizontal support near the pit bottom, the top support force-adding mechanism can apply thrust to the lower oblique support pile based on the horizontal support near the pit bottom, so that the top support end of the lower oblique support pile applies top support prestress to the surrounding area near the pit bottom;

[0041] The top support end of the lower inclined support pile and the top support retaining structure are located in the soil below the current bottom of the foundation pit.

[0042] Furthermore, a grouting passage is provided in the lower diagonal support pile;

[0043] The method for connecting the top support end of the lower oblique support pile with the retaining structure includes: using a grouting machine to inject high-strength bonding slurry from the force-applying end of the lower oblique support pile into a grouting passage in the lower oblique support pile, and the bonding slurry is delivered to the position where the top support end of the lower oblique support pile contacts the retaining structure through the grouting passage. After the bonding slurry solidifies, the top support end of the lower oblique support pile is connected to the retaining structure.

[0044] Furthermore, before pouring the bonding slurry, water is sprayed through the grouting passage of the lower diagonal support pile to the position where the top support end of the lower diagonal support pile contacts the surrounding structure to remove soil debris.

[0045] Furthermore, a claw tooth head is provided at the top support end of the lower oblique support pile;

[0046] The method for connecting the top support end of the lower oblique support pile with the retaining structure includes: using an inclined pile driver to force the top support end of the lower oblique support pile against the retaining structure, so that the claws of the claw head at the top support end of the lower oblique support pile are embedded in the retaining structure body, thereby realizing a bite-type connection, and the top support end of the lower oblique support pile is connected to the retaining structure.

[0047] Furthermore, the method for implementing the top support force adding mechanism based on the horizontal support near the bottom of the pit includes:

[0048] The jacking force adding mechanism is a corbel-based reaction mechanism, and the corbel-based reaction mechanism includes a reaction corbel, a first jack and a reaction frame;

[0049] The reaction bullneck is arranged on a horizontal support near the bottom of the pit, the reaction frame has a reaction beam, the reaction frame is fixed on the reaction bullneck, a jack retention space is reserved between the reaction beam of the reaction frame and the reaction bullneck, the first jack is placed in the jack retention space, the first jack is between the reaction beam of the reaction frame and the force-applying end of the lower oblique support pile, and the first jack applies thrust to the force-applying end of the lower oblique support pile based on the reaction beam of the reaction frame.

[0050] Furthermore, the method for implementing the top support force adding mechanism based on the horizontal support near the bottom of the pit includes:

[0051] The supporting force adding mechanism is a casing-based reaction mechanism, and the casing-based reaction mechanism includes a second jack and a casing;

[0052] One end of the sleeve is used as an oblique end, and the other end of the sleeve is used as a reaction end, and a jack accommodation space is provided at the reaction end of the sleeve;

[0053] The casing is fixed on a horizontal support near the bottom of the pit, the force-adding end of the lower oblique support pile is passed through the casing, the second jack is arranged in the jack accommodating space, and a reaction steel is arranged in the jack accommodating space, and the second jack applies thrust to the force-adding end of the lower oblique support pile based on the reaction steel.

[0054] Furthermore, the method for applying prestress in advance also includes:

[0055] In the process of applying top support prestress to the part of the enclosure near the bottom of the pit using the constructed oblique downward advance prestressed top support structure, the deformation condition of the part of the enclosure near the bottom of the pit is monitored. According to the deformation condition of the part of the enclosure near the bottom of the pit, the top support force-adding mechanism is controlled to apply top support prestress to the part of the enclosure near the bottom of the pit, so that the deformation of the part of the enclosure near the bottom of the pit can be better controlled.

[0056] Compared with the prior art, the main beneficial effects of the oblique downward advanced prestressed top support structure and the advanced prestressing method of the present invention are:

[0057] After completing the construction of the horizontal support near the pit bottom, immediately start to construct the oblique downward advance prestressed top support structure. The constructed oblique downward advance prestressed top support structure has an oblique downward support component, which is based on the horizontal support near the pit bottom and supports the surrounding area near the pit bottom. A top support force-adding mechanism is arranged for the oblique downward support component, which can drive the oblique downward support component to apply top support prestress to the surrounding area near the pit bottom based on the horizontal support near the pit bottom, and the oblique downward advance prestressed top support structure is completed before the subsequent lower-level excavation operation and is set in advance; in this way, measures to apply top support prestress can be taken at the first time when displacement and deformation may occur at the surrounding area near the pit bottom, which is conducive to timely preventing displacement and deformation of the surrounding area near the pit bottom. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 It is a structural schematic diagram of an advanced prestressed top support structure inclined downward in a foundation pit based on Embodiment 1 of the present invention;

[0059] Figure 2 This is a schematic diagram of the connection between the lower diagonal support pile and the retaining structure using bonding slurry;

[0060] Figure 3 It is a schematic diagram of the connection between the lower inclined support pile and the surrounding structure using the claw-tooth gripping method;

[0061] Figure 4 Schematic diagram of the structure of the corbel base reaction mechanism used in Implementation Method 1;

[0062] Figure 5 It is a schematic diagram of setting a sleeve in implementation mode 2;

[0063] Figure 6 Schematic diagram of the structure of the casing base reaction mechanism used in Implementation Method 2;

[0064] Figure 7 It is a structural schematic diagram of an advanced prestressed top support structure inclined downward in a foundation pit based on Embodiment 3 of the present invention;

[0065] Figure 8It is a structural schematic diagram of an advanced prestressed top support structure inclined downward in a foundation pit based on embodiment 4 of the present invention. DETAILED DESCRIPTION

[0066] 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:

[0067] 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".

[0068] 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.

[0069] Definition 3: 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, and the first layer of horizontal support structure is no longer the horizontal support near the pit bottom.

[0070] Definition 4: The "position of the enclosure near the pit bottom" mentioned in this article refers to the position of the enclosure structure close to the current pit bottom, more precisely, the position from the "horizontal support near the pit bottom" to the "current pit bottom" and a certain distance below the "current pit bottom". The "position of the enclosure near the pit bottom" is a dynamic concept, which changes with the position of the current pit bottom.

[0071] Definition 5: The "upper part of the retaining structure's support near the pit bottom" mentioned in this article refers to the part of the retaining structure that is adjacent to the horizontal support near the pit bottom and is located above the horizontal support near the pit bottom.

[0072] 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".

[0073] 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.

[0074] 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.

[0075] The main idea of ​​the present invention is:

[0076] Based on the horizontal support 16 near the pit bottom, a downward slanting support component facing the foundation pit retaining structure is provided, and the downward slanting support component is supported at a position near the pit bottom of the retaining structure of the foundation pit.

[0077] Then, a top support force adding mechanism is arranged for the oblique downward support component, and the top support force adding mechanism can drive the oblique downward support component to apply top support prestress to the position near the bottom of the pit based on the near-pit bottom horizontal support 16. In this way, the top support prestress can be applied to the position near the bottom of the pit without completing the construction of the lower-level foundation pit structure, so that active response measures can be taken in time to the displacement and deformation of the position near the bottom of the pit, without having to wait until the lower-level foundation pit structure is completed.

[0078] The main concept of the present invention is roughly as described above.

[0079] The concept of the present invention is further described below with specific embodiments:

[0080] Implementation 1:

[0081] See also Figure 1 , the foundation pit engineering structure involved in this embodiment 1 is first introduced below.

[0082] Those skilled in the art can understand that the overall engineering structure of the foundation pit mainly includes the enclosure structure 5 and the enclosure support system, and its specific structure is set as follows:

[0083] The retaining structure 5 is constructed around the foundation pit, and the retaining support system is usually arranged inside the foundation pit to support the retaining structure 5 .

[0084] In this embodiment 1, the enclosure support system is mainly composed of several layers of horizontal support structures 1, which are arranged on the inner side of the foundation pit, and the enclosure structure 5 is supported by these horizontal support structures 1; in this embodiment, the number of horizontal support structures 1 is three.

[0085] For each layer of horizontal support structure 1, a corresponding purlin 2 is arranged on the enclosure structure 5. The purlin 2 is arranged on the air-facing side of the enclosure structure 5. Each layer of horizontal support structure 1 is connected to the enclosure structure 5 through the purlin 2, thereby forming support for the enclosure structure 5.

[0086] In this embodiment 1, the retaining support system also includes a certain number of pull-out piles 6, which are fixed in the foundation pit by pull-out devices 8 arranged at the bottom of the foundation pit. Then, the several layers of horizontal support structures 1 mentioned above (including the horizontal support 16 near the bottom of the pit) are connected together with the pull-out piles 6, and these pull-out piles 6 provide vertical support for the horizontal support structure 1.

[0087] In addition, in order to conveniently monitor the displacement and deformation of the enclosure structure 5 and obtain corresponding data, in this embodiment, an inclinometer 19 (existing technology) is pre-buried inside the enclosure structure 5, and the displacement and deformation related data of the enclosure structure 5 can be monitored and obtained through the inclinometer 19.

[0088] Those skilled in the art can understand that the above-mentioned foundation pit engineering structure is a structure of the prior art.

[0089] See also Figures 1 to 4 Implementation method 1 provides a downward inclined advance prestressed top support structure in a foundation pit. The downward inclined advance prestressed top support structure is arranged based on the foundation pit engineering structure described above. The downward inclined advance prestressed top support structure is used to 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 at the first time.

[0090] See also Figure 1 The oblique downward advanced prestressed top support structure mainly includes a large number of lower oblique support piles 3, and the lower oblique support piles 3 are equivalent to the oblique downward support components mentioned above.

[0091] For the convenience of description, one end of the lower inclined support pile 3 is called the top support end, and the other end of the lower inclined support pile 3 is called the force-adding end. The force-adding ends of these lower inclined support piles 3 are all arranged based on the horizontal support 16 near the bottom of the pit, and the top support end of the lower inclined support pile 3 is supported obliquely downward at the position of the enclosure near the bottom of the pit to prevent the enclosure near the bottom of the pit from being displaced and deformed toward the inside of the foundation pit.

[0092] It should be noted that the top support end of the finally constructed lower inclined support pile 3 is in the soil, that is, the surrounding near the bottom of the pit is in the soil below the current bottom of the foundation pit. Therefore, before the subsequent lower level excavation operation, the surrounding structure 5 that is still in the soil can be supported to achieve advanced top support prestressing intervention, which is also an important innovation of the present invention.

[0093] For each lower inclined support pile 3, a top support force-adding mechanism is provided at the position of the lower inclined support pile 3 based on the horizontal support 16 near the pit bottom. The top support force-adding mechanism can apply thrust to the lower inclined support pile 3 based on the horizontal support 16 near the pit bottom, so that the top support end of the lower inclined support pile 3 actively applies top support prestress to the retaining structure 5 near the pit bottom, thereby actively suppressing the displacement deformation of the retaining structure near the pit bottom toward the inside of the foundation pit.

[0094] More specifically,

[0095] For each lower diagonal support pile 3,

[0096] For the lower oblique support pile 3, a reaction corbel 9 is arranged on the horizontal support 16 near the bottom of the pit, and a top support force-adding mechanism (existing technology) is installed on the reaction corbel 9. The force-adding end of the lower oblique support pile 3 is assembled together with the top support force-adding mechanism, or in other words, the force-adding end of the lower oblique support pile 3 is assembled and connected with the horizontal support 16 near the bottom of the pit through the top support force-adding mechanism and the reaction corbel 9. In this way, the top support force-adding mechanism can apply thrust to the lower oblique support pile 3 based on the horizontal support 16 near the bottom of the pit.

[0097] It should be noted that the reaction bracket 9 is a component of the prior art, and a through hole is opened inside the bracket as a bracket hole, and the bracket hole is used to pass through the lower diagonal support pile 3. The reaction bracket 9 also has a reaction surface (such as Figure 4 The reaction surface is used to install the top support force mechanism mentioned above.

[0098] See also Figure 2 The top support end of the lower inclined support pile 3 is fixedly connected to the surrounding area near the bottom of the pit by bonding slurry (such as Figure 2 In this way, when the top support force-adding mechanism applies thrust to the lower oblique support pile 3, the top support end of the lower oblique support pile 3 forms a top support effect on the surrounding area near the bottom of the pit.

[0099] More specifically,

[0100] Four grouting passages (not shown in the figure) are arranged inside the lower diagonal support pile 3 , and the openings at both ends of the grouting passages are respectively located at the two ends (force application end and top support end) of the lower diagonal support pile 3 .

[0101] When constructing the oblique downward advanced prestressed top support structure, when it is necessary to connect the top support end of the lower oblique support pile 3 with the part of the enclosure near the bottom of the pit, first place the top support end of the lower oblique support pile 3 against the enclosure structure 5, and then, through the grouting passage, pour the pre-prepared bonding slurry from the force-applying end of the lower oblique support pile 3 to the top support end, that is, the part between the top support end of the lower oblique support pile 3 and the part of the enclosure near the bottom of the pit, and after the bonding slurry solidifies, the two are connected together.

[0102] It should be noted that the "bonding method through adhesive slurry" is not the only way to connect the "top support end of the lower inclined support pile 3" and the part of the enclosure near the bottom of the pit. In other embodiments, the connection can also be achieved by using claw gripping.

[0103] Specifically, see Figure 3 ,

[0104] A claw head 14 may be provided at the top support end of the lower inclined support pile 3. The claw head 14 is provided with a plurality of claws. The claw head 14 may be fixed at the top support end of the lower inclined support pile 3, or may be assembled at the top support end of the lower inclined support pile 3 through a hinge (ball hinge or axle pin hinge). When the top support end of the lower inclined support pile 3 is supported on the retaining structure 5, the claw head 14 can firmly grasp the retaining structure 5, thereby realizing the connection between the "top support end of the lower inclined support pile 3" and the position of the retaining structure near the bottom of the pit.

[0105] As mentioned above, an inclinometer 19 is pre-buried inside the retaining structure 5. During the construction of the foundation pit, the top support force mechanism can be controlled to apply thrust to the lower diagonal support pile 3 according to the monitoring data of the inclinometer 19, thereby controlling the top support prestress applied by the lower diagonal support pile 3 to the retaining near the bottom of the pit, so that the displacement deformation of the retaining near the bottom of the pit meets the design requirements of the foundation pit project.

[0106] It should be noted that the previously mentioned "a reaction corbel 9 is provided on the horizontal support 16 near the pit bottom" refers specifically to the reaction corbel 9 being provided on the upper portion of the horizontal support 16 near the pit bottom. The force-applying end of the lower oblique support pile 3 is assembled and connected with the reaction corbel 9 above the horizontal support 16 near the pit bottom, while the top support end of the lower oblique support pile 3 is supported together with the surrounding near the pit bottom below the horizontal support 16 near the pit bottom. Therefore, the lower oblique support pile 3 needs to penetrate the horizontal support 16 near the pit bottom and the reaction corbel 9. For this reason, before installing the lower oblique support pile 3, an oblique through hole is pre-opened at the position where the reaction corbel 9 is provided on the horizontal support 16 near the pit bottom as a support through hole. The direction of the support through hole matches the direction of "the lower oblique support pile 3 penetrating the horizontal support 16 near the pit bottom", and the lower oblique support pile 3 penetrates the horizontal support 16 near the pit bottom through the support through hole.

[0107] In this embodiment, the top support force-adding mechanism adopts a corbel-based reaction mechanism 11 (existing technology). Figure 4 The specific structure of the corbel base reaction mechanism 11 is implemented as follows:

[0108] The bull leg base reaction mechanism 11 mainly includes a first jack 110 and a reaction frame 116 .

[0109] The reaction frame 116 is configured like a door frame, and has a reaction beam 115. The reaction frame 116 is fixed to the reaction bracket 9, specifically to the reaction surface of the reaction bracket 9, through fixing parts such as anchor bolts 111 and anchor steel plates 112. In this way, the reaction beam 115 of the reaction frame 116 faces the force-applying end of the lower diagonal support pile 3 (the lower diagonal support pile is not shown in the figure).

[0110] A certain spacing is left between the reaction beam 115 and the reaction corbel 9 as a jack retention space, and the first jack 110 is placed in the jack retention space and is arranged between the "reaction beam 115 of the reaction frame 116" and the "force-applying end of the lower diagonal support pile 3". In this way, the first jack 110 can apply a thrust to the force-applying end of the lower diagonal support pile 3 based on the reaction beam 115 of the reaction frame 116, or in other words, the corbel-based reaction mechanism 11 can apply a thrust to the force-applying end of the lower diagonal support pile 3 based on the reaction corbel 9, so that the top support end of the lower diagonal support pile 3 can apply a top support prestress to the surrounding area near the bottom of the pit.

[0111] It should be noted that the reaction bracket 9 can also be regarded as a component of the bracket base reaction mechanism 11.

[0112] This embodiment 1 also provides a method for applying prestress in advance to the retaining wall in the foundation pit. The method for applying prestress in advance adopts the above-mentioned oblique downward advance prestressed top support structure to apply top support prestress to the retaining wall near the bottom of the pit.

[0113] Specifically, the method for applying prestress in advance of this embodiment includes:

[0114] S1, constructing a horizontal support 16 near the bottom of the foundation pit at the construction location of the foundation pit;

[0115] It should be noted that the horizontal support 16 near the pit bottom is constructed based on the pull-out piles 6 pre-constructed in the foundation pit, and the constructed horizontal support 16 near the pit bottom is provided with a surrounding purlin 2 around it, and the horizontal support 16 near the pit bottom is connected to the retaining structure 5 through the surrounding purlin 2.

[0116] S2, after completing the construction of the horizontal support 16 near the pit bottom in step S1, immediately start to construct the oblique downward advance prestressed top support structure, and complete the construction of the oblique downward advance prestressed top support structure before the subsequent lower level excavation operation.

[0117] Those skilled in the art will understand that the displacement and deformation of the retaining structure 5 usually occurs after the lower level excavation operation. After the lower level excavation operation, the free surface of the retaining structure 5 is no longer supported by the soil, and the retaining structure 5 will be displaced and deformed toward the inside of the foundation pit.

[0118] In the present embodiment, an advanced prestressed top support structure inclined downward for the surrounding area near the bottom of the pit is constructed before the lower-level excavation operation. During the lower-level excavation operation, the application of top support prestress can be adjusted at any time according to the displacement and deformation of the surrounding area near the bottom of the pit, including the surrounding structure 5 that is still in the soil below the current pit bottom. That is, measures for applying top support prestress can be taken as soon as displacement and deformation occur in the surrounding area near the bottom of the pit, which is conducive to timely preventing displacement and deformation of the surrounding area near the bottom of the pit.

[0119] The specific structural composition of the constructed oblique downward advanced prestressed top support structure is as described above and will not be repeated here.

[0120] The following describes a specific construction method of the oblique downward advanced prestressed top support structure, which specifically includes steps S21 to S24.

[0121] S21, opening a support hole on the horizontal support 16 near the pit bottom;

[0122] Then, a reaction bracket 9 is constructed on the constructed horizontal support 16 near the pit bottom, and the bracket hole of the reaction bracket 9 should correspond to the support through hole on the horizontal support 16 near the pit bottom;

[0123] In addition, the anchor bolts 111 and the anchor steel plates 112 must be buried in advance.

[0124] S22, at the current bottom of the foundation pit, according to the pre-designed position angle, use an inclined pile driver to obliquely send the lower inclined support pile 3 through the corbel hole of the reaction corbel 9 and the support through hole on the horizontal support near the bottom of the pit into the soil, and the top support end of the lower inclined support pile 3 faces the direction of sending until the top support end of the lower inclined support pile 3 contacts the top support to the retaining structure 5.

[0125] As mentioned above, in this embodiment, four grouting passages are arranged in the lower inclined support pile 3, while in other embodiments, the lower inclined support pile 3 may not be provided with a grouting passage, but a claw head 14 is arranged at the top support end of the lower inclined support pile 3. These arrangements are all prepared for the subsequent connection between the "top support end of the lower inclined support pile 3" and the part of the enclosure near the bottom of the pit.

[0126] It is important to explain here that "using an inclined pile driver to obliquely send the lower inclined support pile 3 into the soil until the top support end of the lower inclined support pile 3 contacts the top support to the retaining structure 5" is a key step in realizing the advance application of top support prestress. It is the "oblique downward sending" that enables the top support end of the lower inclined support pile 3 to be supported in the soil below the pit bottom on the retaining near the pit bottom, thereby creating conditions for the advance intervention of top support prestress. Therefore, before the subsequent lower-level excavation operation, the retaining structure 5 that is still in the soil can be supported to realize the advance intervention of top support prestress. This is also an important innovation of the present invention.

[0127] S23, connecting the top support end of the lower diagonal support pile 3 to the enclosure structure 5;

[0128] Specifically, in this embodiment,

[0129] The high-strength bonding slurry prepared in advance by a grouting machine is poured from the force-applying end of the lower oblique support pile 3 into the grouting passage inside the lower oblique support pile 3. The bonding slurry is delivered to the portion where the "top supporting end of the lower oblique support pile 3" is in contact with the retaining structure 5 via the grouting passage. After the bonding slurry solidifies, the "top supporting end of the lower oblique support pile 3" is connected to the retaining structure 5.

[0130] If, as mentioned above, in other embodiments, the lower inclined support pile 3 is not provided with a grouting passage, but a claw head 14 is provided at the top support end of the lower inclined support pile 3, then the inclined pile driver can directly force the top support end of the lower inclined support pile 3 against the retaining structure 5, so that the claws of the claw head 14 at the top support end of the lower inclined support pile 3 are embedded in the main body of the retaining structure 5, thereby realizing a bite-type connection, and the "top support end of the lower inclined support pile 3" is connected to the retaining structure 5.

[0131] It should be noted that if the connection is made by bonding with adhesive slurry, before pouring the adhesive slurry, water can be sprayed through the grouting passage of the lower oblique support pile 3 to the "position where the top support end of the lower oblique support pile 3 and the surrounding structure 5 are in contact" to remove the soil debris at that position, so as to ensure the firmness of the subsequent adhesive connection.

[0132] S24, a top support force-adding mechanism is installed based on the horizontal support 16 near the pit bottom.

[0133] Specifically, the top support force-adding mechanism is installed based on the reaction bracket 9 pre-arranged on the horizontal support 16 near the bottom of the pit.

[0134] The force-adding end of the lower diagonal support pile 3 is assembled together with the top support force-adding mechanism, or in other words, the force-adding end of the lower diagonal support pile 3 is assembled and connected with the reaction corbel 9 through the top support force-adding mechanism. In this way, the top support force-adding mechanism can apply a thrust to the lower diagonal support pile 3 based on the reaction corbel 9, so that the top support end of the lower diagonal support pile 3 can be stably supported on the retaining structure 5.

[0135] In this embodiment, the jacking force applying mechanism is a corbel base reaction mechanism 11. The specific structure of the corbel base reaction mechanism 11 can be found in the previous introduction and will not be repeated here.

[0136] S3, using the constructed oblique downward advanced prestressed top support structure to apply top support prestress to the surrounding area near the bottom of the pit:

[0137] Specifically, the top support force-adding mechanism is controlled to apply thrust to the force-adding end of the lower inclined support pile 3, so that the top support end of the lower inclined support pile 3 applies top support prestress to the surrounding area near the bottom of the pit.

[0138] During this process, existing monitoring methods are used to monitor 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 top support force mechanism is controlled to apply appropriate top support prestress to the enclosure near the bottom of the pit, so as to better control the deformation of the enclosure near the bottom of the pit.

[0139] In this embodiment, a large number of inclinometers 19 (existing technology) are provided inside the enclosure structure 5, and the deformation condition of the enclosure structure 5, including the deformation condition of the enclosure near the bottom of the pit, can be monitored through these inclinometers 19.

[0140] In addition, an axial force monitoring device 20 is provided on the horizontal support 16 near the pit bottom. The axial force monitoring device 20 is used to monitor the support axial force (the magnitude of the horizontal force) of the horizontal support 16 near the pit bottom.

[0141] It should be noted that the lower diagonal support pile 3 can be made of one of steel pipes, precast concrete structures, composite steel or steel rods.

[0142] It should be noted that the anti-pullout device 8 provided in the foundation pit may be one of the column piles, anti-pullout anchor rods or pile loads under the support system.

[0143] It should be noted that the oblique downward advanced prestressed top support structure can be applied to the entire enclosure structure or to a partial enclosure structure.

[0144] The main advantages of the oblique downward advanced prestressed top support structure and the advanced prestressing method of the first embodiment are:

[0145] 1) The oblique downward advance prestressed jacking structure of the present embodiment 1 has a lower oblique support pile 3, which is based on a horizontal support 16 near the pit bottom and is supported at a position near the pit bottom of the enclosure. A jacking force-adding mechanism is arranged on the horizontal support 16 near the pit bottom, and the jacking force-adding mechanism can apply a thrust to the lower oblique support pile 3 based on the horizontal support 16 near the pit bottom, so that the jacking end of the lower oblique support pile 3 applies jacking prestress to the position near the pit bottom of the enclosure, and the oblique downward advance prestressed jacking structure is constructed before the subsequent lower-level excavation operation, and is arranged in advance; in this way, measures for applying jacking prestress can be taken at the first time when displacement and deformation may occur at the position near the pit bottom of the enclosure, which is conducive to timely preventing displacement and deformation of the position near the pit bottom of the enclosure, and then effectively controlling the deformation during the foundation pit excavation process.

[0146] In addition, the oblique downward advanced prestressed top support structure and the advanced prestressing method of the first embodiment also have the following advantages:

[0147] 2) The lower inclined support piles 3 provided can reduce the distance between the horizontal support 16 near the bottom of the pit and the bottom of the foundation pit, supplementing the effect of the advanced prestressing of the middle road support, thereby effectively controlling the deformation of the surrounding area near the bottom of the pit;

[0148] 3) A top support force-adding mechanism is provided for the lower oblique support pile 3, which plays an active control role on the deformation of the surrounding area near the bottom of the pit, and has a better deformation control effect;

[0149] 4) The top support and force-adding mechanism can be recycled, which is green and environmentally friendly.

[0150] Implementation 2:

[0151] See also Figures 5 and 6 This embodiment 2 provides a diagonally downward advanced prestressed top support structure. The basic structure of the diagonally downward advanced prestressed top support structure is similar to that of the diagonally downward advanced prestressed top support structure of embodiment 1. It is obtained by making some changes on the basis of the diagonally downward advanced prestressed top support structure of embodiment 1.

[0152] Compared with the embodiment 1, the main changes of the oblique downward advanced prestressed top support structure of the embodiment 2 are as follows:

[0153] Changes to the top support force mechanism:

[0154] In the second embodiment, the supporting force applying mechanism is a casing-based reaction force mechanism 12 .

[0155] See also Figure 5 and Figure 6 The specific structure of the casing-based reaction mechanism 12 is implemented as follows:

[0156] The sleeve-based reaction mechanism 12 mainly includes a second jack 120 and a sleeve 124 .

[0157] The second jack 120 is the same as the first jack 110 in the aforementioned corbel-based reaction mechanism 11 .

[0158] The sleeve 124 is tubular as a whole, with one end of the sleeve 124 serving as an oblique end and the other end serving as a reaction end. Both ends of the sleeve 124 have conventional transparent pipe openings, and a transverse opening is provided at the reaction end of the sleeve 124 as a jack accommodating space. The function of the jack accommodating space is similar to that of the jack retaining space of the previously mentioned bullneck base reaction mechanism 11.

[0159] The sleeve 124 is passed through and fixed in the support through hole on the horizontal support 16 near the bottom of the pit, the oblique end of the sleeve 124 is located below the horizontal support 16 near the bottom of the pit, and the reaction end of the sleeve 124 is located above the horizontal support 16 near the bottom of the pit. The force-adding end of the lower oblique support pile 3 is passed through the sleeve 124, and the second jack 120 is arranged in the jack accommodating space at the reaction end of the sleeve 124, and a reaction steel 127 is also arranged in the jack accommodating space. Between the second jack 120 and the reaction end of the casing 124, that is, on the side of the jack accommodating space close to the reaction end of the casing 124, to block the pipe opening at the reaction end of the casing 124, the second jack 120 can apply a thrust to the force-applying end of the lower diagonal support pile 3 based on the reaction steel 127, or in other words, the casing-based reaction mechanism 12 can apply a thrust to the force-applying end of the lower diagonal support pile 3 based on the horizontal support 16 near the bottom of the pit, so that the top support end of the lower diagonal support pile 3 can apply top support prestress to the surrounding area near the bottom of the pit.

[0160] This embodiment 2 provides a method for applying prestress in advance, which is basically similar to the method for applying prestress in advance of embodiment 1, and is obtained by making some changes on the basis of the method for applying prestress in advance of embodiment 1.

[0161] Compared with the method for applying prestress in advance in the second embodiment, the main changes of the method in the first embodiment are as follows:

[0162] Changes to step S21:

[0163] After completing the "opening of support holes on the horizontal support 16 near the bottom of the pit", the reaction corbels are no longer constructed and the anchor bolts and anchor steel plates are no longer buried. Instead, a pre-prepared sleeve 124 is set in the support hole, and a transverse anti-slip device (existing technology) is used to fix the sleeve 124 in the support hole.

[0164] Changes to step S22:

[0165] The lower inclined support pile 3 is driven obliquely into the soil through the casing 124 by an inclined pile driver.

[0166] Changes to step S24:

[0167] The supporting force adding mechanism adopts a casing-based reaction force mechanism 12 .

[0168] Implementation 3:

[0169] See also Figure 7 , this embodiment 3 provides an oblique downward advance prestressed top support structure, which has a similar basic structure to the oblique downward advance prestressed top support structure of embodiment 1, and is obtained by making some changes on the basis of the oblique downward advance prestressed top support structure of embodiment 1.

[0170] In this embodiment, the edge of the horizontal support 16 near the pit bottom is not directly connected to the purlin 2 on the retaining structure 5, but a certain spacing distance is left, that is, the two are separated by air. For the convenience of subsequent description, the separated portion is referred to as the "device assembly interval".

[0171] A large number of transverse supporting mechanisms 17 are arranged at the assembly interval of the device, so that the transverse supporting mechanisms 17 apply transverse supporting force to the purlin 2 based on the edge of the horizontal support 16 near the bottom of the pit, thereby being able to apply transverse supporting prestress to the enclosure structure 5 through the purlin 2, that is, actively controlling the displacement deformation of the enclosure structure 5 in the transverse direction.

[0172] Afterwards, some piers are set at the device assembly intervals to achieve permanent support for the enclosure structure 5.

[0173] This achieves the "combination of downward oblique support components with horizontal prestressed concrete supports."

[0174] It should be noted that, in some other embodiments, if the enclosure purlin 2 is not provided on the enclosure structure 5 , the device assembly interval refers to the space between the edge of the horizontal support 16 near the pit bottom and the enclosure structure 5 .

[0175] Implementation 4:

[0176] See also Figure 8 , this embodiment 4 also provides a diagonally downward advanced prestressed top support structure, and the diagonally downward advanced prestressed top support structure is also realized based on the main concept of the present invention.

[0177] The oblique downward advance prestressed supporting structure of embodiment 4 is mainly different from the previous embodiments 1 and 2 in that the oblique downward supporting component in the oblique downward advance prestressed supporting structure adopts the supporting telescopic rod 13 of the prior art, and a driving telescopic cylinder (electric telescopic cylinder or hydraulic telescopic cylinder) is provided in the supporting telescopic rod 13. When driven by the driving telescopic cylinder, the supporting telescopic rod 13 can perform telescopic action.

[0178] One end of the top support telescopic rod 13 is connected to the horizontal support 16 near the pit bottom through a hinge, and the other end of the top support telescopic rod 13 is connected to the enclosure near the pit bottom through a bearing seat 131; in this way, the technical effect of "applying top support prestress to the enclosure near the pit bottom based on the horizontal support 16 near the pit bottom" can also be achieved. The top support telescopic rod 13 is equivalent to the "oblique downward support component", and the driving telescopic cylinder is equivalent to the "top support force mechanism".

[0179] In addition, in other embodiments, various other forms of combinations of downwardly inclined support components and top support force-adding mechanisms may be used to implement the main concept of the present invention.

[0180] It should be noted that in some other embodiments, a mechanical passage can be set in the lower diagonal support pile 3, which can be used for subsequent mechanical equipment to enter the connection between the lower diagonal support pile 3 and the surrounding structure to perform partial reinforcement and subsequent maintenance work on this part.

[0181] 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 prestressed top support structure inclined downward in a foundation pit, characterized in that: The oblique downward advanced prestressed top support structure comprises an oblique downward support component, which is based on a horizontal support (16) near the bottom of the pit and is supported at a position near the bottom of the pit.

2. The prestressed top support structure inclined downward in the foundation pit according to claim 1 is characterized in that: A top support force-adding mechanism is arranged for the oblique downward support component, and the top support force-adding mechanism can drive the oblique downward support component to apply top support prestress to the surrounding area near the bottom of the pit based on the horizontal support (16) near the bottom of the pit.

3. The prestressed top support structure inclined downward in the foundation pit according to claim 2 is characterized in that: The oblique downward supporting component is a lower oblique supporting pile (3), one end of the lower oblique supporting pile (3) serves as a top supporting end, and the other end of the lower oblique supporting pile (3) serves as a force-applying end; The oblique downward supporting component is based on the horizontal support (16) near the bottom of the pit and is supported at the bottom of the pit near the enclosure. The specific structural form is: the force-applying end of the lower oblique support pile (3) is based on the horizontal support (16) near the bottom of the pit, and the top support end of the lower oblique support pile (3) is supported obliquely downward at the bottom of the pit near the enclosure; The inclined downward support component is provided with a top support force-adding mechanism, which can drive the inclined downward support component to apply top support prestressing to the surrounding pit bottom position based on the horizontal support (16) near the pit bottom. The specific structural form is: a top support force-adding mechanism is arranged at the position of the lower inclined support pile (3) based on the horizontal support (16) near the pit bottom, and the top support force-adding mechanism can apply a thrust to the force-adding end of the lower inclined support pile (3) based on the horizontal support (16) near the pit bottom, so that the top support end of the lower inclined support pile (3) applies top support prestressing to the surrounding pit bottom position.

4. The prestressed top support structure inclined downward in the foundation pit according to claim 3 is characterized in that: The supporting force-adding mechanism is a corbel-based reaction mechanism (11), and the corbel-based reaction mechanism (11) comprises a reaction corbel (9), a first jack (110) and a reaction frame (116); The reaction bracket (9) is arranged on a horizontal support (16) near the bottom of the pit, the reaction frame (116) has a reaction beam (115), the reaction frame (116) is fixed on the reaction bracket (9), a jack retention space is reserved between the reaction beam (115) of the reaction frame (116) and the reaction bracket (9), the first jack (110) is arranged in the jack retention space, the first jack (110) is located between the reaction beam (115) of the reaction frame (116) and the force-applying end of the lower oblique support pile (3), the first jack (110) can apply a thrust to the force-applying end of the lower oblique support pile (3) based on the reaction beam (115) of the reaction frame (116), thereby realizing that the top support force-applying mechanism can apply a thrust to the force-applying end of the lower oblique support pile (3) based on the horizontal support (16) near the bottom of the pit.

5. The prestressed top support structure inclined downward in the foundation pit according to claim 3 is characterized in that: The supporting force-adding mechanism is a casing-based reaction force mechanism (12), and the casing-based reaction force mechanism (12) comprises a casing (124) and a second jack (120); One end of the sleeve (124) serves as an oblique end, and the other end of the sleeve (124) serves as a reaction end, and a jack accommodation space is provided at the reaction end of the sleeve (124); The sleeve (124) is fixed on the horizontal support (16) near the bottom of the pit, the force-applying end of the lower oblique support pile (3) is inserted into the sleeve (124), the second jack (120) is arranged in the jack accommodating space, and a reaction steel (127) is arranged in the jack accommodating space, and the second jack (120) applies a thrust to the force-applying end of the lower oblique support pile (3) based on the reaction steel (127), so that the top support force-applying mechanism can apply a thrust to the force-applying end of the lower oblique support pile (3) based on the horizontal support (16) near the bottom of the pit.

6. The prestressed top support structure inclined downward in the foundation pit according to claim 3, characterized in that: The top support end of the lower oblique support pile (3) is fixedly connected to the surrounding area near the bottom of the pit by bonding with adhesive slurry.

7. The prestressed top support structure inclined downward in the foundation pit according to claim 6, characterized in that: The lower inclined support pile (3) is provided with a grouting passage, which is used to: inject bonding slurry to the position between the top support end of the lower inclined support pile (3) and the position of the surrounding pit bottom through the grouting passage, so as to bond the top support end of the lower inclined support pile (3) and the position of the surrounding pit bottom together.

8. The prestressed top support structure inclined downward in the foundation pit according to claim 3 is characterized in that: A claw tooth head (14) is provided at the top supporting end of the lower oblique support pile (3). When the top supporting end of the lower oblique support pile (3) is supported at a position near the bottom of the pit of the enclosure, the claw tooth head (14) can firmly grasp the enclosure structure (5).

9. The prestressed top support structure inclined downward in the foundation pit according to claim 8, characterized in that: The claw tooth head (14) is fixed at the top supporting end of the lower oblique supporting pile (3); or, the claw tooth head (14) is assembled at the top supporting end of the lower oblique supporting pile (3) through a hinge.

10. The prestressed top support structure inclined downward in the foundation pit according to claim 1, characterized in that: An inclinometer (19) is provided in the enclosure structure (5) of the foundation pit.

11. The prestressed top support structure inclined downward in the foundation pit according to claim 1, characterized in that: A device assembly space is left between the edge of the horizontal support (16) near the pit bottom and the surrounding structure (5); The obliquely downward advanced prestressed supporting structure also includes a transverse supporting mechanism (17), which is arranged at the device assembly interval, and the transverse supporting mechanism (17) applies transverse supporting prestress to the enclosure structure (5) based on the edge of the horizontal support (16) near the pit bottom.

12. The prestressed top support structure inclined downward in the foundation pit according to claim 3, characterized in that: The lower diagonal support pile (3) is a steel pipe, a prefabricated concrete structure, a combined steel or a steel rod.

13. The prestressed top support structure inclined downward in the foundation pit according to claim 1, characterized in that: An anti-pullout device (8) is provided in the foundation pit, and the anti-pullout device (8) is a column pile, an anti-pullout anchor rod or a pile load under the support system.

14. The prestressed top support structure inclined downward in the foundation pit according to claim 3, characterized in that: A mechanical passage is provided in the lower diagonal support pile (3), and the mechanical passage is used for subsequent mechanical equipment to enter the connection portion between the lower diagonal support pile (3) and the surrounding structure to carry out partial reinforcement and subsequent maintenance work at the portion.

15. The prestressed top support structure inclined downward in the foundation pit according to claim 1, characterized in that: An axial force monitoring device (20) is provided on the horizontal support (16) near the pit bottom, and the axial force monitoring device (20) is used to monitor the support axial force of the horizontal support (16) near the pit bottom.

16. The prestressed top support structure inclined downward in the foundation pit according to claim 3, characterized in that: The lower oblique support piles (3) extend below the soil at the bottom of the pit.

17. A method for applying prestress to the enclosure in advance in a foundation pit, characterized in that: The method for applying prestress in advance comprises: S1, constructing a horizontal support near the bottom of the pit (16); S2, constructing a prestressed top support structure that is inclined downward and completed before the subsequent lower level excavation operation; The constructed oblique downward advanced prestressed top support structure comprises an oblique downward support component, which is based on a horizontal support (16) near the bottom of the pit and is supported at a position near the bottom of the pit; A top support force adding mechanism is arranged for the oblique downward support component, and the top support force adding mechanism can drive the oblique downward support component to apply top support prestress to the surrounding area near the bottom of the pit based on the horizontal support (16) near the bottom of the pit; S3, using the constructed oblique downward advanced prestressed top support structure to apply top support prestress to the surrounding area near the bottom of the pit.

18. The method for applying prestress to the enclosure in advance in the foundation pit according to claim 17, characterized in that: The oblique downward supporting component adopts a lower oblique supporting pile (3), one end of the lower oblique supporting pile (3) serves as a top supporting end, and the other end of the lower oblique supporting pile (3) serves as a force-applying end; The method for constructing the oblique downward advanced prestressed top support structure specifically includes: S21, presetting a support through hole on a horizontal support (16) near the pit bottom; S22, using an inclined pile driver to obliquely drive the lower inclined support pile (3) from the support through hole on the horizontal support (16) near the bottom of the pit into the soil until the top support end of the lower inclined support pile (3) contacts the top support to the retaining structure (5); the constructed lower inclined support pile (3), the top support end of which supports the retaining structure (5) is located in the soil below the current bottom of the foundation pit; S23, connecting the top support end of the lower inclined support pile (3) to the surrounding structure (5); S24, installing a top support force-adding mechanism based on the horizontal support (16) near the pit bottom, the top support force-adding mechanism can apply a thrust to the lower oblique support pile (3) based on the horizontal support (16) near the pit bottom, so that the top support end of the lower oblique support pile (3) applies a top support prestress to the surrounding area near the pit bottom; The top supporting end of the lower oblique supporting pile (3) and the top supporting enclosure structure (5) are located in the soil below the current bottom of the foundation pit.

19. The method for applying prestress to the enclosure in advance in the foundation pit according to claim 18, characterized in that: A grouting passage is provided in the lower inclined support pile (3); The method of connecting the top support end of the lower inclined support pile (3) with the enclosure structure (5) comprises: using a grouting machine to inject high-strength bonding slurry from the force-applying end of the lower inclined support pile (3) into a grouting passage in the lower inclined support pile (3); the bonding slurry is delivered to the contact portion between the top support end of the lower inclined support pile (3) and the enclosure structure (5) via the grouting passage; after the bonding slurry solidifies, the top support end of the lower inclined support pile (3) is connected with the enclosure structure (5).

20. The method for applying prestress to the enclosure in advance in the foundation pit according to claim 19, characterized in that: Before pouring the bonding slurry, water is sprayed through the grouting passage of the lower diagonal support pile (3) to the part where the top support end of the lower diagonal support pile (3) contacts the surrounding structure (5) to remove soil debris.

21. The method for applying prestress to the enclosure in advance in the foundation pit according to claim 18, characterized in that: A claw tooth head (14) is provided at the top supporting end of the lower oblique supporting pile (3); The method for connecting the top support end of the lower inclined support pile (3) with the enclosure structure (5) specifically comprises: using an inclined pile driver to forcibly press the top support end of the lower inclined support pile (3) against the enclosure structure (5), so that the claws of the claw head (14) at the top support end of the lower inclined support pile (3) are embedded in the enclosure structure (5) body, thereby realizing a bite-type connection, and the top support end of the lower inclined support pile (3) is connected with the enclosure structure (5).

22. The method for applying prestress to the enclosure in advance in a foundation pit according to claim 18, characterized in that: The method for installing the top support force-adding mechanism based on the horizontal support (16) near the bottom of the pit comprises: The supporting force-adding mechanism is a corbel-based reaction mechanism (11), and the corbel-based reaction mechanism (11) comprises a reaction corbel (9), a first jack (110) and a reaction frame (116); The reaction bracket (9) is arranged on a horizontal support (16) near the bottom of the pit, the reaction frame (116) has a reaction beam (115), the reaction frame (116) is fixed on the reaction bracket (9), a jack retention space is reserved between the reaction beam (115) of the reaction frame (116) and the reaction bracket (9), the first jack (110) is arranged in the jack retention space, the first jack (110) is located between the reaction beam (115) of the reaction frame (116) and the force-applying end of the lower oblique support pile (3), and the first jack (110) applies a thrust to the force-applying end of the lower oblique support pile (3) based on the reaction beam (115) of the reaction frame (116).

23. The method for applying prestress to the enclosure in advance in the foundation pit according to claim 18, characterized in that: The method for installing the top support force-adding mechanism based on the horizontal support (16) near the bottom of the pit comprises: The supporting force-adding mechanism is a casing-based reaction force mechanism (12), and the casing-based reaction force mechanism (12) comprises a second jack (120) and a casing (124); One end of the sleeve (124) serves as an oblique end, and the other end of the sleeve (124) serves as a reaction end, and a jack accommodation space is provided at the reaction end of the sleeve (124); The sleeve (124) is fixed on a horizontal support (16) near the bottom of the pit, the force-applying end of the lower diagonal support pile (3) is inserted into the sleeve (124), the second jack (120) is arranged in the jack accommodating space, and a reaction steel (127) is arranged in the jack accommodating space, and the second jack (120) applies a thrust to the force-applying end of the lower diagonal support pile (3) based on the reaction steel (127).

24. The method for applying prestress to the enclosure in advance in a foundation pit according to claim 18, characterized in that: The method for applying prestress in advance also includes: In the process of applying top support prestress to the part of the enclosure near the bottom of the pit using the constructed oblique downward advance prestressed top support structure, the deformation condition of the part of the enclosure near the bottom of the pit is monitored. According to the deformation condition of the part of the enclosure near the bottom of the pit, the top support force-adding mechanism is controlled to apply top support prestress to the part of the enclosure near the bottom of the pit, so that the deformation of the part of the enclosure near the bottom of the pit can be better controlled.

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