Structure and method for loading prestress on enclosure in foundation pit

Abstract

The invention discloses a structure and method for loading prestress on an enclosure in a foundation pit. The pre-stress loading structure comprises a pit bottom pre-stress supporting structure (6), wherein the pit bottom pre-stress supporting structure comprises a reinforcement cushion layer (61), a hidden beam (62) and a pit bottom back shore forcing device (63); the hidden beam is constructed at the bottom of a foundation pit and is arranged along a foundation pit support structure (1), and the pit bottom support forcing device loads support force to the bottom of the support structure based on the hidden beam; the reinforcement cushion layer is arranged at the bottom of the foundation pit and located on the side, back on to the enclosure structure, of the hidden beam. The prestressing force loading method comprises the steps that the pit bottom prestressing force supporting structure is constructed before the bottom plate is constructed, and the pit bottom prestressing force supporting structure is adopted to load jacking prestressing force to the bottom of the enclosure structure. According to the prestress loading structure and method, the jacking prestress can be loaded to the bottom of the enclosure structure at the first time, and therefore measures can be taken for displacement deformation of the bottom of the enclosure structure as soon as possible.

Description

Technical Field

[0001] The invention relates to the technical field of deep foundation pit construction, and in particular to a prestressed structure and method for loading enclosures in a foundation pit. Background Art

[0002] In urban renewal projects, foundation pit engineering is one of the key links. The stability of the foundation pit engineering is crucial to the success of the entire project. In order to ensure the stability of the foundation pit, loading prestress on the retaining structure at the bottom of the foundation pit is an effective method, which can control the deformation of the retaining structure at the bottom of the pit. At present, there are some methods for loading prestress on the bottom of the pit.

[0003] The main problems at present are:

[0004] Problem 1: The main time node for loading the prestress at the bottom of the pit in the existing method is usually after the bottom plate is poured. Since the bottom plate has been constructed, it can be used as part of the support structure to jointly bear the soil pressure and improve the stability of the entire foundation pit; however, this time arrangement limits the effect of prestress loading because it cannot control the deformation of the pit bottom enclosure before the bottom plate is constructed. This is also the most important problem solved by the present invention.

[0005] In addition, there are still some problems as follows:

[0006] Problem 2: The existing methods are mainly applied to the replacement of support conditions, with the aim of reducing the deformation of the foundation pit caused by the removal of the foundation pit support, which limits its application in controlling the deformation of the pit bottom enclosure before the bottom plate construction;

[0007] Problem 3: Before the foundation pit is constructed to the bottom and the bottom slab is constructed, the bottom of the foundation pit lacks effective support because the bottom slab is not completed. This causes the deformation speed of the retaining structure to be the fastest, and the deformation control of the retaining structure is more urgent.

[0008] Question 4: Although servo technology is already quite mature in modern foundation pit projects, in traditional construction methods, the application of servo devices is limited due to the lack of stable support points at the bottom of the pit, making it difficult to effectively control deformation near the bottom of the pit. Summary of the invention

[0009] The object of the present invention is to provide a prestressed loading structure and method, which can load the top support prestress to the bottom of the enclosure structure at the first time, so that measures can be taken as soon as possible to deal with the displacement deformation at the bottom of the enclosure structure.

[0010] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0011] A prestressed structure for loading enclosures in a foundation pit, the prestressed structure comprising a prestressed support structure at the bottom of the pit, the prestressed support structure at the bottom of the pit comprising a reinforced cushion layer, a hidden beam and a top support force-adding device at the bottom of the pit;

[0012] The hidden beam is constructed at the bottom of the foundation pit, the hidden beam is along the foundation pit retaining structure, an assembly interval is left between the hidden beam and the retaining structure, the pit bottom top support force adding device is installed at the assembly interval between the hidden beam and the retaining structure, and the pit bottom top support force adding device applies a top support force to the bottom of the retaining structure based on the hidden beam;

[0013] The reinforcement cushion layer is arranged at the bottom of the foundation pit and is located at the side of the concealed beam facing away from the surrounding structure.

[0014] Furthermore, a prestressed receiving member is arranged in the assembly interval between the hidden beam and the enclosure structure, and the prestressed receiving member forms a top support for the bottom of the enclosure structure based on the hidden beam.

[0015] Furthermore, a cushioning member is provided at the assembly interval between the concealed beam and the enclosure structure;

[0016] The pit bottom top support force adding device can load the top support force to the bottom of the enclosure structure based on the hidden beam and through the bottom pad;

[0017] The prestressed bearing member is based on the hidden beam and forms a top support for the bottom of the enclosure structure through the base member.

[0018] Furthermore, the prestressed bearing member is a prestressed bearing steel or a prestressed bearing pier;

[0019] The prestressed receiving pier is constructed based on the hidden beam.

[0020] Furthermore, there are some local deep pits at the positions of the reinforcement cushion layer bordering the hidden beam, and local steel sections are arranged in the local deep pits. The local steel sections form top supports for the hidden beam based on the local deep pits.

[0021] Furthermore, the enclosure structure is a continuous wall enclosure structure, and the installation position of the top support force-adding device corresponds to the wall joint position of the continuous wall enclosure structure.

[0022] Further, the loading prestressed structure includes an upper and middle prestressed support structure in the pit;

[0023] The upper and middle prestressed support structure in the pit includes a pit top prestressed support structure and a pit middle prestressed support structure;

[0024] The prestressed support structure on the pit top includes a pit top horizontal support and a pit top support force-adding device;

[0025] An assembly gap is left between the peripheral portion of the horizontal support of the pit top and the surrounding structure;

[0026] The pit top support force adding device is installed at the assembly interval between the pit top horizontal support and the enclosure structure, and the pit top support force adding device applies a support force to the enclosure structure based on the pit top horizontal support;

[0027] The prestressed support structure in the pit includes a horizontal support in the pit and a top support force-adding device in the pit;

[0028] An assembly gap is left between the peripheral portion of the horizontal support in the pit and the surrounding structure;

[0029] The top support force-adding device in the pit is installed at the assembly interval between the horizontal support in the pit and the surrounding structure. The top support force-adding device in the pit applies a top support force to the surrounding structure based on the horizontal support in the pit.

[0030] Furthermore, a pit top purlin is arranged on the top of the enclosure structure, and the pit top support force adding device can load the top support force on the enclosure structure through the pit top purlin based on the horizontal support of the pit top;

[0031] A pit purlin is arranged at the position of the pit horizontal support corresponding to the retaining structure, and the pit top support force-adding device can load the top support force on the retaining structure through the pit purlin based on the pit horizontal support.

[0032] Furthermore, the pit top horizontal support includes a pit top support purlin, which is arranged at the peripheral part of the pit top horizontal support, and the pit top support force-adding device is fixedly installed based on the pit top support purlin of the pit top horizontal support; the pit mid-horizontal support includes a pit mid-horizontal support purlin, which is arranged at the peripheral part of the pit mid-horizontal support, and the pit top support force-adding device is fixedly installed based on the pit mid-horizontal support purlin of the pit mid-horizontal support.

[0033] A method for loading prestress on a retaining wall in a foundation pit, the method comprising:

[0034] S1, construct the upper and middle prestressed support structure in the pit;

[0035] S2, constructing a prestressed support structure at the bottom of the pit before constructing the bottom plate, and using the prestressed support structure at the bottom of the pit to load the top support prestress on the bottom of the enclosure structure.

[0036] Furthermore, step S2 specifically includes:

[0037] S21, performing excavation operations in the current foundation pit until the depth of the current foundation pit reaches the design depth of the foundation pit engineering;

[0038] S22, at the bottom of the current foundation pit, a hidden beam is constructed along the retaining structure, and an assembly interval is reserved between the constructed hidden beam and the retaining structure;

[0039] S23, at the bottom of the current foundation pit, a reinforced cushion layer is constructed in the area enclosed by the hidden beam;

[0040] S24, assembling a plurality of pit bottom top support force adding devices in the assembly interval between the hidden beam and the enclosure structure; the pit bottom top support force adding devices are fixedly installed based on the hidden beam, and the pit bottom top support force adding devices can load a top support force on the bottom of the enclosure structure based on the hidden beam;

[0041] S25, according to the deformation condition of the bottom of the retaining structure, controlling the top support force adding device at the bottom of the pit to apply a top support force to the bottom of the retaining structure;

[0042] S26, arranging a plurality of prestressed bearing members in the assembly interval between the hidden beam and the enclosure structure, so that the prestressed bearing members form a top support for the bottom of the enclosure structure based on the hidden beam, and then removing the pit bottom top support force adding device;

[0043] S27, pour the casting material in the assembly interval between the hidden beam and the surrounding structure.

[0044] Further, after the hidden beam is constructed, a padding member is provided at the assembly interval between the hidden beam and the enclosure structure;

[0045] The pit bottom top support force adding device can load the top support force to the bottom of the enclosure structure based on the hidden beam and through the bottom pad;

[0046] The prestressed bearing member is based on the hidden beam and forms a top support for the bottom of the enclosure structure through the base member.

[0047] Furthermore, the prestressed bearing member is a prestressed bearing steel or a prestressed bearing pier;

[0048] The prestressed receiving pier is constructed based on the hidden beam.

[0049] Further, in step S23, when there are some local deep pits at the junction of the reinforcement cushion layer and the hidden beam, local steel sections are arranged in the local deep pits, and the local steel sections form a top support for the hidden beam based on the local deep pits.

[0050] Further, step S1 includes:

[0051] S11, construct the prestressed support structure on the top of the pit, including:

[0052] S111, excavating the foundation pit until the depth of the current foundation pit reaches the designed position of the prestressed support structure at the top of the pit;

[0053] S112, constructing a pit top horizontal support at the designed position of the pit top prestressed support structure, and reserving an assembly interval between the peripheral portion of the constructed pit top horizontal support and the surrounding structure;

[0054] S113, installing a plurality of pit top support force adding devices at the assembly interval between the pit top horizontal support and the enclosure structure; the pit top support force adding devices are fixedly installed based on the pit top horizontal support, and the pit top support force adding devices can apply a support force to the enclosure structure based on the pit top horizontal support;

[0055] S114, according to the deformation condition of the top of the retaining structure, controlling the top support force adding device of the pit top to apply appropriate top support force to the retaining structure;

[0056] S12, construct the prestressed support structure in the pit, including:

[0057] S121, performing excavation operations in the current foundation pit until the depth of the current foundation pit reaches the designed position of the prestressed support structure in the pit;

[0058] S122, constructing a horizontal support in the pit at the designed position of the prestressed support structure in the pit, and reserving an assembly interval between the peripheral portion of the constructed horizontal support in the pit and the surrounding structure;

[0059] S123, installing a plurality of top support force adding devices in the pit at the assembly interval between the horizontal support in the pit and the enclosure structure; the top support force adding devices in the pit are fixedly installed based on the horizontal support in the pit, and the top support force adding devices in the pit can apply a top support force to the enclosure structure based on the horizontal support in the pit;

[0060] S124, according to the deformation condition of the middle part of the retaining structure, control the top support force device in the pit to load appropriate top support force on the retaining structure.

[0061] A prestressed structure for loading enclosures in a foundation pit, the prestressed structure comprising a prestressed support structure at the bottom of the pit, the prestressed support structure at the bottom of the pit comprising a steel structure plate, a hidden beam and a top support force-adding device at the bottom of the pit;

[0062] The hidden beam is constructed at the bottom of the foundation pit, the hidden beam is along the foundation pit retaining structure, an assembly interval is left between the hidden beam and the retaining structure, the pit bottom top support force adding device is installed at the assembly interval between the hidden beam and the retaining structure, and the pit bottom top support force adding device applies a top support force to the bottom of the retaining structure based on the hidden beam;

[0063] The steel structure plate is arranged at the bottom of the foundation pit and is located at the side of the hidden beam facing away from the surrounding structure.

[0064] Compared with the prior art, the prestressed loading structure of the present invention has the following beneficial effects:

[0065] In the prestressed loading structure and method of the present invention, after the construction of the middle and upper prestressed support structure in the pit is completed, the construction of the prestressed support structure at the bottom of the pit is immediately started, and the construction process is carried out before the construction of the bottom plate of the pit; in this way, the prestress can be loaded on the bottom of the retaining structure at the first time, so as to take measures as soon as possible to deal with the displacement and deformation of the bottom of the retaining structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figures 1 to 3 is a schematic structural diagram of a prestressed loading structure according to Embodiment 1 of the present invention, wherein:

[0067] Figure 1 is a side view,

[0068] Figure 2 This is a top view, showing the local deep pit where the reinforcement cushion layer and the hidden beam meet and the local steel section therein.

[0069] Figure 3 It is a top view, showing the prestressed bearing pier between the continuous wall enclosure structure and the hidden beam;

[0070] Figures 4 to 6 is a schematic structural diagram of a prestressed loading structure according to Embodiment 2 of the present invention, wherein:

[0071] Figure 4 is a side view,

[0072] Figure 5 is a top view,

[0073] Figure 6 It is a top view, showing the prestressed supporting piers between the continuous wall enclosure structure and the hidden beam. DETAILED DESCRIPTION

[0074] The following provides specific embodiments to further illustrate the present invention:

[0075] Implementation 1:

[0076] See also Figures 1 to 3 This embodiment 1 provides a prestressed loading structure, which is used to load prestress on the retaining structure 1 around the foundation pit to achieve the purpose of preventing the retaining structure 1 from displacement and deformation, especially the displacement and deformation of the retaining structure at the bottom of the pit.

[0077] It should be noted that in this embodiment 1, the retaining structure 1 constructed around the foundation pit is a continuous wall retaining structure, which is different from the embodiment 2 to be mentioned later.

[0078] See also Figure 1The prestressed loading structure of this embodiment 1 is mainly composed of three parts, namely the prestressed supporting structure 4 on the top of the pit, the prestressed supporting structure 5 in the pit and the prestressed supporting structure 6 at the bottom of the pit.

[0079] The prestressed support structure 4 on the pit top and the prestressed support structure 5 in the pit can be collectively referred to as the upper and middle prestressed support structure in the pit.

[0080] The pit top prestressed support structure 4 is arranged at the pit top of the foundation pit, and the pit top prestressed support structure 4 specifically includes a pit top horizontal support 41 and a plurality of pit top support force adding devices 43 .

[0081] A certain interval is left between the peripheral portion of the pit top horizontal support 41 and the foundation pit retaining structure 1 , and the interval serves as an assembly interval to reserve space for the installation of the pit top support force device 43 .

[0082] It should be noted that the pit top support force adding device 43 and the pit middle support force adding device 53 and pit bottom support force adding device 63 to be mentioned later are support force adding devices of the same configuration. Those skilled in the art can understand that the support force adding device has a support end, which can extend outward based on the device body and output support force to the outside.

[0083] The numerous pit top support force boosting devices 43 mentioned above are all installed at the assembly interval between the pit top horizontal support 41 and the surrounding structure 1, and these pit top support force boosting devices 43 are regularly and discretely arranged along the periphery of the pit top horizontal support 41.

[0084] For each pit top support force adding device 43 , the device body of the pit top support force adding device 43 is fixedly installed based on the peripheral part of the pit top horizontal support 41 , and the top support end of the pit top support force adding device 43 is assembled and connected to the top of the retaining structure 1 .

[0085] In this way, the pit top support force adding device 43 can load the top support force on the top of the retaining structure 1 based on the peripheral part of the pit top horizontal support 41 to counteract the "influence of the displacement and deformation of the soil around the foundation pit on the top of the retaining structure 1".

[0086] It should be noted that, in this embodiment, the pit top horizontal support 41 is provided with a pit top support purlin 42, and the pit top support purlin 42 is arranged at the periphery of the pit top horizontal support 41. In this way, the device body of the pit top support force adding device 43 is fixedly installed based on the pit top support purlin 42.

[0087] In addition, it should be noted that a purlin is also provided on the top of the enclosure structure 1 , and the purlin is called a pit top purlin 31 .

[0088] In this embodiment 1, the jacking force device is essentially a hydraulic telescopic cylinder, the telescopic end of the hydraulic telescopic cylinder (commonly known as the "cylinder head") is equivalent to the jacking end of the jacking force device, and the cylinder body of the hydraulic telescopic cylinder is equivalent to the device body of the jacking force device.

[0089] The aforementioned "the device body of the pit top support force adding device 43 is fixedly installed based on the peripheral part of the pit top horizontal support 41, and the top support end of the pit top support force adding device 43 is assembled and connected with the top of the enclosure structure 1",

[0090] Specifically

[0091] "The cylinder body of the hydraulic telescopic cylinder is fixedly installed based on the pit top support purlin 42 around the pit top horizontal support 41, and the telescopic end of the hydraulic telescopic cylinder is assembled and connected with the pit top purlin 31 at the top of the retaining structure 1."

[0092] The prestressed support structure 5 in the pit is arranged at a position inside the foundation pit that is neither the top nor the bottom. The prestressed support structure 5 in the pit specifically includes a horizontal support 51 in the pit and a plurality of top support force adding devices 53 in the pit.

[0093] There is a certain gap between the periphery of the horizontal support 51 in the pit and the foundation pit retaining structure 1, and the gap is used as an assembly gap to reserve space for the installation of the pit top support force device 53. The aforementioned many pit top support force devices 53 are all installed at the assembly gap between the horizontal support 51 in the pit and the retaining structure 1, and these pit top support force devices 53 are regularly and discretely arranged along the periphery of the horizontal support 51 in the pit.

[0094] For each top support force boosting device 53 in the pit, the device body of the top support force boosting device 53 in the pit is fixedly installed based on the peripheral part of the horizontal support 51 in the pit, and the top support end of the top support force boosting device 53 in the pit is assembled and connected with the middle part of the enclosure structure 1.

[0095] In this way, the top support force device 53 in the pit can load the top support force on the middle part of the retaining structure 1 based on the peripheral part of the horizontal support 51 in the pit to counteract the "influence of the displacement and deformation of the soil around the foundation pit on the middle part of the retaining structure 1".

[0096] It should be noted that the "middle part of the retaining structure 1" mentioned here refers to the "part of the retaining structure 1 in the middle part in the depth direction of the foundation pit".

[0097] It should be noted that in this embodiment, the pit horizontal support 51 is provided with a pit support purlin 52, and the pit support purlin 52 is arranged at the periphery of the pit horizontal support 51. In this way, the device body of the pit top support force device 53 is fixedly installed based on the pit support purlin 52.

[0098] As mentioned above, in this embodiment, the top support and boosting device adopts a hydraulic telescopic cylinder. In this way, the previously mentioned "the device body of the top support and boosting device 53 in the pit is fixedly installed based on the peripheral part of the horizontal support 51 in the pit, and the top support end of the top support and boosting device 53 in the pit is assembled and connected with the middle part of the enclosure structure 1"

[0099] Specifically,

[0100] "The cylinder body of the hydraulic telescopic cylinder is fixedly installed based on the pit support purlin 52 around the pit horizontal support 51, and the telescopic end of the hydraulic telescopic cylinder is assembled and connected to the middle part of the enclosure structure 1."

[0101] It should be noted that the above-mentioned prestressed support structure 4 on the top of the pit and the prestressed support structure 5 in the pit can be collectively referred to as the upper and middle prestressed support structure in the pit.

[0102] It should be noted that the "prestressed support structure in the middle and upper part of the pit" is a general term for the "prestressed support structure arranged at all parts of the inner side of the foundation pit except the bottom".

[0103] The most important innovation of the prestressed loading structure of the present embodiment 1 lies in the provision of the prestressed supporting structure 6 at the bottom of the pit.

[0104] Specifically, the pit bottom prestressed support structure 6 mainly includes a reinforcement cushion layer 61, a hidden beam 62 and a large number of pit bottom top support force adding devices 63.

[0105] The hidden beam 62 is constructed at the bottom of the foundation pit. The hidden beam 62 is constructed along the direction of the foundation pit retaining structure 1, and a certain interval is left between the hidden beam 62 and the foundation pit retaining structure 1 as an assembly interval. The assembly interval is a reserved space for the installation of the pit bottom top support force device 63.

[0106] The numerous pit bottom support force boosting devices 63 mentioned above are all installed at the assembly interval between the hidden beam 62 and the surrounding structure 1, and these pit bottom support force boosting devices 63 are regularly and discretely arranged along the hidden beam 62 (or, along the periphery of the foundation pit).

[0107] For each pit bottom top support force adding device 63 , the device body of the pit bottom top support force adding device 63 is fixedly installed based on the hidden beam 62 , and the top support end of the pit bottom top support force adding device 63 is assembled and connected to the bottom of the enclosure structure 1 .

[0108] In this way, the pit bottom top support force adding device 63 can load the top support force on the bottom of the retaining structure 1 based on the hidden beam 62 to counteract the "influence of the displacement and deformation of the soil around the foundation pit on the bottom of the retaining structure 1". It should be noted that the "bottom of the retaining structure 1" mentioned in this article refers to the "part of the retaining structure 1 at the bottom of the foundation pit".

[0109] The reinforcement cushion layer 61 is arranged at the side of the hidden beam 62 at the bottom of the foundation pit facing away from the enclosure structure 1. The thickness of the reinforcement cushion layer 61 is arranged in the range of 150 to 500 mm. The reinforcement is determined according to the thickness, and the diameter of the reinforcement is in the range of 6 to 25 mm.

[0110] It should be noted that the reinforcement cushion layer 61 is constructed based on the engineering piles 7 pre-constructed at the bottom of the foundation pit. The reinforcement cushion layer 61 is rigidly connected to the engineering piles 7, and the friction between the engineering piles 7 and the reinforcement cushion layer 61 and the soil is used to provide horizontal force.

[0111] Furthermore, at the junction of the reinforcement cushion layer 61 and the hidden beam 62 , the reinforcement cushion layer 61 is fixedly connected with the hidden beam 62 through a steel bar structure to form a whole.

[0112] It should be noted that in other embodiments, no connection structure may be provided between the reinforcement cushion layer 61 and the engineering pile 7 , and only the friction between the reinforcement cushion layer and the soil is used to provide the horizontal force.

[0113] A preferred solution:

[0114] See also Figure 2 When there are some local deep pits 65 at the junction of the reinforcement cushion layer 61 and the hidden beam 62, a number of local steel sections 66 can be set in each local deep pit 65. These local steel sections 66 form top supports for the hidden beam 62 based on the local deep pits 65.

[0115] It should be noted that the local deep pit 65 is mainly used as an elevator shaft, a water collection well or other purposes, and these locations may be exactly at the edge of the foundation pit, or close to the edge of the foundation pit. Due to the appearance of the local deep pit, the original top support force-adding device does not transmit force continuously, that is, a disconnection phenomenon occurs in the pit, so it is necessary to pass a piece of steel in the pit, one end of which contacts the top support force-adding device for force transmission, and the other end presses against the side of the deep pit to achieve the purpose of force transmission.

[0116] It should be noted that the number of local steel sections 66 provided in the local deep pit 65 can be determined according to actual needs.

[0117] A plurality of steel sections are arranged in the assembly interval between the concealed beam 62 and the enclosure structure 1 as prestressed bearing steel sections (not shown in the figure, but can be referred to Figure 3 The prestressed bearing buttress 67).

[0118] These prestressed bearing steel sections are regularly and discretely arranged along the direction of the hidden beam 62 in the assembly interval, and these prestressed bearing steel sections are arranged at intervals from the numerous pit bottom top support force adding devices 63 mentioned.

[0119] These prestressed bearing steel sections form a supporting posture for the bottom of the enclosure structure 1 based on the hidden beam 62, thus creating conditions for removing the pit bottom supporting force device 63 (detailed description will be given later).

[0120] An optimal solution to replace prestressed bearing steel:

[0121] See also Figure 3 Based on the hidden beam 62, a large number of piers are arranged. These piers are arranged as prestressed receiving piers 67 in the assembly interval between the hidden beam 62 and the enclosure structure 1. These prestressed receiving piers 67 are regularly and discretely arranged along the direction of the hidden beam 62 in the assembly interval. The functions of these prestressed receiving piers 67 are the same as those of the prestressed receiving steel mentioned above, which forms a top support posture for the bottom of the enclosure structure 1 based on the hidden beam 62.

[0122] The prestressed receiving support pier 67 is a steel concrete structure, which is cast into an integral body with the hidden beam 62. The prestressed receiving support pier 67 can also be a steel structure, which can be connected to the hidden beam 62 as a whole by pre-embedded or pre-embedded welding.

[0123] The prestressed bearing steel and the prestressed bearing pier 67 can be collectively referred to as "prestressed bearing parts". In other embodiments, other forms of components can be used as prestressed bearing parts to replace the prestressed bearing steel or the prestressed bearing pier 67 to achieve their functions.

[0124] It should be noted that when installing the pit top support force boosting device 43, the pit middle support force boosting device 53 and the pit bottom support force boosting device 63, the installation position of the support force boosting device should correspond to the wall joint of the continuous wall retaining structure. Since the wall joint is the weak part of the continuous wall retaining structure, such an installation method is conducive to the stable support of the continuous wall retaining structure.

[0125] This embodiment 1 also provides a method for loading prestress on the enclosure in a foundation pit, and the method for loading prestress specifically includes steps S1 to S3.

[0126] S1, construct the upper and middle prestressed support structure in the pit.

[0127] The step S1 specifically includes steps S11 to S12.

[0128] S11, constructing a prestressed support structure 4 on the top of the pit.

[0129] Specifically, it includes steps S111 to S114.

[0130] S111, excavation work is performed at the location of the foundation pit project (i.e., excavation of the soil) until the depth of the current foundation pit reaches the designed position of the prestressed support structure 4 on the top of the pit.

[0131] S112, constructing a pit top horizontal support 41 at the designed position of the pit top prestressed support structure 4 (position of the foundation pit top).

[0132] An assembly interval is left between the peripheral portion of the constructed pit top horizontal support 41 and the surrounding structure 1, thereby reserving space for the subsequent installation of the pit top support force device 43.

[0133] Preferably, while constructing the pit top horizontal support 41 , a pit top support purlin 42 can be constructed on the periphery of the pit top horizontal support 41 , thereby establishing a good installation foundation for the subsequent installation of the pit top support force adding device 43 .

[0134] S113, a plurality of pre-prepared top support force-adding devices are installed as pit top top support force-adding devices 43 at the assembly interval between the pit top horizontal support 41 and the retaining structure 1, and these pit top top support force-adding devices 43 are regularly and discretely arranged along the periphery of the pit top horizontal support 41.

[0135] For each pit top support force adding device 43 , the device body of the pit top support force adding device 43 is fixedly installed based on the peripheral part of the pit top horizontal support 41 , and the top support end of the pit top support force adding device 43 is assembled and connected to the top of the retaining structure 1 .

[0136] Preferably, if in step S112, while constructing the pit top horizontal support 41, a pit top support purlin 42 is constructed on the periphery of the pit top horizontal support 41, then the device body of the pit top support force adding device 43 is fixedly installed based on the pit top support purlin 42.

[0137] S114, use the existing detection means to detect the deformation condition (deformation data) of the top of the retaining structure 1. According to the deformation condition of the top of the retaining structure 1 and in accordance with the design standards, control the pit top support force device 43 to load appropriate support force (prestress) on the top of the retaining structure 1, so that the deformation condition of the top of the retaining structure 1 meets the design standards.

[0138] S12, constructing a prestressed support structure 5 in the pit.

[0139] Specifically, it includes steps S121 to S124.

[0140] S121, excavation work is performed in the current foundation pit (i.e., excavation of soil) until the depth of the current foundation pit reaches the designed position of the prestressed support structure 5 in the pit.

[0141] S122, constructing a horizontal support 51 in the pit at the designed position of the prestressed support structure 5 in the pit.

[0142] An assembly interval is left between the peripheral portion of the constructed horizontal support 51 in the pit and the enclosure structure 1, thereby reserving space for the subsequent installation of the top support force device 53 in the pit.

[0143] Preferably, while constructing the horizontal support 51 in the pit, the pit support purlin 52 can be constructed on the periphery of the horizontal support 51 in the pit, thereby establishing a good installation foundation for the subsequent installation of the pit top support force device 53.

[0144] S123, a plurality of pre-prepared top support force-enhancing devices are installed as the top support force-enhancing devices 53 in the pit at the assembly interval between the horizontal support 51 in the pit and the surrounding structure 1, and these top support force-enhancing devices 53 in the pit are regularly and discretely arranged along the periphery of the horizontal support 51 in the pit.

[0145] For each top support force boosting device 53 in the pit, the device body of the top support force boosting device 53 in the pit is fixedly installed based on the peripheral part of the horizontal support 51 in the pit, and the top support end of the top support force boosting device 53 in the pit is assembled and connected with the middle part of the enclosure structure 1.

[0146] Preferably, if in step S122, while constructing the horizontal support 51 in the pit, the pit support purlin 52 is constructed on the periphery of the horizontal support 51 in the pit, then the device body of the pit top support force device 53 is fixedly installed based on the pit support purlin 52.

[0147] S124, use the existing detection means to detect the deformation condition (deformation data) of the middle part of the retaining structure 1. According to the deformation condition of the middle part of the retaining structure 1 and in accordance with the design standards, control the top support force device 53 in the pit to load appropriate top support force (prestress) on the middle part of the retaining structure 1, so that the deformation condition of the middle part of the retaining structure 1 meets the design standards.

[0148] S2, after completing the construction of the middle and upper prestressed support structure in the pit in step S1, immediately start the construction of the prestressed support structure 6 at the bottom of the pit. This construction process should be carried out before the construction of the bottom plate; then the prestressed support structure 6 at the bottom of the pit is used to load the top support prestress on the bottom of the retaining structure 1.

[0149] In this way, the bottom of the retaining structure 1 can be supported and prestressed at the top support can be loaded at the first time, thereby avoiding the situation of "displacement and deformation of the bottom of the retaining structure 1 before the construction of the bottom plate is completed", thereby ensuring the construction quality of the entire foundation pit project.

[0150] The step S2 specifically includes steps S21 to S27.

[0151] S21, performing excavation operations in the current foundation pit (i.e., digging out the soil) until the depth of the current foundation pit reaches the design depth of the foundation pit engineering.

[0152] S22, at the bottom of the current foundation pit, a hidden beam 62 is constructed along the retaining structure 1, and a certain interval is reserved between the constructed hidden beam 62 and the retaining structure 1 as an assembly interval.

[0153] Preferred solution:

[0154] While constructing the hidden beam 62, some prestressed receiving piers 67 can be constructed based on the hidden beam 62. These prestressed receiving piers 67 are arranged in the assembly interval between the hidden beam 62 and the enclosure structure 1. These prestressed receiving piers 67 are regularly and discretely arranged along the direction of the hidden beam 62 in the assembly interval. The prestressed receiving piers 67 are steel concrete structures, which are cast as a whole with the hidden beam 62. These prestressed receiving piers 67 form a top support posture for the bottom of the enclosure structure 1 based on the hidden beam 62.

[0155] S23, at the bottom of the current foundation pit, at the side of the hidden beam 62 facing away from the retaining structure 1, a reinforcement cushion layer 61 is constructed based on the "engineering piles 7 pre-constructed at the bottom of the current foundation pit".

[0156] The thickness of the reinforcement cushion layer 61 is within the range of 150 to 500 mm, the reinforcement is determined according to the thickness, and the diameter of the reinforcement is within the range of 6 to 25 mm.

[0157] Preferred solution:

[0158] When there are some local deep pits at the junction of the reinforcement cushion layer and the hidden beam, local steel sections are arranged in the local deep pits, and the local steel sections form top supports for the hidden beam based on the local deep pits.

[0159] For each local deep pit 65 , two local steel sections 66 are arranged in the local deep pit 65 , and the two local steel sections 66 form a top support for the hidden beam 62 based on the local deep pit 65 .

[0160] S24, assembling a plurality of pre-prepared hydraulic telescopic cylinders as pit bottom support force adding devices 63 in the assembly interval between the hidden beam 62 and the enclosure structure 1, and these pit bottom support force adding devices 63 are regularly and discretely arranged along the hidden beam 62;

[0161] For each pit bottom top support force adding device 63, the device body of the pit bottom top support force adding device 63 is fixedly installed based on the hidden beam 62, and the top support end of the pit bottom top support force adding device 63 is assembled and connected with the bottom of the enclosure structure 1, so that the pit bottom top support force adding device 63 can load the top support force on the bottom of the enclosure structure 1 based on the hidden beam 62;

[0162] After the arrangement and installation of the pit bottom top support force adding device 63 is completed, the pit bottom top support force adding device 63 can be controlled in advance to load appropriate top support prestress on the bottom of the retaining structure 1.

[0163] S25, adopt the detection means of the existing technology to detect the deformation condition (deformation data) of the bottom of the retaining structure 1, according to the deformation condition of the bottom of the retaining structure 1 and in accordance with the design standards, control the top support force device 63 at the bottom of the pit to load appropriate top support prestress on the bottom of the retaining structure 1, so that the deformation condition of the bottom of the retaining structure 1 meets the design standards.

[0164] S26, placing a plurality of pre-prepared steel sections as prestressed receiving steel sections in the assembly interval between the hidden beam 62 and the enclosure structure 1 (not shown in the figure);

[0165] These prestressed bearing steel sections are regularly and discretely arranged along the direction of the hidden beam 62 within the assembly interval. These prestressed bearing steel sections and the numerous pit bottom support force devices 63 mentioned are arranged at intervals from each other. For each prestressed bearing steel section, the prestressed bearing steel section is close to the retaining structure 1, and the pre-prepared grouting material is poured and filled in the joint between the prestressed bearing steel section and the hidden beam 62. After the grouting material at the joint is cured to a suitable strength, the prestressed bearing steel section can form a top support for the bottom of the retaining structure 1 based on the hidden beam 62, and then all the pit bottom support force devices 63 can be removed.

[0166] Preferred solution:

[0167] If the preferred solution described in the previous step S22 is "while constructing the hidden beam 62, some prestressed receiving piers 67 can be constructed based on the hidden beam 62", then there is no need to set up prestressed receiving steel, but the pre-prepared grouting material is poured and filled in the joint between the prestressed receiving pier 67 and the enclosure structure 1. After the grouting material at the joint is cured to a suitable strength, the prestressed receiving pier 67 can form a top support for the bottom of the enclosure structure 1 based on the hidden beam 62, and then all the pit bottom top support force-adding devices 63 can be removed. In other words, the role of the prestressed receiving steel is achieved by the prestressed receiving pier 67.

[0168] In other embodiments, wedge-shaped steel materials may be used to fill the joints between the prestressed bearing pier 67 and the enclosure structure 1 instead of grouting materials.

[0169] It should be noted that the prestressed bearing steel and the prestressed bearing pier 67 can be collectively referred to as "prestressed bearing parts". In other embodiments, other forms of components can be used as prestressed bearing parts to replace the prestressed bearing steel or prestressed bearing pier 67 to achieve their functions.

[0170] S27, pouring the pre-prepared pouring material in the assembly space between the hidden beam 62 and the enclosure structure 1, thereby forming a permanent support for the bottom of the enclosure structure 1.

[0171] S3, after completing the permanent support for the bottom of the retaining structure 1, the pit bottom slab can be constructed according to the construction schedule. During this process, there is no need to worry about the deformation of the bottom of the retaining structure 1.

[0172] It should be noted that the reinforcement cushion layer 61 can be generally summarized as a cushion layer, which can also be implemented by a steel plate. The thickness of the steel plate is 5 to 30 mm. The steel plate can be connected by welding or bolts; the steel plate and the engineering pile 7 can be connected or disconnected according to the size of the reaction force to be provided. The steel plate can be replaced by a composite steel structure, and the composite steel structure and the engineering pile 7 can be connected or disconnected according to the size of the reaction force to be provided.

[0173] If the number of engineering piles 7 is insufficient, temporary piles or structures can be used to supplement them.

[0174] It should be noted that the hidden beam 62 can be a steel beam or a concrete beam. The steel beam is a section steel or a composite steel structure.

[0175] The advantages of the prestressed loading structure and method of the first embodiment are:

[0176] 1) In the prestressed loading structure and method of the present embodiment, after the construction of the middle and upper prestressed support structure in the pit is completed, the construction of the prestressed support structure 6 at the bottom of the pit is started immediately. This construction process is carried out before the construction of the bottom plate of the pit. In this way, prestress can be loaded on the bottom of the retaining structure 1 as soon as possible, so as to take measures as soon as possible to deal with the displacement and deformation at the bottom of the retaining structure 1, thereby solving all the technical problems mentioned in the background technology.

[0177] Implementation 2:

[0178] See also Figures 4 to 6 , this embodiment 2 provides a loading prestressed structure. Compared with the loading prestressed structure provided in embodiment 1, the overall concept of the two is basically the same. The main difference is that the foundation pit retaining structure 1 involved in this embodiment is a pile retaining structure, such as bored cast-in-place pile rows, steel pile rows, precast pile rows, and the like.

[0179] For the pile row enclosure structure, the prestressed loading structure of the second embodiment is modified on the basis of the first embodiment to adapt to the pile row enclosure structure. In other words, the embodiment mainly solves how to apply the concept of the first embodiment to the pile row enclosure structure.

[0180] Specifically, the main changes are as follows:

[0181] Regarding the changes of the prestressed support structure 5 in the pit:

[0182] A purlin is provided at the middle of the enclosure structure 1 at a position corresponding to the horizontal support 51 in the pit, and the purlin is referred to as the pit purlin 32 .

[0183] The top supporting end of the top supporting force boosting device 53 in the pit is assembled and connected with the surrounding purlin 32 in the pit, or in other words, the top supporting end of the top supporting force boosting device 53 in the pit is assembled and connected with the middle part of the retaining structure 1 through the surrounding purlin 32 in the pit. In this way, the top supporting force boosting device 53 in the pit can load the top supporting force on the middle part of the retaining structure 1 based on the peripheral part of the horizontal support 51 in the pit and through the surrounding purlin 32 in the pit.

[0184] Changes to the prestressed support structure 6 at the bottom of the pit:

[0185] A long I-beam is provided at the assembly interval between the concealed beam 62 and the enclosure structure 1 as a bottom pad 68 , and the bottom pad 68 is fixedly connected to the bottom of the enclosure structure 1 by bonding with casting material.

[0186] The top supporting end of the pit bottom top supporting force boosting device 63 is assembled and connected with the bottom pad 68, or in other words, the top supporting end of the pit bottom top supporting force boosting device 63 is assembled and connected with the bottom of the retaining structure 1 through the bottom pad 68. In this way, the pit bottom top supporting force boosting device 63 can load the top supporting force on the bottom of the retaining structure 1 based on the hidden beam 62 and through the bottom pad 68.

[0187] The prestressed bearing member mentioned above (prestressed bearing pier 67 or prestressed bearing steel section) also forms a top support for the bottom of the enclosure structure 1 through the base member 68.

[0188] In the second embodiment, the bottom member 68 is made of I-beams, but in other embodiments, other suitable components may be used as the bottom member 68, and the present invention is not limited thereto.

[0189] This embodiment 2 also provides a method for loading prestress.

[0190] The basic concept of the prestressing method of the present embodiment 2 is substantially the same as that of the prestressing method provided in the embodiment 1, and the main difference lies in: corresponding changes are made in response to the changes in the above-mentioned prestressing structure.

[0191] Specifically, the main changes are as follows:

[0192] Changes to step S122:

[0193] While constructing the horizontal support 51 in the pit, a pit purlin 32 is constructed at the position of the middle part of the retaining structure 1 corresponding to the horizontal support 51 in the pit, and an assembly interval is left between the peripheral part of the constructed horizontal support 51 in the pit and the pit purlin 32 constructed on the retaining structure 1, thereby reserving space for the subsequent installation of the pit top support force device 53.

[0194] Changes to step S123:

[0195] The top supporting end of the top supporting force adding device 53 in the pit is assembled and connected with the surrounding purlin 32 in the pit, or in other words, the top supporting end of the top supporting force adding device 53 in the pit is assembled and connected with the middle part of the enclosure structure 1 through the surrounding purlin 32 in the pit.

[0196] Changes to step S22:

[0197] After the hidden beam 62 is constructed, a long I-beam is arranged at the assembly interval between the hidden beam 62 and the enclosure structure 1 as a pad 68, and the pad 68 is fixedly connected to the bottom of the enclosure structure 1 by bonding with casting material.

[0198] Changes to step S24:

[0199] The top supporting end of the pit bottom top supporting force adding device 63 is assembled and connected with the bottom pad 68 , or in other words, the top supporting end of the pit bottom top supporting force adding device 63 is assembled and connected with the bottom of the enclosure structure 1 through the bottom pad 68 .

[0200] Changes to step S26:

[0201] The prestressed bearing steel is in contact with the bottom pad 68 provided at the bottom of the enclosure structure 1 . The prestressed bearing steel can form a top support for the bottom of the enclosure structure 1 based on the hidden beam 62 and through the bottom pad 68 .

[0202] The changes of the second embodiment compared with the first embodiment are roughly as described above.

[0203] It should be noted that the reason for adding the pit purlin 32 and the bottom pad 68 is that the pile row retaining structure is composed of a large number of pile bodies, wherein the pile bodies are not connected to each other, and it is impossible to support the entire pile row retaining structure by supporting a certain point of the pile row retaining structure. The pit purlin 32 and the bottom pad 68 can connect the large number of pile bodies together, so that the entire pile row retaining structure can be supported by supporting a certain point.

[0204] 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 structure for loading enclosure in a foundation pit, characterized in that: The loading prestressed structure comprises a pit bottom prestressed support structure (6), and the pit bottom prestressed support structure (6) comprises a reinforcement cushion layer (61), a hidden beam (62) and a pit bottom top support force adding device (63); The hidden beam (62) is constructed at the bottom of the foundation pit, the hidden beam (62) is along the foundation pit retaining structure (1), and an assembly gap is left between the hidden beam (62) and the retaining structure (1). The pit bottom top support force adding device (63) is installed at the assembly gap between the hidden beam (62) and the retaining structure (1), and the pit bottom top support force adding device (63) applies a top support force to the bottom of the retaining structure (1) based on the hidden beam (62); The reinforcement cushion layer (61) is arranged at the bottom of the foundation pit and is located at the side of the concealed beam (62) facing away from the enclosure structure (1).

2. According to claim 1, the prestressed structure for the enclosure in the foundation pit is characterized in that: A prestressed receiving member is arranged in the assembly interval between the hidden beam (62) and the enclosure structure (1), and the prestressed receiving member forms a top support for the bottom of the enclosure structure (1) based on the hidden beam (62).

3. According to claim 2, the prestressed structure for the enclosure in the foundation pit is characterized in that: A cushion member (68) is provided at the assembly interval between the concealed beam (62) and the enclosure structure (1); The pit bottom supporting force adding device (63) can apply supporting force to the bottom of the enclosure structure (1) based on the hidden beam (62) and through the padding member (68); The prestressed bearing member is based on the hidden beam (62) and forms a top support for the bottom of the enclosure structure (1) through the bottom pad (68).

4. According to claim 2, the prestressed structure for the enclosure in the foundation pit is characterized in that: The prestressed bearing member is a prestressed bearing steel or a prestressed bearing buttress (67); The prestressed receiving pier (67) is constructed based on the concealed beam (62).

5. According to claim 1, the prestressed structure for the enclosure in the foundation pit is characterized in that: There are some local deep pits (65) at the part of the reinforcement cushion layer (61) bordering the hidden beam (62), and local steel sections (66) are arranged in the local deep pits (65). The local steel sections (66) form a top support for the hidden beam (62) based on the local deep pits (65).

6. The prestressed structure for loading the enclosure in the foundation pit according to claim 1 is characterized in that: The enclosure structure (1) is a continuous wall enclosure structure, and the installation position of the top support force-adding device corresponds to the wall joint position of the continuous wall enclosure structure.

7. The prestressed structure for loading the enclosure in the foundation pit according to claim 1 is characterized in that: The loading prestressed structure includes a middle and upper prestressed support structure in the pit; The upper and middle prestressed support structure in the pit comprises a pit top prestressed support structure (4) and a pit middle prestressed support structure (5); The pit top prestressed support structure (4) comprises a pit top horizontal support (41) and a pit top support force adding device (43); An assembly gap is left between the peripheral portion of the pit top horizontal support (41) and the enclosure structure (1); The pit top support force adding device (43) is installed at the assembly interval between the pit top horizontal support (41) and the enclosure structure (1), and the pit top support force adding device (43) applies a support force to the enclosure structure (1) based on the pit top horizontal support (41); The prestressed support structure (5) in the pit comprises a horizontal support (51) in the pit and a top support force-adding device (53) in the pit; An assembly gap is left between the peripheral portion of the horizontal support (51) in the pit and the enclosure structure (1); The in-pit top support force adding device (53) is installed at the assembly interval between the in-pit horizontal support (51) and the enclosure structure (1), and the in-pit top support force adding device (53) applies a top support force to the enclosure structure (1) based on the in-pit horizontal support (51).

8. The prestressed structure for loading the enclosure in the foundation pit according to claim 7 is characterized in that: A pit top purlin (31) is arranged on the top of the enclosure structure (1), and a pit top support force adding device (43) can load a support force on the enclosure structure (1) based on the pit top horizontal support (41) and through the pit top purlin (31); A pit purlin (32) is arranged at a position of the enclosure structure (1) corresponding to the pit horizontal support (51), and the pit top support force adding device (53) can load a top support force on the enclosure structure (1) based on the pit horizontal support (51) and through the pit purlin (32).

9. The prestressed structure for loading the enclosure in the foundation pit according to claim 7 is characterized in that: The pit top horizontal support (41) includes a pit top support purlin (42), which is arranged at the periphery of the pit top horizontal support (41), and the pit top support force-adding device (43) is fixedly installed based on the pit top support purlin (42) of the pit top horizontal support (41); the pit mid-level support (51) includes a pit mid-level support purlin (52), which is arranged at the periphery of the pit mid-level support (51), and the pit top support force-adding device (53) is fixedly installed based on the pit mid-level support purlin (52) of the pit mid-level support (51).

10. A method for prestressing enclosure in a foundation pit, characterized in that: The prestressing method comprises: S1, construct the upper and middle prestressed support structure in the pit; S2, constructing a prestressed support structure (6) at the bottom of the pit before constructing the bottom plate, and using the prestressed support structure (6) at the bottom of the pit to load the top support prestress on the bottom of the enclosure structure (1).

11. The method for prestressing the enclosure in a foundation pit according to claim 10, characterized in that: Step S2 specifically includes: S21, performing excavation operations in the current foundation pit until the depth of the current foundation pit reaches the design depth of the foundation pit engineering; S22, at the bottom of the current foundation pit, construct a hidden beam (62) along the retaining structure (1), and reserve an assembly space between the constructed hidden beam (62) and the retaining structure (1); S23, constructing a reinforcement cushion layer (61) in the area enclosed by the hidden beam (62) at the bottom of the current foundation pit; S24, assembling a plurality of pit bottom top support force adding devices (63) in the assembly interval between the hidden beam (62) and the enclosure structure (1); the pit bottom top support force adding devices (63) are fixedly installed based on the hidden beam (62), and the pit bottom top support force adding devices (63) can load a top support force on the bottom of the enclosure structure (1) based on the hidden beam (62); S25, according to the deformation condition of the bottom of the enclosure structure (1), controlling the pit bottom support force adding device (63) to apply a support force to the bottom of the enclosure structure (1); S26, arranging a plurality of prestressed bearing members in the assembly interval between the hidden beam (62) and the enclosure structure (1), so that the prestressed bearing members form a top support for the bottom of the enclosure structure (1) based on the hidden beam (62), and then removing the pit bottom top support force adding device (63); S27, pouring casting material in the assembly interval between the hidden beam (62) and the enclosure structure (1).

12. The method for prestressing the enclosure in a foundation pit according to claim 11, characterized in that: After the hidden beam (62) is constructed, a cushion member (68) is arranged at the assembly interval between the hidden beam (62) and the enclosure structure (1); The pit bottom supporting force adding device (63) can apply supporting force to the bottom of the enclosure structure (1) based on the hidden beam (62) and through the padding member (68); The prestressed bearing member is based on the hidden beam (62) and forms a top support for the bottom of the enclosure structure (1) through the bottom pad (68).

13. The method for prestressing the enclosure in a foundation pit according to claim 11, characterized in that: The prestressed bearing member is a prestressed bearing steel or a prestressed bearing buttress (67); The prestressed receiving pier (67) is constructed based on the concealed beam (62).

14. The method for prestressing the enclosure in a foundation pit according to claim 11, characterized in that: In step S23, when encountering a working condition where there are some local deep pits (65) at the junction of the reinforcement cushion layer (61) and the hidden beam (62), local steel sections (66) are arranged in the local deep pits (65), and the local steel sections (66) form a top support for the hidden beam (62) based on the local deep pits (65).

15. The method for prestressing the enclosure in a foundation pit according to claim 10, characterized in that: Step S1 includes: S11, constructing a prestressed support structure for the pit top (4), including: S111, excavating the foundation pit until the depth of the current foundation pit reaches the designed position of the prestressed support structure (4) at the top of the pit; S112, constructing a pit top horizontal support (41) at the designed position of the pit top prestressed support structure (4), and reserving an assembly gap between the peripheral portion of the constructed pit top horizontal support (41) and the enclosure structure (1); S113, installing a plurality of pit top support force adding devices (43) at the assembly interval between the pit top horizontal support (41) and the enclosure structure (1); the pit top support force adding devices (43) are fixedly installed based on the pit top horizontal support (41), and the pit top support force adding devices (43) can load a support force on the enclosure structure (1) based on the pit top horizontal support (41); S114, according to the deformation condition of the top of the enclosure structure (1), controlling the pit top support force adding device (43) to apply appropriate support force to the enclosure structure (1); S12, constructing a prestressed support structure in the pit (5), including: S121, excavating the current foundation pit until the depth of the current foundation pit reaches the designed position of the prestressed support structure (5) in the pit; S122, constructing a horizontal support (51) in the pit at the designed position of the prestressed support structure (5) in the pit, and reserving an assembly gap between the peripheral portion of the constructed horizontal support (51) in the pit and the enclosure structure (1); S123, installing a plurality of pit top support force adding devices (53) at the assembly interval between the pit horizontal support (51) and the enclosure structure (1); the pit top support force adding devices (53) are fixedly installed based on the pit horizontal support (51), and the pit top support force adding devices (53) can load the enclosure structure (1) with a top support force based on the pit horizontal support (51); S124, according to the deformation condition of the middle part of the enclosure structure (1), the top support force adding device (53) in the pit is controlled to apply appropriate top support force to the enclosure structure (1).

16. A prestressed structure for loading enclosure in a foundation pit, characterized in that: The prestressed loading structure comprises a pit bottom prestressed support structure (6), and the pit bottom prestressed support structure (6) comprises a steel structure plate, a hidden beam (62) and a pit bottom top support force adding device (63); The hidden beam (62) is constructed at the bottom of the foundation pit, the hidden beam (62) is along the foundation pit retaining structure (1), and an assembly gap is left between the hidden beam (62) and the retaining structure (1). The pit bottom top support force adding device (63) is installed at the assembly gap between the hidden beam (62) and the retaining structure (1), and the pit bottom top support force adding device (63) applies a top support force to the bottom of the retaining structure (1) based on the hidden beam (62); The steel structure plate is arranged at the bottom of the foundation pit and is located at the side of the concealed beam (62) facing away from the enclosure structure (1).

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