Double-brace prestressed top support structure in foundation pit and prestress applying method

Abstract

The application discloses a prestressed top support structure and a prestress applying method in a foundation pit. The prestressed top support structure comprises a double telescopic top support assembly (9), the double telescopic top support assembly comprises an upper telescopic top support mechanism and a lower telescopic top support mechanism, and the top support end of the lower telescopic top support mechanism can be obliquely extended downward and supported on a lower load-bearing enclosing purlin (921); the top support end of the upper telescopic top support mechanism can be obliquely extended upward and supported on an upper load-bearing enclosing purlin (922). The prestress applying method comprises the following steps: constructing a prestressed top support structure based on a near-pit-bottom horizontal support (41), and completing the construction of the prestressed top support structure before subsequent lower-layer soil excavation; and applying top support prestress to the enclosing near-pit-bottom part by using the prestressed top support structure. The prestressed top support structure and the prestress applying method can timely load top support prestress on the enclosing near-pit-bottom part based on the near-pit-bottom horizontal support.

Description

Technical Field

[0001] This invention relates to the field of foundation pit engineering technology, and more particularly to a double-braced prestressed jacking structure and a method for applying prestress in a foundation pit. Background Technology

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

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

[0004] The current problem is:

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

[0006] The purpose of this invention is to provide a double-braced prestressed top support structure and a method for applying prestress in a foundation pit. This prestressed top support structure and method can apply top support prestress to the retaining wall near the bottom of the pit based on the horizontal support near the bottom of the pit.

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

[0008] A double-braced prestressed jacking structure for foundation pits, the prestressed jacking structure comprising a double telescopic jacking assembly.

[0009] The dual telescopic support assembly includes an upper telescopic support mechanism and a lower telescopic support mechanism, both of which have telescopic support ends.

[0010] The upper telescopic top support mechanism is assembled and connected to the horizontal support near the bottom of the pit, and the lower telescopic top support mechanism is assembled and connected to the horizontal support near the bottom of the pit.

[0011] A lower load-bearing waler is installed near the bottom of the pit, and an upper load-bearing waler is installed above the bottom support of the retaining wall.

[0012] The lower telescopic top support mechanism can swing from a near-bottom horizontal support to an angle where its top support end is inclined downward toward the lower load-bearing waler, and the top support end of the lower telescopic top support mechanism can extend obliquely downward and support the lower load-bearing waler.

[0013] The upper telescopic support mechanism can swing from a horizontal support near the bottom of the pit to an angle where its top support end is inclined upward toward the upper load-bearing waler. The top support end of the upper telescopic support mechanism can extend obliquely upward and support the upper load-bearing waler.

[0014] Furthermore, both the upper and lower telescopic support mechanisms are constructed using segmented telescopic steel pipes; each segmented telescopic steel pipe is equipped with a telescopic hydraulic cylinder, which can drive the segmented telescopic steel pipe to perform telescopic movements.

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

[0016] The main body of the upper telescopic top support mechanism is assembled with the top support base through a shaft pin mechanism, thereby realizing the assembly connection of the main body of the upper telescopic top support mechanism with the horizontal support near the bottom of the pit through the shaft pin mechanism.

[0017] The body of the lower telescopic top support mechanism is assembled with the top support base through a shaft pin mechanism, thereby realizing the assembly connection of the body of the lower telescopic top support mechanism with the horizontal support near the bottom of the pit through the shaft pin mechanism.

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

[0019] The prestressed jacking structure also includes cantilevered supports, which are located at the edge of the horizontal support near the bottom of the pit and at the assembly interval; the cantilevered supports form a jacking posture for the retaining structure based on the edge of the horizontal support near the bottom of the pit.

[0020] A jack receiving groove is provided on the side of the cantilevered support facing the retaining structure, which is used to house the jack.

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

[0022] The cantilevered support piers are based on the horizontal support edge near the bottom of the pit and form a top support posture for the retaining structure through the walers.

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

[0024] Furthermore, the lower telescopic support mechanism and the part where the lower telescopic support mechanism is assembled and connected with the horizontal support near the bottom of the pit are located at the connection point between the horizontal support near the bottom of the pit and the pull-out pile.

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

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

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

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

[0029] S2, a prestressed top support structure is constructed based on the horizontal support near the bottom of the pit, and the construction of the prestressed top support structure is completed before the subsequent excavation of the next layer;

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

[0031] The dual telescopic support assembly includes an upper telescopic support mechanism and a lower telescopic support mechanism, both of which have telescopic support ends.

[0032] The upper telescopic top support mechanism is assembled and connected to the horizontal support near the bottom of the pit, and the lower telescopic top support mechanism is assembled and connected to the horizontal support near the bottom of the pit.

[0033] A lower load-bearing waler is installed near the bottom of the pit, and an upper load-bearing waler is installed above the bottom support of the retaining wall.

[0034] S3, applying prestressed bracing to the enclosure structure using a prestressed bracing structure, including:

[0035] Apply top bracing prestress to the retaining wall near the bottom of the pit:

[0036] Swing the lower telescopic jacking mechanism to an angle where its jacking end is angled downward toward the lower load-bearing waler, so that the jacking end of the lower telescopic jacking mechanism extends downward and supports the lower load-bearing waler; according to the deformation of the embankment near the bottom of the pit, control the lower telescopic jacking mechanism to apply jacking prestress to the embankment near the bottom of the pit.

[0037] Swing the upper telescopic support mechanism to an angle where its support end is angled upward toward the upper load-bearing waler, so that the support end of the upper telescopic support mechanism extends upward and supports the upper load-bearing waler.

[0038] Furthermore, the constructed prestressed top support structure also includes cantilevered supports, which are set at the edge of the horizontal support near the bottom of the pit and at the assembly interval; the cantilevered supports form a top support posture for the retaining structure based on the edge of the horizontal support near the bottom of the pit.

[0039] A jack receiving groove is provided on the side of the cantilevered support facing the retaining structure;

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

[0041] Apply transverse top bracing prestress to the enclosure structure:

[0042] Place the jacks in the jack receiving slots of the outward-projecting support, so that the jack bodies abut against the outward-projecting support, and that the supporting ends of the jacks extend laterally and support the retaining structure.

[0043] Based on the deformation of the enclosure structure, control the jacks to apply top support prestress to the enclosure structure;

[0044] Adhesive grout is injected between the cantilevered support and the retaining structure to connect the cantilevered support and the retaining structure together.

[0045] Furthermore, when constructing the prestressed top support structure, the soil near the bottom of the pit is removed to facilitate the construction of a load-bearing waler near the bottom of the pit.

[0046] A double-braced prestressed jacking structure for foundation pits, the prestressed jacking structure comprising a double telescopic jacking assembly.

[0047] The dual telescopic support assembly includes an upper telescopic support mechanism and a lower telescopic support mechanism, both of which have telescopic support ends.

[0048] The upper telescopic top support mechanism is assembled and connected to the horizontal support near the bottom of the pit, and the lower telescopic top support mechanism is assembled and connected to the horizontal support near the bottom of the pit.

[0049] A lower load-bearing waler is installed near the bottom of the pit, and an upper load-bearing waler is installed above the bottom support of the retaining wall.

[0050] The top end of the lower telescopic support mechanism is inclined downward toward the lower load-bearing waler, and the top end of the lower telescopic support mechanism can extend obliquely downward and support the lower load-bearing waler.

[0051] The top support end of the upper telescopic support mechanism is inclined upward toward the upper load-bearing waler, and the top support end of the upper telescopic support mechanism can extend obliquely upward and support the upper load-bearing waler.

[0052] A double-braced prestressed jacking structure for foundation pits, the prestressed jacking structure comprising a double telescopic jacking assembly.

[0053] The dual telescopic support assembly includes an upper telescopic support mechanism and a lower telescopic support mechanism, both of which have telescopic support ends.

[0054] The upper telescopic top support mechanism is assembled and connected to the horizontal support near the bottom of the pit, and the lower telescopic top support mechanism is assembled and connected to the horizontal support near the bottom of the pit.

[0055] The lower telescopic top support mechanism can swing from a horizontal support near the bottom of the pit to an angle where its top support end is obliquely downward toward the bottom of the pit and the top support end of the lower telescopic top support mechanism can extend obliquely downward and support the bottom of the pit.

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

[0057] The main advantages of the prestressed top support structure and prestressing application method of the present invention compared with the prior art are as follows:

[0058] After the construction of the horizontal support near the bottom of the pit is completed, the construction of the prestressed top support structure based on the horizontal support near the bottom of the pit begins immediately, and the construction of the prestressed top support structure is completed before the subsequent excavation of the next layer. The constructed prestressed top support structure can apply top support prestress to the bottom of the pit based on the horizontal support near the bottom of the pit. In this way, the bottom of the pit can receive the applied top support prestress in the first time, so that the displacement deformation of the bottom of the pit can be controlled in a timely manner, thereby improving the overall engineering quality of the foundation pit project. Attached Figure Description

[0059] Figures 1 to 3 This is a schematic diagram of the double-braced prestressed jacking structure in the foundation pit according to the present invention.

[0060] in,

[0061] Figure 1 This is a side view.

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

[0063] Figure 3 This is a schematic diagram showing the assembly and connection of the double telescopic top support assembly with the horizontal support near the bottom of the pit.

[0064] Figure 4This is a schematic diagram of applying prestressed top support structure to the retaining structure using the prestressed top support structure of the present invention. The diagram shows the situation where the soil near the bottom of the pit is removed from the retaining structure. Detailed Implementation

[0065] First, to facilitate a clear and accurate description of the technical solution later in the text, the following definitions are made in advance:

[0066] Definition 1: The “current pit bottom” mentioned in this article refers to the bottom of the pit during the excavation process of foundation pit construction. The “current pit bottom” is a dynamic concept. Wherever the foundation pit is excavated, that is the “current pit bottom”.

[0067] Definition 2: The “design pit bottom” mentioned in this article refers to the bottom of the foundation pit in the foundation pit engineering design. The “design pit bottom” is a static concept.

[0068] Definition 3: The term "near the bottom of the retaining structure" as used in this article refers to the portion of the retaining structure that is close to the current bottom of the pit (e.g., Figure 1 (Pointed by the middle arrow B). The "retaining structure near the bottom of the pit" is a dynamic concept that changes with the current position of the pit bottom. For example, when the "current pit bottom" is excavated to a depth of 1 meter, the part of the retaining structure at a depth of 1 meter is the "retaining structure near the bottom of the pit".

[0069] Definition 4: The "near-bottom horizontal support" mentioned in this article refers to the horizontal support structure that has been constructed within the foundation pit and is closest to the current pit bottom. This "near-bottom horizontal support" is a dynamic concept. For example, when the first layer of horizontal support structure is completed, this first layer of horizontal support structure is the near-bottom horizontal support; when the second layer of horizontal support structure is completed, this second layer of horizontal support structure is the near-bottom horizontal support.

[0070] Definition 5: The term "upper part of the retaining structure near the bottom support" as used in this document refers to the portion of the retaining structure that is adjacent to and above the horizontal support near the bottom of the pit (e.g., Figure 1 (The location indicated by the middle arrow A).

[0071] Definition 6: The “retaining support system” mentioned in this article is a broad concept that encompasses all forms of “support structures” and their combinations within the foundation pit that support the retaining structure, such as “upward-sloping support structures” and “horizontal support structures”.

[0072] Definition 7: The "lower-level foundation pit structure" mentioned in this article refers to the deeper foundation pit structure that will be constructed in the next stage of foundation pit construction. This "lower-level foundation pit structure" is a dynamic concept. For example, if the foundation pit is designed with two layers of horizontal support structures, after the first layer of horizontal support structure is constructed, the second layer of horizontal support structure to be constructed next is the lower-level foundation pit structure. After the second layer of horizontal support structure is constructed, the foundation pit bottom structure to be constructed next is also the lower-level foundation pit structure.

[0073] Definition 8: The term "lower-level excavation work" as used in this article refers to the excavation work performed during the construction of a foundation pit before the construction of a deeper layer of the pit structure. This excavation is necessary to create space for the deeper layer of the pit structure. For example, if a foundation pit has two layers of horizontal support structures, after the first layer is completed, excavation is required to create space for the second layer. This excavation work is considered a lower-level excavation operation.

[0074] The main concept of this invention is:

[0075] Based on the horizontal support near the bottom of the pit, a downwardly inclined support component is installed towards the pit retaining structure. This downwardly inclined support component supports the retaining structure near the bottom of the pit. Then, a supporting force-applying mechanism is installed for the downwardly inclined support component, which can drive the downwardly inclined support component to apply supporting prestress to the retaining structure near the bottom of the pit.

[0076] The main concept of this invention is roughly as described above. In this way, prestressed top support can be applied to the retaining wall near the bottom of the pit before the lower-level foundation pit structure is completed, so as to take corresponding measures to deal with the possible displacement and deformation of the retaining wall near the bottom of the pit in a timely manner, thereby improving the overall engineering quality of the foundation pit project.

[0077] The concept of the present invention will be further illustrated below with specific embodiments:

[0078] See Figure 1 The following is a brief introduction to the foundation pit engineering structure involved in this embodiment.

[0079] Those skilled in the art will understand that the overall engineering structure of the foundation pit mainly includes the retaining structure 6 and the retaining support system, the specific structural configuration of which is as follows:

[0080] The retaining structure 6 is constructed around the perimeter of the foundation pit, and the retaining support system is usually set inside the foundation pit to provide support for the retaining structure 6.

[0081] In this embodiment, the retaining support system mainly consists of several layers of horizontal support structures 4. These layers of horizontal support structures 4 are located inside the foundation pit, and they support the retaining structure 6. In this embodiment, three layers of horizontal support structures 4 are provided.

[0082] For each layer of horizontal support structure 4, a corresponding waler 7 is provided on the retaining structure 6. Except for the waler 7 provided for the pit top horizontal support structure 4, which is located at the top of the retaining structure 6, the remaining walers 7 are all located on the free side of the retaining structure 6. The upper two layers of horizontal support structures 4 in the pit are connected to the retaining structure 6 through the walers 7, thus forming support for the retaining structure 6. The third layer of horizontal support structure 4, namely the horizontal support 41 near the pit bottom, has a certain gap between its edge and the waler 7. That is to say, the two are separated. This gap is specifically used to install the prestressing mechanism. The edge of the horizontal support 41 near the pit bottom is connected to the waler 7 through the installed prestressing mechanism, and then connected to the retaining structure 6 through the waler 7, thus forming support for the retaining structure 6.

[0083] For ease of subsequent description, the gap will be referred to as the assembly interval. It should be noted that in other embodiments, if the waler 7 is not provided on the enclosure structure 6, the assembly interval refers to the gap between the edge of the horizontal support 41 near the bottom of the pit and the enclosure structure 6.

[0084] In this embodiment, the retaining support system also includes a certain number of tension piles 5, which are fixedly installed in the foundation pit. Then, the previously mentioned multi-layer horizontal support structure 4 is connected to the tension piles 5 (the connection between the upper two layers of horizontal support structure 4 and the tension piles 5 is not shown in the figure). It should be noted that the tension piles 5 are columns, column piles, etc.

[0085] In this embodiment, a ring beam 3 is provided at the edge of the horizontal support 41 near the bottom of the pit. The ring beam 3 is connected to a number of anti-uplift piles 5, which provide vertical support, especially downward support, to the edge of the horizontal support 41 near the bottom of the pit. This provides a strong support foundation for the double telescopic top support assembly 9, which will be mentioned later.

[0086] In addition, in order to facilitate the detection of displacement and deformation of the enclosure structure 6 and obtain the corresponding data, in this embodiment, an inclinometer (existing technology) is pre-embedded inside the enclosure structure 6. The inclinometer can detect and obtain relevant data on displacement and deformation of the enclosure structure 6.

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

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

[0089] The prestressed jacking structure mainly consists of two substructures: the transverse prestressed jacking substructure and the diagonal prestressed jacking substructure.

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

[0091] The inclined prestressed top support substructure is used to apply inclined top support prestress to the bottom of the enclosure based on the horizontal support 41 near the bottom of the pit, thereby preventing displacement and deformation of the enclosure near the bottom of the pit in the first instance.

[0092] The transverse prestressed top support substructure includes numerous cantilevered supports 8, which are set at the edge of the horizontal support 41 near the bottom of the pit (i.e., at the ring beam 3) by being "cast together with the edge of the horizontal support structure 4".

[0093] These numerous cantilever supports 8 are all located at the assembly intervals, that is, between the edge of the horizontal support 41 near the bottom of the pit and the waler 7, and are evenly and discretely arranged around the edge of the horizontal support 41 near the bottom of the pit. These numerous cantilever supports 8 are arranged at intervals with the numerous double telescopic top support assemblies 9, which will be mentioned later.

[0094] Each cantilevered support 8 is based on the edge of the horizontal support 41 near the bottom of the pit to form a supporting posture for the waler 7. In essence, the waler 7 forms a supporting posture for the retaining structure 6.

[0095] It should be noted that at this time, the cantilevered support 8 only forms a "supporting posture" and does not come into contact with the waler 7. The two are very close to each other, thus forming a "supporting posture".

[0096] See Figure 2 For each of the cantilevered support 8,

[0097] A groove is provided on the side of the cantilever support 8 facing the retaining structure 6. The opening of the groove faces the retaining structure 6. For ease of description, this groove is referred to as the jack receiving groove. The jack receiving groove is used to house the jack 81.

[0098] Specifically, when it is necessary to permanently "apply lateral support prestress to the retaining structure 6 based on the near-bottom horizontal support 41", a jack 81 is installed in the jack receiving groove of the cantilever support 8. The body of the jack 81 abuts against the cantilever support 8, and then the supporting end of the jack 81 supports the waler 7, thereby applying a large lateral support prestress to the retaining structure 6 through the waler 7. Then, adhesive grout is poured into the area where the "support posture" is formed between the cantilever support 8 and the waler 7. After the adhesive grout has completely solidified, the cantilever support 8 and the waler 7 are truly connected together, and the cantilever support 8 truly applies lateral support prestress to the retaining structure 6 based on the near-bottom horizontal support 41 and through the waler 7. At this point, the jack 81 can be disassembled.

[0099] It should be noted that in other embodiments, if the waler 7 is not provided on the retaining structure 6, then when applying transverse top bracing prestress to the retaining structure 6, the cantilevered support 8 and the jack 81 directly support the retaining structure 6. For example, when the retaining structure 6 is a continuous wall retaining structure, it is not necessary to provide the waler 7.

[0100] The inclined prestressed top support substructure mainly includes numerous double telescopic top support components 9, among which the lower segment telescopic steel pipe 911 is equivalent to the inclined downward support component.

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

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

[0103] The two segmented telescopic steel pipes, of which,

[0104] The single-section telescopic steel pipe serves as the lower section telescopic steel pipe 911.

[0105] Another segmented telescopic steel pipe is used as the upper segmented telescopic steel pipe 912.

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

[0107] See Figure 3 Each section of the telescopic steel pipe is a two-section telescopic steel pipe.

[0108] For ease of description,

[0109] One segment is called the body segment, and the end where the body segment is located is called the body end;

[0110] The other section is called the top support section, and the end where the top support section is located is called the top support end.

[0111] A telescopic hydraulic cylinder 917 is installed in the segmented telescopic steel pipe. The body (cylinder body) of the telescopic hydraulic cylinder 917 is connected to the main body section of the segmented telescopic steel pipe through a flange connection (or welding). The telescopic end (cylinder head) of the telescopic hydraulic cylinder 917 is connected to the top support section of the segmented telescopic steel pipe through a flange connection (or welding). In this way, the telescopic hydraulic cylinder 917 can drive the segmented telescopic steel pipe to perform telescopic movements.

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

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

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

[0115] In other implementations, for example, an extended jack can be used as a telescopic support mechanism to replace the segmented telescopic steel pipe, achieving the same effect.

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

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

[0118] For each pair of telescopic top support components 9

[0119] The top support base 913 is installed on the edge of the horizontal support 41 near the bottom of the pit, specifically on the end face of the edge of the horizontal support 41 near the bottom of the pit. The main bodies of the lower segment telescopic steel pipe 911 and the upper segment telescopic steel pipe 912 are both assembled with the top support base 913 through a quick-detachable shaft pin mechanism. In this way, the lower segment telescopic steel pipe 911 and the upper segment telescopic steel pipe 912 can swing up and down based on the edge of the horizontal support 41 near the bottom of the pit (or, rotate around their own main bodies at a certain angle).

[0120] After installation, the lower telescopic steel pipe 911 of the double telescopic support assembly 9 is located below the upper telescopic steel pipe 912, or in other words, the upper telescopic steel pipe 912 is located above the lower telescopic steel pipe 911. In this way, the upper telescopic steel pipe 912 mainly swings up and down from above, while the lower telescopic steel pipe 911 mainly swings up and down from below.

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

[0122] See Figure 1 For all double telescopic top support components 9, two ring beams are fixedly installed on the enclosure structure 6, one ring beam serving as the lower load-bearing waler 921 and the other ring beam serving as the upper load-bearing waler 922.

[0123] The lower load-bearing waler 921 is designed for the lower segmented telescopic steel pipe 911. The lower load-bearing waler 921 is located near the bottom of the pit in the enclosure. The lower load-bearing waler 921 has an upwardly inclined load-bearing surface, which is used to support the lower segmented telescopic steel pipe 911.

[0124] The upper load-bearing waler 922 is designed for the upper segmented telescopic steel pipe 912. The upper load-bearing waler 922 is located at the upper part of the enclosure near the bottom support. The upper load-bearing waler 922 has a downwardly sloping load-bearing surface, which is used to support the top of the upper segmented telescopic steel pipe 912.

[0125] The lower segment telescopic steel pipe 911 can swing downwards to an azimuth angle where the top support end of the lower segment telescopic steel pipe 911 is angled downwards toward the bearing surface of the lower bearing waler 921. Then, the telescopic hydraulic cylinder 917 is controlled to drive the lower segment telescopic steel pipe 911 to extend until the top support end of the lower segment telescopic steel pipe 911 is angled downwards against the bearing surface of the lower bearing waler 921. Then, the extension of the lower segment telescopic steel pipe 911 is controlled to achieve the effect of "applying top support prestress to the bottom of the enclosure based on the horizontal support 41 near the bottom of the pit".

[0126] The upper segment telescopic steel pipe 912 can swing upward to an azimuth angle where "the top support end of the upper segment telescopic steel pipe 912 is obliquely upward toward the bearing surface of the upper bearing waler 922". Then, the telescopic hydraulic cylinder 917 is controlled to drive the upper segment telescopic steel pipe 912 to extend until the top support end of the upper segment telescopic steel pipe 912 is obliquely upward against the bearing surface of the upper bearing waler 922. Then, the upper segment telescopic steel pipe 912 is further extended. In this way, the effect of "applying a downward oblique supporting force to the edge of the horizontal support 41 near the bottom of the pit based on the retaining structure 6 to counteract the reaction force of the lower segment telescopic steel pipe 911, thereby preventing deformation of the edge of the horizontal support 41 near the bottom of the pit" can be achieved.

[0127] This embodiment also provides a method for applying prestress to the retaining structure within the excavation pit. This method is used to achieve "applying top-support prestress to the retaining structure 6", and more particularly, "applying top-support prestress to the retaining structure near the bottom of the pit". In essence, this method uses the previously described concept of a prestressed top-support structure to achieve "applying top-support prestress to the retaining structure 6".

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

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

[0130] It should be noted that the near-bottom horizontal support 41 is constructed based on the pre-built anti-uplift piles 5 in the foundation pit.

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

[0132] S2, after the construction of the near-bottom horizontal support 41 is completed in step S1, the construction of the prestressed top support structure based on the near-bottom horizontal support 41 is immediately started, and the construction of the prestressed top support structure is completed before the subsequent excavation work of the next layer.

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

[0134] See Figure 4 It should be noted that when constructing the inclined prestressed jacking substructure, it is necessary to first excavate the soil near the bottom of the pit in the retaining wall, removing the soil in the vicinity of the pit bottom. The purpose of doing this is...

[0135] On the one hand, it is to enable the construction and installation of a load-bearing waler 921 near the bottom of the pit.

[0136] On the other hand, it provides operating space for "the lower segment telescopic steel pipe 911 to swing downward toward the bearing surface of the lower bearing waler 921, and then for the top support end of the lower segment telescopic steel pipe 911 to abut against the bearing surface of the lower bearing waler 921".

[0137] It should be noted that "excavating soil near the bottom of the pit" here does not fall under the category of "lower-level excavation work".

[0138] S3, apply prestressed bracing to the enclosure structure 6 using the constructed prestressed bracing structure.

[0139] Step S3 specifically includes S31 to S32.

[0140] S31, apply transverse prestress to the enclosure structure 6 using a transverse prestressed top support substructure.

[0141] Specifically

[0142] A jack 81 is placed in the jack receiving groove of the cantilever support 8, so that the body of the jack 81 abuts against the cantilever support 8. Then, the extension and retraction of the top support end of the jack 81 is controlled so that the top support end of the jack 81 extends laterally and supports the waler 7. The top support prestress applied by the jack 81 is then applied to the enclosure structure 6 through the waler 7.

[0143] Existing detection methods are used to detect the deformation of the enclosure structure 6 (deformation data). Based on the deformation of the enclosure structure 6 and in accordance with the design standards, the jacks 81 are controlled to apply appropriate top support prestress to the enclosure structure 6 so that the deformation of the enclosure structure 6 meets the design standards.

[0144] Then, adhesive grout is injected at the location where a "top-support posture" is formed between the cantilever support 8 and the waler 7. After the adhesive grout has completely solidified, the cantilever support 8 and the waler 7 are truly connected together. The cantilever support 8 is truly based on the horizontal support 41 near the bottom of the pit and applies transverse top-support prestress to the retaining structure 6 through the waler 7.

[0145] Finally, the jack 81 is disassembled, and the cantilever support 8 plays the role of applying lateral support prestress.

[0146] It should be noted that in other embodiments, if the retaining structure 6 is not provided with a waler 7, then the top support end of the jack 81 and the cantilever support 8 directly support the retaining structure 6.

[0147] S32 utilizes an inclined prestressed top support substructure to apply top support prestress to the area near the bottom of the pit in the retaining structure.

[0148] Specifically

[0149] Swing the lower section telescopic steel pipe 911 downwards to the position angle where "the top support end of the lower section telescopic steel pipe 911 is obliquely downwards toward the bearing surface of the lower bearing waler 921". Then control and adjust the extension and retraction of the lower section telescopic steel pipe 911 so that the top support end of the lower section telescopic steel pipe 911 extends obliquely downwards and abuts against the bearing surface of the lower bearing waler 921. The top support prestress applied by the lower section telescopic steel pipe 911 is then applied to the area near the bottom of the pit through the lower bearing waler 921.

[0150] Existing detection methods are used to detect the deformation of the retaining wall near the bottom of the pit (deformation data). Based on the deformation of the retaining wall near the bottom of the pit and in accordance with the design standards, the lower segmented telescopic steel pipe 911 is controlled to apply appropriate top support prestress to the retaining wall near the bottom of the pit so that the deformation of the retaining wall near the bottom of the pit meets the design standards.

[0151] Swing the upper section telescopic steel pipe 912 upwards to the position angle where "the top support end of the upper section telescopic steel pipe 912 is obliquely upward toward the bearing surface of the upper bearing waler 922". Then control and adjust the extension and retraction of the upper section telescopic steel pipe 912 so that the top support end of the upper section telescopic steel pipe 912 extends obliquely upwards and abuts against the bearing surface of the upper bearing waler 922.

[0152] Once the prestressing method is completed, the excavation work for the next layer can begin.

[0153] It should be noted that in this embodiment, numerous inclinometers (existing technology) are installed inside the retaining structure 6. These inclinometers can detect the deformation of the retaining structure 6, including the deformation near the bottom of the pit.

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

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

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

[0157] The advantages of the prestressed support structure and prestressing application method in this embodiment are:

[0158] 1) After the construction of the near-bottom horizontal support 41 is completed, the construction of the prestressed top support structure based on the near-bottom horizontal support 41 shall begin immediately, and the construction of the prestressed top support structure shall be completed before the subsequent excavation of the next layer.

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

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

[0161] 2) The double telescopic top support assembly 9 also includes an upper segment telescopic steel pipe 912, which can apply a downward oblique top support force to the edge of the horizontal support 41 near the bottom of the pit based on the enclosure structure 6, so as to counteract the reaction force of the lower segment telescopic steel pipe 911, thereby preventing the edge of the horizontal support 41 near the bottom of the pit from deforming.

[0162] 3) The constructed prestressed top support structure has an outward cantilever support 8, which can apply transverse top support prestress to the retaining structure 6 based on the horizontal support 41 near the bottom of the pit (with the help of the jack 81), so that the displacement deformation of the retaining structure part corresponding to the horizontal support 41 near the bottom of the pit can be controlled in a timely manner.

[0163] 4) The double telescopic support component 9 in the prestressed support structure can be flexibly disassembled, which is green, environmentally friendly and saves resources.

[0164] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A double-braced prestressed jacking structure for foundation pits, characterized in that: The prestressed jacking structure includes a double telescopic jacking assembly (9). The dual telescopic top support assembly (9) includes an upper telescopic top support mechanism and a lower telescopic top support mechanism, both of which have telescopic top support ends. The body of the upper telescopic top support mechanism is assembled and connected to the horizontal support (41) near the bottom of the pit, and the body of the lower telescopic top support mechanism is assembled and connected to the horizontal support (41) near the bottom of the pit. A lower load-bearing waler (921) is installed near the bottom of the pit, and an upper load-bearing waler (922) is installed above the bottom support of the pit. The lower telescopic top support mechanism can swing to the angle of its top support end facing the lower load-bearing waler (921) based on the near pit bottom horizontal support (41). The top support end of the lower telescopic top support mechanism can extend obliquely downward and support the lower load-bearing waler (921). The upper telescopic top support mechanism can swing to the angle of its top support end obliquely upward toward the upper load-bearing waler (922) based on the near pit bottom horizontal support (41). The top support end of the upper telescopic top support mechanism can extend obliquely upward and support the upper load-bearing waler (922). Both the upper telescopic support mechanism and the lower telescopic support mechanism adopt segmented telescopic steel pipes; a telescopic hydraulic cylinder (917) is provided in the segmented telescopic steel pipe, and the telescopic hydraulic cylinder (917) can drive the segmented telescopic steel pipe to perform telescopic actions; The double telescopic top support assembly (9) also includes a top support base (913), which is installed at the edge of the horizontal support (41) near the bottom of the pit; The main body of the upper telescopic top support mechanism is assembled with the top support base (913) through the shaft pin mechanism, thereby realizing the assembly connection of the main body of the upper telescopic top support mechanism with the horizontal support (41) near the bottom of the pit through the shaft pin mechanism. The body of the lower telescopic top support mechanism is assembled with the top support base (913) through the shaft pin mechanism, thereby realizing the assembly connection of the body of the lower telescopic top support mechanism with the horizontal support (41) near the bottom of the pit through the shaft pin mechanism. An assembly gap is left between the edge of the near-bottom horizontal support (41) and the enclosure structure (6); The prestressed top support structure also includes an outward-cantilevered support (8), which is located at the edge of the horizontal support (41) near the bottom of the pit and at the assembly interval; the outward-cantilevered support (8) forms a top support posture for the retaining structure (6) based on the edge of the horizontal support (41) near the bottom of the pit.

2. The double-braced prestressed jacking structure in the foundation pit according to claim 1, characterized in that: A jack receiving groove is provided on the side of the cantilever support (8) facing the retaining structure (6), and the jack receiving groove is used to place the jack (81). The cantilevered support (8) and the double telescopic top support assembly (9) are arranged alternately.

3. The double-braced prestressed jacking structure in the foundation pit according to claim 2, characterized in that: A waler (7) is provided on the enclosure structure (6) for the horizontal support (41) near the bottom of the pit, and the assembly interval is the space between the edge of the horizontal support (41) near the bottom of the pit and the waler (7); The cantilevered support (8) is based on the edge of the horizontal support (41) near the bottom of the pit and forms a top support posture for the retaining structure (6) through the waler (7); The jack (81) is supported on the waler (7). Adhesive grout is poured into the part where the cantilever support (8) and the waler (7) form a supporting posture. After the adhesive grout has completely solidified, the cantilever support (8) and the waler (7) are connected together. The cantilever support (8) applies transverse supporting prestress to the retaining structure (6) based on the horizontal support (41) near the bottom of the pit.

4. The double-braced prestressed jacking structure in the foundation pit according to claim 2, characterized in that: A ring beam (3) is provided at the edge of the horizontal support (41) near the bottom of the pit.

5. The double-braced prestressed jacking structure within the foundation pit according to claim 1, characterized in that: The lower telescopic support mechanism and the part where the lower telescopic support mechanism is assembled and connected to the near-bottom horizontal support (41) are located at the connection between the near-bottom horizontal support (41) and the pull-out pile (5).

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

7. A method for applying prestress to the retaining wall within a foundation pit, wherein the method employs the double-braced prestressed top support structure within the foundation pit as described in claim 2, characterized in that: The method for applying prestress includes: S1, construct a horizontal support near the bottom of the pit (41). S2, based on the horizontal support (41) near the bottom of the pit, a prestressed top support structure is constructed, and the construction of the prestressed top support structure is completed before the subsequent excavation of the next lower level. The constructed prestressed top support structure includes a double telescopic top support assembly (9). The dual telescopic top support assembly (9) includes an upper telescopic top support mechanism and a lower telescopic top support mechanism, both of which have telescopic top support ends. The body of the upper telescopic top support mechanism is assembled and connected to the horizontal support (41) near the bottom of the pit, and the body of the lower telescopic top support mechanism is assembled and connected to the horizontal support (41) near the bottom of the pit. A lower load-bearing waler (921) is installed near the bottom of the pit, and an upper load-bearing waler (922) is installed above the bottom support of the pit. S3, applying prestressed bracing to the enclosure structure (6) using a prestressed bracing structure, including: Apply top bracing prestress to the retaining wall near the bottom of the pit: Swing the lower telescopic top support mechanism to an angle where its top support end is inclined downward toward the lower load-bearing waler (921), so that the top support end of the lower telescopic top support mechanism extends obliquely downward and supports the lower load-bearing waler (921); according to the deformation of the enclosure near the bottom of the pit, control the lower telescopic top support mechanism to apply top support prestress to the enclosure near the bottom of the pit. Swing the upper telescopic top support mechanism to an angle where its top support end is inclined upward toward the upper load-bearing waler (922), so that the top support end of the upper telescopic top support mechanism extends obliquely upward and supports the upper load-bearing waler (922); The constructed prestressed top support structure also includes an outward cantilever support (8), which is set at the edge of the horizontal support (41) near the bottom of the pit and at the assembly interval; the outward cantilever support (8) forms a top support posture for the retaining structure (6) based on the edge of the horizontal support (41) near the bottom of the pit. A jack receiving groove is provided on the side of the cantilever support (8) facing the retaining structure (6); The method of applying prestressed support to the enclosure structure (6) using a prestressed support structure further includes: Apply transverse top bracing prestress to the enclosure structure (6): A jack (81) is placed in the jack receiving groove of the cantilever support (8), so that the body of the jack (81) abuts against the cantilever support (8), and the supporting end of the jack (81) extends laterally and supports the enclosure structure (6). According to the deformation of the enclosure structure (6), control the jack (81) to apply top support prestress to the enclosure structure (6); Inject bonding grout between the cantilever support (8) and the retaining structure (6) to connect the cantilever support (8) and the retaining structure (6) together.

8. The method for applying prestress to the retaining wall within the foundation pit according to claim 7, characterized in that: When constructing the prestressed top support structure, the soil near the bottom of the pit is removed to facilitate the construction of a load-bearing waler (921) near the bottom of the pit.

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