Prestress back shore structure in foundation pit adopting back shore cross frame

Abstract

The utility model discloses a prestress back shore structure in a foundation pit adopting a back shore cross frame. The prestress jacking structure comprises a telescopic jacking mechanism, and the telescopic jacking mechanism is provided with a telescopic jacking end. A body of the telescopic jacking and supporting mechanism is connected with a horizontal support (41) close to the pit bottom in an assembled mode, and the telescopic jacking and supporting mechanism can swing up and down based on the horizontal support close to the pit bottom. And a back shore cross frame (51) is assembled at the back shore end of the telescopic back shore mechanism and is provided with a crosspiece enclosing purlin (512). The top supporting end of the telescopic top supporting mechanism can obliquely extend downwards and enable a crosspiece surrounding purlin of the top supporting cross frame to abut against the portion, close to the pit bottom, of the enclosure, and top supporting prestress is applied to the portion, close to the pit bottom, of the enclosure. In this way, a force-bearing enclosing purlin (21) which is originally arranged at the position, close to the pit bottom, of the enclosure is omitted.

Description

Technical Field

[0001] The utility model relates to the technical field of foundation pit engineering, in particular to a prestressed top supporting structure in a foundation pit which adopts a top supporting cross frame. Background Art

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

[0003] At present, a prestressed top support structure and a method for applying prestress have been developed, which has a segmented telescopic steel pipe as a telescopic top support mechanism. The segmented telescopic steel pipe applies top support prestress to the part of the enclosure near the bottom of the pit based on the horizontal support near the bottom of the pit. In this way, the part of the enclosure near the bottom of the pit can obtain the top support prestress at the first time, so that the displacement and deformation of the part of the enclosure near the bottom of the pit can be corrected in time, thereby improving the overall engineering quality of the foundation pit project.

[0004] The current problem is:

[0005] Previously developed prestressed top support structures require a load-bearing purlin fixed near the bottom of the enclosure to support the top support of the segmented telescopic steel pipes. The construction process of the load-bearing purlin is very cumbersome and is not conducive to improving construction efficiency. Summary of the Invention

[0006] The purpose of the utility model is to provide a prestressed top support structure in a foundation pit using a top support cross frame, wherein the top support cross frame is pre-assembled at the top support end of the telescopic top support mechanism, thereby eliminating the need to set a load-bearing purlin at the position of the enclosure near the bottom of the pit.

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

[0008] A prestressed jacking support structure in a foundation pit using a jacking support cross frame, the prestressed jacking support structure includes a telescopic jacking support mechanism, the telescopic jacking support mechanism has a telescopic jacking support end; the body of the telescopic jacking support mechanism is connected to a horizontal support assembly near the pit bottom, and the telescopic jacking support mechanism can swing up and down based on the horizontal support near the pit bottom; the jacking support end of the telescopic jacking support mechanism is equipped with a jacking support cross frame, and the jacking support cross frame has a horizontal purlin.

[0009] Furthermore, the telescopic top support mechanism can swing to an angle where its top support end is tilted downward toward the position of the enclosure near the bottom of the pit; the top support end of the telescopic top support mechanism can extend tilted downward and make the cross purlin of the top support cross frame rest against the position of the enclosure near the bottom of the pit, thereby applying top support prestress to the position of the enclosure near the bottom of the pit based on the horizontal support near the bottom of the pit.

[0010] Furthermore, the specific structural form of the top support cross frame is: the top support cross frame includes a support column and a cross purlin; one end of the support column is welded to the middle part of the cross purlin, and the other end of the support column serves as an assembly end and is assembled and connected to the top support end of the telescopic top support mechanism.

[0011] Furthermore, at the position of the enclosure near the bottom of the pit, the cross purlins of adjacent top supporting cross frames are butt-jointed together.

[0012] Furthermore, the cross purlins of adjacent top supporting cross frames are connected together by bolt connection plates.

[0013] Furthermore, waist-shaped holes are provided at the bolt connection points of the bolt connection plates.

[0014] Furthermore, the cross purlins of adjacent top supporting cross frames are connected together by welding connecting plates.

[0015] Furthermore, the prestressed supporting structure includes an inclinometer tube, which is arranged in the outer soil of the retaining structure or pre-buried in the body of the retaining structure.

[0016] Furthermore, the top support cross frame includes a reinforcement rod, which is obliquely connected between the support column and the cross purlin to form a triangular stable structure.

[0017] Furthermore, the telescopic supporting mechanism is a segmented telescopic steel pipe.

[0018] Compared with the prior art, the prestressed support structure of the present invention has the following main beneficial effects:

[0019] A top support cross frame is pre-installed at the top support end of the telescopic top support mechanism. The top support end of the telescopic top support mechanism can be extended obliquely downward to make the cross purlin of the top support cross frame rest against the bottom of the enclosure near the pit, thereby applying top support prestress to the bottom of the enclosure near the pit. In this way, the load-bearing purlin originally set at the bottom of the enclosure near the pit is eliminated, and the assembly and setting of the top support cross frame is very convenient, thereby greatly improving construction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a side view of the prestressed top support structure in embodiment 1;

[0021] Figure 2 A top view of the prestressed support structure in embodiment 1;

[0022] Figure 3 This is a top view of the horizontal support near the pit bottom in Implementation Method 1;

[0023] Figure 4 Schematic diagram of the assembly connection of the segmented telescopic steel pipe and the horizontal support near the pit bottom in Implementation Method 1;

[0024] Figure 5 Schematic diagram of applying transverse supporting prestress to the enclosure structure using a prestressed supporting structure in Implementation Method 1;

[0025] Figure 6 Schematic diagram of applying prestress to the retaining wall near the bottom of the pit using a prestressed support structure in Implementation Method 1;

[0026] Figure 7 Schematic diagram of the prestressed top support structure in Implementation Method 2;

[0027] Figure 8 Schematic diagram of the top support cross frame in embodiment 2;

[0028] Figure 9 A schematic diagram of adjacent top support cross frames connected by bolted connecting plates in embodiment 2;

[0029] Figure 10 This is a schematic diagram of adjacent top support cross frames connected by welded connecting plates in Implementation Method 2. DETAILED DESCRIPTION

[0030] First, in order to facilitate a clear and accurate description of the technical solution in the following text, the following definitions are made in advance:

[0031] Definition 1: The "current pit bottom" mentioned in this article refers to the pit bottom during the foundation pit construction excavation process. The "current pit bottom" is a dynamic concept. Wherever the foundation pit is excavated is the "current pit bottom".

[0032] Definition 2: The "designed pit bottom" mentioned in this article refers to the pit bottom designed for foundation pit engineering. The "designed pit bottom" is a static concept.

[0033] Definition 3: The "retaining structure near the pit bottom" mentioned in this article refers to the portion of the retaining structure closest to the current pit bottom. This "retaining structure near the pit bottom" is a dynamic concept that changes with the current pit bottom position. For example, when the "current pit bottom" is excavated to a depth of 1 meter, the upper and lower portions of the retaining structure near the 1-meter depth are considered the "retaining structure near the pit bottom."

[0034] Definition 4: The "horizontal support near the pit bottom" mentioned in this article refers to the completed horizontal support structure closest to the current pit bottom within the foundation pit. This "horizontal support near the pit bottom" is a dynamic concept. For example, when the first layer of horizontal support structure is completed, it becomes the horizontal support near the pit bottom. When the second layer of horizontal support structure is completed, it becomes the horizontal support near the pit bottom, and the previously constructed first layer of horizontal support structure is no longer the horizontal support near the pit bottom.

[0035] Definition 5: The "supporting system" mentioned herein is a broad concept, which is a generalization of all forms of "supporting structure" and combinations thereof for the enclosure structure in the foundation pit, such as "inclined upward supporting structure", "horizontal supporting structure".

[0036] Definition 6: The "lower level foundation pit structure" mentioned herein refers to the deeper level foundation pit structure to be constructed in the next stage during the construction of the foundation pit project. The "lower level foundation pit structure" is a dynamic concept. For example, when two layers of horizontal supporting structures are designed in the foundation pit, the second layer of horizontal supporting structure to be constructed next is the lower level foundation pit structure after the first layer of horizontal supporting structure is constructed and completed. When the second layer of horizontal supporting structure is constructed and completed, the foundation pit bottom structure to be constructed next is the lower level foundation pit structure.

[0037] Definition 7: The "lower level excavation operation" mentioned herein refers to the need to excavate soil downward in the foundation pit to create a construction space for the deeper level foundation pit structure before the deeper level foundation pit structure is constructed in the next stage during the construction of the foundation pit project. The excavation operation during this period is called "lower level excavation operation". For example, when two layers of horizontal supporting structures are designed in the foundation pit, the excavation operation during the period when the second layer of horizontal supporting structure is constructed next after the first layer of horizontal supporting structure is constructed and completed is called the lower level excavation operation.

[0038] It should be noted that the prestressed top support structure in the foundation pit of the utility model is improved based on a developed prestressed top support structure and prestress application method. The developed prestressed top support structure and prestress application method will be introduced first as follows.

[0039] The main idea of the prestressed top support structure and prestress application method is:

[0040] Based on the near-bottom horizontal support, a downward inclined support part is arranged towards the foundation pit enclosure structure, and the downward inclined support part is supported at the near-bottom part of the foundation pit enclosure structure. Then, a top support force applying mechanism is configured for the downward inclined support part, and the top support force applying mechanism can drive the downward inclined support part to apply top support prestress to the near-bottom part of the enclosure based on the near-bottom horizontal support. In this way, the top support prestress can be applied to the near-bottom part of the enclosure without constructing the lower level foundation pit structure, so that the displacement deformation of the near-bottom part of the enclosure can be actively addressed in time, instead of waiting for the lower level foundation pit structure to be built.

[0041] The main idea of the prestressed bracing structure and the prestressing method is as above, and the prestressed bracing structure and the prestressing method will be described in detail through a specific embodiment (Embodiment 1) as below.

[0042] Embodiment 1:

[0043] Referring to Figure 1 , the foundation pit engineering structure involved in the present embodiment will be introduced first as below.

[0044] As can be understood by those skilled in the art, the overall engineering structure of the foundation pit mainly comprises the enclosure structure 6 and the enclosure support system, and the specific structural arrangement is as follows:

[0045] The enclosure structure 6 is constructed at the periphery of the foundation pit, and the enclosure support system is usually arranged inside the foundation pit and used to support the enclosure structure 6.

[0046] In the present embodiment, the enclosure support system mainly comprises a plurality of horizontal support structures 4 arranged inside the foundation pit and used to support the enclosure structure 6. In the present embodiment, the number of the horizontal support structures 4 is three. For each layer of the horizontal support structures 4, a corresponding enclosure purlin 7 is arranged on the enclosure structure 6. Except that the enclosure purlin 7 arranged for the top horizontal support structure 4 is arranged at the top end of the enclosure structure 6, the other enclosure purlins 7 are arranged at the free side of the enclosure structure 6. The upper two horizontal support structures 4 in the foundation pit are connected together with the enclosure structure 6 through the enclosure purlins 7, thereby forming the support for the enclosure structure 6. The third horizontal support structure 4, i.e. the near-bottom horizontal support 41, has a certain interval distance between the edge portion thereof and the enclosure purlin 7, that is to say, the two are spaced apart. The spaced-apart part is specially used to arrange the prestressing mechanism, and the edge portion of the near-bottom horizontal support 41 is connected together with the enclosure purlin 7 through the prestressing mechanism, and then connected together with the enclosure structure 6 through the enclosure purlin 7, thereby forming the support for the enclosure structure 6.

[0047] For the convenience of subsequent description, the spaced-apart part is referred to as an assembly interval.

[0048] It should be noted that in other embodiments, if no enclosure purlin 7 is arranged on the enclosure structure 6, the assembly interval refers to the spacing between the edge portion of the near-bottom horizontal support 41 and the enclosure structure 6.

[0049] In the present embodiment, the enclosure support system further comprises a certain number of uplift piles 5 fixedly arranged in the foundation pit, and then the aforementioned plurality of horizontal support structures 4 are connected together with the uplift piles 5 (the connection between the upper two horizontal support structures 4 and the uplift piles 5 is not shown in the figure). It should be noted that the uplift piles 5 are columns, column piles, etc.

[0050] In this embodiment, a ring beam 3 is provided at the edge of the horizontal support 41 near the pit bottom, and the ring beam 3 is connected to a plurality of pull-out piles 5. These pull-out piles 5 provide vertical support to the edge of the horizontal support 41 near the pit bottom, especially downward support, which provides a strong support basis for the segmented telescopic steel pipe 11 to be mentioned later, and the edge of the horizontal support 41 near the pit bottom will not be deformed due to the "reaction force generated by the prestressed top support of the segmented telescopic steel pipe 11".

[0051] In addition, in order to conveniently detect the displacement and deformation of the enclosure structure 6 and obtain corresponding data, in this embodiment, an inclinometer device (existing technology) is pre-buried inside the enclosure structure 6, and the displacement and deformation related data of the enclosure structure 6 can be detected and obtained through the inclinometer device.

[0052] Those skilled in the art will appreciate that the above-mentioned foundation pit engineering structure is a structure of the prior art.

[0053] See also Figures 1 to 3 On the basis of the foundation pit engineering structure of this embodiment, a prestressed top support structure is also set up. The prestressed top support structure can apply top support prestress to the part of the enclosure near the bottom of the pit, thereby preventing the displacement and deformation of the part of the enclosure near the bottom of the pit in the first time.

[0054] The prestressed support structure mainly includes numerous segmented telescopic steel tubes 11, which are equivalent to downward-sloping support components. These numerous segmented telescopic steel tubes 11 are arranged at the aforementioned assembly intervals and are evenly and discretely arranged around the edge of the horizontal support 41 near the pit bottom.

[0055] See also Figure 4 For each segmented telescopic steel tube 11, the segmented telescopic steel tube 11 is a two-section type.

[0056] For the convenience of description,

[0057] One section is called the body section, and the end of the body section is called the body end;

[0058] 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.

[0059] A telescopic hydraulic cylinder 17 is provided in the segmented telescopic steel pipe 11. The main body (cylinder body) of the telescopic hydraulic cylinder 17 is connected to the main body section of the segmented telescopic steel pipe 11 through a flange connection method (it can also be a welding method), and the telescopic end (cylinder head) of the telescopic hydraulic cylinder 17 is connected to the top support section of the segmented telescopic steel pipe 11 through a flange connection method (it can also be a welding method). In this way, the telescopic hydraulic cylinder 17 can drive the segmented telescopic steel pipe 11 to perform telescopic movements.

[0060] In summary, the telescopic hydraulic cylinder 17 is provided in the segmented telescopic steel tube 11 as a telescopic driving device, and the segmented telescopic steel tube 11 can apply a supporting force to the outside under the drive of the telescopic driving device.

[0061] The segmented telescopic steel tube 11 can be understood as a telescopic support mechanism. In other embodiments, other forms of telescopic support mechanisms can also be used to replace the segmented telescopic steel tube 11.

[0062] In summary, the telescopic supporting mechanism should have a supporting end that can be telescopic (equivalent to the supporting end of the segmented telescopic steel pipe 11), and the main body of the telescopic supporting mechanism (equivalent to the main body end of the segmented telescopic steel pipe 11) is assembled and connected with the horizontal support 41 near the bottom of the pit through an axle pin mechanism.

[0063] In other embodiments, for example, an extended jack may be used as a telescopic supporting mechanism to replace the segmented telescopic steel pipe 11 to achieve the same effect.

[0064] For each segmented telescopic steel pipe 11,

[0065] The main end of the segmented telescopic steel tube 11 is attached to the edge of the horizontal support 41 near the pit bottom via a quickly removable pin mechanism, specifically to the end surface of the edge of the horizontal support 41 near the pit bottom. This allows the segmented telescopic steel tube 11 to swing up and down (or, in other words, rotate around its main end at a certain angle) relative to the edge of the horizontal support 41 near the pit bottom.

[0066] For all segmented telescopic steel pipes 11 , a circle of ring beams is fixedly installed near the bottom of the pit as a load-bearing purlin 21 . The load-bearing purlin 21 has an upwardly inclined load-bearing surface 211 , which is used to receive the top support of the segmented telescopic steel pipes 11 .

[0067] The segmented telescopic steel tube 11 can swing to the azimuth angle of "the top support end of the segmented telescopic steel tube 11 is tilted downward toward the bearing surface 211 of the load-bearing purlin 21", and then the telescopic hydraulic cylinder 17 is controlled to drive the segmented telescopic steel tube 11 to extend until the top support end of the segmented telescopic steel tube 11 is tilted downward against the bearing surface 211 of the load-bearing purlin 21, and then the segmented telescopic steel tube 11 is continued to be controlled to extend, so that the effect of "applying top support prestress to the near-bottom-of-the-pit-bottom position of the enclosure based on the horizontal support 41 near the bottom of the pit" can be achieved.

[0068] In addition, the segmented telescopic steel pipe 11 can not only apply supporting prestress to the position of the enclosure near the bottom of the pit, but also apply supporting prestress to the enclosure structure 6 laterally. It is only necessary to swing the segmented telescopic steel pipe 11 to a horizontal azimuth angle. At this time, the segmented telescopic steel pipe 11 is at the assembly interval, that is, between the edge of the horizontal support 41 near the bottom of the pit and the enclosure structure 6. Then, the supporting end of the segmented telescopic steel pipe 11 is supported on the purlin 7, and the supporting prestress applied by the segmented telescopic steel pipe 11 acts on the enclosure structure 6 through the purlin 7.

[0069] The benefits of this setting are:

[0070] The segmented telescopic steel tubes 11 can be used to temporarily apply a large amount of supporting prestress to the enclosure structure 6 in the horizontal direction, slightly increasing the assembly interval. Then, spacers (such as piers or steel sections) can be placed in the assembly interval. In this way, the spacers can replace the segmented telescopic steel tubes 11 to achieve the effect of "applying horizontal supporting prestress to the enclosure structure 6 based on the horizontal support 41 near the pit bottom."

[0071] In this embodiment, the prestressed supporting structure further includes a plurality of cantilevered piers 8 .

[0072] The cantilevered piers 8 are arranged at the edge of the horizontal support 41 near the bottom of the pit (i.e., the ring beam 3) by "casting together with the edge of the horizontal support structure 4". These numerous cantilevered piers 8 are all located at the assembly interval, i.e., between the edge of the horizontal support 41 near the bottom of the pit and the surrounding purlin 7, and are evenly and discretely arranged around the edge of the horizontal support 41 near the bottom of the pit.

[0073] These numerous cantilevered piers 8 and numerous segmented telescopic steel pipes 11 are arranged at intervals from each other. Each cantilevered pier 8 forms a supporting posture for the purlin 7 based on the edge of the horizontal support 41 near the bottom of the pit. In essence, the surrounding structure 6 is supported by the purlin 7.

[0074] It should be noted that at this time, the cantilevered pier 8 only forms a "supporting posture" and is not in contact with the purlin 7, but the two are very close to each other, thus forming a "supporting posture".

[0075] These cantilevered piers 8 actually play the role of the pad blocks mentioned above.

[0076] When it is necessary to permanently "apply transverse supporting prestress to the retaining structure 6 based on the horizontal support 41 near the bottom of the pit", the segmented telescopic steel pipe 11 is swung to a horizontal azimuth angle, and then the supporting end of the segmented telescopic steel pipe 11 is supported on the purlin 7, and the segmented telescopic steel pipe 11 is controlled to apply a larger supporting prestress to the retaining structure 6, and then the bonding slurry is poured at the position where the "supporting posture" is formed between the cantilevered pier 8 and the purlin 7. After the bonding slurry is completely solidified, the cantilevered pier 8 and the purlin 7 are truly connected together, and the cantilevered pier 8 truly applies transverse supporting prestress to the retaining structure 6 based on the horizontal support 41 near the bottom of the pit and through the purlin 7.

[0077] It should be noted that, in other embodiments, if the enclosure 6 is not provided with the enclosure purlin 7, then when applying transverse supporting prestress to the enclosure 6, the segmented telescopic steel tubes 11 and the cantilevered buttresses 8 are directly supported on the enclosure 6. For example, when the enclosure 6 is a continuous wall enclosure structure, the enclosure purlin 7 is not required.

[0078] This embodiment also provides a method for applying prestress, which is used to achieve "applying prestress to the enclosure near the bottom of the pit." In essence, this method uses the concept of the prestressed support structure described above to achieve "applying prestress to the enclosure near the bottom of the pit."

[0079] Specifically, the method of applying prestress in this embodiment includes:

[0080] S1, construct a horizontal support 41 near the bottom of the foundation pit at the construction location.

[0081] It should be noted that the horizontal support 41 near the pit bottom is constructed based on the pull-out piles 5 pre-constructed in the foundation pit.

[0082] The constructed horizontal support 41 near the pit bottom is as described above and will not be repeated here.

[0083] S2, after completing the construction of the horizontal support 41 near the pit bottom in step S1, immediately start to construct the prestressed top support structure based on the horizontal support 41 near the pit bottom, and complete the construction of the prestressed top support structure before the subsequent lower level excavation operation.

[0084] The prestressed top support structure constructed is as described above and will not be repeated here.

[0085] See also Figure 5 and Figure 6It should be noted that when constructing the prestressed top support structure, it is necessary to first dig the soil near the bottom of the pit and remove the soil near the bottom of the pit. The purpose of doing this is to

[0086] On the one hand, it is to be able to construct and set the load-bearing purlin 21 near the bottom of the pit.

[0087] On the other hand, it provides operating space for "swinging the segmented telescopic steel tube 11 downward toward the bearing surface 211 of the bearing purlin 21, and then making the top support end of the segmented telescopic steel tube 11 rest against the top support on the bearing surface 211 of the bearing purlin 21".

[0088] It should be noted that the "digging at the bottom of the pit near the enclosure" here does not fall within the scope of lower-level excavation operations.

[0089] S3, applying supporting prestress to the enclosure structure 6 using the constructed prestressed supporting structure.

[0090] The step S3 specifically includes S31 to S32.

[0091] S31, applying a transverse supporting prestress to the enclosure structure 6 using a prestressed supporting structure;

[0092] Specifically,

[0093] The segmented telescopic steel tube 11 is swung to a horizontal state, that is, at the assembly interval, and then the segmented telescopic steel tube 11 is controlled and adjusted to be telescopic, so that the top support end of the segmented telescopic steel tube 11 extends horizontally and supports on the purlin 7, and the top support prestress applied by the segmented telescopic steel tube 11 acts on the enclosure structure 6 through the purlin 7; the detection means of the existing technology are used to detect the deformation condition (deformation data) of the enclosure structure 6, and according to the deformation condition of the enclosure structure 6 and the design standard, the segmented telescopic steel tube 11 is controlled to apply appropriate top support prestress to the enclosure structure 6, so that the deformation condition of the enclosure structure 6 meets the design standard.

[0094] As mentioned above, a cantilevered pier 8 is preset at the edge of the horizontal support 41 near the bottom of the pit, and bonding slurry is poured at the position where a "supporting posture" is formed between the cantilevered pier 8 and the purlin 7. After the bonding slurry is completely solidified, the cantilevered pier 8 and the purlin 7 are truly connected together. The cantilevered pier 8 is truly based on the horizontal support 41 near the bottom of the pit and applies transverse supporting prestress to the retaining structure 6 through the purlin 7.

[0095] At this time, the segmented telescopic steel pipe 11 can be controlled to retract, and the externally cantilevered pier 8 is completely responsible for applying the transverse supporting prestress.

[0096] It should be noted that, in other embodiments, if the enclosure purlin 7 is not provided on the enclosure structure 6 , the supporting ends of the segmented telescopic steel tubes 11 and the cantilevered piers 8 are directly supported on the enclosure structure 6 .

[0097] S32, using a prestressed top support structure to apply top support prestress to the retaining wall near the bottom of the pit.

[0098] Specifically,

[0099] The segmented telescopic steel tube 11 is swung to the azimuth angle of "the top support end of the segmented telescopic steel tube 11 is obliquely downward toward the bearing surface 211 of the load-bearing purlin 21", and then the segmented telescopic steel tube 11 is controlled and adjusted to extend and retract, so that the top support end of the segmented telescopic steel tube 11 extends obliquely downward and abuts against the bearing surface 211 of the load-bearing purlin 21. The top support prestress applied by the segmented telescopic steel tube 11 acts on the bottom of the enclosure near the pit through the load-bearing purlin 21;

[0100] The existing detection means are used to detect the deformation condition (deformation data) of the enclosure near the bottom of the pit. According to the deformation condition of the enclosure near the bottom of the pit and in accordance with the design standards, the segmented telescopic steel pipe 11 is controlled to apply appropriate top support prestressing to the enclosure near the bottom of the pit, so that the deformation condition of the enclosure near the bottom of the pit meets the design standards.

[0101] After the prestressing method is implemented, the excavation work of the lower level can be started.

[0102] It should be noted that, in this embodiment, a large number of inclinometers (existing technology) are provided inside the enclosure structure 6, and the deformation of the enclosure structure 6, including the deformation of the enclosure near the bottom of the pit, can be detected by these inclinometers.

[0103] The following provides a second embodiment to specifically illustrate the prestressed top support structure in the foundation pit using the top support cross frame of the present invention:

[0104] Implementation 2:

[0105] This embodiment 2 provides a prestressed support structure, which is improved based on the prestressed support structure provided in embodiment 1.

[0106] See also Figures 7 to 10 and compare Figure 2 Compared with the embodiment 1, the prestressed support structure of the embodiment 2 has the following improvements:

[0107] Improvement 1:

[0108] See also Figure 7 and Figure 8For each segmented telescopic steel pipe 11, a top supporting cross frame 51 is set. The top supporting cross frame 51 mainly includes a support column 511 and a cross purlin 512, both of which are made of steel.

[0109] One end of the support column 511 is welded to the middle part of the cross purlin 512 as a welding end. The configuration of the entire top support cross frame 51 is like a "T" shape. The other end of the support column 511 is used as an assembly end for assembly and connection with the top support end of the segmented telescopic steel pipe 11.

[0110] A flange is provided on the assembly end of the support column 511, and correspondingly, a flange is also provided on the top supporting end of the segmented telescopic steel tube 11. In this way, the "assembly end of the support column 511" and the "top supporting end of the segmented telescopic steel tube 11" can be assembled and connected together by means of a flange connection.

[0111] In addition, in order to ensure the overall structure of the top supporting cross frame 51 is stable, reinforcement rods 513 are provided on both sides of the support column 511. The reinforcement rods 513 are obliquely connected between the support column 511 and the cross purlin 512 to form a triangular stable structure, thereby ensuring the structural strength of the top supporting cross frame 51.

[0112] It should be noted that the assembly end of the support column 511 can also be regarded as the assembly end of the entire top support cross frame 51.

[0113] Before applying top support prestress to the part of the enclosure near the bottom of the pit, the assembly end of the top support cross frame 51 is assembled and connected to the top support end of the segmented telescopic steel pipe 11, and the segmented telescopic steel pipe 11 is connected to the top support cross frame 51 as a whole. The top support cross frame 51 is equivalent to the extension part of the segmented telescopic steel pipe 11, and the segmented telescopic steel pipe 11 can swing the top support cross frame 51 up and down.

[0114] The segmented telescopic steel pipe 11 is swung toward the position of the enclosure near the bottom of the pit until its top support end is tilted downward toward the angle of the enclosure near the bottom of the pit. The top support end of the segmented telescopic steel pipe 11 is extended tilted downward until the cross purlin 512 of the top support cross frame 51 is against the position of the enclosure near the bottom of the pit. Then, the cross purlin 512 is fixedly connected to the position of the enclosure near the bottom of the pit. The segmented telescopic steel pipe 11 can apply top support prestress to the position of the enclosure near the bottom of the pit based on the horizontal support 41 near the bottom of the pit and through the top support cross frame 51.

[0115] It should be noted that the “fixed connection of the horizontal purlin 512 to the position of the enclosure near the bottom of the pit” can be achieved in the following ways:

[0116] The first method is to weld the horizontal purlin 512 to the reinforcement near the bottom of the pit.

[0117] The second method is that when the segmented telescopic steel pipe 11 is tilted downward at a small angle, the horizontal purlin 512 can be directly pressed against the bottom of the enclosure, and the friction between the two is sufficient to connect the two together.

[0118] In addition, at the position of the enclosure near the bottom of the pit, two adjacent top supporting cross frames 51 (top supporting cross frames 51 configured for two adjacent segmented telescopic steel pipes 11) can be connected together to form a whole.

[0119] Specifically, see Figure 9 and Figure 10 ,

[0120] The opposite (or close to each other) ends of the cross purlins 512 of two adjacent top support cross frames 51 are butted together. The butt joint can be achieved in the following manner:

[0121] In the first docking method, a bolt connection plate 52 is provided between the opposite ends of the two cross purlins 512, and both ends are connected to the bolt connection plate 52 by bolt connectors (such as Figure 9 As shown), the connection between the two can be achieved;

[0122] It should be noted that waist-shaped holes are provided at the connection points of the bolt connectors on the bolt connection plate 52 , so as to facilitate adaptation to the spacing between the ends of the two connected transverse purlins 512 .

[0123] In the second docking method, a welding connecting plate 53 is provided between the opposite ends of the two horizontal purlins 512, and the ends of both are welded together with the welding connecting plate 53 (such as Figure 10 As shown), the connection between the two can be achieved.

[0124] The combined top support cross frame 51 can form a continuous and stable top support for the enclosure near the bottom of the pit, so as to avoid the situation of "uneven prestressing of the top support received by the enclosure near the bottom of the pit".

[0125] Since the top support cross frame 51 is adopted, the load-bearing purlin 21 is no longer provided at the position of the enclosure near the bottom of the pit.

[0126] Improvement 2:

[0127] Numerous inclinometer tubes 31 are installed in the soil surrounding the retaining structure 6. These inclinometer tubes 31 monitor the rheological behavior of the soil surrounding the foundation pit. This data can be used to determine the amount of prestressing applied by the segmented telescopic steel pipes 11 to the retaining structure near the pit bottom, effectively controlling the displacement and deformation of the retaining structure 6.

[0128] In addition, in other embodiments, the inclinometer tube 31 may be pre-buried in the body of the enclosure structure 6 , so that the displacement and deformation of the enclosure structure 6 can be directly detected.

[0129] It should be noted that the prestressed supporting structure can be applied to the entire enclosure structure or to a partial enclosure structure.

[0130] The main advantages of the prestressed top support structure of embodiment 2 are:

[0131] 1) In the prestressed top support structure, a top support cross frame 51 is pre-installed at the top support end of the segmented telescopic steel tube 11. The top support end of the segmented telescopic steel tube 11 can extend obliquely downward and make the cross purlin 512 of the top support cross frame 51 rest against the bottom of the enclosure near the pit, thereby applying top support prestress to the bottom of the enclosure near the pit; in this way, the load-bearing purlin 21 originally set at the bottom of the enclosure near the pit (in embodiment 1) is eliminated, and the assembly and setting of the top support cross frame 51 is very convenient, thereby greatly improving the construction efficiency.

[0132] In addition, the prestressed support structure of embodiment 2 has the following other advantages:

[0133] 2) It can form oblique support to compensate for the large deformation of the pit bottom;

[0134] 3) Prestress can be applied at multiple angles, making up for the deficiency of only being able to apply prestress horizontally;

[0135] 4) The prefabricated assembly structure and force-adding device can be disassembled flexibly and quickly, and can achieve rapid force addition when the foundation pit is excavated to the bottom of the pit, which is conducive to controlling deformation.

[0136] The above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A prestressed support structure in a foundation pit using a support cross frame, characterized by: The prestressed support structure includes a telescopic support mechanism, wherein the telescopic support mechanism has a telescopic support end; the body of the telescopic support mechanism is assembled and connected with the horizontal support (41) near the bottom of the pit, and the telescopic support mechanism can swing up and down based on the horizontal support (41) near the bottom of the pit; The supporting end of the telescopic supporting mechanism is equipped with a supporting cross frame (51), and the supporting cross frame (51) has a horizontal purlin (512).

2. The prestressed supporting structure in the foundation pit using the supporting cross frame according to claim 1 is characterized in that: The telescopic supporting mechanism can swing to an angle where its supporting end is tilted downward toward the bottom of the enclosure near the pit; The supporting end of the telescopic supporting mechanism can extend obliquely downward and make the horizontal purlin (512) of the supporting cross frame (51) abut against the bottom of the enclosure near the pit, thereby applying supporting prestress to the bottom of the enclosure near the pit based on the horizontal support (41) near the bottom of the pit.

3. The prestressed supporting structure in the foundation pit using the supporting cross frame according to claim 1 is characterized in that: The supporting cross frame (51) is specifically implemented in the following structural form: The top support cross frame (51) includes a support column (511) and a cross purlin (512); One end of the support column (511) is welded to the middle of the transverse purlin (512), and the other end of the support column (511) is assembled and connected to the top support end of the telescopic top support mechanism as an assembly end.

4. The prestressed supporting structure in the foundation pit using a supporting cross frame according to claim 1 is characterized in that: At the position of the enclosure near the bottom of the pit, the horizontal purlins (512) of adjacent top supporting cross frames (51) are butt-jointed together.

5. The prestressed supporting structure in the foundation pit using the supporting cross frame according to claim 4 is characterized in that: The cross purlins (512) of adjacent top supporting cross frames (51) are connected together through bolt connection plates (52).

6. The prestressed supporting structure in the foundation pit using a supporting cross frame according to claim 5 is characterized in that: The bolt connection portion of the bolt connection plate (52) is provided with a waist-shaped hole.

7. The prestressed supporting structure in the foundation pit using a supporting cross frame according to claim 4 is characterized in that: The cross purlins (512) of adjacent top supporting cross frames (51) are connected together by welding connecting plates (53).

8. The prestressed supporting structure in the foundation pit using a supporting cross frame according to claim 1 is characterized in that: The prestressed supporting structure includes an inclinometer tube (31), wherein the inclinometer tube (31) Set in the outer soil of the enclosure structure (6) or It is pre-buried in the main body of the enclosure structure (6).

9. The prestressed supporting structure in the foundation pit using a supporting cross frame according to claim 1 is characterized in that: The top support cross frame (51) includes a reinforcement rod (513), and the reinforcement rod (513) is obliquely connected between the support column (511) and the cross purlin (512) to form a triangular stable structure.

10. The prestressed supporting structure in the foundation pit using a supporting cross frame according to claim 1, characterized in that: The telescopic supporting mechanism is a segmented telescopic steel pipe (11).

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