A vertically positionable and adjustable support structure in a foundation pit and a construction method thereof

Abstract

The present invention belongs to the technical field of underground foundation pit engineering, and specifically relates to a support structure in a foundation pit that can be vertically positioned and adjusted, and a construction method, including a retaining structure, a support member, and a vertical adjustment positioning device for supporting and adjusting the vertical position of the support member; a crown beam is provided on the top of the retaining structure, a waist beam is provided on the inner side of the retaining structure, and support members are supported between the opposite sides of the crown beam and between the opposite sides of the waist beam; embedded parts are embedded in the crown beam or the waist beam, and vertical adjustment positioning devices are fixed on the two opposite side walls of the retaining structure, and the two ends of the support member are respectively supported on the vertical adjustment positioning devices on both sides and connected to the embedded parts on both sides. The present invention fixes the vertical adjustment positioning device on the retaining structure, and can accurately locate the vertical position of the support member according to different over-excavation depths and vertical elevations of the support, and can adjust the construction error at any time to achieve vertical precise construction, while providing temporary support for the support member during the construction process.

Description

Technical Field

[0001] The invention belongs to the technical field of underground foundation pit engineering, and in particular relates to a vertically positionable and adjustable support structure in a foundation pit and a construction method. Background Art

[0002] Traditional cast-in-place concrete supports are widely used in underground projects due to their advantages such as high rigidity, good integrity, safety and reliability. However, they also have prominent problems and disadvantages: (1) Costly and high investment: Concrete supports are temporary projects. Once the main structure of the station is completed, they are demolished and transported away. The investment in temporary abandoned projects is high, with a general underground station costing millions and a complex station costing tens of millions; (2) Time-consuming and long construction period: Concrete support formwork, steel bar binding, pouring, vibration, maintenance, and later demolition take several months, which seriously restricts the progress of on-site construction; (3) Laborious and difficult: Concrete support construction is difficult, and demolition after use requires a lot of manpower and material resources; (4) Not environmentally friendly, concrete demolition waste pollutes the environment, which does not conform to the development direction of green construction, environmental protection and energy saving. Advanced products and scientific construction methods are urgently needed to replace traditional concrete supports.

[0003] The weak links of the prefabricated supports currently seen are mostly in the connecting structures. Rigid connections cannot be achieved at the nodes, and the integrity is poor, resulting in insufficient overall stability of the foundation pit. In addition, during the support construction process, it is usually necessary to first construct bearings to temporarily support the prefabricated supports, but it is difficult to ensure the vertical construction accuracy. Summary of the invention

[0004] In order to overcome the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a vertically positionable and adjustable support structure in a foundation pit and a construction method, which can not only ensure the stability and safety of the foundation pit, but also realize precise construction.

[0005] To achieve the above-mentioned purpose, the technical solution of the present invention is a support structure in a foundation pit that can be vertically positioned and adjusted, including a retaining structure, a supporting member and a vertical adjustment positioning device for supporting and adjusting the vertical position of the supporting member; a crown beam is provided on the top of the retaining structure, a waist beam is provided on the inner side of the retaining structure, and the supporting member is supported between the opposite sides of the crown beam and between the opposite sides of the waist beam; embedded parts are embedded in the crown beam or the waist beam, and vertical adjustment positioning devices are fixed on the two opposite side walls of the retaining structure, and the two ends of the supporting member are respectively supported on the vertical adjustment positioning devices on both sides and connected to the embedded parts on both sides.

[0006] Furthermore, the vertical adjustment and positioning device includes a positioning I-beam for positioning the supporting member and an adjustment mechanism for adjusting the vertical position of the supporting member; one end of the adjustment mechanism is fixed to the side wall of the enclosure structure, and the other end is connected to the positioning I-beam; the support of the supporting member is on the positioning I-beam.

[0007] Furthermore, the adjustment mechanism includes a first length-adjustable rod, a second length-adjustable rod, a third length-adjustable rod and a fourth length-adjustable rod; the first length-adjustable rod is horizontally arranged, and the positioning I-beam is fixed on the first length-adjustable rod; the first length-adjustable rod, the second length-adjustable rod and the third length-adjustable rod are connected end to end to form a triangle shape; the connection between the second length-adjustable rod and the third length-adjustable rod is connected to the first fixing piece on the side wall of the enclosure structure; one end of the fourth length-adjustable rod is connected to the connection between the first length-adjustable rod and the third length-adjustable rod, and the other end is connected to the second fixing piece on the side wall of the enclosure structure.

[0008] Furthermore, the first fixing member is located below the second fixing member, and the first fixing member and the second fixing member have the same structure, both including expansion bolts, a fixing steel plate and an ear plate; the fixing steel plate is fixed to the side wall of the enclosure structure by expansion bolts, and the ear plate is fixed to the fixing steel plate; the second length-adjustable rod and the third length-adjustable rod are both connected to the ear plate of the first fixing member, and the fourth length-adjustable rod is connected to the ear plate of the second fixing member.

[0009] Furthermore, a recess for placing the supporting member is provided on the upper flange plate of the positioning I-beam, and the recess matches the supporting member.

[0010] As an embodiment, the support member is formed by splicing a plurality of prefabricated support segments, and a disassembly gasket is provided between at least two adjacent prefabricated support segments.

[0011] As another embodiment, the support member is spliced ​​together by multiple prefabricated support segments, one end of the support member is connected to the corresponding embedded part through a telescopic structure, and a jack is supported between one end of the support member connected to the telescopic structure and the corresponding embedded part, and the jack is electrically connected to the control system.

[0012] Furthermore, the telescopic structure includes a first telescopic joint and a second telescopic joint, the first telescopic joint and the second telescopic joint are respectively connected to the supporting member and the embedded part and have the same structure, both including a solid steel plate, a U-hole steel plate, a U-shaped steel plate and a stiffening plate; one end of the U-shaped steel plate passes through the U-shaped hole on the U-hole steel plate and is welded to the solid steel plate, and a plurality of rows of oblong holes are provided on the two side walls of the other end; the solid steel plate is connected to the U-hole steel plate through a stiffening plate, and the side wall of the U-shaped steel plate is welded to the U-hole steel plate; the U-shaped steel plate of the first telescopic joint is stuck in the U-shaped steel plate of the second telescopic joint, and the oblong hole on the first telescopic joint is connected to the oblong hole on the second telescopic joint by bolts; the front end and the rear end of the jack are respectively pressed against the solid steel plate of the first telescopic joint and the solid steel plate of the second telescopic joint.

[0013] The present invention also provides a construction method for the above-mentioned vertically positionable and adjustable support structure in a foundation pit, comprising the following steps:

[0014] S1. According to the design drawings, prefabricated support segments and embedded parts are manufactured in the factory and transported to the construction site;

[0015] S2, splicing the prefabricated support segments one by one by means of screws and nuts, and installing disassembly gaskets between at least two adjacent prefabricated support segments to assemble the support member; and connecting the embedded parts at both ends of the support member by means of screws;

[0016] S3, over-excavate the foundation pit, and then install the vertical adjustment and positioning device at the designated position on the side wall of the retaining structure;

[0017] S4. The hoisted and assembled support members are placed on the vertical adjustment and positioning device so that the embedded parts at both ends of the support members are placed at the positions of the crown beam or waist beam to be cast;

[0018] S5. Cast the crown beam or waist beam so that the embedded parts are buried therein;

[0019] S6. After the construction is completed, first unscrew the screws on the two prefabricated support segments with disassembly gaskets installed in the middle, and remove the disassembly gaskets;

[0020] S7. Unscrew the screws segment by segment and recycle the prefabricated support segments.

[0021] The present invention also provides another construction method of the above-mentioned vertically positionable and adjustable support structure in a foundation pit, comprising the following steps:

[0022] S1. According to the design drawings, prefabricated support segments, embedded parts, first expansion joints and second expansion joints are manufactured in the factory and transported to the construction site;

[0023] S2, assembling the prefabricated support segments section by section into a support member through screws and nuts; and connecting the first expansion joint to the prefabricated support segment at one end of the support member through screws and nuts;

[0024] S3, placing the embedded parts at the support design position in the crown beam or waist beam to be cast, and then casting the crown beam or waist beam so that the embedded parts are buried therein;

[0025] S4. After the crown beam or waist beam reaches the designed strength, the second expansion joint is fixed to the embedded screw extending from the embedded part on one side through a nut;

[0026] S5, over-excavate the foundation pit, and then install a vertical adjustment and positioning device at a designated position on the side wall of the retaining structure;

[0027] S6. The hoisted and assembled support member is placed on the vertical adjustment and positioning device so that the U-shaped steel plate of the first expansion joint is clamped in the U-shaped steel plate of the second expansion joint, and the prefabricated support segment at the other end of the support member is fixed with the embedded screw extending from the embedded part on the other side through a nut;

[0028] S7, placing a jack in the U-shaped steel plate, applying pressure to the designed value through the control system, so that both ends of the jack are respectively pressed against the solid steel plate of the first expansion joint and the solid steel plate of the second expansion joint;

[0029] S8, insert bolts into the oblong holes on the side walls of the U-shaped steel plate of the first expansion joint and the U-shaped steel plate of the second expansion joint, and tighten them;

[0030] S9. After the construction is completed, loosen the jack, unscrew the bolts and nuts, remove the expansion joints and screws, and recycle the prefabricated support segments.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The present invention fixes a vertical adjustment and positioning device on the side wall of the enclosure structure according to the vertical position of the support, and can accurately locate the vertical position of the support member according to different over-excavation depths and vertical elevations of the support, and can adjust the construction error at any time to achieve vertical precise construction, while providing temporary support for the support member during the construction process;

[0033] (2) The prefabricated support segments of the present invention and the prefabricated support segments and the crown beam or waist beam are rigidly connected to ensure the integrity and safety of the foundation pit;

[0034] (3) The prefabricated support segments of the present invention and the prefabricated support segments and embedded parts are connected by screws, which is convenient for installation and disassembly, so as to facilitate the recycling of the prefabricated support segments. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 A plan view of a vertically positionable and adjustable support structure in a foundation pit provided in an embodiment of the present invention;

[0037] Figure 2 A plan view of another vertically positionable and adjustable support structure in a foundation pit provided by an embodiment of the present invention;

[0038] Figure 3 A longitudinal section view of a prefabricated support segment provided by an embodiment of the present invention;

[0039] Figure 4 A cross-sectional view of a prefabricated support segment when the steel pipe provided in an embodiment of the present invention is circular;

[0040] Figure 5 A cross-sectional view of a prefabricated support segment when the steel pipe provided in an embodiment of the present invention is square;

[0041] Figure 6 A longitudinal section view of a connection node structure of a prefabricated support segment provided in an embodiment of the present invention (without a disassembly gasket);

[0042] Figure 7 A longitudinal section view of a connection node structure of a prefabricated support segment provided in an embodiment of the present invention (with a disassembly gasket);

[0043] Figure 8 A cross-sectional view of a connection node structure of a prefabricated support segment provided by an embodiment of the present invention;

[0044] Fig. 9 A schematic diagram of an inner ring plate when the steel pipe provided in an embodiment of the present invention is circular;

[0045] Fig.10 A schematic diagram of an outer ring plate when the steel pipe provided in an embodiment of the present invention is circular;

[0046] Fig.11 A schematic diagram of a stiffening rib provided in an embodiment of the present invention;

[0047] Fig.12 A schematic diagram of a disassembly gasket provided in an embodiment of the present invention;

[0048] Fig.13A schematic diagram of a prefabricated support segment provided by an embodiment of the present invention being connected to a pre-embedded part in a crown beam via a telescopic structure;

[0049] Fig.14 A schematic diagram of a prefabricated support segment provided by an embodiment of the present invention being directly connected to an embedded component in a crown beam;

[0050] Fig.15 A schematic diagram of a prefabricated support segment on a positioning I-shaped steel when the steel pipe provided in an embodiment of the present invention is circular;

[0051] Fig.16 A schematic diagram of a prefabricated support segment on a positioning I-shaped steel when the steel pipe provided in an embodiment of the present invention is square;

[0052] Fig.17 A side view of a first expansion joint and a second expansion joint provided by an embodiment of the present invention;

[0053] Fig.18 A schematic diagram of a solid steel plate provided in an embodiment of the present invention;

[0054] Fig.19 A schematic diagram of a U-hole steel plate provided in an embodiment of the present invention;

[0055] Fig. 20 A schematic diagram of an embedded part provided in an embodiment of the present invention;

[0056] Fig.21 A schematic diagram of a first fixing member and a second fixing member provided in an embodiment of the present invention;

[0057] Fig. 22 A side view of a first fixing member and a second fixing member provided in an embodiment of the present invention;

[0058] In the figure: 1. enclosure structure; 2. crown beam; 3. prefabricated support segment; 4. embedded parts; 5. first expansion joint; 6. second expansion joint; 7. vertical adjustment positioning device; 8. outer ring plate; 9. stiffening rib; 10. inner ring plate; 11. steel pipe; 12. stirrups; 13. longitudinal reinforcement; 14. sealing plate; 15. perforation plug welding; 16. filling concrete; 17. screw; 18. nut; 19. screw hole; 20. solid steel plate; 21. U-hole steel plate; 22. U shaped steel plate; 23. oblong hole; 24. bolt; 25. jack; 26. wire; 27. control system; 28. drain hole; 29. ​​disassembly gasket; 30. positioning I-shaped steel; 31. first length adjustable rod; 32. second length adjustable rod; 33. third length adjustable rod; 34. fourth length adjustable rod; 35. ear plate; 36. expansion bolt; 37. fixed steel plate; 38. stiffening plate; 39. embedded steel plate; 40. embedded screw. DETAILED DESCRIPTION

[0059] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0060] In the description of the present invention, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0061] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features; in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0062] Embodiment 1

[0063] like Figure 1-Figure 2 As shown, this embodiment provides a support structure in a foundation pit that can be vertically positioned and adjusted, including a retaining structure 1, a support member, and a vertical adjustment positioning device 7 for supporting and adjusting the vertical position of the support member; a crown beam 2 is provided on the top of the retaining structure 1, a waist beam is provided on the inner side of the retaining structure 1, and the support member is supported between the opposite sides of the crown beam 2 and between the opposite sides of the waist beam; embedded parts 4 are embedded in the crown beam 2 or the waist beam, and vertical adjustment positioning devices 7 are fixed on the two opposite side walls of the retaining structure 1, and the two ends of the support member are respectively supported on the vertical adjustment positioning devices 7 on both sides and connected to the embedded parts 4 on both sides. In this embodiment, according to the vertical position of the support, the vertical adjustment positioning device 7 is fixed on the side wall of the retaining structure 1, and the vertical position of the support member can be accurately positioned according to different over-excavation depths and vertical elevations of the support, and the construction error can be adjusted at any time to achieve vertical precise construction, while providing temporary support for the support member. The accompanying drawings of this embodiment take the crown beam 2 as an example for explanation, and the situation of the waist beam refers to the crown beam 2.

[0064] Furthermore, the vertical adjustment and positioning device 7 includes a positioning I-beam 30 for positioning the supporting member and an adjustment mechanism for adjusting the vertical position of the supporting member; one end of the adjustment mechanism is fixed to the side wall of the enclosure structure 1, and the other end is connected to the positioning I-beam 30; the support of the supporting member is on the positioning I-beam 30.

[0065] Furthermore, the adjustment mechanism includes a first length-adjustable rod 31, a second length-adjustable rod 32, a third length-adjustable rod 33 and a fourth length-adjustable rod 34; the first length-adjustable rod 31 is arranged horizontally, and the positioning I-beam 30 is fixed on the first length-adjustable rod 31; the first length-adjustable rod 31, the second length-adjustable rod 32 and the third length-adjustable rod 33 are connected end to end to form a triangle shape; the connection between the second length-adjustable rod 32 and the third length-adjustable rod 33 is connected to the first fixing piece on the side wall of the enclosure structure 1; one end of the fourth length-adjustable rod 34 is connected to the connection between the first length-adjustable rod 31 and the third length-adjustable rod 33, and the other end is connected to the second fixing piece on the side wall of the enclosure structure 1. Figure 13-Figure 14 As shown, in this embodiment, by adjusting the lengths of the second adjustable length rod 32, the third adjustable length rod 33 and the fourth adjustable length rod 34, it is ensured that the first adjustable length rod 31 remains horizontal and reaches the specified vertical elevation, thereby achieving precise positioning of the vertical position; the dimensions of the first adjustable length rod 31, the second adjustable length rod 32, the third adjustable length rod 33 and the fourth adjustable length rod 34, as well as the spacing of the adjustment positioning device 7 and the dimensions of the positioning I-beam 30, should be determined based on force calculations.

[0066] Furthermore, the first fixing member is located below the second fixing member, and the first fixing member and the second fixing member have the same structure, both including expansion bolts 36, fixing steel plates 37 and ear plates 35; the fixing steel plates 37 are fixed to the side wall of the enclosure structure 1 by expansion bolts 36, and the ear plates 35 are fixed to the fixing steel plates 37; the second length adjustable rod 32 and the third length adjustable rod 33 are both connected to the ear plates 35 of the first fixing member, and the fourth length adjustable rod 34 is connected to the ear plates 35 of the second fixing member. Figure 13-Figure 14 As shown, the second length adjustable rod 32 and the third length adjustable rod 33 of this embodiment are hinged to the ear plate 35 of the first fixing member, and the fourth length adjustable rod 34 is hinged to the ear plate 35 of the second fixing member, which facilitates the disassembly of the vertical adjustment and positioning device 7 and realizes recycling.

[0067] Furthermore, a recess for placing the support member is provided on the upper flange plate of the positioning I-shaped steel 30, and the recess matches the support member. In this embodiment, the lower flange plate of the positioning I-shaped steel 30 is fixed to the end of the first length adjustable rod 31 away from the third length adjustable rod 33 and the fourth length adjustable rod 34 through the ear plate 35; when the steel pipe 11 is circular, a recess matching the steel pipe 11 is provided on the upper flange plate of the positioning I-shaped steel 30 to facilitate positioning of the support member, such as Fig.15 As shown, the position of the recess should match the spacing and size of the support member and be prefabricated in the factory; when the steel pipe 11 is square, the positioning support can be directly placed on the upper flange plate of the positioning I-shaped steel 30, such as Fig.16 shown.

[0068] As an embodiment, the support member is formed by splicing a plurality of prefabricated support segments 3, and a disassembly gasket 29 is provided between at least two adjacent prefabricated support segments 3, such as Figure 2 As shown, the connection nodes between the two ends of the supporting member and the crown beam 2 or the waist beam are both Fig.14 The connection method shown in . In the support member of this embodiment, at least one disassembly gasket 29 is provided. By placing the disassembly gasket 29 between two prefabricated support segments 3, the disassembly gasket 29 can be removed first during disassembly to eliminate the axial force between the prefabricated support segments 3, and the remaining prefabricated support segments 3 can be easily disassembled, effectively solving the problem of difficulty in disassembling several-meter-long prefabricated supports and improving the disassembly efficiency of prefabricated supports; wherein, the disassembly gasket 29 can be a solid steel ring with a thickness of 3-10cm, or a solid steel ring spliced ​​from multiple sections, such as two semicircular steel rings or multiple fan-shaped steel rings, and the multiple sections of steel rings are not connected; the surface of the disassembly gasket 29 needs to be smooth, and a layer of lubricant can be applied to both sides of the disassembly gasket 29 before installation, so that the difficulty of removing the disassembly gasket 29 is much smaller, and once the disassembly gasket 29 is removed, the axial force between the prefabricated support segments 3 will also disappear, and the remaining prefabricated support segments 3 can be easily disassembled.

[0069] As another embodiment, the support member is composed of a plurality of prefabricated support segments 3, one end of the support member is connected to the corresponding embedded part 4 through a telescopic structure, and a jack 25 is supported between the end of the support member connected to the telescopic structure and the corresponding embedded part 4, and the jack 25 is electrically connected to the control system 27, such as Figure 1 As shown, the connection node between one end of the supporting member and the crown beam 2 or the waist beam is Fig.13 The connection method shown in the figure is that the connection node between the other end of the supporting member and the crown beam 2 or the waist beam adopts Fig.14The connection method shown in the figure; the end joint length can be adjusted by the retractable structure, so as to adjust the construction error; at the same time, a jack 25 is set, and the jack 25 is an intelligent jack 25, which has sufficient jacking force, and can sense its own stress and transmit it to the control system 27 through the wire 26. The control system 27 makes a corresponding response according to the stress to adjust its jacking force and elongation, forming an intelligent stress compensation device, which can construct prestress according to the needs, meet the needs of prestress loss and support relaxation requiring repeated loading, and in the process of using the assembled support, stress relaxation phenomenon will be timely compensated for, and excessive stress will be timely warned to prevent local instability of the foundation pit and cause damage to the entire foundation pit; the size of the jack 25 should not be too large to avoid affecting the connection of the retractable structure.

[0070] like Fig.13 and Figure 17-19 As shown, the telescopic structure includes a first telescopic joint 5 and a second telescopic joint 6, which are respectively connected to the supporting member and the embedded member 4 and have the same structure, and both include a solid steel plate 20, a U-hole steel plate 21, a U-shaped steel plate 22 and a stiffening plate 38; one end of the U-shaped steel plate 22 passes through the U-shaped hole on the U-hole steel plate 21 and is welded to the solid steel plate 20, and a plurality of rows of oblong holes 23 are provided on the two side walls of the other end; the solid steel plate 20 and the embedded member 4 are connected to each other .... The U-hole steel plate 21 is connected by a stiffening plate 38, and the side wall of the U-shaped steel plate 22 is welded to the U-hole steel plate 21; the U-shaped steel plate 22 of the first expansion joint 5 is stuck in the U-shaped steel plate 22 of the second expansion joint 6, and the oblong hole 23 on the first expansion joint 5 is connected to the oblong hole 23 on the second expansion joint 6 by bolts 24; the front end and the rear end of the jack 25 are respectively pressed against the solid steel plate 20 of the first expansion joint 5 and the solid steel plate 20 of the second expansion joint 6. The U-shaped steel plate 22 of this embodiment is provided with multiple rows of oblong holes 23, and the oblong holes 23 are arranged along the supporting direction. The oblong holes 23 on the first expansion joint 5 are connected with the oblong holes 23 on the second expansion joint 6 by bolts 24. The end of the supporting member and the crown beam 2 or the waist beam node adopt this variable position oblong hole 23 steel box slot node, which can not only meet the needs of rigid connection and equal strength connection of the edge node, ensure the engineering safety and the detachability of the end node, and facilitate the recycling of prefabricated components, but also can adjust the relative position of the oblong hole 23 as needed to change the length of the joint, thereby adjusting the construction error. Optimally, a drainage hole 28 is reserved on the bottom plate of the U-shaped steel plate to prevent rainwater from accumulating in the U-shaped space where the jack 25 is located and damaging the jack 25; at the same time, the size of the drainage hole 28 should not be too large to prevent the steel plate at the joint from being weakened.

[0071] The size of the U-shaped steel plate 22 of the first expansion joint 5 is smaller than that of the U-shaped steel plate 22 of the second expansion joint 6, so that the U-shaped steel plate 22 of the first expansion joint 5 can be just stuck in the U-shaped steel plate 22 of the second expansion joint 6 to form a U-shaped groove, but the oblong holes 23 on the U-shaped steel plate 22 of the first expansion joint 5 and the oblong holes 23 on the U-shaped steel plate 22 of the second expansion joint 6 need to be at the same height and have the same spacing; in addition, the U-shaped hole on the U-hole steel plate 21 matches the size of the U-shaped steel plate 22, and the U-shaped steel plate 22 passes through the U-shaped hole on the U-hole steel plate 21 and is welded to the U-hole steel plate 21. At the same time, a plurality of stiffening plates 38 arranged at intervals along the outer wall of the U-shaped steel plate 22 are used to connect the solid steel plate 20 and the U-hole steel plate 21, and the inner side of the stiffening plate 38 is welded to the U-shaped steel plate 22, so as to improve the stiffness at the connection node, ensure that the edge node and the supporting member have the same or similar integrity, stiffness and bearing capacity as the cast-in-place concrete support, and ensure the safety of the foundation pit. Fig.13 As shown, the stiffening plate 38 of this embodiment has the same structure as the stiffening rib 9 and is slightly larger in size than the stiffening rib 9 .

[0072] In the above two support member implementations, the prefabricated support segment 3 can be supported by hollow steel tube concrete, such as Figure 4 and Figure 5 As shown, pure steel support and pure concrete support can also be used, and high-strength alloy steel materials or composite materials with concrete can also be used; and the prefabricated support segment 3 can be designed with several fixed modulus segments of appropriate lengths as needed. It should not be too long, as a too long length is not suitable for hoisting construction, and a too short length leads to too many joints and difficulty in connection; for example, the prefabricated support segment 3 can be designed with standard moduli of 4m, 5m, 6m and other specifications and an end segment modulus of 2m. According to the actual needs of the foundation pit, prefabricated support segments 3 with completely identical, non-completely identical or completely different length specifications can be selected for assembly to meet the needs of foundation pit supports of different widths and lengths, and have universal applicability.

[0073] Furthermore, the prefabricated support segment 3 includes a steel tube 11, an inner ring plate 10 and an outer ring plate 8; the end faces of both ends of the steel tube 11 are welded with inner ring plates 10, and the outer walls of both ends of the steel tube 11 are circumferentially welded with outer ring plates 8; the inner ring plate 10 and the outer ring plate 8 at the same end of the steel tube 11 are connected by stiffening ribs 9, and the stiffening ribs 9 are welded to the steel tube 11; the inner ring plate 10 and the outer ring plate 8 are both provided with a plurality of screw holes 19 at intervals along the circumferential direction, and the screw holes 19 on the outer ring plate 8 correspond one by one to the screw holes 19 on the inner ring plate 10; the corresponding screw holes 19 on the inner ring plates 10 and the outer ring plates 8 on adjacent prefabricated support segments 3 are respectively installed with screws 17 and fixed by nuts 18. Figure 6 and Figure 7As shown, the inner ring plate 10, the stiffening rib 9 and the outer ring plate 8 at the end of the steel tube 11 constitute a boot beam node to increase the joint stiffness, wherein the outer ring plate 8 is circumferentially welded to the steel tube 11, the inner side of the outer ring plate 8 is welded to the stiffening rib 9, the inner side of the inner ring plate 10 is respectively welded to the stiffening rib 9, the steel tube 11 and the sealing plate 14, and the three sides of the stiffening rib 9 are respectively welded to the outer ring plate 8, the inner ring plate 10 and the steel tube 11 to ensure the stiffness of the connection node at the joint; and the boot beam node at the end of the prefabricated support segment 3 is connected by a plurality of screws 17 , ensuring the rigid connection of the intermediate nodes, achieving equal strength between the nodes and the components, ensuring that the supporting components reach similar or even higher strength and rigidity than cast-in-place concrete supports, ensuring the safety and stability of the foundation pit project, and being easy to install and disassemble, convenient for factory production and large-scale promotion and application; when splicing, align the multiple screw holes 19 on the two prefabricated support segments 3 respectively, and then install the screws 17 in the screw holes 19 located on the same straight line and fix them through the nuts 18 to achieve the splicing between the prefabricated support segments 3. In the case of a supporting component with a disassembly gasket 29 between the prefabricated support segments 3, the disassembly gasket 29 is provided with multiple screw holes 19, and the screw holes 19 on the disassembly gasket 29 correspond one-to-one to the screw holes 19 on the outer ring plate 8 and the screw holes 19 on the inner ring plate 10; the screw 17 passes through the corresponding screw holes 19 on the disassembly gasket 29; as Figure 7 and Fig.12 As shown, in this embodiment, the size of the disassembly gasket 29 can be the same as that of the inner ring plate 10, and a plurality of screw holes 19 are evenly arranged along the circumferential direction on the outer edge, and the screw holes 19 on the disassembly gasket 29 correspond one-to-one to the screw holes 19 on the inner ring plate 10 and the outer ring plate 8 of the prefabricated support segment 3.

[0074] On the basis of the prefabricated support segment 3 of the above-mentioned steel structure, filling concrete 16 is poured in the steel pipe 11, and the filling concrete 16 has a hollow part running through it along the axial direction; the end faces of both ends of the steel pipe 11 are welded with sealing plates 14, and the inner ring plate 10 is welded to the side of the sealing plate 14 facing away from the steel pipe 11. In this embodiment, filling concrete 16 is poured in the steel pipe 11 to form a hollow structure, which can not only give full play to the advantages of the two materials of steel pipe 11 and concrete, but also be cost-effective. At the same time, it is lightweight and high-strength, easy to recycle, transport and install. Compared with pure steel support, it has significant economic benefits. Compared with concrete support, it has higher rigidity, and the steel pipe 11 is the outer skin of the prefabricated support, which can protect the internal filling concrete 16 from damage, so that the prefabricated components can be recycled for many times. At the same time, the sleeve effect of the steel pipe 11 can significantly improve the bearing capacity of the internal filling concrete, so that the hollow hollow steel pipe 11 concrete support has high bearing capacity (strength) and strong deformation resistance (rigidity), which can achieve the same or even higher strength and rigidity as conventional concrete support, ensuring the safety of foundation pit engineering; and the hollow parts of multiple prefabricated support segments 3 of the support member are connected, so that the assembled support has higher bearing capacity and stronger deformation resistance.

[0075] In this embodiment, the cross section of the steel pipe 11 can be circular, square, rectangular, polygonal, etc., and can be made of high-strength steel or alloy steel, etc., as long as it can bear the force and be easy to weld. In this embodiment, the filling concrete 16 can be other materials such as high-strength concrete, lightweight concrete or foam concrete, and the strength must meet the design requirements; the filling concrete 16 is hollow inside, and it can be formed by centrifugal process or other processes. The thickness of the filling concrete 16 is about 100mm-200mm. It is advisable to take a small value under the condition of supporting stiffness to reduce the self-weight of the prefabricated component; the hollow part of the filling concrete 16 can be without any inner wall, or it can be in the form of an inner wall. The inner wall material can be steel pipe, PVC, etc., and its cross section is not limited to circular, and can also be square, polygonal and other shapes. The sealing plate 14 can protect the filling concrete 16 at the end; the sealing plate 14, the inner ring plate 10, the outer ring plate 8, the stiffening rib 9 and the steel pipe 11 can be prefabricated as a whole, or they can be prefabricated separately and then welded into one.

[0076] Furthermore, the sealing plate 14, the inner ring plate 10 and the outer ring plate 8 are all annular, and the inner ring size of the sealing plate 14 and the inner ring size of the inner ring plate 10 are the same as the size of the hollow part filled with concrete 16, and the inner ring size of the outer ring plate 8 is the same as the outer ring size of the steel pipe 11. In this embodiment, the shapes and sizes of the sealing plate 14, the inner ring plate 10 and the outer ring plate 8 match the shapes and sizes of the steel pipe 11; when the steel pipe 11 is circular, the sealing plate 14, the inner ring plate 10 and the outer ring plate 8 are all annular steel plates, such as Figure 4 and Fig. 9 , Fig.10 As shown, the inner diameter of the outer ring plate 8 is the same as the outer diameter of the steel pipe 11, the inner diameter of the inner ring plate 10 and the inner diameter of the sealing plate 14 are the same as the inner diameter of the hollow part filled with concrete 16, the outer diameter of the sealing plate 14 can be the same as the outer diameter of the steel pipe 11, and the outer diameter of the inner ring plate 10 can be the same as the outer diameter of the outer ring plate 8; when the steel pipe 11 is square, as shown in 5, the sealing plate 14, the inner ring plate 10 and the outer ring plate 8 are all square annular steel plates, and the inner ring size and / or outer ring size of the sealing plate 14, the inner ring plate 10 and the outer ring plate 8 are also adjusted accordingly, which will not be described in detail here.

[0077] Furthermore, the filling concrete 16 is provided with a plurality of circumferential stirrups 12 and a plurality of longitudinal bars 13, the plurality of circumferential stirrups 12 are arranged at intervals along the supporting direction, the plurality of longitudinal bars 13 are arranged at intervals along the inner side of the circumferential stirrups 12, and each of the longitudinal bars 13 is connected to the plurality of circumferential stirrups 12, and both ends of the longitudinal bars 13 are connected to the sealing plates 14 at both ends of the steel pipe 11 by perforated plug welding 15. Figure 3-Figure 7As shown, in the filling concrete 16 of this embodiment, a plurality of longitudinal bars 13 are arranged along the supporting direction, and the plurality of longitudinal bars 13 are arranged on the inner side of the annular stirrups 12 and connected to the plurality of annular stirrups 12, so as to enhance the tight connection effect between the concrete and the steel pipe 11, so as to ensure that the steel pipe 11 and the concrete work effectively together, and the rigidity thereof is relatively large, far exceeding the concrete support of the concrete size; wherein, the diameter and the number of the longitudinal bars 13 and the annular stirrups 12 can be determined according to the actual situation, and can be arranged in the middle of the filling concrete 16; the two ends of the longitudinal bars 13 are respectively welded to the sealing plates 14 at the two ends of the steel pipe 11 by perforated plug welding 15 as a whole, so as to promote the integration of the steel pipe 11 structure with the core-filling concrete, improve the integrity of the prefabricated components, and ensure the rigidity of the nodes.

[0078] Furthermore, a plurality of the stiffening ribs 9 are arranged between the inner ring plate 10 and the outer ring plate 8 in an annular direction, and the stiffening ribs 9 and the screw rods 17 are arranged alternately. Figure 8 As shown, the stiffening ribs 9 are arranged between the pairs of screw holes 19 of the inner and outer ring plates, the number of stiffening ribs 9 and the screw holes 19 are consistent, and multiple stiffening ribs 9 and multiple screws 17 are arranged alternately to improve the strength and rigidity of the connection node; the thickness of the stiffening ribs 9 is determined according to the force, and a redundancy is reserved.

[0079] Furthermore, the stiffening rib 9 is a chamfered rectangular steel plate, and the two corners of the side of the stiffening rib 9 connected to the steel pipe 11 are chamfered. Figure 6 , Figure 7 and Fig.11 As shown, this embodiment forms a chamfered structure by chamfering the two side corners where the stiffening rib 9 is connected to the steel pipe 11, thereby effectively reducing stress concentration during welding; wherein, the side of the stiffening rib 9 facing away from the steel pipe 11 can be flush with the outer side of the outer ring plate 8.

[0080] Furthermore, embedded parts 4 are embedded in the crown beam 2 and the waist beam, and the embedded parts 4 include two embedded steel plates 39 and multiple embedded screws 40; one end of the multiple embedded screws 40 passes through the two embedded steel plates 39 in sequence and is welded to the two embedded steel plates 39, and the other end extends out of the crown beam 2 or the waist beam and passes through the multiple screw holes 19 on the inner ring plate 10 and the multiple screw holes 19 on the outer ring plate 8 at the end of the support member in sequence, and then is fixed by the nut 18. Figure 13-Figure 14 and Fig. 20As shown, the two embedded steel plates 39 of this embodiment are arranged relatively to each other and buried in the crown beam 2 or the waist beam to play an anchoring role; a plurality of screw holes 19 are provided on the two embedded steel plates 39, and correspond one to one with the plurality of screw holes 19 on the inner ring plate 10 and the outer ring plate 8, one end of a plurality of embedded screws 40 passes through the corresponding screw holes 19 on the two embedded steel plates 39 and is welded to the embedded steel plates 39, and the other end passes through the plurality of screw holes 19 on the inner ring plate 10 and the plurality of screw holes 19 on the outer ring plate 8 and is fixed by a nut 18.

[0081] In this embodiment, all steel structures such as steel pipe 11, inner ring plate 10, outer ring plate 8 and other parts that are directly in contact with the outside world need to be pre-coated with anti-rust material to prevent rust damage to the surface of the steel structure, which will lead to reduced strength; the nuts 18 should be stacked in two to prevent loosening, and a pad can be provided under the nuts 18 as needed.

[0082] Embodiment 2

[0083] like Figure 2 As described above, this embodiment provides a construction method for a support structure in a foundation pit that can be vertically positioned and adjusted, wherein a disassembly gasket 29 is provided between the prefabricated support segments 3 of the support member, and the method comprises the following steps:

[0084] S1. According to the design drawings, prefabricated support segments 3 and embedded parts 4 are manufactured in the factory and transported to the construction site;

[0085] S2, splicing the prefabricated support segments 3 section by section through screws 17 and nuts, and installing disassembly gaskets 29 between at least two adjacent prefabricated support segments 3 to assemble into a support member; and connecting the embedded parts 4 at both ends of the support member through screws 17;

[0086] S3, over-excavate the foundation pit, and then install the vertical adjustment positioning device 7 at the designated position on the side wall of the retaining structure 1;

[0087] S4, the hoisted and assembled support members are placed on the vertical adjustment and positioning device 7, so that the embedded parts 4 at both ends of the support members are placed at the positions of the crown beam 2 or waist beam to be cast;

[0088] S5, pouring the crown beam 2 or the waist beam, so that the embedded parts 4 are buried therein;

[0089] S6. After the construction is completed, first unscrew the screws 17 on the two prefabricated support segments 3 with the disassembly gaskets 29 installed in the middle, and remove the disassembly gaskets 29;

[0090] S7, unscrewing the screw rod 17 segment by segment and recovering the prefabricated support segment 3.

[0091] In this embodiment, the embedded parts 4 at both ends of the supporting member are first placed at the position of the crown beam 2 or waist beam to be cast, and then the crown beam 2 or waist beam is cast, and the embedded parts 4 at both ends of the supporting member are cast therein at the same time, so as to improve the strength of the nodes between the two ends of the supporting member and the crown beam 2 or waist beam, thereby ensuring the safety and stability of the foundation pit project.

[0092] The specific method for manufacturing the prefabricated support segment 3 in the factory in step S1 of this embodiment may be:

[0093] S11. Prepare the steel pipe 11, the sealing plate 14, the inner ring plate 10 and the outer ring plate 8 according to the design drawings;

[0094] S12, disposing annular stirrups 12 and a plurality of longitudinal bars 13 in the steel pipe 11;

[0095] S13, welding sealing plates 14 to the end surfaces of both ends of the steel pipe 11, and connecting the two ends of the longitudinal reinforcement 13 to the sealing plates 14 at both ends of the steel pipe 11 through perforation plug welding 15;

[0096] S14, first weld the inner ring plate 10 on the side of the closing plate 14 away from the steel pipe 11, circumferentially weld the outer ring plate 8 on the outer walls at both ends of the steel pipe 11, and weld the stiffening ribs 9 between the inner ring plate 10 and the outer ring plate 8; then pour and fill concrete 16 in the steel pipe 11 and reserve a hollow part to complete the production of the hollow steel pipe 11 concrete support prefabricated part; or first pour and fill concrete 16 in the steel pipe 11 and reserve a hollow part, then weld the inner ring plate 10 on the side of the closing plate 14 away from the steel pipe 11, circumferentially weld the outer ring plate 8 on the outer walls at both ends of the steel pipe 11, and weld the stiffening ribs 9 between the inner ring plate 10 and the outer ring plate 8 to complete the production of the hollow steel pipe 11 concrete support prefabricated part.

[0097] In this embodiment, a centrifugal process can be used to pour and fill concrete 16 in the steel pipe 11, which can automatically form an internal hollow, and the steel pipe 11 can be used as an external template for the centrifugal process without removal. At the same time, compared with the conventional cast-in-place vibration process, the centrifugal process is convenient for achieving high-strength concrete, and the concrete of the hollow steel pipe 11 has higher bearing capacity and deformation resistance and better durability; other processes can also be used to complete it.

[0098] When the prefabricated support segments 3 are spliced ​​in step S2 of this embodiment, the inner ring plates 10 at the ends of the two prefabricated support segments 3 are first aligned, and then the screw 17 is passed through the outer ring plate 8 and the inner ring plate 10 at the end of one of the prefabricated support segments 3, and the inner ring plate 10 and the outer ring plate 8 at the end of the other prefabricated support segment 3 in sequence, and fixed by the nut 18, so as to realize the splicing of the two prefabricated support segments 3; and when assembling the two prefabricated support segments 3 with the disassembly gasket 29 installed in the middle, firstly on both sides of the disassembly gasket 29 Apply a layer of lubricant on the surface, then place the disassembly gasket 29 between the two prefabricated support segments 3, and pass the screw 17 through the outer ring plate 8 and the inner ring plate 10 at the end of one of the prefabricated support segments 3, the disassembly gasket 29, the inner ring plate 10 at the end of the other prefabricated support segment 3, and fix it through the nut 18. When disassembling, first remove the screw 17 and the nut 18, then remove the disassembly gasket 29, eliminate the axial force between the prefabricated components, and then disassemble the prefabricated support segments 3 section by section. In this embodiment, due to the wall protection function of the external steel pipe 11, the support is not easily damaged, and the joint is connected by a high-strength screw 17. The removal of the high-strength screw 17 can realize the recovery of the prefabricated support segment 3, and it can be recycled many times to reduce costs.

[0099] Embodiment 3

[0100] like Figure 1 The present embodiment provides a construction method for the above-mentioned supporting structure in the foundation pit with a telescopic structure capable of vertical positioning adjustment, wherein one end of the supporting member is directly connected to the embedded part 4 in the crown beam 2 or the waist beam, and the other end is connected to the embedded part 4 in the crown beam 2 or the waist beam through the telescopic structure. The method comprises the following steps:

[0101] S1. According to the design drawings, prefabricated support segments 3, embedded parts 4, first expansion joints 5 and second expansion joints 6 are manufactured in the factory and transported to the construction site;

[0102] S2, assembling the prefabricated support segments 3 section by section into a support member through screws 17 and nuts 18; and connecting the first expansion joint 5 to the prefabricated support segment 3 at one end of the support member through screws 17 and nuts 18;

[0103] S3, placing the embedded part 4 at the support design position in the crown beam 2 or waist beam to be cast, and then casting the crown beam 2 or waist beam so that the embedded part 4 is buried therein;

[0104] S4, after the crown beam 2 or the waist beam reaches the designed strength, the second expansion joint 6 is fixed to the embedded screw 40 extending from the embedded part 4 on one side through the nut 18;

[0105] S5, over-excavate the foundation pit, and then install the vertical adjustment positioning device 7 at the designated position on the side wall of the retaining structure 1;

[0106] S6. The hoisted and assembled support member is placed on the vertical adjustment and positioning device 7, so that the U-shaped steel plate 22 of the first expansion joint 5 is stuck in the U-shaped steel plate 22 of the second expansion joint 6, and the prefabricated support segment 3 at the other end of the support member is fixed with the embedded screw 40 extending from the embedded part 4 on the other side through the nut 18;

[0107] S7, placing a jack 25 in the U-shaped steel plate 22, applying pressure to a designed value through the control system 27, so that both ends of the jack 25 are respectively pressed against the solid steel plate 20 of the first expansion joint 5 and the solid steel plate 20 of the second expansion joint 6;

[0108] S8, insert bolts 24 into the oblong holes 23 on the side walls of the U-shaped steel plate 22 of the first expansion joint 5 and the U-shaped steel plate 22 of the second expansion joint 6, and tighten them;

[0109] S9. After the construction is completed, release the jack 25, unscrew the bolt 24 and the nut 18, remove the expansion joint and the screw 17, and recover the prefabricated support segment 3.

[0110] The first expansion joint 5 and the second expansion joint 6 of the present embodiment are connected by bolts 24, the first expansion joint 5 and the prefabricated support segment 3 at one end of the assembled support are connected by screws 17, the second expansion joint 6 and the embedded part 4 are connected by embedded screws 40 and nuts 18, and the prefabricated support segment 3 at the other end of the assembled support is connected to the embedded part 4 by embedded screws 40 and nuts 18, which is easy to disassemble. Therefore, after the construction of the foundation pit project is completed, the jack 25 is loosened, the bolts 24 connecting the first expansion joint 5 and the second expansion joint 6 are removed first to release the pressure, and then the screws 17 and nuts 18 are removed, the prefabricated support segments 3 are disassembled one by one, and the prefabricated support segments 3 are recovered to reduce costs.

[0111] The specific method for manufacturing the prefabricated support segment 3 in the factory in step S1 of this embodiment may adopt the preparation method in the second embodiment.

[0112] When the prefabricated support segments 3 are spliced ​​section by section in step S2 of this embodiment, the inner ring plates 10 at the ends of the two prefabricated support segments 3 are first aligned, and then the screw 17 is sequentially passed through the outer ring plate 8 and the inner ring plate 10 at the end of one of the prefabricated support segments 3, and the inner ring plate 10 and the outer ring plate 8 at the end of the other prefabricated support segment 3, and fixed by the nut 18 to achieve the splicing of the two prefabricated support segments 3; when the first expansion joint 5 is spliced ​​with the prefabricated support segment 3 located at the end, the screw hole 19 on the inner ring plate 10 at the end of the prefabricated support segment 3 is first aligned with the screw hole 19 on the solid steel plate 20 of the first expansion joint 5, and then the screw 17 is sequentially passed through the outer ring plate 8 and the inner ring plate 10 at the end of the prefabricated support segment 3, and the screw hole 19 on the solid steel plate 20 of the first expansion joint 5 and the U-hole steel plate 21 and fixed by the nut 18. In this embodiment, due to the wall protection function of the external steel pipe 11, the support is not easily damaged, and the joints are connected by high-strength screws 17. The prefabricated support segments 3 can be recycled by removing the high-strength screws 17, and can be recycled multiple times to reduce costs.

[0113] When the second expansion joint 6 is fixed to the embedded part 4 in step S4 of this embodiment, the multiple embedded screws 40 of the embedded part 4 are respectively passed through the multiple screw holes 19 on the solid steel plate 20 of the second expansion joint 6 and the multiple screw holes 19 on the U-hole steel plate 21 in sequence and then fixed by the nuts 18.

[0114] The assembled support components in the second and third embodiments can be rigidly connected to the crown beam 2 or the waist beam, so that in an ultra-deep foundation pit, the assembled support components can replace multiple traditional concrete supports to improve the assembly rate.

[0115] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A vertically positionable and adjustable support structure in a foundation pit, characterized in that: The frame comprises a protective structure, a supporting member and a vertical adjustment and positioning device for supporting and adjusting the vertical position of the supporting member; a crown beam is provided on the top of the protective structure, a waist beam is provided on the inner side of the protective structure, and the supporting member is supported between the opposite sides of the crown beam and between the opposite sides of the waist beam; embedded parts are embedded in the crown beam or the waist beam, and vertical adjustment and positioning devices are fixed on the two opposite side walls of the protective structure, and the two ends of the supporting member are respectively supported on the vertical adjustment and positioning devices on both sides and connected to the embedded parts on both sides; the vertical adjustment and positioning device comprises a positioning I-shaped steel for positioning the supporting member and an adjustment mechanism for adjusting the vertical position of the supporting member; one end of the adjustment mechanism is fixed to the side wall of the protective structure, and the other end is connected to the positioning I-shaped steel; the supporting member is supported on the fixed on a positioning I-beam; the adjustment mechanism comprises a first length-adjustable rod, a second length-adjustable rod, a third length-adjustable rod and a fourth length-adjustable rod; the first length-adjustable rod is horizontally arranged, and the positioning I-beam is fixed on the first length-adjustable rod; the first length-adjustable rod, the second length-adjustable rod and the third length-adjustable rod are connected end to end to form a triangle shape; the connection between the second length-adjustable rod and the third length-adjustable rod is connected to the first fixing piece on the side wall of the enclosure structure; one end of the fourth length-adjustable rod is connected to the connection between the first length-adjustable rod and the third length-adjustable rod, and the other end is connected to the second fixing piece on the side wall of the enclosure structure; a recess for placing the supporting member is provided on the upper flange plate of the positioning I-beam, and the recess matches the supporting member.

2. The vertically positionable and adjustable support structure in a foundation pit according to claim 1, characterized in that: The first fixing member is located below the second fixing member, and the first fixing member and the second fixing member have the same structure, both including expansion bolts, a fixing steel plate and an ear plate; the fixing steel plate is fixed to the side wall of the enclosure structure by expansion bolts, and the ear plate is fixed to the fixing steel plate; the second length-adjustable rod and the third length-adjustable rod are both connected to the ear plate of the first fixing member, and the fourth length-adjustable rod is connected to the ear plate of the second fixing member.

3. A vertically positionable and adjustable support structure in a foundation pit according to any one of claims 1 to 2, characterized in that: The support member is formed by splicing a plurality of prefabricated support segments, and a disassembly gasket is arranged between at least two adjacent prefabricated support segments.

4. A vertically positionable and adjustable support structure in a foundation pit according to any one of claims 1 to 2, characterized in that: The support member is formed by splicing a plurality of prefabricated support segments, one end of the support member is connected to the corresponding embedded part through a telescopic structure, and a jack is supported between the end of the support member connected to the telescopic structure and the corresponding embedded part, and the jack is electrically connected to the control system.

5. The vertically positionable and adjustable support structure in a foundation pit according to claim 4, characterized in that: The telescopic structure includes a first telescopic joint and a second telescopic joint, which are respectively connected to the supporting member and the embedded part and have the same structure, and both include a solid steel plate, a U-hole steel plate, a U-shaped steel plate and a stiffening plate; one end of the U-shaped steel plate passes through the U-shaped hole on the U-hole steel plate and is welded to the solid steel plate, and a plurality of rows of oblong holes are provided on the two side walls of the other end; the solid steel plate is connected to the U-hole steel plate through a stiffening plate, and the side wall of the U-shaped steel plate is welded to the U-hole steel plate; the U-shaped steel plate of the first telescopic joint is stuck in the U-shaped steel plate of the second telescopic joint, and the oblong hole on the first telescopic joint is connected to the oblong hole on the second telescopic joint by bolts; the front end and the rear end of the jack are respectively pressed against the solid steel plate of the first telescopic joint and the solid steel plate of the second telescopic joint.

6. A construction method for a vertically positionable and adjustable support structure in a foundation pit as claimed in claim 3, characterized in that: The steps include: S1. According to the design drawings, prefabricated support segments and embedded parts are manufactured in the factory and transported to the construction site; S2, splicing the prefabricated support segments one by one by means of screws and nuts, and installing disassembly gaskets between at least two adjacent prefabricated support segments to assemble the support member; and connecting the embedded parts at both ends of the support member by means of screws; S3, over-excavate the foundation pit, and then install the vertical adjustment and positioning device at the designated position on the side wall of the retaining structure; S4. The hoisted and assembled support members are placed on the vertical adjustment and positioning device so that the embedded parts at both ends of the support members are placed at the positions of the crown beam or waist beam to be cast; S5. Cast the crown beam or waist beam so that the embedded parts are buried therein; S6. After the construction is completed, first unscrew the screws on the two prefabricated support segments with disassembly gaskets installed in the middle, and remove the disassembly gaskets; S7. Unscrew the screws segment by segment and recycle the prefabricated support segments.

7. A construction method for a vertically positionable and adjustable support structure in a foundation pit as claimed in claim 5, characterized in that: The steps include: S1. According to the design drawings, prefabricated support segments, embedded parts, first expansion joints and second expansion joints are manufactured in the factory and transported to the construction site; S2, assembling the prefabricated support segments section by section into a support member through screws and nuts; and connecting the first expansion joint to the prefabricated support segment at one end of the support member through screws and nuts; S3, placing the embedded parts at the support design position in the crown beam or waist beam to be cast, and then casting the crown beam or waist beam so that the embedded parts are buried therein; S4. After the crown beam or waist beam reaches the designed strength, the second expansion joint is fixed to the embedded screw extending from the embedded part on one side through a nut; S5, over-excavate the foundation pit, and then install a vertical adjustment and positioning device at a designated position on the side wall of the retaining structure; S6. The hoisted and assembled support member is placed on the vertical adjustment and positioning device so that the U-shaped steel plate of the first expansion joint is clamped in the U-shaped steel plate of the second expansion joint, and the prefabricated support segment at the other end of the support member is fixed with the embedded screw extending from the embedded part on the other side through a nut; S7, placing a jack in the U-shaped steel plate, applying pressure to the designed value through the control system, so that both ends of the jack are respectively pressed against the solid steel plate of the first expansion joint and the solid steel plate of the second expansion joint; S8, insert bolts into the oblong holes on the side walls of the U-shaped steel plate of the first expansion joint and the U-shaped steel plate of the second expansion joint, and tighten them; S9. After the construction is completed, loosen the jack, unscrew the bolts and nuts, remove the expansion joints and screws, and recycle the prefabricated support segments.

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