Post-tensioned precast concrete support member, internal support system and construction method

Abstract

The present invention belongs to the field of underground foundation pit engineering, and specifically relates to a post-tensioned precast concrete support member and construction method, including a concrete structure and two end steel structures; the concrete structure includes concrete with a hollow portion running through the support direction, a steel skeleton and a plurality of corrugated pipes are arranged in the concrete, and the two ends of the steel skeleton are respectively connected to the two end steel structures; each corrugated pipe is tensioned with prestressed longitudinal bars and poured with cement slurry, and both ends of the prestressed longitudinal bars extend out of the corrugated pipe and are anchored in the end steel structure through anchors; the present invention also provides an internal support system and construction method, the assembled internal support adopted by the system is spliced ​​by the above-mentioned post-tensioned precast concrete support members, and the two ends of the assembled support are respectively supported on the vertical adjustment and positioning devices on both sides and connected to the embedded parts on both sides. The present invention can improve the bearing capacity, deformation resistance, integrity and node stiffness of the assembled support, and can also achieve vertical precision construction.

Description

Technical Field

[0001] The invention belongs to the technical field of underground foundation pit engineering, and specifically relates to a post-tensioning precast concrete support component, an internal support system 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] Although traditional steel pipe supports can be recycled and are relatively convenient to construct, they can only withstand pressure between them and the foundation pit retaining structure, have poor integrity and poor deformation resistance, and become a weak link in foundation pit safety. In addition, during the support construction process, it is usually necessary to first construct a bearing to temporarily support the prefabricated support, but it is difficult to ensure the vertical construction accuracy. Summary of the invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a post-tensioned precast concrete support member, an internal support system and a construction method, which can improve the bearing capacity, deformation resistance, integrity and node stiffness of the prefabricated support, and can also achieve vertical precise construction.

[0005] To achieve the above-mentioned purpose, the technical solution of the present invention is a post-tensioned precast concrete support component, comprising a concrete structure and two end steel structures arranged at both ends of the concrete structure in the supporting direction; the concrete structure comprises concrete having a hollow portion running through the supporting direction, a steel skeleton and a plurality of corrugated tubes are arranged in the concrete, and the two ends of the steel skeleton are respectively connected to the two end steel structures; each of the corrugated tubes is tensioned with prestressed longitudinal bars and poured with cement slurry, and the two ends of the prestressed longitudinal bars extend out of the corrugated tubes and are anchored in the two end steel structures respectively through anchors.

[0006] Furthermore, the end steel structure includes an outer flange and an inner flange arranged opposite to each other, an inner ring tube and a plurality of stiffening ribs are provided between the outer flange and the inner flange; the two ends of the inner ring tube are respectively connected to the outer flange and the inner flange, and the three side surfaces of each stiffening rib are respectively connected to the outer flange, the inner ring tube and the inner flange; the steel bar skeleton is connected to the inner flange; prestressed tendon tensioning holes are provided on the inner flange, and the ends of the prestressed longitudinal tendons pass through the prestressed tendon tensioning holes and are anchored to the inner flange through anchors.

[0007] Furthermore, an outer ring tube is connected to the side of the inner flange away from the outer flange, and the end of the concrete structure is located inside the outer ring tube; a circle of engaging teeth is provided on the inner wall of the outer ring tube away from the end of the inner flange, and the engaging teeth are embedded in the concrete.

[0008] Furthermore, the cross section of the concrete structure is polygonal, corner angle steels are provided at the corners of the outer surface of the concrete structure, and adjacent corner angle steels are connected by connecting plates to form a lattice shape.

[0009] The present invention also provides an internal support system, including a protective structure, a crown beam, a waist beam and an assembled internal support; 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 assembled internal support is supported between the opposite sides of the waist beam and between the opposite sides of the crown beam; the assembled internal support is formed by splicing a plurality of the above-mentioned post-tensioned precast concrete support components; embedded parts are embedded in the crown beam or the waist beam, and vertical adjustment and positioning devices for supporting and adjusting the vertical position of the assembled internal support are fixed on the two opposite side walls of the protective structure, and the two ends of the assembled internal support are respectively supported on the vertical adjustment and positioning devices on both sides and connected to the embedded parts on both sides.

[0010] As an embodiment, a disassembly pad is provided between at least two adjacent post-tensioned precast concrete support members on the assembled inner support.

[0011] As another embodiment, one end of the assembled internal support is connected to the corresponding embedded part through a telescopic structure, and a jack is provided between one end of the assembled internal support connected to the telescopic structure and the corresponding embedded part, and the jack is electrically connected to the control system.

[0012] The present invention also provides a construction method for the above-mentioned post-tensioned precast concrete support member, comprising the following steps:

[0013] S1. Make the end steel structure in the steel structure processing plant;

[0014] S2. Tie non-prestressed longitudinal reinforcement and spiral stirrups in a prefabricated component processing plant, and spot weld the non-prestressed longitudinal reinforcement and spiral stirrups to form a steel skeleton;

[0015] S3, transport the end steel structure to the prefabricated component processing plant, weld the non-prestressed longitudinal reinforcement to the inner flange of the end steel structure, fix the corrugated pipe, reserved grouting pipe and grouting pipe at the corresponding position in the steel skeleton, set the corner angle steel at the corner of the prefabricated component and weld it to the tie plate to form a lattice shape;

[0016] S4. Pour concrete into the component mold, vibrate and use high-pressure steam curing to reach the designed strength;

[0017] S5, placing the component mold and the prefabricated component as a whole into the prestressed tensioning workbench, inserting the prestressed longitudinal reinforcement into the corrugated pipe, then tensioning the prestressed longitudinal reinforcement, and anchoring the end of the prestressed longitudinal reinforcement in the end steel structure by using an anchor, and finally pouring cement slurry into the corrugated pipe through the grouting pipe until slurry emerges from the reserved slurry emitting pipe, so that the prestressed longitudinal reinforcement and the prefabricated component become a whole;

[0018] S6. Remove the formwork to form post-tensioned precast concrete support components.

[0019] The present invention also provides a construction method of an internal support system, comprising the following steps:

[0020] S1. Prefabricate the post-tensioned precast concrete support members, embedded parts and disassembly pads in a factory and transport them to the construction site;

[0021] S2. According to the width of the foundation pit, the post-tensioned precast concrete support members of different lengths are spliced ​​section by section by bolts, and at the same time, a disassembly pad is installed between at least two adjacent post-tensioned precast concrete support members to assemble an assembled support with a length matching the width of the foundation pit;

[0022] 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;

[0023] S4. Place the assembled support on the vertical adjustment and positioning device after hoisting, and adjust the assembled support to the designed vertical position; fix the embedded parts at the designed position of the support in the crown beam or waist beam to be cast;

[0024] S5. Cast the crown beam or waist beam and bury the embedded parts therein;

[0025] S6. After the crown beam or waist beam reaches the design strength, fix the end of the assembled support to the embedded parts, complete the installation of the end node, and disassemble and recover the vertical adjustment and positioning device;

[0026] S7. After the construction is completed, first unscrew the bolts on the two post-tensioned precast concrete support members with the disassembly pads installed in the middle, and remove the disassembly pads;

[0027] S8. Unscrew the bolts section by section and recycle the post-tensioned precast concrete support components. Unscrew the threaded steel bars at the end nodes and recycle them.

[0028] The present invention also provides another construction method of an internal support system, comprising the following steps:

[0029] S1, prefabricate the post-tensioned precast concrete support member, embedded parts, first expansion joint and second expansion joint in a factory, and transport them to the construction site;

[0030] S2. According to the width of the foundation pit, the post-tensioned precast concrete support members of different lengths are spliced ​​section by section by bolts to assemble into an assembled support with a length matching the width of the foundation pit; and the first expansion joint of the telescopic structure is connected to the post-tensioned precast concrete support member at one end of the assembled support by a screw rod;

[0031] 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;

[0032] S4. After the crown beam or waist beam reaches the designed strength, the second expansion joint of the expansion structure is extended and fixed to the embedded parts;

[0033] 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;

[0034] S6. The assembled prefabricated support is hoisted and 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 post-tensioned precast concrete support member at the other end of the prefabricated support is fixed to the embedded part on the other side;

[0035] 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;

[0036] S8, inserting adjusting bolts into the oblong bolt holes on the U-shaped steel plate of the first expansion joint and the side wall of the U-shaped steel plate of the second expansion joint, and tightening them, completing the installation of the end nodes, disassembling and recovering the vertical adjustment positioning device;

[0037] S9. After the construction is completed, release the jack, unscrew the adjusting bolts, remove the expansion joints and bolts, and recycle the post-tensioned precast concrete support components.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) The prefabricated support of the present invention is formed by splicing post-tensioned precast concrete support components. The two ends of the post-tensioned precast concrete support components use end steel structures to increase the bearing capacity of the joints. A hollow concrete structure is used in the middle, and a steel skeleton and a plurality of prestressed longitudinal bars are arranged inside to improve the strength. The steel skeleton and the prestressed longitudinal bars are connected to the end steel structure, so that the end steel structure and the concrete structure are integrated, so that the prefabricated support has a high bearing capacity (strength) and a large deformation resistance (rigidity), which can meet or even exceed the safety requirements of conventional concrete supports. At the same time, it is light and high-strength, easy to recycle, easy to transport and install, and more economical than pure prefabricated steel supports. In addition, the manufacturing equipment is simple, no tensioning pedestal is required, and production is flexible.

[0040] (2) 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;

[0041] (3) The prefabricated support components of the present invention are rigidly connected to each other and to the crown beam or waist beam to ensure the integrity and safety of the foundation pit; and the prefabricated support components and to the embedded parts are connected by bolts or screws, which are easy to install and disassemble, so as to facilitate the recycling of the prefabricated support components. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] 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.

[0043] Figure 1 A plan view of one of the internal support systems provided by an embodiment of the present invention;

[0044] Figure 2 A plan view of another internal support system provided by an embodiment of the present invention;

[0045] Figure 3 A longitudinal section view of a post-tensioned precast concrete support member provided by an embodiment of the present invention;

[0046] Figure 4 A longitudinal section of a post-tensioned precast concrete support member provided in an embodiment of the present invention (without prestressed tendons being tensioned);

[0047] Figure 5 A cross-sectional view of a post-tensioned precast concrete support member at a middle position provided by an embodiment of the present invention;

[0048] Figure 6 A cross-sectional view of the end position of a post-tensioned precast concrete support member provided by an embodiment of the present invention;

[0049] Figure 7 A longitudinal section view of a connection node structure of a post-tensioned precast concrete support member provided in an embodiment of the present invention (without a disassembly pad);

[0050] Figure 8 A longitudinal section view of a connection node structure of a post-tensioned precast concrete support member provided in an embodiment of the present invention (with a dismantling pad);

[0051] Fig. 9 A cross-sectional view of a connection node structure of a post-tensioned precast concrete support member provided by an embodiment of the present invention;

[0052] Fig.10 A schematic diagram of a connection between a post-tensioned precast concrete support member and a crown beam provided by an embodiment of the present invention;

[0053] Fig.11 A schematic diagram of a pre-buried inner steel plate provided in an embodiment of the present invention;

[0054] Fig.12 A schematic diagram of a pre-buried outer steel plate provided in an embodiment of the present invention;

[0055] Fig.13 A schematic diagram of the connection between the post-tensioned precast concrete support member and the crown beam through a retractable structure provided in an embodiment of the present invention;

[0056] Fig.14 A schematic diagram of a U-hole steel plate provided in an embodiment of the present invention;

[0057] Fig.15 A schematic diagram of a solid steel plate provided in an embodiment of the present invention;

[0058] Fig.16 A schematic diagram of a stiffening plate provided in an embodiment of the present invention;

[0059] Fig.17 A schematic diagram of an inner flange provided in an embodiment of the present invention;

[0060] Fig.18 A schematic diagram of an outer flange provided in an embodiment of the present invention;

[0061] Fig.19 A schematic diagram of a stiffening rib provided in an embodiment of the present invention;

[0062] Fig. 20 A schematic diagram of a post-tensioned precast concrete support member provided by an embodiment of the present invention on a positioning I-shaped steel;

[0063] Fig.21 A schematic diagram of a first fixing member and a second fixing member provided in an embodiment of the present invention;

[0064] Fig. 22 A side view of a first fixing member and a second fixing member provided in an embodiment of the present invention;

[0065] Fig.23 A schematic diagram of a first length-adjustable rod provided in an embodiment of the present invention;

[0066] In the figure: 1. enclosure structure; 2. crown beam; 3. post-tensioned precast concrete support member; 4. embedded parts; 6. vertical adjustment and positioning device; 7. inner ring pipe; 8. outer flange; 9. stiffening ribs; 10. inner flange; 11. outer ring pipe; 12. non-prestressed longitudinal reinforcement; 13. prestressed longitudinal reinforcement; 14. spiral stirrups; 15. concrete; 16. bolts; 17. corner angle steel; 18. bolt holes; 19. embedded outer steel plate; 20. steel bar spiral sleeve; 21. embedded anchor steel bar; 22. embedded inner steel plate; 23. threaded steel bar; 24. reserved channel for post-tensioned prestressed reinforcement; 25. corrugated pipe; 26. anchor; 27. bite teeth; 28. tie plate; 29. ​​prestressed reinforcement Pull hole; 30. Positioning I-beam; 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. First expansion joint; 39. Second expansion joint; 40. Screw; 41. Screw hole; 42. Solid steel plate; 43. U-hole steel plate; 44. Stiffening plate; 45. U-shaped steel plate; 47. Adjusting bolt; 48. Jack; 49. Wire; 50. Control system; 51. Drain hole; 52. Outer ring plate; 53. Inner ring plate; 54. Embedded screw; 55. Reserved slurry pipe; 56. Disassembly pad; 57. Embedded steel plate. DETAILED DESCRIPTION

[0067] 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. Embodiment 1

[0068] like Figure 3-Figure 6As shown, this embodiment provides a post-tensioned precast concrete support member 3, including a concrete structure and two end steel structures arranged at both ends of the concrete structure in the supporting direction; the concrete structure includes a concrete 15 having a hollow portion passing through along the supporting direction, and a steel skeleton and a plurality of corrugated tubes 25 are arranged in the concrete 15, and the two ends of the steel skeleton are respectively connected to the two end steel structures; each of the corrugated tubes 25 is tensioned with a prestressed longitudinal reinforcement 13 and poured with cement slurry, and both ends of the prestressed longitudinal reinforcement 13 extend out of the corrugated tube 25 and are anchored in the two end steel structures respectively through anchors 26. The precast concrete support member of this embodiment adopts a hollow concrete structure in the middle and an end steel structure at both ends, which can give full play to the advantages of both steel and concrete materials; the end steel structure is added at the end to facilitate the rigid connection between the two precast support members and increase the bearing capacity of the joint; the middle adopts a pure hollow reinforced concrete structure, which has sufficient bearing capacity and can effectively reduce the cost, and the hollow concrete structure in the middle is equipped with a steel skeleton and multiple prestressed longitudinal bars 13. The prestressed longitudinal bars 13 can keep the concrete in a compressed state after the hollow concrete support member is formed, and has higher strength. To prevent concrete cracking during transportation and use, the steel skeleton can solve the bending problem of hollow concrete supports and increase the support strength. The steel skeleton and prestressed longitudinal bars 13 are connected to the end steel structure, which promotes the integration of the end steel structure and concrete 15, so that the prefabricated support components have high bearing capacity (strength) and high deformation resistance (rigidity), which can meet or even exceed the safety requirements of conventional concrete supports and are not easy to damage. At the same time, it is lightweight and high-strength, easy to recycle, easy to transport and install, and more economical than pure assembled steel supports. In addition, the manufacturing equipment is simple, no tensioning pedestal is required, and production is flexible.

[0069] In this embodiment, the concrete 15 can be made of other materials such as ultra-high-strength concrete. The interior of the concrete 15 is hollow and has a thickness of about 100mm-200mm. A smaller value is preferably taken while satisfying the support stiffness condition to reduce the deadweight of the component. The hollow portion in the concrete 15 may not have any inner wall, or may have an inner wall, and the inner wall material may be steel pipe, PVC, etc. The end steel structure is made of high-strength steel; the anchor 26 may be a JM-type anchor.

[0070] Furthermore, the end steel structure includes an outer flange 8 and an inner flange 10 arranged opposite to each other, an inner ring tube 7 and a plurality of stiffening ribs 9 are arranged between the outer flange 8 and the inner flange 10; the two ends of the inner ring tube 7 are respectively connected to the outer flange 8 and the inner flange 10, and the three sides of each stiffening rib 9 are respectively connected to the outer flange 8, the inner ring tube 7 and the inner flange 10; the steel skeleton is connected to the inner flange 10; the inner flange 10 is provided with a prestressed tendon tensioning hole 29, and the end of the prestressed longitudinal tendon 13 passes through the prestressed tendon tensioning hole 29 and is anchored to the inner flange 10 through the anchor 26. Figure 3-Figure 4 As shown, the inner ring tube 7, outer flange 8, inner flange 10 and stiffening rib 9 at the end of the post-tensioned precast concrete support member 3 of this embodiment constitute a boot beam node to increase the joint stiffness, and the three sides of the stiffening rib 9 are respectively welded to the inner ring tube 7, outer flange 8 and inner flange 10 to ensure the stiffness of the connection node at the joint.

[0071] In this embodiment, the inner ring tube 7 can be a steel tube with a wall thickness of 10-30 mm, and the inner diameter is consistent with the inner diameter of the concrete hollow part in the concrete structure. The two ends of the inner ring tube 7 are welded to the outer flange 8 and the inner flange 10 respectively, and the outer wall of the inner ring tube 7 is welded with a stiffening rib 9; Fig.18 As shown, the outer flange 8 can be a steel ring with a wall thickness of 10-30 mm, and its inner and outer diameters are exactly the same as the inner and outer diameters of the concrete 15 in the concrete structure. The outer flange 8 is evenly arranged with a plurality of bolt holes 18 in the circumferential direction; Fig.17 As shown, the size of the inner flange 10 is exactly the same as that of the outer flange 8, the thickness is preferably 10-30mm, the prestressed tendon tensioning holes 29 are evenly arranged in the circumferential direction, the prestressed tendon tensioning holes 29 are aligned with the reserved channels 24 for the post-tensioned prestressed tendons in the corrugated pipe 25, and the number of the prestressed tendon tensioning holes 29 is consistent with the number of the corrugated pipe 25 and the prestressed longitudinal reinforcement 13. One side of the inner flange 10 is welded to the inner ring pipe 7 and the stiffening rib 9, and one side is welded to the non-prestressed longitudinal reinforcement 12, the spiral stirrups 14 and the outer ring pipe 11, which plays the role of connecting the concrete structure and the end steel structure; and the shapes of the inner ring pipe 7, the outer flange 8 and the inner flange 10 match the cross-sectional shape of the concrete structure. For example, when the cross-section of the concrete structure is a square ring, the inner ring pipe 7 is square, and the outer flange 8 and the inner flange 10 are both square rings.

[0072] 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 inner ring tube 7 are chamfered. Figure 3 , Figure 4 and Fig.19As shown, the three sides of the stiffening rib 9 of this embodiment are welded to the inner ring tube 7, the outer flange 8 and the inner flange 10 respectively. The two corners of the side where the stiffening rib 9 is connected to the inner ring tube 7 are chamfered to form a chamfered structure, which effectively reduces the stress concentration during welding; wherein, the thickness of the stiffening rib 9 is preferably 20-30 mm, the length is the same as the inner ring tube 7, and the height is the difference between the inner and outer diameters of the outer flange 8 minus the thickness of the inner ring tube 7; multiple stiffening ribs 9 can be arranged as follows Fig. 9 The arrangement shown is between an outer flange 8 and an inner flange 10 .

[0073] Furthermore, an outer ring tube 11 is connected to the side of the inner flange 10 away from the outer flange 8, and the end of the concrete structure is located in the outer ring tube 11; a circle of bite teeth 27 is provided on the inner wall of the end of the outer ring tube 11 away from the inner flange 10, and the bite teeth 27 are embedded in the concrete 15. The outer ring tube 11 is sleeved on the outside of the end of the concrete structure of this embodiment, which can not only protect the concrete at the end and make the support less susceptible to damage, but also establish a common force-bearing link between the end steel structure and the middle concrete structure through the outer ring tube 11. Among them, the shape of the outer ring tube 11 matches the cross-sectional shape of the concrete structure, and can be a steel tube with a wall thickness of 8-20mm. The material can be high-strength steel or alloy steel and other materials; the length of the outer ring tube 11 is about 300-500mm, and one end is welded to the inner flange 10 to bear force together with it; and by setting an engaging tooth 27 at the end of the outer ring tube 11 away from the inner flange 10, it forms a whole that bears force together with the concrete 15. The engaging tooth 27 is a steel block protruding into the interior of the concrete 15, which is evenly welded to the inner wall of the outer ring tube 11, and the number is preferably 10-20.

[0074] Furthermore, the cross section of the concrete structure is polygonal, and corner angle steels 17 are provided at the corners of the outer surface of the concrete structure, and adjacent corner angle steels 17 are connected by gusset plates 28 to form a lattice. In this embodiment, the cross section of the concrete structure is a concrete tubular structure, which can be a square ring or a regular hexagonal ring, etc. Corner angle steels 17 are provided at each corner of the outer surface of the concrete structure to protect the corner concrete, reduce stress concentration, and prevent damage to the corners. Adjacent corner angle steels 17 are connected by a plurality of gusset plates 28 arranged at intervals along the supporting direction to form a lattice to protect the internal concrete structure. Both ends of the corner angle steels 17 can be connected to the outer ring tubes 11 at both ends of the concrete structure.

[0075] Furthermore, the steel skeleton includes a spiral stirrup 14 and a plurality of non-prestressed longitudinal bars 12, wherein the plurality of non-prestressed longitudinal bars 12 are arranged at intervals along the outer side of the spiral stirrup 14 and are all connected to the spiral stirrup 14; and the plurality of prestressed longitudinal bars 13 are arranged at intervals along the inner side of the spiral stirrup 14. Figure 3-6As shown, in the concrete 15 of this embodiment, a plurality of non-prestressed longitudinal bars 12 are arranged along the support direction, and the plurality of non-prestressed longitudinal bars 12 are arranged at intervals on the outside of the spiral stirrups 14 and welded to the spiral stirrups 14, so as to improve the strength of the concrete structure; and the two ends of the plurality of non-prestressed longitudinal bars 12 are respectively welded to the inner sides of the inner flanges 10 of the two end steel structures, and the two ends of the spiral stirrups 14 can be respectively welded to the inner sides of the inner flanges 10 of the two end steel structures, so that the concrete structure and the end steel structure are tightly connected as one, so as to improve the integrity of the prefabricated component, and the non-prestressed longitudinal bars 12 can solve the bending problem of the assembled support and increase the ductility of the concrete prefabricated support. In the process of pouring concrete, the spiral stirrups 14 can play a hooping role on the concrete 15 and increase the support strength. Embodiment 2

[0076] like Figure 1 and Figure 2 As shown, this embodiment provides an internal support system, including a protective structure 1, a crown beam 2, a waist beam and an assembled internal support; a crown beam 2 is provided on the top of the protective structure 1, a waist beam is provided on the inner side of the protective structure 1, and the assembled internal support is supported between the opposite sides of the waist beam and between the opposite sides of the crown beam 2; the assembled internal support is formed by splicing a plurality of post-tensioned precast concrete support members 3 provided in the first embodiment; embedded parts 4 are embedded in the crown beam 2 or the waist beam, and vertical adjustment and positioning devices 6 for supporting and adjusting the vertical position of the assembled internal support are fixed on the two opposite side walls of the protective structure 1, and the two ends of the assembled internal support are respectively supported on the vertical adjustment and positioning devices 6 on both sides and connected to the embedded parts 4 on both sides. According to the vertical position of the support, the vertical adjustment positioning device 6 is fixed on the side wall of the enclosure 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 precision construction, while providing temporary support for the support member. The accompanying drawings of this embodiment are described by taking the crown beam 2 as an example, and the situation of the waist beam refers to the crown beam 2.

[0077] The hollow parts of multiple post-tensioned precast concrete support members 3 of the prefabricated internal support of this embodiment are connected, so that the bearing capacity of the prefabricated support is higher and the deformation resistance is stronger; and the post-tensioned precast concrete support members 3 can be designed with several fixed module segments of appropriate lengths as needed. They should not be too long, as too long a length is not suitable for hoisting construction, and too short a length leads to too many joints and difficulty in connection; as an implementation method, the post-tensioned precast concrete support members 3 can be designed with standard modules of specifications such as 4m, 5m, 6m, and an end segment module of 2m. According to the actual needs of the foundation pit, post-tensioned precast concrete support members 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.

[0078] Furthermore, the vertical adjustment positioning device 6 includes a positioning I-shaped steel 30 for positioning the post-tensioned precast concrete support member 3 and an adjustment mechanism for adjusting the vertical position of the post-tensioned precast concrete support member 3; 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-shaped steel 30; the positioning support of the post-tensioned precast concrete support member 3 is on the upper flange plate of the positioning I-shaped steel 30, such as Fig. 20 shown.

[0079] 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; Fig.13 As shown, the first length-adjustable rod 31 is arranged horizontally, and the positioning I-shaped steel 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. Fig.10 and Fig.13 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.

[0080] 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; Figure 21-22 As shown, the fixed steel plate 37 is fixed to the side wall of the enclosure structure 1 by expansion bolts 36, and the ear plate 35 is fixed to the fixed steel plate 37; the second length adjustable rod 32 and the third length adjustable rod 33 are both 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.

[0081] Furthermore, a plurality of bolt holes 18 are provided on the outer flange 8 of the end steel structure of the post-tensioned precast concrete support member 3 in the circumferential direction, and the corresponding bolt holes 18 on the adjacent outer flanges 8 of the adjacent post-tensioned precast concrete support members 3 are connected by bolts 16 respectively. Figure 7 and Figure 8 As shown, the end of the post-tensioned precast concrete support member 3 of this embodiment adopts a boot beam node and is connected by multiple bolts 16 to ensure the rigid connection of the intermediate node, achieve equal strength between the node and the member, ensure that the assembled support achieves the same or similar integrity, rigidity and bearing capacity as the cast-in-place concrete support, ensure the safety of the foundation pit, and is easy to install and disassemble, which is convenient for factory production and large-scale promotion and application.

[0082] As an implementation method, a disassembly pad 56 is provided between at least two adjacent post-tensioned precast concrete support members 3 on the assembled inner support; both ends of the assembled inner support are directly connected to the corresponding embedded parts 4. Figure 1 As shown, in the prefabricated inner support of the present embodiment, at least one disassembly pad 56 is provided. By placing the disassembly pad 56 between two post-tensioned precast concrete support members 3, the disassembly pad 56 can be removed first during disassembly to eliminate the axial force between the post-tensioned precast concrete support members 3. The remaining prefabricated members can then be easily disassembled, thereby effectively solving the problem of difficult disassembly of prefabricated supports several meters long and improving the disassembly efficiency of prefabricated supports.

[0083] Among them, the disassembly pad 56 is provided with a plurality of bolt holes along the circumferential direction, and the bolt holes on the disassembly pad 56 correspond to the bolt holes 18 on the outer flange 8 one by one; for the disassembly pad 56 installed between the post-tensioned precast concrete support members 3, the bolts 16 are sequentially passed through the corresponding bolt holes 18 on the outer flange 8 of one of the post-tensioned precast concrete support members 3, the corresponding bolt holes on the disassembly pad 56 and the corresponding bolt holes 18 on the outer flange 8 of the other post-tensioned precast concrete support member 3 to achieve the splicing of adjacent post-tensioned precast concrete support members 3; the disassembly pad 56 can be a steel ring with a thickness of 30-100 mm, the size of which is exactly the same as that of the outer flange 8, or it can be a steel ring spliced ​​together in multiple sections, such as two semicircular steel rings or multiple fan-shaped steel rings, and the multiple sections of the steel rings are not connected; the surface of the disassembly pad 56 needs to be smooth, and a layer of lubricant can be applied to both sides of the disassembly pad 56 before construction to reduce the difficulty of disassembly.

[0084] As another embodiment, one end of the assembled inner support is connected to the corresponding embedded part 4 through a telescopic structure, and the other end is directly connected to the corresponding embedded part 4, and a jack 48 is provided between the end of the assembled inner support connected to the telescopic structure and the corresponding embedded part 4, and the jack 48 is electrically connected to the control system 50. Figure 2As shown, in this embodiment, the length of the end joint can be adjusted through the telescopic structure, so as to adjust the construction error; at the same time, a jack 48 is provided, and the jack 48 is an intelligent jack, which has sufficient jacking force, and can sense its own stress and transmit it to the control system 50 through the wire 49. The control system 50 responds accordingly according to the stress to adjust its jacking force and elongation, forming an intelligent stress compensation device, which can construct prestress as needed, meet the needs of prestress loss and support relaxation requiring repeated loading, and in the use of the prefabricated support, stress relaxation will be promptly compensated, and excessive stress will be promptly warned to prevent local instability of the foundation pit and cause damage to the entire foundation pit; the size of the jack 48 should not be too large to avoid affecting the connection of the telescopic structure.

[0085] like Fig.13 As shown, the telescopic structure includes a first telescopic joint 38 and a second telescopic joint 39, which are respectively connected to the post-tensioned precast concrete support member 3 and the embedded member 4 and have the same structure, and both include a solid steel plate 42, a U-hole steel plate 43, a U-shaped steel plate 45 and a stiffening plate 44; one end of the U-shaped steel plate 45 passes through the U-shaped hole on the U-hole steel plate 43 and is welded to the solid steel plate 42, and a plurality of rows of oblong bolt holes are provided on the two side walls of the other end; the solid steel plate 42 and the U-hole steel plate 43 are connected to the U-shaped hole on the U-hole steel plate 43 and are welded to the solid steel plate 42; the two side walls of the solid steel plate 42 and the U-shaped steel plate 45 are connected to ... U-shaped steel plate 45 and the U-shaped steel plate 45 are connected to the U-shaped steel plate 45; the two side walls of the U-shaped steel plate 45 and the U-shaped steel plate 45 are connected to the U-shaped steel plate 45; the two side walls of the U-shaped steel plate 45 and the U-shaped steel plate 45 are connected to the U-shaped steel plate 45; the two side walls of the The U-hole steel plate 43 is connected by a stiffening plate 44, and the side wall of the U-shaped steel plate 45 is welded to the U-hole steel plate 43; the U-shaped steel plate 45 of the first expansion joint 38 is stuck in the U-shaped steel plate 45 of the second expansion joint 39, and the oblong bolt hole on the first expansion joint 38 is connected with the oblong bolt hole on the second expansion joint 39 through an adjusting bolt 47; the front end and the rear end of the jack 48 are respectively pressed against the solid steel plate 42 of the first expansion joint 38 and the solid steel plate 42 of the second expansion joint 39. The U-shaped steel plate 45 of this embodiment is provided with multiple rows of oblong bolt holes, and the oblong bolt holes are arranged along the supporting direction. The oblong bolt holes on the first expansion joint 38 are connected with the oblong bolt holes on the second expansion joint 39 by adjusting bolts 47. The end of the supporting member and the crown beam 2 or the waist beam node adopt this variable position oblong bolt hole 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 bolt holes as needed to change the length of the joint, thereby adjusting the construction error. Optimally, a drainage hole 51 is reserved on the bottom plate of the U-shaped steel plate 45 to prevent rainwater from accumulating in the U-shaped space where the jack 48 is located and damaging the jack 48; at the same time, the size of the drainage hole 51 should not be too large to prevent the steel plate at the joint from being weakened.

[0086] The size of the U-shaped steel plate 45 of the first expansion joint 38 is smaller than that of the U-shaped steel plate 45 of the second expansion joint 39, so that the U-shaped steel plate 45 of the first expansion joint 38 can be just stuck in the U-shaped steel plate 45 of the second expansion joint 39 to form a U-shaped groove, but the oblong bolt holes on the U-shaped steel plate 45 of the first expansion joint 38 and the oblong bolt holes on the U-shaped steel plate 45 of the second expansion joint 39 must be at the same height and the spacing is also the same; in addition, if Figure 14-15 As shown, the solid steel plate 42 and the U-hole steel plate 43 can be square or other shapes, and the U-shaped hole on the U-hole steel plate 43 matches the size of the U-shaped steel plate 45. The U-shaped steel plate 45 passes through the U-shaped hole on the U-hole steel plate 43 and is welded to the U-hole steel plate 43. At the same time, a plurality of stiffening plates 44 arranged at intervals along the outer wall of the U-shaped steel plate 45 are used to connect the solid steel plate 42 and the U-hole steel plate 43, and the inner side of the stiffening plate 44 is welded to the U-shaped steel plate 45 to improve the rigidity of the connection node, ensure that the edge node and the supporting member have the same or similar integrity, rigidity and bearing capacity as the cast-in-place concrete support, and ensure the safety of the foundation pit. Fig.16 As shown, the stiffening plate 44 of this embodiment has the same structure as the stiffening rib 9.

[0087] In the above two embodiments, the structures of the embedded parts 4 in the crown beam or waist beam at both ends of the assembled support can be the same, and both adopt the following method: Fig.10 or Fig.13 The structure shown in can also be different, where one end adopts Fig.10 The other end adopts the structure shown in Fig.13 The structure shown in Figure 1 and Figure 2 shown.

[0088] in, Fig.10 The structure of the embedded part 4 shown in the figure includes an embedded outer steel plate 19, a steel spiral sleeve 20, an embedded anchor steel bar 21, an embedded inner steel plate 22 and a threaded steel bar 23. The embedded outer steel plate 19 is fixed on the inner wall of the crown beam 2 or the waist beam, and the embedded inner steel plate 22 is embedded in the crown beam 2 or the waist beam. A plurality of embedded anchor steel bars 21 are fixed on the embedded inner steel plate 22, and a steel spiral sleeve 20 is fixed at one end of the embedded anchor steel bar 21. A plurality of threaded steel bars 23 pass through the outer flange 8 and the corresponding bolt holes 18 on the embedded outer steel plate 19 in sequence and are fixed to the steel spiral sleeve 20. The embedded outer steel plate 19 matches the prefabricated support section form and can be a rectangular steel plate with a thickness of 10-20 mm and a size slightly larger than the outer diameter of the prefabricated support section. The embedded outer steel plate 19 is evenly arranged with a plurality of bolt holes 18 along the circumferential direction, and the number and arrangement position of the bolt holes 18 are the same as those of the outer flange 8, such as Fig.12 As shown, it can be used as a template for casting the crown beam 2 or the waist beam; the shape and size of the embedded inner steel plate 22 can be completely consistent with the outer flange 8, such as Fig.11As shown, the thickness is determined according to the needs; the embedded inner steel plate 22 is deeply buried in the crown beam 2 or the waist beam, and mainly plays the role of anchoring the embedded anchor steel bar 21, and it is not recyclable. In order to save costs, its material can be lower than the steel member of the end steel structure; the steel spiral sleeve 20 is a steel sleeve with an inner thread, and the inner diameter is consistent with the outer diameter of the embedded anchor steel bar 21; one end of the steel spiral sleeve 20 is connected to the embedded anchor steel bar 21, and the embedded inner steel plate 22, the embedded anchor steel bar 21 connected with the steel spiral sleeve 20, the embedded outer steel plate 19 and the crown beam are constructed as a whole; when constructing the end node, multiple threaded steel bars 23 can be sequentially passed through the corresponding bolt holes 18 on the outer flange 8, the corresponding bolt holes 18 on the embedded outer steel plate 19 and the corresponding steel spiral sleeve 20 to tighten, so as to realize the connection between the prefabricated component and the crown beam 2 or the waist beam; when disassembling, it is only necessary to screw the shorter length of the threaded steel bar 23 out of the steel spiral sleeve 20 to realize disassembly, and the required construction space is small, which is convenient for construction.

[0089] Fig.13 The embedded part 4 structure shown in the figure includes two embedded steel plates 57 and a plurality of embedded screws 54 arranged relatively to each other; one of the embedded steel plates 57 is fixed to the inner wall of the crown beam 2 or the waist beam, and can be used as a template for pouring the crown beam 2 or the waist beam, and the other embedded steel plate 57 is buried in the crown beam 2 or the waist beam to play an anchoring role; a plurality of screw holes are provided on the two embedded steel plates 57, one end of the plurality of embedded screws 54 passes through the corresponding screw holes on the two embedded steel plates 57 in turn and is welded to the two embedded steel plates 57, and the other end extends out of the crown beam 2 or the waist beam; the end of the post-tensioned precast concrete support member 3 can be adopted Fig.13In the structure shown in the figure, the inner flange 10 is directly welded to an outer ring plate 52, and the inner ring plate 53 is welded to the outside of the outer ring tube 11. The outer ring plate 52 and the inner ring plate 53 are welded by multiple stiffening plates 44. The shapes of the outer ring plate 52 and the inner ring plate 53 match the prefabricated components, and both are provided with multiple screw holes. When the embedded part 4 is directly connected to the post-tensioned precast concrete support member 3, one end of the multiple embedded screws 54 extending out of the crown beam 2 or the waist beam passes through the corresponding screw holes on the outer ring plate 52 and the inner ring plate 53 in turn and is fixed by nuts to realize the connection between the crown beam 2 or the waist beam and the end fixed node of the assembled support. When the embedded part 4 is connected to the post-tensioned precast concrete support member 3 through a telescopic structure, the first telescopic joint A plurality of screw holes are provided on the solid steel plate 42 and the U-hole steel plate 43 of the second expansion joint 38 and the second expansion joint 39, one end of a plurality of embedded screws 54 passes through the corresponding screw holes on the two embedded steel plates 57 in sequence and is welded to the two embedded steel plates 57, and the other end extends out of the crown beam 2 or the waist beam and passes through the corresponding screw holes on the solid steel plate 42 and the U-hole steel plate 43 of the second expansion joint 39 in sequence and is then fixed by a nut, and a plurality of screws 40 pass through the corresponding screw holes on the inner ring plate 53 and the outer ring plate 52 of the prefabricated component and the corresponding screw holes on the solid steel plate 42 and the U-hole steel plate 43 of the first expansion joint 38 in sequence and are then fixed by a nut, thereby realizing the connection between the crown beam 2 or the waist beam and the end telescopic node of the assembled support.

[0090] In this embodiment, all steel structures such as the inner ring tube 7, the outer flange 8, the outer ring tube 11, the inner flange 10, the stiffening ribs 9, the outer ring plate 52, the inner ring plate 53, the solid steel plate 42, the U-hole steel plate 43, the U-shaped steel plate 45 and other parts that are in direct contact with the outside world need to be pre-coated with anti-rust materials to prevent the surface of the steel structure from being rusted and damaged, resulting in a reduction in strength; the bolts 16 use high-strength bolts. Embodiment 3

[0091] This embodiment provides a construction method of the post-tensioned precast concrete support member 3 provided in the first embodiment, comprising the following steps:

[0092] S1. Make the end steel structure in the steel structure processing plant;

[0093] S2, tying the non-prestressed longitudinal reinforcement 12 and the spiral stirrups 14 in a prefabricated component processing plant, and spot welding the non-prestressed longitudinal reinforcement 12 and the spiral stirrups 14 to form a steel reinforcement skeleton;

[0094] S3, transport the end steel structure to the prefabricated component processing plant, and weld the non-prestressed longitudinal reinforcement 12 to the inner flange 10 of the end steel structure, fix the corrugated pipe 25, reserve the grouting pipe 55 and the grouting pipe at the corresponding position in the steel skeleton, set the corner angle steel 17 at the corner of the prefabricated component and weld it to the gusset plate 28 to form a lattice shape;

[0095] S4, pouring high-strength concrete 15 into the component mold, vibrating and then using high-pressure steam curing to reach the design strength;

[0096] S5, placing the component mold and the prefabricated component as a whole on the prestressed tensioning workbench, inserting the prestressed longitudinal reinforcement 13 into the corrugated tube 25, then tensioning the prestressed longitudinal reinforcement 13, and anchoring the end of the prestressed longitudinal reinforcement 13 in the end steel structure by using the anchor 26, and finally pouring cement slurry into the corrugated tube 25 through the grouting pipe until slurry emerges from the reserved slurry emitting pipe 55, so that the prestressed longitudinal reinforcement 13 and the prefabricated component become a whole;

[0097] S6. Remove the formwork to form the post-tensioned precast concrete support member 3.

[0098] In terms of production technology, the end steel structure is prefabricated by a steel structure processing plant, and the pouring of concrete is completed in a prefabricated component processing plant, so that the steel structure processing and concrete pouring work are separated. This can give full play to the advantages of the steel structure processing plant and the prefabricated component processing plant, avoid on-site welding operations in the prefabricated concrete plant, and ensure product quality. Embodiment 4

[0099] like Figure 1 As shown, this embodiment provides a construction method of the inner support system provided in the second embodiment with the disassembly pad 56 installed, comprising the following steps:

[0100] S1, prefabricate the post-tensioned precast concrete support member 3, embedded parts 4 and disassembly pads 56 in a factory, and transport them to the construction site; wherein the post-tensioned precast concrete support member 3 can be manufactured using the construction method provided in Example 3;

[0101] S2. According to the width of the foundation pit, the post-tensioned precast concrete support members 3 of different lengths are spliced ​​section by section by means of bolts 16, and at the same time, a disassembly pad 56 is installed between at least two adjacent post-tensioned precast concrete support members 3 to assemble an assembled support having a length matching the width of the foundation pit;

[0102] When splicing two post-tensioned precast concrete support members 3, first align the outer flanges 8 at the ends of the two precast members, and then sequentially pass the bolts 16 through the outer flanges 8 at the ends of the two precast members to achieve splicing of the two precast members; and when assembling two precast members with a disassembly pad 56 installed in the middle, first apply a layer of lubricant on both sides of the disassembly pad 56, then place the disassembly pad 56 between the two precast members, and sequentially pass the bolts 16 through the bolt holes 18 on the outer flange 8 at the end of one of the precast members, the bolt holes on the disassembly pad 56, and the bolt holes 18 on the outer flange 8 at the end of the other precast member;

[0103] S3, over-excavate the foundation pit, then drive expansion bolts 36 at designated positions every 2-4m on the side wall of the enclosure structure 1, install and fix steel plates 37, weld lug plates 35, and then install and fix vertical adjustment and positioning devices 6; for the foundation pit with intermediate temporary columns, construct steel connecting beams;

[0104] S4. The assembled support after hoisting is placed on the vertical adjustment positioning device 6. The assembled support is adjusted to the designed vertical position by the vertical adjustment positioning device 6. It is necessary to ensure that the center line of the prefabricated support is horizontal and the center is located at the center of the crown beam 2 or the waist beam; for the construction of the steel connecting beam, the assembled support is placed on the vertical adjustment positioning device 6 and the steel connecting beam; the embedded part 4 is fixed at the support design position in the crown beam 2 or the waist beam to be cast;

[0105] When the embedded parts 4 at both ends of the assembled support are Fig.10 In the structure shown in the figure, the embedded outer steel plate 19, the embedded inner steel plate 22 and the embedded anchor steel bar 21 connected with the steel bar spiral sleeve 20 of the embedded part 4 are fixed at the support design position in the crown beam 2 or the waist beam to be cast; when the embedded parts 4 at both ends of the assembled support are Fig.13 In the structure shown in the figure, two embedded steel plates 57 and a plurality of embedded screws 54 of the embedded part 4 are fixed at the support design position in the crown beam 2 or waist beam to be cast; when the embedded part 4 at one end of the assembled support is adopted Fig.10 The structure shown in FIG. 1 is shown in FIG. 2 , and the embedded part 4 at the other end is Fig.13 When the structure shown in , refer to the above practices respectively, and no further details will be given here;

[0106] S5, casting the crown beam 2 or waist beam, using the embedded outer steel plate 19 or the embedded steel plate 57 of the embedded part 4 as the template of the crown beam 2 or waist beam; embedding the embedded inner steel plate 22 and the embedded anchoring steel bar 21 connected with the steel bar spiral sleeve 20 therein, and at the same time leaving a hole for installing the threaded steel bar 23 on the crown beam 2 or waist beam, and / or embedding two embedded steel plates 57 and the embedded screw 54 therein;

[0107] S6. After the crown beam 2 or the waist beam reaches the design strength, the threaded steel bar 23 is passed through the bolt hole 18 on the outer flange 8 of the end steel structure of the assembled support end and the bolt hole 18 of the embedded outer steel plate 19 and is tightened with the steel bar spiral sleeve 20, and / or the embedded screw 54 is passed through the screw hole on the end steel structure of the assembled support end and fixed with a nut to complete the installation of the end node, and the vertical adjustment and positioning device 6 is disassembled and recovered;

[0108] S7. After the construction is completed, first unscrew the bolts 16 on the two post-tensioned precast concrete support members 3 with the disassembly pads 56 installed in the middle, and remove the disassembly pads 56;

[0109] S8. Unscrew the bolts 16 section by section and recycle the post-tensioned precast concrete support member 3. Unscrew the threaded steel bars 23 at the end nodes for recycling.

[0110] In this embodiment, a disassembly pad 56 is installed between at least two adjacent post-tensioned precast concrete support members 3, which serves as the first breakthrough point when disassembling the prefabricated support. The disassembly pad 56 is small in size and coated with lubricant, so the disassembly difficulty is much smaller. Once the disassembly pad 56 is removed, the axial force of the entire prefabricated support disappears, and the prefabricated support members can be easily disassembled one by one, thereby reducing the difficulty of disassembling the precast concrete support members and improving the disassembly efficiency of the prefabricated support. Embodiment 5

[0111] This embodiment provides a construction method of the inner support system with a retractable structure provided in the second embodiment, comprising the following steps:

[0112] S1, prefabricate the post-tensioned precast concrete support member 3, the embedded parts 4, the first expansion joint 38 and the second expansion joint 39 in a factory, and transport them to the construction site; wherein the post-tensioned precast concrete support member 3 can be manufactured using the construction method provided in Example 3;

[0113] S2. According to the width of the foundation pit, the post-tensioned precast concrete support members 3 of different lengths are spliced ​​section by section by means of bolts 16 to assemble into an assembled support having a length matching the width of the foundation pit; and the first expansion joint 38 of the telescopic structure is connected to the post-tensioned precast concrete support member 3 at one end of the assembled support by means of a screw rod 40;

[0114] 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;

[0115] When the embedded parts 4 at both ends of the assembled support are Fig.10 In the structure shown in the figure, the embedded outer steel plate 19, the embedded inner steel plate 22 and the embedded anchor steel bar 21 connected with the steel bar spiral sleeve 20 of the embedded part 4 are fixed at the support design position in the crown beam 2 or the waist beam to be cast; when the embedded parts 4 at both ends of the assembled support are Fig.13 In the structure shown in the figure, two embedded steel plates 57 and a plurality of embedded screws 54 of the embedded part 4 are fixed at the support design position in the crown beam 2 or waist beam to be cast; when the embedded part 4 at one end of the assembled support is adopted Fig.10 The structure shown in FIG. 1 is shown in FIG. 2 , and the embedded part 4 at the other end is Fig.13 When the structure shown in , refer to the above practices respectively, and no further details will be given here;

[0116] When casting the crown beam 2 or waist beam, the embedded outer steel plate 19 or the embedded steel plate 57 of the embedded part 4 is used as the template of the crown beam 2 or waist beam; the embedded inner steel plate 22 and the embedded anchoring steel bar 21 connected with the steel bar spiral sleeve 20 are embedded therein, and at the same time, a hole for installing the threaded steel bar 23 is reserved on the crown beam 2 or waist beam, and / or two embedded steel plates 57 and the embedded screw 54 are embedded therein;

[0117] S4, after the crown beam 2 or the waist beam reaches the design strength, the second expansion joint 39 of the telescopic structure is fixed to the embedded screw 54 extending from the embedded part 4 on one side by a nut, or the threaded steel bar 23 is passed through the second expansion joint 39 and the bolt hole 18 of the embedded outer steel plate 19 and is tightened with the steel bar spiral sleeve 20;

[0118] S5, over-excavate the foundation pit, then drive expansion bolts 36 into the designated positions every 2-4m on the side wall of the enclosure structure 1, install the fixed steel plate 37, weld the ear plate 35, and then install and fix the vertical adjustment positioning device 6;

[0119] S6. The assembled support is hoisted and placed on the vertical adjustment and positioning device 6. The assembled support is adjusted to the designed vertical position by the vertical adjustment and positioning device 6, so that the U-shaped steel plate 45 of the first expansion joint 38 is stuck in the U-shaped steel plate 45 of the second expansion joint 39, and the post-tensioning precast concrete support member 3 at the other end of the assembled support is tightened with the steel spiral sleeve 20 in the embedded part 4 on the other side through the threaded steel bar 23, or fixed with the embedded screw 54 in the embedded part 4 on the other side through the nut;

[0120] S7, placing a jack 48 in the U-shaped steel plate 45, applying pressure to the designed value through the control system, so that both ends of the jack 48 are respectively pressed against the solid steel plate 42 of the first expansion joint 38 and the solid steel plate 42 of the second expansion joint 39;

[0121] S8, insert the adjusting bolts 47 into the oblong bolt holes on the side walls of the U-shaped steel plate 45 of the first expansion joint 38 and the U-shaped steel plate 45 of the second expansion joint 39, and tighten them to complete the installation of the end nodes, disassemble and recover the vertical adjustment positioning device 6;

[0122] S9. After the construction is completed, the jack 48 is loosened, the adjusting bolts 47 and nuts are unscrewed, the expansion joint and the bolts 16 are removed, and the post-tensioned precast concrete support member 3 is recovered.

[0123] In this embodiment, the first expansion joint 38 and the second expansion joint 39 are connected by an adjusting bolt 47, the first expansion joint 38 and the prefabricated support member at one end of the assembled support are connected by a screw 40, the second expansion joint 39 and the embedded part 4 are connected by an embedded screw 54, and the prefabricated support member at the other end of the assembled support is connected to the embedded part 4 by a threaded steel bar 23, which is easy to disassemble. Therefore, after the construction of the foundation pit project is completed, the jack 48 is loosened, and the adjusting bolt 47 connecting the first expansion joint 38 and the second expansion joint 39 is removed to release the pressure, and then the screw 40 and the bolt 16 are removed, and the threaded steel bar 23 is screwed out, and the prefabricated support members can be disassembled one by one, and the prefabricated support members can be recycled to achieve multiple recycling and reduce costs.

[0124] When the prefabricated support members are spliced ​​section by section in step S2 of the present embodiment, the outer flanges 8 at the ends of the two prefabricated support members are first aligned, and then the bolts 16 are sequentially passed through the outer flanges 8 at the ends of the two prefabricated members to achieve the splicing of the two prefabricated members; when the first expansion joint 38 is spliced ​​with the prefabricated support member located at the end, the screw holes on the outer ring plate 52 at the end of the prefabricated support member are first aligned with the screw holes 41 on the solid steel plate 42 of the first expansion joint 38, and then the screws 40 are sequentially passed through the inner ring plate 53 and the outer ring plate 52 at the end of the prefabricated support member, the solid steel plate 42 of the first expansion joint 38, and the screw holes on the U-hole steel plate 43 and fixed by nuts.

[0125] The assembled supports in the fourth and fifth embodiments of the present invention can be rigidly connected to the crown beam 2 or the waist beam, so that in an ultra-deep foundation pit, the assembled supports can replace multiple traditional concrete supports to improve the assembly rate.

[0126] 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. An internal support system, characterized in that: It comprises a protective structure, a crown beam, a waist beam and an assembled inner support; a crown beam is arranged on the top of the protective structure, a waist beam is arranged on the inner side of the protective structure, and the assembled inner support is supported between the opposite sides of the waist beam and between the opposite sides of the crown beam; the assembled inner support is formed by splicing a plurality of post-tensioned precast concrete support members; embedded parts are embedded in the crown beam or the waist beam, and vertical adjustment positioning devices for supporting and adjusting the vertical position of the assembled inner support are fixed on the two opposite side walls of the protective structure, and the two ends of the assembled inner support are respectively supported on the vertical adjustment positioning devices on both sides and connected to the embedded parts on both sides; The post-tensioned precast concrete support member comprises a concrete structure and two end steel structures arranged at two ends of the concrete structure in the support direction; the concrete structure comprises concrete having a hollow portion penetrating along the support direction, a steel skeleton and a plurality of corrugated pipes are arranged in the concrete, and the two ends of the steel skeleton are respectively connected to the two end steel structures; each of the corrugated pipes is tensioned with prestressed longitudinal bars and poured with cement slurry, and both ends of the prestressed longitudinal bars extend out of the corrugated pipes and are respectively anchored in the two end steel structures through anchors; The vertical adjustment and positioning device includes a positioning I-shaped steel for positioning the post-tensioned precast concrete support member and an adjustment mechanism for adjusting the vertical position of the post-tensioned precast concrete support 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-shaped steel; the positioning support of the post-tensioned precast concrete support member is on the upper flange plate of the positioning I-shaped steel; 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 arranged horizontally, 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.

2. The internal support system according to claim 1, characterized in that: The end steel structure includes an outer flange and an inner flange arranged opposite to each other, an inner ring tube and a plurality of stiffening ribs are arranged between the outer flange and the inner flange; the two ends of the inner ring tube are respectively connected to the outer flange and the inner flange, and the three side surfaces of each stiffening rib are respectively connected to the outer flange, the inner ring tube and the inner flange; the steel skeleton is connected to the inner flange; prestressed tendon tensioning holes are arranged on the inner flange, and the ends of the prestressed longitudinal tendons pass through the prestressed tendon tensioning holes and are anchored to the inner flange through anchors.

3. The internal support system according to claim 2, characterized in that: An outer ring pipe is connected to the side of the inner flange away from the outer flange, and the end of the concrete structure is located in the outer ring pipe; a circle of bite teeth is provided on the inner wall of the outer ring pipe away from the inner flange, and the bite teeth are embedded in the concrete.

4. The internal support system according to claim 1, characterized in that: The cross section of the concrete structure is polygonal, and angle steels are arranged at the corners of the outer surface of the concrete structure, and adjacent angle steels are connected by connecting plates to form a lattice structure.

5. The internal support system according to claim 1, characterized in that: A disassembly pad is provided between at least two adjacent post-tensioned precast concrete support members on the assembled inner support.

6. The internal support system according to claim 1, characterized in that: One end of the assembled inner support is connected to the corresponding embedded part through a telescopic structure, and a jack is provided between one end of the assembled inner support connected to the telescopic structure and the corresponding embedded part, and the jack is electrically connected to the control system; 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 assembled inner support and the embedded part and have the same structure, the first telescopic joint and the second telescopic joint are respectively connected to the post-tensioned precast concrete support member and the embedded part and have the same structure, and both include solid steel plates, U-hole steel plates, U-shaped steel plates and reinforced 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 bolt 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 expansion joint is stuck in the U-shaped steel plate of the second expansion joint, and the oblong bolt hole on the first expansion joint is connected to the oblong bolt hole on the second expansion joint through an adjusting bolt; the front end and the rear end 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.

7. The internal support system according to claim 1, characterized in that: The construction method of the post-tensioned precast concrete support member comprises the following steps: S1. Make the end steel structure in the steel structure processing plant; S2. Tie the non-prestressed longitudinal reinforcement and spiral stirrups in the prefabricated component processing plant, and spot weld the non-prestressed longitudinal reinforcement and spiral stirrups to form a steel skeleton; S3, transport the end steel structure to the prefabricated component processing plant, weld the non-prestressed longitudinal reinforcement to the inner flange of the end steel structure, fix the corrugated pipe, reserved grouting pipe and grouting pipe at the corresponding position in the steel skeleton, set the corner angle steel at the corner of the prefabricated component and weld it to the tie plate to form a lattice shape; S4. Pour concrete into the component mold, vibrate and use high-pressure steam curing to reach the designed strength; S5, placing the component mold and the prefabricated component as a whole into the prestressed tensioning workbench, inserting the prestressed longitudinal reinforcement into the corrugated pipe, then tensioning the prestressed longitudinal reinforcement, and anchoring the end of the prestressed longitudinal reinforcement in the end steel structure by using an anchor, and finally pouring cement slurry into the corrugated pipe through the grouting pipe until slurry emerges from the reserved slurry emitting pipe, so that the prestressed longitudinal reinforcement and the prefabricated component become a whole; S6. Remove the formwork to form post-tensioned precast concrete support components.

8. A construction method of the internal support system according to claim 5, characterized in that: The steps include: S1. Prefabricate the post-tensioned precast concrete support members, embedded parts and disassembly pads in a factory and transport them to the construction site; S2. According to the width of the foundation pit, the post-tensioned precast concrete support members of different lengths are spliced ​​section by section by bolts, and at the same time, a disassembly pad is installed between at least two adjacent post-tensioned precast concrete support members to assemble an assembled support with a length matching the width of the foundation pit; 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. Place the assembled support on the vertical adjustment and positioning device after hoisting, and adjust the assembled support to the designed vertical position; fix the embedded parts at the designed position of the support in the crown beam or waist beam to be cast; S5. Cast the crown beam or waist beam and bury the embedded parts therein; S6. After the crown beam or waist beam reaches the design strength, fix the end of the assembled support to the embedded parts, complete the installation of the end node, and disassemble and recover the vertical adjustment and positioning device; S7. After the construction is completed, first unscrew the bolts on the two post-tensioned precast concrete support members with the disassembly pads installed in the middle, and remove the disassembly pads; S8. Unscrew the bolts section by section and recycle the post-tensioned precast concrete support components. Unscrew the threaded steel bars at the end nodes and recycle them.

9. A construction method of the internal support system according to claim 6, characterized in that: The steps include: S1, prefabricate the post-tensioned precast concrete support member, embedded parts, first expansion joint and second expansion joint in a factory, and transport them to the construction site; S2. According to the width of the foundation pit, the post-tensioned precast concrete support members of different lengths are spliced ​​section by section by bolts to assemble into an assembled support with a length matching the width of the foundation pit; and the first expansion joint of the telescopic structure is connected to the post-tensioned precast concrete support member at one end of the assembled support by a screw rod; 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 of the expansion structure is extended and fixed to the embedded parts; 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 assembled prefabricated support is hoisted and 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 post-tensioned precast concrete support member at the other end of the prefabricated support is fixed to the embedded part on the other side; 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, inserting adjusting bolts into the oblong bolt holes on the U-shaped steel plate of the first expansion joint and the side wall of the U-shaped steel plate of the second expansion joint, and tightening them, completing the installation of the end nodes, disassembling and recovering the vertical adjustment positioning device; S9. After the construction is completed, release the jack, unscrew the adjusting bolts, remove the expansion joints and bolts, and recycle the post-tensioned precast concrete support components.

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