Joint node of composite inclined strut pile of foundation pit supporting system

Abstract

The utility model discloses a joint node of a composite diagonal bracing pile of a foundation pit supporting system, the upper end of a steel pipe diagonal bracing abuts against a coping beam of a foundation pit, the lower end of the steel pipe diagonal bracing is in butt joint with a support at the upper end of a prefabricated concrete pile through a transition joint, the prefabricated concrete pile is an octagonal pile, and a steel octagonal hoop plate is fixed at the top of the prefabricated concrete pile. The octagonal hoop plate is provided with a circle of multiple threaded holes; the transition joint is formed by welding an upper circular steel pipe and a lower annular plate, and a circle of positioning holes corresponding to the threaded holes one by one are formed in the annular plate; each positioning hole of the annular plate and the corresponding threaded hole of the octagonal hoop plate are jointly screwed with a positioning bolt; the lower opening of the steel pipe inclined strut sleeves the transition joint circular steel pipe and a circle of positioning bolts; the lower end of the steel pipe inclined strut is butted and welded with the transition joint annular plate; and the annular plate is welded with the octagonal hoop plate. By means of the joint, the steel pipe inclined strut and the prefabricated concrete octagonal pile can be in butt joint firmly and stably, and it can be ensured that the axes of the steel pipe inclined strut and the prefabricated concrete octagonal pile are aligned.

Description

Technical Field

[0001] The utility model relates to the technical field of building foundation pit construction, in particular to a joint node of a composite diagonal bracing pile of a foundation pit support system. Background Art

[0002] At present, the country is vigorously promoting the development and construction of underground space, and many underground buildings such as underground garages, underground shopping malls, subway stations, etc. have sprung up like mushrooms after rain. For the foundation pits of such large underground projects, in order to avoid exceeding the project red line and save costs, a combined foundation pit support system of retaining piles, top beams and inclined support piles is often used.

[0003] The diagonal brace pile is a composite type, consisting of a combined diagonal pile extending below the foundation pit floor and a steel pipe diagonal brace located above the foundation pit floor. The combined diagonal pile consists of a central precast concrete square pile and an externally wrapped cement soil pile; the upper end of the steel pipe diagonal brace is against the top beam of the foundation pit, and the lower end of the steel pipe diagonal brace is connected to the upper end support of the precast concrete square pile through a transition joint. For the convenience of expression, the structure of the lower precast concrete square pile and the upper steel pipe diagonal brace is collectively referred to as a precast core pile. The construction process of the foundation pit support system is roughly as follows: first construct the retaining pile; then construct the inclined cement soil pile, and then insert the precast core pile of the same angle into the center of the inclined cement soil pile. Alternatively, the precast core pile is made hollow from top to bottom, and the drill rod is passed through the upper steel pipe diagonal brace and the lower precast concrete square pile, so that the drill bit and nozzle of the drill rod extend out of the lower end of the precast concrete square pile, and the cement soil pile is sprayed and the steel pipe diagonal brace and the precast concrete square pile are statically pressed synchronously.

[0004] The transition joint of the existing diagonal brace pile is welded by an upper round sleeve and a lower square sleeve; the upper end of the round sleeve covers the lower end of the steel pipe diagonal brace, and the wall of the round sleeve is screwed with a fastening bolt for tightening the steel pipe diagonal brace; the lower end of the square sleeve covers the upper end of the precast concrete square pile, and the top plate of the square sleeve is provided with a rectangular through hole, and a wedge-shaped insert is inserted into the rectangular through hole, and the wedge-shaped insert squeezes the precast concrete square pile and the square sleeve. In this way, the transition joint successfully connects the steel pipe diagonal brace and the precast concrete square pile, and aligns the axes of the two to ensure that the axial pressure can be transmitted smoothly and safely.

[0005] At present, technicians have found in practice that if the precast concrete square pile is changed from a square pile to an octagonal pile, a larger side surface area can be obtained with the same amount of concrete, thus significantly increasing the side friction resistance with the cement soil pile, and thus significantly improving the bearing capacity of the composite diagonal bracing pile. However, the above findings are difficult to apply in practice, and the main obstacle lies in the design of the transition joint. If the lower part of the transition joint is set as an octagonal sleeve accordingly, first of all, the manufacturing process of the octagonal sleeve itself is complicated; even after forming, the octagonal sleeve and the octagonal pile are difficult to fit together firmly, and the number of wedge-shaped inserts that need to be inserted is twice that of the square sleeve, and the operation is cumbersome and laborious; more importantly, it is difficult to align the axis of the steel pipe diagonal brace and the octagonal pile by squeezing multiple wedge-shaped inserts, so it is difficult to ensure the stable transmission of axial pressure between the two, and the connection and fixation of the transition joint to the steel pipe diagonal brace and the precast concrete pile is slightly weak. Therefore, when this position is subjected to a large axial pressure, such as when the power head statically presses the steel pipe diagonal brace and the precast concrete pile into the soil, or when the diagonal brace pile supports the water and soil side pressure transmitted through the retaining piles and the top beam after the later excavation of the foundation pit, it is often easy to fail due to buckling under the axial pressure load. Utility Model Content

[0006] The technical problem to be solved by the utility model is to provide a joint node of a composite diagonal brace pile of a foundation pit support system which can make the steel pipe diagonal brace and the precast concrete octagonal pile firmly and stably connected and can ensure that the axes of the steel pipe diagonal brace and the precast concrete octagonal pile are aligned.

[0007] The technical solution of the utility model is to provide a joint node of a composite diagonal brace pile of a foundation pit support system, which comprises a combined diagonal pile extending below the foundation pit bottom plate and a steel pipe diagonal brace located above the foundation pit bottom plate, wherein the combined diagonal pile is composed of a central precast concrete pile and an externally wrapped cement soil pile; the upper end of the steel pipe diagonal brace abuts against a top pressure beam of the foundation pit, and the lower end of the steel pipe diagonal brace is butted with a support at the upper end of the precast concrete pile via a transition joint, the precast concrete pile is an octagonal pile, and a steel octagonal hoop plate is fixed on the top of the precast concrete pile, and the octagonal hoop plate is provided with a circle of multiple threaded holes; the transition joint is welded by an upper round steel pipe and a lower annular plate, and a circle of positioning holes corresponding to the threaded holes are provided on the annular plate; each positioning hole of the annular plate is screwed together with a positioning bolt corresponding to the threaded hole of the octagonal hoop plate; the lower end of the steel pipe diagonal brace covers the transition joint round steel pipe and a circle of positioning bolts, and the lower end of the steel pipe diagonal brace abuts against and is welded to the transition joint annular plate; the annular plate is welded to the octagonal hoop plate.

[0008] Compared with the prior art, the joint nodes of the composite diagonal bracing piles using the above structural foundation pit support system have the following advantages.

[0009] First of all, the precast concrete pile is an octagonal pile. Under the premise of the same amount of concrete material, the side surface area is large, so the side friction resistance with the cement soil pile is significantly enhanced, and the bearing capacity of the composite diagonal brace pile is significantly improved; more importantly, this structure makes up for the problem that the joint between the octagonal precast concrete pile and the steel pipe diagonal brace is weak and difficult to center. A circle of bolts is used to screw the transition joint annular plate and the octagonal hoop plate of the octagonal pile first and then weld it to ensure that the transition joint and the octagonal pile are firmly and reliably connected, and the lower end of the steel pipe diagonal brace is simultaneously covered with the transition joint round steel pipe and a circle of positioning bolts, and then the bottom end of the steel pipe diagonal brace is welded to the annular plate. In this way, the round steel pipe The steel pipe and a circle of multiple positioning bolts together provide stable and balanced support for the steel pipe brace, significantly enhancing the strength and anti-buckling property of the node, ensuring that the steel pipe brace and the octagonal pile are firmly and stably connected, and ensuring that the axes of the steel pipe brace and the octagonal pile are accurately aligned; in this way, it can be ensured that the steel pipe brace and the octagonal pile can smoothly and safely transmit axial pressure, such as the pressure of the power head statically pressing the steel pipe brace and the octagonal pile into the soil, or the water and soil side pressure outside the foundation pit transmitted by the retaining piles and the top beam after the later excavation, so that the node can withstand the maximum axial pressure of up to 3000kN without deformation or buckling failure.

[0010] Preferably, the precast concrete pile is a hollow prestressed pile, and the threaded hole on the top of the precast concrete pile is the tensioning end hole left after the steel bars are tensioned. In this way, the precast concrete pile is prestressed, which can effectively avoid cracks caused by tensile stress during lifting, and has higher strength and bearing capacity. Moreover, the tensioning end hole left after the steel bars are tensioned can be reused as a threaded hole for screwing in the positioning bolts, which is a two-in-one product. There is no need to pre-embed an internal threaded sleeve at the end of the precast concrete pile to set up another threaded hole, which is more economical. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a structural schematic diagram of a composite diagonal bracing pile of a foundation pit support system where a joint node of the utility model is located.

[0012] Figure 2 It is a structural schematic diagram of a joint node of a composite diagonal bracing pile of a foundation pit support system of the utility model.

[0013] Figure 3 yes Figure 2 Schematic diagram of the decomposed state structure.

[0014] As shown in the figure, 1. foundation pit bottom plate, 2. steel pipe diagonal brace, 3. precast concrete piles, 4. cement soil piles, 5. retaining piles, 6. top beam, 7. octagonal hoop plate, 8. threaded hole, 9. round steel pipe, 10. ring plate, 11. positioning hole, and 12. positioning bolts. DETAILED DESCRIPTION

[0015] The utility model is further described below in conjunction with the accompanying drawings and specific embodiments.

[0016] like Figure 1 to Figure 3 As shown, the composite diagonal brace pile joint node of the foundation pit support system of the utility model comprises a composite diagonal brace pile extending below the foundation pit bottom plate 1 and a steel pipe diagonal brace 2 located above the foundation pit bottom plate 1, and the composite diagonal pile is composed of a precast concrete pile 3 in the center and a cement soil pile 4 wrapped outside. A top beam 6 is cast on the top of each retaining pile 5 of the foundation pit, the upper end of the steel pipe diagonal brace 2 is against the top beam 6, and the lower end of the steel pipe diagonal brace 2 is butted with the upper end support of the precast concrete pile 3 through a transition joint.

[0017] The precast concrete pile 3 is an octagonal pile, i.e., an octagonal column pile body, and in order to synchronously spin-jet the cement soil pile 4 when sinking the pile, the precast concrete pile 3 is set as a hollow pile so that the drill rod can pass through. A steel octagonal hoop plate 7 is fixed on the top of the precast concrete pile 3, i.e., the octagonal hoop plate 7 is anchored at the end of the precast concrete pile 3 and multiple longitudinal main bars of the precast concrete pile 3 are welded and fixed to the octagonal hoop plate 7. The octagonal hoop plate 7 is provided with a circle of multiple threaded holes 8, and in this embodiment, there are 6.

[0018] The transition joint is welded by an upper round steel pipe 9 and a lower annular plate 10. A circle of positioning holes 11 corresponding to the threaded holes 8 are arranged on the annular plate 10. In this embodiment, there are 6 positioning holes 11. Each positioning hole 11 of the annular plate 10 is screwed together with a threaded hole 8 corresponding to the octagonal hoop plate 7 to form a positioning bolt 12; the positioning bolt 12 is provided with an external thread and a hexagonal countersunk hole at the upper end, which is convenient for tightening with a hexagonal wrench.

[0019] The inner diameter of the lower end of the steel pipe brace 2 is slightly larger than the outer diameter of the round steel pipe 9 plus twice the diameter of the positioning bolts 12. In other words, the inscribed circle of the six positioning bolts 12 is slightly larger than the outer diameter of the round steel pipe 9, such as 1.05 times the outer diameter of the round steel pipe 9, and the circumscribed circle of the six positioning bolts 12 is slightly smaller than the inner diameter of the lower end of the steel pipe brace 2, such as 0.95 of the inner diameter of the lower end of the steel pipe brace 2; in this way, the lower end of the steel pipe brace 2 just covers the transition joint round steel pipe 9 and a circle of positioning bolts 12; it can ensure that the steel pipe brace 2 is aligned with the axis of the transition joint and the octagonal pile, and it can also ensure that the round steel pipe 9 and the positioning bolts 12 provide strong support for the lower end of the steel pipe brace 2. The lower end of the steel pipe brace 2 is abutted against and welded to the transition joint annular plate 10; the annular plate 10 is welded to the octagonal hoop plate 7.

[0020] In this embodiment, the precast concrete pile 3 is a hollow prestressed pile, and the threaded hole 8 of the octagonal hoop plate 7 at the top of the precast concrete pile 3 is a tensioning end hole left after the steel bars are tensioned.

[0021] The joint node docking process of the composite diagonal bracing pile of the utility model is as follows.

[0022] The annular plate 10 and the round steel pipe 9 are welded into a cap-shaped integral transition joint;

[0023] Align the annular plate 10 with the octagonal hoop plate 7 of the precast concrete pile 3, especially align each positioning hole 11 with the threaded hole 8 one by one, and then screw the positioning bolt 12 into each set of aligned positioning holes 11 and threaded holes 8;

[0024] Connect the lower drill rod section in the octagonal pile and the upper drill rod section in the steel pipe diagonal brace 2;

[0025] Drive the power head to press down the steel pipe diagonal brace 2, so that its lower end covers the transition joint round steel pipe 9 and a circle of positioning bolts 12, and the lower end of the steel pipe diagonal brace 2 is against the transition joint annular plate 10, and then weld the lower end of the steel pipe diagonal brace 2 to the annular plate 10;

[0026] The annular plate 10 is welded to the octagonal hoop plate 7 at the top of the precast concrete pile 3. If the transition joint is located on the guide frame at this time and the lower semicircular arc of the annular plate 10 is blocked by the guide frame, the upper semicircular arc weld of the annular plate 10 and the octagonal hoop plate 7 is welded first, and the power head is continued to be driven to press down the steel pipe diagonal support 2, the transition joint and the precast concrete pile 3 until the transition joint moves down out of the height of the guide frame, and then the remaining lower semicircular arc weld of the annular plate 10 and the octagonal hoop plate 7 is welded firmly.

Claims

1. A joint node of a composite diagonal brace pile of a foundation pit support system, comprising a composite diagonal pile extending below a foundation pit floor and a steel pipe diagonal brace located above the foundation pit floor, wherein the composite diagonal pile is composed of a central precast concrete pile and an outer cement soil pile; the upper end of the steel pipe diagonal brace is against a top beam of the foundation pit, and the lower end of the steel pipe diagonal brace is butted with the upper end support of the precast concrete pile via a transition joint, and is characterized in that: The precast concrete pile is an octagonal pile, and a steel octagonal hoop plate is fixed on the top of the precast concrete pile. The octagonal hoop plate is provided with a circle of multiple threaded holes; the transition joint is welded by an upper round steel pipe and a lower annular plate, and a circle of positioning holes corresponding to the threaded holes are provided on the annular plate; each positioning hole of the annular plate and the threaded hole corresponding to the octagonal hoop plate are screwed together with a positioning bolt; the lower end of the steel pipe diagonal brace covers the transition joint round steel pipe and a circle of positioning bolts, and the lower end of the steel pipe diagonal brace is welded against the transition joint annular plate; the annular plate is welded to the octagonal hoop plate.

2. The joint node of the composite diagonal bracing pile of the foundation pit support system according to claim 1 is characterized by: The precast concrete pile is a hollow prestressed pile, and the threaded hole on the top of the precast concrete pile is the tensioning end hole left after the steel bars are tensioned.

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