Steel-concrete composite internal support for deep foundation pit near river affected by tides and construction method

Abstract

The present invention relates to a steel-concrete composite internal support and construction method for a deep foundation pit near a river affected by tides. The structure adopts a prestressed steel composite support combined with a reinforced concrete side truss, and the steel composite support is combined with an axial force servo system to accurately apply prestress. A crown beam is cast at the top of the retaining pile, and the steel support is connected to the crown beam at the end of the retaining pile through embedded parts. The prestressed steel composite support is easy to install and dismantle, which can minimize the use of large machinery, thereby minimizing the occupation of the site and optimizing the site layout. Compared with traditional construction technology, it has the advantages of shortened construction period, high construction efficiency, and a high comprehensive cost saving ratio. It has achieved the expected design effect, obtained significant economic, environmental and social benefits, and has a good prospect for promotion and application.

Description

Technical Field

[0001] The invention relates to a steel-concrete combined inner support for a deep foundation pit near a river affected by tide and a construction method, and is suitable for the construction of a steel-concrete combined inner support for a deep foundation pit near a river. Background Art

[0002] With the continuous development and progress of society, the number of deep foundation pit projects has increased dramatically, and the deformation control requirements of foundation pits have become increasingly stringent. Although traditional reinforced concrete supports are flexible in layout and suitable for different foundation pits, they are not economical, the materials are not reusable, and they are prone to safety and environmental problems during installation and dismantling.

[0003] To sum up, in order to ensure the safety of underground engineering construction, it is of utmost importance to seek a reasonable and efficient foundation pit support system and its construction method. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a steel-concrete composite internal support and construction method for a deep foundation pit near a river affected by tides.

[0005] This tide affects the steel-concrete composite internal support of the deep foundation pit near the river, including: retaining piles, water-stop curtains, prestressed steel composite internal support, crown beams, surrounding purlins, steel columns, support casting reusable steel molds, cast-in-place concrete support closed curing devices and support steel bar in-situ binding reusable steel frames; some prestressed steel composite internal supports are connected to the crown beams through the support ends, and some prestressed steel composite internal supports and retaining piles are connected through surrounding purlins;

[0006] The prestressed steel composite internal support includes a top support beam and a steel support. The top support beam is connected to the steel support by bolts to form a support body of the prestressed steel composite internal support. The support body is erected on the bottom support beam. The bottom support beam is connected to the steel column through a bracket.

[0007] The support casting reusable steel mold includes a steel mold bottom plate, steel mold side plates, a top locking rod and a bottom locking rod; the supporting steel bars are lifted into the support casting reusable steel mold through lifting ears; the outer side of the steel mold bottom plate is symmetrically arranged with bottom plate grooves, and the steel mold side plates are arranged on both sides of the steel mold bottom plate through positioning plates.

[0008] Preferably, the top support beams arranged in multiple parallel rows are connected to four steel supports with screw holes through bolts to form the support body of the prestressed steel combined internal support. The support body is erected on the bottom support beam; the bottom support beam is erected on the bracket; the bracket is welded to the steel column, and the brackets connecting the same prestressed steel combined internal support are on the same horizontal plane; the steel supports are connected to the support ends through bolts. Steel diagonal braces are symmetrically arranged on both sides of the support end, and the steel diagonal braces are connected to the crown beam through embedded parts; in addition, jacks are arranged between the support end and the crown beam, and the jacks are connected to a pumping station.

[0009] There are also flange connecting plates and web connecting plates between the steel diagonal braces and the embedded parts.

[0010] Preferably, the top locking bar includes a top locking bar member, nuts on both sides, gaskets and a top limiter; threads are arranged on both sides of the top locking bar member, and a top limiter with an adjusting nut is arranged. The top limiter fits against the outer side of the steel formwork side plate.

[0011] The bottom locking bar includes a bottom locking bar member, nuts on both sides, gaskets and a bottom limiter; threads are arranged on both sides of the bottom locking bar member, and a bottom limiter with an adjusting nut is arranged. The bottom limiter fits against the outer side of the steel formwork side plate; the bottom limiter is also provided with a card slot, and the bottom locking bar is fixedly connected to the bottom groove of the steel formwork bottom plate through the card slot.

[0012] Preferably, the cast-in-place concrete support closed curing device includes a wooden frame, acrylic plates, a temperature and humidity meter, adjusting holes and a cast-in-place concrete support. The acrylic plates are inserted between the wooden frames through grooves, and a temperature and humidity meter is arranged on the inner side of the cast-in-place concrete support closed curing device; adjusting holes are arranged at the top of the cast-in-place concrete support closed curing device.

[0013] Preferably, the in-situ binding of support steel bars and the reusable steel frame include adjusting steel pipes, steel frame branches and steel bars; the adjusting steel pipes fit against the inner wall of the reusable steel formwork for support pouring; the steel bars are erected on the steel frame branches, and the steel frame branches are connected to the adjusting steel pipes through bolts and steel bars.

[0014] Preferably, corbels are welded on the same horizontal plane of the retaining piles, and the waling is supported on the corbels. Different segments of the waling are tightly connected through high-strength bolts.

[0015] Preferably, embedded parts are arranged during the pouring of the crown beam. The embedded parts and the steel diagonal braces are connected by welding, and flange connecting plates and web connecting plates are arranged at the welding joints to assist welding, improving the welding quality and the integrity of the components.

[0016] This construction method for the steel-concrete combined internal support of a deep foundation pit near the river affected by tides includes the following steps:

[0017] Step 1. Foundation pit seepage prevention construction: The external water-stop curtain of the foundation pit is constructed by the one-hole overlapping method of the three-axis mixing pile, adopting the skip-type double-hole full-set re-mixing construction process. Self-flow deep well pipe well dewatering is adopted both inside and outside the pit;

[0018] Step 2. Insertion of the steel section column: The steel section column is vertically inserted into the soil;

[0019] Step 3. Installation of the corbel bracket: Corbels are set at the same height of the retaining piles and the purlins are installed;

[0020] Step 4. Installation of the purlin: After positioning according to the axis reference point, each section is installed in sequence from long to short to form the purlin;

[0021] Step 5. Installation of the bracket and cross beam: Brackets are installed on the steel section columns, and the bottom support beams are erected;

[0022] Step 6. Pouring of the capping beam: The capping beam is poured by using the reusable steel formwork through the support pouring, and curing is carried out through the in-situ concrete support closed curing device;

[0023] Step 7. Installation of the support beam: Assemble the support body of the prestressed steel section combined internal support and erect it on the bottom support beam;

[0024] Step 8. Prestress application and monitoring: Two layers of prestressed steel section combined internal supports are set in the foundation pit, with single-piece support for the first layer and double-piece support for the second layer. Jacks are installed in advance in the steel section supports involving prestress application, and axial force is applied through the pump station.

[0025] The beneficial effects of the present invention are as follows:

[0026] 1) The present invention adopts the structural form of prestressed steel section combined support combined with reinforced concrete side truss, with high construction efficiency and small site occupation. It is convenient for installation and removal, shortening the construction period of the entire foundation pit. At the same time, the use of large-scale machinery can be minimized to the greatest extent, thus minimizing the occupation of the site and optimizing the site layout.

[0027] 2) The present invention combines the steel section combined support with the prestress application system to accurately apply prestress. By adjusting the axial force according to the monitoring data during the foundation pit excavation stage, the overall safety and stability of the support are improved.

[0028] 3) The present invention adopts the reusable steel formwork for support pouring and the reusable steel section frame for in-situ binding of the support, providing convenience for the construction of the concrete support. The installation and disassembly are simple and reusable, with certain economic efficiency. Description of the Drawings

[0029] Figure 1 It is a schematic diagram of the steel-concrete combined internal support;

[0030] Figure 2It is a schematic diagram of a reusable steel formwork for supporting casting;

[0031] Figure 3 It is a schematic diagram of a steel formwork locking rod;

[0032] Figure 4 It is a schematic diagram of a closed curing device for cast-in-place concrete support;

[0033] Figure 5 It is a schematic diagram of a reusable steel frame for in-situ binding of support steel bars;

[0034] Figure 6 It is a schematic diagram of a prestressed steel combination support;

[0035] Figure 7 It is a schematic diagram of the connection between the collar beam and the retaining pile;

[0036] Figure 8 It is a schematic diagram of the connection between the steel inclined support and the capping beam;

[0037] Figure 9 It is a process flow chart of the construction of the present invention.

[0038] In the figure: 1 - retaining pile, 2 - waterproof curtain, 3 - prestressed steel combination internal support, 4 - capping beam, 5 - collar beam, 6 - corbel, 7 - steel column, 8 - support steel bar, 9 - lifting lug, 10 - top locking rod, 11 - bottom locking rod, 12 - steel formwork bottom plate, 13 - positioning plate, 14 - bottom plate groove, 15 - steel formwork side plate, 16 - top locking rod member, 17 - nut, 18 - gasket, 19 - thread, 20 - top limiter, 21 - bottom locking rod member, 22 - bottom limiter, 23 - card slot, 24 - wooden frame, 25 - acrylic board, 26 - temperature and humidity meter, 27 - cast-in-place concrete support, 28 - adjustment hole, 29 - adjustment steel pipe, 30 - screw hole, 31 - steel frame branch, 32 - steel support, 33 - bolt, 34 - bracket, 35 - bottom support beam, 36 - top support beam, 37 - support end, 38 - steel inclined support, 39 - embedded part, 40 - jack, 41 - pump station, 42 - high-strength bolt, 43 - web connecting plate, 44 - flange connecting plate, 45 - reusable steel formwork for supporting casting, 46 - closed curing device for cast-in-place concrete support, 47 - reusable steel frame for in-situ binding of support steel bars. Specific embodiments

[0039] The present invention will be further described below in conjunction with embodiments. The description of the following embodiments is only for helping to understand the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several modifications can still be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0040] Embodiment 1

[0041] As an example, Figures 1 to 8 As shown, a steel-concrete composite internal support for a deep foundation pit near a river affected by tides comprises retaining piles 1, a water-stop curtain 2, a prestressed steel composite internal support 3, a crown beam 4, a surrounding purlin 5, a corbel 6, a steel column 7, a support casting reusable steel mold 45, a cast-in-place concrete support closed curing device 46, and a support steel bar in-situ binding reusable steel frame 47;

[0042] like Figure 1 As shown, a water-stop curtain 2 is arranged outside the foundation pit as a foundation pit anti-seepage measure to solve the groundwater problem, and a crown beam 4 is cast on the top of the retaining pile 1 to connect the retaining pile 1 into a whole; two supports are arranged in the pit, the first support is connected to the crown beam 4, and the second support is connected to the retaining pile 1 through the purlin 5 and the corbel 6.

[0043] A structure of prestressed steel combined internal support 3 combined with reinforced concrete side trusses is adopted. The prestressed steel combined internal support 3 is connected to the crown beam 4 or the retaining pile 1 by a purlin 5, and the purlin 5 relies on a corbel 6 welded to the retaining pile 1.

[0044] like Figure 7 As shown, the corbel 6 is arranged along the retaining pile 1 and welded on the same horizontal plane, and the connection parts between different sections of the upper purlin 5 are fastened and connected by friction-type high-strength bolts 42. The prestressed steel combined internal support 3 is pre-spliced ​​on the ground, and multiple parallel top support beams 36 are connected to four steel supports 32 with screw holes 30 by bolts to form the support body of the prestressed steel combined internal support 3, which is erected on the bottom support beam 35; the bottom support beam 35 is erected on the bracket 34; the bracket is welded on the steel column 7 and is on the same horizontal plane; the steel support 32 and the support end 37 are connected by bolts to form a whole, and two steel diagonal braces 38 are symmetrically arranged on both sides of the support end 37, and the steel diagonal braces 38 are connected to the crown beam 4 by embedded parts 39; in addition, multiple jacks 40 are arranged between the support end 37 and the crown beam 4, and the jacks 40 are controlled by the pump station 41 to apply axial force.

[0045] Furthermore, the steel brace 38 and the embedded parts 39 are reinforced by welding the flange connecting plate 44 and the web connecting plate 43 .

[0046] like Figure 2 As shown, a reusable steel mold 45 is supported for casting, comprising a steel mold base plate 12 at the bottom, steel mold side plates 15 on both sides, and upper and lower top locking rods 10 and bottom locking rods 11; some pre-tied supporting steel bars 8 are hoisted into the mold through lifting ears 9; the outer side of the steel mold base plate 12 has two symmetrically arranged base plate grooves 14, which cooperate with the upright positioning plates 13 on both sides to insert and install the steel mold side plates 15.

[0047] like Figure 3 As shown, further, the top locking rod 10 includes a top locking rod member 16, nuts 17 on both sides, a gasket 18, and a top limiter 20; threads 19 are arranged on both sides of the top locking rod member 16, and the spacing of the top limiter 20 is changed by adjusting the nuts 17 so that it is just close to the outer side of the steel mold side plate 15, thereby fixing the template.

[0048] Furthermore, the bottom locking rod 11 includes a bottom locking rod member 21, nuts 17 on both sides, a gasket 18, and a bottom limiter 22; threads 19 are arranged on both sides of the bottom locking rod member 21, and the bottom limiter 22 is changed by adjusting the nuts 17 so that it is just close to the outer side of the steel mold side plate 15; in addition, the bottom limiter 22 is arranged with a card slot 23, so that it can tightly buckle the steel mold bottom plate 12, and clamp the steel mold side plate 15 together with the positioning plate 13, forming a support for casting and reusable steel mold 45.

[0049] like Figure 4 As shown, the cast-in-place concrete support closed curing device 46 includes a wooden frame 24, an acrylic plate 25, a temperature and humidity meter 26, an adjustment hole 28, and a cast-in-place concrete support 27. A groove is set in the wooden frame 24, and the acrylic plate 25 is inserted into the groove and fixed with glue to form the main body of the cast-in-place concrete support closed curing device 46. A temperature and humidity meter 26 is arranged on the side of the device to intuitively reflect the internal temperature and humidity of the cast-in-place concrete support closed curing device 46; a closable adjustment hole 28 is arranged on the top of the device, and the internal temperature and humidity of the cast-in-place concrete support closed curing device 46 are adjusted by adjusting the hole 28.

[0050] like Figure 5 As shown, the support steel bar in-situ binding reused steel frame 47 is installed in parallel with the support casting reused steel form 45; the support steel bar in-situ binding reused steel frame 47 is welded by square steel pipes and is close to the support casting reused steel form 45; the steel frame branch 31 is connected to the steel frame and the formwork by bolts, and the steel bars are set on the steel frame branch 31;

[0051] like Figure 8 As shown, embedded parts 39 are arranged when the crown beam 4 is cast. The embedded parts 39 and the steel braces 38 are connected by welding. Flange connecting plates 44 and web connecting plates 43 are arranged at the welding points to assist in welding, thereby improving welding quality and component integrity.

[0052] Embodiment 2

[0053] As another embodiment, the construction method of steel-concrete composite internal support for deep foundation pit near the river under the influence of tide proposed in the first embodiment is as follows: Figure 9 As shown, the main construction steps are as follows:

[0054] Step 1. Foundation pit seepage prevention construction: Since the deep foundation pit project near the river is close to the river, a series of seepage prevention measures need to be taken during the construction to solve the problem of groundwater in the foundation pit; when the external cut-off curtain 2 of the foundation pit is constructed by the socketed one-hole method of the three-axis mixing pile, the skip-type double-hole full-set re-mixing construction process is adopted, and self-flow deep well pipe well dewatering is adopted both inside and outside the pit;

[0055] Step 2. Insertion of steel H-pile columns: The steel H-pile columns 7 are directly inserted by a manipulator. During the construction process, the insertion depth, angle, verticality, etc. of the steel H-piles are strictly controlled to facilitate the subsequent connection of the brackets 34 and the bottom support beams 35. After the pile insertion is in place, two theodolites are used to cross at 90° to detect the verticality of the pile body. The verticality deviation of the pile inserted into the soil shall not exceed 1% of the pile length;

[0056] Step 3. Installation of corbel brackets: Corbels 6 are set at the same height of the retaining piles 1, and their positions and elevations shall be determined according to the design drawings. The elevation deviation of the corbel 6 shall not be greater than ±2 mm, and it shall be ensured that the center lines of the steel H-pile girders 5 thereon are on the same horizontal plane;

[0057] Step 4. Installation of girders: Before installing the girders 5, the axis reference points must be determined. The total station or theodolite is used to measure and set the base points inside the adjacent two corners of the foundation pit through coordinate calculation. The plane installation positioning is carried out by the method of hanging a line through these base points. The installation of the girders 5 shall follow the principle of "first long then short, reducing the number of joints and staggering the joints". The longer girders 5 shall be given priority to reduce the number of joints;

[0058] Step 5. Installation of brackets and cross beams: Brackets 34 are installed on the steel H-pile columns 7, and the bottom support beams 35 are erected. The installation requirements of the brackets 34 strictly control the verticality. Even if the steel H-pile columns 7 are displaced, the brackets 34 must reach the verticality requirements by adding steel plates to ensure that the cross beam elevations of the corresponding supports are on the same plane;

[0059] Step 6. Pouring of the capping beam: The capping beam 4 can be poured by reusing the steel formwork 45 through the support pouring, and curing is carried out through the cast-in-place concrete support closed curing device 46;

[0060] Step 7. Installation of support beams: Assemble the support main body of the prestressed steel H-pile combined internal support 3 and erect it on the bottom support beams 35. Before installing each steel H-pile combined support beam, pre-assembly should be carried out on the ground first and the straightness of the pre-assembled support should be checked. For projects where on-site pre-assembly conditions are not available, the total station should be used for positioning, and the control lines of the support beams should be marked on the cross beams, and then pre-assembly should be carried out from one end along the control lines. For those exceeding 100 meters, pre-assembly can be carried out simultaneously from both ends. During the assembly process of the steel H-pile combined support beams, if there is extra space, steel plates with corresponding thicknesses must be used to pad tightly to prevent the overall eccentricity of the support system after being stressed;

[0061] Step 8. Prestress application and monitoring: Two layers of prestressed steel combined internal supports 3 are set in the foundation pit, with single-piece supports for the first layer and double-piece supports for the second layer. Jacks 40 are installed in advance in the steel supports involving prestress application, and axial force is applied through a pump station 41. The pre-axial force of each group of supports during construction is determined according to the design value combined with experience, and during the excavation of the foundation pit, the support axial force is adjusted according to the axial force and deformation monitoring data.

Claims

1. A steel-concrete composite internal support for a deep foundation pit near the river affected by tides. It is characterized in that include: A retaining pile (1), a water-stop curtain (2), a prestressed steel composite internal support (3), a crown beam (4), a purlin (5), a steel column (7), a support casting reusable steel formwork (45) and a support steel bar in-situ binding reusable steel frame (47); the partially prestressed steel composite internal support (3) is connected to the crown beam (4) via a support end (37), and the partially prestressed steel composite internal support (3) and the retaining pile (1) are connected via the purlin (5); embedded parts (39) are arranged when the crown beam (4) is cast; The prestressed steel combined inner support (3) comprises a top support beam (36) and a steel support (32). A plurality of parallel top support beams (36) are connected to four steel supports (32) with screw holes (30) by bolts to form a support body of the prestressed steel combined inner support (3). The support body is mounted on a bottom support beam (35). The bottom support beam (35) is mounted on a bracket (34). The bracket (34) is welded to a steel column (7). The support (34) connected to the same prestressed steel combined inner support (3) is on the same horizontal plane; the steel support (32) is connected to the support end (37) by bolts, and steel diagonal braces (38) are symmetrically provided on both sides of the support end (37), and the steel diagonal braces (38) are connected to the crown beam (4) by embedded parts (39); a jack (40) is arranged between the support end (37) and the crown beam (4), and the jack (40) is connected to a pump station (41); A flange connecting plate (44) and a web connecting plate (43) are also provided between the steel brace (38) and the embedded part (39); The support casting reusable steel mold (45) comprises a steel mold bottom plate (12), a steel mold side plate (15), a top locking rod (10) and a bottom locking rod (11), and is used for casting a crown beam; the support steel bar (8) is hoisted into the support casting reusable steel mold (45) through a lifting lug (9); the outer side of the steel mold bottom plate (12) is symmetrically arranged with bottom plate grooves (14), and the steel mold side plates (15) are arranged on both sides of the steel mold bottom plate (12) through positioning plates (13); The top locking rod (10) comprises a top locking rod member (16) and a top stopper (20); threads (19) and a top stopper (20) with a nut (17) and a gasket are arranged on both sides of the top locking rod member (16); the top stopper (20) is fitted to the outer side of the steel mold side plate (15); The bottom locking rod (11) comprises a bottom locking rod member (21) and a bottom stopper (22); threads (19) and a bottom stopper (22) with a nut (17) and a gasket are arranged on both sides of the bottom locking rod member (21); the bottom stopper (22) fits the outer side of the steel mold side plate (15); the bottom stopper (22) is also provided with a slot (23), and the bottom locking rod (11) is fixedly connected to the steel mold bottom plate (12) through the slot (23); The in-situ binding of the supporting steel bars and the reusable steel frame (47) includes an adjusting steel pipe (29), a steel frame branch (31) and steel bars; the adjusting steel pipe (29) fits against the inner wall of the reusable steel formwork (45) for supporting casting; the steel bars are arranged on the steel frame branch (31), and the steel frame branch (31) is connected to the adjusting steel pipe (29) by bolts (33).

2. The steel-concrete combined internal support for a deep foundation pit near a river affected by tides according to claim 1, characterized in that: it further includes: a cast-in-place concrete support closed curing device (46). After the capping beam is cast, the cast-in-place concrete support closed curing device (46) is used for curing. The cast-in-place concrete support closed curing device (46) includes a wooden frame (24), an acrylic board (25), a temperature and humidity meter (26) and an adjusting hole (28). The acrylic board (25) is inserted between the wooden frames (24) through grooves. A temperature and humidity meter (26) is arranged on the inner side of the cast-in-place concrete support closed curing device (46); an adjusting hole (28) is arranged at the top of the cast-in-place concrete support closed curing device (46).

3. The steel-concrete combined internal support for a deep foundation pit near a river affected by tides according to claim 1, characterized in that: a corbel (6) is welded on the same horizontal plane of the retaining pile (1), the waling (5) is supported on the corbel (6), and different segments of the waling (5) are tightly connected by high-strength bolts (42).

4. The steel-concrete combined internal support for a deep foundation pit near a river affected by tides according to claim 1, characterized in that: the embedded part (39) and the steel inclined strut (38) are connected by welding, and a flange connecting plate (44) and a web connecting plate (43) are arranged at the welding position to assist in welding, improving the welding quality and the integrity of the component.

5. The construction method of the steel-concrete combined internal support for a deep foundation pit near a river affected by tides as described in claim 2, characterized in that, it includes the following steps: Step 1: Foundation pit anti-seepage construction: The external water-stop curtain (2) of the foundation pit is constructed by the one-hole socketting method of a three-axis mixing pile, and the skip-type double-hole full-set re-stirring construction process is adopted. Self-flow deep well pipe well dewatering is carried out both inside and outside the pit; Step 2: Insertion of the H-section steel column: The H-section steel column (7) is vertically inserted into the soil; Step 3: Installation of the corbel support: Corbels (6) are set at the same height of the retaining pile (1) and the waling (5) is installed; Step 4: Installation of the waling: After positioning according to the axis reference point, each segment is installed in sequence from long to short to form the waling (5); Step 5: Installation of the bracket and the cross beam: A bracket (34) is installed on the H-section steel column (7), and the bottom support beam (35) is erected; Step 6: Casting of the capping beam: The capping beam (4) is cast through the reusable steel formwork (45) for supporting casting, and curing is carried out through the cast-in-place concrete support closed curing device (46); Step 7: Installation of the support beam: Assemble the support main body of the prestressed H-section steel combined internal support (3) and erect it on the bottom support beam (35); Step 8. Prestress application and monitoring: Two layers of prestressed steel combined internal supports (3) are provided in the foundation pit, with a single-piece support for the first layer and a double-piece support for the second layer. Jacks (40) are installed in advance in the steel combined internal supports involving prestress application, and axial force is applied through a pumping station (41).

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