Construction Structure and Construction Method for Deep Foundation Pit of Open Cut Tunnel with Low Clearance in Airport Height Limit Area

Abstract

The present invention relates to a construction structure and construction method for a deep foundation pit of an open-cut tunnel with low clearance in an airport height-limited area. The solution includes a sunken access road, an assembled drainage ditch, an assembled support fence, a pile-top sliding track system and a docking support. The construction method includes: S00, cleaning the original ground and leveling the site, and measuring and lofting the excavation boundary; S10, excavating the sunken access road until the designed height is reached; S20, excavating the soil for the drainage ditch along the outside of the excavation boundary and constructing the assembled drainage ditch; S30, constructing the assembled support fence; S40, using a drill rig to carry out the excavation operation of the bored pile holes on the sunken access road; S50, pouring the bored piles and constructing the pile-top capping beam; S60, after the track installation is completed, carrying out the installation operations of the gantry crane and the canopy; S70, carrying out the excavation operation of the foundation pit. This application has the advantages of high construction efficiency and low construction cost.

Description

Technical Field

[0001] The invention relates to the technical field of construction engineering, and in particular to a construction structure and a construction method for a deep foundation pit of a low-headroom open-cut tunnel in a height-restricted area of ​​an airport. Background Art

[0002] When carrying out construction work in height-restricted areas such as those near airports, the pile boring machines and cranes are too high to reach the height limit, so traditional methods of operation are difficult to carry out. In order to avoid the inability to construct due to the excessive height of construction machinery and equipment, small machinery and equipment are generally used to replace the excessively high machinery and equipment. However, for some large foundation pit excavation projects, small machinery and equipment have problems such as low operating efficiency, which seriously affects the progress of the project.

[0003] However, when the prior art uses bored cast-in-place piles to support foundation pits in restricted height areas, due to limited space, the steel cage in the bored cast-in-place pile is usually divided into several small sections, which are then lengthened section by section when lowered into the pile hole. When the steel cages are connected, bolts are mainly used to connect the longitudinal main bars. When tying the steel cages, it is necessary to process threads on the ends of the longitudinal main bars in advance, which is a lot of work, and the threads of the steel cages are easily damaged during transportation, making it difficult to connect at the construction site. In addition, the use of bolts for connection requires high binding accuracy of the steel cages, but the steel cages will inevitably become loose during transportation and hoisting, making it difficult to connect them later.

[0004] Therefore, it is urgent to propose a new construction technology to solve the problem that large mechanical equipment cannot be used in restricted height spaces. Summary of the invention

[0005] The purpose of the present invention is to address the above-mentioned problems existing in the prior art and to provide a low-headroom open-cut tunnel deep foundation pit construction structure and a construction method for an airport height-restricted area.

[0006] In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme: the low-clearance open-cut tunnel deep foundation pit construction structure in the airport height-restricted area includes:

[0007] Further, it includes a sunken access road, a prefabricated drainage ditch, a prefabricated support enclosure, a pile top sliding track system and a docking bracket for connecting the steel cage;

[0008] The sunken access road is located outside the bored piles supporting the foundation pit, and the top elevation of the sunken access road is lower than the original ground elevation. Both the sunken access road and the original ground are provided with cast-in-place concrete slabs;

[0009] The prefabricated drainage ditch includes a U-shaped steel plate groove, a comb tooth plate and a concrete cover plate. Strip-shaped steel bar grooves are provided on the two vertical side plates of the U-shaped steel plate groove. The comb tooth plate is closely attached to the outer side of the vertical side plate of the U-shaped steel plate groove. The steel bars in the cast-in-place concrete slab pass through the strip-shaped steel bar grooves, and the concrete cover plate is laid along the U-shaped steel plate groove and supported on the steel bars;

[0010] The prefabricated support retaining wall is arranged between the sunken access road and the original ground, and the prefabricated support retaining wall includes vertical support ribs, horizontal support ribs and baffles. The upper end of the vertical support ribs is fixed on the cast-in-place concrete slab of the original ground, the lower end of the vertical support ribs is fixed on the cast-in-place concrete slab of the sunken access road, the horizontal support ribs are fixed on the vertical support ribs, and the baffles are clamped between the vertical support ribs and the horizontal support ribs;

[0011] The pile top sliding track system includes a support cross beam and a track. The support cross beam is poured on the surface of the pile top capping beam, and the track is supported on the support cross beam;

[0012] The docking support includes a docking sleeve, a connecting ring and an annular grouting pipe. The docking sleeves are uniformly arranged according to the spacing of the longitudinal main steel bars of the steel reinforcement cage. A connecting ring is arranged at both the upper and lower ends of the docking sleeve and fixed to form a whole. The longitudinal main steel bars of the steel reinforcement cages of adjacent segments are respectively inserted into the docking sleeve from the upper and lower ends of the docking sleeve;

[0013] The annular grouting pipe is arranged at the lower end of the docking sleeve, and the docking sleeves are connected in series through the annular grouting pipe.

[0014] Furthermore, polyurethane foam is filled outside both the U-shaped steel plate groove and the baffle.

[0015] Furthermore, a plurality of drain pipes are arranged inside the prefabricated support retaining wall. One end of each drain pipe is implanted into the soil body, and the other end passes through the drainage holes reserved on the baffle.

[0016] Furthermore, locking bolts are arranged on the docking sleeve, grouting ports are arranged on the annular grouting pipe, and sealing rings are arranged at the top of the docking sleeve.

[0017] Furthermore, a rain shelter and a gantry crane are arranged on the pile top sliding track system. Pulley blocks are arranged below both the rain shelter and the gantry crane. The pulley blocks are supported on the track, and the rain shelter and the gantry crane can slide along the length direction of the track.

[0018] Furthermore, the prefabricated drainage ditches are respectively arranged outside the excavation side line of the foundation pit and outside the sunken access road.

[0019] The construction method for the deep foundation pit of the open-cut tunnel with low clearance in the airport height-limited area is characterized by including the following steps:

[0020] S00. Clean the original ground and level the site, and measure and set out the excavation side line;

[0021] S10. After the cast-in-place concrete slab on the original ground is constructed and reaches the design strength, excavate the sunken access road until the design height is reached.

[0022] S20. Excavate the soil for the drainage ditch outside the excavation edge line, construct the prefabricated drainage ditch, place the U-shaped steel plate groove in the excavated drainage ditch, then bind the steel bars of the cast-in-place concrete slab. The steel bars pass through the steel bar grooves on the U-shaped steel plate groove, and then place the comb-shaped plate closely outside the U-shaped steel plate groove. After the steel bar binding operation is completed, inject polyurethane foam outside the U-shaped steel plate groove, cover the U-shaped steel plate groove with precast concrete cover plates, and then carry out the casting construction of the cast-in-place concrete slab.

[0023] S30. After the cast-in-place concrete slab on the sunken access road is cast and reaches the design strength, construct the prefabricated support enclosure.

[0024] S40. Use a drilling rig to carry out the excavation operation of the bored pile hole on the sunken access road. After the pile hole is excavated, use a crane to lower the steel reinforcement cage into the pile hole section by section. Adjacent steel reinforcement cage sections are connected by a docking support. The lower section of the steel reinforcement cage is temporarily placed on the steel casing with a balance beam. The upper section of the steel reinforcement cage is lifted in the air by a crane. Insert the longitudinal main steel bars of the upper and lower sections of the steel reinforcement cage into the upper and lower ends of the docking sleeve respectively, and then tighten the locking bolts for temporary fixation. Then inject epoxy resin binder into the docking sleeve through the grouting port. After the epoxy resin binder condenses and hardens, remove the balance beam and lower the steel reinforcement cage into the pile hole. Use the same method to lower the steel reinforcement cage section by section and use the docking support to extend it section by section.

[0025] S50. After the steel reinforcement cage is lowered in place, carry out the pouring of the bored pile and the construction of the pile cap beam. When pouring the pile cap beam, pour the support cross beam on the surface of the pile cap beam. After the pile cap beam concrete reaches the design strength, weld and fix the track on the support cross beam.

[0026] S60. After the track is installed, carry out the installation operations of the gantry crane and the awning. The pulley blocks of the gantry crane and the awning are supported on the track.

[0027] S70. Carry out the excavation operation of the foundation pit. The soil and construction materials in the foundation pit are transported by the gantry crane.

[0028] Further, in step S30, the specific steps of the construction of the prefabricated support enclosure are as follows:

[0029] Use anchor bolts to fix the upper and lower ends of the vertical support ribs to the original ground and the cast-in-place concrete slab of the sunken access road respectively. Then, rely on the vertical support ribs, install the baffle and the horizontal support ribs, and use connecting bolts to fix the baffle and the horizontal support ribs to the vertical support ribs. Drill holes into the soil according to the drainage holes reserved on the baffle, then insert the drain pipe into the soil, and then inject polyurethane foam into the gap between the baffle and the soil.

[0030] Further, in step S70, use a rain shelter to shield the foundation pit on rainy days.

[0031] Adopting the technical solution provided by the present invention, compared with the prior art, it has the following beneficial effects:

[0032] 1. The docking bracket proposed in this application can realize the rapid connection of the reinforcement cage segments, while ensuring the connection accuracy and strength, thereby improving the bearing capacity of the bored cast-in-place pile.

[0033] 2. This application adopts a sunken access road, which can effectively avoid the problem that large-scale mechanical equipment cannot enter the site in height-limited areas, and can effectively improve the on-site operation efficiency.

[0034] 3. The prefabricated drainage ditch and the prefabricated support fence proposed in this application adopt standardized splicing components, which can not only improve the on-site construction efficiency, but also effectively reduce the construction cost.

[0035] 4. The pile top sliding track system set up relying on the bored cast-in-place pile in this application provides a stable and reliable support and sliding track for the gantry crane and the rain shelter, which can effectively improve the transportation efficiency of earthwork and construction materials, and at the same time avoid the influence of rain on the foundation pit operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a schematic structural diagram of the sunken construction access road of this application;

[0037] Figure 2 is a detailed drawing of the drainage ditch of this application;

[0038] Figure 3 is an expression view of the prefabricated components of the prefabricated drainage ditch of this application;

[0039] Figure 4 is a three-dimensional structural schematic diagram of the assembly of the prefabricated components of the prefabricated drainage ditch of this application;

[0040] Figure 5 is a process diagram of the installation of the prefabricated fence of this application;

[0041] Figure 6 is a three-dimensional structural schematic diagram of the installed prefabricated fence of this application;

[0042] Figure 7 It is a schematic diagram of the low-clearance excavation operation of the bored pile hole in this application;

[0043] Figure 8 It is a schematic diagram of the low-clearance hoisting operation of the steel reinforcement cage of the bored pile in this application;

[0044] Figure 9 It is a three-dimensional structure schematic diagram of the docking of the standardized support of the steel reinforcement cage in this application;

[0045] Figure 10 It is a three-dimensional structure schematic diagram of the standardized support for the docking of the steel reinforcement cage in this application;

[0046] Figure 11 It is a large-scale drawing of the docking of the standardized support of the steel reinforcement cage in this application;

[0047] Figure 12 It is a schematic diagram of the construction of the deep foundation pit of the low-clearance open-cut tunnel in this application;

[0048] Figure 13 It is a schematic diagram of the track fixing structure on the capping beam in this application;

[0049] Figure 14 It is the construction flow chart of this application.

[0050] In the figure, 11 is the original ground; 12 is the sunken access road; 13 is the cast-in-place concrete slab; 14 is the steel bar; 15 is the polyurethane foam; 2 is the prefabricated drainage ditch; 21 is the U-shaped steel plate groove; 22 is the comb tooth plate; 23 is the steel bar groove; 24 is the concrete cover plate; 31 is the vertical support rib; 32 is the horizontal support rib; 33 is the baffle; 34 is the drain pipe; 35 is the anchor bolt; 36 is the coupling bolt; 41 is the drill rig; 42 is the crane; 43 is the steel casing; 44 is the pile hole; 45 is the steel reinforcement cage; 46 is the longitudinal main steel bar; 48 is the bored pile; 49 is the capping beam; 5 is the docking support; 51 is the docking sleeve; 52 is the coupling ring; 53 is the annular grouting pipe; 54 is the grouting port; 55 is the locking bolt; 56 is the sealing ring; 61 is the support cross beam; 62 is the stud; 63 is the track; 64 is the pulley block; 65 is the awning; 66 is the gantry crane; 67 is the foundation pit. Detailed implementation manners

[0051] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art shall fall within the protection scope of the present invention.

[0052] Those skilled in the art should understand that in the disclosure of the present invention, the orientation or positional relationships indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings. These are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting the present invention.

[0053] The construction structure and method for the deep foundation pit of the low clearance open cut tunnel in the height limit area of this airport are as Figure 12 and Figure 14 shown, and include the following construction steps:

[0054] S00. Clean the original ground 11, level the site, and measure and set out the excavation boundary line;

[0055] S10. After the construction of the cast-in-place concrete slab 13 on the original ground 11 is completed and reaches the design strength, carry out the excavation operation of the sunken access road 12;

[0056] S20. After the sunken access road 12 is excavated to the design height, carry out the construction of the prefabricated drainage ditch 2 and the cast-in-place concrete slab 13 along the outside of the sunken access road 12. As Figure 1-2 shown, excavate the earthwork of the drainage ditch along the outside of the excavation boundary line, then carry out the construction of the prefabricated drainage ditch 2. Place the U-shaped steel plate groove 21 in the excavated drainage ditch, then bind the steel bars 14 of the cast-in-place concrete slab 13. The steel bars 14 pass through the steel bar grooves 23 on the U-shaped steel plate groove 21, then place the comb-shaped plate 22 closely against the outside of the U-shaped steel plate groove 21. After the binding operation of the steel bars 14 is completed, inject polyurethane foam 15 outside the U-shaped steel plate groove 21, cover the U-shaped steel plate groove 21 with the precast concrete cover plate 24, and then carry out the pouring construction of the cast-in-place concrete slab 13;

[0057] Among them, as Figure 3-4 shown, the prefabricated drainage ditch 2 is composed of a U-shaped steel plate groove 21, a comb-shaped plate 22 and a concrete cover plate 24. The cross-section of the U-shaped steel plate groove 21 is U-shaped, and strip-shaped steel bar grooves 23 are provided on the two vertical side plates. The comb-shaped plate 22 is closely against the outside of the vertical side plate. The steel bars 14 in the cast-in-place concrete slab 13 pass through the steel bar grooves 23, and the concrete cover plate 24 is laid along the U-shaped steel plate groove 21 and supported on the steel bars 14 passing through the U-shaped steel plate groove 21;

[0058] Preferably, the prefabricated drainage ditch 2 is arranged along the outside of the foundation pit excavation boundary line and the outside of the sunken access road 12 respectively;

[0059] In this embodiment, polyurethane foam 15 is filled outside both the U-shaped steel plate groove 21 and the baffle 33;

[0060]

[0060] After the cast-in-place concrete slab 13 on the sunken access road 12 is poured and reaches the designed strength, the construction of the prefabricated support retaining wall is carried out. The upper and lower ends of the vertical support rib 31 are respectively fixed to the original ground 11 and the cast-in-place concrete slab 13 of the sunken access road 12 by anchor bolts 35. Then, the baffle 33 and the horizontal support rib 32 are installed relying on the vertical support rib 31, and the baffle 33 and the horizontal support rib 32 are fixed to the vertical support rib 31 by connection bolts 36. Drill holes into the soil according to the drainage holes reserved on the baffle 33, then insert the drain pipe 34 into the soil, and then inject polyurethane foam 15 into the gap between the baffle 33 and the soil;

[0061] In this embodiment, the sunken access road 12 is located outside the bored cast-in-place pile 48 of the support foundation pit. The top elevation of the sunken access road 12 is lower than the elevation of the original ground 11. Cast-in-place concrete slabs 13 are provided on both the sunken access road 12 and the original ground 11.

[0062] In this embodiment, as Figure 5-6 shown, the prefabricated support retaining wall is arranged between the sunken access road 12 and the original ground 11. The prefabricated support retaining wall is composed of a vertical support rib 31, a horizontal support rib 32, and a baffle 33. The upper end of the vertical support rib 31 is fixed to the cast-in-place concrete slab 13 of the original ground 11 by an anchor bolt 35, and the lower end of the vertical support rib 31 is fixed to the cast-in-place concrete slab 13 of the sunken access road 12 by an anchor bolt 35. The horizontal support rib 32 is fixed to the vertical support rib 31 by a connection bolt 36, and the baffle 33 is clamped between the vertical support rib 31 and the horizontal support rib 32.

[0063] In this embodiment, a drain pipe 34 is provided inside the prefabricated support retaining wall. One end of the drain pipe 34 is implanted into the soil, and the other end passes through the drainage hole reserved on the baffle 33.

[0064] S40、As Figure 7-8 shown, the drill rig 41 carries out the excavation operation of the pile hole 44 of the bored cast-in-place pile 48 on the sunken access road 12. After the pile hole 44 is excavated, the steel reinforcement cage 45 is gradually lowered into the pile hole 44 by a crane 42. Adjacent sections of the steel reinforcement cage 45 are connected by a docking support 5. The lower section of the steel reinforcement cage 45 is temporarily placed on the steel casing 43 by a shoulder beam. The upper section of the steel reinforcement cage 45 is suspended in the air by a crane 42. The longitudinal main reinforcement 46 of the upper and lower sections of the steel reinforcement cage 45 is respectively inserted into the upper and lower ends of the docking sleeve 51, and then the locking bolt 55 is tightened for temporary fixation. Then, epoxy resin binder is injected into the docking sleeve 51 through the grouting port 54. After the epoxy resin binder coagulates and hardens, the shoulder beam is removed and the steel reinforcement cage 45 is lowered into the pile hole 44; According to the above method, the steel reinforcement cage 45 is gradually lowered and lengthened section by section using the docking support 5;

[0065] In this embodiment, asFigure 9-10 As shown, the docking bracket 5 is composed of a docking sleeve 51, a connecting ring 52 and an annular grouting pipe 53. The docking sleeves 51 are uniformly arranged according to the spacing of the longitudinal main bars 46 of the reinforcement cage 45. A connecting ring 52 is provided at both the upper and lower ends of the docking sleeve 51 to fix it into a whole. The longitudinal main bars 46 of the reinforcement cages 45 of adjacent segments are respectively inserted into the docking sleeve 51 from the upper and lower ends of the docking sleeve 51; the annular grouting pipe 53 is arranged at the lower end of the docking sleeve 51, and the docking sleeves 51 are connected in series through the annular grouting pipe 53;

[0066] In this embodiment, as Figure 11 shown, the docking sleeve 51 is provided with a locking bolt 55, the annular grouting pipe 53 is provided with a grouting port 54, and the top of the docking sleeve 51 is provided with a sealing ring 56.

[0067] S50. After the reinforcement cage 45 is lowered and in place, the cast-in-place bored pile 48 is poured and the pile cap beam 49 is constructed. When the pile cap beam 49 is poured, the support cross beam 61 is poured on the surface of the pile cap beam 49. After the concrete of the pile cap beam 49 reaches the design strength, the track 63 is welded and fixed on the support cross beam 61 to complete the installation of the pile top sliding track system;

[0068] In this embodiment, as Figure 13 shown, the pile top sliding track system is composed of a support cross beam 61 and a track 63. The support cross beam 61 is poured on the surface of the pile top cap beam 49, the track 63 is supported on the support cross beam 61, and there are stud bolts 62 below the support cross beam 61.

[0069] S60. After the track 63 is installed, the installation operations of the gantry crane 66 and the canopy 65 are carried out. The pulley blocks 64 of the gantry crane 66 and the canopy 65 are supported on the track 63;

[0070] In this embodiment, a canopy 65 and a gantry crane 66 are arranged on the pile top sliding track system. Pulley blocks 64 are provided below the canopy 65 and the gantry crane 66. The pulley blocks 64 are supported on the track 63, and the canopy 65 and the gantry crane 66 can longitudinally slide along the track 63.

[0071] S70. The excavation operation of the foundation pit 67 is carried out. The soil and other construction materials in the foundation pit 67 are transported by the gantry crane 66, and the foundation pit 67 is shielded by the canopy 65 on rainy days.

[0072] In this way, as Figure 12 shown, a low-clearance open-cut tunnel deep foundation pit structure system is composed of a sunken access road 12, an assembled drainage ditch 2, an assembled support fence, a pile top sliding track system and a docking bracket 5 connected to the reinforcement cage 45.

[0073] The parts not detailed in the present invention are prior art, so the present invention does not detail them.

[0074] It will be understood that the term "a" should be construed as "at least one" or "one or more". That is, in one embodiment, the number of an element may be one, while in other embodiments, the number of the element may be multiple. The term "a" should not be construed as a limitation on the number.

[0075] Although many technical terms are used herein, the possibility of using other terms is not excluded. These terms are used only to more conveniently describe and explain the essence of the present invention; construing them as any additional limitation is contrary to the spirit of the present invention.

[0076] The present invention is not limited to the above-described best mode. Any person can obtain other various forms of products under the inspiration of the present invention. However, no matter what changes are made in its shape or structure, as long as it has a technical solution identical or similar to that of the present application, it falls within the protection scope of the present invention.

Claims

1. Construction structure for deep foundation pit of open-cut tunnel with low clearance in airport height-limited area, Characterized in that, It includes a sunken access road (12), an assembled drainage ditch (2), an assembled support retaining wall, a pile top sliding track system and a docking bracket (5) for connecting the steel reinforcement cage (45); The sunken access road (12) is located outside the bored cast-in-place piles (48) of the support foundation pit, and the top elevation of the sunken access road (12) is lower than the elevation of the original ground (11). Cast-in-place concrete slabs (13) are provided on both the sunken access road (12) and the original ground (11); The assembled drainage ditch (2) includes a U-shaped steel plate groove (21), a comb-shaped plate (22) and a concrete cover plate (24). Strip-shaped steel bar grooves (23) are provided on the two vertical side plates of the U-shaped steel plate groove (21). The comb-shaped plate (22) is closely attached to the outer side of the vertical side plate of the U-shaped steel plate groove (21). The steel bars (14) in the cast-in-place concrete slab (13) pass through the strip-shaped steel bar grooves (23), and the concrete cover plate (24) is laid along the U-shaped steel plate groove (21) and supported on the steel bars (14); The assembled support retaining wall is arranged between the sunken access road (12) and the original ground (11), and the assembled support retaining wall includes vertical support ribs (31), horizontal support ribs (32) and a baffle (33). The upper end of the vertical support rib (31) is fixed on the cast-in-place concrete slab (13) of the original ground (11), the lower end of the vertical support rib (31) is fixed on the cast-in-place concrete slab (13) of the sunken access road (12), the horizontal support rib (32) is fixed on the vertical support rib (31), and the baffle (33) is clamped between the vertical support rib (31) and the horizontal support rib (32); The pile top sliding track system includes a support cross beam (61) and a track (63). The support cross beam (61) is cast on the surface of the pile top capping beam (49), and the track (63) is supported on the support cross beam (61); The docking bracket (5) includes a docking sleeve (51), a connecting ring (52) and an annular grouting pipe (53). The docking sleeves (51) are uniformly arranged according to the spacing of the longitudinal main steel bars (46) of the steel reinforcement cage (45). A connecting ring (52) is arranged at both the upper and lower ends of the docking sleeve (51) and fixed to form a whole. The longitudinal main steel bars (46) of adjacent segments of the steel reinforcement cage (45) are respectively inserted into the docking sleeve (51) from the upper and lower ends of the docking sleeve (51); The annular grouting pipe (53) is arranged at the lower end of the docking sleeve (51), and the docking sleeves (51) are connected in series through the annular grouting pipe (53).

2. The construction structure for deep foundation pit of open-cut tunnel with low clearance in airport height-limited area according to claim 1, Characterized in that, Polyurethane foam (15) is filled outside both the U-shaped steel plate groove (21) and the baffle (33).

3. The construction structure for deep foundation pit of open-cut tunnel with low clearance in airport height-limited area according to claim 1, Characterized in that, A plurality of drain pipes (34) are provided inside the prefabricated support retaining wall. One end of each drain pipe (34) is implanted into the soil, and the other end passes through a drain hole reserved on the baffle (33).

4. The deep foundation pit construction structure of the low clearance open cut tunnel in the airport height limit area according to claim 1, characterized in that, a locking bolt (55) is provided on the docking sleeve (51), a grouting port (54) is provided on the annular grouting pipe (53), and a sealing ring (56) is provided on the top of the docking sleeve (51).

5. The deep foundation pit construction structure of the low clearance open cut tunnel in the airport height limit area according to claim 1, characterized in that, a rain shed (65) and a gantry crane (66) are provided on the pile top sliding track system. Pulley groups (64) are provided below both the rain shed (65) and the gantry crane (66). The pulley groups (64) are supported on the track (63), and the rain shed (65) and the gantry crane (66) can slide along the length direction of the track (63).

6. The deep foundation pit construction structure of the low clearance open cut tunnel in the airport height limit area according to claim 1, characterized in that, the prefabricated drainage ditches (2) are respectively arranged outside the excavation side line of the foundation pit and outside the sunken access road (12).

7. The deep foundation pit construction structure of the low clearance open cut tunnel in the airport height limit area according to claim 1, characterized in that, studs (62) are provided below the support cross beam (61).

8. A construction method for the deep foundation pit construction structure of the low clearance open cut tunnel in the airport height limit area according to any one of claims 1-7, characterized in that, comprises the following steps: S00. Clean the original ground (11) and level the site, and measure and set out the excavation side line; S10. After the cast-in-place concrete slab (13) on the original ground (11) is constructed and reaches the design strength, excavate the sunken access road (12) until the design height is reached; S20. Excavate the soil of the drainage ditch outside the excavation side line, construct the prefabricated drainage ditch (2), place the U-shaped steel plate groove (21) in the excavated drainage ditch, then bind the steel bars (14) of the cast-in-place concrete slab (13). The steel bars (14) pass through the steel bar grooves (23) on the U-shaped steel plate groove (21), and then place the comb-shaped plate (22) closely outside the U-shaped steel plate groove (21). After the steel bar binding operation is completed, inject polyurethane foam (15) outside the U-shaped steel plate groove (21), cover the U-shaped steel plate groove (21) with a precast concrete cover plate (24), and then carry out the casting construction of the cast-in-place concrete slab (13); S30. After the cast-in-place concrete slab (13) on the sunken access road (12) is poured and reaches the design strength, carry out the construction of the prefabricated support retaining wall; S40. Use a drilling rig (41) to excavate the pile hole (44) of the cast-in-place pile (48) on the sunken access road (12). After the excavation of the pile hole (44) is completed, use a crane (42) to lower the steel reinforcement cage (45) into the pile hole (44) section by section. The adjacent sections of the steel reinforcement cage (45) are connected by a docking bracket (5). The lower section of the steel reinforcement cage (45) is temporarily placed on the steel casing (43) using a balance beam. The upper section of the steel reinforcement cage (45) is suspended in the air by the crane (42). Insert the longitudinal main reinforcement (46) of the upper and lower sections of the steel reinforcement cage (45) into the upper and lower ends of the docking sleeve (51) respectively, and then tighten the locking bolts (55) for temporary fixation. Then, inject epoxy resin binder into the docking sleeve (51) through the grouting port (54). After the epoxy resin binder solidifies and hardens, remove the balance beam and lower the steel reinforcement cage (45) into the pile hole (44). Use the same method to lower the steel reinforcement cage (45) section by section and use the docking bracket (5) to extend it section by section; S50. After the steel reinforcement cage (45) is lowered in place, carry out the pouring of the cast-in-place pile (48) and the construction of the pile top capping beam (49). When pouring the capping beam (49), pour the support cross beam (61) on the surface of the capping beam (49). After the concrete of the capping beam (49) reaches the design strength, weld and fix the track (63) on the support cross beam (61); S60. After the installation of the track (63) is completed, carry out the installation operations of the gantry crane (66) and the canopy (65). The pulley blocks (64) of the gantry crane (66) and the canopy (65) are supported on the track (63); S70. Carry out the excavation operation of the foundation pit (67). The soil and construction materials in the foundation pit (67) are transported by the gantry crane (66).

9. The construction method according to claim 8, characterized in that, In step S30, the specific steps of the construction of the prefabricated support fence are: Use anchor bolts (35) to fix the upper and lower ends of the vertical support ribs (31) on the original ground (11) and the cast-in-place concrete slab (13) of the sunken access road (12) respectively. Then, rely on the vertical support ribs (31) to install the baffle (33) and the horizontal support ribs (32), and use connecting bolts (36) to fix the baffle (33) and the horizontal support ribs (32) on the vertical support ribs (31). Drill holes into the soil according to the drainage holes reserved on the baffle (33), then insert the drain pipe (34) into the soil, and then inject polyurethane foam (15) into the gap between the baffle (33) and the soil.

10. The construction method according to claim 8, characterized in that, In step S70, use the canopy (65) to shield the foundation pit (67) on rainy days.

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