Construction method of special-shaped arch support

Abstract

This invention provides a construction method for irregular arch support, which uses a cofferdam corner support mechanism to support the cofferdam, ensuring a dry working environment inside the cofferdam. It also solves the problem of arch foot hoisting obstruction caused by conventional steel pipe support structures. By adopting the above method and related structures, this invention solves the problem of insufficient support strength in deep foundation pits leading to a damp working environment inside the foundation pit, and also considers the problem of arch foot pre-embedded hoisting obstruction, ensuring the smooth progress of arch foot pre-embedded pouring operations.

Description

Technical Field

[0001] This invention relates to the field of bridge arch construction technology, specifically a construction method for irregular arch support. Background Technology

[0002] Steel arch abutments are used to support the arch ribs of bridges. The abutments are subjected to pressure from a single arch foot or a double arch foot. For double arch rib abutments, since they need to support two adjacent arch ribs, the abutment structure is generally irregular in shape to solve the overall instability of the abutment caused by pressure from different directions. Because of the use of irregular arch abutments and the need for pre-embedded casting of the arch foot, conventional steel pipe supports are not suitable for supporting foundation pit cofferdams. This results in the arch foot being blocked when hoisting into place and unable to be installed.

[0003] Furthermore, the construction of the steel structure arch supports all took place within deep foundation pits, with an average depth of 5.3 to 6.6 meters. This constitutes a high-risk sub-project exceeding certain scale standards. The geological conditions of the foundation pit strata are mainly soft soil layers, rich in groundwater, and the groundwater level is shallow, averaging only 1 meter. Therefore, how to stabilize the deep foundation pit support and ensure a dry working environment within the pit are issues that need to be considered in deep foundation pit operations. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a construction method for irregular arch support, which solves the problem of insufficient support strength in deep foundation pits leading to a damp working environment in the foundation pit, and at the same time takes into account the problem of obstruction when the arch foot is hoisted into the pit, thus ensuring the normal hoisting operation of the arch foot.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a construction method for irregular arch support, characterized by including the following steps:

[0006] 1) Cofferdam construction

[0007] 1.1) The site is level;

[0008] 1.2) Measurement and positioning;

[0009] 1.3) Guide frame installation;

[0010] 1.4) Drive in steel sheet piles and remove the guide frame;

[0011] 2) Excavation and support construction of the foundation pit

[0012] 2.1) Construction of the upper support structure of the foundation pit;

[0013] 2.2) Excavation of the foundation pit;

[0014] 2.3) Open excavation of dewatering ditches in the foundation pit;

[0015] 2.4) Water pumping;

[0016] 2.5) Break the pile head;

[0017] 2.6) Subbase pouring;

[0018] 3) Dewatering of the foundation pit;

[0019] 4) Foundation pit monitoring;

[0020] 5) Fix the template and pour the arch base.

[0021] In the preferred embodiment, the installation of the guide frame in step 1) specifically includes:

[0022] 1) Use a theodolite and level to control and adjust the position of the guide beam;

[0023] 2) A tracked high-frequency hydraulic pile driver, consisting of an excavator as the main body and a high-frequency hydraulic manipulator, is used for driving steel sheet piles.

[0024] 2.1) Position the pile driver according to the initial sheet pile location on the guide frame;

[0025] 2.2) Clamp the pile into the sluice gate, tighten the clamp, secure the safety device, lift the pile hammer, and lift the sheet pile;

[0026] 2.3) Adjust the verticality or inclination of the pile for precise positioning;

[0027] 2.4) After aligning the pile position, drive the pile, calibrate the verticality and planar position of the pile, and allow the pile to sink. If there is an error in the pile position, pull it out and recalibrate the position. Once the error is controlled within the allowable range, start driving the pile.

[0028] 2.5) First, lightly hammer the pile until it has penetrated to a certain depth, then hammer it heavily until it reaches the designed height.

[0029] 2.6) Measure the deviation and elevation of the stakes;

[0030] 2.7) Hang the steel sheet piles in sequence, secure the grooves, and drive them into the required construction area.

[0031] In the preferred embodiment, in step 2.4), before driving the pile, grease is applied to the interlock of the sheet pile to facilitate driving and pulling it out.

[0032] In the preferred embodiment, the excavation of the foundation pit in step 2) specifically includes:

[0033] 1) Before the large-scale excavation of the foundation pit, a shallow excavation is carried out to create space for the construction of the upper support of the foundation pit, and then the construction of the upper support of the foundation pit begins.

[0034] 2) Earthwork was excavated using a relay excavation method, and the excavated soil was transported away by dump trucks. Long-arm excavators were used to excavate the soil in the difficult sections of the foundation pit where relay excavation was difficult.

[0035] In the preferred embodiment, the excavation of the foundation pit adopts the principle of "vertical layering, middle first then sides, support first then excavation" and the earthwork is excavated in a symmetrical manner, that is, horizontally from the middle to both sides, so as to avoid the phenomenon of eccentric pressure.

[0036] In a preferred embodiment, before the excavation of the foundation pit, a drainage ditch is set around the boundary of the foundation pit, and water leakage and seepage should be prevented from entering the pit and the soil behind the support structure.

[0037] In the preferred embodiment, the dewatering of the foundation pit in step 3) specifically involves:

[0038] 1) A 500*500mm intercepting ditch is set up around the top of the foundation pit to intercept surface water and prevent water from accumulating in the foundation pit. The water collected in the intercepting ditch is pumped to a designated location outside the pit by a sewage pump.

[0039] 2) After the foundation pit is excavated, a 500*500mm dewatering ditch is dug around the inside of the steel sheet pile. Depending on the water accumulation in the foundation pit, 2-4 sewage pumps are deployed to pump the water in the foundation pit to a designated location outside the pit.

[0040] 3) After the precipitation is completed, a 20cm thick C20 concrete layer is poured using a jackpick pump. The top surface elevation of the concrete is controlled to be the same as the bottom elevation of the arch seat.

[0041] In the preferred embodiment, the foundation pit support structure in step 2) includes sheet piles forming a cofferdam, with I-beams installed on the inner side of the sheet piles, and a cofferdam corner support mechanism installed at the corner of the I-beams.

[0042] The cofferdam corner support mechanism includes two arched plates, which are arranged concentrically. Arched plate seats are provided at the ends of the two arched plates. Two baffles perpendicular to the web of the I-beam are provided, and the arched plate seats are installed inside the baffles.

[0043] A lead screw is threaded through the two arched plates. One end of the lead screw is provided with a triangular top plate, which contacts and presses against the contact position of the two I-beams.

[0044] In the preferred embodiment, after the excavation of the foundation pit is completed, a cofferdam corner support mechanism is set at the corner of the I-beam. After the arched plate seats at both ends of the cofferdam corner support mechanism are fixed in the groove formed by the baffle, the screw is driven by an electric drill to rotate and push the triangular top plate to press against the corner of the end of the I-beam.

[0045] In the preferred embodiment, step 5) specifically includes the following steps:

[0046] 5.1) Construct foundation piles and pour concrete cushion layer at the bottom of the foundation pit. During construction, pre-embedded supports are set at the top of the foundation piles and in the concrete cushion layer.

[0047] 5.2) After the foundation piles and concrete cushion layer have been solidified, install the bracket for the inclined support of the arch foot on the pre-embedded support and leave one pre-embedded support remaining.

[0048] 5.3) After hoisting the arch foot into the foundation pit, place the arch foot on the remaining pre-embedded supports and brackets;

[0049] 5.4) Weld the arch foot to the embedded support foot and the arch foot to the bracket;

[0050] 5.5) Erect formwork and pour concrete.

[0051] The construction method for an irregular arch support provided by this invention, by adopting the above-mentioned structure, has the following beneficial effects:

[0052] (1) It solved the problem that the arch foot could not be hoisted into place due to the steel pipe support in conventional cofferdams, and realized the normal progress of the arch foot pre-embedded pouring operation;

[0053] (2) Under the premise of ensuring that the arch foot can be successfully hoisted to the foundation pit, the steel sheet piles were effectively supported by the cofferdam corner support mechanism, which ensured the dry construction environment inside the cofferdam and the stability of the cofferdam. Attached Figure Description

[0054] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0055] Figure 1 This is a schematic diagram of the irregular arch support structure of the present invention.

[0056] Figure 2 This is a top view schematic diagram of the irregular cofferdam structure of the present invention.

[0057] Figure 3 This is a schematic diagram of the cofferdam corner support mechanism of the present invention.

[0058] Figure 4 This is a schematic diagram of the cofferdam structure during the casting of the arch seat of the present invention.

[0059] In the diagram: 1. Arch seat, 2. Slope, 3. Arch foot groove, 4. I-beam, 5. Sheet pile, 6. Cofferdam corner support mechanism, 7. Web plate, 8. Baffle plate, 9. Arch plate seat, 10. Triangular top plate, 11. Screw rod, 12. Foundation pile, 13. Concrete cushion, 14. Support, 15. Embedded support foot, 16. Arch foot. Detailed Implementation

[0060] Example 1:

[0061] A construction method for an irregular arch support includes the following steps:

[0062] 1) Cofferdam construction

[0063] 1.1) The site is level;

[0064] If the initial steel sheet pile construction does not use a stacking method but instead uses a vehicle-mounted method to move the piles along with the construction site, the vehicle-mounted stacking method is the same as the on-site stacking method.

[0065] 1.2) Measurement and positioning;

[0066] 1.3) Guide frame installation;

[0067] 1.4) Drive in steel sheet piles and remove the guide frame;

[0068] In step 1.3) above:

[0069] In sheet pile construction, to ensure the correct alignment of the pile axis and the verticality of the pile, control the driving accuracy, prevent buckling deformation of the sheet pile, and improve the pile's penetration capacity, a rigid and sturdy guide frame is generally required. The guide frame adopts a single-layer, double-sided form, typically composed of guide beams and waler piles. The spacing between the waler piles is generally 2.5–3.5 m, and the spacing between the double-sided guide beams should not be too large, generally slightly larger than the sheet pile wall thickness by 8–15 mm.

[0070] In step 1.4 above:

[0071] The location of the sheet piles should meet the design requirements and facilitate foundation construction, that is, leave a working surface outside the most prominent edge of the foundation.

[0072] The planar layout of the sheet piles for the foundation pit retaining wall should be as straight and neat as possible, avoiding irregular corners, so as to facilitate the use of standard sheet piles and support installation, and the dimensions of each perimeter should conform to the sheet pile module as much as possible.

[0073] Throughout the entire foundation construction period, during excavation, hoisting, and concrete pouring operations, it is strictly forbidden to collide with the supports, arbitrarily dismantle the supports, cut or weld on the supports, or place heavy objects on the supports.

[0074] Vibration driving is recommended for steel sheet pile construction. The allowable deviation of verticality during pile driving is 1 / 150, the allowable deviation of the wall surface along the axis of the foundation pit is 200mm, and the allowable deviation of the pile bottom elevation is 500mm. The small locking method should be used for construction, and the steel sheet piles should be continuously locked and tightly interlocked.

[0075] The construction of sheet piles should ensure that the pile body is straight and the interlocking is tight. To ensure the water-stopping effect at the interlocking points of the sheet piles, use hemp thread wrapped with industrial lubricant and insert a steel rod into the interlocking gaps of the sheet piles. The direction of advancement of the pile tip should be beveled, with a bevel slope of 1:2 to 1:4.

[0076] Before driving steel sheet piles, rust prevention treatment should be carried out, and epoxy coal tar paint can be applied for protection.

[0077] When removing sheet piles, the gaps should be backfilled with cement grout while the piles are being removed.

[0078] According to design requirements, if steel sheet piles are used as a support structure and also serve as a water-stop curtain, the quality of the locking construction should be visually inspected. If the locking is not tight, it should be pulled out and re-driven or remedial measures should be taken.

[0079] 2) Excavation and support construction of the foundation pit

[0080] 2.1) Construction of the upper support structure of the foundation pit;

[0081] 2.2) Excavation of the foundation pit;

[0082] The overall approach to foundation pit excavation is as follows:

[0083] The excavation was carried out using a combination of manual and mechanical methods, with the pit excavation conducted in a continuous flow manner. The excavation strictly adhered to the three key principles of "layered symmetry and time-limited operation," and followed these guidelines:

[0084] 1) Use a long-arm excavator to excavate the soil in the foundation pit. If the environment in the foundation pit allows, manually level the bottom of the foundation pit. If the water accumulation at the bottom of the foundation pit is too deep, over-excavate 30cm and backfill with crushed stone, and then roughly level it with a long-arm excavator.

[0085] 2) Strictly adhere to the principles of "symmetry and balance, support before excavation, and prohibition of over-excavation." Before starting the excavation of the foundation pit, prepare the upper foundation pit support structure to prevent deformation and collapse of the foundation pit.

[0086] 3) During earthwork excavation, care should be taken to ensure that excavating machinery does not damage the support structure, etc. Soil or loads are strictly prohibited around the foundation pit and on the supporting beams, and compaction is prohibited on the capping slab at the top of the pile wall. Excavated soil must be transported away promptly and is strictly prohibited from being piled near the foundation pit. Large loads are strictly prohibited around the foundation pit during earthwork excavation and underground structure construction. Ground overload should be controlled within 15 kPa, and horizontal load distance should be more than 2 meters.

[0087] During the excavation process:

[0088] 1) Construction follows the principle of "vertical layering, middle first then sides, support first then excavation".

[0089] 2) During the earthwork excavation process, pay close attention to the protection of the surrounding environment and effectively reduce the deformation and displacement of the retaining structure and the uneven settlement of the soil.

[0090] 3) The earthwork excavation should be carried out in a symmetrical manner, that is, excavate horizontally from the middle to both sides to avoid the phenomenon of uneven pressure.

[0091] 4) Strengthen the treatment of local abnormal water, identify the water source, cut off the water supply, and take effective preventive measures.

[0092] 5) During construction, in order to avoid collision damage to the retaining structure by earthwork excavation machinery, earthwork excavation near the retaining structure is carried out manually.

[0093] 6) Before excavating the foundation pit, relevant pipeline units should be organized to coordinate and explore underground pipelines and other lines to avoid unnecessary impact and losses during construction.

[0094] 7) Before excavation, drainage ditches shall be set up around the boundary of the foundation pit to prevent water leakage and seepage into the pit and the soil behind the support structure, and the rule of supporting first (constructing the support first) before excavation shall be strictly followed.

[0095] 8) Measures should be taken during the excavation of the foundation pit to prevent collision with the support structure or disturbance of the original soil of the foundation.

[0096] 9) During the excavation of the foundation pit, the excavated soil should be transported away immediately and should not be piled up on the ground around the foundation pit; excavators are strictly prohibited from colliding with the piles (slabs); surveyors should measure at any time to ensure the foundation elevation and the foundation pit line.

[0097] 10) During the excavation of the foundation pit, it is necessary to strictly follow the design requirements to excavate layer by layer, and over-excavation is strictly prohibited.

[0098] 11) During the use of the foundation pit, engineering vehicles shall not be allowed to stay or be loaded on the ground within the design requirements of the top edge of the foundation pit.

[0099] 2.3) Open excavation of dewatering ditches in the foundation pit;

[0100] 2.4) Water pumping;

[0101] 2.5) Break the pile head;

[0102] 2.6) Subbase pouring;

[0103] 3) Dewatering of the foundation pit;

[0104] 4) Foundation pit monitoring;

[0105] 5) Fix the template and pour the arch base 1.

[0106] Example 2:

[0107] Based on Example 1,

[0108] The installation of the guide frame in step 1) specifically includes:

[0109] 1) Use a theodolite and level to control and adjust the position of the guide beam;

[0110] 2) A tracked high-frequency hydraulic pile driver, consisting of an excavator as the main body and a high-frequency hydraulic manipulator, is used for driving steel sheet piles.

[0111] 2.1) Position the pile driver according to the initial sheet pile location on the guide frame;

[0112] 2.2) Clamp the pile into the sluice gate, tighten the clamp, secure the safety device, lift the pile hammer, and lift the sheet pile;

[0113] 2.3) Adjust the verticality or inclination of the pile for precise positioning;

[0114] 2.4) After aligning the pile position, drive the pile, calibrate the verticality and planar position of the pile, and allow the pile to sink. If there is an error in the pile position, pull it out and recalibrate the position. Once the error is controlled within the allowable range, start driving the pile.

[0115] 2.5) First, lightly hammer the pile until it has penetrated to a certain depth, then hammer it heavily until it reaches the designed height.

[0116] 2.6) Measure the deviation and elevation of the stakes;

[0117] 2.7) Hang the steel sheet piles in sequence, secure the grooves, and drive them into the required construction area.

[0118] Example 3:

[0119] Based on Example 1, the excavation of the foundation pit in step 2) specifically includes:

[0120] 1) Before the large-scale excavation of the foundation pit, a shallow excavation is carried out to create space for the construction of the upper support of the foundation pit, and then the construction of the upper support of the foundation pit begins.

[0121] 2) Earthwork was excavated using a relay excavation method, and the excavated soil was transported away by dump trucks. Long-arm excavators were used to excavate the soil in the difficult sections of the foundation pit where relay excavation was difficult.

[0122] Example 4:

[0123] Based on Example 1,

[0124] In the preferred embodiment, the dewatering of the foundation pit in step 3) specifically involves:

[0125] 1) A 500*500mm intercepting ditch is set up around the top of the foundation pit to intercept surface water and prevent water from accumulating in the foundation pit. The water collected in the intercepting ditch is pumped to a designated location outside the pit by a sewage pump.

[0126] 2) After the foundation pit is excavated, a 500*500mm dewatering ditch is dug around the inside of the steel sheet pile. Depending on the water accumulation in the foundation pit, 2-4 sewage pumps are deployed to pump the water in the foundation pit to the designated location outside the pit. In order to ensure dry construction operations in the foundation pit, the groundwater level should be lowered to not less than 0.5m below the bottom of the layer to be excavated.

[0127] 3) After the precipitation is completed, a 20cm thick C20 concrete layer is poured using a jackpick pump. The top surface elevation of the concrete is controlled to be the same as the bottom elevation of the arch seat.

[0128] In addition, during the excavation of the foundation pit and the construction of the main structure, attention should be paid to whether there is water leakage at the interlocking joints of the sheet piles. If there is leakage, it should be plugged. Damaged areas of the sheet piles during construction can be reinforced with electric welding. If obvious leakage is found, it should be treated with special sealing adhesive.

[0129] It is also necessary to closely monitor the water accumulation in the foundation pit and determine whether to install dewatering wells based on the drainage situation.

[0130] Example 5:

[0131] like Figure 1-4 As shown, after the excavation of the foundation pit is completed, a cofferdam corner support mechanism 6 is set at the corner of the I-beam 4. After the arched plate seats 10 at both ends of the cofferdam corner support mechanism 6 are fixed in the groove formed by the baffle 8, the screw rod 12 is driven by an electric drill to rotate and push the triangular top plate 11 to press against the corner of the end of the I-beam 4.

[0132] After the triangular top plate 11 is pressed against the corner position of the end of the I-beam 4, the screw 12 is further driven to rotate slightly. When the triangular top plate 11 is blocked from pushing forward, the arch plate 9 is compressed and deformed outward, thus pressing against the I-beam 4.

[0133] To ensure the tightness of the arched plate 9 against the I-beam 4, a fixing knot can be set at the end of the screw 12 to apply pressure to the center of the convex surface of the arched plate 9.

[0134] In the preferred embodiment, step 5) specifically includes the following steps:

[0135] 5.1) Construct foundation piles and pour concrete cushion layer at the bottom of the foundation pit. During construction, pre-embedded supports are set at the top of the foundation piles and in the concrete cushion layer.

[0136] 5.2) After the foundation piles and concrete cushion layer have been solidified, install the bracket (15) for the inclined support of the arch foot on the pre-embedded support foot and leave one pre-embedded support foot remaining;

[0137] 5.3) After hoisting the arch foot into the foundation pit, place the arch foot on the remaining pre-embedded supports and brackets;

[0138] 5.4) Weld the arch foot to the embedded support foot and the arch foot to the bracket;

[0139] 5.5) Erect formwork and pour concrete.

[0140] After the pouring operation is completed, the final arch support 1 structure is as follows: Figure 1As shown, the arch seat 1 includes two slopes 2, and arch foot grooves 3 connected to the arch foot 17 are provided on the two slopes. The arch seat 1 structure is mainly used for double arch rib support in the middle position of the bridge arch frame.

Claims

1. A construction method of a special-shaped arch support, characterized in that It comprises the following steps: 1) cofferdam construction 1.1) site leveling; 1.2) measurement and positioning; 1.3) installation of guide frame; 1.4) driving of steel sheet pile and removal of guide frame; 2) foundation pit excavation and support construction 2.1) construction of upper support structure of foundation pit; 2.2) excavation of foundation pit; 2.3) construction of open-cut dewatering trench of foundation pit; 2.4) water pumping by water pump; 2.5) pile head breaking; 2.6) cushion pouring; 3) dewatering of foundation pit; 4) monitoring of foundation pit; 5) fixing of formwork and pouring of abutment (1); The support structure of foundation pit in step 2) comprises steel sheet piles (5) forming cofferdam, I-beams (4) arranged inside the steel sheet piles (5), and cofferdam corner support mechanisms (6) arranged at the corner positions of the I-beams (4); The cofferdam corner support mechanism (6) comprises two arcuate plates (9) arranged concentrically, arcuate plate seats (10) arranged at the end portions of the two arcuate plates (9), two baffle plates (8) arranged perpendicularly to the web (7) of the I-beam (4) and arranged on the web (7), and the arcuate plate seats (10) being installed in the baffle plates (8); A lead screw (12) is arranged through the two arcuate plates (9), one end of the lead screw (12) is provided with a triangular top plate (11), and the triangular top plate (11) is in contact with and tightly abuts against the contact position of the two I-beams (4); After the construction of the excavation of the foundation pit is completed, the cofferdam corner support mechanism (6) is arranged at the corner position of the I-beam (4), the arcuate plate seats (10) at the two ends of the cofferdam corner support mechanism (6) are fixed in the baffle plates (8) to form a groove, and then the lead screw (12) is driven to rotate and push the triangular top plate (11) to tightly abut against the end corner position of the I-beam (4) by using an electric drill; The step 5) specifically comprises the following steps: 5.1) constructing foundation piles (13) and pouring concrete cushion (14) at the bottom of the foundation pit, and arranging pre-buried supporting feet (16) on the top of the foundation piles (13) and in the concrete cushion (14) during the construction process; 5.2) after the foundation piles (13) and the concrete cushion (14) are solidified, installing a support (15) for obliquely supporting an abutment (17) on the pre-buried supporting feet (16) and leaving one pre-buried supporting foot (16); 5.3) after hoisting the abutment (17) into the foundation pit, the abutment (17) is placed on the left pre-buried supporting foot (16) and the support (15); 5.4) welding the abutment (17) and the pre-buried supporting foot (16) and the abutment (17) and the support (15); 5.5) erecting the formwork for pouring.

2. The construction method of a special-shaped arch support according to claim 1, characterized in that: The installation of the guide frame in step 1) specifically comprises: 1) using the theodolite and level to control and adjust the position of the guide beam; 2) using a crawler-type high-frequency hydraulic pile driver composed of an excavator as a mother body and a high-frequency hydraulic manipulator to drive the steel sheet pile; 2.1) positioning and placing the pile driver according to the starting steel sheet pile on the guide frame; 2.2) clamping into the entrance, clamping the pile tightly, taking safety measures, lifting the pile hammer, and lifting the steel sheet pile; 2.3) adjusting the perpendicularity or inclination of the pile and accurately positioning. 2.4) pile in the good pile position, calibrate the verticality and the plan position of the pile, make the pile self-sink, if there is error in the pile position, pull it up and re-calibrate the position, control the error within the allowable range, and then start to sink the pile; 2.5) first light hammer, when the pile enters the soil to a certain depth, then heavy hammer, until the design height; 2.6) measure the deviation and elevation of the pile; 2.7) in turn hoist the steel sheet pile, clamp the slot, and drive to the required range of construction.

3. The construction method of a special-shaped arch support according to claim 2, characterized in that: In the step 2.4), before piling, grease is applied in the lock of the sheet pile to facilitate the driving and pulling out.

4. The construction method of a special-shaped arch support according to claim 1, characterized in that: The foundation pit excavation in the step 2) specifically comprises: 1) before the large excavation of the foundation pit, shallowly excavate the upper layer support construction operation space of the foundation pit, and then start the construction of the upper layer support of the foundation pit; 2) the earthwork is excavated by the excavator in a relay mode, the spoil is transported out by the self-unloading truck, and the long-arm excavator is used to excavate the difficult part of the foundation pit.

5. The construction method of a special-shaped arch support according to claim 1, characterized in that: In the process of the foundation pit excavation, the principle of "vertical layering, first middle then both sides, first support then excavation" is adopted for construction, and the earthwork is excavated in a symmetrical manner, i.e. horizontally from the middle to both sides, so as to avoid the deviation phenomenon.

6. The construction method of a special-shaped arch support according to claim 5, characterized in that: Before the foundation pit excavation, a drainage ditch is arranged around the boundary of the foundation pit, and the leakage and seepage into the pit and the soil behind the support structure should be avoided.

7. The construction method of a special-shaped arch support according to claim 1, characterized in that: The foundation pit dewatering in the step 3) specifically comprises: 1) The top of the foundation pit is set around 500 mm water interception ditch, intercepting ground water, preventing water from collecting in the foundation pit, and the water collected by the water interception ditch is pumped to the designated position outside the pit by a sewage pump; 2) After the foundation pit is excavated, a 500mm section is excavated around the inner side of the sheet piles. A 500mm drainage ditch is installed, and 2-4 sewage pumps are deployed to pump the water in the pit to a designated location outside the pit, depending on the water accumulation in the pit. 3) after the dewatering is completed, a C20 concrete with a thickness of 20 cm is poured by a sky pump, and the top surface elevation of the concrete is controlled at the bottom elevation of the arch seat.

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