A foundation pit support system for a bridge facing water on one side and a construction method thereof

Abstract

The unilateral water-facing bridge foundation pit support system and its construction method of the present invention belong to the field of bridge engineering. It adopts a "day"-shaped steel sheet pile enclosure and a support structure is arranged inside the steel sheet pile enclosure. Since the foundation pit extends deeply into the water on one side, there is a certain difference in the water and soil pressures on both sides of the foundation pit. Setting the steel sheet pile enclosure into a "day"-shaped structure can prevent large deformations, support shedding or even overall instability from occurring on the bias side during the foundation pit excavation process. Compared with the foundation pit enclosures of cement mixing piles or bored cast-in-place piles, the construction of the present invention is convenient, the construction speed is fast, and there is no need for a curing period. Compared with the foundation pit enclosure of pine piles, the enclosure effect and waterproof performance of the present invention are better. Compared with the "mouth"-shaped steel sheet pile enclosure, the safety performance of the present invention is good, and it can effectively prevent quality accidents such as the inclination of the enclosure pile and the fracture of the purlin caused by the unilateral water pressure. The steel sheet piles can be recycled later, causing no pollution to the water area, protecting land resources and saving costs.

Description

Technical Field

[0001] The invention relates to the field of bridge engineering, and in particular to a foundation pit support system for a single-sided water-facing bridge and a construction method thereof. Background Art

[0002] At present, in the process of construction of elevated or underground expressways in China, in order to reduce land acquisition and demolition and improve land utilization, elevated or underground expressways are often built along rivers, with the elevated pedestals buried in water.

[0003] At present, the support of bridge foundation pits facing water on one side generally uses bored cast-in-place piles, pine wood piles or steel sheet piles. Bored cast-in-place piles require overlapping of single cement mixing piles to form a pile wall. The construction of cement mixing piles requires high costs and involves mud discharge. For pine wood piles and single steel sheet piles, the support structure is easily damaged, the soil is easily unstable or deformed, and the construction safety is difficult to guarantee. Summary of the invention

[0004] The purpose of the present invention is to provide a single-sided water bridge foundation pit support system and a construction method thereof, so as to solve the technical problems that the support of the bridge foundation pit on one side facing the water adopts bored cast-in-place piles for enclosure, which has high cost and mud discharge; and the support structure is easily damaged, the soil is easily unstable or deformed, and the construction safety is difficult to ensure when using pine piles and single-channel steel sheet piles for enclosure.

[0005] In order to solve the above technical problems, the present invention provides a single-side water bridge foundation pit support system, which is arranged in a "sun" shape as a whole, including:

[0006] The first steel sheet pile enclosure is arranged in a rectangular shape, with a planned river channel to be excavated on its south side and a water area on its north side, including two rows of first transverse steel sheet piles and two rows of first longitudinal steel sheet piles. The first steel sheet pile enclosure surrounds the rectangular bridge construction area inside, and the distances between the first transverse steel sheet piles and the first longitudinal steel sheet piles and the bridge construction area are the same;

[0007] The second steel sheet pile is arranged outside the first transverse steel sheet pile near the water area;

[0008] Connecting the steel sheet piles between the end of the first transverse steel sheet pile and the end of the second steel sheet pile near the water area, thereby connecting all the steel sheet piles into a "sun" shaped structure;

[0009] The steel sheet pile support structure comprises a first steel sheet pile enclosure support structure arranged in a first steel sheet pile enclosure and a second steel sheet pile support structure arranged between first transverse steel sheet piles, second steel sheet piles and connecting steel sheet piles in the vicinity of water areas.

[0010] Preferably, the first steel sheet pile enclosure support structure comprises:

[0011] A perimeter purlin connected to the inner wall of the first steel sheet pile enclosure;

[0012] The columns are inserted into the foundation pit between the transversely arranged surrounding purlins, and the columns are arranged at intervals in the transverse direction;

[0013] Longitudinal braces, connected to the top of the columns and connected at both ends to the transversely arranged perimeter purlins;

[0014] Transverse braces are connected between adjacent longitudinal braces.

[0015] Preferably, the longitudinal support includes a retaining wall longitudinal support arranged at the center of the retaining wall to be constructed and a bridge tunnel longitudinal support arranged at the center of the bridge tunnel to be constructed.

[0016] Preferably, the transverse supports are connected between adjacent retaining wall longitudinal supports and between adjacent bridge hole longitudinal supports.

[0017] Preferably, the second steel sheet pile supporting structure comprises longitudinal fixed steel bars connected between first transverse steel sheet piles and second steel sheet piles adjacent to the water area at laterally intervals.

[0018] Preferably, the purlin is an H400 I-beam, and the longitudinal fixed steel bars are flush with the flange plates of the purlin.

[0019] Preferably, triangular support frames are spaced apart and connected between the bottom of the purlin and the inner side wall of the first steel sheet pile enclosure, and the spacing between laterally adjacent triangular support frames is the same as the spacing between adjacent longitudinal supports.

[0020] Preferably, a bracket diagonal brace is also connected between the inner side of the corner of the surrounding purlin and the inner side wall surrounded by the first steel sheet pile.

[0021] In addition, the present invention provides a construction method for the above-mentioned single-side water-facing bridge foundation pit support system, comprising the following steps:

[0022] Step 1: Place a first rectangular steel sheet pile enclosure outside the bridge construction area and at a position at the same distance from the bridge construction area;

[0023] Step 2: driving a second steel sheet pile on the side of the first steel sheet pile enclosure near the water area and at a position at the same distance from the first steel sheet pile enclosure, and driving a connecting steel sheet pile between the end of the second steel sheet pile and the first steel sheet pile enclosure;

[0024] Step 3: excavate within the first steel sheet pile enclosure area and the area enclosed by the first steel sheet pile enclosure, the second steel sheet pile and the connecting steel sheet pile;

[0025] Step 4: When the soil in the area enclosed by the first steel sheet pile is excavated to the water level elevation and the soil in the area between the first transverse steel sheet pile and the second steel sheet pile and the connecting steel sheet pile near the water area is excavated to the height of the longitudinal fixing steel bars, construct the first steel sheet pile retaining support structure within the first steel sheet pile retaining; Step 5: Construct the second steel sheet pile support structure between the first transverse steel sheet pile and the second steel sheet pile and the connecting steel sheet pile near the water area.

[0026] Preferably, the construction of the first steel sheet pile retaining support structure in Step 4 includes the following steps:

[0027] Step 1: Install the waling through the inner sidewall of the first steel sheet pile retaining.

[0028] Step 2: Drive the columns into the foundation pit between the horizontally arranged walings.

[0029] Step 3: Install the longitudinal supports at the top of the columns, and both ends of the longitudinal supports are firmly connected to the waling.

[0030] Step 4: Connect the transverse supports between adjacent longitudinal supports.

[0031] Compared with the prior art, the features and beneficial effects of the present invention are as follows:

[0032] (1) The unilateral water-facing bridge foundation pit support system of the present invention adopts a "day"-shaped steel sheet pile retaining, and a support structure is arranged within the steel sheet pile retaining. The foundation pit of the present invention extends deeply into the water area on one side, and there is a certain difference in the water and soil pressures on both sides of the foundation pit. Setting the steel sheet pile retaining into a "day"-shaped structure can prevent large deformations, support detachment, or even overall instability on the bias side during the foundation pit excavation process.

[0033] (2) The present invention forms a closed rigid support by connecting the waling along the entire length of the inner sidewall of the first steel sheet pile retaining to limit the horizontal displacement of the steel sheet pile. Insert columns into the foundation pit between the horizontally arranged walings, fixedly connect the longitudinal supports at the top of the columns, the longitudinal supports are arranged at intervals in the transverse direction, and connect the transverse supports between the longitudinal supports. In addition, longitudinal fixing steel bars are tied between the first transverse steel sheet pile and the second steel sheet pile near the water area, and the longitudinal fixing steel bars are arranged at intervals in the transverse direction, thereby forming a stable internal support structure and effectively ensuring the stability of the foundation pit.

[0034] (3) Compared with the foundation pit retaining of cement mixing piles or bored cast-in-place piles, the "day"-shaped steel sheet pile retaining of the present invention is convenient for construction, has a fast construction speed, and does not require a curing period. Compared with the foundation pit retaining of pine wood piles, the "day"-shaped steel sheet pile retaining of the present invention has better retaining effect and waterproof performance. Compared with the "mouth"-shaped steel sheet pile retaining, the "day"-shaped steel sheet pile retaining of the present invention has good safety performance and can effectively prevent quality accidents such as the inclination of the retaining piles and the fracture of the waling caused by unilateral water pressure.

[0035] (4) The "day"-shaped steel sheet pile retaining structure of the present invention allows the steel sheet piles to be recycled and reused in the later stage of construction, causing no pollution to the water area, protecting land resources, and saving costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a construction schematic diagram of the foundation pit support system for a bridge with one side facing water.

[0037] Figure 2 It is a plan schematic diagram of the foundation pit support system for a bridge with one side facing water.

[0038] Figure 3 It is a plan schematic diagram of the bridge construction area.

[0039] Figure 4 For Figure 1 or Figure 2 It is a schematic diagram of the A-A cross-section in

[0040] Figure 5 For Figure 4 It is a sectional schematic diagram of part B in

[0041] Figure 6 For Figure 4 It is a transverse schematic diagram of part B in

[0042] Reference numerals in the drawings: 1 - Bridge construction area, 2 - First steel sheet pile retaining structure, 21 - First transverse steel sheet pile, 22 - First longitudinal steel sheet pile, 3 - Second steel sheet pile, 4 - Connecting steel sheet pile, 5 - Triangular support frame, 6 - Waling, 7 - Column, 8 - Limiting steel plate, 9 - Longitudinal support, 91 - Retaining wall longitudinal support, 92 - Bridge opening longitudinal support, 10 - Transverse support, 11 - Longitudinal fixing steel bars, 12 - Bracket diagonal brace, 13 - Steel bar diagonal brace, 14 - Planned excavation river course, 15 - Retaining wall, 16 - Bridge opening of the bridge. DETAILED DESCRIPTION OF THE INVENTION

[0043] To make the technical means, innovative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below.

[0044] The embodiments described herein are specific specific embodiments of the present invention for explaining the concept of the present invention, and are all explanatory and exemplary, and should not be construed as limiting the embodiments of the present invention and the scope of the present invention. Except for the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of this application, and these technical solutions include technical solutions that make any obvious substitutions and modifications to the embodiments described herein.

[0045] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", "front end", "rear end", "both ends", "one end", "the other end", etc. is based on the orientation or positional relationship shown in the drawings. It is 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, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0046] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "provided with", "connection", etc. should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0047] As Figure 1-6 shown, a unilateral water-facing bridge foundation pit support system is arranged in a "day" shape as a whole, and includes a first steel sheet pile enclosure 2, a second steel sheet pile 3, a connecting steel sheet pile 4, and a steel sheet pile support structure. The first steel sheet pile enclosure 2, the second steel sheet pile 3, and the connecting steel sheet pile 4 all adopt 12m Larssen steel sheet piles.

[0048] The first steel sheet pile enclosure 2 is arranged in a rectangle, with a proposed excavation river 14 on its south side and water area on its north side. It includes two rows of first transverse steel sheet piles 21 and two rows of first longitudinal steel sheet piles 22. The first steel sheet pile enclosure 2 encloses the rectangular bridge construction area 1 inside it, and the distances between the first transverse steel sheet piles 21 and the first longitudinal steel sheet piles 22 to the bridge construction area 1 are the same, specifically 3m.

[0049] The second steel sheet pile 3 is arranged outside the first transverse steel sheet pile 21 near the water area, specifically at a position of 4.5m. In the present invention, it is defined that the side close to the proposed excavation river 14 is the inner side, and the side close to the water area is the outer side. The connecting steel sheet pile 4 is connected between the end of the first transverse steel sheet pile 21 near the water area and the end of the second steel sheet pile 3, thereby connecting all the steel sheet piles into a "day" - shaped structure.

[0050] The steel sheet pile support structure includes a first steel sheet pile enclosure support structure arranged inside the first steel sheet pile enclosure 2 and a second steel sheet pile support structure arranged between the first transverse steel sheet pile 21 near the water area and the second steel sheet pile 3 and the connecting steel sheet pile 4.

[0051] The first steel sheet pile enclosure support structure includes a purlin 6, a column 7, a longitudinal support 9 and a transverse support 10. The purlin 6 is connected to the inner wall of the first steel sheet pile enclosure 2, and the purlin 6 is made of H400 I-beam. The purlin 6 is fully welded to the inner wall of the first steel sheet pile enclosure 2. The adjacent purlins 6 are also fully welded at the joints. A triangular support frame 5 is connected between the bottom of the purlin 6 and the inner wall of the first steel sheet pile enclosure 2, and the spacing between the adjacent triangular support frames 5 is the same as the spacing between the adjacent longitudinal supports 9. The triangular support frame 5 is made of 12mm thick steel plate, with a size of 50cm high × 50cm wide × 20cm long, and one is set every 5m. The triangular support frame 5 is fully welded to the purlin 6. A bracket diagonal brace 12 is also connected between the inner side of the corner of the purlin 6 and the inner wall of the first steel sheet pile enclosure 2. The bracket diagonal brace 12 and the surrounding purlin 6 are fully welded.

[0052] The columns 7 are inserted into the foundation pit between the transversely arranged purlins 6, and the columns 7 are arranged at intervals in the transverse direction. The columns 7 are made of H400 I-beams with a length of 9m. A 12mm thick limit steel plate 8 is constructed on the top of the column 7, and the steel plate size is 609×304×400mm. The limit steel plate 8 is required to be fully welded with the column 7. The limit steel plate 8 is welded to the top of the column 7 on both sides of the longitudinal support 9.

[0053] The longitudinal support 9 is connected to the top of the column 7 and the two ends are connected to the transversely arranged purlin 6, specifically, the longitudinal support 9 is fully welded to the limiting steel plate 8. The longitudinal support 9 includes a retaining wall longitudinal support 91 arranged at the center of the retaining wall 15 to be constructed and a bridge hole longitudinal support 92 arranged at the center of the bridge hole 16 to be constructed. The transverse support 10 is connected between adjacent longitudinal supports 9. The transverse support 10 is preferably connected between adjacent retaining wall longitudinal supports 91 and adjacent bridge hole longitudinal supports 92.

[0054] The second steel sheet pile support structure includes a longitudinal fixed steel bar 11 connected between the first transverse steel sheet pile 21 and the second steel sheet pile 3 near the water area along the transverse interval. A φ16mm circular ring is welded and connected on the side opposite to the second steel sheet pile 3 near the water area, and the two ends of the longitudinal fixed steel bar 11 are respectively hooked on the circular ring, thereby fixing the first transverse steel sheet pile 21 near the water area and the second steel sheet pile 3. The longitudinal fixed steel bar 11 is flush with the flange plate of the surrounding purlin 6. In addition, in order to improve the stability of the first steel sheet pile enclosure 2 and the second steel sheet pile 3, the present invention also connects a steel bar diagonal brace 13 between the two adjacent longitudinal fixed steel bars 11 on both sides.

[0055] The construction method of the above-mentioned single-side water-facing bridge foundation pit support system comprises the following steps:

[0056] Step 1: inject a first rectangular steel sheet pile enclosure 2 outside the bridge construction area 1 and at a position at the same distance from the bridge construction area 1;

[0057] Step 2: driving a second steel sheet pile 3 at a position at the same distance from the first steel sheet pile enclosure 2 on the side of the first steel sheet pile enclosure 2 near the water area, and driving a connecting steel sheet pile 4 between the end of the second steel sheet pile 3 and the first steel sheet pile enclosure 2;

[0058] Step 3: excavate the earth in the area of ​​the first steel sheet pile enclosure 2 and the area enclosed by the first steel sheet pile enclosure 2, the second steel sheet pile 3 and the connecting steel sheet pile 4;

[0059] Step 4: When the earthwork in the area of ​​the first steel sheet pile enclosure 2 is excavated to the water level, and the earthwork in the area between the first transverse steel sheet pile 21 and the second steel sheet pile 3 and the connecting steel sheet pile 4 near the water area is excavated to the height of the longitudinal fixed steel bars 11, the first steel sheet pile enclosure support structure is constructed in the first steel sheet pile enclosure 2. The construction method of the first steel sheet pile enclosure support structure is: install the purlin 6 through the inner wall of the first steel sheet pile enclosure 2, and then drive the column 7 into the foundation pit between the transversely arranged purlins 6. Then install the longitudinal support 9 on the top of the column 7, and both ends of the longitudinal support 9 are firmly connected to the purlin 6. Finally, connect the transverse support 10 between the adjacent longitudinal supports 9.

[0060] Step 5: construct the second steel sheet pile support structure between the first transverse steel sheet pile 21 near the water area and the second steel sheet pile 3 and the connecting steel sheet pile 4. After the second steel sheet pile support structure is constructed, backfill is carried out in the area. After backfill is completed, 100mm thick C25 fine stone concrete is poured on the surface. The finished surface elevation of the fine stone concrete is slightly lower than or flush with the top of the steel sheet pile.

[0061] Taking a certain project as an example, the north side of the foundation pit is directly adjacent to the water, and part of the pile foundation is located in the water. The highest water level in the water area is 2.5m, and the lowest water level is 1.2m. The site of this project is mainly ponds, rivers, cultivated land and rice fields. The terrain of this site is slightly undulating, and the ground elevation is generally between 1.60 and 4.00m. The soil layer involved in the project is mainly clay soil. The foundation soil is divided into 10 engineering geological layers, of which ② and ④ layers can be subdivided into 2 sublayers, ③ layer can be separated into an interlayer, ⑩ layer can be divided into 3 sublayers, ④-2, ⑧, and ⑨ layers are missing, a total of 12 geotechnical engineering geological unit layers, and the characteristics of each unit layer are as follows from new to old: ① layer plain fill soil is grayish yellow, gray, loose, mainly clay soil backfill, and contains a small amount of gravel in some parts, with a layer thickness of 0.50m to 5.00m. ②-1 layer of silty clay al-lQ42: grayish yellow, plastic, saturated, rough section, fast shaking reaction, poor viscosity, local phase change to silt, medium compressibility. Layer thickness 1.00~3.10m, layer top burial depth 0.50~2.50m, local distribution. ②-2 layer of silty silty clay (ml-mQ42): gray, fluid plastic, saturated, easy to thixotropic, local phase change to silt and silty clay, high compressibility. Layer thickness 2.60~20.20m, layer top burial depth 0.00~5.00m, distributed throughout the site. ③ layer of clay al-lQ41: mainly grayish yellow, hard plastic, saturated, medium dry strength, medium toughness, medium compressibility. Layer thickness 2.80~20.20m, layer top burial depth 6.20~27.00m, distributed throughout the site.

[0062] Steel sheet piles have been used for the bridge construction area located in the water area, and backfilling and dewatering measures have been taken. The pile foundation construction has been completed and the construction of the bridge pile cap and superstructure is ready. According to the measurement, the site elevation is about 2.8m-4.0m (absolute elevation of the Yellow Sea). A 1:1 large slope is used around the foundation pit, and the bottom of the slope is at least five meters away from the edge of the foundation pit. Ensure that the top elevation of the soil layer in the bridge foundation pit is below 2m. The water level elevation of the north water area is about 1.24m, while the height of all bridge pile caps is 1.5m, and the bottom elevation of the cap is -2.0m. The method below the bottom elevation of the cap includes 100mm cushion layer + 300mm gravel, so it is necessary to excavate to -2.4m (absolute elevation of the Yellow Sea). When constructing the bridge pile cap, the excavation depth of the local area reaches 4.4m.

[0063] Before the single-sided water bridge foundation pit support system of the present invention, a temporary road is constructed and the temporary road is demolished. The existing cement temporary road located in the longitudinal center area of ​​the bridge is used as the main access for earth-moving vehicles, excavators and other equipment to enter and exit the site. In view of the needs of on-site traffic, a new temporary road is redesigned at a position more than 10 meters south of the slope along the south edge of the proposed bridge. The new construction temporary road is 5 meters wide and is cast with 20 cm thick C20 plain concrete. After the construction equipment is transported to the corresponding operating position, and the construction temporary road is cast and reaches the strength, the temporary road overlapping with the bridge construction area 1 is demolished.

[0064] After the construction of the access road and the demolition of the temporary road, the site needs to be leveled. Ensure that there is no open water and silt in the bridge construction area 1, remove the original retaining steel pillars and beams, backfill and level the site to an elevation of 4.0m (absolute elevation of the Yellow Sea), and use an excavator to tamp and level it. The backfill soil between the two steel sheet piles cannot be cultivated soil, silt, rotten soil, or corrosive soil, and must not be mixed with grass roots, bark, etc., and ensure that the compaction coefficient of the backfill soil is not less than 0.90 after compaction. Then use 100mm thick C20 fine stone concrete to reinforce the surface soil in the backfill area.

[0065] Then the foundation pit support system will be constructed. Specifically, it includes:

[0066] (1) Larsen steel sheet pile construction

[0067] The entire bridge construction area 1 was laid out and positioned, and the 12m long 400-170 first steel sheet pile enclosure 2 was installed at the 3m outward expansion position to enclose the bridge construction area 1. On the outside of the first transverse steel sheet pile 21 near the water area, a 12m long second steel sheet pile 3 of the same specification was installed again at a distance of 4.5m. A 12m long connecting steel sheet pile 4 of the same specification was installed between the end of the first transverse steel sheet pile 21 near the water area and the end of the second steel sheet pile 3, and then all the steel sheet piles were connected into a "sun" shaped structure to form a whole. The Larsen steel sheet piles were completed at a top elevation of 3.000m (absolute elevation of the Yellow Sea), exposing 1m from the top surface of the foundation pit soil layer.

[0068] (2) Earth excavation

[0069] During earthwork excavation, the excavation sequence strictly follows the principles of "layered excavation, symmetrical excavation, support first and then excavation, and over-excavation is strictly prohibited" and "large foundation pit, small excavation". Earthwork excavation must be closely coordinated with support construction. Manual excavation is used when the distance from the bottom of the foundation is 30cm, and over-excavation is strictly prohibited. The slope of the temporary slope between adjacent sections in the pit should be less than 1:2 (height-to-width ratio) and the height difference should be less than 1.5m. During excavation, small excavators excavate inside the foundation pit, and large excavators excavate outside the foundation pit.

[0070] (3) Construction of the first steel sheet pile retaining support structure

[0071] When the excavation reaches the elevation of 1.200m (absolute elevation of the Yellow Sea), the first steel sheet pile retaining support structure is constructed.

[0072] 1) First, the triangular support frame 5 is fully welded on the inner wall of the first steel sheet pile enclosure 2. The triangular support frame 5 is made of 12mm thick steel plate and has a size of 50cm high × 50cm wide × 20cm long. One is set every 5m. Then install the purlin 6. The purlin 6 is set on the top of the triangular support frame 5 along the inner wall of the first steel sheet pile enclosure 2. The purlin 6, the first steel sheet pile enclosure 2, and the triangular support frame 5 are fully welded. The four corners of the purlin 6 are fully welded with the bracket diagonal brace 12.

[0073] 2) Drive the column 7 into the foundation pit between the first transverse steel sheet piles 21. The column 7 is H400 steel and has a length of 9m. The column 7 is specifically arranged at the center between the first transverse steel sheet piles 21. Then, a limit steel plate 8 is fully welded on the top of the column 7. The size of the limit steel plate 8 is 609×304×400mm.

[0074] 3) A retaining wall longitudinal support 91 is welded at the center of the 10m retaining wall 15 and the top of the column 7. Both the retaining wall longitudinal support 91 and the bridge hole longitudinal support 92 are made of 609×16 steel support. The two ends of the retaining wall longitudinal support 91 are welded to the purlin 6. Specifically, two retaining wall longitudinal supports 91 are arranged in the 10m retaining wall 15. A bridge hole longitudinal support 92 is welded at the center of the bridge hole 16 and the top of the column 7. The two ends of the bridge hole longitudinal support 92 are welded to the purlin 6. Specifically, one bridge hole longitudinal support 92 is arranged in the center of the bridge hole 16. A total of 9 longitudinal supports 9. The longitudinal support 9 is fully welded to the column 7 and the limit steel plate 8.

[0075] 4) Two transverse supports 10 are connected between the longitudinal supports 91 of the retaining wall and between the longitudinal supports 92 of the bridge hole, for a total of 12 transverse supports 10.

[0076] (4) Construction of the second steel sheet pile support structure

[0077] The longitudinal fixed steel bars 11 are connected between the first transverse steel sheet pile 21 and the second steel sheet pile 3 near the water area, and the longitudinal fixed steel bars 11 are arranged at intervals along the transverse direction. The specification of the longitudinal fixed steel bars 11 is φ25, and the interval between adjacent longitudinal fixed steel bars 11 is 1.2m. The steel bar diagonal braces 13 are installed at the four corners and fixed to the first transverse steel sheet pile 21. After the construction of the longitudinal fixed steel bars 11 and the steel bar diagonal braces 13 is completed, the soil is backfilled in this area. After the backfilling is completed, 100mm thick C25 fine stone concrete is poured on the surface. The finished surface elevation of the fine stone concrete is slightly lower than or flush with the top of the steel sheet pile.

[0078] During the subsequent construction of the upper structure of the bridge body, the transverse support 10 can be removed in a timely manner while ensuring the stability of the foundation pit. If the transverse support 10 is difficult to remove, the column 7 can be cut off.

[0079] The above embodiments are merely descriptions of preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A foundation pit support system for a bridge on one side facing water, characterized in that: The overall layout is in the shape of a "sun", including: The first steel sheet pile enclosure (2) is arranged in a rectangular shape, with a river channel (14) to be excavated on its south side and a water area on its north side, and includes two rows of first transverse steel sheet piles (21) and two rows of first longitudinal steel sheet piles (22). The first steel sheet pile enclosure (2) surrounds the rectangular bridge construction area (1) inside, and the distances between the first transverse steel sheet piles (21) and the first longitudinal steel sheet piles (22) and the bridge construction area (1) are the same; A second steel sheet pile (3) is arranged outside the first transverse steel sheet pile (21) adjacent to the water area; Connecting steel sheet piles (4) between the end of the first transverse steel sheet pile (21) and the end of the second steel sheet pile (3) near the water area, thereby connecting all the steel sheet piles into a "sun" shaped structure; The steel sheet pile support structure comprises a first steel sheet pile enclosure support structure arranged in a first steel sheet pile enclosure (2) and a second steel sheet pile support structure arranged between a first transverse steel sheet pile (21) and a second steel sheet pile (3) and a connecting steel sheet pile (4) near the water area; The first steel sheet pile enclosure support structure comprises a purlin (6), a column (7), a longitudinal support (9) and a transverse support (10); the purlin (6) is connected to the inner wall of the first steel sheet pile enclosure (2) to form a closed rigid support; The second steel sheet pile support structure comprises longitudinal fixed steel bars (11) connected between first transverse steel sheet piles (21) and second steel sheet piles (3) adjacent to the water area along a transverse interval, thereby effectively ensuring the stability of the foundation pit; Wherein, retaining walls (15) to be constructed are provided on both sides of the river channel (14) to be excavated, and a bridge arch (16) to be constructed is provided in the middle of the retaining walls (15) to be constructed; The longitudinal support (9) comprises a retaining wall longitudinal support (91) arranged at the center of the retaining wall (15) to be constructed and a bridge hole longitudinal support (92) arranged at the center of the bridge hole (16) to be constructed; The transverse supports (10) are connected between adjacent retaining wall longitudinal supports (91) and between adjacent bridge hole longitudinal supports (92).

2. The foundation pit support system for a single-side water-facing bridge according to claim 1 is characterized in that: The first steel sheet pile enclosure support structure comprises: A purlin (6) connected to the inner wall of the first steel sheet pile enclosure (2); The columns (7) are inserted into the foundation pit between the transversely arranged surrounding purlins (6), and the columns (7) are arranged at intervals in the transverse direction; A longitudinal support (9) connected to the top of the column (7) and connected at both ends to the transversely arranged purlins (6); The transverse support (10) is connected between adjacent longitudinal supports (9).

3. The foundation pit support system for a single-side water-facing bridge according to claim 1 is characterized in that: The enclosure purlin (6) is an H400 I-beam, and the longitudinal fixed steel bars (11) are flush with the flange plate of the enclosure purlin (6).

4. The foundation pit support system for a single-side water-facing bridge according to claim 1 is characterized in that: A triangular support frame (5) is spaced apart and connected between the bottom of the enclosure purlin (6) and the inner side wall of the first steel sheet pile enclosure (2), and the spacing between laterally adjacent triangular support frames (5) is the same as the spacing between adjacent longitudinal supports (9).

5. The foundation pit support system for a single-side water-facing bridge according to claim 1 is characterized in that: A bracket diagonal brace (12) is also connected between the inner side of the corner of the enclosure purlin (6) and the inner side wall of the first steel sheet pile enclosure (2).

6. The construction method of the foundation pit support system of a single-side water bridge according to any one of claims 1 to 5, characterized in that The following steps are involved: Step 1: injecting a first rectangular steel sheet pile enclosure (2) at a position outside the bridge construction area (1) and at the same distance from the bridge construction area (1); Step 2: driving a second steel sheet pile (3) at a position on the side of the first steel sheet pile enclosure (2) close to the water area and at the same distance from the first steel sheet pile enclosure (2), and driving a connecting steel sheet pile (4) between the end of the second steel sheet pile (3) and the first steel sheet pile enclosure (2); Step 3: excavating the earth in the area of ​​the first steel sheet pile enclosure (2) and in the area enclosed by the first steel sheet pile enclosure (2), the second steel sheet pile (3) and the connecting steel sheet pile (4); Step 4: When the earthwork in the area of ​​the first steel sheet pile enclosure (2) is excavated to the water level, and the earthwork in the area between the first transverse steel sheet pile (21) and the second steel sheet pile (3) and the connecting steel sheet pile (4) near the water area is excavated to the height of the longitudinal fixed steel bars (11), the first steel sheet pile enclosure support structure is constructed in the first steel sheet pile enclosure (2); Step 5: construct a second steel sheet pile support structure between the first transverse steel sheet pile (21) near the water area and the second steel sheet pile (3) and the connecting steel sheet pile (4).

7. The construction method of the foundation pit support system of a single-side water bridge according to claim 6 is characterized in that: The construction of the first steel sheet pile enclosure support structure in step 4 includes the following steps: Step 1: Install a purlin (6) through the inner wall of the first steel sheet pile enclosure (2); Step 2: driving columns (7) into the foundation pit between the transversely arranged purlins (6); Step 3: Install the longitudinal support (9) on the top of the column (7), and both ends of the longitudinal support (9) are firmly connected to the purlin (6); Step 4: Connect the transverse supports (10) between adjacent longitudinal supports (9).

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