A construction method for reinforced concrete cofferdams on steep slopes with full rock strata in a lake and reservoir area

Abstract

This invention relates to a construction method for a reinforced concrete cofferdam with a steep, all-rock slope in a lake or reservoir area. The method includes the following steps: a rotary drilling rig drills a pre-drill hole in the bedrock on the riverbed → vibratory sinking of steel pipe piles → leveling of the pile tops → laying steel plates on the pile tops as a temporary construction platform → the rotary drilling rig enters the temporary construction platform to drill a pre-drill hole for the cofferdam steel pipe piles → vibratory sinking of the cofferdam steel pipe piles → using steel beams to tie the cofferdam steel pipe piles together → filling the cofferdam steel pipe piles with sand → laying waterproof geotextile from the top of the cofferdam to the riverbed → removing excess steel pipe piles → pouring cofferdam concrete → excavation of the foundation pit. The advantages of this invention are: this construction method allows for the rapid construction of a temporary construction platform, uses concrete as the main body of the cofferdam, thereby accelerating the construction progress, improving the water-retaining performance of the foundation pit, increasing the safety of the foundation pit construction, and saving construction costs.

Description

Technical Field

[0001] This invention belongs to the field of cofferdam construction technology for foundation pits in construction engineering, and particularly relates to a method for constructing a steel-concrete composite filler cofferdam based on a steep slope of all rock strata in a lake or reservoir area. Background Technology

[0002] Because the foundation pit is adjacent to water, with one corner extending into the water area, a cofferdam is needed to fill the gap. The slope from the bedrock to the riverbed is steep, and the bedrock is moderately weathered fine sandstone with high hardness. Traditional methods for filling the gap involve backfilling with earth to a depth of at least 0.5m above the water surface before excavation. To ensure the safety and water-resistant capacity of the foundation pit, large-scale backfilling is required. However, current regulations prohibit encroachment on protected water areas in China, making this method impractical.

[0003] Due to the high hardness of the bedrock and the steep, near-vertical rock face, traditional methods for constructing cofferdams by directly driving steel pipe piles and sheet piles require the use of large floating pontoons as construction platforms. The general work steps are: pontoon arrival, assembly, and launching → rotary drilling rig and steel pipe pile driving / extraction machine driving onto the pontoon → pontoon moving to the cofferdam positioning point → rotary drilling rig pre-drilling → vibratory sinking of steel pipe piles → erection of support beams → dewatering → excavation of the foundation pit. Since rotary drilling rigs and driving / extraction machines are heavy machinery, large floating pontoons are required. The cost of bringing in and out of large floating pontoons is high, making cost control difficult. Furthermore, large floating pontoons need to be moved multiple times, resulting in a long construction period. Large, heavy-tonnage machinery such as rotary drilling rigs and driving / extraction machines require solid and stable foundations. Working on the pontoons near water poses significant safety hazards and increases construction safety risks. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a steel-concrete gap-filling cofferdam construction method based on steep slopes of all rock strata in lake and reservoir areas. This method can close the water gap in the foundation pit of moderately weathered rock in mountainous areas, ensure the safe excavation and construction of the foundation pit, improve the speed of gap-filling construction, reduce the amount of steel used, improve the water-blocking effect of the cofferdam, ensure the safety of foundation pit construction, guarantee the construction period, and save costs.

[0005] The objective of this invention is achieved through the following technical solution: a method for constructing a reinforced concrete cofferdam with gap filling based on steep slopes of all rock strata in a lake or reservoir area. This method includes the following steps:

[0006] S1. First, determine the location of the gap in the cofferdam that needs to be filled in the foundation pit. Then, drive the rotary drilling rig into the bedrock on the bank and drill a pilot hole in the riverbed in sequence. This pilot hole is used to introduce steel pipe piles to the bottom of the riverbed.

[0007] S2. Drive the drilling and pulling machine onto the bedrock on the shore. After the rotary drilling machine drills a row of pilot holes along the edge of the bedrock on the shore, the vibrating hydraulic hammer of the drilling and pulling machine vibrates and drives the steel pipe piles into the pilot holes. Repeat the steps of drilling the pilot holes of the rotary drilling machine and driving the steel pipe piles with the drilling and pulling machine until a full steel pipe pile structure is formed to fill the gap in the cofferdam.

[0008] S3. Level each steel pipe pile on the full-span steel pipe pile, and lay steel plates on the top of the pile as a temporary construction platform.

[0009] S4. The rotary drilling rig drives onto the temporary construction platform and drills boreholes along the outer edge of the full-span steel pipe piles to the cofferdam.

[0010] S5. Drive the drilling and pulling machine onto the temporary construction platform. After the rotary drilling machine drills a row of holes along the outer edge of the full-span steel pipe piles, the hydraulic hammer of the drilling and pulling machine vibrates and sinks the cofferdam steel pipe piles into the holes. Then the rotary drilling machine continues to drill holes along the outer edge of the row of cofferdam steel pipe piles that have just been sunk and sinks the cofferdam steel pipe piles into the holes to form a cofferdam.

[0011] S6. Steel girders and several corbels are welded to the outer sides of the two rows of cofferdam steel pipe piles. The corbels are located below the steel girders, and the two steel girders are connected to the cofferdam by tie rods.

[0012] S7. Fill each cofferdam steel pipe pile with coarse sand;

[0013] S8. Lay waterproof geotextile from the top of the cofferdam to the riverbed and fix it with steel rods at the top of the cofferdam. Use sandbags to weigh down the waterproof geotextile at the bottom of the riverbed.

[0014] S9. Remove the steel plate and use the vibrating hydraulic hammer of the pulling machine to remove the steel pipe piles in the whole steel pipe pile in sequence.

[0015] S10. Use a conduit to pour concrete into the cofferdam to complete the foundation pit filling cofferdam.

[0016] The beneficial effects of this invention are as follows: using this construction method, a temporary construction platform can be quickly erected, and concrete can be used as the main body of the cofferdam, thereby accelerating the construction progress, improving the water-retaining performance of the foundation pit, increasing the safety of foundation pit construction, and saving construction costs; it can seal the water gap of the foundation pit in the mountainous area with moderately weathered rock, ensure the safe excavation and construction of the foundation pit, improve the speed of the filling construction, reduce the amount of steel used, and improve the water-retaining effect of the cofferdam.

[0017] As a preferred embodiment, according to step S4, when the rotary drilling rig drills boreholes along the outer edge of the full-span steel pipe piles to the cofferdam, boreholes are also required at the junctions of the cofferdam and the bedrock on both sides of the bank. These boreholes are located within the bedrock on the bank. This further enhances the water-blocking capacity at the junction of the cofferdam and the bedrock on the bank.

[0018] As a preferred option, according to step S5, the steel pipe piles of the cofferdam are vibrated and driven into the pilot hole in the bedrock on the shore by the vibrating hydraulic hammer of the jacking machine; this makes the stability of the cofferdam better after it is formed and less prone to collapse.

[0019] Preferably, the steel waist beam includes two channel steels, which are fixed to the outside of the two rows of cofferdam steel pipe piles by welding. The bottoms of the two channel steels are relatively distributed and have interlocking slots for the tie rods to pass through. This facilitates construction and installation between the tie rods and the steel waist beam, while also reducing material costs.

[0020] Preferably, the tie rods are provided in a plurality of positions and are distributed at equal intervals along the length of the cofferdam, and the tie rods pass through the interlocking joint and are located in the gap between adjacent steel pipe piles of the cofferdam; this makes the cofferdam less prone to cracking during concrete pouring, thus reducing the risk of collapse during construction and improving the strength and integrity of the cofferdam.

[0021] Preferably, the steel waist beam is located on the top outer side of the steel pipe pile of the cofferdam; this ensures the strength of the upper end of the cofferdam and prevents deformation.

[0022] Preferably, the outer contour of the full-span steel pipe pile is consistent with the contour of the cofferdam; thus, once the full-span steel pipe pile is constructed, the contour of the cofferdam can be determined by referring to the outer contour of the full-span steel pipe pile, which facilitates construction and greatly improves construction efficiency.

[0023] Preferably, the top of the cofferdam is 50 to 80 cm higher than the height of the bedrock on the bank; this ensures the safety and water-proofing capacity of the foundation pit. Attached Figure Description

[0024] Figure 1 This is a structural schematic diagram of the first construction step of the present invention.

[0025] Figure 2 This is a structural schematic diagram of the second construction step of the present invention.

[0026] Figure 3 This is a structural schematic diagram of construction step three of the present invention.

[0027] Figure 4 This is a structural schematic diagram of construction step four of the present invention.

[0028] Figure 5 This is a structural schematic diagram of construction step five of the present invention.

[0029] Figure 6 This is a structural schematic diagram of construction step five of the present invention.

[0030] Figure 7 This is a structural diagram of construction steps six and seven of the present invention.

[0031] Figure 8 This is a structural schematic diagram of construction step eight of the present invention.

[0032] Figure 9 This is a structural schematic diagram of construction step nine of the present invention.

[0033] Figure 10 This is a structural schematic diagram of construction step ten of the present invention.

[0034] Figure 11 This is a schematic diagram of the gap cofferdam forming structure for the construction of this invention.

[0035] The labels in the attached diagram are as follows: 1. Notch; 2. Rotary drilling rig; 3. Bedrock on shore; 4. Pre-hole; 5. Steel pipe pile; 6. Driving and pulling machine; 7. Full-span steel pipe pile; 8. Steel plate; 9. Cofferdam; 10. Cofferdam steel pipe pile; 11. Steel girders; 12. Corbel; 13. Tie rod; 14. Waterproof geotextile; 15. Steel chisel; 16. Sandbag; 17. Guide pipe; 18. Interlocking joint; 19. Concrete; 61. Vibratory hydraulic hammer; 11-1. Channel steel. Detailed Implementation

[0036] The present invention will now be described in detail with reference to the accompanying drawings: The construction method of the steel-concrete composite cofferdam for gap filling of the present invention includes the following steps: as shown in the attached drawings. Figures 1 to 11 As shown,

[0037] S1. First, determine the location of the gap 1 that needs to be filled in the cofferdam of the foundation pit. Then, drive the rotary drilling rig 2 into the bedrock 3 on the bank and drill the pilot hole 4 in sequence. The pilot hole 4 is used to introduce steel pipe piles 5 to the bottom of the riverbed. The bedrock 3 on the bank is the existing bedrock outside the water area, which serves as a construction platform, making the construction safer.

[0038] S2. Drive the drilling and extraction machine 6 onto the bedrock 3 on the shore. After the rotary drilling machine 2 drills a row of pilot holes 4 along the edge of the bedrock 3, the vibratory hydraulic hammer 61 of the drilling and extraction machine 6 vibrates and drives steel pipe piles 5 into the pilot holes 4. The steps of drilling pilot holes with the rotary drilling machine 2 and driving steel pipe piles 5 with the drilling and extraction machine 6 are repeated until a full steel pipe pile 7 structure is formed to fill the gap 1 of the cofferdam. This construction procedure can meet the requirements for the subsequent cofferdam formation and greatly improves the efficiency of subsequent construction.

[0039] S3. Level each steel pipe pile 5 on the full-span steel pipe pile 7, and lay steel plate 8 on the top of the pile as a temporary construction platform; compared with the existing technology, this completely eliminates the need for floating boxes on the water, greatly improving safety and construction efficiency.

[0040] S4. Rotary drilling machine 2 drives into the temporary construction platform and drills borehole 4 along the outer edge of the full-span steel pipe pile 7 to the cofferdam 9.

[0041] S5. Drive the drilling and pulling machine 6 onto the temporary construction platform. After the rotary drilling machine 2 drills a row of holes 4 along the outer edge of the full-span steel pipe piles 7, the vibrating hydraulic hammer 61 of the drilling and pulling machine 6 vibrates and drives the cofferdam steel pipe piles 10 into the holes 4. Then, the rotary drilling machine 2 continues to drill holes 4 along the outer edge of the row of cofferdam steel pipe piles 10 that have just been driven in, and drives the cofferdam steel pipe piles 10 into the cofferdam steel pipe piles 10 through the drilling and pulling machine 6 to form a cofferdam 9. The width of the cofferdam 9 is the distance between the two rows of cofferdam steel pipe piles 10. Based on the erection of the full-span steel pipe piles 7, and the outer contour of the full-span steel pipe piles 7 is consistent with the contour of the cofferdam 9, the cofferdam 9 is formed faster, and its contour can also meet the construction requirements.

[0042] S6. Steel wain beams 11 and several corbels 12 are welded to the outer sides of the two rows of cofferdam steel pipe piles 10. The corbels 12 are located below the steel wain beams 11. The two steel wain beams 11 are connected to the cofferdam 9 by tie rods 13.

[0043] S7. Fill each cofferdam steel pipe pile 10 with coarse sand; filling with coarse sand makes each cofferdam steel pipe pile 10 stronger, thus making the cofferdam stronger and more stable.

[0044] S8. A waterproof geotextile 14 is laid from the top of the cofferdam 9 to the riverbed, and steel rods 15 are used to fix it at the top of the cofferdam 9. Sandbags 16 are used to weigh down the waterproof geotextile 14 located at the bottom of the riverbed. This can prevent the waterproof geotextile 14 from lumping together when pouring concrete, thus failing to prevent the leakage of concrete slurry.

[0045] S9. Remove the steel plate 8 and use the vibrating hydraulic hammer 61 of the pulling machine 6 to remove the steel pipe piles 5 in the full-span steel pipe pile 7 in sequence.

[0046] S10. Use the conduit 17 to pour concrete 19 into the cofferdam 9 to complete the foundation pit filling cofferdam.

[0047] According to step S4, when the rotary drilling rig 2 drills the pilot hole along the outer edge of the full-span steel pipe pile 7 to the cofferdam 9, pilot holes 4 are also required at the junction of the cofferdam 9 and the bedrock 3 on both sides of the bank. The pilot holes 4 are located in the bedrock 3 on the bank. According to step S5, the cofferdam steel pipe pile 10 is driven into the pilot hole 4 in the bedrock 3 by the vibrating hydraulic hammer 61 of the drilling and pulling machine 6.

[0048] The steel waist beam 11 includes two channel steels 11-1. The two channel steels 11-1 are fixed to the outside of the two rows of cofferdam steel pipe piles 10 by welding. The bottom of the two channel steels 11-1 are distributed opposite each other and have an interlocking slot 18 for the tie rods 13 to pass through. There are several tie rods 13, which are distributed at equal intervals along the length of the cofferdam 9. The tie rods 13 pass through the interlocking slot 18 and are located in the gap between adjacent cofferdam steel pipe piles 10. The two ends of the tie rods 13 are screwed with two nut seats by threaded connection. The tightening of the nut seats with the tie rods 13 makes the overall integrity of the cofferdam better.

[0049] The steel waist beam 11 is located on the top of the outer side of the cofferdam steel pipe pile 10, and the steel waist beam 11 extends all the way to the cofferdam steel pipe pile 10 on the bedrock 3 on the shore. This makes the cofferdam 9 and the bedrock 3 on the shore more integrated, and thus the waterproof performance is also better.

[0050] The top of the cofferdam 9 is 50 to 80 cm higher than the bedrock 3 on the bank, which can meet the requirements for water isolation during the excavation of the foundation pit.

[0051] This invention is not limited to the above-described embodiments. Any changes made to its shape or material composition, or any structural design using the methods provided by this invention, are considered variations of this invention and should be considered within the scope of protection of this invention.

Claims

1. A construction method for a reinforced concrete cofferdam with gap filling based on a steep slope of all-rock strata in a lake / reservoir area, characterized in that: The construction method for this reinforced concrete cofferdam includes the following steps: S1. First, determine the location of the gap (1) that needs to be filled in the cofferdam of the foundation pit. Then, drive the rotary drilling rig (2) into the bedrock (3) on the bank and drill the pilot hole (4) in the riverbed in sequence. The pilot hole (4) is used to introduce steel pipe piles (5) to the bottom of the riverbed. S2. Drive the drilling and pulling machine (6) onto the bedrock (3) on the shore. After the rotary drilling machine (2) drills a row of pilot holes (4) along the shoreline of the bedrock (3), the steel pipe piles (5) are driven into the pilot holes (4) by the vibrating hydraulic hammer (61) of the drilling and pulling machine (6). The steps of drilling the pilot holes of the rotary drilling machine (2) and driving the steel pipe piles (5) with the drilling and pulling machine (6) are repeated until a full steel pipe pile (7) structure is formed in the gap (1) of the cofferdam that needs to be filled. S3. Level each steel pipe pile (5) on the full-span steel pipe pile (7), and lay a steel plate (8) on the top of the pile as a temporary construction platform; S4. The rotary drilling rig (2) drives into the temporary construction platform and drills the pilot hole (4) along the outer edge of the full-span steel pipe pile (7) to the cofferdam (9); S5. Drive the excavator (6) onto the temporary construction platform. After the rotary drilling rig (2) drills a row of holes (4) along the outer edge of the full-span steel pipe piles (7), the vibrating hydraulic hammer (61) of the excavator (6) vibrates and sinks the cofferdam steel pipe piles (10) into the holes (4). Then the rotary drilling rig (2) drills holes (4) again along the outer edge of the row of cofferdam steel pipe piles (10) that have just been sunk and sinks the cofferdam steel pipe piles (10) into the holes (4) through the excavator (6) to form a cofferdam (9). S6. Steel waist beams (11) and several corbels (12) are welded to the outer sides of the two rows of cofferdam steel pipe piles (10). The corbels (12) are located below the steel waist beams (11). The two steel waist beams (11) are connected to the cofferdam (9) by tie rods (13). S7. Fill each cofferdam steel pipe pile (10) with coarse sand; S8. Lay waterproof geotextile (14) from the top of the cofferdam (9) to the riverbed and fix it with steel rods (15) at the top of the cofferdam (9). Use sandbags (16) to weigh down the waterproof geotextile (14) at the bottom of the riverbed. S9. Remove the steel plate (8) and use the vibrating hydraulic hammer (61) of the pulling machine (6) to remove the steel pipe piles (5) in the full-span steel pipe piles (7) one by one. S10. Use the conduit (17) to pour concrete (19) into the cofferdam (9) to complete the foundation pit filling cofferdam.

2. The construction method of reinforced concrete cofferdam for supplementary drainage based on steep slopes of all rock strata in a lake / reservoir area according to claim 1, characterized in that: According to step S4, when the rotary drilling rig (2) drills a hole to the cofferdam (9) along the outer edge of the full-span steel pipe pile (7), it is also necessary to drill holes (4) at the junction of the cofferdam (9) and the bedrock (3) on both sides of the bank. The drill holes (4) are located in the bedrock (3) on the bank.

3. The construction method of reinforced concrete cofferdam for supplementary drainage based on steep slopes of all rock strata in a lake / reservoir area according to claim 2, characterized in that: According to step S5, the steel pipe piles (10) of the cofferdam are vibrated and driven into the pilot hole (4) in the bedrock (3) on the shore by the vibrating hydraulic hammer (61) of the jacking machine (6).

4. The construction method of reinforced concrete cofferdam for supplementary drainage based on steep slopes of all rock strata in a lake / reservoir area according to claim 1, characterized in that: The steel waist beam (11) includes two channel steels (11-1). The two channel steels (11-1) are fixed to the outside of the two rows of cofferdam steel pipe piles (10) by welding. The bottom of the two channel steels (11-1) are relatively distributed and have an interlocking slot (18) for the tie rod (13) to pass through.

5. The construction method of reinforced concrete cofferdam for supplementary drainage based on steep slopes of all rock strata in a lake / reservoir area according to claim 4, characterized in that: The tie rods (13) are provided in a plurality of positions and are distributed at equal intervals along the length of the cofferdam (9). The tie rods (13) pass through the interlocking joint (18) and are located in the gap between adjacent cofferdam steel pipe piles (10).

6. The construction method of reinforced concrete cofferdam for steep slopes with full rock strata in a lake / reservoir area according to claim 1 or 4, characterized in that: The steel waist beam (11) is located on the top of the outer side of the cofferdam steel pipe pile (10).

7. The construction method of reinforced concrete cofferdam for supplementary drainage based on steep slopes of all rock strata in a lake / reservoir area according to claim 1, characterized in that: The outer contour of the full-span steel pipe pile (7) is consistent with the contour of the cofferdam (9).

8. The construction method of reinforced concrete cofferdam for supplementary drainage based on steep slopes of all rock strata in a lake / reservoir area according to claim 1, characterized in that: The top of the cofferdam (9) is 50 to 80 cm higher than the height of the bedrock (3) on the shore.

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