A repair structure and repair method for underwater foundation structure scour pit

Abstract

The present invention discloses a repair structure for a scour pit of an underwater foundation structure, including a scour pit foundation solidification structure, a scour pit backfill solidification structure and an anti-scour protection solidification structure. The scour pit foundation solidification structure is a plurality of solidified soil piles driven into the bottom surface of the scour pit and the outer seabed of the scour pit; the scour pit foundation solidification structure is connected to the underwater foundation structure through a curing agent; the scour pit backfill solidification structure is solidified soil blown into the scour pit, and the top elevation of the scour pit backfill solidification structure is the seabed surface elevation; the anti-scour protection solidification structure is solidified soil blown into the top surface of the scour pit backfill solidification structure, and the top surface of the anti-scour protection solidification structure is 80 cm higher than the top surface of the scour pit, and the distance from the outer edge of the bottom surface to the edge of the scour pit is 0.5 times the diameter of the scour pit. The present invention also discloses a repair method for a scour pit of an underwater foundation structure. The present invention can effectively repair the scour pit that has been formed and prevent the scour pit from forming again.

Description

Technical Field

[0001] The invention relates to a repairing structure and a repairing method for an underwater foundation structure scouring pit. Background Art

[0002] In recent years, with the continuous expansion of the scale of development and utilization of marine energy resources, more and more offshore structures have appeared at sea. Piles and piers are common underwater foundation structures in water buildings such as docks, bridges and offshore platforms. When these underwater foundation structures stand in the ocean, the flow field near the underwater foundation structure will change greatly, horseshoe vortices will be generated in front, the flow velocity will be enhanced, and when the waves encounter the underwater foundation structure, diffraction, reflection and wave breaking will occur. These phenomena ultimately cause the shear stress and sediment transport rate of the seabed at the bottom of the underwater foundation structure to increase, and lead to local scouring. In a complex marine environment, the scouring pits generated reduce the contact depth between the underwater foundation structure and the surrounding seabed, reducing the bearing capacity and stability of the underwater foundation structure.

[0003] Existing scour pits are often filled by throwing stones, throwing sand bags, covering with sand blankets, etc. These methods can only play the role of increasing the protective surface layer, and cannot improve the anti-scour properties of the original foundation soil. New scour often occurs at the interface between the protective layer and the original foundation soil. Over time, the protective layer is destroyed under the long-term action of waves and currents, making the foundation subject to the risk of scour again. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a repair structure and repair process for underwater foundation structure scour pits, which can effectively repair the scour pits that have been formed and prevent the scour pits from forming again, thereby ensuring the stability of the underwater foundation structure.

[0005] A technical solution to achieve the purpose of the present invention is: a repair structure of a scour pit of an underwater foundation structure, including a scour pit foundation solidification structure, a scour pit backfill solidification structure and an anti-scour protection solidification structure; wherein,

[0006] The scour pit foundation solidification structure is a plurality of solidified soil piles driven into the bottom surface of the scour pit and the outer seabed of the scour pit, and the plurality of solidified soil piles are mutually engaged to form closed piles; the scour pit foundation solidification structure is connected to the underwater foundation structure through a curing agent; the distance from the outer edge of the scour pit foundation solidification structure to the edge of the scour pit is 0.5 times the diameter of the scour pit, and the depth of the scour pit foundation solidification structure is 3 to 5 meters below the bottom surface of the scour pit, and from shallow to deep from outside to inside;

[0007] The scouring pit backfill solidification structure is solidified soil blown into the scouring pit, and the top elevation of the scouring pit backfill solidification structure is the elevation of the seabed surface outside the scouring pit;

[0008] The anti-scour protection solidification structure is solidified soil blown onto the top surface of the scour pit backfill solidification structure. The top surface of the anti-scour protection solidification structure is a spherical arc surface and the highest point is 80 cm higher than the top surface of the scour pit. The distance from the outer edge of the bottom surface of the anti-scour protection solidification structure to the edge of the scour pit is 0.5 times the diameter of the scour pit.

[0009] In the above-mentioned repair structure for the underwater foundation structure scour pit, the solidified soil piles are mixing piles.

[0010] In the above-mentioned repair structure of the underwater foundation structure scour pit, each of the solidified soil piles is rectangular in shape and has an effective plane size of 1.6m×2m; and the solidified soil piles are interlocked with each other by 10cm.

[0011] Another technical solution to achieve the purpose of the present invention is: a method for repairing an underwater infrastructure scour pit, comprising the following steps:

[0012] Step 1: Scan the scour pit to obtain the diameter and depth of the scour pit;

[0013] Step 2: Take soil from the seabed around the underwater foundation structure, and conduct a curing agent mix ratio test using the 90-day compressive strength as the design standard to determine the optimal curing agent dosage of 8% to 12%;

[0014] Step 3: First prepare the curing agent at the construction site, then carry out the curing soil pile construction, and construct from shallow to deep from the outside to the inside with the underwater foundation structure as the center; when constructing the curing soil pile, inject the curing agent 3 to 5 meters below the bottom of the scouring pit and stir it thoroughly to make the curing agent fully blend with the soil around the underwater foundation structure to form a scouring pit foundation curing structure;

[0015] Step 4, filling the curing agent in the gap between the scouring pit foundation curing structure and the underwater foundation structure by increasing a certain pressure;

[0016] Step 5: Take samples to test the compressive strength 7 days after the construction of the scouring pit foundation solidification structure is completed, and obtain the 7-day compressive strength qu1, and calculate the 90-day compressive strength of the scouring pit foundation solidification structure by the following formula:

[0017] qu1 / qu2=(T1 / T2) a

[0018] Where: qu1 is the compressive strength at age T1, T1 is 7 days; qu2 is the compressive strength at age T2, T2 is 90 days; the value of a is 0.265~0.4;

[0019] Step 6: After the scouring pit foundation solidification structure is initially solidified, use a dredger to take soil from the construction area to a mud barge, add a curing agent to the soil on the mud barge and stir it evenly to form solidified soil, and then use a blow-fill method to pump the solidified soil into the scouring pit to form a scouring pit backfill solidification structure;

[0020] Step seven: no more than two days after the scour pit backfill solidification structure is formed, use a dredger to take soil from the vicinity of the construction waters to a mud barge, add a curing agent to the soil on the mud barge and stir it evenly to form solidified soil, and then use a blow-fill method to pump the solidified soil to the top surface of the scour pit backfill solidification structure to form an anti-scour protection solidification structure.

[0021] In the above-mentioned repair process for underwater infrastructure scour pits, when performing step 2, the curing agent is mixed with high-strength cementitious material, active material, activator and passivating material in a certain ratio, and the water-cement ratio of the curing agent is 0.55-0.7.

[0022] In the above-mentioned repair process of the underwater foundation structure scour pit, when performing step three, the solidified soil pile is a mixing pile, and the mixing pile is constructed by using a mixing pile foundation according to the following procedures: drilling and mixing → lifting and spraying mixing → secondary drilling and mixing → repeated lifting and spraying mixing → displacement;

[0023] When drilling and mixing, start the mixing motor and the lifting motor, and the mixing head drills down along the guide frame to cut the soil. When the mixing head drills to the designed depth, fixed spraying is performed;

[0024] When lifting and spraying, the mixing head is lifted, spraying and mixing are performed, and finally the mixing head rises to the working reference surface;

[0025] When the secondary drilling and mixing is performed, the mixing head drills and mixes again along the guide frame;

[0026] When repeated lifting and spraying mixing is carried out, the mixing head is lifted while spraying and mixing are carried out.

[0027] In the above-mentioned repair process for underwater infrastructure scour pits, when performing steps six and seven, the construction is carried out at low tide on the construction site, and the wave and water flow conditions meet the requirement that the curing agent does not cause scour within the initial setting time.

[0028] The repair structure and repair process of the underwater foundation structure scouring pit of the present invention have the following characteristics:

[0029] 1) At the bottom of the scour pit, an in-situ solidification method is used to reinforce the seabed around the underwater foundation, that is, solidified soil piles are set at a certain depth below the bottom of the scour pit and at a certain depth below the seabed within a certain range outside the scour pit to form a scour pit foundation solidification structure, and then an ex-situ solidification method is used to repair the scour pit, that is, soil is taken near the construction water area and a curing agent is added to the soil to form solidified soil, and then the solidified soil is blown into the scour pit to form a scour pit backfill solidification structure, and then solidified soil is blown again on the scour pit backfill solidification structure to form an anti-scour protection solidification structure. The repair structure of the underwater foundation structure scour pit can effectively improve the strength and water stability of the foundation soil around the underwater foundation structure, improve the anti-scour ability of the original soil, and the anti-scour protection solidification structure naturally transitions with the natural mud surface line of the original seabed, avoiding interface scour caused by sudden changes in water boundary conditions.

[0030] 2) The present invention firstly solidifies and repairs the bottom of the scour pit by an in-situ solidification method, which can reduce the solidification amount of the scour pit backfill solidification structure and the anti-scour protection solidification structure, and ensure that the scour pit backfill solidification structure and the anti-scour protection solidification structure can be completed in one time.

[0031] 3) It can effectively repair the scour pits that have already formed and prevent them from forming again, thus ensuring the stability of the underwater foundation structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is an elevational view of a repair structure for an underwater infrastructure scour pit of the present invention;

[0033] Figure 2 It is a plan view of the repair structure of the underwater infrastructure scour pit of the present invention. DETAILED DESCRIPTION

[0034] The present invention will be further described below in conjunction with the accompanying drawings.

[0035] The repair structure of the scour pit of the underwater foundation structure of the present invention comprises a scour pit foundation solidification structure 30, a scour pit backfill solidification structure 50 and an anti-scour protection solidification structure 60; wherein,

[0036] The scouring pit foundation solidification structure 30 is a plurality of solidified soil piles 3 driven into the bottom surface of the scouring pit 20 and the outer seabed of the scouring pit 20. Each solidified soil pile 3 is a mixing pile. The solidified soil pile 3 is rectangular and has an effective plane size of 1.6m×2m. The plurality of solidified soil piles 3 are engaged with each other by 10cm to form a closed pile. The scouring pit foundation solidification structure 30 is connected to the underwater foundation structure 10 through a curing agent 40. The distance from the outer edge of the scouring pit foundation solidification structure 30 to the edge of the scouring pit 20 is 0.5 times the diameter D of the scouring pit. The depth of the scouring pit foundation solidification structure 30 is 3 to 5m below the bottom surface of the scouring pit 20 and is from shallow to deep from outside to inside.

[0037] The scouring pit backfill solidification structure 50 is solidified soil blown into the scouring pit 20, and the top elevation of the scouring pit backfill solidification structure 50 is the elevation of the seabed surface outside the scouring pit 20;

[0038] The anti-scour protection solidification structure 60 is a solidified soil cover blown onto the top surface of the scour pit backfill solidification structure 50. The top surface of the anti-scour protection solidification structure 60 is a spherical arc surface and the highest point is 80 cm higher than the top surface of the scour pit 20. The distance from the outer edge of the bottom surface of the anti-scour protection solidification structure 60 to the edge of the scour pit 20 is 0.5 times the diameter D of the scour pit.

[0039] The repair structure of the scour pit of the underwater foundation structure of the present invention can effectively repair the scour pit that has been formed, and can prevent the scour pit from forming again, thereby ensuring the stability of the underwater foundation structure.

[0040] The method for repairing an underwater infrastructure scour pit of the present invention comprises the following steps:

[0041] Step 1: Scan the scouring pit 20 around the underwater foundation structure 10 to obtain the diameter D and depth of the scouring pit 20;

[0042] Step 2: Take soil from the seabed around the underwater foundation structure, and conduct a curing agent mix ratio test with 90-day compressive strength as the design standard to determine the optimal curing agent dosage of 8% to 12%; the curing agent is made of high-strength cementitious material, active material, activator and passivation material mixed in a certain ratio, and the water-cement ratio of the curing agent is 0.55 to 0.7; the curing agent uses cement, GS rock and soil curing agent or silt curing agent;

[0043] Step three, first prepare a curing agent at the construction site, and then perform in-situ curing, that is, perform solidification soil pile construction, and perform construction from shallow to deep from the outside to the inside with the underwater foundation structure as the center; during the solidification soil pile construction, inject the curing agent to a certain depth below the bottom of the scouring pit, and fully stir it so that the curing agent is fully integrated with the soil around the underwater foundation structure 10 to form a scouring pit foundation solidification structure 30; the depth of the scouring pit foundation solidification structure 30 is calculated based on the depth of the scouring pit 20;

[0044] Each solidified soil pile is a mixing pile, which is constructed by a mixing pile machine according to the following procedures: drilling and mixing → lifting and spraying mixing → secondary drilling and mixing → repeated lifting and spraying mixing → displacement;

[0045] When drilling and mixing, start the mixing motor and the lifting motor, and the mixing head drills down along the guide frame to cut the soil. When the mixing head drills to the designed depth, fixed spraying is performed;

[0046] When lifting and spraying, the mixing head is lifted, spraying and stirring are performed at the same time, and the lifting speed of the mixing head and the spraying flow rate are controlled to ensure that the curing agent slurry and the soil are fully mixed. Finally, the mixing head is raised to the working reference surface.

[0047] The second drilling and stirring is to ensure that the dosage of the curing agent slurry meets the design requirements. The stirring head drills and stirs again along the guide frame.

[0048] Repeated lifting and spraying mixing is to ensure that the silt soil layer and the curing agent slurry are evenly mixed. During the lifting process of the mixing head, spraying and mixing are carried out at the same time;

[0049] Step 4: Fill the gap between the scouring pit foundation curing structure 30 and the underwater base structure 10 with a curing agent 40 by increasing a certain pressure to ensure the stability of the underwater base structure 10;

[0050] Step 5: Take samples to test the compressive strength 7 days after the construction of the scouring pit foundation solidification structure 30 is completed, and obtain the 7-day compressive strength qu1, and calculate the 90-day compressive strength of the scouring pit foundation solidification structure by the following formula:

[0051] qu1 / qu2=(T1 / T2) a

[0052] Where: qu1 is the compressive strength at age T1, T1 is 7 days; qu2 is the compressive strength at age T2, T2 is 90 days; the value of a is 0.265~0.4;

[0053] Step 6: After the scouring pit foundation solidification structure 30 has initially solidified, the construction is carried out at low tide on the construction site, and the wave and water flow conditions meet the requirement that the curing agent does not cause scouring during the initial setting time; if the working conditions are limited and cannot provide sufficient initial setting time for the curing agent, it is necessary to add an early strength agent and other methods to adjust the mix ratio of the curing agent to shorten the initial setting time of the curing agent to meet the reinforcement effect of the early stage of ex situ solidification; use a dredger to take soil from the vicinity of the construction waters to a mud barge, add a curing agent to the soil on the mud barge and stir it evenly to form solidified soil, and then use a blow-fill method to pump the solidified soil into the scouring pit 20 to form a scouring pit backfill solidification structure 50; the shear strength of the soil around the underwater foundation structure 10 can be effectively improved, and the erosion resistance can be improved;

[0054] Step seven, no more than two days after the formation of the scour pit backfill solidification structure 50, the construction is carried out during low tide at the construction site, and the wave and water flow conditions meet the requirement that the curing agent does not cause scouring during the initial setting time; if the operating conditions are limited and cannot provide sufficient initial setting time for the curing agent, it is necessary to add an early strength agent when designing the mix ratio of the curing agent to shorten the initial setting time of the curing agent to meet the reinforcement effect of the early stage of ex situ curing; use a dredger to take soil near the construction waters to a mud barge, add a curing agent to the soil on the mud barge and stir it evenly to form solidified soil, and then use a blowing and filling method to pump it to the top surface of the scour pit backfill solidification structure 50 to form an anti-scour protection solidification structure 60.

[0055] During step six and step seven, since the fill is high-water content solidified soil, the slurry can flow autonomously to the structural gaps or low-lying areas, thereby ensuring the integrity of the scour pit backfill solidified structure 50 and the anti-scour protection solidified structure 60, and improving the scour protection capability of the solidified structure.

[0056] After the repair construction is completed, the repair range of the scour pit 20 is scanned by multi-beam and other means, and the loss Q of the reinforcement body is statistically calculated based on the scanning results at different stages, and the Qt curve is drawn. When the curve tends to converge, it is considered that the scour protection requirements are met.

[0057] The method for repairing scour pits of underwater foundation structures of the present invention is mainly used for repairing scour pits of underwater foundation structures such as pile foundations and bridge piers.

[0058] The above embodiments are only used to illustrate the present invention, rather than to limit the present invention. Those skilled in the relevant technical field may make various changes or modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions should also belong to the scope of the present invention and should be defined by the claims.

Claims

1. A repair structure for a scour pit of an underwater foundation structure, comprising a scour pit foundation solidification structure, a scour pit backfill solidification structure and an anti-scour protection solidification structure; characterized in that: The scour pit foundation solidification structure is a plurality of solidified soil piles driven into the bottom surface of the scour pit and the outer seabed of the scour pit, and the solidified soil piles are mixing piles; the plurality of solidified soil piles are mutually engaged to form closed piles, and each of the solidified soil piles is rectangular and has an effective plane size of 1.6m×2m; the scour pit foundation solidification structure is connected to the underwater foundation structure through a curing agent; the distance from the outer edge of the scour pit foundation solidification structure to the edge of the scour pit is 0.5 times the diameter of the scour pit, and the depth of the scour pit foundation solidification structure is 3 to 5m below the bottom surface of the scour pit, and from shallow to deep from outside to inside; The scouring pit backfill solidification structure is solidified soil blown into the scouring pit, and the top elevation of the scouring pit backfill solidification structure is the elevation of the seabed surface outside the scouring pit; The anti-scour protection solidification structure is solidified soil blown onto the top surface of the scour pit backfill solidification structure. The top surface of the anti-scour protection solidification structure is a spherical arc surface and the highest point is 80 cm higher than the top surface of the scour pit. The distance from the outer edge of the bottom surface of the anti-scour protection solidification structure to the edge of the scour pit is 0.5 times the diameter of the scour pit.

2. A method for repairing an underwater infrastructure scour pit, characterized in that: The repair method comprises the following steps: Step 1: Scan the scour pit to obtain the diameter and depth of the scour pit; Step 2: Take soil from the seabed around the underwater foundation structure, and conduct a curing agent mix ratio test with 90-day compressive strength as the design standard to determine that the optimal curing agent dosage is 8% to 12%; the curing agent is mixed with high-strength cementitious material, active material, activator and passivation material in a certain ratio, and the water-cement ratio of the curing agent is 0.55 to 0.7; Step 3: First prepare the curing agent at the construction site, and then perform in-situ curing, that is, perform the curing soil pile construction, and construct from shallow to deep from the outside to the inside with the underwater foundation structure as the center; when constructing the curing soil pile, inject the curing agent 3 to 5 meters below the bottom of the scouring pit, and stir it thoroughly to make the curing agent fully blend with the soil around the underwater foundation structure to form a scouring pit foundation curing structure; The solidified soil pile is a mixing pile, and the mixing pile is constructed by using a mixing pile foundation according to the following procedures: drilling and mixing → lifting and spraying mixing → secondary drilling and mixing → repeated lifting and spraying mixing → displacement; When drilling and mixing, start the mixing motor and the lifting motor, and the mixing head cuts the soil and drills down along the guide frame. When the mixing head drills to the designed depth, fixed spraying is performed; When lifting and spraying, the mixing head is lifted, spraying and mixing are performed, and finally the mixing head rises to the working reference surface; When the secondary drilling and mixing is performed, the mixing head drills and mixes again along the guide frame; When repeatedly lifting and spraying, the mixing head is lifted while spraying and mixing; Step 4: Fill the gap between the scouring pit foundation solidification structure and the underwater foundation structure with a curing agent by increasing a certain pressure; Step 5: Take samples to test the compressive strength 7 days after the construction of the scouring pit foundation solidification structure is completed, and obtain the 7-day compressive strength qu1, and calculate the 90-day compressive strength of the scouring pit foundation solidification structure by the following formula: qu1 / qu2=(T1 / T2) a Where: qu1 is the compressive strength at age T1, T1 is 7 days; qu2 is the compressive strength at age T2, T2 is 90 days; the value of a is 0.265~0.4; Step 6: After the scouring pit foundation solidification structure is initially solidified, use a dredger to take soil from the construction area to a mud barge, add a curing agent to the soil on the mud barge and stir it evenly to form solidified soil, and then use a blow-fill method to pump the solidified soil into the scouring pit to form a scouring pit backfill solidification structure; Step 7: No more than two days after the scour pit backfill solidification structure is formed, use a dredger to take soil from the construction waters to a mud barge, add a curing agent to the soil on the mud barge and stir it evenly to form solidified soil, and then use a blow-fill method to pump the solidified soil to the top surface of the scour pit backfill solidification structure to form an anti-scour protection solidification structure; When carrying out steps six and seven, construction is carried out at low tide on the construction site, and the wave and water flow conditions meet the requirement that the curing agent will not be washed away during the initial setting time; if the operating conditions are limited and cannot provide sufficient initial setting time for the curing agent, an early strength agent is added for adjustment when designing the mix ratio of the curing agent.

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