River and lake sludge in-situ solidification treatment method for hydraulic structure dam foundation

Abstract

The invention belongs to the field of river and lake sludge treatment and comprehensive utilization, and discloses a river and lake sludge in-situ curing treatment method for a dam foundation of a hydraulic structure, which comprises the following steps: building earth rock cofferdams at the upstream and downstream of the dam foundation, and driving steel sheet piles into the cofferdams; river and lake open water is led away through the water diversion channel; foundation pit retaining walls are built at the downstream slope toe of the upstream cofferdam, the upstream slope toe of the downstream cofferdam and the upstream slope toes of the embankments on the two sides; curing the dam foundation sludge surrounded by the retaining wall in situ by adopting a supercharged vacuum preloading method; and the solidified dam foundation is subjected to vibro-replacement gravel pile or immersed tube gravel pile reinforcement and compaction treatment, and the requirement for the bearing capacity of the dam foundation is met after treatment. According to the method, the river and lake sludge is comprehensively utilized, the sludge is solidified into the dam foundation of the hydraulic structure on site, a series of problems of outward transportation of the river and lake sludge, land acquisition and storage, sludge treatment and the like are effectively solved, meanwhile, a large amount of cost can be saved, the ecological environment is protected, economic benefits and social benefits are remarkable, and new quality productivity is effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive utilization of river and lake silt treatment, and particularly relates to a method for on-site solidification treatment of river and lake silt in the foundation of hydraulic structures. Background Technology

[0002] my country has vast water resources, with numerous rivers and lakes. Currently, most of these rivers and lakes suffer from severe siltation. However, ecological dredging of rivers and lakes requires the use of cutter suction dredgers to clear the waterways, transporting the dredged silt through closed pipelines to silt dumps for storage, followed by sedimentation, solidification, and further treatment. This process is not only complex and involves a large amount of engineering work and high costs, but also requires a significant amount of land, impacting the environment and ecology. Furthermore, improper handling can lead to landslides and safety hazards. Because the silt has a high water content, large porosity, and high compressibility, it is extremely difficult, if not feasible, to solidify it in situ to form the foundation for dams, dikes, or sluices using traditional construction techniques.

[0003] Constructing dams or sluices in coastal and plain waterways, building dikes around rivers and lakes, or raising and thickening dikes all require foundation treatment of silt or soft soil, which presents numerous difficulties and challenges. Therefore, how to transform waste into treasure and comprehensively utilize river and lake silt, solidifying it in situ to create foundations for dikes, dams, or sluices around rivers and lakes, is a technical problem worthy of research. Summary of the Invention

[0004] In view of the problems existing in the prior art, the present invention provides a method for on-site solidification treatment of river and lake silt in the foundation of hydraulic structures, which effectively solves a series of problems such as the transportation of river and lake silt, land acquisition and storage, and silt treatment.

[0005] This invention is implemented as follows: a method for on-site solidification treatment of river and lake silt in the foundation of hydraulic structures includes the following steps: S1. Construct earth-rock cofferdams upstream and downstream of the foundation of hydraulic structures, and drive steel sheet piles into the cofferdams; S2. Use water diversion channels to divert open water from rivers and lakes; S3. Construct retaining walls for the foundation pit at the downstream slope toe of the upstream cofferdam, the upstream slope toe of the downstream cofferdam, and the water-facing slope toe of the dikes on both banks, and excavate a sealing trench on top of the retaining walls for the foundation pit. S4. For the silt in the dam foundation surrounded by the retaining wall of the foundation pit, insert plastic drainage boards, reverse vacuum pipes or pressurized vacuum pipes, cover with sealing film, bury the sealing film in the surrounding sealing trench, backfill with clay, and use pressurized vacuum preloading technology for on-site solidification. S5. Reinforce the solidified foundation with vibro-compacted crushed stone piles or driven crushed stone piles to meet the bearing capacity requirements of the dam foundation.

[0006] Furthermore, in step S1, the steel sheet piles driven into the upstream and downstream earth-rock cofferdams extend 0.5 to 0.8 meters into the bedrock or relatively impermeable layer of the riverbed.

[0007] Furthermore, in step S2, the water diversion channel is a tunnel or open channel, using unpressurized flow with a maximum flow velocity of 2-4 m / s.

[0008] Furthermore, in step S3, the width of the retaining wall in the foundation pit is 2-4m, and the distance L between the outer edge of the upstream and downstream retaining walls and the outer edge of the dam foundation is 5-10m.

[0009] Furthermore, in step S3, the retaining wall of the foundation pit is formed by silt expansion soil mixing piles, cement clay mixing piles or high-pressure jetting piles, with a pile diameter of 60-80cm, a pile spacing of 45-60cm, 3-9 rows, and a pile length extending to the bedrock of the riverbed or a relatively impermeable layer.

[0010] Furthermore, the top of the retaining wall of the foundation pit is excavated with a depth of 120-150cm, a bottom width of 50-70cm, and a top width of 70-100cm for sealing trenches, and the sealing trenches around the foundation pit are connected.

[0011] Furthermore, in step S4, the sealing trench is backfilled with clay with a compaction degree of 90% to 93%.

[0012] Furthermore, in step S4, the spacing between the anti-clogging plastic drainage boards and the spacing between the reverse vacuum tubes are calculated using the following formula:

[0013] In the formula, d1 is the spacing between the anti-clogging plastic drainage boards; β is the soil influence coefficient; K h t is the horizontal permeability coefficient of the soil; t is the consolidation time; C h s is the soil consolidation coefficient; s is the coefficient of influence of smearing and well resistance;

[0014] In the formula, d2 is the spacing between the reverse vacuum tubes; η is the vacuum transfer coefficient; K v ξ is the dynamic coefficient; ξ is the pipeline resistance coefficient. This is the total length of the vacuum pipeline.

[0015] Furthermore, in step S4, the bearing capacity of the silt foundation of the dam foundation after consolidation reaches 80-150 kPa, the settlement is less than 5-20 cm, and the degree of consolidation is ≥85%.

[0016] Furthermore, in step S5, the vibratory crushed stone piles or driven stone piles have a pile diameter of 50-120cm, a pile spacing of 1.5-2.2m, and are arranged in an equilateral triangle or square. The pile length extends to the bedrock of the riverbed or a relatively impermeable layer. After treatment, the foundation bearing capacity reaches 200-350kPa, which meets the bearing capacity requirements of the dam foundation.

[0017] The advantages and technical effects of this invention are as follows: This invention solidifies silt in situ into dam foundations or sluice gate foundations, effectively solving a series of problems such as the transportation of river and lake silt, land acquisition for storage, and silt treatment. At the same time, it can save a lot of costs, protect the ecological environment, and has significant economic and social benefits, effectively improving new quality productivity. Attached Figure Description

[0018] Figure 1 This is a schematic plan view of the in-situ solidification of river and lake silt in the foundation of the hydraulic structure dam according to the present invention; Figure 2 This is a schematic cross-sectional view of the in-situ solidification of river and lake silt in the foundation of the hydraulic structure dam according to the present invention; Figure 3 This is a schematic cross-sectional view of the river and lake silt after in-situ solidification treatment of the dam foundation of the hydraulic structure according to the present invention.

[0019] In the diagram: 1—Dam foundation; 2—Upstream and downstream cofferdams; 3—Sheet piles; 4—Water diversion channel; 5—Dikes on both banks; 6—Retaining wall of the foundation pit; 7—Sealing ditch; 8—Silt in the dam foundation; 9—Plastic drainage board; 10—Reverse vacuum pipe; 11—Sealing membrane; 12—Gravel pile; L—Length of the foundation pit retaining wall from the dam foundation. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0021] like Figure 1-3 As shown, the method for on-site solidification of river and lake silt in the foundation of hydraulic structures according to the present invention includes the following steps: S1. Construct earth-rock cofferdams 2 upstream and downstream of the dam foundation 1 of the hydraulic structure, and drive steel sheet piles 3 into the cofferdams; S2. Use water diversion channel 4 to divert open water from rivers and lakes; S3. Construct foundation pit retaining walls 6 at the downstream slope toe of the upstream cofferdam, the upstream slope toe of the downstream cofferdam, and the water-facing slope toe of the dikes on both banks; excavate a sealing trench 7 on top of the foundation pit retaining walls 6. S4. For the silt 8 of the dam foundation surrounded by the retaining wall of the foundation pit, insert plastic drainage boards 9, reverse vacuum pipes or pressurized vacuum pipes 10, cover with sealing film 11, after the sealing film is buried in the surrounding sealing trench 7, backfill with clay, and use pressurized vacuum preloading technology for on-site solidification. S5. Reinforce the solidified foundation with vibro-compacted crushed stone piles or driven crushed stone piles to meet the bearing capacity requirements of the dam foundation.

[0022] Furthermore, in step S1, the steel sheet piles 3 driven into the upstream and downstream earth-rock cofferdams 2 extend into the bedrock or relatively impermeable layer of the riverbed by 0.5 to 0.8 m.

[0023] Furthermore, in step S2, the water diversion channel 4 is a tunnel or open channel, using unpressurized flow with a maximum flow velocity of 2-4 m / s.

[0024] Furthermore, in step S3, the width of the retaining wall 6 in the foundation pit is 2 to 4 m, and the distance between the outer edge of the upstream and downstream retaining walls and the outer edge L of the dam foundation 1 is 5 to 10 m.

[0025] Furthermore, in step S3, the foundation pit retaining wall 6 is formed by silt expansion soil mixing piles, cement clay mixing piles or high-pressure jetting piles, with a pile diameter of 60-80cm, a pile spacing of 45-60cm, 3-9 rows, and a pile length extending to the riverbed bedrock or a relatively impermeable layer.

[0026] Furthermore, the top of the retaining wall 6 is excavated to a depth of 120-150cm and a bottom width of 50-70cm, and a sealing trench 7 with a top width of 70-100cm is connected around the foundation pit.

[0027] Furthermore, in step S4, the sealing trench 7 is backfilled with clay with a compaction degree of 90% to 93%.

[0028] Furthermore, in step S4, the spacing of the anti-clogging plastic drainage plates 9 and the spacing of the reverse vacuum tubes 10 are calculated according to the following formula:

[0029] In the formula, d1 is the spacing between the anti-clogging plastic drainage boards; β is the soil influence coefficient; K h t is the horizontal permeability coefficient of the soil; t is the consolidation time; C h s is the soil consolidation coefficient; s is the coefficient of influence of smearing and well resistance;

[0030] In the formula, d2 is the spacing between the reverse vacuum tubes; η is the vacuum transfer coefficient; K v ξ is the dynamic coefficient; ξ is the pipeline resistance coefficient. This is the total length of the vacuum pipeline.

[0031] Furthermore, in step S4, the bearing capacity of the silt 8 foundation after consolidation reaches 80-150 kPa, the settlement is less than 5-20 cm, and the degree of consolidation is ≥85%.

[0032] Furthermore, in step S5, the vibratory crushed stone piles or driven stone piles have a pile diameter of 50-120cm, a pile spacing of 1.5-2.2m, and are arranged in an equilateral triangle or square. The pile length extends to the bedrock of the riverbed or a relatively impermeable layer. After treatment, the foundation bearing capacity reaches 200-350kPa, which meets the bearing capacity requirements of the dam foundation.

[0033] The following description, using a sluice gate project employing the technical solution of this invention as an example, is further illustrated with reference to the accompanying drawings: This sluice gate project is a small-scale project. The sluice gate is 60.60m long along the river, including a 7.25m upstream embankment, a 23.35m gate chamber section, and a 30.00m downstream apron section, with a transverse length of 95m. The sluice gate is 9.35m high and is an open type with a flat-bottomed, wide-crested weir at the bottom. The riverbed silt cover is approximately 8m thick, consisting of, from top to bottom, sub-clay, silt and silty sub-clay, silt and silty clay, sandy sub-clay, and bedrock. Due to the high water content of the silt and its very low unconfined compressive strength, the foundation treatment of the sluice gate presents numerous challenges. Excavating the silt is too costly and difficult, and land acquisition is also challenging. Direct reinforcement using methods such as crushed stone piles and dynamic compaction is impractical and difficult to implement. Therefore, the series of treatment methods of this invention are adopted.

[0034] Earth-rock cofferdams were constructed upstream and downstream of the river channel, with steel sheet piles driven into the riverbed bedrock along the cofferdam's centerline. The cofferdams impounded water. An unpressurized open channel was built on the left bank upstream of the upstream cofferdam to divert the river water downstream. Cement-clay mixing piles were used to construct retaining walls at the downstream toe of the upstream cofferdam, the upstream toe of the downstream cofferdam, and the water-facing slopes of the dikes on both banks. Seven rows of cement-clay mixing piles were used, with the retaining walls 4m wide and the outer edges of the upstream and downstream retaining walls 5m from the outer edge of the sluice gate foundation. The cement-clay mixing piles had a diameter of 80cm, a spacing of 60cm, and a length extending to the riverbed bedrock. To prevent insufficient quality at the top of the cement-clay mixing piles, the top 1.0m of the pile body was excavated and filled with clay to a height of 1.0m, with a compaction degree of 90%–93%. A sealing trench 120cm wide at the top, 50cm wide at the bottom, and 70cm wide at the top was excavated and connected to the top of the retaining walls.

[0035] Inside the foundation pit enclosed by the retaining wall, 1) lay a layer of woven fabric, insert FDPS-B type anti-clogging plastic drainage boards and reverse vacuum pipes. The spacing between the forward plastic drainage boards is 0.80m, and the spacing between the reverse vacuum pipes is 2.40m, arranged in two rows of forward plastic drainage boards and one row of reverse vacuum pipes. The plastic drainage boards are 8.50m long, with an average insertion depth of 8.50m and an exposed length of 50cm. The reverse vacuum pipes are 6m long, with an 8mm air pipe at the top directly connected to the pressurization system. 4-6 air jet holes with a diameter of 3mm are installed within 200mm of the pipe end, using 150g / m³ external spray. 21) Wrap with geotextile. 2) Connect the vacuum pipeline and build a pressurization system; the vacuum system consists of vacuum pipeline, gas-liquid separator, and vacuum unit. Vacuum branch pipes are connected to the main vacuum pipe through four-way connectors and reducing tees. The horizontal spacing of the pipeline network is 0.8m, and the longitudinal spacing is 30-40m, which finally forms the vacuum pipeline. 3) Lay non-woven geotextile and three layers of polyethylene sealing film. Bury the sealing film in the surrounding sealing trench and backfill with clay with a compaction degree of 90%-93%. 4) Vacuuming and pressurization. The trial vacuuming should be done for 7-10 days. The vacuum pressure under the membrane should reach 0.08MPa and remain stable for 3 consecutive days before entering the formal vacuuming stage. The vacuum pressure under the membrane should be stable at 0.08MPa. The vacuuming should reach the design requirement of constant load full load time. The pump should be stopped and unloaded when the monitoring results meet the design unloading requirements. After consolidation, the foundation bearing capacity reaches 120kPa, and the settlement is less than 7cm. Remove the sealing membrane, geotextile, pipelines, and drainage boards.

[0036] Vibro-compacted stone piles were used for reinforcement. The vibro-compactor was 75kW, the stone piles were 80cm in diameter, and the piles were spaced 1.5m apart in an equilateral triangle arrangement, extending to the bedrock of the riverbed. After treatment, the foundation bearing capacity reached 250kPa, meeting the dam foundation bearing capacity requirements.

[0037] This invention presents a series of methods for treating river and lake silt in situ to solidify dam foundations, turning waste into treasure. It solidifies river and lake silt beneath dams into dam foundations, avoiding the costs of ecological dredging and silt transportation, and reducing the difficulties of land acquisition and sludge storage. Furthermore, it utilizes waste resources, directly treating and reinforcing the silt after solidification into the dam foundation. It boasts a high degree of resource utilization, is safe and environmentally friendly, and has a wide range of applications, possessing significant guiding and promotional value.

[0038] This invention is applicable to the following situations: (1) constructing water conservancy projects on river and lake silt and soft soil foundation covering layers less than 10m; (2) foundation treatment for raising and thickening river and lake dikes in coastal areas; (3) land acquisition is difficult and the cost of dredging and stockpiling is high.

[0039] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for on-site solidification treatment of river and lake silt in the foundation of hydraulic structures, characterized in that, Includes the following steps: S1. Construct earth-rock cofferdams (2) upstream and downstream of the foundation of the hydraulic structure dam (1), and drive steel sheet piles (3) into the cofferdams. S2. Use the water diversion channel (4) to divert the open water from the river and lake; S3. Construct foundation pit retaining walls (6) at the downstream slope toe of the upstream cofferdam, the upstream slope toe of the downstream cofferdam, and the water-facing slope toe of the dikes on both banks (5). Excavate a sealing trench (7) on the top of the foundation pit retaining wall (6). S4. For the silt (8) of the dam foundation surrounded by the retaining wall of the foundation pit, insert plastic drainage boards (9), reverse vacuum pipes or pressurized vacuum pipes (10), cover with sealing film (11), after the sealing film is buried in the surrounding sealing trench (7), backfill with clay, and use pressurized vacuum preloading technology for on-site solidification. S5. Reinforce the solidified foundation with vibro-compacted crushed stone piles or driven crushed stone piles to meet the bearing capacity requirements of the dam foundation.

2. The method for on-site solidification treatment of river and lake silt in the foundation of hydraulic structures according to claim 1, characterized in that, In step S1, the steel sheet piles (3) driven into the upstream and downstream earth-rock cofferdams (2) extend into the bedrock or relatively impermeable layer of the riverbed by 0.5 to 0.8 m.

3. The method for on-site solidification treatment of river and lake silt in the foundation of hydraulic structures according to claim 1, characterized in that, In step S2, the water diversion channel (4) is a tunnel or open channel, using unpressurized flow with a maximum flow velocity of 2 to 4 m / s.

4. The method for on-site solidification treatment of river and lake silt in the foundation of hydraulic structures according to claim 1, characterized in that, In step S3, the width of the foundation pit retaining wall (6) is 2 to 4 m, and the distance between the outer edge of the upstream and downstream retaining walls and the outer edge L of the dam foundation (1) is 5 to 10 m.

5. The method for on-site solidification treatment of river and lake silt in the foundation of hydraulic structures according to claim 1, characterized in that, In step S3, the foundation pit retaining wall (6) is formed by silt expansion soil mixing piles, cement clay mixing piles or high pressure jet piles, with a pile diameter of 60-80cm, a pile spacing of 45-60cm, 3-9 rows, and a pile length extending to the riverbed bedrock or a relatively impermeable layer.

6. The method for on-site solidification treatment of river and lake silt in the foundation of hydraulic structures according to claim 4, characterized in that, The top of the retaining wall (6) of the foundation pit is excavated to a depth of 120-150cm and a bottom width of 50-70cm. The top width of the sealing trench (7) is 70-100cm. The sealing trench (7) around the foundation pit is connected.

7. The method for on-site solidification treatment of river and lake silt in the foundation of hydraulic structures according to claim 1, characterized in that, In step S4, clay is used to backfill the sealing trench (7), with a compaction degree of 90% to 93%.

8. The method for on-site solidification treatment of river and lake silt in the foundation of hydraulic structures according to claim 1, characterized in that, In step S4, the spacing of the anti-clogging plastic drainage boards (9) and the spacing of the reverse vacuum tubes (10) are calculated according to the following formula: In the formula, d1 is the spacing between the anti-clogging plastic drainage boards; β is the soil influence coefficient; K h t is the horizontal permeability coefficient of the soil; t is the consolidation time; C h s is the soil consolidation coefficient; s is the coefficient of influence of smearing and well resistance; In the formula, d2 is the spacing between the reverse vacuum tubes; η is the vacuum transfer coefficient; K v ξ is the dynamic coefficient; ξ is the pipeline resistance coefficient. This is the total length of the vacuum pipeline.

9. The method for on-site solidification treatment of river and lake silt in the foundation of hydraulic structures according to claim 1, characterized in that, In step S4, the bearing capacity of the silt (8) foundation after consolidation reaches 80-150 kPa, the settlement is less than 5-20 cm, and the degree of consolidation is ≥85%.

10. The method for on-site solidification treatment of river and lake silt in the foundation of hydraulic structures according to claim 1, characterized in that, In step S5, the vibratory crushed stone piles or driven stone piles have a pile diameter of 50-120cm, a pile spacing of 1.5-2.2m, and are arranged in an equilateral triangle or square. The pile length extends to the bedrock of the riverbed or a relatively impermeable layer. After treatment, the foundation bearing capacity reaches 200-350kPa, which meets the bearing capacity requirements of the dam foundation.

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