Cofferdam high-efficiency pressure-reducing and inrush-resisting construction method based on dynamic monitoring
The cofferdam construction method using dynamic monitoring and pressure relief well deployment solves the problems of high cost and poor reliability of concrete bottom sealing technology, achieves efficient and safe anti-surge construction, adapts to complex hydrogeological conditions, and reduces project costs and resource consumption.
Patent Information
- Application Number
- CN202512040955.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-31
- Publication Date
- 2026-02-24
AI Technical Summary
Existing concrete bottom sealing construction technology has problems such as high engineering cost, large resource consumption and poor structural reliability in the construction of underwater structures such as bridges. It is difficult to cope with the risk of leakage and sudden surge under complex hydrogeological conditions, and cannot meet the dual requirements of economic efficiency and safety of the project.
A dynamic monitoring-based cofferdam construction method for efficient pressure reduction and anti-surge is adopted. A database is established through a full-parameter survey, pressure reduction wells and interconnected water collection structures are deployed, the water head value and outflow at the bottom of the weak permeable layer are monitored in real time, the elevation of the water collection structure is dynamically adjusted, and a multi-dimensional monitoring system is combined to achieve isolation and dynamic control of the water bodies inside and outside the cofferdam.
It reduced construction costs, saved resources, shortened the construction period, improved construction safety and reliability, adapted to construction needs under different geological conditions, and significantly reduced the total investment in the project.
Smart Images
Figure CN121556487A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of cofferdam construction technology, and in particular to a method for efficient pressure reduction and anti-surge construction of cofferdams based on dynamic monitoring. Background Technology
[0002] In the construction of underwater structures such as bridges, a land-like construction environment is typically created by using cofferdams to enclose the pre-defined construction area and then pumping out the internal water. However, after pumping, a significant water level difference forms inside and outside the cofferdam, leading to additional water pressure at the bottom of the weakly permeable layer. Therefore, anti-surge design becomes a key technical challenge in such projects—especially under special geological conditions where a strongly permeable layer is overlaid with a weakly permeable layer (such as a sand layer overlaid with silt or a sand layer overlaid with silty clay). In such strata, the strongly permeable layer is highly permeable and thick, making it difficult for cofferdam structures (such as sheet pile cofferdams) to completely sever the hydraulic connection between the strongly permeable layer and the external water, even if embedded to a certain depth. Conversely, the weakly permeable layer is thin and has a low natural density, resulting in limited pull-out resistance due to its own weight. After pumping, the water pressure at the bottom can easily exceed the pull-out limit, triggering a surge failure, leading to cofferdam instability, soil heave at the base, and ultimately, construction failure of the internal structure.
[0003] Currently, the conventional solution for preventing water inrush in engineering projects is the concrete bottom sealing construction process. Its core principle is: after the cofferdam is installed, a continuous, sealed concrete base slab is poured into the base inside the cofferdam (poured to the design base elevation). Once the concrete reaches the design strength, the internal water is pumped out. The self-weight of the concrete base slab generates a continuous and stable pull-out resistance, balancing the water pressure at the bottom of the weakly permeable layer, ensuring that the water inrush safety factor meets the specifications. Simultaneously, the concrete base slab can block groundwater leakage and maintain the dryness of the near-terrestrial construction environment.
[0004] However, the concrete bottom sealing construction process has two major drawbacks, making it difficult to adapt to complex engineering needs: 1. High project cost and resource consumption: The greater the water depth, the more significant the head difference between the inside and outside of the cofferdam, and the water pressure at the bottom of the weakly permeable layer increases linearly. To ensure that the anti-surge safety factor meets the standards, a thicker bottom sealing concrete needs to be poured, leading to a surge in concrete usage, formwork support costs, and construction machinery investment, resulting in a significant increase in the total project cost; 2. Poor structural reliability and prominent risks: The hydrogeological conditions of the underwater construction environment are complex. Temperature changes and cofferdam deformation can easily cause micro-cracks at the joint between the bottom sealing concrete and the cofferdam; moreover, the concrete itself may have shrinkage cracks. Once a seepage channel is formed, the seepage flow inside the cofferdam will rapidly increase to near the unsealed state. The seeping water carries sand particles from the highly permeable layer, which can cause "sandblasting" at the bottom sealing edge, thereby hollowing out the base soil, destroying the collaborative working mechanism between the cofferdam and the concrete bottom slab, and seriously threatening the structural stability of the cofferdam and the safety of internal construction.
[0005] In summary, conventional concrete sealing technology has significant cost disadvantages and is difficult to cope with the risks of leakage and sudden surge under complex hydrogeological conditions, thus failing to meet the dual requirements of economy and safety in engineering projects. Summary of the Invention
[0006] The purpose of this invention is to provide a method for efficient pressure reduction and anti-surge construction of cofferdams based on dynamic monitoring, thereby solving the above-mentioned technical problems.
[0007] To achieve the above objectives, this invention provides a method for efficient pressure reduction and anti-surge construction of cofferdams based on dynamic monitoring, comprising the following steps: S1. Conduct a full parameter survey of the construction area to clarify the geological conditions, cofferdam structure type and construction area boundary dimensions, and establish a standardized engineering parameter database. S2. Based on the standardized engineering parameter database, determine the layout scheme of the pressure relief wells, set up cofferdam facilities in the pre-set construction area to isolate the internal and external water bodies, and then use land prefabricated segmented well pipes according to the pressure relief well layout scheme. The installation of the pressure relief wells is completed by inserting guide tubes or underwater drilling and casting. L-shaped PVC drainage pipes are used to realize the seepage prevention connection between the pressure relief wells and the interconnected water collection structure. S3. The base of the cofferdam is leveled and a permeable crushed stone material is laid to form a drainage layer to protect the subsequent concrete cushion layer. At the same time, a crushed stone protective layer is laid on the outside of the cofferdam to block the scouring of the bottom of the cofferdam by external water flow, thus constructing a dual protection system of base protection and outer perimeter scouring. Meanwhile, a multi-dimensional monitoring system was deployed inside the cofferdam to monitor the water head value at the bottom of the weakly permeable layer, the water output of the pressure relief well, and the clarity of the water output. S4. Start the pumping operation inside the cofferdam, and during the pumping process, monitor the water head value at the bottom of the weak permeable layer, the water output of the pressure relief well and the clarity of the water in real time. Adjust the elevation of the water collection structure dynamically according to the monitoring results, and verify the pressure relief effect by calculating the anti-surge safety factor.
[0008] Preferably, the geological conditions described in step S1 include the thickness of a highly permeable layer. Permeability coefficient of highly permeable layers Thickness of the permeable layer Permeability coefficient of weakly permeable layer and naturally heavy-duty weakly permeable layers ; The boundary dimensions of the construction area include the area of the construction area. , and These represent the length and width of the construction area, respectively.
[0009] Preferably, the pressure relief well layout scheme described in step S2 includes the number of pressure relief wells. ,diameter and well casing length , The pressure relief wells are evenly distributed; Furthermore, the well casing of the pressure relief well is divided into a blind pipe section and a filter pipe section from top to bottom. The filter pipe section is wrapped with a filter screen and a gravel filter layer in sequence and then placed in a highly permeable layer. The porosity of the gravel filter layer is ≥20%. The blind pipe section is placed in a weakly permeable layer, and its exterior is reinforced with concrete well walls to provide structural support and block the seepage channels of the weakly permeable layer. The external connection between the blind pipe section and the filter pipe section is sealed and waterproofed to prevent leakage at the connection point and avoid soil loss or water seepage that may interfere with the overall effectiveness of the pressure relief system.
[0010] Preferably, in step S4, the water collection structure is assembled from modular steel components, and its dynamic elevation... The adjustment strategy is as follows: When detected When this happens, the following elevation adjustment formula is triggered until... : ; In the formula, This indicates the actual head value at the bottom of the weakly permeable layer; Indicates the maximum allowable elevation of the water collection structure, and , Indicates the safety factor against sudden surges. Indicates the specific gravity of water. and represents the natural unit weight and thickness of the soil layer above the weakly permeable layer, respectively, and z represents the location water head.
[0011] Preferably, in step S4, the anti-surge safety factor The verification expression is as follows: .
[0012] Therefore, the present invention employs the above-mentioned efficient pressure reduction and anti-surge construction method for cofferdams based on dynamic monitoring, which has the following beneficial effects: 1. Reduce construction costs: By reducing the amount of materials such as concrete and steel, the increased cost of thick concrete pouring due to the increased head difference in traditional bottom sealing process is avoided, thus significantly reducing the total investment in the project. 2. Resource conservation: The concrete sealing method replaces the traditional steel caisson or sheet pile cofferdam, reducing the consumption of steel and concrete, avoiding resource waste, and conforming to the concept of green construction. 3. Shorten construction period: Pressure relief well construction does not require long-term pouring and curing, and the operation is simple and quick. Compared with the traditional bottom sealing process, it can significantly reduce construction time and improve construction efficiency. 4. Safe and reliable: Equipped with a monitoring system covering the entire process from pumping to cofferdam removal, it monitors key indicators such as the water head value at the bottom of the weak permeable layer, the water output of the pressure relief well, and the clarity of the water in real time, which can promptly detect potential safety hazards. At the same time, by dynamically adjusting the elevation of the water collection structure and evenly distributing the pressure relief wells, it avoids local surges and ensures construction safety.
[0013] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description
[0014] Figure 1 This is a flowchart of the efficient pressure reduction and anti-surge construction method for cofferdams based on dynamic monitoring, as described in this invention. Figure 2 This is a cross-sectional view of the cofferdam structure described in this invention; Figure 3 This is a plan view of the cofferdam structure described in this invention; Figure 4 This is a schematic diagram of the calculation model for Example 1; Figure 5 This is a plan view of Example 1; Figure 6 The diagram shows the finite element analysis of Example 1; Figure 7 This is a schematic diagram of the calculation model for Example 2; Figure 8 This is a plan view of Example 2; Figure 9 The figure shows the finite element analysis results of Example 2; Figure 10 This is a schematic diagram of the calculation model for Example 3; Figure 11 This is a plan view of Example 3; Figure 12 The figure shows the finite element analysis results of Example 3.
[0015] Figure Labels 1. Cofferdam; 2. Water collection structure; 3. Pressure relief well; 31. Blind pipe section; 32. Filter pipe section; 4. Drainage layer; 5. Concrete well wall; 6. Multi-dimensional monitoring system; 7. Filter screen; 8. Gravel and sand reverse filter layer; 9. Weakly permeable layer; 10. Highly permeable layer. Detailed Implementation
[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the embodiments of the present invention and are not intended to limit the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout.
[0017] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, such as a process, method, system, product, or server that includes a series of steps or units, not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such process, method, product, or device.
[0018] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
[0019] like Figures 1-3 As shown, the efficient pressure reduction and anti-surge construction method for cofferdams based on dynamic monitoring includes the following steps: S1. Conduct a full parameter survey of the construction area to clarify the geological conditions, cofferdam structure type and construction area boundary dimensions, and establish a standardized engineering parameter database. The geological conditions described in step S1 include a highly permeable layer with a thickness of 10 mm. Highly permeable layer with a permeability coefficient of 10 9mm thick weak permeable layer 9. Permeability coefficient of the weakly permeable layer and the weakly permeable layer 9 natural heavy-duty ; The boundary dimensions of the construction area include the area of the construction area. , and These represent the length and width of the construction area, respectively.
[0020] S2. Based on the standardized engineering parameter database, determine the layout scheme of the pressure relief well 3, set up the cofferdam 1 facility in the preset construction area to isolate the internal and external water bodies, and then use the land prefabricated segmented well pipe according to the layout scheme of the pressure relief well 3. The installation of the pressure relief well 3 is completed by inserting the guide tube or underwater drilling and casting. The L-shaped PVC drainage pipe is used to realize the seepage prevention connection between the pressure relief well 3 and the interconnected water collection structure 2. The layout scheme of relief wells 3 described in step S2 includes the number of relief wells 3. ,diameter and well casing length , Three pressure relief wells are evenly distributed; Furthermore, the well casing of the pressure relief well 3 is divided into a blind pipe section 31 and a filter pipe section 32 from top to bottom. The filter pipe section 32 is wrapped with a filter screen 7 and a gravel sand reverse filter layer 8 in sequence and then placed in the highly permeable layer 10. The porosity of the gravel sand reverse filter layer 8 is ≥20%. The blind pipe section 31 is placed in the weakly permeable layer 9, and a concrete well wall 5 is poured on its outside to provide structural support and block the seepage channels of the weakly permeable layer 9. The external connection between the blind pipe section 31 and the filter pipe section 32 is sealed and waterproofed to prevent leakage at the connection point and avoid soil loss or water seepage interfering with the overall effectiveness of the pressure relief system.
[0021] S3. The inner base of the cofferdam 1 is leveled and a permeable crushed stone material is laid to form a drainage layer 4 to protect the subsequent concrete cushion layer. At the same time, a crushed stone protective layer is laid on the outer perimeter of the cofferdam 1 to block the external water flow from scouring the bottom of the cofferdam 1, thus constructing a dual protection system of base protection and outer perimeter scouring. Meanwhile, a multi-dimensional monitoring system 6 is deployed inside the cofferdam 1 to monitor the water head value at the bottom of the weakly permeable layer 9, the water output of the pressure relief well 3, and the clarity of the water output. S4. Start the pumping operation inside the cofferdam 1, and during the pumping process, monitor the water head value at the bottom of the weak permeable layer 9, the water output of the pressure relief well 3 and the clarity of the water in real time. Adjust the elevation of the water collection structure 2 dynamically according to the monitoring results, and verify the pressure relief effect by calculating the anti-surge safety factor.
[0022] In step S4, the water collection structure 2 is assembled from modular steel components, and its dynamic elevation... The adjustment strategy is as follows: When detected When this happens, the following elevation adjustment formula is triggered until... : ; in, This indicates the actual head value at the bottom of the weakly permeable layer; Indicates the maximum allowable elevation of the water collection structure, and , Indicates the surge protection safety factor. In this embodiment, , Indicates the specific gravity of water. and represents the natural unit weight and thickness of the soil layer above the weakly permeable layer, respectively, and z represents the location water head.
[0023] Preferably, in step S4, the anti-surge safety factor The verification expression is as follows: .
[0024] Example 1: Construction of a square cofferdam to prevent sudden inrush.
[0025] Project Overview: This example illustrates a square steel sheet pile cofferdam anti-surge project. The construction area is an aquatic environment with a sand layer overlaid with silt (a highly permeable layer overlaid with a less permeable layer). The core parameters are as follows: thickness of the highly permeable layer. Thickness of the permeable layer Naturally heavy-duty permeable layer Water level outside the construction area The dimensions of the construction site enclosed by the cofferdam are: (Square), length of the cofferdam into the highly permeable layer The total height is 20m; the construction requires the water level inside the cofferdam to be lowered to the top of the weakly permeable layer.
[0026] Example 2: Construction of a rectangular cofferdam to prevent sudden surge.
[0027] Project Overview: This example illustrates a rectangular steel sheet pile cofferdam anti-surge project. The construction area is an underwater environment consisting of a sand layer overlaid with silty clay (a highly permeable layer overlaid with a less permeable layer). Key parameters are as follows: thickness of the highly permeable layer. Thickness of the permeable layer Naturally heavy-duty permeable layer Water level outside the construction area The dimensions of the construction site enclosed by the cofferdam are: (Rectangular) Length of the cofferdam extending into the highly permeable layer The total height is 24m; the construction requires the water level inside the cofferdam to be lowered to the top of the weakly permeable layer.
[0028] Example 3: Construction of a triangular cofferdam to prevent sudden inrush.
[0029] Project Overview: This example illustrates a triangular sheet pile cofferdam anti-surge project. The construction area is an aquatic environment consisting of sand overlaid with silt (a highly permeable layer overlaid with a less permeable layer). Key parameters are as follows: thickness of the highly permeable layer. Thickness of the permeable layer Naturally heavy-duty permeable layer Water level outside the construction area The area of the construction site enclosed by the cofferdam (Triangle) Length of the cofferdam extending into the highly permeable layer The total height is 15m; the construction requires the water level inside the cofferdam to be lowered to the weakly permeable layer.
[0030] If no other measures are taken and water is directly pumped out from inside the cofferdam, calculate the safety factor against sudden inrush. In Example 1, In Example 2, In Example 3, None of them meet the requirements for resisting sudden surges.
[0031] If a bottom sealing concrete design is adopted, according to calculations: Example 1 requires at least 3m of bottom sealing concrete, totaling 1200m of concrete. 3 The cost is approximately 504,000 yuan; Example 2 requires at least 3.12m of sealing concrete, totaling 1872m³ of concrete. 3 The cost is approximately 786,000 yuan; Example 3 requires at least 2.9m of sealing concrete, totaling 4680m³ of concrete. 3 The cost is approximately 1.966 million yuan.
[0032] If the method provided by this invention is used: Regarding Example 1, the following is added: Figure 4 and Figure 5 The deployment of anti-surge facilities shown - pressure relief wells: evenly distributed inside the cofferdam 8, total length of well casing The filter pipe section is 3000mm long (placed in a highly permeable layer), and the blind pipe section is 2300mm long (placed in a less permeable layer). The pipe diameter... The hole depth penetrates the weakly permeable layer and extends 3m into the highly permeable layer. The inner diameter of the hole in the weakly permeable layer is 1600mm, and the inner diameter of the hole in the highly permeable layer is 1400mm. The filter pipe section is wrapped with a wire mesh, and the space between it and the hole wall is filled with gravel to form a reverse filter layer. A concrete well wall (300mm higher than the surface of the weakly permeable layer) is poured between the blind pipe section and the hole wall.
[0033] Drainage pipes: PVC pipes are used, arranged in an "L" shape. After connecting to the pressure relief well, they first extend horizontally to the vicinity of the cofferdam, and then vertically to the water collection structure. The connection points are treated to prevent leakage.
[0034] Water collection structure: Located next to the cofferdam, at an absolute elevation of +5.00m, using a "one well, one structure" connection method.
[0035] Drainage layer: The cofferdam is lined with crushed stone material with a natural density of 25.4 kN / m³. 3 The cofferdam is 1m thick; the outer perimeter of the cofferdam is paved with gravel to prevent bottom erosion.
[0036] Key points of construction implementation: Follow the construction steps of this invention, with the following key adaptations: Step 1: Clarify the above-mentioned core parameters; Step 2: Complete the layout of the square steel sheet pile cofferdam to isolate the internal and external water bodies; Step 3: Install the pressure relief well, drainage pipe and water collection structure according to the above parameters, ensuring that the well pipe is vertically centered, the gravel filling of the filter pipe section is dense, and the concrete well wall of the blind pipe section is poured in place; At the same time, a multi-dimensional monitoring system is set up at the contact point between the cofferdam and the weakly permeable layer and at the center of the site to monitor the water head value at the bottom of the weakly permeable layer, the water output of the pressure relief well and the clarity of the water output; Step 4: Start the pumping operation inside the cofferdam and monitor the monitoring data throughout the process.
[0037] For Example 2, the following is added: Figure 7 and Figure 8 The deployment of anti-surge facilities shown - pressure relief wells: evenly distributed inside the cofferdam One, total length of well casing The filter pipe section is 1000mm long (placed in a highly permeable layer), and the blind pipe section is 4000mm long (placed in a less permeable layer). The pipe diameter... The hole depth penetrates the weakly permeable layer and extends 1m into the highly permeable layer. The inner diameter of the hole in the weakly permeable layer is 1500mm, and the inner diameter of the hole in the highly permeable layer is 1300mm. The filter pipe section is wrapped with a wire mesh, and the space between it and the hole wall is filled with gravel to form a reverse filter layer. A concrete well wall (300mm higher than the surface of the weakly permeable layer) is poured between the blind pipe section and the hole wall.
[0038] Drainage pipes: PVC pipes are used, arranged in an "L" shape. After connecting to the pressure relief well, they first extend horizontally to the vicinity of the cofferdam, and then vertically to the water collection structure. The connection points are treated to prevent leakage.
[0039] Water collection structure: Located next to the cofferdam at an absolute elevation of +5.00m, it adopts an interconnected arrangement of "4 pressure relief wells sharing 1 water collection structure" to form a zoned pressure relief system.
[0040] Drainage layer: The cofferdam is lined with crushed stone material with a natural density of 21.4 kN / m³. 3 The cofferdam is 1m thick; the outer perimeter of the cofferdam is paved with gravel to prevent bottom erosion.
[0041] Key points of construction implementation: Follow the construction steps of this invention, with the following key adaptations: Step 1: Clarify the above-mentioned core parameters; Step 2: Complete the layout of the rectangular steel sheet pile cofferdam to isolate the internal and external water bodies; Step 3: Install the pressure relief wells, drainage pipes, and water collection structures according to the above parameters, ensuring that the multiple wells and the water collection structure are tightly connected and leak-free; At the same time, deploy a multi-dimensional monitoring system at the contact point between the cofferdam and the weakly permeable layer and at the center of the site to cover all zoned pressure relief areas; Step 4: Start the pumping operation inside the cofferdam.
[0042] For Example 3, the following is added: Figure 10 and Figure 11 The deployment of anti-surge facilities shown - pressure relief wells: evenly distributed inside the cofferdam One, total length of well casing The filter pipe section is 1000mm long (placed in a highly permeable layer), and the blind pipe section is 3000mm long (placed in a less permeable layer), with a pipe diameter of... m; the drilling depth penetrates the weakly permeable layer and extends 2m into the highly permeable layer, with an inner hole diameter of 1700mm in the weakly permeable layer and 1500mm in the highly permeable layer; the filter pipe section is wrapped with an iron wire mesh, and the space between it and the hole wall is filled with gravel to form a reverse filter layer; a concrete well wall is poured between the blind pipe section and the hole wall (300mm higher than the surface of the weakly permeable layer).
[0043] Drainage pipes: PVC pipes are used, arranged in an "L" shape. After connecting to the pressure relief wells, they first extend horizontally to the vicinity of the cofferdam, and then vertically to the water collection structure. The connection points are treated to prevent leakage. Water collection structure: Located next to the cofferdam, at an absolute elevation of +6.00m, it adopts an interconnected arrangement of "3 pressure relief wells sharing 1 water collection structure".
[0044] Drainage layer: The cofferdam is lined with crushed stone material with a natural density of 28.6 kN / m³. 3 The cofferdam is 1m thick; the outer perimeter of the cofferdam is paved with gravel to prevent bottom erosion.
[0045] Key points of construction implementation: Follow the construction steps of this invention, with the following key adaptations: Step 1: Clarify the above core parameters and optimize the placement of pressure relief wells based on the triangular site morphology to ensure uniform coverage; Step 2: Complete the triangular steel sheet pile cofferdam layout to isolate internal and external water bodies; Step 3: Install pressure relief wells, drainage pipes, and water collection structures according to the above parameters, adapting the pipeline routing to the triangular site; Simultaneously, deploy a multi-dimensional monitoring system at the contact point between the cofferdam and the weakly permeable layer and at the center of the site, focusing on monitoring water pressure in the corner areas; Step 4: Start pumping operations within the cofferdam, monitor data in real time, and avoid localized surges in the corner areas.
[0046] As Figure 6 , Figure 9 and Figure 12 The finite element calculation results show that in Example 1, the total drainage volume after pumping water to the designated height is approximately 94.24 m³. 3 / d, the average absolute height of water head in the construction area is 4.2m, and the calculated safety factor against sudden surge is... The cost is approximately 100,000 yuan; in Example 2, the total drainage volume after pumping water to the designated height is approximately 110.81m³. 3 / d, the average absolute height of the water head in the construction area is 5.1m, and the calculated safety factor against sudden surge is... The cost is approximately 200,000 yuan; in Example 3, the total drainage volume after pumping water to the designated height is approximately 216.07 m³. 3 / d, the average absolute height of the water head in the construction area is 5.3m, and the calculated safety factor against sudden surge is... The cost is approximately 250,000 yuan.
[0047] Table 1 Cost Comparison Table
[0048] In summary, the efficient pressure reduction and anti-surge construction method for cofferdams based on dynamic monitoring described in this invention can significantly reduce engineering costs in various cofferdam construction scenarios, such as square, rectangular, and triangular cofferdams with weak permeability layers over highly permeable layers, while ensuring an anti-surge safety factor of not less than 1.1. Example 1 reduces costs by approximately 80.1% compared to traditional concrete bottom sealing technology, Example 2 by approximately 74.5%, and Example 3 by approximately 87.3%. Simultaneously, the total drainage volume is controlled within the range of 94.24~216.07 m³. 3 Within a reasonable range of / d, there was no problem of excessive drainage and waste of resources.
[0049] This invention, through the collaborative design of "directional pressure relief well + efficient transmission of the drainage system + full-process monitoring", not only solves the pain points of high cost and easy cracking failure of traditional concrete bottom sealing process, but also can be adapted to construction areas with different geometric shapes. It takes into account the safety against sudden surge, engineering economy and scenario adaptability, and has significant engineering application value. It can be widely promoted to underwater cofferdam construction projects in the formation of weak permeable layer overlying strong permeable layer.
[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.
Claims
1. A method for efficient pressure reduction and anti-surge construction of cofferdams based on dynamic monitoring, characterized in that: Includes the following steps: S1. Conduct a full parameter survey of the construction area to clarify the geological conditions, cofferdam structure type and construction area boundary dimensions, and establish a standardized engineering parameter database. S2. Based on the standardized engineering parameter database, determine the layout scheme of the pressure relief wells, set up cofferdam facilities in the pre-set construction area to isolate the internal and external water bodies, and then use land prefabricated segmented well pipes according to the pressure relief well layout scheme. The installation of the pressure relief wells is completed by inserting guide tubes or underwater drilling and casting. L-shaped PVC drainage pipes are used to realize the seepage prevention connection between the pressure relief wells and the interconnected water collection structure. S3. The base of the cofferdam is leveled and a permeable crushed stone material is laid to form a drainage layer to protect the subsequent concrete cushion layer. At the same time, a crushed stone protective layer is laid on the outside of the cofferdam to block the scouring of the bottom of the cofferdam by external water flow, thus constructing a dual protection system of base protection and outer perimeter scouring. Meanwhile, a multi-dimensional monitoring system was deployed inside the cofferdam to monitor the water head value at the bottom of the weakly permeable layer, the water output of the pressure relief well, and the clarity of the water output. S4. Start the pumping operation inside the cofferdam, and during the pumping process, monitor the water head value at the bottom of the weak permeable layer, the water output of the pressure relief well and the clarity of the water in real time. Adjust the elevation of the water collection structure dynamically according to the monitoring results, and verify the pressure relief effect by calculating the anti-surge safety factor.
2. The method for efficient pressure reduction and anti-surge construction of cofferdams based on dynamic monitoring according to claim 1, characterized in that: The geological conditions described in step S1 include the thickness of the highly permeable layer. Permeability coefficient of highly permeable layers Thickness of the permeable layer Permeability coefficient of weakly permeable layer and naturally heavy-duty weakly permeable layers ; The boundary dimensions of the construction area include the area of the construction area. , and These represent the length and width of the construction area, respectively.
3. The method for efficient pressure reduction and anti-surge construction of cofferdams based on dynamic monitoring according to claim 1, characterized in that: The pressure relief well layout scheme described in step S2 includes the number of pressure relief wells. ,diameter and well casing length , The pressure relief wells are evenly distributed; Furthermore, the well casing of the pressure relief well is divided into a blind pipe section and a filter pipe section from top to bottom. The filter pipe section is wrapped with a filter screen and a gravel filter layer in sequence and then placed in a highly permeable layer. The porosity of the gravel filter layer is ≥20%. The blind pipe section is placed in a weakly permeable layer, and its exterior is reinforced with concrete well walls to provide structural support and block the seepage channels of the weakly permeable layer. The external connection between the blind pipe section and the filter pipe section is sealed and waterproofed to prevent leakage at the connection point and avoid soil loss or water seepage that may interfere with the overall effectiveness of the pressure relief system.
4. The method for efficient pressure reduction and anti-surge construction of cofferdams based on dynamic monitoring according to claim 2, characterized in that: In step S4, the water collection structure is assembled from modular steel components, and its dynamic elevation... The adjustment strategy is as follows: When detected When this happens, the following elevation adjustment formula is triggered until... : ； In the formula, This indicates the actual head value at the bottom of the weakly permeable layer; Indicates the maximum allowable elevation of the water collection structure, and , Indicates the safety factor against sudden surges. Indicates the specific gravity of water. and represents the natural unit weight and thickness of the soil layer above the weakly permeable layer, respectively, and z represents the location water head.
5. The method for efficient pressure reduction and anti-surge construction of cofferdams based on dynamic monitoring according to claim 2, characterized in that: In step S4, the anti-surge safety factor The verification expression is as follows: 。