A method for construction measurement control of a thin-wall steel cofferdam on an underwater inclined bank slope

Abstract

The application discloses a kind of thin-wall steel cofferdam construction measurement control methods on underwater inclined bank slope, and the application is guided steel cofferdam section processing, in-situ assembly, overall lowering, etc., by steel cofferdam construction measurement control method.This application includes steel cofferdam processing acceptance based on line orientation method, in-situ assembly measurement based on ranging method, riverbed scanning based on echo sounding principle, magnetic adsorption prism is used to lay deformation monitoring point, and the three-dimensional posture and deformation of steel cofferdam during lowering process are observed, which guides steel cofferdam heightening and sinking construction, and ensures the smooth construction of thin-wall steel cofferdam on inclined bank slope.The application has the advantages of completing steel cofferdam processing and manufacturing, on-site assembly, full-process observation during lowering and heightening, ensuring smooth steel cofferdam construction, structural safety and accurate position, effectively solving the problem that the perpendicularity of steel cofferdam cannot be directly observed in the method of platform first and steel cofferdam construction.

Description

Technical Field

[0001] This invention relates to the field of bridge engineering foundation construction surveying technology, and in particular to a method for surveying and controlling the construction of thin-walled steel cofferdams on underwater inclined slopes. Background Technology

[0002] The main tower on the Huanggang side of the Yanji Yangtze River Bridge is located 330–370m inside the Huanggang Yangtze River embankment, with a riverbed elevation of +3.0 to +8.0m at the pier location, resulting in a significant elevation difference. The foundation construction employed a method of first building the platform and then constructing the steel cofferdam. The steel cofferdam is designed as a dumbbell-shaped double-walled steel box girder structure, with a wall thickness of 1.5m. The top elevation of the steel cofferdam is +26.0m, the bottom elevation is -0.3m, and the plan dimensions are 91.2 × 42.0m, with a total height of 26.3m.

[0003] The steel cofferdam for the Yanji Yangtze River Bridge was manufactured in three sections at the processing yard. The bottom and middle sections are double-walled structures, while the top section is a single-walled structure. The bottom section is 10.0m high, the middle section is 11.6m high, and the top section is 4.7m high. After each section of the steel cofferdam was processed, it needed to pass inspection before leaving the factory. Due to space constraints, no trial assembly was conducted on-site. Virtual pre-assembly was performed based on the acceptance data of the steel cofferdam sections, followed by in-situ assembly on-site.

[0004] During the lowering process of the steel cofferdam for the Yanji Yangtze River Bridge, continuous monitoring of its horizontal position is necessary. Due to the thin walls of the cofferdam, the significant elevation difference of the underground riverbed, and the complex environment, the bottom section of the cofferdam is affected by lateral earth pressure from the riverbed on both the riverbank and river side. To ensure the accurate positioning of the cofferdam, timely correction is required. Furthermore, to guarantee the structural safety of the cofferdam, deformation monitoring of the entire structure is essential. The method of constructing the platform first and then the cofferdam for foundation construction presents significant challenges to the measurement and control of the cofferdam construction. During the lowering process, the cofferdam is below the construction platform, obstructing the observation line of sight. Verticality cannot be directly observed, and the deviation of the bottom section of the cofferdam cannot be monitored after the cofferdam is extended. Summary of the Invention

[0005] The purpose of this invention is to provide a measurement and control method for the construction of thin-walled steel cofferdams on underwater inclined slopes, which can complete the entire process of steel cofferdam processing and manufacturing, on-site assembly, lowering and raising construction, and ensure the smooth construction, structural safety and accurate positioning of the steel cofferdam.

[0006] The objective of this invention is achieved as follows:

[0007] A method for measurement and control during the construction of a thin-walled steel cofferdam on an underwater inclined slope, characterized by the following steps:

[0008] A. Before the steel cofferdam is manufactured, the jig is processed according to the design line of the steel cofferdam. After the jig is processed, the line orientation method is used to inspect the jig processed according to the design line of the steel cofferdam.

[0009] B. After each segment of the steel cofferdam is processed, the segment is inspected using the line orientation method. The rise, radius, and arc length of the steel cofferdam are calculated to determine whether the segment processing is qualified. The cutting edge radius, arc length, and rise of the processed segment are checked.

[0010] C. Based on the acceptance data of each of the 20 segments of the steel cofferdam, the steel cofferdam is virtually assembled according to the assembly principle from the middle to both ends. Check whether there are excessive gaps or spatial conflicts between adjacent segments, and make pre-adjustments to the steel cofferdam assembly to ensure a smooth assembly process.

[0011] D. Before the steel cofferdam is assembled in situ, the polar coordinate method of the total station is used to lay out the edge line of the steel cofferdam. The jig is installed according to the edge line and the geometric leveling method is used to level it. When the steel cofferdam is assembled in situ for inspection, the total station is set up at the center of the steel cofferdam using the distance measurement method to observe the horizontal distance from the center of the circle to the inner wall of the steel cofferdam and calculate the verticality of the steel cofferdam.

[0012] E. After the steel cofferdam is assembled, according to the structural characteristics of the steel cofferdam, a magnetic adsorption prism is installed on the top of the steel cofferdam as a deformation monitoring point.

[0013] F. Use an echo sounder based on the principle of echo sounding to scan the riverbed before and during the lowering of the steel cofferdam, so as to provide a basis for the lowering of the steel cofferdam;

[0014] G. Before lowering the steel cofferdam, a second-order GNSS plane densification network and a second-order elevation densification network are set up around the main pier. The three-dimensional coordinates of the magnetic adsorption prism at the top of the steel cofferdam are observed using the free station method of total station, and the initial values ​​of the steel cofferdam are collected. During the lowering of the steel cofferdam, the three-dimensional coordinates of the deformation monitoring points are observed. The deformation magnitude and deviation of the steel cofferdam are analyzed in combination with the riverbed scanning data. When the deformation warning value of the steel cofferdam is exceeded, the riverbed is treated in time to prevent the steel cofferdam from cracking.

[0015] H. When extending the steel cofferdam, the plumb line method is used to ensure that the bottom and middle sections of the steel cofferdam are aligned vertically without any bends. After the middle section is extended, deformation monitoring points corresponding to the top of the bottom section are set up on the top of the middle section steel cofferdam. An independent coordinate system is established with the deformation monitoring points on the top of the middle section steel cofferdam as the reference origin. Based on the three-dimensional coordinates of the deformation monitoring points on the top of the middle section steel cofferdam, the verticality of the steel cofferdam and the actual deviation of the bottom of the bottom section steel cofferdam are calculated. After the cofferdam is lowered into place, the cofferdam as-built measurement is carried out, and the magnetic adsorption prism is removed.

[0016] Furthermore, in step E, 32 deformation monitoring points are set up on the steel cofferdam, including 16 points on the top of the bottom section of the steel cofferdam and 16 points on the top of the middle section of the steel cofferdam. Magnetic adsorption prisms are installed at the monitoring points.

[0017] Furthermore, in step F, when the steel cofferdam is lowered, the riverbed on the bank side is 5m higher than the riverbed on the river side. The cutting edge of the cofferdam on the bank side contacts the riverbed surface first. After the cofferdam on the bank side contacts the riverbed surface, due to the large difference in elevation between the riverbed on the bank side and the river side, the steel cofferdam is affected by the earth pressure on the bank side, resulting in an imbalance of forces in the horizontal direction. The adjustment value of the steel cofferdam is determined based on the three-dimensional coordinates of the magnetic adsorption prism at the top of the steel cofferdam and the changes in the riverbed.

[0018] Furthermore, in step G, the adjustment value of the steel cofferdam needs to be determined during the lowering process based on the three-dimensional coordinates of the magnetic adsorption prism at the top of the steel cofferdam and the changes in the riverbed.

[0019] This invention includes steel cofferdam processing and acceptance based on line orientation method, in-situ assembly measurement based on distance measurement method, riverbed scanning based on echo sounding principle, and setting up deformation monitoring points with magnetic adsorption prism to observe the three-dimensional posture and deformation of steel cofferdam during the lowering process. This guides the construction of steel cofferdam heightening and sinking, ensuring the smooth construction of thin-walled steel cofferdam on inclined slopes.

[0020] Therefore, this invention has the advantages of being able to complete the entire process of steel cofferdam processing and manufacturing, on-site assembly, lowering and raising, and control and measuring, ensuring smooth construction, structural safety and accurate positioning of the steel cofferdam, and effectively solving the problem that the verticality of the steel cofferdam cannot be directly observed in the platform-before-steel cofferdam construction method. Attached Figure Description

[0021] Figure 1 This is a diagram of the installation device for a magnetically adsorbed prism.

[0022] Figure 2 This is a diagram showing the segmented layout of the steel cofferdam.

[0023] Figure 3 This is a layout diagram of the deformation monitoring points;

[0024] Figure 4 This is a schematic diagram of a thin-walled steel cofferdam.

[0025] Figure 5 This is a layout diagram of the control points for the construction of the steel cofferdam;

[0026] In the diagram: 1. Left guide magnet; 2. Bar magnet; 3. Rotary switch; 4. Copper block; 5. Connecting base; 6. Connecting pipe; 7. Fixing knob; 8. Connecting joint; 9. Right guide magnet; 10. Base adsorption device; 11. Prism connecting device; 12. Prism assembly; 13. Left magnet groove; 14. Right magnet groove; 15. Thin-walled steel cofferdam; 16. Steel casing; 17. Centerline of steel cofferdam bridge; 18. Centerline of steel cofferdam pier; 19. Magnetic adsorption prism; 20. Assembly platform; 21. Heightened steel casing; 22. Suspension system. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0028] A method for measurement and control during the construction of a thin-walled steel cofferdam on an underwater inclined slope includes the following steps:

[0029] A. Before the steel cofferdam is manufactured, the steel cofferdam base is processed in the factory according to the design line of the steel cofferdam. After the steel cofferdam base is processed, the line orientation method is used to inspect the base processed according to the design line of the steel cofferdam. A total station is set up next to the steel cofferdam base to observe the three-dimensional coordinates of the feature points at both ends of the base. The direction of the line connecting the two ends is taken as the false north direction. The first observed feature point is taken as the origin of the assumed coordinate system. The horizontal direction is perpendicular to the line connecting the two ends and passes through the origin of the assumed coordinate system as the false east direction. The vertical direction is perpendicular to the line connecting the two ends and passes through the origin of the assumed coordinate system as the assumed elevation direction.

[0030] B. The three-dimensional coordinates of each vertical angle steel of the base are observed using the line orientation method. In the assumed coordinate system, the X value of the observed three-dimensional coordinates is the horizontal distance between the observation point and the origin of the assumed coordinate system along the chord of the base, the Y value is 0, and the Z value is the height difference with the origin of the assumed coordinate system. After the observation is completed, the point map of the vertical angle steel of the base is drawn in CAD according to the coordinates (X, Z) of the vertical angle steel of the base. The points of each vertical angle steel of the base are fitted, and the design radius circle is drawn according to the center of the fitted circle. The difference between the measured points of the vertical angle steel of the base and the design line shape is measured. Angle steel with a large difference is processed according to the difference. After the line shape is consistent, the steel cofferdam processing and manufacturing begins.

[0031] C. After the steel cofferdam is manufactured, the assumed coordinate system is established by using the line orientation method according to step A above. The three-dimensional coordinates of the bottom and top ends of the steel cofferdam and any point in the middle are checked according to step B above. The radius of the steel cofferdam segment is calculated by the three-point circle method based on the three observation points. The segment acceptance posture is established in CAD. The arc length, sag and radius of the actual steel cofferdam are calculated. The unqualified steel cofferdam segments are reprocessed.

[0032] D. After the 20 sections of the bottom steel cofferdam are processed and pass inspection, according to Figure 2The steel cofferdam is arranged in sections in CAD according to the principle of assembling from the middle to both ends. First, the absolute positions of the steel cofferdam bridge centerline 17 and the steel cofferdam pier centerline 18 are determined in CAD. The assembly starts from the middle block of the straight section of the steel cofferdam and proceeds to the upstream and downstream sides. The closing section is the upstream and downstream round ends of the steel cofferdam. After the virtual assembly is completed, check whether there are gaps or spatial conflicts after the virtual assembly of adjacent sections. According to the virtual assembly situation, the steel cofferdam sections that affect the actual assembly on site are processed or the assembly sequence is adjusted in a timely manner to ensure that the steel cofferdam line is smooth and complete.

[0033] E. The steel cofferdam is assembled in situ on the construction platform. The design outline of the steel cofferdam is laid out on the construction platform using the polar coordinate method of a total station. The elevation of the steel cofferdam outline is collected using the geometric leveling method. The elevation of the steel cofferdam assembly base is determined based on the elevation of the highest point of the steel cofferdam outline. The elevation difference between the construction platform elevation and the steel cofferdam assembly base elevation is calculated. Steel plates of appropriate height are selected to pad the steel cofferdam assembly base to ensure that the top surface of the steel cofferdam assembly base is level after it is installed.

[0034] F. After the steel cofferdam assembly base is installed, the steel cofferdam assembly base is checked using the total station polar coordinate method and geometric leveling method to ensure that the position of the steel cofferdam assembly base is correct and that the top surface elevation of the steel cofferdam assembly base is consistent; the center point of the steel cofferdam is laid out on the construction platform and marked using the total station polar coordinate method.

[0035] G. Erect the bottom segment of the steel cofferdam on the steel cofferdam assembly base. Use the distance measurement method to check the verticality and deviation of the steel cofferdam assembly. Set up a total station at the center of the steel cofferdam and use the prism-free mode of the total station to observe any position on the inner wall of the steel cofferdam to obtain the horizontal distance from the center of the steel cofferdam to the observation point. Compare it with the design radius of the steel cofferdam to obtain the assembly deviation value of the steel cofferdam at the observation point. Check 3 sections of the cofferdam vertically for each segment, and check 3 positions for each section. Analyze the plane deviation and verticality of the steel cofferdam based on the inspection data of each segment, and adjust the steel cofferdam to meet the assembly specifications.

[0036] H. After the bottom section of the steel cofferdam is assembled, the top surface of the steel cofferdam is prepared according to... Figure 3 The layout diagram of deformation monitoring points shows that 16 magnetic adsorption prisms 19 are arranged in the direction of the cofferdam bridge centerline 17, the direction of the cofferdam pier centerline 18, the 45° direction of the cofferdam bridge centerline 17, and the 45° direction of the cofferdam pier centerline 18; the monitoring points use magnetic adsorption prisms 19, according to... Figure 1As shown in the installation diagram of the magnetic adsorption prism, first adjust the rotary switch 3 to the closed state, then place the magnetic adsorption prism 19 at the monitoring point position on the top of the steel cofferdam. After placement, adjust the rotary switch 3 to the open state to adsorb the magnetic adsorption prism 19 onto the top surface of the thin-walled steel cofferdam 15. Finally, loosen the fixing knob 7 of the prism assembly 12, adjust the height and direction of the connecting joint 8 and the prism assembly 12, and tighten the fixing knob 7 after adjustment.

[0037] I. The elevation of the top surface of the bottom section of the steel cofferdam was lowered from +36m to +10m, while the elevation of the top surface of the main pier construction platform was +26m. During the lowering process, the top surface of the steel cofferdam was lower than the construction platform. To ensure that the entire lowering process of the steel cofferdam could be observed using the total station's free stationing method with the magnetic adsorption prism 19, according to... Figure 5 The layout diagram of the control points for the steel cofferdam construction shows that a densified control point YJJM1 and YJJM2 are buried 500m upstream and downstream of the steel cofferdam, which together with the original control points DQ05, DQ06 and DQ07 on the embankment form a densified control network. The plane coordinates are observed using second-order GNSS precision, and the elevation coordinates are observed using second-order geometric leveling.

[0038] J. After the steel cofferdam is assembled on the mounting base and there are no other external forces affecting it, the three-dimensional coordinates of the magnetic adsorption prism 19 on the top surface of the steel cofferdam are observed using the free stationing method with a total station. After the coordinates are collected, they are analyzed according to... Figure 4 The structural schematic diagram of the thin-walled steel cofferdam shows the trial lifting of the steel cofferdam. After the steel cofferdam is vertically lifted by 0.2m, the stress on the hanging system 22 is observed. At the same time, the three-dimensional coordinates of the magnetic adsorption prism 19 are observed using the free station method of a total station, and the deformation of the steel cofferdam after vertical lifting is analyzed.

[0039] K. Once the hoisting system 22 is confirmed to be safe and stable, the steel cofferdam will be lowered. In the first stage, the steel cofferdam will be lowered above the water surface. The three-dimensional coordinates of the magnetic adsorption prism 19 of the steel cofferdam will be observed before it enters the water. Based on the lowering monitoring data, the plane of the steel cofferdam will be adjusted to the design state using the hoisting system 22, and the verticality will not be greater than 1 / 100. After the adjustment is completed, the lowering stage will be carried out.

[0040] L. During the underwater lowering stage of the steel cofferdam, the magnetic adsorption prism 19 of the steel cofferdam is continuously observed using the free stationing method of a total station to ensure that the steel cofferdam is lowered synchronously. The asynchronous displacement of each lowering is controlled within 5cm. When the steel cofferdam is lowered to the vicinity of the limiting device, the elevation of the magnetic adsorption prism 19 on the top surface of the steel cofferdam is measured. The overall verticality of the steel cofferdam is calculated based on the height difference of the monitoring points. The verticality of the steel cofferdam is adjusted using the hanging system 22. After the verticality adjustment is completed, the plane deviation of the steel cofferdam is adjusted using the guide device based on the deviation of the longitudinal and transverse axes of the steel cofferdam.

[0041] M. Lower the steel cofferdam to a self-floating state and observe the steel cofferdam using the free stationing method with a total station. After the steel cofferdam's planar deviation and verticality meet the specifications, pour the wall concrete to lower the steel cofferdam at a uniform speed.

[0042] N. Before the steel cofferdam is lowered into the riverbed, 64 riverbed monitoring points are set up circumferentially on the sidewall of the steel cofferdam. A depth sounder is used to scan the range of the steel cofferdam's cutting edge and the riverbed monitoring points around the cutting edge. According to the riverbed scanning results, the riverbed on the side of the steel cofferdam is 5m higher than the riverbed on the other side. When the steel cofferdam's sidewall contacts the riverbed and cannot continue to sink due to its own weight, concrete is poured into the sidewall chamber of the steel cofferdam to offset the side friction resistance of the outer sidewall of the riverbed. At the same time, mud washing is carried out on the riverbed on the sidewall to ensure that the entire cross-section of the steel cofferdam contacts the mud and enters the riverbed.

[0043] After the steel cofferdam is lowered into the mud, the same method is used to monitor the lowering and deformation monitoring points of the steel cofferdam. Monitoring continues until the top of the bottom section of the steel cofferdam is 2m above the water surface. Then, the riverbed is washed with mud and concrete is poured into the wall chambers to ensure that the horizontal position deviation and verticality of the bottom section of the steel cofferdam meet the specifications. After adjustment, the middle section of the steel cofferdam on the bank is assembled first, and then assembled towards both ends. During the assembly process, the plumb line method is used to check the straightness of the steel cofferdam joints to ensure that there are no bends between the bottom and middle sections of the steel cofferdam.

[0044] After the middle section of the steel cofferdam is assembled, according to... Figure 3 The layout of deformation monitoring points involves setting up 16 magnetic adsorption prisms 19 on the top of the middle section of the steel cofferdam, corresponding to the bottom section of the steel cofferdam. An independent coordinate system is established with the magnetic adsorption prisms 19 on the top of the middle section of the steel cofferdam as the reference origin. The direction perpendicular to the top surface of the middle section of the steel cofferdam is the Z-axis, and the X-axis and Y-axis of the construction coordinate system are used as the independent coordinate system X-axis and Y-axis. The actual deviation of the bottom of the bottom section of the steel cofferdam is calculated based on the measured three-dimensional coordinates of the top of the middle section of the steel cofferdam, the straightness deviation of the middle and bottom sections of the steel cofferdam, and the height difference of the bottom section of the steel cofferdam.

[0045] Q. The steel cofferdam is lowered into place through sludge removal and concrete pouring. During the lowering process, the actual deviation of the steel cofferdam bottom is calculated based on monitoring data from the top of the cofferdam, combined with changes in the riverbed.

[0046] Set the adjustment value for the steel cofferdam and make adjustments accordingly;

[0047] R. When the steel cofferdam is lowered to the design position, the total station is set up freely and the three-dimensional coordinate method of the total station is used to observe the magnetic adsorption prism 19. The actual deviation of the bottom section of the steel cofferdam is calculated. After meeting the specification requirements, the magnetic adsorption prism 19 is removed. Loosen the rotary switch 3, the base adsorption device 10 is demagnetized, loosen the fixing knob 7, and retract the prism assembly 12 to its original position to complete the removal of the magnetic adsorption prism.

[0048] S. After the concrete pouring of the steel cofferdam's bulkhead was completed and the hanging system 22 was dismantled, the steel cofferdam was measured as a result using the total station's free stationing method.

[0049] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for measurement and control during the construction of a thin-walled steel cofferdam on an underwater inclined slope, characterized in that: Includes the following steps: A. Before the steel cofferdam is manufactured, the jig is processed according to the design line of the steel cofferdam. After the jig is processed, the line orientation method is used to inspect the jig processed according to the design line of the steel cofferdam. B. After each segment of the steel cofferdam is processed, the segment is inspected using the line orientation method. The rise, radius, and arc length of the steel cofferdam are calculated to determine whether the segment processing is qualified. The cutting edge radius, arc length, and rise of the processed segment are checked. C. Based on the acceptance data of each of the 20 segments of the steel cofferdam, the steel cofferdam is virtually assembled according to the assembly principle from the middle to both ends. Check whether there are excessive gaps or spatial conflicts between adjacent segments, and make pre-adjustments to the steel cofferdam assembly to ensure a smooth assembly process. D. Before the steel cofferdam is assembled in situ, the polar coordinate method of the total station is used to lay out the edge line of the steel cofferdam. The jig is installed according to the edge line and the geometric leveling method is used to level it. When the steel cofferdam is assembled in situ for inspection, the total station is set up at the center of the steel cofferdam using the distance measurement method to observe the horizontal distance from the center of the circle to the inner wall of the steel cofferdam and calculate the verticality of the steel cofferdam. E. After the steel cofferdam is assembled, according to the structural characteristics of the steel cofferdam, a magnetic adsorption prism is installed on the top of the steel cofferdam as a deformation monitoring point. F. Use an echo sounder based on the principle of echo sounding to scan the riverbed before and during the lowering of the steel cofferdam, so as to provide a basis for the lowering of the steel cofferdam; G. Before the steel cofferdam is lowered, a second-order GNSS plane densification network and a second-order elevation densification network are set up around the main pier. The three-dimensional coordinates of the magnetic adsorption prism at the top of the steel cofferdam are observed using the free stationing method of a total station, and the initial values ​​of the steel cofferdam lowering are collected. During the lowering of the steel cofferdam, the three-dimensional coordinates of the deformation monitoring points are observed. The deformation magnitude and deviation of the steel cofferdam are analyzed in combination with the riverbed scanning data. When the deformation warning value of the steel cofferdam is exceeded, the riverbed is treated in time to prevent the steel cofferdam from cracking. H. When extending the steel cofferdam, the plumb line method is used to ensure that the bottom and middle sections of the steel cofferdam are aligned vertically without any bends. After the middle section of the cofferdam is extended, deformation monitoring points corresponding to the top of the bottom section are set up on the top of the middle section of the steel cofferdam. An independent coordinate system is established with the deformation monitoring points on the top of the middle section of the steel cofferdam as the reference origin. Based on the three-dimensional coordinates of the deformation monitoring points on the top of the middle section of the steel cofferdam, the verticality of the steel cofferdam and the actual deviation of the bottom of the bottom section of the steel cofferdam are calculated. After the cofferdam is lowered into place, the cofferdam as-built measurement is carried out, and the magnetic adsorption prism is removed.

2. The method for construction measurement and control of thin-walled steel cofferdams on underwater inclined slopes according to claim 1, characterized in that: In step E, 32 deformation monitoring points are set up on the steel cofferdam, including 16 points on the top of the bottom section of the steel cofferdam and 16 points on the top of the middle section of the steel cofferdam. Magnetic adsorption prisms are installed at the monitoring points.

3. The method for construction measurement and control of thin-walled steel cofferdams on underwater inclined slopes according to claim 1, characterized in that: In step F, when the steel cofferdam is lowered, the riverbed on the bank side is 3m higher than the riverbed on the river side. The cutting edge of the cofferdam on the bank side contacts the riverbed surface first. After the cofferdam on the bank side contacts the riverbed surface, due to the large difference in elevation between the riverbed on the bank side and the river side, the steel cofferdam is affected by the earth pressure on the bank side, resulting in an imbalance of forces in the horizontal direction.

4. The method for construction measurement and control of thin-walled steel cofferdams on underwater inclined slopes according to claim 1, characterized in that: In step G, the adjustment value of the steel cofferdam needs to be determined during the lowering process based on the three-dimensional coordinates of the magnetic adsorption prism at the top of the steel cofferdam and the changes in the riverbed.

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