Internal force and deformation analysis method for double-row sheet pile cofferdam

Abstract

The invention discloses an internal force and deformation analysis method for a double-row sheet-pile cofferdam, and the method comprises the steps: building a structural analysis model of a two-dimensional plane bar system according to the size and section form of the double-row sheet-pile cofferdam; setting parameters of all parts in the structural analysis model are determined on the basis of soil mass parameters of the application environment of the double-row sheet pile cofferdam; construction stages are divided according to the hydrological conditions of the double-row sheet-pile cofferdam and the filling process of the cofferdam, and then the operation conditions of the double-row sheet-pile cofferdam under all the working conditions are determined according to the preset load conditions; and obtaining a stress analysis result of the double-row sheet pile cofferdam under each working condition based on the structural analysis model according to the operation condition of each working condition. According to the method, through accurate model establishment and comprehensive parameter consideration, the design precision and reliability of the double-row sheet pile cofferdam can be remarkably improved, and the stability and safety of the cofferdam under various complex hydrological and geological conditions are ensured.

Description

Technical Field

[0001] The present invention relates to top drive load calibration, and particularly to a method for analyzing internal forces and deformations of a double-row sheet pile cofferdam. Background Art

[0002] The double-row sheet pile cofferdam is a widely used and flexibly arranged cofferdam structure, which has the advantages of convenient and fast construction, recyclability, and small floor area. The double-row sheet pile cofferdam generally consists of sheet piles, purlins, steel tie rods, and components such as backfilled sand and gravel between the two rows of sheet piles. Sometimes, riprap is used on the water-facing side or a counterweight platform is used on the water-back side to enhance the overall stability of the cofferdam. The sheet pile cofferdam is often in a complex hydrological working environment, and the water level outside the cofferdam varies greatly with time, resulting in a changing state of the water pressure difference between the inside and outside.

[0003] At present, the design and calculation of double-row sheet pile cofferdams mainly emphasize checking the stability of the cofferdams. There is still no mature and reliable method for the internal forces and deformations of the cofferdams. Some related research simplifies the double-row sheet pile cofferdam into a single-row pile + anchor-pull structure or establishes a finite element numerical analysis of the stratum structure. There are certain errors in the calculation results and it cannot accurately reflect the stress state of the sheet piles at each working stage. Summary of the Invention

[0004] The present invention aims to solve the problems of related technical limitations to at least a certain extent. For this purpose, the present invention proposes a method for analyzing internal forces and deformations of a double-row sheet pile cofferdam, which can accurately perform stress analysis of the double-row sheet pile cofferdam.

[0005] On the one hand, an embodiment of the present invention provides a method for analyzing internal forces and deformations of a double-row sheet pile cofferdam, including the following steps:

[0006] According to the size and cross-sectional form of the double-row sheet pile cofferdam, a structural analysis model of a two-dimensional plane bar system is established;

[0007] Among them, the double-row sheet pile cofferdam includes double-row sheet piles and the steel tie rods between them; the structural analysis model is established based on preset force units, and the force units include a tie rod force unit, a soil body force unit between the double-row sheet piles simulated by springs, a force unit of the outer soil-embedded section of the double-row sheet piles, and a pile-end vertical spring force unit;

[0008] Based on the soil parameters of the application environment of the double-row sheet pile cofferdam, the setting parameters of each component in the structural analysis model are determined;

[0009] According to the hydrological conditions of the double-row sheet pile cofferdam and the filling process of the cofferdam, the construction stages are divided, and then the preset load conditions are implemented to determine the operation conditions of the double-row sheet pile cofferdam under each working condition;

[0010] Based on the operating conditions of each working condition, the force analysis results of the double-row sheet pile cofferdam under each working condition are obtained based on the structural analysis model.

[0011] Optionally, to establish a structural analysis model of a two-dimensional plane bar system, the following steps are included:

[0012] Determine the two-dimensional plane bar system corresponding to the structure of the double-row sheet pile cofferdam, and then use different force units to simulate and establish a structural analysis model, and assign corresponding force characteristics and connection methods to each force unit.

[0013] Optionally, to establish a structural analysis model by simulating with different force units, the following steps are included:

[0014] Use the truss element 101 to simulate the tension rod force unit; among them, the double-row sheet piles are simulated by the beam element 100;

[0015] Use the two-end free spring element 103 to simulate the soil body force unit between the double-row sheet piles;

[0016] Use the one-end fixed spring element 104 to simulate the force unit of the soil body in the outer soil-embedded section of the double-row sheet piles;

[0017] Use the one-end fixed spring element 105 to simulate the pile-end vertical spring force unit.

[0018] Optionally, to assign corresponding force characteristics and connection methods to each force unit, the following steps are included:

[0019] Pre-define that the tension rod and its corresponding tension rod force unit only bear tension and do not bear pressure; set that the connection between the tension rod force unit and the sheet pile is a hinge 102, and pre-define that only axial force can be transmitted between the tension rod force unit and the front and rear sheet piles, and bending moment cannot be transmitted;

[0020] Pre-define that the corresponding spring unit 103 of the soil body force unit between the double-row sheet piles can only bear pressure and cannot bear tension, the length is the net distance between the double-row sheet piles, and the direction is horizontal;

[0021] Pre-define that the force direction of the spring unit 104 inside the cofferdam can only be in the positive x-axis direction, and the force direction of the spring unit 104 outside the cofferdam can only be in the negative x-axis direction;

[0022] Pre-define that the force direction of the spring unit 105 can only be in the negative y-axis direction.

[0023] Optionally, to determine the setting parameters of each component in the structural analysis model based on the soil parameters of the application environment of the double-row sheet pile cofferdam, the following steps are included:

[0024] Based on the compression modulus of the soil mass and the spring in the soil force unit simulating the soil between the double-row sheet piles, where a single spring represents the cross-sectional area of the soil between the piles, the soil spring stiffness corresponding to the soil force unit between the double-row sheet piles is set in combination with the net spacing between the two rows of sheet piles; the expression for the soil spring stiffness between the piles is: k c = Es * A / L; where Es represents the compression modulus of the soil mass, A represents the cross-sectional area of the soil between the piles represented by a single spring, and L represents the net spacing between the two rows of sheet piles;

[0025] Based on the soil reaction coefficient and the penetration depth of the double-row sheet pile cofferdam, the soil spring stiffness corresponding to the soil outside the penetration section of the double-row sheet piles is set; the expression for the soil spring stiffness outside the sheet piles is: k s = mz; where m represents the soil reaction coefficient and z represents the penetration depth;

[0026] Based on the cohesion and internal friction angle of the soil mass, the soil reaction coefficient is determined in combination with the horizontal displacement of the double-row sheet pile cofferdam at the penetration position, and then the soil spring stiffness corresponding to the soil outside the penetration section of the double-row sheet piles is set in combination with the penetration depth of the double-row sheet pile cofferdam;

[0027] The pile tip vertical spring stiffness corresponding to the pile tip vertical spring force unit is set to the compression modulus of the soil mass.

[0028] Optionally, the method further includes the following steps:

[0029] Based on the cohesion and internal friction angle of the soil mass, the soil reaction coefficient is determined in combination with the horizontal displacement of the double-row sheet pile cofferdam at the penetration position;

[0030] Among them, the expression for the soil reaction coefficient is:

[0031] m = (0.2Φ 2 - Φ + c) / v b ;

[0032] In the formula, c represents the cohesion of the soil mass, Φ represents the internal friction angle of the soil mass, and v b represents the horizontal displacement.

[0033] Optionally, the load conditions include the initial water and soil pressure P1 inside the cofferdam, the initial water and soil pressure P2 outside the cofferdam, the water and soil pressure P3 inside the sheet piles, the water and soil pressure P4 inside the cofferdam after dewatering, and the water and soil pressure P5 outside the cofferdam under the design water level; when the hydrological condition is a non-tidal water area, according to the hydrological condition of the double-row sheet pile cofferdam and the filling process of the cofferdam, the construction stage is divided, and then the preset load conditions are implemented, including the following steps:

[0034] After the sheet piles are driven and the sand in the cofferdam is filled to the design elevation, apply the initial water and soil pressure P1 inside the cofferdam, the initial water and soil pressure P2 outside the cofferdam, and the water and soil pressure P3 inside the sheet piles.

[0035] After the cofferdam is closed, lower the water level inside the cofferdam to the elevation of the riverbed bottom, remove the initial water and soil pressure P1 inside the cofferdam, and apply the water and soil pressure P4 inside the cofferdam after dewatering.

[0036] After the water level outside the cofferdam rises to the design water level condition, remove the initial water and soil pressure P2 outside the cofferdam, and apply the water and soil pressure P5 outside the cofferdam under the design water level.

[0037] Among them, G1, G2, and G3 represent the working conditions of the double-row sheet pile cofferdam at different construction stages.

[0038] Optionally, the load conditions include the initial water and soil pressure P1 inside the cofferdam, the initial water and soil pressure P2 outside the cofferdam, the water and soil pressure P3 inside the sheet piles, the water and soil pressure P4 inside the cofferdam after dewatering, the water and soil pressure P5 outside the cofferdam under the design water level, the water and soil pressure P6 outside the cofferdam at high tide, and the water and soil pressure P7 outside the cofferdam at low tide; when the hydrological condition is a tidal water area, divide the construction stages according to the hydrological conditions of the double-row sheet pile cofferdam and the filling process of the cofferdam, and then implement the preset load conditions, including the following steps:

[0039] After the sheet piles are driven and the sand in the cofferdam is filled to the design elevation, apply the initial water and soil pressure P1 inside the cofferdam, the initial water and soil pressure P2 outside the cofferdam, and the water and soil pressure P3 inside the sheet piles.

[0040] After the cofferdam is closed, remove the initial water and soil pressure P2 outside the cofferdam and load in two sub-working conditions respectively:

[0041] G2-1: Apply the water and soil pressure P6 outside the cofferdam at high tide; G2-2: Apply the water and soil pressure P7 outside the cofferdam at low tide.

[0042] After dewatering inside the cofferdam, remove the initial water and soil pressure P1 inside the cofferdam and load in two sub-working conditions respectively:

[0043] G3-1: Apply the water and soil pressure P6 outside the cofferdam at high tide and the water and soil pressure P4 inside the cofferdam after dewatering; G3-1: Apply the water and soil pressure P7 outside the cofferdam at low tide and the water and soil pressure P4 inside the cofferdam after dewatering.

[0044] G4: After the water level outside the cofferdam rises to the design water level condition, remove the water and soil pressure P6 outside the cofferdam at high tide or the water and soil pressure P7 outside the cofferdam at low tide, and load the water and soil pressure P5 outside the cofferdam under the design water level.

[0045] Among them, G1, G2-1, G2-2, G3-1, G3-2, and G4 represent the working conditions of the double-row sheet pile cofferdam at different construction stages.

[0046] In an embodiment of the present invention, a structural analysis model of a two-dimensional planar rod system is established according to the dimensions and cross-sectional forms of a double-row sheet pile cofferdam. The double-row sheet pile cofferdam includes double-row sheet piles and the steel bar tie rods between them. The structural analysis model is established based on preset force units, and the force units include a tie rod force unit, a soil body force unit between the double-row sheet piles simulated by springs, a force unit for the soil entry section on the outside of the double-row sheet piles, and a pile end vertical spring force unit. The setting parameters of each component in the structural analysis model are determined based on the soil parameters of the application environment of the double-row sheet pile cofferdam. The construction stages are divided according to the hydrological conditions of the double-row sheet pile cofferdam and the filling process of the cofferdam, and then the preset load conditions are implemented to determine the operation conditions of the double-row sheet pile cofferdam under various working conditions. According to the operation conditions of each working condition, the force analysis results of the double-row sheet pile cofferdam under each working condition are obtained based on the structural analysis model. The beneficial effects of the present invention include:

[0047] 1. Precise simulation of the stress state: By establishing a structural analysis model of a two-dimensional planar rod system, the stress state of the double-row sheet pile cofferdam in the actual working environment can be more precisely simulated. The tie rod force unit, soil body force unit, soil entry section force unit, and pile end vertical spring force unit are introduced into the model, and these units can more comprehensively reflect the stress conditions of the cofferdam under different working conditions.

[0048] 2. Consideration of soil parameters and hydrological conditions: The model is set based on the soil parameters and hydrological conditions of the actual application environment, and can more accurately reflect the working state of the cofferdam under different geological and hydrological conditions. This consideration makes the analysis results closer to the actual situation and improves the reliability of the design.

[0049] 3. Simulation of staged construction: The construction stages are divided according to the filling process of the cofferdam, and the preset load conditions are implemented, so that the operation conditions of the cofferdam in different construction stages can be simulated. This staged simulation helps to discover potential problems in advance, optimize the construction plan, and ensure the construction safety and the stability of the cofferdam.

[0050] 4. Improvement of design accuracy: By obtaining the force analysis results of the double-row sheet pile cofferdam under various working conditions through the structural analysis model, more accurate data support can be provided for the design. Compared with traditional simplified calculation methods or finite element numerical analysis, this technical solution can more accurately reflect the stress state of the sheet piles in each working stage, thereby improving the accuracy and reliability of the design.

[0051] In summary, through precise model establishment and comprehensive parameter consideration, the present invention can significantly improve the accuracy and reliability of the design of the double-row sheet pile cofferdam, and ensure the stability and safety of the cofferdam under various complex hydrological and geological conditions. Brief Description of the Drawings

[0052] The accompanying drawings are used to provide a further understanding of the technical solution of the present invention, and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the technical solution of the present invention and do not constitute a limitation to the technical solution of the present invention.

[0053] Figure 1 It is a schematic flow chart of a method for analyzing the internal force and deformation of a double-row sheet pile cofferdam provided by an embodiment of the present invention;

[0054] Figure 2 It is a schematic diagram of an example of a plane bar system force analysis model provided by an embodiment of the present invention;

[0055] Figure 3 It is a schematic diagram of an example of the overall process of a method for analyzing the internal force and deformation of a double-row sheet pile cofferdam provided by an embodiment of the present invention;

[0056] Figure 4 It is a schematic diagram of an example of the load conditions under various working conditions in a non-tidal water area provided by an embodiment of the present invention;

[0057] Figure 5 It is a schematic diagram of an example of the load conditions in a tidal water area under working conditions G1 and G2 provided by an embodiment of the present invention;

[0058] Figure 6 It is a schematic diagram of an example of the load conditions in a tidal water area under working conditions G3 and G4 provided by an embodiment of the present invention;

[0059] Figure 7 It is a schematic diagram of an example of a calculation example calculation model provided by an embodiment of the present invention;

[0060] Figure 8-1 It is a schematic diagram of an example of the displacement of the cofferdam in the G1 stage of a calculation example provided by an embodiment of the present invention;

[0061] Figure 8-2 It is a schematic diagram of an example of the force on the cofferdam in the G1 stage of a calculation example provided by an embodiment of the present invention;

[0062] Figure 9-1 It is a schematic diagram of an example of the displacement of the cofferdam in the G2 stage of a calculation example provided by an embodiment of the present invention;

[0063] Figure 9-2 It is a schematic diagram of an example of the force on the cofferdam in the G2 stage of a calculation example provided by an embodiment of the present invention;

[0064] Figure 10-1 It is a schematic diagram of an example of the displacement of the cofferdam in the G3 stage of a calculation example provided by an embodiment of the present invention;

[0065] Figure 10-2 It is a schematic diagram of an example of the force on the cofferdam in the G3 stage of a calculation example provided by an embodiment of the present invention. Detailed implementation manners

[0066] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0067] It should be noted that although functional module division is performed in the system schematic diagram and the logical sequence is shown in the flowchart, in some cases, the steps shown or described can be executed in a different module division in the system or a different order in the flowchart. Terms such as "first / S100", "second / S200", etc. in the specification, claims and the above-mentioned drawings are used to distinguish similar objects and do not necessarily need to be used to describe a specific order or sequence.

[0068] Referring to

[0069] Referring to Figure 1 , Figure 1 is a flowchart of the internal force and deformation analysis method of the double-row sheet pile cofferdam applied to cofferdam force analysis provided by the embodiment of the present invention. Referring to Figure 1 , the method includes the following steps:

[0070] S100. Establish a structural analysis model of a two-dimensional plane rod system according to the size and cross-sectional form of the double-row sheet pile cofferdam;

[0071] Among them, the double-row sheet pile cofferdam includes double-row sheet piles and the steel bar tie rods between them; the structural analysis model is established based on preset force units, and the force units include a tie rod force unit and a soil body force unit between the double-row sheet piles simulated by springs, a force unit of the outer soil-embedded section of the double-row sheet piles, and a pile-end vertical spring force unit;

[0072] It should be noted that in some embodiments, establishing a structural analysis model of a two-dimensional plane rod system may include the following steps: determining the two-dimensional plane rod system corresponding to the structure of the double-row sheet pile cofferdam, and then establishing a structural analysis model by simulating with different force units, and assigning corresponding force characteristics and connection methods to each force unit.

[0073] Exemplarily, in some specific embodiments, the present invention first establishes a two-dimensional plane bar system stress analysis model according to the size and cross-sectional form of the cofferdam. Specifically, different stress units are used to simulate each component in the two-dimensional plane bar system, and different stress characteristics and connection methods are assigned to the units to more accurately simulate the actual stress characteristics of each component in the cofferdam system.

[0074] Among them, in some embodiments, using different stress units to simulate and establish a structural analysis model may include the following steps: using a truss element 101 to simulate the tensile stress unit of the tie rod; among them, a double-row sheet pile is simulated by a beam element 100; using a two-end free spring element 103 to simulate the soil stress unit between the double-row sheet piles; using a one-end fixed spring element 104 to simulate the stress unit of the soil-embedded section outside the double-row sheet piles; using a one-end fixed spring element 105 to simulate the vertical spring stress unit at the pile end.

[0075] In some embodiments, assigning corresponding stress characteristics and connection methods to each stress unit may include the following steps: pre-defining that the tie rod and its corresponding tensile stress unit only bear tensile force and do not bear compressive force; setting that the connection between the tensile stress unit of the tie rod and the sheet pile is a hinge 102, and pre-defining that only axial force can be transmitted between the tensile stress unit of the tie rod and the front and rear sheet piles, and no bending moment can be transmitted; pre-defining that the spring unit 103 corresponding to the soil stress unit between the double-row sheet piles can only bear compressive force and cannot bear tensile force, the length is the net distance between the double-row sheet piles, and the direction is horizontal; pre-defining that the stress direction of the spring unit 104 inside the cofferdam can only be in the positive x-axis direction, and the stress direction of the spring unit 104 outside the cofferdam can only be in the negative x-axis direction; pre-defining that the stress direction of the spring unit 105 can only be in the negative y-axis direction.

[0076] Exemplarily, in some specific embodiments, as Figure 2 shown, generally, a double-row steel sheet pile is composed of front and rear row sheet piles and a steel bar tie rod. Among them, the sheet pile is simulated by a beam element 100, and the spring unit 103 is used to connect between the two rows of sheet piles; the tie rod is simulated by a truss element 101, and the connection with the two rows of sheet piles is a hinge, and the spring units 104 and 105 are used to simulate the connection between the sheet pile and the soil. Specifically, the following can be achieved:

[0077] Tensile stress unit of the tie rod: simulated by a truss element 101, and it is defined that the tie rod only bears tensile force and does not bear compressive force. The connection between the tie rod and the sheet pile is a hinge 102, and only axial force can be transmitted between the tie rod and the front and rear sheet piles, and no bending moment can be transmitted.

[0078] Soil stress unit between the double-row sheet piles: simulated by a two-end free spring unit 103, and it is defined that the spring can only bear compressive force and cannot bear tensile force, the spring stiffness is k c , the length is the net distance between the two rows of sheet piles, and the direction is horizontal.

[0079] Force unit of the outer soil penetration section of the double-row sheet piles: It is simulated by a spring element 104 fixed at one end, and it is defined that the force direction of the spring inside the cofferdam can only be in the positive x-axis direction, and the force direction of the spring outside the cofferdam can only be in the negative x-axis direction, and the spring stiffness is k s , and the length is taken as the unit width of 1 m.

[0080] Vertical spring force unit at the pile tip: It is simulated by a spring element 105 fixed at one end, and it is defined that the force direction of the spring can only be in the negative y-axis direction, and the spring stiffness is k d The length is taken as the unit width of 1 m.

[0081] S200. Determine the setting parameters of each component in the structural analysis model based on the soil parameters of the application environment of the double-row sheet pile cofferdam;

[0082] It should be noted that in some embodiments, step S200 may include the following steps: Based on the compression modulus of the soil and the cross-sectional area of the soil between the single piles represented by the springs in the soil force unit simulating the soil between the double-row sheet piles, combined with the net spacing between the two rows of sheet piles, set the spring stiffness of the soil between the piles corresponding to the soil force unit between the double-row sheet piles; The expression of the spring stiffness of the soil between the piles is: k c = Es*A / L; where Es represents the compression modulus of the soil, A represents the cross-sectional area of the soil between the single piles represented by the spring, and L represents the net spacing between the two rows of sheet piles; Based on the soil reaction proportion coefficient and the penetration depth of the double-row sheet pile cofferdam, set the spring stiffness of the soil outside the sheet piles corresponding to the force unit of the outer soil penetration section of the double-row sheet piles; The expression of the spring stiffness of the soil outside the sheet piles is: k s = mz; where m represents the soil reaction proportion coefficient and z represents the penetration depth; Based on the cohesion and internal friction angle of the soil, combined with the horizontal displacement of the double-row sheet pile cofferdam at the penetration position, determine the soil reaction proportion coefficient, and then combined with the penetration depth of the double-row sheet pile cofferdam, set the spring stiffness of the soil outside the sheet piles corresponding to the force unit of the outer soil penetration section of the double-row sheet piles; Set the spring stiffness of the vertical spring at the pile tip corresponding to the vertical spring force unit at the pile tip to the compression modulus of the soil.

[0083] Among them, in some embodiments, the method may further include the following steps: Based on the cohesion and internal friction angle of the soil, combined with the horizontal displacement of the double-row sheet pile cofferdam at the penetration position, determine the soil reaction proportion coefficient; where the expression of the soil reaction proportion coefficient is: m = (0.2Φ 2 -Φ + c) / v b ; where c represents the cohesion of the soil, Φ represents the internal friction angle of the soil, and v b represents the horizontal displacement.

[0084] Exemplarily, in some specific embodiments, determining the relevant parameters of each component of the model can be implemented as follows: The sheet pile and tie rod units determine their flexural or tensile stiffness according to the physical and mechanical parameters of the material and the geometric cross-section. The soil units between the double-row piles and the embedded part of the sheet pile use spring units to simulate the stress state of the soil, and the modulus of the soil spring is determined according to the compression modulus of the soil. Specifically, the set parameters include: the stiffness k of the soil spring between piles c , the stiffness k of the soil spring outside the sheet pile s , and the vertical spring stiffness k of the pile tip d :

[0085] The stiffness k of the soil spring between piles c = Es*A / L, where Es is the compression modulus of the soil, A is the cross-sectional area of the soil represented by a single spring between piles, and L is the net spacing between the two rows of sheet piles.

[0086] The stiffness k of the soil spring outside the sheet pile s = mz, where m is the soil reaction proportion coefficient, m = (0.2Φ 2 - Φ + c) / v b , c and Φ are the cohesion and internal friction angle of the soil, v b is the horizontal displacement of the cofferdam at the embedded position, generally taking 10 mm. z is the embedded depth of the cofferdam sheet pile.

[0087] The vertical spring stiffness k of the pile tip d can take the compression modulus E of the soil at the pile tip s .

[0088] S300. Divide the construction stages according to the hydrological conditions of the double-row sheet pile cofferdam and the filling process of the cofferdam, and then implement the preset load conditions to determine the operation conditions of the double-row sheet pile cofferdam under each working condition;

[0089] Among them, the hydrological conditions include non-tidal waters and tidal waters; the load conditions include the initial water and soil pressure P1 inside the cofferdam, the initial water and soil pressure P2 outside the cofferdam, the water and soil pressure P3 inside the sheet pile, the water and soil pressure P4 inside the cofferdam after precipitation, the water and soil pressure P5 outside the cofferdam under the design water level, the water and soil pressure P6 outside the cofferdam at high tide level, and the water and soil pressure P7 outside the cofferdam at low tide level;

[0090] It should be noted that in some embodiments, when the hydrological condition is a non-tidal water area, the construction stages are divided according to the hydrological conditions of the double-row sheet pile cofferdam and the filling process of the cofferdam, and then the preset load conditions are implemented, which may include the following steps: G1. After the sheet piles are driven and the sand in the cofferdam is filled to the design elevation, apply the initial water and soil pressure P1 inside the cofferdam, the initial water and soil pressure P2 outside the cofferdam, and the water and soil pressure P3 inside the sheet piles; G2. After the cofferdam is closed, lower the water level inside the cofferdam to the elevation of the riverbed bottom, remove the initial water and soil pressure P1 inside the cofferdam, and apply the water and soil pressure P4 inside the cofferdam after dewatering; G3. After the water level outside the cofferdam rises to the design water level condition, remove the initial water and soil pressure P2 outside the cofferdam, and apply the water and soil pressure P5 outside the cofferdam under the design water level; where G1, G2, and G3 represent the working conditions of the double-row sheet pile cofferdam at different construction stages.

[0091] It should also be noted that in some embodiments, when the hydrological condition is a tidal water area, the construction stages are divided according to the hydrological conditions of the double-row sheet pile cofferdam and the filling process of the cofferdam, and then the preset load conditions are implemented, which may include the following steps: G1. After the sheet piles are driven and the sand in the cofferdam is filled to the design elevation, apply the initial water and soil pressure P1 inside the cofferdam, the initial water and soil pressure P2 outside the cofferdam, and the water and soil pressure P3 inside the sheet piles; after the cofferdam is closed, remove the initial water and soil pressure P2 outside the cofferdam, and load in two sub-working conditions respectively: G2-1. Apply the water and soil pressure P6 outside the cofferdam at high tide; G2-2. Apply the water and soil pressure P7 outside the cofferdam at low tide; after dewatering inside the cofferdam, remove the initial water and soil pressure P1 inside the cofferdam, and load in two sub-working conditions respectively: G3-1. Apply the water and soil pressure P6 outside the cofferdam at high tide and the water and soil pressure P4 inside the cofferdam after dewatering; G3-1. Apply the water and soil pressure P7 outside the cofferdam at low tide and the water and soil pressure P4 inside the cofferdam after dewatering; G4. After the water level outside the cofferdam rises to the design water level condition, remove the water and soil pressure P6 outside the cofferdam at high tide or the water and soil pressure P7 outside the cofferdam at low tide, and load the water and soil pressure P5 outside the cofferdam under the design water level; where G1, G2-1, G2-2, G3-1, G3-2, and G4 represent the working conditions of the double-row sheet pile cofferdam at different construction stages.

[0092] Exemplarily, in some specific embodiments, the hydrological conditions are divided into tidal water areas and non-tidal water areas. The load conditions under each working condition include: the initial water and soil pressure P1 inside the cofferdam, the initial water and soil pressure P2 outside the cofferdam, the water and soil pressure P3 inside the sheet piles, the water and soil pressure P4 inside the cofferdam after dewatering, the water and soil pressure P5 outside the cofferdam under the design water level, the water and soil pressure P6 outside the cofferdam at high tide, and the water and soil pressure P7 outside the cofferdam at low tide.

[0093] During the implementation process, the hydrological conditions should be determined first, that is, whether the cofferdam belongs to a tidal water area, and then the load conditions of each working condition should be determined according to the construction process of the general cofferdam.

[0094] G1, G2, G3, and G4 represent the working conditions of the cofferdam at different operation stages. The implementation process of the load conditions under each working condition is as follows.

[0095] Non-tidal waters: For G1, after the sheet piles are driven and the sand inside the cofferdam is filled to the design elevation, apply the initial water and soil pressure P1 inside the cofferdam, the initial water and soil pressure P2 outside the cofferdam, and the water and soil pressure P3 inside the sheet piles; for G2, after the cofferdam is closed, lower the water level inside the cofferdam to the riverbed elevation, remove the initial water and soil pressure P1 inside the cofferdam, and apply the water and soil pressure P4 inside the cofferdam after dewatering; for G3, after the water level outside the cofferdam rises to the design water level condition, remove the initial water and soil pressure P2 outside the cofferdam, and apply the water and soil pressure P5 outside the cofferdam under the design water level.

[0096] Tidal waters: For G1, after the sheet piles are driven and the sand inside the cofferdam is filled to the design elevation, apply the initial water and soil pressure P1 inside the cofferdam, the initial water and soil pressure P2 outside the cofferdam, and the water and soil pressure P3 inside the sheet piles; after the cofferdam is closed, remove the initial water and soil pressure P2 outside the cofferdam and load in two sub-working conditions respectively: G2-1, apply the water and soil pressure P6 outside the cofferdam at high tide, G2-2, apply the water and soil pressure P7 outside the cofferdam at low tide; after dewatering inside the cofferdam, remove the initial water and soil pressure P1 inside the cofferdam and load in two sub-working conditions respectively: G3-1, apply the water and soil pressure P6 outside the cofferdam at high tide + the water and soil pressure P4 inside the cofferdam after dewatering, G3-1, apply the water and soil pressure P7 outside the cofferdam at low tide + the water and soil pressure P4 inside the cofferdam after dewatering; for G4, after the water level outside the cofferdam rises to the design water level condition, remove the water and soil pressure P6 outside the cofferdam at high tide or the water and soil pressure P7 outside the cofferdam at low tide, and load the water and soil pressure P5 outside the cofferdam under the design water level.

[0097] S400. According to the operation conditions of each working condition, obtain the stress analysis results of the double-row sheet pile cofferdam under each working condition based on the structural analysis model.

[0098] It should be noted that after the structural analysis model is established, data simulation analysis can be directly carried out through the finite element analysis software for the load conditions preset for different working conditions, and then the final analysis results can be obtained.

[0099] To explain the principle of the technical solution of the present invention in detail, the overall process of the present invention will be described below in combination with some specific embodiments. It is easy to understand that the following is an explanation of the technical principle of the present invention and should not be regarded as a limitation of the present invention.

[0100] In view of the related problems of the prior art, the present invention provides a method for analyzing the internal force and deformation of a double-row sheet pile cofferdam. As Figure 3 shown, the object of the present invention is achieved as follows:

[0101] S1. According to the size and cross-sectional form of the cofferdam, establish a two-dimensional plane bar system structural stress analysis model. As Figure 2As shown in the figure, a general double-row steel sheet pile consists of front and rear row sheet piles and steel bar tie rods. Among them, the sheet piles are simulated by beam elements 100, and the two rows of sheet piles are connected by spring elements 103; the tie rods are simulated by truss elements 101, and are hinged to the two rows of sheet piles, and the spring elements 104 and 105 are used to simulate between the sheet piles and the soil.

[0102] S2. Determine the relevant parameters of each component of the model. The bending or tensile stiffness of the sheet pile and tie rod elements is determined according to the physical and mechanical parameters of the material and the geometric cross-section. The soil elements between the double-row piles and the embedded part of the sheet pile are simulated by spring elements to simulate the stress state of the soil, and the modulus of the soil spring is determined according to the compression modulus of the soil.

[0103] S3. According to the hydrological conditions of the cofferdam and the filling process of the cofferdam, divide the construction stages and determine the load conditions under the working conditions.

[0104] S4. According to the calculation results of each working condition, respectively obtain the internal force and deformation of the sheet pile, the tension of the tie rod, etc. under each working condition, and determine the most unfavorable working condition and results of the cofferdam stress.

[0105] Among them, in S1, different force-bearing units are used to simulate each component in the two-dimensional plane rod system, and different force-bearing characteristics and connection methods are given to the units, so as to more accurately simulate the actual force-bearing characteristics of each component in the cofferdam system.

[0106] Tie rod force-bearing unit: Simulated by truss element 101, and it is defined that the tie rod only bears tension and does not bear compression. The tie rod and the sheet pile are hinged by 102, and only axial force can be transmitted between the tie rod and the front and rear sheet piles, and bending moment cannot be transmitted.

[0107] Soil force-bearing unit between double-row sheet piles: Simulated by a spring unit 103 with both ends free, and it is defined that the spring can only bear pressure and cannot bear tension, and the spring stiffness is k c , the length is the net distance between the two rows of sheet piles, and the direction is horizontal.

[0108] Force-bearing unit of the embedded section on the outside of the double-row sheet pile: Simulated by a spring unit 104 with one end fixed, and it is defined that the force direction of the spring on the inside of the cofferdam can only be in the positive direction of the x-axis, and the force direction of the spring on the outside of the cofferdam can only be in the negative direction of the x-axis, and the spring stiffness is k s , and the length is taken as the unit width of 1m.

[0109] Force-bearing unit of the vertical spring at the pile end: Simulated by a spring unit 105 with one end fixed, and it is defined that the force direction of the spring can only be in the negative direction of the y-axis, and the spring stiffness is k d The length is taken as the unit width of 1m.

[0110] The parameters of each component of the plane rod system structure include: the spring stiffness k of the soil between piles c 、the spring stiffness k of the soil outside the sheet piles , the vertical spring stiffness k at the pile tip d , specifically:

[0111] the spring stiffness k of the soil between piles c = Es*A / L, where Es is the compression modulus of the soil, A is the cross-sectional area of the soil between piles represented by a single spring, and L is the net spacing between two rows of sheet piles.

[0112] the spring stiffness k of the soil outside the sheet pile s = mz, m is the coefficient of soil reaction, m = (0.2Φ 2 - Φ + c) / v b , c and Φ are the cohesion and internal friction angle of the soil, v b is the horizontal displacement of the cofferdam at the soil entry position, generally taken as 10 mm. z is the penetration depth of the cofferdam sheet pile.

[0113] the vertical spring stiffness k at the pile tip d can be taken as the compression modulus E of the soil at the pile tip s .

[0114] Among them, the hydrological conditions in S3 are divided into tidal waters and non-tidal waters. The load conditions under each working condition include: the initial water and soil pressure P1 inside the cofferdam, the initial water and soil pressure P2 outside the cofferdam, the water and soil pressure P3 inside the sheet pile, the water and soil pressure P4 inside the cofferdam after dewatering, the water and soil pressure P5 outside the cofferdam under the design water level, the water and soil pressure P6 outside the cofferdam at high tide, and the water and soil pressure P7 outside the cofferdam at low tide.

[0115] During the implementation process, the hydrological conditions should be determined first, that is, whether the cofferdam belongs to tidal waters, and then the load conditions under each working condition should be determined according to the construction process of a general cofferdam.

[0116] G1, G2, G3, and G4 represent the working conditions of the cofferdam at different operation stages. The implementation process of the load conditions under each working condition is as follows.

[0117] Non-tidal waters: G1, after driving the sheet piles and filling the sand inside the cofferdam to the design elevation, apply the initial water and soil pressure P1 inside the cofferdam, the initial water and soil pressure P2 outside the cofferdam, and the water and soil pressure P3 inside the sheet pile; G2, after the cofferdam is closed, lower the water level inside the cofferdam to the riverbed elevation, remove the initial water and soil pressure P1 inside the cofferdam, and apply the water and soil pressure P4 inside the cofferdam after dewatering; G3, after the water level outside the cofferdam rises to the design water level condition, remove the initial water and soil pressure P2 outside the cofferdam, and apply the water and soil pressure P5 outside the cofferdam under the design water level. As Figure 4 shown, it is a schematic diagram of an example of the load conditions under each working condition in non-tidal waters.

[0118] Tidal waters: G1. After the sheet piles are driven and the sandy soil inside the cofferdam is filled to the design elevation, apply the initial water and soil pressure P1 inside the cofferdam, the initial water and soil pressure P2 outside the cofferdam, and the water and soil pressure P3 inside the sheet piles. After the cofferdam is closed, remove the initial water and soil pressure P2 outside the cofferdam. G2 is loaded in two sub - working conditions respectively: G2 - 1. Apply the water and soil pressure P6 on the outside of the cofferdam at high tide; G2 - 2. Apply the water and soil pressure P7 on the outside of the cofferdam at low tide. After the water is lowered inside the cofferdam, remove the initial water and soil pressure P1 inside the cofferdam. G3 is loaded in two sub - working conditions respectively: G3 - 1. Apply the water and soil pressure P6 on the outside of the cofferdam at high tide + the water and soil pressure P4 inside the cofferdam after the water is lowered; G3 - 2. Apply the water and soil pressure P7 on the outside of the cofferdam at low tide + the water and soil pressure P4 inside the cofferdam after the water is lowered. G4. After the water level outside the cofferdam rises to the design water level, remove the water and soil pressure P6 on the outside of the cofferdam at high tide or the water and soil pressure P7 on the outside of the cofferdam at low tide, and load the water and soil pressure P5 on the outside of the cofferdam at the design water level. As Figure 5 shown, it is a schematic diagram of an example of the load conditions of the tidal waters under the G1 and G2 working conditions; as Figure 6 shown, it is a schematic diagram of an example of the load conditions of the tidal waters under the G3 and G4 working conditions.

[0119] The following is an example description of the embodiments of the present invention in combination with specific application scenarios. Taking non - tidal waters as an example, the present invention can achieve the following:

[0120] 1. For a double - row sheet - pile cofferdam, the type of sheet piles used is Larsen IV. The spacing between the front and rear rows of sheet piles is 6.0 m, the length of the sheet piles is 18 m, and a steel bar tie rod is set at the top. The tie rod is located 1 m below the top of the sheet pile, the diameter of the tie rod is 50 mm, and the spacing is 1.0 m. The space between the two rows of sheet piles is backfilled with medium sand, and the sheet piles enter the soil layer of medium sand. The unit weight of the medium sand = 20 kN / m 3 , the internal friction angle = 30°, and the deformation modulus E0 = 20 MPa. The elastic modulus of the steel E = 2.1×10 9 kN / ㎡. The sheet - pile cofferdam is 5 m above the riverbed surface, and the water - retaining height on the outside is 4.5 m. After the cofferdam is closed, dry - land construction is carried out inside the cofferdam, and the groundwater level inside is at the ground elevation. The calculation model is as Figure 7 shown.

[0121] 2. Establish a two - dimensional plane bar - system stress model, in which the sheet piles are adopted as beam elements, the steel bar tie rods are adopted as truss elements, and the truss elements are defined as only in tension. The truss elements and the sheet piles are connected by hinges. The front and rear rows of sheet piles are connected by spring elements, and the spring elements are defined as only in compression.

[0122] 3. Determine the relevant parameters of each component of the model. Among them, the flexural rigidity of the sheet pile EI = 8.32×10 4kN / ㎡, the spring stiffness of the steel bar tie rod = EA / L = 687 MPa. The soil springs between the piles are set at a vertical spacing of 1 m, and their stiffness per unit width = E0A / L = 3.3 MPa. The soil spring stiffness of the soil in the embedded sections on both sides of the cofferdam is calculated according to the "m method" in Section 4.1.5 of the "Code for Design of Building Foundation Pit Support" (JGJ120 - 2012).

[0123] 4. According to the construction process of the cofferdam, the stress stages of the cofferdam are roughly divided into 3 stages, namely: G1 after driving the sheet piles and filling the sand inside the cofferdam to the elevation of the cofferdam top; G2 after the cofferdam is closed, the water level outside the cofferdam is the normal water level, and the water level inside the cofferdam is lowered to the elevation of the riverbed bottom; G3 when the water level outside the cofferdam rises to the design water level, and the inside of the cofferdam is still in a dry state.

[0124] 5. In stage G1, after driving the sheet piles and filling the sand inside the cofferdam to the elevation of the cofferdam top, applying the initial water and soil pressure P1 inside the cofferdam, the initial water and soil pressure P2 outside the cofferdam, and the water and soil pressure P3 inside the sheet piles, the stress displacement and stress state of the cofferdam are obtained as Figure 8-1 and Figure 8-2 shown. Since the sand is filled inside the double-row steel sheet piles and the water level outside the sheet piles is in a low-water state, the double-row piles displace outward.

[0125] 6. In stage G2, after the cofferdam is closed, the water level inside the cofferdam is lowered to the elevation of the riverbed bottom, removing the initial water and soil pressure P1 inside the cofferdam, and applying the water and soil pressure P 4， inside the cofferdam after dewatering, the stress displacement and stress state of the cofferdam are obtained as Figure 9-1 and Figure 9-2 shown. Due to the dewatering inside the cofferdam, the stress is unbalanced, and the overall displacement is towards the inside of the cofferdam;

[0126] 7. In stage G3, after the water level outside the cofferdam rises to the design water level, removing the initial water and soil pressure P2 outside the cofferdam, and applying the water and soil pressure P 5， outside the cofferdam under the design water level, the stress displacement and stress state of the cofferdam are obtained as Figure 10-1 and Figure 10-2 shown. After the water level outside the cofferdam further rises to the design water level, the displacement further develops towards the inside of the cofferdam.

[0127] In summary, the purpose of the present invention is to provide a method for analyzing the internal force and deformation of a double-row sheet pile cofferdam. This method has clear forces, reasonable model simplification, fully considers the stress conditions of the cofferdam under different hydrological conditions, and the calculation results can reflect the stress states of the cofferdam structure at each stage during operation. Engineering technicians can use this method to check the internal forces of components such as sheet piles and tie rods and the displacement of the cofferdam, so as to further complete the selection and layout of the cofferdam components.

[0128] In some alternative embodiments, the functions / operations recited in the block diagrams may not occur in the order presented in the operational illustrations. For example, depending on the functions / operations involved, two blocks shown in succession may actually be executed substantially concurrently or the blocks may sometimes be executed in the reverse order. Further, the embodiments presented and described in the flowcharts of the present invention are provided by way of example in order to provide a more thorough understanding of the technology. The disclosed methods are not limited to the operations and logical flows presented herein. Alternative embodiments are contemplated in which the order of various operations is altered and in which sub-operations described as part of a larger operation are executed independently.

[0129] In the description of the present specification, the descriptions with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In the present specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0130] Although embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the claims and their equivalents.

[0131] The above has specifically described the preferred embodiments of the present invention, but the present invention is not limited to the embodiments. Those skilled in the art can also make various equivalent deformations or substitutions without departing from the spirit of the present invention, and these equivalent deformations or substitutions are all included within the scope defined by the claims of the present invention.

Claims

1. A method for analyzing the internal forces and deformations of a double-row sheet pile cofferdam, characterized in that, Including the following steps: According to the dimensions and cross-sectional form of the double-row sheet pile cofferdam, establish a structural analysis model of a two-dimensional plane rod system; Among them, the double-row sheet pile cofferdam includes double-row sheet piles and the steel bar tie rods between them; the structural analysis model is established based on preset force units, and the force units include a tie rod force unit and soil force units between the double-row sheet piles simulated by springs, the force unit of the soil outside the double-row sheet piles in the penetration section, and the vertical spring force unit at the pile end; Determine the setting parameters of each component in the structural analysis model based on the soil parameters of the application environment of the double-row sheet pile cofferdam; Divide the construction stages according to the hydrological conditions of the double-row sheet pile cofferdam and the filling process of the cofferdam, and then implement the preset load conditions to determine the operation conditions of the double-row sheet pile cofferdam under each working condition; According to the operation conditions of each working condition, obtain the force analysis results of the double-row sheet pile cofferdam under each working condition based on the structural analysis model.

2. The internal force and deformation analysis method of the double-row sheet pile cofferdam according to claim 1, characterized in that, The establishment of the structural analysis model of the two-dimensional plane rod system includes the following steps: Correspondingly determine the two-dimensional plane rod system according to the structure of the double-row sheet pile cofferdam, and then use different force units to simulate and establish the structural analysis model, and endow each force unit with corresponding force characteristics and connection methods.

3. The internal force and deformation analysis method of the double-row sheet pile cofferdam according to claim 2, characterized in that The use of different force units to simulate and establish the structural analysis model includes the following steps: Use a truss element (101) to simulate the tie rod force unit; among them, the double-row sheet piles are simulated by beam elements (100); Use a free-end spring element (103) at both ends to simulate the soil force unit between the double-row sheet piles; Use a fixed-end spring element (104) at one end to simulate the force unit of the soil in the penetration section outside the double-row sheet piles; Use a fixed-end spring element (105) at one end to simulate the vertical spring force unit at the pile end.

4. The internal force and deformation analysis method of the double-row sheet pile cofferdam according to claim 3, characterized in that The endowing of each force unit with corresponding force characteristics and connection methods includes the following steps: Pre-define that the tie rod and its corresponding tie rod force unit only bear tension and do not bear compression; set the connection between the tie rod force unit and the sheet pile to be hinged (102), and pre-define that only axial force can be transmitted between the tie rod force unit and the front and rear sheet piles, and bending moment cannot be transmitted; Pre-define that the spring unit (103) corresponding to the soil force unit between the double-row sheet piles can only bear compression and cannot bear tension, the length is the net distance between the double-row sheet piles, and the direction is horizontal; Pre-define that the force direction of the spring unit (104) inside the cofferdam can only be in the positive x-axis direction, and the force direction of the spring unit (104) outside the cofferdam can only be in the negative x-axis direction; Pre-define that the force direction of the spring unit (105) can only be in the negative y-axis direction.

5. The internal force and deformation analysis method of the double-row sheet pile cofferdam according to claim 1, characterized in that The determination of the setting parameters of each component in the structural analysis model based on the soil parameters of the application environment of the double-row sheet pile cofferdam includes the following steps: Based on the compression modulus of the soil mass and the spring in the soil force unit simulating the soil between the double-row sheet piles, where a single spring represents the cross-sectional area of the soil between the piles, the soil spring stiffness corresponding to the soil force unit between the double-row sheet piles is set in combination with the net spacing between the two rows of the sheet piles; the expression of the soil spring stiffness between the piles is: k c = Es * A / L; where Es represents the compression modulus of the soil mass, A represents the cross-sectional area of the soil between the piles represented by a single spring, and L represents the net spacing between the two rows of the sheet piles; Set the soil spring stiffness of the soil outside the double-row sheet pile corresponding to the stressed unit of the soil outside the double-row sheet pile based on the soil reaction proportion coefficient and the penetration depth of the double-row sheet pile cofferdam; the expression of the soil spring stiffness outside the sheet pile is: k s = mz; where m represents the soil reaction proportion coefficient and z represents the penetration depth; The cohesion and internal friction angle of the soil, combined with the horizontal displacement of the double-row sheet pile cofferdam at the penetration position, determine the soil reaction proportional coefficient, and then combine the penetration depth of the double-row sheet pile cofferdam to set the spring stiffness of the soil outside the sheet piles corresponding to the force unit of the soil in the penetration section outside the double-row sheet piles; The pile end vertical spring stiffness corresponding to the pile end vertical spring force unit is set as the compression modulus of the soil.

6. The internal force and deformation analysis method of the double-row sheet pile cofferdam according to claim 5, characterized in that The method further comprises the following steps: Based on the cohesion and internal friction angle of the soil, the soil reaction force proportionality coefficient is determined in combination with the horizontal displacement of the double-row sheet pile cofferdam at the buried position; The expression of the soil reaction proportional coefficient is: m = (0.2Φ 2 - Φ + c) / v b ; where c represents the cohesion of the soil mass, Φ represents the internal friction angle of the soil mass, and v b represents the horizontal displacement.

7. The internal force and deformation analysis method of the double-row sheet pile cofferdam according to claim 1, characterized in that The load conditions include the initial water and soil pressure P1 inside the cofferdam, the initial water and soil pressure P2 outside the cofferdam, the water and soil pressure P3 inside the sheet piles, the water and soil pressure P4 inside the cofferdam after precipitation, and the water and soil pressure P5 outside the cofferdam under the design water level; when the hydrological conditions are non-tidal waters, the construction stages are divided according to the hydrological conditions of the double-row sheet pile cofferdam and the filling process of the cofferdam, and then the preset load conditions are implemented, including the following steps: G1. After the sheet piles are driven and the sand and soil in the cofferdam are filled to the designed elevation, the initial water and soil pressure P1 inside the cofferdam, the initial water and soil pressure P2 outside the cofferdam and the water and soil pressure P3 inside the sheet piles are applied; G2, after the cofferdam is closed, the water level inside the cofferdam is reduced to the riverbed bottom elevation, the initial water and soil pressure P1 inside the cofferdam is removed, and the water and soil pressure P4 inside the cofferdam after the reduction is applied; G3, after the water level outside the cofferdam rises to the design water level, the initial water and soil pressure P2 outside the cofferdam is removed, and the water and soil pressure P5 outside the cofferdam under the design water level is applied; Among them, G1, G2 and G3 represent the working conditions of the double-row sheet pile cofferdam at different construction stages.

8. The internal force and deformation analysis method of the double-row sheet pile cofferdam according to claim 1, characterized in that, The load conditions include initial water and soil pressure P1 inside the cofferdam, initial water and soil pressure P2 outside the cofferdam, water and soil pressure P3 inside the sheet piles, water and soil pressure P4 inside the cofferdam after precipitation, water and soil pressure P5 outside the cofferdam under the design water level, water and soil pressure P6 outside the cofferdam at high tide, and water and soil pressure P7 outside the cofferdam at low tide. When the hydrological condition is a tidal water area, the construction stages are divided according to the hydrological conditions of the double-row sheet pile cofferdam and the filling process of the cofferdam, and then the preset load conditions are implemented, including the following steps: G1. After the sheet piles are driven and the sand and soil in the cofferdam are filled to the designed elevation, the initial water and soil pressure P1 inside the cofferdam, the initial water and soil pressure P2 outside the cofferdam and the water and soil pressure P3 inside the sheet piles are applied; After the cofferdam is closed, the initial water and soil pressure P2 outside the cofferdam is removed and loaded in two sub-conditions: G2-1, applying the water and soil pressure P6 on the outside of the high tide cofferdam; G2-2, applying the water and soil pressure P7 on the outside of the low tide cofferdam; After precipitation in the cofferdam, the initial water and soil pressure P1 in the cofferdam is removed, and two sub-conditions are loaded separately: G3-1, applying the water and soil pressure P6 on the outer side of the high tide cofferdam and the water and soil pressure P4 on the inner side of the cofferdam after precipitation; G3-1, applying the water and soil pressure P7 on the outer side of the low tide cofferdam and the water and soil pressure P4 on the inner side of the cofferdam after precipitation; G4, after the water level outside the cofferdam rises to the design water level, remove the water and soil pressure P6 outside the cofferdam at the high tide level or the water and soil pressure P7 outside the cofferdam at the low tide level, and load the water and soil pressure P5 outside the cofferdam at the design water level; Among them, G1, G2-1, G2-2, G3-1, G3-2 and G4 represent the working conditions of the double-row sheet pile cofferdam at different construction stages.

Images