Method for determining fixed inclination height of variable cross-section immersed tube joint

Abstract

The invention discloses a method for determining the fixed inclination height of a variable-cross-section immersed tube joint, which can standardly calculate the fixed inclination height of the variable-cross-section immersed tube joint aiming at a special variable-cross-section immersed tube joint structure and control the stability of the tube joint under various working conditions by determining the fixed inclination height of the tube joint. And the safety and the stability of floating transportation in water saving of the variable-cross-section immersed tube are ensured. According to the method, the stress problem of the variable cross-section immersed tube joint in floating and floating transportation is solved, the design difficulty of the tube joint is effectively reduced, and the construction control risk is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of immersed tube tunnels, in particular to a method for determining the fixed inclination height of a variable-section immersed tube segment. Background Art

[0002] Immersed tube tunnels have to go through a lot of complex underwater operations, including floating, sinking, docking, etc. The loads, combined effects, and construction conditions at each stage are very different from those of other tunnel construction methods. Due to the effects of water flow and construction loads at different stages, the force process is a dynamic change process.

[0003] There is relatively mature experience available for the floating, transporting and sinking of straight and large radius pipe sections with equal cross-sections, and the construction difficulty is relatively low and the risk is small. However, for variable cross-section pipe sections, their characteristics are as follows:

[0004] 1. The particularity of variable cross-section pipe sections

[0005] Cross-section change: The cross-section width of the variable cross-section pipe section is not constant, but gradually changes along the length direction. This change makes the stress situation of the pipe section during floating complicated.

[0006] Asymmetry between the center of gravity and the center of buoyancy: Due to the change in cross-sectional width, the longitudinal and transverse center of gravity and center of buoyancy of the variable-section pipe segment often do not coincide, which increases the instability of the pipe segment during floating.

[0007] Complex fluid dynamic characteristics: Variable-section pipe segments will be affected by various fluid dynamics such as water flow and waves during the floating process. The points of action and magnitude of these forces will change with the changes in the cross-section of the pipe segment, further increasing the risk of capsizing of the pipe segment.

[0008] 2. Analysis of the causes of capsizing

[0009] Fluid dynamic imbalance: When a variable-section pipe segment is subjected to uneven fluid dynamics during floating, such as one side being subjected to greater water flow impact or wave force while the other side is subjected to less force or no force, it will cause the pipe segment to generate an overturning moment.

[0010] Center of gravity shift: Since the center of gravity and the center of buoyancy of the pipe section do not coincide, when the pipe section is subjected to external forces (such as water flow, waves, wind, etc.), the center of gravity is easily shifted, thereby causing the pipe section to capsize.

[0011] Improper operation: During the floating process, improper operation (such as towing too fast, turning too sharply, etc.) may easily cause the pipe section to lose balance and capsize.

[0012] However, for variable cross-section pipe sections, the cross-sectional characteristics change along the longitudinal direction, and the position of the center of buoyancy and center of gravity is difficult to determine and control, which can easily cause the pipe section to tilt laterally in the water and produce a negative fixed inclination height. If the tilt continues to exceed a certain angle, it is difficult to ensure the stability of the pipe section. The fixed inclination height of the submerged tube refers to the height when the submerged tube tilts horizontally to one side during operation until the liquid exceeds the side wall and enters a stable position on the outside. In the design and operation of the pipe section, it is very important to understand and control the fixed inclination height of the submerged tube because it directly affects the stability and safety of the pipe section. The definition of the fixed inclination height and its function are as follows:

[0013] 1. Definition and function of fixed tilt height

[0014] The fixed inclination height refers to the height or distance at which an object can maintain a certain stable state when subjected to external forces. In immersed tunnel projects, the fixed inclination height is closely related to the distance between the center of buoyancy and the center of gravity of the pipe section. Increasing the fixed inclination height can reduce the risk of the pipe section heeling during floating and improve the stability of the pipe section.

[0015] 2. The influence of fixed tilt height on capsizing problem

[0016] Reduce the distance between the center of buoyancy and the center of gravity: By adjusting the design of the pipe section and increasing its fixed inclination height, the distance between the center of buoyancy and the center of gravity of the pipe section can be reduced. This helps to reduce the overturning moment generated by the pipe section when it is subjected to external forces, thereby improving the anti-overturning ability of the pipe section.

[0017] Improve initial stability: Increasing the fixed inclination height can also improve the initial stability of the pipe section, that is, the ability of the pipe section to quickly return to a stable state when subjected to a small external force. This helps to reduce the heeling phenomenon of the pipe section caused by slight disturbances during floating.

[0018] In summary, determining the fixed inclination height is an effective means to alleviate the overturning problem of variable-section pipe segments during floating. The importance of the fixed inclination height of the immersed tube lies in that it directly affects the stability of the pipe segment. When the pipe segment tilts, the liquid in the immersed tube will tilt outward, and the pressure will also be unbalanced, resulting in unstable operation of the pipe segment. If the fixed inclination height of the immersed tube is too low, the safety and stability of the pipe segment will be affected. Designers need to reasonably determine the fixed inclination height of the immersed tube to ensure that the pipe segment can remain stable under various circumstances. There is no clear method for calculating the fixed inclination height for variable-section pipe segments to ensure floating safety, and there is no standardized method for calculating the fixed inclination height for variable-section immersed tube tunnels. In summary, it is very necessary to determine the fixed inclination height for special variable-section immersed tube segment structures. Therefore, a method for determining the fixed inclination height of variable-section immersed tube segments is proposed. Summary of the invention

[0019] The purpose of the present invention is to provide a method for determining the fixed inclination height of a variable cross-section immersed tube segment, which can standardize the calculation of the fixed inclination height of a variable cross-section immersed tube tunnel, reasonably determine the fixed inclination height of the immersed tube, and ensure that the segment can remain stable under various conditions.

[0020] The present invention is achieved through the following technical solutions:

[0021] A method for determining the fixed inclination height of a variable cross-section immersed tube segment, comprising the following steps:

[0022] Step 1: Establish the plane forms of immersed tube segments with different variable cross-sections; the plane forms of immersed tube segments with different variable cross-sections include equal cross-section-variable cross-section form, equal cross-section-variable cross-section form, and variable cross-section-equal cross-section form;

[0023] Step 2: Calculate the fixed inclination height of the variable cross-section immersed tube segment using a theoretical formula;

[0024] Step 3: The fixed inclination height is divided into two aspects: the floating stage without ballast water and the floating stage with ballast water. As a further improvement of the technical solution of the present invention, the floating stage: without ballast water:

[0025] Form 1: The calculation formula for the fixed tilt height in step 2 is:

[0026]

[0027]

[0028] Where: H is the height of the pipe section structure (m); h is the freeboard value (m); B1 and B2 are the diameters of the two ends of the variable cross-section immersed tube segment; L1 and L2 are the axial lengths of different cross-sections of the variable cross-section immersed tube segment; H f is the distance between the buoyancy center and the gravity center of the pipe section (m), H wdl is the fixed inclination height (m), the center of gravity of the pipe section is above the center of buoyancy; under the premise that the inclination of the pipe section is less than 10°, the freeboard height can be calculated by the following formula:

[0029]

[0030] Where: G k is the standard value of the deadweight of the pipe section (kN); G a is the standard value of the weight of the pipe section outfitting and temporary components (kN); H1 is the thickness of the anti-anchor layer adjustment (m); γ w is the water density (kN / m 3 ), S is the projected area of ​​the variable cross-section pipe section;

[0031] Form 2:

[0032]

[0033] Where: H is the height of the pipe section structure (m); h is the freeboard value (m); B1 and B2 are the diameters of the two ends of the variable-section immersed tube segment respectively; L1, L2, and L3 are the axial lengths of different sections of the variable-section immersed tube segment respectively;

[0034] Form three:

[0035]

[0036] Where: H is the height of the pipe section structure (m); h is the freeboard value (m); B1 and B2 are the diameters of the two ends of the variable-section immersed tube segment; L1 and L2 are the axial lengths of different sections of the variable-section immersed tube segment;

[0037] Form 4:

[0038]

[0039] In the formula: H is the structural height of the pipe section (m); h is the freeboard value (m); B1 is the diameter of one end of the variable-section immersed tube segment; B2 is the vertical height of the other end of the variable-section immersed tube segment tilted downward based on the diameter of B1; B3 is the vertical height of the other end of the variable-section immersed tube segment tilted upward based on the diameter of B1; L1 and L2 are the axial lengths of different sections of the variable-section immersed tube segment respectively.

[0040] As a further improvement of the technical solution of the present invention, during the floating stage: there is ballast water:

[0041] Form 1: The calculation formula for the fixed tilt height in step 2 is:

[0042]

[0043] Where: H is the height of the pipe section structure (m); h is the freeboard value (m); B1 and B2 are the diameters of the two ends of the variable cross-section immersed tube segment; L1 and L2 are the axial lengths of different cross-sections of the variable cross-section immersed tube segment; H f is the distance between the buoyancy center and the gravity center of the pipe section (m), H wdl is the fixed inclination height (m), ∑I W It is the sum of the moments of inertia of the ballast water surface of each part of the pipe section around its own axis. The center of gravity of the pipe section is above the center of buoyancy. The freeboard height can be calculated by the following formula:

[0044]

[0045] Where: G k is the standard value of the deadweight of the pipe section (kN); G a is the standard value of the weight of the pipe section outfitting and temporary components (kN); H1 is the thickness of the anti-anchor layer adjustment (m); γ w is the water density (kN / m3 ), S is the projected area of ​​the variable cross-section pipe section;

[0046] Form 2:

[0047]

[0048] Where: H is the height of the pipe structure (m); h is the freeboard value (m); B1 and B2 are the diameters of the two ends of the variable cross-section immersed tube segment; L1, L2, L3 are the axial lengths of different cross-sections of the variable cross-section immersed tube segment, ∑I W is the sum of the moments of inertia of the ballast water surface of each part of the pipe section around its own axis;

[0049] Form three:

[0050]

[0051] Where: H is the height of the pipe section structure (m); h is the freeboard value (m); B1 and B2 are the diameters of the two ends of the variable cross-section immersed tube segment; L1 and L2 are the axial lengths of different cross-sections of the variable cross-section immersed tube segment, ∑I W is the sum of the moments of inertia of the ballast water surface of each part of the pipe section around its own axis;

[0052] Form 4:

[0053]

[0054] Where: H is the pipe section structure height (m); h is the freeboard value (m); B1 is the diameter of one end of the variable cross-section immersed tube segment; B2 is the vertical height of the other end of the variable cross-section immersed tube segment tilted downward based on the diameter of B1; B3 is the vertical height of the other end of the variable cross-section immersed tube segment tilted upward based on the diameter of B1;

[0055] L1 and L2 are the axial lengths of different sections of the variable-section immersed tube segment, ∑I W It is the sum of the moments of inertia of the ballast water surface in each part of the pipe section around its own axis.

[0056] The present invention has the following beneficial effects:

[0057] The present invention is aimed at the special variable-section immersed tube segment structure, and can standardize the calculation of the fixed inclination height of the variable-section immersed tube tunnel. By determining the fixed inclination height of the segment, the stability of the segment under various working conditions is controlled, and the safety and stability of the variable-section immersed tube segment floating in water are ensured. The present invention solves the problem of the force of the variable-section immersed tube segment during floating and floating, effectively reduces the design difficulty, and reduces the construction control risk. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1It is a structural schematic diagram of a variable cross-section form of a variable cross-section immersed tube segment according to an embodiment of the present invention;

[0059] Figure 2 It is a schematic diagram of the structure of the second variable cross-section type of the variable cross-section immersed tube segment according to an embodiment of the present invention;

[0060] Figure 3 It is a schematic diagram of the third structure of the variable cross-section immersed tube segment of the embodiment of the present invention;

[0061] Figure 4 It is a schematic diagram of the fourth structure of the variable cross-section form of the variable cross-section immersed tube segment in an embodiment of the present invention. DETAILED DESCRIPTION

[0062] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. The exemplary embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0063] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, upper end, lower end, top, bottom...) are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0064] In the present invention, unless otherwise clearly defined and limited, the term "connection" should be understood in a broad sense, for example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0065] In addition, in the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features; in addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0066] The following combination Figures 1 to 4The present invention is further described in detail. Currently, there is no standardized method for calculating the fixed inclination height for a variable cross-section immersed tube tunnel. For a uniform cross-section immersed tube tunnel, the plane position of the gravity center is consistent, while the inconsistent position of the gravity center of the variable cross-section immersed tube section will lead to an eccentric moment causing the tube section to overturn. Therefore, it is very necessary to confirm the fixed inclination height and this eccentric moment and adjust the position of the gravity center.

[0067] Example 1: Please refer to Figures 1 to 4 The present invention provides a technical solution, a method for determining the fixed inclination height of a variable cross-section immersed tube segment, which comprises the following steps:

[0068] Step 1: Establish the plane forms of immersed tube segments with different variable cross-sections; the plane forms of immersed tube segments with different variable cross-sections include equal cross-section-variable cross-section form, equal cross-section-variable cross-section form, and variable cross-section-equal cross-section form;

[0069] Step 2: Calculate the fixed inclination height of the variable cross-section immersed tube segment using a theoretical formula;

[0070] Step 3: The fixed inclination height is divided into two aspects: the floating stage without ballast water and the floating stage with ballast water.

[0071] Specifically, in this embodiment, during the floating stage: there is no ballast water:

[0072] Form 1: The calculation formula for the fixed tilt height in step 2 is:

[0073]

[0074]

[0075] Where: H is the height of the pipe section structure (m); h is the freeboard value (m); B1 and B2 are the diameters of the two ends of the variable cross-section immersed tube segment; L1 and L2 are the axial lengths of different cross-sections of the variable cross-section immersed tube segment; H f is the distance between the buoyancy center and the gravity center of the pipe section (m), H wdl is the fixed inclination height (m), the center of gravity of the pipe section is above the center of buoyancy; under the premise that the inclination of the pipe section is less than 10°, the freeboard height can be calculated by the following formula:

[0076]

[0077] Where: G k is the standard value of the deadweight of the pipe section (kN); G a is the standard value of the weight of the pipe section outfitting and temporary components (kN); H1 is the thickness of the anti-anchor layer adjustment (m); γ w is the water density (kN / m 3 ), S is the projected area of ​​the variable cross-section pipe section;

[0078] Form 2:

[0079]

[0080] Where: H is the height of the pipe section structure (m); h is the freeboard value (m); B1 and B2 are the diameters of the two ends of the variable-section immersed tube segment respectively; L1, L2, and L3 are the axial lengths of different sections of the variable-section immersed tube segment respectively;

[0081] Form three:

[0082]

[0083] Where: H is the height of the pipe section structure (m); h is the freeboard value (m); B1 and B2 are the diameters of the two ends of the variable-section immersed tube segment; L1 and L2 are the axial lengths of different sections of the variable-section immersed tube segment;

[0084] Form 4:

[0085]

[0086] In the formula: H is the structural height of the pipe section (m); h is the freeboard value (m); B1 is the diameter of one end of the variable-section immersed tube segment; B2 is the vertical height of the other end of the variable-section immersed tube segment tilted downward based on the diameter of B1; B3 is the vertical height of the other end of the variable-section immersed tube segment tilted upward based on the diameter of B1; L1 and L2 are the axial lengths of different sections of the variable-section immersed tube segment respectively.

[0087] Specifically, in this embodiment, during the floating stage: there is ballast water:

[0088] Form 1: The calculation formula for the fixed tilt height in step 2 is:

[0089]

[0090] Where: H is the height of the pipe section (m); h is the freeboard value (m); B1 and B2 are the diameters of the two ends of the variable cross-section immersed tube segment; L1 and L2 are the axial lengths of different cross-sections of the variable cross-section immersed tube segment, H f is the distance between the buoyancy center and the gravity center of the pipe section (m), H wdl is the fixed inclination height (m), ∑I W It is the sum of the moments of inertia of the ballast water surface of each part of the pipe section around its own axis. The center of gravity of the pipe section is above the center of buoyancy. The freeboard height can be calculated by the following formula:

[0091]

[0092] Where: G k is the standard value of the deadweight of the pipe section (kN); G ais the standard value of the weight of the pipe section outfitting and temporary components (kN); H1 is the thickness of the anti-anchor layer adjustment (m); γ w is the water density (kN / m 3 ), S is the projected area of ​​the variable cross-section pipe section;

[0093] Form 2:

[0094]

[0095] Where: H is the height of the pipe structure (m); h is the freeboard value (m); B1 and B2 are the diameters of the two ends of the variable cross-section immersed tube segment; L1, L2, L3 are the axial lengths of different cross-sections of the variable cross-section immersed tube segment, ∑I W is the sum of the moments of inertia of the ballast water surface of each part of the pipe section around its own axis;

[0096] Form three:

[0097]

[0098] Where: H is the height of the pipe section structure (m); h is the freeboard value (m); B1 and B2 are the diameters of the two ends of the variable cross-section immersed tube segment; L1 and L2 are the axial lengths of different cross-sections of the variable cross-section immersed tube segment, ∑I W is the sum of the moments of inertia of the ballast water surface of each part of the pipe section around its own axis;

[0099] Form 4:

[0100]

[0101] Where: H is the pipe section structure height (m); h is the freeboard value (m); B1 is the diameter of one end of the variable cross-section immersed tube segment; B2 is the vertical height of the other end of the variable cross-section immersed tube segment tilted downward based on the diameter of B1; B3 is the vertical height of the other end of the variable cross-section immersed tube segment tilted upward based on the diameter of B1; L1 and L2 are the axial lengths of different sections of the variable cross-section immersed tube segment respectively; ∑I W It is the sum of the moments of inertia of the ballast water surface in each part of the pipe section around its own axis.

[0102] Example 2: Please refer to Figures 1 to 3 The present invention provides a technical solution: a method for determining and correcting the weight and buoyancy center position of a variable-section immersed tube, comprising the following steps:

[0103] Step 1: Establish the plane form of immersed tube segments with different variable cross-sections;

[0104] Step 2: Use theoretical formulas to calculate the center of gravity and buoyancy of the variable-section immersed tube segment under different plane forms under the sealing walls on both sides;

[0105] Step 3: Use theoretical formulas to calculate the weight, buoyancy center spacing and unbalanced moment of the variable cross-section immersed tube segment;

[0106] Step 4: Determine the scheme for adjusting the center of gravity position according to the distance between the center of gravity and the center of buoyancy and the structure of the variable-section immersed tube segment, and calculate the load arrangement method required to adjust the center of gravity position when the moment required to adjust the center of gravity and the center of buoyancy position is consistent;

[0107] Reference Figure 1 Specifically, in this embodiment, the positions of the gravity center of different cross-sectional forms in step 2 are:

[0108] Form 1:

[0109] Center of buoyancy calculation formula:

[0110] When the component is axisymmetric

[0111] Center of gravity calculation formula:

[0112] When the component is axisymmetric G =0,

[0113] Where: H is the height of the pipe section structure (m); h is the freeboard value (m); B1 and B2 are the diameters of the two ends of the variable cross-section immersed tube segment respectively; L1 and L2 are the axial lengths of different cross-sections of the variable cross-section immersed tube segment respectively; L3 and L4 are the bottom widths of the two ends of the variable cross-section immersed tube segment respectively; G1 is the weight of the bottom section at one end; G2 is the weight of the hollow equal cross-section; G3 is the weight of the hollow variable cross-section; G4~G5 are the weights of the bottom section at the other end; y G , z G , x G are the horizontal axis, vertical axis and height above the vertical bottom;

[0114] Form 2: Figure 2 As shown,

[0115] Center of buoyancy calculation formula:

[0116] When the component is axisymmetric G =0,

[0117]

[0118] Center of gravity calculation formula:

[0119] When the component is axisymmetric G =0,

[0120]

[0121] Where: H is the height of the pipe structure (m); h is the freeboard value (m); B1 and B2 are the diameters of the two ends of the variable cross-section immersed tube segment respectively; L1, L2, L3 are the axial lengths of different cross-sections of the variable cross-section immersed tube segment respectively; L4 and L5 are the bottom widths of the two ends of the variable cross-section immersed tube segment respectively; G1 is the weight of the bottom section at one end; G2 is the weight of the hollow equal cross-section; G3 is the weight of the hollow variable cross-section; G4 is the weight of the bottom section at the other end; y G , z G , x G are the horizontal axis, vertical axis and height above the vertical bottom;

[0122] Form 3: Figure 3 As shown,

[0123] Center of buoyancy calculation formula:

[0124] When the component is axisymmetric G =0,

[0125]

[0126] Center of gravity calculation formula:

[0127] When the component is axisymmetric G =0,

[0128]

[0129] Where: H is the height of the pipe section structure (m); h is the freeboard value (m); B1 and B2 are the diameters of the two ends of the variable cross-section immersed tube segment respectively; L1 and L2 are the axial lengths of different cross-sections of the variable cross-section immersed tube segment respectively; L3 and L4 are the bottom widths of the two ends of the variable cross-section immersed tube segment respectively; G1~G5 are the weights of the bottom section at one end; G2 is the weight of the hollow equal cross-section; G3 is the weight of the hollow equal cross-section; G4 is the weight of the bottom section at the other end; y G , z G , x G are the horizontal axis, vertical axis and height above the vertical bottom.

[0130] Specifically, in this embodiment, the unbalanced moments of the weight and buoyancy center distances of different cross-sectional forms in step 3 are Δx respectively. G With G 总 ΔxG.

[0131] Specifically, in the present embodiment, the balancing torque required in step 4 is considered to be the case where no additional volume is added to the variable-section immersed tube segment.

[0132] Specifically, in this embodiment, the correction method is to consider the uniform weight increase or pressurization mode of the internal part, and the q distribution under the condition of uniform weight over the entire length on the other side of the buoyancy center is 2G.总 ΔxG / L 2 , L is the total length from the buoyancy center to the other side of the sealing wall, at this time, the position of the gravity and buoyancy center is consistent; the correction method is considered to be F under concentrated load conditions G 总 ΔxG / distance between concentrated load and center of buoyancy.

[0133] Compared with the existing technology, the present invention has the following beneficial effects:

[0134] The present invention is aimed at the special variable-section immersed tube segment structure, and can standardize the calculation of the gravity buoyancy center position and the fixed inclination height of the variable-section immersed tube tunnel. By determining the gravity buoyancy center position and reasonably determining the fixed inclination height of the immersed tube, and by determining the fixed inclination height of the segment, the stability of the segment under various working conditions is controlled, and the safety and stability of the floating transportation of the variable-section immersed tube segment in water are ensured. The present invention solves the problem of the force of the variable-section immersed tube segment during floating and floating transportation, effectively reduces the design difficulty, and reduces the construction control risk.

[0135] The technical solutions provided by the embodiments of the present invention are introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, according to the embodiments of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for determining the fixed inclination height of a variable cross-section immersed tube segment, characterized in that: The following steps are involved: Step 1: Establish the plane forms of immersed tube segments with different variable cross-sections; the plane forms of immersed tube segments with different variable cross-sections include equal cross-section-variable cross-section form, equal cross-section-variable cross-section form, and variable cross-section-equal cross-section form; Step 2: Calculate the fixed inclination height of the variable cross-section immersed tube segment using a theoretical formula; Step 3: The fixed inclination height is divided into two aspects: the floating stage without ballast water and the floating stage with ballast water.

2. The method for determining the fixed inclination height of a variable cross-section immersed tube segment according to claim 1, characterized in that: Floating stage: without ballast water: Form 1: The calculation formula for the fixed tilt height in step 2 is: Where: H is the height of the pipe section structure (m); h is the freeboard value (m); B1 and B2 are the diameters of the two ends of the variable cross-section immersed tube segment; L1 and L2 are the axial lengths of different cross-sections of the variable cross-section immersed tube segment; H f is the distance between the buoyancy center and the gravity center of the pipe section (m), H wdl is the fixed inclination height (m), the center of gravity of the pipe section is above the center of buoyancy; under the premise that the inclination of the pipe section is less than 10°, the freeboard height can be calculated by the following formula: Where: G k is the standard value of the deadweight of the pipe section (kN); G a is the standard value of the weight of the pipe section outfitting and temporary components (kN); H1 is the thickness of the anti-anchor layer adjustment (m); γ w is the water density (kN / m 3 ), S is the projected area of ​​the variable cross-section pipe section; Form 2: Where: H is the height of the pipe section structure (m); h is the freeboard value (m); B1 and B2 are the diameters of the two ends of the variable-section immersed tube segment respectively; L1, L2, and L3 are the axial lengths of different sections of the variable-section immersed tube segment respectively; Form three: Where: H is the height of the pipe section structure (m); h is the freeboard value (m); B1 and B2 are the diameters of the two ends of the variable-section immersed tube segment; L1 and L2 are the axial lengths of different sections of the variable-section immersed tube segment; Form 4: In the formula: H is the structural height of the pipe section (m); h is the freeboard value (m); B1 is the diameter of one end of the variable-section immersed tube segment; B2 is the vertical height of the other end of the variable-section immersed tube segment tilted downward based on the diameter of B1; B3 is the vertical height of the other end of the variable-section immersed tube segment tilted upward based on the diameter of B1; L1 and L2 are the axial lengths of different sections of the variable-section immersed tube segment respectively.

3. The method for determining the fixed inclination height of a variable cross-section immersed tube segment according to claim 1, characterized in that: Floating stage: with ballast water: Form 1: The calculation formula for the fixed tilt height in step 2 is: Where: H is the height of the pipe section structure (m); h is the freeboard value (m); B1 and B2 are the diameters of the two ends of the variable cross-section immersed tube segment; L1 and L2 are the axial lengths of different cross-sections of the variable cross-section immersed tube segment, H f is the distance between the buoyancy center and the gravity center of the pipe section (m), H wdl is the fixed inclination height (m), ∑I W It is the sum of the moments of inertia of the ballast water surface of each part of the pipe section around its own axis. The center of gravity of the pipe section is above the center of buoyancy. The freeboard height can be calculated by the following formula: Where: G k is the standard value of the deadweight of the pipe section (kN); G a is the standard value of the weight of the pipe section outfitting and temporary components (kN); H1 is the thickness of the anti-anchor layer adjustment (m); γ w is the water density (kN / m 3 ), S is the projected area of ​​the variable cross-section pipe section; Form 2: In: H is the height of the pipe section structure (m); h is the freeboard value (m); B1 and B2 are the diameters of the two ends of the variable cross-section immersed tube segment; L1, L2, L3 are the axial lengths of different cross-sections of the variable cross-section immersed tube segment; ∑I W is the sum of the moments of inertia of the ballast water surface of each part of the pipe section around its own axis; Form three: Where: H is the height of the pipe section structure (m); h is the freeboard value (m); B1 and B2 are the diameters of the two ends of the variable cross-section immersed tube segment; L1 and L2 are the axial lengths of different cross-sections of the variable cross-section immersed tube segment, ∑I W is the sum of the moments of inertia of the ballast water surface of each part of the pipe section around its own axis; Form 4: Where: H is the height of the pipe section structure (m); h is the freeboard value (m); B1 is the diameter of one end of the variable cross-section immersed tube segment; B2 is the vertical height of the other end of the variable cross-section immersed tube segment tilted downward based on the diameter of B1; B3 is the vertical height of the other end of the variable cross-section immersed tube segment tilted upward based on the diameter of B1; L1 and L2 are the axial lengths of different sections of the variable cross-section immersed tube segment, respectively, ∑I W It is the sum of the moments of inertia of the ballast water surface in each part of the pipe section around its own axis.

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