Segmented rigidity collaborative design method for underwater floating tunnel

Abstract

The invention discloses a sectional rigidity collaborative design method for an underwater floating tunnel, and relates to the technical field of civil engineering. According to the method disclosed by the invention, the technical blank of the structural rigidity design of the underwater floating tunnel is filled, the development of the underwater floating tunnel is promoted, the design method with higher controllability and universality is provided, the joint rigidity design is a brand new design concept, and the joint rigidity design is a novel design concept. The problem of unmanned research and unmanned design of a suspended tunnel joint structure at the present stage is solved, an innovative segmentation method is adopted in the anchor cable rigidity design method, the coupling effect among multiple pipe joints is decoupled, a good effect is achieved after design, and the construction efficiency is improved. Compared with an existing pre-tightening force optimization design, a displacement curve which is better in structural response and relaxation is generated; moreover, the method can also be used for cable adjustment of a cable-stayed bridge, a segmentation method is also adopted, and finally, the vertical rigidity of each stay cable is designed according to the stress and displacement requirements of each segment, so that the total rigidity is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of civil engineering, and in particular to a segmented stiffness collaborative design method for an underwater suspended tunnel. Background Art

[0002] Submerged Floating Tunnel (SFT), as a spanning structure with a high possibility of implementation and a continuous research interest from the 20th century to the 21st century, is the most competitive in deep and large straits, complex seabed geological conditions, and complex navigation conditions. For structures with the same spanning capacity, such as underwater immersed tube tunnels, it has the advantages of strong confidentiality, high stability, and stable force, but it is more dependent on hydrogeological conditions. Deep straits or too bumpy geological conditions will greatly affect its construction difficulty. For water-crossing bridges, it has the advantages of mature construction technology, safe driving, and high ornamental value, but it is highly sensitive to the use environment. In an operating environment with high waves, complex navigation requirements, and high wind loads, it will have a greater impact on the safety of the structure.

[0003] After the concept of underwater floating tunnels was proposed, some idealized designs, external load type exploration, pipe cross-section forms and wave and current loads, as well as various detailed structure studies gradually emerged. After years of exploration, the research on external structures has become more complete, and scholars have gradually shifted their research direction from external to internal, from research to design. They have studied the stress characteristics of the inner wall of underwater floating tunnels, the dynamic response of tunnel structures under safety accidents, the design of underwater breakwaters for underwater floating tunnels, the working state of the joint structure of the floating tunnel, the seismic performance of underwater floating tunnels including some joint mechanical characteristics, and the influence of changes in joint structure stiffness on the dynamic response of the tunnel pipe under wave action.

[0004] It can be seen from the existing research results that the pipe body stiffness, joint stiffness and anchor cable stiffness of the underwater floating tunnel have a great influence on its dynamic response and traffic safety and comfort. Studies have shown that under the appropriate anchor cable pre-tension configuration conditions (i.e., different anchor cable initial stiffness configuration conditions), uniform internal force can be generated to achieve full utilization of materials and obtain a more gentle structural displacement curve. Under the appropriate joint stiffness, higher comfort and higher economy will be produced.

[0005] Therefore, a reasonable design method for the pipe body stiffness, anchor cable stiffness and joint stiffness is the key to the safety and comfort of underwater floating tunnels. However, there is no research on the joint structure stiffness configuration, anchor cable stiffness configuration, and pipe body stiffness configuration.

[0006] Therefore, a new solution to the above problems needs to be proposed. Summary of the invention

[0007] The purpose of the present invention is to provide a segmented stiffness collaborative design method for an underwater suspended tunnel, which can design the stiffness of the pipe body, anchor cable and joint that meet the driving requirements, and is a direct design method to solve the technical problems raised in the background technology.

[0008] To achieve the above object, the present invention provides the following technical solution: a segmented stiffness collaborative design method for an underwater suspended tunnel, comprising at least the following steps:

[0009] S1: Based on the topographic data of the underwater floating tunnel site, the anchor cable layout position and layout spacing are preliminarily determined;

[0010] S2: According to the design requirements for underwater floating tunnel passage, the clearance of pipe section is formulated, and various standards under passage requirements are determined, such as the maximum vertical and horizontal displacement of pipe section, the maximum horizontal and vertical deformation of joint, the maximum rotation angle of joint, etc.;

[0011] S3: Based on the formula of the maximum deflection of a single pipe segment and the deflection of the beam body, the minimum bending stiffness of the pipe body or the minimum elastic modulus under a constant moment of inertia is obtained. The tunnel pipe segment is segmented, and two groups of anchor cables are disconnected in the middle or one group of anchor cables is divided into two groups of anchor cables with half the area. It is assumed that the pipe segments other than the revetment segment are not affected by the adjacent pipe segments and can form a force balance with the connected anchor cables.

[0012] S4: From the pipe sections and loads obtained from the S3 segmentation, it can be seen that the load on a single pipe section is f i (x) Under force equilibrium, calculate the load on the anchor cable and the stiffness of the anchor cable;

[0013] S5: According to the design traffic requirements, the maximum deflection of the pipe segment and the maximum deformation of the whole span are known. The beam deflection curve under uniform load is the quadratic parabola as a reference. A quadratic parabola is taken as the full span deformation control curve. The quadratic parabola is opened downward. The two ends of the underwater suspension tunnel are taken as the two ends of the curve, with coordinates (0, 0) and (L, 0). The vertex is the midpoint of the tunnel, with coordinates (L / 2, Δ max );

[0014] S6: The displacement of the anchor cable is obtained by subtracting the deflection of the single tube segment from the displacement design of each anchor cable position point, and then the vertical total stiffness of the anchor cable is obtained through the stiffness formula (K=F / Δ), and the cross-sectional area of ​​the anchor cable at each position under the fixed material is calculated through the formula to complete the anchor cable stiffness design;

[0015] S7: After the anchor cable stiffness design is completed, the bending moment at the end of the pipe segment under load can be obtained based on the simplified model of the single pipe segment and the basic formula of the displacement method. Combined with the maximum rotation angle of the joint obtained in S2, the rotation angle limit of the pipe end is obtained, and the bending stiffness of the joint (KJ =M / θ);

[0016] S8: Calculation of joint axial stiffness. The main component of the joint axial stiffness is the GINA waterstop, and the stiffness of the waterstop is determined by the water pressure used in the underwater floating tunnel;

[0017] S9: The shear stiffness calculation of the joint structure is the ratio of the total force on the single pipe section to the shear displacement limit of the joint structure;

[0018] S10: Using the anchor cable as the medium, the torque of the joint caused by horizontal displacement is calculated from the relationship between the force and displacement at the joint position, and the torsional stiffness of the joint structure is calculated based on the maximum torsional deformation limit of the joint.

[0019] Furthermore, the formula for the maximum deflection of a single pipe segment and the deflection of the beam in S3 is as follows:

[0020] δ tube =5ql 4 / 384EI V (1)

[0021] Where: tube represents the deflection of the tube under uniform load q; l represents the length of the tube; E represents the elastic modulus of the tube; I v Represents the vertical moment of inertia of the tube.

[0022] Furthermore, the load on the anchor cable and the anchor cable stiffness are calculated in S4 as shown in the following formula 2 and formula 3:

[0023]

[0024] K c,i =f i (p) / Δ i =f i (p) / (g i (x)-δ tube )(3)

[0025] Where: f i,side (x) represents the total vertical load distributed to the anchor cable group i of the side span after the tunnel segmentation; f i,mid (x) represents the total vertical load distributed to the anchor cable group i in the middle span after the tunnel is segmented; C side represents the correction parameter of the total vertical load distributed to the anchor cable i of the side span; s represents the length of the tunnel segment; p(x) represents the load function of the tunnel, which is equivalent to q when the load is uniformly distributed; x represents the horizontal coordinate, with one end of the tunnel as the starting point and the other end as the end point; f i (p) represents the total vertical load on anchor cable group i under load function p; Δ iIt represents the maximum deflection of a single pipe segment that meets the design deformation function g(x) under the load function p.

[0026] Furthermore, the formula for calculating the cross-sectional area of ​​the anchor cable at each position under the fixed material is as follows:

[0027] k c,i =E c A c ={K c,i l c / 2sin 2 α,K c,i l c / 2cos 2 α} Max (4)

[0028] Where: k c,i represents the tensile stiffness of a single anchor in anchor group i; E c represents the elastic modulus of the anchor cable; A c represents the cross-sectional area of ​​the anchor cable; l c represents the length of the anchor cable; α represents the inclination angle of the anchor cable.

[0029] Furthermore, the algorithm adopted by S7 refers to the following formulas 5 to 7:

[0030] θ H,V =q H,V l 3 / 12(2+K JH,JV l / EI H,V )EI H,V (5)

[0031]

[0032] Where: θ H,V Represents the horizontal or vertical load q in the pipe segment H,V Below, the deformation at the joint position; K JH,JV Represents the horizontal or vertical stiffness of the joint; EI H,V Represents the horizontal or vertical bending stiffness of the pipe segment; θ Max Represents the maximum rotation angle limit of the pipe end; θ Cable,1 The rotation deformation of the side span caused by the deformation of the anchor cable is equal to Δ H1,V1 .

[0033] Furthermore, the axial stiffness of the joint in S8 is calculated as follows:

[0034] K u =2πR GINA k u (8)

[0035] Where: K u Represents the axial stiffness of the joint; R GINA Represents the radius of the GINA waterstop; k u Represents the axial stiffness of GINA waterstop per unit length.

[0036] Furthermore, the shear stiffness of the joint structure in S9 is calculated as follows:

[0037] K q =ql / Δ q,design (9)

[0038] Where: K q Represents the tangential stiffness of the joint; Δ q,design Represents the maximum tangential deformation limit of the joint.

[0039] Furthermore, the torque of the joint caused by the horizontal displacement is calculated in S10 as follows:

[0040] F θ =K J,Shear r(tanαsinβ-cosβ)Δ h,Design (10)

[0041] Among them: F θ Represents the torque generated when the joint is displaced horizontally; K J,Shear represents the joint shear stiffness; r represents the joint radius; α represents the anchor cable installation angle; β represents the anchor cable inclination angle; Δ h,Design Represents the maximum horizontal displacement limit of the joint.

[0042] Furthermore, the process of obtaining the torsional stiffness of the joint structure in S10 is as follows:

[0043] K θ =K J,Shear r(tanαsinβ-cosβ)Δ h,Design / Δ θ,Design (11)

[0044] Where: K θ Represents the torsional stiffness of the joint; Δ θ,Design Represents the maximum torsion limit of the joint.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] 1. The method disclosed in the present invention fills the technical gap in the structural stiffness design of underwater floating tunnels, promotes the development of underwater floating tunnels, and provides a more controllable and universal design method.

[0047] 2. The joint stiffness design in the present invention is a brand-new design concept, which solves the problem that no one is currently researching and designing the joint structure of suspended tunnels.

[0048] 3. The anchor cable stiffness design method of the present invention adopts an innovative segmentation method to decouple the coupling effect between multiple tube segments, and achieves a better effect after design, producing a better structural response and a more relaxed displacement curve compared to the existing preload optimization design;

[0049] In addition, this method can also be used for cable adjustment of cable-stayed bridges. The same segmented method is used. Finally, the vertical stiffness of each cable is designed according to the force and displacement requirements of each segment to obtain the total stiffness.

[0050] 4. The pipe body stiffness design method of the present invention provides assistance and suggestions on stiffness performance for pipe body material selection and reinforcement design. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0052] Figure 1 It is the technical roadmap of the present invention;

[0053] Figure 2 This is a diagram illustrating the segmentation method used in the present invention;

[0054] Figure 3 The difference diagram of displacement and moment response when using the design method of the present invention and the existing method under static load;

[0055] Figure 4 The difference diagram of displacement and moment response when using the design method of the present invention and the existing method under dynamic load;

[0056] Figure 5 This is a preliminary design drawing for the application of the present invention to a certain strait;

[0057] Figure 6 The wave force borne by an underwater floating tunnel in a strait using the design method of the invention;

[0058] Figure 7 The anchor cable stiffness designed for a strait based on static and dynamic loads after using the design method of the invention;

[0059] Figure 8The displacement and bending moment response diagram of an underwater floating tunnel of a strait using the design method of the invention under static load;

[0060] Fig. 9 The displacement response diagram of an underwater floating tunnel of a strait using the design method of the invention under dynamic load;

[0061] Fig.10 The present invention is used for a strait and the bending moment response diagram of an underwater suspended tunnel under dynamic load after the design method of the invention is applied. DETAILED DESCRIPTION

[0062] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0063] Embodiment 1:

[0064] This embodiment discloses a segmented stiffness collaborative design method for an underwater floating tunnel. Of course, it should be noted that it can be divided into a segmented simplification method of the model and a detailed stiffness design method for the pipe body, anchor cable, and joint.

[0065] See also Figure 1 , a segmented stiffness collaborative design method for an underwater suspended tunnel, comprising at least the following steps:

[0066] S1: Based on the topographic data of the underwater floating tunnel site, the anchor cable layout position and layout spacing are preliminarily determined;

[0067] S2: According to the design requirements for underwater floating tunnel passage, the clearance of pipe section is formulated, and various standards under passage requirements are determined, such as the maximum vertical and horizontal displacement of pipe section, the maximum horizontal and vertical deformation of joint, the maximum rotation angle of joint, etc.;

[0068] S3: Based on the formula of the maximum deflection of a single pipe segment and the deflection of the beam body, the minimum bending stiffness of the pipe body or the minimum elastic modulus under a constant moment of inertia is obtained. The tunnel pipe segment is segmented, and two groups of anchor cables are disconnected in the middle or one group of anchor cables is divided into two groups of anchor cables with half the area. It is assumed that the pipe segments other than the revetment segment are not affected by the adjacent pipe segments and can form a force balance with the connected anchor cables.

[0069] The formula for the maximum deflection of a single pipe segment and the deflection of the beam body can be found in the following formula 1:

[0070] δ tube =5ql 4 / 384EI V (1)

[0071] Where: tuberepresents the deflection of the tube under uniform load q; l represents the length of the tube; E represents the elastic modulus of the tube; I v Represents the vertical moment of inertia of the tube.

[0072] S4: From the pipe sections and loads obtained from the S3 segmentation, it can be seen that the load on a single pipe section is f i (x) Calculate the load and stiffness of the anchor cable under force equilibrium. Please refer to Figure 2 ;

[0073] The load on the anchor cable and the anchor cable stiffness are calculated as shown in Equation 2 and Equation 3:

[0074]

[0075] K c,i =f i (p) / Δ i =f i (p) / (g i (x)-δ tube )(3)

[0076] Where: f i,side (x) represents the total vertical load distributed to the anchor cable group i of the side span after the tunnel segmentation; f i,mid (x) represents the total vertical load distributed to the anchor cable group i in the middle span after the tunnel is segmented; C side represents the correction parameter of the total vertical load distributed to the anchor cable i of the side span; s represents the length of the tunnel segment; p(x) represents the load function of the tunnel, which is equivalent to q when the load is uniformly distributed; x represents the horizontal coordinate, with one end of the tunnel as the starting point and the other end as the end point; f i (p) represents the total vertical load on anchor cable group i under load function p; Δ i It represents the maximum deflection of a single pipe segment that meets the design deformation function g(x) under the load function p.

[0077] S5: According to the design traffic requirements, the maximum deflection of the pipe segment and the maximum deformation of the whole span are known. The beam deflection curve under uniform load is the quadratic parabola as a reference. A quadratic parabola is taken as the full span deformation control curve. The quadratic parabola is opened downward. The two ends of the underwater suspension tunnel are taken as the two ends of the curve, with coordinates (0, 0) and (L, 0). The vertex is the midpoint of the tunnel, with coordinates (L / 2, Δ max );

[0078] S6: The displacement of the anchor cable is obtained by subtracting the deflection of the single tube segment from the displacement design of each anchor cable position point, and then the vertical total stiffness of the anchor cable is obtained through the stiffness formula (K=F / Δ), and the cross-sectional area of ​​the anchor cable at each position under the fixed material is calculated through the formula to complete the anchor cable stiffness design;

[0079] The formula for calculating the cross-sectional area of ​​the anchor cable at each position under the fixed material is as follows:

[0080] k c,i =E c A c ={K c,i l c / 2sin 2 α,K c,i l c / 2cos 2 α} Max (4)

[0081] Where: k c,i represents the tensile stiffness of a single anchor in anchor group i; E c represents the elastic modulus of the anchor cable; A c represents the cross-sectional area of ​​the anchor cable; l c represents the length of the anchor cable; α represents the inclination angle of the anchor cable.

[0082] S7: After the anchor cable stiffness design is completed, the bending moment at the end of the pipe segment under load can be obtained based on the simplified model of the single pipe segment and the basic formula of the displacement method. Combined with the maximum rotation angle of the joint obtained in S2, the rotation angle limit of the pipe end is obtained, and the bending stiffness of the joint (K J =M / θ);

[0083] The algorithm used is shown in the following formula 5-7:

[0084] θ H,V =q H,V l 3 / 12(2+K JH,JV l / EI H,V )EI H,V (5)

[0085]

[0086] Where: θ H,V Represents the horizontal or vertical load q in the pipe segment H,V Below, the deformation at the joint position; K JH,JV Represents the horizontal or vertical stiffness of the joint; EI H,V Represents the horizontal or vertical bending stiffness of the pipe segment; θ Max Represents the maximum rotation angle limit of the pipe end; θ Cable,1 The rotation deformation of the side span caused by the deformation of the anchor cable is equal to Δ H1,V1 .

[0087] S8: Calculation of joint axial stiffness. The main component of joint axial stiffness is GINA waterstop, and the stiffness of waterstop is determined by the water pressure used in the underwater floating tunnel.

[0088] The axial stiffness of the joint is calculated as follows:

[0089] K u =2πR GINA k u (8)

[0090] Where: K u Represents the axial stiffness of the joint; R GINA Represents the radius of the GINA waterstop; k u Represents the axial stiffness of GINA waterstop per unit length.

[0091] S9: The shear stiffness calculation of the joint structure is the ratio of the total force on the single pipe section to the shear displacement limit of the joint structure;

[0092] The shear stiffness of the joint structure is calculated as follows:

[0093] K q =ql / Δ q,design (9)

[0094] Where: K q Represents the tangential stiffness of the joint; Δ q,design Represents the maximum tangential deformation limit of the joint.

[0095] S10: Using the anchor cable as the medium, the torque of the joint caused by horizontal displacement is calculated from the relationship between the force and displacement at the joint position, and the torsional stiffness of the joint structure is calculated based on the maximum torsional deformation limit of the joint.

[0096] The torque of the joint caused by horizontal displacement is calculated as follows:

[0097] F θ =K J,Shear r(tanαsinβ-cosβ)Δ h,Design (10)

[0098] Among them: F θ Represents the torque generated when the joint is displaced horizontally; K J,Shear represents the joint shear stiffness; r represents the joint radius; α represents the anchor cable installation angle; β represents the anchor cable inclination angle; Δ h,Design Represents the maximum horizontal displacement limit of the joint.

[0099] The process of obtaining the torsional stiffness of the joint structure is as follows:

[0100] K θ =K J,Shear r(tanαsinβ-cosβ)Δ h,Design / Δ θ,Design (11)

[0101] Where: K θ Represents the torsional stiffness of the joint; Δ θ,Design Represents the maximum torsion limit of the joint.

[0102] Embodiment 2:

[0103] In this embodiment, the anchor cable design method in the method is used as the main variable. In order to reduce the influence of other variables on the embodiment, the design method of the pipe body and the joint is not used temporarily. Under static and dynamic loads, the displacement and bending moment response of the underwater floating tunnel are studied, proving that the method of the present invention has good controllability and universality. The details are as follows:

[0104] The total length of the suspended tunnel in this embodiment is 1000m, the length of a single pipe section is 100m, the pipe body is made of high-strength waterproof concrete, the tunnel cross-section is annular, the inner diameter is 6.5m, the outer diameter is 7.5m, the material density is 3066kg / m3 determined by the buoyancy weight ratio of 1.3, and the Young's modulus and Poisson's ratio of the pipe wall material are determined to be 34.5GPa and 0.2 respectively; the anchor cable of the suspended tunnel is hinged with the anchor under the seabed, and the installation angle and inclination angle are both 60°; the anchor cable is a high-strength steel rope with a length of 180m and a diameter of 0.347m, and its material density, Young's modulus and Poisson's ratio are 8000kg / m3, 195GPa, and 0.3 respectively. The anchor cables are evenly distributed along the axial direction of the tunnel, with a total of 9 groups at intervals of 100m. In the design environment, the suspended tunnel is subjected to periodic wave loads, with a wave height of 7m and a period of 12.69s. The wave force is calculated by potential flow theory.

[0105] The static and dynamic response analysis of the suspended tunnel structure whether to install the structure of the invention comprises the following steps:

[0106] Step 1: Select 10 tunnel pipe segments with a length of 100m. The material density, Young's modulus and Poisson's ratio are 3066kg / m3, 34.5GPa and 0.2 respectively. The pipe segments are connected by joints with the same stiffness as the pipe body. Both ends of the tunnel are hinged to the ground and torsion is constrained.

[0107] Step 2: Select anchor cables with a length of 180m and a diameter of 0.347m, with material density, Young's modulus, and Poisson's ratio of 8000kg / m3, 195GPa, and 0.3 respectively. The anchor cables are evenly distributed along the tunnel axis, with an interval of 100m, for a total of 9 groups. The upper end of each group of anchor cables is set to be connected to the left and right ends of the installation position on the outer surface of the tunnel segment with MPC beam constraints, and the lower end of the anchor cable is hinged to the ground.

[0108] Step 3: Adjust the preload value of the anchor cables at each location by using the anchor cable preload adjustment method to obtain the best displacement and bending moment response results;

[0109] Step 4: Repeat steps 1, 2 and 3, but in step 3, use the segmented design method of the present invention to directly determine the required vertical stiffness at each anchor position, thereby obtaining the diameter of each anchor.

[0110] Step 5: Apply static loads (self-weight and buoyancy) and dynamic loads (static load plus wave force) to the two models respectively, and compare the dynamic response results of the suspended tunnel structure with and without the structure of the invention.

[0111] like Figure 3 As shown in the figure, the structural dynamic response of the suspended tunnel under static load is compared before and after the design method of the invention is used. It can be seen that the suspended tunnel structure using the invention has a greater positive impact on the vertical displacement and vertical bending moment response. Under the same conditions, the displacement is smaller and the bending moment is more uniform.

[0112] like Figure 4 As shown in FIG. 1 , the structural displacement response comparison of the suspended tunnel before and after the design method of the invention is used under periodic wave load. It can be seen that under the action of periodic wave load, the displacement of the suspended tunnel structure equipped with the invention is smaller, and the displacement curve is more gentle.

[0113] Embodiment three:

[0114] In this example, the actual terrain of a planned project in a certain area of ​​the Mediterranean is used as an application scenario, the design method is applied in detail, and finally compared with multiple constraints, proving that the method of the present invention has good controllability and universality. The details are as follows:

[0115] First, the anchor cable layout and pipe segment submergence depth of the structure are preset through the topographic map, such as Figure 5 , where l C1 is the vertical height of the middle span anchor cable (the length of the middle span anchor cable is l 1 =235m); l C0 is the vertical height of the side span anchor cable (the length of the middle span anchor cable is l 0 =142m); S 1 is the length of the mid-span pipe segment (S 1 =100m); S 0 is the length of the side span pipe segment (S 0 =150m). According to existing research, the submerged depth can be 40m, the buoyancy-to-weight ratio can be 1.3, and the total length of the structure can be 2900m. The specific parameters are shown in Table 1.

[0116] Table 1

[0117]

[0118] The maximum wave height in this area is about 3m, and the period is 12.69s. Therefore, the wave load, gravity and buoyancy under this sea condition are used as the research load, and the wave force on the structure is calculated by the potential flow theory method (such as Figure 6 ), since the horizontal and vertical wave forces acting on the structure are similar in magnitude, and there is also residual buoyancy in the vertical direction (one order of magnitude larger than the two), the horizontal displacement requirements can be met by limiting the deformation of the pipe segments in the vertical direction as the main design criterion.

[0119] Assuming that the traffic requirement of the tunnel is a speed of 200 km / H, according to the current design standards, the standards for ensuring safe driving are shown in Table 3. According to the restrictions on the deformation of the pipe body, the required vertical stiffness of each anchor cable supplement point is determined, such as Figure 7 , and thus determine the required cross-sectional area of ​​the anchor cable according to the length and angle of each anchor cable. The shear, axial, torsional stiffness of the joint and the bending stiffness determined by the internal force optimization method in this paper are shown in Table 2.

[0120] Table 2

[0121]

[0122] like Figure 8 , Fig. 9 , Fig.10 As shown in Table 3, under static and cyclic loads, the displacement and moment responses of the structure are in line with expectations and meet the use requirements.

[0123] Table 3

[0124]

[0125] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A segmented stiffness collaborative design method for an underwater suspended tunnel, characterized in that: At least the following steps are included: S1: Based on the topographic data of the underwater floating tunnel site, the anchor cable layout position and layout spacing are preliminarily determined; S2: According to the design requirements for underwater floating tunnel passage, the clearance of pipe section is formulated, and various standards under passage requirements are determined, such as the maximum vertical and horizontal displacement of pipe section, the maximum horizontal and vertical deformation of joint, the maximum rotation angle of joint, etc.; S3: Based on the formula of the maximum deflection of a single pipe segment and the deflection of the beam body, the minimum bending stiffness of the pipe body or the minimum elastic modulus under a constant moment of inertia is obtained. The tunnel pipe segment is segmented, and two groups of anchor cables are disconnected in the middle or one group of anchor cables is divided into two groups of anchor cables with half the area. It is assumed that the pipe segments other than the revetment segment are not affected by the adjacent pipe segments and can form a force balance with the connected anchor cables. S4: From the pipe sections and loads obtained from the S3 segmentation, it can be seen that the load on a single pipe section is f i (x) Under force equilibrium, calculate the load on the anchor cable and the stiffness of the anchor cable; S5: According to the design traffic requirements, the maximum deflection of the pipe segment and the maximum deformation of the whole span are known. The beam deflection curve under uniform load is the quadratic parabola as a reference. A quadratic parabola is taken as the full span deformation control curve. The quadratic parabola is opened downward. The two ends of the underwater suspension tunnel are taken as the two ends of the curve, with coordinates (0, 0) and (L, 0). The vertex is the midpoint of the tunnel, with coordinates (L / 2, Δ max ); S6: The displacement of the anchor cable is obtained by subtracting the deflection of the single tube segment from the displacement design of each anchor cable position point, and then the vertical total stiffness of the anchor cable is obtained through the stiffness formula (K=F / Δ), and the cross-sectional area of ​​the anchor cable at each position under the fixed material is calculated through the formula to complete the anchor cable stiffness design; S7: After the anchor cable stiffness design is completed, the bending moment at the end of the pipe segment under load can be obtained based on the simplified model of the single pipe segment and the basic formula of the displacement method. Combined with the maximum rotation angle of the joint obtained in S2, the rotation angle limit of the pipe end is obtained, and the bending stiffness of the joint (K J =M / θ); S8: Calculation of joint axial stiffness. The main component of the joint axial stiffness is the GINA waterstop, and the stiffness of the waterstop is determined by the water pressure used in the underwater floating tunnel; S9: The shear stiffness calculation of the joint structure is the ratio of the total force on the single pipe section to the shear displacement limit of the joint structure; S10: Using the anchor cable as the medium, the torque of the joint caused by horizontal displacement is calculated from the relationship between the force and displacement at the joint position, and the torsional stiffness of the joint structure is calculated based on the maximum torsional deformation limit of the joint.

2. The segmented stiffness collaborative design method for an underwater floating tunnel according to claim 1, characterized in that: The formula for the maximum deflection of a single pipe segment and the deflection of the beam in S3 is as follows: δ tube =5ql 4 / 384EI V (1) Where: tube represents the deflection of the tube under uniform load q; l represents the length of the tube; E represents the elastic modulus of the tube; I v Represents the vertical moment of inertia of the tube.

3. The segmented stiffness collaborative design method for an underwater floating tunnel according to claim 2 is characterized in that: The load on the anchor cable and the anchor cable stiffness calculated in S4 are shown in the following equations 2 and 3: K c,i (f i (p) / Δ i (f i (p) / (g i (x)-δ tube )(3) Where: f i,side (x) represents the total vertical load distributed to the anchor cable group i of the side span after the tunnel segmentation; f i,mid (x) represents the total vertical load distributed to the anchor cable group i in the middle span after the tunnel is segmented; C side represents the correction parameter of the total vertical load distributed to the anchor cable i of the side span; s represents the length of the tunnel segment; p(x) represents the load function of the tunnel, which is equivalent to q when the load is uniformly distributed; x represents the horizontal coordinate, with one end of the tunnel as the starting point and the other end as the end point; f i (p) represents the total vertical load on anchor cable group i under load function p; Δ i It represents the maximum deflection of a single pipe segment that meets the design deformation function g(x) under the load function p.

4. The segmented stiffness collaborative design method for an underwater floating tunnel according to claim 3 is characterized by: The formula for calculating the cross-sectional area of ​​the anchor cable at each position under the fixed material is as follows: k c,i =E c A c ={K c,i l c / 2sin 2 a,K c,i l c / 2cos 2 a} Max (4) Where: k c,i represents the tensile stiffness of a single anchor in anchor group i; E c represents the elastic modulus of the anchor cable; A c represents the cross-sectional area of ​​the anchor cable; l c represents the length of the anchor cable; α represents the inclination angle of the anchor cable.

5. A segmented stiffness collaborative design method for an underwater floating tunnel according to claim 4, characterized in that: The algorithm adopted by S7 is shown in the following formula 5-7: θ H,V =q H,V l 3 / 12(2+K JH,JV l / NO H,V )NO H,V (5) Where: θ H,V Represents the horizontal or vertical load q in the pipe segment H,V Below, the deformation at the joint position; K JH,JV Represents the horizontal or vertical stiffness of the joint; EI H,V Represents the horizontal or vertical bending stiffness of the pipe segment; θ Max Represents the maximum rotation angle limit of the pipe end; θ Cable,1 The rotation deformation of the side span caused by the deformation of the anchor cable is equal to Δ H1,V1 .

6. The segmented stiffness collaborative design method for an underwater floating tunnel according to claim 5, characterized in that: The axial stiffness of the joint in S8 is calculated as follows: K u =2πR GINA k u (8) Where: K u Represents the axial stiffness of the joint; R GINA Represents the radius of the GINA waterstop; k u Represents the axial stiffness of GINA waterstop per unit length.

7. The segmented stiffness collaborative design method for an underwater floating tunnel according to claim 6 is characterized in that: The shear stiffness of the joint structure in S9 is calculated as follows: K q =ql / Δ q,design (9) Where: K q Represents the tangential stiffness of the joint; Δ q,design Represents the maximum tangential deformation limit of the joint.

8. The segmented stiffness collaborative design method for an underwater floating tunnel according to claim 7, characterized in that: The torque caused by the horizontal displacement of the joint calculated in S10 is as follows: F θ =K J,Shear r(tanαsinβ-cosβ)Δ h,Design (10) Among them: F θ Represents the torque generated when the joint is displaced horizontally; K J,Shear represents the joint shear stiffness; r represents the joint radius; α represents the anchor cable installation angle; β represents the anchor cable inclination angle; Δ h,Design Represents the maximum horizontal displacement limit of the joint.

9. The segmented stiffness collaborative design method for an underwater floating tunnel according to claim 8, characterized in that: The process of obtaining the torsional stiffness of the joint structure in S10 is as follows: K θ =K J,Shear r(tanαsinβ-cosβ)Δ h,Design / D θ,Design (11) Where: K θ Represents the torsional stiffness of the joint; Δ θ,Design Represents the maximum torsion limit of the joint.

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