A method for evaluating the waterproof capability of shield tunnel segment joint sealing pads and its application

Abstract

The invention relates to a shield tunnel sealing pad, and discloses a method for evaluating the waterproof capability of a shield tunnel segment joint sealing pad and its application, comprising: establishing a segment joint sealing pad waterproof structure simulation model; using the VDLOAD subroutine in ABAQUS finite element software to perform numerical simulation, determining the leakage failure water pressure of the sealing pad-sealing pad contact interface and the sealing pad-concrete groove contact interface, and taking the smaller value of the two as the waterproof capability P of the sealing pad waterproof structure. Wlim . In addition, the present invention also proposes a waterproof capacity prediction model to predict the waterproof capacity of the gasket in the actual project. The present invention innovatively uses the VDLOAD subroutine to simulate the progressive application of the water pressure of the gasket leakage, which has the advantages of being consistent with the actual gasket opening leakage situation, easy convergence, convenient and fast modeling, and applicable to various cross-sections. It takes into account the leakage between the gasket and the groove, greatly shortens the calculation time, improves the calculation efficiency, and the simulation results are more accurate.

Description

Technical Field

[0001] The invention relates to a rubber sealing pad for a shield tunnel, and in particular to a method for evaluating the waterproof capability of a sealing pad for a segment joint of a shield tunnel and an application thereof. Background Art

[0002] Due to its unique prefabricated structure, shield tunnels have a lot of joint structures (leakage channels): longitudinal joints (gaps between segments) and annular joints (gaps between lining rings). This requires that the waterproofing ability of the joints be effectively guaranteed. The main waterproofing structure at the joints of shield tunnels is an elastic rubber gasket. Groundwater usually leaks gradually from the outside of the gasket to the inside, and a large contact stress is generated through the extrusion between the gasket-gasket and the gasket-concrete groove to resist the intrusion of external water pressure. The waterproofing ability of the gasket can generally be measured by indoor waterproofing tests, but this will take a lot of time and money, and often there will be large test errors. Therefore, most scholars in the industry currently prefer to use numerical simulation to calculate the waterproofing ability of the gasket. The existing simulation methods mainly include the following: Contact stress discrimination method [1] 、MSM+FPP [2] , CEL [3] , Python language and ABAQUS finite element software secondary programming method [4] Although there are many simulation methods available, they all have certain limitations.

[0003] The original contact stress discrimination method only considers the effects of assembly extrusion and conventional static side water pressure on the waterproof gasket, ignores the enhancement of the self-sealing effect caused by water seepage pressure, and fails to reveal the dynamic evolution of the water seepage process; the MSM+FPP method only considers the leakage channels between the gaskets, but does not consider the leakage channels between the gaskets and the segment grooves. The calculation process is quite time-consuming and difficult to converge; although the CEL method is closer to the actual situation, its structure is quite complex, and the calculation process is extremely time-consuming and difficult to converge, especially when the gasket is excessively deformed, penetration is likely to occur; the method combining Python language with secondary programming of ABAQUS finite element software requires secondary development using Python language, and the simulation process is divided into many steps and is relatively cumbersome; the leakage channel between the gasket and the concrete groove is not considered.

[0004] Therefore, it is necessary to propose a new simulation method that is fast and efficient, does not worry about convergence problems, and can take into account the progressive leakage of multiple contact interfaces of shield tunnel joint sealing pads, so as to achieve a quick and smooth prediction of the waterproof capacity of shield tunnel joint rubber sealing pads and provide new measures for the design of shield tunnels.

[0005] References:

[0006] [1]Gong, C., Ding, W., Soga, K., Mosalam, K., Tuo, Y., 2018b. Sealant behavior of gasketed segmental joints in shield tunnels: An experimental and numerical study. Tunnelling Underground Space Technology, 77, 127-141.

[0007] [2]Gong, C., Ding, W., 2018a. A computational framework to predict the water-leakage pressure of segmental joints in underwater shield tunnels using an advanced finite element method. International Journal for Numerical and Analytical Methods in Geo-mechanics 42, 1957-1975.

[0008] [3]Zhou, W., Liao, S., Men, Y., 2021. A fluid-solid coupled modeling on water seepage through gasketed joint of segmented tunnels. Tunnelling and Underground Space Technology, 114, 104008.

[0009] [4]Yan, Q., Zhong, H., Zhang, C., Zhao, Z., Wen, Y., Wang, P., 2023. Novel numerical model to simulate water seepage through segmental gasketed joints of underwater shield tunnels considering the superimposed seepage squeezing effect. Underground Space 13, 104-120. Summary of the Invention

[0010] In order to solve the problems existing in the prior art, such as not considering the leakage between the sealing gasket and the segment groove, the cumbersome and time-consuming calculation and the difficulty in convergence, the present invention provides a method and application for evaluating the waterproof capacity of rubber sealing gaskets at the joints of shield tunnel segments, adopts finite element software ABAQUS and its VDLOAD subroutine to perform numerical simulation on the leakage of the sealing gasket, and establishes a sealing gasket waterproof capacity prediction model to predict the ultimate water pressure of leakage damage.

[0011] VDLOAD is an explicit subroutine of ABAQUS, which can be used for load application in finite element analysis. It applies a certain load to the structure to simulate the stress conditions under actual working conditions, so that the magnitude and position of the force it applies can move accordingly with the analysis time. This is the same as the situation when water pressure acts on the waterproof structure of the sealing pad and progressive leakage occurs. Therefore, it can be used to simulate the leakage of multi-contact interfaces of the joint sealing pad of the shield tunnel.

[0012] To achieve the above object, the present invention adopts the following technical solutions:

[0013] A method for evaluating the waterproof capability of a shield tunnel segment joint sealing gasket comprises the following steps:

[0014] S1: Establish a simulation model of the waterproof structure of the pipe segment joint sealing pad based on actual projects;

[0015] The simulation model includes a first tube segment and a second tube segment, two identical sealing gaskets are arranged between two corresponding grooves on the first tube segment and the second tube segment, one end surface of the two sealing gaskets is in close contact with each other, and the other end surface is in close contact with the two grooves respectively;

[0016] It should be noted that, in S1, the two completely identical sealing gaskets refer to two sealing gaskets having the same shape, structure and material.

[0017] S2: Set the relative displacement of the segments according to the actual working conditions;

[0018] In the simulation model, the first segment is constrained so that it does not move, and the relative displacement of the second segment relative to the first segment is adjusted according to the actual working conditions;

[0019] It should be noted that in S2, the relative displacement between the first segment and the second segment includes any one or more combinations of pure opening (ΔP), misalignment (ΔS), and rotation angle (Δθ), wherein the rotation angle is divided into positive rotation angle and negative rotation angle (a positive rotation angle means that the first segment and the second segment are open inside the joint and closed outside the joint, and vice versa for a negative rotation angle).

[0020] S3: Determine the leakage failure water pressure of the gasket-gasket contact interface using numerical simulation method;

[0021] The VDLOAD subroutine in ABAQUS software was used to gradually apply a constant water pressure along the gasket-gasket contact interface from the outside to the inside (i.e., from the outside of the tunnel to the inside of the tunnel) in the simulation model. Numerical simulation was performed to make the gasket-gasket contact interface leak and fail. According to the principle of dichotomy, the water pressure was Optional water pressure within the range Numerical simulations were performed until the pressure difference When it is less than or equal to the threshold value Y (Y≤0.01MPa), select the water pressure when there is no leakage As leakage destroys water pressure

[0022] It should be noted that in S3, a constant water pressure is gradually applied from the outside to the inside along the gasket-gasket contact interface. or The process is as follows: the state where the gasket is not subjected to water pressure is set as the initial state (the second pipe segment and the first pipe segment have relative displacement), the state where leakage damage occurs at the gasket-gasket contact interface is set as the final state, and the outer end point position of the gasket-gasket interface in the initial state is set as the starting force application position abscissa X=A R , set the inner end point position of the gasket-gasket contact interface at the final state as the end force application position, and the horizontal coordinate X = B R , and B R =A R +L R +X R , where L R is the width of the gasket-gasket contact interface in the initial state, X R is the displacement of the inner end point of the gasket-gasket contact interface in the final state, and the time step is set to T R , then the speed V at which the water pressure is gradually applied from the outside to the inside along the gasket-gasket contact interface is R =(B R -A R ) / T R .

[0023] It should be noted that in S3, the leakage damage judgment standard of the gasket-gasket contact interface is: the two gaskets are completely separated, that is, they are not in contact with each other.

[0024] S4: Determine the leakage failure water pressure of the gasket-groove contact interface using numerical simulation method;

[0025] The VDLOAD subroutine is used to gradually apply a constant water pressure along the gasket-groove contact interface from the outside to the inside in the simulation model. Numerical simulation was performed to make the sealing gasket-groove contact interface leak and fail. According to the principle of dichotomy, the water pressure was Optional water pressure within the range Numerical simulations were performed until the pressure difference When it is less than or equal to the threshold value Y (Y≤0.01MPa), select the water pressure when there is no leakage As leakage destroys water pressure

[0026] It should be noted that in S4, a constant water pressure is gradually applied from the outside to the inside along the gasket-groove contact interface. or The process is as follows: the state where the gasket is not subjected to water pressure is set as the initial state (the second segment and the first segment have relative displacement), the state where leakage damage occurs at the gasket-groove contact interface is set as the final state, and the outer end point position of the gasket-groove contact interface in the initial state is set as the starting force application position abscissa X=A G , set the inner end point of the sealing pad-groove contact interface at the final state as the end force application position, and the horizontal coordinate X = B G , and B G =A G +L G +X G , where L G is the width of the gasket-groove contact interface in the initial state, X G is the displacement of the inner end point of the gasket-groove contact interface in the final state, and the time step is set to T G , then the speed V at which the water pressure is gradually applied from the outside to the inside along the gasket-gasket contact interface is G =(B G -A G ) / T G .

[0027] It should be noted that the leakage damage judgment standard of the gasket-groove contact interface is: the column foot of the gasket is completely separated from the groove, that is, there is no contact with the groove and no contact stress is exerted to prevent water pressure intrusion.

[0028] Through a large number of waterproof tests and leakage simulations, it is known that most of the leakage of gaskets occurs at the contact interface between gaskets, and leakage between gaskets and grooves is rare, which generally occurs when the opening amount is large and there is misalignment. Whether leakage occurs between gaskets or between gaskets and grooves, the method of the present invention can take it into account, so the prediction simulation results are more accurate.

[0029] S5: Determine the waterproof capability of the gasket (limit water pressure for leakage damage);

[0030] The breaking water pressure of the gasket-gasket contact interface obtained by S3 The breaking water pressure of the gasket-groove contact interface obtained by S4 The smaller value is taken as the waterproof capability of the gasket (limit water pressure of leakage damage) P Wlim .

[0031] A method for evaluating the waterproof capability of shield tunnel segment joint sealing gaskets is proposed. When applied, for any sealing gasket with the same shape and structure, sealing gaskets of different materials (elastic modulus) are selected, and different relative displacements of the segments are set to form a variety of different simulated working conditions. The waterproof capability (limit water pressure of leakage damage) of the sealing gasket under each simulated working condition is determined by numerical simulation method. Wlim , regression analysis was used to establish P Wlim The changing relationship with different simulated working conditions is used as a prediction model for the waterproof capacity of gaskets with corresponding shapes and structures. According to the relative displacement of the pipe segments and the type of gasket materials (including shape, structure, and material) in actual projects, the waterproof capacity prediction model is used to predict the waterproof capacity (limit water pressure of leakage damage) of the gasket.

[0032] It should be noted that the sealing gasket waterproof ability prediction model is established according to formula (1):

[0033]

[0034] Where: P Wlim is the waterproof ability of the gasket, K1~K5 are all unknown coefficients, E0 is the Young's modulus of the gasket, ΔP is the opening amount of the joint, and ΔS is the misalignment of the joint.

[0035] When the segment has a relative angular displacement θ, ΔP is replaced by ΔP+ΔP θ , where ΔP θ It is the opening amount caused by the relative rotation angle (which can be calculated according to the structure of the pipe segment joint), that is, converting the influence of the relative rotation angle of the joint on the waterproof ability of the sealing gasket into its influence on the opening amount of the joint.

[0036] It should be noted that, for the sealing gasket in Example 2, the sealing gasket waterproof ability prediction model is established according to formula (2):

[0037]

[0038] The technical principle of the present invention is: using the explicit subroutine VDLOAD in the ABAQUS finite element software to realize the progressive application of water pressure along the contact interface between the sealing pad and the sealing pad (pad-pad interface) and the contact interface between the sealing pad and the concrete groove (pad-groove interface), by defining the magnitude of the water pressure acting on the contact interface and the corresponding water pressure path, to simulate the leakage process of the sealing pad multiple contact interfaces in real conditions, and then determine the leakage water pressure along the pad-pad interface and the leakage water pressure along the pad-groove interface By comparison and The size of the sealing gasket can obtain the waterproof ability P Wlim .

[0039] Compared with the prior art, the present invention can bring the following beneficial effects:

[0040] 1) Different from the previous numerical simulation of gasket leakage, the technical solution of the present invention innovatively uses the explicit subroutine VDLOAD of ABAQUS to apply progressive water pressure to the contact interface, which can dynamically consider the enhancement of the sealing effect of the gasket due to water seepage pressure, and overcomes the limitations of previous methods such as contact stress discrimination method, MSM+FPP method, CEL method, and the combination of Python language and secondary programming of ABAQUS finite element software, which are unreasonable, prone to convergence problems, cumbersome and complex modeling, and time-consuming and labor-intensive simulation process. It can realize one-time leakage simulation of a single working condition, greatly shorten the calculation time, improve the calculation efficiency, and make the simulation results more accurate.

[0041] 2) The leakage at the two contact interfaces between the gaskets and between the gaskets and the grooves is taken into account, and various situations in which the gaskets may leak are considered more completely. It is applicable to any form of gasket cross-section and can more accurately predict the waterproof ability of the gaskets.

[0042] 3) Based on the numerical simulation results, the present invention establishes a prediction model for the waterproof ability of sealing gaskets of different materials at different relative displacements of pipe segments when the shape and structure are the same. According to the relative displacement of the pipe segments and the type of sealing gasket materials in actual projects, the model can be used to predict the waterproof ability of the sealing gasket. The prediction method has high accuracy and great engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The flowchart of the method for evaluating the waterproof capability of a sealing gasket based on the VDLAOD subroutine is shown in FIG.

[0044] Figure 2 Schematic diagram of pure opening, misalignment and corner rotation of the segment joints; Figure (a) shows the case of pure opening and misalignment of the joints, and Figure (b) shows the case of corner rotation of the joints.

[0045] Figure 3 Schematic diagram of the progressive application of water pressure based on the VDLOAD subroutine (taking the application of water pressure on the gasket-gasket contact surface as an example).

[0046] Figure 4 Schematic diagram of geometric parameters of the cross section of the sealing gasket used in Example 1.

[0047] Figure 5 Schematic diagram of the change of the gasket-gasket contact interface before and after the water pressure.

[0048] Figure 6 This is a relationship diagram between the waterproof ability of the sealing gasket and the opening amount when the misalignment amount is 0 mm in Example 2.

[0049] Figure 7 This is a relationship diagram between the waterproof ability of the sealing gasket and the Young's modulus when the opening amount is 8 mm and the misalignment amount is 0 mm in Example 2.

[0050] Figure 8 This is a relationship diagram between the decrease in the waterproof ability of the sealing gasket and the misalignment when the opening amount is 8 mm in Example 2.

[0051] Fig. 9 It is a simulation result diagram of the working condition of the misalignment amount of 15mm and the opening amount of 7.87mm in Example 1; among them, Figure (a) is 0.62MPa, and Figure (b) is 0.63MPa (leaking).

[0052] Fig.10 It is a simulation result diagram of the working condition of the misalignment amount of 15mm and the opening amount of 6.89mm in Example 1; among them, Figure (a) is 0.78MPa, and Figure (b) is 0.80MPa (leaking).

[0053] Fig.11 It is a simulation result diagram of the working condition of the misalignment amount of 15mm and the opening amount of 5.95mm in Example 1; among them, Figure (a) is 1.4MPa, and Figure (b) is 1.5MPa (leaking).

[0054] Fig.12 It is a simulation result diagram of the working condition of the misalignment amount of 15mm and the opening amount of 3.88mm in Example 1; among them, Figure (a) is 2.1MPa, and Figure (b) is 2.2MPa (leaking).

[0055] Fig.13 It is a simulation result diagram of the working condition of the misalignment amount of 0mm and the opening amount of 1.91mm in Example 1; among them, Figure (a) is 3.1MPa, and Figure (b) is 3.2MPa (leaking).

[0056] Fig.14It is a simulation result diagram of the working condition of the misalignment amount of 0mm and the opening amount of 3.96mm in Example 1; among them, Figure (a) is 2.6MPa, and Figure (b) is 2.7MPa (leaking).

[0057] Fig.15 It is a simulation result diagram of the working condition of the misalignment amount of 0mm and the opening amount of 5.79mm in Example 1; among them, Figure (a) is 1.8MPa, and Figure (b) is 1.9MPa (leaking).

[0058] Fig.16 It is a simulation result diagram of the working condition of the misalignment amount of 0mm and the opening amount of 6.75mm in Example 1; among them, Figure (a) is 1.3MPa, and Figure (b) is 1.45MPa (leaking).

[0059] Fig.17 It is a simulation result diagram of the working condition of the misalignment amount of 0mm and the opening amount of 7.62mm in Example 1; wherein, Figure (a) is 1.1MPa, and Figure (b) is 1.2MPa (leaking). DETAILED DESCRIPTION

[0060] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0061] Embodiment 1:

[0062] Taking the waterproof sealing rubber pad used in a shield tunnel project as an example, the method of the present invention is described in detail. Figure 1 The flowchart of the method for evaluating the waterproof capability of the sealing gasket based on the VDLAOD subroutine is shown in Figure 2. The geometric parameters of the sealing gasket cross section are as follows: Figure 4 As shown, the unit is mm.

[0063] The relative displacement of the first pipe segment and the second pipe segment includes any one or more combinations of pure opening (ΔP), misalignment (ΔS), and rotation angle (Δθ), wherein the rotation angle is divided into positive rotation angle and negative rotation angle (a positive rotation angle means that the first pipe segment and the second pipe segment are opened inside the joint and closed outside the joint, and vice versa is a negative rotation angle). Figure 2 Schematic diagram of pure opening, misalignment and corner rotation of the segment joint; Figure (a) shows the case of pure opening and misalignment of the joint, and Figure (b) shows the case of corner rotation of the joint. For the convenience of simulation, this embodiment only considers the cases of pure opening and misalignment in numerical simulation, and the corner displacement is converted into opening displacement for consideration.

[0064] The rubber elastic sealing gasket is simulated using the Mooney-Rivlin constitutive model in ABAQUS software. The two-parameter strain energy function of the model is expressed as follows according to formula (3):

[0065] W=C 10 (I1-3)+C 01 (I2-3) (3)

[0066] Where: W is strain energy; C 10 and C 01 is the material parameter; I1 and I2 are the first and second invariants respectively.

[0067] For most rubber materials, the two-parameter model can obtain a reasonable approximation within a strain of 150%. Gent (Gent AN. Engineering with rubber: how to design rubber components (3rd edition) [M]. Hanser Publisher, 2012.) proposed a method to determine the model parameter C based on a large amount of test data fitting and regression analysis. 10 and C 01 Empirical simplified method: Assume that the initial shear modulus of the rubber material (G g ) is equal to twice the sum of the model parameters, and the Young's elastic modulus (E0) of the rubber material is equal to 3 times the initial shear modulus, C 10 Equal to C 01 0.25 times of . The specific expression is as follows:

[0068] G g =2(C 10 +C 01 ) (4)

[0069] E0=3G g (5)

[0070] C 01 =0.25C 10 (6)

[0071] For elastic sealing gaskets made of rubber, the hardness H A (Shaw A grade) and Young's modulus E0 have the following relationship:

[0072]

[0073] Therefore, once the hardness of the elastic sealing gasket is determined, the model parameter C can be calculated using the above formula: 10 and C 01 Table 1 gives four types of Shore hardness H A(or Young's modulus E0) under the sealing gasket material parameters.

[0074] Table 1 Mooney-Rivlin constitutive parameters of rubber materials at different Shore hardness (Young's modulus)

[0075]

[0076] The Shore hardness of the gasket used in this embodiment is 70. The waterproof ability evaluation method of the shield tunnel segment joint gasket described in the present invention is used to determine the ultimate water pressure of the gasket leakage damage. At the same time, the ultimate water pressure is determined by the gasket waterproof test. The two are compared to verify the accuracy and feasibility of the simulation. Table 2 is a comparison of the numerical simulation results and the indoor test results. There are 5 working conditions for no misalignment and 4 working conditions for 15mm misalignment. The detailed simulation results can be seen in Figure 9-Figure 17 .

[0077] It should be noted that, in the simulation of the above-mentioned working conditions, the water pressure at the contact interface between the sealing gasket and the concrete groove is greater than the water pressure at the contact interface between the sealing gaskets. Therefore, the leakage at the contact interface between the sealing gasket and the concrete groove is not shown. However, this does not mean that this method is unnecessary, because for sealing gaskets with other cross-sectional forms, leakage at the contact interface between the sealing gasket and the groove may still occur, which requires simulation and judgment through the above-mentioned method to determine.

[0078] According to the working conditions in Table 2, simulation and calculation are performed according to steps S1-S4 in the above invention scheme to obtain the limit water pressure (i.e. waterproof capacity) of the leakage damage of the sealing gasket waterproof structure under each working condition. It should be noted that since the sealing gasket is a porous structure, it will be greatly deformed after being subjected to water pressure, and it is easy to fold, etc., and the initial water pressure range cannot take into account the folding of the sealing gasket, such as Figure 5 As shown, Figure 5 The figure is a schematic diagram of the change of the gasket-gasket contact interface before and after the water pressure acts. The gasket-gasket contact interface will gradually extend inward as the water pressure leaks from the outside to the inside of the gasket. In order to achieve the breakdown of the gasket and make the simulation of the gasket more consistent with the actual situation, the present invention sets the water pressure to be applied gradually from the initial state to the final state. Figure 3 Schematic diagram of the progressive application of water pressure based on the VDLOAD subroutine (taking the application of water pressure on the gasket-gasket contact surface as an example).

[0079] Table 2 Comparison of numerical simulation results and indoor test results

[0080]

[0081] Therefore, in the actual simulation, it is necessary to observe the folding of the gasket by looking for the visualization results of the simulation, that is, to obtain the displacement X of the inner end point of the gasket-gasket contact interface. R , dynamically adjust the water pressure action surface range and determine the water pressure progressive application speed V R , to achieve smooth penetration of the gasket, otherwise even if the water pressure is adjusted to a higher level, it may not be completely penetrated, and the leakage damage cannot be accurately simulated. Since the numerical simulation speed is fast at this time, even if the water pressure action surface range needs to be dynamically adjusted, the total simulation time is still short. When applying water pressure to the gasket-groove contact surface, it is also necessary to perform dynamic adjustment in the above manner, and then determine the displacement X of the inner end point when the interface leaks and damages. G and the speed V at which the water pressure is gradually applied G For the convenience of simulation, this embodiment selects the outer end point of the groove as the starting force horizontal coordinate X=A R , replacing the outer end point of the gasket-gasket interface, when the starting force application point is between the outer end point of the groove and the outer end point of the gasket-gasket interface, the leakage situation of the model will not change.

[0082] In the above process of selecting constant water pressure for numerical simulation according to the principle of dichotomy, the constant water pressure at which the gasket leaks and fails is It is difficult to find manually, so the constant water pressure There is great uncertainty, and improper selection will lead to too many simulations. Usually, a rough range can be preliminarily determined based on engineering experience, such as: the sealing gasket is compressed by 5mm, and the approximate waterproof capacity is 0.5-1.0MPa; the sealing gasket is compressed by 10mm, and the approximate waterproof capacity is 1.0-2.0MPa; the compression is 15mm, and the waterproof capacity is generally 2.0-3.0MPa, or even more than 3.0MPa, etc. In actual numerical simulation, in order to solve this time-consuming and highly uncertain problem, you can write Python code files to batch generate INP files with VDLOAD subroutines (where the water pressure defined in the subroutine is set from a certain pressure range (such as 0.0-10.0MPa) according to a certain increment (such as 0.1MPa)), so that the numerical simulation of different constant water pressures can be quickly realized.

[0083] According to Table 2, the results of numerical simulation and indoor test are consistent with each other, with errors less than ±20%. As the opening amount decreases, the results are more consistent, which is within the acceptable range in engineering. The physical waterproof test itself also has certain errors. Therefore, it can be considered that the results simulated by this method are more real and reasonable, and can well reflect the deformation response and mechanical properties of the sealing gasket under water pressure.

[0084] Embodiment 2:

[0085] The present embodiment provides a method for evaluating the waterproof capability of a shield tunnel segment joint sealing gasket. When applied, for any sealing gasket of the same shape and structure, sealing gaskets with different elastic moduli are selected, and different relative displacements are set for the first segment and the second segment to form a plurality of different working conditions. A numerical simulation method is used to determine the waterproof capability (limit water pressure of leakage damage) P of the sealing gasket under each working condition. Wlim , regression analysis was used to establish P Wlim The changing relationship under different working conditions is used as a prediction model for the waterproof capacity of gaskets with corresponding shapes and structures. According to the gasket material type and the relative displacement of the pipe segments in actual projects, the waterproof capacity prediction model is used to predict the waterproof capacity of the gasket (the ultimate water pressure of leakage damage).

[0086] In this embodiment, a sealing gasket with a Shore hardness of 55 to 70 is selected. The cross-sectional form of the sealing gasket is the same as that of Embodiment 1. The working conditions simulated by the VDLOAD method are shown in Table 3.

[0087] Table 3 Working conditions simulated by VDLOAD in Example 2

[0088]

[0089]

[0090] According to the method described in Example 1, numerical simulation is performed on each of the above working conditions to obtain the waterproof capability (limit water pressure of leakage damage) of the sealing gasket under each working condition. Wlim Then all the data were statistically analyzed, and the Shore hardness was converted into Young's modulus according to formula (7).

[0091] By comparing the waterproof ability of the gasket under different Young's modulus, it can be found that there is a good linear relationship between the waterproof ability of the gasket and the Young's modulus, which can be expressed as follows:

[0092] P Wlim =K1E0 (8)

[0093] Where: P Wlim is the waterproof ability of the sealing gasket; E0 is the Young's modulus of the sealing gasket; K1 is the fitting coefficient;

[0094] Take the sealing gaskets with different Shore hardness in working conditions 1 to 4 in Table 3 as an example, when the opening amount is 8mm and the misalignment amount is 0mm. Figure 7 , Figure 7 The relationship between the waterproof ability of the sealing gasket and the Young's modulus when the opening amount is 8 mm and the misalignment amount is 0 mm is shown in Figure 9. The relationship between the waterproof ability of the sealing gasket and the Young's modulus is obtained by fitting using the regression analysis method, K1 = 0.19663, as shown in formula (9):

[0095] P Wlim =0.19663E0 (9)

[0096] By comparing the waterproof ability of the gasket at different opening amounts, it can be found that there is a good exponential function relationship between the waterproof ability of the gasket and the opening amount of the pipe segment, which can be expressed as follows:

[0097]

[0098] Where: P Wlim is the waterproof ability of the sealing gasket, E0 is the Young's modulus of the sealing gasket, ΔP is the opening amount of the sealing gasket; K1, K2, K3 are fitting coefficients.

[0099] Take the waterproof capability of the sealing gaskets of working conditions 5 to 11 in Table 3 at different opening amounts under the condition of 0 mm misalignment as an example. Figure 6 , Figure 6 The relationship between the waterproof ability of the sealing gasket and the opening amount when the misalignment is 0 mm is shown in Figure 1. The nonlinear regression analysis method is used for fitting, and the nonlinear function expression between the opening amount and the waterproof ability of the sealing gasket is obtained, K2 = 4.52964, K3 = 5.19096, as shown in formula (11):

[0100]

[0101] By comparing the waterproof ability of the gasket at different misalignments, it can be found that there is a good power function relationship between the decrease in the waterproof ability of the gasket and the misalignment of the segment, which can be expressed as follows:

[0102]

[0103] Where: ΔP W is the decrease in the waterproof ability of the sealing gasket, E0 is the Young's modulus of the sealing gasket, ΔS is the misalignment of the pipe segment; K1, K4, K5 are fitting coefficients.

[0104] Take working conditions 12 to 15 in Table 3 with an opening amount of 8 mm as an example. Figure 8 , Figure 8 The relationship between the decrease in waterproof ability and the misalignment of the sealing gasket when the opening amount is 8 mm is shown in the figure. The nonlinear regression analysis method is used to fit different misalignments and the decrease in waterproof ability, and the functional expression between the decrease in waterproof ability and the misalignment of the sealing gasket is obtained, K4 = 0.09962, K5 = 0.52987, as shown in formula (13):

[0105] ΔP W =-0.019589E0ΔS 0.52987 (13)

[0106] Combining the above results, we can finally get the functional relationship between the waterproof ability of the gasket and the gasket opening amount, misalignment amount, and Young's modulus. That is, the prediction model of the waterproof ability of the gasket is expressed as follows:

[0107]

[0108] Substituting the values ​​of each fitting coefficient into the above formula, we get formula (2):

[0109]

[0110] In order to verify the accuracy of formula (2) in predicting the waterproof ability of the gasket, the prediction results of formula (2) are compared with the indoor test results. The results are shown in Table 4. It can be seen that the maximum error between the prediction results and the test results is 22.6%, and the rest are all less than 20%, indicating that the formula can better predict the waterproof ability of the gasket under different deformation conditions of the joint. It should be noted that the waterproof ability of the gasket calculated by the prediction model is conservative (safe), and the prediction results are all less than the test results, and the difference is small. In actual engineering design, this is in line with the expectations of the prediction.

[0111] It should be noted that the calculation formula for the waterproof capacity of the sealing gasket is only applicable to the sealing gasket cross-sectional form used in this embodiment. Other cross-sectional forms need to be explored through the simulation method and indoor test methods described in the present invention. However, the above embodiments can prove that the new simulation method proposed in the present invention is fast and effective, and can also be applied to the simulation of sealing gaskets with other cross-sectional forms. The regression analysis method can also be used to further fit the mathematical expression between the waterproof capacity of the sealing gasket and the elastic modulus of the sealing gasket and the relative displacement of the pipe segment, so as to obtain the waterproof capacity prediction model corresponding to the cross-sectional form of the sealing gasket. Prediction through this model is more convenient and quick.

[0112] Table 4 Comparison of the waterproof ability of the sealing gasket obtained by the prediction model and the test results

[0113]

[0114] When the segment has a relative angular displacement θ, ΔP is replaced by ΔP+ΔP θ , where ΔP θ is the opening amount caused by the relative rotation angle (which can be calculated according to the joint structure of the pipe segment), that is, converting the influence of the relative rotation angle of the joint on the waterproof ability of the sealing gasket into its influence on the opening amount of the joint;

[0115] Where ΔP θ It can be roughly determined by the following formula:

[0116] ΔP θ =|L S tanθ or ΔPθ =|L S θ(14)

[0117] Where: L S is the distance from the center of the gasket to the other end of the segment joint; θ is the relative angular displacement of the segment joint; the angular displacement is divided into positive and negative angles (a positive angle means that the first segment and the second segment are opened inside the joint and closed outside the joint, and vice versa). For a single-channel gasket joint waterproof structure, the gasket is generally set outside the joint. Therefore, a positive angular displacement will reduce the opening of the joint at its location, thereby enhancing the waterproof ability of the gasket, and a negative angle will increase the opening of the joint at its location, thereby reducing the waterproof ability of the gasket. Under normal circumstances, the angular displacement θ is small, and tanθ can also be simplified to θ.

[0118] In actual engineering, a waterproof capability prediction model corresponding to the type of sealing gasket can be established according to the method of the present invention based on the sealing gasket products of different shapes and structures to form a set of prediction models. When used in engineering, the corresponding prediction model can be selected from the set of prediction models according to the specific type of the sealing gasket to predict the waterproof capability.

[0119] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for evaluating the waterproof capability of shield tunnel segment joint sealing pads, characterized in that: The steps include: S1: Establish a simulation model of the waterproof structure of the pipe segment joint sealing pad based on actual projects; The simulation model includes a first tube segment and a second tube segment, two identical sealing gaskets are arranged between two corresponding grooves on the first tube segment and the second tube segment, one end surface of the two sealing gaskets is in close contact with each other, and the other end surface is in close contact with the two grooves respectively; S2: Set the relative displacement of the segments according to the actual working conditions; In the simulation model, the first pipe segment is constrained so that it does not move, and the relative displacement of the second pipe segment with respect to the first pipe segment is adjusted according to the actual working conditions; S3: Determine the leakage failure water pressure of the gasket-gasket contact interface using numerical simulation method; The VDLOAD subroutine in ABAQUS software was used to gradually apply a constant water pressure from the outside to the inside along the gasket-gasket contact interface in the simulation model. Numerical simulation was performed to make the gasket-gasket contact interface leak and fail. According to the principle of dichotomy, the water pressure was Optional water pressure within the range Numerical simulations were performed until the pressure difference When it is less than or equal to the threshold value Y, select the water pressure when there is no leakage As leakage destroys water pressure S4: Determine the leakage failure water pressure of the gasket-groove contact interface using numerical simulation method; The VDLOAD subroutine is used to gradually apply a constant water pressure along the gasket-groove contact interface from the outside to the inside in the simulation model. Numerical simulation was performed to make the sealing gasket-groove contact interface leak and fail. According to the principle of dichotomy, the water pressure was Optional water pressure within the range Numerical simulations were performed until the pressure difference When it is less than or equal to the threshold value Y, select the water pressure when there is no leakage As a destructive leak water pressure S5: Determine the waterproof capability of the gasket; The breaking water pressure of the gasket-gasket contact interface obtained by S3 The breaking water pressure of the gasket-groove contact interface obtained by S4 The smaller value is taken as the waterproof capability P of the sealing gasket. Wlim .

2. The method for evaluating the waterproof capability of shield tunnel segment joint sealing pads according to claim 1, characterized in that: In S1, the two completely identical sealing gaskets refer to two sealing gaskets having the same shape, structure and material.

3. The method for evaluating the waterproof capability of shield tunnel segment joint sealing pads according to claim 1, characterized in that: In S2, the relative displacement between the second pipe segment and the first pipe segment includes any one or more combinations of pure opening, staggering, and rotation.

4. The method for evaluating the waterproof capability of shield tunnel segment joint sealing pads according to claim 1, characterized in that: In S3, a constant water pressure is applied gradually from the outside to the inside along the gasket-gasket contact interface. or The process is as follows: the state where the gasket is not subjected to water pressure is set as the initial state, the state where leakage damage occurs at the gasket-gasket contact interface is set as the final state, and the outer end point position of the gasket-gasket interface in the initial state is set as the starting force application position, the horizontal coordinate X=A R , A R The horizontal coordinate of the starting point of the outer side of the groove of the first segment in the simulation model is set. The inner end point of the gasket-gasket contact interface in the final state is set as the end force application position. The horizontal coordinate X=B R , and B R =A R +L R +X R , where L R is the width of the gasket-gasket contact interface in the initial state, X R is the displacement of the inner end point of the gasket-gasket contact interface in the final state, and the time step is set to T R , then the speed V at which the water pressure is gradually applied from the outside to the inside along the gasket-gasket contact interface is R =(B R -A R ) / T R .

5. The method for evaluating the waterproof capability of shield tunnel segment joint sealing gaskets according to claim 1, characterized in that: In S4, a constant water pressure is applied gradually from the outside to the inside along the gasket-groove contact interface. or The process is as follows: the state where the gasket is not subjected to water pressure is set as the initial state, the state where the gasket-groove contact interface is leaked and damaged is set as the final state, and the outer end point position of the gasket-groove contact interface in the initial state is set as the starting force application position abscissa X=A G , A G The horizontal coordinate of the outer starting point of the groove of the first segment in the simulation model is set. The inner end point of the sealing gasket-groove contact interface in the final state is set as the end force application position. The horizontal coordinate X=B G , and B G =A G +L G +X G , where L G is the width of the gasket-groove contact interface in the initial state, X G is the displacement of the inner end point of the gasket-groove contact interface in the final state, and the time step is set to T G , then the speed V at which the water pressure is gradually applied from the outside to the inside along the gasket-gasket contact interface is G =(B G -A G ) / T G .

6. The method for evaluating the waterproof capability of shield tunnel segment joint sealing gaskets according to claim 1, characterized in that: In S3, the leakage damage judgment standard of the gasket-gasket contact interface is: the two gaskets are completely separated.

7. The method for evaluating the waterproof capability of shield tunnel segment joint sealing gaskets according to claim 1, characterized in that: In S4, the leakage damage judgment standard of the gasket-groove contact interface is: the column foot of the gasket is completely separated from the groove.

8. The method for evaluating the waterproof capability of shield tunnel segment joint sealing gaskets according to any one of claims 1 to 7, characterized in that: When applying, for any gasket with the same shape and structure, different materials of gaskets are selected, and different relative displacements of the segments are set to form a variety of different simulation conditions; the numerical simulation method is used to determine the waterproof capacity P of the gasket under each simulation condition. Wlim , regression analysis was used to establish P Wlim The changing relationship with different simulated working conditions is used as a prediction model for the waterproof capacity of gaskets with corresponding shapes and structures; according to the relative displacement of the pipe segments and the type of gaskets in actual projects, the waterproof capacity prediction model is used to predict the waterproof capacity of the gaskets.

9. Application of the method for evaluating the waterproof capability of shield tunnel segment joint sealing pads as claimed in claim 8, characterized in that: The sealing gasket waterproof ability prediction model is established according to formula (1): Where: P Wlim is the waterproof ability of the gasket, K1~K5 are all undetermined coefficients, E0 is the Young's modulus of the gasket, ΔP is the opening of the joint, and ΔS is the misalignment of the joint; When the segment has a relative angular displacement θ, ΔP is replaced by ΔP+ΔP θ , where ΔP θ is the opening amount caused by the relative rotation angle.

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