Shield tunnel anti-seismic toughness design method considering time-varying effect

Abstract

The invention relates to the technical field of tunnel anti-seismic toughness design, in particular to a shield tunnel anti-seismic toughness design method considering a time-varying effect, which comprises the following steps: step 1, determining to-be-optimized structural design parameters of a shield tunnel and a specific value range of a feasible region of the to-be-optimized structural design parameters; 2, constructing a degradation time-varying model under a long-term service condition, and obtaining calculation parameters when the shield tunnel is in service time T; 3, constructing a correlation function Re (T) IM between the tunnel design parameters and the shock resistance toughness; 4, constructing a function Cost of tunnel structure design parameters and tunnel construction cost; step 5, establishing a multi-objective optimization design mathematical model of anti-seismic toughness Re (T) IM and tunnel construction cost Cost; step 6, determining a final shield tunnel anti-seismic toughness design scheme from the solution set by adopting different optimization strategies based on constraint conditions of anti-seismic toughness objectives and construction cost. According to the method, the real risk of the long-term operation tunnel under the earthquake action can be evaluated more accurately.

Description

Technical Field

[0001] The present invention relates to the technical field of seismic resilience design of tunnels, and in particular to a seismic resilience design method for shield tunnels considering time-varying effects. Background Art

[0002] As a key infrastructure of the urban underground transportation network, the safety and functionality of shield tunnels are crucial in the face of natural disasters such as earthquakes. With the in-depth development of urban underground space, the seismic resilience design of shield tunnels has received more and more extensive attention.

[0003] The seismic resilience of a shield tunnel refers to the ability of the tunnel structure to reduce the probability of failure, mitigate seismic damage, and quickly recover under earthquake action. Alexander (2013) proposed introducing the concept of resilience in the design stage of infrastructure, emphasizing the importance of resilience design. Currently, the research on the seismic resilience of shield tunnels mainly focuses on the establishment of structural performance indicators, seismic vulnerability analysis, and performance-based seismic design methods. Research shows that the seismic resilience of shield tunnels can be effectively improved by optimizing the design method. The seismic resilience design of shield tunnels based on codes includes measures to improve the seismic performance of the shield tunnel structure itself and shock-absorbing measures to reduce the seismic energy transmitted from the stratum to the tunnel structure. Existing design methods generally rely on empirical design of tunnel parameters first, then consider more seismic measures to ensure structural safety, and finally conduct seismic resilience verification. However, such design concepts are difficult to directly apply the idea of tunnel seismic resilience to the initial structural design process of the tunnel, and lack a method for quantitatively considering the relationship between construction cost and resilience indicators, thus unable to comprehensively evaluate and conduct multi-objective optimization design of the tunnel, resulting in over-conservative and redundant design.

[0004] In addition, traditional tunnel seismic design methods often focus on newly built tunnels and ignore the performance degradation problems that occur during the long-term operation of the tunnels. During the operation of the tunnels, problems such as material aging, surrounding environment erosion, and load accumulation are faced. Over time, the resilience level of the tunnels is also reduced due to the degradation of various structural parameters of the tunnels. And the occurrence of earthquake disasters often occurs during the operation period after the tunnels are built. Since the traditional design concept fails to fully reflect the dynamic change characteristics of the tunnel structural performance, it may underestimate the actual risk of the tunnels under earthquake action. Summary of the Invention

[0005] The purpose of this application is to provide a seismic resilience design method for shield tunnels considering time-varying effects, aiming to solve the problems in the prior art.

[0006] The embodiments of this application provide a seismic resilience design method for shield tunnels considering time-varying effects, including the following steps:

[0007] Step 1: Determine the design parameters of the shield tunnel to be optimized and the specific value ranges of their feasible regions.

[0008] Step 2: Construct a time-varying deterioration model of reinforced concrete materials affected by chloride ion erosion deterioration under long-term service conditions for the shield tunnel, and obtain the calculation parameters at the service time T of the shield tunnel.

[0009] Step 3: Based on the calculation parameters considering the time-varying effect of the tunnel obtained in Step 2, design an orthogonal test scheme and conduct a large number of numerical simulation calculations to construct the correlation function Re(T)|IM between the tunnel design parameters and the seismic resilience under different ground motion intensities.

[0010] Step 4: Calculate the corresponding tunnel construction cost according to different structural design parameters, and construct the function Cost of the tunnel structural design parameters and the tunnel construction cost.

[0011] Step 5: Based on the correlation functions constructed in Step 3 and Step 4, establish a multi-objective optimization design mathematical model of the seismic resilience Re(T)|IM considering the time-varying effect of the tunnel and the tunnel construction cost Cost, and use the genetic algorithm and conduct a large number of iterations to obtain the set containing all Pareto optimal solutions; the mathematical model is as follows:

[0012]

[0013] Among them, Re(T)|IM represents the seismic resilience of the shield tunnel with a service time of T under the design seismic intensity IM, and Cost represents the tunnel construction cost per unit length.

[0014] Step 6: Based on the constraints of the seismic resilience target and construction cost of the shield tunnel, adopt different optimization strategies to determine the final required seismic resilience design scheme of the shield tunnel from the solution set in Step 5.

[0015] Furthermore, the design parameters to be optimized in Step 1 include the lining segment thickness h, the cross-sectional reinforcement ratio ρ, and the steel strength f y , and determine the reasonable range of the feasible regions of the above design parameters according to the preliminary design scheme.

[0016] Furthermore, the deterioration time-varying model in Step 2 includes a steel corrosion rate model, a steel strength deterioration model, and a concrete cover strength reduction model under long-term erosion, and obtain the values of the relevant calculation parameters of the shield tunnel at the service time of T through the above models.

[0017] Further, the specific operation of step 3 is to design an orthogonal experiment according to the tunnel design parameters and their feasible range obtained in step 1 under different earthquake intensities IM, and perform numerical modeling calculations using the relevant calculation parameters after the tunnel is deteriorated by chloride ion erosion at the service time T obtained in step 2. By fitting regression analysis, the functional relationship between the lining segment thickness h, cross-sectional reinforcement ratio ρ, and steel strength fy of the tunnel design parameters to be optimized and the seismic resilience Re of the tunnel is constructed, and a relevant model Re(T)|IM between seismic resilience and design parameters is established.

[0018] Further, the specific operation of step 4 is to construct a calculation model Cost between the lining segment thickness h, cross-sectional reinforcement ratio ρ, and steel strength f of the tunnel design parameters and the construction cost per unit length of the tunnel considering the market prices of steel bars and concrete. y

[0019] Further, the optimization strategies in step 6 include the equal-cost optimal solution strategy, the equal-seismic-resilience optimal solution strategy, and the Knee Point optimization strategy.

[0020] The beneficial effects of the present invention are as follows: The present invention can consider the influence of the degradation of material properties caused by chloride ion erosion on the seismic resilience of shield tunnels under long-term service; comprehensively consider the seismic resilience of shield tunnels under long-term service and the construction cost of tunnels, and at the same time provide an optimization scheme selection strategy, which is convenient for engineering practitioners to use, can more accurately evaluate the true risks and recovery capabilities of long-term operating tunnels under earthquake action, and can provide a basis for decision-makers to formulate tunnel engineering construction policies and plan disaster prevention and mitigation measures, which is conducive to the popularization and application of the project. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a flow chart of the seismic resilience design method for shield tunnels considering long-term service provided by the present invention.

[0022] Figure 2 It is a flow chart of the NSGA-II algorithm adopted by the present invention.

[0023] Figure 3 It is a schematic diagram of the Pareto front, equal-cost optimal solution, equal-resilience optimal solution, and Kneepoint obtained in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a 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 those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0025] A seismic resilience design method for shield tunnels considering time-varying effects, specifically including the following steps:

[0026] Step 1: Determine the structural design parameters P1, P2... Pn to be optimized for the shield tunnel and the specific value ranges of their feasible regions. Among them, considering the key parameters most sensitive to the seismic resilience of the shield tunnel, select the lining segment thickness h, cross-sectional reinforcement ratio ρ, and steel strength f y etc. as design parameters, and determine the reasonable value ranges of the feasible regions of the design parameters to be optimized according to the preliminary tunnel design scheme; among them, the preliminary design ranges of each parameter are first obtained by methods such as engineering experience and numerical calculation, and a certain expansion is carried out based on the initially determined parameter levels to obtain a reasonable parameter feasible region range.

[0027] Step 2: Construct a time-varying model for the deterioration of reinforced concrete materials affected by chloride ion erosion under long-term service conditions of the shield tunnel to obtain the calculation parameters at the service time T of the shield tunnel. Among them, consider the erosion of chloride ions on the steel bars and concrete materials of the shield tunnel, including the steel bar corrosion rate model, steel bar strength deterioration model, and concrete segment strength reduction model under long-term erosion, etc.; then, based on the above time-varying model, obtain the relevant calculation parameters of the shield tunnel at the service time T.

[0028] Step 3: Based on the calculation parameters considering the time-varying effects of the tunnel obtained in Step 2, design an orthogonal test scheme and conduct a large number of numerical simulation calculations to construct a correlation function Re(T)|IM between the tunnel design parameters and seismic resilience under different ground motion intensities; for example, select the peak ground acceleration PGA as the ground motion intensity index IM and the relative bending moment ratio DI as the structural damage index. Under different horizontal ground motion intensities IM, according to the tunnel design parameters and their feasible regions obtained in Step 1, design an orthogonal test and use the relevant parameters of the tunnel after chloride ion erosion deterioration at the service time T obtained in Step 2 for numerical modeling calculations. Through methods such as fitting regression analysis, construct the relationship between the tunnel design parameters h, ρ, and f y and the Re function of the tunnel seismic resilience, and establish a correlation model between seismic resilience and design parameters Re(T)|IM;

[0029] Step 4: Calculate the corresponding tunnel construction costs according to different structural design parameters, and construct a function Cost between the tunnel structural design parameters and the tunnel construction costs. Investigate the market prices of steel bars and concrete, and according to the shield tunnel design parameters h, ρ, and f selected in Step 1 y , construct a calculation model Cost between the construction cost per unit length of the shield tunnel and the tunnel design parameters.

[0030] Step 5: Based on the objective functions Re(T)|IM and Cost constructed in Step 3 and Step 4, establish a multi-objective optimization design mathematical model for the seismic resilience Re(T)|IM considering the time-varying effect of the tunnel and the construction cost Cost of the tunnel:

[0031]

[0032] Among them, Re(T)|IM represents the seismic resilience index of the shield tunnel with a service time of T under the design earthquake intensity IM, and Cost represents the construction cost per unit length of the tunnel; a suitable genetic algorithm is adopted and a large number of iterations are carried out to obtain a set containing all Pareto optimal solutions. The purpose of the multi-objective optimization mathematical model is to obtain tunnel design parameters with the largest possible seismic resilience of the tunnel and the smallest possible construction cost of the tunnel. For example, using the NSGA-II genetic algorithm, based on the calculation parameters of the shield tunnel considering the long-term effect determined in Step 2, an initial population is set, the seismic resilience value and construction cost of the tunnel for each set of parameters are calculated, the offspring population is generated through crossover and mutation and merged with the parent population, and then non-dominated sorting and crowding degree calculation are carried out to evaluate the advantages and disadvantages of each solution and maintain the diversity of the population. Finally, the elitist strategy is adopted to obtain the parent population for the new round of iteration, and the iterative calculation is repeated multiple times to finally obtain a set containing all Pareto optimal solutions.

[0033] Step 6: Based on the constraints such as the seismic resilience objective of the shield tunnel and the construction cost, adopt a suitable optimization strategy to determine a suitable optimization plan from all the Pareto solution sets calculated in Step 5. For example, adopt the equal-cost optimal strategy, that is, under the condition of the same cost as the initial plan, obtain the tunnel design parameters with the largest seismic resilience of the tunnel; the equal-seismic-resilience optimal strategy means that under the condition of the same seismic resilience as the initial plan, select the tunnel design parameters with the lowest construction cost; the Knee Point optimization strategy refers to that after a certain point (Knee Point) on the Pareto solution set, any further optimization in any direction will only bring a slight improvement in one objective performance while sacrificing the performance of another objective.

[0034] Based on the multi-objective optimization genetic algorithm, the present invention proposes an optimized design method for the structure of a shield tunnel considering the seismic resilience of the tunnel, which can consider the performance degradation of the tunnel during long-term service and the construction cost of the tunnel, more accurately evaluate the real risk of the long-term operating tunnel under earthquake action, and can provide a basis for decision-makers to formulate tunnel engineering construction policies and plan disaster prevention and mitigation measures.

[0035] The following is a detailed description through specific embodiments:

[0036] Such as Figure 1As shown in the figure, this embodiment provides a seismic resilience design method for shield tunnels considering time-varying effects, which is illustrated by taking the seismic optimization design of a soft soil shield tunnel in Shanghai as an example.

[0037] First, determine the design parameters P1, P2... Pn of the shield tunnel to be optimized and the specific ranges of their feasible regions. In this embodiment, the tunnel design parameters are selected as the lining segment thickness h, the cross-sectional reinforcement ratio ρ, and the steel strength fy. The feasible region ranges of the above parameters are as follows: the lining segment thickness is 0.2 m to 0.5 m, the cross-sectional reinforcement ratio is 0.2% to 3.7%, and the steel strength is 300 MPa to 500 MPa. Other parameters required for the calculation are selected as appropriate values according to the engineering design.

[0038] Then, construct a time-varying model for the deterioration of reinforced concrete materials affected by chloride ion erosion under long-term service conditions of the shield tunnel to obtain the calculation parameters at the service time T of the shield tunnel. Establish a deterioration model for the performance of steel bars over time to obtain the yield strength f y , ultimate strength f u , strain hardening ε sh and ultimate strain ε su and other variation laws with the steel bar corrosion rate η, and establish a strength model Cc for the compressive strength f c and tensile strength f t of the cover concrete with steel bar corrosion to obtain the change law of the strength of the shield tunnel segment concrete under long-term erosion; according to the time-varying deterioration model obtained above, calculate the tunnel calculation parameters at the tunnel service time T = 100 years. At this time, the steel bar corrosion rate η is 49.6%, and the corresponding yield strength f y is 441.48 MPa, the ultimate strength f u is 575.44 MPa, the strain hardening ε sh is 0.002, the ultimate strain ε su is 0.060, the compressive strength f c of the cover concrete is 5.1 MPa, and the tensile strength f t is 0.74 MPa.

[0039] Then, an orthogonal test scheme is designed based on the parameters to be optimized and their feasible regions determined above. A large number of numerical simulation calculations are carried out according to the reinforced concrete strength parameters after the material deterioration of the shield tunnel under long-term service above. A correlation function Re(T)|IM between the tunnel structure design parameters and seismic resilience under different ground motion intensities is constructed. The peak ground acceleration PGA is selected as the ground motion intensity index IM, and the range of the ground motion intensity PGA is 0.1g - 1.0g. The relative bending moment ratio ID of the shield tunnel is selected as the structural failure index. The lining segment thickness h (0.25m, 0.30m, 0.35m, 0.40m, 0.45m), the cross-sectional reinforcement ratio ρ (0.5%, 1.0%, 1.5%, 2.0%, 2.5%), and the steel strength f y (300MPa, 350MPa, 400MPa, 450MPa, 500MPa) are used to design an orthogonal test scheme with three factors and five levels. The obtained calculation results are subjected to fitting regression analysis to calculate the Re value, and a quadratic polynomial fitting is performed on the calculation results of the seismic resilience Re value to obtain a correlation model Re(T)|IM between the seismic resilience of the shield tunnel under long-term service and the design parameters.

[0040] Then, the corresponding tunnel construction costs are calculated according to different structural design parameters, and a function Cost between the tunnel structure design parameters and the tunnel construction cost is constructed. For example, according to the price information in January 2024 on the Shanghai Construction Market Information Service Platform, the steel price of HRB400 hot-rolled ribbed steel with a diameter of 16mm is 4255 yuan / t (C s ), and the steel density is taken as 7.8t / m 3 ; the price of C50 ordinary concrete is 721 yuan / m 3 (C c ). A calculation model Cost of the construction cost per unit length of the tunnel and the structural design parameters is constructed.

[0041] As Figure 2 shown, based on the constructed objective functions Re(T)|IM and Cost, a multi-objective optimization mathematical model of the seismic resilience Re(T)|IM considering the time-varying effect of the tunnel and the tunnel construction cost Cost is established. Based on the above steps, the NSGA-II genetic algorithm is used to randomly generate an initial population within the feasible region, calculate the tunnel seismic resilience value Re and the construction cost Cost of each group of parameters, generate offspring populations through crossover and mutation and merge them with the parent population, and then perform non-dominated sorting and crowding degree calculation to evaluate the advantages and disadvantages of each solution and maintain the diversity of the population. Finally, the elite strategy is used to obtain the parent population for the new round of iteration, and the iterative calculation is repeated multiple times to obtain a set containing all Pareto optimal solutions.

[0042] Finally, based on the constraints such as the seismic resilience objectives and construction costs of shield tunnels, different optimization strategies are adopted, such as the equal-cost optimal solution strategy, the equal-seismic resilience optimal solution strategy, and the Knee Point optimization strategy, to determine a suitable optimized design solution from all the Pareto solution sets obtained by the above steps. As Figure 3 shown, the equal-cost optimal solution is the optimal solution on the Pareto front that is closest to the cost of the actual design point, with design parameters of h = 0.20 m, ρ = 1.57%, f y = 500 MPa, and the seismic resilience is improved by approximately 12.3%; the equal-seismic resilience optimal solution is the optimal solution on the Pareto front that is closest to the seismic resilience value of the actual design point, with design parameters of h = 0.20 m, ρ = 0.66%, f y = 500 Mpa, and the cost is reduced by approximately 33.9%; the Knee Point is a design point recommended after evaluation and analysis without clear preset design objectives or restrictive conditions, with design parameters of h = 0.20 m, ρ = 1.02%, f y = 500 Mpa. Compared with the actual design point, it reduces the construction cost by 20.5% while increasing the seismic resilience value by 6.0%.

[0043] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claimed rights involved.

Claims

1. A seismic resilience design method for shield tunnels considering time-varying effects, characterized in that, It includes the following steps: Step 1: Determine the design parameters of the shield tunnel to be optimized and the specific value ranges of their feasible regions; Step 2: Construct a time-varying deterioration model of reinforced concrete materials affected by chloride ion erosion deterioration under long-term service conditions of the shield tunnel, and obtain the calculation parameters at the service time T of the shield tunnel; Step 3: Based on the calculation parameters considering the time-varying effect of the tunnel obtained in Step 2, design an orthogonal test scheme and conduct a large number of numerical simulation calculations to construct the correlation function Re(T)|IM between the tunnel design parameters and seismic resilience under different ground motion intensities; Step 4: Calculate the corresponding tunnel construction costs according to different structural design parameters, and construct the function Cost of the tunnel structural design parameters and the tunnel construction cost; Step 5: Based on the correlation functions constructed in Step 3 and Step 4, establish a multi-objective optimization design mathematical model of seismic resilience Re(T)|IM and tunnel construction cost Cost considering the time-varying effect of the tunnel, and use the genetic algorithm and conduct a large number of iterations to obtain a set containing all Pareto optimal solutions; the mathematical model is as follows: Among them, Re(T)|IM represents the seismic resilience of the shield tunnel with a service time of T under the design seismic intensity IM, and Cost represents the construction cost per unit length of the tunnel; Step 6: Based on the constraints of the seismic resilience objective and construction cost of the shield tunnel, adopt different optimization strategies to determine the final required seismic resilience design scheme of the shield tunnel from the solution set in Step 5.

2. The seismic resilience design method for shield tunnels considering time-varying effects according to claim 1, characterized in that The design parameters to be optimized in the first step include the lining segment thickness h, the cross-sectional reinforcement ratio ρ, and the steel strength f y , and the reasonable range of the feasible region of the above design parameters is determined according to the preliminary design scheme.

3. The seismic resilience design method for shield tunnels considering time-varying effects according to claim 1, characterized in that The deterioration time-varying model in Step 2 includes a steel bar corrosion rate model, a steel bar strength deterioration model, and a strength reduction model of the concrete segment protective layer under long-term erosion. The relevant calculation parameter values of the shield tunnel at the service time T are obtained through the above models.

4. The seismic resilience design method for shield tunnels considering time-varying effects according to claim 1, characterized in that The specific operation of Step 3 is to design an orthogonal test according to the tunnel design parameters and their feasible region ranges obtained in Step 1 under different seismic intensities IM, and use the relevant calculation parameters after the tunnel is deteriorated by chloride ion erosion at the service time T obtained in Step 2 for numerical modeling calculations. Through fitting regression analysis, construct the function relationship between the thickness h of the lining segment, the section reinforcement ratio ρ, and the steel bar strength fy of the tunnel design parameters to be optimized and the seismic resilience Re of the tunnel, and establish a correlation model Re(T)|IM between the seismic resilience and the design parameters.

5. The seismic resilience design method for shield tunnels considering time-varying effects according to claim 1, characterized in that The specific operation of step 4 is to construct a calculation model Cost between the lining segment thickness h, cross-section reinforcement ratio ρ, and steel strength f of the tunnel design parameters considering the market prices of steel bars and concrete. y And the construction cost per unit length of the tunnel.

6. The seismic resilience design method for shield tunnels considering time-varying effects according to claim 1, characterized in that The optimization strategies in Step 6 include the equal-cost optimal solution strategy, the equal-seismic-resilience optimal solution strategy, and the Knee Point optimization strategy.

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