Method for evaluating vulnerability of underground station under influence of excavation disturbance of adjacent foundation pit

Abstract

The invention discloses a method for evaluating the vulnerability of an underground station under the influence of excavation disturbance of an adjacent foundation pit, and relates to the field of underground station structural damage evaluation.The method comprises the steps that (1) corresponding engineering geological survey reports and structural design parameters are collected for an underground station to be researched; (2) determining a probability distribution model of the maximum lateral deflection of the continuous wall; (3) establishing a finite difference numerical model of influence of adjacent foundation pit excavation on the underground station, and calculating interlayer displacement angles of the underground station under different disturbance working conditions; (4) constructing a demand model under excavation disturbance of the adjacent foundation pit, determining a threshold value of the ratio of the excavation depth to the horizontal distance of the station in each damage state based on the model, and obtaining a logarithmic standard deviation of a disturbance demand through statistical analysis; and (5) constructing a disturbance vulnerability curve of the underground station structure. According to the method, the damage probability of the underground station under different disturbance intensities can be quantitatively evaluated, and the occurrence possibility of various damage states of the underground station is effectively revealed.

Description

Technical Field

[0001] This invention relates to the field of structural damage assessment for underground stations, and more specifically to a method for assessing the vulnerability of underground stations under the influence of disturbance from adjacent foundation pit excavation. Background Technology

[0002] With the rapid development of underground space, the commercial demand for building parking lots or underground supermarkets near subway stations is increasing. Geotechnical engineering activities in adjacent areas, such as deep foundation pit excavation and surface loading, will inevitably alter the stress state of the geological environment, causing movement of the soil around nearby underground stations. This leads to deformation of surrounding building structures, accelerating the degradation of structural performance, causing potential adverse effects or even damage, and directly threatening the safe operation of subway traffic. Therefore, accurately assessing the damage evolution of adjacent structures under construction disturbance is an important issue in the field of geotechnical engineering. The standard GB 50911-2013 divides the area outside deep foundation pits into three zones based on the degree of influence: i-main influence zone, ii-minor influence zone, and iii-potential influence zone. In recent years, many scholars have explored the displacement and deformation of existing underground station structures caused by deep foundation pit excavation and have improved the classification of influence zones (Zheng Gang et al., 2016, 2017; Zhang Jinzhang, 2022).

[0003] The degree of disturbance caused by deep foundation pit excavation depends primarily on the relative position of the pit to adjacent structures and the system stiffness level of the support structure. To reduce the impact of foundation pit excavation on surrounding buildings, technical measures to control the maximum lateral deflection of diaphragm walls are typically employed during design and construction. However, most existing studies are based on deterministic parameters and rarely consider the uncertainties in the construction disturbance environment, thus limiting the applicability and reliability of the assessment results.

[0004] To address the aforementioned shortcomings, this application employs numerical simulation to assess the vulnerability of underground stations to adjacent disturbances. It fully considers the spatial relationship between deep foundation pits and nearby underground stations, and uses the cloud map method to construct a disturbance probability demand model. By incorporating structural damage assessment criteria, a damage probability function for underground stations under different disturbance intensities is established, enabling a quantitative assessment of the structural resistance to construction disturbances in underground stations. Given the high uncertainty of disturbances to adjacent underground stations caused by large-scale foundation pit excavations such as those for underground commercial centers, and the lack of systematic and scientific performance assessment methods, the risk to the safety of subway structures is significantly increased. Summary of the Invention

[0005] The purpose of this invention is to provide a method for evaluating the vulnerability of underground railway stations under the influence of disturbance from adjacent foundation pit excavation, effectively considering the uncertainty of the relative positional relationship between the foundation pit and the underground station. Through literature review, a probability distribution model for the maximum deflection deformation of diaphragm walls is determined. Combined with finite difference numerical software, a structural vulnerability analysis model incorporating the disturbance from adjacent foundation pit excavation is constructed. Based on existing standards, a damage assessment standard for underground station structures is established, enabling a quantitative evaluation of the disturbance resistance performance of underground stations. This provides technical support for subsequent optimization of foundation pit excavation design schemes and the formulation of construction safety management measures.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for evaluating the vulnerability of underground stations under the influence of adjacent foundation pit excavation disturbance, comprising the following steps:

[0007] Step 1: Based on the survey report of the proposed underground station, determine the soil cross-section, the burial depth of the underground station, and the type of the main span;

[0008] Step 2: Determine the probability distribution model of the maximum deflection deformation of the underground continuous wall during the foundation pit excavation, as well as the burial depth and column span structure type of the underground station;

[0009] Step 3: Establish a finite difference numerical model of the impact of adjacent foundation pit excavation on the underground station, and calculate the inter-story drift angle of the underground station under different disturbance conditions;

[0010] Step 4: Perform linear regression on the numerical calculation results to obtain the disturbance demand model for the excavation of the foundation pit near the station. Based on this model, determine the threshold for the ratio of excavation depth to horizontal distance from the station under each damage state, and calculate the standard deviation.

[0011] Step 5: Combining the log-normal distribution function and the damage state threshold classification standard, the vulnerability curve of the underground station under the disturbance of adjacent foundation pit excavation is obtained, thereby obtaining the probability of minor, moderate and severe damage to the underground station under different ratios of excavation depth to station horizontal distance.

[0012] Furthermore, the vulnerability function is expressed as:

[0013]

[0014] In the formula, P(·) represents the state beyond which a certain destruction state ds is exceeded. j The probability is given by H / L, which is the ratio of the excavation depth H of the foundation pit to the horizontal distance L between the continuous wall and the underground station, and Φ is the standard normal density cumulative probability function. j β is the threshold that leads to the j-th damaged state, and β is the logarithmic standard deviation, which expresses the variation of the vulnerability curve.

[0015] Optionally, step 1 includes: obtaining the stratigraphic structure and soil profile information of the study area based on the engineering geological survey report of the proposed underground station, and clarifying the distribution of physical and mechanical parameters of each soil layer; and determining the burial depth, structural form, main span size and column span arrangement characteristics of the underground station in conjunction with the structural design drawings of the station.

[0016] Optionally, step 2 includes defining the ratio H / L of the excavation depth H of the foundation pit and the horizontal distance L between the foundation pit and the underground station as a disturbance intensity index.

[0017] Furthermore, the system stiffness index EI / γ is introduced. w h 4 Describes the performance level of the support structure, where EI is the flexural stiffness of the diaphragm wall, h is the spacing between lateral supports, and γ is... w The specific weight of water;

[0018] Establish the normalized maximum lateral deflection u hm / H and system stiffness EI / γ w h 4 Relational expressions between the two:

[0019]

[0020] In the formula, p1, p2, and p3 are three fitting parameters.

[0021] Furthermore, step 2 also includes: using the Latin hypercube sampling method to sample the normalized maximum deflection u of the continuous wall. hm Nine representative sample values ​​were drawn from the log-normal distribution of / H, and the corresponding system stiffness index EI / γ was derived by combining the established relational equation. w h 4 .

[0022] Optionally, step 3 includes: using the inter-story drift angle θ as a deformation failure criterion to determine the damage state of the underground station structure, the calculation formula of which is expressed as:

[0023]

[0024] In the formula, W s H represents the horizontal displacement of the station roof relative to the floor. s This refers to the station's floor height.

[0025] Optionally, step 4 includes: using regression analysis to determine the excavation depth H of the foundation pit, the horizontal distance L between the underground station and the foundation pit, and the stiffness EI / γ of the support structure system. w h 4 A demand model for the disturbance intensity H / L of adjacent foundation pit excavation is constructed in relation to the inter-story drift angle θ of the station structure.

[0026] ln(θ) = a + bln(H / L)

[0027] In the formula, θ is the inter-story drift angle of the underground station under the disturbance of adjacent excavation, and a and b are two fitting parameters.

[0028] Furthermore, step 4 also includes: calculating the logarithmic standard deviation β of the disturbance demand by analyzing the residual between the simulation results and the regression values, which is used to characterize the uncertainty of the model.

[0029] Furthermore, the formula for calculating the standard deviation β is expressed as follows:

[0030]

[0031] In the formula, N is the total number of data points, and θ i The maximum inter-story drift angle of the underground station corresponding to each data point.

[0032] Based on the above, this invention fits the normalized maximum deflection deformation (u) of the diaphragm wall by organizing a large amount of monitoring data. hm The distribution of / H) is used to draw a sufficient number of u using Latin hypercube sampling (LHS). hm The / H data points effectively incorporate the uncertainty factors of excavation disturbance. Based on this, a structural damage probability assessment method for underground stations under adjacent excavation disturbance was established. This method reveals the damage evolution law of underground station structures under different disturbance intensities from a probabilistic perspective, providing a theoretical basis for subsequent structural safety assessment and risk control under adjacent construction conditions.

[0033] Compared with the prior art, the features and innovations of this invention are as follows:

[0034] (1) A disturbance index for excavation of foundation pits near underground stations was proposed, which can quantitatively describe the damage response characteristics of the structure under disturbance from a probabilistic perspective.

[0035] (2) This method can comprehensively consider the impact of the uncertainty of disturbance intensity on the structural response, assess the vulnerability distribution of underground stations under different construction conditions, and provide reliable support for optimized design and subsequent toughness assessment. Attached Figure Description

[0036] To clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the embodiments will be described one by one below.

[0037] Figure 1 This is a flowchart of the underground station disturbance vulnerability evaluation method of the present invention;

[0038] Figure 2The distribution law of maximum deflection deformation of diaphragm wall during foundation pit excavation is summarized for this invention;

[0039] Figure 3 The relationship between the disturbance intensity index and the damage index in Example 1;

[0040] Figure 4 This is the probability requirement model for resisting disturbance from adjacent excavation in Example 1;

[0041] Figure 5 The vulnerability curve of the underground station in Example 1 under the disturbance of excavation of the adjacent foundation pit. Detailed Implementation

[0042] To make the above-mentioned objectives, technical solutions and advantages of the present invention clearer and easier to understand, the present invention will be further explained and described below in conjunction with the accompanying drawings and specific embodiments.

[0043] A method for evaluating the vulnerability of underground stations under the influence of disturbance from adjacent foundation pit excavation includes the following steps:

[0044] Step 1: Based on the survey report of the proposed underground station, determine the characteristics of the soil cross-section, the burial depth of the underground station, and the main span type.

[0045] Step 1 specifically includes: based on the engineering geological survey report of the proposed underground station, obtaining detailed information on the stratigraphic structure, physical and mechanical properties of the soil, and cross-sectional distribution characteristics of the study area, and clarifying key parameters such as the compression modulus, cohesion, and internal friction angle of each soil layer. Simultaneously, in conjunction with the design scheme of the underground station, determining key engineering characteristics such as the station's burial depth, main span dimensions, column span arrangement, and structural form.

[0046] Step 2: Literature review to determine the probability distribution model of maximum deflection deformation of the underground continuous wall during foundation pit excavation.

[0047] Step 2 specifically includes: through research and data statistics on typical foundation pit excavation engineering cases worldwide, and after normalization processing, it was found that u hm / H follows a log-normal distribution, and its distribution is verified to be reasonable by the Kolmogorov–Smirnov (KS) test.

[0048] Based on this, the ratio H / L, representing the excavation depth H of the foundation pit and the horizontal distance L between the foundation pit and the underground station, is defined as an index of disturbance intensity. Simultaneously, the system stiffness index EI / γ is introduced. w h 4 Describe the performance level of the support structure in the foundation pit excavation system, where EI is the flexural stiffness of the diaphragm wall, h is the spacing of the lateral supports, and γ is the flexural stiffness of the diaphragm wall. w This refers to the unit weight of water.

[0049] By designing different combinations of working conditions and conducting systematic numerical simulation analysis, the normalized maximum lateral deflection u of the continuous wall was established. hm / H and system stiffness EI / γ w h 4 The relational expression has the following specific form:

[0050]

[0051] In the formula, p1, p2, and p3 are three fitting parameters.

[0052] Step 3: Establish a finite difference numerical model of the impact of adjacent foundation pit excavation on the underground station.

[0053] Step 3 specifically includes: developing and running a batch calculation program based on the MATLAB platform that automatically calls the numerical simulation software FLAC3D. This program can calculate the foundation pit depth H, horizontal distance L, and system stiffness EI / γ. w h 4 The automatic input of disturbance condition parameters, model calling, calculation control, and result extraction significantly improve the efficiency and stability of the simulation.

[0054] Using this program, a systematic analysis of the disturbance response of the underground station structure under the action of adjacent foundation pit excavation was carried out. The key response indicators, such as the inter-story drift angle θ of the main station structure under various working conditions, were extracted, providing reliable data support for the subsequent establishment of probabilistic demand models and vulnerability assessment.

[0055] In this invention, the inter-story drift angle θ is used as a deformation failure criterion to determine the damage state of the underground station structure. The inter-story drift angle can effectively reflect the relative deformation between different stories under disturbance, thereby revealing the degree of structural damage. Its calculation formula is defined as follows:

[0056]

[0057] In the above formula: W s H represents the horizontal displacement of the station roof relative to the floor. s The station floor height is given. Zhuang Haiyang et al., regarding the elastoplastic working state and seismic resistance of two-story, three-span frame-type underground subway station structures, provided a reference value for the inter-story drift angle as a damage indicator:

[0058] Table 1. Values ​​of Inter-level Displacement Angle Index for Underground Stations

[0059]

[0060] Step 4: Perform linear regression on the results of a large number of numerical calculations to obtain the disturbance demand model for the excavation of the foundation pit near the station, and further calculate the standard deviation.

[0061] Step 4 specifically includes: based on the numerical simulation results, using regression analysis, the excavation depth H of the foundation pit, the horizontal distance L between the underground station and the foundation pit, and the stiffness EI / γ of the support structure system are analyzed. w h 4 By correlating disturbance factors with response indicators such as the inter-story drift angle θ of the station structure, a demand model for the disturbance intensity H / L of the adjacent foundation pit excavation is constructed.

[0062] This model can quantitatively characterize the intensity of disturbances experienced by underground stations under different operating conditions, revealing the intrinsic relationship between disturbance intensity and structural response. Simultaneously, through statistical analysis of the residuals between simulation results and regression predictions, the logarithmic standard deviation β of the disturbance demand is calculated to reflect the model's uncertainty, providing key parameter support for the subsequent construction of a probability-based vulnerability function.

[0063] ln(θ) = a + bln(H / L)

[0064] In the formula, θ is the inter-story drift angle of the underground station under the disturbance of adjacent excavation, a and b are two fitting parameters, and the ratio of excavation depth to horizontal distance H / L is the disturbance intensity index.

[0065] The formula for calculating the standard deviation β is as follows:

[0066]

[0067] In the formula: N is the total number of data points, θ i The maximum inter-story drift angle of the underground station corresponding to each data point.

[0068] Step 5: Combining the log-normal distribution function and the damage state threshold classification standard, the vulnerability curve of the underground station under the disturbance of the adjacent foundation pit excavation is further obtained, thereby obtaining the probability of the underground station experiencing minor, moderate, and severe damage under different ratios of excavation depth to station horizontal distance.

[0069] Step 5 specifically includes: based on the underground station disturbance probability demand model established in Step 4, and combining the damage judgment criteria for the station structure with the current specifications for the threshold of each damage state, further constructing the vulnerability curve of the underground station under the disturbance of adjacent foundation pit excavation. This vulnerability curve can quantitatively reflect the probability distribution characteristics of the underground station structure reaching or exceeding a specific damage state under different disturbance intensity levels.

[0070] Drawing on relevant research findings, it is generally accepted that the deformation response of underground structures under adjacent excavation disturbance follows a log-normal distribution. Based on this assumption, the vulnerability function can be described using a log-normal distribution function, clarifying the statistical relationship between the disturbance intensity index H / L and the probability of structural damage, thus providing a scientific basis for risk assessment and safety management of underground stations. Therefore, the vulnerability function of an underground station under adjacent excavation disturbance can be expressed as:

[0071]

[0072] Where P(·) represents the state beyond a certain destruction state ds j The probability is given by H / L, which is the ratio of the excavation depth H of the foundation pit to the horizontal distance L between the continuous wall and the underground station, and Φ is the standard normal density cumulative probability function. j β is the threshold that leads to the j-th damaged state, and β is the logarithmic standard deviation, which expresses the variability of the vulnerability curve.

[0073] Example 1

[0074] This embodiment provides a method for evaluating the vulnerability of underground stations under the influence of disturbance from adjacent foundation pit excavation. The specific implementation process is as follows: Figure 1 As shown, it includes the following steps:

[0075] Step 1: Based on the geological survey report of the proposed underground station, determine the soil cross-section, the burial depth of the underground station, and the type of the main span, etc. Specifically, based on the engineering geological survey report of the proposed underground station, obtain detailed information on the stratigraphic structure, physical and mechanical properties of the soil, and cross-sectional distribution characteristics of the study area, and clarify key parameters such as the compression modulus, cohesion, and internal friction angle of each soil layer. Simultaneously, in conjunction with the design scheme of the underground station, determine key engineering characteristics such as the station's burial depth, main span dimensions, column span arrangement, and structural form.

[0076] An underground station (single span) in a certain city is 20m long, 16m high, and 3.2m deep. The station's frame structure and soil are simulated using solid elements. The underground station's frame columns are C50, while the side walls, top slab, bottom slab, middle slab, and longitudinal beams are all C35. The concrete is simulated using elastic constitutive models, the soil is simulated using Mohr-Coulomb constitutive models, the underground continuous wall is simulated using Liner elements, and the internal support of the foundation pit excavation is simulated using Beam elements. The specific parameter values ​​are shown in the geological survey report, as shown in Tables 2 and 3.

[0077] Table 2 Physical and mechanical parameters of the station and its supporting structure

[0078]

[0079] Table 3 Soil Types and Parameter Distribution

[0080]

[0081] Step 2: Literature review to determine the probability distribution model of maximum deflection deformation of diaphragm walls in foundation pit excavation. Specifically, through a survey and statistical analysis of typical foundation pit excavation engineering cases worldwide, a large amount of data on the relationship between the foundation pit excavation depth H and the maximum lateral deflection u of the diaphragm wall was extracted. hm The measured data. After normalization, it was found that u hm / H follows a log-normal distribution, as shown in the attached figure. Figure 2 As shown, the reasonableness of its distribution is verified by the Kolmogorov–Smirnov (KS) test.

[0082] Based on this, the ratio H / L, representing the excavation depth H of the foundation pit and the horizontal distance L between the foundation pit and the underground station, is defined as an index of disturbance intensity. Simultaneously, the system stiffness index EI / γ is introduced. w h 4 Describe the performance level of the support structure in the foundation pit excavation system, where EI is the flexural stiffness of the diaphragm wall, h is the spacing of the lateral supports, and γ is the flexural stiffness of the diaphragm wall. w This represents the unit weight of water. This index can be used to indirectly quantify the control capability of support stiffness on the deformation response of adjacent underground stations.

[0083] By designing different combinations of working conditions and conducting systematic numerical simulation analysis, the normalized maximum lateral deflection u of the continuous wall was established. hm / H and system stiffness EI / γ w h 4 The relational expression has the following specific form:

[0084]

[0085] In the formula, p1, p2, and p3 are three fitting parameters. The fitting coefficients obtained by different combinations of working conditions are 5.516, -2.159, and -0.148, respectively.

[0086] Step 3: Establish a finite-difference numerical model of the impact of adjacent foundation pit excavation on the underground station. Specifically, based on the MATLAB platform, a batch calculation program that can automatically call the numerical simulation software FLAC3D was developed and run. This program realizes the calculation of foundation pit depth H, horizontal distance L, and system stiffness EI / γ. w h 4 Automatic input of parameters for disturbance conditions, model calling, calculation control and result extraction.

[0087] Based on FLAC3D numerical simulation software, a disturbance model for the excavation of the foundation pit adjacent to the underground station was established. The specific excavation steps are as follows: ① Stress equilibrium; ② Station excavation and diaphragm wall construction; ③ Construction of the first support, excavating to 4m below the ground surface; ④ Construction of the second support, excavating to 8m below the ground surface; ⑤ Construction of the third support, excavating to 12m below the ground surface; ⑥ Construction of the fourth support, excavating to 16m below the ground surface. Through extensive numerical calculations, the relationship between the inter-story drift angle of the underground station and the ratio of the foundation pit depth to the horizontal distance was obtained, as shown in the attached figure. Figure 3 As shown. For all working conditions, the inter-story drift angle of the underground station increases with the increase of the ratio of the pit depth to the horizontal distance; with the same H / L, the maximum deflection of the diaphragm wall has a greater impact on the inter-story drift angle of the station.

[0088] Nine maximum lateral displacement data points of the diaphragm wall were randomly selected using Latin hypercube sampling, with sample points ranging from 0.158% to 0.912%. The corresponding system stiffness EI / γ was then calculated. w h 4 Where EI is the stiffness of the diaphragm wall, and γ w Where is the specific weight of water, and h is the average vertical spacing of the supports. Adjust the ratio H / L of the pit depth to the horizontal distance, and input it into the finite difference model using a Matlab program.

[0089] Using this program, the system conducted a disturbance response analysis of the underground station structure under the action of adjacent foundation pit excavation. It focused on extracting key response indicators such as the inter-story drift angle θ of the main station structure under various working conditions, providing reliable data support for the subsequent construction of the disturbance probability demand model and vulnerability assessment.

[0090] Step 4: Linear regression is performed on the results of a large number of numerical calculations to obtain the disturbance demand model for the excavation of the foundation pit near the station, and the standard deviation β is further calculated. Specifically, the cloud map method is used to perform regression analysis on the data points obtained from a large number of numerical simulations. Logarithmic analysis of the ratio of inter-story drift angle to foundation pit depth to horizontal distance is set, and linear regression fitting is performed to obtain the probabilistic disturbance demand model for the station, as shown in the attached figure. Figure 4 As shown. Furthermore, the standard deviation β is calculated to reflect the uncertainty of the model, providing key parameter support for the subsequent construction of a probability-based vulnerability function.

[0091] ln(θ) = a + bln(H / L)

[0092] In the formula, θ is the inter-story drift angle of the underground station under the disturbance of adjacent excavation, and a and b are two fitting parameters with fitting coefficients of 1.235 and -8.912, respectively, as shown in the attached figure. Figure 4 As shown.

[0093] Step 5: Combining the log-normal distribution function and the damage state threshold classification standard, the vulnerability curve of the underground station under the disturbance of adjacent foundation pit excavation is further obtained. Specifically, based on the underground station disturbance probability demand model established in Step 4, and combining the damage judgment criteria of the station structure and the classification of various damage state thresholds in the current specifications, Table 1 gives the values ​​of the threshold related to the inter-story drift angle of the underground station, and further constructs the vulnerability curve of the underground station under the disturbance of adjacent foundation pit excavation. This vulnerability curve can quantitatively reflect the probability distribution characteristics of the underground station structure reaching or exceeding a specific damage state under different disturbance intensity levels, such as... Figure 5 As shown.

[0094] Drawing on relevant research findings, it is generally accepted that the deformation response of underground structures under adjacent excavation disturbance follows a log-normal distribution. Based on this assumption, the vulnerability function can be described using a log-normal distribution function, clarifying the statistical relationship between the disturbance intensity index H / L and the probability of structural damage, thus providing a scientific basis for risk assessment and safety management of underground stations. Therefore, the vulnerability function of an underground station under adjacent excavation disturbance can be expressed as:

[0095]

[0096] Where P(·) represents the state beyond a certain destruction state ds j The probability is given by H / L, which is the ratio of the excavation depth H of the foundation pit to the horizontal distance L between the continuous wall and the underground station, and Φ is the standard normal density cumulative probability function. j β is the threshold that leads to the j-th damaged state, and β is the logarithmic standard deviation, which expresses the variability of the vulnerability curve.

[0097] The threshold values ​​(H / L) for the ratio of pit depth to horizontal distance corresponding to different damage states were obtained using the station probabilistic disturbance demand model. j (j represents different damage states), and the standard deviation β is calculated using the following formula:

[0098]

[0099] In the above formula: N is the total number of data points, θ i The maximum inter-story drift angle of the underground station corresponding to each data point.

[0100] The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described herein. Although the present invention has been described in detail with reference to the above embodiments, the present invention is not limited to the specific embodiments described above. Therefore, any modifications or equivalent substitutions to the present invention, as well as all technical solutions and improvements that do not depart from the spirit and scope of the invention, are covered within the scope of the claims of the present invention.

Claims

1. A method for evaluating the vulnerability of underground stations under the influence of disturbance from adjacent foundation pit excavation, characterized in that, Includes the following steps: Step 1: Based on the survey report of the proposed underground station, determine the soil cross-section, the burial depth of the underground station, and the type of the main span; Step 2: Determine the probability distribution model of the maximum deflection deformation of the underground continuous wall during the foundation pit excavation, as well as the burial depth and column span structure type of the underground station; Step 3: Establish a finite difference numerical model of the impact of adjacent foundation pit excavation on the underground station, and calculate the inter-story drift angle of the underground station under different disturbance conditions; Step 4: Perform linear regression on the numerical calculation results to obtain the disturbance demand model for the excavation of the foundation pit near the station. Based on this model, determine the threshold for the ratio of excavation depth to horizontal distance from the station under each damage state, and calculate the standard deviation. Step 5: Combining the log-normal distribution function and the damage state threshold classification standard, the vulnerability curve of the underground station under the disturbance of adjacent foundation pit excavation is obtained, thereby obtaining the probability of minor, moderate and severe damage to the underground station under different ratios of excavation depth to station horizontal distance.

2. The method for evaluating the vulnerability of underground stations under the influence of adjacent foundation pit excavation disturbance as described in claim 1, characterized in that, The vulnerability function is expressed as follows: In the formula, P(·) represents the state beyond which a certain destruction state ds is exceeded. j The probability is given by H / L, which is the ratio of the excavation depth H of the foundation pit to the horizontal distance L between the continuous wall and the underground station, and Φ is the standard normal density cumulative probability function. j The threshold that leads to the j-th disruptive state is β, where β is the logarithmic standard deviation.

3. The method for evaluating the vulnerability of underground stations under the influence of adjacent foundation pit excavation disturbance as described in claim 1, characterized in that, Step 1 includes: obtaining the stratigraphic structure and soil profile information of the study area based on the engineering geological survey report of the proposed underground station, and clarifying the distribution of physical and mechanical parameters of each soil layer; and determining the burial depth, structural form, main span size and column span arrangement characteristics of the underground station in conjunction with the structural design drawings of the station.

4. The method for evaluating the vulnerability of underground stations under the influence of adjacent foundation pit excavation disturbance as described in claim 1, characterized in that, Step 2 includes defining the ratio H / L of the excavation depth H of the foundation pit and the horizontal distance L between the foundation pit and the underground station as the disturbance intensity index.

5. The method for evaluating the vulnerability of underground stations under the influence of adjacent foundation pit excavation disturbance as described in claim 4, characterized in that, Introducing the system stiffness index EI / γ w h 4 Describes the performance level of the support structure, where EI is the flexural stiffness of the diaphragm wall, h is the spacing between lateral supports, and γ is... w The specific weight of water; Establish the normalized maximum lateral deflection u hm / H and system stiffness EI / γ w h 4 Relational expressions between the two: In the formula, p1, p2, and p3 are three fitting parameters.

6. The method for evaluating the vulnerability of underground stations under the influence of adjacent foundation pit excavation disturbance as described in claim 5, characterized in that, Step 2 further includes: using the Latin hypercube sampling method to obtain the normalized maximum deflection u of the continuous wall. hm Nine representative sample values ​​were drawn from the log-normal distribution of / H, and the corresponding system stiffness index EI / γ was derived by combining the established relational equation. w h 4 .

7. The method for evaluating the vulnerability of underground stations under the influence of adjacent foundation pit excavation disturbance as described in claim 1, characterized in that, Step 3 includes: using the inter-story drift angle θ as a deformation failure criterion to determine the damage state of the underground station structure, the calculation formula of which is expressed as: In the formula, W s H represents the horizontal displacement of the station roof relative to the floor. s This refers to the station's floor height.

8. The method for evaluating the vulnerability of underground stations under the influence of adjacent foundation pit excavation disturbance as described in claim 1, characterized in that, Step 4 includes: using regression analysis to determine the excavation depth H, the horizontal distance L between the underground station and the excavation pit, and the stiffness EI / γ of the support structure system. w h 4 A demand model for the disturbance intensity H / L of adjacent foundation pit excavation is constructed in relation to the inter-story drift angle θ of the station structure. ln(θ) = a + bln(H / L) In the formula, θ is the inter-story drift angle of the underground station under the disturbance of adjacent excavation, and a and b are two fitting parameters.

9. The method for evaluating the vulnerability of underground stations under the influence of adjacent foundation pit excavation disturbance as described in claim 7, characterized in that, Step 4 further includes: calculating the logarithmic standard deviation β of the disturbance demand by analyzing the residual between the simulation results and the regression values, which is used to characterize the uncertainty of the model.

10. The method for evaluating the vulnerability of underground stations under the influence of adjacent foundation pit excavation disturbance as described in claim 9, characterized in that, The formula for calculating the standard deviation β is as follows: In the formula, N is the total number of data points, and θ i The maximum inter-story drift angle of the underground station corresponding to each data point.

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