Lining construction monitoring method for extra-large-section underground excavation station meeting TBM station crossing

Abstract

The invention discloses a lining construction monitoring method for an extra-large-section underground excavation station meeting TBM station crossing, and belongs to the technical field of TBM construction safety monitoring. The method comprises the steps that when a lining section is constructed, a strain sensor is pre-buried, and data are collected to obtain a time-strain curve of concrete; establishing a time-varying mechanical property prediction model based on the data of the constructed lining section; a TBM system planned station crossing moment and a corresponding new form removal lining section are obtained, and a finite element model is established to simulate TBM load movement to obtain a main tensile stress extreme value; calculating a stress compensation value of the new form stripping lining section based on the time-strain curve, and superposing the stress compensation value and the main tensile stress extreme value to obtain a predicted total stress; the TBM passage plan is decided by comparing the predicted total stress and the predicted tensile strength, real-time monitoring of the stress state of the early-age lining section, time-varying performance prediction and load coupling analysis are achieved, and the technical blank of quantitative safety evaluation of the concrete structure in TBM dynamic station crossing is filled.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of TBM construction safety monitoring. More particularly, the present application relates to a lining construction monitoring method for a large-section excavated station that satisfies TBM passing. BACKGROUND

[0002] In large-scale urban underground transportation systems, a tunnel boring machine (TBM) needs to pass through a large-scale excavated station structure after completing the tunnel excavation, which is called TBM passing. However, this working condition faces a series of unique technical challenges. First, the standard lining section is usually constructed by a lining trolley in a separate warehouse, and the demolding time is usually 12 to 48 hours after concrete pouring, at which time the concrete strength only reaches 20%-50% of the design value, and the tensile and compressive capacity is limited. Although the direct force component of TBM passing is the bottom plate structure and the guide table structure, the passing process of the TBM system will also affect the lining section. Second, the newly demolded lining concrete is still in the peak period of hydration heat release, and the internal temperature can reach 30-50℃, which will cause significant internal tensile stress of the concrete. At this time, if the TBM system passes, it is very likely that the newly demolded or demolded lining section will be damaged by the combined action of the mechanical stress and the internal tensile stress.

[0003] At present, since the TBM system disassembly, transportation preparation and station lining construction are all complex key processes, and their progress is subject to various site uncertainties, both cannot lock the exact execution date in the planning stage of the construction period. Only when the TBM system is assembled or disassembled on site and the passing preparation work is completed, a passing notice can be sent to the lining section construction party in a short lead time. In response to the complex working conditions of the TBM system passing through the station multiple times and intermittently during the construction of a large station, engineering practice mainly relies on two measures. One is to determine the TBM system passing based on the fixed age, and the construction party sets a unified and long enough minimum maintenance age for all lining sections according to conservative experience, to ensure that the concrete of all lining sections reaches a safe strength threshold when the TBM passes. The other is to use a temporary structure reinforcement scheme. On the path planned to be passed by the TBM, for the lining sections with short age or considered to be weak, additional steel supports are erected, temporary columns are added, or additional grouting is performed between the lining and the surrounding rock, to artificially share and transfer the influence of the TBM passing load on the lining section, so as to reduce its effect on the newly formed structure.

[0004] However, the aforementioned traditional measures have significant limitations in dealing with dynamic, overlapping construction. During the construction cycle of large railway station lining sections, multiple TBM systems may pass through, or the same TBM system may pass through in batches due to the segmented transportation of TBMs after dismantling. This makes the fixed-age-based TBM transit strategy too rigid, requiring strict waiting for each segment of the TBM system to pass through, resulting in a long overall cumulative delay.

[0005] Currently, the management of TBM system passage issues in subway station construction is still in a relatively crude manner. The existing technical system lacks the ability to dynamically assess the actual stress state of lining sections of different ages at specific passage times. It cannot combine the time-varying laws of material properties, measured structural response and dynamic construction plan. Every TBM passage decision is blind or conservative, and cannot achieve a precise balance between safety and efficiency.

[0006] Therefore, there is a need to propose a new method for monitoring lining construction that meets the requirements of TBM transit. This method provides a quantitative scientific basis for determining whether the lining section is structurally safe when the TBM system transits and when the TBM system can transit. Under the premise of ensuring structural safety, it maximizes the optimization of the critical path schedule and resource allocation. Summary of the Invention

[0007] This invention provides a monitoring method for the lining construction of extra-large cross-section tunnel stations that meet the requirements of TBM passing through the station. It provides a quantitative scientific basis for whether the lining layer is safe when the TBM system passes through the station and when the TBM system can pass through the station. Under the premise of ensuring structural safety, it optimizes the critical path schedule and resource allocation to the maximum extent.

[0008] To achieve these objectives and other advantages according to the present invention, a method for monitoring the lining construction of extra-large cross-section cut-and-cover railway stations with TBM passage is provided, comprising the following steps: S1: After the main body of the station is excavated and initially supported, the station base slab structure and guide platform structure are constructed in sequence. S2. Starting from one end of the self-guided platform structure, construct the lining section segment by segment towards the other end, and pre-embed strain sensors inside each lining section. S3. Continuously collect the readings of the strain sensors in each lining section to obtain the time-strain curve of the concrete in the lining section under the action of no TBM passing load. S4. Based on the test data of the test blocks cured under the same conditions corresponding to the constructed lining section, establish a time-varying mechanical property prediction model for concrete. The time-varying mechanical property prediction model takes the concrete age as input and concrete material parameters including the predicted tensile strength as output. S5. Obtain the planned time of the TBM system's passage and determine the lining segment in the newly demolded state at that time. Establish a finite element analysis model including the surrounding rock, bottom plate structure, guide platform structure and lining segment. Based on the time-varying mechanical performance prediction model, define the concrete material parameters of the newly demolded lining segment at the planned time of passage. By simulating the process of the load movement of the TBM system, obtain the extreme value of the principal tensile stress generated in the newly demolded lining segment. S6. Select the time-strain curve established by the constructed lining section with the same material and curing conditions as the newly demolded lining section as the reference curve, calculate the stress compensation value of the newly demolded lining section at the planned time of passing the station, and superimpose the stress compensation value with the extreme value of the principal tensile stress to obtain the predicted total stress of the newly demolded lining section. S7. Compare the predicted total stress of the newly demolded lining section with its predicted tensile strength at the planned time of passage. If the predicted total stress exceeds the predicted tensile strength, it is determined that the lining section does not meet the safety conditions for TBM passage. Based on the comparison results, the passage plan of the TBM system and the demolding plan of the lining section are decided.

[0009] Preferably, step S5 includes the following steps: S51. Establish a finite element model including surrounding rock, structural base plate, guide platform structure and lining section, so that the lining section that is latest demolded at the time when the TBM system is scheduled to pass through the station and its adjacent lining section constitute the core analysis area, and extend the core analysis area along both sides of the TBM system's travel route by a set length to form the load application area. S52. Based on the time-varying mechanical performance prediction model, define the concrete material parameters of each lining segment in the core analysis area at the planned time of TBM system passage. S53. Based on the actual axle load distribution of the most unfavorable load segment in the TBM system, a load simulation window is defined on the guide platform structure model. According to the empty push step size of the TBM system, the load simulation window is discretized on the guide platform structure model. A static finite element analysis is performed once for each discrete position to simulate the entire process of the most unfavorable load segment stepping through the core analysis area. S54. Collect the maximum value of concrete tensile stress in each lining section within the core analysis area of ​​all static finite element analyses as the extreme value of principal tensile stress in that lining section.

[0010] Preferably, the finite element model on one side of the core analysis area includes the completed lining section, while the finite element model on the other side of the core analysis area consists only of the surrounding rock, the structural base plate, and the guide platform structure. The set length extending on each side of the core analysis area is greater than or equal to the length of the load simulation window.

[0011] Preferably, the load-bearing weight of each traveling device in the TBM system is obtained, and at least two groups of adjacent traveling devices with the largest total load-bearing weight are selected. The area covered by these two groups is taken as the most unfavorable load segment. The length of the most unfavorable load segment is greater than the length of the lining segment. The concentrated load of all traveling devices in the most unfavorable load segment is equivalently transformed into several segments of uniformly distributed line loads acting on the guide platform structure model in the finite element model. The load simulation window is a fixed load mode composed of these segments of uniformly distributed line loads, wherein the action length of a single uniformly distributed line load is equal to the center distance between the first and last traveling wheels in the corresponding traveling device.

[0012] Preferably, the concrete material parameters include predicted compressive strength, predicted tensile strength, and predicted elastic modulus, and the expression of the time-varying mechanical property prediction model is: in, t Concrete age ， For concrete at age t The predicted parameters for weather conditions are shown, with the subscript 'i' used to distinguish different concrete material parameters. These are the design standard values ​​for the corresponding parameters at 28 days of age. s i The model development coefficients are the concrete material parameters confirmed by test blocks cured under the same conditions.

[0013] Preferably, the cross-section of the lining section is divided into five structural zones: the left arch starting zone, the left arch shoulder zone, the arch crown zone, the right arch shoulder zone, and the right arch starting zone. Strain sensors are independently installed in each structural zone to monitor and obtain the time-strain curve of the concrete in that structural zone. In step S5, for each newly demolded lining segment, the extreme values ​​of principal tensile stress calculated by the finite element analysis model at the locations corresponding to the five structural partitions are extracted; In step S6, for each structural partition, the stress compensation value is calculated based on the reference curve of the structural partition and superimposed with the corresponding principal tensile stress extreme value to obtain the predicted total stress of the structural partition. In step S7, if the predicted total stress of any structural section exceeds its corresponding predicted tensile strength, then the lining section is determined not to meet the safety conditions for TBM passage.

[0014] Preferably, in step S6, the method for selecting the reference curve includes the following steps: A1. Obtain the early time-strain monitoring sequence of the newly demolded lining section from the initial setting time to the current decision time, and record it as the measured sequence. e n (t) Retrieve from the database jFor each constructed lining section, the early time-strain sequence within the same time period is denoted as a candidate sequence. e c，j (t) ; A2. Calculate the measured sequences respectively. e n (t) With each candidate sequence e c，j (t) The goodness of fit, with the coefficient of determination R j 2 As a quantitative similarity indicator; A3, Select R j 2 The complete time-strain curve of the constructed lining section corresponding to the highest candidate sequence is determined as the reference curve for calculating stress compensation values.

[0015] Preferably, the TBM system's access plan and the lining section formwork removal plan are determined based on the following: (a) If, at the scheduled time of station crossing, the predicted total stress of the latest demolded lining section and the adjacent lining section does not exceed the corresponding predicted tensile strength, the TBM system will cross the station at the originally scheduled time. (b) If, at the scheduled time of the station crossing, the predicted total stress of the latest demolded lining segment exceeds its predicted tensile strength and the demolding process has not yet been carried out at the current time, while the adjacent lining segment meets the stress conditions, then the demolding process of the latest demolded lining segment shall be stopped until the TBM system passes through the station at the originally scheduled time. (c) If, at the planned transit time, the predicted total stress of the latest demolded lining segment exceeds its predicted tensile strength and the demolding has already occurred, the finite element analysis shall be performed again to determine the corrected transit time of the TBM system, provided that the latest demolded lining segment meets the stress conditions at the planned transit time of the TBM system. The demolding process for the next lining segment shall be stopped until the TBM system completes the transit according to the corrected transit time.

[0016] Preferably, the strain sensor is one or more FRP bars with embedded grating sensors. The FRP bars are arranged in parallel between the circumferential main bars of the lining section and fixed to the steel reinforcement skeleton.

[0017] Preferably, the recording of the time-strain curve begins at a unified strain monitoring reference point, which is defined as the initial setting time of the concrete test block poured in the same batch as the lining section. At the strain monitoring reference point, the readings of all grating sensors on the FRP reinforcement are initialized.

[0018] The present invention has at least the following beneficial effects: First, this invention can accurately quantify the actual safety status of lining sections of different ages at the planned time of TBM system passage, changing the traditional conservative decision-making mode that relies on fixed maintenance cycles. This enables the TBM system to achieve precise passage while ensuring structural safety, avoiding equipment idle waiting and improving the construction efficiency and resource utilization of critical lines in subway construction.

[0019] Secondly, this invention constructs a comprehensive construction monitoring system covering material time-varying characteristics, environmental effects, and mechanical loads, solving the technical problem of difficulty in accurately assessing the stress state under the coupling effect of complex time-varying effects and external loads after concrete demolding, and providing a full-process, refined safety guarantee for lining section structures that cannot be achieved by traditional methods.

[0020] Third, this invention avoids unnecessary temporary structural investment and process interference through accurate condition assessment, reducing direct construction costs. At the same time, by maximizing the reduction of the TBM system's waiting time at stations, it effectively controls indirect costs caused by project delays, achieving the optimal balance between long-term structural safety and overall project economic benefits.

[0021] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a large-section station cross-section in one technical solution of the present invention; Figure 2 This is a plan view of a large-section station in one technical solution of the present invention; Figure 3 This is a schematic diagram of a load simulation window in one technical solution of the present invention; Figure 4 This is a schematic diagram of the structural zoning of the lining section and the setting of strain sensors in one technical solution of the present invention. Detailed Implementation

[0023] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0024] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0025] It should be noted that, unless otherwise specified, the experimental methods described in the following embodiments are conventional methods, and the reagents and materials mentioned are commercially available. In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "setting" should be interpreted broadly. For example, they can refer to fixed connection or setting, detachable connection or setting, or integral connection or setting. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. The terms "lateral," "longitudinal," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0026] This invention provides a method for monitoring the lining construction of extra-large cross-section cut-and-cover railway stations that accommodate TBMs, comprising the following steps: S1: After the main excavation and initial support of the station are completed, the station base slab structure and guide platform structure are constructed in sequence. Specifically, after the initial support is completed, the integrated grounding, the bedding layer, the waterproof layer and the base slab structure are completed through layered construction. The integrated grounding system provides reliable grounding protection for the station's electromechanical equipment, the bedding layer provides a flat working surface for the superstructure, the waterproof layer forms a continuous waterproof barrier, and the base slab structure serves as the main vertical load-bearing component of the station. The above-mentioned node processes are implemented in accordance with the design drawings and specifications provided by the design institute.

[0027] The guide platform structure built on the base plate structure is used to provide a stable travel track and load transfer path for the TBM system and the supporting construction equipment of the lining section, such as... Figure 1 As shown, the guide platform structure consists of two parts. The centrally located TBM guide platform is used to support the TBM system's traveling device, while the symmetrically arranged traveling guide platforms on both sides provide moving tracks for the rebar trolley and the lining trolley, respectively. The TBM system passes under the rebar trolley or the lining trolley without interfering with each other. The reinforcement, track installation, and other process of the guide platform structure are carried out in accordance with the design drawings and specifications provided by the design institute.

[0028] S2. Starting from one end of the self-guiding platform structure, construct the lining sections segment by segment towards the other end. Pre-embed strain sensors inside each lining section, such as... Figure 2 As shown, the construction process of the station lining section adopts segmented flow operation. After the waterproof layer is completed, the steel reinforcement trolley moves along the tunnel axis from the large mileage to the small mileage direction to complete the steel reinforcement skeleton binding and strain sensor installation of each lining section. Then the lining trolley follows to pour concrete.

[0029] Strain sensors can be selected using resistance strain gauges as sensing elements. When using resistance strain gauges, firstly, the surface of the predetermined monitoring points of the circumferential main reinforcement is ground smooth using an angle grinder. The strain gauges are then attached using epoxy resin adhesive, aligning them with the axis of the circumferential reinforcement. After attachment, the strain gauges are fully sealed with silicone rubber. The connected signal wires are bundled and fixed along the reinforcement skeleton and centrally introduced into a dedicated junction box. The junction box is sealed with moisture-proof filler. The placement of the strain sensors should fully cover the cross-sectional area of ​​the lining section. Before the lining trolley is positioned, the strain sensor wiring must be checked. Operating openings should be specifically provided on the formwork of the lining trolley for the passage of signal wires. During the demolding operation of the lining section, priority should be given to releasing the formwork constraints in the junction box area to ensure that the signal wires are not damaged.

[0030] S3. Continuously collect the readings of the strain sensors in each lining section to obtain the time-strain curve of the concrete in the lining section under the action of no TBM load. Specifically, the recording of the time-strain curve begins at a unified monitoring reference point, which is defined as the initial setting time of the concrete test block poured in the same batch as the lining section. At this moment, an initialization operation is performed on the readings of all strain sensors in the lining section that has not yet been demolded, thereby ensuring that all data are recorded from the same mechanical zero point. The time-strain curve collected by the strain sensors includes the combined effects of concrete hydration heat release, shrinkage, and creep.

[0031] The time-strain curve comprises two stages. The first stage is from the initial setting of the concrete to formwork removal. During this stage, the self-weight and construction load of the lining section are entirely borne by the lining trolley formwork system. The concrete is in a stable stress state with fully constrained boundaries and can be considered unaffected by external construction loads. At this time, the sensors mainly record the autogenous stress and strain generated within the concrete due to time-varying effects such as hydration heat release and shrinkage. The second stage is from formwork removal to the TBM's transit (or long-term monitoring if there is no transit plan). After formwork removal, the lining section, as a complete thin-walled arch shell, begins to work together with the guide platform, base plate, and surrounding rock. At this time, the strain monitoring data includes three main components: elastic strain caused by the structure's self-weight, temperature strain caused by hydration heat, and time-varying strain caused by material shrinkage and early creep. Therefore, the complete time-strain curve records the entire process from initial setting, through formwork removal, temperature rise, peak temperature, to cooling and shrinkage.

[0032] S4. Based on the test data of the test blocks cured under the same conditions corresponding to the constructed lining section, establish a time-varying mechanical property prediction model for concrete. The time-varying mechanical property prediction model takes the age of concrete as input and outputs concrete material parameters including the predicted tensile strength. Specifically, the time-varying mechanical property prediction model is a mathematical relationship model used to accurately reflect the development law of concrete tensile strength, compressive strength and elastic modulus with age. This model can be obtained by calibrating the parameters of existing mature prediction models (such as CEB-FIP model and ACI 209 model) to adapt them to the material characteristics of the concrete used in the current project.

[0033] In one technical solution, the concrete material parameters include predicted compressive strength, predicted tensile strength, and predicted elastic modulus, and the expression of the time-varying mechanical property prediction model is as follows: in, t The age of the concrete. These are the predicted parameter values ​​for concrete at age t days. The subscript i is used to distinguish different concrete material parameters. These are the design standard values ​​for the corresponding parameters at 28 days of age. s i These are the model development coefficients, determined by testing concrete material parameters under the same curing conditions. s i The dimensionless values ​​were determined by fitting experimental data from test blocks cured under the same conditions. The specific fitting method is as follows: At the construction site, concrete test blocks poured in the same batch and cured under the same conditions as the lining structure were placed, and mechanical property tests were conducted at specified ages (e.g., 1d, 3d, 7d, 14d, 28d) to obtain measured data sequences of compressive strength, tensile strength, and modulus of elasticity. Subsequently, using MATLAB scientific computing software, the three datasets of compressive strength-age, tensile strength-age, and modulus of elasticity-age were imported separately. The `fit` function or curve fitting toolbox in MATLAB was called, and the expression of the aforementioned time-varying mechanical property prediction model was selected as the custom fitting equation. Nonlinear regression analysis was performed on each dataset. This process automatically optimizes the calculation and independently solves for the three model development coefficients that minimize the error between the fitted curve and the experimental data. The obtained coefficients accurately reflect the strength and modulus growth trajectory under the specific concrete mix proportion and curing environment of this project, thus providing precise time-varying material parameter inputs for finite element analysis.

[0034] S5. Obtain the planned transit time of the TBM system and determine the lining segment in the newly demolded state at that time. Establish a finite element analysis model including the surrounding rock, bottom plate structure, guide structure, and lining segment. Based on the time-varying mechanical performance prediction model, define the concrete material parameters of the newly demolded lining segment at the planned transit time. By simulating the process of the TBM system load movement, obtain the extreme values ​​of the principal tensile stress generated in the newly demolded lining segment. Specifically, finite element analysis can accurately consider the complex interaction between the surrounding rock and the structure, the spatial stress characteristics of the thin-shell lining structure, and the time-varying effect of the TBM moving load, making it an effective means to solve such complex engineering mechanics problems. A three-dimensional calculation model can usually be established using general-purpose finite element analysis software such as ANSYS, ABAQUS, or MIDAS.

[0035] In one technical solution, step S5 includes the following steps: S51. Establish a finite element model including surrounding rock, structural base plate, guide platform structure and lining section, so that the lining section that is latest demolded at the time when the TBM system is scheduled to pass through the station and its adjacent lining section constitute the core analysis area, and extend the core analysis area along both sides of the TBM system's travel route by a set length to form the load application area. Specifically, based on the station design drawings and geological survey data, a three-dimensional solid model is established in a general finite element platform (such as ABAQUS or ANSYS) to accurately represent the surrounding rock, station floor slab, guide platform, and all constructed lining sections. The core analysis area consists of the lining section that has been most recently demolded at the time the TBM system is scheduled to pass through the station, and its adjacent lining sections. Adjacent lining sections do not include lining sections that have not yet been demolded. To fully simulate the entire process of the TBM load entering, covering, and leaving the core analysis area, a model area needs to be extended on both sides of the core analysis area along the TBM's direction of travel to form a load application zone. To reduce the amount of modeling and finite element analysis calculations, the finite element model on one side of the core analysis area includes the completed lining section, while the finite element model on the other side of the core analysis area consists only of the surrounding rock, structural floor slab, and guide platform structure.

[0036] Fixed constraints are applied to the bottom boundary of the model, and normal displacement constraints are applied to the four sides. Due to the presence of a waterproof layer, the contact relationship between the inner wall of the surrounding rock and the outer wall of the lining section is defined as "hard" contact in the normal direction, and a Coulomb friction model with a low friction coefficient is adopted in the tangential direction. The interface contact between the lining section and the guide structure, as well as between adjacent lining sections, is considered as deformation coordination and is subject to binding constraints.

[0037] The mesh generation adopts a structured mesh, and the lining structure in the core analysis area is locally refined to accurately resolve the stress gradient; the mesh in the load application area is moderately refined; and the remaining areas use a relatively sparse mesh to improve computational efficiency.

[0038] S52. Based on the time-varying mechanical property prediction model, define the concrete material parameters for each lining segment within the core analysis area at the planned arrival time of the TBM system. Specifically, determine the pouring completion time of each lining segment according to the construction records, and calculate the actual age from the initial setting time to the planned arrival time of the TBM system. Input this age into the time-varying mechanical property prediction model to calculate the predicted elastic modulus, predicted tensile strength, and other parameters of the concrete at that age. Assign the predicted concrete material parameters to the corresponding lining segment elements in the finite element model.

[0039] The constitutive relations of the remaining components in the finite element model are defined according to the following principles: the surrounding rock adopts the Mohr-Coulomb elastoplastic model, and its parameters such as cohesion, internal friction angle, elastic modulus, and Poisson's ratio are determined based on field geological survey and experimental data. The base plate structure and guide platform structure are simulated using a linear elastic model. The lining section outside the core analysis area uses design standard values ​​or measured values.

[0040] S53. Based on the actual axle load distribution of the most unfavorable load segment in the TBM system, a load simulation window is defined on the guide platform structure model. According to the TBM system's push-out step size, the load simulation window is discretized on the guide platform structure model. A static finite element analysis is performed once for each discrete position to simulate the entire process of the most unfavorable load segment passing through the core analysis area. Specifically, due to the uneven axle load distribution of each traveling device in the TBM system and the continuous change of its position relative to the core analysis area during the propulsion process, the load form and action position of the same lining segment in the core analysis area are completely different at different times. Analyzing only a single static load case cannot capture the most unfavorable stress state that the lining segment may experience during the TBM system's passage through the station. Therefore, it is necessary to set a separate loading scheme according to the TBM system passing through the station. In actual engineering, the TBM's traveling wheels transfer the load to the guide platform structure through the steel guide rails below them. Therefore, in finite element modeling, the concentrated loads of all traveling devices within the most unfavorable load segment are equivalently transformed into several uniformly distributed line loads acting on the corresponding projected area of ​​the top surface of the guide platform structure, based on their actual wheelbase and ground contact length. This approach realistically reflects the actual distribution of pressure transmitted from the traveling devices to the guide platform via the guide rails, avoiding the false stress concentration caused by directly applying concentrated force to a single point. The effective length of a single line load is equal to the center distance between the first and last traveling wheels in the corresponding traveling device, and the load intensity is calculated and determined based on the total axle load and effective length of the traveling device. These several uniformly distributed line loads arranged according to their actual spatial positions collectively constitute a fixed load pattern, i.e., a load simulation window.

[0041] The method for obtaining the most unfavorable load segment is as follows: obtain the load-bearing weight of each traveling device in the TBM system, select at least two groups of adjacent traveling devices with the largest total load-bearing weight, and take the area covered by them as the most unfavorable load segment. The length of the most unfavorable load segment is greater than the length of the lining segment. The concentrated load of all traveling devices in the most unfavorable load segment is equivalently transformed into several segments of uniformly distributed line loads acting on the guide structure model in the finite element model. The load simulation window is a fixed load mode composed of these segments of uniformly distributed line loads, wherein the action length of a single uniformly distributed line load is equal to the center distance between the first and last traveling wheels in the corresponding traveling device.

[0042] like Figure 3 As shown, when the TBM system advances unloaded on the guide platform structure, it typically moves at a fixed cycle step size (i.e., the unloaded push step size). This step size is determined by the stroke of the equipment's propulsion cylinders or the spacing of the rail clamps (e.g., 1.5 meters). In the finite element analysis, the defined load simulation window is incremented by this unloaded push step size and gradually and discretely moved towards the other end along the planned travel path of the TBM system, starting from the beginning of the load application area. Each time it moves to a new discrete position, a fixed set of line load patterns is applied to the corresponding area of ​​the guide platform structure model in the finite element model, and a static solution is performed on the finite element model. The stress components of all lining sections within the core analysis area at this time are extracted and saved. This "move-load-solve-record" cycle is repeated until the end of the load simulation window completely moves beyond the end boundary of the load application area. This discrete moving loading method fully and approximately reproduces the entire process of the TBM system's most unfavorable load segment stepping through the core area of ​​the station, thus enabling a systematic traversal and capture of all mechanical stress responses generated by the lining structure within the core analysis area when the load is at different locations.

[0043] S54. Collect the maximum value of concrete tensile stress in each lining segment within the core analysis area of ​​all static finite element analyses as the principal tensile stress extreme value of that lining segment. Specifically, after completing the static finite element analysis corresponding to each discrete load position, systematically read the concrete tensile stress field data of all mesh elements in the core analysis area under the current load condition by calling the post-processing module of the finite element software or writing a dedicated result extraction script. For each lining segment in the core analysis area, identify and select the maximum value of tensile stress that appears in all load steps, and define this value as the principal tensile stress extreme value of that lining segment under the action of the TBM system.

[0044] S6. Select the time-strain curve of the existing lining section with the same material and curing conditions as the newly demolded lining section as the reference curve, calculate the stress compensation value of the newly demolded lining section at the planned time of crossing the station, and superimpose the stress compensation value with the extreme value of the principal tensile stress to obtain the predicted total stress of the newly demolded lining section. Specifically, under the standardized construction process control of mature commercial concrete using lining trolleys, the concrete mix proportions used by all lining sections are similar, and the formwork support and demolding conditions and on-site curing conditions are basically the same. Their material time-varying characteristics are highly similar, so the time-strain curve of the existing lining section can be used as the reference curve.

[0045] In one technical solution, the method for selecting the reference curve includes the following steps: A1. Obtain the early time-strain monitoring sequence of the newly demolded lining section from the initial setting time to the current decision time, and record it as the measured sequence. e n (t) Retrieve from the database j For each constructed lining section, the early time-strain sequence within the same time period is denoted as a candidate sequence. e c，j (t) In practice, strain monitoring data sequences continuously collected from the monitoring reference point up to the moment when a decision needs to be made are extracted from strain sensors deployed within the newly demolded lining section. These data sequences are then organized chronologically to form a measured sequence. e n (t) At the same time, data is retrieved from the pre-established construction monitoring database. j Historical monitoring data of completed lining sections with similar materials and maintenance conditions were collected, and early time-strain data of these sections within the same time period were extracted to form... j candidate sequences e c，j (t) .

[0046] A2. Calculate the measured sequences respectively. e n (t) With each candidate sequence e c，j (t) The goodness of fit, with the coefficient of determination R j 2 As a quantitative similarity index, to objectively evaluate the similarity between the measured sequence and each candidate sequence in terms of their development patterns, statistical goodness-of-fit is used for quantitative analysis, with the coefficient of determination being a key indicator. R j2 The calculation process is as follows: A21. The measured sequence e n (t) With candidate sequences e c，j (t) Align to the same time point and pair them. That is, for a series of common time points. t i ( i =1,2,..., m This forms m data point pairs: e c,j (t 1 e n (t 1 e c,j (t 2 ), Figure 4 n (t 2 m c,j (t m m n (t m )) .

[0047] A22. Calculate the measured sequence m n (t) Arithmetic mean of strain values ​​at all time points The calculation formula is: .

[0048] A23. Calculate the sum of squares. The calculation formula is: .

[0049] A24. Calculate the sum of squared residuals. The calculation formula is: .

[0050] A25. Calculate the coefficient of determination. R j 2 The calculation formula is: .

[0051] A3, Select R j 2The complete time-strain curve of the constructed lining section corresponding to the highest candidate sequence is used as the reference curve for calculating stress compensation values. Specifically, all calculated values ​​are compared... R j 2 The maximum value is identified, and the corresponding constructed lining section is determined as the optimal matching object. Subsequently, the complete time-strain monitoring data of the optimal matching lining section from initial setting to a sufficiently long age is retrieved from the database as a reference curve for calculating the stress compensation value of the newly demolded lining section.

[0052] S7. Compare the predicted total stress of the newly demolded lining section with its predicted tensile strength at the planned time of passage. If the predicted total stress exceeds the predicted tensile strength, it is determined that the lining section does not meet the safety conditions for TBM passage. Based on the comparison results, the passage plan of the TBM system and the demolding plan of the lining section are decided.

[0053] In one technical solution, the TBM system's passage plan and the lining section formwork removal plan are determined based on the following: (a) If, at the planned time of station crossing, the predicted total stress of the latest demolded lining segment and the adjacent lining segment does not exceed the corresponding predicted tensile strength, the TBM system will cross the station according to the original planned time. For example, the nth ring lining segment (planned crossing age 1.5 days) and the adjacent (n-1)th ring lining segment (planned crossing age 4 days) are evaluated. Finite element analysis yields the following principal tensile stress extremes: nth ring +1.15 MPa, n-1th ring +0.95 MPa. The stress compensation values ​​obtained from their respective reference curves based on the corresponding ages are: nth ring +0.45 MPa, n-1th ring -0.25 MPa. The superimposed predicted total stress is: nth ring +1.60 MPa, n-1th ring +0.70 MPa. The predicted tensile strength for the corresponding ages is obtained through a time-varying mechanical property prediction model: nth ring +1.75 MPa, n-1th ring +2.35 MPa. After comparison, the predicted total stress of both ring lining sections was lower than the corresponding predicted tensile strength, meeting the safety requirements. Therefore, the project team approved the TBM system to proceed with the project as originally planned.

[0054] (b) If, at the planned station crossing time, the predicted total stress of the latest demolded lining segment exceeds its predicted tensile strength and demolding has not yet commenced, while the adjacent lining segment meets the stress requirements, then the demolding of the latest demolded lining segment shall be halted until the TBM system passes through the station as originally planned. For example, the (n+1)th ring lining segment of a certain station (planned crossing time approximately 1 day) has not yet been demolded at the time of assessment but is expected to be demolded by the time the TBM system passes through the station. Its principal tensile stress extreme value is +1.25 MPa. After superimposing the stress compensation value of +0.68 MPa obtained from the reference curve, the predicted total stress is +1.93 MPa, exceeding its predicted tensile strength of +1.45 MPa. The predicted total stress of the adjacent (nth ring lining) (planned crossing time 3 days) is +1.35 MPa, lower than its predicted tensile strength of +1.85 MPa. Based on this, the project team suspends the demolding operation of the (n+1)th ring lining segment and approves the TBM crossing as originally planned. During the passage of the TBM system, the n+1 ring lining section that was not demolded was protected by the formwork, and the stress level of the nth ring lining section did not exceed the limit.

[0055] (c) If, at the planned transit time, the predicted total stress of the latest demolded lining segment exceeds its predicted tensile strength and demolding has already occurred, the finite element analysis shall be re-performed to determine the corrected transit time of the TBM system, assuming that the latest demolded lining segment meets the stress conditions at the planned transit time of the TBM system. Demolding of the next lining segment shall be halted until the TBM system completes transit according to the corrected transit time. For example, the predicted total stress of the (n+2)th ring lining segment (planned transit time of 1 day, already demolded) is +2.05 MPa, exceeding its predicted tensile strength of +1.45 MPa; simultaneously, the predicted total stress of the adjacent (n+1)th ring lining segment (planned transit time of 3 days) is +1.92 MPa, also exceeding its predicted tensile strength of +1.85 MPa. Based on this, the project can instruct the (n+3)th ring lining segment to proceed with all construction procedures except demolding, thus delaying the TBM system's transit. Re-analysis using the time-varying mechanical property prediction model shows that when the (n+2)th ring reaches 3 days of age, its predicted tensile strength will increase to +1.95 MPa, and its stress compensation value will decrease to +0.25 MPa. The superimposed and verified principal tensile stress extreme value is +1.30 MPa, and the predicted total stress is +1.55 MPa, which meets the safety requirements. Therefore, the TBM system's operation time is postponed until the (n+2)th ring lining reaches 3 days of age.

[0056] This technical solution achieves three core advantages by establishing a technical chain of "real-time monitoring - time-varying prediction - mechanical simulation - stress synthesis": First, it elevates the decision-making process for TBM system transit from relying on experience-based judgment to scientific evaluation based on quantitative data, thereby improving the reliability of the decision; second, by accurately predicting the early stress state of concrete, it effectively reduces the waiting time for TBM system transit while ensuring structural safety, thus improving construction efficiency; and finally, it constructs a complete construction monitoring system, providing a scalable technical paradigm for the construction of large stations under similar conditions with frequent TBM system transit.

[0057] In another technical solution, the cross-section of the lining section is divided into five structural zones: the left arch starting zone, the left arch shoulder zone, the arch crown zone, the right arch shoulder zone, and the right arch starting zone. Strain sensors are independently deployed within each structural zone to monitor and acquire the time-strain curve of the concrete in that zone. This is because long-term monitoring of the lining structures of large-section tunnel railway stations has revealed that, for an arched lining section, the time-varying strain development process of concrete in different parts of its cross-section is not entirely precise and uniform, but exhibits certain spatial differences. These differences mainly stem from the different boundary constraints, temperature field distributions, and hydration processes at each location. To further refine the true and differentiated time-varying stress states of each key component, it is necessary to divide the lining section into structural zones.

[0058] The crown zone, located at the highest point of the arch structure, primarily bears bending moments under its own weight and external loads. It is the region where tensile stress first appears, and its heat dissipation is relatively poor, resulting in a typically high concrete hydration temperature rise and significant temperature stress. The shoulder zone, situated in the transition area between the crown and the arch initiation point, experiences complex stress conditions, acting as a region of combined bending moments and axial forces, with significant stress gradient variations. The arch initiation zone, as the connection between the arch foot and the substructure, primarily bears substantial axial pressure and shear forces, exhibiting the strongest boundary constraints. However, its temperature variation is significantly influenced by the surrounding rock, with a temperature rise typically lower than that of the crown. These five structural zones essentially cover various key mechanical states of the arch ring, from compression and combined bending-compression to bending, as well as typical thermal conditions ranging from strong constraint to relative freedom and from high to low temperatures. Independent monitoring of these five zones can most effectively characterize the non-uniformity of stress and deformation across the entire lining section. In actual engineering implementation, the zones can be divided according to the arch axis in the design drawings, ensuring continuity between structural zones and eliminating monitoring blind spots. The strain sensor signal lines for all structural zones should be independently led to the data acquisition station to ensure that time-strain data for each structural zone can be acquired and recorded synchronously and independently.

[0059] mThe data presented is typical monitoring data, which shows that in the early stages after concrete pouring, although the five structural zones experienced the same four development stages, their strain values ​​differed at key stages.

[0060] During the concrete expansion stage, the peak tensile strain of each structural zone was as follows: left arch zone +69 m Left shoulder area +56 m vault area +42 m Right shoulder area +62 m The right arch area +72 ​ At this point, the elastic modulus of the concrete is approximately 25 GPa. Based on a preliminary estimate using the generalized Hooke's law, the autogenous tensile stress generated by the combined effects of temperature expansion, structural weight, and concrete creep is approximately +1.05 MPa in the arch crown region, and approximately +1.73 MPa and +1.80 MPa in the left and right arching regions, respectively. Conversely, during the cooling and shrinkage stage, all structural zones transition to a compressive state, but the compressive strain value also exhibits a variation of -31... ​ to -41 ​ The difference corresponds to an estimated autogenous compressive stress of approximately -0.78 MPa to -1.03 MPa. This indicates that after actual demolding, if only the cross-sectional average strain is used for evaluation, the actual tensile stress level in local areas such as the arching zone may be underestimated, which may mask the cracking risk generated when the TBM system passes through the station.

[0061] In step S5, for each newly demolded lining section, the extreme values ​​of principal tensile stress calculated by the finite element analysis model at the locations corresponding to the five structural partitions are extracted. The most representative mechanical tensile stresses caused by the moving load at each key location when the TBM system passes through the station are obtained, providing load input for subsequent refined evaluation of the partitions.

[0062] In step S6, for each structural partition, the stress compensation value is calculated based on the reference curve of the structural partition and superimposed with the corresponding principal tensile stress extreme value to obtain the predicted total stress of the structural partition. In step S7, if the predicted total stress of any structural section exceeds its corresponding predicted tensile strength, the lining section is determined not to meet the TBM transit safety conditions. This ensures that the evaluation criteria can cover the weakest link that may appear on the lining ring, thereby greatly improving the reliability and conservatism of safety decisions.

[0063] In another technical solution, the strain sensor is one or more FRP (fiberglass reinforced plastic) reinforcing bars embedded with several grating sensors. These FRP reinforcing bars are arranged parallel to the circumferential main reinforcing bars of the lining section and fixed to the reinforcing steel frame. FRP reinforcing bars are a fiber-reinforced composite material, manufactured by pre-embedding grating sensors within them during the glass fiber reinforced plastic molding process. The FRP reinforcing bars have dual functions of load bearing and sensing. The embedded grating sensors are primarily fiber Bragg gratings, arranged axially within the FRP reinforcing bars to form multiple measuring points. The parallel arrangement of the FRP reinforcing bars between the circumferential main reinforcing bars can replace some of the circumferential load-bearing reinforcing bars, directly integrating them into the reinforcing steel frame. During the reinforcing steel binding process, the FRP reinforcing bars are arranged together with ordinary reinforcing bars and fixed to the reinforcing steel mesh by binding or welding, ensuring accurate positioning and shared load-bearing with the concrete in the lining section.

[0064] In another technical solution, the recording of the time-strain curve begins at a unified strain monitoring reference point, which is defined as the moment when the concrete test block poured in the same batch as the lining section reaches initial setting. At the strain monitoring reference point, the readings of all grating sensors on the FRP reinforcement are initialized. When initial setting occurs, the lining section is in an unformed state, and its concrete self-weight and construction load are entirely borne by the lining trolley formwork system. At this time, the concrete itself is not subject to external mechanical loads and is in a relatively stable initial mechanical state.

[0065] At the initial setting stage, the concrete has just formed its initial structural strength, and the cooperative deformation relationship between the sensor and the concrete begins to stabilize and is not affected by external factors such as TBM loads or surrounding rock pressure after demolding. Initializing at this point ensures that the subsequently recorded time-strain curves purely reflect the autogenous strain caused by the time-varying properties of the material, such as hydration heat release, shrinkage, and creep, after the concrete has hardened, providing a reliable basis for accurately calculating stress compensation values.

[0066] The initialization operation can be implemented in two equivalent forms: one is a direct zeroing operation, which sets the current readings of all sensors to zero at the initial freezing point using a fiber optic demodulator; the other is a reference recording method, which records the absolute readings of each sensor at the initial freezing point as the initial reference value, and all subsequent measurements are calculated by difference from this reference value. Regardless of the form used, it ensures that the monitoring data of all sensors have a unified spatiotemporal reference and accurately reflects the net strain development process from the initial freezing point.

[0067] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

[0068] It should be noted that although the steps are described in a specific order above, this does not mean that they must be performed in that order. In fact, some of these steps can be executed concurrently, or even in a different order, as long as the required functionality is achieved. The number of devices and processing scale described herein are for simplification of the invention; applications, modifications, and variations of this invention will be readily apparent to those skilled in the art.

Claims

1. A method for monitoring the lining construction of extra-large cross-section tunnel stations with TBM passageways, characterized in that, Includes the following steps: S1: After the main body of the station is excavated and initially supported, the station base slab structure and guide platform structure are constructed in sequence. S2. Starting from one end of the self-guided platform structure, construct the lining section segment by segment towards the other end, and pre-embed strain sensors inside each lining section. S3. Continuously collect the readings of the strain sensors in each lining section to obtain the time-strain curve of the concrete in the lining section under the action of no TBM passing load. S4. Based on the test data of the test blocks cured under the same conditions corresponding to the constructed lining section, establish a time-varying mechanical property prediction model for concrete. The time-varying mechanical property prediction model takes the concrete age as input and concrete material parameters including the predicted tensile strength as output. S5. Obtain the planned time of the TBM system's passage and determine the lining segment in the newly demolded state at that time. Establish a finite element analysis model including the surrounding rock, bottom plate structure, guide platform structure and lining segment. Based on the time-varying mechanical performance prediction model, define the concrete material parameters of the newly demolded lining segment at the planned time of passage. By simulating the process of the load movement of the TBM system, obtain the extreme value of the principal tensile stress generated in the newly demolded lining segment. S6. Select the time-strain curve established by the constructed lining section with the same material and curing conditions as the newly demolded lining section as the reference curve, calculate the stress compensation value of the newly demolded lining section at the planned time of passing the station, and superimpose the stress compensation value with the extreme value of the principal tensile stress to obtain the predicted total stress of the newly demolded lining section. S7. Compare the predicted total stress of the newly demolded lining section with its predicted tensile strength at the planned time of passage. If the predicted total stress exceeds the predicted tensile strength, it is determined that the lining section does not meet the safety conditions for TBM passage. Based on the comparison results, the passage plan of the TBM system and the demolding plan of the lining section are decided.

2. The method for monitoring the lining construction of extra-large cross-section tunnel stations with TBM passage as described in claim 1, characterized in that, Step S5 includes the following steps: S51. Establish a finite element model including surrounding rock, structural base plate, guide platform structure and lining section, so that the lining section that is latest demolded at the time when the TBM system is scheduled to pass through the station and its adjacent lining section constitute the core analysis area, and extend the core analysis area along both sides of the TBM system's travel route by a set length to form the load application area. S52. Based on the time-varying mechanical performance prediction model, define the concrete material parameters of each lining segment in the core analysis area at the planned time of TBM system passage. S53. Based on the actual axle load distribution of the most unfavorable load segment in the TBM system, a load simulation window is defined on the guide platform structure model. According to the empty push step size of the TBM system, the load simulation window is discretized on the guide platform structure model. A static finite element analysis is performed once for each discrete position to simulate the entire process of the most unfavorable load segment stepping through the core analysis area. S54. Collect the maximum value of concrete tensile stress in each lining section within the core analysis area of ​​all static finite element analyses as the extreme value of principal tensile stress in that lining section.

3. The method for monitoring the lining construction of extra-large cross-section tunnel stations with TBM passageways as described in claim 2, characterized in that, The finite element model located on one side of the core analysis area includes the completed lining section, while the finite element model on the other side of the core analysis area consists only of the surrounding rock, the structural base plate, and the guide platform structure. The set length of the extension on each side of the core analysis area is greater than or equal to the length of the load simulation window.

4. The method for monitoring the lining construction of extra-large cross-section tunnel stations with TBM passage as described in claim 2, characterized in that, Obtain the load-bearing weight of each traveling device in the TBM system, select at least two adjacent traveling devices with the largest total load-bearing weight, and take the area covered by them as the most unfavorable load segment. The length of the most unfavorable load segment is greater than the length of the lining segment. The concentrated load of all traveling devices in the most unfavorable load segment is equivalently transformed into several segments of uniformly distributed line loads acting on the guide structure model in the finite element model. The load simulation window is a fixed load mode composed of these segments of uniformly distributed line loads, wherein the action length of a single uniformly distributed line load is equal to the center distance between the first and last traveling wheels in the corresponding traveling device.

5. The method for monitoring the lining construction of extra-large cross-section tunnel stations with TBM passageways as described in claim 1, characterized in that, The concrete material parameters include predicted compressive strength, predicted tensile strength, and predicted elastic modulus. The expression for the time-varying mechanical property prediction model is as follows: in, t Concrete age ， For concrete at age t Predicted parameters for weather conditions, subscript i Used to distinguish different concrete material parameters These are the design standard values ​​for the corresponding parameters at 28 days of age. s i The model development coefficients are the concrete material parameters confirmed by test blocks cured under the same conditions.

6. The method for monitoring the lining construction of extra-large cross-section tunnel stations with TBM passage as described in claim 1, characterized in that, The cross section of the lining section is divided into five structural zones: left arch starting zone, left arch shoulder zone, arch crown zone, right arch shoulder zone, and right arch starting zone. Strain sensors are independently installed in each structural zone to monitor and obtain the time-strain curve of the concrete in that structural zone. In step S5, for each newly demolded lining segment, the extreme values ​​of principal tensile stress calculated by the finite element analysis model at the locations corresponding to the five structural partitions are extracted; In step S6, for each structural partition, the stress compensation value is calculated based on the reference curve of the structural partition and superimposed with the corresponding principal tensile stress extreme value to obtain the predicted total stress of the structural partition. In step S7, if the predicted total stress of any structural section exceeds its corresponding predicted tensile strength, then the lining section is determined not to meet the safety conditions for TBM passage.

7. The method for monitoring the lining construction of extra-large cross-section tunnel stations with TBM passage as described in claim 1, characterized in that, In step S6, the method for selecting the reference curve includes the following steps: A1. Obtain the early time-strain monitoring sequence of the newly demolded lining section from the initial setting time to the current decision time, and record it as the measured sequence. ε n (t) Retrieve from the database j For each constructed lining section, the early time-strain sequence within the same time period is denoted as a candidate sequence. ε c，j (t) ; A2. Calculate the measured sequences respectively. ε n (t) With each candidate sequence ε c，j (t) The goodness of fit, with the coefficient of determination R j 2 As a quantitative similarity indicator; A3, Select R j 2 The complete time-strain curve of the constructed lining section corresponding to the highest candidate sequence is determined as the reference curve for calculating stress compensation values.

8. The method for monitoring the lining construction of extra-large cross-section tunnel stations with TBM passage as described in claim 1, characterized in that, The passage plan and lining section formwork removal plan for the TBM system are determined based on the following: (a) If, at the scheduled time of station crossing, the predicted total stress of the latest demolded lining section and the adjacent lining section does not exceed the corresponding predicted tensile strength, the TBM system will cross the station at the originally scheduled time. (b) If, at the scheduled time of the station crossing, the predicted total stress of the latest demolded lining segment exceeds its predicted tensile strength and the demolding process has not yet been carried out at the current time, while the adjacent lining segment meets the stress conditions, then the demolding process of the latest demolded lining segment shall be stopped until the TBM system passes through the station at the originally scheduled time. (c) If, at the planned transit time, the predicted total stress of the latest demolded lining segment exceeds its predicted tensile strength and the demolding has already occurred, the finite element analysis shall be performed again to determine the corrected transit time of the TBM system, provided that the latest demolded lining segment meets the stress conditions at the planned transit time of the TBM system. The demolding process for the next lining segment shall be stopped until the TBM system completes the transit according to the corrected transit time.

9. The method for monitoring the lining construction of extra-large cross-section tunnel stations with TBM passage as described in claim 1, characterized in that, The strain sensor is one or more FRP bars with embedded grating sensors. The FRP bars are arranged in parallel between the circumferential main bars of the lining section and fixed to the steel reinforcement skeleton.

10. The method for monitoring the lining construction of extra-large cross-section tunnel stations with TBM passage as described in claim 9, characterized in that, The recording of the time-strain curve begins at a unified strain monitoring reference point, which is defined as the initial setting time of the concrete test block poured in the same batch as the lining section. At the strain monitoring reference point, the readings of all grating sensors on the FRP reinforcement are initialized.

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