Method and system for analyzing influence of double-line shield tunneling on ground surface settlement

Abstract

The application provides a method and system for analyzing the influence of double-line shield tunneling on ground surface settlement, and relates to the technical field of tunnel construction. In view of the problems that the prior art lacks fine description of the dynamic evolution of ground surface settlement in the whole process of the construction of the following line, it is difficult to capture the settlement mutation and peak value, and it is impossible to quantitatively represent the superimposed influence, the application divides the whole process of double-line construction into multiple key time nodes based on the spatial relative position of the shield machine face and the monitoring section, groups the corresponding monitoring ground surface transverse settlement tank data, draws the transverse settlement curves of each group, integrates to form a multi-curve superimposed graph, finely describes the dynamic evolution process of the ground surface settlement under the double-line superposition of the leading line and the following line from the time dimension, captures the settlement mutation and peak value, realizes the quantitative representation of the settlement superimposed influence in the whole process, and reveals the change law of the depth, width and symmetry axis offset of the settlement tank, thereby providing quantitative basis for the optimization of the tunnel spacing and the dynamic settlement control in construction.

Description

Technical Field

[0001] This invention relates to the field of tunnel construction technology, and in particular to a method and system for analyzing the impact of sequential excavation of a double-track shield tunnel on surface settlement. Background Technology

[0002] With the acceleration of urbanization, underground space development is increasingly extending in depth. Twin-track shield tunnels, due to their efficient utilization of underground space, are widely used in subway, highway, and municipal pipeline projects. In actual construction, due to limitations in route planning and project schedule, twin-track tunnels often adopt a sequential excavation sequence, meaning the first tunnel is completed before the second tunnel begins excavation. This construction mode inevitably leads to secondary disturbance of the already disturbed strata caused by the excavation of the second tunnel, resulting in a cumulative effect of surface subsidence.

[0003] Currently, scholars both domestically and internationally have conducted extensive research on the surface settlement problem caused by shield tunneling, primarily employing methods including empirical formulas, theoretical analysis, numerical simulation, and model testing. However, existing technologies still have the following shortcomings when dealing with the cumulative effects of settlement in twin tunnels: Existing analytical methods mostly focus on the surface settlement patterns caused by single-track tunnel construction, or simply perform superimposed analysis on the settlement of the final stable state of double-track tunnels. They lack in-depth revelation of the dynamic evolution mechanism of surface settlement throughout the entire process of subsequent tunnel excavation. Traditional static assessment methods usually only focus on the final settlement value and fail to finely depict the settlement changes over the entire time span from the excavation of the first track to the completion of the subsequent track construction. They are unable to capture the abrupt changes and peak values ​​of settlement during the subsequent track excavation process, resulting in the inability to quantitatively characterize the superimposed impact of settlement throughout the entire process of double-track tunnel construction. Consequently, they cannot provide accurate quantitative basis for tunnel spacing design and dynamic settlement control during construction. Summary of the Invention

[0004] To address the problem that existing technologies only focus on the final settlement and cannot reflect the dynamic changes in settlement throughout the entire construction process, this invention proposes a method for analyzing the impact of sequential excavation of a dual-track shield tunnel on surface settlement, including: Acquire surface transverse settlement trough data from multiple monitoring points in the monitoring section to be analyzed; Based on the spatial relative position of the tunnel boring machine face and the section to be analyzed and monitored, the entire process of dual-line construction is divided into multiple key time nodes; The surface transverse subsidence trough data is divided into multiple data groups based on multiple key time nodes; Plot the lateral settlement curve for each of the data sets; By integrating the transverse settlement curves of all data sets into the same coordinate system, a multi-curve overlay diagram of the transverse settlement trough is obtained. Analysis of the multi-curve overlay diagram of the transverse settlement trough reveals the depth, width, and symmetry axis offset patterns of the settlement trough under the effects of advance line excavation, follow line excavation, and double-line overlay.

[0005] Furthermore, the key time nodes include: the initial state time node, the time node when the face of the preceding shield tunnel reaches the section to be analyzed and monitored, the time node when the tail of the preceding shield tunnel exits the section to be analyzed and monitored, the time node when the face of the subsequent shield tunnel reaches the section to be analyzed and monitored, and the final stable settlement time node.

[0006] Furthermore, the analysis of the multi-curve overlay diagram of the transverse settlement trough yields the characteristics of the settlement trough depth, width, and symmetry axis offset under the effects of the preceding line excavation, the following: Obtain the preliminary stable settlement curve and the final stable settlement curve from the multi-curve overlay diagram of the transverse settlement trough; Extract the first maximum settlement, the first settlement trough width, and the first axis of symmetry from the leading line stable settlement curve; Extract the second maximum settlement, the second settlement trough width, and the position of the second axis of symmetry from the final stable settlement curve; Calculate the difference between the second maximum settlement and the first maximum settlement, and use the difference as the settlement trough depth under the double-line superposition effect; Calculate the offset of the second axis of symmetry position relative to the first axis of symmetry position, and use the offset as the axis of symmetry offset under the double-line superposition effect; Calculate the width difference between the second settling trough width and the first settling trough width, and use the width difference as the settling trough width under the double-line superposition effect.

[0007] Furthermore, the analysis of the multi-curve overlay diagram of the transverse settlement trough to obtain the settlement trough depth, width, and symmetry axis offset patterns under the effects of the preceding line excavation, the following steps are also included: Obtain a multi-curve overlay diagram of the transverse settlement trough of at least one double-track tunnel with different axis center distances, and use the obtained multi-curve overlay diagram of the transverse settlement trough as a comparison curve diagram; Based on the aforementioned comparative curve diagram and the aforementioned multi-curve superimposed diagram of the transverse settlement trough, the influence of the axis distance between the two tunnels on the morphological evolution of the transverse settlement trough is analyzed. Based on the aforementioned influence patterns, the recommended design value for the center-to-center distance during the construction of a dual-track tunnel is determined.

[0008] Furthermore, the comparative analysis of the influence of the center-to-center distance of the twin tunnels on the evolution of the lateral settlement trough morphology includes: When the center-to-center distance between the two tunnels is not less than the critical distance, during the excavation of the subsequent line, the transverse settlement trough gradually evolves from a single-core morphology formed by the excavation of the preceding line to a multi-core morphology, and retains the multi-core morphology after the excavation of the subsequent line is completed. When the center-to-center distance between the two tunnels is less than the critical distance, during the excavation of the subsequent tunnel: If the tunneling of the lead line forms a non-single peak settlement pattern, the non-single peak settlement pattern will gradually evolve into a single core pattern, and the single core pattern will be maintained after the tunneling of the follow line is completed. If the tunneling of the lead line forms a single core shape, then this shape will remain a single core shape during and after the tunneling of the follow line. As the center-to-center distance between the two tunnels decreases, the interaction between the soil excavated by the first and second lines intensifies, the settlement deformation in the jointly disturbed area intensifies, the depth of the transverse settlement trough gradually increases, and the morphology of the settlement trough evolves from a multi-trough core morphology to a single-trough core morphology.

[0009] Furthermore, it also includes: In the multi-trough configuration, the trough center in the final stable settlement curve is offset away from the trough center in the stable settlement curve of the preceding line from the direction of the central axis of the dual-line tunnel. The width and depth of the settlement trough of the preceding line tunnel are both greater than the width and depth of the settlement trough of the following line tunnel. In the case of a single core, the core of the final stable settlement curve and the core of the preliminary stable settlement curve are both within the preset range of the central axis of the dual-track tunnel.

[0010] Furthermore, after obtaining the multi-curve overlay diagram of the transverse settlement trough, the following is also included: The incremental displacement of the subsequent line is calculated based on the cumulative vertical displacement corresponding to the stable settlement curve of the preceding line and the cumulative vertical displacement corresponding to the final stable settlement, so as to characterize the degree of secondary disturbance of the soil already disturbed by the construction of the subsequent line to the soil already disturbed by the preceding line. Based on the backward line increment, a backward line increment curve is plotted and added to the multi-curve overlay diagram of the transverse settlement trough.

[0011] Furthermore, before acquiring the surface transverse settlement trough data of multiple monitoring points in the monitoring section to be analyzed, the method further includes: A monitoring section is set up along the longitudinal direction of the tunnel at a predetermined number of rings, and multiple monitoring points are symmetrically arranged on both sides of the central axis of the double-track tunnel for each monitoring section. Acquire settlement time history data for each of the monitoring points; Extract the transverse cross-sectional settlement value corresponding to each key time node in the settlement time history data to obtain the transverse settlement trough data of the land surface.

[0012] A system for analyzing the impact of sequential excavation of a dual-track shield tunnel on surface settlement, the system employing the method described above for analyzing the impact of sequential excavation of a dual-track shield tunnel on surface settlement, specifically including the following modules: The acquisition module is used to acquire surface transverse settlement trough data from multiple monitoring points in the monitoring section to be analyzed; The first division module, connected to the acquisition module, is used to divide the entire process of dual-line construction into multiple key time nodes based on the spatial relative position of the tunnel boring machine face and the section to be analyzed and monitored. The second partitioning module is connected to the first partitioning module and divides the surface transverse subsidence trough data into multiple data groups based on multiple key time nodes. A drawing module, connected to the second division module, is used to draw the transverse settlement curve corresponding to each data group; An integration module, connected to the drawing module, is used to integrate the transverse settlement curves of all data sets into the same coordinate system to obtain a multi-curve overlay diagram of the transverse settlement trough. The analysis module, connected to the integration module, is used to analyze the multi-curve overlay diagram of the transverse settlement trough to obtain the depth, width, and symmetry axis offset of the settlement trough under the effects of the leading line excavation, the following line excavation, and the double-line overlay effect.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: Firstly, a key time node segmentation method based on the spatial relative position of the tunnel boring machine face and the monitoring section is adopted. This method divides the entire dual-track construction process into multiple key time nodes and correspondingly segments the acquired transverse settlement trough data into multiple data groups. By plotting the transverse settlement curve corresponding to each data group and integrating all curves into the same coordinate system, a multi-curve overlay map of the transverse settlement trough is constructed. This method meticulously depicts the dynamic evolution of surface settlement under the superimposed effects of the preceding and subsequent tunnel excavation, as well as the dual-track superposition effect, from a temporal perspective. It effectively captures settlement abrupt changes and peak values, achieving a quantitative characterization of the superimposed settlement impact throughout the entire dual-track tunnel construction process. It reveals the variation patterns of settlement trough depth, width, and symmetry axis offset, providing precise quantitative basis for the optimized design of tunnel spacing and dynamic settlement control during construction, thereby improving construction safety and the effectiveness of surface environmental protection. Secondly, the entire construction process of the dual-line shield tunnel is divided into several stages with clear physical significance. Taking the initial state as the benchmark, the arrival of the tunnel face and the exit of the shield tail of the lead line define its initial and main impacts. The corresponding nodes of the follow line capture secondary disturbances, and the final stable settlement reflects the long-term effects. This allows the settlement data to be accurately grouped, thereby clearly capturing the dynamic evolution of the entire process from the lead line to the follow line, including abrupt changes and peak values. This effectively quantifies the superimposed effect of the two lines and provides a more accurate basis for tunnel spacing design and construction settlement control. Attached Figure Description

[0014] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0015] Figure 1 This is a flowchart illustrating the method for analyzing the impact of sequential excavation of a dual-track shield tunnel on surface settlement in Example 1. Figure 2 This is a multi-curve overlay diagram of the transverse settlement trough at the monitoring section of tunnel 1 in Example 1; Figure 3 This is a multi-curve overlay diagram of the transverse settlement trough at the monitoring section of tunnel 2, as shown in Example 1. Figure 4 This is a multi-curve overlay diagram of the transverse settlement trough at the monitoring section of tunnel 3, as shown in Example 1; Figure 5 This is a structural block diagram illustrating the impact of sequential excavation of a dual-track shield tunnel on surface settlement, as shown in Example 2. Detailed Implementation To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0016] The specific embodiments of the present invention will be described below.

[0017] Existing technologies for analyzing surface settlement during the sequential excavation of twin-track shield tunnels are mainly limited to static assessments of the final settlement value. They lack in-depth insights into the dynamic evolution mechanism of surface settlement throughout the entire excavation process of the subsequent track, and cannot precisely depict the complete time-series settlement changes from the excavation of the first track to the completion of the subsequent track. They also struggle to capture abrupt settlement changes and peak values ​​during the excavation of the subsequent track, thus failing to quantitatively characterize the cumulative settlement impact throughout the entire construction process of twin-track tunnels. This makes it difficult to provide precise quantitative data for tunnel spacing design and dynamic settlement control during construction. This invention adopts a shield-based... The time node division method for the relative position of the tunnel face and the monitoring section divides the entire process of dual-track construction into multiple key time nodes. The surface settlement data of the key time nodes are plotted as transverse settlement curves and integrated into a multi-curve overlay diagram of transverse settlement trough. This clearly shows the evolution of the depth, width and symmetry axis offset of the settlement trough under the superposition of the first line tunneling, the second line tunneling, and the double-track overlay. It effectively captures the dynamic changes and peak values ​​of settlement during construction, providing accurate quantitative basis for tunnel spacing optimization and construction dynamic control, and improving construction safety and surface protection.

[0018] Example 1 like Figure 1 As shown, this invention proposes a method for analyzing the impact of sequential excavation of a dual-track shield tunnel on surface settlement, specifically including the following steps: Step S1: Obtain surface transverse settlement trough data from multiple monitoring points in the monitoring section to be analyzed.

[0019] In this embodiment, one or more monitoring sections to be analyzed are pre-selected within the tunnel construction area. Using measuring instruments, such as a level, the monitoring points are periodically measured to obtain the vertical settlement amount for each measurement, i.e., the data of the transverse settlement trough on the ground surface.

[0020] Before acquiring the surface transverse settlement trough data of multiple monitoring points in the monitoring section to be analyzed, the method further includes: setting up a monitoring section at a preset number of rings along the longitudinal direction of the tunnel, and symmetrically arranging multiple monitoring points on both sides of the central axis of the double-track tunnel for each monitoring section; acquiring the settlement time history data of each monitoring point; extracting the transverse section settlement value corresponding to each key time node in the settlement time history data to obtain the surface transverse settlement trough data.

[0021] In this embodiment, by deploying monitoring sections along the longitudinal direction of the tunnel at preset ring intervals, different stages and areas of tunnel excavation can be evenly covered, thereby avoiding data blind spots caused by sparse or unreasonable monitoring points. The preset ring number can be determined comprehensively based on factors such as engineering geological conditions, tunnel depth, tunnel boring machine type, and construction risk level. For example, a monitoring section can be deployed every 5, 10, or 20 rings. Furthermore, the preset ring number can be adjusted according to the sensitivity of the construction stage. For example, when crossing sensitive buildings or areas with complex geological conditions, the density of monitoring sections can be increased, while the interval can be widened in stable strata.

[0022] In this embodiment, multiple monitoring points are symmetrically arranged on both sides of the central axis of the double-track tunnel within each monitoring section to obtain settlement distribution data on the transverse profile, thereby depicting key parameters such as the depth, width, and symmetry of the settlement trough. For example, the monitoring points can be leveling points, automated settlement monitoring instruments such as total stations, GNSS receivers, etc., and are arranged to extend to both sides in a direction perpendicular to the central axis of the tunnel, with equal or non-equal spacing, until they are outside the settlement influence range. The number and spacing of the monitoring points can be designed according to the tunnel burial depth to diameter ratio, geological conditions, and the expected width of the settlement trough. For example, a measuring point is set above the central axis of the tunnel, and then a measuring point is set at certain distances on both sides, such as 2 meters or 5 meters, until the settlement tends to stabilize.

[0023] Settlement time history data is crucial information for the dynamic evolution of surface settlement, characterizing the trajectory of settlement over time. This reveals the impact of construction processes such as tunnel boring, segment assembly, and grouting on surface settlement. For example, settlement time history data is acquired through periodic leveling measurements at monitoring points or continuous collection by automated monitoring systems. In this embodiment, "periodic" refers to daily, per shift, or per tunnel segment. Furthermore, real-time or near-real-time monitoring can be achieved by installing sensors with automatic data recording and transmission capabilities, such as hydrostatic levels and fiber optic grating sensors, ensuring data continuity and timeliness.

[0024] In this embodiment, by filtering settlement values ​​corresponding to key time nodes from continuous settlement time history data, the instantaneous state of surface settlement at key moments can be identified. For example, by manually comparing construction logs and settlement time history curves, the settlement values ​​corresponding to key time nodes can be found. Alternatively, settlement data at the corresponding moment can be automatically extracted from the settlement time history database according to a preset list of key time nodes. No specific limitations are made in this regard.

[0025] In this embodiment, the surface transverse settlement trough data can be stored in tabular form, with each row representing a measuring point and each column representing the settlement value at a key time node. It can also be stored in the form of a structured database to facilitate subsequent data query, processing and visualization.

[0026] In this embodiment, by uniformly distributing monitoring sections and symmetrically arranging monitoring points along the longitudinal direction of the tunnel, comprehensive data coverage without blind spots is ensured, and the symmetrical characteristics of settlement are effectively reflected. Settlement time history data of each monitoring point are collected to achieve dynamic monitoring of the entire construction process. At the same time, the transverse settlement values ​​at key time nodes are extracted, so that the number of transverse settlement troughs on the ground surface closely corresponds to the construction stage, which to a certain extent lays the foundation for subsequent drawing of transverse settlement trough curves and multi-curve overlay analysis.

[0027] Step S2: Based on the spatial relative position of the tunnel boring machine face and the section to be analyzed and monitored, the entire process of dual-line construction is divided into multiple key time nodes.

[0028] The key time nodes include: the initial state time node, the time node when the face of the preceding shield tunnel reaches the section to be analyzed and monitored, the time node when the tail of the preceding shield tunnel exits the section to be analyzed and monitored, the time node when the face of the subsequent shield tunnel reaches the section to be analyzed and monitored, and the final stabilization settlement time node. The initial state time point is the time point before the start of construction of the double-line shield tunnel, when the ground surface is undisturbed or has reached a stable state. It is used to establish a baseline zero point for surface settlement, providing a clear reference starting point for changes in surface settlement during subsequent construction. For example, at least one week before the shield machine starts, continuous observations are conducted on the monitoring section, and the average value is taken as the initial state. The time point when the leading shield face reaches the monitoring section to be analyzed is the time when the face of the leading shield machine first arrives directly below the monitoring section to be analyzed. It is used to mark the initial state. The starting moment of the impact of tunneling on the surface settlement of the monitoring section can be determined, thus capturing the initial response and early development trend of surface settlement. For example, the position of the tunnel face can be monitored in real time through the positioning system of the tunnel boring machine itself, such as GPS or total station. When its longitudinal coordinates coincide with the coordinates of the monitoring section, the time node is recorded. The time node when the tail of the pilot tunnel boring machine exits the monitoring section to be analyzed is the time when the tail of the pilot tunnel boring machine completely passes directly below the monitoring section to be analyzed. This marks the basic end of the direct disturbance of the monitoring section by the pilot tunnel boring machine to the monitoring section, and the surface settlement... Settlement enters a stable stage caused by the consolidation of the lining structure and the stratum. This stage is used to analyze the settlement patterns of the lead tunnel alone. For example, it can be calculated based on the length and speed of the tunnel boring machine (TBM) combined with the arrival time of the tunnel face. The arrival time of the tunnel face of the follow-up TBM at the monitoring section to be analyzed is the time when the tunnel face of the follow-up TBM first reaches directly below the preset monitoring section. This time is used to mark the initiation time of the secondary disturbance of the stratum already disturbed by the lead tunnel during the follow-up tunneling. It is crucial for analyzing the initial manifestations of the superposition effect of the two lines. For example, it can be used to analyze the settlement patterns of the lead tunnel alone. The positioning system of the tunnel boring machine monitors and records in real time, or it can be estimated through construction logs and tunneling speed. The final stable settlement time node is the time when the surface settlement rate tends to zero or reaches the preset stability standard after the completion of the construction of the double-line shield tunnel. It is used to determine the final impact of the double-line construction on the surface settlement and to provide a basis for long-term settlement assessment and project acceptance. For example, after the tail of the rear shield exits, the surface settlement can be continuously monitored. When the settlement is less than a certain small threshold for a continuous period of time, such as a week or a month, it is determined that the final stable settlement has been reached.

[0029] Step S3: Divide the surface transverse subsidence trough data into multiple data groups based on multiple key time nodes.

[0030] In this embodiment, data within the corresponding time period is filtered out from the original settlement data based on the determined key time nodes, and then classified into different data groups. For example, one data group may contain the surface transverse settlement trough data of all monitoring points before the tunnel face of the advance line arrives, and another data group may contain the surface transverse settlement trough data of all monitoring points after the tunnel face of the advance line has passed.

[0031] Step S4: Plot the transverse settlement curve corresponding to each data group.

[0032] In this embodiment, general plotting software, such as spreadsheet programs, can be used to input the lateral settlement data points of the land surface in each data group and connect these data points to form a line graph, thereby visually displaying the shape of the land surface settlement trough during that time period.

[0033] Step S5: Integrate the transverse settlement curves of all data sets into the same coordinate system to obtain a multi-curve overlay diagram of the transverse settlement trough.

[0034] In this embodiment, the transverse settlement curves drawn at different key time points are copied and pasted one by one into the same coordinate system in the drawing software to ensure that all curves have the same range of horizontal and vertical coordinates, thereby forming an overlay graph containing multiple curves.

[0035] Step S6: Analyze the multi-curve overlay diagram of the transverse settlement trough to obtain the depth, width, and symmetry axis offset of the settlement trough under the effects of the leading line excavation, the following line excavation, and the double-line overlay effect.

[0036] Specifically, the process involves obtaining the leading line stable settlement curve and the final stable settlement curve from the multi-curve overlay diagram of the transverse settlement channel; extracting the first maximum settlement, the first settlement channel width, and the position of the first axis of symmetry from the leading line stable settlement curve; extracting the second maximum settlement, the second settlement channel width, and the position of the second axis of symmetry from the final stable settlement curve; calculating the settlement difference between the second maximum settlement and the first maximum settlement, and using the settlement difference as the settlement channel depth under the double-line overlay effect; calculating the offset of the second axis of symmetry position relative to the first axis of symmetry position, and using the offset as the axis of symmetry offset under the double-line overlay effect; and calculating the width difference between the second settlement channel width and the first settlement channel width, and using the width difference as the settlement channel width under the double-line overlay effect. Among them, the stable settlement curve of the pilot line is the shape curve of the transverse settlement trough on the ground surface after the pilot line shield tunnel is completed and reaches a stable state, and the final stable settlement curve is the shape curve of the transverse settlement trough on the ground surface after all the double-line shield tunnels are completed and reach a final stable state.

[0037] In this embodiment, based on key time nodes, such as the time node for the tail of the tunnel boring machine to exit the monitoring section to be analyzed and the time node for the final stable settlement, the data of the corresponding curves are identified and extracted from the multi-curve overlay diagram; or, the operator can interactively select and mark the preliminary line stable settlement curve and the final stable settlement curve on the displayed multi-curve overlay diagram through the graphical user interface (GUI) tool.

[0038] In this embodiment, the first maximum settlement is the maximum vertical displacement value on the leading line stable settlement curve, i.e., the lowest point of the settlement trough. The first settlement trough width is the lateral range of the leading line stable settlement curve at a certain preset settlement threshold, such as 10% of the maximum settlement or a certain fixed value. The first axis of symmetry position is the abscissa corresponding to the maximum settlement in the leading line stable settlement curve. The above parameters can be extracted using various technical means. For example, the maximum value and its position can be directly found by performing numerical analysis on the curve data, and the width of the settlement trough can be determined by interpolation or fitting methods.

[0039] In this embodiment, the second maximum settlement is the maximum vertical displacement value on the final stable settlement curve; the second settlement trough width is the lateral range of the final stable settlement curve under the same preset settlement threshold; and the second axis of symmetry position is the lateral coordinate corresponding to the maximum settlement in the final stable settlement curve.

[0040] In this embodiment, the settlement difference is used as the settlement trench depth under the double-line superposition effect, thereby quantifying the additional impact of the subsequent line excavation on the surface settlement depth. At the same time, the offset is used as the symmetry axis offset under the double-line superposition effect, thereby quantifying the lateral movement of the settlement trench center relative to the initial line construction after the double-line construction. The width difference is used as the settlement trench width under the double-line superposition effect, thereby reflecting the change in the lateral influence range of the settlement trench after the double-line construction. All the above calculations are completed by numerical subtraction.

[0041] The analysis of the multi-curve overlay diagram of the transverse settlement trough, obtaining the depth, width, and symmetry axis offset patterns of the settlement trough under the effects of the preceding line excavation, the following steps are also included: obtaining multi-curve overlay diagrams of the transverse settlement trough of the twin tunnels at at least one different axis distance, and using the obtained multi-curve overlay diagrams of the transverse settlement trough as comparison curves; analyzing the influence of the axis distance of the twin tunnels on the morphological evolution of the transverse settlement trough based on the comparison curves and the multi-curve overlay diagrams of the transverse settlement trough; and determining the recommended design value of the axis distance during the construction process of the twin tunnels based on the influence patterns.

[0042] In this embodiment, by acquiring at least one multi-curve overlay map of transverse settlement troughs of twin-track tunnels at different center-center distances and designating it as a comparison curve map, a multi-dimensional settlement database can be established to reveal the potential impact of changes in center-center distance on surface settlement morphology. The method for acquiring the comparison curve map is as follows: in actual engineering projects, selected existing or under-construction twin-track tunnel projects with different center-center distances are selected, and their surface transverse settlement time history data are acquired through monitoring points deployed on site. Subsequently, the surface transverse settlement time history data is processed according to steps S1 to S5 to generate a multi-curve overlay map of transverse settlement troughs at different center-center distances, which serves as a benchmark for comparative analysis.

[0043] In this embodiment, by comparing the comparative curves at different center distances with the multi-curve overlay of the transverse settlement trough to be analyzed, the key role of center distance in settlement characteristics is identified. The analysis of the influence can include: using a combination of graphical overlay and visual interpretation, displaying the multi-curve overlay of the transverse settlement trough at different center distances in the same coordinate system; and visually observing the changes in the peak value, valley value, width, axis of symmetry position, and center shape of the settlement trough with the construction process at different center distances to derive the qualitative law of the influence of center distance on the evolution of settlement morphology. Alternatively, a combination of parameter extraction and quantitative analysis can be used to accurately extract key settlement parameters from the comparative curves and the overlay to be analyzed, such as maximum settlement, settlement trough width, axis of symmetry offset, and settlement increment at different construction stages. Subsequently, statistical methods, such as regression analysis and correlation analysis, are used to establish a mathematical relationship model between center distance and settlement parameters, thereby quantifying the specific degree and trend of the influence of center distance on the evolution of settlement trough morphology.

[0044] One method for determining the recommended design value can be: based on the influence of the center distance on the evolution of the settlement trough shape, combined with the specific geological conditions, structural safety requirements, and settlement control standards of surface sensitive structures of the project, a maximum allowable surface settlement or settlement trough shape variation range is set. Then, based on this control objective, the range of center distances that meet the conditions is deduced from the influence law, and a recommended value that is optimal in terms of construction feasibility and economy is selected, such as 2.5D. Alternatively, an optimization model based on the influence law can be constructed. This model uses the center distance as a variable, settlement characteristics such as surface settlement, settlement trough width, and symmetry axis offset as constraints, and engineering cost or construction efficiency as the optimization objective. By solving this optimization model, the optimal recommended design value of the center distance that meets all constraints can be obtained.

[0045] In this embodiment, a multi-curve overlay diagram of transverse settlement troughs at different center-center distances is used as a comparison benchmark. Based on this, the influence of center-center distance on the evolution of settlement trough morphology is analyzed in depth. This allows for a quantitative revelation of the intrinsic relationship between center-center distance and dynamic response of surface settlement. This effectively solves the problem of insufficient settlement control caused by neglecting the center-center distance factor in existing methods, making the prediction and control of surface settlement during the construction of twin-track tunnels more accurate. Finally, based on the analyzed influence patterns, this application can determine specific design recommendations for center-center distance, providing a scientific and quantitative basis for tunnel spacing design. This optimizes the tunnel layout, effectively controls the risk of surface settlement, and balances the economy and feasibility of the project while ensuring engineering safety.

[0046] The comparative analysis of the influence of the center-to-center distance of the two tunnels on the evolution of the transverse settlement trough morphology includes: when the center-to-center distance of the two tunnels is not less than the critical distance, during the excavation of the subsequent line, the transverse settlement trough gradually evolves from a single-core morphology formed by the excavation of the preceding line to a multi-core morphology, and maintains the multi-core morphology after the excavation of the subsequent line is completed; when the center-to-center distance of the two tunnels is less than the critical distance, during the excavation of the subsequent line: if the excavation of the preceding line forms a non-single-peak settlement morphology, then the non-single-peak settlement morphology gradually evolves into a single-core morphology, and maintains the single-core morphology after the excavation of the subsequent line is completed; if the excavation of the preceding line forms a single-core morphology, then this morphology maintains the single-core morphology during and after the excavation of the subsequent line; wherein, as the center-to-center distance of the two tunnels decreases, the interaction between the soil excavated by the preceding and subsequent lines intensifies, the settlement deformation of the jointly disturbed area intensifies, the depth of the transverse settlement trough gradually increases, and the morphology of the settlement trough evolves from a multi-core morphology to a single-core morphology.

[0047] The center-to-center distance of a double-track tunnel is the horizontal distance between the centerlines of the two shield tunnels. It is a key parameter in the design of double-track tunnels, directly affecting the scope and extent of the impact of tunnel construction on surface settlement. Its measurement method can be determined through design drawings or on-site measurements. For example, it can be measured accurately using a total station or extracted from a BIM model. The critical distance is a specific threshold for the center-to-center distance of the double-track tunnel. When the actual center-to-center distance is greater than or less than this specific threshold, the morphological evolution of the surface settlement trough will change significantly. The determination of this critical distance is usually based on a large amount of engineering experience, numerical simulation analysis, or model test results. For example, it can be determined by regression analysis of settlement data under different center-to-center distances, or by verification through theoretical calculations combined with on-site monitoring data.

[0048] The evolution of the lateral settlement trough morphology is the process by which the shape of the lateral settlement curve changes as the construction of the twin-track tunnel progresses. The evolution of the lateral settlement trough morphology can be observed by continuously monitoring the surface settlement points and drawing lateral settlement curves at different construction stages. For example, the morphological changes can be analyzed by comparing the stable settlement curve of the first line, the curve during the excavation of the second line, and the final stable settlement curve. The single trough core morphology refers to the lateral settlement curve of the surface showing a clear and concentrated settlement low point, that is, only one settlement peak. This morphology usually occurs when single-track tunnel construction or when the axial distance between twin-track tunnels is large. It can be achieved by curve fitting of the monitoring data to determine whether there is a single minimum point, or by visually inspecting the shape of the settlement curve.

[0049] A multi-core morphology is characterized by two or more distinct settlement depressions on the transverse settlement curve of the ground surface, i.e., the presence of multiple settlement peaks. The multi-core morphology usually occurs when the center-to-center distance between two tunnels is moderate and the settlement influence areas of the two tunnels have not yet fully overlapped and merged. It can be identified by performing second derivative analysis on the settlement curve to find multiple local minimum points, or by observing whether there are two or more depression areas on the curve.

[0050] During the excavation of the rear tunnel, from the time the rear tunnel boring machine reaches the section to be analyzed and monitored from the time the shield tail exits the section to be analyzed and monitored, the construction of the rear tunnel causes secondary disturbance to the already disturbed soil. This is a critical stage in the evolution of settlement patterns. After the excavation of the rear tunnel is completed, the surface settlement tends to stabilize after the shield tail of the rear tunnel boring machine exits the section to be analyzed and monitored. At this time, the final impact of the construction of the dual tunnels on surface settlement is basically formed.

[0051] Among them, the non-single peak settlement pattern is that after the surface transverse settlement curve is completed, its settlement pattern does not show a single, concentrated settlement peak. It may show a gentle, wide settlement area, or it may have begun to show a trend of bi-peaks. The non-single peak settlement pattern can be identified by analyzing the stable settlement curve of the pilot line to determine whether it has a clear single lowest point. For example, it can be identified by calculating the curvature change of the curve.

[0052] In this embodiment, the enhanced soil interaction refers to the increased mutual influence between the soil stress and displacement fields caused by the excavation of the leading and trailing tunnels as the axial distance between the two tunnels decreases. This enhancement can be quantified by finite element analysis to simulate soil stress distribution or indirectly reflected by on-site monitoring of soil pressure changes. The increased settlement deformation in the common disturbance area occurs between or near the two tunnels. Due to the enhanced soil interaction, the surface settlement in this area increases significantly. This intensification can be observed by comparing the settlement at the same location under different axial distances or characterized by calculating the settlement increment. The gradually increasing trench depth refers to the gradual increase in the absolute value of the lowest point of the transverse settlement curve, indicating that the overall surface settlement is more severe as the axial distance decreases. The evolution of the settlement trench morphology from a multi-core to a single-core morphology is due to the gradual merging of the curves that originally presented two independent settlement points as the axial distance between the two tunnels decreases, eventually forming a deeper and wider single settlement point. This evolution is a macroscopic manifestation of the enhanced soil interaction.

[0053] In this embodiment, the following rules are also included: In the multi-core configuration, the core of the final stable settlement curve is offset away from the core of the preceding line stable settlement curve in a direction away from the central axis of the dual-track tunnel, and the width and depth of the settlement groove of the preceding line tunnel are both greater than the width and depth of the settlement groove of the following line tunnel; In the single-core configuration, the core of the final stable settlement curve and the core of the preceding line stable settlement curve are both within a preset range of the central axis of the dual-track tunnel.

[0054] In the case of multiple core morphology, the core of the final stable settlement curve is offset away from the core of the stable settlement curve of the preceding line in a direction away from the central axis of the dual-track tunnel. This describes the positional relationship between the core of the final surface settlement trough after the completion of the dual-track tunnel construction and the final surface settlement trough after the completion of the preceding line construction. When the axis distance between the dual-track tunnels is large, resulting in the formation of two relatively independent settlement troughs, the soil disturbance caused by the excavation of the subsequent line will cause the core of the final stable settlement curve to shift away from the central axis of the dual-track tunnel relative to the core of the settlement curve affected only by the preceding line.

[0055] In this embodiment, by comparing the lateral coordinates of the minimum settlement points of the final stable settlement curve and the leading line stable settlement curve, if the distance between the lateral coordinate of the center of the groove of the final stable settlement curve and the central axis of the double-track tunnel is greater than the distance between the lateral coordinate of the center of the groove of the leading line stable settlement curve and the central axis of the double-track tunnel, it can be determined that there is a shift away from the central axis of the double-track tunnel. Alternatively, after obtaining the positions of the groove centers of the two curves, their relative positional changes with respect to the central axis of the double-track tunnel can be calculated. For example, if the leading line stable settlement curve is located to the left of the central axis and the final stable settlement curve is located to the right of the central axis, then moving away from the central axis of the double-track tunnel means that the groove center has moved further to the left or right, depending on which line is the leading line. By calculating the difference between these lateral coordinates and combining it with the position of the central axis of the double-track tunnel, this shift can be quantified.

[0056] Among them, the width and depth of the settlement trough of the first-line tunnel are greater than those of the second-line tunnel, thus quantifying the relative scale of the settlement troughs caused by the first-line tunnel and the second-line tunnel under the multi-trough core morphology. In the construction of the double-line tunnel, the first-line tunnel, as the first disturbance, usually has a greater impact on the surface settlement than the incremental settlement caused by the second-line tunnel in its own area or the width and depth of the settlement trough formed independently.

[0057] In this embodiment, the maximum settlement and the corresponding settlement trough width are extracted from the stable settlement curve of the preceding line. At the same time, the local settlement troughs of the subsequent line area are identified from the final stable settlement curve, and their maximum settlement and width are extracted and then directly compared. Alternatively, based on the stable settlement curve of the preceding line and the final stable settlement curve, the additional settlement curve caused by the construction of the subsequent line can be calculated by difference. Then, the additional settlement curve is analyzed, its maximum settlement and width are extracted, and compared with the depth and width of the stable settlement curve of the preceding line.

[0058] In the single-core configuration, the core of both the final stable settlement curve and the core of the initial stable settlement curve lie within a predetermined range along the central axis of the dual-track tunnel. This describes the stability of the core position when the axial distance between the two tunnels is small, causing the two settlement troughs to merge into a single, integrated settlement trough. In this merged configuration, both the core of the settlement trough after the initial track construction is completed and the core of the final stable settlement trough after all dual-track construction is completed will be located within a predetermined defined area near the geometric central axis of the dual-track tunnel.

[0059] In this embodiment, a preset range can be defined, for example, extending a certain distance to both sides from the centerline of the double-track tunnel, such as 0.1 times or 0.2 times the outer diameter D of the tunnel. Then, the transverse coordinates of the center of the trench of the final stable settlement curve and the preliminary stable settlement curve are extracted, and it is determined whether both coordinates fall within the preset range. Alternatively, the absolute difference between the transverse coordinates of the center of the trench of the final stable settlement curve and the preliminary stable settlement curve and the transverse coordinates of the centerline of the double-track tunnel can be calculated, and it can be determined whether these differences are all less than a preset threshold. If they are all less than the preset threshold, the center of the trench is considered to be within the preset range.

[0060] After obtaining the multi-curve overlay diagram of the transverse settlement trough, the method further includes: calculating the increment of the subsequent line based on the cumulative vertical displacement corresponding to the stable settlement curve of the preceding line and the cumulative vertical displacement corresponding to the final stable settlement, so as to characterize the degree of secondary disturbance of the soil already disturbed by the preceding line during the construction of the subsequent line; drawing the subsequent line increment curve based on the subsequent line increment, and adding the subsequent line increment curve to the multi-curve overlay diagram of the transverse settlement trough.

[0061] In this embodiment, calculating the subsequent line increment aims to quantify the additional settlement impact of subsequent line construction on soil already disturbed by the preceding line, thereby separating and identifying secondary disturbance effects. This calculation process can be implemented in various ways. For example, for each monitoring point in the monitoring section, the cumulative vertical displacement value corresponding to the stable settlement curve of the preceding line and the cumulative vertical displacement value corresponding to the final stable settlement curve are obtained. Then, the cumulative vertical displacement of the final stable settlement is subtracted from the cumulative vertical displacement of the stable settlement of the preceding line, and the difference is the subsequent line increment of that monitoring point.

[0062] The subsequent track increment is used to characterize the degree of secondary disturbance to the soil already disturbed by the preceding track during the construction of the subsequent track. By measuring the size and distribution of the subsequent track increment, the degree of further disturbance caused by the subsequent track excavation to the soil that has already settled can be directly assessed. For example, a larger subsequent track increment indicates a significant secondary disturbance effect, requiring more stringent settlement control measures.

[0063] One method for plotting the backward linear increment curve is to use the backward linear increment value of each monitoring point as the ordinate and its corresponding lateral position as the abscissa, plot the points in a coordinate system, and connect them to form a line. Alternatively, professional plotting software can be used to generate smooth backward linear increment curves through interpolation algorithms. These curves can then be overlaid on an existing multi-curve overlay map of the transverse settlement trough with different colors, line types, or markers to ensure that all curves are presented in a unified coordinate system.

[0064] The following example illustrates the characteristics of settlement trench depth, width, and symmetry axis offset under the effects of advance line excavation, follow line excavation, and the superposition of two lines: Figure 2 This is a multi-curve overlay diagram of the transverse settlement trough at the monitoring section of Tunnel 1. Figure 3 This is a multi-curve overlay diagram of the transverse settlement trough at the monitoring section of Tunnel 2. Figure 4 This is a multi-curve overlay diagram of the transverse settlement trough at the monitoring section of Tunnel 3. Tunnel 1, Tunnel 2, and Tunnel 3 are all located in soft soil areas.

[0065] like Figure 1 , Figure 2 and Figure 3 As shown, when the tunnel boring machine (TBM) arrived, compared to the initial state of the ground surface, many monitoring sections of tunnels 1 and 3 exhibited uplift deformation. However, the monitoring points of the section to be analyzed in tunnel 2 did not show significant surface deformation. After the TBM left the section to be analyzed and the surface settlement stabilized, most monitoring points on the sections to be analyzed in tunnels 1 and 2 experienced significant settlement, with the settlement troughs deepening considerably. The surface settlement curves showed a distinct "V" shape, i.e., a single trough center, with the trough centers located near the TBM, where the subsequent settlement increase was the largest, approximately 9mm and 8mm respectively. Conversely, tunnel 2 experienced a settlement increase of 5-6mm within a range of (-10, 20)m on both sides of the centerline of the double-track tunnel. The settlement increments at each monitoring point were evenly distributed, and the settlement trough curves were roughly trapezoidal.

[0066] When the subsequent tunnel reaches the section to be analyzed and monitored again, the soil above the subsequent tunnels of Tunnel 1 and Tunnel 3 rises slightly. This phenomenon is related to the compression and uplift of the soil in front of the excavation face caused by the setting of the shield tunneling construction parameters. The cross-section begins to change from a "V" shaped single trench to a "W" shaped double trench, that is, from a single trench center to multiple trench centers. At this time, the subsequent tunnel of Tunnel 2 and the area near the central axis of the two tunnels experience a settlement increment of about 5-8 mm, and the cross-section begins to change from an inverted trapezoid to a "V" shape.

[0067] After the retracing line departs from the monitoring section to be analyzed and stabilizes, the settlement trough of Tunnel 1 still maintains a "W" shape. At this time, the center of the trough of the retracing line (i.e., the center of the trough of the final stable settlement curve) shifts away from the central axis of the double-track tunnel. The width and depth of the trough of the leading line tunnel are both greater than those of the retracing line, with depths of -5.25 mm and -4.18 mm respectively. The maximum net settlement increment at the center of the trough of the retracing line is -5.28 mm. The spacing between the centers of the "W"-shaped settlement trough of Tunnel 3 decreases. After the retracing line departs from the monitoring section to be analyzed, the center of the trough of the retracing line moves closer to the central axis of the double-track tunnel, with a depth of -11.27 mm. The monitoring point with the largest net settlement increment is located between the central axes of the retracing line tunnel and the double-track tunnel, at -9.92 mm. The "V"-shaped settlement trough curve of Tunnel 2 remained unchanged after the shield tunneling machine left the rear line. The monitoring point that generated the maximum net settlement increment was located near the central axis of the double-track tunnel. The center of the "V"-shaped settlement trough was also located at this point, with a trough depth of -17.17 mm and a settlement increment of -10.52 mm.

[0068] In summary, the center-to-center distance of the twin-track tunnels is highly sensitive to the distribution of lateral settlement troughs in soft soil areas. The center-to-center distances of tunnels 1, 2, and 3 are 15m, 12m, and 14m, respectively. As the center-to-center distance of the twin-track tunnels decreases, the interaction between the soil excavated from the preceding and following tunnels intensifies, exacerbating settlement deformation in the jointly disturbed area. The lateral settlement curve shape of the monitoring section changes from "W" to "V," and the depth of the settlement trough in the cross-section gradually increases. Based on the analysis of measured data, it is recommended that the design value of the center-to-center distance of the shield-tunnel twin-track tunnel should be as large as possible, where D is the outer diameter of the tunnel.

[0069] Example 2 like Figure 5 As shown, this invention also proposes a system for analyzing the impact of sequential excavation of a dual-track shield tunnel on surface settlement, using a method for analyzing the impact of sequential excavation of a dual-track shield tunnel on surface settlement as described in any of Embodiment 1, comprising the following modules: The acquisition module is used to acquire surface transverse settlement trough data from multiple monitoring points in the monitoring section to be analyzed; The first division module, connected to the acquisition module, is used to divide the entire process of dual-line construction into multiple key time nodes based on the spatial relative position of the tunnel boring machine face and the section to be analyzed and monitored. The second partitioning module is connected to the first partitioning module and divides the surface transverse subsidence trough data into multiple data groups based on multiple key time nodes. A drawing module, connected to the second division module, is used to draw the transverse settlement curve corresponding to each data group; An integration module, connected to the drawing module, is used to integrate the transverse settlement curves of all data sets into the same coordinate system to obtain a multi-curve overlay diagram of the transverse settlement trough. The analysis module, connected to the integration module, is used to analyze the multi-curve overlay diagram of the transverse settlement trough to obtain the depth, width, and symmetry axis offset of the settlement trough under the effects of the leading line excavation, the following line excavation, and the double-line overlay effect.

[0070] To address the problem that existing technologies only focus on final settlement and fail to reflect the dynamic changes in settlement throughout the entire construction process, this invention employs a time-node division method based on the relative positions of the tunnel boring machine face and the monitoring section. This divides the entire dual-track construction process into multiple key stages, and plots the surface settlement data for each stage as transverse settlement curves, integrating them into a multi-curve overlay graph. This method can demonstrate the evolution of settlement trough depth, width, and symmetry axis offset under the combined effects of the leading and trailing tunnels, effectively capturing the dynamic changes and peak values ​​of settlement during construction. This provides precise quantitative data for tunnel spacing optimization and dynamic construction control, improving construction safety and surface protection.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A method for analyzing the impact of sequential excavation of a dual-track shield tunnel on surface settlement, characterized in that, include: Acquire surface transverse settlement trough data from multiple monitoring points in the monitoring section to be analyzed; Based on the spatial relative position of the tunnel boring machine face and the section to be analyzed and monitored, the entire process of dual-line construction is divided into multiple key time nodes; The surface transverse subsidence trough data is divided into multiple data groups based on multiple key time nodes; Plot the lateral settlement curve for each of the data sets; By integrating the transverse settlement curves of all data sets into the same coordinate system, a multi-curve overlay diagram of the transverse settlement trough is obtained. Analysis of the multi-curve overlay diagram of the transverse settlement trough reveals the depth, width, and symmetry axis offset patterns of the settlement trough under the effects of advance line excavation, follow line excavation, and double-line overlay.

2. The method for analyzing the impact of sequential excavation of a double-track shield tunnel on surface settlement according to claim 1, characterized in that, The key time nodes include: the initial state time node, the time node when the tunnel face of the first shield tunnel reaches the section to be analyzed and monitored, the time node when the tail of the first shield tunnel exits the section to be analyzed and monitored, the time node when the tunnel face of the second shield tunnel reaches the section to be analyzed and monitored, and the final stable settlement time node.

3. The method for analyzing the impact of sequential excavation of a double-track shield tunnel on surface settlement according to claim 1, characterized in that, The analysis of the multi-curve overlay diagram of the transverse settlement trough yields the characteristics of the settlement trough depth, width, and symmetry axis offset under the effects of the preceding line excavation, the following: Obtain the preliminary stable settlement curve and the final stable settlement curve from the multi-curve overlay diagram of the transverse settlement trough; Extract the first maximum settlement, the first settlement trough width, and the first axis of symmetry from the leading line stable settlement curve; Extract the second maximum settlement, the second settlement trough width, and the position of the second axis of symmetry from the final stable settlement curve; Calculate the difference between the second maximum settlement and the first maximum settlement, and use the difference as the settlement trough depth under the double-line superposition effect; Calculate the offset of the second axis of symmetry position relative to the first axis of symmetry position, and use the offset as the axis of symmetry offset under the double-line superposition effect; Calculate the width difference between the second settling trough width and the first settling trough width, and use the width difference as the settling trough width under the double-line superposition effect.

4. The method for analyzing the impact of sequential excavation of a double-track shield tunnel on surface settlement according to claim 3, characterized in that, The analysis of the multi-curve overlay diagram of the transverse settlement trough, to obtain the settlement trough depth, width, and symmetry axis offset patterns under the effects of the preceding line excavation, the following also includes: Obtain a multi-curve overlay diagram of the transverse settlement trough of at least one double-track tunnel with different axis center distances, and use the obtained multi-curve overlay diagram of the transverse settlement trough as a comparison curve diagram; Based on the aforementioned comparative curve diagram and the aforementioned multi-curve superimposed diagram of the transverse settlement trough, the influence of the axis distance between the two tunnels on the morphological evolution of the transverse settlement trough is analyzed. Based on the aforementioned influence patterns, the recommended design value for the center-to-center distance during the construction of a dual-track tunnel is determined.

5. The method for analyzing the impact of sequential excavation of a double-track shield tunnel on surface settlement according to claim 4, characterized in that, The comparative analysis of the influence of the center-to-center distance of the twin tunnels on the evolution of the morphology of the transverse settlement trough includes: When the center-to-center distance between the two tunnels is not less than the critical distance, during the excavation of the subsequent line, the transverse settlement trough gradually evolves from a single-core morphology formed by the excavation of the preceding line to a multi-core morphology, and retains the multi-core morphology after the excavation of the subsequent line is completed. When the center-to-center distance between the two tunnels is less than the critical distance, during the excavation of the subsequent tunnel: If the tunneling of the lead line forms a non-single peak settlement pattern, the non-single peak settlement pattern will gradually evolve into a single core pattern, and the single core pattern will be maintained after the tunneling of the follow line is completed. If the tunneling of the lead line forms a single core shape, then this shape will remain a single core shape during and after the tunneling of the follow line. As the center-to-center distance between the two tunnels decreases, the interaction between the soil excavated by the first and second lines intensifies, the settlement deformation in the jointly disturbed area intensifies, the depth of the transverse settlement trough gradually increases, and the morphology of the settlement trough evolves from a multi-trough core morphology to a single-trough core morphology.

6. The method for analyzing the impact of sequential excavation of a double-track shield tunnel on surface settlement according to claim 5, characterized in that, Also includes: In the multi-trough configuration, the trough center in the final stable settlement curve is offset away from the trough center in the stable settlement curve of the preceding line from the direction of the central axis of the dual-line tunnel. The width and depth of the settlement trough of the preceding line tunnel are both greater than the width and depth of the settlement trough of the following line tunnel. In the case of a single core, the core of the final stable settlement curve and the core of the preliminary stable settlement curve are both within the preset range of the central axis of the dual-track tunnel.

7. The method for analyzing the impact of sequential excavation of a double-track shield tunnel on surface settlement according to claim 1, characterized in that, After obtaining the multi-curve overlay diagram of the transverse settlement trough, the following is also included: The incremental displacement of the subsequent line is calculated based on the cumulative vertical displacement corresponding to the stable settlement curve of the preceding line and the cumulative vertical displacement corresponding to the final stable settlement curve, so as to characterize the degree of secondary disturbance of the soil already disturbed by the construction of the subsequent line to the soil already disturbed by the preceding line. Based on the backward line increment, a backward line increment curve is plotted and added to the multi-curve overlay diagram of the transverse settlement trough.

8. The method for analyzing the impact of sequential excavation of a double-track shield tunnel on surface settlement according to claim 1, characterized in that, Before acquiring the surface transverse settlement trough data of multiple monitoring points in the monitoring section to be analyzed, the method further includes: A monitoring section is set up along the longitudinal direction of the tunnel at a predetermined number of rings, and multiple monitoring points are symmetrically arranged on both sides of the central axis of the double-track tunnel for each monitoring section. Acquire settlement time history data for each of the monitoring points; Extract the transverse cross-sectional settlement value corresponding to each key time node in the settlement time history data to obtain the transverse settlement trough data of the land surface.

9. A system for analyzing the impact of sequential excavation of a dual-track shield tunnel on surface settlement, characterized in that, The system employs the method for analyzing the impact of sequential excavation of a dual-track shield tunnel on surface settlement as described in any one of claims 1 to 8, and specifically includes the following modules: The acquisition module is used to acquire surface transverse settlement trough data from multiple monitoring points in the monitoring section to be analyzed; The first division module, connected to the acquisition module, is used to divide the entire process of dual-line construction into multiple key time nodes based on the spatial relative position of the tunnel boring machine face and the section to be analyzed and monitored. The second partitioning module is connected to the first partitioning module and divides the surface transverse subsidence trough data into multiple data groups based on multiple key time nodes. A drawing module, connected to the second division module, is used to draw the transverse settlement curve corresponding to each data group; An integration module, connected to the drawing module, is used to integrate the transverse settlement curves of all data sets into the same coordinate system to obtain a multi-curve overlay diagram of the transverse settlement trough. The analysis module, connected to the integration module, is used to analyze the multi-curve overlay diagram of the transverse settlement trough to obtain the depth, width, and symmetry axis offset of the settlement trough under the effects of the leading line excavation, the following line excavation, and the double-line overlay effect.

Images