Tunnel centerline fitting method and system for adjusting plane control survey results

Abstract

This invention relates to a method and system for fitting the centerline of a tunnel by adjusting the results of plane control surveying in the field of tunnel engineering construction surveying technology. The method includes: S1, Data acquisition and preprocessing: obtaining the coordinates of control points by re-measuring the control network, obtaining over-excavation and under-excavation data by scanning the cross-section, and establishing a database; S2, Centerline fitting and calculation: setting the correction values ​​for control points and curve parameters, constructing a weighted least squares problem, assigning the highest weight to clearance and under-excavation, a medium weight to centerline smoothness, and the lowest weight to uniform over-excavation, and calculating the correction values; S3, Result adjustment and verification: updating the control point coordinates and verifying the threshold, fitting a new centerline, calculating over-excavation and under-excavation by projection, and determining whether the clearance meets the requirements; S4, Iterative optimization: if the under-excavation elimination rate, over-excavation standard deviation, centerline deviation, or clearance qualification rate does not meet the standards, adjusting the weights and repeating S2 and S3 until the standards are met; S5, Construction application; This invention solves the problems of traditional methods being prone to repetition, uneconomical, and disconnected from engineering engineering.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering construction surveying technology, and in particular to a method and system for fitting the centerline of a tunnel by adjusting the results of plane control surveying. Background Technology

[0002] In tunnel engineering, before secondary lining construction, it is usually necessary to measure the centerline of the line based on the tunnel's horizontal control network to guide the placement of the formwork trolley and concrete pouring. However, due to factors such as traverse angle and distance measurement errors, instrument alignment and aiming errors, and construction disturbances, the measured centerline often deviates from the design position, leading to a series of problems: local under-excavation results in insufficient lining clearance, which must be addressed; excessive local over-excavation increases concrete usage and costs; and substandard overall clearance directly affects operational safety and equipment installation.

[0003] To address the above problems, existing technologies mainly employ the following two approaches:

[0004] First, local treatment of the cross-section: the under-excavated parts are re-excavated, and the over-excavated parts are filled with shotcrete or secondary lining. Although this method can solve the problem of individual cross-sections, it is essentially a "stopgap measure" - it only eliminates the surface defects that have appeared, but does not eliminate the systematic measurement errors that cause the centerline to deviate. Since the plane control benchmark has not been adjusted, the subsequent construction will still use the same set of biased measurement results, which will cause the over-excavation and under-excavation problems to recur in other sections of the tunnel. This method often requires multiple treatments, which is not only uneconomical, but also seriously affects the construction period.

[0005] Secondly, the design parameters such as the curve radius are adjusted as a whole to refit the centerline, but this method may deviate from the original design intent and lacks a closed-loop verification mechanism, making the adjustment effect uncontrollable. In addition, many methods involving mathematical optimization remain at the algorithm level and are not bound to measurement and construction equipment, resulting in poor implementability. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the present invention discloses a method and system for fitting the centerline of a tunnel by adjusting the results of plane control measurement, so as to solve the technical problems of traditional local processing methods being prone to repetition, uneconomical and unable to fundamentally eliminate centerline deviation, and overcome the defects of the existing technology in which mathematical optimization and engineering implementation are disconnected.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for fitting the centerline of a tunnel by adjusting the results of plane control surveys, applicable to tunnel clearance rectification before secondary lining, includes the following steps: S1, Data acquisition and preprocessing; re-surveying and adjusting the plane control network inside the tunnel to obtain the measured coordinates and azimuth of each control point; acquiring the measured contours and over- and under-excavation data of each section, and integrating them to establish a database containing mileage, deviation, and over- and under-excavation values; S2, Centerline fitting and solution; based on the database, setting the control point coordinate correction and curve parameter correction, with the constraints of eliminating under-excavation, homogenizing over-excavation, maintaining centerline smoothness, and meeting clearance requirements as the objectives, constructing a weighted least squares problem. The objective function of the weighted least squares problem includes at least: the weighted sum of the squares of the under-excavation amounts of each section, the weighted sum of the squares of the second difference of the centerline lateral deviation, and the weighted sum of the squares of the difference between the over-excavation amount of each section and the mean of the over-excavation amount of that section; wherein, the constraint of not meeting the clearance and the existence of under-excavation is given the highest weight, the centerline smoothness deviation term is given a medium weight, and the over-excavation term is given a lower weight. The deviation from the mean is assigned the lowest weight, and the weight assignment follows the engineering priority order of safety hard constraints first, smoothness second, and economy last. The control point coordinate correction and curve parameter correction are calculated. S3, result adjustment and verification: The control point coordinates are updated according to the calculated correction. After the verification coordinate correction and the change in the side length of adjacent points are both less than the preset threshold, a new centerline is generated using the updated control point coordinates and the calculated curve parameter correction. The measured contour is then projected onto the new centerline, and the over-excavation and under-excavation are recalculated and it is determined whether the clearance meets the sum of the design limit value and the construction allowance. S4, iterative optimization: If any of the indicators such as the under-excavation elimination rate, the standard deviation of over-excavation, the absolute value of the maximum deviation of the centerline, or the limit qualification rate does not reach the preset standard value, the values ​​of the highest, medium, and lowest weights are adjusted and steps S2 to S3 are repeated until all indicators reach the preset standard value. S5, construction application: The new centerline data is output to guide the layout of the secondary lining formwork and to handle under-excavation and over-excavation accordingly.

[0009] Furthermore, in S1, the resurvey of the plane control network adopts the form of main and secondary traverses or cross double traverses, with no less than 2 rounds of angle measurement, and the side length is measured in both directions. Gyro azimuth angles are added every 800 to 1200m as weighted observations. After adjustment, the mean square error of angle measurement is no greater than ±1.5″, and the mean square error of the weakest point position is no greater than ±20mm.

[0010] Furthermore, in S1, a three-dimensional laser scanner or laser profiler is used to scan the cross-section. A cross-section is formed every 4 to 6 meters for straight sections and every 2 to 3 meters for curved sections. Over-excavation sections with an over-excavation amount greater than 150 mm and under-excavation sections are marked.

[0011] Furthermore, in S2, the ratio of the highest, medium, and lowest weights is 8-12:4-6:1.

[0012] Furthermore, in S2, the curve parameter corrections include the intersection point correction δ. JD , radius correction number δ R and the correction δ for the length of the transition curve l , where δ JD The absolute value does not exceed 20mm, δ R The absolute value does not exceed 5‰ of the original design radius R0.

[0013] Furthermore, in S3, the preset threshold for the control point coordinate correction is ±15mm, the preset threshold for the change in the side length of adjacent points is ±3mm, and the construction allowance is 10mm.

[0014] Furthermore, in S4, the preset compliance values ​​are: 100% under-excavation elimination rate, over-excavation standard deviation not exceeding 30mm, absolute value of maximum centerline deviation not exceeding 30mm, and clearance compliance rate of 100%.

[0015] A tunnel centerline fitting system includes: a data acquisition module, comprising a total station for acquiring measured control point data and a 3D scanning device for acquiring cross-section scanning data; a data processing device, communicatively connected to the data acquisition module, for calculating control point coordinate corrections and curve parameter corrections based on the received data, generating a new centerline using the updated control point coordinates and the calculated curve parameter corrections, and performing over- and under-excavation recalculation and iterative optimization, wherein the data processing device is an industrial computer or embedded processing platform, internally storing program instructions for executing the calculation, generation, and iterative optimization processes; and an output module, connected to the data processing device, for outputting an adjusted plane control point coordinate table, a new centerline pile-by-pile coordinate table, and a construction layout guide.

[0016] By employing the technical solution described above, the present invention has the following beneficial effects:

[0017] This invention discloses a method and system for fitting the centerline of a tunnel by adjusting the results of plane control surveys. It systematically eliminates centerline deviations from the measurement benchmark level by finely adjusting the overall plane control network results within the tunnel, i.e., the coordinates of control points, and allowing curve parameters to be corrected within the allowable limits specified in the standards. Simultaneously, it introduces a weighted least squares optimization model, mapping safety constraints (under-excavation elimination and clearance compliance) to the highest weight, smoothness to a medium weight, and economy to the lowest weight, and ensuring all indicators meet the standards through closed-loop iteration. Finally, the optimization results are directly output to the construction layout equipment, forming a fully digital physical closed loop of "scanning, adjustment, fitting, and layout." This method retains the original design intent while achieving precise control of over-excavation, under-excavation, and clearance, combining safety, economy, and feasibility. Attached Figure Description

[0018] Figure 1This is a schematic flowchart of the method of the present invention;

[0019] Figure 2 This is a flowchart of the steps for adjusting and verifying the results of the method of this invention;

[0020] Figure 3 This is a flowchart of the iterative optimization steps of the method of the present invention;

[0021] Figure 4 This is a schematic block diagram of the system of the present invention. Detailed Implementation

[0022] The technical solution of the present invention will now be described with reference to the accompanying drawings in the embodiments of the present invention.

[0023] Combined with appendix Figure 1-3 The method for fitting the tunnel centerline based on the adjusted planar control survey results includes the following steps:

[0024] Step 1: Data Acquisition and Preprocessing;

[0025] The total station was used to re-measure and rigorously adjust the plane control network inside the tunnel, and the measured coordinates, azimuth and mean square error of each control point were obtained; the entire tunnel cross section was scanned using a 3D scanning device to obtain the measured profile, over-excavation and under-excavation data and centerline lateral deviation of each section; the control point coordinates, mileage, centerline deviation and over-excavation and under-excavation values ​​were integrated into the same coordinate system to establish a database;

[0026] As required, the resurvey of the plane control network adopts a cross-traverse network form, with at least four rounds of angle measurement and forward and backward measurements of side lengths. Gyro azimuth angles are added every 800–1200 m as weighted observations. After adjustment, the mean square error of angle measurement is no greater than ±1.5″, and the mean square error of the weakest point position is no greater than ±20 mm. Cross-section scanning uses a three-dimensional laser scanner or laser profiler. A cross-section is set every 4–6 m for straight sections, usually 5 m, and every 2–3 m for curved sections. Over-excavation sections with an over-excavation amount greater than 150 mm and under-excavation sections are marked.

[0027] Step 2: Establish and solve the midline fitting model;

[0028] Based on the aforementioned database and using the measured control points as a reference, a control point coordinate correction (δX) is set. i ,δY i ) and curve parameter corrections (including intersection correction δ) JD , radius correction number δ R δ, the correction for the length of the transition curve lThe objectives are to minimize under-excavation, homogenize over-excavation, achieve centerline smoothness, and meet clearance standards. Clearance and under-excavation conditions are assigned a first weight, centerline smoothness condition (i.e., centerline smoothness deviation term, measured by the second difference of the centerline lateral deviation) is assigned a second weight, and homogenization of over-excavation is assigned a third weight. The first weight is greater than the second weight, and the second weight is greater than the third weight. The weighted least squares method is used to calculate the control point coordinate corrections and curve parameter corrections, minimizing the weighted sum of squared residuals for all constraints. The weighting is a direct mapping of the priority of engineering safety specifications: clearance compliance and under-excavation elimination are mandatory hard constraints and are assigned the highest weight; centerline smoothness affects driving comfort and safety and is assigned a medium weight; homogenization of over-excavation is an economic objective, allowing for some flexibility and is assigned the lowest weight.

[0029] As needed, the first weight is set to 10, the second weight to 5, and the third weight to 1; or, the ratio of the first, second, and third weights is adjusted within the range of 8–12:4–6:1; among the curve parameter corrections, the intersection point correction δ JD The absolute value does not exceed 20mm, and the radius correction δ R The absolute value does not exceed 5‰ of the original design radius R0.

[0030] Specifically, based on the database settings for coordinate corrections and curve parameter corrections for each control point, a weighted least squares objective function is established:

[0031] Minimize: ∑(w1·(under-digging amount j)²)+∑(w2·(Δ²Yk)²)+∑(w3·(over-digging amount m-μ)²)

[0032] Here, the under-excavation amount j represents the radial absolute value of the insufficient clearance at the j-th cross-section, Δ²Yk is the second-order difference of the lateral deviation of the centerline of the k-th control segment, the control segment is defined as the line segment between two adjacent plane control points, and μ is the arithmetic mean of the over-excavation amounts at all cross-sections; the constraint condition is that the clearance at each cross-section must not be less than the sum of the design limit value and the construction allowance. This constraint is automatically enforced by setting the under-excavation amount term as the highest weight w1 and incorporating it into the objective function as a penalty function term. During the iterative solution process, a large penalty is imposed on the search direction that deviates from the constraint, making... The solution process is forced to converge to and ultimately satisfy the constraints; in terms of weight allocation, the under-excavation term takes the highest weight w1, the smoothness term takes the medium weight w2, and the over-excavation uniformity term takes the lowest weight w3, clearly reflecting the order of priority for hard safety constraints, followed by smoothness, and lastly economy; the over-excavation uniformity term, in the form of the sum of squared deviations, promotes the over-excavation amount of each section to approach the overall average, thereby reducing the dispersion of over-excavation and avoiding large local over-excavation. Then, the iterative weighted least squares method is used to solve the problem with the penalty function. In this method, a set of control point coordinate corrections (δX) are given. i,δY i ) and curve parameter correction (δ) JD δ R δ l The adjusted tunnel centerline spatial position can be determined using the conventional railway or highway line centerline coordinate calculation method. Projecting the measured cross-sectional profile point cloud onto this new centerline allows for the recalculation of over- and under-excavation amounts for each cross-section and the lateral deviation Y of the centerline, thus yielding the values ​​of each term in the aforementioned objective function. This optimization problem can be solved using a commonly used nonlinear least squares optimization algorithm in this field—such as the Levenberg-Marquardt algorithm—in conjunction with the external penalty function method. This involves transforming the constraints into penalty terms in the objective function by assigning the highest weight, and iteratively approximating the optimal correction number that minimizes the sum of squared weighted residuals. The iterative weighted least squares method described here refers to a solution strategy that updates the equivalent weight matrix based on the current residuals in each iteration to enhance robustness. This strategy is compatible with the aforementioned nonlinear optimization framework, ultimately yielding the control point coordinate corrections and curve parameter corrections.

[0033] Step 3: Adjustment of planar control results and generation of new centerline;

[0034] Update the control point coordinates based on the calculated correction values, and verify that the coordinate correction values ​​and the changes in the side lengths of adjacent points do not exceed the preset thresholds; recalculate the horizontal curve elements using the updated control points to generate the new centerline pile-by-pile coordinates; project the measured contour points onto the new centerline, recalculate the over-excavation and under-excavation values ​​for each section, and check whether the section clearance is not less than the sum of the design limit value and the preset construction allowance.

[0035] As needed, the preset threshold for the control point coordinate correction is ±15mm, and the preset threshold for the change in side length of adjacent points is ±3mm; the sum of the design limit value and the preset construction allowance is the design clearance value plus 10mm, wherein the preset construction allowance is 10mm.

[0036] Step 4: Adjustment effect evaluation and optimization iteration;

[0037] The under-excavation elimination rate, over-excavation standard deviation, centerline maximum deviation and clearance compliance rate are used as evaluation indicators to determine whether all indicators meet the standards. If any indicator fails to meet the standards, the values ​​of the first, second and third weights are adjusted, and steps two to three are repeated until all indicators meet the standards.

[0038] As required, the specific evaluation indicators are: under-excavation elimination rate of 100%, over-excavation standard deviation of no more than 30mm, absolute value of maximum centerline deviation of no more than 30mm, and clearance qualification rate of 100%; this iterative process is automatically executed by the data processing device until convergence.

[0039] Step 5: Output of Results and Construction Application;

[0040] Output the adjusted coordinates of the plane control points, the coordinates of each pile of the new centerline, the comparison diagram of over-excavation and under-excavation, and the construction layout guide; based on the new centerline, perform secondary lining formwork layout, and perform local treatment of under-excavation sections and backfilling of over-excavation sections.

[0041] The present invention also provides a tunnel centerline fitting system for implementing the method, comprising:

[0042] Data acquisition module: includes a total station for acquiring measured data of control points, and a 3D laser scanner or laser profiler for acquiring cross-sectional scanning data;

[0043] Data processing device: Communicatively connected to the data acquisition module, configured to execute steps two to four of the above method, namely, establishing a midline fitting model and calculating corrections, generating a new midline using the updated control point coordinates and the calculated curve parameter corrections, and performing effect evaluation and iterative optimization; the data processing device is an industrial computer or embedded processing platform, internally storing program instructions to implement the above calculation, generation, and iterative optimization.

[0044] Output module: Connected to the data processing device, used to output the adjusted plane control point coordinate table, the new centerline pile coordinate table, the over-excavation and under-excavation comparison diagram, and the construction layout guide.

[0045] Example 1:

[0046] A railway tunnel is 2.8km long and is designed with a complex alignment including straight lines, transition curves and circular curves. After the initial support was completed and before the secondary lining was completed, 18 under-excavated sections (total length 120m) and 35 over-excavated sections (>150mm) were found. The maximum measured deviation of the centerline reached +42mm.

[0047] Step 1: Data Acquisition and Preprocessing

[0048] A high-precision total station (angle measurement accuracy 1″) was used to form a cross-traverse network inside the tunnel. A full survey and resurvey were conducted, with two rounds of angle measurement and one round trip measurement of the side length. Three gyro azimuth angle observations were added at the entrance, middle, and exit. After rigorous adjustment of the entire network, the mean square error of the angle measurement at the control points was ±1.2″, and the mean square error of the position at the weakest point was ±15mm, which meets the specifications.

[0049] Simultaneously, a phase-type 3D laser scanner was used to scan the entire tunnel cross-section at intervals of 3m (curved sections) and 5m (straight sections) to obtain the measured contour point cloud of each cross-section; and specialized software was used to calculate the radial over-excavation / under-excavation value and the lateral deviation ΔY of the centerline relative to the original design centerline for each cross-section. iMark all sections with under-excavation (Δ<0) and over-excavation >150mm; unify all data into a construction-independent coordinate system to form a database containing mileage, measured coordinates of control points, centerline deviation, over-excavation amount, and under-excavation amount;

[0050] Step 2: Establish and solve the midline fitting model.

[0051] Based on the measured coordinates of the control points, a small coordinate correction (δX) is set for each control point. i , δY i ) and the horizontal curve parameter correction (δ) JD , δ R , δ l Establish an objective function with the following optimization objectives: minimizing the sum of squares of under-excavation values, minimizing the variance of over-excavation, and minimizing the sum of squares of the second-order difference of the centerline lateral deviation. Strictly constrain the clearance of any section to be no less than the design limit + 10mm.

[0052] The weighted least squares method is used to solve the problem. The weight matrix is ​​set according to the asymmetric engineering priority order proposed in this invention: the first weight (boundary and under-excavation constraints) is 10, the second weight (centerline smoothness constraints) is 5, and the third weight (over-excavation homogenization target) is 1. The optimal correction number is obtained by iterative calculation through the data processing device.

[0053] Step 3: Adjustment of Planar Control Results and Generation of New Center Line

[0054] According to the calculation results, the coordinate correction of each control point is between ±8mm and ±14mm, and the side length change of adjacent points is less than 3mm, which meets the preset threshold (coordinate correction ≤15mm, side length change ≤3mm). After updating the control point coordinates, the horizontal curve elements of the entire line are recalculated to generate a new coordinate table of the tunnel centerline. The same set of measured contour point clouds are projected onto the new centerline, and the over-excavation and under-excavation are recalculated. The inspection results show that there are no under-excavated sections, all over-excavation is within 150mm (arch) / 100mm (sidewall), and the net clearance of all sections is ≥ design limit + 10mm.

[0055] Step 4: Effect Evaluation and Iteration

[0056] All evaluation indicators met the standards: 100% elimination rate of under-excavation; standard deviation of over-excavation decreased from 58mm before treatment to 27mm, less than 30mm; maximum deviation of the new centerline from the original design centerline was +26mm, less than the allowable value of ±30mm; clearance compliance rate was 100%; no iteration was required.

[0057] Step 5: Output and Application of Results

[0058] Output the final version of the control point results table and the coordinates of the new centerline layout; the construction unit erected the secondary lining formwork trolley according to the new centerline, and only carried out minor chiseling treatment on the original under-excavated section, and used the same grade of concrete to backfill the over-excavated part; in the end, the amount of concrete used for the secondary lining of the whole tunnel was reduced by about 1200m³ compared with the original plan, and the construction period was shortened by 15 days.

[0059] Example 2:

[0060] This embodiment is basically the same as Embodiment 1, except that: considering the high risk level of the tunnel, the first weight is increased to 12, the second weight is increased to 6, and the third weight remains at 1; after optimization and iteration, all indicators are met, and the safety redundancy is greater, which shows that the weight system of the present invention can be adjusted within a specific ratio range to adapt to different engineering scenarios.

[0061] The parts of this invention not described in detail are prior art. It will be apparent to those skilled in the art that this invention is not limited to the details of the above exemplary embodiments, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the above embodiments should be regarded as exemplary and non-limiting in all respects. The scope of this invention is defined by the appended claims rather than the foregoing description. Therefore, it is intended to include all changes falling within the meaning and scope of the equivalents of the claims within this invention, and no reference numerals in the claims should be regarded as limiting the content of the claims.

Claims

1. A method for fitting the centerline of a tunnel by adjusting the results of plane control surveys, applicable to tunnel clearance rectification before secondary lining, characterized in that: it includes... The following steps: S1. Data acquisition and preprocessing: The plane control network inside the tunnel is re-measured and adjusted to obtain the measured coordinates and azimuth of each control point; the measured profiles and over- and under-excavation data of each section are obtained and integrated to establish a database containing mileage, deviation, and over- and under-excavation values. S2. Centerline Fitting and Solution: Based on the database, control point coordinate corrections and curve parameter corrections are set. The constraints are to eliminate under-excavation, homogenize over-excavation, maintain centerline smoothness, and meet clearance requirements. A weighted least squares problem is constructed. The objective function of the weighted least squares problem includes at least: the weighted sum of the squares of the under-excavation amounts at each section, the weighted sum of the squares of the second-order differences of the centerline lateral deviation, and the weighted sum of the squares of the differences between the over-excavation amount at each section and the mean over-excavation amount at that section. The constraints of non-compliance with clearance requirements and under-excavation are assigned the highest weight, the centerline smoothness deviation term is assigned a medium weight, and the over-excavation deviation term is assigned the lowest weight. The weight assignment follows the engineering priority order: safety hard constraints first, smoothness second, and economy last. The control point coordinate corrections and curve parameter corrections are then calculated. S3. Results Adjustment and Verification: Update the control point coordinates based on the calculated corrections, and after the verification coordinate corrections and the changes in the side lengths of adjacent points are both less than the preset thresholds, use the updated control point coordinates and the calculated curve parameter corrections to generate a new centerline. Then, project the measured contour onto the new centerline, recalculate the over-excavation and under-excavation, and determine whether the clearance meets the sum of the design limit value and the construction allowance. S4. Iterative optimization: If any of the following indicators fails to reach the preset target value: under-excavation elimination rate, over-excavation standard deviation, absolute value of maximum deviation of centerline, or clearance pass rate, adjust the values ​​of the highest, medium, and lowest weights and repeat steps S2 to S3 until all indicators reach the preset target value. S5. Construction Application: Output new centerline data to guide the layout of secondary lining formwork, and handle under-excavation and over-excavation accordingly.

2. The method for fitting the tunnel centerline based on the adjusted plane control survey results according to claim 1, characterized in that: in In S1, the resurvey of the plane control network adopts the form of main and secondary traverses or cross double traverses, with no less than 2 rounds of angle measurement, and the side length is measured in both directions. Gyro azimuth angles are added every 800-1200m as weighted observations. After adjustment, the mean error of angle measurement is no greater than ±1.5″, and the mean error of the weakest point position is no greater than ±20mm.

3. The method for fitting the tunnel centerline based on the adjusted plane control survey results according to claim 1, characterized in that: in In S1, a three-dimensional laser scanner or laser profiler is used to scan the cross-section. A cross-section is taken every 4 to 6 meters for straight sections and every 2 to 3 meters for curved sections. Over-excavation sections with an over-excavation amount greater than 150 mm and under-excavation sections are marked.

4. The method for fitting the tunnel centerline based on the adjusted plane control survey results according to claim 1, characterized in that: In S2, the ratio of the highest, medium, and lowest weights is 8-12:4-6:

1.

5. The method for fitting the tunnel centerline based on the adjusted plane control survey results according to claim 1, characterized in that: In S2, the curve parameter corrections include the intersection point correction δ. JD , radius correction number δ R and the correction δ for the length of the transition curve l , where δ JD The absolute value does not exceed 20mm, δ R The absolute value does not exceed 5‰ of the original design radius R0.

6. The method for fitting the tunnel centerline based on the adjusted plane control survey results according to claim 1, characterized in that: In S3, the preset threshold for the control point coordinate correction is ±15mm, the preset threshold for the change in the side length of adjacent points is ±3mm, and the construction allowance is 10mm.

7. The method for fitting the tunnel centerline based on the adjusted plane control survey results according to claim 1, characterized in that: In S4, the preset compliance values ​​are: 100% under-excavation elimination rate, over-excavation standard deviation not exceeding 30mm, absolute value of maximum centerline deviation not exceeding 30mm, and clearance pass rate of 100%.

8. A tunnel centerline fitting system for implementing the method according to any one of claims 1 to 7, characterized in that, Include: The data acquisition module includes a total station for acquiring measured data of control points and a three-dimensional scanning device for acquiring cross-sectional scanning data. The data processing device is communicatively connected to the data acquisition module and is configured to execute S2 to S4 of the method described in claim 1, namely, calculating the control point coordinate correction and curve parameter correction based on the received data, generating a new centerline using the updated control point coordinates and the calculated curve parameter correction, and performing over-excavation / under-excavation recalculation and iterative optimization; the data processing device is an industrial computer or embedded processing platform, which internally stores program instructions for executing the calculation, generation, and iterative optimization processes; The output module, connected to the data processing device, is used to output the adjusted plane control point coordinate table, the new centerline pile-by-pile coordinate table, and the construction layout guide.

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