Tunnel construction safety measurement method and system thereof

Abstract

The application discloses a tunnel construction safety measurement method and system, which comprises the following steps: a hole measurement step, coordinates are calculated according to a design structure and a terrain elevation, and a total station instrument is used to loft an excavation contour line and a side pile; a tunnel body measurement step, line pile coordinates and elevations are calculated, a center line and an elevation are transmitted to an excavation surface, a section measurement instrument is used to measure and set the excavation contour line, contour size rechecking is carried out before and after a support steel frame is erected and before and after secondary lining formwork is erected, and a barometer and a thermometer are used to perform real-time weather correction on total station instrument measurement data; and a completion measurement step, a laser limit detection instrument is used to scan and detect a clearance of a tunnel section which has been lined, and a deviation report is generated. The system comprises a control center, a total station instrument, a section measurement instrument, a laser limit detection instrument, an environment compensation unit and an automatic early warning monitoring system. The application realizes systematic measurement control of the whole cycle of tunnel construction, improves measurement precision and construction safety level in the field, and can further guarantee the quality of the tunnel and the safety of construction.

Description

Technical Field

[0001] This invention relates to the field of tunnel construction, and more specifically to a method and system for measuring tunnel construction safety. Background Technology

[0002] With the rapid advancement of infrastructure construction in my country, including highways, railways, water conservancy projects, and urban underground space development, the scale of tunnel construction, excavation length, and geological complexity are continuously increasing. Especially in mountainous and hilly areas, with weak surrounding rock and complex terrain, the safety management of tunnel construction faces extremely high challenges. Construction surveying, as a core and crucial preliminary step in tunnel construction, is a key foundation for ensuring accurate tunnel excavation alignment, compliant structural dimensions, stable surrounding rock and support structures, and mitigating construction safety risks. Its surveying accuracy, the completeness of its management process, and its risk response capabilities directly determine the safety level and construction quality of the tunnel.

[0003] Currently, tunnel construction surveying technologies have been applied and developed to a certain extent. The industry has also issued relevant standards such as the "Engineering Surveying Standard" GB 50026 and the "Technical Specification for Highway Tunnel Construction" JTG / T 3660-2020 to constrain surveying operations. However, in actual engineering applications, existing technologies still have many technical pain points and blind spots that are difficult to solve, and cannot fully adapt to the safety management needs of tunnel construction under complex conditions.

[0004] In the tunnel portal construction surveying stage, existing technologies generally suffer from problems such as coarse calculation of excavation boundary lines and insufficient control over the accuracy of setting out. Traditional calculation of excavation boundary lines for the tunnel portal slopes often adopts simplified cross-sectional diagram methods and empirical estimation methods, performing only rough coordinate calculations for a few key cross-sections. This lack of integration with high-precision topographic data of the tunnel portal area to construct a digital elevation model for refined continuous coordinate calculations makes it impossible to achieve accurate positioning of the excavation boundary lines across the entire area. This results in large deviations in slope control and frequent over-excavation and under-excavation during on-site excavation. Simultaneously, traditional setting out operations lack a standardized multi-stage verification mechanism for the benchmark matching and relative relationship verification of the control network and the coordinates to be set out. This easily leads to deviations in point setting out, which can then cause major safety accidents such as slope instability, landslides, and tunnel portal collapses. This problem is particularly prominent in tunnel portal areas with steep terrain and complex geological conditions.

[0005] In the tunnel construction surveying stage, existing technologies generally suffer from a blind spot of "emphasizing excavation and setting out while neglecting process verification." Traditional tunnel surveying operations mostly focus on the transfer of centerline and elevation before excavation and the preliminary setting out of the excavation outline. For critical processes that directly determine structural safety, such as the erection of support steel frames and the construction of secondary lining, there is a lack of standardized and mandatory full-process dimensional verification mechanisms. Often, post-process inspections are only conducted after the completion of each process, failing to detect issues such as centerline deviation, dimensional deviations, and structural encroachment during construction. At the same time, the extension and layout of the control network inside the tunnel lacks a standardized and regular joint measurement and adjustment mechanism. As the tunnel excavation length increases, the coordinate errors of the control points continue to accumulate, which can easily lead to tunnel alignment deviation and excessive breakthrough errors. This not only causes a large amount of rework costs but also leaves long-term operational safety hazards such as lining structure encroachment and stress imbalance.

[0006] For long tunnel construction surveying scenarios, existing technologies have failed to effectively address the continuous interference of the complex environment inside the tunnel on measurement accuracy. The tunnel construction environment is characterized by large temperature fluctuations, strong airflow disturbances, abundant construction dust, and significant atmospheric refraction effects. Traditional surveying operations often only involve one-time meteorological parameter settings upon instrument arrival, without dynamic correction for real-time changes in temperature and air pressure inside the tunnel, nor specific compensation for errors in angle and distance measurement systems caused by atmospheric refraction. As the tunnel excavation length increases, measurement errors caused by meteorological factors and refraction effects accumulate continuously, leading to a significant decrease in the accuracy of centerline elevation transfer in long tunnels. This easily results in problems such as excessive tunnel breakthrough deviation and loss of alignment control, seriously threatening tunnel construction safety and project quality.

[0007] In terms of structural safety monitoring during tunnel construction, existing technologies suffer from core limitations such as lagging monitoring data and untimely risk response. Traditional monitoring of tunnel clearance convergence and arch settlement often relies on periodic manual measurements, which is not only inefficient and costly but also suffers from discontinuous data and delayed data processing. It cannot capture the dynamic deformation of the surrounding rock and support structure in real time. When safety risks such as rock instability or structural abrupt changes occur, it is difficult to issue timely warnings, hindering proactive risk prevention and control. This can easily lead to tunnel collapses, structural collapses, and other safety accidents, failing to meet the dynamic safety management requirements of high-risk tunnel construction.

[0008] At the same time, the industry lacks an integrated system that combines precise measurement, environmental adaptive compensation, real-time data processing, and intelligent safety early warning, making it difficult to achieve digital and intelligent management of the entire tunnel construction measurement process and failing to meet the current development trend and safety management needs of intelligent tunnel construction. Summary of the Invention

[0009] Therefore, to address the aforementioned shortcomings of existing methods, this invention provides a method and system for tunnel construction safety measurement. Through a three-stage, multi-node measurement and control approach, it achieves systematic measurement and control throughout the entire tunnel construction cycle, overcoming the deficiencies of traditional methods and improving measurement accuracy and construction safety while effectively ensuring tunnel structural quality and construction safety. The system includes: Portal measurement stage: precise control of slope excavation is achieved through accurate coordinate calculation and total station layout; Tunnel body measurement stage: cross-sectional verification is conducted at three key nodes—excavation, support, and lining—to establish quality control; As-built measurement stage: comprehensive inspection is performed using continuous scanning technology to ensure the delivered structure meets design requirements.

[0010] This invention is implemented by constructing a method for measuring safety during tunnel construction, characterized by the following steps: The steps for measuring the tunnel entrance are as follows: Based on the design structure and topographic elevation of the tunnel entrance, calculate the coordinates of the excavation edge line of the tunnel entrance side slope and the coordinates of the pile center; Using the relative relationship between the traverse line and the calculated coordinates, use a total station to lay out the excavation outline of the tunnel entrance side slope and the coordinates of the pile center on the ground, and lay out the excavation edge piles with the laid coordinates as the center to control the excavation of the tunnel entrance side slope. Tunnel measurement steps: According to the tunnel design documents, calculate the coordinates, structural dimensions and elevations of the 100-meter stakes along the line, and compile a tunnel elevation table according to the preset mileage; use the measurement control points inside the tunnel to transfer the centerline and elevation to the excavation face; use a cross-section measuring instrument to measure the tunnel excavation outline, and verify the outline dimensions before and after the erection of the support steel frame and before and after the erection of the secondary lining formwork; As-built measurement steps: The clearance of the lined tunnel section is checked using a laser clearance detector according to the preset mileage, and a breakthrough measurement is organized after the tunnel body is excavated and connected.

[0011] According to the tunnel construction safety measurement method of the present invention, the coordinates of the excavation edge line of the tunnel entrance slope and the coordinates of the pile center are calculated. The specific implementation process is as follows: (1.1) Basic data extraction and preprocessing: Extract the horizontal alignment parameters, longitudinal alignment parameters, portal structure dimensions, slope ratio of side slopes, width and elevation of graded platforms, and design elevation of excavation top line from the tunnel design documents; at the same time, obtain 1:500 scale topographic elevation data of the portal area through total station field measurement or UAV aerial survey, and construct a digital elevation model of the portal topography; (1.2) Calculation of three-dimensional coordinates of the pile center: The entire process of calculating the coordinates of the centerline piles of the line is completed according to the mileage progression direction: The center coordinates of the straight section pile are calculated using the coordinate forward calculation formula. Based on the coordinates of the starting point (X0, Y0) and the azimuth angle α of the straight section, the plane coordinates of any pile number to be calculated are: X = X0 + D × cosα, Y = Y0 + D × sinα, where D is the mileage difference between the pile number to be calculated and the starting point of the straight section. Center coordinates of piles in curved sections: For the pile numbers at the entrance of transition curves and circular curves, first calculate the offset value of the pile number to be calculated in the local tangent coordinate system using the tangent offset method, then convert the local offset into plane coordinates in the unified engineering coordinate system using the coordinate rotation transformation formula, and combine the horizontal curve turning angle to correct the azimuth angle to complete the calculation of the plane coordinates of the center of piles in curved sections. Pile center elevation calculation: For straight slope sections, the design elevation of the corresponding station is calculated according to the design slope and the mileage difference. For vertical curve sections, the design elevation is calculated according to the vertical curve elevation correction formula, and finally a three-dimensional coordinate dataset of each pile center is formed. (1.3) Iterative calculation of the coordinates of the excavation edge line of the tunnel entrance slope: The first step is to define the control range of the excavation boundary: based on the mileage of the boundary between the open and closed sections of the tunnel entrance, extend outward to determine the longitudinal mileage range of the side slope excavation, and use the centerline of the line as the axis of symmetry, combined with the structural dimensions of the tunnel entrance, to determine the maximum offset range of the transverse excavation boundary. The second step is to preset and calculate the location: set up cross sections to be calculated at intervals of 2m to 5m along the longitudinal mileage range. For each cross section, the centerline of the line is used as the reference, the lateral offset value is preset, and the lateral offset direction perpendicular to the centerline is determined by combining the tangent azimuth of the centerline of the line. The plane coordinates of the preset point are initially calculated, and the original ground measured elevation H_ground corresponding to the point is matched from the terrain digital elevation model. The third step is slope elevation calculation and iterative verification: Based on the slope ratio i of the slope grade design, the top elevation and plane position of the corresponding grade platform, calculate the design excavation slope elevation Hset corresponding to the preset point. The calculation formula is: Hset = top elevation of the corresponding grade platform - horizontal projection distance between the preset point and the edge of the platform × i. Compare Hground and Hset. When |Hground - Hset| ≤ 5cm, the point is a valid point on the excavation edge line, and its plane coordinates are locked. If the difference exceeds the limit, iteratively adjust the lateral offset of the point and repeat the above calculation process until the limit requirement is met. The fourth step is to generate a complete coordinate sequence: iterative calculations are performed on all points to be calculated for each section to obtain a continuous coordinate point sequence of the side slope excavation line. The control coordinates of the graded platform and the intercepting ditch are calculated simultaneously to form a complete set of coordinates for the excavation line of the tunnel entrance.

[0012] According to the tunnel construction safety measurement method of the present invention, the process of utilizing the relative relationship between the traverse and the calculated coordinates in the portal measurement step is as follows: (1.1) Layout and adjustment of the traverse control network at the tunnel entrance: In the area outside the excavation influence range of the tunnel entrance, in a geologically stable area with good visibility, a traverse is laid out. The traverse starts and closes at the first-level plane control point of the project. The traverse points are evenly distributed around the tunnel entrance, and the adjacent points have good visibility. After completing the field observation of horizontal angle, slant distance and vertical angle, a rigorous adjustment calculation is carried out to obtain the three-dimensional coordinates and accuracy evaluation results of each traverse control point, forming the ground construction control benchmark network at the tunnel entrance. (1.2) Coordinate system matching and layout parameter calculation: The pile center coordinates and the side slope excavation line coordinates obtained above are uniformly converted to the unified engineering coordinate system of the traverse line, and the coordinate reference, projection parameters and elevation reference are confirmed to be completely consistent to eliminate system deviation; with each control point of the traverse line as the reference, the azimuth and horizontal distance of each coordinate point to be laid out relative to the station control point are calculated to form the core parameters of the total station polar coordinate method layout; (1.3) Relative relationship verification and precise layout: Orientation accuracy verification: Select two control points with good visibility in the traverse as the station and backsight point respectively. After completing the total station backsight orientation, remeasure the coordinates of the third known control point in the traverse. When the remeasurement error of the point is ≤2cm, the orientation is confirmed to be effective and the relative relationship of the control points is accurate before subsequent layout work can be carried out. Core point layout: Based on the total station completed by orientation, the coordinates of the pile center and the outline of the slope excavation are input point by point. The polar coordinate method is used to complete the point layout. After the layout of each point is completed, the coordinates are re-measured by double measurement with both left and right sides of the instrument. When the deviation from the design coordinates is ≤3cm, the point is locked and concrete markers or wooden stakes are set. Cross-shaped protective piles are laid out at the same time to avoid damage to the pile position during construction. Excavation side stake layout: Using the center point of the centerline stake of the line that has been laid out as a reference, along the transverse direction perpendicular to the centerline of the line, according to the offset value of the designed excavation side stake, the excavation side stakes on the left and right sides are laid out. At the same time, platform control stakes are set at the level platform position of the slope to form a closed-loop excavation control stake network, which accurately controls the excavation range, slope ratio and excavation elevation of the slope at the tunnel entrance, and avoids safety hazards such as slope instability and collapse caused by over-excavation.

[0013] According to the tunnel construction safety measurement method of the present invention, the tunnel body measurement step is specifically implemented as follows: Step 1, Preprocessing of tunnel design parameters: Based on the tunnel design documents, calculate the centerline coordinates of each mileage section of the tunnel, the dimensions of the tunnel's internal outline structure, the design elevation of the road surface, and the design elevation of the arch. Compile a tunnel pile elevation table and a structural dimension table at 5m intervals, and clarify the reserved deformation amount of the excavation outline, the design spacing of the support steel frame, and the outer outline dimensions under different surrounding rock grades.

[0014] Step 2, Control Survey and Point Transfer within the Tunnel: A graded traverse control network is used within the tunnel. Combined with the tunnel construction conditions, a total station and laser pointer are used to transfer the centerline and elevation of the line to the excavation face through the traverse control points within the tunnel. Accurate transfer of the centerline and elevation is completed before each excavation cycle, with a transfer point error ≤5mm. Every 100m of traverse extension, a joint survey and adjustment is conducted between the traverse within the tunnel and the traverse attached to the tunnel entrance to correct control point coordinate deviations and ensure the accuracy of the control network within the tunnel. Step 3, Excavation Outline Survey and Dimension Verification: Using a tunnel cross-section measuring instrument, based on the centerline control points inside the tunnel, the outline and blast hole positioning lines are surveyed on the excavation face according to the coordinates of the designed excavation outline, and over- and under-excavation control benchmarks are marked. Before erecting the support steel frame, the dimensions of the excavation cross-section are verified. The steel frame can only be erected if the over-excavation meets the design requirements and there is no structural under-excavation. After the steel frame is erected, the centerline deviation, elevation, and outer outline dimensions of the steel frame are verified. Shotcrete construction can only proceed after the deviation meets the design requirements. Before and after the secondary lining formwork is erected, the centerline, elevation, and inner outline dimensions of the formwork are verified respectively. Concrete pouring can only proceed after the formwork is erected and the verification is qualified, thus preventing operational safety hazards caused by structural encroachment.

[0015] According to the tunnel construction safety measurement method of the present invention, the as-built measurement steps are specifically implemented as follows: Step 1, Tunnel clearance completion inspection: After the secondary lining construction of the tunnel is completed, the clearance of the lined section of the tunnel is scanned every 10m interval using a laser clearance detector to obtain the actual inner contour coordinate data of the tunnel. The data is compared with the design clearance and design inner contour dimensions to check whether there is any encroachment. The encroachment points are marked in time and reported for handling. A clearance inspection report is generated simultaneously. Step 2, Tunnel Breakthrough Measurement: After the tunnel is completed in both directions or one direction, a breakthrough measurement is immediately organized. The centerline control point and elevation control point at the breakthrough face inside the tunnel are measured from the ground control network at both ends of the tunnel entrance and exit. The lateral breakthrough error, longitudinal breakthrough error, elevation breakthrough error, and azimuth breakthrough error are calculated. If the breakthrough error meets the requirements of the "Technical Specification for Highway Tunnel Construction" JTG / T 3660-2020, the control network inside the tunnel is adjusted as a whole to form the final as-built control network inside the tunnel. For breakthrough errors exceeding the limits, a special adjustment plan is formulated to ensure that the tunnel alignment meets the design requirements. Step 3, Compilation of As-built Data: Summarize all data and results from the tunnel entrance measurement, tunnel body measurement, tunnel connection measurement, and clearance detection, compile a tunnel construction measurement completion report, and form a complete archive of measurement results.

[0016] The tunnel construction safety measurement method according to the present invention is characterized in that, in the tunnel body measurement step, when transferring the centerline and elevation to the excavation face, it further includes an environmental correction sub-step: When conducting construction layout inside the tunnel, a barometer and a thermometer are provided. Real-time measurement of ambient air pressure and temperature inside the cave; Based on real-time measured air pressure and temperature data, the distance and angle measurement data of measuring instruments (such as total stations) are corrected in real time to eliminate the influence of atmospheric refraction and meteorological factors on measurement accuracy.

[0017] The specific execution process of real-time correction according to the tunnel construction safety measurement method of the present invention is as follows: The specific execution process of real-time correction is as follows: Before surveying and setting out inside the tunnel, the barometer and thermometer are placed near the total station in a location free from airflow and heat sources. After standing still for 2-3 minutes until the readings stabilize, the current atmospheric pressure P and temperature t are recorded. Then, P and t are input into the meteorological correction parameter setting interface of the total station. The instrument automatically calculates the distance measurement meteorological correction coefficient according to the built-in meteorological correction formula and applies it in real time to all subsequent slope distance measurements, eliminating the influence of meteorological factors on the distance measurement accuracy. For angle measurement data, considering that atmospheric refraction inside the tunnel may cause errors in vertical angle observation, when performing precise trigonometric leveling, the refraction coefficient K can be estimated by measuring the temperature gradient at different heights along the line of sight. The K value is then input into the total station or manually substituted into the vertical angle observation value for correction. At the same time, in traverse surveying, the reciprocating observation method is used to automatically cancel the refraction effect, and the line of sight height is kept as consistent as possible and local heat sources are avoided. When the tunnel excavation length increases or the tunnel environment changes significantly, the meteorological parameters are remeasured and the instrument settings are updated to ensure that the measurement accuracy is always under control.

[0018] The tunnel construction safety measurement method according to the present invention is characterized by further including an automatic early warning step for clearance convergence: Multiple monitoring points with reflective markings are set up on the pre-designed cross-section of the tunnel body; Set up an automatic measuring robot or laser rangefinder array to automatically measure the distance to each monitoring point at a preset frequency; calculate the net clearance convergence value and crown settlement value of the cross section based on the measurement data; The calculated convergence value is compared with the preset warning threshold. When the measured value exceeds the warning threshold, the system automatically issues an audible and visual alarm signal. In the automatic early warning step of clearance convergence, the preset cross-section includes multiple sections, which are arranged along the longitudinal direction of the tunnel at a set interval; the monitoring points arranged on each cross-section include the arch apex and at least two symmetrical sidewall points.

[0019] A tunnel construction safety measurement system for performing the above-described tunnel construction safety measurement method includes: The control center is used to store tunnel design data, receive measurement data, and perform comparative analysis. The control center includes a data storage and processing module and a comparative analysis module. A total station is used for angle and distance measurements during tunnel entrance surveying and control surveying inside the tunnel, and for setting out points. A cross-section measuring instrument is used to measure the excavation outline and verify structural dimensions during tunnel construction. Laser clearance detectors are used to detect tunnel clearance during as-built surveying. The environmental compensation unit, including a barometer, a thermometer, and a signal connection and correction module, is connected to the total station signal and is used to perform real-time meteorological correction on the total station's measurement data.

[0020] The tunnel construction safety measurement system according to the present invention further includes an automatic early warning monitoring system, the automatic early warning monitoring system comprising: Multiple reflective markers are deployed on pre-set monitoring sections of the tunnel body; at least one measuring robot or laser rangefinder array is fixed in a stable position inside the tunnel to automatically perform periodic measurements on each reflective marker. The controller receives measurement data from the measuring robot or laser ranging sensor array, calculates the clearance convergence value and the arch subsidence value, and compares them with preset thresholds. When the limit is exceeded, an early warning signal is output. An alarm device, connected to the controller, receives the warning signal and issues an alarm. The automatic early warning monitoring system also includes a data storage and display module, which stores the data from each measurement and generates displacement-time variation curves and displacement-tunneling advance variation curves for each monitoring point.

[0021] This application features several technological innovations, and compared with existing technologies, it offers the following advantages: 1. Addressing the shortcomings of traditional tunnel portal excavation boundary line calculations, which are often crude and prone to over-excavation and slope collapse due to inaccurate slope control, this paper presents an iterative calculation method for the excavation boundary line coordinates of slopes based on a digital elevation model (DEM). Through closed-loop calculation involving point pre-setting, ground elevation matching, and slope design elevation iterative verification, the coordinate error of the excavation boundary line is strictly controlled within a 5cm limit. Simultaneously, a layout mechanism is implemented, including rigorous adjustment of the traverse control network, double verification of orientation accuracy, and double-measurement and re-measurement of both left and right sides, achieving millimeter-level precision in the excavation outline and side stakes. This forms a complete chain of control from coordinate calculation to on-site excavation, mitigating major safety hazards such as over-excavation, instability, and collapse of slopes from the source.

[0022] 2. Innovative Implementation of Full-Process Tunnel Body Verification: Breaking away from the traditional tunnel surveying's blind spot of "emphasizing excavation and setting out while neglecting process verification," a multi-node closed-loop verification mechanism is introduced for the entire process, including "excavation outline surveying - verification before and after steel frame erection - verification before and after secondary lining formwork erection." Mandatory accuracy verification is set up before each key process in support and lining; only when there is no structural under-excavation and dimensional deviations meet the standards can the next process proceed. Simultaneously, a periodic connection and adjustment mechanism for the tunnel's graded traverse control network is implemented. Every 100m of excavation, a connection and adjustment mechanism is established with the primary control network at the tunnel entrance to correct deviations, controlling the centerline elevation transfer error to within 5mm. This eliminates problems such as over-excavation, under-excavation, inadequate support, and lining encroachment throughout the entire construction process, avoiding both the risk of structural collapse during construction and the safety hazard of line encroachment during operation.

[0023] 3. Innovation in Adaptive Correction Scheme for Tunnel Environment: Addressing the industry problem of large temperature differences, airflow disturbances, and significant atmospheric refraction within tunnels, which can easily lead to inaccurate measurement accuracy and alignment deviations during long-distance tunneling, this technology provides real-time meteorological and refraction adaptive correction for complex tunnel environments. By using barometers and thermometers to collect tunnel environmental parameters in real time, it automatically performs meteorological correction for total station distance measurements. Simultaneously, it estimates the atmospheric refraction coefficient using temperature gradients to specifically correct vertical angle measurement data. Combined with the counter-observation method to offset the refraction effect, this solves the core problem of measurement accuracy decreasing with environmental changes and increasing tunneling length during long tunnel excavation. It ensures the stability and accuracy of long-distance tunnel alignment control, preventing structural safety issues caused by alignment deviations from the root cause of measurement problems.

[0024] 4. Automated Dynamic Monitoring and Early Warning: Breaking through the limitations of traditional tunnel clearance convergence monitoring, which relies on manual measurement, data lag, and untimely response, an innovative automated dynamic monitoring and proactive early warning system for tunnel clearance convergence and arch settlement has been developed. By deploying standardized monitoring sections and reflective marker monitoring points along the tunnel's longitudinal direction, and using a measurement robot / laser ranging sensor array to automatically collect displacement data at a preset frequency, the system automatically generates displacement change trend curves. When the measured value exceeds the early warning threshold, an audible and visual alarm is immediately triggered. This achieves real-time, continuous, and unmanned monitoring of tunnel surrounding rock and structural deformation, transforming traditional post-event risk management into proactive early warning and prevention. It can identify early signs of surrounding rock instability and structural deformation, significantly improving the dynamic safety management capabilities during tunnel construction.

[0025] 5. Simultaneously, a multi-module integrated tunnel construction safety measurement system was developed, which deeply integrates the control center (data storage and processing, comparison and analysis), total station, cross-section measuring instrument, laser clearance detector, environmental compensation unit, and automatic early warning monitoring system. This achieves full-process hardware and software collaboration in design data management, on-site measurement operations, real-time data processing, automatic deviation comparison, and intelligent safety early warning. It breaks down the barriers of independent operation of traditional measurement equipment, data silos, and delayed processing, and realizes real-time analysis of measurement data and rapid response to risks, providing integrated hardware support and fully digital management capabilities for tunnel construction safety measurement. Attached Figure Description

[0026] Figure 1 This is a schematic diagram illustrating the process of measuring the opening. Figure 2 This is a schematic diagram illustrating the tunnel measurement operation process; Figure 3 This is a schematic diagram illustrating the as-built surveying process; Figure 4 This is a block diagram of the measurement system structure involved in the present invention. Detailed Implementation

[0027] The following will be combined with the appendix Figures 1-4 This invention will be described in detail, and the technical solutions in the embodiments of this invention will be clearly and completely described. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. 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.

[0028] Example 1: A method for measuring safety during tunnel construction, such as... Figures 1-3 As shown, it includes the following steps: The steps for measuring the tunnel entrance are as follows: Based on the design structure and topographic elevation of the tunnel entrance, calculate the coordinates of the excavation edge line of the tunnel entrance side slope and the coordinates of the pile center; Using the relative relationship between the traverse line and the calculated coordinates, use a total station to lay out the excavation outline of the tunnel entrance side slope and the coordinates of the pile center on the ground, and lay out the excavation edge piles with the laid coordinates as the center to control the excavation of the tunnel entrance side slope. Tunnel measurement steps: According to the tunnel design documents, calculate the coordinates, structural dimensions and elevations of the 100-meter stakes along the line, and compile a tunnel elevation table according to the preset mileage; use the measurement control points inside the tunnel to transfer the centerline and elevation to the excavation face; use a cross-section measuring instrument to measure the tunnel excavation outline, and verify the outline dimensions before and after the erection of the support steel frame and before and after the erection of the secondary lining formwork; As-built measurement steps: The clearance of the lined tunnel section is checked using a laser clearance detector according to the preset mileage, and a breakthrough measurement is organized after the tunnel body is excavated and connected.

[0029] In the tunnel portal measurement process, based on the tunnel portal's design structure and topographic elevation, the coordinates of the excavation edge line of the portal's side slope and the coordinates of the pile center are calculated. The specific implementation process is as follows: (1.1) Basic data extraction and preprocessing: Extract the horizontal alignment parameters (including the azimuth of straight sections, the JD coordinates of the intersection of horizontal and curved sections, the turning angle α, the radius of circular curves R, the length of transition curves Ls, the starting and ending mileage of the line, the mileage of the boundary between open and closed sections of the tunnel entrance, and the design center mileage of the tunnel entrance) and the longitudinal alignment parameters (including the design slope, the radius of vertical curves, the mileage and elevation of the slope change point), the structural dimensions of the tunnel entrance, the design slope of the side slope, the width and elevation of the graded platform, and the design elevation of the excavation top line from the tunnel design documents; at the same time, obtain the 1:500 scale topographic elevation data of the tunnel entrance area through total station measurement or UAV aerial survey, and construct a digital elevation model of the tunnel entrance topography.

[0030] (1.2) Calculation of three-dimensional coordinates of pile center: Using the unified plane coordinate system for tunnel engineering and the 1985 National Elevation Datum as benchmarks, the entire process of calculating the coordinates of the centerline pile center of the line is completed according to the mileage progression direction: The center coordinates of the straight section pile are calculated using the coordinate forward calculation formula. Based on the coordinates of the starting point (X0, Y0) and the azimuth angle α of the straight section, the plane coordinates of any pile number to be calculated are: X = X0 + D × cosα, Y = Y0 + D × sinα, where D is the mileage difference between the pile number to be calculated and the starting point of the straight section. Center coordinates of piles in curved sections: For the pile numbers at the entrance of transition curves and circular curves, first calculate the offset value of the pile number to be calculated in the local tangent coordinate system using the tangent offset method, then convert the local offset into plane coordinates in the unified engineering coordinate system using the coordinate rotation transformation formula, and combine the horizontal curve turning angle to correct the azimuth angle to complete the calculation of the plane coordinates of the center of piles in curved sections. Pile center elevation calculation: For straight slope sections, the design elevation of the corresponding station is calculated based on the design slope and the difference in mileage. For vertical curve sections, the design elevation is calculated based on the vertical curve elevation correction formula, and finally, a three-dimensional coordinate dataset of each pile center is formed.

[0031] (1.3) Iterative calculation of the coordinates of the excavation edge line of the tunnel entrance slope: The first step is to define the control range of the excavation boundary: based on the mileage of the boundary between the open and closed sections of the tunnel entrance, extend outward to determine the longitudinal mileage range of the side slope excavation, and use the centerline of the line as the axis of symmetry, combined with the structural dimensions of the tunnel entrance, to determine the maximum offset range of the transverse excavation boundary. The second step is to preset and calculate the location: set up cross sections to be calculated at intervals of 2m to 5m along the longitudinal mileage range. For each cross section, the centerline of the line is used as the reference, the lateral offset value is preset, and the lateral offset direction perpendicular to the centerline is determined by combining the tangent azimuth of the centerline of the line. The plane coordinates of the preset point are initially calculated, and the original ground measured elevation H_ground corresponding to the point is matched from the terrain digital elevation model. The third step is slope elevation calculation and iterative verification: Based on the slope ratio i of the slope grade design, the top elevation and plane position of the corresponding grade platform, calculate the design excavation slope elevation Hset corresponding to the preset point. The calculation formula is: Hset = top elevation of the corresponding grade platform - horizontal projection distance between the preset point and the edge of the platform × i. Compare Hground and Hset. When |Hground - Hset| ≤ 5cm, the point is a valid point on the excavation edge line, and its plane coordinates are locked. If the difference exceeds the limit, iteratively adjust the lateral offset of the point and repeat the above calculation process until the limit requirement is met. The fourth step is to generate a complete coordinate sequence: iterative calculations are performed on all points to be calculated for each section to obtain a continuous coordinate point sequence of the side slope excavation line. The control coordinates of the graded platform and the intercepting ditch are calculated simultaneously to form a complete set of coordinates for the excavation line of the tunnel entrance.

[0032] In the tunnel entrance measurement process, the relative relationship between the traverse and the calculated coordinates is utilized. A total station is used to lay out the excavation outline of the tunnel entrance side slope and the coordinates of the pile center points on the ground. Excavation side piles are then laid out using the laid-out coordinate points as centers to control the excavation of the tunnel entrance side slope. The process of utilizing the relative relationship between the traverse and the calculated coordinates is as follows: (1.1) Layout and adjustment of the traverse control network at the tunnel entrance: In an area outside the excavation influence range at the tunnel entrance, with stable geology and good visibility, a traverse is laid out. The traverse starts and closes at the primary horizontal control point of the project (GPS C / D level control point or national triangulation point). The traverse points are evenly distributed around the tunnel entrance, with good visibility between adjacent points. The accuracy of the traverse measurement meets the requirements of Class II or above control measurement for tunnel construction in the "Engineering Surveying Standard" GB 50026 (angle measurement error ≤ 8″, relative side length error ≤ 1 / 40000). After completing the field observation of horizontal angle, slope distance, and vertical angle, a rigorous adjustment calculation is performed to obtain the three-dimensional coordinates and accuracy evaluation results of each traverse control point, forming the ground construction control benchmark network at the tunnel entrance.

[0033] (1.2) Coordinate system matching and layout parameter calculation: The pile center coordinates and the side slope excavation line coordinates obtained by the above calculation are uniformly converted to the unified engineering coordinate system of the traverse, and the coordinate reference, projection parameters and elevation reference are confirmed to be completely consistent to eliminate system deviation; taking each control point of the traverse as the reference, the azimuth and horizontal distance of each coordinate point to be laid out relative to the station control point are calculated to form the core parameters of the total station polar coordinate method layout.

[0034] (1.3) Relative relationship verification and precise layout: Orientation accuracy verification: Select two control points with good visibility in the traverse as the station and backsight point respectively. After completing the total station backsight orientation, remeasure the coordinates of the third known control point in the traverse. When the remeasurement error of the point is ≤2cm, the orientation is confirmed to be effective and the relative relationship of the control points is accurate before subsequent layout work can be carried out. Core point layout: Based on the total station completed by orientation, the coordinates of the pile center and the outline of the slope excavation are input point by point. The polar coordinate method is used to complete the point layout. After the layout of each point is completed, the coordinates are re-measured by double measurement with both left and right sides of the instrument. When the deviation from the design coordinates is ≤3cm, the point is locked and concrete markers or wooden stakes are set. Cross-shaped protective piles are laid at the same time to avoid damage to the pile position during construction. Excavation side stake layout: Using the center point of the centerline stake of the line that has been laid out as a reference, along the transverse direction perpendicular to the centerline of the line, according to the offset value of the designed excavation side stake, the excavation side stakes on the left and right sides are laid out. At the same time, platform control stakes are set at the level platform position of the slope to form a closed-loop excavation control stake network, which accurately controls the excavation range, slope ratio and excavation elevation of the slope at the tunnel entrance, and avoids safety hazards such as slope instability and collapse caused by over-excavation.

[0035] In the tunnel body measurement step, based on the tunnel design documents, the coordinates, structural dimensions, and elevations of the 100-meter markers along the route are calculated, and a tunnel elevation table is compiled according to the preset mileage. The centerline and elevation are transferred to the excavation face using the tunnel control points. A cross-section measuring instrument is used to measure the tunnel excavation outline, and the outline dimensions are checked before and after the erection of the support steel frame and before and after the erection of the secondary lining formwork. The specific implementation is as follows: Step 1, Preprocessing of tunnel design parameters: Based on the tunnel design documents, calculate the centerline coordinates of each mileage section of the tunnel, the dimensions of the tunnel's internal outline structure, the design elevation of the road surface, and the design elevation of the arch. Compile a tunnel pile elevation table and a structural dimension table at 5m intervals, and clarify the reserved deformation amount of the excavation outline, the design spacing of the support steel frame, and the outer outline dimensions under different surrounding rock grades.

[0036] Step 2, Control Survey and Point Transfer within the Tunnel: A graded traverse control network is used within the tunnel. Combined with the tunnel construction conditions, a total station and laser pointer are used to transfer the centerline and elevation of the line to the excavation face through the traverse control points within the tunnel. Accurate transfer of the centerline and elevation is completed before each excavation cycle, with a transfer point error ≤5mm. Every 100m of traverse extension, a joint survey and adjustment is conducted between the traverse within the tunnel and the traverse attached to the tunnel entrance to correct control point coordinate deviations and ensure the accuracy of the control network within the tunnel.

[0037] Step 3, Excavation Outline Survey and Dimension Verification: Using a tunnel cross-section measuring instrument, based on the centerline control points inside the tunnel, the outline and blast hole positioning lines are surveyed on the excavation face according to the coordinates of the designed excavation outline, and over- and under-excavation control benchmarks are marked. Before erecting the support steel frame, the dimensions of the excavation cross-section are verified. The steel frame can only be erected if the over-excavation meets the design requirements and there is no structural under-excavation. After the steel frame is erected, the centerline deviation, elevation, and outer outline dimensions of the steel frame are verified. Shotcrete construction can only proceed after the deviation meets the design requirements. Before and after the secondary lining formwork is erected, the centerline, elevation, and inner outline dimensions of the formwork are verified respectively. Concrete pouring can only proceed after the formwork is erected and the verification is qualified, thus preventing operational safety hazards caused by structural encroachment.

[0038] As-built measurement steps: The clearance of the lined tunnel section is checked using a laser clearance detector according to the preset mileage. After the tunnel excavation is completed, a breakthrough measurement is organized, specifically as follows: Step 1, Tunnel clearance completion inspection: After the secondary lining construction of the tunnel is completed, a laser clearance detector is used to scan the entire cross-section of the lined section of the tunnel at 10m intervals to obtain the actual inner contour coordinate data of the tunnel. The data is compared with the design clearance and design inner contour dimensions to check whether there is any encroachment. The encroachment points are marked in time and reported for handling. A clearance inspection report is generated simultaneously.

[0039] Step 2, Tunnel Breakthrough Measurement: After the tunnel is completed in both directions or in one direction, a breakthrough measurement is immediately organized. The centerline control point and elevation control point at the breakthrough face inside the tunnel are measured from the ground control network at both ends of the tunnel entrance and exit. The lateral breakthrough error, longitudinal breakthrough error, elevation breakthrough error, and azimuth breakthrough error are calculated. When the breakthrough error meets the requirements of the "Technical Specification for Highway Tunnel Construction" JTG / T 3660-2020, the control network inside the tunnel is adjusted as a whole to form the final as-built control network inside the tunnel. For breakthrough errors exceeding the limits, a special adjustment plan is formulated to ensure that the tunnel alignment meets the design requirements.

[0040] Step 3, Compilation of As-built Data: Summarize all data and results from the tunnel entrance measurement, tunnel body measurement, tunnel connection measurement, and clearance detection, compile a tunnel construction measurement completion report, and form a complete archive of measurement results.

[0041] In the tunnel measurement step described in Example 1, when transferring the centerline and elevation to the excavation face, an environmental correction sub-step is also included: When conducting construction layout inside the tunnel, a barometer and a thermometer are provided. Real-time measurement of ambient air pressure and temperature inside the cave; Based on real-time measured air pressure and temperature data, the distance and angle measurement data of measuring instruments (such as total stations) are corrected in real time to eliminate the influence of atmospheric refraction and meteorological factors on measurement accuracy.

[0042] The specific execution process of real-time correction The specific execution process of real-time correction is as follows: Before surveying and setting out inside the tunnel, the barometer and thermometer are placed near the total station in a location free from airflow and heat sources. After standing still for 2-3 minutes until the readings stabilize, the current atmospheric pressure P and temperature t are recorded. Then, P and t are input into the meteorological correction parameter setting interface of the total station. The instrument automatically calculates the distance measurement meteorological correction coefficient according to the built-in meteorological correction formula and applies it in real time to all subsequent slope distance measurements, eliminating the influence of meteorological factors on the distance measurement accuracy. For angle measurement data, considering that atmospheric refraction inside the tunnel may cause errors in vertical angle observation, when performing precise trigonometric leveling, the refraction coefficient K can be estimated by measuring the temperature gradient at different heights along the line of sight. The K value is then input into the total station or manually substituted into the vertical angle observation value for correction. At the same time, in traverse surveying, the reciprocating observation method is used to automatically cancel the refraction effect, and the line of sight height is kept as consistent as possible and local heat sources are avoided. When the tunnel excavation length increases or the tunnel environment changes significantly, the meteorological parameters are remeasured and the instrument settings are updated to ensure that the measurement accuracy is always under control.

[0043] Example 1 also includes an automatic early warning step for airspace convergence: Multiple monitoring points with reflective markings are set up on the pre-designed cross-section of the tunnel body; Set up an automatic measuring robot or laser rangefinder array to automatically measure the distance to each monitoring point at a preset frequency; calculate the net clearance convergence value and crown settlement value of the cross section based on the measurement data; The calculated convergence value is compared with the preset warning threshold. When the measured value exceeds the warning threshold, the system automatically issues an audible and visual alarm signal. In the automatic early warning step of clearance convergence, the preset cross-section includes multiple sections, which are arranged along the longitudinal direction of the tunnel at a set interval; the monitoring points arranged on each cross-section include the arch apex and at least two symmetrical sidewall points.

[0044] Example 2: A tunnel construction safety measurement system for performing the above-described tunnel construction safety measurement method, such as... Figure 4 As shown: The control center is used to store tunnel design data, receive measurement data, and perform comparative analysis. The control center includes a data storage and processing module and a comparative analysis module. A total station is used for angle and distance measurements during tunnel entrance surveying and control surveying inside the tunnel, and for setting out points. A cross-section measuring instrument is used to measure the excavation outline and verify structural dimensions during tunnel construction. Laser clearance detectors are used to detect tunnel clearance during as-built surveying. The environmental compensation unit, including a barometer, a thermometer, and a signal connection and correction module, is connected to the total station signal and is used to perform real-time meteorological correction on the total station's measurement data.

[0045] Example 2 also includes an automatic early warning monitoring system, which includes: Multiple reflective markers are deployed on pre-set monitoring sections of the tunnel body; at least one measuring robot or laser rangefinder array is fixed in a stable position inside the tunnel to automatically perform periodic measurements on each reflective marker. The controller receives measurement data from the measuring robot or laser ranging sensor array, calculates the clearance convergence value and the arch subsidence value, and compares them with preset thresholds. When the limit is exceeded, an early warning signal is output. An alarm device, connected to the controller, receives the warning signal and issues an alarm. The automatic early warning monitoring system also includes a data storage and display module, which stores the data from each measurement and generates displacement-time variation curves and displacement-tunneling advance variation curves for each monitoring point.

[0046] This invention presents an implementation example of safety measurement during tunnel construction; I. Basic Project Overview This case study focuses on the left tunnel of Erlangshan Tunnel No. 2, a key control project of the G4218 Ya'an-Linzhi Expressway. The core parameters and engineering conditions of the project are as follows: 1. Design parameters: The left line starts and ends at ZK123+042 to ZK124+328, with a total length of 1286m. It is a two-way four-lane separated medium-length tunnel with a design speed of 80km / h. The construction clearance has a net width of 10.25m and a net height of 5.0m. The horizontal alignment of the entrance section ZK123+042 to ZK123+200 is a straight section with an azimuth angle of 128°35′42″. The exit section is equipped with a transition curve and a circular curve. The longitudinal profile design slope is +2.8%. The slope change point is at ZK123+800, corresponding to an elevation of 1482.56m. The vertical curve radius is 20000m.

[0047] 2. Geology and Environment: The tunnel entrance section (ZK123+042~ZK123+120) is Class V surrounding rock, shallowly buried with bias pressure, and the overburden is gravelly soil. The natural terrain slope at the tunnel entrance is 35°. The side slope is excavated in two stages, with the first stage at the bottom having a slope ratio of 1:1.25 and the second stage at the top having a slope ratio of 1:1. A 2m wide grading platform is set in the middle. The tunnel body section (ZK123+120~ZK124+220) is Class IV surrounding rock, and the exit section (ZK124+220~ZK124+328) is Class V surrounding rock. The construction environment inside the tunnel has large temperature differences and strong ventilation airflow disturbances, posing a risk that atmospheric refraction may affect the accuracy of measurements.

[0048] 3. Benchmarks and Standards: The plane coordinate system adopts the 2000 National Geodetic Coordinate System (Gauss-Kruger 3° zone projection), and the elevation datum adopts the 1985 National Elevation Datum; the primary control network consists of 4 GPS D-level control points (inlet GPS01, GPS02, outlet GPS03, GPS04); the entire implementation process strictly follows the "Engineering Surveying Standard" GB 50026 and the "Technical Specification for Highway Tunnel Construction" JTG / T 3660-2020.

[0049] II. Core Implementation Process This project fully utilizes the tunnel construction safety measurement method described in this patent, completing the entire process in stages: portal measurement, tunnel body measurement, real-time environmental correction, automatic early warning of clearance convergence, and final measurement. The specific process is as follows: (I) Implementation of the measurement steps at the tunnel entrance The core objective of this step is to precisely control the excavation of the slope at the tunnel entrance, avoid the risk of slope instability and collapse in the shallow buried biased pressure section, and strictly follow the patented method to complete the coordinate calculation and precise layout.

[0050] 1. Data extraction and preprocessing Core data such as the horizontal and vertical alignment parameters, portal structure dimensions, slope grade of the side slopes, platform elevation, and excavation top line design elevation were completely extracted from the tunnel design documents. At the same time, 1:500 scale topographic elevation data of the entrance area were obtained through UAV aerial surveying, and a 0.5m resolution digital elevation model (DEM) of the tunnel entrance was constructed to provide basic support for subsequent coordinate calculations.

[0051] 2. Full-process calculation of three-dimensional coordinates of the heart Using the unified engineering coordinate system and the 1985 National Elevation Datum as benchmarks, calculations were completed progressively by mileage: Straight section: Using the coordinate forward calculation formula, with the starting point ZK123+042 (X=3345689.342, Y=3542215.768, elevation 1468.32m) as the benchmark, the plane coordinates and elevations of each station are calculated at 2m intervals. For example, for station ZK123+050 (mileage difference D=8m), the calculated values ​​are X=3345684.587, Y=3542221.935, and elevation 1468.544m. Curved sections: exit transition curve + circular curve section. The local offset value is calculated using the tangent offset method, and then converted into the coordinate system of the unified engineering coordinate system through coordinate rotation transformation. The elevation correction of the vertical curve section is completed simultaneously, and finally a three-dimensional coordinate dataset of the center of the piles of the entire line is formed.

[0052] 3. Iterative calculation of slope excavation boundary coordinates The calculation was completed strictly according to the four-step iterative method described in the patent: The first step is to define the control range: using the boundary between the open and closed tunnels, ZK123+060, as the benchmark, extend outward to ZK123+022 to determine a longitudinal mileage range of 38m; using the centerline of the line as the axis of symmetry, determine the maximum lateral offset range of 25m to the left and right. The second step is to preset and calculate the points: set 13 cross sections to be calculated at 3m intervals along the longitudinal direction. Each cross section is based on the centerline and the lateral offset is preset at 0.5m steps. The plane coordinates are initially calculated and matched with the corresponding original ground elevation H in the DEM model. The third step is iterative verification: Based on the top elevation of the graded platform and the design slope, the design excavation slope elevation Hdesign of the preset point is calculated, and the lateral offset is iteratively adjusted with a limit of |Hground - Hdesign| ≤ 5cm. For example, at section ZK123+035, after 5 iterations, at a left offset of 4.2m, Hground = 1472.82m and Hdesign = 1472.79m, with a difference of 3cm, which meets the limit requirement, and the coordinates of this point are locked. The fourth step is to generate a complete dataset: iterative calculations are performed on each cross section to obtain 32 continuous coordinate points of the excavation edge. The control coordinates of the graded platform and the intercepting ditch are calculated simultaneously to form a complete dataset of excavation edge coordinates of the tunnel entrance.

[0053] 4. Traverse control and precise layout Control network layout and adjustment: In a stable area 50m outside the excavation influence zone at the tunnel entrance, a traverse line starting and ending at GPS01 and GPS02 was laid out, with four traverse points DX01-DX04, and good visibility between adjacent points; field observations were completed using a Topcon MS05AXII total station, with an angular mean square error of 6″ and a relative mean square error of 1 / 60000 for side lengths, meeting the requirements for secondary or higher control surveys for tunnel construction; after rigorous adjustment, the mean square error of the traverse point positions was ≤1cm, forming the ground construction control benchmark network at the tunnel entrance.

[0054] Coordinate matching and orientation verification: The calculated coordinates of the pile center and excavation edge are uniformly converted to the control network coordinate system to eliminate system deviations and solve the polar coordinate method layout parameters; After selecting DX01 as the station and DX02 as the backsight point to complete the orientation, the coordinates of the DX03 control point are re-measured. The re-measurement error is 1.2cm≤2cm, confirming the orientation is valid.

[0055] Point layout and excavation control: The polar coordinate method was used to complete the layout of the pile center and excavation outline. Each point was re-measured by double measurement on both the left and right sides of the screen. The deviation from the design coordinates was ≤2.5cm, which meets the limit requirement of ≤3cm. After locking the point, concrete marker stones and cross-shaped protective piles were set. Based on the centerline pile, the left and right side excavation edge piles and graded platform control piles were laid out to form a closed-loop excavation control pile network.

[0056] Implementation results: The slope at the tunnel entrance was excavated in one go with a slope deviation of ≤3%, and there were no problems of over-excavation or under-excavation. The slope remained stable throughout the excavation process, and no safety hazards such as instability or collapse occurred.

[0057] (II) Implementation of the tunnel body measurement steps The core objective of this stage is to ensure the accuracy of the tunnel's alignment and compliance with structural dimensions, eliminate safety and operational risks caused by structural encroachment, and strictly implement the closed-loop review mechanism for the entire process described in the patent.

[0058] 1. Design parameter preprocessing Based on the tunnel design documents, a tunnel pile elevation table and structural dimension table were compiled at 5m intervals to clarify the control parameters for different rock grades: for Grade V rock sections, the excavation outline width is 12.56m, the height is 10.28m, the allowance for deformation is 12cm, and the steel frame spacing is 0.6m; for Grade IV rock sections, the excavation outline width is 12.24m, the height is 10.05m, the allowance for deformation is 8cm, and the steel frame spacing is 1.0m, providing a benchmark for on-site construction and verification.

[0059] 2. Control surveying and point transfer A graded traverse control network is used inside the tunnel, with one traverse point (numbered ND01, ND02, etc.) set up every 50m. A total station is used in conjunction with a laser pointer. Before each excavation cycle (each cycle advances 3m), the centerline and elevation are transferred to the excavation face. The positional error of the transferred points is ≤3mm, meeting the accuracy requirement of ≤5mm. Every time the traverse extension length exceeds 100m, it is connected to the traverse at the tunnel entrance for adjustment and correction of the control point coordinate deviation. The positional error of the points is always ≤2cm, ensuring the long-term stability of the accuracy of the control network inside the tunnel.

[0060] 3. Contour surveying and dimensional verification of all processes Using a Leica TunnelScan profile measuring instrument, based on the centerline control points inside the tunnel, the excavation outline and blast hole positioning lines were accurately measured on the excavation face, and over- and under-excavation control benchmarks were marked. The multi-node closed-loop verification described in the patent was strictly implemented. Before steel frame erection: The outline dimensions of the excavation section are checked to confirm that the over-excavation meets the design requirements and there is no structural under-excavation before steel frame erection can be carried out. After the steel frame is erected: check that the centerline deviation of the steel frame is ≤8mm, the elevation deviation is ≤5mm, and the outer contour dimension deviation is ≤1cm. Only after all of these meet the design requirements can the shotcrete construction be carried out. Before and after the secondary lining formwork erection: Before erecting the formwork, verify that the initial support section has no encroachment. After erecting the formwork, re-measure the centerline deviation of the formwork to be ≤6mm, the elevation deviation to be ≤4mm, and the inner contour dimension deviation to be ≤2mm. Only after the re-measurement is qualified can concrete be poured.

[0061] Implementation results: No structural under-excavation or lining encroachment occurred during the entire tunnel construction process, and the over-excavation was controlled within the design allowable range, thus avoiding safety hazards such as structural collapse and operational encroachment from the source.

[0062] (III) Implementation of Real-time Correction of Measurement Environment Inside the Tunnel To address the challenges of large temperature differences inside the tunnel and the impact of atmospheric refraction on measurement accuracy, the environmental correction sub-steps described in the patent are strictly implemented to ensure stable measurement accuracy during long-distance tunneling.

[0063] 1. Equipment configuration: The underground measurement operation is equipped with a Vaisala PTB330 high-precision barometer and a TESTO 175-T1 thermometer, which are linked with the total station to realize real-time acquisition and correction of meteorological parameters.

[0064] 2. Real-time correction operation: Before each tunnel measurement and layout, place the barometer and thermometer near the total station in a location not affected by ventilation airflow or concrete curing heat sources. Let them stand for 3 minutes until the readings stabilize. Record the current tunnel temperature t=22.5℃ and atmospheric pressure P=86.2kPa. Input the meteorological correction parameter into the total station's interface. The instrument will automatically calculate the distance measurement meteorological correction coefficient and apply it to the slope distance measurement in real time.

[0065] 3. Angle and refraction correction: During precise trigonometric leveling, the temperature is measured at heights of 1.2m, 1.5m, and 1.8m along the line of sight. The atmospheric refraction coefficient K=0.12 is estimated based on a temperature gradient of 0.2℃ / m and input into the total station to complete the correction of the vertical angle observation value. The reciprocating observation method is used throughout the traverse survey to cancel the effect of refraction. The line of sight height is kept at a uniform height of about 1.5m, avoiding areas with fans and heat sources.

[0066] 4. Dynamic updates: Meteorological parameters are remeasured and instrument settings are updated every 200m of tunneling or when ventilation conditions or temperature inside the tunnel change significantly.

[0067] Implementation results: The relative error of distance measurement throughout the tunnel is ≤1 / 80000, and the error of angle measurement is ≤5″. This effectively eliminates the influence of meteorological factors and atmospheric refraction on measurement accuracy and solves the industry problem of measurement accuracy decay during long-distance tunnel excavation.

[0068] (iv) Implementation of automatic early warning for airspace convergence To achieve proactive prevention and control of surrounding rock deformation risks, the automatic early warning steps for clearance convergence described in the patent should be strictly implemented, and an automated dynamic monitoring system should be constructed.

[0069] 1. Monitoring point layout: Along the longitudinal direction of the tunnel, a monitoring section is set up every 10m in the Class V surrounding rock section and every 20m in the Class IV surrounding rock section; each section is set up with 5 monitoring points with reflective markings, including 1 at the top of the arch, 1 on each of the left and right arch waists, and 1 in the middle of each of the left and right sidewalls. The monitoring points are affixed with Leica prism reflective markings and are firmly fixed to prevent them from being disturbed by construction.

[0070] 2. Automated Measurement and Data Processing: On the initial stable support at position ZK123+080, a Leica TS60 surveying robot is installed to automatically measure the distance and angle of each monitoring point at a preset frequency of once every 2 hours. The controller receives the measurement data in real time, automatically calculates the cross-sectional clearance convergence value and the arch settlement value, and the data storage and display module synchronously generates the displacement-time change curve and displacement-tunneling advance change curve of each monitoring point.

[0071] 3. Early warning thresholds and emergency response: The preset early warning thresholds are: daily change in arch crown settlement ≥ 5mm, cumulative value ≥ 100mm, daily change in net clearance convergence ≥ 3mm, cumulative value ≥ 80mm; during construction, when the daily settlement of the arch crown at section ZK123+070 reaches 6mm, the system immediately triggers an audible and visual alarm, and the excavation at the working face is immediately stopped. Temporary invert arches and anchor pipe reinforcement measures are taken. Construction is resumed after the deformation stabilizes, successfully avoiding the risk of surrounding rock instability and collapse.

[0072] (v) Implementation of As-Built Measurement Procedures After the main tunnel construction is completed, the as-built survey is completed strictly in accordance with the steps described in the patent, resulting in a complete as-built survey report.

[0073] 1. Tunnel clearance completion inspection: After the secondary lining construction was completed, the entire cross-section clearance of the left tunnel was scanned every 10m interval using a Faro Focus S350 laser clearance detector to obtain the actual inner contour coordinate data of the tunnel. The data was compared with the design clearance and design inner contour dimensions one by one. A total of 129 cross-sections were inspected. Only 3 cross-sections showed local over-excavation, and there were no encroachments. The points exceeding the standard were marked and feedback was provided. A formal clearance inspection report was generated simultaneously.

[0074] 2. Tunnel Breakthrough Measurement: After the left tunnel was excavated and completed in both directions, a breakthrough measurement was immediately organized. The centerline and elevation control points at the breakthrough face ZK123+685 were measured from the GPS primary control network at both ends of the tunnel entrance and exit. The calculated transverse breakthrough error was 18mm, longitudinal breakthrough error was 25mm, elevation breakthrough error was 12mm, and azimuth breakthrough error was 3″, which is much smaller than the standard allowable limit of ≤150mm for transverse breakthrough error and ≤70mm for elevation breakthrough error. After meeting the standard requirements, the control network inside the tunnel was adjusted as a whole to form the final tunnel as-built control network.

[0075] 3. Compilation of As-built Data: Summarize all data and results from tunnel entrance measurement, tunnel body measurement, breakthrough measurement, clearance detection, and deformation monitoring; compile a tunnel construction measurement completion report; and create complete archival data of measurement results to ensure successful completion acceptance.

[0076] III. Application of Supporting Measurement Systems This project simultaneously applies the tunnel construction safety measurement system described in the patent to achieve full-process collaborative digital management and control of both hardware and software. The system composition and application are as follows: 1. Control Center: Deployed in the project department, equipped with data storage and processing modules and comparison and analysis modules, it uniformly stores tunnel design data, receives on-site data from various measuring devices in real time, and automatically completes deviation comparison, accuracy analysis and report generation.

[0077] 2. Core surveying equipment: Topcon MS05AXII total station and Leica TS60 surveying robot are configured for control surveying and point layout; Leica TunnelScan cross-section measuring instrument is used for excavation outline surveying and cross-section verification; FaroFocus S350 laser clearance detector is used for as-built clearance inspection.

[0078] 3. Environmental compensation unit: It consists of a barometer, thermometer, and signal connection and correction module. It is linked with the total station signal to realize real-time acquisition of meteorological parameters and automatic correction of measurement data.

[0079] 4. Automatic Early Warning and Monitoring System: Composed of reflective marker monitoring points, measuring robot, controller, audible and visual alarm, and data storage and display module, it realizes automated and continuous monitoring and proactive early warning of surrounding rock deformation.

[0080] IV. Summary of Implementation Results This project, through the complete application of the tunnel construction safety measurement method and supporting system based on this patent, has achieved precise control of measurement accuracy and proactive prevention of safety risks throughout the entire construction cycle. The core achievements are as follows: 1. Significant achievements in safety management: The entire process of excavating the slope at the tunnel entrance was stable and without instability. No structural encroachment or collapse occurred during tunnel construction. One risk of surrounding rock deformation was successfully handled through the automatic early warning system. No production safety accidents related to measurement occurred.

[0081] 2. Measurement accuracy fully meets standards: the tunnel breakthrough error is far below the standard limit, the deviation of the layout of all points along the route and the deviation of the structural dimension verification all meet the design and specification requirements, and the first-time acceptance rate of measurement results is 100%.

[0082] 3. Significantly improved construction efficiency: Through standardized measurement procedures, automated data processing and real-time correction, measurement efficiency has been increased by 30%, and the measurement rework rate has been reduced to 0, effectively shortening the total construction period of the tunnel.

[0083] 4. Standardized and replicable results: A standardized measurement and control scheme covering the entire life cycle of tunnel construction has been formed, which can provide a complete technical reference for the construction measurement of similar mountain highway tunnels and railway tunnels.

[0084] The implementation of this invention yields the following social benefits and application value: First, it can promote technological progress in the tunnel construction industry: This invention organically integrates traditional, decentralized measurement methods with intelligent environmental compensation units and automatic early warning systems, constructing a systematic measurement solution covering the entire tunnel construction cycle. This represents a transformation and upgrade of tunnel measurement technology from "experience-driven" to "data-driven".

[0085] The "three-stage, multi-node" measurement and control process proposed in this invention—precise layout at the tunnel entrance, closed-loop verification of the tunnel body, and continuous inspection upon completion—provides a standardized technical paradigm for tunnel construction quality control. This process is rationally designed and has clearly defined nodes, making it applicable to various types of highway tunnels, railway tunnels, subway sections, and water conservancy tunnels. Particularly in extra-long tunnels and tunnels with complex geological conditions, the systematic process control of this invention effectively solves the problems of "separation of measurement and control, and data silos" in traditional measurement methods, and can promote technological progress throughout the tunnel construction industry.

[0086] II. Enhancing the security level of major infrastructure: Regarding long-term structural safety, the invention's full-process quality control mechanism involves cross-sectional verification at three key stages: excavation, support, and lining. This allows for timely detection and correction of issues such as over-excavation, under-excavation, steel frame misalignment, and formwork deformation, ensuring reasonable initial support stress and that the secondary lining thickness meets design requirements. Continuous scanning and detection during the completion phase generates complete cross-sectional deviation chromatograms, providing reliable basic data for tunnel delivery and operation. This quality assurance system, extending from the construction phase to the operation phase, effectively reduces the risk of tunnel defects and maintenance costs during tunnel operation.

[0087] Third, this invention integrates various advanced equipment such as total stations, cross-section measuring instruments, laser clearance measuring instruments, and surveying robots, as well as intelligent functions such as environmental correction, automatic early warning, and data analysis, constructing a technical system covering the entire process of measurement, monitoring, and inspection. The widespread application of this system will significantly reduce the frequency of manual on-site measurements and lower the operational risks for surveyors in complex tunnel environments, thus improving construction efficiency and cost optimization. The rapid scanning functions of the cross-section measuring instrument and the laser clearance measuring instrument shorten the time between work processes and improve the overall efficiency of tunnel construction. Actual measurement data shows that similar technology applications can reduce the number of personnel for a single measurement operation from four to two, significantly shortening the operation time. As-built inspection uses track-based continuous scanning, which is more than five times more efficient than traditional fixed-point inspection. These efficiency improvements directly translate into cost savings in engineering projects—the innovative application of this technology in similar tunnel engineering projects has already demonstrated the effect of achieving milestone targets ahead of schedule and creating direct economic benefits.

[0088] In terms of data value mining, this invention establishes a unified database through a control center, enabling structured storage and management of measurement data throughout the entire process, from construction layout to final inspection. The automatically generated displacement-time and displacement-tunneling advance curves provide a scientific basis for dynamic optimization design, embodying the technical concept of "measurement guiding construction." In-depth mining of massive monitoring data can further optimize the tunnel health big data model, predict deformation risks, and provide valuable technical references for similar projects.

[0089] In summary, this invention not only solves specific technical problems such as accuracy, safety, efficiency, and quality control in tunnel construction surveying, but also generates broad and far-reaching social benefits in terms of industry technological progress, public safety assurance, and industry talent training, and has important engineering application value and promising prospects for technology promotion.

Claims

1. A method for measuring safety during tunnel construction, characterized in that, Includes the following steps: The steps for measuring the tunnel entrance are as follows: Based on the design structure and topographic elevation of the tunnel entrance, calculate the coordinates of the excavation edge line of the tunnel entrance side slope and the coordinates of the pile center; Using the relative relationship between the traverse line and the calculated coordinates, use a total station to lay out the excavation outline of the tunnel entrance side slope and the coordinates of the pile center on the ground, and lay out the excavation edge piles with the laid coordinates as the center to control the excavation of the tunnel entrance side slope. Tunnel surveying steps: Calculate the coordinates, structural dimensions, and elevation of the 100-meter stakes along the route, and compile a tunnel elevation table according to the preset mileage; use the measurement control points inside the tunnel to transfer the centerline and elevation to the excavation face; use a cross-section measuring instrument to measure the tunnel excavation outline, and verify the outline dimensions before and after the erection of the support steel frame and before and after the erection of the secondary lining formwork; As-built measurement steps: The clearance of the lined tunnel section is checked using a laser clearance detector according to the preset mileage, and a breakthrough measurement is organized after the tunnel body is excavated and connected.

2. The tunnel construction safety measurement method according to claim 1, characterized in that, The specific implementation process for calculating the coordinates of the excavation edge line of the slope at the tunnel entrance and the coordinates of the pile center is as follows: (1.1) Basic data extraction and preprocessing: Extract the horizontal alignment parameters, longitudinal alignment parameters, portal structure dimensions, slope ratio of side slopes, width and elevation of graded platforms, and design elevation of excavation top line from the tunnel design documents; at the same time, obtain 1:500 scale topographic elevation data of the portal area through total station field measurement or UAV aerial survey, and construct a digital elevation model of the portal topography; (1.2) Calculation of three-dimensional coordinates of the pile center: The entire process of calculating the coordinates of the centerline piles of the line is completed according to the mileage progression direction: The center coordinates of the straight section pile are calculated using the coordinate forward calculation formula. Based on the coordinates of the starting point (X0, Y0) and the azimuth angle α of the straight section, the plane coordinates of any pile number to be calculated are: X = X0 + D × cosα, Y = Y0 + D × sinα, where D is the mileage difference between the pile number to be calculated and the starting point of the straight section. Center coordinates of piles in curved sections: For the pile numbers at the entrance of transition curves and circular curves, first calculate the offset value of the pile number to be calculated in the local tangent coordinate system using the tangent offset method, then convert the local offset into plane coordinates in the unified engineering coordinate system using the coordinate rotation transformation formula, and combine the horizontal curve turning angle to correct the azimuth angle to complete the calculation of the plane coordinates of the center of piles in curved sections. Pile center elevation calculation: For straight slope sections, the design elevation of the corresponding station is calculated according to the design slope and the mileage difference. For vertical curve sections, the design elevation is calculated according to the vertical curve elevation correction formula, and finally a three-dimensional coordinate dataset of each pile center is formed. (1.3) Iterative calculation of the coordinates of the excavation edge line of the tunnel entrance slope: The first step is to define the control range of the excavation boundary: based on the mileage of the boundary between the open and closed sections of the tunnel entrance, extend outward to determine the longitudinal mileage range of the side slope excavation, and use the centerline of the line as the axis of symmetry, combined with the structural dimensions of the tunnel entrance, to determine the maximum offset range of the transverse excavation boundary. The second step is point pre-setting and preliminary calculation: Cross-sections to be calculated are set at intervals of 2m to 5m along the longitudinal mileage range. For each cross-section, the centerline of the line is used as a reference, and a pre-set lateral offset value is established. Combined with the tangent azimuth angle of the centerline, the lateral offset direction perpendicular to the centerline is determined. The plane coordinates of the preset point are initially calculated, and the original ground measured elevation H of the point is matched from the terrain digital elevation model. The third step is slope elevation calculation and iterative verification: Based on the slope ratio i of the slope grade design, the top elevation and plane position of the corresponding grade platform, calculate the design excavation slope elevation Hset corresponding to the preset point. The calculation formula is: Hset = top elevation of the corresponding grade platform - horizontal projection distance between the preset point and the edge of the platform × i. Compare Hground and Hset. When |Hground - Hset| ≤ 5cm, the point is a valid point on the excavation edge line, and its plane coordinates are locked. If the difference exceeds the limit, iteratively adjust the lateral offset of the point and repeat the above calculation process until the limit requirement is met. The fourth step is to generate a complete coordinate sequence: iterative calculations are performed on all points to be calculated for each section to obtain a continuous coordinate point sequence of the side slope excavation line. The control coordinates of the graded platform and the intercepting ditch are calculated simultaneously to form a complete set of coordinates for the excavation line of the tunnel entrance.

3. The tunnel construction safety measurement method according to claim 1, characterized in that, In the process of measuring the opening, the utilization of the relative relationship between the traverse and the calculated coordinates is as follows: (1.1) Layout and adjustment of the traverse control network at the tunnel entrance: In the area outside the excavation influence range of the tunnel entrance, in a geologically stable area with good visibility, a traverse is laid out. The traverse starts and closes at the first-level plane control point of the project. The traverse points are evenly distributed around the tunnel entrance, and the adjacent points have good visibility. After completing the field observation of horizontal angle, slant distance and vertical angle, a rigorous adjustment calculation is carried out to obtain the three-dimensional coordinates and accuracy evaluation results of each traverse control point, forming the ground construction control benchmark network at the tunnel entrance. (1.2) Coordinate system matching and layout parameter calculation: The pile center coordinates and the side slope excavation line coordinates obtained above are uniformly converted to the unified engineering coordinate system of the traverse line, and the coordinate reference, projection parameters and elevation reference are confirmed to be completely consistent to eliminate system deviation; with each control point of the traverse line as the reference, the azimuth and horizontal distance of each coordinate point to be laid out relative to the station control point are calculated to form the core parameters of the total station polar coordinate method layout; (1.3) Relative relationship verification and precise layout: Orientation accuracy verification: Select two control points with good visibility in the traverse as the station and backsight point respectively. After completing the total station backsight orientation, remeasure the coordinates of the third known control point in the traverse. When the remeasurement error of the point is ≤2cm, the orientation is confirmed to be effective and the relative relationship of the control points is accurate before subsequent layout work can be carried out. Core point layout: Based on the total station completed by orientation, the coordinates of the pile center and the outline of the slope excavation are input point by point. The polar coordinate method is used to complete the point layout. After the layout of each point is completed, the coordinates are re-measured by double measurement with both left and right sides of the instrument. When the deviation from the design coordinates is ≤3cm, the point is locked and concrete markers or wooden stakes are set. Cross-shaped protective piles are laid out at the same time to avoid damage to the pile position during construction. Excavation side stake layout: Using the center point of the centerline stakes after layout as a reference, along the transverse direction perpendicular to the centerline, excavation side stakes on both the left and right sides are laid out according to the designed offset values. Platform control stakes are simultaneously set at the graded platform positions on the slope, forming a closed-loop excavation control stake network. This precisely controls the excavation range, slope ratio, and excavation elevation of the slope at the tunnel entrance, avoiding... Avoid over-excavation to prevent safety hazards such as slope instability and landslides.

4. The tunnel construction safety measurement method according to claim 1, characterized in that, The specific implementation of the tunnel body measurement step is as follows: Step 1, Preprocessing of tunnel design parameters: Based on the tunnel design documents, calculate the centerline coordinates of each mileage section of the tunnel, the dimensions of the tunnel outline structure, the design elevation of the road surface, and the design elevation of the arch. Compile a tunnel pile elevation table and structural dimension table at 5m intervals, and clarify the reserved deformation amount of the excavation outline, the design spacing of the support steel frame, and the outer outline dimensions under different surrounding rock grades. Step 2, Control Survey and Point Transfer within the Tunnel: A graded traverse control network is used within the tunnel. Combined with the tunnel construction conditions, a total station and laser pointer are used to transfer the centerline and elevation of the line to the excavation face through the traverse control points within the tunnel. Accurate transfer of the centerline and elevation is completed before each excavation cycle, with a transfer point error ≤5mm. Every 100m of traverse extension, a joint survey and adjustment is conducted between the traverse within the tunnel and the traverse attached to the tunnel entrance to correct control point coordinate deviations and ensure the accuracy of the control network within the tunnel. Step 3, Excavation outline surveying and dimension verification: Using a tunnel cross-section measuring instrument, based on the centerline control points inside the tunnel, the outline line and blast hole positioning lines are surveyed on the excavation face according to the coordinates of the designed excavation outline line, and the over-excavation and under-excavation control benchmarks are marked; before the support steel frame is erected, the excavation cross-section outline dimensions are verified. The over-excavation amount meets the design requirements and there is no structural under-excavation before the steel frame can be erected. After the steel frame is erected, the centerline deviation, elevation, and outer contour dimensions of the steel frame are checked. Shotcrete construction can only proceed after the deviation meets the design requirements. Before and after the secondary lining formwork is erected, the centerline, elevation, and inner contour dimensions of the formwork are checked respectively. Concrete pouring can only proceed after the formwork is erected and the re-measurement is qualified, in order to prevent operational safety hazards caused by structural encroachment.

5. The tunnel construction safety measurement method according to claim 1, characterized in that, The specific implementation steps for as-built surveying are as follows: Step 1, Tunnel clearance completion inspection: After the secondary lining construction of the tunnel is completed, the clearance of the lined section of the tunnel is scanned every 10m interval using a laser clearance detector to obtain the actual inner contour coordinate data of the tunnel. The data is compared with the design clearance and design inner contour dimensions to check whether there is any encroachment. The encroachment points are marked in time and reported for handling. A clearance inspection report is generated simultaneously. Step 2, Tunnel Breakthrough Measurement: After the tunnel is completed in both directions or in one direction, breakthrough measurement is immediately organized. The centerline control point and elevation control point at the breakthrough face inside the tunnel are measured from the ground control network at both ends of the tunnel entrance and exit. The transverse breakthrough error, longitudinal breakthrough error, elevation breakthrough error and azimuth breakthrough error are calculated. Step 3, Compilation of As-built Data: Summarize all data and results from the tunnel entrance measurement, tunnel body measurement, tunnel connection measurement, and clearance detection, compile a tunnel construction measurement completion report, and form a complete archive of measurement results.

6. The tunnel construction safety measurement method according to claim 1 or 4, characterized in that, The tunnel body measurement step, when transferring the centerline and elevation to the excavation face, also includes an environmental correction sub-step: When conducting construction layout inside the tunnel, a barometer and a thermometer are provided. Real-time measurement of ambient air pressure and temperature inside the cave; Based on real-time measured air pressure and temperature data, the distance and angle measurement data of measuring instruments (such as total stations) are corrected in real time to eliminate the influence of atmospheric refraction and meteorological factors on measurement accuracy.

7. The tunnel construction safety measurement method according to claim 6, characterized in that, The specific execution process of real-time correction The specific execution process of real-time correction is as follows: Before surveying and setting out inside the tunnel, the barometer and thermometer are placed near the total station in a location free from airflow and heat sources. After standing still for 2-3 minutes until the readings stabilize, the current atmospheric pressure P and temperature t are recorded. Then, P and t are input into the meteorological correction parameter setting interface of the total station. The instrument automatically calculates the distance measurement meteorological correction coefficient according to the built-in meteorological correction formula and applies it in real time to all subsequent slope distance measurements, eliminating the influence of meteorological factors on the distance measurement accuracy. For angle measurement data, considering that atmospheric refraction inside the tunnel may cause errors in vertical angle observation, when performing precise trigonometric leveling, the refraction coefficient K can be estimated by measuring the temperature gradient at different heights along the line of sight. The K value is then input into the total station or manually substituted into the vertical angle observation value for correction. At the same time, in traverse surveying, the reciprocating observation method is used to automatically cancel the refraction effect, and the line of sight height is kept as consistent as possible and local heat sources are avoided. When the tunnel excavation length increases or the tunnel environment changes significantly, the meteorological parameters are remeasured and the instrument settings are updated to ensure that the measurement accuracy is always under control.

8. The tunnel construction safety measurement method according to claim 1, characterized in that, It also includes an automatic early warning step for airspace convergence: Multiple monitoring points with reflective markings are set up on the pre-designed cross-section of the tunnel body; Set up an automatic measuring robot or laser rangefinder array to automatically measure the distance to each monitoring point at a preset frequency; calculate the net clearance convergence value and crown settlement value of the cross section based on the measurement data; The calculated convergence value is compared with the preset warning threshold. When the measured value exceeds the warning threshold, the system automatically issues an audible and visual alarm signal. In the automatic early warning step of clearance convergence, the preset cross-section includes multiple sections, which are arranged along the longitudinal direction of the tunnel at a set interval; the monitoring points arranged on each cross-section include the arch apex and at least two symmetrical sidewall points.

9. A tunnel construction safety measurement system for performing the tunnel construction safety measurement method according to any one of claims 1-8, characterized in that, include: The control center is used to store tunnel design data, receive measurement data, and perform comparative analysis. The control center includes a data storage and processing module and a comparative analysis module. A total station is used for angle and distance measurements during tunnel entrance surveying and control surveying inside the tunnel, and for setting out points. A cross-section measuring instrument is used to measure the excavation outline and verify structural dimensions during tunnel construction. Laser clearance detectors are used to detect tunnel clearance during as-built surveying. The environmental compensation unit, including a barometer, a thermometer, and a signal connection and correction module, is connected to the total station signal and is used to perform real-time meteorological correction on the total station's measurement data.

10. The tunnel construction safety measurement equipment according to claim 9, characterized in that, It also includes an automatic early warning and monitoring system, which comprises: Multiple reflective markers are deployed on pre-set monitoring sections of the tunnel body; at least one measuring robot or laser rangefinder array is fixed in a stable position inside the tunnel to automatically perform periodic measurements on each reflective marker. The controller receives measurement data from the measuring robot or laser ranging sensor array, calculates the clearance convergence value and the arch subsidence value, and compares them with preset thresholds. When the limit is exceeded, an early warning signal is output. An alarm device, connected to the controller, receives the warning signal and issues an alarm. The automatic early warning monitoring system also includes a data storage and display module, which stores the data from each measurement and generates displacement-time variation curves and displacement-tunneling advance variation curves for each monitoring point.

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