Hidden type double-shield TBM shield tail gap monitoring device and method
By combining concealed design with laser ranging technology, the problems of accuracy, real-time performance, and environmental adaptability in shield tail gap monitoring have been solved, providing an efficient and reliable shield tail gap monitoring solution that is adaptable to harsh construction environments and supports intelligent diagnosis and remote monitoring.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SINOHYRDO ENG BUREAU 3 CO LTD
- Filing Date
- 2026-03-30
- Publication Date
- 2026-05-05
AI Technical Summary
Existing technologies for monitoring shield tail gaps suffer from problems such as low measurement efficiency, unstable accuracy, high safety risks, and poor environmental adaptability, making it difficult to achieve real-time and reliable monitoring, especially in complex construction environments.
By combining a concealed design with laser ranging technology, a laser rangefinder is embedded in the prefabricated installation slot of the shield shell. Non-contact measurement is achieved using a 45° refractive prism, and data is processed and fed back in real time by an industrial control computer, forming a 360° all-around monitoring system.
It achieves high-precision, real-time monitoring of the shield tail gap, avoids mechanical wear and environmental pollution, ensures the stability of the equipment and the reliability of the measurement, and supports intelligent diagnosis and remote monitoring.
Smart Images
Figure CN121977461A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of TBM tail monitoring technology, and in particular relates to a device and method for monitoring the gap between the tail of a concealed double-shield TBM. Background Technology
[0002] In the construction of a double-shield TBM, the shield tail gap refers to the annular gap between the inner wall of the TBM shield tail and the outer wall of the assembled tunnel segments. Its proper control is directly related to construction safety, project quality and economic benefits. Therefore, real-time monitoring and control of the shield tail gap has become a key technical challenge in modern tunnel engineering.
[0003] From an engineering practice perspective, there are two key thresholds for shield tail clearance control: a lower threshold and an upper threshold. When the lower threshold is exceeded (i.e., the clearance is too small), it leads to difficulties in segment assembly and, in severe cases, may cause pressure damage to the lining structure. When the upper threshold is exceeded (i.e., the clearance is too large), it can easily cause quality accidents such as incomplete grouting, ground settlement, or even tunnel axis deviation. More seriously, in water-rich strata, an excessively large shield tail clearance can also become a channel for groundwater inflow, causing major safety accidents such as water and mud inrushes.
[0004] Currently, methods for monitoring the shield tail gap include manual measurement, mechanical monitoring, and image visual monitoring. However, while traditional manual measurement methods are simple to operate, they suffer from inherent defects such as low measurement efficiency, unstable data accuracy, and high safety risks, making them unsuitable for the needs of intelligent development in tunnel engineering. Mechanical automatic monitoring systems, although achieving automated measurement, introduce numerous problems due to their mechanical contact measurement principle: continuous wear of mechanical transmission components directly affects measurement accuracy and shortens equipment lifespan; in high-pressure, high-humidity, and dusty construction environments, the reliability of the sealing structure is difficult to guarantee; and the installation, commissioning, and maintenance of mechanical devices can interfere with normal construction processes. Non-contact image visual monitoring technology, while avoiding mechanical wear problems, still faces significant technical bottlenecks: mud adhesion, water mist interference, and mechanical vibration in complex construction environments severely affect measurement stability; the computational efficiency of image processing and 3D reconstruction algorithms is insufficient to meet real-time monitoring requirements; and the high system deployment cost and complex installation and commissioning limit its widespread application in engineering practice. Summary of the Invention
[0005] The technical problem to be solved by this invention is to address the shortcomings of the existing technology by providing a concealed tail gap monitoring device for dual-shield TBMs. Through an innovative combination of concealed design and laser ranging technology, it overcomes the deficiencies of traditional monitoring methods in terms of accuracy, real-time performance, environmental adaptability, and engineering practicality, providing an efficient and reliable tail gap monitoring solution for dual-shield TBM construction. By embedding the laser rangefinder into the prefabricated installation slot of the shield shell and fixing it with a slotted welded blocking steel plate, interference with the segment assembly construction is avoided. Simultaneously, it effectively prevents pollution and damage to the equipment from dust, water vapor, etc., during construction. By employing non-contact laser ranging technology, the laser is vertically projected onto the outer wall of the segment through a 45° refractive prism, resulting in high measurement accuracy and avoiding wear and errors caused by mechanical contact.
[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a concealed double-shield TBM tail gap monitoring device and method, the method comprising the following steps: including multiple laser rangefinders all installed on the tail of the double-shield TBM, a relay box installed inside the double-shield TBM, and an industrial control computer installed in the main control room of the tail of the double-shield TBM, wherein the laser rangefinders are connected to the relay box via wires, and the relay box is connected to the industrial control computer via wires; Multiple laser rangefinders are arranged at 60° intervals along the circumferential direction of the tail of the dual-shield TBM, and no laser rangefinders are installed at the bottom of the tail of the dual-shield TBM; the tail of the dual-shield TBM has a mounting groove, the laser rangefinder is installed in the mounting groove, and a baffle is provided at the opening of the mounting groove.
[0007] Furthermore, the laser rangefinder includes an integrated protective housing, the laser rangefinder sensor is disposed inside the integrated protective housing, and a 45° refractive prism is also provided inside the integrated protective housing. The laser emitted by the laser rangefinder sensor is redirected by the 45° refractive prism and then projected vertically onto the outer wall surface of the tube segment.
[0008] Furthermore, the industrial control computer is equipped with a circuit board, on which a controller is integrated, and the signal output terminal of the laser ranging sensor is connected to the signal input terminal of the controller.
[0009] This invention also provides a method for monitoring the tail gap of a concealed dual-shield TBM using a tail gap monitoring device, characterized in that the method includes the following steps: Step 1: Install the shield tail gap monitoring device. The process is as follows: Step 101: Using the position directly above the tunnel cross-section as a reference, i.e., the 0° position, equally spaced mounting slots are made along the circumference of the tail of the double-shield TBM, with a 60° difference between adjacent mounting slots; wherein, no mounting slot is required at the bottom of the tail of the double-shield TBM; the laser rangefinder is installed in the mounting slot and fixed with a baffle. Step 102: Weld a relay box inside the double-shield TBM and connect the relay box and the laser rangefinder with wires; Step 103: Place an industrial control computer in the main control room of the double-shield TBM tail shield, and connect the industrial control computer to the relay box using wires; complete the installation of the tail shield gap monitoring device; Step 2: Shield tail gap monitoring, the process is as follows: Step 201: After the two sets of hydraulic cylinders of the dual-shield TBM main propulsion system retract and reset, the controller first controls the laser ranging sensor at the 0° position to work, continuously emits 5 laser ranging signals, obtains 5 ranging data at the 0° position, removes outliers and calculates the arithmetic mean of the ranging data, which is used as the shield tail gap value at the reference position. Step 202: Along the clockwise direction of the tunnel cross section, the controller sequentially controls the laser ranging sensors at 60°, 120°, 240° and 300° on the tail of the double-shield TBM to work. Each point continuously emits 5 laser ranging signals to obtain 5 ranging data at that point. After removing outliers, the arithmetic mean of the ranging data at that point is calculated as the tail gap value at that point. Step 203: Based on the five measured points obtained in steps 201 and 202, respectively... , , , , and 1 virtual point The gap value is converted into three-dimensional coordinates and fitted with an circumscribed virtual circle. Based on the fitted center coordinates and radius, the theoretical position of the 180° point on the outer wall of the segment of the double-shield TBM is calculated. The difference between the calculated theoretical position of the 180° point on the outer wall of the segment and the design radius of the shield tail is the virtual shield tail gap value of the 180° point. Step 204: Compare and verify the measurement data of the 6 points. When the difference between two adjacent measurement points exceeds the set threshold, start the verification measurement and finally output the verified shield tail gap distribution data. Step 3: Process the shield tail gap value as follows: Step 301: The five measured points obtained are as follows , , , , and 1 virtual point The gap value is converted into three-dimensional coordinates, and a circumscribed virtual circle is fitted to establish the target fitting function of the circumscribed circle of the shield tail gap. Where n takes values of 0, 1, 2, 3, 4, 5, (a, b) are the coordinates of the center of the circumcircle, and r is the fitted radius of the circumcircle; Step 302: Take the partial derivatives of a, b, and r in the target fitting function, and then obtain the optimal solution by solving the following system of equations:
[0010]
[0011] ; Obtain the offset of the fitted circle center The shield tail clearance value Δr=rR, roundness deviation ; Step 303: Determine whether the fitting of the data at each point is valid. If the fitting result meets the test conditions, proceed to step four; otherwise, proceed to step 304. Step 304: Remove the data points with the largest deviations, repeat step 203, and refit the data with the remaining data points to obtain the data points that were removed; repeat steps 301 to 303 until the measured data points meet the test conditions.
[0012] Step 4: Optimize the dual-shield TBM propulsion parameters: Transmit the processed point data to the main control room in real time, and adjust the dual-shield TBM propulsion parameters in real time based on the data of each point.
[0013] Furthermore, in steps 201 and 202, the outliers are determined according to the 3δ criterion, and data that exceed the normal range in the ranging data of the 5 points are regarded as outliers and removed.
[0014] Furthermore, in step 204, the threshold is set to five per thousand of the tunnel design diameter.
[0015] Furthermore, when fitting the circumscribed virtual circle in steps 203 and 301, the five measured points obtained in the previous steps are as follows: , , , , and 1 virtual point Converting the gap value into three-dimensional coordinates, and setting the center of the shield tail as the origin, the coordinates of each point are represented as follows: Then, the target fitting function of the circumcircle of the shield tail gap is established. Where R is the design radius of the shield tail; θ is the azimuth angle of each point, corresponding to the values of n as 180°, 0°, 60°, 120°, 240° and 300° respectively.
[0016] Furthermore, in step 303, the test conditions include the correlation coefficient, the maximum residual, and the center offset; and the correlation coefficient must be satisfied simultaneously. Maximum residual Center offset .
[0017] Furthermore, in step four, the propulsion parameters of the dual-shield TBM include the number of times the line structured light is emitted, the test interval at the same point, and the test interval at different points.
[0018] Compared with the prior art, the present invention has the following advantages: 1. This invention, through the innovative combination of concealed design and laser ranging technology, solves the shortcomings of traditional monitoring methods in terms of accuracy, real-time performance, environmental adaptability, and engineering practicality, and provides an efficient and reliable solution for monitoring the tail gap in double-shield TBM construction.
[0019] 2. This invention embeds the laser rangefinder into the prefabricated installation slot of the shield shell and fixes it by welding a blocking steel plate with slots, thus avoiding interference with the segment assembly construction; the compact structural design adapts to the narrow space at the tail of the shield, while effectively preventing dust, water vapor and other contaminants from polluting and damaging the equipment during construction; the equipment has an IP67 protection rating and can withstand the effects of harsh construction environments such as high humidity, high dust and strong vibration.
[0020] 3. This invention employs non-contact laser ranging technology, using a 45° refractive prism to project the laser vertically onto the outer wall of the tube segment, resulting in high measurement accuracy and avoiding wear and errors caused by mechanical contact. Furthermore, the five laser rangefinders are symmetrically arranged at 60° intervals to form a regular hexagonal measurement network, and the data is cross-validated through geometric relationships, further improving measurement accuracy.
[0021] 4. This invention eliminates data blind spots through a 360° omnidirectional monitoring design and provides real-time feedback on the overall distribution characteristics of the shield tail gap; the redundant design ensures that the system can still operate stably when some sensors fail; the industrial-grade wired data transmission scheme ensures data real-time performance and reliability; and it supports dynamic display and real-time alarm functions.
[0022] 5. The modular design of this invention facilitates installation and maintenance, the system is easy to install, each component is structurally robust, and the later maintenance cost is low; the industrial control computer is used as the control center, supporting intelligent diagnosis, remote monitoring and data storage functions, providing comprehensive data support for construction management.
[0023] In summary, this invention, through the innovative combination of concealed design and laser ranging technology, solves the shortcomings of traditional monitoring methods in terms of accuracy, real-time performance, environmental adaptability, and engineering practicality, providing an efficient and reliable solution for monitoring the shield tail gap in dual-shield TBM construction. By embedding the laser rangefinder into the prefabricated installation slot of the shield shell and fixing it with a slotted welded blocking steel plate, interference with the segment assembly construction is avoided. At the same time, it effectively prevents pollution and damage to the equipment from dust, water vapor, etc. during construction. By adopting non-contact laser ranging technology, the laser is vertically projected onto the outer wall of the segment through a 45° refraction prism, resulting in high measurement accuracy and avoiding wear and errors caused by mechanical contact.
[0024] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description
[0025] Figure 1 This is a schematic diagram illustrating the measurement principle of the laser rangefinder of the present invention for measuring gap values.
[0026] Figure 2 This is a circuit block diagram of the present invention.
[0027] Figure 3 This is a flowchart of the method of the present invention.
[0028] Explanation of reference numerals in the attached figures: 1—Double-shield TBM tail shield; 2—Tube segments; 3—Laser rangefinder sensor; 4—Controller; 5—Integrated protective housing; 6—45° refractive prism. Detailed Implementation
[0029] like Figure 1 and Figure 2 The concealed dual-shield TBM tail gap monitoring device shown includes multiple laser rangefinders all installed on the tail 1 of the dual-shield TBM, a relay box installed inside the dual-shield TBM, and an industrial control computer installed in the main control room of the tail 1 of the dual-shield TBM. The laser rangefinders are connected to the relay box via wires, and the relay box is connected to the industrial control computer via wires. Multiple laser rangefinders are arranged at 60° intervals along the circumferential direction of the tail of the double-shield TBM, and no laser rangefinder is installed at the bottom of the tail of the double-shield TBM; the tail of the double-shield TBM has a mounting groove, the laser rangefinder is installed in the mounting groove, and a baffle is provided at the opening of the mounting groove.
[0030] This invention, through the innovative combination of concealed design and laser ranging technology, solves the shortcomings of traditional monitoring methods in terms of accuracy, real-time performance, environmental adaptability, and engineering practicality, providing an efficient and reliable solution for monitoring the tail gap in double-shield TBM construction.
[0031] This invention embeds a laser rangefinder into a prefabricated installation slot in the shield shell and fixes it by welding a blocking steel plate with slots, thus avoiding interference with the segment assembly construction. The compact structural design adapts to the narrow space at the tail of the shield and effectively prevents dust, water vapor and other contaminants from polluting and damaging the equipment during construction. The equipment has an IP67 protection rating and can withstand the effects of harsh construction environments such as high humidity, high dust and strong vibration.
[0032] This invention employs non-contact laser ranging technology, using a 45° refractive prism to project laser light vertically onto the outer wall of the tube segment, resulting in high measurement accuracy and avoiding wear and errors caused by mechanical contact. Furthermore, five laser rangefinders are symmetrically arranged at 60° intervals to form a regular hexagonal measurement network, and the data is cross-validated through geometric relationships, further improving measurement accuracy.
[0033] This invention eliminates data blind spots through a 360° omnidirectional monitoring design, providing real-time feedback on the overall distribution characteristics of the shield tail gap; redundant design ensures stable system operation even when some sensors fail; industrial-grade wired data transmission scheme ensures data real-time performance and reliability; and supports dynamic display and real-time alarm functions.
[0034] This invention adopts a modular design for easy installation and maintenance. The system is easy to install, and each component has a robust structure, resulting in low maintenance costs. The industrial control computer serves as the control center, supporting intelligent diagnostics, remote monitoring, and data storage functions, providing comprehensive data support for construction management.
[0035] In this embodiment, the laser rangefinder includes an integrated protective housing 5, and the laser rangefinder 3 is arranged inside the integrated protective housing 5. A 45° refractive prism 6 is also provided inside the integrated protective housing 5. The laser emitted by the laser rangefinder 3 is redirected by the 45° refractive prism 6 and then projected vertically onto the outer wall surface of the tube segment 2.
[0036] In actual use, the laser rangefinder 3 emits a laser, which is then redirected by a 45° refracting prism 6 to project the laser vertically onto the outer surface of the segment 2, enabling real-time measurement of the shield tail gap. At the same time, the laser rangefinder is fixed in position by using a slotted welded blocking steel plate to ensure its stability and impact resistance in harsh environments.
[0037] In this embodiment, the industrial control computer is equipped with a circuit board, on which a controller 4 is integrated. The signal output terminal of the laser rangefinder 3 is connected to the signal input terminal of the controller 4.
[0038] like Figure 1 , Figure 2 and Figure 3 The method for monitoring the tail gap of a concealed dual-shield TBM using a tail gap monitoring device includes the following steps: Step 1: Install the shield tail gap monitoring device. The process is as follows: Step 101: Using the position directly above the tunnel cross-section as a reference, i.e., the 0° position, equally spaced mounting slots are made along the circumference of the tail of the double-shield TBM, with a 60° difference between adjacent mounting slots; wherein, no mounting slot is required at the bottom of the tail of the double-shield TBM; the laser rangefinder is installed in the mounting slot and fixed with a baffle. Step 102: Weld a relay box inside the double-shield TBM and connect the relay box and the laser rangefinder with wires; Step 103: Place an industrial control computer in the main control room of the tail shield 1 of the double-shield TBM, and connect the industrial control computer to the relay box using wires; complete the installation of the tail shield gap monitoring device; Step 2: Shield tail gap monitoring, the process is as follows: Step 201: After the two sets of hydraulic cylinders of the dual-shield TBM main propulsion system retract and reset, the controller 4 first controls the laser ranging sensor 3 at the 0° position to work, continuously emits 5 laser ranging signals, obtains 5 ranging data at the 0° position, removes outliers and calculates the arithmetic mean of the ranging data, which is used as the shield tail gap value at the reference position. Step 202: Along the clockwise direction of the tunnel cross section, the controller 4 sequentially controls the laser ranging sensors 3 at 60°, 120°, 240° and 300° positions on the tail of the double-shield TBM to work. Each position continuously emits 5 laser ranging signals to obtain 5 ranging data at that position. After removing outliers, the arithmetic mean of the ranging data at that position is calculated as the tail gap value at that position. Step 203: Based on the five measured points obtained in steps 201 and 202, respectively... , , , , and 1 virtual point The gap value is converted into three-dimensional coordinates and fitted with an circumscribed virtual circle. Based on the fitted center coordinates and radius, the theoretical position of the 180° point on the outer wall of the segment of the double-shield TBM shield tail 1 is calculated. The difference between the calculated theoretical position of the 180° point on the outer wall of the segment and the design radius of the shield tail is the virtual shield tail gap value of the 180° point. Step 204: Compare and verify the measurement data of the 6 points. When the difference between two adjacent measurement points exceeds the set threshold, start the verification measurement and finally output the verified shield tail gap distribution data. Step 3: Process the shield tail gap value as follows: Step 301: The five measured points obtained are as follows , , , , and 1 virtual point The gap value is converted into three-dimensional coordinates, and a circumscribed virtual circle is fitted to establish the target fitting function of the circumscribed circle of the shield tail gap. Where n takes values of 0, 1, 2, 3, 4, 5, (a, b) are the coordinates of the center of the circumcircle, and r is the fitted radius of the circumcircle; Step 302: Take the partial derivatives of a, b, and r in the target fitting function, and then obtain the optimal solution by solving the following system of equations:
[0039]
[0040] ; Obtain the offset of the fitted circle center The shield tail clearance value Δr=rR, roundness deviation ; Step 303: Determine whether the fitting of the data at each point is valid. If the fitting result meets the test conditions, proceed to step four; otherwise, proceed to step 304. Step 304: Remove the data points with the largest deviations, repeat step 203, and refit the data with the remaining data points to obtain the data points that were removed; repeat steps 301 to 303 until the measured data points meet the test conditions.
[0041] Step 4: Optimize the dual-shield TBM propulsion parameters: Transmit the processed point data to the main control room in real time, and adjust the dual-shield TBM propulsion parameters in real time based on the data of each point.
[0042] It should be noted that in step 101, considering the potential damage to the equipment caused by the water-rich environment at the bottom of the tunnel, a rangefinder is not directly deployed in this area. Instead, the bottom gap value is indirectly calculated by combining the monitoring data from the other five points with a geometric algorithm. This symmetrical layout forms a regular hexagonal measurement network, which not only achieves 360° monitoring without blind spots, but also improves data redundancy through the collaborative work of multiple sensors. At the same time, geometric relationships are used to cross-validate the data of adjacent measuring points to eliminate random errors. While ensuring measurement accuracy, this not only enhances the reliability of the system in harsh environments, but also maintains stable system operation through data reconstruction when some sensors fail. This provides a technical guarantee that balances accuracy, reliability, and engineering practicality for real-time monitoring of the shield tail gap.
[0043] In step 102, the welding position of the relay box is a location within the double-shield TBM that needs to provide power without interfering with other components.
[0044] In step 203, since the five laser rangefinders are symmetrically arranged at 60° intervals (0°, 60°, 120°, 240°, 300°), these five points, together with the 180° virtual point, form a regular hexagonal measurement network. Ideally, the gap between the outer wall of the tunnel segment and the inner wall of the shield tail geometrically follows a circular curve distribution. Therefore, the gap value at the 180° point can be obtained through interpolation or a geometric reconstruction method based on center fitting.
[0045] In this embodiment, in steps 201 and 202, the outliers are determined according to the 3δ criterion, and the data that exceed the normal value range in the ranging data of 5 points are regarded as outliers and removed.
[0046] In practical applications, the 3δ criterion assumes that the data follows a normal or approximately normal distribution. In a normal distribution, approximately 99.7% of the data points fall within the range of the mean plus or minus three standard deviations. Therefore, if a data point exceeds this range, it is considered an outlier.
[0047] In this embodiment, in step 204, the threshold is set to five per thousand of the tunnel design diameter.
[0048] In this embodiment, when fitting the circumscribed virtual circle in steps 203 and 301, the five measured points obtained are first... , , , , and 1 virtual point Converting the gap value into three-dimensional coordinates, and setting the center of the shield tail as the origin (0, 0, 0), the coordinates of each point are represented as follows: Then, the target fitting function of the circumcircle of the shield tail gap is established. Where R is the design radius of the shield tail; θ is the azimuth angle of each point, corresponding to the values of n as 180°, 0°, 60°, 120°, 240° and 300° respectively.
[0049] In this embodiment, step 303 includes the following test conditions: correlation coefficient, maximum residual, and center offset; and the correlation coefficient must be satisfied simultaneously. Maximum residual Center offset .
[0050] In this embodiment, in step four, the dual-shield TBM propulsion parameters include the number of line structure light emission times, the test interval at the same point, and the test interval at different points.
[0051] In step four, adjusting the number of times the line structured light is emitted is to adjust the number of shield tail gap measurements.
[0052] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, or equivalent structural changes made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.
Claims
1. A concealed dual-shield TBM shield tail gap monitoring device, characterized in that: It includes multiple laser rangefinders installed on the tail (1) of the double-shield TBM, a relay box installed inside the double-shield TBM, and an industrial control computer installed in the main control room of the tail (1) of the double-shield TBM. The laser rangefinders are connected to the relay box via wires, and the relay box is connected to the industrial control computer via wires. Multiple laser rangefinders are arranged at 60° intervals along the circumferential direction of the double-shield TBM tail (1), and the laser rangefinders are not installed at the bottom of the double-shield TBM tail (1); the double-shield TBM tail (1) is provided with a mounting groove, the laser rangefinders are installed in the mounting groove, and the groove opening is provided with a baffle.
2. The concealed double-shield TBM shield tail gap monitoring device according to claim 1, characterized in that: The laser rangefinder includes an integrated protective housing (5), and the laser rangefinder (3) is installed inside the integrated protective housing (5). A 45° refractive prism (6) is also installed inside the integrated protective housing (5). The laser emitted by the laser rangefinder (3) is redirected by the 45° refractive prism (6) and then projected vertically onto the outer wall surface of the tube segment (2).
3. The concealed double-shield TBM shield tail gap monitoring device according to claim 2, characterized in that: The industrial computer is equipped with a circuit board, on which a controller (4) is integrated. The signal output terminal of the laser ranging sensor (3) is connected to the signal input terminal of the controller (4).
4. The method for monitoring the tail gap of a concealed dual-shield TBM using a tail gap monitoring device according to claim 3, characterized in that, The method includes the following steps: Step 1: Install the shield tail gap monitoring device. The process is as follows: Step 101: Using the position directly above the tunnel cross-section as a reference, i.e., the 0° position, equally spaced installation slots are made along the circumference of the double-shield TBM tail (1), with a 60° difference between adjacent installation slots; wherein, no installation slot is required at the bottom of the double-shield TBM tail (1); the laser rangefinder is installed in the installation slot, and the laser rangefinder is fixed using a baffle; Step 102: Weld a relay box inside the double-shield TBM and connect the relay box and the laser rangefinder with wires; Step 103: Place an industrial control computer in the main control room of the double-shield TBM tail (1) and connect the industrial control computer and the relay box with wires; complete the installation of the tail gap monitoring device. Step 2: Shield tail gap monitoring, the process is as follows: Step 201: After the two sets of hydraulic cylinders of the dual-shield TBM main propulsion system retract and reset, the controller (4) first controls the laser ranging sensor (3) at the 0° position to work, continuously emits 5 laser ranging signals, obtains 5 ranging data at the 0° position, removes outliers and calculates the arithmetic mean of the ranging data, which is used as the shield tail gap value of the reference position. Step 202: Along the clockwise direction of the tunnel cross section, the controller (4) sequentially controls the laser ranging sensors (3) at 60°, 120°, 240° and 300° on the tail of the double-shield TBM shield (1). Each point continuously emits 5 laser ranging signals to obtain 5 ranging data at that point. After removing outliers, the arithmetic mean of the ranging data at that point is calculated as the tail gap value at that point. Step 203: Based on the five measured points obtained in steps 201 and 202, respectively... , , , , and 1 virtual point The gap value is converted into three-dimensional coordinates and fitted with an circumscribed virtual circle; based on the fitted center coordinates and radius, the theoretical position of the 180° point on the outer wall of the segment of the double-shield TBM shield tail (1) is calculated. The difference between the calculated theoretical position of the 180° point on the outer wall of the segment and the design radius of the shield tail is the virtual shield tail gap value of the 180° point. Step 204: Compare and verify the measurement data of the 6 points. When the difference between two adjacent measurement points exceeds the set threshold, start the verification measurement and finally output the verified shield tail gap distribution data. Step 3: Process the shield tail gap value as follows: Step 301: The five measured points obtained are as follows , , , , and 1 virtual point The gap value is converted into three-dimensional coordinates, and a circumscribed virtual circle is fitted to establish the target fitting function of the circumscribed circle of the shield tail gap. Where n takes values of 0, 1, 2, 3, 4, 5, (a, b) are the coordinates of the center of the circumcircle, and r is the fitted radius of the circumcircle; Step 302: Take the partial derivatives of a, b, and r in the target fitting function, and then obtain the optimal solution by solving the following system of equations: ； Obtain the offset of the fitted circle center The shield tail clearance value Δr=rR, roundness deviation ; Step 303: Determine whether the fitting of the data at each point is valid. If the fitting result meets the test conditions, proceed to step four; otherwise, proceed to step 304. Step 304: Remove the data points with the largest deviations, repeat step 203, and refit the data with the remaining data points to obtain the data points that were removed; repeat steps 301 to 303 until the measured data points meet the test conditions. Step 4: Optimize the dual-shield TBM propulsion parameters: Transmit the processed point data to the main control room in real time, and adjust the dual-shield TBM propulsion parameters in real time based on the data of each point.
5. The concealed double-shield TBM shield tail gap monitoring device and method according to claim 4, characterized in that: In steps 201 and 202, the outliers are determined according to the 3δ criterion, and data that exceed the normal range in the distance measurement data of 5 points are regarded as outliers and removed.
6. The concealed double-shield TBM shield tail gap monitoring device and method according to claim 4, characterized in that: In step 204, the threshold is set to five per thousand of the tunnel design diameter.
7. The concealed double-shield TBM shield tail gap monitoring device and method according to claim 4, characterized in that: When fitting the circumscribed virtual circle in steps 203 and 301, the five measured points obtained in the first step are as follows: , , , , and 1 virtual point Converting the gap value into three-dimensional coordinates, and setting the center of the shield tail as the origin (0, 0, 0), the coordinates of each point are represented as follows: Then, the target fitting function of the circumcircle of the shield tail gap is established. Where R is the design radius of the shield tail; θ is the azimuth angle of each point, corresponding to the values of n as 180°, 0°, 60°, 120°, 240° and 300° respectively.
8. The concealed double-shield TBM shield tail gap monitoring device and method according to claim 4, characterized in that: In step 303, the test conditions include the correlation coefficient, the maximum residual, and the center offset; and the correlation coefficient must be satisfied simultaneously. Maximum residual Center offset .
9. The concealed double-shield TBM shield tail gap monitoring device and method according to claim 4, characterized in that: In step four, the propulsion parameters of the dual-shield TBM include the number of times the line structured light is emitted, the test interval at the same point, and the test interval at different points.