Construction tunnel primary support intrusion detection device and method based on three-dimensional laser technology

Abstract

The application belongs to the technical field of tunnel construction, and provides a device and method for detecting initial support intrusion of a construction tunnel based on three-dimensional laser technology. The device comprises a cantilever support installed on the inner wall of the tunnel, a two-way pitching mechanism, a three-dimensional laser radar and a measuring prism installed on the cantilever support in sequence from bottom to top; the two-way pitching mechanism, the three-dimensional laser radar and the measuring prism are in communication with an upper computer; the two-way pitching mechanism is used to drive the three-dimensional laser radar and the measuring prism; the three-dimensional laser radar is used to obtain three-dimensional point cloud data of the initial lining of the construction tunnel; the measuring prism is used to establish a geodetic coordinate system and a three-dimensional laser radar relative coordinate system, and to calculate the absolute coordinate of the three-dimensional laser radar according to the known control point coordinates; the upper computer is used to conduct overall intrusion detection analysis and initial support local intrusion detection analysis according to the three-dimensional point cloud data and the absolute coordinate of the three-dimensional laser radar. The application realizes initial support intrusion monitoring of tunnel excavation surrounding rock deformation.

Description

Technical Field

[0001] This invention belongs to the field of tunnel construction technology, specifically relating to a device and method for detecting the initial support encroachment limit of a construction tunnel based on three-dimensional laser technology. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] During the drill-and-blast method for highway tunnel construction, when the stress in the surrounding rock exceeds the deformation resistance of the initial support, it easily leads to cracking and deformation that encroaches on the clearance limit. Severe deformation and clearance of the initial support in highway tunnels pose a significant safety hazard. If not addressed promptly and effectively, tunnel collapse can easily occur, seriously threatening the lives and property of construction workers. Therefore, during highway tunnel construction, once construction personnel discover that the initial support has deformed and encroached on the clearance limit, they need to conduct precise measurements and analyze the specific circumstances of this deformation.

[0004] Due to the limitations of space and environmental conditions in drill-and-blast tunnel construction, monitoring during the construction phase typically relies on manual labor combined with total stations or levels. Traditional manual measurements are time-consuming, infrequent, and prone to errors, disrupting normal tunnel construction procedures and failing to provide timely, rapid, and accurate information on tunnel structural deformation. If excessive deformation of the initial support occurs and timely and effective support measures are not implemented, it can lead to overall or localized large deformations of the initial support, far exceeding the design allowance. This can cause the initial support to encroach on the secondary lining clearance, severely impacting the safety and service life of the secondary lining structure. Furthermore, if the deformation rate of the initial support is too high and timely and effective control measures are not implemented, there is a risk of initial support collapse, seriously threatening the safety of drill-and-blast tunnel construction. Summary of the Invention

[0005] To address the issue of encroachment detection caused by initial support deformation during the construction period of highway tunnels, this invention proposes a device and method for detecting encroachment of initial support in construction tunnels based on three-dimensional laser technology. This invention enables the acquisition of overall deformation point cloud data of the initial support section of the tunnel, achieving monitoring of initial support encroachment of surrounding rock deformation during tunnel excavation, ensuring construction safety, and improving the overall safety management level of tunnel construction.

[0006] According to some embodiments, the present invention adopts the following technical solution:

[0007] In the first aspect, the present invention provides a device for detecting the encroachment of initial support in construction tunnels based on three-dimensional laser technology.

[0008] A tunnel initial support encroachment detection device based on three-dimensional laser technology includes: a cantilever support installed on the inner wall of the tunnel; a bidirectional pitch mechanism is installed on the cantilever support; a three-dimensional laser radar is installed on the bidirectional pitch mechanism; and a measuring prism is installed on the three-dimensional laser radar; the bidirectional pitch mechanism, the three-dimensional laser radar, and the measuring prism all communicate with a host computer.

[0009] The bidirectional pitch mechanism is used to drive the three-dimensional lidar and the measuring prism;

[0010] The three-dimensional lidar is used to acquire three-dimensional point cloud data of the initial lining of the construction tunnel and upload it to the host computer.

[0011] The measuring prism is used to establish the geodetic coordinate system and the relative coordinate system of the three-dimensional lidar. The absolute coordinates of the three-dimensional lidar are calculated based on the known control point coordinates and uploaded to the host computer.

[0012] The host computer is used to perform overall intrusion detection analysis and initial support local intrusion detection analysis based on the three-dimensional point cloud data and the absolute coordinates of the three-dimensional lidar.

[0013] Furthermore, the cantilever support is installed near the invert arch of the construction tunnel using expansion bolts.

[0014] Furthermore, the driving of the three-dimensional lidar and measuring prism includes driving the three-dimensional lidar and measuring prism to pitch and rotate circumferentially.

[0015] Furthermore, the three-dimensional point cloud data includes spatial coordinate information covering the initial support surface points at that time.

[0016] Furthermore, the three-dimensional lidar performs automatic scanning operations within a specified time interval according to monitoring and measurement requirements.

[0017] Secondly, this invention provides a method for detecting the encroachment of initial supports in construction tunnels based on three-dimensional laser technology.

[0018] The method for detecting encroachment to the initial support of a construction tunnel based on three-dimensional laser technology, employing the three-dimensional laser technology-based detection device for detecting encroachment to the initial support of a construction tunnel as described in the first aspect, includes:

[0019] Establish a geodetic coordinate system and a relative coordinate system for the 3D lidar, and calculate the absolute coordinates of the 3D lidar based on the known control point coordinates;

[0020] Obtain three-dimensional point cloud data of the initial lining of the tunnel under construction;

[0021] Based on the absolute coordinates and 3D point cloud data of 3D LiDAR, overall encroachment detection and analysis and initial support local encroachment detection and analysis are performed.

[0022] Furthermore, after acquiring the three-dimensional point cloud data of the initial lining of the construction tunnel, the process includes: filtering and noise reduction, interpolation, simplification and pose adjustment of the three-dimensional point cloud data to obtain three-dimensional point cloud data in which the tunnel orientation is parallel to a certain coordinate axis of the Cartesian coordinate system.

[0023] The tunnel slices are projected, and the 3D point cloud data is divided into equally spaced slices along the direction parallel to the tunnel's central axis. Each slice is then dimensionality-reduced by projecting onto the mid-surface of the slice, replacing the thick slice with the mid-surface of the slice without thickness, while retaining the slice point cloud data.

[0024] Furthermore, the overall intrusion limit detection and analysis process includes:

[0025] The slice point cloud data is cropped along the elevation direction, and the slice projection of the cropped segment contour is circle fitted by RANSAC or least squares method.

[0026] Obtain the coordinates of the center of the fitted circle and the radius R parameter;

[0027] The obtained center coordinates and radius R are compared and analyzed with the tunnel design parameters to determine whether the initial support of the tunnel has deformed and encroached on the limit.

[0028] Furthermore, the process of initial branch local encroachment detection and analysis includes:

[0029] Based on the target area where the initial branch intrudes, super voxels are constructed from the sliced ​​point cloud data of the target area using Octree, and the curvature of each voxel within its neighborhood is calculated. By comparing the difference in curvature within the neighborhood, the local intrusion location of the initial branch is determined.

[0030] Furthermore, after detecting the overall and local encroachment of the initial support, the monitoring of the encroachment deformation rate includes: based on the multi-time three-dimensional point cloud data of the tunnel's initial support structure, establishing voxels for each phase of the initial support point cloud data using Octree, and encoding each voxel; comparing and analyzing voxels with the same encoding, calculating the spatial coordinate difference of the centroid of the point cloud voxels, and the difference is the encroachment deformation value; and obtaining the encroachment deformation rate based on the ratio of the encroachment deformation value to the encroachment deformation time.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] This invention acquires point cloud data of the overall deformation of the initial support section of a tunnel through a tunnel initial support encroachment detection device, and performs local and overall encroachment detection to achieve monitoring of the initial support encroachment of the surrounding rock deformation during tunnel excavation, ensuring construction safety and improving the overall safety management level of tunnel construction.

[0033] After detecting the overall and local encroachment of the initial support, this invention can monitor the deformation encroachment rate of the initial support. Attached Figure Description

[0034] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0035] Figure 1 This is a structural diagram of the construction tunnel initial support encroachment detection device based on three-dimensional laser technology shown in this invention;

[0036] Figure 2 This is a schematic diagram of the overall intrusion limit detection of the initial branch shown in this invention;

[0037] Figure 3 This is a schematic diagram illustrating the creation of voxels from the initial pivot cloud data of each period using Octree, as shown in this invention.

[0038] Figure 4 This is a schematic diagram of the initial branch local encroachment detection shown in this invention;

[0039] Among them, 1. Measuring prism, 2. Three-dimensional lidar, 3. Two-way pitch mechanism, 4. Cantilever support, 5. Area where overall encroachment occurs, 6. Area where overall encroachment does not occur, 7. Area where partial encroachment occurs, 8. Initial support data for the first phase, and 9. Initial support data for the second phase. Detailed implementation method:

[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0041] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0042] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0043] In this invention, terms such as "upper," "lower," and "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are merely relational terms determined for the convenience of describing the structural relationship of the various components or elements of this invention, and do not specifically refer to any component or element in this invention, nor should they be construed as limiting this invention.

[0044] In this invention, terms such as "connected" and "linked" should be interpreted broadly, indicating a fixed connection, an integral connection, or a detachable connection; a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can determine the specific meaning of these terms in this invention based on the specific circumstances, and they should not be construed as limitations on the invention.

[0045] like Figure 1 As shown in the figure, this embodiment provides a construction tunnel initial support encroachment detection device based on three-dimensional laser technology, including a wall-mounted initial support encroachment detection device, including a cantilever support 4, on which a bidirectional pitching mechanism 3, a three-dimensional laser radar 2 and a measuring prism 1 are installed sequentially from bottom to top.

[0046] The bidirectional pitch mechanism, the three-dimensional lidar, and the measuring prism all communicate with the host computer. The host computer is used to perform overall intrusion detection analysis and initial support local intrusion detection analysis based on the three-dimensional point cloud data and the absolute coordinates of the three-dimensional lidar.

[0047] The 3D LiDAR 2 is used to scan tunnel scenes, mainly to acquire 3D point cloud data of the initial lining of the tunnel under construction. The 3D point cloud data mainly refers to a large number of point data covering the appearance of the initial support at that time, mainly including the spatial coordinate information of the points on the surface of the initial support. According to the monitoring and measurement requirements, automatic scanning operations are performed within a specified time interval to acquire multi-temporal point cloud data of the initial support of the tunnel under construction, which can be used for initial support encroachment detection and encroachment deformation rate analysis.

[0048] The three-dimensional lidar 2 is mounted on the cantilever support 4 by a bidirectional pitch mechanism 3. The bidirectional pitch mechanism 3 can realize pitch swing and circumferential rotation, and can realize manual mode and automatic mode through the host computer program. It can be set to automatic by default when powered on, so as to run automatically according to the previously set parameters. The bidirectional pitch mechanism 3 and the three-dimensional lidar 2 work together to complete the automated timed scanning and monitoring of the tunnel's initial support.

[0049] The cantilever support 4 is installed on the inner wall of the tunnel. To better obtain point cloud data of the initial support section of the tunnel, it is usually installed near the invert of the tunnel under construction. The advantage of installing it on the inner wall of the tunnel is that the space inside the construction tunnel is limited, there are many construction machinery and other auxiliary facilities, and construction vehicles are constantly passing by. Using a stand-alone acquisition mode can easily disrupt the normal tunnel construction order and cause delays in the construction period. The advantage of installing it near the invert of the tunnel is that after the invert is constructed, the tunnel closes into a ring, reducing the deformation of the initial support. The initial support between the invert and the tunnel face is the key monitoring target for encroachment deformation.

[0050] The measuring prism is fixedly installed on the three-dimensional lidar. After calibration, each time a measurement is performed, the absolute coordinates of the three-dimensional lidar can be calculated based on the known coordinates of the control points, and a geodetic coordinate system and a relative coordinate system of the three-dimensional lidar can be established.

[0051] The method for detecting encroachment of the initial support of a construction tunnel based on the above-mentioned construction tunnel initial support encroachment detection device includes:

[0052] Step 1: Fix and install the cantilever support at a suitable location near the invert arch of the construction tunnel using expansion bolts or other means, and calculate the geodetic space coordinates of the measuring prism of the initial support encroachment detection device of the construction tunnel using the coordinates of the known control points in the construction tunnel, and establish a local coordinate system based on the initial support encroachment detection device.

[0053] Step 2: Perform multiple scans of the tunnel during the construction period to obtain multi-temporal high-precision 3D point cloud data of the tunnel's initial support structure. Then, sequentially perform filtering and noise reduction, interpolation, simplification, and pose adjustment on the tunnel's 3D point cloud data to obtain tunnel point cloud data with the tunnel's direction parallel to a certain coordinate axis of the Cartesian coordinate system; and obtain high-quality point cloud data of the tunnel's initial support structure.

[0054] Step 3: Conduct initial support deformation encroachment detection of the construction tunnel based on point cloud data. This mainly includes local encroachment detection, overall encroachment detection, and extraction of the initial support encroachment deformation rate. A schematic diagram of the overall encroachment detection is shown below. Figure 2 As shown in the figure, region 5 is the area where overall encroachment occurred and region 6 is the area where overall encroachment did not occur; a schematic diagram of the initial branch local encroachment detection is shown below. Figure 2 As shown in the figure, the local encroachment area 7 is the region where the encroachment occurred.

[0055] Here, the Cartesian coordinate system is the three-dimensional user coordinate system (UCS), which satisfies the right-hand rule. For example, if the tunnel cross-section profile is specified to be parallel to the XOY plane of this Cartesian coordinate system, perpendicular to the Z-axis, and oriented along the positive Z-axis direction of the Cartesian coordinate system, the main steps include:

[0056] ① Extract a portion of the tunnel point cloud data, perform planar fitting on the bottom of the tunnel, and move the tunnel bottom plane to the XOZ plane;

[0057] ② Dimensionally reduce the tunnel point cloud data and project it onto the XOZ plane, then extract the Z-axis of the projected point cloud. min and Z max ;

[0058] ③ Set the tunnel point cloud slice step size L step1 In (Z) min +w / 2, Z max Within the interval -w / 2), the tunnel point cloud is sliced ​​along the Z-axis, where w is the width of the projected point cloud and L is the length of the projected tunnel point cloud.

[0059] z i =Z min +w / 2+i·L step1 (i≤(Lw) / L step1 (i = 1, 2, 3...)

[0060] ④ Extract the sliced ​​point cloud based on the point cloud index, and obtain the Xi for each sliced ​​point cloud. min and Xi max Then the coordinates of the midpoint of each slice point cloud are:

[0061] ((Xi min +Xi max ) / 2,0,z i )

[0062] ⑤ The indexes of all the points in the slice point cloud form the two-dimensional horizontal centerline of the tunnel point cloud data. The obtained two-dimensional horizontal centerline is fitted with a straight line using the least squares method to obtain the direction vector of the two-dimensional horizontal centerline, which is the tangent value tanθ between the two-dimensional horizontal centerline and the YOZ plane.

[0063] ⑥ Define the stiffness transformation matrix T1 for the tunnel point cloud data. Rotate the tunnel around the Y-axis by θ to make the tunnel orientation follow the positive Z-axis of the Cartesian coordinate system, and translate it by -Z along the positive Z-axis of the Cartesian coordinate system. min Make the initial cross-section of the tunnel point cloud data coincide with the XOY plane.

[0064] Specifically, the steps of the above-mentioned method for detecting encroachment in the initial support of a construction tunnel include:

[0065] (1) Project the tunnel slices and divide the tunnel point cloud data into equally spaced slices along the direction parallel to the tunnel central axis. Perform a dimension reduction projection on each slice to the slice mid-surface, replace the thick slice with the slice mid-surface without thickness, and retain the slice point cloud data.

[0066] In this embodiment, the tunnel point cloud is re-sliced, and the slice step size is set to the side length L of the unit to be generated. step2 Each slice is taken along the tangent to the horizontal midline of the slice in two dimensions, and the slice thickness is σ.

[0067] 0<σ≤L step2

[0068] The slice thickness σ should not be too small, as this will result in insufficient data at the slice points. For each slice, a dimension-reduction projection is performed onto the slice's mid-surface, which transforms the Z-coordinates of all points in each slice into the Z-coordinate z of the slice's center. i ;

[0069] The Z-axis coordinate range of the slice is (z i-σ / 2, z i +σ / 2).

[0070] (2) First, the overall encroachment detection of the initial support is carried out. Since highway tunnels are mostly three-centered or five-centered circles, the obtained tunnel point cloud slice data is first cut according to the elevation direction and circle fitting is performed separately. The slice projection of the cut segment contour is circle fitted by RANSAC or least squares method to obtain the center coordinates and radius R of the fitted circle. The obtained center coordinates and radius R are compared and analyzed with the tunnel design parameters to determine whether the initial support of the tunnel has deformed and encroached.

[0071] Specifically, a circle is fitted to the slice projection segment, and the fitted radius is R. The initial support design radius parameter for this part of the tunnel is R. s The allowable deformation is d. If the fitted radius R is smaller than the design radius R s The difference between the value of the initial support section and the reserved deformation amount d indicates that the tunnel's initial support section has undergone overall deformation encroachment; if the fitted radius R is greater than the design radius R... s The difference between the value of the initial support section and the reserved deformation amount d indicates that the tunnel initial support section has not undergone overall deformation and encroachment at this time. Multi-temporal point cloud data of the tunnel initial support can be collected to realize the deformation encroachment monitoring of the tunnel initial support and analyze its deformation rate.

[0072] (3) Then, local encroachment detection of the initial branch is performed. After obtaining the target area where the initial branch encroaches globally, super voxels are constructed from the point cloud of the target area using Octree, and the curvature of each voxel within its neighborhood is calculated. By comparing the difference in curvature within the neighborhood, local encroachment detection of the initial branch is achieved. Figure 3 As shown in the figure, 8 and 9 represent the initial support data for the two periods, respectively.

[0073] Specifically, by establishing voxels, the initial support section of the tunnel is downsampled. The radius of curvature of each voxel can be calculated by using the center of the fitted circle of the tunnel section. Then, the radius of curvature of each voxel in the neighborhood of the voxel is compared to obtain its curvature. By setting a curvature change threshold, the area with obvious curvature change is obtained, which is the area where the initial support of the tunnel is locally encroached.

[0074] (4) After detecting overall and local encroachment on the initial support, monitoring or timely handling is required based on the severity of the encroachment. Monitoring the encroachment deformation rate mainly includes: using multi-temporal high-precision three-dimensional point cloud data of the tunnel's initial support structure, establishing voxels for each phase of the initial support point cloud data using Octree, and encoding each voxel. After processing the multi-temporal initial support point cloud data in this way, comparing and analyzing voxels with the same encoding, and calculating the spatial coordinate difference of the centroid of the point cloud voxels, the difference is the encroachment deformation value. The encroachment deformation rate is obtained based on the ratio of the encroachment deformation value to the encroachment deformation time.

[0075] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A construction tunnel initial support encroachment detection device based on three-dimensional laser technology, characterized in that, include: A cantilever support is installed on the inner wall of the tunnel. A bidirectional pitching mechanism is installed on the cantilever support. The cantilever support is installed near the invert arch of the construction tunnel by expansion bolts. A three-dimensional lidar is installed on the bidirectional pitching mechanism. A measuring prism is installed on the three-dimensional lidar. The bidirectional pitching mechanism, the three-dimensional lidar, and the measuring prism all communicate with a host computer. The bidirectional pitch mechanism is used to drive the three-dimensional lidar and the measuring prism; The three-dimensional lidar is used to acquire three-dimensional point cloud data of the initial lining of the construction tunnel and upload it to the host computer. The measuring prism is used to establish the geodetic coordinate system and the relative coordinate system of the three-dimensional lidar. The absolute coordinates of the three-dimensional lidar are calculated based on the known control point coordinates and uploaded to the host computer. The host computer is used to perform overall intrusion detection analysis and initial support local intrusion detection analysis based on the three-dimensional point cloud data and the absolute coordinates of the three-dimensional lidar.

2. The tunnel initial support encroachment detection device based on three-dimensional laser technology according to claim 1, characterized in that, The driving three-dimensional lidar and measuring prism include... It drives the 3D lidar and measuring prism to pitch and rotate.

3. The tunnel initial support encroachment detection device based on three-dimensional laser technology according to claim 1, characterized in that, The three-dimensional point cloud data includes the spatial coordinates of the points covering the initial support surface at that time.

4. The tunnel initial support encroachment detection device based on three-dimensional laser technology according to claim 1, characterized in that, The three-dimensional lidar performs automatic scanning operations within specified time intervals according to monitoring and measurement requirements.

5. A method for detecting encroachment on the initial support of a construction tunnel based on three-dimensional laser technology, characterized in that, The tunnel initial support encroachment detection device based on three-dimensional laser technology according to any one of claims 1-4 includes: Cantilever supports are fixedly installed at a suitable location near the invert arch of the construction tunnel using expansion bolts. The geodetic space coordinates of the measuring prism of the initial support encroachment detection device of the construction tunnel are calculated using the coordinates of known control points within the construction tunnel. A geodetic coordinate system and a relative coordinate system of the three-dimensional lidar are established. The absolute coordinates of the three-dimensional lidar are calculated based on the coordinates of the known control points. Obtain three-dimensional point cloud data of the initial lining of the tunnel under construction; Based on the absolute coordinates and 3D point cloud data of 3D LiDAR, overall encroachment detection and analysis and initial support local encroachment detection and analysis are performed.

6. The method for detecting the encroachment of initial supports in construction tunnels based on three-dimensional laser technology according to claim 5, characterized in that, After acquiring the three-dimensional point cloud data of the initial lining of the construction tunnel, the following steps are taken: filtering and noise reduction, interpolation, simplification and pose adjustment are performed on the three-dimensional point cloud data to obtain three-dimensional point cloud data in which the tunnel orientation is parallel to a certain coordinate axis of the Cartesian coordinate system. The tunnel slices are projected, and the 3D point cloud data is divided into equally spaced slices along the direction parallel to the tunnel's central axis. Each slice is then dimensionality-reduced by projecting onto the mid-surface of the slice, replacing the thick slice with the mid-surface of the slice without thickness, while retaining the slice point cloud data.

7. The method for detecting the encroachment of initial supports in construction tunnels based on three-dimensional laser technology according to claim 6, characterized in that, The overall intrusion detection and analysis process includes: The slice point cloud data is cropped along the elevation direction, and the slice projection of the cropped segment contour is circle fitted by RANSAC or least squares method. Obtain the coordinates of the center of the fitted circle and the radius R parameter; The obtained center coordinates and radius R parameters are compared and analyzed with the tunnel design parameters to determine whether the initial support of the tunnel has deformed and encroached on the limit.

8. The method for detecting the encroachment of initial supports in construction tunnels based on three-dimensional laser technology according to claim 7, characterized in that, The process of initial branch local invasion limit detection and analysis includes: Based on the target area where the initial branch intrudes, super voxels are constructed from the sliced ​​point cloud data of the target area using Octree, and the curvature of each voxel within its neighborhood is calculated. By comparing the difference in curvature within the neighborhood, the local intrusion location of the initial branch is determined.

9. The method for detecting the encroachment of initial support in construction tunnels based on three-dimensional laser technology according to claim 5, characterized in that, After detecting the overall and local encroachment of the initial support, the encroachment deformation rate is monitored by: based on the multi-time three-dimensional point cloud data of the tunnel's initial support structure, voxels are established for each phase of the initial support point cloud data using Octree, and each voxel is encoded; voxels with the same encoding are compared and analyzed, and the spatial coordinate difference of the centroid of the point cloud voxels is calculated, which is the encroachment deformation value; the encroachment deformation rate is obtained according to the ratio of the encroachment deformation value to the encroachment deformation time.

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