A method for analyzing the deformation of surrounding rock in deep-buried tunnels based on 3D laser scanning point clouds

Abstract

The present invention discloses a method for analyzing the deformation of surrounding rock of a deep-buried tunnel based on three-dimensional laser scanning point cloud, comprising the following steps: determining a section of the deep-buried tunnel for surrounding rock deformation analysis, and obtaining the point cloud of the deep-buried tunnel at different times by using a ground three-dimensional laser scanning system; establishing a simplified coordinate transformation relationship for the point cloud of the deep-buried tunnel at different times; calculating the independent unknown components of the simplified coordinate transformation matrix by a two-step method; calculating the local normal vector of the point cloud of the deep-buried tunnel, and defining a projection cylinder for calculating the point cloud, obtaining a point cloud subset of the tunnel point cloud at different times on the projection cylinder, and obtaining the deformation of the calculated point cloud based on the geometric distance between the average projection centers corresponding to the respective point cloud subsets, so as to obtain the deformation magnitudes of all the calculated point clouds. The present invention solves the technical problems of aligning the point cloud of the deep-buried tunnel at different times and calculating the three-dimensional deformation of the point cloud of the deep-buried tunnel at different times.

Description

Technical Field

[0001] The present invention relates to the technical field of deep-buried tunnel surrounding rock deformation analysis, and particularly relates to a method for analyzing deep-buried tunnel surrounding rock deformation based on three-dimensional laser scanning point cloud. Background Art

[0002] Due to the characteristics of three-dimensional laser scanning technology such as fast scanning speed, high scanning accuracy, non-contact, and being unaffected by the scanning environment, it has a wide range of applications in the deformation monitoring and early warning of deep-buried tunnel surrounding rock. The deformation of the surrounding rock of a tunnel in deep strata has the characteristic of increasing continuously with time, and it is impossible to provide a constant reference coordinate system or rely on external reference points. Aligning the tunnel point clouds at different times is a prerequisite for the deformation analysis of deep-buried tunnel point clouds, which makes the problem of aligning the tunnel surrounding rock point clouds at different times one of the difficult problems in the deformation analysis of deep-buried tunnel surrounding rock. In addition, the current methods for tunnel surrounding rock point cloud deformation mainly focus on comparing the actual contour point cloud of the tunnel in the plane with the designed contour, calculating the distance from the actual contour point of the tunnel to the center of the cross-section, and considering the size of the designed cross-section size, so as to obtain the deformation of each point on the two-dimensional contour. This method is mainly applicable to tunnels with circular or elliptical cross-sections, or calculating the difference between the two-dimensional contour point clouds of the tunnel at two different times by calculating the ray from the center of the cross-section (or the fitted center) to the calculation point. These two types of methods are only applicable to tunnels with circular or elliptical cross-sections. For example, a patent document with the application number 202310030488.1 discloses a method and system for detecting the deformation of a horseshoe-shaped mountain tunnel based on laser point cloud segmentation; on the other hand, the surrounding rock characteristics obtained by comparing the two-dimensional cross-section contours of the tunnel can only indirectly reflect the two-dimensional deformation of the surrounding rock cross-section, and cannot comprehensively reflect the true three-dimensional deformation characteristics of the tunnel surrounding rock. Summary of the Invention

[0003] The main purpose of the present invention is to propose a method for analyzing deep-buried tunnel surrounding rock deformation based on three-dimensional laser scanning point cloud, aiming to solve the technical problems of aligning the deep-buried tunnel point clouds at different times and calculating the three-dimensional deformation of the deep-buried tunnel point clouds at different times.

[0004] To achieve the above object, the present invention provides a method for analyzing deep-buried tunnel surrounding rock deformation based on three-dimensional laser scanning point cloud. Among them, the method for analyzing deep-buried tunnel surrounding rock deformation based on three-dimensional laser scanning point cloud includes the following steps:

[0005] S1. Determine the section of the deep-buried tunnel surrounding rock deformation analysis, and use the ground three-dimensional laser scanning system to obtain the deep-buried tunnel point clouds of the section at different times;

[0006] S2. Establish a simplified coordinate transformation relationship between the deep-buried tunnel point clouds at different times;

[0007] S3. Calculate the independent unknown components of the simplified coordinate transformation matrix by a two-step method;

[0008] S4. Calculate the local normal vectors of the point cloud of the deep-buried tunnel, define the projection cylinder for calculating the point cloud, obtain the subsets of the point cloud of the tunnel at different times on the projection cylinder, and obtain the deformation of the calculated point cloud based on the geometric distance between the average projection centers corresponding to the respective subsets of the point cloud, thereby obtaining the deformation magnitudes of all the calculated point clouds.

[0009] One of the preferred solutions is that before step S2, it includes: performing a first coordinate transformation on the point cloud of the deep-buried tunnel, specifically:

[0010] Establish a global coordinate system for the deformation analysis of the point cloud of the deep-buried tunnel;

[0011] Calculate the angle between the extension direction of the point cloud of the deep-buried tunnel and the Y-axis in the global coordinate system, obtain the coordinate rotation matrix, and perform coordinate rotation transformation to make the extension direction of the point cloud of the deep-buried tunnel consistent with the Y-axis direction in the global coordinate system; the coordinate rotation matrix is specifically:

[0012]

[0013] where α is the angle between the extension direction of the point cloud of the deep-buried tunnel and the Y-axis in the global coordinate system, (X, Y, Z) is the coordinate of the point cloud of the deep-buried tunnel before coordinate rotation transformation, and (X new , Y new , Z new ) is the coordinate of the point cloud of the deep-buried tunnel after coordinate rotation transformation.

[0014] One of the preferred solutions is that after performing the first coordinate transformation on the point cloud of the deep-buried tunnel, it includes:

[0015] Perform filtering processing on the point cloud of the deep-buried tunnel to obtain the tunnel contour point cloud and the non-contour point cloud;

[0016] Perform a second coordinate transformation based on the tunnel contour point cloud to obtain a coordinate transformation matrix, so that the point clouds of the deep-buried tunnel at different times are in the same coordinate system; the coordinate transformation matrix is:

[0017]

[0018] where (x g , y g , z g ) is the coordinate of the tunnel contour point cloud after coordinate transformation, is the coordinate rotation matrix, (x s , y s , z s ) is the coordinate of the tunnel contour point cloud before coordinate transformation, r ij is the rotation component of the coordinate rotation matrix, (t x , t y,t z ) are the translation components along the X, Y, and Z axes of the global coordinate system.

[0019] One of the preferred solutions is that the simplified coordinate transformation relationship is:

[0020]

[0021] where θ z is the rotation angle about the Z axis in the global coordinate system.

[0022] One of the preferred solutions is that in step S3, the independent unknown components of the simplified coordinate transformation matrix are calculated by a two-step method, specifically:

[0023] S31. Use the ICP algorithm to align the nominal axes of the buried tunnel point clouds at different times, and obtain the rotation component of the simplified coordinate transformation matrix about the Z axis and the translation components along the X and Y axes;

[0024] S32. Fit the top arch of the tunnel and match the fitting centers at different times to obtain the translation component along the Z axis.

[0025] One of the preferred solutions is that step S31 is specifically:

[0026] Divide the buried tunnel point cloud into several thin sheet-like segmented point clouds with equal thickness along the positive direction of the Y axis of the global coordinate system. According to the projection of the buried tunnel segmented point cloud on the XOY plane, calculate the midpoint along the X axis of the global coordinate system, and combine the longitudinal position of the buried tunnel segmented point cloud to define the point set (x i ,y i ) on the nominal axis of the buried tunnel;

[0027] Set the iteration threshold, and use the ICP algorithm to align the point set (x i ,y i ) on the nominal axis of the buried tunnel at different times of the buried tunnel point cloud, and calculate the rotation component θ z about the Z axis and the translation components t x ,t y .

[0028] One of the preferred solutions is that step S32 is specifically:

[0029] Use the elliptical fitting method to determine the fitting center of the same cross-section at different times;

[0030] Based on the fitting calculation of the point clouds of multiple cross-sections, calculate the translation component t z along the Z axis; the translation component t z is:

[0031]

[0032] where t z is the translation component along the Z-axis, N is the number of cross-sectional point clouds, and c zf,i is the coordinate component z of the fitting center of the i-th cross-section in the reference point cloud, and c zm,i is the coordinate component z of the fitting center of the i-th cross-section in the comparison point cloud.

[0033] One of the preferred solutions is that in step S4, the local normal vector of the deep-buried tunnel point cloud is calculated as follows:

[0034] Select the deep-buried tunnel point clouds of the same tunnel section at two different times and in the same coordinate system. Define the point cloud with the earlier scanning time as the reference point cloud, and the point cloud with the later scanning time as the comparison point cloud;

[0035] Calculate the point set within a spherical neighborhood centered at each point in the reference point cloud with a radius of 1 / 2 of the normal scale D. Obtain the corresponding plane equation by plane fitting, and use the plane normal as the local normal vector N corresponding to each point in the reference point cloud, and determine the direction of the local normal vector N.

[0036] One of the preferred solutions is that after step S4, it further includes:

[0037] Obtain the confidence interval reflecting the local roughness of any point i in the reference point cloud;

[0038] Based on the confidence interval of the local roughness, judge the authenticity of the deformation of the surrounding rock of the deep-buried tunnel.

[0039] One of the preferred solutions is that after step S4, it further includes:

[0040] Based on the deformation results of the deep-buried tunnel point clouds of the surrounding rock of the deep-buried tunnel at different times, obtain the deformation characteristics of the surrounding rock of the deep-buried tunnel and perform result visualization; the visualization of the deep-buried tunnel point cloud includes the deformation history curve of any point of the surrounding rock of the deep-buried tunnel at different times, the deformation characteristics and evolution process of any cross-section of the surrounding rock of the deep-buried tunnel, and the spatial deformation distribution characteristics and evolution process of the surrounding rock of the deep-buried tunnel.

[0041] In the above technical solution of the present invention, the method for analyzing the deformation of the surrounding rock of a deep-buried tunnel based on 3D laser scanning point cloud includes the following steps: determining the section of the deep-buried tunnel for surrounding rock deformation analysis, and using a ground 3D laser scanning system to obtain the point cloud of the deep-buried tunnel at different times; establishing a simplified coordinate transformation relationship for the point cloud of the deep-buried tunnel at different times; calculating the independent unknown components of the simplified coordinate transformation matrix by a two-step method; calculating the local normal vector of the deep-buried tunnel point cloud, and defining a projection cylinder for calculating the point cloud, obtaining the point cloud subset of the tunnel point cloud at different times on the projection cylinder, and obtaining the deformation of the calculated point cloud based on the geometric distance between the average projection centers corresponding to the point cloud subsets respectively, so as to obtain the deformation magnitudes of all calculated point clouds. The present invention solves the technical problems of aligning the point clouds of deep-buried tunnels at different times and calculating the three-dimensional deformation of the point clouds of deep-buried tunnels at different times.

[0042] In the present invention, through the first coordinate transformation, the point cloud of the deep-buried tunnel is made consistent with the direction of the Y-axis of the global coordinate system, and through the second coordinate transformation, the point cloud of the deep-buried tunnel in the same coordinate system is used for the deformation analysis of the deep-buried tunnel, so as to establish the coordinate transformation matrix of the tunnel point cloud at different times, and make the deformation analysis of the deep-buried tunnel point cloud in a constant and unified reference coordinate system.

[0043] In the present invention, since there are a large number of auxiliary facilities fixed on the surface of the surrounding rock, as well as moving construction personnel and machinery in the deep-buried tunnel, some areas of the tunnel surrounding rock are inevitably blocked during the scanning process, resulting in missing corresponding point clouds and interference such as uneven characteristics of the surrounding rock contour surface. By calculating the confidence interval reflecting the local roughness of the reference point cloud and judging the authenticity of the deformation of the deep-buried tunnel surrounding rock, the influence of interference factors on the deformation of the deep-buried tunnel point cloud is excluded.

[0044] In the present invention, by visualizing the deformation calculation results of the deep-buried tunnel surrounding rock in different periods, a more intuitive display of the cross-section and spatial deformation distribution of the tunnel surrounding rock is realized. Description of the Drawings

[0045] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on the structures shown in these drawings without creative efforts.

[0046] Figure 1 It is a schematic diagram of a method for analyzing the deformation of the surrounding rock of a deep-buried tunnel based on 3D laser scanning point cloud according to an embodiment of the present invention;

[0047] Figure 2The point cloud of the deep-buried tunnel obtained by the ground 3D laser scanning system in the embodiment of the present invention;

[0048] Figure 3 The recognition result of the original point cloud of the segmented deep-buried tunnel in the embodiment of the present invention;

[0049] Figure 4 The recognition result of the segmented contour point cloud of the deep-buried tunnel in the embodiment of the present invention;

[0050] Figure 5 The recognition result of the contour point cloud of the deep-buried tunnel in the embodiment of the present invention;

[0051] Figure 6 The schematic diagram of aligning the nominal axis of the tunnel of the reference point cloud and the comparison point cloud in the embodiment of the present invention;

[0052] Figure 7 The schematic diagram of the ellipse fitting result of the segmented point cloud of the deep-buried tunnel at different times in the embodiment of the present invention;

[0053] Figure 8 The deformation history curve of a certain point of the surrounding rock of the deep-buried tunnel in the embodiment of the present invention;

[0054] Figure 9 The cross-sectional deformation diagram of the surrounding rock of the deep-buried tunnel in the embodiment of the present invention;

[0055] Figure 10 The three-dimensional space deformation distribution diagram of the surrounding rock of the deep-buried tunnel in the embodiment of the present invention;

[0056] Figure 11 The schematic diagram of the plane mapping result of the three-dimensional space deformation of the surrounding rock of the deep-buried tunnel in the embodiment of the present invention.

[0057] The realization, functional characteristics and advantages of the object of the present invention will be further described with reference to the accompanying drawings in conjunction with the embodiments. Specific Embodiments

[0058] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0059] It should be noted that all the directional indications (such as up, down,...) in the embodiments of the present invention are only used to explain the relative position relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0060] In addition, in the present invention, descriptions such as "first", "second", etc. are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one such feature.

[0061] Moreover, the technical solutions between various embodiments of the present invention can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or is unable to be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0062] See Figures 1 - 11 , according to one aspect of the present invention, the present invention provides a method for analyzing the deformation of surrounding rock of a deep-buried tunnel based on three-dimensional laser scanning point cloud. Wherein, the method for analyzing the deformation of surrounding rock of a deep-buried tunnel based on three-dimensional laser scanning point cloud includes the following steps:

[0063] S1. Determine the section for analyzing the deformation of the surrounding rock of the deep-buried tunnel, and use a ground three-dimensional laser scanning system to obtain the point cloud of the deep-buried tunnel at different times for the section;

[0064] S2. Establish a simplified coordinate transformation relationship for the point cloud of the deep-buried tunnel at different times;

[0065] S3. Calculate the independent unknown components of the simplified coordinate transformation matrix through a two-step method;

[0066] S4. Calculate the local normal vector of the point cloud of the deep-buried tunnel, and define a projection cylinder for calculating the point cloud, obtain the point cloud subset of the tunnel point cloud at different times on the projection cylinder, and obtain the deformation of the calculated point cloud based on the geometric distance between the average projection centers corresponding to the point cloud subsets, thereby obtaining the deformation magnitudes of all the calculated point clouds.

[0067] Specifically, in this embodiment, before the step S1 of using a ground three-dimensional laser scanning system to obtain the point cloud of the deep-buried tunnel at different times, it further includes: converting the special point cloud format obtained by the ground three-dimensional laser scanning system into a general point cloud format, and uniformly sampling the deep-buried point cloud under the condition of ensuring the deformation accuracy of the deep-buried tunnel point cloud, so as to reduce the density of the original deep-buried tunnel point cloud and improve the calculation efficiency of the deformation analysis of the deep-buried tunnel point cloud; the ground three-dimensional laser scanning system can use a conventional three-dimensional laser scanning system, and the present invention does not make specific limitations.

[0068] Specifically, in this embodiment, before the step S2, it includes: performing a first coordinate transformation on the point cloud of the deep-buried tunnel, specifically:

[0069] Establish a global coordinate system for the deformation analysis of the point cloud of the deep-buried tunnel;

[0070] Calculate the angle between the extension direction of the deep-buried tunnel point cloud and the Y-axis in the global coordinate system, obtain the coordinate rotation matrix, and perform coordinate rotation transformation to make the extension direction of the deep-buried tunnel point cloud consistent with the Y-axis direction in the global coordinate system; the coordinate rotation matrix is specifically:

[0071]

[0072] where α is the angle between the extension direction of the deep-buried tunnel point cloud and the Y-axis in the global coordinate system, and (X, Y, Z) is the coordinate of the deep-buried tunnel point cloud before coordinate rotation transformation, and (X new , Y new , Z new ) is the coordinate of the deep-buried tunnel point cloud after coordinate rotation transformation.

[0073] Specifically, in this embodiment, after the first coordinate transformation of the deep-buried tunnel point cloud, it includes:

[0074] Perform filtering processing on the deep-buried tunnel point cloud to obtain the tunnel contour point cloud and the non-contour point cloud; since the deep-buried tunnel point cloud obtained by the ground three-dimensional laser scanning system inevitably includes auxiliary equipment inside the tunnel surrounding rock and active construction personnel, machinery, etc., and the analysis object of the tunnel point cloud deformation is the tunnel contour point cloud, therefore, before analyzing the deformation of the deep-buried tunnel point cloud, it is necessary to perform filtering processing on the collected deep-buried tunnel point cloud to distinguish the tunnel contour point cloud and the non-contour point cloud;

[0075] Perform a second coordinate transformation based on the tunnel contour point cloud to obtain a simplified coordinate transformation matrix, so that the deep-buried tunnel point clouds at different times are in the same coordinate system; ensuring that the deep-buried tunnel point clouds at different times are in the same coordinate system is a prerequisite for the deformation analysis of the deep-buried tunnel; the coordinate transformation matrix consists of two parts: a coordinate rotation matrix and a translation vector. Among them, the coordinate rotation matrix consists of three rotation components and three translation components, a total of 6 independent components; when coordinate positioning is achieved by means of GPS or with the help of a constant reference object, the independent components can be completely determined. However, the deep-buried tunnel is different from the laser point cloud obtained on the ground or in the air. It is difficult to obtain the global coordinate system through GPS. At the same time, during the long-term use stage of the deep-buried tunnel surrounding rock, large deformations will inevitably occur. Therefore, the tunnel surrounding rock deep below cannot provide a constant reference coordinate system; the present invention provides a constant reference coordinate system by performing coordinate transformation on the tunnel point clouds at different times; the coordinate transformation matrix is:

[0076]

[0077] where (x g , y g , z g ) is the coordinate of the tunnel contour point cloud after coordinate transformation, is the coordinate rotation matrix, (x s ,y s ,z s ) is the coordinate of the tunnel contour point cloud before coordinate transformation, r ij is the rotation component of the coordinate rotation matrix, (t x ,t y ,t z ) are the translation components along the X, Y, and Z axes of the global coordinate system.

[0078] Specifically, in this embodiment, the deep-buried tunnel point cloud is obtained by the laser scanner of the ground three-dimensional laser scanning system in a horizontal state. At the same time, the laser scanner has a dual-axis real-time compensation function, which can correct a certain range of horizontal deviations. In addition, the object used for the deformation analysis of the deep-buried tunnel point cloud is the deep-buried tunnel point cloud within a certain radius centered on the three-dimensional laser scanner. Therefore, it can be determined that the point cloud used for the tunnel deformation analysis is obtained by the ground three-dimensional laser scanning system in a completely horizontal state, and its accuracy meets the accuracy of the deformation analysis of the deep-buried tunnel point cloud, so that the coordinate transformation matrix is ​​transformed to obtain a simplified coordinate transformation matrix; the simplified coordinate transformation relationship is:

[0079]

[0080] Among them, θ z is the rotation angle around the Z axis in the global coordinate system.

[0081] Specifically, in this embodiment, step S3 calculates the independent unknown components of the simplified coordinate transformation matrix through a two-step method, specifically:

[0082] S31. Use the ICP algorithm to align the nominal axes of the deep-buried tunnel point clouds at different times, and obtain the rotation component of the simplified coordinate transformation matrix around the Z axis and the translation components along the X and Y axes; specifically:

[0083] The deep-buried tunnel point cloud is divided into several thin slice-shaped segmented point clouds of equal thickness along the positive direction of the Y axis of the global coordinate system. According to the projection of the deep-buried tunnel segmented point cloud on the XOY plane, the midpoint along the X axis of the global coordinate system is calculated. Combined with the longitudinal position of the deep-buried tunnel segmented point cloud, the point set (x i ,y i );

[0084] The iteration threshold is set and the ICP algorithm is used to align the point set (x i ,y i ), calculate the rotation component θ around the Z axis z and the translational components t along the X and Y axes x , t y; Considering the irregular characteristics of the point cloud surface of the deep-buried tunnel, the accuracy of a single calculation cannot fully meet the requirements of tunnel deformation analysis. Therefore, calculations are carried out iteratively until the alignment of the projection points of the nominal axis of the deep-buried tunnel in the XOY plane at different times meets the required accuracy; among them, the coordinate rotation matrix R obtained through iterative calculation is R n+1 ...R2R1;

[0085] The coordinate translation vector T' in the XOY plane is: where n is the number of iterations and T' is the coordinate translation vector;

[0086] According to the coordinate rotation matrix and coordinate translation vector obtained through iterative calculation, the coordinate transformation matrix C' is finally obtained, and the coordinate transformation matrix C' is:

[0087]

[0088] In the present invention, the iteration threshold can be set to 2 or 3 to meet the accuracy requirements. The present invention does not make specific limitations and can be specifically set according to needs; coordinate transformation is performed on the point clouds of the deep-buried tunnel at different times to obtain the point cloud X' after the alignment of the nominal axis of the deep-buried tunnel new = C'X old ;

[0089] S32. Fit the top arch of the tunnel and match the fitting centers at different times to obtain the translation component along the Z axis; specifically:

[0090] The elliptical fitting method is used to determine the fitting centers of the same cross-section at different times; the deformation of the top arch of the tunnel after lining shows deformation along the direction perpendicular to the free face and points to the center of the upper half of the interface. The surrounding rock of the tunnel after lining can be approximately considered to be uniformly deformed. Therefore, it can be assumed that the cross-section center of the surrounding rock of the tunnel after lining remains unchanged at the top arch part. The elliptical fitting method is used to determine the fitting centers of the same cross-section within different time periods, assuming that its center remains unchanged, so as to be used to calculate the translation component t in the simplified coordinate transformation matrix z ;

[0091] Based on the fitting calculations of multiple cross-section point clouds, the translation component t along the Z axis is calculated z ; Considering the unevenness of the surface and deformation of the surrounding rock of the deep-buried tunnel, the fitting calculations of multiple cross-sections are used to calculate the translation component t along the Z axis z , and its average value is used as the final translation component t z ; The translation component t z is:

[0092]

[0093] where t zis the translation component along the Z-axis, N is the number of cross-section point clouds, c zf,i is the coordinate component z of the fitting center of the i-th cross-section in the reference point cloud, c zm,i is the coordinate component z of the fitting center of the i-th cross-section in the comparison point cloud; the coordinate translation vector T is:

[0094]

[0095] The coordinate transformation matrix C is:

[0096]

[0097] Specifically, in this embodiment, the coordinate transformation matrix between the point clouds of the deep-buried tunnel at different times can be obtained through step S3, so as to align it to a unified global coordinate system. Since the calculation of point cloud deformation involves the comparison of a large number of point clouds in the space coordinate system, and at the same time, considering the particularity of the deep-buried tunnel, there are certain differences between its point cloud deformation calculation and other types of projects. Therefore, the present invention establishes a dedicated detection method for the deformation of the point cloud of the deep-buried tunnel. The local normal vector is calculated through the geometric characteristics of the point cloud of the deep-buried tunnel, and the deformation detection of the point cloud of the deep-buried tunnel is realized by directly calculating the difference between the point clouds of the deep-buried tunnel.

[0098] Specifically, in this embodiment, step S4 calculates the local normal vector of the point cloud of the deep-buried tunnel, specifically:

[0099] Select the point clouds of the deep-buried tunnel in the same tunnel section at two different times and in the same coordinate system. Define the point cloud with the earlier scanning time as the reference point cloud, and the point cloud with the later scanning time as the comparison point cloud;

[0100] Calculate the point set within the spherical neighborhood with a radius of 1 / 2 of the normal scale D centered on each point of the reference point cloud, obtain the corresponding plane equation through plane fitting, use the plane normal as the local normal vector N corresponding to each point in the reference point cloud, and determine the direction of the local normal vector N;

[0101] In order to facilitate the determination and analysis of the deformation of the tunnel surrounding rock, make the local normal vector of the tunnel design profile calculation point point to the tunnel free face, and establish a determination method for the local normal vector of the tunnel with the tunnel center line as the reference; the determination of the direction of the local normal vector N is specifically: taking the tunnel interface center as the symmetry plane, divide all the calculation points in the tunnel cross-section into left and right two regions; for the region on the right side of the tunnel cross-section center line, when the angle between the local normal vector N of the tunnel design profile calculation point and the positive direction of the X-axis is an obtuse angle, the local normal vector is negative; for the region on the left side of the tunnel cross-section center line, when the angle between the local normal vector N of the tunnel design profile calculation point and the positive direction of the X-axis is an acute angle, the local normal vector is positive; adjust the direction of the local normal vector of all the calculation points of the tunnel design profile through this method so that it points to the tunnel free face.

[0102] Specifically, in this embodiment, in step S4, a projection cylinder of the calculation point cloud is defined to obtain subsets of the tunnel point clouds at different times in the projection cylinder, specifically: with the local normal vector N passing through the calculation point i as the central axis, the projection size d as the diameter, and the length L, a projection cylinder belonging to the calculation point i is defined. The subsets of the point clouds in the projection cylinder corresponding to the calculation point i in the reference point cloud and the comparison point cloud are respectively calculated and denoted as M(i) and N(i); where the calculation point i is any current calculation point in the reference point cloud.

[0103] Specifically, in this embodiment, in step S4, the deformation of the calculation point cloud is obtained based on the geometric distance between the average projection centers respectively corresponding to the point cloud subsets, so as to obtain the deformation magnitudes of all the calculation point clouds, specifically: the projections of each point in the point cloud subsets M(i) and N(i) of the projection cylinder corresponding to the point i along its local normal vector N are respectively calculated, so as to obtain the average projection centers m(i) and n(i) of the reference point cloud and the comparison point cloud corresponding to the calculation point i; the algebraic distance L(i) from the average projection center m(i) of the reference point cloud corresponding to the point i to the average projection center n(i) of the comparison point cloud is calculated, and L(i) is the deformation magnitude corresponding to the point i; when the direction of the algebraic distance L(i) is consistent with the local normal vector corresponding to the point i, the deformation is positive, otherwise, the deformation is negative; by repeating the above steps, the deformation magnitudes corresponding to all the calculation points in the reference point cloud can be obtained.

[0104] Specifically, in this embodiment, since there are a large number of auxiliary devices fixed on the surrounding rock surface and moving construction personnel, machinery, etc. in the deep-buried tunnel, some areas of the tunnel surrounding rock will inevitably be blocked during the scanning process, resulting in the missing of the corresponding point clouds in these areas. In addition, the large deformation of the deep-buried tunnel surrounding rock results in obvious uneven features on the surface of the surrounding rock contour, which has a certain interference on the calculated deformation of the point cloud; in order to consider the influence of these factors on the deformation of the deep-buried tunnel surrounding rock, after step S4, it further includes: obtaining the confidence interval reflecting the local roughness of any point i in the reference point cloud; the confidence interval of the local roughness is:

[0105]

[0106] where CI 95％(i) is the local roughness confidence interval of point i. σ1(i) and σ2(i) are the standard deviations of the local point cloud roughness calculated from the point cloud subsets belonging to the reference point cloud and the comparison point cloud respectively within the projection cylinder corresponding to point i. The standard deviations σ1(i) and σ2(i) are calculated respectively through the absolute distance distributions of each point in the point cloud subsets M(i) and N(i) corresponding to the projection cylinder of point i along the direction of the local normal vector of point i to the average projection centers m(i) and n(i). n1 and n2 are the numbers of points in the corresponding point cloud subsets of the reference point cloud and the comparison point cloud respectively;

[0107] Based on the local roughness confidence interval, judge the authenticity of the surrounding rock deformation of the deep-buried tunnel; to meet the requirements of statistical characteristics, both n1 and n2 should be greater than or equal to 4. Therefore, the diameter d of the projection cylinder should be greater than 1.5 times the average point cloud interval. If there is a lack of point cloud in the corresponding area of the reference point cloud corresponding to point i, then n2 is equal to 0, and the corresponding deformation will not be calculated at this time; judge the authenticity of the surrounding rock deformation of the deep-buried tunnel according to the magnitude of the local roughness confidence level. Specifically: if the absolute value of the calculated deformation corresponding to point i is less than the local roughness confidence level CI 95％ (i), it means that the calculated deformation is difficult to distinguish from the roughness reflecting the surface topography of the deep-buried surrounding rock. In other words, only when the absolute value of the deformation corresponding to point i is greater than the absolute value of the local roughness confidence level corresponding to point i, the deformation of point i is the real deformation of the surrounding rock of the deep-buried tunnel; the present invention judges the authenticity of the surrounding rock deformation of the deep-buried tunnel by obtaining the local roughness confidence level of the point cloud of the deep-buried tunnel, considering the surface topography characteristics of the surrounding rock of the deep-buried tunnel and the characteristics of local point cloud loss, so as to more objectively and truly reflect the real deformation of the surrounding rock of the deep-buried tunnel.

[0108] Specifically, in this embodiment, after step S4, it also includes: based on the deformation results of the deep tunnel point cloud of the deep tunnel surrounding rock at different times, the deformation characteristics of the deep tunnel surrounding rock are obtained, and the results are visualized; the visualization of the deep tunnel point cloud includes the deformation history curve of any point of the deep tunnel surrounding rock at different times, the deformation characteristics and evolution process of any cross-section of the deep tunnel surrounding rock, and the spatial deformation distribution characteristics and evolution process of the deep tunnel surrounding rock; for the deformation history curve of a certain point in the deep tunnel, since the point to be found does not necessarily have a one-to-one correspondence with the point cloud of the deep tunnel surrounding rock, the deformation and its change characteristics are reflected by the nearest deformation and change of the point to be found. For this purpose, the k nearest neighbor algorithm is used to search for the point closest to the point to be found in space, and the nearest distance to the point to be found is obtained. and its deformation, which reflects the deformation of the point to be found. Through the calculation results of the deformation of the surrounding rock point cloud of the deep-buried tunnel at multiple different time periods, the deformation history curve of the point to be found can be obtained by using the nearest point search method; the deformation of the section of the surrounding rock of the deep-buried tunnel usually refers to the section deformation perpendicular to the extension direction of the tunnel, that is, the section deformation perpendicular to the positive direction of the Y-axis of the global coordinate system. For this reason, a thin sheet point cloud with a point cloud thickness of 2-3 times the average interval of the point cloud is selected according to this longitudinal position, and it is projected to the XOZ plane. According to the coordinates of the points in the plane and the local normal vector and the corresponding deformation, the deformation distribution characteristics from the reference point cloud to the comparison point cloud in the section are obtained. Through the calculation results of multiple continuous times, the deformation evolution process of the section is obtained; the deformation distribution characteristics from the reference point cloud to the comparison point cloud in the section are:

[0109] pe x (i) = p x (i)+L(i)N x (i)

[0110] pe z (i) = p z (i)+L(i)N z (i)

[0111] Among them, pe x (i) X coordinate of contour point i after deformation, p x (i) X coordinate of contour point i before deformation, L(i) is the algebraic distance, N x (i) is the x component of the local normal vector of point i, pe z (i) is the Z coordinate of contour point i after deformation, p z (i) is the Z coordinate of contour point i before deformation, N z (i) is the z component of the local normal vector of point i;

[0112] The spatial deformation distribution characteristics and evolution process of the surrounding rock of a deep-buried tunnel. Referring to the three-dimensional coordinates of each point in the point cloud and its corresponding algebraic deformation amount, the spatial deformation magnitude of the surrounding rock of the deep-buried tunnel is reflected by color mapping. Through the scanned point clouds at multiple consecutive times, the spatial deformation evolution process of the tunnel surrounding rock can be obtained; for the convenience of analysis and application, it is necessary to map the deformation of the tunnel surrounding rock in the three-dimensional space coordinate system to a two-dimensional plane. For this purpose, the tunnel contour point cloud is divided into three parts, namely the calculation points in the crown area, the left sidewall area, and the right sidewall area. For the left and right sidewall areas, the Z coordinate component of the calculation point in the space coordinate system is mapped to the X' component of the two-dimensional plane, and the Y coordinate component of the calculation point in the space coordinate system is mapped to the Y' component of the two-dimensional plane, then the deformation corresponding to the left and right sidewalls in the plane coordinate system can be obtained. For the calculation points in the crown area, an ellipse equation is used to fit the point cloud at the crown part to obtain the fitting center (c x ,c z ) and the corresponding major and minor semi-axis lengths a and b. Calculate the angle θ between the ray formed by the fitting center and the calculation point and the positive direction of the X-axis and the corresponding arc length s. Map the arc length s to the X' component of the two-dimensional plane, and map the Y coordinate component of the calculation point in the space coordinate system to the Y' component of the two-dimensional plane. Thus, the deformation of all calculation points in the three-dimensional space coordinate system can be mapped to the two-dimensional plane. By establishing a mapping relationship between the surrounding rock deformation and color, the intuitive and rapid identification of the spatial deformation distribution of the tunnel surrounding rock can be realized; the arc length is:

[0113]

[0114] where s is the arc length, θ is the angle between the ray formed by the calculation points and the positive direction of the X-axis, a is the major semi-axis length in the ellipse equation, and b is the minor semi-axis length in the ellipse equation;

[0115] where i z is the Z coordinate component of the contour point i at the crown part, and i x is the X coordinate component of the contour point i at the crown part, and (c x ,c z ) is the fitting center obtained by fitting the point cloud at the crown part.

[0116] Specifically, in this embodiment, the present invention starts from the geometric features of the deep-buried tunnel point cloud, establishes the alignment method of the deep-buried tunnel point cloud at different times, and the deformation detection method of the deep-buried tunnel point cloud at different times, thereby realizing the calculation and analysis of the three-dimensional space deformation of the surrounding rock of the deep-buried tunnel for the tunnel point cloud at different times, solving the problem of alignment of the deep-buried tunnel at different times, overcoming the problem that the existing tunnel point cloud deformation method is only applicable to tunnels with circular or elliptical cross-sections. At the same time, by directly calculating the difference between the three-dimensional space point clouds, the calculation of the tunnel space deformation is realized, which more truly reflects the spatial deformation characteristics of the tunnel surrounding rock.

[0117] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural transformation made by using the content of the specification and drawings of the present invention under the inventive concept of the present invention, or direct / indirect application in other related technical fields is included in the patent protection scope of the present invention.

Claims

1. A method for analyzing the deformation of surrounding rock in deep-buried tunnels based on 3D laser scanning point clouds, characterized in that, It includes the following steps: S1. Determine the analysis section of the surrounding rock deformation of the deep-buried tunnel, and use the ground three-dimensional laser scanning system to obtain the point clouds of the deep-buried tunnel at different times for the section; S2. Establish the simplified coordinate transformation relationship of the deep-buried tunnel point clouds at different times; S3. Calculate the independent unknown components of the simplified coordinate transformation matrix through a two-step method; specifically: S31. Align the nominal axes of the deep-buried tunnel point clouds at different times using the ICP algorithm to obtain the rotation component of the simplified coordinate transformation matrix around the Z-axis and the translation components along the X and Y axes; S32. Fit the top arch of the tunnel and match the fitting centers at different times to obtain the translation component along the Z-axis; S4. Calculate the local normal vectors of the deep-buried tunnel point clouds, and define the projection cylinders for calculating the point clouds, to obtain the point cloud subsets of the tunnel point clouds at different times on the projection cylinders. Based on the geometric distances between the average projection centers corresponding to the respective point cloud subsets, obtain the deformation of the calculated point clouds, and thus obtain the deformation magnitudes of all calculated point clouds; Calculate the local normal vectors of the deep-buried tunnel point clouds, specifically: Select the deep-buried tunnel point clouds of the same section at two different times and in the same coordinate system. Define the point cloud with the earlier scanning time as the reference point cloud, and the point cloud with the later scanning time as the comparison point cloud; Calculate the point sets within the spherical neighborhoods centered at each point of the reference point cloud with a radius of half of the normal scale D. Obtain the corresponding plane equations through plane fitting, and use the plane normal as the local normal vector N corresponding to each point in the reference point cloud, and determine the direction of the local normal vector N; Calculate the projection cylinders of the point clouds to obtain the point cloud subsets of the tunnel point clouds at different times on the projection cylinders, specifically: Define the projection cylinder belonging to the calculation point i with the local normal vector N passing through the calculation point i as the central axis, a projection size d as the diameter, and a length of L. Calculate the point cloud subsets within the projection cylinders corresponding to the calculation point i in the reference point cloud and the comparison point cloud respectively, and denote them as M(i) and N(i); where, the calculation point i is any current calculation point in the reference point cloud; Based on the geometric distances between the average projection centers corresponding to the respective point cloud subsets, obtain the deformation of the calculated point clouds, and thus obtain the deformation magnitudes of all calculated point clouds, specifically: Calculate the projections of each point of the point cloud subsets M(i) and N(i) of the projection cylinder corresponding to the calculation point i along their local normal vectors N respectively, so as to obtain the average projection centers m(i) and n(i) of the reference point cloud and the comparison point cloud corresponding to the calculation point i respectively; Calculate the algebraic distance L(i) from the average projection center m(i) of the reference point cloud corresponding to the calculation point i to the average projection center n(i) of the comparison point cloud. L(i) is the deformation magnitude corresponding to the calculation point i; When the direction of the algebraic distance L(i) is consistent with the local normal vector corresponding to the calculation point i, the deformation is positive, otherwise, the deformation is negative; Repeat the above steps to obtain the deformation magnitudes corresponding to all calculation points in the reference point cloud.

2. The method for analyzing the deformation of surrounding rock of a deep-buried tunnel based on 3D laser scanning point cloud according to claim 1, wherein, Before the step S2, it includes: performing the first coordinate transformation on the deep-buried tunnel point clouds, specifically: Establish the global coordinate system for the analysis of the surrounding rock deformation of the deep-buried tunnel; Calculate the angle between the extension direction of the point cloud of the deep-buried tunnel and the Y-axis in the global coordinate system, obtain the coordinate rotation matrix, and perform coordinate rotation transformation to make the extension direction of the point cloud of the deep-buried tunnel consistent with the Y-axis direction in the global coordinate system; the coordinate rotation matrix is specifically: where α is the angle between the extension direction of the point cloud of the deep-buried tunnel and the Y-axis in the global coordinate system, and (X, Y, Z) are the coordinates of the point cloud of the deep-buried tunnel before coordinate rotation transformation, and (X new , Y new , Z new ) are the coordinates of the point cloud of the deep-buried tunnel after coordinate rotation transformation.

3. A method for analyzing the deformation of surrounding rock in deep-buried tunnels based on 3D laser scanning point clouds according to claim 2, characterized in that After the first coordinate transformation of the point cloud of the deep-buried tunnel, it includes: Perform filtering processing on the point cloud of the deep-buried tunnel to obtain the tunnel contour point cloud and the non-contour point cloud; Based on the tunnel contour point cloud, perform a second coordinate transformation to obtain the coordinate transformation matrix, so that the point clouds of the deep-buried tunnel at different times are in the same coordinate system; the coordinate transformation matrix is: Among them, (x g , y g , z g ) are the coordinates of the tunnel contour point cloud after coordinate transformation, is the coordinate rotation matrix, (x s , y s , z s ) are the coordinates of the tunnel contour point cloud before coordinate transformation, r ij is the rotation component of the coordinate rotation matrix, (t x , t y , t z ) are the translation components along the X, Y, and Z axes of the global coordinate system.

4. A method for analyzing the deformation of surrounding rock in deep-buried tunnels based on 3D laser scanning point clouds according to claim 3, characterized in that The simplified coordinate transformation relationship is: Among them, θ z is the rotation angle about the Z-axis in the global coordinate system.

5. A method for analyzing the deformation of surrounding rock in deep-buried tunnels based on 3D laser scanning point clouds according to claim 4, characterized in that The step S31 is specifically: Divide the point cloud of the deep-buried tunnel into several thin-sheeted segmented point clouds with equal thickness along the positive direction of the Y-axis of the global coordinate system. According to the projection of the segmented point cloud of the deep-buried tunnel on the XOY plane, calculate the midpoint along the X-axis direction of the global coordinate system, and combine with the longitudinal position of the segmented point cloud of the deep-buried tunnel to define the point set (x i , y i ) on the nominal axis of the deep-buried tunnel; Set the iteration threshold, and use the ICP algorithm to align the point sets (x i , y i ) on the nominal axis of the deep-buried tunnel at different times of the deep-buried tunnel point cloud, and calculate the rotation component θ z about the Z-axis and the translation components t x , t y .

6. The method for analyzing the deformation of surrounding rock of deep-buried tunnels based on 3D laser scanning point clouds according to claim 4, wherein, The step S32 is specifically: Use the ellipse fitting method to determine the fitting center of the same cross-section at different times; Calculating the translation component t along the Z-axis based on the fitting of multiple cross-sectional point clouds z ; The translation component t z is as follows: where t z is the translation component along the Z-axis, N is the number of cross-section point clouds, c zf,i is the coordinate component z of the fitting center of the i-th cross-section in the reference point cloud, c zm,i is the coordinate component z of the fitting center of the i-th cross-section in the comparison point cloud.

7. A method for analyzing the deformation of surrounding rock in deep-buried tunnels based on three-dimensional laser scanning point clouds according to any one of claims 1-6, characterized in that, After the step S4, it also includes: Obtain the confidence interval reflecting the local roughness of any point i in the reference point cloud; Based on the confidence interval of the local roughness, judge the authenticity of the deformation of the surrounding rock of the deep-buried tunnel.

8. A method for analyzing the deformation of surrounding rock in deep-buried tunnels based on 3D laser scanning point clouds according to any one of claims 1-6, characterized in that, After the step S4, it also includes: Based on the deformation results of the point cloud of the deep-buried tunnel of the surrounding rock of the deep-buried tunnel at different times, obtain the deformation characteristics of the surrounding rock of the deep-buried tunnel and perform result visualization; the visualization of the point cloud of the deep-buried tunnel includes the deformation history curve of any point of the surrounding rock of the deep-buried tunnel at different times, the deformation characteristics and evolution process of any cross-section of the surrounding rock of the deep-buried tunnel, and the spatial deformation distribution characteristics and evolution process of the surrounding rock of the deep-buried tunnel.

Images