Background
At present, the method mainly adopted for monitoring tunnels such as subway tunnels, highway tunnels, high-speed rail tunnels and the like is to obtain point position coordinates and point position change information by using traditional monitoring instruments such as a total station, a level gauge, a convergence gauge and the like through arrangement of monitoring points, design of an observation scheme and various adjustment, so as to obtain information in the aspects of section deformation, convergence deformation, horizontal displacement, tunnel settlement and the like of the tunnels. However, the methods are based on a single-point acquisition three-dimensional coordinate method, long observation time is needed, the obtained point density is small, the observation precision is influenced by the observation conditions, and the description of the deformation of the whole tunnel structure which needs mass data is not comprehensive enough. The main problems of the traditional method are as follows:

a large number of monitoring point locations need to be arranged in the early monitoring period, and only the changes of the point locations can be monitored during monitoring, so that tunnel deformation at other positions cannot be obtained;
instrumental nature of traditional monitoring meansThe monitoring method is limited, each monitoring project is separately carried out, so that the monitoring is slow, the tunnel monitoring can only be carried out in the time of vehicle outage or small vehicle flow, for example, the subway monitoring can only be carried out within 3-4 hours after the subway is shut down, a long time is required for monitoring a section of tunnel, and the deformation of the tunnel cannot be obtained in time by the traditional monitoring method;
the traditional monitoring method can only monitor the tunnel change of the part where the monitoring point is arranged, and cannot obtain the whole change of the tunnel, which is very unfavorable for measuring the tunnel safety.
The three-dimensional laser scanning technology is a breakthrough innovation in the mapping history after GPS, the three-dimensional laser scanner can finely scan a space scene, acquire three-dimensional laser point cloud for three-dimensional modeling, and perform various post-processing on point cloud data, such as metering, analysis, mapping, monitoring, display and the like. The data volume of collection is more, and the data characteristic point of collection is more comprehensive, and the collection rate is also faster. The three-dimensional laser scanning technology is mature, the application of the three-dimensional laser scanning technology to tunnel monitoring becomes a hotspot of domestic and foreign researches, the monitoring efficiency can be improved, and the integral deformation of the tunnel can be obtained. The most critical technology for monitoring tunnel deformation by using a three-dimensional laser scanner is how to determine the deformation of a tunnel, and at present, the method mainly adopted for measuring the tunnel deformation is as follows: firstly, extracting section information, convergence information and the like in the tunnel point cloud, and then determining the tunnel deformation condition through a traditional evaluation method. There are two main schemes for extracting section or convergence information:

extracting a central axis, intercepting a cross section point cloud of the tunnel in the direction vertical to the central axis, and fitting the point cloud to obtain a cross section and convergence information;
the method comprises the steps of firstly carrying out three-dimensional modeling on tunnel point cloud to obtain a tunnel three-dimensional model, and then intercepting a model section as a section or convergence information. Above theThe following problems should be solved:
when point cloud interception is carried out firstly and then point cloud fitting is carried out, fitting errors exist, and when modeling is carried out firstly and then section interception is carried out, modeling errors exist, which are very unfavorable for the tunnel with small deformation value;
the tunnel deformation analysis needs comparison of data in at least two stages, different from the traditional data acquisition method, a fixed monitoring point does not need to be arranged when the laser scanner scans the tunnel, so that when the traditional analysis method is adopted to extract the section or convergence information, the data positions in the two stages cannot be completely the same, and great deviation exists when the tunnel deformation is measured.
Aiming at the problem that the three-dimensional laser scanning technology is applied to tunnel monitoring, units such as Shanghai subway, Shanghai rock soil, Nanjing subway, Wuhan university and the like are researched, and the high-precision point cloud monitoring system has good precision in the aspects of station arrangement scheme, point cloud filtering and the like, but the current researchers all adopt a model for extracting section information and convergence information as evaluation indexes when the traditional single-point monitoring point is acquired. The three-dimensional laser scanner obtains a large number of surface point space coordinates of the target object through scanning, the surface point space coordinates are high-density discrete three-dimensional data point sets, and the evaluation of the tunnel deformation is unreasonable only by adopting a traditional analysis method for measuring the tunnel deformation. The method for measuring the tunnel deformation has low precision, and the method for improving the precision of the tunnel deformation analysis has important significance. In order to improve the precision and the practicability of the three-dimensional laser scanning technology applied to tunnel monitoring and change the defects of the existing analysis method, the invention provides a novel integral analysis method for measuring tunnel deformation according to the point cloud characteristics by taking the monitoring project of Nanjing subway No. 2 line protection area which is monitoring in progress as a basis and jumping out of the index of the traditional evaluation of tunnel deformation. The research of the invention provides reference for analyzing the deformation of the tunnel structure, provides support for applying a three-dimensional laser scanning technology and provides a new evaluation method for measuring the deformation of the tunnel.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for measuring the integral deformation of a tunnel, which reduces unnecessary intermediate links, can accurately compare multi-period monitoring data, can accurately obtain the integral deformation of the tunnel, and has simple calculation and strong operability.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a method for measuring the integral deformation of a tunnel comprises the following steps:
step 1, scanning a tunnel to obtain point cloud data;
step 2, processing the point cloud data in the step 1 to obtain three-dimensional point cloud data without deviation;
step 3, establishing a regular cylinder model in the three-dimensional point cloud data obtained in the step 2;
step 4, calculating the distance from each three-dimensional point cloud data to the surface of the regular cylinder model;
step 5, generating a distribution gridding graph of the distance from the three-dimensional point cloud data to the surface of the regular cylinder model;
and 6, obtaining gridding images of two-stage or multi-stage tunnel scanning data by using the steps 1-5, and calculating the difference value of the gridding images of each stage and the first stage gridding images to obtain the overall deformation value distribution map of the tunnel.
The scanning instrument used in the step 1 is a three-dimensional laser scanner.
The point cloud data processing method in the step 2 comprises the operations of registration, trimming, repairing, filtering and the like, and high-precision three-dimensional point cloud data is obtained.
The center of the regular cylinder model coincides with the central axis of the tunnel, the radius of the cylinder is smaller than the inner diameter of the point cloud tunnel of the three-dimensional point cloud data, and the length of the cylinder is larger than the length of the central axis of the tunnel.
Because the tunnel structure is generally in a regular circle or an approximate circle, scanning is carried out to obtain tunnel point cloud data which are formed by combining point clouds with three-dimensional coordinates into a regular circle or an approximate circle; and calculating the distances from all point clouds to the cylinder in a coordinate system where the point clouds are located, wherein the vertical distances from the tunnel point clouds to the surface of the cylinder can be directly calculated through a formula because the three-dimensional coordinates of all tunnel point clouds are known.
And expanding all the tunnel point clouds into planes according to the relative positions of the tunnel point clouds in the cylinder, and performing grid formation on the numerical values of the distances from all the tunnel point clouds to the surface of the cylinder according to a certain grid size by using a grid formation method to generate a grid formation image, wherein the size distribution of the distance values from the tunnel point clouds to the surface of the cylinder can be seen in the grid formation image.
The invention provides a new method for measuring the whole deformation of the tunnel according to the point cloud characteristics when the tunnel deformation is monitored by utilizing the three-dimensional laser scanning technology, the method reduces unnecessary intermediate links, can accurately compare monitoring data in multiple periods, can obtain the whole deformation of the tunnel, and is simple to calculate.
The research content of the invention changes the traditional analysis method for evaluating the tunnel deformation and establishes a new technical method for evaluating the tunnel deformation. The method has the advantages that the thought of tunnel slicing research in the traditional method is changed, the tunnel is taken as a whole for analysis and research, the tunnel deformation condition can be comprehensively measured, unnecessary intermediate link errors such as modeling and fitting are reduced, accurate positioning and accurate comparison of multi-stage tunnel deformation are guaranteed, the method has the characteristic of high precision, operation is simple in practice, and the characteristics are very important for monitoring the tunnel with small deformation value. The research result of the invention provides a new thought for researching tunnel deformation and measuring the evaluation method of the tunnel deformation, and provides a good foundation for the practical application of the three-dimensional laser scanning technology in the tunnel.
Detailed Description
The present invention will be further described below.
The method combining theoretical research and experiments is adopted in the embodiment; on the basis of mastering the research of various conventional tunnel monitoring methods, tunnel deformation analysis theories, point cloud processing methods, point cloud modeling methods, data processing theories and gridding methods, a total control scheme is determined, a tunnel scanning experiment is performed, the effectiveness and pertinence of collected data are ensured, and the quality of the collected data is evaluated, analyzed and selected preferentially. Then, an effective theoretical model is selected for simulation analysis, a model and a method with good effect are screened out, tight process experiment and comparison experiment are carried out, the scientificity and accuracy of research are ensured, relevant technical parameters are fed back in time, and the reasonability and effectiveness of the experiment are ensured.
The embodiment also adopts a comparative analysis method; since the research content of the embodiment is proposed for the first time and no related research results can be referred to, in order to ensure the effectiveness of the research, a comparison experiment needs to be performed in each process to screen out appropriate parameters and methods, and whether the scheme adopted in each process is reasonable and effective is judged until the experiment is completed.
The technical route and the test scheme are as follows:
the technical scheme of the embodiment mainly comprises the following steps:
based on monitoring projects of Nanjing subway No. 2 line protection areas which are monitoring, advanced instruments such as FARO Focus 3D ground three-dimensional laser scanners and Leica TM30 measuring robots provided by laboratories are utilized, a multi-stage subway tunnel monitoring and scanning experiment is carried out through a reasonably designed monitoring scheme, and professional point cloud processing software such as RealWorks Survey, Geomagic Studio 12 and Imageware is utilized to carry out operations such as filtering, registering and trimming on tunnel point cloud so as to obtain appropriate point cloud data;

firstly, converting the point cloud data format by using software such as Imageware and the like, then using software such as AutoCAD, 3DMAX and the like to cooperate with secondary development software VC + + and the like, inserting a regular cylinder model into the tunnel point cloud, and enabling the central axis of the tunnel and the cylinder to be parallel to each otherThe centers are overlapped; the tunnel construction is influenced by different excavation modes and the operation period of the tunnel is influenced by complex external factors, so that the tunnel structure is generally an irregular circular structure, and irregular circular tunnel point cloud with three-dimensional coordinates is obtained after laser scanning. The important step of this embodiment is to newly build a regular cylinder in the point cloud coordinate system, and require the center of the cylinder to coincide with the central axis of the tunnel, and the radius of the cylinder is smaller than the inner diameter of the point cloud tunnel;
the distance between the point cloud and the cylinder is calculated by using programming software such as MATLAB, VC + +, and the like, and certain difficulty exists in the aspects of programming method, storage operation and the like due to large data volume of the point cloud; calculating the distances from all tunnel point clouds to the cylinder in the coordinate system, wherein the vertical distances from the point clouds to the surface of the cylinder can be directly calculated through a related formula because the three-dimensional coordinates of the point clouds are known;
performing gridding processing on the point cloud distance value by using software such as SURFER and the like in cooperation with secondary development software OpenGL and the like, emphasizing the influence of a gridding method and the selection of the size of a grid on a processing result, and finally selecting a proper quantization index for evaluation; and expanding all the point clouds into planes according to the relative positions of the point clouds in the cylinder, and performing grid formation on the numerical values of the distances from all the point clouds to the cylinder according to a certain grid size by using a grid formation method to generate a grid formation image. The size distribution of the distance values from the point cloud to the cylinder can be seen in the gridding graph;
and the grid numerical value of each stage point is contrasted and analyzed by using related software and methods, and an accurate and visual tunnel integral deformation map is generated. Obtaining gridding images of two-stage or multi-stage observation data by the method, and then carrying out gridding images of each stage and first stage or last stage gridding imagesAnd calculating the difference to obtain the overall change distribution map of the tunnel. Under the theoretical condition, under the condition that the size of the two grids is the same as that of the gridding method, the gridding numerical values at two stages are the same, and actually, the grid numerical values change due to the deformation of the tunnel, and the integral change condition of the tunnel is obtained by subtracting the grid numerical values at two stages. From which the magnitude of the tunnel deformation magnitude and the overall deformation profile can be derived.
The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the invention.