A method for extracting axis and constructing section in long roadway deformation monitoring

The 3D laser scanning technology is widely used in the research of deformation monitoring technology for long roadways. But there is a phenomenon of benchmark point displacement in the point cloud data collected through multiple scans in current research. The common features of adjacent point cloud data collected are not obvious, and the splicing of multi site clouds will lead to an increase in cumulative errors. The deformation of advanced roadways is affected by advanced supports. In order to solve the above problems, based on the traditional cross point method, which involves the intersection of the midpoint of the roof and floor and the two key points of the two sides, a method for extracting the axis of the roadway based on the least squares method is proposed. The origin of the rectangular coordinate system defined by the roadway is located at the laser beam emission point. The z-axis is located within the vertical scanning plane of the laser scanner. The x-axis and y-axis are located within the horizontal scanning plane of the scanner. The central axis reflects the overall direction and position and posture of the roadway. When the roadway excavation is completed without being affected by mining, the entire roadway is scanned for the first time, and the center point of the entire roadway is determined by the least squares method. Each center point is connected and fitted to form a complete central axis. In the subsequent monitoring of roadway deformation, point cloud data is superimposed based on the midpoint position of the first monitoring to accurately obtain the changes in various point clouds within the roadway cross-section, and thus obtain the deformation of the roadway. And the roadway section is constructed based on the fitted central axis. A 3D laser scanning system is used to test the deformation of the 30507 working face return air roadway in Tashan Coal Mine. The results showed the following points. ① The deformation of the roadway decreases with the increase of the distance from the measuring point to the working face, and the leading influence range of the 30507 working face return air roadway is 150 meters. The maximum point of roadway deformation is located on the side near the goaf of the floor. ② The advanced range determined by the 3D laser scanning and microseismic monitoring system is close, indicating that the supporting coal body has started to be under stress when entering 150 meters. The maximum point of roadway deformation is located on the side near the goaf of the floor, rather than the floor observed by the cross point observation method. This proves that the 3D laser scanning results are more accurate and greatly reduces the intensity of the operation.