Research On Dangerous Rock Investigation Technology And Application Based On UAV Photography

As a serious geological disaster,the collapse of dangerous rock has the basic characteristics of extensiveness,rapidity,concealment and strong destructive.Every year,various dangerous rock collapses and falling rocks events abound,seriously affecting the construction of various infrastructures and threatening the lives and property of the people.Therefore,it is very important to conduct investigations on dangerous rock beforehand and analyze the stability.At present,the traditional dangerous rock investigation methods will be difficult to reach due to the limitation of the site topography.The use of rope climbing will make this work too dangerous.Based on the UAVs,this paper proposes a standardized set of shooting procedures for dangerous rock,compares the image processing software on the market,and summarizes the advantages and disadvantages of each software;Based on the 3D point cloud data,a set of interpretation and calculation methods for geometric information of dangerous rock was proposed using an abandoned quarry in Shangyu Zhejiang Province as a test site,and the reliability of the technology was verified;The failure mode and stability of dangerous rock are analyzed by using stereographic projection method and limit equilibrium theory.Finally,the author applies this technique to elevator shaft project of "Qiong Tai Xian Gu" scenic spot in Tiantai Mountain.In the geological survey,the basic engineering geological data are provided for the design and construction.The main research contents and results are as follows:(1)Combined with the principle of computer vision,the 3D reconstruction technology of rock mass based on UAV photography is summarized.And the standardized dangerous rock shooting process is proposed.Mainly includes:(1)Selection criteria for drones;(2)Before the shooting,the flight site needs to be surveyed;(3)Two flight route planning methods for "slow slope grid type" and "steep grid type" for the developmental form of dangerous rock;(4)3?5 GCPs should be arranged as much as possible.Through these tasks,the shooting operability is enhanced,the success rate of the 3D reconstruction of the dangerous rock and the point cloud quality are improved.(2)Compare the four image processing software and laser scanning on the market with four indicators: Interface operation difficulty,Visual effect,Point cloud density and Point cloud accuracy.It is found that the four indexes of Visual SFM are worse than the other three commercial software and are not recommended for research.Pix4 d Mapper has simple operation logic and good precision of point cloud,but the density of point cloud is uneven and the noise is too much.The operation logic of Context Capture is a little complex but the comprehensive ability is strong,whether it is the visual effect of point cloud,the density of point cloud and the precision of point cloud are very good;Photo Scan performance is more balanced,but the accuracy is average.(3)Experiments in Laoying Mountain show that the measurement of dangerous rock size can be achieved based on the extraction of point cloud coordinates,and the comparison with the GCPs proves that the accuracy of point cloud measurement can reach centimeter level;Based on the mathematical analysis of the geometric relationship of structural planes,a calculation method of structural planes production based on point cloud data is proposed.In practice,"three-point fitting method" or "multi-point fitting method" can be used to extract and fit structural planes of dangerous rock.The reliability of the method for calculating the structural planes is verified by comparison with the measurement results of the geological compass.(4)The stability of the WY1 dangerous rock in the southern area was evaluated.It is found by the stereographic projection method that the WY1 dangerous rock has a structural planes combination which is not conducive to stability and has a large collapse possibility;Through the mechanical calculation method,it is found that the WY1 dangerous rock stability coefficient is 0.9,which is in an unstable state.(5)In the elevator shaft project of "Qiong Tai Xian Gu" in Tiantai Mountain,the investigation technology studied in this paper was actually used,and the geometric information interpretation and stability analysis of the dangerous rock found were carried out.