| Open-pit mining has the advantages of high mining efficiency,large production scale and low mining cost,and plays an important role in the development of mineral resources.In the whole life cycle of open-pit mining,the mining design,planning,block design,blasting design and block division of open-pit mining are mainly supported by the data of step line and mining and stripping amount.With the continuous development of intelligent mine construction,China’s open-pit mines have made important progress in intelligent mining,but there are still problems in the collection and processing of geographic information such as less data collection,low efficiency and low degree of automation.Therefore,it is of great significance to study the construction of three-dimensional point cloud model of open-pit mine and the automatic acquisition of step line and mining and stripping amount.The main research contents of this paper are as follows:(1)Construction of three-dimensional point cloud in open pit mine based on UAV tilt photogrammetry.Firstly,the UAV tilt photogrammetry technology is used to collect the image data of the open pit in the imitation flight mode,and the three-dimensional point cloud model of the open pit is constructed.On this basis,experiments were conducted to compare the processing effects of current mainstream point cloud simplification and de-noising algorithms on open pit point clouds.Finally,voxel-based uniform mesh method and statistical filter were selected to simplify and de-noising the point clouds,and noise-free three-dimensional point clouds in open pit were constructed,which laid the data foundation for extraction of step lines and calculation of mining and stripping quantity.(2)Step line extraction of open-pit mine considering geometric characteristics of point cloud neighborhood.Firstly,regular resampling of open-pit point cloud is carried out,and the characteristic point cloud of open-pit slope is extracted according to the geometric characteristic that the Angle between the normal vector of point cloud and the vertical plane is obviously different.On this basis,the region growth algorithm is used to segment the slope point cloud,and the concave envelope algorithm is used to extract the contour boundary of the slope point cloud after segmentation to obtain the feature points of the step line.Finally,the three-order Bessel curve is used to fit the feature points to generate the open-pit step line.This method solves the problems such as local feature loss and discontinuity of step line extraction in open-pit mine.The method was verified in two open-pit mines with different geological conditions and mine geometry in Shaanxi and Inner Mongolia.The results show that the extraction results can meet the accuracy requirements of the step line with a scale of 1:2000,which proves that the method proposed in this thesis can accurately extract the step line of open-pit mine.(3)Calculation of stripping capacity of open-pit mine by using European-style clustering improved point cloud slice method.Firstly,the opencast point cloud is sliced at equal intervals according to specific direction sequence.Secondly,the slice point cloud with multi-contour boundary is segmented by European clustering method,and the concave envelope algorithm is used to extract the outer contour polygon of slice point cloud accurately.Finally,the polygon area was calculated,and the volume of point cloud slice was calculated according to the section area and section spacing.The volume of each type of point cloud was calculated by summing the volume of each section,and the volume of each type of point cloud was accumulated to obtain the stripping quantity.This method solves the problem that the traditional point cloud slicing method cannot distinguish the multi-contour boundary and extract the boundary polygon when calculating the stripping amount of open-pit mine.The results show that the average relative error of point cloud volume calculation of the proposed method is1.17%,which is superior to the traditional point cloud slicing method.It proves that the proposed method is suitable for the calculation of stripping engineering quantity of an open-pit mine.(4)Design and implementation of intelligent surveying and mapping system for open-pit mine.Firstly,combined with the actual situation of an open-pit mine in Inner Mongolia,the demand analysis and system design of intelligent mapping system for open-pit mine are carried out.Then using C++ programming tool Qt and open source point cloud processing library PCL system development,research and development of surface mine intelligent mapping system.The system realizes the basic processing and display of point cloud model,automatic extraction of open-pit step line and calculation of stripping amount.After practical application,good results have been obtained. |
