Rock Structure Information Acquisition Based On UAV Photogrammetry

In rock mass engineering,the structure of rock mass will affect the mechanical properties of rock mass to some extent,and then affect the failure form of rock mass.Therefore,it is very important to obtain rock mass structure information quickly and accurately for rock mass stability analysis.In view of the traditional methods such as artificial compass measurement method and drilling method work intensity,low efficiency and vulnerable to environmental impact,it is hard to meet the requirements of modern rapid construction,close range photogrammetry technology and 3D laser scanning technology to its advantage of fast non-contact measurement are gradually applied to rock mass discontinuities information acquisition,but the two methods remain vulnerable to topography and environmental impact,such as photography or scanning deficiencies.In recent years,UAV photogrammetry technology has gradually developed and matured.With its advantages of low cost,convenience,easy to operate,flexibility and efficiency,and rapid establishment of 3d models of photographed objects,it has been widely used in industry,agriculture,construction and other fields,and has become an important means of obtaining spatial data.Therefore,this paper mainly explores the rock mass structure information acquisition technology based on uav photogrammetry to provide a new method for rock mass structure information acquisition in rock mass engineering.Combining surveying and mapping with engineering geology,this study compared and analyzed the modeling process and modeling precision of different modeling software(taking Pix4Dmapper and ContextCapture as examples)by setting ground control points in the field and obtaining uav images,and explored the technical process of identifying and interpreting rock mass discontinuities.In combination with the studied discontinuities orientation calculation model,discontinuities trace calculation model and fracture width calculation model,a computer program was prepared to obtain the information of rock mass discontinuities orientation,trace length and fracture width,and the probability distribution test of rock mass discontinuities trace length and fracture width was conducted according to the K-S test method.In this paper,Changchun Jingyue Dongsheng quarry and the Jiba bridge in Tongka town,Baisu county,xizang autonomous region are used as study areas to obtain rock structure information based on uav photogrammetry,and the feasibility and reliability of this method are verified.The following research results are obtained:(1)Technical method and process of rock mass structure information acquisition based on uav photogrammetry.Based on the application practice,the method and process of rock mass structure information acquisition based on uav photogrammetry are summarized,as well as the matters needing attention in each technical link.In the control and measurement stage,the principle of hierarchical control is laid out,and the first control is the ground control and measurement in the research area.According to the different environmental conditions in the research area,three kinds of control point marks,such as natural markers,concrete and plastic woven bags,are proposed.In order to study the slope surface control measurement,the basic principle of selecting control points is proposed.For uav image should give attention to both machine performance and weather environment at the same time,and the uav images obtained in the study area parameter Settings:in the study area covers an area of about 1 km~2,course overlap is 60%,side lap is 40%,line 100 meters high to get the image of the established 3D model in the study area satisfies the requirement of rock mass structural plane information acquisition precision;In terms of 3D modeling and rock mass structure interpretation,geological environment survey and rock mass structure interpretation method based on Pix4Dmapper modeling and its measurement function were studied,and rock mass structure interpretation method was carried out by using ContextCapture modeling and EPS 3D mapping system.The latter 3D model output OSGB format can be connected to EPS,using EPS for information interpretation operation convenience.(2)Rock mass structure information acquisition and statistical analysis.The orientation,trace and fracture width information of a large number of random discontinuities in the study area are obtained by interpretation,and the probability distribution characteristics of trace length and fracture width information are statistically tested.For the fine measurement of the fracture width,the variable direction measurement algorithm of the fracture width is proposed,that is,the crack central axis is obtained,and the crack central axis perpendicular to the change of the direction vector is laid out to calculate the fracture width.This method can avoid the large deviation of the calculation of the fracture width due to the large fracture curvature,and is suitable for the calculation of the fracture width of various surface rock mass fractures,thus improving the accuracy of the calculation of the fracture width.(3)Rock mass structure information calculation and comprehensive analysis system.Through the application practice,this paper summarizes the structural plane information calculation,data file processing and graphics drawing work involved in this study,and based on C#and MATLAB prepared rock mass structure information calculation and comprehensive analysis system.This system realizes the automatic batch calculation of rock mass discontinuities orientation,trace information,trace information for the probability distribution feature test,the number of dominant groups of discontinuities division and the drawing of related graphics.All data support the import and output of TXT text and Excel spreadsheet.The study shows that this method can effectively reduce the cost of obtaining rock mass structure information,improve the work efficiency,and the result is accurate and reliable,which can meet the requirements of modern rapid construction,and provides a new method for obtaining rock mass structure information.