| The structural planes of rock mass can also be called discontinuities,including faults,joints,bedding,etc.Its spatial location and production state affect the mechanical properties and distribution state of the rock mass.Therefore,it is of great significance to quickly and precisely identify and extract discontinuity information for rock mass stability analysis.However,the traditional compass measurement method and scanning line method are often unable to precisely and quickly count the discontinuity information,and it is difficult to meet the rapid investigation and construction requirements of large-scale slope and high and steep slope.Photogrammetry technology and 3D laser scanning technology can collect 3D spatial information of target objects quickly and non-contact,and are gradually applied to the field of engineering geological survey,especially 3D laser scanning technology,the collection process is less affected by factors such as time and external environment.The collected point cloud data can fully reflect the real situation of discontinuity of the rock mass slope,and provides important basic data for rock slope stability analysis,slope deformation monitoring and other work.This paper closely combines the requirements of automatic measurement of rock mass structure in geological hazard investigation,based on the point cloud data obtained by 3D laser scanning technology,takes typical road rock slopes and artificial quarry slopes as the research objects.The identification of rock mass structure discontinuity,the automatic extraction of geometric information and the estimation of the mean trace length of rock mass traces are carried out.It realizes automatic extraction and analysis of geometrical information of rock mass structure,change the high consumption and low efficiency of manual measurement of structural plane,improve the working environment of geologists and improve the safety and scientific nature of work.The results achieved are as follows:(1)A new method of rock mass discontinuity recognition and automatic extraction of geometric information based on point cloud data is proposed.Grouping the dominant orientation of rock mass by improved K-means algorithm based on Clustering by fast search and find of density peaks(DPCA)and average silhouette coefficient,dividing the dominant group by Hierarchical Density-Based Spatial Clustering of Applications with Noise(HDBSCAN),optimizing the discontinuities based on computer graphics combined with geological knowledge,fitting the discontinuities by Random Sample Consensus(RANSAC)algorithm,and finally calculates the orientation according to the normal vector of the discontinuity and obtain the trace information by the coordinate data of the discontinuity.(2)A three-dimensional mean trace length estimation model is proposed.This study based on the idea of establishing a probability density function in a twodimensional plane according to the intersection of the trace and the window based on the rectangular window method,the extension of the rectangle to cuboid,and the probability density function is established by counting the intersection of the trace and the six faces of the cuboid,so as to establish a new model to estimate the mean trace length in three-dimensional space,and finally the mean trace length is estimated for the rock mass trace.The three-dimensional mean trace length estimation results at different spatial positions and heights of cuboid are compared with the estimation results of the traditional Laslett model,H-H model and generalized H-H model under different window positions and heights.Experiments show that the relative error of threedimensional mean trace length estimation model is small,which can reflect the mean trace length of rock mass more truly,and has certain innovation and stability.(3)Combined with two point cloud datasets of typical road rock slopes and artificial quarry slopes,the theories and methods proposed in this paper are verified and analyzed.The discontinuity automatic extraction method proposed in this paper was using to extracted discontinuities of the two data sets,and the extracted orientation results are compared with the compass measurement results.Then,based on the obtained rock mass trace,the mean trace length estimated by the three-dimensional mean trace length estimation model proposed in this paper is compared with the measured value,which verifies that the theory and method proposed in this paper have certain feasibility and applicability.This study realizes the automatic extraction of rock mass discontinuity orientation,trace geometry information and three-dimensional mean trace length estimation,which greatly improves the measurement accuracy and efficiency.It is practical and advanced,and solves the problems of automation measurement of key geometry information of rock mass structure,innovative rock structure survey work mode,can quickly and accurately provide the required rock mass structure data for rock slope stability analysis. |
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