Research On Structural Plane Recognition And 3D Seepage Pipe Network Model Based On 3D Point Cloud Of Photogrammetry

The study on the development characteristics of rock mass discontinuities and the connectivity and permeability evaluation are very important for high-level radioactive waste disposal sites.Based on the digital photogrammetry,taking the national nuclear waste disposal site,the typical section of Gansu disposal site as an example,using multi view photogrammetry technology,a large number of three dimensional dense point cloud model of outcrop surface is obtained based on the principle of computer vision.Under this background,the main work and conclusions of this paper are as follows:(1)the method of identifying the discontinuities based on 3D point cloud is studied.The subset plane of each point and its corresponding adjacent points is used to form a candidate for the identification of the structural plane.The principal component analysis method is used to calculate the normal vector of the subplane and eliminate the abnormal points.To change the time consuming fully automatic recognition,the user identifies the points on the discontinuities,searches the subplane of the point and recognizes the whole structure step by step with the region growth method,and improves the recognition efficiency.The program is used to identify multiple structural planes and compare their occurrence with measured data.The error is small,which proves that the method is efficient,accurate and reliable.(2)calculate the occurrence of the discontinuities and divide the dominant discontinuities according to the occurrence,and code the program to estimate the mean and strength of the trace length based on the two-dimensional and three-dimensional circular windows.The least squares method and principal component analysis method are used to fit the effect of discontinuities based on point cloud,and the principal component analysis method is more suitable.The shape of the structure surface is obtained by fitting the normal vector.A three dimensional circular window is set up on the outcrop point cloud,which corresponds to the position and size of the two-dimensional circular window.Two methods are used to estimate the mean and trace strength of the trace length.The results show that the applicability of the true value calculation method is more stable.At the same time,it is pointed out that the use of the estimation method is needs to meet certain conditions.(3)propose a new modeling and evaluation method for 3D network model of discontinuities.The steps of the proposed method are described in detail,including the random generation of the parameters used.The discontinuities is regarded as a disc,and the program is programmed to generate the three-dimensional network model of the discontinuities corresponding to the outcrop according to the method proposed.The evaluation of the generated model shows that the method is effective in generating models.This study provides a basis for the establishment of pipe network model and seepage analysis.(4)the three-dimensional network model of discontinuities is transformed into the pipe network model and the seepage analysis method based on the discontinuities network.Based on the graph theory,the three-dimensional network model of the discontinuities is taken out of a specific area and transformed into a pipe network model through the judgement of the intersection relationship between the discs.Based on the pipe network model,the water head difference in the specified direction is realized by programming,and the seepage analysis is carried out and the equivalent permeability coefficient of different paths is calculated.