Research On The Techniques For3D Reconstruetion And Visualization Of Slicing Image Sequence Of Granular Soil

With the continual construction of the slag dam, high embankment dam, highway andrailway, high building and other projects, granular soil as the main filling mateiral, has anincreasingly wide application and it is also more and more attractive to the dam sectors. Inorder to meet the needs of the stress and deformation analysis of the slag dam and otherstructures, the intensity and stress-strain relationship of granular soil under high pressureor other complex stress state becomes an important research content of rock mechanics.And the micro-fabirc characteristic of granular soil is the basis of the research forstress-strain relations. The micro-fabric of granular soil is one of the key factors whichaffects the engineering characteirstics, and the computer processing of the image ofgranular soil is also the key technology which make the micro-fabric research from thequalitative to the quantitative. The current research of the micro-fabric of granular soil ismainly based on2D image processing, while the actual granular soil is in3D space, so ithas some limitations in accuracy and objectives of2D method. According to the featuresof granular soil image, as to satisfy the practical needs of application, this thesis tires touse the CT technique to obtain the image sequences of granular soil, then reconstruct the3D model based on the2D granular soil images with3D reconstruction and visualizationtechnology, and also extract and analyze the features of granular fabric through the3Dmodel, which lays the foundation for the next stage research for establishing themechanical model of granular soil fabric. Focusing on the descirbed above problems andideas, the thesis, supported by Yangtze River Academy of Science of Hubei province, hasdeveloped the specific study and obtained many achievements with practical applicationvalue.Firstly, the thesis lists the research status of the micro-fabirc of granular soil, andpresents the reason and basis of our study method and introduces the related concepts andtheoires of3D reconstruction technology based on slicing image sequence, then also makethe analysis and summary of the key studies of3D reconstruction and visualizationtechnology, then leads to the specific content and method of the whole study.Secondly, This article studies and analyzes the slicing image segmentation technology,based on the features of granular soil image, atfer some pre-processing like ifltering andinterpolating, we can get the slicing granular soil image sequence with higher quality andcontinuity, then presents a new method with the watershed segmentation algorithm basedon fast clustering to accomplish the effective segmentation of linking particles of granularsoil in the image, here we adopt respective measures to deal with the over segmentation ofpatricles, which guarantee the accuracy of the segmentation, then also proposed a methodto extract the2D image sequence of a target particle rfom the slicing image of granular soil based on the different pressure conditions. The observation and analysis of thegeometric shape and motion-state of target particles under different pressure conditionswill become the considerable image data support to the following analysis and buildingthe micro-fabric mechanical model.Thirdly, the thesis proposed the algorithm of3D reconstruction and virtual cuttingbased on the segmentation technology of granular soil slicing image sequence. This partstarts with the basic lfow of3D reconstruction, and does the analysis and summary of thecommon algorithm of3D reconstruction, then presents a fast ray casting volume rendeirngalgorithm based on the data classification. The algorithm first needs to classify the originalreconstruction data using the presented segmentation method then make the differentrendeirng algorithm according to the different data. The choose of rendeirng detaileddegree is based on the signiifcance of data classification, which will not only guaranteesthe quality of the rendeirng3D model, but also increase the rendeirng speed.Lastly, the thesis further proposed the method to extract the micro-fabric elementsand the surface simpliifcation of the reconstructed3D model. The thesis gives anextensive study on the traditional2D extraction methods of the micro-fabirc, that is makethe research and analysis in3D space, including3D geometric shape extraction and thespatial distirbution features of granular soil particles under the different pressure condition,which will make a better data and basis for the further research of building the mechanicalmodel of granular soil particles in3D space. Then because of the3D model atfer thereconstruction has more detail information and make the data very huge, the visualizationof such data sets is already a bottleneck and it will become impossible unless newmethodologies are developed. Therefore, it is necessary to develop computer graphicsrendeirng techniques that use data abstraction and allow for different levels of detail, thethesis also presents a surface simpliifcation method based on the3D center long-axis andnon-uniform B-spline fitting algorithm to reduce the redundant data. The proposedalgorithm could give a smoother surface approximation representation, requires lessabstraction time, and uses a smaller descirption for data abstraction.Finally, the research achievements are summarized and directions for further researchare pointed out.In the end, this thesis summarizes and expects the above research results, analyze theproposed3D reconstruction and visualization technology of slicing image sequence ofgranular soil, and birelfy discussed the ifirther research of the thesis.