Study on Three Dimension Mathematical Physical Reconstruction of Pore Structure in the Rock

Author:Xiao Na

Supervisor:Zhou Xiaoping

Database:Doctor

Degree Year:2018

Download:162

Pages:164

Size:6357K

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Rock physical tests are the objective method to study rock physical and mechanical properties.In order to make it predict the engineering,the cost of experiment usually is high and the cycle is long.In some cases,the complexity of engineering geology leads to the large error.In the same research area,it is difficult to obtain rock samples with various micro-structures for testing,and therefore it is difficult to study the influence of the micro-structures on rock physical and mechanical properties.With the development of computer technology,numerical simulation has become the most economical and effective method for scientific research.For example,the numerical simulation of the building structure is used to determine its reliability,and the numerical simulation of underground caverns can be used to determine the area of the possible rock burst.At present,numerical simulation of geotechnical engineering has become an important means of geotechnical research.Compared with the rock physical and mechanical experiments,it can save a lot of human resources,material resources and funds,and can quantitatively examine the influence of various factors(such as pore)on rock physical and mechanical properties at micro scale.In addition,the numerical simulation can be used to calculate the physical and mechanical properties which can not be measured directly in the conventional rock physical and mechanical tests,such as the three phase relative permeability.This paper uses CT scanning experiment to obtained CT images of Chongqing sandstone.Compared with conventional digital image processing methods,this paper proposes a variational model for image denoising,and uses edge detection operator to get the appropriate parameters,noise removal in CT images at the same time,retains its edge and texture details information and reflects the distribution law of pore in the CT image as accurately as possible in space.According to the CT scan image,in mathematical reconstruction,the marching cubes algorithm is used,and two ambiguity resolution table is constructed,the surface of the ambiguity problem in topology is solved in grid generation to ensure the accuracy of the surface model.With the combination of vertex weight removal and adaptive branching octree algorithm,the duplication of the grid is removed,and the quality of the grid is improved.On the surface mesh model in the input domain,the internal node adaptive tetrahedral mesh generation algorithm is proposed,the tetrahedral mesh model is set up by the Delaunay tetrahedronalgorithm;In physical reconstruction,the three-dimensional tetrahedral mesh model is regared as the reference model.In the simulated annealing reconstruction,by using the two-point probability function,lineal path function and fractal control function,the reconstructed model is obtained,which is different from the reference model on geometry but is equivalent to the reference model in topology and mechanics.The generated numerical model can be used to predict the physical and mechanical properties of the rock mass in the macro scale according to the limited information obtained from experiment.The fracture mechanism of the reconstructed model is discussed preliminarily.This study provides a new method for the study of rock numerical simulation,and provides a visual description means for the study of rock fracture mechanism.