Digital Method To Acquire Geometric Parameters Of Discontinuity And Research On 3D Network Model

Systematical study on characteristics of rock discontinuity structural plane is significant to construct repository of high-level radioactive waste (HLW). The Jijicao block of Beishan area in Gansu which is preselected as a repository of HLW is our study region. Thus, substantial information of discontinuity traces in Jijicao block has been obtained by means of measurement methods such as GPS-RTK, digital close range photogrammetry and manual measurement. Against this background, this dissertation has completed several works and studies as following:(1)Based on data measured in field, a digital method has been developed to acquire geometric parameters of fractures. The establishment of three-dimensional (3D) traces model was a critical and first step in this method. Visualization of fracture information was realized in terms of this model, and trace length, spacing, orientation, two-dimensional (2D) density of discontinuity could be calculated by developed program. This method improved the efficiency of statistical analyzing on measurement data and solved the problem of obtaining abundant information of spacing and 2D density. Moreover, it could be used in the post-processing of many measuring technologies.(2)Statistical analysis on trace length, spacing, and two-dimensional density of discontinuity has been accomplished with the help of digital method. Results showed:trace length obeyed lognormal distribution; discontinuity spacing and 2D density both obeyed two-parameter negative exponential distribution. Meanwhile, a further research on estimation of 2D density was carried out. Results indicated that estimation method raised by Mauldon was accurate and there were slight differences in the estimation using rectangular and circular sampling window. In addition, the influence ranges of faults were concluded by means of digital method and measurement in field.(3)After the statistical analysis, the results obtained were used to generate a 3D fractured rock mass model. Compared with traditional model, the initial 3D model in this paper was more realistic, because discontinuity structural planes which were represented by discs distributed non-uniformly. Since then, Differential Evolution (DE) algorithm was used to optimize diameter of discs depend on trace length data measured in field. The final result of verification showed optimization of model was effective.(4)Based on optimized 3D network model, this paper did study on block identification in simulation of tunnel excavation. Referring to topology theory and simplifying search method for closed loop and block, an algorithm was programed to identify finite block on tunnel. After that, statistical analysis was carried out on geometric shape, volume of block and orientation distribution of discs which made up blocks. Thus, dominant discontinuity group in constitution of block could be judged from the orientation distribution. The identification result could provide a positive reference for real tunnel support engineering.