Post-processing Technology For Discrete Element Method And Its Application In Structural Simulation

The discrete element method(DEM)is a numerical simulation method which uses microscopic particle systems to simulate the deformation of macroscopic objects.It is widely used in geotechnical engineering,structural simulation,material movement and other fields.Tectonic numerical simulation is an important quantitative structural research method.By establishing the relationship between structural deformation mechanism and geometric analysis,to a certain extent,it can get rid of the limitations of traditional structural analysis methods in the study of saline fold thrust belt.Discrete element numerical simulation could show the state of the stress and strain of the system and the velocity and displacement field by tracking the force and motion state of the particles at each moment in the simulation on the basis of presenting structural deformation,and then researchers are able to study small-scale deformation and fractures,to realize the quantitative research on the thrust structure of saline fold thrust belt.It has important scientific value and economic significance.Therefore,how to efficiently express the distribution of dynamics and kinematics in structural simulation has important application value.Based on literature research,algorithm design and development,calculation examples,and construction of numerical simulation experiments,this thesis completed the following work:1)Surveyed the literature and discussed the importance of multi-dimensional post-processing analysis for structural simulation: on the basis of structural deformation reflecting the overall shape of the structure,the distribution of strain can reflect the small-scale structural deformation in the model,and the distribution of velocity field could derive the movement of different structural units in the state,the displacement gradient is able to show the crack distribution more finely.2)Designed and developed DEMpost,a post-processing calculation and visual analysis module suitable for discrete element software YADE.The particle system is presented as an image through a rasterization algorithm,and the stress-strain and other features of the particle system are presented as an image through an inverse distance weighted interpolation algorithm.The quality of the above image is improved by other image processing algorithms.The structural deformation images in the form of images could be correlated with feature maps,which is convenient for tracking the dynamic and kinematic characteristics of specific structural units during the structural evolution.3)Designed the discrete element numerical simulation experiment systematically and analyzed the influence of common factors in the structure of the saline fold thrust belt.Based on DEMpost,the post-processing visualization of structural simulation is realized,and the mapping relationship between structural deformation and dynamic and kinematic characteristics is discussed.The results show that the presence of a single gypsum salt layer at the bottom allows stress and strain to quickly propagate to the tectonic boundary,shrinkage and squeeze occurs inside the entire model,and a "box" structure develops;the presence of the double gypsum salt layer will be accompanied by conjugate fracture The rigid uplift is transformed into a crumpled structure with rheological properties.The stress-strain state inside the gypsum salt layer is stable.The effect on the structure is that it produces strain dispersion and triangular shear bands,and has a certain radiation range;the existing fault promotes the upper plate to move upward along the fault.Factors such as the preexisting fault's tendency,dip angle,and scale affect the direction and distance of the upper wall,which in turn affects the propagation range of deformation.