Study On Technology Of Visulization In 3D Engineering Geological Modeling And Calculation

The 3D engineering geological modeling is one branch of 3DGIS in geology, whose application is mainly under geological professional background. It has been the interdisciplinary frontier and hot point of geosciences, computer science and etc; Moreover, for the purpose on figuring out the influences for human activities (such as excavation, mining and so on), the engineers hope the existing 3D geological model can be used not only for displaying but also for calculation according to some mechanics principle, which is also the difficulty in research. So some key problems of 3D geological modeling and calculation are discussed in this paper, which are mainly including several aspects listed below.(1) The development of 3D geological model combining BRep(Boundary Representation) and element decomposition model based on AQE data structure.BRep model is used as the primary modeling way through the comparison among wireframe, surface, and the other solid models. There are mainly two reasons, on one hand it is the tie of other models, the mutual transformation of BRep and one of the other model is available; On the other hand, it can be used to represent geological object surface shape in accuracy and efficiency. Moreover, in order to describe geological body precisely, element decomposition model is introduced as the auxiliary modeling method.AQE data structure is more appropriate for geological model which can be applied to calculation by the analysis of other data structures expressing BRep model. Because it can be used to organize structures among surfaces and establish topological relationships among solids. In the end, the 3D geological model is developed and some algorithms involving DT decomposition, clipping and sewing between surfaces are implemented based on AQE data structure.(2) The fast 3D geological modeling method based on GA-Kriging interpolation algorithmThis method mainly consists of 3 steps. First of all, the regular and irregular point datum containing soil stratum attribute number by GA-Kriging interpolation; Secondly, using these points Delaunay tetrahedrons or hexahedrons are generated with VTK; At last, the stratum can be displayed and extracted in the form of soil attribute number cloud map of geological body or some cutting planes. Main characteristic of the method is the interpolation for soil stratum attribute number and the complex procedures of judgment and clipping calculation of different surfaces in other stratum modeling methods. Therefore, the method is automatic and easy to be implemented.(3) Triangular mesh generation based on TIN surface and the implementation of excavation simulation by FEMThe FEM triangular mesh is generated based on CDT(Conforming Delaunay Triangulation) through introducing Delaunay refinement algorithm, which made the TIN for visualization and FEM computational grid unified; There are 3 constrain condition for triangular decomposition including minimum angle and maximum area of every triangle and whether every triangle conforms to Delaunay attribute. Furthermore, the CDT(Conforming Delaunay Triangulation) mesh is more suitable for the application on FVM and fluid numerical simulation.The algorithm of triangular planar strain and stress element is programmed, and excavation simulation is implemented by obtain equivalent nodal released force on the excavation boundary.(4) The calculation of pile bearing capability and low strain curve simulationFirstly, the algorithm to determine the special relation between pile and stratum is presented; Secondly, the calculation for the pile bearing capacity is accomplished by BS(British Standard) and German specification of DIN; In the end, based on the pile-soil interaction model, the simulated low strain curve is achieved using Newmark algorithm.(5) The developments and applications of the system so-called 3DPyGeoMA based on Python composite platformIn order to improve the efficiency of system development, a kind of composite development platform is proposed which uses Python language as binder. Its core idea is calling other models programmed by C,C++ or Fortran language by Python. Moreover, the structure frame and the concrete implementation procedures are put forward in this paper. Furthermore, the VTK is selected as visual interface and the B/S structured 3D geological information system is established based on the technology of middleware.At last the system is used in highway slope, subway and hydropower projects 3D geological modeling, navigation, calculation and analysis, the results show the feasibility of system development method and validity of the basic theories presented in this paper.