| The 3D geological model can visually present the morphology of various underground geological bodies,geological structures and geological hazards,which is of great significance to urban spatial planning and urban geological hazard prevention and control.In order to overcome the technical problems such as poor accuracy,poor aesthetics and difficulty in post-modification of 3D urban geological models under complex geological conditions,based on a comprehensive study of the current situation and problems of 3D geological modelling technology at home and abroad,this paper proposes a 3D urban geological modelling technology based on multiple sources of heterogeneous data,geological a priori knowledge and geological laws.This technique can use multiple modelling data,such as DEM elevation data,planar geological map,comprehensive geological profile,borehole data,physical interpretation data and tectonic outline map,as modelling data sources,and adopt block modelling technique under the joint constraint of geological a priori knowledge and geological laws to complete the construction of urban geological 3D model under complex geological conditions.The paper uses the construction of a 3D geological model of Chengdu as a model,focusing on the geological overview of Chengdu,the urban geological 3D modelling method,the pre-processing of urban geological 3D modelling data,and the construction and demonstration application of urban geological 3D models.The construction of a 3D geological model of Chengdu city was completed using a multifaceted complex geological structure urban geological 3D modelling technique based on multi-source heterogeneous data,geological a priori knowledge and geological law constraints,and good modelling results were achieved.Through the research,the main results and understandings achieved in this paper are as follows:(1)The geological background,stratigraphic features,magmatic features and tectonic features of Chengdu city and other geological a priori knowledge and geological laws were basically clarified,which provided geological theoretical support for the construction of a 3D geological model of Chengdu city.Based on this,a comprehensive geological profile of Chengdu city was drawn up by combining existing geological sections,physical interpretation data,digital geological maps and DEM elevation data,which completely portrayed the geological structure of Chengdu city at a depth of 2000 m.This provides a geological basis for the construction of a three-dimensional model of Chengdu,and lays the foundation for the data.(2)For the construction of a 3D geological model of a large area under complex geological conditions,a block modelling method based on "multiple sources of heterogeneous data,geological a priori knowledge and geological laws jointly constrained" is proposed,and various geological elements(such as fracture boundaries,unconformity boundaries and rock intrusion boundaries)should be fully considered in the selection of block interfaces.This method enables the efficient construction of large-area 3D geological models under complex geological conditions.Based on the idea of block construction and seamless splicing technology,the 3D geological models of different scales and different accuracies can be fused efficiently and accurately,and the model construction process is constrained by geological a priori knowledge and geological laws,thus improving the reliability,accuracy and aesthetics of the 3D geological models.(3)By carrying out consistency processing of multi-source heterogeneous data,the mutual constraints and validation between different data are realised,effectively avoiding the multi-solution of 3D geological models and improving the accuracy of3 D geological models.In carrying out the process of consistency processing of multi-source heterogeneous data,not only the accuracy and reliability of the data itself is considered,but also the interconnection and influence between the data is paid attention to.By superimposing,matching and correcting different data,operations are carried out to fill in and reconstruct missing information in data gaps,thus improving the integrity and continuity of the 3D geological model.In addition,the accuracy of the 3D geological model was further optimised by combining geological a priori knowledge and empirical laws in the process of data constraint and validation,and by establishing methods such as inversion models and multi-scale analysis.These measures have effectively improved the application value and reliability of the 3D geological model,providing strong support for areas such as urban spatial planning and urban geological disaster prevention and control.(4)The use of block modelling technology can significantly reduce the difficulty of constructing 3D geological models for large areas with complex geological conditions,which not only improves the modelling efficiency,but also facilitates model integration and post-modification of the model.Based on the idea of block modelling,the large-area geological model is divided into several small modelling geological units,and different modelling strategies and parameter settings are adopted for different geological conditions and data characteristics.At the same time,as each small block is independent and decoupled from each other,it is easy to carry out model integration and later modification and improvement.(5)Under the joint constraint of multi-source heterogeneous data,geological a priori knowledge and geological laws,a three-dimensional geological model of Chengdu City was constructed using the block modelling technique,and the modelling results were good,further proving the feasibility of the modelling theory and technical method.This study gives full play to the advantages of interdisciplinary disciplines such as geology and computer science,and through in-depth exploration and analysis of geological a priori knowledge and geological laws,a highly detailed and practical 3D geological model of Chengdu City has been successfully established,which can provide accurate and comprehensive 3D geological model support for various fields such as urban spatial planning and urban geological disaster prevention and control,and is of great practical application value,as well as It can also provide an effective technical reference for the construction of 3D geological models in other regions,and is expected to be widely used and promoted nationwide.(6)The technology of constructing a grid-profile vector-grid integrated attribute model,the technology of efficient rendering of multi-scale and high-precision 3D model data on the Web side and the technology of evaluating the accuracy of 3D geological models are important directions for research on 3D geological modelling technology in the future.Grid dissection and vector-grid model construction technology refers to the use of grid dissection technology to decompose the regional space into a large number of grid cells,and assign each grid cell with corresponding attribute data,so as to integrate vector data and raster data from different data sources into a unified model for spatial data analysis and evaluation.The Web-based efficient rendering technology of multi-scale and high-precision 3D model data can ensure the image quality and rendering speed,realise online interaction and real-time display of3 D model data,and provide a more visual and three-dimensional experience for the public to understand geology and 3D geological modelling;the 3D geological model accuracy evaluation technology can help test and confirm the advantages and disadvantages of different modelling methods and techniques,and provide a more objective and quantifiable evaluation system for scientific research and application practice.The continuous innovation and advancement of these technologies will have a profound impact on the future of geology,urban planning and natural resource development. |
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