Research And Application For Key Technologies Of Digitalizing Railway Alignment Design

Alignment design, as the premise and basis of railway construction, is a core work that controls the whole situation. In the recent years, with the rapid development of railway in our country, railway design tasks become increasingly onerous. As one of the important ways to improve the quality and efficiency, technology of digitalizing alignment design needs to be studied.Since1960s, scholars have been working on the technology of digitalizing railway alignment design, and a series of railway alignment design systems have been developed. However, the existing researches just aim at some parts of railway alignment design stages and content. Actually, at present, the complete solution of the overall railway alignment design process has not been found.Firstly, the thesis analyzes the requirements and research status quo of railway alignment design in different stages, and then summarizes the key technical problems which need to be solved at present. In the planning stage, the thesis focuses on the alignment optimization technology; in the detailed design stage, it mainly studies on the alignment model in new-built railway, existing railway and railway hub, theory and method of associated constraints alignment design, existing railway routes recovery and reconstruction. The geographic information model and web three-dimensional interactive visualization as the core technology in all stages are studied. It try to solve the digitalizing alignment design problem from planning to the detailed design stage, including new-built railway, existing railway and railway hub. The main research contents and achievements are as follows:1. Comprehensive geographic information model for railway alignment design including terrain, geology and environment is established. Based on the existing digital geology model, the construction of digital terrain model is studied. Firstly, fault plane model is built by stretching the fault line in3D spaces. Secondly, Kriging interpolation algorithm is introduced to supplement virtual control points in areas where control points are sparse. Thirdly, taking the control points of actual measurement and virtual control points as vertex assembles, and the stratum boundaries as constraint assemble, based on constraint Delaunay triangulation network theory, the stratum is set up. By adopting conservative minimum encompass cuboid to represent the complicate shaped karst caves, the modelling process is simplified. In allusion to the dispersed and continuous distribution of geographic information, Grid-R tree index, Grid-Triangle-Pont index are built and fast retrieve of geographic information is achieved.2. Railway alignment optimization model is established. The parameter vector that reflects the characteristics of alignment is the independent variable. Considering the construction cost, operating costs, environmental impacts, and various design constraints, objective function is built. A genetic algorithm based stepwise encoding is proposed. A genetic series that consists of offsets of intersection point, radii of circular curve and elevations of grade change points is designed. A stepwise encoding method is presented. The horizontal genes generated firstly, then vertical genes are created considering horizontal constraints; the whole genes are formed by adjusting lastly. In the process of generating chromosomes, the thesis designs4cross operators (simple crossover, two-point crossover, arithmetic crossover and non-uniform heuristic crossover) and3mutation operators (single point mutations, multipoint mutation, straightening). Based on this method, a group of alignments conforming to railway constraints with low comprehensive costs can be generated.3. Three kinds of alignments models are built to exhaustively solve alignment design problem in new-built railway, existing railway and railway hub. Boundary constraint alignment is modeled to alignment design for single track and the based route of double track new-built railways, which never refer to other alignments. The alignment is indicated by geometric parameters and constraints of alignment-units. Based on this alignment model, all kinds of complex geometric design can be worked out. Reference alignment is modeled for the alignment design of ? route in new-built railway, whose alignment only refers to the based route.8intersection point reference relationships and2section reference relationships are defined. The alignment geometric parameters and mileages of the ? route are figured out by intersection point and section reference relationships matrix. The ? route alignment can be designed integrally instead of tedious segmentation processing based on this alignment model. Part-reference alignment model is extended from the reference alignment model, by adding reference route index vector to above2matrixes. This alignment model solves the alignment design problem of existing railway reconstruction and railway hub, which refer to different alignments in different sections.4. Existing digitalizing railway alignment systems mainly focus on single object design, ignoring the complex relationships between the objects. Firstly, the coupling and dynamic characteristics of the associated constraints are revealed after system analysis, Secondly, associated graph data structure is designed, to construct the associated objects and the mutual constraint relationships as a whole entity (constraint route group). Then, dynamic update algorithm for constraint route group is developed. Based on that, the constraints can be automatically checked and the associated objects can be automatically updated in the design. Lastly, the associated constraints alignment design method has been established and applied to routes group location, alignment design that associate with bridges, tunnels and stations.5. The method for the recovery of existing railway alignment is proposed. Firstly, a longest linear search algorithm is designed to automatically identify straight and curve segments. Then radius and transition curve length are optimized based on direction acceleration method. Lastly, the recovery of the horizontal alignment of existing railway is realized. The " ? route modeling" method for the addition and reconstruction of existing railway is presented. The additional and reconstruct alignments is considered as the ? route of the existing alignment. Based on part-reference alignment model, all kinds of addition and reconstruction can be designed by using the reference relationships of intersection points. Besides, the alignment can be designed integrally, avoid the traditional and tedious segmentation processing.6. Railway web3D interactive visualization theory and methodology are developed. Key problems such as the management of railway3D scene, model simplification, data compression and network transmission strategy are studied. Based on the directed acyclic graph, railway scene is efficiently organized and managed. Railway scene is subdivided from general to detail in depth, brother nodes were divided by mileage-section or sense type in breadth, standard model nodes are shared by related father nodes. A half-edge collapse error metric considering a large number of road constrained edges is proposed. Based on it, original road model is simplified by half-edge collapse and operating hierarchical tree is built on the server. Remote view-dependent reconstruction criterions are established. According to these criterions, minimum nodes data that need to be transferred to client is quickly selected in the operating hierarchical tree. A predictive coding method is proposed to effectively compress data. Combined with constrained edges priority strategy, integrating multithreading and caching technology, railway scene remote interactive visualization is finally realized.7. Based on the theory and method presented in this thesis and existing research achievements, the author as a key member of the research group has developed a series of railway digital alignment designing systems, including railway intelligent alignment design system, new-built railway digital alignment design system, existing railway reconstruction and addition digital alignment design system, railway hubs digital alignment design system, metro digital alignment design system, etc. These software systems have been widely applied in80%railway survey and design institutions in China, and have become the most popular digital railway alignment design system with the most abundant function.