Precise digital models for construction surveying of highway tunnels

Abstract

The applications of tunnel surveying systems are, in general, restricted by technical, instrumental, economical and user-oriented conditions. The major technical problems are: (1) different coding and alignment systems have been proliferated among tunnel projects, (2) insufficient geometric models and representations for tunnel objects, (3) inadequate accuracy standards and tolerance criteria governing the surveying of geometric models for construction processes, and (4) incomplete understanding of the surveying techniques and computational geometry for the construction of highway tunnels. Therefore, this thesis describes the current state of the art surveying techniques and different boundary-based geometric modeling systems suitable for use with microcomputer computers to tackle the aforementioned technical problems in construction surveying of highway tunnels. These precise geometric modeling systems consist of Sweep models, Skinning models, Mesh models, combined Constructive Solid Geometry ( CSG ) and Boundary Representation ( B-Rep ) models, and computational geometry for irregular surfaces and tunnel intersections. While the Sweep models are commonly adopted in existing tunnel software, the other models are not adopted and are conceptualised and designed by the author for future applications in tunnel construction. The research involves the investigation of parametric models, data structures, algorithms, file formats and other technical information for creating, representing, and manipulating the precise geometric models of the physical parts of highway tunnels to expedite the surveying operations. Profitability is a product of highly efficient and cost-effective automation in construction surveying. The demand for high accuracy standards in tunnel surveying is highlighted by the increasing adoption of precast or prefabricated components for modem building structures, and the setting-out of computerized machines in driving tunnels. Therefore, these geometric modeling systems are adopted and being developed by the author to fulfill the requirements of the quality control system and accuracy standards in pursuit of such excellence and profitability in tunnel construction projects. Accuracy standards and codes of practice, which govern the accuracy of these geometric models, are investigated and summarized in this thesis. Finally, in order to inspect the overall geometrical deviations of a physical object in tunnel construction, the concept of geometrical tolerances and its applications are proposed by the author.