Design and analysis of the vertical control for the Superconducting Super Collider Project in Texas

Description

The stringent accuracy requirements for the Superconducting Super Collider (SSC) have required a rigorous approach in designing and analyzing the vertical control required for the construction of the tunnel. All possible sources of errors are estimated to determine a realistic value for the achievable accuracy. This thesis deals with the design of the network and the dev elopement of standards, specification and procedures, unique to the SSC Project. All forms of vertical control were included in the standards, specifications and procedures, such as surface control (Primary Vertical Control Network), densification on the service areas where the shafts are located, elevation transfer techniques, and propagation of control in the tunnels. Geodetic effects that are deemed important in the Primary Vertical Control Network are analyzed to ensure the adjusted elevations are accurate and reliable. The use of a corrected weighting scheme is analyzed through the use of the Minimum Norma Quadratic Estimation (MINQE) and adjusted accordingly. Densification, elevation transfers, tunnel control and the initial tunnel breakthroughs are analyzed to be all within the tunneling requirements. The final tunnel elevations are calculated by the combined adjustment of all densification and shaft transfer surveys. The improvement of accuracy of the combined adjustment with that of the adjustment prior to breakthrough shows an increase of up to 2.8 mm at the 00 percent level of confidence. The determination of an appropriate geoidal model was performed using a combination of Global Positioning System (GPS) and levelling to acquire a micro-geoid for accurate final invert elevations. The geoid undulations were determined to an accuracy of 13 mm at the 99 percent level of confidence. Final estimated accuracy of 14 mm to 17 mm at the 99 percent level of confidence can be achieved for the invert elevations of the main tunnel.