ABSTRACT
The paper presents the application using least squares theory to adjust tunnel movements measured from real-time monitoring. It is aware that existing tunnels in use may move due to construction activities nearby or ground and structure natures so nowadays real-time monitoring using total station with objective prism (OP) is recognized as one of the most effective solutions in measuring said displacements. However, considering the reliability which the equipment could achieve as well as the relative distances between total stations as well as total station and OP, the monitoring results may need to be further adjusted to eliminate the measurement error. Thus, the real-time GEOAUTO and the least squares adjustment START*NET software were adopted to present and analyze the monitoring data from measurements of total station. Associated with the advanced least squares techniques using the free network adjustment solution, two total stations could be installed in the influence zone of each tunnel (i.e. upward and downward tunnels) without further concern about the impact from instability of the equipment and could still possibly obtain reliable monitoring results. In order to improve the accurate measurements of the whole system for each tunnel, the two 360° prisms were installed in the deformation zone while the four benchmark (BM) points were set outside the movement zone. The initial results of real-time monitoring for the existing twin tunnels movements are also presented herein to further confirm that this reliable and cost-competitive monitoring method using least squares adjustment could be highly recommended to apply in engineering practice.
