Influence of Given Parameter Errors on Accuracy of Tunnel Breakthrough by Height

Abstract

There are two types of geodetic 2D and 1D networks for tunnel construction: overhead and underground. The purpose of these networks is to perform tunnel stake out with allowable deviation in transverse, longitudinal and height terms. Overhead network is developed before a tunnel is built and it connects entry and exit portal into a unique system. Underground network expands during tunnel construction. When evaluating the coordinates of newly assigned underground network points, previously established points are considered as given points. In order to realistically estimate the accuracy of underground network, it is necessary to include all previous measured quantities in the adjustment, and to define a minimum trace at all points. With this approach, estimated coordinates of network points would change each time when network is extended. To avoid this problem, when estimating new points, errors of given parameters must be taken into account. In the example of the Tunnel Vežešnik in Montenegro, when designing a 1D underground network, a case was reviewed when previously established points were taken as given and when their error was considered. To validate this procedure, an accuracy calculation was applied only when the overhead network points were defined as given. The network quality criteria were compared for all cases and it was shown that errors of the given parameters must be taken into account.