Original scientific paper

Independent Astronomic Control of the External Geodetic Network above the Tunnel ''Mala Kapela''

Nikola Solarić ; Faculty of Geodesy, University of Zagreb, Zagreb, Croatia
Drago Špoljarić orcid.org/0000-0002-6979-5222 ; Faculty of Geodesy, University of Zagreb, Zagreb, Croatia

Abstract

The paper describes the automated control of the external geodetic network above the tunnel "Mala Kapela" and possible increase of accuracy in tunnel cutting especially if the sides for the orientation of traverses used for entering in the tunnel are short and steep.
Independent astronomic controls of geodetic networks above tunnels applied so far have had only the astronomic azimuth determined in automated manner. The components of vertical deflection have been computed out of topographic masses or geoids, which is more inaccurate than the components determined in astrogeodetic measurements. In autumn 2003, the automated astronomic control of GPS networks above the 6 km long tunnel "Mala Kapela" has been applied on the whole for the first time.
After cutting the tunnel, the obtained transversal deflection from the axis was 1.0 cm.
Considering the influence of vertical deflection, the transversal deflection runs up to 0.2 cm. If the sides for the orientation of traverses used for entering in the tunnel were e.g. 30° steep, and the azimuths of sides were 144°, the influence of vertical deflection would be 20.2 cm. Such a significant deflection from the axis would cause additional expenses for concreting two tunnel tubes amounting up to approximately 1 800 000 US$. Hence, if we taken the deflection of the vertical into consideration, we can reduce the additional concreting expenses. The Ordinance on Technical Standards for Design and Construction of Tunnels in the Republic of Croatia allow large tolerances in cutting the tunnels, which might cause additional financial costs. We could reduce the tolerances allowed today, if we would apply the additional independent astronomic control in the determination of tunnel cutting direction, and take the deflection of the vertical in consideration.

Keywords

Independent control of external geodetic network above tunnels; automated determination of azimuth; automated determination of astronomic latitude and longitude

Hrčak ID:

2308

URI

https://hrcak.srce.hr/2308

Publication date:

14.3.2005.

Article data in other languages: croatian

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