For infrastructure projects with shallow overburden a comprehensive geotechnical monitoring program and its implementation in the daily operation is essential for a successful and safe completion of the works. A continuous control of both the tunnel and the surface according to the observational method within a strict geotechnical safety management is one of the most challenging tasks for such projects. The paper gives a short overview about the geotechnical design and monitoring at the large OeBB railway project Lainzer Tunnel lot LT 31 in Vienna/Austria. Two case histories shall illustrate the implementation of the geotechnical safety management.

1 Introduction

Core of the OeBB Lainzer Tunnel project with 12.8 km is lot LT31, having a length of 3.6 km, where residential areas and major traffic infrastructure are situated along the tunnel route (see Figure 1).

The tunnel was constructed as a double-track tube with an excavation cross-section of about 130 m2 using NATM. Due to the hydrogeological conditions dewatering and groundwater relaxations in advance to the excavation were necessary. Excavation started from the shafts at "Klimtgasse" and "Lainzerstraße" in both directions. 2/3 of the tunnel alignment follows a major railway line ("Verbindungsbahn") under operation. The overburden ranges from approx. 6 m (southern part) to 26 m in the soft ground sections and to approx. 55 m (western part) in the bedrock region. Due to the difficult geotechnical conditions and the potential direct impact of the project activities on the public, a Geotechnical Safety Management Plan (GSMP) including a comprehensive monitoring concept was established and strictly followed (Moritz et al. 2011).

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