Obstacle Investigation RandstadRail in Rotterdam, The Netherlands

Abstract.

RandstadRail is a light rail project connecting the cities of Rotterdam, The Hague, and Zoetermeer in The Netherlands. Part of the project is the connection of the Rotterdam metro system to an existing railway line. This section is called the ‘Statenwegtracé’, 3 km in length of which 2.4 km will be realised by two single track bored tunnels. Halfway a new underground station will be built. Part of the integral design was an extensive underground obstacle investigation programme carried out by the Engineering Department of Rotterdam, Public Works. The goal of the obstacle research was to assess the type and extent of subsurface objects along the alignment in general and more specifically in the bored tunnel sections. This in order to minimize the risks caused by subsurface obstacles and take preliminary actions against such an event. As part of the obstacle investigation a desk study was performed which included historical research in public and private archives. For two locations where foundation remnants were identified, an 18^th century steam driven pum** station and an 19^th century gas factory, this resulted in additional field-investigation consisting of geophysical techniques and “blind” cone penetration tests. A tailor made design philosophy was adopted because of the presence of wooden piles in the bored tunnel alignment. Both cases and design solutions are presented in this paper and will be concluded with recommendations of how to deal with obstacle investigation during the design process of large line infrastructure projects.