ABSTRACT
The upcoming boring of the North-South metro line in Amsterdam (Netzel & Kaalberg 2000, Kaalberg et al. 2005) will involve TBM excavation close to the pile tips of the wooden piles on which much of the historic inner city is founded. The influence of a volume loss due to tunnelling on the bearing capacity of these piles is relatively uncertain and hard to quantify even by numerical means (Broere & van Tol 2006). This prompted a different approach, to visualise the influence of volume loss on the stresses around the pile tips using the photo-elastic method. Photoelasticity has been used extensively to quantify stresses in homogeneous materials (e.g. Frocht 1948). And is extended to particle assemblies in index matching liquids by Drescher (1976).
