Evaluation of traditional deformation limits for segmental tunnels in soft soils

Abstract

The aim of the research reported in this paper was to evaluate the recommendations commonly used for limiting the deformations of segmental reinforced concrete tunnels built in soft soil. These traditional deformation limits are empirical and do not consider the slenderness ratio or soil-pressure distribution around tunnels. Furthermore, while they are generally assumed to relate to the serviceability limit state, this is not clear. Parametric analyses were therefore performed by means of finite-element models in which the non-linear behaviour of joints and materials was taken in account. The serviceability deformation was defined to prevent typical problems that could jeopardise the serviceability states of segmental linings. These serviceability deformations were then compared with traditional deformation limits. The results showed that the serviceability deformation depends on the slenderness ratio and the soil-pressure distribution. It was concluded that empirical recommendations are only suitable for certain slenderness ratios and soil-pressure distributions.