A compact blowout model for shallow tunnelling in soft soils

Tunnelling in soft soil conditions, especially with a shallow overburden, faces the risk of face instability due to blowout. Although several blowout models have been proposed to estimate the blowout pressure, mostly based on limit analysis or limit equilibrium, there is a significant gap between the allowable blowout pressures predicted by...

Structural design model for tunnels in soft soils: From construction stages to the long-term

In bored tunnel design, most recent structural design models for tunnel linings concentrate on the behaviour of the tunnel lining in the long-term. The load on the tunnel lining in these models is derived from the original soil stresses, often simplified for a single homogeneous layer. Field observations show that higher loads may occur in...

Structural analysis for shallow tunnels in soft soils

Generally, studies on structural design for bored tunnels focus on moderate to deep tunnels (cover-to-diameter ratio C/D ≥ 2). Such tunnel design methods cannot be used for shallow-situated bored tunnels because the influence of buoyancy is discounted, and actual loads on the tunnel lining are not taken into account properly. This paper...

Volume loss in shallow tunnelling

Reducing the cover-to-diameter ratio for shallow tunnels in soft soils

Despite the fact that shallow tunnels have the benefits of low short-term construction costs and long-term operational costs primarily due to the shallow depth of the station boxes, the limited understanding of shallow tunnelling in soft soils is an obstacle to the development of shallow tunnels in urban areas. This study carries out a...