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...

Correlation between the kinematics of a Tunnel Boring Machine and the observed soil displacements

Constructing tunnels in soft soil with the use of Tunnel Boring Machines (TBMs) may induce settlements. A considerable amount of the total soil displacements is correlated with the passage of the TBM-shield. Even so, the TBM-induced soil displacements are so far only coarsely correlated to the total settlements. This paper relates the shield...

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...

On the face support of microtunnelling TBMs

Face stability of microtunnelling TBMs is an important aspect for a safe and controlled project execution. Lack of proper face support can lead to sudden collapse with resulting large settlements. Guidelines for minimal and maximal support pressures in most codes do not take the infiltration of bentonite suspension in coarser soils into account....

Tunnelling in Soft Soil: Tunnel Boring Machine Operation and Soil Response

Constructing tunnels in soft soil with the use of Tunnel Boring Machines may induce settlements including soil movements ahead of the face, soil relaxation into the tail void, possible heave due to grouting, long lasting consolidation processes, and potentially several other mechanisms. A considerable amount of the total soil displacements seems...