Determination of internal pressure for the stability of dual elliptical tunnels in soft clay

ABSTRACT

The stability of dual elliptical tunnels in soft clay has been investigated by using lower bound finite element limit analysis with second-order conic programming (SOCP). A uniform compressive normal pressure (σ_i) is required to apply at the tunnel periphery with the help of lining or anchorage system to maintain the stability. The magnitude of compressive pressure (σ_i) is determined in the form of normalised pressure (σ_i/c_u0) for different combinations of D/B, H/B, S/B, γB/c_u0 and m, where H refers to soil cover depth, B and D refer to width and height of an elliptical tunnel, respectively, γ is unit weight of soil, c_u0 is the undrained shear strength at the ground surface and m is the normalised rate at which the undrained shear strength of the soil increases linearly with depth. The results are presented in the form of dimensionless charts expressing the effect of S/B on the magnitude of σ_i/c_u0 for different values of D/B, H/B, γB/c_u0 and m.

KEYWORDS:

• Dual tunnels
• stability
• finite element
• limit analysis
• SOCP

Disclosure statement

No potential conflict of interest was reported by the authors.