ABSTRACT
The application of computational limit analysis to the stability of shallow tunnels has been pioneered by Sloan & Assadi (1992) who investigated the stability of a plane strain tunnel in a cohesive soil with shear strength varying linearly with depth using linear programming techniques. The stability of the tunnel was described conveniently by two load parameters ( ) / uc 0 and γ D cu/ 0. Lyamin & Sloan (2000) considered the stability of a plane strain circular tunnel in a cohesive-frictional soil. The nonlinear programming technique
1 INTRODUCTION
The accurate assessment of the stability of foundations above shallow tunnels is a very important task due to the increasing demand on construction of buildings and tunnels in urban areas. Unfortunately, no generally accepted design or analysis method is available at the moment to evaluate the ultimate bearing capacity of cohesive-frictional soils with shallow tunnel inclusions. The design of tunnels for roads and railways often utilize separate tunnels to carry traffic in opposite directions. Also, in the expansion of underground transportation systems new tunnels have recently been designed and then constructed near existing tunnels. In practice, it is often seen that the construction of dual circular tunnels is a better option than a single large circular tunnel.
