Numerical simulation of tunnel construction in volcanic rocks

For the design of tunnels, numerical simulation plays an important role. In general 3-D analyses are required and with currently available domain based methods such as the Finite element method the effort is considerable. In this paper the numerical simulation of tunnel excavation using an alternative approach to the FEM, which results in an order of magnitude increase in efficiency and user friendliness, will be discussed. The method of analysis is the less well known Boundary Element Method (BEM), which has not been used for tunneling to date because of the inability of available programs to consider sequential excavation, heterogeneity and non-linear behavior. The new program, developed within a European research project, has the capability to deal with these aspects and can be applied to tunnel design. An example of analysis is presented where a tunnel is excavated near a preexisting cavity, a situation that can occur in volcanic rocks. It is shown that the BEM has distinct advantages over domain based methods.