Bearing capacity of cohesive-frictional soils with multiple tunnels

The ultimate bearing capacity and the failure mechanism of cohesive-frictional soils with the inclusion of dual tunnels have been theoretically and numerically investigated assuming plane strain conditions. A continuous loading is applied to the ground surface. For a series of tunnel geometries, shapes and material properties, rigorous lower and upper bound solutions for the ultimate bearing capacity of the considered soil mass are obtained by applying recently developed numerical limit analysis. For practical suitability the results are presented in the form of dimensionless stability charts. As an additional check and also a handy practical means, several upper bound rigid block mechanisms for dual tunnels have been developed and the predicted collapse loads were compared with the results from numerical limit analysis.