Implementation of a nonlinear elastoplastic model for tunneling in sandstone

The most active infrastructure constructions for transportation take place in the western Taiwan due to dense population. Hillside development is a vital issue for urban planning. Adequate understanding of sedimentary rocks, e.g. sandstone, mostly weak rock, plays an important role in the construction of tunnels; therefore, properly evaluating deformation of rock is essential. To mimic the deformation characteristics of sandstone, such as shear stress and volumetric strain coupling behavior, a nonlinear elastoplastic model based on the theory of Green elasticity and generalized plasticity has been implemented into finite element code ABAQUS through user-defined subroutine UMAT. A series of triaxial tests of a single element are first simulated to verify the model. After the verification, excavation of a tunnel is simulated under plain stain condition. This study concludes that the model is capable of describing the deformation characteristics of tunnel excavation in sandstone and provides a valuable tool for future engineering practice.