Ground reaction analyses in conventional tunnelling excavation

Based on the axial symmetrical plane strain assumption, given that the rock mass satisfies the Mohr–Coulomb failure criterion and exhibits strain-softening behavior, this paper represents two categories of theoretical methods for ground reaction analyses in conventional tunnelling excavation. They distinguish from each other according to their treatments for plastic strain: one is the simplified method in terms of total plastic strain (i.e. does not consider the unloading process of ground), the other is the rigorous method in terms of incremental plastic strain (i.e. takes the unloading process into account). Although the philosophies of these two categories of theoretical methods have been proposed by former researchers, the discrepancy between them has never been noticed and reported. Through case studies, this paper highlights the discrepancy quantitatively, estimates the maximum error caused by the simplified method, and further discusses their applicability.