Analysis of elastoplastic solution of tunnel surrounding rock pressure considering intermediate principal stress and rock dilatancy under groundwater seepage

Abstract

When calculating the surrounding rock pressure of a deep tunnel in watery strata, the effect of seepage pressure caused by ground water is usually underestimated, this occasionally results in poor tunnel lining design and durability. In order to study the interaction between surrounding rock and deep tunnel support under groundwater seepage, the intermediate principal stress is introduced in Drucker-Prager yield criterion, and non-associated flow rule is adopted as well as the dilatancy effect of surrounding rock is also considered. The elastoplastic pressure and deformation laws of surrounding rock and tunnel support at greater depth are analyzed using theoretical derivation and numerical simulation. In addition, the influence of the important parameters involved in the theoretical analysis on the plastic zone of surrounding rock is discussed. The results show that the analytical solution is strongly consistent with the results obtained from numerical simulation; Considering groundwater seepage, the calculation method in which intermediate principal stress is considered has a non-negligible influence on the elastoplastic solution of the surrounding rock pressure; Three important factors including permeability coefficient, internal friction angle as well as seepage pressure reduction factor play a dominant role in determining rock pressure and plastic zone around deep tunnel due to groundwater seepage. The work presented in the paper enriches the elastoplastic theory to analyze surrounding rock pressure applied to deep tunnel under seepage conditions in watery strata, and is beneficial to further explore the interaction between surrounding rock and tunnel support in water-rich strata.