A Simple Solution and Dilatancy Characterization for a Circular Tunnel Excavated in the Nonlinear Strain-Softening and Nonlinear Dilatancy Rock Mass

Tunnel opening or excavation in the strain-softening rock masses primarily leads to initial stress release and deformation. The increasing plastic shear strain induces a nonlinear variation of dilatancy masses. Therefore, tunnel stability is strongly dependent on state behaviors In view this, this paper proposes an elastoplastic finite difference solution based triple-shear element (TS) unified strength criterion (USC) nonassociative flow law; thereafter, some typical examples are referred verify its validity. This allows for description intermediate principal effect, mass. Parametric analysis finally determines influence characteristics effect (b), critical softening parameter ( η ∗ ), factor (δ), support force (pi) dilation angle (ψ) mass zone. findings confirm that mainly affects peak values ψ, which increases as b grows. rate change ψ depends id="M2"> , tends be slower with id="M3"> . pattern residual zone under different δ generally consistent, while variability significant. For given behavior mass, developed form independent pi.