Equivalent mechanical model for post-peak behaviors of deep soft rock and numerical computation

Based on the continuum theory, quantitative GSI rock rating system and Hoek-Brown strength criterion and by using the FLAC^3D program as the development platform, the conventional plastic model and strain-softening model are adopted to comparatively analyze the spatial excavation surface effect curves of deep rock. Combined with engineering design and field applications of deep shaft support, numerical validation is performed. The equivalent strain softening model for jointed soft rock reflecting attenuation of the post-peak strength parameters shows that: the post-peak behaviors of rock mass are dominated by quality grade and confining pressure, and during unloading after the peak, the process of softening parameter is not a constant value and varies with the size of the confining pressure. By computing the excavation face spatial constraint response curves of deep soft rock, the calculated results based on Mohr-Coulomb and Hoek-Brown criterion ideal elastoplastic models are basically the same. The results of the elastoplastic model are quite different from those of the strain-softening model, mainly in the middle range of geological indices. Practical application shows that the equivalent strain softening model for jointed rock more truly reflects the post-peak mechanical behaviors of the deep soft rock, and furthermore, the link between the geological strength indices and the continuum theory is established for engineering applications so as to provide a reference for similar projects.