Failure morphologies in grouted and ungrouted double fissured specimens: experiments and SPH simulations

Abstract

To reveal the mechanisms associated with the fracture of grouted and ungrouted double-fissured rock masses, crack propagation of double-fissured rock masses with different dip angles α is studied by combining experiments and numerical simulations. Rock-like samples are produced through sand-based three-dimensional printing technique, and grouted/ungrouted double-fissured models were constructed through cement grouting. Uniaxial compression experimentation and DIC technology are adopted to evaluate the damage modes and stress-strain properties. A modified particle-based model was established by embedding a particle failure treatment method into SPH method, which reproduces the crack evolution process and is validated against experimental results. The research indicates that mechanical responses of specimens are highly consistent with that of natural sandstone, enabling effective simulation of rock mass properties. Modified SPH method is able to precisely capture interface debonding between grout and rock mass as well as the dynamic crack evolution. For ungrouted specimens, with the rise in fracture dipping angle, the crack initiation position shifts from the middle of the fissures to the outer tips, forming “wing cracks”, and the inner tips tend to directly coalesce. After grouting, peak strength significantly enhanced (with the maximum improvement of 126.9% at α = 0°), the concentrated stress effect is diminished, the crack path transitions to passing the grout, the localized tensile stress zone moves from fissure tips to the interior of the grout. The present research offers experimental and numerical fundamentals for elucidating the mechanical response of grouting-reinforced double-fissured rock masses, meanwhile provides important reference value for stability control in rock engineering.