Numerical Simulation Of The Rockburst Process In The Circular Tunnel Surrounding Rock Based On Stress Criterion And Effects Of Parameters

Using with shear failure and tension cut-off compound of strain-softeningMohr-Coulomb constitutive model. In numerical simulation, a circular tunnel isexcavated after the plane strain model has reached a static equilibrium state.To clear figure out whether elements occurred rockburst in the model, rockburstcriterion proposed by Xu and Wang is introduced to assess the distribution of rockburstsin the surrounding rock at the typical timesteps, and tangential stress of a row ofelements in the surrounding rock is monitored. The tangential stress rockburst criterionproposed by Xu and Wang is used to determine the state of elements. Numerical resultsshow that the angle between the line (linking the V-shaped notch tip and the centralpoint of the tunnel) and the horizontal axis of the tunnel increases to45°from that lessthan45°as the horizontal stress is increased. As the horizontal stress increases, thenumber of failed elements and that occurring rockburst increase and the peak tangentialstress is increased. At higher post-peak brittleness of rock, shear bands become apparent,forming the V-shape notches easier; the number of failed elements and that occurringrockburst increase; the distance between the peak tangential stress and the tunnelsurface is increased.To clear figure out whether elements occurred and the level of rockburst moreaccurately in the model, the rockburst criterion proposed by Gu and Tao is introduced toasses the distribution of rockbursts in the surrounding rock at every timestep. Rockburstprocesses of the surrounding rock of a circular tunnel at different diameters anddilations are modeled. Analyzed and discussed the influence of different diameters anddilations to the level of rockburst and the distribution of tangential stress of monitoredelements in the surrounding rock. Numerical results show that the number of elementsoccurring different magnitudes of rockbursts are increased and the fluctuation oftangential stress distribution increased obviously as the diameters of tunnel is increased.The higher dilations, the rockbursts notches are formed, the shear strain incrementextends to internal surrounding rock more difficultly, and the fluctuation of tangentialstress distribution is less obvious.