Numerical modeling for rockbursts in circular tunnels using a nodal-based continuous-discontinuous deformation analysis method

As a complex phenomenon induced by underground excavation, rockburst poses a severe threat to the construction and operation of deep tunnels. Since rockburst involves dynamic response of large deformation and rigid movement, discontinuum-based numerical schemes are more suitable for assessing rockburst risks. By enhancing mesh generation and contact modeling, a node-based continuous-discontinuous analysis (NCDDA) method is presented for assessment of rockburst. Indestructible and destructible regions are introduced to divide computational domains to model failure of jointed rock masses and reduce computational costs. The indestructible region merely involves continuum modeling, while joint elements with a bilinear constitutive relation are used to model failure of the destructible region. Contact model based on the contact potential is used to further enhance the computational performance. Introducing the viscous boundary and element deactivation technique, dynamic processes involving large deformation, failure and fracturing induced by tunnel excavation can be simulated by the NCDDA efficiently and accurately. Benchmark simulations verify capability of the NCDDA in modeling dynamic and quasi-static response, rock fracturing and rockburst. Influences of strength parameters and exposed structural planes on the rockburst occurrence time and zone are also investigated. Simulations show that internal friction and cohesion rank the first and second most influential factors. As the internal friction increases, rockburst occurrence delays and rockburst zone expands. Structural planes can result in rockburst in advance. The less the dip angle, the earlier the rockburst occurrence. Rise rate of the consumed energy in breaking joint elements is mainly influenced by the internal friction.