Stability investigations around a mine tunnel through three-dimensional discontinuum and continuum stress analyses

To exploit an underground mine effectively and safely, it is important to have a good understanding of the geotechnical behavior around the underground excavations made in the mine. The aim of this study was to investigate the geotechnical behavior around a tunnel excavated in a metal mine in China at the three-dimensional level. Using the information available on lithology, geological structures, in situ stress measurements, physical and mechanical properties of intact rock, discontinuities and interfaces between different rocks, a three-dimensional numerical model was built by using the 3DEC software package to simulate a tunnel excavation under a high in situ stress condition. Effect of the discontinuity network, possible intact rock and discontinuity parameter variability, representation of rock masses as discontinuum or equivalent continuum material and rock support system on the deformation, and stability around the tunnel was investigated. A very good agreement was obtained between the collected field deformation monitoring results and the results of the conducted numerical stress analyses.

► Discontinuity presence increased maximum tunnel deformations by 2.4–4.4 times.
► 20–30% variability of rock properties produced 57–126% variability on deformations.
► A good comparison was obtained between the discrete and continuum based results.
► Rock support decreased the rib and roof deformations by 43–51% and 29–39%.
► The monitored field deformations compared very well with the numerical results.