Tunnel stress analyses in 3-D using equivalent continuum and discontinuum procedures

Deformation and stability around a tunnel in a limestone rock mass is investigated using both (a) an equivalent continuum/discontinuum model and (b) a fully discontinuum model through three-dimensional stress analyses. In model (a), the Representative Elementary Volume (REV) mechanical properties estimated in a previous paper are used to represent the combined behavior of intact rock and 4 of the 5 fracture sets that had significantly smaller sizes compared to the fifth fracture set (bedding planes). To this system, the bedding plane fractures were added according to its statistical geometric properties. In model (b), all 5 fracture sets were generated according to the obtained fracture geometry statistical models. Using model (a), effect of several factors, such as REV property values, bedding plane modeling method, the average horizontal stress to the vertical stress and tunnel depth, on the geotechnical behavior around the tunnel was studied in detail. A comparison is made between the stress analyses results obtained through the aforementioned two models.