A model for rock mass bulking around underground excavations.

摘要

The volume increase of stress-fractured rock near an excavation results from three sources: (1) dilation due to new fracture growth, (2) shear along existing fractures or joints, and most importantly, (3) dilation due to geometric incompatibilities when blocks of broken rock move relative to each other as they are forced into the excavation. This dilation process is called Rock Mass Bulking, and is quantified by a Bulking Factor, defined as the percentage increase in radial deformation due to fracturing inside the failure zone extending to a depth of failure (d_f).; To develop a model for the calculation of the Bulking Factor ( BF), it is necessary to consider two options: (1) develop a non-continuum theory for rock mass behavior, or (2) adapt continuum mechanics principles to the problem and introduce an empirical component to calibrate the model. In this thesis, the second approach is adopted. A semi-empirical Rock Mass Bulking Model was developed, using as starting concepts dilation angle, plastic strain rates, effective deformation modulus, effective Poisson's ratio, Griffith locus, and the definition of BF introduced by Kaiser et al. (1996). The model was calibrated in order to obtain BFs in accordance with experimental data, and case studies were used to account for bulking around underground excavations. (Abstract shortened by UMI.)