Abstract

The term ‘characterization’ will be used to describe methods of collection and interpretation of the physical attributes of the joints and other discontinuities, in other words those which control their mechanical and hydraulic properties, and the behavior of jointed rock as an engineering medium. Rock discontinuities vary widely in terms of their origin (joints, bedding, foliation, faults/shears, etc.) and associated physical characteristics. They can be very undulating, rough or extremely planar and smooth, tightly interlocked or open, filled with soft, soil-type inclusions or healed with hard materials. Therefore, when loaded in compression or shear, they exhibit large differences in the normal and shear deformability and strength, resulting in surface separation and therefore permeability. Such variability calls for innovative, objective and practical methods of joint characterization for engineering purposes. The output must be quantitative and meaningful and the cost kept at reasonable levels. The practical methods to be described will be biased in the direction of quantifying the non-linear shear, deformation and permeability behavior of joints, based on the Barton-Bandis (BB) rock engineering modeling concepts. The term ‘modeling’ will be used to introduce the basic stress-displacement-dilation behavior of joints in shear, and the basic stress-closure behavior when joints are compressed by increased normal stress. These are the basic elements of the (non-linear) behavior, which are used when modeling the two- or three-dimensional behavior of a jointed rock mass. They are the basic BB (Barton-Bandis) components of any UDEC-BB distinct element numerical model (used commercially and for research since 1985). The BB approach can also be used to determine improved MC (Mohr-Coulomb) strength components for a 3DEC-MC three-dimensional distinct element numerical model. In other words for acquiring input at the appropriate levels of effective stress, prior to BB introduction into 3DEC, believed to be a project underway. Due to space limitations, constant stiffness BB behavior of rock joints is given elsewhere.