INTRODUCTION
A correct understanding of the mechanical properties of jointed rock masses is vital to arrive at safe and economical designs for structures built in and on rock masses. Due to the presence of joints, jointed rock masses show anisotropic and scale (size) dependent mechanical properties. At present, satisfactory procedures are not available in the rock mechanics literature to estimate anisotropic, scale dependent deformability properties of jointed rock. The study described in this paper was aimed at making a contribution in this direction.
NUMERICAL PROCEDURE
The numerical technique used for this study has emerged from a linking between joint geometry modeling schemes [1] and a distinct element method [2]. A previous paper provides the details of the technique, as well as the material parameter values used for this study [3]. Using the technique, each rock block (cube of side dimension 2 m) having a different generated joint configuration was subjected to stress analyses (a) to estimate the moduli of deformation along the directions normal to the three perpendicular planes and (b) to estimate the shear moduli on the three perpendicular planes.
RESULTS
Relationships between deformability parameters of jointed rock and joint geometry parameters such as joint density, joint size/block size and joint orientation are shown through 3D plots (for example, see Fig.l). In Fig. la, Ev and Ei denote the rock mass deformability modulus in the y direction (at a certain stress revel) and the intact rock Young's modulus, respectively. In Fig.1 b, Gxz and G i denote the rock mass shear modulus on the xz plane (at a certain stress level) and the intact rock shear modulus, respectively. These plots show clearly the possibility for the rock mass deformability parameters to reach REV (representative elementary volume) or equivalent continuum behavior with increasing values of joint density (number of joints/vol) and joint size/block size. Relationships are developed between deformability properties of jointed rock and fracture tensor [4] parameters (Figs. 2 and 3). Fig. 2 shows the possibility of obtaining a unique relationship between the rock mass deformability modulus (Em) in any direction and the fracture tensor component in the same direction. Fig. 3 shows the possibility of obtaining a unique relationship between the rock mass shear modulus (Gm) on any plane and the summation of the fracture tensor components on that plane. These two plots also show the possibility of obtaining REV behavior. Also, it was found that the anisotropy of the rock mass deformation modulus in 3D can be represented through an ellipsoidal relationship for the cases dealt with in this study [5].
