MODELING OF ROCK MASS DISCONTINUITIES FOR DEFORMATION ANALYSIS (MESH GENERATORS, INTERPENETRATION, JOINT BEHAVIOR, BLOCK THEORY)

This work investigates a problem central to interpretation of displacement measurements in a blocky rock mass. The geometry of a typical rock mass frequently can be treated as a collection of separate blocks tightly fitted into a three-dimensional mosaic. The stability of an excavation in rock depends on: the geometry of individual blocks and the interaction behavior between them. Although numerical methods have the capability of describing the stress-strain distributions in rock with limited discontinuities, it is neither feasible nor highly reliable to perform a full numerical analysis on blocks in a discrete system using a continuum approach. The displacement field is usually too large. Before the modes of failure can be evaluated, there must be a clear understanding of which instability-initiating block regions need to be analyzed. Subsequent analysis can then show how the deformation mechanisms of individual blocks will influence the overall mode of failure for the entire system. Identifying the instability-initiating blocks from excavation trace maps can be done using block theory. Analyzing the deformation mechanisms can be done using discontinuous deformation analysis (DDA).;Developed from the kinematics of deformation, is a generalized 2nd-order displacement equation for the motion of an arbitrary point within a block. It includes the 2nd-order bending, stretching, torsion, etc. behaviors contributing to large displacements in a finite-rotational deformation field. The relationships between block boundaries are developed using non-planar block faces. Using both types of non-linearities ties surface curvature to 2nd-order block deformations. The developed relationships are used to constrain block edges from numerical interpenetration during the solution phase of the DDA model. From measured displacements it is then possible to determine which discontinuities have open or closed, and which blocks have slid or strained based on a best fit to the displacement equation.;The new analytical method introduced by this work provides a sound basis for untangling behavior modes of a rock mass from an array of displacement measurements. It has a place in engineering and mining for understanding: the stability of open excavations; support of underground shafts, tunnels and chambers; the retrievability of nuclear waste packages; caving operations for mineral extraction; stability of openings under high level dynamic blasts; and load transfer mechanisms in natural arching environments. Because the analysis is general, it is easily coupled to existing stress-strain analyses such as finite element or boundary element methods.