EXPERIMENTS ON SURFACE DEFORMATION ARISING FROM A SUBSURFACE FRACTURE

Laboratory model simulation of large-scale earth processes is rarely u ndertaken because of scale effects, nonlinearity, and questions of rep resentativeness with respect to the real case. Hydraulic fractures gen erate distortion fields that can be measured with high precision both in the laboratory and in the field. A combination of field and laborat ory data allows us to test our ability to measure displacements, make forward predictions, and invert real measurements; thus it is importan t to have some means of simulation, other than purely numerical simula tion. This paper contains the results of a set of experiments on the s urface deformation arising from a pressurized fracture, using laser ho lography and Fizeau interferometry of noncontacting techniques to prec isely sample the displacement field above a scale model. The results a re remarkably accurate and consistent, and compare reasonably well wit h analytical and numerical model predictions. The techniques have pote ntial applications in geomechanics and geotechnical engineering for la boratory study of various linear and nonlinear problems.