| Although much attention has been devoted to understanding the dynamic response of earth embankments to seismic loadings, relatively little effort has been devoted to improving our understanding of fault rupture propagation through soils. It would seem appropriate to first review case histories which describe how earth dams respond to base rock fault displacements. Unfortunately, however, few well-documented case studies exist for this special case. Geologic studies of fault rupture, however, do provide insights into how soils respond to fault movements. Because the case histories available exhibit variability due to the complexities of the geologic materials and processes involved, previous investigations involving physical model tests and numerical analyses of this class of problem have also been reviewed.;This study presents the results of a program of base deformation testing using 1 g small-scale models composed of a weak saturated clay mixture. A 3:1 mixture of kaolinite and bentonite produces a material with undrained shear strengths on the order of 10-100 psf and well-scaled stress deformation behavior for small-scale model testing without the need for a centrifuge apparatus. The 1 g small-scale models tested demonstrated failure behavior in close agreement with that observed in the field. It was found that the height of the shear rupture zone in the soil above the base rock fault rupture was controlled primarily by the amount of base movement and the stress-strain behavior of the soil (particularly, the axial failure strain of the soil).;The results from numerical analyses suggest that the finite element method can be successfully applied to this class of problem provided that the soil's nonlinear stress-dependent stress-strain behavior is adequately modeled. Linear elastic and linear elastic-perfectly plastic constitutive models produced inconsistent results, but nonlinear models provided significantly better predictions of observed behavior. The results of these studies have led to the development of analytical techniques for modeling fault rupture propagation through overlying clays and recommendations for design provisions to minimize the resulting potentially adverse effects on dam integrity. |
