Influence Zones in Alluvium Over Dip‐Slip Faults

Tests were performed on dense and loose sand in a glass‐walled fault test box to investigate the shapes and locations of failure surfaces that may occur in alluvium overlying active dip‐slip faults. The experimental procedure is reviewed and the results of the tests with reverse and with normal movements along the bedrock faults are presented. Based on the experimental results, a simple model is developed to predict the shapes and locations of failure surfaces in the soil. These are determined as a function of the depth of the soil, the angle of dilation for the soil, and the dip angle of the fault. The conditions for development of a graben structure, as observed during normal movement on the bedrock fault, are also determined. The emphasis of the study is on the mechanics of deformation and failure in cohesionless soil above dip‐slip faults in relation to principles of soil mechanics. The simple model is also evaluated in relation to real field conditions.