Date of Award

1-2025

Degree Name

MS in Civil and Environmental Engineering

Department/Program

Civil and Environmental Engineering

College

College of Engineering

Advisor

Robb Moss

Advisor Department

Civil and Environmental Engineering

Advisor College

College of Engineering

Abstract

The behavior of soils during surface fault rupture is a serious concern in the planning and design of infrastructure that may be located within or near a fault zone. Challenges associated with developing mitigation measures for surface fault rupture include the uncertainty of fault rupture and the variability of fault behavior. Current analytical procedures define surface fault rupture according to the type of fault movement (strike slip, normal or reverse), the amount of displacement on the fault, and the mechanics of the material overlying the fault. The purpose of this thesis is to reconfirm analytical solutions and gain a better understanding of the mechanics of dip slip surface fault rupture. Specifically, this study focuses on analyzing the influence of soil density/stiffness and fault angle on rupture propagation and distributed surface displacements. While direct experimental results are not obtained, a constructed fault box and planned trials inform a framework for predicting the outcomes of these trials using existing literature. These prior studies provide a basis for forecasting the surface deformation patterns and propagation behavior that the planned trials would have revealed, offering valuable insights into fault rupture mechanics. The fault box, a 2-meter-long by 0.5-meter-wide fault box filled with 0.45 meters of Monterey #2/16 sand, was designed to examine the factors that influence the rupture propagation of alluvial soils overlying dip slip faults. The faulting apparatus consists of a scissor jack mechanism that replicates basal displacement by moving one half of the box relative to the stationary half at interchangeable fault angles. Planned trials involved using Monterey #2/16 sand prepared configurations of dense, loose, and layered loose-over-dense material to represent different geological conditions. In these planned experiments, ruptures would be driven until a clear shear band developed in the overlying sand and reached the surface. By synthesizing findings from prior studies, this research predicts that dense sands create concentrated shear bands with larger surface displacements and distinct surface ruptures, while loose sands result in more diffuse deformations over broader shear bands with less defined surface expressions. Additionally, shallow fault angles result in broader deformation zones, as the lower angle directs stress over a wider area. In layered soil configurations, density contrasts further influence deformation patterns, with transitions between layers influencing the extent and localization of surface displacements. These findings demonstrate that fault orientation and soil density control the nature of surface fault rupture.

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