ORCID

https://orcid.org/0009-0005-8642-6428

Keywords

DEM, Critical State, Granular Material, Pile Driving, Bonded-Particles

Subject Categories

Civil Engineering | Geological Engineering | Mechanics of Materials

Abstract

This thesis investigates the use of the Discrete Element Method (DEM) to study two complementary aspects of granular soil mechanics: critical state behavior of granular materials and dynamic response of driven piles in sand, both of which are governed by the same particle-scale mechanisms of dilation, contraction, and fabric evolution.

The first examines the critical state behavior and fabric anisotropy of granular soils through DEM simulations of direct shear, direct simple shear, and true triaxial tests. Sphere-cluster particles representative of a uniform sand are used in two assemblages of approximately twenty-five thousand and one hundred twenty-five thousand spheres to evaluate particle quantity effects across a range of relative densities and confining pressures. The simulations show convergence to a unique critical state line in both deviatoric stress versus mean effective stress and void ratio versus mean effective stress spaces, independent of initial density, loading path, and particle quantity. Maximum dilation angles follow a linear relationship with relative density consistent with empirical correlations, and contact-normal and particle-orientation fabric anisotropies converge to stable critical-state values, supporting the existence of a unique critical-state fabric.

The second study presents a three-dimensional DEM framework for dynamic pile driving in a layered sand deposit. The pile is represented with a bonded-particle model and the soil with sphere-cluster particles refined near the pile-soil interface. Centrifuge scaling is employed to reproduce prototype stress levels in a reduced-scale numerical model. The framework reproduces one-dimensional wave propagation along the pile, force time histories from strain and velocity measurements, and decomposition into downward- and upward-traveling waves. The CASE method is applied to the simulated signals to estimate the static pile capacity, which compares favorably with the resistance obtained from a quasi-static load-settlement analysis. The results demonstrate the ability of DEM to bridge particle-scale mechanisms and engineering-scale predictions in both fundamental soil mechanics and applied foundation engineering.

Completion Date

2026

Semester

Summer

Committee Chair

Arboleda Monsalve, Luis

Degree

Master of Science in Civil Engineering (M.S.C.E.)

College

College of Engineering and Computer Science

Department

Department of Civil, Environmental, and Construction Engineering

Format

PDF

Document Type

Thesis

Language

English

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