Effects of Dynamic Loading on Soil-Pipe Interface Shear Strength of Buried Pipelines

Date of Award

5-9-2026

Degree Name

Ph.D. in Mechanical Engineering

Department

Department of Mechanical and Aerospace Engineering

Advisor/Chair

Ömer Bilgin

Abstract

Buried pipelines form a critical component of modern infrastructure systems, providing essential services such as water supply, wastewater transport, and energy distribution. The performance of these underground lifelines during earthquakes is strongly influenced by the mechanical interaction between the pipe surface and surrounding soil. In particular, the shear resistance developed along the soil–pipe interface governs the axial restraint of pipelines subjected to ground shaking and permanent ground deformation. Despite extensive research on soil–pipe interaction under static conditions, limited experimental data exist on how seismic shaking influence interface behavior for dry and moist soil conditions. This research addresses this knowledge gap through a combined experimental and numerical investigation. The primary objective of this study is to evaluate the influence of soil type, moisture content, pipe material, compaction degree, and seismic excitation on soil–pipe interface shear behavior. A series of small-scale laboratory pullout tests were conducted using a custom-designed sandbox mounted on a shake table. Two granular soils—uniform Ottawa sand and mixed sand — were tested with two pipe materials, PVC and steel. Soil specimens were prepared at multiple moisture contents and compaction levels, and tests were performed under both pre-shaking and post-shaking conditions using a scaled 1994 Northridge California earthquake acceleration record. Measured pullout forces were converted to interface shear stresses to characterize peak and residual behavior. Complementary three-dimensional finite element simulations were performed to reproduce the experimental response and evaluate stress and deformation mechanisms around the pipe. The experimental results show that interface shear resistance increases with soil density and pipe surface roughness with steel pipes mobilizing higher interface strength than PVC pipes under comparable conditions. Moisture content significantly influences interface behavior, with moderate moisture levels altering peak shear stress and post-peak response. Seismic shaking modifies soil fabric and particle arrangement, resulting in measurable changes in interface shear resistance between pre-shaking and post-shaking conditions. The numerical simulations reproduce the overall response trends and comparable peak values and provide additional insight into displacement fields and stress redistribution around the pipe. This study provides experimentally validated interface parameters and improved understanding of how soil gradation, moisture conditions, pipe material, and seismic excitation influence soil–pipe interaction. The findings contribute to more reliable modeling and seismic design of buried pipeline systems installed in granular backfills.

Keywords

Geotechnology

Comments

OCLC No. 1591829878

Rights Statement

Copyright 2026, author.

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