Degree Type


Date of Award


Degree Name

Master of Science


Civil, Construction, and Environmental Engineering


As an alternative to long-established soil improvement techniques such as overexcavation and replacement, deep foundations, sand drains and preloading (preconsolidation) methods, rammed aggregate piers (Geopier[Superscript registered trademark symbol] foundation elements) were installed within and around the Ramp "C" abutment footprint for the I-35 overpass at the Hwy 5/I-35 interchange in Des Moines, IA. The rammed aggregate piers were installed in an effort to reduce total settlement and increase the rate of settlement in the soft alluvial clay. The primary goal of the pier installation was to reduce the construction delay between embankment and abutment construction. At the adjacent Ramp "B" bridge abutment stone columns were installed in the foundation soils to increase slope stability at the interface between the silty alluvium and weathered shale.;Although the main focus of this investigation is to evaluate embankment foundation reinforcement using rammed aggregate piers, the stone column reinforced soil has been investigated for a comparative analysis to the rammed aggregate pier reinforced soil. In-situ testing including piezocone penetrometer (CPTU), pressuremeter (PMT), K0- stepped blade and borehole shear (BST) tests as well as extensive laboratory testing have been conducted to investigate rammed aggregate piers' and stone columns' effects on lateral stress, settlement, stress concentrations and rate of consolidation settlement. Comparative stiffness and densities of rammed aggregate piers and stone columns were also evaluated based on full-scale load tests and standard penetration (SPT) tests. Vibrating wire instrumentation including settlement cells and total pressure cells were installed for continuous and long-term (5 year) monitoring of the piers, columns and embankments. Settlement plates were installed and monitored by conventional survey methods.



Digital Repository @ Iowa State University,

Copyright Owner

Aaron Jon Gaul



OCLC Number


File Format


File Size

165 pages