Graduation Year

2024

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Civil and Environmental Engineering

Major Professor

Gray Mullins, Ph.D.

Co-Major Professor

Zachary Haber, Ph.D.

Committee Member

Michael Stokes, Ph.D.

Committee Member

Miguel Goni Rodrigo, Ph.D.

Committee Member

Kevin Johnson, Ph.D.

Keywords

Auger Cast Piles, Drilled Shafts, Durability, Thermal Integrity Testing, Thermal Modeling

Abstract

Construction of cast-in-place concrete deep foundation elements is a common practice, yet performed almost entirely blind, leaving uncertainty in the quality of the as-built, below-ground element. This dissertation focuses on three quality assurance aspects of cast-in-place foundations: an automated concrete tracking system for drilled shafts, an alternate approach to identifying if mass concrete conditions exist in cast-in-place foundations, and as-built auger cast pile grout volume determination.

The volume of concrete in a drilled shaft is relatively easy to track on a truck-by-truck basis, as well as the height of the rising concrete per truck. However, a more detailed volume distribution was shown to benefit the concreting process assessment via the development of an automated, weighted-tape device to track the rising concrete. The as-placed concrete distribution is accurately tracked when coupled to concrete pump stroke counts. Follow-up temperature profiles confirm the concreting volume distribution to match the temperature distribution routinely used to estimate effective element size.

Temperature measurements can also identify that drilled shafts, through a combination of mix design and element size, can exceed safe temperature limits described as mass concrete. This research examined probe-collected thermal integrity data from six drilled shafts to develop a relationship between the temperature gradient measured in access tubes to the peak center temperature of a foundation element. The proposed thermal analysis method enables mass concrete assessment without center or edge of shaft temperature sensors.

Finally, proper assessment of foundation element size requires the volume of placed cementitious material (pile grout or shaft concrete) to be precisely known. Where shaft concrete volume can be tracked relatively easily, the final grout volume of auger cast piles presents a challenge because of the necessary overpour and the inability to delineate between that which ends up in-excavation or on-ground-surface in the final stage of construction. This study examined 650 auger cast piles and identified a means to improve pile volume estimation.

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