Graduation Year

2018

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Civil and Environmental Engineering

Major Professor

Austin G. Mullins, Ph.D.

Committee Member

Rajan Sen, Ph.D.

Committee Member

Michael J. Stokes, Ph.D.

Committee Member

Ryan Toomey, Ph.D.

Committee Member

Sarah Kruse, Ph.D.

Keywords

Drilling Slurry, Exposure Time, Rock Socket, Temporary Casing, Pullout Strength

Abstract

Design methods for side shear of drilled shafts, including the resistance factors that should be applied, do not account for any specific construction procedure. Instead, design often relies on analysis of case studies which include all construction methods used in each geomaterial type (e.g. clays, sands and rocks), or on parametric analysis. Nonetheless, literature suggests that different construction procedures result in varying side shear.

This research investigated 2 types of construction: (1) slurry stabilization in sandy soils using bentonite and polymer products that are commonly used on the field, with exposure times from near 0h to 96h, and (2) temporary casing stabilization in simulated limestone using 3 different methods for installation and extraction of the casings which included: driven, coarse-tooth rotated and fine-tooth rotated. All specimens were 1/10th scale in relation to the most common shafts sizes constructed in the field.

The results showed that bentonite slurry causes a significant reduction on the side shear within relatively short periods of time (between 2h and 4h of open excavation), whereas polymer slurry did not show appreciable variations up to 96h.

The driven and coarse-tooth rotated temporary casing exhibited lower side shear resistance than the fine-tooth rotated casings, which can be attributed to the larger annulus outside the casing and the additional crumbled pieces of rock that degrades the contact interface with the socket concrete.

Construction-based resistance factors are suggested for each construction procedure investigated in this study and clearly show the effects from different methods.

Download

Share

COinS