University of Texas at Austin. Center for Transportation Research

FHWA/TX-09/0-5825-1

Tech Report

Texas

624618619

Technical report; Sept. 2006-Aug. 2008.

University of Texas at Austin. Center for Transportation Research

NTL-HIGHWAY/ROAD TRANSPORTATION-Soils and Geology

This research addressed two key issues: 1) Will verification cores holes fill during concrete backfilling? If so, what are the mechanical properties of the filling material? In dry conditions, verification core holes always completely fill with concrete whose compressive strength is of equal strength to the concrete in the drilled shaft column. In wet conditions, the bottom half of the verification core hole fills with non-cemented gravel-sand mixture (φ = 52°), while the upper half of the verification core hole filled with weakly cemented material (Vp = 2000 fps). 2) When drilling in materials, such as shales, susceptible to degradation: does this degradation specifically around shaft verification core holes affect point bearing capacity? The shear strength of Del Rio Clay and Eagle Ford Shale is not affected by drying-duration, but is related to water content; the shear strength of Taylor Marl and Navarro Shale decreases considerably as drying-duration increases. The elastic modulus of all four clay shales drops significantly when clay shales are dried and then wetted. When shales are first dried and then rewetted and concrete is poured in the wet, the verification core hole reduces tip capacity by a maximum of 10% (14% for Taylor Marl). In all other cases, the verification core does not decrease the tip capacity.

PDF

0-5825

US Transportation Collection