Abstract

This report documents findings from a three-year research study that examined the pullout resistance of
inextensible MSE reinforcements in backfills typically used in Texas. The study involved an extensive laboratory test program in which a total of 650 pullout tests were completed. These tests were conducted using a large scale pullout test system that consisted of a test box with dimensions of 12ft x 12ft x 4ft and capability to simulate overburden pressures equivalent to 40 feet of fill. Tests were conducted on ribbed strip reinforcements, welded steel grid reinforcements, and a limited number of smooth bars embedded in two types of backfill, designated as Type A (gravelly) and Type B (sandy) select backfill as per TxDOT specifications. A subset of strip and grid reinforcements in each backfill type was instrumented with strain gages to provide further insight into mechanisms that control pullout resistance. The research design evaluated pullout resistance factors for both strip and grid reinforcements for a variety of independent variables including overburden pressure, reinforcement length, skew or splay angle, grid wire size, and grid geometry including both transverse and longitudinal wire spacing. Appropriate statistical analyses were used to interpret the data within the context of published AASHTO design guidance for inextensible MSE reinforcements.

Project PI: William Lawson

Project Researchers:

Jayawickrama, P.W.
J.G. Surles

Research Associate: Timothy Wood

Research Assistant:

Asitha Senanayake
Mert Bildiren
Yiqing Wei
Allen Johnson

Student Assistant:

Jon Link
Roderick Henderson
Ernest Terrell
Michael Nichols
Samir Blanchet