Details:

Creators:
Weldu, Mehari T. ; Han, Jie ; Rahmaninezhad, Sayed Mustapha ; Parsons, Robert L. ; Kakrasul, Jamal I.
Weldu, Mehari T. ; Han, Jie ; Rahmaninezhad, Sayed Mustapha ; Parsons, Robert L. ; Kakrasul, Jamal I. Less -
Corporate Creators:
University of Kansas. Dept. of Civil, Environmental and Architectural Engineering
Corporate Contributors:
Kansas. Dept. of Transportation. Bureau of Research
Subject/TRT Terms:
[+]
Aggregate Gradation Backfilling Earth Walls Pull Out Test Reinforcement (Engineering) Steel
Publication/ Report Number:
K-TRAN: KU-14-7
Resource Type:
Tech Report
Geographical Coverage:
Kansas
Corporate Publisher:
University of Kansas. Dept. of Civil, Environmental, and Architectural Engineering
Abstract:
A wide range of reinforcement-backfill combinations have been used in mechanically stabilized earth (MSE) walls. Steel

strips are one type of reinforcement used to stabilize aggregate backfill through anchorage. In the current MSE wall design, pullout

capacity of steel strips is evaluated to ensure internal stability of the reinforced mass. The pullout resistance of reinforcement is

expressed in terms of pullout resistance factor that measures the reinforcement-backfill interaction. This pullout resistance factor is

commonly determined by performing pullout tests.

AASHTO (2012) LRFD Bridge Design Specifications provides default values of pullout resistance factor, F*, for strip

reinforcement embedded in backfill material with a uniformity coefficient of Cu ≥ 4, where the uniformity coefficient is defined as

the ratio of the particle size at 60% finer to that at 10% finer. However, for backfill with a uniformity coefficient of Cu < 4,

AASHTO recommends project-specific pullout tests. This AASHTO requirement has disqualified a large amount of aggregates

produced in Kansas quarries, or made them difficult and/or costly to be used in MSE wall construction. To address this problem,

an experimental study was undertaken in the Geotechnical Engineering Laboratory at The University of Kansas to examine the

effect of aggregate uniformity on pullout resistance of steel strips when the uniformity coefficient of aggregate is Cu < 4.

Eighteen pullout tests were carried out on ribbed steel strip reinforcements embedded in six aggregate backfills with

uniformity coefficients ranging from 1.4 to 14. The pullout resistance of each reinforcement-backfill combination was investigated

under three normal stresses to simulate reinforcements placed at different depths of fill. Each test sample was prepared in a

consistent way to minimize variations. One of the important influence factors was degree of compaction.

The test results demonstrated that the overall trend for all types of aggregates was similar. The uniform aggregates

generally behaved the same way as the well-graded aggregates in terms of pullout resistance. The effect of aggregate uniformity

was more obvious in the tests under a lower normal stress than under a higher normal stress. When the normal stress was at 10 psi,

there was no obvious effect of aggregate uniformity.

Furthermore, the pullout resistance factors obtained from this study were compared with the default F* values for ribbed

strip reinforcement provided by AASHTO (2012). The comparison shows that the pullout resistance factor for ribbed steel strips

decreased with depth in the same way as suggested by AASHTO. However, the F* values recommended by AASHTO are

conservative as compared with the test results when aggregate backfills with uniformity coefficients ranging from 1.4 to 14 were

used. In other words, the F* values recommended by AASHTO can be used to design MSE walls with ribbed steel strips in

aggregate backfills with a uniformity coefficient as low as 1.4.


Format:
PDF
Funding:
C1970
Collection(s):
US Transportation Collection
Main Document Checksum:
[+]
urn:sha256:557a4ffff7c61b0484ab83ef7b21272025d0228ea2346225f259459dd18f8a09
Download URL:
https://rosap.ntl.bts.gov/view/dot/29544/dot_29544_DS1.pdf
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