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Creep Behavior of Soil Nail Walls in High Plasticity Index (PI) Soils

Project Summary

"An aspect of particular concern in the Geotechnical Engineering Circular No. 7: Soil Nail Walls (i.e., the soil nail wall manual and construction guidelines) is the creep behavior of soil nail systems in high-plasticity clays. This research project was aimed at gaining a better understanding of the long-term behavior of the soil nail walls in fine-grained soil with plasticity index higher than 20. The project was composed of field, laboratory, and numerical modeling investigations. Pullout tests were performed at the National Geotechnical Experimental Site at Texas A&M University (NGES-TAMU) and at the actual soil nail wall project site selected by the Texas Department of Transportation (TxDOT). The TxDOT site was also instrumented and monitored for more than one year. The tests at the NGES-TAMU were focused on the effect of the load level on creep behavior of soil nails in a natural clay deposit of high plasticity. The tests were conducted on 10 existing anchors, which were installed in 1991, along with 16 vertical soil nails installed in this research project, and six sacrificial soil nails installed during the construction of a TxDOT soil nail wall. This wall corresponds to a new excavation project in an embankment fill, in which nine permanent soils nails were instrumented with the aim of monitoring the long-term behavior and performance of the wall in a high-plasticity clay. Complementary laboratory tests to learn about the creep behavior of the clays involved in this research project were performed at Texas A&M University using samples gathered from the two investigated sites. The numerical modeling had three goals: 1) to calibrate the constitutive models using the information gathered from the laboratory and the pullout tests; 2) to simulate the long-term behavior of the actual soil nail wall and compare the model and monitoring results; and 3) to perform a parametric analysis to study the effect of different factors, among others, wall geometry and soil parameters. Based on the information obtained from the project activities, a procedure was proposed to take into account the creep effects in the design of soil nail wall in high-plasticity soils. In addition, the Federal Highway Administration is considering adding these test methods in an update of the Geotechnical Engineering Circular No. 7, thereby increasing the exposure of these test methods to a nationwide level." --AASHTO RAC's 2016 Research Impacts: Better-Faster-Cheaper, p.182

Project Number

0-6784

Status

Completed

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Project Details

Start Date

9/12/2012

Renewal date

9/1/2014

End Date

8/31/2015

Performing Institution(s)

Texas A & M Transportation Institute (TTI)

Research Team

RS: Marcelo Sanchez

Sponsor

Project Manager

Wade Odell

Publications from this Project

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Functional Area

Structures and Hydraulics

Index Terms

Clay soils
Creep
Embankments
Load tests
Plasticity
Soil nailing
Tendons

Lead University

TTI

Researcher

Sanchez Castilla, Marcelo J.

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Comments

kevyn

This project was included in the "2016 Research Impacts: Better--Faster--Cheaper" publication by AASHTO RAC (Research Advisory Council) http://research.transportation.org/Documents/RAC%20Docs/HVR_2016.pdf

8/3/2016 at 3:43 PM

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Record Added:

3/19/2015

Record Updated:

7/22/2023 5:32 AM EDT

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