Geotechnical and Geoenvironmental|
RESEARCH ACTIVITIES
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Performance of Reinforced Soil Slopes under Working Stress Conditions
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Participants: Fabiana Arriaga, Joe Friedrichsen, Carina Costa Description: This project involves centrifuge modeling of reinforced soil slope models. Digital image analysis is used to investigate the strain distribution in the model. This project will benefit reinforced soil structure design, as well as the understanding of the confined behavior of geosynthetics. Time-dependent response of geosynthetic reinforced soil structures also under investigation
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Professor Zornberg and Fabiana inspect a reinforced soil slope |
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Centrifuge Modeling of Unsaturated Flow |
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Participant: John McCartney, Eduardo Dell'Avanzi Description: Centrifuge modeling of soil columns under 1g and Ng levels is being conducted to investigate the scaling factors of variables governing unsaturated flow through soil. This project seeks new methodologies for investigating the suction-saturation and suction-hydraulic conductivity curves. The overall objective is to contribute towards understanding of evapotranspirative cover systems. |
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Test equipment for analysis of unsaturated flow through a sand column
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| Behavior of Alternative Landfill Cover Systems | |
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Participants: John McCartney, Jeffrey Kuhn, Eduardo Dell'Avanzi Description: This project involves the analysis of field monitoring data for evapotranspirative covers. In addition numerical modeling is being performed of the different parameters governing the behavior of evapotranspirative covers (i.e. unsaturated flow, evapotranspiration, infiltration, percolation, runoff, etc.). Laboratory research includes full-scale column testing, centrifuge modeling of unsaturated flow, and unsaturated soil property characterization. This project will benefit the future design of alternative landfill cover systems. |
Eduardo and John discuss a model for unsaturated flow |
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Behavior of Fiber-Reinforced Soil |
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Participants: Chunling Li Description: Experimental verification is being conducted of a theoretical framework for prediction of the shear strength of fiber reinforced soil. Unreinforced soil and soil-fiber mixtures are testing using triaxial compression and extension tests with varying dosages of fibers to find the optimum improvement. The results of the compression and extension tests are also used to investigate the effect of anisotropy induced by the addition of fiber reinforcements.
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Chunling and Professor Zornberg monitor a test in progress |
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| Reinforcement of Poorly Draining Soils | |
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Participants: YoungCheol Kang, Sidnei Teixeira, Sean Sanchez Description: This project involves pullout of geogrid from saturated and unsaturated cohesive soils. In addition, the effect of in-plane drainage, used along geogrid reinforcement, on the generation of pore pressures during shearing is investigated. |
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The pullout box ready to perform a test
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Characterization of Tire Bales Used for Light-Weight Backfill |
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Participant: Christopher LaRoque Description: An extensive testing program is underway to characterize the mechanical properties of tire bales used for light-weight backfill. In addition, full scale direct-shear testing is being conducted.
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Direct shear testing of tire bales
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| Performance of Buried Pipes Overlying a Void | |
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Participant: Yuri Costa Description: Centrifuge tests will be performed to observe the deformation mechanisms in a buried pipe and the surrounding soil when a trapdoor beneath the soil is released.
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Mechanical Characterization of Solid Waste |
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Participant: Amaro Lins, Lindsay Ashworth Description: Several landfills in Brazil and the Colorado area have been characterized for the unit weight of the soil, percentage of organic and inorganic materials and other features.
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Municipal solid waste
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Hydraulic Characterization of Geomembrane Defects |
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Participant: Christine Weber Description: The mechanisms of flow through geomembrane defects are being investigated. Small and large-scale permeameters are being used to quantify the interaction between soil and geomembrane holes.
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| Internal and Interface Shear Strength of Geosynthetic Clay Liners | |
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Participant: John McCartney Description: A
database of 375 large-scale direct shear tests was assembled in this
investigation to identify and quantify the variables governing the
internal shear strength of geosynthetic clay liners (GCLs).
Analysis of the database allows a thorough investigation of the
effect of reinforcement, conditioning of specimens and normal stress
during shearing on internal shear strength, and of sources of internal
shear strength variability. The
investigation benefited from test results obtained for a wide range of
GCL types (unreinforced, needle-punched, thermal-bonded and
stitch-bonded), normal stresses (from 2.4 kPa to 2759 kPa), and shear
displacement rates (testing duration from 1.25 hs to 35 days).
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Close-up of a disassembled GCL |
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Time-Dependent Behavior of Geosynthetic Reinforcements |
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Participants: Brett Byler, Justin Knudsen, Carina Costa Description: Research involves temperature-accelerated testing of geosynthetics to characterize their creep and stress-relaxation behavior, define the creep-failure curve and estimate the residual strength. An approximate 8-hour test, using the Stepped Isothermal Method (SIM), can provide data in excess of 100 years, circumventing many of the impracticalities of conventional creep testing. SIM data correlates well with conventional creep data. Better understanding of long-term behavior leads to more realistic design procedures, and ultimately cost savings. |
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Justin monitors the progress of a test
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Shear Strength Characterization using Non-Conventional Testing |
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Participants: Curtis Mathis, Satoshi Takata Description: This project involves the determination of residual shear strength of Colorado claystones obtained using both ring shear and direct shear devices. This project also involves the development of a large-scale direct shear device with large-displacement capabilities representative of residual conditions for most soils. In addition, a cubical cell capable of testing a tire shred-soil or fiber reinforcement- soil mixture as an elemental cube has been developed. This project allows determination of the effects of reinforcement on soil improvement and anisotropy. |
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Curtis examines the normal stress application mechanism of the direct shear device
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Geosynthetic-Reinforced Retaining Walls |
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Participant: Carlos Vinicius Benjamim Description: This project involves the monitoring and evaluation of full-scale prototype geotextile-reinforced retaining walls. A total of 8 walls were constructed in the state of São Paulo, Brazil using local soils. Moisture contents, horizontal and vertical internal displacements of the reinforced backfill, and face displacements were monitored.
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Vinicius, Professor Zornberg, and Professor Benedito Bueno posing at the full-scale reinforced soil walls
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| Geosynthetic-Reinforced Bridge Abutments | |
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Participant: Jakraphob Watcharamonthein Description: This project involves the evaluation of the monitored performance of a geosynthetic-reinforced bridge abutment (the Founder's-Meadows Parkway bridge on I-25 near Denver, CO). Stress distribution and deformation response was evaluated to validate the design procedure
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| Laboratory and Field Characterization of Tire-Soil Mixtures | |
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Participants: Hailey Wappett, Tim Fitzgerald, Brent Vollenweider, Alex Cabral, Erich Kroll, Chardphoom Vitranjandr, Satoshi Takata Description: This project involves analytical developments, laboratory characterization, and field evaluation of soil-tire shred mixture and layering techniques. Analytical formulations, suitable for future design projects, were developed. Laboratory tests are conducted to evaluate the shear strength of tire shred-soil specimens using large-scale triaxial devices. The project also involves extensive field monitoring of the mechanical response as well as of the environmental interactions of tire shreds and soil to evaluate the long-term performance of the composite system. Current research includes thermal conductivity of soil-tire shred mixtures.
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The tire-shred reinforced prototype embankment |
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| SPONSORING AND COLLABORATING AGENCIES | |
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National Science
Foundation
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Colorado Advanced Software Institute |
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Colorado
Advanced Materials Institute
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Colorado Department of Transportation |
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Synthetic Industries
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SGI Testing Services |
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