Prototype reinforced soil embankment for reconstruction of US route 62 slope failure in Chickasha, OK.

PDFTech ReportFHWA-OK-15-03ODOT SP&R Item Number 2160EmbankmentsSoil structureSlope stabilityShear strengthService lifeGeotextilesSoil suctionPrototypesOklahomaOklahoma. Dept. of Transportation. Materials and Research DivisionHatami, KianooshMiller, Gerald A.Esmaili, DanialUniversity of Oklahoma. School of Civil Engineering and Environmental ScienceUnited States. Federal Highway AdministrationUS Transportation CollectionOne of the main concerns in internal stability of reinforced soil structures constructed with fine-grained ormarginal quality soils is the change in shear strength of the soil-reinforcement interface when the soil gravimetric watercontent (GWC) increases. This increase can occur during construction or service life of the structure, e.g. due to prolongedprecipitation. The resulting loss in the soil matric suction could reduce the interface shear strength leading toserviceability problems or even failure of the reinforced soil structure. In this study, three (3) 1 m-high and two (2) 1.7 m-high model embankments were constructed, which were all subjected to strip footing loading in plane-strain condition. Themodel embankments were constructed using a mixture of lean clay (CL), sand and a small percentage of commerciallyavailable sodium bentonite at the GWC values ranging between OMC-2% and OMC+2% (OMC: Optimum Moisture Content).The purpose for building smaller embankment models was to study the behavior of a single soil-geotextile interface in anembankment configuration. Therefore, the smaller models included only a single reinforcement layer which was placed 180mm below the embankment surface. In contrast, the larger models were intended to simulate field reinforcedembankments. Hence, those models were reinforced with four (4) layers of reinforcement with a uniform vertical spacing of300 mm. The location of single reinforcement layer in smaller models was selected based on preliminary embankment testsand numerical simulations to ensure that it would intercept the failure surface that developed underneath the strip footingnear the embankment slope. The embankments were instrumented to measure the footing load, earth pressure,reinforcement strains and the soil GWC and matric suction values during the tests. A primary objective of the embankmenttests was to investigate the influence of the as-compacted GWC value of the soil on the performance of the modelembankments and thereby, validate or make necessary adjustments in the values of the moisture reduction factors (MRF)for reinforced embankment design that the authors had developed based on their prior pullout and interface shear tests