Browsing by Author "Ravichandran, Nadarajah"

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    Combined portable free fall penetrometer and chirp sonar measurements of three Texas river sections post hurricane Harvey
    Jaber, Reem; Stark, Nina; Jafari, Navid; Ravichandran, Nadarajah (2021-12-05)
    The US Gulf of Mexico coastal region has repeatedly been subjected to major flood events. Local geotechnical site characteristics and geomorphology can change due to sediment transport processes during such events. However, field measurements during extreme conditions are challenging. This paper discusses initial attempts at a combined geotechnical and geophysical site investigation of the uppermost layers of riverbeds following severe flooding events at three different rivers in Texas: the Guadalupe, Brazos, and Colorado Rivers in terms of sediment strength derived from a portable free fall penetrometer, backscatter intensity recorded by a chirp sonar, and soil sample characterization. Results show low strength sediments (<40 kPa) along the investigated sections of the Guadalupe and Brazos riverbanks. Although sediments in the center of the Brazos River were characterized with higher strength (>50 kPa) and larger grain sizes (d(50) similar to 0.3 mm), sediment strength of the Guadalupe and Colorado Rivers displayed more variations around bridge piers. The spatial variations likely resulted from sediment remobilization processes and local scour under severe hydrodynamic conditions. Both, geotechnical and geophysical results, reflected the observed variations in the riverbed sediments; nonetheless, a quantitative correlation among the rivers was impeded by challenges primarily related to limitations of spatial accuracy and the significant riverbed heterogeneity, as well as shallow water limitations of the chirp sonar.
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    Post hurricane Harvey dataset: Portable free fall penetrometer and chirp sonar measurements of Texas rivers
    Jaber, Reem; Stark, Nina; Jafari, Navid; Ravichandran, Nadarajah (Elsevier, 2022-06)
    This data article includes datasets collected at three sections of the Guadalupe River, Brazos River, and Colorado River in Texas, USA, almost ten months post Hurricane Harvey. Instruments used include a Portable Free Fall Penetrometer (PFFP), Chirp Sonar, Side Scan Sonar (SSS), Acoustic Doppler Current Profiler (ADCP) and sediment grab sampler. Measurements were collected from small vessels such as canoes and a 6-feet inflatable zodiac and were supported by long term hydrodynamic data from local river water level and discharge gages. Laboratory testing performed on samples collected included grain size analysis, Atterberg test, and erodibility testing using an Erosion Function Apparatus (EFA). Data collected were analyzed to estimate sediment strength derived from the PFFP, backscatter intensity recorded by the chirp sonar, and soil sample characteristics. The dataset includes raw and processed data for the measurements recorded by the instruments, location of measurements, and laboratory testing grouped for each river with a readme file which gives a potential for reuse by other researchers for further analysis if needed. This data article is representing supplementary data to the following research article published in Engineering Ge-ology [1] : Jaber, R., Stark, N., Jafari, N., & Ravichandran, N. "Combined Portable Free Fall Penetrometer and Chirp Sonar Measurements of three Texas River Sections Post Hurricane Harvey." Raw data was published [2] : Stark, N. Jafari, N. Ravichandran, R. Jaber, R. (2020). Combined Geotechnical and Geo-physical Investigation of Texas Rivers Post Hurricane Har-vey. in Combined Geotechnical and Geophysical Investigation of Texas Rivers Post Hurricane Harvey. (C) 2022 The Author(s). Published by Elsevier Inc.