American Society of Civil Engineers


Measuring Erodibility of Cohesive Soils Using Laboratory Jet Erosion Tests


by A. T. Al-Madhhachi, (School of Civil and Environmental Engineering, Oklahoma State University, Stillwater, OK 74078. E-mail: abdu@okstate.edu), G. J. Hanson, (Location Coordinator and Research Leader, USDA-ARS Hydraulic Laboratory, 1301 N. Western, Stillwater, OK 74075. E-mail: greg.hanson@ars.usda.gov), G. A. Fox, (Associate Professor, Department of Biosystems and Agricultural Engineering, Oklahoma State University, 120 Ag Hall, Stillwater, OK 74078. E-mail: garey.fox@okstate.edu), A. K. Tyagi, (School of Civil and Environmental Engineering, Oklahoma State University, Stillwater, OK 74078), and R. Bulut, (School of Civil and Environmental Engineering, Oklahoma State University, Stillwater, OK 74078)
Section: Hydraulics and Waterways, pp. 2350-2359, (doi:  http://dx.doi.org/10.1061/41173(414)244)

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Document type: Conference Proceeding Paper
Part of: World Environmental and Water Resources Congress 2011: Bearing Knowledge for Sustainability
Abstract: Many factors affect the erodibility of cohesive soils, such as the soil characteristics, soil moisture content, and properties of the eroding fluid. Typically the erosion rate of cohesive soils is quantified using an excess shear stress equation, dependent on two major soil parameters: the critical shear stress (τc) and the erodibility coefficient (kd). A submerged jet test (JET — Jet Erosion Test) is one method for measuring these parameters. In this study, a laboratory JET and a new miniature version of the device ("mini" JET), with the advantage of being easier to use in the field, were used to measure τc and kd for various soils. The objective of this study was to determine if the "mini" JET estimated equivalent values for τc and kd. Two different soils types (silty sand and clayey sand) were used in comparing the performance of the two devices. Sieve analysis, hydrometer, and plasticity index tests were also performed to characterize these two soils. Test samples of the soils were prepared at three to seven different water contents with equivalent compaction effort (25 blows per layer). In-order to compare the performance and repeatability of both JET devices, tests were performed on paired samples prepared in the same way and tested at the same time. Reasonably equivalent measured kd were obtained with the two JET devices for both soils. Results indicated some variability in measuring τc and kd due to variability in the subsamples of the cohesive soil and differences in soil moisture levels. These results also indicated that settling back of some of the eroded soil into the scour area of the new "mini" JET device may have caused differences in measured τc relative to the original JET device. Even though there was an observed difference in the observed τc, the differences were consistent. The relationships between measured τc and kd obtained from both JET devices also compared reasonably well with those observed in previous field research.


ASCE Subject Headings:
Soil erosion
Cohesive soils
Measurement
Laboratory tests