Title page for ETD etd-06032010-142638


Type of Document Master's Thesis
Author Charonko, Cami Marie
Author's Email Address cmj@vt.edu
URN etd-06032010-142638
Title Evaluation of an In Situ Measurement Technique for Streambank Critical Shear Stress and Soil Erodibility
Degree Master of Science
Department Biological Systems Engineering
Advisory Committee
Advisor Name Title
Mostaghimi, Saied Committee Co-Chair
Wynn, Theresa M. Committee Co-Chair
Diplas, Panayiotis Committee Member
Keywords
  • submerged jet test device
  • flume erosion test
  • cohesive soil erosion
  • critical shear stress
  • soil erodibility
Date of Defense 2010-05-18
Availability unrestricted
Abstract
The multiangle submerged jet test device (JTD) provides a simple in situ method of measuring streambank critical shear stress (τc) and soil erodibility (kd). Previous research showed streambank kd and τc can vary by up to four orders of magnitude at a single site; therefore, it is essential to determine if the large range is due to natural variability in soil properties or errors due to the test method. The study objectives were to evaluate the repeatability of the JTD and determine how it compares to traditional flume studies.

To evaluate the repeatability, a total of 21 jet tests were conducted on two remolded soils, a clay loam and clay, compacted at uniform moisture content to a bulk density of 1.53 g/cm^3 and 1.46 g/cm^3, respectively. To determine the similarity between JTD and a traditional measurement method, JTD τc and kd measurements were compared with measurements determined from flume tests.

The JTD kd and τc ranged from 1.68-2.81 cm^3/N-s and 0.28-0.79 Pa, respectively, for the clay loam and 1.36-2.69 cm^3/N-s and 0.30-2.72 Pa, respectively, for the clay. The modest variation of kd and τc for the remolded soils suggests the JTD is repeatable, indicating the wide range of parameters measured in the field was a result of natural soil variability. The JTD median kd and τc, except clay loam kd (clay loam kd = 2.31 cm^3/N-s, τc = 0.45 Pa; clay kd = 2.18 cm^3/N-s, τc = 1.10 Pa) were significantly different than the flume values (clay loam kd = 2.43 cm^3/N-s, τc = 0.23 Pa; clay kd = 4.59 cm^3/N-s, τc = 0.16 Pa); however, considering the range of potential errors in both test methods, the findings indicate the multiangle submerged jet test provides reasonable measurement of erosion parameters in a field setting.

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