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Title: Development a fluvial detachment rate model to predict the erodibility of cohesive soils under the influence of seepage

Author
item AL-MADHHACHI, ADBUL-SAHIB - Oklahoma State University
item FOX, GAREY - Oklahoma State University
item HANSON, GREGORY - Retired ARS Employee
item TYAGI, AVDESH - Oklahoma State University
item BULUT, RIFAT - Oklahoma State University

Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: 6/1/2012
Publication Date: 7/30/2012
Citation: Al-Madhhachi, A.T., Fox, G.A., Hanson, G.J., Tyagi, A.K., Bulut, R. 2012. Development a fluvial detachment rate model to predict the erodibility of cohesive soils under the influence of seepage. ASABE Annual International Meeting, July 29 – August 2, 2012, Dallas, TX. Paper No. 12-1337239. CDROM.

Interpretive Summary:

Technical Abstract: Seepage influences the erodibility of streambanks, streambeds, dams, and embankments. Usually the erosion rate of cohesive soils due to fluvial forces is computed using an excess shear stress model, dependent on two major soil parameters: the critical shear stress (tc) and the erodibility coefficient (kd). A submerged jet test apparatus (JET – Jet Erosion Test) is one method for measuring these parameters. However, no mechanistic approaches are available for incorporating seepage forces into the excess shear stress equation. The objective of this study was to incorporate seepage forces into a mechanistic fundamental detachment rate model to predict the erosion rate of cohesive soils. The new detachment model, which is referred to as a "Modified Wilson Model", was based on two modified dimensional soil parameters (b0s and b1s) with seepage forces due to localized groundwater flow. A new miniature version of the jet test device, referred as the "min" JET, and a seepage column were utilized to independently measure the excess shear stress parameter kd, and the "Modified Wilson Model" parameters, b0s and b1s, of a sandy loam and a sandy clay loam soils influenced by seepage. The experimental setup was intended to mimic a streambed and a streambank when the "mini" JET and seepage column were placed in vertical and horizontal directions, respectively. The soils were packed in three equal lifts in a standard mold at a uniform bulk density (1.5 to 1.6 Mg/m3) near the soil's optimum water contents. The models were fit to the experimental data to derive the two soil parameters (b0s and b1s) and the erodibility coefficient (kd) with and without the influence of seepage. The "Modified Wilson Model" predicted the observed data as well as or even better than the excess shear stress model. Seepage forces influenced the observed erosion rate with a non-uniform influence on measured kd, b0s, and b1s relative to dry density. However, the influence of seepage forces can be predicted by the "Modified Wilson Model" parameters in both vertical and horizontal experimental setups.