Effect of Aggregate Size and Porosity of Clay Soils on the Hydraulic Parameters of the Green-Ampt Infiltration Model

To study the effect of aggregate size and total porosity of soil on the hydraulic parameters of the Green-Ampt (GA) infiltration model, eight laboratory constant-head infiltration tests were conducted on a clay soil with different values of aggregate size and porosity. Hydraulic conductivity, wetting front suction head, and air entrapment coefficient behind the wetting front of the GA model were measured for the conducted tests. With the use of double-ring infiltrometers, falling-head infiltration tests were also conducted in a field with soil of a clay texture, and a new theoretically based method was proposed for simultaneous estimation of the hydraulic parameters of GA model from falling-head infiltration test data. The results indicated that the estimated hydraulic conductivity of the GA model for laboratory soil columns followed the Kozeny-Carman equation. The air entrapment coefficient is nearly independent from soil aggregate size, but it increases as soil porosity increases. Furthermore, a perfect agreement between the measured infiltration field data and the falling-head approach of the GA model validated the capability of the proposed method to correctly estimate the hydraulic parameters of the GA model. (c) 2018 American Society of Civil Engineers.