Impacts of Shear Stress on Saturated Hydraulic Conductivity of a Polyacrylamide Treated Soil

Polyacrylamides (PAMs) have been historically used in industrial and environmental settings in food packaging, paper manufacturing, waste water treatment, and soil loss prevention. Recently, PAM has been considered for use in unlined earthen irrigation canals to reduce seepage losses. To evaluate the potential benefits and risks associated with PAM applications to irrigation canals, a series of studies have been conducted by the Desert Research Institute (DRI) in collaboration with the US Bureau of Reclamation (USBR). The purpose of this research was to investigate the impacts of shear stress on soil hydraulic conductivity of a PAM treated soil. A small experimental flume was built to accommodate four soil columns attached to its bed. The soil columns were filled with engineered sand and treated with three PAM concentrations and a control (no PAM). Water flux and K_sat were measured through the soil columns over a period of several hours. Experiments were completed for three flowrates and a control (no flow). Four major conclusions were drawn from the experimental results: 1) a reduction in water flux was observed as a function of PAM concentration; 2) when the PAM application was free of imperfections, the PAM layer was resistant to shearing; 3) imperfections in the PAM layer (e.g. bubbles or rips) caused a substantial increase in water flux; and 4) failure of the PAM layer occurred abruptly and was highly variable, although typically associated with a flaws in the PAM layer.