Influence of Hydraulic Response Time of Tensiometer in Hydraulic Characteristics Estimation for Riverbank Sand

摘要

The knowledge of the continuous evolution of soil hydraulic characteristics is required for several environmental geotechnical applications such as capillary barrier systems and river bank slope stability analysis. Such data are obtained in the field by embedding suction sensors in slopes for stability analysis. The hydraulic equilibrium time and other limitations of sensors in establishing the hydraulic characteristics are not available for the compacted soils. Thus the influence of initial soil moisture content, initial wetting condition of the suction sensor, and soil compaction density on the hydraulic equilibrium time of the tensiometer was studied on riverbank sand. A laboratory method considering the equilibrium data at each saturation/drying state was proposed for establishing the equilibrium-SWCC data. The hydraulic equilibrium time of the tensiometer for the studied soil was found to vary from a few hours to several days depending upon the magnitude of suction and state of the sensor. The conventional method for estimating the instantaneous SWCC severely overestimated the suction values at a given water content. The sensor response time was found to be the single most influencing factor in the estimation of soil hydraulic characteristics. The in-situ tensiometer application should be replaced with the moisture sensor readings combined with the lab-based proposed equilibrium SWCC approach.