Piezometer/permeameter probe

摘要

The hydraulic conductivity as a function of the suction pressure can be determined in a series of steady-state, radially symmetric infiltration flows from a spherical source surface. For this flow shape, the Darcy equation can be solved exactly independently of the type of conductivity function. In practical application of this method, a tensiometer has to date simultaneously been used as the infiltration source as well. The high flow resistance of the tensiometer restricts the method to pressure ranges of above 200 hPa. Very long measuring times at very low infiltration rates prevent the use of this method for a surveying instrument. An infiltration source and a tensiometer are combined to form a piezometer/permeameter probe. The infiltration source has a very small flow resistance and allows constant infiltration rates to be set up to saturation of the adjacent ground volume. A tensiometer on the probe axis below the infiltration source exactly indicates the soil pressure on the effective source surface. At a predetermined infiltration rate, steady-state flow conditions are indicated by a constant limit value of this pressure. Piezometer/permeameter probe for determining the hydraulic conductivity in the near-saturated range.