Percolation testing and hydraulic conductivity of soils for percolation areas

• Published in: Water research (Oxford) 2001-11, Vol.35 (16), p.3909-3915
• Main Authors: Mulqueen, J, Rodgers, M
• Format: Article
• Language: English
• Subjects: Applied sciences; Biological and physicochemical properties of pollutants. Interaction in the soil; design standards; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Models, Theoretical; percolation rates; Pollution; Pollution, environment geology; Porosity; septic tanks; Silicon Dioxide; Soil; Soil and sediments pollution; unsaturated hydraulic conductivity; Waste Disposal, Fluid; Water Movements
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/S0043-1354(01)00122-1

The results of specific percolation tests are expressed in terms of field saturated hydraulic conductivity ( K fs) of the soil. The specific tests comprise the Irish SR 6 and the UK BS 6297 standard tests and the inversed auger hole and square hole tests employed for the design of land drainage. Percolation times from these tests are converted to K fs values using unit gradient theory and the Elrick and Reynolds (Soil Sci. 142(5) (1986) 308) model which takes into account gravitational, pressure head and matric potential gradients. K fs is then expressed as the inverse of the percolation rate times a constant; in this way the percolation rate can be directly related to K fs of the soil. A plot of K fs against percolation rate for the Irish SR 6 and the UK BS 6297 standard tests is asymptotic at K fs values less than 0.2 m/d and greater than 0.8 m/d. This behaviour creates difficulty in setting limits for percolation rates in standards. Curves are provided which enable K fs values to be read off from percolation tests without the restrictions of head range currently enforced, for example in the Irish SR 6 and BS 6297 standards. Experimental measurements of percolation rates and K fs were carried out on two sands in the laboratory and in the field on two soils. K fs of these four materials was also measured using a tension infiltrometer and the Guelph permeameter. The saturated hydraulic conductivities ( K s) of the sands were also estimated in a falling head laboratory apparatus and by the Hazen formula. There was good agreement between the different tests for K fs on each material. Because percolation time continued to increase significantly in consecutive tests in the same test hole while K fs became constant, the latter is a better measure of the suitability of soils for percolation.