Determining permeability function of unsaturated loess by using instantaneous profile method

The instantaneous profile method is generally applied to determine the unsaturated permeability function. In this paper, a laboratory model of the instantaneous profile is used to determine the permeability function of unsaturated loess. The loess sample was collected from the typical Malan loess in southern bank of the Jinghe River, near Jingyang County, Shaanxi Province. The grinded loess powder was sieved into a 2 meter high glass cylinder, and then it was consolidated with a certain load on the top till stable. A 10cm layer of fine sand was covered on the top of the column to avoid the hardening of loess. As start to do the test, to fill a certain amount of water on the top, the water will penetrate into the loess through sand bed. Water content profiles of the loess column were obtained in certain time by measuring water content at intervals of 5 cm along the depth. The sample in the same density with model test was made to measure the soil-water characteristic curve by TEN-15 tensionmeter. Then the soil-water characteristic curve and water content profiles at different time were applied to calculate the water flow rate, the hydraulic head gradient and the unsaturated coefficient. At last, the permeability equation was fitted with exponent function which can apply for seepage analysis of loess.