Osmotic technique is an important method for measuring the matrix suction of unsaturated soil. It is very important to control the osmotic time

which is one of the key points to obtain the accurate measurement result. Based on the finite element numerical analysis software SEEP/W

we set up a numerical model of osmotic technique to analyze water movement during the osmotic process. Then

we analyzed the influences of the suction of solution

the hydraulic properties of soil sample

the initial gravity moisture content

the initial dry density and the size of soil sample on equilibrium time of the osmotic technique for unsaturated clay in the process of humidification. The results show that with the increase of osmotic time

the difference of suction between the solution and the soil sample will decrease and then the osmotic process will become slower. Soil samples should not be too large. For small samples

the equilibrium time for the osmotic technique is about 1.5-8.0 days in most cases. The equilibrium time increases greatly when the suction of solution is high or the saturated hydraulic conductivity of soil sample is low. The equilibrium time decreases with the increase of the fitting parameters (a

n) for soil-water characteristic curve

the saturated hydraulic conductivity

the initial moisture content and the initial dry density. On the contrary

the equilibrium time increases with the increase of saturated volumetric moisture content.