Individual Effect of Matric Suction on Soil Microstructure and Hydraulic Conductivity

Abstract

The reduction of the soil micro-pore volume and hydraulic conductivity by unsaturated infiltration have been widely recognized. Among other factors responsible for this phenomenon, matric suction plays a key role in such a process. It is quite difficult to figure out the individual contribution of matric suction on soil microstructure and hydraulic conductivity change during unsaturated infiltration due to the complexity of the infiltration process. In this paper, individual effect of matric suction on soil microstructure and hydraulic conductivity was quantified using lab tests and Kozeny-Carman equation. A series of experiments with different matric suction actions were performed using unsaturated triaxial testing apparatus without axial stress. Nuclear magnetic resonance test equipment was used to quantify the imperceptible effect of the matric suction action on the soil micro-pore change. Results show that: under different matric suction actions, porosity of the specimens decreases gradually with the increase of matric suction and the matric suction action frequency. Soil is gradually compressed under matric suction action. Hydraulic conductivity of remolded silty clay was predicted based on the test data and Kozeny-Carman equation. With the increase of matric suction and the matric suction action frequency, hydraulic conductivity can be decreased by up to 25%.