Measurement of stress dependent permeability of unsaturated clay

• Importance of studying permeability of soil based on stress factor is addressed.
• An optimization framework of Genetic programming (GP) is introduced.
• GP based permeability model fits with higher accuracy on the testing data.
• 2-D analysis of the GP based permeability model is conducted.
• Suction influences the permeability of clay the most.

Unsaturated permeability in soil is useful in assessment of water consumption by roots and suction distribution in slopes, which in turn, helps in design for the stability of slopes/covers. Stress factor is important in understanding the behavior of the unsaturated soils because it has a significant effect on its permeability as it brings micropores and minipores changes in the soil structure. Past studies have often neglected to measure its effect on the permeability property of the soil. The present study will introduce an optimization framework of genetic programming (GP) in developing the explicit relation of the permeability and the stress of the unsaturated clay. Experimental validation of the GP model will be done using the metrics such as the coefficient of determination, the root mean square error and the mean absolute percentage error. 2-D analysis of the model will be useful for experts to monitor the permeability property unsaturated clay.