Influence of Confining Pressure on Water Retention Characteristics of Compacted Soil

Sustainability of earth structures is one of the major concerns in the field of geotechnical engineering. Recurring evaluation and maintenance related to earth structures can often lead to faulty decisions due to errors in analysis. A prominent such concern is related to compacted soils in earth structures which are unsaturated in nature and subjected to stress variations in field. Under the effect of stress state, the key parameters to assess the strength and deformation behavior of unsaturated soils might undergo various changes. In general, key parameters are obtained from soil water characteristic curve (SWCC). In the present study, an effort has been made to understand the influence of confining pressure on the SWCC of compacted soil through experimental and analytical studies. The SWCC of compacted soil at zero net confinement was obtained using tensiometers (HYPROP) and dew point potentiometer (WP4C) while for various net confining pressures, modified triaxial apparatus (using axis translation technique) is used. The measured soil suction-water content data was fitted with five most widely used SWCC models available in literature. The key parameters of SWCC fitted with least square regression technique was compared for all the five models to assess the effectiveness of the models in predicting the SWCC correctly over the entire suction range. Results indicate that there is a disparity in the obtained key parameters from various SWCC models. The influence of stress state on the SWCC obtained experimentally is compared with the analytical solution accounting the influence of stress state.