Soil Water Characteristic Curves of Soils Exhibiting Different Plasticity

Experiments have been conducted to study the effects of anisotropy and remolding on the soil water characteristic curves (SWCCs) of soils exhibiting different plasticity characteristics. The soil samples were collected from IIT Hyderabad, Sangareddy, Telangana, India. Anisotropy and remolding effects were quantified based on the factor of safety of unsaturated finite slopes. The combination of the Hydraulic Property Analyzer (HYPROP) for low soil suctions and the dew point potentiometer (WP4C) for the high suction range is employed to obtain the full range of SWCCs. The SWCCs of the remolded soil samples compacted at field density and water contents of dry of optimum (DOP) and wet of optimum (WOP) are estimated. The SWCCs are plotted using the data obtained from HYPROP and WP4C. The experimental results indicated that there is a profound change in the shape of SWCC when it is estimated using HYPROP and HYPROP along with WP4C data. Moreover, the SWCC fitting parameter af related to air entry value is underestimated from the SWCC, which is obtained employing HYPROP data. The fitting parameter (af) values of expansive clay obtained from HYPROP and HYPROP in conjunction with WP4C are 12.34 kPa and 3342.7 kPa, respectively. The present study suggests combining HYPROP and WP4C data to accurately estimate the SWCCs. Further, the investigations revealed that the SWCC fitting parameter af is higher in remolded soil compacted at WOP than at DOP. When the expansive clay is compacted at DOP and WOP, the values of the SWCC fitting parameter (af) are determined to be 9.54 kPa and 59.47 kPa, respectively. The SWCCs obtained from the remolded soils are compared with the SWCCs of the undisturbed soil samples. It is observed that the influence of anisotropy on SWCCs of clayey sand and expansive clay is minimal. The factor of safety (FoS) of unsaturated finite slope increases by 11% in clayey sands and 7.9% in expansive clays when water content changes from DOP to WOP. Moreover, the percentage increase in FoS is higher in the case of the flat slope. When the moisture content changes from DOP to WOP, percentages increase in FoS of expansive clayey slopes are 12.12% and 7.89% for slope angles of 35° and 50°, respectively. The FoS of the unsaturated finite slope is quite sensitive to the initial water content due to significant shifts in the location of critical slip surfaces.