Behavior of Bentonite-Sand Mixture Soil Subjected to History Load

The purpose of this study is to demonstrate how variations in soil suction impact shear strength, swelling pressure, and volume changes. To that end, small-scale tests were conducted on both pure bentonite and bentonite in mixtures of 30%, 40%, and 50% with sand under dry conditions, using values selected from compaction curves. A model with dimensions of 700 x 700 x 650 mm for the same starting dry unit weight and water content was utilized to demonstrate the impact of the initial load and history load by loading a surface footing to the permitted bearing capacity. A tensiometer was used to measure the soil suction at 20 and 50 cm depths from the surface footing.  The study found that for all soil types, the values of swelling pressure and potential are affected by the initial load. The initial load decreases pressure and swelling potential for pure bentonite by approximately 29% and 30%, respectively, at optimal drying conditions. Conversely, when the void ratio stays the same, overconsolidated soil expands more than typically consolidated soil by about 19% and 46% for the swelling potential and swelling pressure, respectively, for a pure bentonite soil sample at optimal drying conditions.