Abstract — The problem of soil stabilization has been one of the important issues in geotechnical engineering. Nowadays, nanomaterials have revolutionized many industries. In this research, improvement of the Kerman fine-grained soil by nanozeolite and nanobentonite additives separately has been investigated using Atterberg Limits and unconfined compression test. In unconfined compression test, the samples were prepared with 3, 5 and 7% nano additives, with 1, 7 and 28 days curing time with strain control method. Finally, the effect of different percentages of nanozeolite and nanobentonite on the geotechnical behavior and characteristics of Kerman fine-grained soil was investigated. The results showed that with increasing the amount of nanozeolite and also nanobentonite to fine-grained soil, the soil exhibits more compression strength. So that by adding 7% nanozeolite and nanobentonite with 1 day curing, the unconfined compression strength is 1.18 and 2.1 times higher than the unstabilized soil. In addition, the failure strain decreases in samples containing nanozeolite, whereas it increases in the presence of nanobentonite. Increasing the percentage of nanozeolite and nanobentonite also increased the elasticity modulus of soil.
The biocementation-based soil improvement technique that has been recently developed is enzyme-induced calcite precipitation (EICP).Previous studies on the EICP technique used pure commercial urease enzyme as a reaction catalyst to precipitate calcite from urea and calcium chloride.However, pure commercial urease enzyme is inefficient for application on a large scale due to its high price.Therefore, studies reported that soybean is a potential alternative for pure commercial urease enzymes.This study evaluates the strength of sandy soil by treatment using EICP grouting solution with soybean extracts as the bio-catalyst.The extracts used in this study were obtained by filtration and centrifugation treatment.Based on the calcite mass quantification and precipitation ratio, 20 g/L soybean extract concentration in both treatments is used for treating the solution.Then, the unconfined compressive strength (UCS) tests were conducted to evaluate the increase of the strength of sandy soil.The maximum UCS value was obtained at the 28 days of curing time in both treatments.The centrifugation treatment has a higher UCS value with 65.6 kPa than the filtration treatment with 53.6 kPa.Thus, this study elucidated that soybean extract has a great potential to be a bio-catalyst in the calcite precipitation method.
