Soil improvement in Qom City under the influence of montmorillonite nanoclay

Abstract Improving problematic soils using economical and appropriate methods is a major focus in geotechnical research. Recently, nanoparticles such as nanoclay have gained attention as a cost-effective and eco-friendly solution for enhancing soil quality. Nanoclay’s high specific surface area and ion exchange capacity make it economically viable, while its environmental friendliness comes from its derivation from bentonite minerals. This case study aims to improve a local sandy soil with low shear strength in an earthquake-prone region south of Qom City, Iran. The study uses nanoclay stabilization and compares its effectiveness on improving the local soil under both static and dynamic loading conditions, providing a novel approach. Thus, a series of direct shear and simple shear tests were performed to accomplish this specified task. After adding nanoclay to the soil, the sandy soil pores were filled with a cohesive mixture, increasing its agglomeration, which ultimately led to the following results. The results showed that incorporating nanoclay significantly increased the cohesion (c) value by an average of 12 times and raised the internal friction angle (Φ) by 15% compared to the untreated soil. Furthermore, the shear modulus (G) increased 1.4 times on average, while the damping ratio (D) decreased by 25% relative to the original soil. Overall, the use of montmorillonite nanoclay proved to be highly effective in enhancing the strength of non-cohesive sandy soils, especially under static loading. Additionally, the method of stabilizing soil with nanoclay was found to be economical for improving its strength in both static and dynamic conditions.