Study on small strain characteristics and microscopic mechanism of rice husk ash modified lime soil

Abstract

As a solid waste residue from rice husk combustion, rice husk ash (RHA) has volcanic ash activity. The application of RHA in lime soil can both realize the resource utilization of solid waste and improve the performance of lime soil. In this experiment, lime soil was modified by using rice husk ash (RHA). Following this, the dynamic characteristics of rice husk ash modified lime soil (RLS) were examined by a series of resonant column tests, which indicated the effects of confining pressure, RHA content, and age of curing on the small strain shear modulus G and damping ratio D of RLS. The micro-mechanisms of the RHA modified limestone soil were analyzed by using SEM, EDS, and TEM tests. The results show that: (1) The dynamic shear modulus G exhibits a growing pattern due to increasing confining pressure and curing age, but the damping ratio D indicates a contrary tendency. (2) The dynamic shear modulus G and the damping ratio D both show an increasing and then decreasing trend with RHA content increasing, and the optimal content of RHA can be seen as 4% according to the experimental data. (3) The added RHA led to generate a larger amount of hydration silicate hydrate on the surface of soil particles, and the hydration products tends to densify the soil by filling the pores between soil particles. The test results verified the feasibility of RHA modified lime soil applied to roadbed treatment, which is of great significance for the practical engineering.