Nonlinear decay behavior of small strain dynamic shear modulus of lime-treated expansive soil

PurposeExpansive soil is a kind of problematic soil with poor engineering properties, and it needs to be treated before reusing it as engineering construction material. The soil under dynamic load in engineering often has small strain behavior. The purpose of this study is to investigate the dynamic behavior of lime-treated expansive soil in the small strain range.MethodsIn this study, a series of resonant column tests were conducted to investigate the nonlinear decay behavior of small strain dynamic shear modulus (SSDSM) of lime-treated expansive soil under various lime content (2-8%), consolidation pressure (50-400 kPa), and curing time (0-28d) conditions. SEM test was used to reveal the microstructure of lime-treated expansive soil. Two mathematical models were introduced to describe the decay law of SSDSM of lime-treated expansive soil.ResultsThe results show that the addition of lime can significantly improve the SSDSM of expansive soil, as evidenced by an increase of approximately 2.7-5 times in the maximum dynamic shear modulus caused by the addition of lime in the range of 2-8%. On the other hand, the addition of lime also increases the brittleness of expansive soil. Curing time has less effect on improving SSDSM than lime content, which is reflected in the increase of the maximum dynamic shear modulus of expansive soil containing various lime contents by approximately 1.2-2 times after sufficient curing (28d curing time). The consolidation pressure has the effect of increasing the SSDSM and reducing its nonlinear decay rate. The role of lime additive is to reduce the void ratio of soil and increase the integrity of the soil. In engineering practice, considering the dual effects of improving stiffness and increasing brittleness, as well as engineering costs, it is recommended to use a lime content of 2-4% as the optimal ratio for improving SSDSM of weak expansive soil. The Stokoe model is more suitable for describing the nonlinear decay behavior of SSDSM of lime-treated expansive soil.ConclusionFrom the perspective of dynamic behavior in small strain range, a small amount of lime additive (2-4% content) is a worthwhile solution for reusing weak expansive soil.