Shear strength attenuation law and mechanism of gravel-soil under immersion

Abstract

After a reservoir is filled with water, the gravel-soil of a slope is immersed, and the mechanical properties are changed, which affects the stability of the slope. To investigate the influence of immersion on the mechanical properties of gravel-soil, the gravel-soil at the back edge of the slope that has not been immersed was used and large-scale direct shear tests were performed to obtain the shear mechanical properties of gravel-soil after different immersion days. The test results show that after 40 days of immersion, the cohesion of gravel-soil decreases by 39% and the internal friction angle decreases by 8.3%; the cohesion of gravel-soil decreases significantly in the initial stage of immersion and the decay rate decreases with the increasing number of days of immersion.After 20 days of immersion, the cohesion does not decrease significantly with the increase of immersion days. To reveal the reason and mechanisms of shear reduction in gravel-soil, triaxial shear tests, laser particle size analysis and leachate cation analysis were performed on silty clay (fine-grained component of gravel-soil). The results indicate that the shear strength of gravel-soil is attenuated by mineral dissolution, ion exchange and adsorption of the silty clay in gravel-soil. The large particles in the soil are refined, and the cementation is reduced, which reduces the overall shear strength of the gravel-soil. This study has certain significance for the evaluation and management of gravel soil landslides in reservoir areas.

Keywords

• gravel-soil
• immersion
• large-scale direct shear test
• triaxial compression test
• shear strength
• shear strength attenuation
• attenuation mechanism