화강풍화토의 세립분 함량에 따른 역학적 특성

초록

Decomposed granite soil is widely used as a subgrade material in Korea. The mechanical behavior of the soil can differ depending on the fines content of the soil. It may behave as either cohesive or cohesionless soils due to particle crushing during loading and compaction. In order to evaluate the effects of fines content on the mechanical properties of compacted decomposed granite soils, a direct shear test, a triaxial shear test as well as some fundamental property tests were performed on samples with five different fines contents (10, 20, 30, 40, and 50%) by weight. Results of the triaxial tests show that as the percentage of fines content decreases, cohesion decreases but internal friction angle increases. In the direct shear test, soils with low fines content exhibit a hardening/softening stress/deformation relationship with a small residual strength/ peak strength ratio. In contrast, soils with high fines content show a hardening-constant relationship with a large residual strength/ peak strength ratio. The effect of the fines contents on the critical state friction parameter shows that the parameter decreases with an increase of the fines content. Results of triaxial and direct shear tests also indicate that fines content of 30% can be a good indicator to determine if the compacted decomposed granite soil behaves as either a sand or a clay.