The unsaturated shear strength of calcareous soil in comparison with silicate soil

Abstract

Marine calcareous sediments are quite prevalent in coasts of tropical regions. Significant differences have been observed between marine calcareous and silicate soils in terms of mechanical behaviors, shear strength, liquefaction resistance, etc., mainly due to considerable intra-particle voids in calcareous sediments. In the present study, constant water content (CW) triaxial tests were performed on two similar grain size distributions of both calcareous and silicate specimens to evaluate unsaturated shear behavior of calcareous soil for the first time, and compare it with a reference silicate soil. Saturated triaxial tests were also conducted to obtain saturated shear strength parameters of both soils. Porous structure of calcareous soil was studied using scanning electron microscopy and mercury intrusion porosimetry tests. Soil–water retention curves resulting from pressure plate tests were also obtained for both soils. Calcareous soil showed higher water retention capacity, attributing to its porous microstructure, and it experienced higher suction changes during CW tests. Effective stress parameter (χ) and capillary cohesion of calcareous soil were indirectly influenced by its microstructure, and were higher compared to silicate soil. Like the silicate soil, for the calcareous soil, critical state line was unique and close to saturated state.