Characterisation of nano magnesia–cement-reinforced seashore soft soil by direct-shear test

Abstract

In this study, the mechanical behaviour of nano magnesia–cement-reinforced seashore soft soil (NmC3S) was evaluated and characterised by the direct-shear testing of seashore soft soil (3S), cement reinforced seashore soft soil (C3S) and NmC3S. The comparison among these three types of soils indicates that NmC3S has greater shear strength and deformation modulus than C3S and 3S. The shear stress of both C3S and NmC3S increase significantly prior to a shear displacement of 1.0 mm, followed by a sharp decline before reaching the critical state. The failure displacement increases as the applied normal stress increases. NmC3S demonstrated greater friction angle than both C3S and 3S; however, the magnitude of its cohesion lies between that of C3S and 3S. Moreover, a mathematical model that describes the shear stress–displacement curve was proposed, which can effectively model the strain-hardening and strain-softening curves of these three types of clays. Finally, a generalised formula for capturing the stress–displacement behaviour of these three materials is presented with the explanations for the physical meaning of each parameter.