Abstract: The interlayered soil is a type of widely distributed special soil. Its mechanical behavior has not been fully understood so far. The soil samples of silty clay interlayered by silty sand are artificially prepared for experiments. The consolidated-undrained triaxial tests are carried out to study the basic mechanical behavior of the prepared interlayered soils. The effects of the layer thickness ratio on the stress-strain relationship, pore pressure responses, shear strength and sample failure modes are analyzed. The results show that the mechanical behavior of the interlayered soil falls in between the behavior of the two constituent layers of soil, i.e., a normally consolidated silty clay and a medium dense sand, but it is not a simple combination of the two. Instead, the layer thickness ratio plays an important role. As the thickness ratio of silt clay increases in the interlayered soil, its stress-strain curve transits from the softening type to the hardening one, the pore pressure changes from negative to positive, and the shear band type localization is suppressed, implying an enhanced role of silty clay layer.