The effects of dry density and moisture content on the shear characteristics of clay-type muddy interlayer

Shear strength parameter is one of the important indexes of soil, which is the key factor to determine the stability of the project. In order to study the shear characteristics of clay-type muddy interlayer, an improved direct shear apparatus was used to carry out indoor direct shear tests under different dry density and moisture content conditions. The results show that the shear stress increases with the increase of dry density and decreases with the increase of moisture content. When the moisture content is 20%, the shear stress-shear displacement of the muddy interlayer shows obvious strain-softening phenomenon. When the moisture content is 23% and 25%, the sample shows hardening characteristics at low normal stress level. With the increase of stress level, the curve transits from softening type to hardening type. When the moisture content is 28%, the curves show slight strain softening. Under the condition of low moisture content, the internal friction angle decreases with the increase of dry density, while the cohesion increases with the increase of dry density. At medium moisture content, both of them fluctuated with dry density, but the amplitude was not large. At high water content, the response effects of internal friction angle, cohesion and dry density are not obvious. The research results can provide a reference for the research on disaster prevention and early warning of related projects of clay-type muddy interlayer.