On the Primacy of the Exchange Complex on the Shear Strength of Marly Soil

The influence of the exchange complex on shear strength behavior and the initial tangent modulus of elasticity of marly soil (a low active soil) were investigated. The investigation involved transformation of the naturally heterogeneous exchange complex into homogeneous exchange complex having only one type of exchangeable cation species present in the exchange complex. This step constitutes a fundamental step for assessing soil behavior of natural heterogeneous exchange complexes based on the physicochemical approach. Although the investigated soil is a low active soil, the influence of the exchange complex on shear strength was significant, or even substantial in some cases. Differences in soil cohesion associated with the tested exchange complexes reached 3 folds, and differences in the angle of friction reached about 50% to 90%, depending on the dry density of the soil and its moisture content. Influence of the exchange complex was minor on the exponent "n" of Janbu’s formula; maximum variation was about 25%. A change in Kur which is the second parameter of Janbu’s formula due to changes in the exchange complex was substantial; variation reached as much as three folds.