Undrained shear strength of soils with fine fraction content derived from compression and extension loading triaxial tests

In the stability analysis of dams or deep excavations a calculation scheme of soil response is assumed that considers the rotation of main stresses. In the case of tailings dams constructed of granular material with fine fraction content (FC <0.075 mm), an additional factor is to be considered i.e. liquefaction phenomenon. Soil response to undrained shearing in compression loading (increase of vertical stress) and extension loading (increase of horizontal stress) differs significantly, giving various strength values. The paper presents the results of triaxial tests carried out on soils with fine fraction content. The tests were performed under compression loading and extension loading conditions. The test results' analysis was performed, considering grain size impact and main stresses application method at the shearing stage.