Correlation between physical properties and shear strength of undisturbed slip surfaces

This paper describes the relation between physical properties and shear strength of undisturbed slip surfaces in Tertiary stratalandslides, shear zone landslides and solfataric landslides. The number of tested slip surfaces is 124 and almost all samples weretaken from the drainage well. Both Slip Surface Direct Shear test (SSDS) that would be able to adjust the position of slip surfacewith the shear surface of the apparatus and ring shear test were executed. Slip surfaces and shear surfaces at residual state wereobserved by scanning electron microscope. The roughness of these surfaces was measured by laser focus displacement sensor.For the investigation of physical properties grain size analysis and Atterberg plasticity limits tests were conducted. From the testresults, it became clear that all samples taken from both Tertiary strata landslides and solfataric landslides included smectite inthe slip surface clay and such slip surfaces were covered with smectite. The relation between residual friction angle and plasticityindex for such samples were divided into three groups. Also it was shown that the sample contaminated by sand fraction builtcoarse grains into rough shear surface with high shear strength.