The Estimation of the Residual Shear Strength of High Plastic Clays Based on Direct Shear Test Results

Landslides are the most common incidents with a rate of 45% considering the distribution of natural disaster numbers to disaster types. In order to make remedial measures for the landslides, the residual shear strength parameters formed in the shear plane during the landslide must be estimated as close to the reality as possible. These parameters can be determined by multi-reversal direct shear, ring shear tests, back calculations, correlations in the literature by means of physical properties of the soil. The difficulty of predicting the groundwater conditions during landslide is obvious and it directly affects the residual shear strength values when shear strength parameters are determined using the back analysis method. On the other hand, residual shear strength parameters obtained from the literature can give a wide range. Besides, ring shear tests are not commonly performed in laboratories and depending on the type of soil, multi reveral direct shear tests may need to be performed at very low speeds. Relatively long test time adversely affects the practical use of the multi reversal direct shear tests. In this study, the relationship between peak and residual shear strength in normally consolidated high plastic clays was studied within the framework of the above restrictions. Firstly, the empirical correlation between the residual shear strength and the index porperties and peak shear strength was predicted by evaluating the results of the studies in our country's literature. Then, the results obtained from the multi reversal direct shear tests with remoulded high plastic clay samples and the predicted values were compared.