Evaluation of Soil Shear Strengths for Slope and Retaining Wall Stability Analyses with Emphasis on High Plasticity Clays

15. Supplementary Notes Project performed in cooperation with the Texas Department of Transportation and the Federal Highway Administration; Project Title: Implementation of Research Results Regarding Shear Strength and Stability of Embankments 16. Abstract A number of TxDOT-sponsored studies and research projects have been conducted over the years regarding shear strength and slope stability issues of embankments. These projects span approximately 15 years, and each developed relationships and theories for soil strength relationships in different areas of the state. In addition, some findings from earlier projects have been refined or disputed in later studies. Data from these studies are spread throughout numerous reports, and in some cases unpublished, making the data are difficult to utilize. This implementation project was undertaken to review the data and develop a single, unified data set and guidelines that can be utilized in refining the Geotechnical Manual and presented to the geotechnical community in other publications. In this report important fundamentals pertaining to the shear strength of soils are reviewed and guidelines for determining appropriate values of soil shear strength parameters are presented for both undrained (short-term) and drained (long-term) stability conditions. Particular attention is given to the long-term strength properties of compacted high PI clay fills used for embankment construction. 17.