Shear Strength Correlations and Remedial Measure Guidelines for Long-Term Stability of Slopes Constructed of Highly Plastic Clay Soils

The Texas Department of Transportation has experienced many small slides in earth embankments that are constructed of highly plastic clays. This report addresses several issues related to (1) the design of new slopes and (2) the evaluation of remedial measures to repair slides in slopes constructed of highly plastic clays. Simple means were examined for estimating soil shear strength based on correlations with results of relatively simple index property tests. Specific procedures and recommendations are presented for estimating soil shear strength for new slopes, as well as for slopes that have experienced previous sliding. Various remedial measures are provided. Also, a number of maintenance activities that may be detrimental to slope stability are identified and suggestions are given for how such actions can be avoided. Finally, an evaluation of geosynthetic reinforcement for slope repair was conducted. Finite element computations were performed using a range of soil types and embankment geometry to investigate the forces mobilized in horizontal, geogrid reinforcement in embankments during construction.