Summary Report for Long-Term Strength of High-Pl Clays (0-2100-S)

High-plasticity clays occur in many areas of Texas and often offer the most economical material for construction of highway embankments. When constructed with proper moisture and compaction control, embankments constructed of plastic clays can perform adequately with regard to overall stability. However, experience shows that the outer layers of these embankments can experience dramatic strength loss. Softening of the surficial soils can begin soon after construction and continue for decades. The consequent sloughing and shallow slide failures represent a significant maintenance problem for the Texas Department of Transportation (TxDOT). The problem of strength loss in high-plasticity clay soils can impact other structures such as retaining walls, pavements, and riprap. This report describes an approach for estimating soil strength loss as a function of time and space for typical slopes and earth structures used in TxDOT projects.