Shear Strength and Stability of Highway Embankment Slopes in Ohio

Highway embankment is one of the most commonly constructed geotechnical facilities. In Ohio, the design of these embankments has been based largely on previously published empirical correlations and/or crude soil testing results. Because of this practice, there have been some cases in Ohio where embankment slopes developed instability problems. Structural stability of these embankments is vital to the state economy and public safety. A need existed in Ohio to conduct a comprehensive study to measure shear strength properties of actual embankment fill materials and develop reliable tools for designing highway embankments. This paper describes a three-year project completed recently in Ohio. In the first stage of the project, soil samples from nine embankment sites were tested extensively both in the field and laboratory. The sites were placed strategically across Ohio to cover a wide range of geological and geographical features existing in the state. In the second stage of the project, the large volume of the data produced in the first stage was subjected to further examinations to evaluate the empirical correlations and develop statistically reliable alternative approaches for estimating soil shear strength properties from basic data. In the third stage of the project, the average properties of each major soil type were incorporated into a series of highway embankment slope stability analyses to gain additional insights into the topic and formulate general geotechnical guidelines for constructing/designing highway embankments.