Cohesive Slope Surface Failure and Evaluation

This paper highlights the mechanism of slope surface failure that occurs on highway embankments with cohesive soils. Based on systematic instrumentation in the field, the major reason for such surface failures is ascribed to the reduction of soil strength due to the seasonal variation of moisture content in embankment soils. Shrinkage cracks develop in an embankment during dry seasons. A great amount of rainfall then infiltrates into embankment soils through these cracks in subsequent wet seasons. As such, the shear strength of embankment soils progressively decreases as soils swell until a surface failure occurs. This surface failure mechanism was indirectly studied through a series of shrinkage and unconfined compressive tests on cohesive soil similar to that at the highway embankment. A limit equilibrium analysis method was also suggested accordingly for the back calculation of slope stability. Finally, a rehabilitation technique using nonwoven geotextile was recommended for highway maintenance engineers to repair such slope surface failures.