Forensic Investigations into Recurrent Pavement Heave from Underlying Expansive Soil Deposits

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Pavement sections constructed over expansive soil deposits often exhibit excessive distresses due to volume changes in the underlying soil strata. Differential movements within these deposits resulting from fluctuations in the moisture content manifest themselves in the form of localized heaves on the pavement surface. A pavement section near the western border of Idaho has experienced recurrent damage due to volume changes in the underlying expansive soil layer; traditional treatment methods such as lime stabilization and moisture barrier installation have provided partial relief over the years. A recently concluded forensic research study at Boise State University investigated the causes for failure of earlier treatment methods. This study involved extensive laboratory characterization of expansive soil samples collected from underneath this pavement section to identify location of the problematic soil strata, and to propose suitable rehabilitation measures. Laboratory characterization included tests such as moisture content, Atterberg limits and One-Dimensional swell test to determine the potential vertical rise (PVR) and establish approximate active zone. Laboratory test results indicated that the most expansive soil deposits were at a depth of at least 1.83 m from the pavement surface. PVR values calculated closely matched with the surface profile trends observed in the field. In addition, the soluble sulfate tests performed on various soil samples indicated that sulfate heaving could be a problem for calcium-based stabilizer. Based on the findings, the research team proposed that the pavement section be reinforced using a flexible mechanical system that dissipates the swell pressures originating from the underlying clay layers.