Insitu Measurement of Pavement Distress and Causal Mechanisms in Expansive Soil along Alabama Highway 5

Abstract

Alabama Highway 5 is a farm-to-market road built directly on an expansive clay subgrade. Moisture fluctuations cause the soil to shrink and swell, resulting in severe pavement distress. Laboratory testing has been performed to characterize the shrink-swell behavior of the subgrade soil. Swell pressures of up to 1500 psf have been observed in the laboratory. Several remediation strategies have been implemented at AL-5 in an attempt to reduce the need for pavement maintenance. These techniques include increased drainage, vertical moisture barriers, lime stabilization, and paved shoulders. To evaluate the performance of these test sections and further characterize the soil behavior, field instrumentation has been installed including soil moisture sensors, soil suction sensors, pore water pressure sensors, and asphalt strain gages. Monitoring is ongoing and will continue for the next two years.