Estimation of subgrade soils mechanical properties and frost sensitivity through the use of simple tests

Resumé

Subgrade soils properties are one of the main inputs for pavement design. In cold climates, these subgrade properties are associated with stiffness, water sensitivity and frost susceptibility and can be obtained through reliable but complex and costly resilient modulus and segregation potential laboratory tests. Portable instruments such as light weight deflectometer (LWD) allow to rapidly and easily quantifying mechanical properties of soils to a limited extent. The mathematical models associated with these measurements are poorly adapted to take into account stress state and water content on the mechanical properties determination. Regarding the frost susceptibility of soils, a default value is often used or it is often estimated with charts or estimated from its physical properties. Therefore, the project focused on the development of simple tests using portable tools (LWD and percometer) to perform a reliable estimation of resilient modulus and segregation potential. Ten typical subgrade soils were sampled and a laboratory deflection based test (using a LWD and a 300 mm diameter mold), validated with field measurements, and was correlated with triaxial resilient modulus test results to take into account non linearity. Percometer measurements (dielectric value) were also performed on the laboratory samples for various water contents. The water sensitivity measured with the percometer data were correlated with laboratory segregation potential values of the tested soils. The developed resilient modulus and segregation potential estimation techniques allowed obtaining an adequate estimation of these important pavement design properties based on soils in situ characteristics.