Implementing an Analytical Framework to Quantify the Magnitude and Rate of Subgrade Pumping in Flexible Pavement

Particle transport in porous media can significantly compromise the serviceability of civil infrastructure. For example, pumping or migration of saturated subgrade soil to pavement subbase, adversely affects the performance of the pavement and leads to its failure. In this study, an analytical framework is implemented to 1) understand mechanisms of pumping, and 2) estimate the amount of subgrade fines migration into subbase under traffic loads. The model is verified using results obtained from experimental investigations previously conducted to quantify the amount of pumping. The experimental tests were conducted using one-third model mobile load simulator (MMLS3), an accelerated pavement testing (APT) device. Results showed that the analytical model provided a reasonable prediction of the amount of fines migration from a saturated pavement subgrade to subbase. The study also revealed that the subgrade pumping and the deposition process is governed by hydraulic condition, erodibility of subgrade, grain size of subgrade, grain size and pore size of subbase, permeability of subbase, and viscosity of pore fluid in the subbase.