Unsteady Pressure‐Driven Viscous Flows Beneath Concrete Pavement Slabs

Abstract

Water pumping flows beneath concrete pavement slabs are experimentally measured and mathematically modeled. A solution for the velocity profile and the wall shear stress is found for the condition of a constant imposed pressure gradient. The solution shows that the core flow is not significantly affected by viscosity if the time of application is less than 0.2 times the film thickness squared divided by the fluid kinematic viscosity. A finite difference method is described and used to determine the velocity profile and wall shear stress when the imposed pressure gradient is an arbitrary function of time. The velocity profile is then calculated using experimental pressure data for flow beneath a concrete pavement slab. The experimental pressure data is obtained from a 189,000‐N three‐axle truck crossing the joint between two concrete pavement slabs. The calculated mid‐plane velocity of the water between the pavement slab and the subbase compares favorably with measured velocities. The maximum water velocity is approximately 0.9 m/s.