Exploring the nonlinear behavior of flow through cracked concrete by water permeability test

Abstract

This study investigates the nonlinear behavior of flow passing through 28 crack topographies in concrete at various pressure gradients using water permeability test. Artificial cracks were generated and quantified by point-cloud matching technique. Results indicate Darcy's law becomes biased for calculating an apparent transmissivity of cracked concrete at a high Reynolds number. As an alternative, Forchheimer's parabolic equation is employed to model the flow rates at different pressure gradients, constructing an equivalent energy conversion model to calculate inertial and viscous pressure gradients and determine intrinsic transmissivity. A numerical model is proposed in which transport efficiency is represented as a function of dimensionless parameter J of pressure gradient. The model is validated by experimental data and further used to explore the onset of nonlinear flow. It is observed that the flow exhibits a significant nonlinear behavior once the transport efficiency reaches 0.9305. This threshold is utilized to delimit the flow regimes and construct a Moody chart for permeability assessment of concrete in practice. It provides an effective way to characterize the behaviors of water flow in concrete and evaluate its transport properties.